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An amplitude modulator plays an essential role in the implementation of continuous-variable quantum key distribution (CVQKD), whereas it may bring about a potential security loophole in the practical system. The high-frequency modulation of the actual transmitter usually results in the high rate of the system. However, an imperfect amplitude modulator (AM) can give birth to a potential information leakage from the modulation of the transmitter. To reveal a potential security loophole from the high-frequency AM embedded in the transmitter, we demonstrate an influence on the practical security of the system in terms of the secret key rate and maximal transmission distance. The results indicate the risk of this security loophole in the imperfect AM-embedded transmitter. Fortunately, the legal participants can trace back the potential information leakage that has been produced from the imperfect transmitter at high frequencies, which can be used for defeating the leakage attack in CVQKD. We find the limitations of the imperfect AM-embedded transmitter of the high-frequency quantum system, and hence, we have to trade off the practical security and the modulation frequency of the AM-embedded transmitter while considering its implementation in a practical environment. [ABSTRACT FROM AUTHOR]

This paper proposes a programmable solar‐powered radio frequency (RF) transmitter. It employs a novel five‐layer structure that effectively integrates solar cells, active circuits, and broadband antenna. This design can directly emit RF signals without the need for additional power supply, enabling efficient energy conversion and transmission. In addition, a U‐shaped coupling line model is introduced to evaluate the performance of the active circuit. We fabricated a sample and measured it. The results of the measurements indicate that the proposed RF transmitter can achieve self‐powering and programmable output at any frequency within the range of 2.08–4.1 GHz, with an output power of no less than 14 dBm. Moreover, the solar cells are placed on both sides of the circuits and antenna for energy harvesting, achieving 100% sunlight insolation with a 75.5% coverage ratio. This design can be used for self‐powered green wireless system applications. [ABSTRACT FROM AUTHOR]

Localization of wireless transmitters is traditionally done using Radio Frequency (RF) sensors that measure the propagation delays between the transmitter and a set of anchor receivers. One of the major challenges of wireless localization systems is the need for anchor nodes to be time-synchronized to achieve accurate localization of a target node. Using a reference transmitter is an efficient way to synchronize the anchor nodes Over-The-Air (OTA), but such algorithms require multiple periodic messages to achieve tight synchronization. In this paper, we propose a new synchronization method that only requires a single message from a reference transmitter. The main idea is to use the Carrier Frequency Offset (CFO) from the reference node, alongside the Time of Arrival (ToA) of the reference node messages, to achieve tight synchronization. The ToA allows the anchor nodes to compensate for their absolute time offset, and the CFO allows the anchor nodes to compensate for their local oscillator drift. Additionally, using the CFO of the messages sent by the reference nodes and the target nodes also allow us to estimate the speed of the targets. The error of the proposed algorithm is derived analytically and is validated through controlled laboratory experiments. Finally, the algorithm is validated by realistic outdoor vehicular measurements with a software-defined radio testbed. [ABSTRACT FROM AUTHOR]

The ability to sense propagating electromagnetic plane waves based on their directions of arrival (DOAs) is fundamental to a range of radio frequency (RF) sensing, communications, and imaging applications. This paper introduces an algorithm for the wideband true time delay digital delay Vandermonde matrix (DVM), utilizing Thiran fractional delays that are useful for realizing RF sensors having multiple look DOA support. The digital DVM algorithm leverages sparse matrix factorization to yield multiple simultaneous RF beams for low-complexity sensing applications. Consequently, the proposed algorithm offers a reduction in circuit complexity for multi-beam digital wideband beamforming systems employing Thiran fractional delays. Unlike finite impulse response filter-based approaches which are wideband but of a high filter order, the Thiran filters trade usable bandwidth in favor of low-complexity circuits. The phase and group delay responses of Thiran filters with delays of a fractional sampling period will be demonstrated. Thiran filters show favorable results for sample delay blocks with a temporal oversampling factor of three. Thiran fractional delays of orders three and four are mapped to Xilinx FPGA RF-SoC technologies for evaluation. The preliminary results of the APF-based Thiran fractional delays on FPGA can potentially be used to realize DVM factorizations using application-specific integrated circuit (ASIC) technology. [ABSTRACT FROM AUTHOR]

In this paper, an event-driven wireless sensor node is proposed and demonstrated. The primary design objective is to devise a wireless sensor node with miniaturization, integration, and high-accuracy recognition ability. The proposed wireless sensor node integrates two vibration-threshold-triggered energy harvesters that sense and power a threshold voltage control circuit for power management, a microcontroller unit (MCU) for system control, a one-dimensional convolutional neural network (1D-CNN) environment data analysis and vibration events distribution, and a radio frequency (RF) digital baseband transmitter with IEEE 802.15.4-/.6 protocols. The dimensions of the wireless sensor node are 4 × 2 × 1 cm3. Finally, the proposed wireless sensor node was fabricated and tested. The alarming time for detecting the vibration event is less than 6 s. The measured recognition accuracy of three events (knock, shake, and heat) is over 97.5%. The experimental results showed that the proposed integrated wireless sensor node is very suitable for wireless environmental monitoring systems. [ABSTRACT FROM AUTHOR]

