Any form of education in an engineering or science discipline is incomplete without a means of testing and appreciating theories learned in class. The ability to carry out experimentation demonstrating theories through laboratory work is an integral part of an engineering, science and technology education. In laboratories, students can learn how to process real data, understand and appreciate discrepancies between their observations and the predictions according to theories. Not only do students appreciate those discrepancies, they learn how to make compromises to minimize the imperfections of their observations. This is a valuable skill for an engineer to have as engineers are problem solvers.
Dielectric resonator antenna excited using t strip feed line for wideband app...Conference Papers
The document presents a dielectric resonator antenna (DRA) excited using a T-strip feed line for wideband applications. The proposed antenna structure achieves an impedance bandwidth of 1.5 GHz covering 27.5-29 GHz with a peak gain of 6.6 dBi and high radiation efficiency of 89%. Simulation results show that the T-strip feed line improves the bandwidth of the DRA compared to other feeding methods. The proposed antenna is suitable for wideband communication applications such as 5G.
Digital Wave Simulation of Quasi-Static Partial Element Equivalent Circuit Me...Piero Belforte
This is an extended version of the paper published on IEEE Transactions on EMC, October 2016. PEEC modeling is a well established technique for obtaining a circuit equivalent for an electromagnetic problem. The time domain solution of such models is usually performed using nodal voltages and branch currents, or sometimes charge and currents. The present paper describes a possible alternative approach which can be obtained expressing and solving the problem in the waves domain. The digital wave theory is used to find an equivalent representation of the PEEC circuit in the wave domain. Through a pertinent continuous to discrete time transformation, the constitutive relations for partial inductances, capacitances and resistances are translated in an explicit form. The combination of such equations with Kirchhoff laws allows to achieve a semi-explicit resolution scheme. Three different physical configurations are analyzed and their extracted Digital Wave PEEC models are simulated at growing sizes using the general-purpose Digital Wave Simulator (DWS). The results are compared to those obtained by using standard SPICE simulators in both linear and nonlinear cases. When the size of the model is manageable by SPICE, an excellent accuracy and a speed-up factor of up to three orders of magnitude are observed with much lower memory requirements. PEEC model sizes manageable by DWS are also an order of magnitude larger than SPICE. A comparative analysis of results including the effect of parameters like the simulation time step choice is also presented.
The document provides the syllabus for the third year second semester of the B.Tech ECE program at JNTU Hyderabad. It includes details of 9 courses that are part of the semester. The courses cover topics like Antennas and Propagation, Digital Signal Processing, VLSI Design, and Object Oriented Programming through Java. The syllabus provides course objectives, outcomes and unit-wise topics for each course. It also lists the textbooks and references for further reading. The summary provides an overview of the key courses and topics covered in the semester without including unnecessary details.
Chapter 1 introduction to radio communication systemskiên lý
This document provides an introduction to RF communication systems from Dr. Cuong Huynh of the Telecommunications Department at HCMUT. It discusses wireless communication systems using radio waves, the RF spectrum, and major cellular systems. It also describes RF transceivers, modulation, and components like antennas, mixers, and frequency synthesizers. Fabrication technologies for RF circuits are introduced, including hybrid MICs, MMICs, and CMOS technology. Mobile communication principles are summarized, including frequency reuse and cellular network layout.
The document discusses electromagnetic (EM) simulation software used for modeling antennas and other electromagnetic devices. It describes the importance of EM simulation for designing complex antennas. Several EM simulation methods are covered, including the method of moments (MoM), finite element method (FEM), and finite difference time domain (FDTD). Popular commercial EM simulators are also listed that use these various techniques, such as HFSS, CST, and FEKO. The document provides guidance on selecting the appropriate EM simulation tool based on factors like the geometry of the device being modeled and the frequency domain or time domain nature of the simulation.
The document provides the syllabus for the B.E. (Electronics and Telecommunications Engineering) program at Shivaji University, Kolhapur. It outlines the teaching and examination schemes for Parts I and II of the program.
Part I includes subjects like Digital Communication, Computer Communication Network, Industrial and Power Electronics, and Satellite Communication. It also lists three elective subjects: VLSI Technology, Image Processing, and Fuzzy Logic. The syllabus provides details on the topics covered, textbooks, and experiments for each subject.
Part II focuses on subjects such as Broadband Communication, Mobile Communication, Audio-Video Engineering, and elective subjects including Digital Signal Processors and Embedded Systems. It concludes with
Any form of education in an engineering or science discipline is incomplete without a means of testing and appreciating theories learned in class. The ability to carry out experimentation demonstrating theories through laboratory work is an integral part of an engineering, science and technology education. In laboratories, students can learn how to process real data, understand and appreciate discrepancies between their observations and the predictions according to theories. Not only do students appreciate those discrepancies, they learn how to make compromises to minimize the imperfections of their observations. This is a valuable skill for an engineer to have as engineers are problem solvers.
Dielectric resonator antenna excited using t strip feed line for wideband app...Conference Papers
The document presents a dielectric resonator antenna (DRA) excited using a T-strip feed line for wideband applications. The proposed antenna structure achieves an impedance bandwidth of 1.5 GHz covering 27.5-29 GHz with a peak gain of 6.6 dBi and high radiation efficiency of 89%. Simulation results show that the T-strip feed line improves the bandwidth of the DRA compared to other feeding methods. The proposed antenna is suitable for wideband communication applications such as 5G.
Digital Wave Simulation of Quasi-Static Partial Element Equivalent Circuit Me...Piero Belforte
This is an extended version of the paper published on IEEE Transactions on EMC, October 2016. PEEC modeling is a well established technique for obtaining a circuit equivalent for an electromagnetic problem. The time domain solution of such models is usually performed using nodal voltages and branch currents, or sometimes charge and currents. The present paper describes a possible alternative approach which can be obtained expressing and solving the problem in the waves domain. The digital wave theory is used to find an equivalent representation of the PEEC circuit in the wave domain. Through a pertinent continuous to discrete time transformation, the constitutive relations for partial inductances, capacitances and resistances are translated in an explicit form. The combination of such equations with Kirchhoff laws allows to achieve a semi-explicit resolution scheme. Three different physical configurations are analyzed and their extracted Digital Wave PEEC models are simulated at growing sizes using the general-purpose Digital Wave Simulator (DWS). The results are compared to those obtained by using standard SPICE simulators in both linear and nonlinear cases. When the size of the model is manageable by SPICE, an excellent accuracy and a speed-up factor of up to three orders of magnitude are observed with much lower memory requirements. PEEC model sizes manageable by DWS are also an order of magnitude larger than SPICE. A comparative analysis of results including the effect of parameters like the simulation time step choice is also presented.
