This document analyzes the performance of a Bluetooth system using an optimized differential Gaussian frequency-shift keying (GFSK) demodulator. It first introduces Bluetooth technology and the GFSK modulation scheme. It then presents the system model and signal model for the Bluetooth transmission. The key contribution is developing an optimized differential GFSK demodulator that averages the phase over a portion of each symbol to improve performance compared to conventional differential demodulation that uses a single phase sample per symbol. Simulation results show the proposed demodulator achieves better bit error rate than conventional techniques.
Cancellation of Zigbee interference in OFDM based WLAN for multipath channelIDES Editor
Zigbee is one of the major sources of interference
in 2.4GHz band for WLANs. It is seen whenever any Zigbee
system is operating near to the WLAN system and
transmitting signal at same frequency, time as of WLAN’s, the
later ones performance detoriate severely. So in this paper an
algorithm is proposed to estimate Zigbee interference
component present in all OFDM based WLANs sub-carriers
and cancel out the Zigbee interference from the received
signal of WLANs receiver for multipath fading channels in
frequency domain. Simulation results shows for high SNR
values full cancellation of Zigbee interference or zero BER is
possible.
Comparative Analysis of Distortive and Non-Distortive Techniques for PAPR Red...IDES Editor
OFDM is a popular and widely accepted modulation
and multiplexing technique in the area of wireless
communication. IEEE 802.15, a wireless specification defined
for WPAN is an emerging wireless technology for short range
multimedia applications. Two general categories of 802.15
are the low rate 802.15.4 (ZigBee) and high rate 802.15.3
(UWB). In their physical (PHY) layer design, OFDM is a
competing technique due to the various advantages it renders
in the practical wireless media. OFDM has been a popular
technique for many years and adopted as the core technique
in a number of wireless standards. It makes the system more
immune to interference like InterSymbol Interference (ISI)
and InterCarrier Interference (ICI) and dispersive effects of
the channel. It is also a spectrally efficient scheme since the
spectra of the signal are overlapping in nature. Despite these
advantages OFDM suffers from a serious problem of high
Peak to Average Power. This limits the system’s capabilities
and increases the complexity. This paper compares the signal
distortion technique of Amplitude Clipping and the
distortionless technique of SLM for Peak to Average Power
reduction
This document summarizes a study of modified noise-shaper architectures for oversampled sigma-delta digital-to-analog converters (ΣΔDACs). Two hybrid architectures, A1 and A2, are investigated to trade off noise-shaper and digital-to-analog converter (DAC) complexity while maintaining signal-to-noise ratio (SNR). Simulation results show that architecture A1 achieves fairly good SNR by reducing the number of bits to the noise shaper, while architecture A2 further reduces DAC complexity at the cost of doubling the number of DACs. The number of required DAC unit elements is computed and compared for different architectures and parameter values, illustrating the complexity tradeoffs between noise shaping
This document analyzes the performance of energy detection algorithms for spectrum sensing in cognitive radio systems. It discusses how energy detection works by formulating the spectrum sensing problem as a binary hypothesis test to determine if a primary user is present or absent. It finds that increasing the signal-to-noise ratio, sample size, or dynamic detection threshold can improve detection performance. However, it also notes that energy detection is very sensitive to noise uncertainty, which can seriously degrade performance, especially in low signal-to-noise environments. A dynamic thresholding approach is proposed to improve robustness to noise uncertainty.
This document presents a pilot-tone assisted log-likelihood ratio (PT-LLR) metric for LDPC-coded coherent optical OFDM systems with linear phase noise. The PT-LLR incorporates knowledge of the common phase error (CPE) obtained from the pilot-tone, eliminating the need for prior CPE estimation and compensation. It is derived and shown to outperform the conventional LLR metric for higher-order modulations at smaller pilot-tone to signal power ratios, with similar complexity. Blind intercarrier interference mitigation prior to LLR calculation further improves performance under larger laser linewidths. Simulation results demonstrate the LDPC coded CO-OFDM system using the new PT-LLR metric.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document summarizes design issues in OFDM systems. It discusses the OFDM modem block diagram and signal description. It then focuses on key receiver design issues like time and frequency synchronization through techniques like frequency offset correction, carrier phase tracking, and channel equalization. It also addresses signal dynamic range issues and how they are handled in standards like IEEE 802.11a/g. The document provides illustrations of effects of different impairments and solutions used in practical OFDM systems.
1) The document describes using a Chebyshev filter to remove noise from radar signal data to obtain a clear picture of the radar target track for display. Chebyshev filters have steeper roll-off and more ripple than Butterworth filters but minimize error between the ideal and actual frequency response.
2) The radar signal is passed through a designed 5th order Chebyshev filter with parameters like passband frequency and ripple defined. This significantly increases the signal-to-noise ratio from 10.0085dB to over 10.06dB.
3) The pole-zero plot shows the Chebyshev filter poles lie on an ellipse to minimize frequency response errors over the passband range, with ripp
Cancellation of Zigbee interference in OFDM based WLAN for multipath channelIDES Editor
Zigbee is one of the major sources of interference
in 2.4GHz band for WLANs. It is seen whenever any Zigbee
system is operating near to the WLAN system and
transmitting signal at same frequency, time as of WLAN’s, the
later ones performance detoriate severely. So in this paper an
algorithm is proposed to estimate Zigbee interference
component present in all OFDM based WLANs sub-carriers
and cancel out the Zigbee interference from the received
signal of WLANs receiver for multipath fading channels in
frequency domain. Simulation results shows for high SNR
values full cancellation of Zigbee interference or zero BER is
possible.
Comparative Analysis of Distortive and Non-Distortive Techniques for PAPR Red...IDES Editor
OFDM is a popular and widely accepted modulation
and multiplexing technique in the area of wireless
communication. IEEE 802.15, a wireless specification defined
for WPAN is an emerging wireless technology for short range
multimedia applications. Two general categories of 802.15
are the low rate 802.15.4 (ZigBee) and high rate 802.15.3
(UWB). In their physical (PHY) layer design, OFDM is a
competing technique due to the various advantages it renders
in the practical wireless media. OFDM has been a popular
technique for many years and adopted as the core technique
in a number of wireless standards. It makes the system more
immune to interference like InterSymbol Interference (ISI)
and InterCarrier Interference (ICI) and dispersive effects of
the channel. It is also a spectrally efficient scheme since the
spectra of the signal are overlapping in nature. Despite these
advantages OFDM suffers from a serious problem of high
Peak to Average Power. This limits the system’s capabilities
and increases the complexity. This paper compares the signal
distortion technique of Amplitude Clipping and the
distortionless technique of SLM for Peak to Average Power
reduction
This document summarizes a study of modified noise-shaper architectures for oversampled sigma-delta digital-to-analog converters (ΣΔDACs). Two hybrid architectures, A1 and A2, are investigated to trade off noise-shaper and digital-to-analog converter (DAC) complexity while maintaining signal-to-noise ratio (SNR). Simulation results show that architecture A1 achieves fairly good SNR by reducing the number of bits to the noise shaper, while architecture A2 further reduces DAC complexity at the cost of doubling the number of DACs. The number of required DAC unit elements is computed and compared for different architectures and parameter values, illustrating the complexity tradeoffs between noise shaping
This document analyzes the performance of energy detection algorithms for spectrum sensing in cognitive radio systems. It discusses how energy detection works by formulating the spectrum sensing problem as a binary hypothesis test to determine if a primary user is present or absent. It finds that increasing the signal-to-noise ratio, sample size, or dynamic detection threshold can improve detection performance. However, it also notes that energy detection is very sensitive to noise uncertainty, which can seriously degrade performance, especially in low signal-to-noise environments. A dynamic thresholding approach is proposed to improve robustness to noise uncertainty.
This document presents a pilot-tone assisted log-likelihood ratio (PT-LLR) metric for LDPC-coded coherent optical OFDM systems with linear phase noise. The PT-LLR incorporates knowledge of the common phase error (CPE) obtained from the pilot-tone, eliminating the need for prior CPE estimation and compensation. It is derived and shown to outperform the conventional LLR metric for higher-order modulations at smaller pilot-tone to signal power ratios, with similar complexity. Blind intercarrier interference mitigation prior to LLR calculation further improves performance under larger laser linewidths. Simulation results demonstrate the LDPC coded CO-OFDM system using the new PT-LLR metric.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document summarizes design issues in OFDM systems. It discusses the OFDM modem block diagram and signal description. It then focuses on key receiver design issues like time and frequency synchronization through techniques like frequency offset correction, carrier phase tracking, and channel equalization. It also addresses signal dynamic range issues and how they are handled in standards like IEEE 802.11a/g. The document provides illustrations of effects of different impairments and solutions used in practical OFDM systems.
