Radio Frequency Technology Research Articles

Recent advances in food processing by radio frequency heating techniques: A review of equipment aspects

Radio frequency (RF) treatment, as an emerging thermal technology, has been studied for various purposes in food processing. In addition to optimal design of the RF processing conditions, the overall performance of the equipment is a key factor in determining the process efficiency and product quality. Although different types and scales of RF equipment have been used in food processing, the growing demand has exposed certain drawbacks of the RF equipment applications, especially for the heating uniformity, convenience of operation, treating efficiency, and product quality, and therefore, custom designed or combined equipment based on the specific application scenarios has attracted wider attentions. This paper systematically reviews the current state on applications of RF equipment for various purposes of food processing. The heating principles, typical equipment, customized accessories, and combination modes of RF systems are summarized, and some important findings and conclusions are provided in detail. Moreover, the challenges and future directions of RF equipment used in food processing are also discussed, which may help to better design and optimize RF equipment used for future food processing. This review would improve the understanding of RF equipment for food processing and promote the application of RF technology in the industrial scale.

A comprehensive review of performance analysis of RF-FSO hybrid communication systems

The combination of radio frequency (RF) and free-space optical (FSO) communication has grown in importance as a study area for wireless communication systems in recent years. This technology has the ability to address the rising need for high-speed, high-capacity wireless communication in a variety of applications by successfully integrating the benefits of both RF and FSO communication. The performance analysis of various communication systems based on RF-FSO hybrid technology is covered in detail in this research. An overview of the RF-FSO hybrid technology and its many architectures follows the introduction of the key features and benefits of RF and FSO communication. The performance analysis of several RF-FSO hybrid communication systems, including relay-assisted RF-FSO systems, cooperative diversity RF-FSO systems, and dual-hop RF-FSO systems, are discussed in detail. The performance metrics, such as bit error rate (BER), outage probability, and channel capacity, is analyzed and compared for these systems. Based on the analysis of existing literature, several key conclusions are drawn. First, RF-FSO hybrid technology can provide higher data rates and greater reliability than traditional communication systems. Secondly, the performance of the RF-FSO hybrid system, which combines the advantages of RF technology and FSO technology, has bright development prospects. Finally, the RF-FSO hybrid system can also be combined with other systems for better performance and wider application scenarios.

UAV Detection and Tracking in Urban Environments Using Passive Sensors: A Survey

Unmanned aerial vehicles (UAVs) have gained significant popularity across various domains, but their proliferation also raises concerns about security, public safety, and privacy. Consequently, the detection and tracking of UAVs have become crucial. Among the UAV-monitoring technologies, those suitable for urban Internet-of-Things (IoT) environments primarily include radio frequency (RF), acoustic, and visual technologies. In this article, we provide a comprehensive review of passive UAV surveillance technologies, encompassing RF-based, acoustic-based, and vision-based methods for UAV detection, localization, and tracking. Our research reveals that certain lightweight UAV depth detection models have been effectively downsized for deployment on edge devices, facilitating the integration of edge computing and deep learning. In the city-wide anti-UAV, the integration of numerous urban infrastructure monitoring facilities presents a challenge in achieving a centralized computing center due to the large volume of data. To address this, calculations can be performed on edge devices, enabling faster UAV detection. Currently, there is a wide range of anti-UAV systems that have been deployed in both commercial and military sectors to address the challenges posed by UAVs. In this article, we provide an overview of the existing military and commercial anti-UAV systems. Furthermore, we propose several suggestions for developing general-purpose UAV-monitoring systems tailored for urban environments. These suggestions encompass considering the specific requirements of the application scenario, integrating detection and tracking mechanisms with appropriate countermeasures, designing for scalability and modularity, and leveraging advanced data analytics and machine learning techniques. To promote further research in the field of UAV-monitoring systems, we have compiled publicly available datasets comprising visual, acoustic, and radio frequency data. These datasets can be employed to evaluate the effectiveness of various UAV-monitoring techniques and algorithms. All of the datasets mentioned are linked in the text or in the references. Most of these datasets have been validated in multiple studies, and researchers can find more specific information in the corresponding papers or documents. By presenting this comprehensive overview and providing valuable insights, we aim to advance the development of UAV surveillance technologies, address the challenges posed by UAV proliferation, and foster innovation in the field of UAV monitoring and security.

