Wireless RF Research Articles

A Highly Pattern-Reconfigurable Planar Antenna With 360° Single- and Multi-Beam Steering

A novel single-fed horizontally polarized pattern-reconfigurable antenna is proposed with the key feature that is highly pattern-reconfigurable. The antenna is able to generate a large variety of radiation patterns, including omnidirectional, single-directive, and multi-beam patterns without using phase shifters. The antenna is based on a planar geometry, which consists of an Alford loop and four compact parasitic pixel rings with 60 integrated controlling units utilizing p-i-n diodes. Experimental and simulation results are provided for the proposed antenna design operating at 5 GHz. The results show that the single-beam steering with 7.3 dBi gain through 360° in the azimuth plane is achieved. Moreover, flexible dual-beam steering with one beam fixed and the other beam scanning independently among 360° in the azimuth plane is also demonstrated where each beam has 5 dBi gain. Other radiation modes, such as the omnidirectional mode, the tri-beam-steering mode, and the elevation plane steering mode, are also verified. The features of high pattern reconfigurability, 360° single-beam- and multi-beam-steering ability, full 3-D space scanning, planar geometry, and compatibility with a digital controller make it useful in various sub-6 GHz wireless applications, such as wireless power transfer, RF sensing, and analog precoding.

Design of remote injury diagnosis system for Wushu competition based on wireless sensor network

INTRODUCTION: In this paper, a remote injury diagnosis system for Wushu competition based on wireless sensor network is designed to improve the safety of athletes in the process of Wushu competition. OBJECTIVES: Improve the safety of athletes during martial arts competitions. METHODS: The pulse sensor, temperature sensor and ECG sensor are set as the terminal nodes of the remote injury diagnosis system for Wushu competition. The physiological parameters of athletes in Wushu competition are collected by the sensor, and the collected parameters are transmitted to the wireless RF module. The wireless RF module uses the wireless sensor network to realize the wireless communication of various parameter data through the routing node and terminal node, and transmits the data to the remote diagnosis module. The remote diagnosis module uses the collected physiological parameters of athletes to realize the remote diagnosis of injury in Wushu competition through particle swarm optimization-support vector machine diagnosis model. RESULTS: The experimental results show that the designed system can remotely collect the physiological parameters of athletes in Wushu competition, and remotely diagnose the injury of Wushu competition according to the collected data, and the diagnosis accuracy is as high as 99%. CONCLUSION: It has good safety performance and is of practical significance.

Investigation of link due to atmospheric turbulence in free space optical communication for optical wireless terrestrial networks

Abstract In recent years, wireless communication systems have exploded in popularity. Optical wireless technology is an excellent alternative to RF wireless, but it has high capacity, data speed, frequency, and license-free spectrum, and it is simple to implement. Optical wireless communication sends data through air using optical beams. Atmospheric turbulence degrades the functioning of free-breathing space photosensitive interaction methods by causing interruptions due to weather conditions like fog, smoke, and different pollutants. In this paper, free-space optical communications using snow and fog attenuations and Numerical Weather Prediction (NWP) method is used to determine the turbulence due to the atmosphere. This method improves the data transmission during unfavorable weather conditions by changing the various parameters like receiver aperture size, the wavelength of the transmitter, etc. Furthermore it shows that decrease in air quality and instability are the double significant causes, that can degrade general usage routine, especially when it’s foggy or raining heavily. The result shows that the aperture size and wavelength should be changed as per the weather condition.

Blind Stick Using Ultrasonic Sensor with Voice Announcement

Abstract: Traditionally visually impaired people used a stick to find out if any obstacles are present in front of them. The ultrasonic blind walking stick is way more advanced than the traditional walking stick as the use of sensors makes object detection easier. The system has one more advanced feature integrated to help the blind find their stick if they forget where they kept it. A wireless RF based remote is used for finding the lost stick by pressing the remote button and buzzer sounds on stick. Thus this system allows for obstacle detection as well as finding stick if misplaced by visually disabled person. The another feature of this stick is to detect water on the ground. This stick also indicate day or night vision for blind person. This project discuss about how this stick is built and how it will help blind people.

Hybrid 10 Gbps/20 GHz RF wireless and 10 Gbps FSO communication network employing POLMUX with OFDM modulation technique

Hybrid 10 Gbps/20 GHz RF wireless and 10 Gbps FSO communication network employing POLMUX with OFDM modulation technique

Deep Unfolding of Iteratively Reweighted ADMM for Wireless RF Sensing.