1) The document describes using a Chebyshev filter to remove noise from radar signal data to obtain a clear picture of the radar target track for display. Chebyshev filters have steeper roll-off and more ripple than Butterworth filters but minimize error between the ideal and actual frequency response.
2) The radar signal is passed through a designed 5th order Chebyshev filter with parameters like passband frequency and ripple defined. This significantly increases the signal-to-noise ratio from 10.0085dB to over 10.06dB.
3) The pole-zero plot shows the Chebyshev filter poles lie on an ellipse to minimize frequency response errors over the passband range, with ripp
This document provides an overview of OFDM (Orthogonal Frequency Division Multiplexing) including:
1. The basic principles of OFDM including modulation using IDFT and demodulation using DFT.
2. How a cyclic prefix is used to mitigate multipath interference.
3. A block diagram of a basic OFDM system showing key components like mapping, IFFT/FFT, insertion of cyclic prefix, and demapping.
4. Examples of OFDM parameters used in standards like IEEE 802.11a.
The document describes a high-resolution time-to-digital converter (TDC) implemented in a 90nm CMOS process. It uses two gated ring oscillators (GROs) as delay lines in a Vernier structure to achieve both a high time resolution and first-order noise shaping. The TDC achieves less than 10ps coarse resolution, consumes 3.6mA from a 1.2V supply, and occupies an active area of 0.18mm by 0.15mm. Simulation results show the quantization noise is pushed to high frequencies, improving the in-band noise performance for applications like all-digital phase-locked loops.
This three day course is intended for practicing systems engineers who want to learn how to apply model-driven systems Successful systems engineering requires a broad understanding of the important principles of modern spacecraft communications. This three-day course covers both theory and practice, with emphasis on the important system engineering principles, tradeoffs, and rules of thumb. The latest technologies are covered. <p>
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document summarizes a research paper that proposes an improved Selective Mapping (SLM) technique to reduce Peak-to-Average Power Ratio (PAPR) in OFDM-LTE networks. SLM is a common technique for PAPR reduction but has high complexity due to side information that must be transmitted. The paper proposes using a Riemann matrix instead of random phase sequences to generate converted data blocks in SLM. This eliminates the need for side information transmission and reduces complexity. The paper then presents simulation results of the improved SLM technique using parameters of LTE networks to evaluate PAPR reduction performance.
Optimum FIR Filtersfor Digital Pulse Compression of Biphase Barker Codes with...IJERA Editor
This document discusses techniques for reducing sidelobes in digital pulse compression of biphase codes. It presents a two-stage approach using a matched filter followed by a sidelobe suppression filter (SSF) designed through linear programming. To reduce logic requirements for implementation, it clusters the SSF filter weights using k-means clustering. Simulation results show the SSF filters designed this way can achieve peak-to-sidelobe ratios of -35 to -40 dB while reducing the number of multipliers needed compared to linear programming alone. Tables provide examples of optimized SSF designs for specific biphase codes.
This document discusses signal processing techniques for removing distortion in ultra-wideband radar and enabling network aided positioning. It describes how the synchronous impulse reconstruction technique is used to digitize wideband radar signals with relatively slow ADCs. However, when the radar is moving, phase and amplitude distortions are introduced in the reconstructed signal. The document then presents a signal processing method to compensate for this motion-induced distortion using the radar's speed and location data. It also discusses how network aided positioning systems can estimate the location of an object using signal strength characteristics and pattern matching techniques.
This document provides a draft for an FSAN NG-PON white paper. Section 1 outlines requirements for NG-PON, including supporting gradual migration from existing Gigabit PON networks. NG-PON1 would coexist on the same fiber infrastructure as Gigabit PON using WDM, while NG-PON2 does not require coexistence. The document proposes an evolution scenario where NG-PON1 acts as a mid-term upgrade and NG-PON2 as a long-term solution. It calls for contributions to further clarify requirements for both NG-PON1 and NG-PON2.
Suppression of Chirp Interferers in GPS Using the Fractional Fourier TransformCSCJournals
In this paper we apply the Fractional Fourier Transform (FrFT) to remove chirp interferers that corrupt Global Positioning System (GPS) signals. The concept is based on the fact that in the time-frequency plane, known as the Wigner Distribution (WD), chirps are represented as lines. Using an FrFT with some rotational parameter ‘a’, we rotate to a new time axis ta that transforms the chirp to a tone, in which the energy of the tone is contained in usually just one or two samples. The best `a', and the correct time sample along the ta axis, may be found without a priori knowledge by searching for the peak in the FrFT, since compression to one or two time samples results in an energy spike. Once the peak is found, we zero out the tone, and hence the underlying chirp. Rotation back to the original time domain via an inverse FrFT produces an improved GPS signal. This method can apply to multiple chirp interferers, and we describe how to easily determine the number of interferers, K, by finding peaks in the FrFT space over the parameter `a'. We also describe how to easily notch the interferers once converted to tones by computing a threshold based on the power of the coarse acquisition (C/A) code and noise. We show that for signal-to-noise ratios (SNRs) greater than at least 10 dB, interferers can be notched regardless of the ratio of the C/A code power to the combined interferer power, denoted as carrier-to-interference ratio (CIR).
The document discusses several speech compression techniques:
1) Uncompressed audio rates are 64kbps for voice and 1.5Mbps for CD audio.
2) ADPCM reduces the data rate to 32kbps by transmitting differences between predicted and actual sample values.
3) SB-ADPCM splits audio into lower and upper sub-bands, compressing each at different rates (48kbps and 16kbps respectively) for total of 64kbps.
4) LPC represents speech as a combination of previous samples and residual error, transmitting just coefficients, enabling lower rates like those in GSM and other standards.
This document summarizes research on reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It discusses using a companding technique with Gaussian distribution to compress the signal before transmission and decompress it upon reception. The key aspects covered are: applying a compander and decompander with Gaussian distribution parameters at the transmitter and receiver; how the central limit theorem allows the sum of subcarriers to approximate a Gaussian distribution for large numbers; and how this technique reduces PAPR by increasing average power while keeping peak power the same. Performance is analyzed by simulating PAPR and bit error rate with and without companding under different parameters.
The document describes a thesis submitted by Hsu Kuan Chun Issac to the Hong Kong University of Science and Technology for a Master of Philosophy degree in Electrical and Electronic Engineering. The thesis proposes designing a 70 MHz CMOS band-pass sigma-delta analog-to-digital converter for wireless receivers. It describes implementing a second-order continuous-time band-pass sigma-delta modulator using transconductor-capacitor integrators for the loop filter. The design includes a latched comparator and TSPC D flip-flop as the quantizer. The performance of prototypes fabricated in 0.8um and 0.5um CMOS processes are evaluated.
INITIAL OBSERVATION RESULTS FOR PRECIPITATION ON THE KU-BAND BROADBAND RADAR ...grssieee
This document describes initial observation results from Japan's Ku-band Broadband Radar (Ku-BBR) Network. The Ku-BBR uses high-resolution pulse compression and wide bandwidth to achieve range resolution of a few meters. A network of these radars in the Osaka area allows for precipitation attenuation correction and high-resolution gridded data. Initial tests show the Ku-BBR provides accurate measurements of rainfall when compared to ground disdrometer measurements.
Localization of Objects Using Cross-Correlation of Shadow Fading Noise and Co...Rana Basheer
When a radio transmitter is mobile, obstacles in the
radio path can cause temporal variation in Received Signal Strength Indicator (RSSI) measured by receivers due to multipath and shadow fading. While fading, in general, is detrimental to accurately localizing a target, fading correlation between adjacent receivers may be exploited to improve localization accuracy. However, multipath fading correlation is a short range phenomenon that rapidly falls to zero within a wavelength whereas,
shadow fading correlation is independent of signal wavelength and has longer range thereby making it suitable for localization with wireless transceivers that operate at shorter wavelength. Therefore,
this paper presents a novel wireless localization scheme that employs a combination of cross-correlation between shadow fading noise and copula technique to recursively estimate the location of a transmitter. A stochastic filter that models multipath fading as an Ornstein-Uhlenbeck process followed by a Generalized Auto Regressive Conditional Heteroskedasticity (GARCH) filtering is
proposed to extract shadow fading residuals from measured RSSI values. Subsequently, Student-T Copula function is used to create the log likelihood function, which acts as the cost function for localization, by combining spatial shadow fading correlation arising among adjacent receivers due to pedestrian traffic in the area. Maximum Likelihood Estimate (MLE) is used for position estimation as it inherits the statistical consistency and asymptotic
normality. The performance of our proposed localization method is validated over simulations and hardware experiments.