The document provides the syllabus for the third year second semester of the B.Tech ECE program at JNTU Hyderabad. It includes details of 9 courses that are part of the semester. The courses cover topics like Antennas and Propagation, Digital Signal Processing, VLSI Design, and Object Oriented Programming through Java. The syllabus provides course objectives, outcomes and unit-wise topics for each course. It also lists the textbooks and references for further reading. The summary provides an overview of the key courses and topics covered in the semester without including unnecessary details.
Chapter 1 introduction to radio communication systemskiên lý
This document provides an introduction to RF communication systems from Dr. Cuong Huynh of the Telecommunications Department at HCMUT. It discusses wireless communication systems using radio waves, the RF spectrum, and major cellular systems. It also describes RF transceivers, modulation, and components like antennas, mixers, and frequency synthesizers. Fabrication technologies for RF circuits are introduced, including hybrid MICs, MMICs, and CMOS technology. Mobile communication principles are summarized, including frequency reuse and cellular network layout.
The document discusses electromagnetic (EM) simulation software used for modeling antennas and other electromagnetic devices. It describes the importance of EM simulation for designing complex antennas. Several EM simulation methods are covered, including the method of moments (MoM), finite element method (FEM), and finite difference time domain (FDTD). Popular commercial EM simulators are also listed that use these various techniques, such as HFSS, CST, and FEKO. The document provides guidance on selecting the appropriate EM simulation tool based on factors like the geometry of the device being modeled and the frequency domain or time domain nature of the simulation.
The document provides the syllabus for the B.E. (Electronics and Telecommunications Engineering) program at Shivaji University, Kolhapur. It outlines the teaching and examination schemes for Parts I and II of the program.
Part I includes subjects like Digital Communication, Computer Communication Network, Industrial and Power Electronics, and Satellite Communication. It also lists three elective subjects: VLSI Technology, Image Processing, and Fuzzy Logic. The syllabus provides details on the topics covered, textbooks, and experiments for each subject.
Part II focuses on subjects such as Broadband Communication, Mobile Communication, Audio-Video Engineering, and elective subjects including Digital Signal Processors and Embedded Systems. It concludes with
2x2 Wi-Fi Circularly Polarized Microstrip Patch ArraySteafán Sherlock
This document describes the design and simulation of a circularly polarized microstrip antenna array by Steafán Sherlock for his Bachelor of Engineering degree. It includes chapters on microstrip antennas, antenna parameters, the design of a single patch antenna and a 2x2 array, and results from simulating and measuring the array's performance. The antenna was designed to operate at 2.4GHz for Wi-Fi applications and incorporate circular polarization to overcome issues from device orientation. Simulation and measurement results showed the antenna array had high gain, directivity, and circular polarization as required.
This document provides information about an electronics and communications course taught by Dr. Cuong Huynh at Ho Chi Minh city University of Technology. The course covers basic principles of high frequency circuit design and how such circuits are used in communication systems. By the end of the course students will understand radio communication system components, design concepts, modulation schemes, and how to analyze and design circuits like LNAs, mixers, power amplifiers and oscillators. The document lists textbooks, objectives, grading breakdown, and chapter topics for the course.
The document provides information about the Engineering Mathematics - III course, including details about 8 units that will be covered in the course. It lists the topics that will be discussed in each unit, such as Fourier series, Fourier transforms, partial differential equations, curve fitting, numerical methods, difference equations, and Z-transforms. It also provides information about the course code, credit hours, examination hours and marks. Textbooks and reference books for the course are also specified.
This document presents a method to estimate the weights of main materials (copper, iron, oil) for transformers using an artificial neural network (ANN) with the Levenberg-Marquardt backpropagation algorithm. Training data consisting of 24 input/output pairs obtained from a transformer manufacturing company are used to train the ANN, with inputs like short circuit impedance, installation height, and temperature and outputs of material weights. The trained ANN is then able to accurately estimate the material weights of transformers, providing a method to forecast transformer costs for manufacturers.
Study on performance of capacitor less ldo with different types of resistorConference Papers
The document summarizes a study on the performance of a capacitor-less low dropout (LDO) voltage regulator using different types of resistors. A 1.8V LDO voltage regulator was designed and simulated using five different resistor types in Cadence. The performance metrics compared included output voltage accuracy, phase margin, unity gain bandwidth, and power supply rejection ratio. Simulation results showed differences in LDO performance depending on the resistor type. The LDO with hpoly resistor had the best stability performance, while the LDO with pdiffb resistor produced the highest power supply rejection ratio. In conclusion, the type of resistor used can significantly impact key performance characteristics of a capacitor-less LDO regulator.
Iaetsd adaptive modulation in mimo ofdm system for4 gIaetsd Iaetsd
This paper proposes applying hybrid adaptation techniques in MIMO OFDM systems to improve spectral efficiency and reduce transmit power. It first analyzes the bit error rate of M-QAM modulation in OFDM systems with different numbers of subcarriers. Channel estimation is performed using MMSE, which estimates the channel with less error than LS. Feedback from channel estimation is then used with hybrid adaptation techniques. Simulation results show MMSE has lower MSE and symbol errors than LS estimation.
The document discusses network survivability and protection techniques in optical networks. It covers protection in ring networks like UPSR and BLSR, protection in mesh networks using path and line protection, and multi-layer network resilience. The key aspects are the need for fast restoration at the optical layer to minimize outage times, different protection schemes, and the interaction between layers for resilient multi-layer networks.
Design of wideband dielectric resonator antenna with square slots excited usi...Conference Papers
The document describes the design of a wideband dielectric resonator antenna (DRA) with square slots for 5G communication applications operating at 26 GHz. Square slots of two different sizes are introduced in the DRA to reduce its quality factor and achieve a bandwidth of 3 GHz (11.5%) from 25-28 GHz. The DRA is excited using a microstrip feed line. Simulation results show the proposed antenna achieves a peak gain of 4.8 dBi and radiation efficiency of 93%. Compared to reference DRAs, the proposed antenna with slots provides the widest bandwidth for 5G millimeter-wave applications.
