Wireless RF Research Articles

Enhanced RF Energy Harvesting System Utilizing Piezoelectric Transformer

RF energy harvesting converts ambient signals into electrical power, providing a sustainable energy source. This study demonstrates the use of a piezoelectric transformer for efficient RF energy harvesting. In this work, a piezoelectric transformer (PT) is employed as a high-gain, efficient inverting amplifier to enhance RF wireless energy harvesting. The PT, composed of lead zirconate titanate (PZT), is placed after the receiving loop antenna, with its output connected to an AC-to-DC converter circuit. Maximum harvested power was observed at the PT’s resonance frequency of 50 kHz, with an optimal load of 40 kΩ. The system, comprising the antenna, transformer, and rectifier circuit, continues to resonate at 50 kHz, as confirmed by input impedance measurements, demonstrating stable and effective performance. The overall system efficiency was characterized to be 88%.

Enhancing Security of Telemedicine Data: A Multi-Scroll Chaotic System for ECG Signal Encryption and RF Transmission.

Protecting sensitive patient data, such as electrocardiogram (ECG) signals, during RF wireless transmission is essential due to the increasing demand for secure telemedicine communications. This paper presents an innovative chaotic-based encryption system designed to enhance the security and integrity of telemedicine data transmission. The proposed system utilizes a multi-scroll chaotic system for ECG signal encryption based on master-slave synchronization. The ECG signal is encrypted by a master system and securely transmitted to a remote location, where it is decrypted by a slave system using an extended state observer. Synchronization between the master and slave is achieved through the Lyapunov criteria, which ensures system stability. The system also supports Orthogonal Frequency Division Multiplexing (OFDM) and adaptive n-quadrature amplitude modulation (n-QAM) schemes to optimize signal discretization. Experimental validations with a custom transceiver scheme confirmed the system's effectiveness in preventing channel overlap during 2.5 GHz transmissions. Additionally, a commercial RF Power Amplifier (RF-PA) for LTE applications and a development board were integrated to monitor transmission quality. The proposed encryption system ensures robust and efficient RF transmission of ECG data, addressing critical challenges in the wireless communication of sensitive medical information. This approach demonstrates the potential for broader applications in modern telemedicine environments, providing a reliable and efficient solution for the secure transmission of healthcare data.

Power-efficient wideband programmable pseudo differential ring oscillator CP-PLL

A power-efficient, wide-band, programmable pseudo-differential ring-oscillator charge-pump phase-locked loop (CP-PLL) is proposed. The ring-VCO, characterized by its low power consumption and broadband, is achieved based on a feedforward pseudo-differential configuration. The linearity of ring-VCO is improved by using the source negative feedback topology. Through the rail-to-rail operatingamplifier clamping current source, the current matching accuracy is improved to realize a high-performance CP circuit. The results show that the output frequency range of the phase-locked loop is 0.6–6 GHz at a 1.2 V supply voltage, and the power consumption is 1.372 mW at 5 GHz with a lock-up time of 1.72 μs and RMS jitter of 9.3 ps. The power consumption is as low as 0.643 mW at 2.5 GHz and 1.067 mW at 4 GHz, and the final layout area is 0.00716 mm2. The implemented CP-PLL can be used effectively in wireless RF communication system of NB-IoT and intelligent edge computing scenario.

Improvement of MRS at ultra-high field using a wireless RF array.

We aim to assess a straightforward technique to enhance spectral quality in the brain, particularly in the cerebellum, during 7 T MRI scans. This is achieved through a wireless RF array insert designed to mitigate signal dropouts caused by the limited transmit field efficiency in the inferior part of the brain. We recently developed a wireless RF array to improve MRI and 1H-MRS at 7 T by augmenting signal via inductive coupling between the wireless RF array and the MRI coil. In vivo experiments on a Siemens 7 T whole-body human scanner with a Nova 1Tx/32Rx head coil quantified the impact of the dorsal cervical array in improving signal in the posterior fossa, including the cerebellum, where the transmit efficiency of the coil is inherently low. The 1H-MRS experimental protocol consisted of paired acquisition of data sets, both with and without the RF array, using the semi-LASER and SASSI sequences. The overall results indicate that the localized 1H-MRS is improved significantly in the presence of the array. Comparison of in vivo 1H-MRS plots in the presence versus absence of the array demonstrated an average SNR enhancement of a factor of 2.2. LCModel analysis reported reduced Cramér-Rao lower bounds, indicating more confident fits. This wireless RF array can significantly increase detection sensitivity. It may reduce the RF transmission power and data acquisition time for 1H-MRS and MRI applications, specifically at 7 T, where 1H-MRS requires a high-power RF pulse. The array could provide a cost-effective and efficient solution to improve detection sensitivity for human 1H-MRS and MRI in the regions with lower transmit efficiency.