The proliferation of radar technology has given rise to a growing demand for advanced, high-performance transmitter front-ends operating in the 24 GHz frequency band. This paper presents a design analysis of a radio frequency (RF) transmitter (TX) front-end operated at a 24 GHz frequency and designed using 65 nm complementary metal-oxide-semiconductor (CMOS) technology for radar applications. The proposed TX front-end design includes the integration of an up-conversion mixer and power amplifier (PA). The up-conversion mixer is a Gilbert cell-based design that translates the 2.4 GHz intermediate frequency (IF) signal and 21.6 GHz local oscillator (LO) signal to the 24 GHz RF output signal. The mixer is designed with a novel technique that includes a duplex transconductance path (DTP) for enhancing the mixer's linearity. The DTP of the mixer includes a primary transconductance path (PTP) and a secondary transconductance path (STP). The PTP incorporates a common source (CS) amplifier, while the STP incorporates an improved cross-quad transconductor (ICQT). The integrated PA in the TX front-end is a class AB tunable two-stage PA that can be tuned with the help of varactors as a synchronous mode to increase the PA bandwidth or stagger mode to obtain a high gain. The PA is tuned to 24 GHz as a synchronous mode PA for the TX front-end operation. The proposed TX front-end showed an excellent output power of 11.7 dBm and dissipated 7.5 mW from a 1.2 V supply. In addition, the TX front-end achieved a power-added efficiency (PAE) of 47% and 1 dB compression point (OP1dB) of 10.5 dBm. In this case, the output power is 10.5 dBm higher than the linear portion of the response. The methodologies presented herein have the potential to advance the state of the art in 24 GHz radar technology, fostering innovations in fields such as autonomous vehicles, industrial automation, and remote sensing. [ABSTRACT FROM AUTHOR]

Emergency exit lights in public buildings are necessary for safety and evacuation. International safety standards require such lighting in many public places, like airports, schools, malls, hospitals, and other spaces, to prevent human casualties in emergencies. Emergency exit lights have become an essential part of casualty reduction projects. They can pose several application problems, including fire safety concerns. The issue of providing a safe way and operating emergency exit lights along one side of a long path arises during an emergency. Many studies in this field consider the case in which emergency exit lights' battery or main power fails. Power failures in dangerous situations such as fires or terrorist attacks make it difficult for people to escape. The lighting in open areas and stairwells during an emergency should be at least 2 lux. This work proposes an innovative technique for wirelessly powering emergency lights using microwave energy. Specifically, the study designed and fabricated a new wirelessly powered emergency lighting prototype. This prototype's wireless power transfer (WPT) base comprises an RF/DC converter circuit and an RF microwave transmitter station. The device can harvest RF microwave energy to energize the emergency light. This research aimed to develop a compact device that captures maximum RF strength to power emergency lights. As a prototype, the proposed device was designed to provide sufficient microwave energy to power an emergency light at 3 W over a 62 m distance. [ABSTRACT FROM AUTHOR]

The power take-off (PTO) torque measuring system was designed, which includes a torque transducer and a digital wireless system to receive, process, and display the observed PTO torque. A dynamic PTO torque transducer was developed using strain gauges to fit in between the PTO shaft of the tractor and the universal shaft of the implement and simulated using SolidWorks software with 1000 Nm twisting moment along with 100 N load. To transmit torque signals from the revolving PTO shaft, an embedded system was developed. The embedded system was tested in the laboratory and under actual field conditions. The digital wireless embedded system comprised an amplifier cum analog to digital converter to amplify the received signal from the torque transducer and convert it into a digital value. A microcontroller processes the digital value given by the amplifier, and radio frequency (RF) receiver module was mounted on the Xbee explorer to receive the transmitted data from the RF module of signal processing and transmitter unit. The developed system was tested under field conditions, and data were compared with the existing commercial torque transducer. The results showed that the relative deviation between the observed mean PTO torque values obtained from the developed torque transducer and that from the existing torque transducer was 8.57% and 9.06% at 2.5 km/h and 3.5 km/h, respectively. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a Doherty power amplifier (DPA) based on Class‐J power amplifier (PA) and Class‐J−1 PA is proposed for configurable Internet of things (IoT) transmitters. A post‐matching structure is used to achieve wider bandwidth performance, high efficiency, and power gain flatness. Different drain biases on the main and peaking devices are used to perform asymmetric operations. The proposed DPA structure achieves 62.4% power‐added efficiency (PAE) with a maximum output range of 37.38–38.20 dBm for the frequency band of 5.1–5.8 GHz and a power gain range of 13.24–12.24 dB. It has a maximum drain efficiency of 42.7%–51.5% at a back‐off power level of 9 dB. In order to validate the linearity of the proposed design, an analysis of the adjacent channel leakage ratio (ACLR) for various gate‐biased voltage operations is performed. The microchip occupies a compact die area of 2.1 mm × 1.2 mm, which is fabricated with GaAs 0.25 μm PHEMT to validate the enhanced broadband characteristics of the proposed configuration. Compared to the existing DPAs, the proposed DPA exhibits higher efficiency, output power, and compact size. [ABSTRACT FROM AUTHOR]

On-line performance monitoring of RF integrated circuits throughout their operating lifetime is a promising way to enhance their reliability. This paper explores the feasibility of adapting the indirect test strategy to implement on-line RF performance monitoring. After stating the principle of the proposed solution, we consider the fundamental requirements necessary to adapt the indirect test strategy. Finally, a proof of concept is established through a practical case of study by monitoring the power level delivered by the RF transmitter of a wireless microcontroller: hardware measurement results demonstrate the potential of this approach. [ABSTRACT FROM AUTHOR]

The fast development of the fifth-generation (5G) wireless systems and substantial growth of data usage have imposed stringent requirements for high-frequency and wideband radio frequency devices. Here, it is reported on a longitudinal leaky surface acoustic wave (LLSAW) mode acoustic resonator with a large electromechanical coupling factor ( k t 2 ), high operating frequency, and efficient spurious suppression. Through systematical finite element method simulations, available design spaces such as supporting substrate, propagation angle, and lithium niobate (LN) thickness have been fully investigated with the aim of stimulating the intended LLSAW and suppressing spurious modes concurrently. Optimization results reveal that the LLSAW mode wave propagating in X-35°Y LN/SiC piezoelectric-on-insulator (POI) bilayer structure possesses a large k t 2 without significant interference from other spurious modes. To verify the theoretical analyses, LLSAW resonators were fabricated and exhibited a near spurious-free response with the operating frequency over 6 GHz, and k t 2 as large as 22.7%. This work demonstrates a high-performance LLSAW resonator on the POI platform with a simple prototype as well as potentially providing a high-frequency filtering solution for 5G applications in the 6-GHz spectrum. [ABSTRACT FROM AUTHOR]