Reconfigurable Impedance Matching Network using RF MEMS Based Switch for 5G T...IJSRED
This document discusses the design of a reconfigurable impedance matching network using RF MEMS switches for 5G transceivers. Impedance matching networks are needed to maximize power transfer between antennas and transmitters by reducing mismatch losses, but traditional designs require redundant circuits for different frequencies. The proposed design uses MEMS switches to reconfigure a single matching network to operate at Bluetooth and Wi-Fi frequencies, avoiding redundant hardware. A cantilever beam ohmic switch in series and a fixed-fixed beam capacitive switch in shunt are modeled and selected. Simulation results showed the design achieves optimal impedance matching at the desired frequencies.
This document provides a synopsis for implementing Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) in MATLAB. The objectives are to implement the physical layer of Long Term Evolution (LTE) using SC-FDMA and OFDMA and investigate efficiency in terms of peak-to-average power ratio and bit error rate. SC-FDMA is used for uplink and OFDMA is used for downlink in LTE. Simulation results from implementing the techniques in MATLAB will evaluate efficiency based on modulation order, bit error rate, and signal-to-noise ratio. The document outlines related work, expected results, and conclusions regarding LTE physical layer
EFFICIENCY ENHANCEMENT BASED ON ALLOCATING BIZARRE PEAKSijwmn
A new work has been proposed in this paper in order to overcome one of the main drawbacks that found in
the Orthogonal Frequency Division Multiplex (OFDM) systems, namely Peak to Average Power Ratio
(PAPR). Furthermore, this work will be compared with a previously published work that uses the neural
network (NN) as a solution to remedy this deficiency.
The proposed work could be considered as a special averaging technique (SAT), which consists of wavelet
transformation in its first stage, a globally statistical adaptive detecting algorithm as a second stage; and
in the third stage it replaces the affected peaks by making use of moving average filter process. In the NN
work, the learning process makes use of a previously published work that is based on three linear coding
techniques.
In order to check the proposed work validity, a MATLAB simulation has been run and has two main
variables to compare with; namely BER and CCDF curves. This is true under the same bandwidth
occupancy and channel characteristics. Two types of tested data have been used; randomly generated data
and a practical data that have been extracted from a funded project entitled by ECEM. From the achieved
simulation results, the work that is based on SAT shows promising results in reducing the PAPR effect
reached up to 80% over the work in the literature and our previously published work. This means that this
work gives an extra reduction up to 15% of our previously published work. However, this achievement will
be under the cost of complexity. This penalty could be optimized by imposing the NN to the SAT work in
order to enhance the wireless systems performance.
IRJET- A Review Paper of Performance Analysis Slotted CSMA/CAIRJET Journal
This document summarizes and reviews research on analyzing the performance of the CSMA/CA protocol used in the IEEE 802.15.4 standard for wireless personal area networks (WPANs). Specifically, it analyzes performance in the contention access period (CAP) where CSMA/CA is employed. It discusses previous studies that evaluated throughput, energy consumption, and transmission failure rates under varying loads and across different frequency bands. The document also reviews literature on developing Markov chain models to analyze throughput and energy efficiency of the 802.15.4 standard and exploring how parameters like frame size, backoff times, and network size impact performance.
Energy Efficient Wireless CommunicationsJingon Joung
The tutorial begins with a brief introduction of spectral efficiency (SE) and energy efficiency (EE) in communications. Various definitions of EE will also be covered briefly. One typically used EE, i.e., bits-per-Joule, is theoretically derived and the ideal SE-EE tradeoff is introduced. It is recognized that a power amplifier (PA) is one of the most critical components in wireless communication systems and consumes a significant fraction of the total energy. The fundamental properties of PA, such as linearity and efficiency, are introduced. With the practical characteristics of PA, the detrimental effects of the signal non-linearity and power inefficiency of the PA on the SE, EE, and their tradeoff, are quantified.
Next, various existing EE-improving techniques are categorized from three perspectives: PA design, signal design and network design. This broad understanding based on the three categories will help motivate holistic design approaches to mitigate the non-ideal effects in real-life PA devices, and accelerate cross-domain research to further enhance the available techniques for high EE or good SE-EE tradeoff.
Last, the remaining challenges and future work for EE issue will be discussed.
This document discusses survivable network systems. It defines survivability as a system's ability to fulfill its mission in a timely manner despite attacks, failures, or accidents. The document outlines various topics related to survivable networks including characteristics of survivable systems, expressing survivability requirements, design and implementation strategies, and a case study on survivability in optical networks. It also discusses research directions such as modeling intruder environments and future scopes like developing more intelligent and risk-free networks.
Performance evolution of automatic switched beam antenna for indoor WLAN syst...marwaeng
1) The document describes a study that designed a compact low-cost switched-beam antenna array for indoor wireless local area networks (WLANs).
2) It consisted of a 2x2 array of antenna elements and a modified Butler matrix beamforming network. Computer simulations and prototype testing confirmed its performance.
3) Signal strength measurements in an existing WLAN found that the switched-beam antenna improved average received power by 4.37 dB over an omni-directional antenna.
Performance evaluation of route selection schemes over a clustered cognitive ...Conference Papers
This document evaluates the performance of different route selection schemes over a clustered cognitive radio network (CRN) using a testbed with Universal Software Radio Peripheral (USRP) and GNU Radio platforms. The experimental results show that an enhanced reinforcement learning (RL)-based route selection scheme (C-ERL) selects stable routes in a clustered CRN while improving cluster stability and network scalability without significantly impacting quality of service metrics like throughput, packet delivery rate, and end-to-end delay. C-ERL adjusts its learning rate based on route capacity to reduce the number of route breakages and number of clusters compared to other non-clustered and clustered non-RL and RL-based route selection schemes.
This document discusses cooperative wireless communications. It introduces cooperative communications where users help each other by relaying signals. Some of the research problems discussed include evaluating the performance of cooperative networks, improving current techniques, and finding new techniques to achieve better performance. The document outlines cooperative communications and research challenges, such as channel estimation and the effect of user mobility.
1. The document describes the design and analysis of a dynamic Erbium Doped Fiber Amplifier (EDFA) simulator using MATLAB.