IBeacon-based indoor positioning system: from theory to practical deployment

<span lang="EN-US">Developing an indoor positioning system became essential when global positioning system signals could not work well in indoor environments. Mobile positioning can be accomplished via many radio frequency technology such as Bluetooth low energy (BLE), wireless fidelity (Wi-Fi), ultra-wideband (UWB), and so on. With the pressing need for indoor positioning systems, we, in this work, present a deployment scheme for smartphone using Bluetooth iBeacons. Three main parts, hardware deployment, software deployment, and positioning accuracy assessment, are discussed carefully to find the optimal solution for a complete indoor positioning system. Our application and experimental results show that proposed solution is feasible and indoor positioning system is completely attainable.</span>

High Average Gradient in a Laser-Gated Multistage Plasma Wakefield Accelerator.

Plasma wakefield accelerators driven by particle beams are capable of providing accelerating gradient several orders of magnitude higher than currently used radio-frequency technology, which could reduce the length of particle accelerators, with drastic influence on the development of future colliders at TeV energies and the minimization of x-ray free-electron lasers. Since interplasma components and distances are among the biggest contributors to the total accelerator length, the design of staged plasma accelerators is one of the most important outstanding questions in order to render this technology instrumental. Here, we present a novel concept to optimize interplasma distances in a staged beam-driven plasma accelerator by drive-beam coupling in the temporal domain and gating the accelerator via a femtosecond ionization laser.

A Review of Cognitive Hybrid Radio Frequency/Visible Light Communication Systems for Wireless Sensor Networks.

The development and growth of Wireless Sensor Networks (WSNs) is significantly propelled by advances in Radio Frequency (RF) and Visible Light Communication (VLC) technologies. This paper endeavors to present a comprehensive review of the state-of-the-art in cognitive hybrid RF-VLC systems for WSNs, emphasizing the critical task of seamlessly integrating Cognitive Radio Sensor Networks (CRSNs) and VLC technologies. The central challenge addressed is the intricate landscape of this integration, characterized by notable trade-offs between performance and complexity, which escalate with the addition of more devices and increased data rates. This scenario necessitates the development of advanced cognitive radio strategies, potentially facilitated by Machine Learning (ML) and Deep Learning (DL) approaches, albeit introducing new complexities such as the necessity for pre-training with extensive datasets. The review scrutinizes the fundamental aspects of CRSNs and VLC, spotlighting key areas like Energy Efficient Resource Allocation, Industrial Scenarios, and Energy Harvesting, and explores the synergistic amalgamation of these technologies as a promising pathway for enhanced spectrum utilization and network performance. By delving into the integration of cognitive radio technology with visible light, this study furnishes valuable insights into the potential for innovative applications in wireless communication, presenting a balanced overview of the current advancements and prospective avenues in the field of cognitive hybrid RF/VLC systems.

Micro-plasma radiofrequency and silicone gel dressings for treating early post-traumatic facial scars: A retrospective study

Although different options are available for treating post-traumatic facial scars, they remain a therapeutic challenge. To evaluate the safety and effectiveness of combined therapy using micro-plasma radiofrequency (MPRF) technology and silicone gel (SG) dressings for treating post-traumatic facial scars. This retrospective study was conducted at a single center. Patients with facial injuries in the outpatient and emergency units of the Department of Plastic Surgery at our hospital underwent debridement and cosmetic sutures performed by the same surgeon from October 2020 to October 2021. In the first arm, patients with facial injuries were treated with MPRF technology and SG, and in the second arm, they were treated with SG dressings alone. We observed the safety and effectiveness of these treatments in both arms. A total of 32 patients with facial injuries were treated with MPRF technology and SG dressings (combined treatment group), and 28 patients were treated with SG dressings alone (SG group). After 6 months of treatment, the Vancouver Scar Scale scores of the combined treatment and SG groups were 1.38±0.71 and 4.39±0.50, respectively, and the difference was statistically significant (P<0.01). After 6 months of treatment, the effectiveness rate in the combined treatment group was 93.8%, which was significantly higher than that in the SG group (67.9%), and the difference between the two groups was statistically significant (P<0.05). No obvious adverse reactions occurred in the two arms. Treating early post-traumatic facial scars with combined MPRF technology and SG is significantly better than treating them with SG alone; moreover, the combined therapy is safe and effective.