The document discusses performing a discrete wavelet transform (DWT) on a 1D signal using MATLAB. It loads a test signal, performs a 5-level DWT decomposition using the coif3 wavelet, then reconstructs the approximation and detail signals at each level. Plots of the original, approximation, and detail signals are generated.
Using contactless probing techniques, this feature allows you to perform calibrated in-circuit voltage and current time-domain measurements under large-signal conditions, on printed-circuit boards (PCB) or on wafer, at locations which are normally unreachable using standard VNA techniques.
This paper presents 2D and 3D modeling of a hysteresis motor using a high temperature superconducting material, YBCO, in the rotor. Both modeling approaches are simulated using COMSOL Multiphysics finite element software. The 3D modeling provides a more precise analysis of motor performance compared to the 2D modeling by accounting for the 3D magnetic properties of the rotating magnetic domains in the rotor. Simulation results of the magnetic flux distribution, torque, and AC losses calculated from the 3D model show good agreement with experimental data.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document describes the design and development of an assembly fixture for mounting a circlip to the piston pin hole of an engine piston. Several concepts for the fixture were generated and evaluated using a concept scoring matrix. Concept 4, which uses a profile locator to position the piston and a push rod actuated by a lever to insert the circlip, was selected as the best concept. The detailed design of the selected fixture concept is described, including its components like the base plate, piston rest, riser block, push rod assembly and guide blocks. An estimated cost of $337 for manufacturing the fixture is also provided. The implemented fixture is able to assemble 2,160 pistons per day with a cycle time of 33 seconds per piston.
This document summarizes the F5 steganography algorithm and the JHRF steganalysis algorithm. F5 embeds messages into JPEG images by decreasing quantized DCT coefficients. It uses techniques like permutative straddling and matrix encoding to distribute changes regularly. JHRF is designed to detect messages hidden with F5. It analyzes DCT coefficients in the frequency domain, looking for patterns that indicate embedding with normal or reverse rules around a demarcation point. The goal of JHRF is to effectively detect hidden data and obtain accurate extraction results.
This document analyzes water quality parameters of Chandlodia Lake in Ahmedabad, Gujarat over a one year period to assess pollution levels. Water samples were collected monthly from 5 points around the lake and were analyzed for various physical, chemical and biological parameters including temperature, pH, dissolved oxygen, biochemical oxygen demand, turbidity, conductivity, nutrients and more. The results found that most parameters exceeded acceptable limits, with the highest pollution occurring during the monsoon season when waste and runoff entered the lake. Therefore, the study concluded that Chandlodia Lake shows very high levels of pollution.
This document provides an overview of OFDM (Orthogonal Frequency Division Multiplexing) including:
1. The basic principles of OFDM including modulation using IDFT and demodulation using DFT.
2. How a cyclic prefix is used to mitigate multipath interference.
3. A block diagram of a basic OFDM system showing key components like mapping, IFFT/FFT, insertion of cyclic prefix, and demapping.
4. Examples of OFDM parameters used in standards like IEEE 802.11a.
The document describes a high-resolution time-to-digital converter (TDC) implemented in a 90nm CMOS process. It uses two gated ring oscillators (GROs) as delay lines in a Vernier structure to achieve both a high time resolution and first-order noise shaping. The TDC achieves less than 10ps coarse resolution, consumes 3.6mA from a 1.2V supply, and occupies an active area of 0.18mm by 0.15mm. Simulation results show the quantization noise is pushed to high frequencies, improving the in-band noise performance for applications like all-digital phase-locked loops.
This three day course is intended for practicing systems engineers who want to learn how to apply model-driven systems Successful systems engineering requires a broad understanding of the important principles of modern spacecraft communications. This three-day course covers both theory and practice, with emphasis on the important system engineering principles, tradeoffs, and rules of thumb. The latest technologies are covered. <p>
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document summarizes a research paper that proposes an improved Selective Mapping (SLM) technique to reduce Peak-to-Average Power Ratio (PAPR) in OFDM-LTE networks. SLM is a common technique for PAPR reduction but has high complexity due to side information that must be transmitted. The paper proposes using a Riemann matrix instead of random phase sequences to generate converted data blocks in SLM. This eliminates the need for side information transmission and reduces complexity. The paper then presents simulation results of the improved SLM technique using parameters of LTE networks to evaluate PAPR reduction performance.
Optimum FIR Filtersfor Digital Pulse Compression of Biphase Barker Codes with...IJERA Editor
This document discusses techniques for reducing sidelobes in digital pulse compression of biphase codes. It presents a two-stage approach using a matched filter followed by a sidelobe suppression filter (SSF) designed through linear programming. To reduce logic requirements for implementation, it clusters the SSF filter weights using k-means clustering. Simulation results show the SSF filters designed this way can achieve peak-to-sidelobe ratios of -35 to -40 dB while reducing the number of multipliers needed compared to linear programming alone. Tables provide examples of optimized SSF designs for specific biphase codes.
This document discusses signal processing techniques for removing distortion in ultra-wideband radar and enabling network aided positioning. It describes how the synchronous impulse reconstruction technique is used to digitize wideband radar signals with relatively slow ADCs. However, when the radar is moving, phase and amplitude distortions are introduced in the reconstructed signal. The document then presents a signal processing method to compensate for this motion-induced distortion using the radar's speed and location data. It also discusses how network aided positioning systems can estimate the location of an object using signal strength characteristics and pattern matching techniques.
This document provides a draft for an FSAN NG-PON white paper. Section 1 outlines requirements for NG-PON, including supporting gradual migration from existing Gigabit PON networks. NG-PON1 would coexist on the same fiber infrastructure as Gigabit PON using WDM, while NG-PON2 does not require coexistence. The document proposes an evolution scenario where NG-PON1 acts as a mid-term upgrade and NG-PON2 as a long-term solution. It calls for contributions to further clarify requirements for both NG-PON1 and NG-PON2.
Suppression of Chirp Interferers in GPS Using the Fractional Fourier TransformCSCJournals
In this paper we apply the Fractional Fourier Transform (FrFT) to remove chirp interferers that corrupt Global Positioning System (GPS) signals. The concept is based on the fact that in the time-frequency plane, known as the Wigner Distribution (WD), chirps are represented as lines. Using an FrFT with some rotational parameter ‘a’, we rotate to a new time axis ta that transforms the chirp to a tone, in which the energy of the tone is contained in usually just one or two samples. The best `a', and the correct time sample along the ta axis, may be found without a priori knowledge by searching for the peak in the FrFT, since compression to one or two time samples results in an energy spike. Once the peak is found, we zero out the tone, and hence the underlying chirp. Rotation back to the original time domain via an inverse FrFT produces an improved GPS signal. This method can apply to multiple chirp interferers, and we describe how to easily determine the number of interferers, K, by finding peaks in the FrFT space over the parameter `a'. We also describe how to easily notch the interferers once converted to tones by computing a threshold based on the power of the coarse acquisition (C/A) code and noise. We show that for signal-to-noise ratios (SNRs) greater than at least 10 dB, interferers can be notched regardless of the ratio of the C/A code power to the combined interferer power, denoted as carrier-to-interference ratio (CIR).
The document discusses several speech compression techniques:
1) Uncompressed audio rates are 64kbps for voice and 1.5Mbps for CD audio.
2) ADPCM reduces the data rate to 32kbps by transmitting differences between predicted and actual sample values.
3) SB-ADPCM splits audio into lower and upper sub-bands, compressing each at different rates (48kbps and 16kbps respectively) for total of 64kbps.
4) LPC represents speech as a combination of previous samples and residual error, transmitting just coefficients, enabling lower rates like those in GSM and other standards.
This document summarizes research on reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. It discusses using a companding technique with Gaussian distribution to compress the signal before transmission and decompress it upon reception. The key aspects covered are: applying a compander and decompander with Gaussian distribution parameters at the transmitter and receiver; how the central limit theorem allows the sum of subcarriers to approximate a Gaussian distribution for large numbers; and how this technique reduces PAPR by increasing average power while keeping peak power the same. Performance is analyzed by simulating PAPR and bit error rate with and without companding under different parameters.