We address the detection of material defects, which are inside a layered material structure using compressive sensing-based multiple-input and multiple-output (MIMO) wireless radar. Here, strong clutter due to the reflection of the layered structure’s surface often makes the detection of the defects challenging. Thus, sophisticated signal separation methods are required for improved defect detection. In many scenarios, the number of defects that we are interested in is limited, and the signaling response of the layered structure can be modeled as a low-rank structure. Therefore, we propose joint rank and sparsity minimization for defect detection. In particular, we propose a non-convex approach based on the iteratively reweighted nuclear and -norm (a double-reweighted approach) to obtain a higher accuracy compared to the conventional nuclear norm and -norm minimization. To this end, an iterative algorithm is designed to estimate the low-rank and sparse contributions. Further, we propose deep learning-based parameter tuning of the algorithm (i.e., algorithm unfolding) to improve the accuracy and the speed of convergence of the algorithm. Our numerical results show that the proposed approach outperforms the conventional approaches in terms of mean squared errors of the recovered low-rank and sparse components and the speed of convergence.

Simultaneous Transmission of 5G MMW and Sub-THz Signals Through a Fiber-FSO-5G NR Converged System

Simultaneous transmission of fifth-generation (5G) millimeter-wave (MMW) and sub-THz signals through a fiber-free-space optical (FSO)-5G new radio (NR) converged system is successfully achieved. It is an inventive demonstration that utilizes a cross medium of optical fiber, optical wireless, and RF wireless to enhance the aggregate transmission rate to 60 Gb/s. We transmitted 20 Gb/s in the 50-GHz MMW, 100-GHz sub-THz, and 150-GHz sub-THz bands at the same time through the seamless fiber-FSO-5G NR convergence, comprising 20-km single-mode fiber (SMF), 500-m optical wireless, and 2-m (50-GHz MMW)/1-m (100-GHz sub-THz)/0.5-m (150-GHz sub-THz) 5G wireless transmissions. Sufficiently low bit error rate (< forward error correction criterion of 3.8×10^−3) and error vector magnitude (<third-generation partnership project limit of 12.5%) are attained to satisfy the requirements of 5G NR communications in MMW and sub-THz bands. This newly-built fiber-FSO-5G NR converged system shows promise for the development of long-haul wired-wireless transmissions with wider service areas and higher access data rates.

A Highly Miniaturized, Chronically Implanted ASIC for Electrical Nerve Stimulation.

We present a wireless, fully implantable device for electrical stimulation of peripheral nerves consisting of a powering coil, a tuning network, a Zener diode, selectable stimulation parameters, and a stimulator IC, all encapsulated in biocompatible silicone. A wireless RF signal at 13.56 MHz powers the implant through the on-chip rectifier. The ASIC, designed in TSMC's 180 nm MS RF G process, occupies an area of less than 1.2 mm2. The IC enables externally selectable current-controlled stimulation through an on-chip read-only memory with a wide range of 32 stimulation parameters (90-750 µA amplitude, 100 µs or 1 ms pulse width, 15 or 50 Hz frequency). The IC generates the constant current waveform using an 8-bit binary weighted DAC and an H-Bridge. At the most power-hungry stimulation parameter, the average power consumption during a stimulus pulse is 2.6 mW with a power transfer efficiency of ∼5.2%. In addition to benchtop and acute testing, we chronically implanted two versions of the device (a design with leads and a leadless design) on two rats' sciatic nerves to verify the long-term efficacy of the IC and the full system. The leadless device had the following dimensions: height of 0.45 cm, major axis of 1.85 cm, and minor axis of 1.34 cm, with similar dimensions for the device with leads. Both devices were implanted and worked for experiments lasting from 21-90 days. To the best of our knowledge, the fabricated IC is the smallest constant-current stimulator that has been tested chronically.

Low Phase-Noise, 2.4 and 5.8 GHz Dual-Band Frequency Synthesizer with Class-C VCO and Bias-Controlled Charge Pump for RF Wireless Charging System in 180 nm CMOS Process

This paper presents an integer-N phase-locked loop (PLL) for an RF wireless charging system. To improve the phase-noise characteristics under low power, a constant amplitude control class-C voltage-controlled oscillator (VCO) with a DC-DC converter, and a bias-controlled charge pump with a feedback loop are proposed. The frequency range of the VCO is 4.5–6.1 GHz, the target frequency of the proposed PLL is 2.4 and 5.8 GHz in the industry–science–medical band. It is designed with a same phase margin and bandwidth using one loop filter. The proposed PLL consumes less than 8 mW from a 1.8 V power supply with a settling time of fewer than 20 μs and an area of 1200 μm × 800 μm in the 180 nm CMOS process. For a carrier frequency offset of 1 MHz, the measured phase noise is −118.5 dBc/Hz at 2.4 GHz and −116.6 dBc/Hz at 5.8 GHz. Its FoM including the phase noise is −197 dB at 2.4 GHz and −202.8 GHz at 5.8 GHz, outperforming other PLLs designed in the 180 nm CMOS process.