Effect of microwave and hot air radiofrequency treatments on physicochemical and functional properties of foxtail millet flour and its protein isolate

The current study investigated the impact of microwave (MW) and hot-air assisted radiofrequency (HARF) technologies on physicochemical characteristics of foxtail millet (FM) flour. Besides, the physicochemical characteristics of foxtail millet protein (FMP) from MW and HARF treated FM flour were also evaluated. Residual relative lipase activity (LA) (10.86%) was least at 15% moisture (w.b.) for two passes-28 min treatment in HARF, while the MW heating showed lower LA at 786.80W power level for 6 min (0.27%) and 4 min (8.17%). Peak viscosities of MW and HARF treated FM flour exhibited a decreasing trend compared to untreated. An increase was observed in emulsifying, and oil/water absorption properties of MW and HARF treated FMP in comparison with the untreated sample, while it was vice versa with the foaming properties, and protein purity. This changes can be attributed to the decrease in relative crystallinity and modifications in the secondary structural elements (i.e., increase in β-turn, and decrease in α-helix, β-sheets), as confirmed by FTIR and XRD analyses performed.

Superconducting radio frequency linear collider HELEN

This article discusses a proposed Higgs-Energy LEptoN (HELEN) e + e - linear collider based on advanced traveling wave superconducting radio frequency technology. The proposed collider offers cost and AC power savings, smaller footprint (relative to the ILC), and could be built at Fermilab. After the initial physics run at 250 GeV, the collider could be upgraded either to higher luminosity or to higher, up to 500 GeV, energies.

Therapeutic effect of the temperature-controlled radio frequency technology in female sexual dysfunction.

To explore the therapeutic effect of the temperature-controlled radiofrequency technology in female sexual dysfunction (FSD). From July 2020 to June 2021, patients with FSD who visited the Gynecology Clinic of Peking University Shenzhen Hospital were treated with the temperature-controlled radiofrequency technology once every two weeks, for a total of five times. The therapeutic effect was objectively evaluated with pelvic floor dysfunction (PFD) indicators (FSFI score, pelvic floor muscles surface electromyography, sexual function test). The pre- and post-treatment (2 weeks)/follow-up (3 months) results were compared to evaluate the feasibility of this technology for treating FSD, as well as using PFD-related indicators in objective evaluation of FSD patients. Fifty patients completed treatment; 31 patients completed follow-up. The mean FSFI score for post-treatment/follow-up was significantly higher than pre-treatment (p < 0.05). There were no significant changes in the mean pelvic floor resting surface myoelectric potential and its variability and mean myoelectric potential of sexual function test between pre- and post-treatment/follow-up. The mean surface myoelectric potential of the patients' type I and II muscle fibers of the pelvic floor for post-treatment/follow-up was significantly higher than pre-treatment (p < 0.05). The mean peak myoelectric potential for post-treatment was significantly higher than pre-treatment (p < 0.05). Temperature-controlled radiofrequency technology has a certain therapeutic effect on FSD. Pelvic floor surface electromyography and sexual function test can be used as an objective indicator for PFD in FSD patients. Subsequent studies may involve a larger size sample and evaluate the effect over a consecutive time-point, to develop a better therapeutic approach.