The document describes a thesis submitted by Hsu Kuan Chun Issac to the Hong Kong University of Science and Technology for a Master of Philosophy degree in Electrical and Electronic Engineering. The thesis proposes designing a 70 MHz CMOS band-pass sigma-delta analog-to-digital converter for wireless receivers. It describes implementing a second-order continuous-time band-pass sigma-delta modulator using transconductor-capacitor integrators for the loop filter. The design includes a latched comparator and TSPC D flip-flop as the quantizer. The performance of prototypes fabricated in 0.8um and 0.5um CMOS processes are evaluated.
INITIAL OBSERVATION RESULTS FOR PRECIPITATION ON THE KU-BAND BROADBAND RADAR ...grssieee
This document describes initial observation results from Japan's Ku-band Broadband Radar (Ku-BBR) Network. The Ku-BBR uses high-resolution pulse compression and wide bandwidth to achieve range resolution of a few meters. A network of these radars in the Osaka area allows for precipitation attenuation correction and high-resolution gridded data. Initial tests show the Ku-BBR provides accurate measurements of rainfall when compared to ground disdrometer measurements.
Localization of Objects Using Cross-Correlation of Shadow Fading Noise and Co...Rana Basheer
When a radio transmitter is mobile, obstacles in the
radio path can cause temporal variation in Received Signal Strength Indicator (RSSI) measured by receivers due to multipath and shadow fading. While fading, in general, is detrimental to accurately localizing a target, fading correlation between adjacent receivers may be exploited to improve localization accuracy. However, multipath fading correlation is a short range phenomenon that rapidly falls to zero within a wavelength whereas,
shadow fading correlation is independent of signal wavelength and has longer range thereby making it suitable for localization with wireless transceivers that operate at shorter wavelength. Therefore,
this paper presents a novel wireless localization scheme that employs a combination of cross-correlation between shadow fading noise and copula technique to recursively estimate the location of a transmitter. A stochastic filter that models multipath fading as an Ornstein-Uhlenbeck process followed by a Generalized Auto Regressive Conditional Heteroskedasticity (GARCH) filtering is
proposed to extract shadow fading residuals from measured RSSI values. Subsequently, Student-T Copula function is used to create the log likelihood function, which acts as the cost function for localization, by combining spatial shadow fading correlation arising among adjacent receivers due to pedestrian traffic in the area. Maximum Likelihood Estimate (MLE) is used for position estimation as it inherits the statistical consistency and asymptotic
normality. The performance of our proposed localization method is validated over simulations and hardware experiments.
The document discusses performing a discrete wavelet transform (DWT) on a 1D signal using MATLAB. It loads a test signal, performs a 5-level DWT decomposition using the coif3 wavelet, then reconstructs the approximation and detail signals at each level. Plots of the original, approximation, and detail signals are generated.
Using contactless probing techniques, this feature allows you to perform calibrated in-circuit voltage and current time-domain measurements under large-signal conditions, on printed-circuit boards (PCB) or on wafer, at locations which are normally unreachable using standard VNA techniques.
This paper presents 2D and 3D modeling of a hysteresis motor using a high temperature superconducting material, YBCO, in the rotor. Both modeling approaches are simulated using COMSOL Multiphysics finite element software. The 3D modeling provides a more precise analysis of motor performance compared to the 2D modeling by accounting for the 3D magnetic properties of the rotating magnetic domains in the rotor. Simulation results of the magnetic flux distribution, torque, and AC losses calculated from the 3D model show good agreement with experimental data.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document describes the design and development of an assembly fixture for mounting a circlip to the piston pin hole of an engine piston. Several concepts for the fixture were generated and evaluated using a concept scoring matrix. Concept 4, which uses a profile locator to position the piston and a push rod actuated by a lever to insert the circlip, was selected as the best concept. The detailed design of the selected fixture concept is described, including its components like the base plate, piston rest, riser block, push rod assembly and guide blocks. An estimated cost of $337 for manufacturing the fixture is also provided. The implemented fixture is able to assemble 2,160 pistons per day with a cycle time of 33 seconds per piston.
This document summarizes the F5 steganography algorithm and the JHRF steganalysis algorithm. F5 embeds messages into JPEG images by decreasing quantized DCT coefficients. It uses techniques like permutative straddling and matrix encoding to distribute changes regularly. JHRF is designed to detect messages hidden with F5. It analyzes DCT coefficients in the frequency domain, looking for patterns that indicate embedding with normal or reverse rules around a demarcation point. The goal of JHRF is to effectively detect hidden data and obtain accurate extraction results.
This document analyzes water quality parameters of Chandlodia Lake in Ahmedabad, Gujarat over a one year period to assess pollution levels. Water samples were collected monthly from 5 points around the lake and were analyzed for various physical, chemical and biological parameters including temperature, pH, dissolved oxygen, biochemical oxygen demand, turbidity, conductivity, nutrients and more. The results found that most parameters exceeded acceptable limits, with the highest pollution occurring during the monsoon season when waste and runoff entered the lake. Therefore, the study concluded that Chandlodia Lake shows very high levels of pollution.
This document describes a fully programmable frequency divider and dual-modulus prescaler for high-speed frequency operation between 1.8 GHz and 2.4 GHz in a phase locked loop (PLL) system using 250nm CMOS technology. It presents the architecture of a programmable frequency divider consisting of a dual-modulus prescaler, programmable counter, and swallow counter. A high-speed dynamic D flip-flop is used to reduce power consumption. The paper also describes the operation of a divide-by-2 frequency divider circuit using a true single-phase clock logic topology and explains how this can be extended to a divide-by-2/3 prescaler. The maximum operating frequency is 2.
The document discusses preprocessing techniques for historical Sanskrit text documents before optical character recognition (OCR). It describes the basic steps of preprocessing which include scanning, noise removal through filtering techniques like mean, median and Wiener filters, and binarization. Newer techniques discussed are non-local means and total variation methods for noise removal, which help preserve details and edges while removing noise. The document evaluates the effect of different preprocessing filters and binarization on sample text images.
This document presents a robust speech enhancement method using an adaptive Kalman filtering algorithm. It aims to overcome drawbacks of conventional Kalman filtering for speech enhancement. The proposed algorithm only constantly updates the first value of the state vector, eliminating matrix operations and reducing computational complexity. It also includes a forgetting factor to automatically adjust the estimation of environmental noise based on observation data, allowing the algorithm to better estimate real noise. Experimental results show the proposed robust algorithm is more effective for speech enhancement than the conventional Kalman filtering approach.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document summarizes a paper that describes the simulation and control of a doubly fed induction generator (DFIG) using artificial neural networks. The DFIG is a type of induction generator that is widely used in wind power generation because it allows variable speed operation while only requiring a power converter rated at 25-30% of the generator rating. The paper presents the mathematical model of the DFIG in the d-q reference frame and describes how to control the rotor voltages using PI and ANN controllers to maintain a constant terminal voltage. Simulation results verify that the model meets the requirements of a variable speed constant frequency wind energy conversion system.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document describes a study investigating the performance of triangular microstrip patch antennas on six different dielectric substrates for X-band applications. The six substrates analyzed are Bakelite, FR4 glass epoxy, RO4003, Taconic TLC, RT Duroid, and polyester. For each substrate, the side length of the triangular patch is calculated based on the dielectric constant to achieve a resonant frequency of 10GHz. The triangular patch antennas are simulated using IE3D software to analyze parameters such as return loss, bandwidth, directivity and gain. The results show that the polyester substrate provides the most optimum performance with high directivity, gain, bandwidth and efficiency compared to the other substrates.
1. The document discusses teaching electricity concepts to primary school students and identifies challenges.
2. It analyzes surveys of 170 primary students and their teachers to assess knowledge of electricity, issues with textbooks, and additional support needed.
3. The surveys found average electricity knowledge of 48% from textbooks alone, indicating a need for supplemental teaching materials and techniques to make the topics more interesting and effective to teach.
This document discusses the design and simulation of low noise amplifier (LNA) circuits with different matching circuit combinations at the input and output sides. It compares the performance of LNA circuits using 'T' and 'L' type matching networks. The circuits are simulated using Advanced Design System (ADS) software. Simulation results show that the T-L matching configuration provides better gain and noise figure than L-L, L-T, and T-T matching under stability conditions. Specifically, the T-L matching achieved a forward gain of 14.14 dB and noise figure of 1.81 dB, outperforming the other matching configurations. Stabilization circuits are also applied and analyzed.
