Wireless RF Research Articles

Guest Editorial

Radio and Wireless Week (RWW) has emerged as the flagship winter meeting point of the IEEE Microwave Theory and Techniques Society (MTT-S). Its last edition was held in Orlando (Rosen Plaza Hotel), FL, USA, on January 20–23, 2019, and consisted of five related conferences in a four-day event that focused on the intersection between wireless communication theory, systems, circuits, and device technologies, and emerging applications, including RF wireless sensing. It resulted in a unique forum for engineers and practitioners to exchange their ideas about main RF technologies and techniques for the state-of-the-art wireless systems and their end-use applications. In particular, RWW 2019 was composed of the Radio and Wireless Symposium (RWS), the Topical Conference on Power Amplifiers for Wireless and Radio Applications (PAWR), the Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SIRF), the Topical Conference on Wireless Sensors and Sensor Networks (WiSNet), and the Topical Workshop on the Internet of Space (TWIoS). This was the first year that the RWW was co-located with the ARFTG Microwave Measurement Conference, as the premier forum in RF, microwave, and millimeter-wave measurements, calibration, and uncertainty, as well as with the IEEE Internet-of-Things (IoT) Summit, to bring together researchers, policy makers, and companies in the Internet-of-Space (IoS) sector.

Design of Ultra Wideband Rectenna for Ambient RF Energy Harvesting Applications

In this paper a single fed microstrip patch ultra-wideband rectenna for harvesting ambient radio frequency energy is presented. The rectenna comprises of a rectangular shaped radiating patch operating at L band frequencies. The rectifier circuit is placed in the same plane of radiating patch to minimize the overall rectenna profile. The rectenna is modelled and are fabricated on low loss roger dielectric substrate. Measured results shows that the rectenna attains a maximum gain of 5 dB in the operating L band with maximum RF conversion efficiency of 81%. The rectenna designed is appropriate for harvesting wireless RF signals operating in L band.

Wearable Wireless Sensor System with RF Remote Activation for Industrial Applications

These days , Sensors are playing very important role in the world with combination of Wireless Technology.Wireless Sensor System makes the human life simpler and smarter . This emerging Technology helps in Industrial Applications .Safety and Security standards to employee position observation and industrial premises monitoring is also important towards safety Industrials. In this paper we are introducing advanced sensor system called Wearable Wireless Sensor System . It is the combination of Wireless Sensors and Wearable Technology for significant safety enhancement in Industrials. We built up a wearable wireless sensor framework which is appended in a consistent wearable format & utilized to work environment observation. Wireless Sensors are temperature, smoke sensor and LPG Gas sensor. The fundamental element of designed framework is likelihood could be actuated wirelessly through a RF module with radio signal at a frequency of 850MHz to 865MHz .It performs different wearable sensing module framework, for example, changing the framework from rest, estimation, and information transmission modes when outside RF sign is accessible. The exploratory information exhibit that the actuation separation distance is 2.8 m to a RF module with an intensity of 28 dBm. Advanced Wearable System framework can signalize about worker nearness in connection to offices. If any alert through high temperature, smoke or gas leakage RF wireless module alert us through buzzer and we control the same thing through Wireless Technology. All info and out modules are interfaced to ARDUINO Microcontroller with procedure input information and furnish yield with assistance of 5V controlled power supply. In this task we utilized Arduino ide programming to compose c program and accumulating.

Recent Advances and Future Directions on Underwater Wireless Communications

More than 75% of the Earth surface is covered by water in the form of oceans. The oceans are unexplored and very far-fetched to investigate due to distinct phenomenal activities in the underwater environment. Underwater wireless communication (UWC) plays a significant role in observation of marine life, water pollution, oil and gas rig exploration, surveillance of natural disasters, naval tactical operations for coastal securities and to observe the changes in the underwater environment. In this regard, the widespread adoption of UWC has become a vital field of study to envisage various military and commercial applications that have been growing interest to explore the underwater environment for numerous applications. Acoustic, Optical and RF wireless carriers have been chosen to be used for data transmission in an underwater environment. The internet of underwater things (IoUT) and next-generation (5G) networks have a great impact on UWC as they support the improvement of the data rate, connectivity, and energy efficiency. In addition to the potential emerging UWC techniques, assisted by 5G network and improve existing work is also focusing in this study. This survey presents a comprehensive overview of existing UWC techniques, with possible future directions and recommendations to enable the next generation wireless networking systems in the underwater environment. The current project schemes, applications and deployment of latest amended UWC techniques are also discussed. The main initiatives and contributions of current wireless communication schemes in underwater for improving quality of service and quality of energy of the system over long distances are also mentioned.