Online computation offloading and trajectory scheduling for UAV-enabled wireless powered mobile edge computing

The unmanned aerial vehicle (UAV)-enabled mobile edge computing (MEC) architecture is expected to be a powerful technique to facilitate 5G and beyond ubiquitous wireless connectivity and diverse vertical applications and services, anytime and anywhere. Wireless power transfer (WPT) is another promising technology to prolong the operation time of low-power wireless devices in the era of Internet of Things (IoT). However, the integration of WPT and UAV-enabled MEC systems is far from being well studied, especially in dynamic environments. In order to tackle this issue, this paper aims to investigate the stochastic computation offloading and trajectory scheduling for the UAV-enabled wireless powered MEC system. A UAV offers both RF wireless power transmission and computation services for IoT devices. Considering the stochastic task arrivals and random channel conditions, a long-term average energy-efficiency (EE) minimization problem is formulated. Due to non-convexity and the time domain coupling of the variables in the formulated problem, a low-complexity online computation offloading and trajectory scheduling algorithm (OCOTSA) is proposed by exploiting Lyapunov optimization. Simulation results verify that there exists a balance between EE and the service delay, and demonstrate that the system EE performance obtained by the proposed scheme outperforms other benchmark schemes.

Flexible boron nitride composite membranes with high thermal conductivity, low dielectric constant and facile mass production

With the ever-increasing development of 5G technology, high signal propagation loss and high heating flux in miniaturizing devices bring about simultaneous and urgent requirement for thermal management materials with insulating, flexible, highly thermal conductive and low dielectric properties. However, these properties are not easy to simultaneous implement due to the phonon scattering and interfacial polarization, bringing a negative impact on working efficiency and service life of high-power electronics and portable devices. Herein, the flexible boron nitride composite membranes with high thermal conductivity, low dielectric constant and facile mass production was successfully prepared by coating directional forming and vacuum pressure technology. The directional arrangement of 2D boron nitride nanosheets (BNNS) in boron nitride-enhanced heat spreaders (BNHS) made the heat diffuse along in-plane direction and effectively improve the TC as high as 81.49 Wm−1K−1. In addition, the BNHS had a series of advantages of good electric insulation (the order of 1013 Ω cm), low dielectric constant (ϵ＜3) and low dielectric loss in the frequency range of 1 MHz–1 GHz. The BNHS also exhibited excellent flexibility (bending 20,000 times), high thermal stability and low water absorption. Distinguishing from electroconductive and heat-conducting graphite or graphene films, such superior BNHS with electric insulation but high TC and low dielectric constant will carve a distinctive path in the application of thermal management materials, such as RF antenna, filter, resonator and wireless charger.

Mobility-Aware Performance in Hybrid RF and Terahertz Wireless Networks

Using tools from stochastic geometry, this paper develops a tractable framework to analyze the performance of a mobile user in a two-tier wireless network operating on sub-6GHz and terahertz (THz) transmission frequencies. Specifically, using an equivalence distance approach, we characterize the overall handoff (HO) probability in terms of the horizontal and vertical HO and mobility-aware coverage probability. In addition, we characterize novel coverage probability expressions for THz network in the presence of molecular absorption noise and highlight its significant impact on the users’ performance. Specifically, we derive a novel closed-form expression for the Laplace Transform of the cumulative molecular noise and interference observed by a mobile user in a hybrid RF-THz network. Furthermore, we provide a novel approximation to derive the conditional distance distributions of a typical user in a hybrid RF-THz network. Finally, using the overall HO probability and coverage probability expressions, the mobility-aware probability of coverage has been derived in a hybrid RF-THz network. Our mathematical results validate the correctness of the derived expressions using Monte-Carlo simulations. The results offer insights into the adverse impact of users’ mobility and molecular noise in THz transmissions on the probability of coverage of mobile users. Our results demonstrate that a small increase in the intensity of terahertz base-stations (TBSs) (about 5 times) can increase the HO probability much more compared to the case when the intensity of RF BSs (RBSs) is increased by 100 times. Furthermore, we note that high molecular absorption can be beneficial (in terms of minimizing interference and molecular noise) for specific deployment intensity of TBSs and the benefits can outweigh the drawbacks of signal degradation due to molecular absorption.