The nonlinearity of the fifth-generation (5G) millimeter-wave (mmWave) phased array transmitter (TX) depends on the variations in the beamforming coefficients, e.g., due to unwanted amplitude errors of the phase shifters or purposely introduced amplitude variations to shape the beam, as well as other analog component variations. Therefore, also the digital predistortion (DPD) coefficients depend on the beamforming coefficients and require a continuous update for different beamsteering directions in a conventional DPD. We propose a robust DPD approach that uses the average array response for DPD training. The average array response is estimated using the known experimental histogram of power amplifier (PA) input power variation resulting from the amplitude variations due to beamforming. The DPD training based on the average array response makes the DPD coefficients insensitive to beamforming variations. The proposed DPD strategy requires a shared feedback path for training and only a single set of DPD coefficients to linearize the array response in all beamsteering directions. The performance of the proposed DPD strategy is validated by over-the-air (OTA) measurements of a 28-GHz phased array TX over different steering angles. Experimental results show that the proposed DPD method using one set of DPD coefficients provides similar linearization performance across the steering angles compared with the DPD trained to all steering angles through the OTA reference antenna. [ABSTRACT FROM AUTHOR]

We propose a novel double-layered insulator configuration for a human-brain-implanted impulse radio ultra-wideband (IR-UWB) antenna. The dimension of the antenna is $10.0\times 11.0\times0.954$ mm3, including the dual-layer insulator. The insulator provides a dielectric loading effect of $\varepsilon _{r}~\approx ~50$ (lossless) for obtaining an improved radiating power and the broadband-impedance-matching characteristic in brain tissues. The outer layer is made of biocompatible 3-D printing material, and the inner insulator is filled with deionized water with $\varepsilon _{r}~\approx ~80$ and loss tangent (tan $\delta$) $\approx ~0.25$ at 4 GHz. A slotted UWB antenna with the proposed insulator is located between the emulated dura and CSF tissues inside the skull for brain signal detection. The design uses a multilayer phantom, mimicking the seven tissue layers of the brain. The impedance and radiation performance of the proposed antenna configuration are also discussed using the commercial high-precision human phantom model. The designed IR-UWB antenna shows a boresight radiation characteristic toward the top of the head with a proper high gain in the target frequency of 3–5 GHz. The computed expectations are verified experimentally. Furthermore, it is demonstrated that the UWB spectrum generated from a UWB radio-frequency (RF) transmitter can be transmitted stably using the proposed antenna as a transmitting antenna. In addition, the link budget of the system setup is analyzed. The improved gain characteristic of the antenna from the proposed dual-layer insulator can be utilized to retain the link margins while satisfying the UWB communication regulation and average specific absorption rate (SAR) limitation. [ABSTRACT FROM AUTHOR]

This paper describes the use of the Murchison Widefield Array, a low-frequency radio telescope at a radio-quiet Western Australian site, as a radar receiver forming part of a continent-spanning multistatic radar network for the surveillance of space. This paper details the system geometry employed, the orbit-specific radar signal processing, and the orbit determination algorithms necessary to ensure resident space objects are detected, tracked, and propagated. Finally, the paper includes the results processed after a short collection campaign utilising several FM radio transmitters across the country, up to a maximum baseline distance of over 2500 km. The results demonstrate the Murchison Widefield Array is able to provide widefield and persistent coverage of objects in low Earth orbit. [ABSTRACT FROM AUTHOR]

With the development of the Internet of Things (IoT) technology and the rapid deployment of open wireless access mobile networks (such as 5th Generation Wireless Networks [5G], New Radio [NR], Long Term Evolution [LTE], Wi-Fi, etc.), more and more devices result in multi-user interference (MUI) within the signal transmission range, and may even suffer attacks or interceptions from some malicious users. Therefore, while wireless communication brings convenience, the security of users’ private information is also facing a huge challenge. As a communication signal waveform sent from a transmitter has its unique radio frequency fingerprint (RF fingerprint), which can be used to identify and authorize the transmitter device. In this article, we investigate the RF fingerprint of waveforms sent from a Wi-Fi transmitter, and discuss how to reduce receiver influence on the RF fingerprint associated with a transmitter. In this work, we propose a receiver calibration method, and a weighted classifier combining decision algorithm to improve the RF fingerprint identification rate. We hope this research can be extended to a more complex electromagnetic environment like 5G networks. It is expected that the self-interference phenomenon between these 5G devices can be mitigated if RF fingerprint identification technology can be adopted. Additionally, the RF fingerprint technology can be helpful for the functions of unified management and cost-saving of telecommunication operators. [ABSTRACT FROM AUTHOR]

Nonorthogonal multiple access (NOMA) constitutes a promising technique in the fifth‐generation (5G) mobile networks. On the transmitter side, the concurrent usage of multiple antennas needs an appropriate count of parallel Radio Frequency (RF) chains at the front end. Owing to this consequence, it maximizes the power consumption, cost, and system complexity along with maximization in the antenna count. In order to tackle these aforesaid problems, some researchers prefer the Transmit Antenna Selection (TAS) for modeling the transmitter structure simple. The best antenna is selected opportunistically by an efficient TAS technique from multiple antennas and deploys a single RF chain for transmission. In this paper, a novel approach for optimized antenna selection in overlay CR networks using NOMA and SM is proposed via the usage of optimization tactics. To choose the desired respective antenna, this paper introduces a new Mean and Median Fitness Centered Moth flame Optimization (MM‐FCMO), which is the modified Moth Flame Optimization (MFO) Algorithm, which taken the core objectives such as power consumption and Mean Square Error (MSE). The MSE and power consumption of the chosen antennas have to be lower for the system to attain maximum antenna gain with lower noise. Finally, to exhibit that the presented work is much significant than the traditional works, a comparative analysis is made in terms of error minimization and statistical evaluation. [ABSTRACT FROM AUTHOR]

