This document discusses the design considerations for analog circuits that process signals before they are digitized for further digital signal processing. It compares all-analog systems to hybrid analog-digital systems. Key factors for digitized systems are noise floor, quantization noise, jitter, resolution, dynamic range, and bandwidth. Real-world signals can have a wide range of amplitudes, from thermal noise up to nearby strong signals. Maximizing dynamic range is challenging and requires techniques like filtering, high-linearity components, and gain/attenuation control. Practical digital radio designs will continue to rely on downconversion and other established analog methods to meet performance needs until ADC technology improves.
Implementation of Wide Band Frequency Synthesizer Base on DFS (Digital Frequ...IJMER
Wide Band Frequency Synthesizer has become essential components in wireless communication
systems. They are used as frequency synthesizers with precise and convenient digital control in both traditional
electronics, such as televisions and AM/FM radios, and modern consumer products among which cellular
mobile phone is a striking example.
IC fabrication technology advances have made monolithic integration possible. More and more
electronic devices can be put on the same chip to reduce the number of external components and then the costs.
Therefore, on a single chip we can accomplish many functions for which we might need to make several chips
work together a few years ago. A monolithic wide-band PLL is of great interests to wireless communication
applications due to both its low cost and convenience to switch between different communication standards.
The focus of this work is to implement a wide-band Frequency Synthesizer using as few as possible building
blocks and also as simple as possible structure.
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
Implementation of Wide Band Frequency Synthesizer Base on DFS (Digital Frequ...IJMER
Wide Band Frequency Synthesizer has become essential components in wireless communication
systems. They are used as frequency synthesizers with precise and convenient digital control in both traditional
electronics, such as televisions and AM/FM radios, and modern consumer products among which cellular
mobile phone is a striking example.
IC fabrication technology advances have made monolithic integration possible. More and more
electronic devices can be put on the same chip to reduce the number of external components and then the costs.
Therefore, on a single chip we can accomplish many functions for which we might need to make several chips
work together a few years ago. A monolithic wide-band PLL is of great interests to wireless communication
applications due to both its low cost and convenience to switch between different communication standards.
The focus of this work is to implement a wide-band Frequency Synthesizer using as few as possible building
blocks and also as simple as possible structure.
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
Introduction to Software Defined Radio (SDR)Pamela O'Shea
For less than $20 anyone can listen to the airwaves! In this workshop, we will look at what is around us in the airwaves, including frequency scanning, pagers, airplanes, remote controls and more. Please see associated worksheet for the exercises.
Implementation of Algorithms For Multi-Channel Digital Monitoring ReceiverIOSR Journals
Abstract: Monitoring Receivers form an important constituent of the Electronic support. In Monitoring
Receiver we can monitor, demodulate or scan the multiple channels.
In this project, the Implementation of algorithm for multi channel digital monitoring receiver. The
implementation will carry out the channelization by the way of Digital down Converters (DDCs) and Digital
Base band Demodulation. The Intermediate Frequency (IF) at 10.7 MHz will be digitalized using Analog to
Digital Converter (ADC) with sampling frequency 52.5 MHz and further converted to Base band using DDCs.
Virtually all the digital receivers perform channel access using a DDC. The Base band data will be streamed to
the appropriate demodulators. Matlab Simulink will be used to simulate the logic modules before the
implementation. This system will be prototyped on an FPGA based COTS (Commercial-off-the-shelf)
development board. Xilinx System Generator will be used for the implementation of the algorithms.
Keywords: DDC, ADC, Digital Base band demodulation, IF, Monitoring Receiver.
Matlab Based Decimeter Design Analysis Wimax Appliacationiosrjce
A Digital down Converter (DDC), which is basically used to convert an intermediate frequency (IF)
signal to its baseband form, forms an integral part of wireless receivers. The major functional blocks of a DDC
constitute a mixer, Numerically Controlled Oscillator (NCO) and an FIR filter chain. In this paper, We can
comparison of two window and see the costs of all Window filters
SDR Training with HackRF - Tonex TrainingBryan Len
Length: 3 Days
SDR Training with HackRF, Advanced Software Defined Radio Training is a 3-day hands-on advanced SDR training course, Software-Defined Radio Development with GNU Radio utilizing HackRF One. The 3-day advanced SDR covers both hypothesis and application of SDR utilizing HackRF One.
.
SDR Training with HackRF. Advanced Software Defined Radio Training.