2. The simulator is based on a one-dimensional nonlinear differential equation that describes the time-dependent population density. It uses MATLAB blocks to simulate gain flattening of multiplexed channels at different wavelengths.
3. The performance of the EDFA simulator is analyzed in both the C-band and L-band, including calculations of noise figure for different signal wavelengths based on a designed amplified spontaneous emission noise generator.
Performance Analysis of Bus Topology in Fiber Optic Communicationijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
Subsystems of radar and signal processing Ronak Vyas
This document discusses subsystems of radar and signal processing, specifically focusing on ST (Stratosphere Troposphere) radar. It begins by introducing the goals of understanding basic radar concepts and studying ST radar. It then provides an overview of key radar subsystems including antennas, duplexers, transmitters, and receivers. The document concludes by describing common signal processing techniques used in radar like correlation, Doppler filtering, and detection processing.
2x2 Wi-Fi Circularly Polarized Microstrip Patch ArraySteafán Sherlock
This document describes the design and simulation of a circularly polarized microstrip antenna array by Steafán Sherlock for his Bachelor of Engineering degree. It includes chapters on microstrip antennas, antenna parameters, the design of a single patch antenna and a 2x2 array, and results from simulating and measuring the array's performance. The antenna was designed to operate at 2.4GHz for Wi-Fi applications and incorporate circular polarization to overcome issues from device orientation. Simulation and measurement results showed the antenna array had high gain, directivity, and circular polarization as required.
This document provides information about an electronics and communications course taught by Dr. Cuong Huynh at Ho Chi Minh city University of Technology. The course covers basic principles of high frequency circuit design and how such circuits are used in communication systems. By the end of the course students will understand radio communication system components, design concepts, modulation schemes, and how to analyze and design circuits like LNAs, mixers, power amplifiers and oscillators. The document lists textbooks, objectives, grading breakdown, and chapter topics for the course.
The document provides information about the Engineering Mathematics - III course, including details about 8 units that will be covered in the course. It lists the topics that will be discussed in each unit, such as Fourier series, Fourier transforms, partial differential equations, curve fitting, numerical methods, difference equations, and Z-transforms. It also provides information about the course code, credit hours, examination hours and marks. Textbooks and reference books for the course are also specified.
This document presents a method to estimate the weights of main materials (copper, iron, oil) for transformers using an artificial neural network (ANN) with the Levenberg-Marquardt backpropagation algorithm. Training data consisting of 24 input/output pairs obtained from a transformer manufacturing company are used to train the ANN, with inputs like short circuit impedance, installation height, and temperature and outputs of material weights. The trained ANN is then able to accurately estimate the material weights of transformers, providing a method to forecast transformer costs for manufacturers.
Study on performance of capacitor less ldo with different types of resistorConference Papers
The document summarizes a study on the performance of a capacitor-less low dropout (LDO) voltage regulator using different types of resistors. A 1.8V LDO voltage regulator was designed and simulated using five different resistor types in Cadence. The performance metrics compared included output voltage accuracy, phase margin, unity gain bandwidth, and power supply rejection ratio. Simulation results showed differences in LDO performance depending on the resistor type. The LDO with hpoly resistor had the best stability performance, while the LDO with pdiffb resistor produced the highest power supply rejection ratio. In conclusion, the type of resistor used can significantly impact key performance characteristics of a capacitor-less LDO regulator.
Iaetsd adaptive modulation in mimo ofdm system for4 gIaetsd Iaetsd
This paper proposes applying hybrid adaptation techniques in MIMO OFDM systems to improve spectral efficiency and reduce transmit power. It first analyzes the bit error rate of M-QAM modulation in OFDM systems with different numbers of subcarriers. Channel estimation is performed using MMSE, which estimates the channel with less error than LS. Feedback from channel estimation is then used with hybrid adaptation techniques. Simulation results show MMSE has lower MSE and symbol errors than LS estimation.
The document discusses network survivability and protection techniques in optical networks. It covers protection in ring networks like UPSR and BLSR, protection in mesh networks using path and line protection, and multi-layer network resilience. The key aspects are the need for fast restoration at the optical layer to minimize outage times, different protection schemes, and the interaction between layers for resilient multi-layer networks.
Design of wideband dielectric resonator antenna with square slots excited usi...Conference Papers
The document describes the design of a wideband dielectric resonator antenna (DRA) with square slots for 5G communication applications operating at 26 GHz. Square slots of two different sizes are introduced in the DRA to reduce its quality factor and achieve a bandwidth of 3 GHz (11.5%) from 25-28 GHz. The DRA is excited using a microstrip feed line. Simulation results show the proposed antenna achieves a peak gain of 4.8 dBi and radiation efficiency of 93%. Compared to reference DRAs, the proposed antenna with slots provides the widest bandwidth for 5G millimeter-wave applications.
Reconfigurable Impedance Matching Network using RF MEMS Based Switch for 5G T...IJSRED
This document discusses the design of a reconfigurable impedance matching network using RF MEMS switches for 5G transceivers. Impedance matching networks are needed to maximize power transfer between antennas and transmitters by reducing mismatch losses, but traditional designs require redundant circuits for different frequencies. The proposed design uses MEMS switches to reconfigure a single matching network to operate at Bluetooth and Wi-Fi frequencies, avoiding redundant hardware. A cantilever beam ohmic switch in series and a fixed-fixed beam capacitive switch in shunt are modeled and selected. Simulation results showed the design achieves optimal impedance matching at the desired frequencies.
This document provides a synopsis for implementing Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) in MATLAB. The objectives are to implement the physical layer of Long Term Evolution (LTE) using SC-FDMA and OFDMA and investigate efficiency in terms of peak-to-average power ratio and bit error rate. SC-FDMA is used for uplink and OFDMA is used for downlink in LTE. Simulation results from implementing the techniques in MATLAB will evaluate efficiency based on modulation order, bit error rate, and signal-to-noise ratio. The document outlines related work, expected results, and conclusions regarding LTE physical layer
EFFICIENCY ENHANCEMENT BASED ON ALLOCATING BIZARRE PEAKSijwmn
A new work has been proposed in this paper in order to overcome one of the main drawbacks that found in
the Orthogonal Frequency Division Multiplex (OFDM) systems, namely Peak to Average Power Ratio
(PAPR). Furthermore, this work will be compared with a previously published work that uses the neural
network (NN) as a solution to remedy this deficiency.