Radar-Beat: Contactless beat-by-beat heart rate monitoring for life scenes

Background and objective:Heartbeat is a crucial vital sign, and radio-frequency technology can measure the micro-vibration of the body surface from a distance and extract the heartbeat signal, which can solve the compliance problem caused by wearable sensors. However, most existing works verify short-term controlled experiments and seldom consider the challenges posed by random body movements and posture changes during long-term monitoring in daily life scenarios. In this article, we propose a systematic solution called Radar-Beat, which enables accurate heartbeat monitoring using an mmWave FMCW radar device. Our goal is to promote the integration of contactless heartbeat monitoring into life scenarios. Methods:We proposes a sensitive body motion detection algorithm and an optimal Range-bin selection algorithm, which can automatically identify body motion and update the best heartbeat signal channel. Then, we construct a personalized heartbeat template for each signal segment and propose a global optimization model to improve the accuracy of heartbeat length estimation. Results:We use the synchronized ECG signal as the ground truth, results show strong agreement between Radar-Beat and synchrony ECG devices for heart rate and inter-beat interval (IBI) measurements in healthy subjects. In the heartbeat monitoring experiment for a total of 72 h and 56 min involving 11 participants, under a time coverage of 91.2%, the median error of IBI estimation was 12 ms. Conclusion:Radar-Beat has strong robustness to different individuals in different postures and positions. It can be deployed in a hospital bed or home to enable continuous heartbeat monitoring in an unobtrusive way.

3-D Indoor Positioning Based on Passive Radio Frequency Signal Strength Distribution

In recent years, indoor positioning systems (IPSs) have received attention from many research fields, such as robotics, navigation, human-computer interaction, etc. However, IPS based on passive radio frequency (PRF) technology is still rare. This paper proposes an three-dimensional (3D) IPS based on received signal strength (RSS) distribution and Gaussian process regression (GPR). Traditional RSS-based positioning systems have a transmitter with known frequencies, while in the proposed PRf signal of Opportunity -3D IPS (PRO-3DIPS), the system neither deploys new transmitters nor uses any a priori knowledge of transmitters. Furthermore, PRO-3DIPS integrates multiple Signal of Opportunity (SoOP) sources, shadowing, fading, and also captures scenario signatures. Data collection and analysis of PRF-based RSS distribution in 3D space enables the capability of 3D positioning. Three methods are applied and compared to find the frequency band most impacted by the scenario to achieve the best positioning performance as well as used in the estimation of RSS distribution. The RSS distribution is estimated by measuring the PRF spectrum on a fixed grid in the scenario. Using the RSS distribution, the GPR can accurately locate the receiver position. RSS at 90-gridded positions were collected in the experiment scenario, with one hundred samples at each position. The experimental result shows that a root mean square error (RMSE) of the proposed PRO-3DIPS is 0.292 meters when the sampling distance is 1 meter. The result demonstrates that the PRF spectrum is a new modality for the positioning task, which demonstrates better performance than most existing RF-based technologies.

Radio Frequency-Based Diagnostics for Superconducting Magnets

Operation of high-field superconducting magnets relies on diagnostic instrumentation for measuring strain, temperature, and magnetic field variations, detecting quenching, and identifying performance problems. Discrete sensor implementation is costly, requires multi-channel data acquisition systems, and sensor density is often insufficient to resolve problematic locations spatially. Distributed sensing is a viable alternative approach providing location-specific diagnostic information over single terminal output. In particular, it can be the key to quench protection of high-temperature superconductor (HTS)-based magnets where hot spots are known to form and persist before a quench. Fiber-optic technology offers distributed sensing solution for magnets but suffers from drawbacks such as fiber fragility, high costs of optical interrogators, and difficulty in differentiating between physical quantities such as temperature and strain. We propose an alternative, robust, and easily integrable way of implementing distributed sensing in magnets using radio-frequency (RF) technologies. RF Time Domain Reflectometry (TDR) technique has been around for nearly 60 years, and it is an essential diagnostic tool used in multiple areas of technology and applied research. We discuss operational principles and practical implementation of RF TDR sensors capable of detecting local variations of strain, temperature, and magnetic field through changes in RF impedance and wave propagation time. Results of cryogenic testing of our TDR sensors with HTS tape conductors are presented. The perspective of enabling a new diagnostics paradigm for high-energy physics and fusion energy applications based on distributed RF sensing is discussed.

Liquid Crystals for Advanced Smart Devices with Microwave and Millimeter-Wave Applications: Recent Progress for Next-Generation Communications.