Application of wireless energy delivery system in automobile charging

With the popularity of electric vehicles, wireless charging technology has become a key area to address the convenience of charging electric vehicles. The aim of this study is to explore the principles of wireless energy transfer technology and its application in the field of electric vehicles. We first provide a background introduction to the field of electric vehicles, emphasising the importance of wireless charging technology. Subsequently, we delve into the charging and discharging characteristics of power batteries to better understand the need for energy transfer. Then, we carefully selected wireless charging methods suitable for electric vehicles and developed a corresponding wireless charging system architecture. In this paper, we also provide theoretical analyses of two major wireless energy transfer technologies, including electromagnetic coupled wireless energy transfer and resonant wireless energy transfer, as well as exploring the principles of RF wireless energy transfer technology. Finally, we propose an architecture for a static wireless charging system including five modules: pre-processing, transmission, reception, charging control and battery load. The contribution of this study is to provide an in-depth research and a comprehensive theoretical foundation for wireless charging technology in the field of electric vehicles, which helps to improve the charging efficiency and convenience of electric vehicles.

Understanding TETRA Radio RF Jamming and Interference: A Comprehensive Overview

This publication provides a detailed examination of the issues surrounding TETRA Radio RF jamming and interference, essential factors impacting critical communication systems. By investigating the root causes, effects, and potential remedies for RF interference, this paper aims to equip stakeholders with a thorough understanding needed to develop effective strategies to mitigate these disruptions in TETRA networks, thereby enhancing their security and resilience.

Voice Over for Home Security System

The Smart Home Voice Control Hub is an advanced, integrated system design to seamlessly manage and operate a variety of smart home devices using voice commands. Recent years have witnessed significant advancements in home automation driven by wireless technologies. Among these, the IEEE 802.15.4 standard, RF, stands out for its low data rate, extended battery lif e, and secure networking capabilities. This article details a method for testing voice control implementation in smart homes, emphasizing compatibility with existing infrastructure. Utilizing low-power RF wireless modules and a microcontroller, the system caters to the needs of elderly and disabled individuals living independently. By focusing on voice recognition, it off ers enhanced security and control over household lighting and appliances. Experimental validation demonstrates the system's effectiveness in practical applications.

High-Efficiency Reconfigurable CMOS RF-to-DC Converter System for Ultra-Low-Power Wireless Sensor Nodes with Efficient MPPT Circuitry

This paper presents a novel CMOS RF-to-DC converter for ultra-low-power wireless sensor nodes powered by RF wireless power transfer. The proposed converter achieves 10% higher power conversion efficiency than a conventional rectifier, with only a 1% increase in power consumption. The system employs a reconfigurable Dickson topology, operates on the unlicensed 868 MHz ISM band, and includes a built-in power-efficient MPPT system architecture. Experimental measurements show a maximum power conversion efficiency of 55% in the power range from −22 dBm to 0 dBm, with a power sensitivity of −22 dBm for a DC output voltage of 2.4 V. The proposed converter offers a promising solution for efficient wireless power transfer and energy harvesting in ultra-low-power wireless sensor nodes.

Energy Beamforming for RF Wireless Power Transfer With Dynamic Metasurface Antennas

Energy Beamforming for RF Wireless Power Transfer With Dynamic Metasurface Antennas

Detection of atmospheric turbulence parameters in free space optical communication

Abstract These days usage of wireless communication has become vast compared to wired communication. The landline is replaced with a mobile, wi-fi with DAS. From the era of 1970 to the 1980s, wireless communication has evolved and wireless communication uses RF waves to communicate which is called RF communication. As the demand for the speed of data rate, the new technology is evolving in the unguided medium due to its range, cost, and availability. In this evolution, it first came with optical fiber and after RF wireless or electromagnetic wireless technologies. Later, researchers have been found optical communication. In present days it is facing a lot of challenges and trials. Optical communication means communication using the light ray or light spectrum which can achieve great speed and long distance with secure data transfer. The major challenge to achieve this communication is atmospheric turbulence. Although lots of experiments have been done still the problem is the detection of atmospheric conditions and making communication possible according to atmospheric turbulence. In this paper, we are going to discuss a few techniques to detect atmospheric turbulence.

High-efficiency rectifying circuit for 5.8GHz wireless RF energy harvesting applications

High-efficiency rectifying circuit for 5.8GHz wireless RF energy harvesting applications

Radiation Patterns of RF Wireless Devices Implanted in Small Animals: Unexpected Deformations Due to Body Resonance.