GNU Radio based Real Time Data Transmission and ReceptionIRJET Journal
This document describes a study on real-time data transmission and reception using digital modulation techniques in GNU Radio. The researchers implemented Gaussian Minimum Shift Keying (GMSK), Gaussian Frequency Shift Keying (GFSK), and Differential Phase Shift Keying (DPSK) using GNU Waveguru and GNU Octave tools. GNU Radio was used as a software-defined radio framework to generate and analyze baseband signals and implement the digital modulations. GNU Octave accepted real-time text input from the user and saved it to a file. The modulation techniques were then used to transmit the text data over a wireless medium.
Optimization of Cmos 0.18 µM Low Noise Amplifier Using Nsga-Ii for UWB Applic...VLSICS Design
A design and optimization of 3-5 GHz single ended Radio Frequency (RF) Low Noise Amplifier (LNA) for
ultra-wide-band (UWB) applications using standard UMC 0.18 μm CMOS technology is reported.
Designing of RF circuit components is a challenging job, since even after performing lengthy calculations
and finding parameter values it is less guarantee that the design performs as expected. In view of this the
optimization tool; Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II); has been employed to get
the optimized starting values of components in the proposed LNA design. The obtained NSGA-II
parameters were simulated using Cadence Spectre- RF simulator. The designed Low Noise Amplifier
achieves a power gain of 22 dB and a minimum Noise Figure of 3 dB is achieved. It dissipates 12.5 mW of
power out of 1.8 V supply.
This document describes the design and analysis of a single-ended inductively degenerated interstage matched common-source cascode CMOS low noise amplifier (LNA). The LNA is implemented using a 90nm CMOS process. It employs a cascode topology with single-ended source degeneration using an inductor to achieve high gain. An interstage inductor between the common source and common gate stages is used to further increase the overall gain. Simulation results show the LNA has a noise figure of 1.986dB at 2.4GHz, a voltage gain of 19.1dB, and operates with low noise and high gain as required for applications such as wireless communications.
Raman Pumping as an Energy Efficient Solution for NyWDM Flexible-grid Elastic ...IJECEIAES
This paper investigates transparent wavelength routed optical networks using three dif- ferent fiber types NZDSF, SMF and PSCF - and validates the effectiveness of Hybrid Raman/EDFA Fiber Amplification (HFA) with different pumping levels, up to the moderate 60% pumping regime. Nodes operate on the basis of flexible-grid elastic NyWDM transponders able to adapt the modulation format to the quality-of-transmission of the available lightpath, exploiting up to five 12.5 GHz spectral slots. Results consider a 37node Pan-European network for variable Raman pumping level, span length and average traffic per node. We show that HFA in moderate pumping regime reduces the power consumption and enhances spectral efficiency for all three fiber types with particular evidence in NZDSF. In essence to that, introduction of HFA is also beneficial to avoid blocking for higher traffic loads.
1) The document presents channel estimation methods for MIMO-OFDM systems using QPSK modulation.
2) It compares the performance of least squares (LS), minimum mean square error (MMSE) and discrete Fourier transform (DFT) based channel estimation techniques.
3) The analysis finds that applying DFT to the estimated channel power improves the performance of the channel estimators.
Optical Spatial Modulation with Transmitter-Receiver AlignmentsMarwan Hammouda
This paper proposes an optical spatial modulation (OSM) technique to enhance the data rate of indoor optical wireless communication systems. OSM works by activating only one out of multiple light emitting diodes at each time instant to transmit data. The paper shows that properly aligning the positions and orientations of the transmit and receive units can significantly improve the performance of OSM by decorrelating the optical MIMO channel. Through alignment, the paper achieves a 14 dB gain in signal-to-noise ratio required for a bit-error rate of 10^-3 compared to misaligned setups. The paper also compares the power and bandwidth efficiency of OSM to on-off keying, pulse position modulation, and pulse amplitude modulation.
FPGA Implementation of Large Area Efficient and Low Power Geortzel Algorithm ...IDES Editor
Spectrum analysis is very essential requirement in
instrumentation and communication signal interception
.Spectrum analysis is normally carried out by online or offline
FFT processing. But the FFT being highly mathematical
intensive, is not suitable for low area and low power
applications. Offline FFT processing can’t give the real time
spectrum estimation which is essential in communication
signal interception. Online FFT computation takes very high
resources, which makes the system costly and power hungry.
The Goertzel algorithm is a digital signal processing (DSP)
technique for identifying frequency components of a signal,
published by Dr. Gerald Goertzel in 1958. While the general
Fast Fourier transform (FFT) algorithm computes evenly
across the bandwidth of the incoming signal, the Goertzel
algorithm looks at specific, predetermined frequency. However
the implementation of Goertzel algorithm for spectrum
computation is not explored for FPGA implementation. The
FPGA being capable of offering high frequency data paths in
them become suitable for realizing high speed spectrum
analysis algorithms.
This document presents the design of a 4th order continuous-time bandpass sigma-delta modulator operating at 280 MHz for digitizing narrowband signals at 70 MHz. A novel transconductance amplifier was developed with high linearity at high frequencies. Simulation results show the modulator achieves a signal-to-noise ratio of 55 dB over a 5 MHz bandwidth while consuming 25 mW of power. The modulator uses a Gm-C loop filter and was implemented in a 0.18 μm CMOS process.
This document discusses a proposed architecture for a higher Nyquist-range digital-to-analog converter (DAC) that employs sinusoidal interpolation.
[1] Conventional DACs operate within the Nyquist range, but the proposed architecture aims to utilize higher Nyquist ranges by approximating an oscillating signal from an RF DAC concept using sinusoidal interpolation in the time domain.
[2] The proposed architecture quantizes both the input signal and pulse amplitude modulation waveform and combines them digitally, replacing analog oscillatory circuits with a digital data stream. This reduces analog complexity compared to existing techniques.
[3] Simulation results and theoretical analysis are presented to support that the proposed architecture can provide similar performance
This document provides an overview of synthetic aperture radar (SAR) and pulse compression techniques. It discusses how pulse compression allows radar systems to achieve fine range resolution while transmitting long duration, lower power pulses. This compromises between range resolution, signal strength, and transmitter power requirements. Pulse compression techniques like chirp modulation and stretch processing are described. The document also covers topics like range and azimuth resolution, geometric distortions, and signal processing methods used in SAR systems.
First order sigma delta modulator with low-power consumption implemented in a...eSAT Journals
Abstract
This paper presents a design of a switched-capacitor discrete time 1st order Delta-Sigma modulator used for a resolution of 8 bits
Sigma-Delta analog to digital converter. For lower power consumption, the use of operational transconductance amplifier is
necessary in order to provide wide output voltage swing and moderate DC gain. Simulation results showed that with 0.35um CMOS
technology, 80 KHz signal bandwidth and oversampling rate of 64, the modulator achieved 49.25 dB Signal to Noise Ratio (SNR) and
the power consumption was 5.5 mW under ±1.5V supply voltage .
Index terms: Analog-to-Digital conversion, Delta-Sigma modulation, CMOS technology, Transconductance operational
amplifier.
OPTIMIZATION OF CMOS 0.18 M LOW NOISE AMPLIFIER USING NSGA-II FOR UWBVLSICS Design
A design and optimization of 3-5 GHz single ended Radio Frequency (RF) Low Noise Amplifier (LNA) for ultra-wide-band (UWB) applications using standard UMC 0.18 µm CMOS technology is reported. Designing of RF circuit components is a challenging job, since even after performing lengthy calculations and finding parameter values it is less guarantee that the design performs as expected. In view of this the optimization tool; Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II); has been employed to get the optimized starting values of components in the proposed LNA design. The obtained NSGA-II parameters were simulated using Cadence Spectre- RF simulator. The designed Low Noise Amplifier achieves a power gain of 22 dB and a minimum Noise Figure of 3 dB is achieved. It dissipates 12.5 mW of power out of 1.8 V supply
Mimo radar detection in compound gaussian clutter using orthogonal discrete f...ijma
This paper proposes orthogonal Discrete Frequency Coding Space Time Waveforms (DFCSTW) for
Multiple Input and Multiple Output (MIMO) radar detection in compound Gaussian clutter. The proposed
orthogonal waveforms are designed considering the position and angle of the transmitting antenna when
viewed from origin. These orthogonally optimized show good resolution in spikier clutter with Generalized
Likelihood Ratio Test (GLRT) detector. The simulation results show that this waveform provides better
detection performance in spikier Clutter.
A Compact Reconfigurable Dual Band-notched Ultra-wideband Antenna using Varac...TELKOMNIKA JOURNAL
In this paper, a reconfigurable dual band-notched ultra-wideband (UWB) antenna is presented.