Liquid crystals (LCs) technology have a well-established history of applications in visible light, particularly in the display industry. However, with the rapid growth in communication technology, LCs have become a topic of current interest for high-frequency microwave (MW) and millimeter-wave (mmWave) applications due to promising characteristics such as tunability, continuous tuning, low losses, and price compatibility. To improve the performance of future communication technology using LCs, it is not sufficient only with the perspective of radio-frequency (RF) technology. Therefore, it is imperative to understand not only the novel structural designs and optimization of MW engineering but also the perspective of materials engineering when implementing advanced RF devices with maximum performance for next-generation satellite and terrestrial communication. Herein, based on advanced nematic LCs, polymer-modified LCs, dual-frequency LCs, and photo-reactive LCs, this article summarizes and examines the modulation principles and key research directions for the design strategies of LCs for advanced smart RF devices with improved driving performance and novel functionality. Furthermore, the challenges in development of state-of-the-art smart RF devices that use LCs are discussed.

High-brightness electron injectors for high-duty cycle X-ray free electron lasers

The successful development in the last two decades of X-ray free electron lasers (FELs) with their revolutionary brightness performance has been tightly dependent on the parallel development of electron guns and injectors capable of providing the high-brightness electron beams required by FELs lasing at these short wavelengths. The ultimate brightness delivered by a linear accelerator (linac) is already set at its injector and the remaining part of the accelerator can be only designed to preserve the injector performance. The technology to be used for the accelerator part of an X-Ray FEL strongly depends on the duty-cycle at which the FEL operates. Normal-conducting, room-temperature, copper-based radio frequency (RF) technology is typically used for low duty-cycles of up to approximately 10−3. For higher duty-cycles and up to continuous wave (CW) operation, the linac must rely on superconductive RF technology because, with the higher duty-cycle, the increasingly higher power dissipated in normal conducting RF structures becomes excessive for the warm technology. The situation changes in the lower energy part of the accelerator, where injector schemes, based on direct current, normal-conducting, and superconducting RF electron guns, are demonstrating the beam quality performance required by high-duty-cycle X-ray FELs. In this paper we start with a description of the requirements for such injectors, followed by an overview of the pursued technologies and schemes, and by a discussion on the main differences in terms of beam dynamics between low and high duty-cycle injectors.

FSO communication system for high-speed trains under varying visibility conditions

High-speed train systems are rapidly growing in complexity and coverage, demanding efficient high-speed internet services. Existing radio frequency technology struggles to meet these demands due to handover mechanisms and limited connectivity times. Furthermore, current free-space optics (FSO) techniques require a large number of base stations (BSs), resulting in high costs. This study presents a novel high-speed train communication technique, using FSO, that significantly reduces the number of required BSs while maintaining sufficient coverage and data speeds. The proposed technique can be adapted for fixed or variable representations of transmitted and received power, providing a fixed or variable data rate. The research also investigates the impact of divergence angle on transmitted and received power. By employing the proposed communication technique, a system with a fixed data rate, such as 1.25 Gbps, can be achieved. The results demonstrate the potential of this approach in high-speed train applications, reducing the number of BSs from 113, as reported in the best existing literature, to less than 10. Weather conditions, including clear, haze, thin fog, light fog, and heavy fog, are considered when calculating the required BS locations to achieve a target data rate. Additionally, this work introduces a new handover mechanism and mathematical formulation, providing a more comprehensive solution for high-speed train communication systems. The simulations and evaluations conducted in this study are based on parameters and equations from previous works to ensure a fair comparison.

Parallel Contactless Transmission of Power and Rotor Temperature of Electrical Machines via Magnetically-Coupled Resonance and Capacitive Radio Frequency

Over-temperature of the rotor may cause a series of insulation deterioration of electrical machines. In severe cases, it can lead to insulation failure and even faults, such as broken rotor bars and end ring fracture. The temperature online monitoring can effectively avoid the aforementioned insulation failure; however, the conventional temperature measurement by embedded sensors is difficult to utilize due to the power and data transmission of sensors at the rotor side. This paper proposes a contactless strategy to supply power and send rotor temperature data between the stator and rotor sides of electrical machines. With the proposed method, contactless power transfer is realized by means of magnetically-coupled resonance, while the data signal is transferred by capacitive radio frequency (RF) technology. An experimental prototype was developed and installed on a 22-kW induction motor. The results show that the embedded sensors are contactless powered effectively. At the same time clear temperature data signal can be received on the stator side without filtering, and rotor temperature can be monitored in real-time accurately.