One challenge in designing RF wireless bioelectronic devices is the impact of the interaction between electromagnetic waves and host body tissues on far-field wireless performance. In this article, we investigate a peculiar phenomenon of implantable RF wireless devices within a small-scale host body related to the deformation of the directivity pattern. Radiation measurements of subcutaneously implanted antennas within rodent cadavers show that the direction of maximum radiation is not always identical with the direction to the closest body-air interface, as one would expect in larger-scale host bodies. For an implanted antenna in the back of a mouse, we observed the maximum directivity in the ventral direction with 4.6 dB greater gain compared to the nearest body-air interface direction. Analytic analysis within small-scale spherical body phantoms identifies two main factors for these results: the limited absorption losses due to the small body size relative to the operating wavelength and the high permittivity of the biological tissues of the host body. Due to these effects, the entire body acts as a dielectric resonator antenna, leading to deformations of the directivity pattern. These results are confirmed with the practical example of a wirelessly powered 2.4-GHz optogenetic implant, demonstrating the significance of the judicious placement of external antennas to take advantage of the deformation of the implanted antenna pattern. These findings emphasize the importance of carefully designing implantable RF wireless devices based on their placements and relative electrical dimensions in small-scale animal models.

Enhancing Human Activity Recognition with LoRa Wireless RF Signal Preprocessing and Deep Learning

This paper introduces a novel approach for enhancing human activity recognition through the integration of LoRa wireless RF signal preprocessing and deep learning. We tackle the challenge of extracting features from intricate LoRa signals by scrutinizing the unique propagation process of linearly modulated LoRa signals—a critical aspect for effective feature extraction. Our preprocessing technique involves converting intricate data into real numbers, utilizing Short-Time Fourier Transform (STFT) to generate spectrograms, and incorporating differential signal processing (DSP) techniques to augment activity recognition accuracy. Additionally, we employ frequency-to-image conversion for the purpose of intuitive interpretation. In comprehensive experiments covering activity classification, identity recognition, room identification, and presence detection, our carefully selected deep learning models exhibit outstanding accuracy. Notably, ConvNext attains 96.7% accuracy in activity classification, 97.9% in identity recognition, and 97.3% in room identification. The Vision TF model excels with 98.5% accuracy in presence detection. Through leveraging LoRa signal characteristics and sophisticated preprocessing techniques, our transformative approach significantly enhances feature extraction, ensuring heightened accuracy and reliability in human activity recognition.

Time-Transient Wireless RF Sensor With Differentiative Detection Capability in Ionic Aqueous Environment for Water Conservation and Green Cleaning

Time-Transient Wireless RF Sensor With Differentiative Detection Capability in Ionic Aqueous Environment for Water Conservation and Green Cleaning

Environmental Life-Cycle Assessment (LCA) of Wireless RF Systems: A Comparative Sustainability Analysis and a Microwave Engineers' Guide to LCA

Environmental Life-Cycle Assessment (LCA) of Wireless RF Systems: A Comparative Sustainability Analysis and a Microwave Engineers' Guide to LCA

High-Power and Safe RF Wireless Charging: Cautious Deployment and Operation

High-Power and Safe RF Wireless Charging: Cautious Deployment and Operation

Investigation of graded channel effect on analog/linearity parameter analysis of junctionless surrounded gate graded channel MOSFET

Linearity analysis of nanoscale devices is a vital issue as nonlinearity behavior is exhibited by them when employed in circuits for microwave and RF applications. In this work, a junctionless surrounded gate-graded channel MOSFET (JLSGGC MOSFET) is investigated thoroughly to analyze its linearity performance with the help of ATLAS tool of technology computer-aided design. The proposed device is compared systematically with the conventional junstionless surrounded gate MOSFET(JLSG MOSFET) to investigate their linearity. To evaluate the linearity, the figure of merits such as higher-order transconductance (Gm1, Gm2), intercept points(VIP2, VIP3, IIP3), IMD3 and 1 dB—compression point(P1 dB) are considered. The linearity of our proposed device improves by 35.5% in view of the compression point in comparison to JLSG MOSFET before the threshold voltage region of operation. The simulation results reveal a substantial enhancement in the linearity performance of the JLSGGC MOSFET. The improved linearity behavior of JLSGGC MOSFET makes it suitable for wireless RF and system-on-chip applications.Analog/RF performance is studied in terms of intrinsic gain (Gm/Gds), cut-off frequency (fT),maximum frequency of oscillation (fmax).Improved analog/RF performances of JLSGGC MOSFET suggests its applications in high frequency operating range.