The proposed work could be considered as a special averaging technique (SAT), which consists of wavelet
transformation in its first stage, a globally statistical adaptive detecting algorithm as a second stage; and
in the third stage it replaces the affected peaks by making use of moving average filter process. In the NN
work, the learning process makes use of a previously published work that is based on three linear coding
techniques.
In order to check the proposed work validity, a MATLAB simulation has been run and has two main
variables to compare with; namely BER and CCDF curves. This is true under the same bandwidth
occupancy and channel characteristics. Two types of tested data have been used; randomly generated data
and a practical data that have been extracted from a funded project entitled by ECEM. From the achieved
simulation results, the work that is based on SAT shows promising results in reducing the PAPR effect
reached up to 80% over the work in the literature and our previously published work. This means that this
work gives an extra reduction up to 15% of our previously published work. However, this achievement will
be under the cost of complexity. This penalty could be optimized by imposing the NN to the SAT work in
order to enhance the wireless systems performance.
IRJET- A Review Paper of Performance Analysis Slotted CSMA/CAIRJET Journal
This document summarizes and reviews research on analyzing the performance of the CSMA/CA protocol used in the IEEE 802.15.4 standard for wireless personal area networks (WPANs). Specifically, it analyzes performance in the contention access period (CAP) where CSMA/CA is employed. It discusses previous studies that evaluated throughput, energy consumption, and transmission failure rates under varying loads and across different frequency bands. The document also reviews literature on developing Markov chain models to analyze throughput and energy efficiency of the 802.15.4 standard and exploring how parameters like frame size, backoff times, and network size impact performance.
Energy Efficient Wireless CommunicationsJingon Joung
The tutorial begins with a brief introduction of spectral efficiency (SE) and energy efficiency (EE) in communications. Various definitions of EE will also be covered briefly. One typically used EE, i.e., bits-per-Joule, is theoretically derived and the ideal SE-EE tradeoff is introduced. It is recognized that a power amplifier (PA) is one of the most critical components in wireless communication systems and consumes a significant fraction of the total energy. The fundamental properties of PA, such as linearity and efficiency, are introduced. With the practical characteristics of PA, the detrimental effects of the signal non-linearity and power inefficiency of the PA on the SE, EE, and their tradeoff, are quantified.
Next, various existing EE-improving techniques are categorized from three perspectives: PA design, signal design and network design. This broad understanding based on the three categories will help motivate holistic design approaches to mitigate the non-ideal effects in real-life PA devices, and accelerate cross-domain research to further enhance the available techniques for high EE or good SE-EE tradeoff.
Last, the remaining challenges and future work for EE issue will be discussed.
This document discusses survivable network systems. It defines survivability as a system's ability to fulfill its mission in a timely manner despite attacks, failures, or accidents. The document outlines various topics related to survivable networks including characteristics of survivable systems, expressing survivability requirements, design and implementation strategies, and a case study on survivability in optical networks. It also discusses research directions such as modeling intruder environments and future scopes like developing more intelligent and risk-free networks.
Performance evolution of automatic switched beam antenna for indoor WLAN syst...marwaeng
1) The document describes a study that designed a compact low-cost switched-beam antenna array for indoor wireless local area networks (WLANs).
2) It consisted of a 2x2 array of antenna elements and a modified Butler matrix beamforming network. Computer simulations and prototype testing confirmed its performance.
3) Signal strength measurements in an existing WLAN found that the switched-beam antenna improved average received power by 4.37 dB over an omni-directional antenna.
Performance evaluation of route selection schemes over a clustered cognitive ...Conference Papers
This document evaluates the performance of different route selection schemes over a clustered cognitive radio network (CRN) using a testbed with Universal Software Radio Peripheral (USRP) and GNU Radio platforms. The experimental results show that an enhanced reinforcement learning (RL)-based route selection scheme (C-ERL) selects stable routes in a clustered CRN while improving cluster stability and network scalability without significantly impacting quality of service metrics like throughput, packet delivery rate, and end-to-end delay. C-ERL adjusts its learning rate based on route capacity to reduce the number of route breakages and number of clusters compared to other non-clustered and clustered non-RL and RL-based route selection schemes.
This document discusses cooperative wireless communications. It introduces cooperative communications where users help each other by relaying signals. Some of the research problems discussed include evaluating the performance of cooperative networks, improving current techniques, and finding new techniques to achieve better performance. The document outlines cooperative communications and research challenges, such as channel estimation and the effect of user mobility.
1. The document describes the design and analysis of a dynamic Erbium Doped Fiber Amplifier (EDFA) simulator using MATLAB.
2. The simulator is based on a one-dimensional nonlinear differential equation that describes the time-dependent population density. It uses MATLAB blocks to simulate gain flattening of multiplexed channels at different wavelengths.
3. The performance of the EDFA simulator is analyzed in both the C-band and L-band, including calculations of noise figure for different signal wavelengths based on a designed amplified spontaneous emission noise generator.
Performance Analysis of Bus Topology in Fiber Optic Communicationijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
Subsystems of radar and signal processing Ronak Vyas
This document discusses subsystems of radar and signal processing, specifically focusing on ST (Stratosphere Troposphere) radar. It begins by introducing the goals of understanding basic radar concepts and studying ST radar. It then provides an overview of key radar subsystems including antennas, duplexers, transmitters, and receivers. The document concludes by describing common signal processing techniques used in radar like correlation, Doppler filtering, and detection processing.
This document outlines a unit plan on radar communication. It includes sections on radar principles and applications, radar frequency bands, pulse-related terms, the radar range equation, duplexer and display systems, types of radar including pulse, CW, FMCW, MTI and secondary radar, landing systems including ILS and GCA, and an introduction to SONAR. Various radar concepts are defined and block diagrams of radar systems are provided with explanations. The unit plan allocates 1 hour for each sub-section and includes learning objectives.