Participants will learn about:
Software Defined Radio and Digital Signal Processing
Theory and practice with hands-on SDR implementations using the Universal Software Radio Peripheral (USRP) SDR platforms
Necessary SDR signal processing building blocks, SDR application development using Python and C++ concepts required for GNU Radio development
How to apply HackRF and GNU Radio
How to use and apply GNU Radio Companion (GRC)
Security applications of SDR and RF Vulnerabilities
Course Agenda
Principles of Signal processing and applied RF
Overview of SDR
Overview of GNU Radio
Overview of GNU Radio software libraries
Overview of GNU Radio Companion (GRC)
Overview of Python and C++
Overview of Linux
Overview of Universal software radio peripherals
SDR and GNU Radio modules
Systems using HackRF One
Assessments of physical RF devices
How to Fingerprint on RF spectrum?
Hunting signals
Hardware Hacking 101
Reversing and Instrumentation (embedded RF systems)
IoT Hacking with SDR
Overview of Wi-Fi and Bluetooth
Open source SDR LTE software / FM Radio
Principles of Radar detector
Principles of Remote Controlled Cars
SDR Offensive Security
Request more information regarding SDR Training with HackRF. Visit tonex.com for course and workshop detail.
SDR Training with HackRF - Tonex Training
https://www.tonex.com/training-courses/sdr-training-with-hackrf-advanced-software-defined-radio-training/
This includes discussion of DSP applications such as two band digital crossover system,woofers, sqawkers, tweeters, interference cancellation in ECG, speech noise reduction, speech coding and compression, CD recording system
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
For effective implementation of Software Defined
Radio (SDR) in any RF application, a proper choice of data
converter is an essential requirement. This paper describes the
requirement of data converters in SDR, their key specificati
ons that impact the SDR performance and a comparison of
various data converters from leading vendors, which are
suitable in an SDR application.
HIGH SPEED CONTINUOUS-TIME BANDPASS Σ∆ ADC FOR MIXED SIGNAL VLSI CHIPSVLSICS Design
With the unremitting progress in VLSI technology, there is a commensurate increase in performance demand on analog to digital converter and are now being applied to wideband communication systems. sigma Delta (Σ∆) converter is a popular technique for obtaining high resolution with relatively small bandwidth. Σ∆ ADCs which trade sampling speed for resolution can benefit from the speed advantages of nm-CMOS technologies. This paper compares various Band pass sigma Delta ADC architectures, both
continuous-time and discrete-time, in respect of power consumption and SNDR. Design of 2nd order multibit continuous time band pass Σ∆ modulator is discussed with the methods to resolve DAC non-idealities.
Introduction to Software Defined Radio (SDR)Pamela O'Shea
For less than $20 anyone can listen to the airwaves! In this workshop, we will look at what is around us in the airwaves, including frequency scanning, pagers, airplanes, remote controls and more. Please see associated worksheet for the exercises.
Implementation of Algorithms For Multi-Channel Digital Monitoring ReceiverIOSR Journals
Abstract: Monitoring Receivers form an important constituent of the Electronic support. In Monitoring
Receiver we can monitor, demodulate or scan the multiple channels.
In this project, the Implementation of algorithm for multi channel digital monitoring receiver. The
implementation will carry out the channelization by the way of Digital down Converters (DDCs) and Digital
Base band Demodulation. The Intermediate Frequency (IF) at 10.7 MHz will be digitalized using Analog to
Digital Converter (ADC) with sampling frequency 52.5 MHz and further converted to Base band using DDCs.
Virtually all the digital receivers perform channel access using a DDC. The Base band data will be streamed to
the appropriate demodulators. Matlab Simulink will be used to simulate the logic modules before the
implementation. This system will be prototyped on an FPGA based COTS (Commercial-off-the-shelf)
development board. Xilinx System Generator will be used for the implementation of the algorithms.
Keywords: DDC, ADC, Digital Base band demodulation, IF, Monitoring Receiver.
Matlab Based Decimeter Design Analysis Wimax Appliacationiosrjce
A Digital down Converter (DDC), which is basically used to convert an intermediate frequency (IF)
signal to its baseband form, forms an integral part of wireless receivers. The major functional blocks of a DDC
constitute a mixer, Numerically Controlled Oscillator (NCO) and an FIR filter chain. In this paper, We can
comparison of two window and see the costs of all Window filters
SDR Training with HackRF - Tonex TrainingBryan Len
Length: 3 Days
SDR Training with HackRF, Advanced Software Defined Radio Training is a 3-day hands-on advanced SDR training course, Software-Defined Radio Development with GNU Radio utilizing HackRF One. The 3-day advanced SDR covers both hypothesis and application of SDR utilizing HackRF One.
.
SDR Training with HackRF. Advanced Software Defined Radio Training.