Ageing Characterization Under Thermal Test of a Receiver Unit for a Radio Telescope

The Square Kilometer Array low (SKAlow) is an outstanding project aiming at building the world’s largest and most sensitive radio telescope. The Australian Murchison Shire desert has been chosen as location for the low-frequency antennas because of many reasons, such as the atmospheric above the site and the radio quietness due to one of the most remote location worldwide. This location is the optimal choice by a radio astronomy and RF engineering point of views. However, it brings several drawbacks in terms of system availability due to the high temperature conditions that deeply affect the electronics reliability, and the difficulties and the costs associated to maintenance tasks performed in a remote location. Thus, it is fundamental to study the reliability and functional performances of the auxiliary electronic devices in the antennas array using adequate aging tests under temperature stress conditions. The experimental activities carried out in this work allowed to investigate the outbreak of failure mechanisms due to aging and hot temperature conditions in the receiver unit for low-frequency antennas of the SKA project. The experimental results are intended to better determine the strengths and weaknesses of the device under test in order to optimize its installation, its maintenance operations and its functionalities.

Design of a Compact Novel Stub Loaded Pentaband Bandpass Filter for Next Generation Wireless RF Front Ends

This paper presents a compact novel pentaband bandpass filter using a dual path stub loaded step impedance resonator (SLSIR). The proposed topology consists of a dual path λ/4 and 2λ/3 long uniform impedance resonator centered separated by 2λ/3 open and λ/12 short circuit stubs respectively. The superposition of signals from the two transmission routes results in a fifth-order pentaband bandpass response with six finite frequency transmission zeroes and out-of-band rejection of 11dB from 12 GHz up to 20 GHz. The filter produces five frequency bands at 1.06 GHz, 3.24 GHz, 5.36 GHz, 8.55 GHz and 10.78 GHz with fractional bandwidth (FBW) of 25.59%, 22.22%, 19.48%, 16.03% and 17.17% respectively. The proposed design is fabricated on a high-frequency substrate with a physical size of (0.23λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>g</i></sub> × 0.14 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>g</i></sub> ). The new pentaband bandpass filter has a simple and compact design with good electrical performance. A fair match can be found between the simulated and experimental results.

Performance Analysis of Wireless Power Transfer Enabled Dual Hop Relay System Under Generalised Fading Scenarios

Dual-hop relay communication systems have received extensive research attention due to their property of improving system reliability, spectral and power efficiency. RF wireless power transfer has also become a popular green technology for remote supply of energy to communication devices. In this paper a RF wireless power transfer enabled dual hop relay system is analysed over generalised fading scenarios. A closed form expression is derived for the outage probability of the decode and forward as well as amplify and forward systems valid for all fading scenarios. Based on this analysis, the optimum design parameter settings for the system are also presented which serve as reference point for measuring the outage performance of other variant of the generalised system. The numerical results obtained from derived expressions are compared with Monte-Carlo simulations and are found to be in excellent agreement with each other.

Compact and High-Efficiency Rectenna for Wireless Power-Harvesting Applications

A compact, single-layer microstrip rectenna for dedicated far-field RF wireless power-harvesting applications is presented. The proposed rectenna circuit configurations including multiband triple L-Arms patch antenna with diamond slot ground are designed to resonate at 10, 13, 17, and 26 GHz with 10 dB impedance bandwidths of 0.67, 0.8, 2.45, and 4.3 GHz, respectively. Two rectifier designs have been fabricated and compared, a half wave rectifier with a shunted Schottky diode and a voltage doubler rectifier. The measured and simulated maximum conversion efficiencies of the rectifier using the shunted diode half-wave rectifier are 41%, and 34%, respectively, for 300 Ω load resistance, whereas they amount to 50% and 43%, respectively, for voltage doubler rectifier with 650 Ω load resistance. Compared to the shunted rectifier circuit, it is significant to note that the voltage doubler rectifier circuit has higher efficiency. Both rectifier’s circuits presented are tuned for a center frequency of 10 GHz and implemented using 0.81 mm thick Rogers (RO4003c) substrate. The overall size of the antenna is 16.5 × 16.5 mm2, and the shunted rectifier is only 13.3 × 8.2 mm2 and 19.7 × 7.4 mm2 for the voltage doubler rectifier. The antenna is designed and simulated using the CST Microwave Studio Suite (Computer Simulation Technology), while the complete rectenna is simulated using Agilent’s ADS tool with good agreement for both simulation and measurements.