The antenna design consists of a circular shape with two pairs of the L-resonator. To realize the notch
characteristics in WLAN at 5.2 GHz and 5.8 GHz bands, the half wavelength of the L-resonator is
introduced in the design. The T-shaped notch is etched in the ground to enhance the bandwidth which
covers the UWB operating frequency range from 3.219–10.863 GHz. The proposed reconfigurable dual
band-notched UWB antenna shows good impedance matching for the simulated in the physical layout.
Furthermore, the proposed antenna has a compact size of 37.6x28 mm2. This proposed reconfigurable
design can provide an alternative solution for the wireless system in the designing of a band-notched
antenna with a good tuning capability.
Design and fabrication of A Ku-band low noise amplifier using FR-4 substrateTELKOMNIKA JOURNAL
The low noise amplifier (LNA) plays an important role in many communication systems, especially at the receiver’s front-ends. In modern RF designs, The LNA is usually fabricated on a microstrip printed circuit board (PCB) due to its simplicity and ability of integrating flexibly with other components in a receiving circuitry unit. At frequencies lower than 6 GHz, the most prevalent substrate material for a microstrip LNA is FR-4 while at higher frequencies of over 10 GHz, it is challenging to design the LNA using this material without causing considerable losses to the RF signal. There are many works related to design microstrip LNA at high frequencies, however, the dielectric substrates used in most of them were high-cost materials for low dielectric loss. This paper introduces an LNA topology using the common, low-cost FR-4 substrate which can be operated in Ku-band for applications such as small satellites’ receivers, with the expected noise figure of lower than 1 dB, gain of around 10 dB and the return loss of around -10 dB. The stepped impedance matching technique has been used for transmission line optimization. The simulated and measured results are presented.
Noise modeling of SiGe HBT based on the characterization of extracted y and ...Pradeep Kumar
The document summarizes a study on modeling the noise characteristics of a 0.1 μm silicon-germanium (SiGe) heterojunction bipolar transistor (HBT). It first discusses various noise sources in SiGe HBTs such as thermal noise, shot noise, and generation-recombination noise. It then presents a noise model and analytical equations to extract noise parameters including noise resistance (Rn), optimum source admittance (GSopt, BSopt), and minimum noise figure (NFmin) in terms of device parameters. Simulation results validating the noise modeling approach are also presented. The accurate noise modeling of SiGe HBTs is important for low noise circuit design in high frequency applications.
Pres Simple and Practical Algorithm sft.pptxDonyMa
1. The Sparse Fourier Transform (SFT) algorithm takes advantage of the sparsity of signals to efficiently compute their frequency spectra. It does this by mapping frequency points into "bins" and only calculating the non-zero frequency components, reducing computational load.
2. The core ideas of SFT are permuting the signal spectrum, filtering it using a flat-top window function, and taking a subsampled fast Fourier transform (FFT). This converts the signal into a shorter sequence for FFT while maintaining spectral accuracy.
3. By adding up frequency points in each "bin" and ignoring empty bins, SFT reconstructs the original spectrum using far fewer computations than a standard discrete Fourier transform, allowing it to handle
DONY Simple and Practical Algorithm sft.pptxDonyMa
The Sparse Fourier Transform (SFT) algorithm provides an efficient method to compute the frequency spectrum of sparse signals. It takes advantage of signal sparsity by only calculating non-zero frequency components, greatly reducing computational load compared to the Discrete Fourier Transform (DFT). The SFT works by permuting the signal spectrum, filtering it using window functions, taking a subsampled FFT to locate non-zero frequencies, and then estimating their amplitudes. This allows it to handle much larger signals faster than the DFT, with applications in areas like signal processing, image compression, and machine learning.
1. N.M.Sai Krishna Kumar, K.Steven / International Journal of Engineering Research and
Applications (IJERA) ISSN: 2248-9622 www.ijera.com
Vol. 2, Issue4, July-August 2012, pp.1566-1571
Performance Analysis Of Bluetooth System Using Optimized
Differential GFSK Demodulator
N.M.SAI KRISHNA KUMAR K.STEVEN
M.Tech Student Scholar, DECS, M.Tech Asst Professor
Dept of Electronics and Communication Dept of Electronics and Communication
Engineering, Engineering,
Nalanda Institute of Engineering and technology, Nalanda Institute of Engineering and technology,
Sattenapalli (M); Guntur (Dt); A.P, India. Sattenapalli (M); Guntur (Dt); A.P, India
Abstract
In this project, a simple demodulator for development of the specification, manages the
GFSK receivers is developed, which averages the qualification program, and protects the trademarks.
phase based on the signal-to-noise ratio (SNR) To be marketed as a Bluetooth device, it must be
maximizing criterion, and does not require qualified to standards defined by the SIG. A network
knowledge of the exact modulation index. of patents is required to implement the technology
Compared to demodulators with similar and are licensed only for those qualifying devices;
complexity, such as the LDI, the presented thus the protocol, whilst open, may be regarded as
receiver can achieve superior performance. In proprietary. GFSK is an important digital modulation
digital modulation, Gaussian frequency shift scheme. It is widely used in low cost and low power
keying(GFSK) is one of the shifting technique. we consumption systems such as Bluetooth in the
are facing a challenging task in simple and high unlicensed 2.4 GHz industrial, scientific and medical
performance receivers for GFSK. In our project (ISM) band due to its spectral efficiency, constant
we develop an optimized differential GFSK signal envelope property and the possibility for low
demodulator and investigate the phase wrapping complexity receivers. The optimum GFSK receiver
issue in its implementation. The Experimental consists of a correlator followed by a maximum-
results shows performance of bit error rate likelihood sequence detector that searches for the
improvement in with conventional differential minimum Euclidean distance path through the state
demodulators in both AWGN and flat fading trellis based on Viterbi algorithm.
channels. We also compare the simulation results
with other exiting techniques like fading channels . However, due to the complexity of the
matched filter bank and carrier synchronization, such
Keywords Gaussian frequency shift keying a receiver has very limited applications. In addition,
(GFSK), differential demodulation, phase these designs always assume a certain nominal value
wrapping. for the modulation index ℎ . However, the modulation
index may vary in a relatively wide range (for
I. INTRODUCTION Bluetooth, the modulation index is allowed to vary
Gaussian Frequency-Shift Keying (GFSK) is between 0.28 and 0.35), leading to a varying trellis
a type of Frequency Shift Keying modulation that structure for sequence detection with possibly
uses a Gaussian filter to smooth positive/negative tremendous number of states. All these render this
frequency deviations, which represent a binary 1 or 0. optimum receiver impractical.
It is used by DECT, Bluetooth. Bluetooth is a
proprietary open wireless technology standard for Hence non-coherent suboptimal receivers
exchanging data over short distances (using short- are typically preferred, especially in systems where it
wavelength radio transmissions in the ISM band from is desirable to have a simpler receiver structure. The
2400–2480 MHz) from fixed and mobile devices, technique phase wrapping shown is successful
creating personal area networks (PANs) with high provided that the true gradient is bounded to < π. It is
levels of security. Created by telecoms vendor unlikely so when both the sampled topography is
Ericsson in 1994, it was originally conceived as a rough and elevations are > Δ Hamb. Slow varying
wireless alternative to RS-232 data cables. It can topographies are not a problem even if elevations are
connect several devices, overcoming problems of large. Rough topographies are not a problem if
synchronization. elevations are contained. We adopt a high-
Bluetooth is managed by the Bluetooth performance GFSK receiver that achieves near
Special Interest Group, which has more than 16,000 optimum performance in AWGN [1] but uses a
member companies in the areas of prohibitively complex bank of filters to match a large
telecommunication, computing, networking, and set of legitimate waveforms over several bit intervals.
consumer electronics. The SIG oversees the However, we reduce the computational cost by
1566 | P a g e
2. N.M.Sai Krishna Kumar, K.Steven / International Journal of Engineering Research and
Applications (IJERA) ISSN: 2248-9622 www.ijera.com
Vol. 2, Issue4, July-August 2012, pp.1566-1571
performing filtering over a single bit interval, and ℎ0~𝒞𝒩(0, 1), 𝑛(𝑡) is zero mean white Gaussian noise
propagating the results over successive bit periods, with single-sided spectral density 𝑁0, and 𝑠𝑙(𝑡) is the
thereby eliminating redundancy in providing the complex envelope of the GFSK transmitted signal
matched filter outputs. We also propose a blind 𝜃(𝑡) is the time-varying channel phase, ℎ( 𝑡) is the
algorithm for carrier frequency correction. It is based channel impulse response.
on the observation of the phase gain in the transmit
sl (t ) exp j t , 0 (5
signal over a finite time-interval. Our derivation
concurs with work by other researchers [7].