Efficient Clustering of Visible Light Communications in VANET

The deployment of vehicular ad hoc network (VANET) is crucial to the development of autonomous vehicles. Radio frequency (RF) technology has been employed to transmit messages between vehicles and infrastructure in VANET. However, the limited RF bands may cause interference when vehicles transmit messages in a high-density environment. Moreover, when numerous vehicles transmit messages to the infrastructure at the same time, the simultaneous transmissions may cause channel congestion. While the issue of signal interference can be solved by the techniques of Visible Light Communication (VLC), vehicle clustering can be employed to improve the transmission performance of vehicles. VLC is an emerging technology with the advantage of immunity to electromagnetic interference. The technique of vehicle clustering categorizes vehicles into different sets, where each set has a leader for intra-cluster messaging. In this work, we present a clustering algorithm for VANET based on VLC. Our algorithm estimates the positions of vehicles based on their current movements. Then, it selects cluster heads based on the number of neighboring vehicles and generates clusters. We evaluate the performance of our scheme for both urban and highway scenarios. The simulation results show that the proposed algorithm can minimize the number of clusters and improve the transmission data rate for vehicles.

Wireless Power Transfer: A Review of Existing Technologies

Wireless Power Transfer (WPT) can be described as the processing of transmitting electricity without the use of wires. It has been increasingly used in places where battery depletion and replacement are major issues. WPT Technology are being used in different sectors. They include wireless charging, Electric vehicles, consumer electronics, etc. The paper describes the various types of WPT technologies; Inductive Coupling, Magnetic Resonance and Radio Frequency (RF) technology. It also discusses the advantages and shortfalls of each type. An extensive survey of past works was discussed. Results from the research findings showed that distance and conversion efficiency were limiting factors in implementing wireless transfer technology.

Plasma Lipid Analysis of Simultaneous Application of Radiofrequency Synchronized With HIFEM for Fat Reduction in Same-Day Multiple Sessions.

High-intensity focused electromagnetic field (HIFEM) and synchronized radiofrequency (RF) technologies have been shown to be safe and effective on multiple body parts. To determine the plasma lipid levels and liver function tests of consecutive HIFEM + RF procedures delivered on the same day. Eight women and 2 men (24-59 years, BMI 22.4-30.6 kg/m 2 ) underwent 4 30-minute consecutive HIFEM + RF procedures. The treated area differed according to gender (females: abdomen and lateral and inner thighs; males: abdomen and front and back thighs). Liver function (aspartate aminotransferase [AST], alanine aminotransferase [ALT], gamma-glutamyltransferase [GGT], alkaline phosphatase [ALP]) and lipid profile (cholesterol, high-density lipoprotein [HDL], low-density lipoprotein [LDL], triglycerides [TG]) was monitored from blood samples drawn before the treatment, 1 hour, 24 to 48 hours, and 1 month after treatment. The subject's satisfaction, comfort, abdominal circumference, and digital photographs were also monitored. All 10 patients completed planned treatments and follow-up blood draws. No significant fluctuation or notable deviation in the measured blood parameters was observed. The average values during the study were in a range of AST 15.7 to 16.7IU/L, ALT 11.9 to 13.4IU/L, GGT 11.6 to 13.8IU/L, and ALP 71.4 to 77.2IU/L, TG 1.0 mmol/L, HDL 1.7 mmol/L, LDL 3.0 mmol/L, and cholesterol 5.0 to 5.1 mmol/L corresponded to the normal ranges. Subjects reported high comfort during the treatment and satisfaction with their results. No adverse event occurred. Plasma levels remained stable and normal or lipids and LFTs for multiple same-day treatments of RF plus HIFEM.