Abstract
Terahertz sub-surface imaging offers an effective solution for surface and 3D imaging because of minimal
sample preparation requirements and its ability to “see” below the surface. Another important property is the ability
to inspect on a layer-by layer basis via a non-contact route, non-destructive route. Terahertz 3D imager designed
at Applied Research and Photonics (Harrisburg, PA) has been used to demonstrate reconstructive imaging with a
resolution of less than a nanometer. Gridding with inverse distance to power equations has been described for 3D
image formation. A continuous wave terahertz source derived from dendrimer dipole excitation has been used for
reflection mode scanning in the three orthogonal directions. Both 2D and 3D images are generated for the analysis
of silver iodide quantum dots’ size parameter. Layer by layer image analysis has been outlined. Graphical analysis
was used for particle size and layer thickness determinations. The demonstrated results of quantum dot particle
size checks well with those determined by TEM micrograph and powder X-ray diffraction analysis. The reported
non-contact measurement system is expected to be useful for characterizing 2D and 3D naomaterials as well as for process development and/or quality inspection at the production line.
Microwave Planar Sensor for Determination of the Permittivity of Dielectric M...journalBEEI
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This lesson describes the concept of VPN and introduces some VPN terminology.
Importance
This lesson is the foundation lesson for the MPLS VPN Curriculum.
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Upon completion of this lesson, the learner will be able to perform the following
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This lesson is the foundation lesson for the MPLS VPN Curriculum.
Objectives
Upon completion of this lesson, the learner will be able to perform the following
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This lesson is the foundation lesson for the MPLS VPN Curriculum.
Objectives
Upon completion of this lesson, the learner will be able to perform the following
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Atomic Receiver by Utilizing Multiple Radio-Frequency Coupling at Rydberg States of Rubidium
1. applied
sciences
Article
Atomic Receiver by Utilizing Multiple
Radio-Frequency Coupling at Rydberg States
of Rubidium
Haiyang Zou 1,2, Zhenfei Song 2,* , Huihui Mu 1,2, Zhigang Feng 2, Jifeng Qu 2 and
Qilong Wang 1,*
1 Joint International Research Laboratory of Information Display and Visualization, Southeast University,
Nanjing 210000, China; zouhy@seu.edu.cn (H.Z.); skzxmhh@seu.edu.cn (H.M.)
2 Center for Advanced Measurement Science, National Institute of Metrology, Beijing 100029, China;
fengzg@nim.ac.cn (Z.F.); qujf@nim.ac.cn (J.Q.)
* Correspondence: songzf@nim.ac.cn (Z.S.); northrockwql@seu.edu.cn (Q.W.)
Received: 24 January 2020; Accepted: 12 February 2020; Published: 16 February 2020
Abstract: Rydberg atoms have been extensively utilized in microwave measurement with high
sensitivity, which has great potential in the field of communication. In this study, we discuss the digital
communication based on a Rydberg atomic receiver under simultaneously coupling by resonant
and near detuning microwaves. In addition, we verify the feasibility of the Rydberg atom-based
frequency division multiplexing (FDM) in microwave communication. We demonstrate the principle
and performance of the atom-based FDM receiver by applying amplitude modulation (AM) and
frequency modulation (FM), respectively. To demonstrate the actual communication performance at
different data transfer rates, we consider monochromatic images as an example. The experimental
results show that the maximum acceptable data transfer rate of both AM and FM is about 200 kbps,
whereas their maximum bit error rates (BER) is less than 5%. When compared with the traditional
electronic receiver, this atomic receiver, which is compatible with FDM, has numerous advantages,
such as small size, low power consumption, and high sensitivity. Furthermore, this receiver has a
strong ability of anti-electromagnetic interference, and the signals transmitted do not interfere with
each other in different channels.
Keywords: Rydberg atoms; microwave communication; frequency-division multiplexing; antennas
1. Introduction
With the new developments in precision measurement technology, numerous atom-based sensors
and communication devices have been proposed and verified in laboratories. Many new concepts
and technologies of Radio Frequency Electric field (RF E-field) measurements in the quantum sensing
domain have been presented, such as Rydberg atoms. Because of their high precision, sensitivity,
and as the measurement results can be directly traced to the international system of units (SI) via
atomic constant [1,2], they have great potential in many application scenarios. Rydberg atoms are
some kinds of atoms with large principal quantum numbers [3]. Their large dc polarizabilities
and microwave-transition dipole moments [4], Ref. [5] make them very suitable for the RF E-field
measurement. Combining the electromagnetically induced transparency (EIT) [6,7] Autler–Townes
(AT) [8] effects, measurement of the RF E-field with Rydberg atoms can be converted into frequency
measurement. The sensitivity of the RF E-field has been observed to be less than 1 µV·cm−1·Hz−1/2 [9]
under the predictable noise limit, and the measurement uncertainty has been observed to be less than
0.5% [2].
Appl. Sci. 2020, 10, 1346; doi:10.3390/app10041346 www.mdpi.com/journal/applsci
2. Appl. Sci. 2020, 10, 1346 2 of 8
Rydberg atoms are also extensively employed in many fields, like high-resolution imaging,
millimeter-wave/terahertz [10], and antenna measurement [11]. Owing to the high sensitivity of
Rydberg atoms to RF E-field, the concept of wireless communication using Rydberg atoms has
been recently proposed and verified. Deb et al. [12] proposed a new Rydberg atom-based wireless
fiber-optic signal transmission system, which utilized the Rydberg atoms as a receiving antenna, and the
signals were directly recovered at the baseband without any demodulation means. Meyer et al. [13]
used Rydberg atoms as an optical antenna to realize the 8-state phase-shift-keying (PSK) digital
communication protocol. Anderson et al. [14] demonstrated an atomic receiver for amplitude
modulation (AM) and frequency modulation (FM) communication with a 3 dB bandwidth in the
baseband of 100 kHz. Song et al. [15,16] investigated the feasibility of this atom-based receiver
over a continuously tunable RF-carrier; the authors showed that the communication at a rate of
500 kbps can be reliably performed within a tunable bandwidth of 200 MHz near a 10.22 GHz
carrier. Holloway et al. [17] observed that the receiving system based on Rydberg atoms can
detect and demodulate binary-phase-shift-keying (BPSK), quadrature-amplitude-modulation (QAM),
and quadrature-phase-shift-keying (QPSK) signals. Due to numerous available resonant frequencies of
the Rydberg states from 100 MHz to sub-THz, it is possible to achieve the broadband communication by
changing the coupling frequency between RF E-field and the Rydberg States. Therefore, Rydberg atoms
are good candidates for microwave communication applications.