A flexible and transparent pliers shaped antenna for ultra-wideband applications

Flexible transparent antennas have broad potential applications in wireless communication and RF energy harvesting, providing visualization, small size, and integration functions for electronic devices. The use of optically transparent materials is an essential direction in the development of flexible transparent antennas. In this paper, a flexible and transparent antenna is designed by indium tin oxide material and photolithography process, which is suitable for wideband communication field. The broadband characteristics of the antenna are realized by using irregular slots and rectangular microstrip lines on the ground plane. The antenna operates in the frequency range of 1.73–20 GHz with a relative bandwidth of 168%, which is suitable for ultra-wideband (UWB) applications. The antenna has a compact structure and the relative size of 0.33 λ 0 × 0.28 λ 0. The measured results of the antenna are in good agreement with the simulated results, and the bending and folding tests show that the antenna has good mechanical flexibility and can cover the surface of irregular objects. This pliers-shaped antenna is applicable to a variety of UWB and wireless applications, such as LTE, Wi Max, 5G network, IoT, WIFI, mobile phone keys, and mobile payment.

Enhancing Electrochemical Performance of Stretchable Li-Ion Microbatteries by Tuning Microstructured Electrode Dimensions

With the spectacular rise of wearable technologies, R&D on microbatteries is rapidly emerging on the world market. For example, smart electronic textiles require new features and battery designs that traditional battery technologies simply cannot provide. This has opened the door to innovation and added a new dimension to the global competition in battery research.1 The potential sector that can be impacted includes Internet of Things (IoT), healthcare (skin patches, medical sensors, medical diagnostic devices), smart cards, etc. To date, the soft microbattery technology is still in its infancy because it requires the pooling of complementary knowledges in different scientific domains. Indeed, key competences in microelectronics, materials science, electrochemistry, polymer, and inorganic chemistry have to be gathered to overcome all technical challenges. Recently, we have reported a new concept for the development of stretchable Li-ion microbatteries.2-4 A prototype has been also integrated in a scleral eye contact lens5. The innovative approach is based on the assembly of two flexible substrates comprising arrays of micro-pillars on serpentine current collectors that are separated by a polymer electrolyte. Besides achieving high areal capacity values like 2.5 mA h cm-2 at C/10 (i.e., 0.07 mA cm-2), the micropillars make the system reversibly stretchable. Electrochemical tests revealed excellent performance when the stretchable micropower source was subjected to different mechanical strains. Indeed, 73% of the capacity is retained over 100 cycles under 30% strain and all fatigue tests showed that capacity retention remains higher than 70%. Preliminary results have shown the possibility to power low-consumption devices such as a light emitting diodes. It will be also discussed the parameters and treatments that have been investigated to increase the capacity and optimize the systems.6 During this presentation, it will be also presented how to achieve the RF wireless charging of the battery.

Self-Sustainable IoT-Based Remote Sensing Powered by Energy Harvesting Using Stacked Piezoelectric Transducer and Thermoelectric Generator.

We propose a self-powered remote multi-sensing system for traffic sensing which is powered by the collective energy harvested from the mechanical vibration of the road caused by the passing vehicles and from the temperature gradient between the asphalt of the road and the soil underneath. A stacked piezoelectric transducer converts mechanical vibrations into electrical energy and a thermoelectric generator harvests the thermal energy from the thermal gradient. Electrical energy signals from the stacked piezoelectric transducer and the thermoelectric generators are converted into usable DC power to recharge the battery using AC-DC and DC-DC converters working simultaneously. The multi-sensing system comprises an embedded system with a microcontroller that acquires data from the sensors and sends the sensory data to an IoT transceiver which transmits the data as RF packets to an ethernet gateway. The gateway converts the RF packets into Internet Protocol (IP) packets and sends them to a remote server. Laboratory and road-testing results showed over 98% sensory data accuracy with the system functioning solely powered by the energy harvested from the alternative energy sources. The successful maximum transmission distance obtained between the IoT, and the gateway was approximately 1 mile, which is a considerable transmission distance achieved in an urban environment. Successful operation of the self-powered multi-sensing system under both laboratory and road conditions contributes considerably to the fields of energy harvesting and self-powered remote sensing systems. The energy flow chart and efficiency for the steps in the system were found to be mechanical power from vehicles to the energy harvester of 0.25%, stacked PZT transducer efficiency was found to be 37%, and for the TEGs the efficiency is 11%. AC-to-DC and DC-to-DC converters' efficiencies were found to be 90% and 11%. The wireless communication RF transceiver efficiency was found to be 62.5%.