Participants will learn about:
Software Defined Radio and Digital Signal Processing
Theory and practice with hands-on SDR implementations using the Universal Software Radio Peripheral (USRP) SDR platforms
Necessary SDR signal processing building blocks, SDR application development using Python and C++ concepts required for GNU Radio development
How to apply HackRF and GNU Radio
How to use and apply GNU Radio Companion (GRC)
Security applications of SDR and RF Vulnerabilities
Course Agenda
Principles of Signal processing and applied RF
Overview of SDR
Overview of GNU Radio
Overview of GNU Radio software libraries
Overview of GNU Radio Companion (GRC)
Overview of Python and C++
Overview of Linux
Overview of Universal software radio peripherals
SDR and GNU Radio modules
Systems using HackRF One
Assessments of physical RF devices
How to Fingerprint on RF spectrum?
Hunting signals
Hardware Hacking 101
Reversing and Instrumentation (embedded RF systems)
IoT Hacking with SDR
Overview of Wi-Fi and Bluetooth
Open source SDR LTE software / FM Radio
Principles of Radar detector
Principles of Remote Controlled Cars
SDR Offensive Security
Request more information regarding SDR Training with HackRF. Visit tonex.com for course and workshop detail.
SDR Training with HackRF - Tonex Training
https://www.tonex.com/training-courses/sdr-training-with-hackrf-advanced-software-defined-radio-training/
This includes discussion of DSP applications such as two band digital crossover system,woofers, sqawkers, tweeters, interference cancellation in ECG, speech noise reduction, speech coding and compression, CD recording system
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
For effective implementation of Software Defined
Radio (SDR) in any RF application, a proper choice of data
converter is an essential requirement. This paper describes the
requirement of data converters in SDR, their key specificati
ons that impact the SDR performance and a comparison of
various data converters from leading vendors, which are
suitable in an SDR application.
HIGH SPEED CONTINUOUS-TIME BANDPASS Σ∆ ADC FOR MIXED SIGNAL VLSI CHIPSVLSICS Design
With the unremitting progress in VLSI technology, there is a commensurate increase in performance demand on analog to digital converter and are now being applied to wideband communication systems. sigma Delta (Σ∆) converter is a popular technique for obtaining high resolution with relatively small bandwidth. Σ∆ ADCs which trade sampling speed for resolution can benefit from the speed advantages of nm-CMOS technologies. This paper compares various Band pass sigma Delta ADC architectures, both
continuous-time and discrete-time, in respect of power consumption and SNDR. Design of 2nd order multibit continuous time band pass Σ∆ modulator is discussed with the methods to resolve DAC non-idealities.
This presentation demonstrate:
- Different RF receiver architectures.
- Basics of Multi-Standard receivers.
- How to select receiver's specifications from the selected standard.
- Subsampling basics.
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
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
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.
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.
A to D Convertors
work to convert analog (continuous, infinitely variable) signals to digital (discrete-time, discrete-amplitude) signals. In more practical terms, an ADC converts an analog input, such as a microphone collecting sound, into a digital signal.
A Low power discrete time sigma delta ADC consisting of a second order sigma delta modulator and third order Cascaded Integrated Comb (CIC) filter is proposed. The second order modulator is designed to work at a signal band of 20K Hz at an oversampling ratio of 64 with a sampling frequency of 2.56 MHz. It achieves a signal to noise ratio of 85.2dB and a resolution of 14 bits. The CIC digital filter is designed to implement a decimation factor of 64, operating at a maximum sampling frequency of 2.56 MHz. A second order sigma delta modulator is implemented in 0.18micron CMOS technology using full custom design and the third order digital CIC decimation filter is implemented in verilog HDL. The complete Sigma Delta ADC, consisting of analog block of second order modulator and digital block of decimator consumes a
total power 1.96mW.
Digital Implementation of Costas Loop with Carrier RecoveryIJERD Editor
Demodulator circuit is a basic building block of wireless communication. Digital implementation of
demodulator is attracting more attention for the significant advantages of digital systems than analog systems.
The carrier signal extraction is the main problem in synchronous demodulation in design of demodulator based
on Software Defined Radio. When transmitter or receiver in motion, it is difficult for demodulator to generate
carrier signal same in frequency and phase as transmitter carrier signal due to Doppler shift and Doppler rate.
Here the digital implementation of Costas loop for QPSK demodulation in continuous mode is discussed with
carrier recovery using phase locked loop.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
2. 46 High Frequency Electronics
High Frequency Design
ANALOG/DIGITAL
the next. Low jitter allows the great-
est improvement with dithering,
while poor jitter performance would
reduce the enhancement.