All the aforementioned communication experiments transmitted data over a single RF-carrier
at atomic resonance frequency. As the development of wireless communications, spectrum resource
is increasingly scarce, and interference between systems has become increasingly serious. It is
of great necessity to find an optimal way to make better use of the limited spectrum resource.
Using the abundant microwave-transition energy levels between Rydberg states, instead of recovering
the time-varying signal on the specific RF-carrier frequency, we simultaneously couple resonant
and detuning microwaves to verify the feasibility of dual-carrier communication and achieve
frequency division multiplexing (FDM). This can improve spectral performance and allow real-time
channel multiplexing.
In this paper, the feasibility of digital FDM communication is proposed, together with the atomic
receiver by using multiple RF couplings. Additionally, we analyze the change of signal-to-noise ratio
(SNR) by scanning the coupling laser frequency. The feasible experimental conditions which are
selected by the SNR judgment are discussed. Finally, the image data reception is performed and
practical indicators for AM and FM communication are discussed, respectively.
2. Methods
2.1. Measurement Set-Up
The details of how to use the Rydberg atoms as a receiving antenna for communication have been
discussed in some previously conducted studies [15,16]. At both RF-resonance and RF-detuning,
time-variant characteristics of complex signals could be captured by the change of the probe
transmission, and modulation on a RF-carrier can cause synchronous modulation of the probe
transmission. Thus, it is possible to retrieve the characteristics of the modulation signal by detecting
the probe transmission in real-time.
FDM is a multiplexing technique that modulates multiple baseband signals onto different frequency
carriers and then combines them to form a composite signal. In this paper, the communication of the
atom-based receiver in the case of RF-resonance and RF-detuning carriers is proposed. Figure 1
illustrates the experimental set-up. A vapor cell containing rubidium (87Rb) atoms was used as an active
medium for real-time field sensing. 87Rb atoms were excited to Rydberg states by counter-propagating
probe laser and coupling laser via a two-photon transition. Meanwhile, through an external signal
generator, two RF-carriers were amplitude or frequency modulated. Here, we use CH1 and CH2 to
represent two RF-carriers, respectively. Then, they were coupled into the atomic vapor cell by the
3. Appl. Sci. 2020, 10, 1346 3 of 8
X-band horn antenna after the combiner, and different modulation parameters were selected for each
modulation mode. The probe laser passing through the atomic vapor was detected by a photodiode,
and recorded by a spectrum analyzer or the oscilloscope; signal components of the multiple basebands
can be separated by a band-pass filter.
Figure 1. The experimental set-up. Frequency division multiplexing (FDM) receiver basing on Rydberg
atoms is shown in the right part. Abbreviations: RM: reflector mirror; DM: dichroic mirror; PD:
photodetector.
Figure 2a illustrates the experiment-related Rydberg energy levels. The probe laser (∼780 nm)
generated from an external-cavity diode laser was frequency-locked to the atomic transition 5S1/2 (F = 2)
and 5P3/2 (F’ = 3), and the coupling laser (∼480 nm) generated from a high-power doubled-frequency
diode laser system was frequency scanned across 5P3/2 (F’ = 3) and Rydberg state 59D5/2. By regulating
and controlling the laser, the phenomenon of a ladder three-level electromagnetically induced
transparency (EIT) [18] appeared. When RF E-field at a resonant frequency of 10.22 GHz between 59D5/2
and 60P3/2 was applied, it made EIT spectroscopy split, known as Autler–Townes (AT) effect. At the
same time, another detuning RF E-field simulated by a microwave signal source was applied. When the
RF E-field was frequency-detuned from the resonant transition, the observed AT-splitting spectroscopy
became asymmetrical and two transmission peaks are not equal in height [16] (as shown in Figure 2b).
In essence, the change of RF E-field frequency leads to the change of lineshape of AT-splitting, so both
AM and FM baseband signals at multiple channels can be detected through the change of lineshape of a
mixed AT-splitting [14].
Figure 2. (a) Experiment-related energy levels. (b) RF-induced symmetric or asymmetric Autler–
Townes splitting.
2.2. Performance Test
To verify the actual performance of the Rydberg atom-based FDM receiver, it was necessary to
study the SNR, which is the main technical indicator for measuring the quality of communication
systems. Moreover, to detect time-varying modulated signals, both the frequency of the probe and
the coupling laser must be locked [15]. In this study, two modulated RF carriers for dual-channel
4. Appl. Sci. 2020, 10, 1346 4 of 8
communication were investigated. Signals received from a photodetector were separated by a
high-pass filter and a low-pass filter. The modulation signals of the two channels were set as single-tone
signals. The probe laser was frequency-locked to the D2 transition of 87Rb atoms, and the best SNR was
obtained by scanning the frequency of the coupling laser. SNR values of receiving signals of channel 1
(CH1) and channel 2 (CH2) were separately determined by a spectrum analyzer. The frequency of the
modulation signal of CH1 was 15 kHz with a peak-to-peak value of 3 V, whereas the frequency of the
modulation signal of CH2 was 10 kHz with a peak-to-peak value of 4 V. The purpose of adjusting the
amplitude of the modulation signal was to make the amplitude of actually receiving signal identical.
As the resonant responses of Rydberg atoms were dependent on the amplitude and frequency of RF
E-field [19], to achieve optimal communication, the performance of the atomic receiver needs to be
optimized to the best experimental SNR. The coupling laser was frequency-swept from −80 MHz to
80 MHz respect to a resonance. The experimental results are presented in Figure 3. From Figure 3a,
it can be seen that to achieve a high SNR in both channels for FM communication, the frequency of
coupling laser should be locked away from the resonance (with zero coupling laser detuning). This is
because, at this point, the dynamic range of probe transmission change caused by FM signals was
the largest. For receiving AM signals, the frequency of the coupling laser should be locked at the
resonance. The working points of coupling laser are indicated in Figure 3.
-80 -60 -40 -20 0 20 40 60 80
0
10
20
30
40
50
60
-80 -60 -40 -20 0 20 40 60 80
10
20
30
40
50
60
SNR
(dB)
FM-CH1
FM-CH2
Working point
Working point
SNR
(dB)
Coupling laser detuning (MHz)
AM-CH1
AM-CH2
(a)
(b)
Figure 3. Observed signal-to-noise ratio (SNR) and working points of coupling laser. Results for
dual-channel AM and FM communication are shown in (a) and (b), respectively.