The complexity of electronic systems for RF and digital applications is ever increasing, and the corresponding compliance analysis for ensuring the required specifications in terms of performances, signal and power integrity is a challenging task often accomplished by relying on commercial circuit simulators. The modeling of multiport devices involves the assembly of electrical networks usually described in terms of S‐parameter. This work proposes a new single‐step algorithm that computes the global S‐parameter matrix for a cascade of multiple networks with multiple ports without the need of any S‐parameter transformation in T‐parameters and their inverse transformation. The proposed method involves the construction of a large matrix filled with all S‐parameters of all networks, and the subsequent evaluation of only one matrix expression. The proposed method is shown to be very efficient and reliable, since it can be easily automated without the need of a manual connections of tens or even hundreds of ports of the multiple blocks, which is an action that needs to be performed within a typical circuit simulator environment. Also, the proposed method overcomes the limitation of the standard method based on S‐to‐T parameter transformation since it is of general applicability to networks with different number of input and output ports. Examples involving the cascade of multiple 2‐ports and multiports networks are considered, and the results are validated and compared with the reference results obtained from a commercial circuit simulator. The proposed method is shown to be effective and fast compared to its counterpart based on the T‐parameters. [ABSTRACT FROM AUTHOR]

A novel type of photonic background-free multiband arbitrarily phase-coded microwave signal generator with power fading elimination capability is reported. An $x$ -polarized phase modulated optical signal and a $y$ -polarized radio frequency (RF) modulated harmonic single-sideband (HSSB) optical signal are produced based on a dual-polarization quadrature phase shift-keying modulator (DP-QPSKM). After polarization modulation to intensity modulation conversion, a microwave signal with arbitrarily phase encoding in multiple frequency bands is generated. Benefiting from the phase modulation state of the driven electrical coded signal, the generated arbitrarily phase-coded signal has no baseband components. Moreover, the equivalent HSSB modulation ensures the system can realize antidispersion transmission of one-to-multi base stations (BSs). The main distinct highlights of our generator are multifunction. The proposed single-modulator-based photonic scheme can achieve phase encoding in arbitrary format over multiple frequency bands and transmit over long-distance single-mode fiber with the elimination of power fading simultaneously. This work is pretty promising in multiband radar systems for one-to-multi BSs transmission and can increase the detection range, range resolution, Doppler tolerance, and sensitivity of objective recognition of radars. [ABSTRACT FROM AUTHOR]

In anticipation of the hybrid utilisation of the radio frequency (RF) wireless transceiver technology embedded in future smart Li-ion battery cells to deliver hybrid links based on power line communication (PLC) and wireless connections, herein we present an empirical high-frequency investigation of the direct current (DC) bus. The focus is to determine, via statistical tools including correlation coefficient (CC), root mean squared error (RMSE) and feature selective validation (FSV) method, the impedance and signal change impact on a possible communication link when fully charged cells are present or completely missing from the bus. Moreover, to establish if technological differences may be accounted for during the empirical experiments, Li-ion cells from two different manufacturers were selected and connected via three subsequent capacitive couplings of 1 µF, 1 nF and 1 pF. According to a methodical comparison by employing CC, RMSE, and FSV over the measured impedance and signal attenuation, this study has shown that the physical DC network is the dominant impedance at high frequencies and that the signal attenuation on the DC line supports communication in the investigated spectrum. The reported findings are critical for in situ hybrid PLC and wireless communication implementation of BMS for Li-ion systems supported through only one RF transceiver. [ABSTRACT FROM AUTHOR]

In recent days, Radio Frequency (RF) transmitter plays an important role in the Wireless Sensor Network (WSN). This transmitter uses Pulse Width Modulation (PWM) approach due to its lower power requirement. But, it is the major source of Electromagnetic Interference (EMI) because of its carrier frequency harmonics. In this work, a new RF transmitter is proposed using a chaotic sequence generator and modulation process for the reduction of EMI. The proposed chaotic sequence generator consumes less area and minimizes the hysteresis on the output signal. Furthermore, a Voltage-controlled Oscillator (VCO) with transmission gate tuning logic is proposed to control the oscillating frequency of VCO during RF carrier wave generation. The proposed VCO allows full swing among power rails by consuming less area and power. The proposed RF transmitter is simulated in Xilinx and LTspice working platforms by considering 0.18 μ m CMOS process. The simulation results show that the peak EMI of the proposed RF transmitter is reduced to 39.52 dB μ V, which is 10.56 dB less than that of the standard mode design. Furthermore, the proposed RF transmitter consumes only 0.475 mW power to transmit the RF signal. • Recently, RF transmitter plays an important role in WSNs. This transmitter uses PWM due to its lower power requirement. • he proposed chaotic sequence generator consumes less area and minimizes hysteresis on the output.signal. • A VCO with transmission gate tuning logic is proposed to control oscillating frequency during RF carrier wave generation. [ABSTRACT FROM AUTHOR]

A new dynamical model with five rigid frames (RFs), driven by two counter-rotating exciters, is proposed to explore the synchronization, stability, and motion characteristics of the system in this paper. The motion differential equations and the corresponding responses of the system are given firstly. Using the average method, the average torque balance equations for the two exciters are deduced. According to the relationship between the difference of the dimensionless effective output electromagnetic torques for the two motors and the coupling torques of the system, the theory condition of realizing synchronization is obtained. Based on the Hamilton's theory, the theory condition of stability of the system is deduced. The stability and motion characteristics of the system for different resonant regions are qualitatively discussed in numeric, including the stable phase difference of the two exciters, relative phase relationships among the five rigid frames, amplitude-frequency characteristics, stability coefficients, and the effective load torque between the two exciters. Simulations are carried out to further quantitatively validate the feasibility of the above theoretical and numerical qualitative results. It is shown that in engineering the reasonable working points of the system should be selected in Region II, only in this way, can the synchronous and stable relative linear motion of the system with the zero stable phase difference in vertical direction be realized, and in this case, the vibrations of the four inner rigid frames (IRFs) in the horizontal direction are compensated with each other, and the energy is also saved due to utilizing the resonant effect. Based on the present work, some new types of vibrating coolers/dryers or vibrating screening machines can be designed. [ABSTRACT FROM AUTHOR]