The dynamic range of the system
is the range from the weakest
detectable signal to the strongest. It
is very hard to measure dynamic
range directly in the digital domain,
so it is usually evaluated at the ana-
log input to the ADC, just at it would
be for any analog circuit.
The bandwidth of the digitized
signal is a maximum of one-half the
clock frequency, as determined by
Nyquist many years ago. Dithering
may reduce the effective bandwidth
by “stealing” samples from the ADC.
Some designs even use two ADCs to
obtain the additional samples.
Real World Signals
Any receiver must deal with the
entire range of signals and noise that
is present. The theoretical minimum
thermal noise at room temperature is
–174 dBm in 1 Hz bandwidth. All cir-
cuits have a finite noise figure and a
bandwidth appropriate to the signals
being detected. For a noise figure of 5
dB and a 10 kHz bandwidth, the
noise floor in dBm is then:
Nmin = –174 + 10log(10,000) + 5
= –129 dBm
At the other end of the range, the
strongest signals presented to the
receiver will be from nearby spec-
trum users. This can easily be –10
dBm or higher at multi-user sites, or
even between the handsets of users
sitting next to one another. With a
–10 dBm upper limit, the maximum
dynamic range that must be handled
becomes:
DR = (–10) – (–129)
= 119 dB
This corresponds to an ideal 20-
bit ADC, which is not practical at this
time for high frequencies. This is at
the high end of performance capabil-
ity in analog circuits, as well. The
point is that a wide range of ampli-
tudes must be handled if we want
reliable communications.
This total dynamic range is
reduced somewhat by the amount of
distortion on strong signals, created
by nonlinearities in the circuit. The
reduction of distortion is easily the
greatest challenge in achieving the
desired dynamic range.
The most common techniques for
reduction of distortion and, therefore,
maximization of usable dynamic
range (often referred to as spurious-
free dynamic range or SFDR) are:
• Removal of strong unwanted sig-
nals by filtering
• The use of high-linearity ampli-
fiers, mixers, switches and other
circuit elements
• Applying attenuation or gain to
shift signals to the circuit’s best-
performing range of amplitudes
As we will see in the next section,
some of these choices are not well-
suited for digitized signals.
System Considerations
A key objective of digitizing sig-
nals in modern radios is to reduce the
analog circuit content to a minimum.
Obviously, this means that there is
less opportunity for analog signal
processing such as filtering, frequen-
cy conversion and gain control. But
unless significant strides are made in
the dynamic range of ADCs, highly-
digital radios must either accept
greater analog complexity ahead of
the digital circuit, or accept greatly-
reduced dynamic range. As of today,
both of these scenarios are in play.
Dynamic range is key with digi-
tized radios. A major reason is that
digital circuitry does not have the
“graceful degradation” of analog cir-
cuits. In an analog radio, distortion
increases the noise and spurious sig-
nal levels, but the desired signal is
still present and may even be ade-
quately detected if spurious energy is
not located exactly on its frequency.
When all signals fall within the
input range of the ADC, digital signal
paths react similarly in the presence
of distortion, but when strong signals
saturate the input to the ADC, all
other signals are blocked, since no
codes can be output until the strong
signal ceases or is reduced.
Since the primary cause of distor-
tion is strong unwanted signals, the
above list of methods for reducing
distortion all have the objective of
eliminating or controlling these sig-
nals. Let’s look at each in the context
of delivering a signal to the ADC:
Filtering
Front-end filtering and IF filter-
ing have been the primary means of
achieving the required rejection of
unwanted strong signals. However,
two objectives of digital radios are
wideband frequency coverage and
reduction of analog circuitry. The
reduction of analog circuitry often
means eliminating frequency conver-
sion stages and IF filters. Thus, the
ADC is presented with the band-
width established by the front-end
filter.
An analog radio can use a rela-
tively simple front-end filter and a
high dynamic range mixer to main-
tain the necessary signal handling
performance prior to the narrowband
filtering at the IF. A digital radio may
only have the front-end filter ahead
of the ADC.
Currently, most high performance
digital radios use a downconversion
stage ahead of the ADC. One reason
is to take advantage of the selectivity
afforded by the combination of front-
end and IF filtering. The other main
reason is to operate the ADC at a
lower frequency, where higher-resolu-
tion devices are available.
A midway solution is direct con-
version (D-C), which can use high
dynamic range mixers to convert the
RF to baseband (or a low IF), where
3. 48 High Frequency Electronics
High Frequency Design
ANALOG/DIGITAL
low-frequency 16-bit ADCs are avail-
able with good signal handling prop-
erties.