Integrated On-Chip Transformers: Recent Progress in the Design, Layout, Modeling and Fabrication.

On-chip transformers are considered to be the primary components in many RF wireless applications. This paper provides an in-depth review of on-chip transformers, starting with a presentation on the various equivalent circuit models to represent transformer behavior and characterize their performance. Next, a comparative study on the different design and layout strategies is provided, and the fabrication techniques for on-chip implementation of transformers are discussed. The critical performance parameters to characterize on-chip transformers, such as the Q-factor, coupling factor (k), resonance frequency (fSR), and others, are discussed with reference to trade-offs in silicon chip real-estate. The performance parameters and area requirements for different types of on-chip transformers are summarized in tabular form and compared. Several techniques for performance enhancement of on-chip transformers, including the different types of micromachining and integration approaches stemming from MEMS (microelectromechanical systems) technologies are also analyzed. Lastly, the different uses and applications of on-chip transformers are discussed to highlight the evolution of on-chip transformer technology over the recent years and provide directions for future work in this field.

A 5.8 GHz Low-Power Energy Harvester for RF Wireless Power Transfer Systems

This paper presents the design and implementation of an RF energy harvester system at 5.8[Formula: see text]GHz for low-power wireless transmission applications. The potential application of the proposed system is to wirelessly power sensor nodes. First, a design methodology of the rectifier based on a theoretical approach is presented. The simulation results show an excellent correlation with the theoretical ones, proving the accuracy of the proposed design methodology. A prototype is fabricated and the simulation results are validated by the measurements. Then, the rectenna is combined to a commercial power management circuit and a load which emulates the behavior of a sensor. The power management circuit boosts and regulates the output DC voltage as well as stores the collected energy into a capacitor. Finally, the complete system is experimentally tested and excellent performances are demonstrated. The efficiency of the RF energy harvester is 24% at [Formula: see text]10[Formula: see text]dBm input power and 47% at [Formula: see text]5[Formula: see text]dBm input power which are the highest reported measured efficiencies at this frequency and at those power levels. The complete rectenna system is able to harvest 4.62[Formula: see text]mJ in 40 s and 192[Formula: see text]s for [Formula: see text]6[Formula: see text]dBm and [Formula: see text]10[Formula: see text]dBm input power, respectively allowing us to power wirelessly low-power electronic devices.

Wireless charging system using spectral energy harvesting technique

<p>This paper presented the energy harvester circuit to enable wireless charging method. The wireless RF spectrum is abundant and potent in the public locations, which can be used for energy harvesting purpose. This is supported by the fact that RF signals are ubiquitous and do not require propagation media of any sort. The system is developed using optimal antenna, matching circuit and charge pump circuit. The 2x2 array type patch antenna operated at 924 MHz is designed and simulated using High Frequency Simulator. The antenna works as a transducer to capture and measure the RF signals from freely available energy source. The field study was conducted at three different highly populated locations such as place of education, place of residence, and place of transport using Software Defined Radio (SDR). The respective acquired RF energy values are -10.45 dBFS (morning), -10.45 dBFS (noon), and -13.33 dBFS (night) at the place of transport for the demonstration purpose. The antenna parameters study also conducted and proved that the antenna gain is good which is greater than 6.6 dB and also return loss greater than -43dB. In addition, charge pump circuit is designed and shown to be capable of boosting the voltage more than 2.5 V easily at the different frequencies for wireless charging purpose.<em></em></p>

Selective switching dual-transmission scheme in multi-LED Hybrid VLC-P2P networking system