Bitstream modulated transmitters may offer improved power efficiency and linearity simultaneously in RF power amplifiers. Several modulation techniques including envelop delta-sigma modulation and envelope pulse width modulation have been applied. The out-of-band quantization noise associated with these modulations may be rejected by a high-quality factor output filter, yet the in-band quantization noise needs to be further suppressed to meet the requirement of the emission mask. The proposed channelized active noise elimination technique can offer additional quantization noise suppression through software control without involving a passive filter. The essential concept is based on combining the outputs of multiple channels of Pas that have digitally controlled delays to form a FIR filter in analogue domain. A two-channel and a four-channel GaN power amplifiers are built to demonstrate this noise suppression concept and power combiners based on T-junction with quarter wavelength transmission line are proposed to retain the high power efficiency of the transmitters. [ABSTRACT FROM AUTHOR]

In this article, we design and experiment a far-field wireless power transfer (WPT) architecture based on a distributed antenna system (DAS), so-called WPT DAS, that dynamically selects transmit antenna and frequency to increase the output dc power. Uniquely, spatial and frequency diversities are jointly exploited in the proposed WPT DAS with low complexity, low cost, and flexible deployment to combat the wireless fading channel. A numerical experiment is designed to show the benefits using antenna and frequency selections in spatially and frequency selective fading channels for single-user and multiuser cases. Accordingly, the proposed WPT DAS for single-user and two-user cases is prototyped. At the transmitter, we adopt antenna selection to exploit the spatial diversity and adopt frequency selection to exploit the frequency diversity. A low-complexity over-the-air limited feedback using an IEEE 802.15.4 RF interface is designed for antenna and frequency selections and reporting from the receiver to the transmitter. The proposed WPT DAS prototype is demonstrated in a real indoor environment. The measurements show that WPT DAS can boost the output dc power by up to 30 dB in a single-user case and boost the sum of the output dc power by up to 21.8 dB in the two-user case and broaden the service coverage area in a low cost, low complexity, and flexible manner. [ABSTRACT FROM AUTHOR]

Error vector magnitude (EVM) or alternately offset EVM (OEVM) is one of the most important performance to verify for RF circuits, such as ZigBee transmitters in order to ensure that the quality of the generated modulated signal complies with the requirements of the wireless communication standard. The conventional solution to measure this performance relies on the use of an automatic test equipment (ATE) equipped with expensive RF channels. This article presents a low-cost solution that permits to realize EVM measurement using only a standard digital ATE. The approach is based on 1-bit undersampled acquisition of the RF modulated signal by a digital tester channel associated with a specifically tailored processing algorithm. This algorithm involves many different steps that are detailed in this article, including phase and amplitude fluctuation extraction, RF signal reconstruction, symbol clock recovery, symbol bits detection, and synthesis of reference data for EVM calculation. The proposed digital test solution is first evaluated through lab hardware experiments and then validated with EVM measurements on an industrial ATE. [ABSTRACT FROM AUTHOR]

Introduction A protocol has not yet been developed to perform electroacoustic measurements and behavioral tests to fit the frequency modulation (FM) system in bone conduction hearing aid (BCHA) users. Electroacoustic verification, with “FM transparency”achieved, ensures user audibility of FM transmitter and hearing aid signals. Objective To propose and validate a protocol for electroacoustic verification of the FM system coupled to the BCHA. Method Twenty-four sets of FM system and BCHA were submitted to electroacoustic verification, using a receiver and a plastic adapter to connect the BCHA to a 2cc coupler in the hearing instrument analyzer. The measurements were performed in the acoustic box, at 65 dB sound pressure level (SPL), with International Speech Test Signal (ISTS), first to the BCHA microphone and then to the FM system microphone, to determine the transparency, in which equivalent inputs for both microphones result in equivalent outputs. The FM gain or volume has been adjusted to try to gain transparency for the outputs of the two input devices. Results Transparency was achieved for all sets evaluated, but in some combinations, adjustments to the FM receiver gain over the manufacturer’s default setting were required. Conclusion The proposed protocol proved to be effective for the electroacoustic verification of the FM system coupled to the BCHA. [ABSTRACT FROM AUTHOR]

In this study, harvesters, sensors and data acquisition cards were designed and tested to obtain data from transmission lines. In this context; numerical analyses of harvesters with two different core geometries were performed with Ansys Maxwell software. Then the voltage and power harvested by the harvesters at different line currents were measured with pre-tests in the laboratory. Analyses’ results and pre-test’s results were examined and it was determined that the geometric structure (double C) model suitable for use in overhead transmission lines with high current could be used. The field test was carried out on a distribution transformer. In the field test, the harvester mounted on the transformer supply line has charged the battery supplying the sensor circuit with sufficient power to ensure normal operation of the system. A circuit is designed to measure air temperature, humidity, pressure, altitude, air quality and transformer temperature and to transmit them to the remote distance with RF transmitter. Data received on the data collection card can be recorded at certain periods and time-based graphs of the data can be obtained by a computer interface program. The energy of this circuit is to meet the energy harvested from the electromagnetic field. [ABSTRACT FROM AUTHOR]

In this paper, a dynamic model is adopted to investigate the stability and response characteristics of a vibrating system driven by four vibrators placed on two different rigid frames (RFs). Using the equations of motion of the system derived, the conditions for synchronization and stable operation of the system are studied by the average method and Hamilton's rules, respectively. Based on the theoretical results obtained, some factors are further studied concerning the stable phase differences (SPDs), the coefficients for ensuring stability, and the vibration amplitudes of the two RFs in different resonant regions. These serve to reveal the stability and response characteristics of the system that determine the ultimate function of the vibrating machine. Finally, numerical simulations are carried out to examine the validity of the theoretical methods and numerical qualitative results. Based on the results from the theory and simulation analyses, it is suggested that the working region of the system should be selected in the sub-resonant region corresponding to the natural frequency (NF) of the main vibrating system in the x - and y -directions. In this case, the ideal relative circular motion for two RFs with a well isolation effect can be achieved, and the energy is saved. [ABSTRACT FROM AUTHOR]