The front-end filter is one of the
biggest new challenges for the widest
bandwidth digital radio applications,
such as software defined radio (SDR)
or electronic warfare (EW) systems.
These radios rely on wide instanta-
neous bandwidth, which is essential-
ly unfiltered. However, when focused
on a specific task, filtering can be
added to enhance operation at that
particular frequency and bandwidth.
This requires a tunable filter with
sufficient flexibility in center fre-
quency and bandwidth—a signficant
design challenge.
Another new task for filters that
may prove to be the most important
is the reduction, or notching, of
strong unwanted signals. If there are
only a few of these strong signals,
they may be reduced to levels that
allow the ADC to maintain its
dynamic range and deliver the full
input bandwidth. The notch filters
must have sufficient rejection, be fre-
quency agile and accurately tunable.
In addition, the system must have
the capability of spectrum monitor-
ing to identify the interfering signals
and steer the filters.
High Linearity Circuits
As noted above, high dynamic
range mixers are a key element in
downconversion and direct conver-
sion schemes. Mixer design has
advanced to the point where nearly
any practical dynamic range can be
handled well.
A digital radio with no mixer may
require other means of obtaining
high dynamic range. One method is
to use a preamplifier with a high
dynamic range and low noise figure.
This boosts signal levels well above
the minimum necessary for the ADC.
The excess capacity allows for the use
of narrow bandwidth front-end fil-
ters, which may be quite lossy. It also
allows for a flexible range of attenua-
tion, which will be addressed in the
next section.
A highly linear preamplifier
allows fast, inexpensive solid state
switches to be used for both trans-
mit/receive and the selection of ana-
log signal processing options. These
switches may only have a loss of a
fraction of a dB, but some front-end
schemes can cascade several stages of
filtering, which increases the loss.
Gain/Attenuation Control
Ultimately, if the ADC does not
have sufficient dynamic range, signal
levels must be controlled to keep the
input within the amplitude range
where the ADC has its best perfor-
mance. While this is a simple con-
cept, its execution in a digital system
is not. Analog radios could get by
quite well with an IF-derived DC cor-
rection signal for automatic gain con-
trol (AGC). While not perfect, the
time delay between onset of an over-
range strong signal and reduced gain
was acceptable, being only the propa-
gation delay through the narrowband
IF filter, plus the time constant of the
DC detection and control circuits.
A digital radio must derive the
AGC signal from the data stream,
which has a slow response time due
to latency through the ADC and fol-
lowing digital signal processor (DSP).
Some combination of a fast analog
AGC and a more precise digital AGC
may be the right solution.
The gain control circuitry can
take different forms. A high dynamic
range low noise amplifier (LNA) and
a digitally-controlled attenuator
offers the best performance and pre-
cision. These devices are available
now. Analog AGC methods using PIN
diodes, transistors and ICs are also
common and readily available.
Summary and Comments
Digitizing radio signals is an
essential part of the advancement of
communications technology, as has
been demonstrated in numerous
wireless applications. As these tech-
niques spread to other applications,
and as the analog content of the
radios decreases, the design chal-
lenges for the remaining analog cir-
cuitry change.
The major design differences deal
with the restricted dynamic range of
current high-speed/high-frequency
ADCs. In most cases, that required
control must be done within the limi-
tations of much simplified analog cir-
cuitry.
Although the goal of some digital
radio efforts is to nearly eliminate
analog circuitry, practical designs in
the near-term will use the well-estab-
lished analog methods of downcon-
version and direct conversion to meet
performance requirements. It is
expected that these techniques will
continue for some time when higher
performance is needed.
Fully-digital radios with simple
analog front-ends will soon become
common for applications where a
restricted dynamic range and occa-
sional interfering signals can be tol-
erated. This includes most consumer
wireless applications, since the sys-
tem operator has significant control
over signal levels and interference
through the number and location of
base stations. Eventually, the experi-
ence gained from these systems will
aid in the next step forward.
References
1. J. DiPilato, D. Terlep, T. Hofner,
“Optimize the Amplifier/ADC
Connection,” High Frequency Elec-
tronics, Sep. 2006, p. 38.
2. R. Groulx, S. Mason, “Mini-
mization of DDS Spurious Content in
Multi-Channel Systems, High Fre-
quency Electronics, Oct. 2006, p. 18.
3. G. Breed, “Noise and Spurious
in Digital Systems and Digitized
Signals,” High Frequency Electronics,
Sep. 2006, p. 50.
4. J. Tsui, Digital Techniques for
Wideband Receivers, Artech House,
1995.
5. K. Feher, editor, “Advanced
Digital Communications,” Prentice-
Hall, 1987.