In practical FDM communication, it is also very important that different channels should
concurrently work together without any mutual interference. Interchannel interference (ICI) refers to
the interference caused by signals in one or more channels in a given transmission channel. To analyze
the ICI, we studied the variation of SNR of receiving signals with ∆RF, and the cross-talk between the
actual signals obtained on the spectrum analyzer; here, ∆RF represents the frequency difference
between two carriers. A 10.22 GHz carrier was applied to CH1, and a single-tone signal with
an amplitude of 2.5 V and a frequency of 500 kHz was modulated on the carrier. In addition,
another carrier modulated by a single-tone signal with an amplitude of 2.5 V and a frequency of
550 kHz was applied to CH2, and its frequency was scanned between 10.22 and 10.23 GHz (i.e.,
∆RF was between 0 and 10 MHz). The corresponding results are shown in Figure 4. By observing
the relative change in the SNR of receiving signals, the obtained SNR range of the two channels is
from 26.4 to 28.2 dB when the ∆RF is less than 10 MHz. By observing the signal from the spectrum
analyzer, it can be seen that the two signals have a relatively pure spectrum even at a very close ∆RF
and there is no other spurious spectrum component, which can meet the requirements for practical
5. Appl. Sci. 2020, 10, 1346 5 of 8
communication and solve the problem of cross-talk. The same investigation was also carried out for
AM communication and a similar conclusion has been reached. Traditional electronic-based receivers
often produce spurious, harmonic, intermodulation, and other unnecessary signals, which will cause
interference within the frequency band, whereas the atomic receiver will not cause cross-talk between
signals while ensuring high SNR, so it has great potential in many applications.
Figure 4. Interchannel interference performance of FM communication. (a) SNR of two channels
changes with ∆RF. (b) Received signals when ∆RF is 0, 5 and 10 MHz respectively.
2.3. Wireless Reception of Image Data
Based on different data transfer rates, more experiments were carried out to test the capability
of data retrieving by the proposed atom-based FDM receiver. The transmitted images (letters “A”,
“B”, “C”, and “D”) are 36 by 36 pixel Portable Network Graphics (PNG) with lossless compression.
Image data is encoded into a one-dimensional digital flow from corresponding two-dimensional array
data, and then transmitted in different channels. Actually, images with different pixel sizes and formats
can be used. The experimental probe laser power was 30 µW, whereas the coupling laser power was
100 mW. The RF-carrier frequency of the CH1 was with a resonance frequency of 10.22 GHz and a
power of 3 dBm. The RF-carrier frequency of the CH2 had a detuning frequency of 10.25 GHz and a
power of 4 dBm. To achieve the port matching, the cable attenuation was calibrated before conducting
the experiment. Moreover, power adjustment of the two channels made the actual antenna feeding
power from the two channels identical, and both carriers were modulated by an external signal source.
In the experiment of receiving FM signals, CH1 and CH2 transmitted the images of letters “C” and
“D”, respectively. The FM modulation depth in the experiment was 30 MHz. Figure 5 shows an image
recovered by the proposed atomic receiver at various data transfer rates. It is clear that, with both
modulation modes, the experimental results demonstrated an acceptable performance with a data
transfer rate up to 500 kbps.
In digital transmission, bit error ratio (BER) was used to study the probability of receiving bits of
data stream on the communication channel, which is often due to noise, interference, distortion, or bit
synchronization error. In our experiment, a classical definition of BER is used, that is, the number of
bit errors divided by the total transferred bits. BER values of different channels and modulation are
shown in Figure 6. Generally, BER for data transfer in the detuning carrier was higher than that in the
resonance situation. In the experiment of receiving the AM signal, the BER of the two channels can be
kept at nearly 0 when the data transfer rate was less than 100 kbps. For receiving FM signals, the BER
was close to 0 when the data transfer rate was less than 300 kbps, and even with the data transfer rate
going up to 500 kbps, the BER increased to approximately 2%.
6. Appl. Sci. 2020, 10, 1346 6 of 8
Figure 5. Test results of the proposed atomic FDM receiver for image data reception at different data
transfer rates.
In the latest released technical specification document (3GPP TS 23.107 V15.0.0) within the
3rd-Generation Partnership Project (3GPP), the BER value ranges for Universal Mobile Communication
System (UTMS) bearer service attributes are recommended. For some applications of Class 2 bits,
a higher BER (5%) might be feasible. The experimental results show that the maximum acceptable
data transfer rate of both AM and FM is ~200 kbps, whereas their maximum BER is less than 5%.
0 100 200 300 400 500
0
2
4
6
8
10
12
14
BER
(%)
Data Transfer Rate (kbps)
AM (letter 'A')
AM (letter 'B')
FM (letter 'C')
FM (letter 'D')
Figure 6. Bit error ratio (BER) for image data reception at different channels.
3. Conclusions
In this paper, the feasibility of an atom-based FDM receiver was discussed in detail through the
method of dual RF-carrier. Various factors affecting the communication quality, such as BER and
SNR, were studied. Our new scheme is of great significance to the field of atomic communication. By
using Rydberg atom as a receiving antenna, the AM and FM signal was directly captured by the fast
photodetector and can be obtained without any demodulation means. A demo experiment of image
7. Appl. Sci. 2020, 10, 1346 7 of 8
data reception at two channels has shown that the maximum acceptable data transfer rate was 200 kHz
with a BER of less than 5%, for both AM and FM communication. Comparing with the traditional
electronic-based receivers, the new atomic approach can realize the communication with high
sensitivity and weak signal detection ability. Moreover, the signals transmitted by the two channels
worked in parallel, and do not interfere with each other under a certain bandwidth, which greatly
saved the spectrum resources. Based on the above excellent performance, these atomic receivers have
great development potential in numerous applications. In the future, the performance of the atomic
receiver will also be optimized for various communication technologies in our subsequent experiments.
Author Contributions: Conceptualization, Z.S.; Formal analysis, H.Z., H.M., Z.F., J.Q., Q.W., and Z.S.;
Methodology, Z.S., H.Z., and Z.F.; Writing—original draft, H.Z.; Writing—review editing, Z.F., Q.W., and Z.S.
All authors have read and agreed to the published version of the manuscript.
Funding: This work was funded by the National Key Research and Development Program of China (Grant No.
2016YFF0200104).
Conflicts of Interest: The authors declare no conflicts of interest.
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