The rapid growth of the so-called Internet of Things is expected to significantly expand and support the deployment of resource-limited devices. Therefore, intelligent scheduling protocols and technologies such as wireless power transfer, are important for the efficient implementation of these massive low-powered networks. This paper studies the performance of a wireless powered communication network, where multiple batteryless devices harvest radio-frequency from a dedicated transmitter in order to communicate with a common information receiver (IR). We investigate several novel selection schemes, corresponding to different channel state information requirements and implementation complexities. In particular, each scheme schedules the $k$ -th best device based on: a) the end-to-end (e2e) signal-to-noise ratio (SNR), b) the energy harvested at the devices, c) the uplink transmission to the IR, and d) the conventional/legacy max-min selection policy. We consider a non-linear energy harvesting (EH) model and derive analytical expressions for the outage probability of each selection scheme by using tools from high order statistics. Moreover, an asymptotic scenario in terms of the number of devices is considered and, by applying extreme value theory, the system’s performance is evaluated. We derive a complete analytical framework that provides useful insights for the design and realization of such networks. [ABSTRACT FROM AUTHOR]

Design methodologies are developed for complementary frequency modulated (FM) waveforms and for optimised complementary mismatched filtering (MMF) of arbitrary non‐repeating waveforms. The former is a sub‐class of random FM waveforms denoted as complementary FM (Comp‐FM) while the latter extends a practical instantiation of least‐squares mismatched filtering yielding the mismatched complementary‐on‐receive filtering (MiCRFt) scheme. Both of these approaches have an emphasis on the non‐ideal physical effects of the radar transmitter and receiver, thereby permitting high‐fidelity simulation analysis and subsequent experimental demonstration of their efficacy using open‐air measurements. [ABSTRACT FROM AUTHOR]

To develop low-power, low-cost Narrowband Internet-of-Things (NB-IoT) radio frequency (RF) transceiver chips, a novel hybrid polar transmitter architecture with an on-chip switching power amplifier (PA) is proposed. The transmitter consists of a hybrid supply modulator with a linear class-AB amplifier and a switching class-D amplifier for amplitude modulation. A two-point modulation frequency synthesizer is used for frequency modulation to achieve the error vector magnitude (EVM) and transmission spectrum optimization. Neither the receiver nor the transmitter requires an expensive surface acoustic wave (SAW) filter. The key parameters, such as the noise figure of the low-noise amplifier (LNA), phase noise and loop filter bandwidth of the frequency synthesizer, frequency step of the delta-sigma modulator and resolution of the digital-to-analog converter for the frequency modulation, are defined by the system-level simulation platform developed in the paper. Effects of the nonlinearity of the frequency-modulation varactor in the voltage-controlled oscillator (VCO) on EVM and transmission spectrum are also characterized. The architecture design and the system-level simulation provide a clear and quantifiable guidance to the circuit design of the NB-IoT RF transceiver. [ABSTRACT FROM AUTHOR]

Space modulation techniques (SMTs) have emerged as a family of multiple-input multiple-output (MIMO) transmitter designs that require a maximum of a single RF-chain. SMTs have been analyzed in the context of cost, power, and error performance in past studies and have shown to exert favorable advantages over traditional implementations such as spatial multiplexing (SMX). However, given future application requirements, analysis of the hardware also in the context of reliability becomes essential. In this work, an SMT hardware reliability analysis framework is devised using two quantitative analysis tools consisting of reliability block diagrams (RBDs) and Markov Chains. In addition, a comparative study using commercial component failure rates is performed to analyze how SMTs compare to each other. [ABSTRACT FROM AUTHOR]

In this communication, based upon a squeezed-state trial wave function, we have performed a simple variational study of the spectral collapse in the anisotropic two-photon Rabi model. Our analysis indicates that the light-matter interaction and the spin-flipping (together with the anisotropy) effectively constitute two competing impacts upon the radiation mode. Whilst the former tries to decrease the radiation mode frequency, the latter may counteract or reinforce it. The light-matter interaction appears to dominate the frequency modulation as its coupling strengths go beyond the critical values, leading to the emergence of the spectral collapse. However, at the critical couplings the dominance of the light-matter interaction is not complete, and incomplete spectral collapse appears. Accordingly, at the critical couplings the eigenenergy spectrum comprises both a set of discrete energy levels and a continuous energy spectrum. The discrete eigenenergy spectrum can be derived via a simple one-to-one mapping to the bound state problem of a particle of variable effective mass in a finite potential well, and the number of bound states available is determined by the energy difference between the two atomic levels. Each of these eigenenergies has a twofold degeneracy corresponding to the spin degree of freedom. [ABSTRACT FROM AUTHOR]

This article presents the hardware implementation of a space shift keying (SSK) multiple-input multiple-output (MIMO) system with no radio frequency (RF)-chain at the transmitter. The transmitter design was solely based on RF-switches. SSK relays information strictly through spatial symbols and does not require the generation of any modulated symbol. It has been always anticipated in literature that SSK can be implemented with a single or no RF chain, but the physical realizations were never accomplished. This work demonstrates a 4 × 2 and 2 × 2 MIMO implementation of an SSK system using commercial-off-the-shelf (COTS) RF-switches. As a result, the achieved implementation paves the way towards commercial deployments of space modulation techniques. A detailed discussion of the hardware implementation is presented and results reveal an accurate match with theoretical SSK results over a Rician fading channel with variant Rician K-factors. [ABSTRACT FROM AUTHOR]