II. GFSK SIGNAL MODEL )
A pass-band transmitted GFSK signal can be We assume that the receiver filter has
represented as sufficient band width such that it will introduce
negligible distortion on the signal while band limiting
the noise. Thus the output of the receiver filter is
2 Eb h(t ) * sl (t ) (t )
j ( t )
s(t, ) cos 2 f 0 t t, 0 r (t ) e
T (6)
Where (𝑡) = (𝑡) + 𝑗𝜂𝑖(𝑡)is band limited zero mean
(1) Gaussian noise with autocorrelation
2
Where 𝐸 𝑏is the energy per bit, 𝑇is the
R (T ) N 0 Hr ( f )
exp( j 2f T )df ,
symbol period, 𝑓0 is the carrier frequency, 0 is an
arbitrary constant phase shift. The output phase (7)
deviation (𝑡,) is determined by the input data And average power
sequence 𝜶= ..., 𝛼−2, 𝛼−1, 𝛼0, 𝛼1, 𝛼2, with 𝛼 𝑖∈+/- 2
P R (0) N 0 Hr ( f ) df N 0 Bn
1.
n n L
t, 2h i qt iT h i
(8)
i n L 1 i (2) Where 𝐵𝑛 is the equivalent noise bandwidth
Where h is the modulation index of the receiver filter. We assume that (𝑡) does not
t
change over a symbol period. For the phase
q(t) g(T)dT .With differential demodulation, we take the difference of
- consecutive phase samples; the unknown phase is
t 1 t 1 thus canceled. In addition, 𝜂𝑟and 𝜂𝑖are independent
g (t ) Q .BT Q .BT ,
and each has a distribution of (0, 𝜍2), where the
T 2 T 2 (3) variance 𝜍2 is defined as 𝜍2 =(0) = 𝑁0𝐵𝑛. Hence the
joint distribution of 𝜂𝑟 and is
Being the frequency pulse with constant 𝛾= x2 y 2
2𝜋/√(In(2)) and 𝑄(x) is the Gaussian Q-function. 𝐵𝑇 1
fri ( x, y ) e 2 2
2 2
is the 3 dB bandwidth-time product. Generally
speaking, the smaller the 𝐵𝑇values, the more
significant the ISI introduced due to the increase of (9)
the effective frequency pulse duration. In the
Bluetooth standard, ℎ can vary between 0.28 and 0.35
III. OPTIMIZED GFSK DEMODULATOR
and 𝐵𝑇equals 0.5 with 𝑇= 10−6s, giving rise to a (𝑡) In this section, we first present the basic
with effective duration of 2T.
ideas of conventional phase differential
demodulation. To facilitate the design of our
A. Baseband Equivalent System Model: optimized differential demodulator, the phase noise
The channel model considered is Rayleigh distribution is then derived. Based on the phase noise
flat fading with additive white Gaussian noise distribution, we will then propose an optimized
(AWGN). The received signal is first passed through
differential demodulator and investigate the phase
a receiver filter with transfer function (𝑓), then the wrapping problem.
phase differential detection is performed on the
output signal of the filter. The input signal to the A. Differential GFSK Demodulation;
receiver filter is In this subsection, we consider the basic
r(t) e j t h(t ) * sl (t ) n(t ) ideas about differential demodulation in AWGN. For
Bluetooth standard, the effective frequency pulse
(4)
1567 | P a g e
3. N.M.Sai Krishna Kumar, K.Steven / International Journal of Engineering Research and
Applications (IJERA) ISSN: 2248-9622 www.ijera.com
Vol. 2, Issue4, July-August 2012, pp.1566-1571
duration is 2𝑇, giving rise to a piecewise monotonic
phase trellis within each symbol duration. The
direction of the monotonic change is determined by
the binary symbol value. Hence, a phase differential 2 2 sin 2 cos
demodulator can be employed. We first extract the 1 2 2 cos Q
e e 2 2
phase of the received signal.
2 2
t r (t ) (t ) (t )
(10) (14)
Where 𝜑 (𝑡)is determined by the transmitted For 𝜋/2 < (𝑡) <2𝜋, only the integral interval
phase and ( 𝑡)is a random variable due to the AWGN. in (10)is slightly different for each quadrant, and it
Essentially, the conventional differential demodulator can be readily shown that the final PDF results are the
involves sampling ( 𝑡) in (9) at symbol rate to obtain () same as (11) for all(𝑡)values. At high SNR (large 𝜌),
and then taking the difference of the neighboring we have exp (− 𝜌2 2𝜍2 ) ≈ 0and 𝑄(−𝜌coos𝜙𝜍) ≈ 1.
samples. As a result, the complicated noise distribution can be
(nT ) (nT ) (nT T ) (11
approximated as:
1 2
.
) 1 2 / 2
A decision can then be made based on the f ( ) .e
sign of Δ(𝑛𝑇).However, due to the randomness of the
phase noise, the decision based on a single phase
2 / (1
sample per symbol lacks sufficient reliability so that
5)
conventional differential demodulator suffers from
Which is simply the Gaussian distribution
degraded performance. Intuitively, one can average a
with zero mean and variance ( 𝜍/ 𝜌)2. Such a Gaussian
portion of every symbol long trellis segment instead
approximation of the phase noise distribution can be
of a single sample at each end before taking the
very useful if the approximation is accurate. This is
difference. This may provide some gain in the signal-
because our demodulator design is intended to
to-noise ratio (SNR). In the case of Gaussian noise,
optimize the ultimate BER performance of the
the gain in SNR leads to improvement in BER. To
system. In the case of Gaussian noise, minimizing
facilitate the design of an optimum differential
BER is equivalent to maximizing the SNR, leading to
demodulator, we will next study the distribution of
a readily-achievable SNR maximizing system
phase noise (𝑡). For the simplification of analysis, we
optimization criterion. This is generally not true for
will first consider the AWGN channel. The result can
non-Gaussian noise. In order to assess the accuracy of
then be easily extended to flat fading channels.
our approximation; we perform two sets of
simulations. In the first simulation, we compare the
B. Phase Noise Distribution:
true and approximate PDF curves at various SNR
For notational simplicity, let (𝑡) = 0in (9)
values. As below shown in Figure 1, we observe that
without loss of generality. It then follows that (𝑡) =
these curves are already very close at 𝜌2/ (2𝜍2) = 2
(𝑡). Denote the probability density function (PDF)
dB, and are nearly identical at 𝜌2/(2𝜍2) = 8 dB. We
and the cumulative density function (CDF) of the
also simulate and compare the BER performance of a
random variable (𝑡) as (𝜑) and (𝜑), respectively. We
simple binary system where the additive noise
first consider 0 ≤ (𝑡) ≤ 𝜋/2, on which.
follows either the true noise PDF or the Gaussian
F ( ) Pr (0 ) approximation. The result in Below Figure. 2 shows
x tan
that the BER performances of the two are very
similar. You may note that the BER gap at higher
fri ( x, y ) dydx. SNR seems to be larger than the gap at lower SNR.
0 However, since the scale is different in the BER axis,
the approximation is actually much better at higher
SNR, which confirms our previous analysis .So far,
(12)
we have verified that the noise in the extracted phase
Then by Leibnitz’s rule, the PDF is derived as
can be well approximated as Gaussian distributed.
f
d
F ( ) With all the knowledge above, we will develop our
d
optimized differential GFSK demodulator in the
( x) tan 2
2
x2
following subsection.
1
e 2 2 d
x tan dx
2 2
d
C. Optimized Differential GFSK Demodulator:
Each symbol-long phase trellis segment can
take one of the four shapes depending on the specific
(13)
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Vol. 2, Issue4, July-August 2012, pp.1566-1571
2
symbol sequence. For example, for an input data T t T0
t
sequence of (1,−1, 1,−1, 1, 1, 1, 1), dt dt
T T T 0 T
SNR A T0 0
2T0 2
(16)
As we have shown in the preceding
subsection, the phase noise can be well approximated
as Gaussian distributed even at fairly low SNR.