In this paper, we propose a technique to solve the physical interference phenomenon occurring in the hybrid VLC-P2P network system Visible light communication (VLC) utilizing indoor lighting infrastructure is advantageous for establishing a wireless peer-to-peer (P2P) network environment. However, unlike RF wireless network environments, adjacent lighting and the optical wavelengths of multiple light sources cause interference among one another, greatly degrading the performance of the network system. In an actual indoor environment in which a plurality of lights exist, the received signal power differs for each LED according to the position of the receiver, and the LEDs interfere with each other. In addition, since each LED light source has a narrow field of view (FOV), the receiver located at the cell boundary receives increased interference. Since the visible light communication system uses the IM-DD system, the system performance is significantly degraded from such interference. To solve this problem, we propose selective switching dual –transmission (SSDT) for a multi-LED-VLC system. The proposed scheme can divide the received power range into three areas of the cell where the receiver is located. These include: area 1, where the target receiving signal power range is largest; area 2, where the range of interference signal power of adjacent LED is large; and area 3, where the received power occurs at cell boundary. Therefore, the receiver detects a signal having a different received power according to the receiver position in the current cell. If the target signal has the largest received power, it is used as it is. If interference signals from adjacent LEDs are detected, the interference cancellation technique using the difference in received power is used to eliminate the interference. If the receiver is located at the boundary of the cell, it becomes difficult to distinguish the interference signal component of each LED, so each LED is switched to cooperative communication. Through this scheme, the performance of the whole VLC-P2P network system can be improved by selective transmission according to the position of the receiver.

A High-Frequency Inverter for Variable-Load Operation

This paper presents a new inverter architecture suitable for driving widely varying load impedances at high frequency (HF, 3–30 MHz) and above. We present the underlying theory and design considerations for the proposed architecture along with a physical prototype and efficiency optimizing controller. The HF variable-load inverter (HFVLI) architecture comprises two HF inverters with independently controllable amplitude and phase connected together and to the load via a lossless power combining network, implemented here as an immittance converter. By controlling the amplitudes and relative phase of the two constituent inverters, the loading seen by each constituent inverter can be kept in a desirable range even for wide variations in load impedance. This allows for the use of highly efficient zero-voltage switching inverters that would otherwise be precluded or limited in applications presenting wide impedance ranges, such as wireless power transfer and RF plasma generation. The prototype HFVLI system demonstrates the benefits of the proposed approach. It operates at 13.56 MHz and can supply a maximum output power of 1 kW into a 21.8 + 0.3j load at an efficiency of 95.4% and is able to drive a wide range of capacitive and inductive loads at high power with high efficiency.

인지 라디오 RF 하베스팅 IoT 네트워크의 자원 최적화

인지 라디오 RF 하베스팅 IoT 네트워크의 자원 최적화

Highly Linear Low-Power Wireless RF Receiver for WSN

This paper introduces a low-power wireless RF receiver for the wireless sensor network. The receiver has improved linearity with incorporated current-mode circuits and high-selectivity filtering. The receiver operates at the 900-MHz industrial, scientific, and medical band and is implemented in 130-nm CMOS technology. The receiver has a frequency multiplication mixer, which uses a 300-MHz clock from a local oscillator (LO). The LO is implemented using vertical delay cells to reduce power consumption. The receiver conversion gain is 40 dB and the receiver noise figure is 14 dB. The receiver’s input third-order intercept point (IIP3) is −6 dBm and the total power consumption is 1.16 mW.

RF Wireless Power Transfer Using Integrated Inductor

Wireless power transfer (WPT) is an ideal power delivery solution for many light-load applications, such as for the Internet of Things. A regulated solution for WPT may utilize a power distribution unit (PDU). Previous works have designed planar inductors for integration with switched-inductor buck regulators, but these inductors will not be as efficient for light-load applications. This paper reevaluates the inductor loss for light-load applications by taking into account the frequency spectrum of the inductor current. Using this revised analysis, a planar inductor with screen printed NiZn ferrite epoxy composite magnetic core is designed for an RF near-field coupling system with 1–10-mW load power. In measurement with a 6-MHz buck converter, the PDU with designed inductor demonstrated up to 3% improved efficiency compared to surface-mount technology inductor in the pulse-frequency modulation mode and pulsewidth modulation mode. The designed embedded inductor was subsequently demonstrated in an integrated, compact RF near-field coupling system with peak 43% system efficiency.

Multidimensional vector quantization-based fast statistical estimation in compressed digitalized radio-over-fiber systems.