A scheme for transportation of information with minimum Rayleigh backscattering (RB) noise to the multi-users by employing Qdash laser diode as a source is designed and evaluated. In this paper, employing digital phase shift keying, millimeter wave, 16-quadrature amplitude modulation orthogonal frequency division multiplexing (16-QAM OFDM), and 32-QAM OFDM techniques, the data rates of 4 × 10 Gbps are transmitted simultaneously over 50 km single mode fiber, plus 15 m wireless link, 50 m free space optical (FSO) link, 10 m wireless respectively. Four selective self-injection locked modes of Qdash laser are utilized as optical carriers for downstream and upstream transmission. To ensure the matter of mitigation of RB noise, which mainly arises due to the transmission of light-wave of same wavelengths in bidirectional transportation, the carrier signals of different wavelength are used for modulation and remodulation in optical line terminal and optical network unit. Besides being a strong support to increase the tolerance level against RB noise, this architecture is capable to transmit less noisy information wirelessly in radio frequency sensitive areas too. The constancy of the proposed architecture is evaluated by very low power penalty (~ 1.5–1.7 dB, ~ 2.4–2.6 dB, ~ 1.4–1.6 dB, ~ 1.7–1.8 dB for four channels respectively), clear constellation, prominent eye opening, low bit-error-rate (< 10–9 for pseudo random bit sequence data stream and < 3.8 × 10–3 for OFDM signal) and low error vector magnitude (< 12.4% for 16 QAM, < 10% for 32 QAM). Therefore, the proposed architecture could be promising alternative not only due to the scheme for mitigation of RB noise but also be a potent in the field of applications of the communication world to provide less noisy information to the multi-users (wired/wireless/FSO). [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) and ambient backscatter communication have been envisioned as two promising technologies for the Internet-of-things due to their high spectral efficiency and energy efficiency. Motivated by this fact, we consider an ambient backscatter NOMA system in the presence of a malicious eavesdropper. Under the realistic assumptions of residual hardware impairments (RHIs), channel estimation errors (CEEs) and imperfect successive interference cancellation (ipSIC), we investigate the physical layer security (PLS) of the ambient backscatter NOMA systems with emphasis on reliability and security. In order to further improve the security of the considered system, an artificial noise scheme is proposed where the radio frequency (RF) source acts as a jammer that transmits interference signals to the legitimate receivers and eavesdropper. On this basis, the analytical expressions for the outage probability (OP) and the intercept probability (IP) are derived. To gain more insights, the asymptotic analysis and corresponding diversity orders for the OP in the high signal-to-noise ratio (SNR) regime are carried out, and the asymptotic behaviors of the IP in the high main-to-eavesdropper ratio (MER) region are explored as well. Finally, the correctness of the theoretical analysis is verified by the Monte Carlo simulation results. These results show that compared with the non-ideal conditions, the reliability of the considered system is high under ideal conditions, but the security is low. [ABSTRACT FROM AUTHOR]

This research study was aimed to examine the role of radio communication in the adoption of modern agricultural technology among the farmers of district Jhang. Presently 33 governments owned public radio channels along with 57 FM Radio Transmitters while 240 private FM Radio channels (180 commercials and 60 non-commercials) are working in Pakistan. The study statement has been proved through empirical evidence as, "more the farmers will listen radio agri. programs, more they will adopt latest information and modern agricultural technology". This research was conducted among the farming community of district Jhang, which is a historical territory and agricultural hub of Punjab province and moreover mostly public and private radio channels are being listened there. The study provides a deep insight about land holding of farmers and it is proved that most of the farmers hold up to 12.5 acres' land (small scale farmers). It was noted that mostly farmers were illiterate while around one-fourth were matriculate. Less than a half of the farmers were listening agricultural radio programs regularly. Majority of the farmers reported that radio communication is helpful "to some extent" about the information for the preparation of soil, crop varieties, suitable fertilizers, sowing time and improved inputs (regarding drip irrigation, tunnel farming and hydroponic agriculture etc.). However mostly farmers adopted these technologies. Majority (67.3%) farmers told that information related to agriculture provided by the radio programs is helpful to increase the agricultural production and they were satisfied with the information disseminated by radio communication. It was found that there is a positive relationship between listening of broadcasted agricultural radio programs and awareness of agri. machinery and equipment. More duration of using radio resulted in the higher use of water management techniques. A positive relationship was observed between satisfaction with the dissemination of information through radio communication and increase in the agricultural production. It is also recommended that agricultural extension programs broadcasted by radio channels should be related to the actual needs of the farmers with the special focus to aware the farmers for the adoption of latest techniques and agricultural technologies having greater potential of production like as hydroponic agriculture, tunnel farming and drip irrigation etc. [ABSTRACT FROM AUTHOR]

To efficiently determine the plasma electron density fluctuations using the MIR diagnostic technique, a 55–75 GHz 65 nm-CMOS transmitter has been developed where four separate intermediate frequency (IF) signals are up-converted, amplified, and then combined to generate an 8-tone RF output; a broadband 90 nm-CMOS receiver has also been constructed, which consists of an RF-low noise amplifier (LNA), mixer, and IF amplifier. The circuits and their corresponding modules will soon be deployed on the DIII-D and NSTX-U fusion devices. A 110–140 GHz 65 nm-CMOS receiver has also been designed, which is suitable for measuring the deep-core temperature fluctuations in the DIII-D tokamak using the electron cyclotron emission imaging diagnostic system. In addition to the RF-LNA/balun, mixer, and IF amplifier, an LO balun/tripler and driving amplifier are now included in this highly integrated circuit chip. By adopting the microwave and millimeter-wave system-on-chip concept in the front-end system design, this paper demonstrates that compact transmitter and receiver modules can be easily built, which, in turn, facilitates array implementation and maintenance. [ABSTRACT FROM AUTHOR]