Hence, the SNR-maximizing 𝑇𝑜is essentially also
BER-minimizing. Maximizing SNR 𝐴for a given
symbol duration 𝑇and 𝐴2/𝜍2, we obtain
T0 (T T0 )
2
max SNRA (T0 ) max ,
0T0 T 2 0T0 T 2 2T 2 2
(17)
Figure 1: PDF curves for 𝜌/( 𝜍) = 0.2828 and 𝜌/( 𝜍) Which results in 𝑇𝑜= 𝑇/3. This indicates that
=0.6083 one should average the first and last 33% of each
phase trellis during [0, 𝑇) is linear in the first symbol-long phase segment and then take their
half and nonlinear in the second half (which we term difference on which a decision can be made. Next we
as type 𝐷); the phase trellis during [𝑇, 2𝑇) is consider the type-C phase segment during [𝑇, 2). The
nonlinear throughout the entire duration (which we exact function for this segment does not have a closed
term as type 𝐶); the phase trellis during [4𝑇, 5𝑇) is form (containing the integral of Gaussian Q function).
nonlinear in the first half and How ever we notice that each half of the segment
curves in the shape of parabola approximately. Hence
we use two second-order polynomials to fit each half;
that is 𝑥1(𝑡) = −0.9202(𝑡/𝑇)2 − 0.1797(𝑡/𝑇) + 0.8158,
𝑡∈[0, 0.5𝑇), and 𝑥2(𝑡) = 0.9202(𝑡/𝑇)2 − 1.9911(𝑡/𝑇)+
1.273, 𝑡∈[0.5𝑇,𝑇).Accordingly, the resultant SNR
after averaging and difference taking is:
2
T T0
x2 (t )dt x1(t )dt
T T
SNRC (T0 )
0 0
2T0 2
(18)
As a result, the optimal portion should be
chosen as 𝑇𝑜=0.3675.Similar results can be obtained
for type-B and type-D phase segments. Due to the
space limit, these are omitted here. Since the four
Figure 2: BER performance for the exact phase noise different shapes occur with equal probability, one can
and the approximated Gaussian phase noise also find the overall optimum𝑇 𝑜by solving
linear in the second half (which we term as
type 𝐵); and the phase trellis during [5𝑇, 6𝑇) is linear max SNR A T0 SNRB (T0 ) SNRC T0 SNRD (T0 ),
0T0 T 2
throughout (which we term as type 𝐴). Without loss
of generality, we will start from the linear phase (19)
segment and then generalize to the nonlinear and which results in 𝑇𝑜= 0.35𝑇.The continuous-
partly nonlinear ones. A linear phase curve segment time analysis can be readily extended to the discrete-
has a function (𝑡) = 𝐴⋅𝑡/𝑇, 𝑡∈[0, ). Note that the time sampled phase segments. Let 2 𝐾 denote the
scalar 𝐴is proportional to the modulation index ℎ. number of samples per symbol. The problem now is
However, since its value does not affect the to determine the optimum 𝑀, which is the number of
optimization result, we will normalize it to 1 for samples to be averaged at each end of the 2𝐾samples
notational simplicity (the same for the nonlinear per symbol. Denote the second group of 𝑀samples as
phase curve cases). Let𝑇𝑜be the portion at each end 𝑆1, ....,𝑆𝑀,
of this segment over which we average before taking
the difference, as illustrated in Then the resultant
SNR is:
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5. N.M.Sai Krishna Kumar, K.Steven / International Journal of Engineering Research and
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Vol. 2, Issue4, July-August 2012, pp.1566-1571
results can be readily extended to the flat fading
channels since each realization of the channel fading
coefficient is essentially an AWGN case. All these
results will be verified by simulations.
D. Phase Wrapping Problem:
When realizing these phase differential
demodulation algorithms, however, there is an
implementation problem. Recall that our differential
operations are performed on the phase function (𝑡)in
(9). Unlike the original phase trellis (𝑡,) in (2), (𝑡)is
not only noisy, but also suffers from the phase
wrapping problem since it assumes a finite range of
2𝜋.To solve this problem, conventional differential
demodulator in takes the following structure: the
Figure 3:Cumulative Distribution Function received signal (𝑡)is multiplied by a 𝑇-delayed and
and the first group of 𝑀samples as 𝑆′1, ...., 𝑆′𝑀. It 𝜋/2phase-shifted version of itself and then sampled at
then follows that 𝑆𝑖= (𝐾− 1 + 𝑖)/ (2𝐾− 1) + 𝜂𝑖and 𝑆′ the symbol rate to give the decision statistic. These
𝑖= (𝑖− 1)/(2𝐾− 1) + 𝜂′ 𝑖, 𝑖= 1, . . .,𝑀. Consider again operations will essentially give sin[Δ(𝑛𝑇)]without
the type-A linear phase segment. With the Gaussian explicitly extracting 𝜙(𝑡), thus avoiding the phase
approximation of the phase noise, the difference wrapping problem. Since the decision only relies on
between the two averages is Σ𝑀 𝑖=1(𝑆𝑖− 𝑆′𝑖)/𝑀, the sign of Δ(𝑛𝑇), the above operations leading to
leading to an SNR of sin[Δ𝜙(𝑛𝑇)]generally preserves this sign information.
However, for large modulation index ℎ≥ 1, the phase
M (2K M )
2
change Δ(𝑛𝑇)over one symbol duration may exceed𝜋.
SNRAd )
(
M , In this case, the sin operator cannot preserve the sign
2(2K 1)
2
2
of Δ(𝑛𝑇)any more. Hence, in both the conventional
( and optimized differential demodulators, we directly
deal with the phase extracted from the received
20) signal. Specifically, the phase is unwrapped by
simply adding 2𝜋 when the absolute change between
Where superscript ( 𝑑) indicates discrete- the Consecutive phase samples is greater than the
time. Clearly, SNR( 𝑑 𝐴( 𝑀)bears a form very similar jump tolerance𝜋. Both methods are tested and
to SNR( 𝑇𝑜) in (13).Not surprisingly, maximizing compared by simulations.
SNR (𝑑) 𝐴(𝑀)results in 𝑀=2 𝐾/3, which agrees
perfectly with the continuous-time result. Using the IV. PERFORMANCE EVALUATION OF
same methodology, we can obtain the optimum 𝑀for PROPOSED CONCEPT AND AND DISCUSSION
the general case as 𝑀= 0.7𝐾. Thus, by choosing the
optimal 𝑀, the SNR is maximized and the error
probability minimized. The block diagram of our
optimized differential demodulator is shown in Fig. 4.
We can see that the only difference between this new
demodulator and the conventional differential one is
the averaging part. To evaluate the performance gain
by using the optimized differential demodulator, we
notice that the conventional differential demodulator
can be considered as a special case with 𝑀= 1 for any
𝐾values. Considering again the type-A phase
segment, and evaluating(17) at 𝑀= 2𝐾/3 and 𝑀=
1and taking the relative ratio, we obtain the SNR gain
over conventional differential demodulator as:
SNR Ad ) 2 K
(
3 32 K3
.
27 272 K 12
Figure 4 BER Performance in AWGN Channel
SNR Ad )
(
(21) We will evaluate the performance of our
proposed demodulator by simulations in terms of
This gain is a function of because the optimum BER versus 𝐸𝑏/𝑁0, where 𝐸𝑏is the signal energy per
number of averaged samples 𝑀is dependent on the information bit and 𝑁0 is the power spectral density
total number of available samples 2𝐾. The above of the additive noise. In all simulations, we set 𝐵𝑇=
1570 | P a g e
6. N.M.Sai Krishna Kumar, K.Steven / International Journal of Engineering Research and
Applications (IJERA) ISSN: 2248-9622 www.ijera.com
Vol. 2, Issue4, July-August 2012, pp.1566-1571
0.5, 𝐵𝑛𝑇= 1 and take 8 samples per symbol. Show Simulation results coincides with the concept of
the BER performance of our optimized differential GFSk distribution (PDF) employed in Bluetooth
demodulator together with that of the conventional which is simply the gaussin distribution with zero
one and the LDI demodulator with different mean and variance (𝜍/𝜌)2. The simulation results of
modulation indices ℎ in AWGN and flat fading BER (Bit Error Rate) performance of a simply binary
channels, respectively. In particular, for the system using DPSK are compared where the additive
conventional differential demodulator, we simulated noise follows the true noise PDF as this basic
both the system in which avoids phase wrapping as demodulator designed is intended to optimize the
well as our direct unwrapping approach. We observe ultimate BER performance of the system.
that, the optimized demodulator shows about 1∼2 dB
improvement over the conventional differential References
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V. CONCLUSION
In this project the operation of GFSK
demodulator in Bluetooth radio signals is explained.
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