A multidimensional vector quantization-based fast statistical-estimation (VQ-FSE) algorithm is proposed to enhance data compression performance in digitalized radio over fiber (D-RoF) systems. The original samples with Gaussian distribution are first transformed into these with uniform distribution via companding transformation. After the companding transformation operation, the signal vector is constructed by grouping multiple samples in a certain way so that there is little correlation among them. The constructed signal vector may follow approximately multidimensional uniform distribution, and then multidimensional uniform quantization can be easily carried out, where the complex optimized process in nonuniform quantization is not required. For the proposed two-dimensional (2D) VQ-FSE algorithm, the proposed scheme is numerically verified in a 20km D-RoF system with 2Gbit/s RF wireless signal. Compared with the scalar-quantization-based FSE algorithm, its compression ratio is significantly enhanced. In comparison to the 2D k-means-clustering-based VQ algorithm, the proposed scheme shares a similar compression ratio and offers lower computational complexity. Therefore, the proposed algorithm has the ability to provide better compression and lower complexity for the digitized D-RoF system when the original sample follows Gaussian distribution.

Development of Electronic Water Meter Based on Wireless Network and RF

Development of Electronic Water Meter Based on Wireless Network and RF

Development of Electronic Water Meter Based on Wireless Network and RF

The global need for water is increasing. Water must be used more economically in order to be sustainable. Water consumption per capita in Turkey is below the world regarding its geographical location. Manual reading water meters are inconvenient and time-consuming, they have low accuracy, they are very slow and resource wasting. Using wireless communication will mitigate these unwanted states. Consumers will be able to observe their water consumption in real time and be able to compare with the average water consumption in their district. With this system water pressure of whole pipes could be observed.

Dynamically Reconfigurable SIR Filter Using Rectenna and Active Booster

A novel dynamically reconfigurable bandpass filter (BPF) employing stepped-impedance resonators (SIRs) that can operate as either a single-band or a dual-band filter is demonstrated. The reconfigurable BPF uses four positive-intrinsic-negative (p-i-n) diodes as switching elements. With the four p-i-n diodes in the “OFF” state, the filter behaves as a low-loss (0.85 dB) single-band BPF with a passband around 2.45 GHz. The reconfigurable SIR filter can operate as a dual-band BPF with two center frequencies at 1.6 and 2.45 GHz. The diodes are dynamically set to the “ON” state in the presence of a 1.6-GHz RF signal that is received by an RF triggered power management unit (PMU), integrated on the back side of the microstrip filter in a dual-layer architecture. The RF triggered PMU consists of a planar inverted-F antenna, a high-efficiency voltage doubler rectifier (47% at −13 dBm) and an active dc-to-dc power booster. The rectified output voltage is used as the enabling voltage for the dc-to-dc power booster. This, in turn, provides the required dc power for the diodes biasing. The filter switches from single-band to dual-band when a wireless input RF signal (> −13 dBm) is received by the RF triggered PMU antenna.

Design and realization of an ultra-low power sensing RF energy harvesting module with its RF and DC sub-components

Herein, design, development, and analysis of ultra-low power sensing energy harvesting modules and their subcomponents for ISM band applications have been studied with a holistic approach in an effort to achieve a feasible and high efficient RF energy harvesting performance. The complete harvester system designed and developed here consists of a zero-bias RF energy rectifying antenna (rectenna), DC boost converters and energy storage super-capacitors. Compared with the counterpart energy sources, the surrounding or transmitted wireless energy has low intensity which requires designs with high efficiency. To achieve a successful harvester performance, rectifier circuits with high sensitivity Schottky diodes and proper impedance matching circuits are designed. Dedicated RF signals at various levels from nanowatts to miliwatts are applied at the input of the rectenna and the measured input power versus the scavenged DC output voltage are tabulated. Furthermore, by connecting the rectifier to a high gain antenna and using a RF signal transmitter, the wireless RF power harvesting performance at 2.4 GHz was tested up to 5 m. The performance of the rectenna is analyzed for both low-power detection and efficiencies. Impedance matching network is implemented to reduce the reflected input RF power, DC to DC converters are evaluated for their compatibility to the rectifiers, and super-capacitor behaviors are investigated for their charging and storage capabilities. The measured results indicate that a wide operating power range with an ultra-low power sensing and conversion performance have been achieved by optimizing the efficiency of the Schottky rectifier as low as −50 dBm. The system can be used for battery free applications or expanding battery life for ultra-low power electronics, such as; RFID, LoRa, Bluetooth, ZigBee, and low power remote sensor systems.