In this paper, a reconfigurable multi-mode Class-AB/F power amplifier (PA) is proposed for 0.1–4.2 GHz multistandard applications. The PA operates in linear mode (class-AB) for variable-envelope modulated signals and switching mode (class-F) for constant-envelope modulated signals. The proposed linear mode PA design is suitable for multi-band LTE, IOT, WSN and multi-standard RF transmitter, while switching mode PA design can be used in multi-band IOT-LPWA and BLE (Bluetooth Low Energy) RF transmitter. The proposed PA has a reconfigurable off-chip inter-stage and output matching networks over the specified frequency band, while the input stage is Complementary Current-Reuse common-gate with active shunt feedback configuration to achieve Ultra-Wideband (UWB) input matching. The proposed multi-mode PA is designed using a 130 nm CMOS process. Class-AB PA has a saturated output power of 23.5 dBm ± 1 dB over 0.1–4.2 GHz, a power-added efficiency (PAE) of 41%, a third-order intercept point (OIP3) of 17 dBm, and adjacent channel power ratio (ACPR) of − 29.3 dBc for LTE 15 MHz channel bandwidth. The maximum PAE of 62.1% under the class-F operation is achieved at output power of 24.5 dBm. The PA occupies 0.64 mm2 of chip area, while the estimated off-chip area is 13.3 mm2. The proposed PA consumes 164 mW, and 16 mW in class-AB and class-F, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the design, construction, and testing of a 183-GHz FMCW transceiver module for wireless fuse applications. The transmitter consists of a square-triangle wave converter, a Ku-band VCO, a 91.5-GHz × 2 × 3 multiplying and amplifying chain, a 10-dB multi-hole directional coupler, and a 183-GHz frequency doubler. For the multiplying chain, the generated 91.5-GHz signal power is partly coupled out by the 10-dB coupler. The coupled output power is used as local oscillator (LO) signal to pump the 183-GHz subharmonic mixer (SHM). The receiver is cascaded by a 183-GHz SHM and a low-noise immediate frequency (IF) amplifier. The measured typical output power of the 183-GHz transceiver is 48 mW and the minimum noise temperature of the receiver is 620 K at 181 GHz. At 5-mm and 10-mm detection distance, the measured signal noise ratio (SNR) of transceiver IF signal is higher than 30 dB and 17 dB at 10 KHz bandwidth, respectively. The SNR is high enough for the following signal processing. [ABSTRACT FROM AUTHOR]

A new behavioral model based on augmented time‐delay support vector regression (SVR) for multi‐device radio frequency (RF) nonlinear power amplifiers (PAs), is proposed in this paper. The theory of the proposed modeling technique is provided, along with a detailed modeling procedure. Experimental results show that the proposed new augmented SVR (NASVR) model leads to significant performance improvements when compared with basic SVR models and existing Augmented SVR (ASVR) models. When applied to a multi‐device Doherty PA, a normalized mean square error (NMSE) between model prediction and measurement data of −44.4 dB is obtained, representing a more than 9 and 4.5 dB improvement compared with the basic SVR model and the existing ASVR model, respectively. [ABSTRACT FROM AUTHOR]

This article presents an efficient digital telemetry transmitter with Offset Quadrature Phase Shift Keying (OQPSK) modulation for launch vehicle applications with direct modulation in RF carrier. Analog transmitters with phase modulation are widely used for data transmission in launch vehicles. To gain the advantage of digital modulation like bandwidth efficiency and power efficiency, a digital telemetry transmitter with OQPSK modulation and half rate Turbo coding was flown in ISRO's Human Space Programme Pad Abort Test Crew Escape System. In OQPSK, compared to conventional QPSK, the quadrature channel bits lag the in-phase channel bits by one bit period. This feature is an advantage of the OQPSK modulation technique as it overcomes the 180° phase transitions, eliminating the possibility of crossing through the origin. Thus it provides a narrow power spectrum with less inter-symbol interference. This transmitter is employed with direct modulation in S-band RF carrier as it provides a less complex and simple architecture compared to the conventional IF modulation and up-conversion techniques. [ABSTRACT FROM AUTHOR]

In this article, a novel duplexing rectenna with harmonic feedback capability is proposed for efficient wireless power transfer (WPT) applications. The proposed duplexing rectenna can harvest the incoming radio frequency (RF) energy efficiently and also make use of an inherent harmonic signal, which is sent back to the RF transmitter (Tx) for positioning in order to guide the radiation patterns from Tx antenna array for optimum WPT. A novel duplexing dipole antenna is designed based on the top loading and capacitive gap effects. It is used to receive RF power at fundamental frequency 0.915 GHz and transmit the second harmonic signals at 1.83 GHz as a feedback. Experimental validation of a complete WPT system with beam-scanning capability has been carried out. It is shown that the fabricated rectifier has realized a maximum RF-dc conversion efficiency of 71% (at 15-dBm input power) and a measured peak second harmonic power of −1 dBm. Thus, the proposed duplexing rectenna can form a closed-loop system by providing its location information for efficient WPT applications. [ABSTRACT FROM AUTHOR]

Space modulation techniques (SMTs) are shown to facilitate multiple-input multiple-output transmitter designs with a maximum of a single RF-chain. This article aims to review and summarize recent advancements in SMTs' hardware design and implementations. This includes a discussion of challenges, implementation issues, and the state of the art. Related contents covered in this article are transceiver designs, hardware challenges, practical deployment, and reliability. As well, potential future directions are highlighted. [ABSTRACT FROM AUTHOR]

Designing an active mixer such as Gilbert mixer for applications at high frequencies is always a challenging task for the designers to deal with. In this article, a double-balanced mixer is proposed using 90-nm CMOS technology for the unlicensed spectrum of 7 GHz around 60 GHz. The design of a mixer for the same frequency range was studied by various authors using 130-nm CMOS technology, but for the purpose of low-power applications, a well-suited method is proposed. The proposed mixer showed very good response and isolation between various ports of mixing circuit. The isolation between RF and LO ports is very crucial for the up-conversion mixers, and in communication systems, the RF isolation will be a critical area to design successful transmitters. The double-balanced up-conversion mixer in this work achieved a better isolation of 40 dB within the range of 56–67 GHz and a conversion gain of 4 dB for the defined frequency range with a power consumption of only 18 mW. [ABSTRACT FROM AUTHOR]