Wireless Power Transfer and RF Technologies

This book contains the successful submissions [...]

Van der Waals crystal radio with Pt/MoSe2 Schottky diode and h-BN capacitor for RF energy harvesting

Two-dimensional (2D) semiconductor-based devices are mostly using in-plane direction current in their device architecture, to justify the novelty of 2D-like ultrathin electron devices beyond conventional 3D devices. Those ultrathin 2D devices, however, would unavoidably meet high contact resistance issue. In the present study, thick 2D-layered crystals are rather chosen for a meaningful vertical device, which alleviates the contact resistance issue using a large contact area. Here, we have fabricated Pt/120 nm-thick MoSe2 Schottky diodes with different Ohmic metal contacts of Au, Ti/Au, and MoTi/Au. These diodes are then monolithically integrated with a capacitor of ~20 nm-thick h-BN or 50 nm-thick ALD Al2O3. This way, van der Waals crystal radios are successfully fabricated for wireless RF energy harvesting. In terms of crystal radio device performance, the best results come from Pt/n-MoSe2 Schottky diode with MoTi contact and h-BN capacitor combination. This superiority is attributed to the excellent Ohmic behavior of MoTi alloy contact. At last, when AM demodulation experiments are conducted with 1 MHz carrier frequency/audio frequency-mixed signals, the crystal radio with MoTi demonstrates the highest output DC voltage envelope, allowing loud audio sound.

CP Antenna with 2 × 4 Hybrid Coupler for Wireless Sensing and Hybrid RF Solar Energy Harvesting.

The main challenge faced by RF energy harvesting systems is to supply relatively small electrical power to wireless sensor devices using microwaves. The solution is to implement a new device in a circularly polarized rectenna with circular polarization sensitivity integrated with a thin-film solar cell. Its dual-feed antennas are connected to a 2 × 4 asymmetric hybrid coupler and a multi-stage voltage doubler rectifier circuit. This configuration has a 2 × 4 asymmetric hybrid coupler used to produce 4 outputs with a 90-degree waveform phase difference. The two ports can independently be connected to the wireless sensor circuit: radiofrequency harvesting of hybrid energy solar and information equipment can be carried out with these two antennas. The Dual-Feed circular patch antenna has a two-port bandwidth of 137 MHz below −15 dB and an axial ratio of less than 3 dB, with a center frequency of 2.4 GHz with directional radiation and a high gain of 8.23 dB. It can be sensitive to arbitrary polarization of the input voltage multiplier waveform to overcome uncertainty in empirical communication environments. A parallel structure is arranged with a thin film solar cell integration from the transmitter with an output voltage of 1.3297 V with a compact composition and RF energy. The importance of adopting a wireless sensor strategy with circular polarization sensitivity and integrated RF solar energy harvesting rather than a single source method makes this research a significant novelty by optimizing the analysis of multiple wireless sensor signal access.

Bi-Directional Fiber-FSO-5G MMW/ 5G New Radio Sub-THz Convergence

A bi-directional fiber-free-space optical (FSO)-fifth-generation (5G) millimeter-wave (MMW)/5G new radio (NR) sub-THz convergence with intensity-modulated downlink 40 Gbit/s/100 GHz 5G NR sub-THz signals ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -polarizations), and phase-modulated uplink 10 Gbit/s/28 GHz and 10 Gbit/s/24 GHz 5G MMW signals is established practicably, by adopting a parallel/orthogonally polarized dual-carrier mechanism, phase modulators, and remote injection locking distributed feedback laser diodes (DFB LDs) for demonstration. It is a pioneering work to realize a bi-directional fiber-FSO-5G MMW/5G NR sub-THz convergence for providing high downlink/uplink traffic capacity with accepted transmission performance. Through 20 km single-mode fiber transmission, 500 m free-space link, and 1 m/4 m RF wireless transport, impressively low bit error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> and accepted PAM4/NRZ eye diagrams are acquired. Such established bi-directional fiber-FSO-5G MMW/5G NR sub-THz convergence accelerates a feasible solution that can afford high traffic capacity with qualified transmission performance, and develops the state achieved by the incorporation of optical fiber network with FSO-5G MMW/5G NR sub-THz convergence. It discloses a brilliant convergence developed for bi-directional high-speed and long-reach transmission with given transmission performance.