Wearable Sport Activity Classification Based on Deep Convolutional Neural Network

This paper develops a wearable sport activity classification system and its associated deep learning-based sport activity classification algorithm for accurately recognizing sport activities. The proposed wearable system used two wearable inertial sensing modules worn on athletes’ wrist and ankle to collect sport motion signals and utilized a deep convolutional neural network (CNN) to extract the inherent features from the spectrograms of the short-term Fourier transform (STFT) of the sport motion signals. The wearable inertial sensing module is composed of a microcontroller, a triaxial accelerometer, a triaxial gyroscope, an RF wireless transmission module, and a power supply circuit. All ten participants wore the two wearable inertial sensing modules on their wrist and ankle to collect motion signals generated by sport activities. Subsequently, we developed a deep learning-based sport activity classification algorithm composed of sport motion signal collection, signal preprocessing, sport motion segmentation, signal normalization, spectrogram generation, image mergence/resizing, and CNN-based classification to recognize ten types of sport activities. The CNN classifier consisting of two convolutional layers, two pooling layers, a fully-connected layer, and a softmax layer can be used to divide the sport activities into table tennis, tennis, badminton, golf, batting baseball, shooting basketball, volleyball, dribbling basketball, running, and bicycling, respectively. Finally, the experimental results show that the proposed wearable sport activity classification system and its deep learning-based sport activity classification algorithm can recognize 10 sport activities with the classification rate of 99.30%.

Random Drift Modeling and Compensation for MEMS-Based Gyroscopes and Its Application in Handwriting Trajectory Reconstruction

Microelectromechanical system (MEMS)-based gyroscopes have been widely applied to various inertial-sensing-based human–computer interaction (HCI) devices. However, the random drift of MEMS-based gyroscopes limits their applications. Hence, studies pay attention to develop various models to model and compensate the random drift for improving the performance of the MEMS-based gyroscopes. This paper presents a self-constructing Wiener-type recurrent neural network (SCWRNN) with its false nearest-neighbors-based self-constructing strategy and recursive recurrent learning algorithm to model the random drift of the MEMS-based gyroscopes and then compensate them from the calibrated gyroscope measurement. Subsequently, the proposed random drift modeling and compensation algorithm is integrated into the handwriting trajectory reconstruction algorithm of the inertial-sensing-based HCI device, called IMUPEN, for accurately obtaining the reconstructed handwriting trajectory. Users can hold the IMUPEN, which is composed of an accelerometer, two gyroscopes, a microcontroller, and an RF wireless transmission module, to write numerals at normal speed. The accelerations and angular velocities measured by the accelerometer and gyroscopes are transmitted to a personal computer through the RF module for further reconstructing the handwriting trajectory via the handwriting trajectory reconstruction algorithm. In addition, we have developed the SCWRNN-based random drift modeling and compensation algorithm to eliminate the cumulative errors caused by the random drift of the MEMS-based gyroscopes for further increasing the accuracy of handwriting trajectory reconstruction. Our experimental results have successfully validated the effectiveness of the proposed random drift modeling and compensation algorithm and its application in handwriting trajectory reconstruction.

Performance Analysis of MICS-Based RF Wireless Power Transfer System for Implantable Medical Devices

In medical applications, implant devices are used to measure and remotely transmit the human biological signals to off-body devices. To date, providing the implantable medical devices (IMDs) with a constant and perpetual energy source remains an ongoing challenge. Accordingly, a far-field radio-frequency powering, represented by an access point (AP), in conjunction with energy-harvesting capability is deployed in this paper for continuous powering of the IMDs. In this respect, theoretical analysis is used to establish safe powering conditions in order to comply with the safety limits established by the Federal Communications Commission. The feasibility of the wireless power transfer to the IMDs is investigated by deriving the analytical closed-form expressions for outage probability and average harvested energy, both of which are validated with Monte Carlo simulations. The findings of this paper suggest not to exceed a distance of 0.5 m between the AP and the body surface, as the system performance has experienced high outage probability beyond this value, while the minimum allowable distance is 17 cm at a powering frequency of 403 MHz. It is also presented that the AP should be equipped with a minimum transmit power of 0.4 W in order to maintain an outage probability for the energy harvesting to be less than 10 -1 .