Radio Frequency System Research Articles

Effect of substitution and processing on the morphology and dielectric properties of Pr2/3Cu3Ti4O12 (PCTO) ceramic

AbstractLow‐cost, large dielectric constant, and resistivity materials have wide range of applications for radio frequency systems, flash memory devices to ferroelectric switches, and energy storage applications. The paper reports on the development and characterization of high‐resistivity Pr2/3Cu3Ti4O12 (PCTO) ceramics developed by doping with Ca2+ and Sr2+ ions under various processing conditions. In particular, synthesis and growth were performed at 1173 and 1273 K resulting in significant difference in both electrical and morphological properties. To alter the distortion and polarity of ceramics, low concentration (0.15 mole fraction) of Ca2+ and Sr2+ hetero‐valent ions with different size were substituted for Pr3+. The evolution and sizes of non‐spherical, non‐faceted grains altered to facet shapes due to changes in the anisotropy developed with increased copper concentration in the grains. The morphology analysis at these low processing temperatures revealed that grain growth occurs by engulfment of smaller grains by larger grains, necking process, and channel formation, with particles growing in nanometer size to greater than 10 µm and forming new layers on top of grains. The migration of copper‐rich phases above 1173 K from boundaries to grains causes faceted morphology in both pure and substituted PCTO. Finally, by substituting Ca2+ and Sr2+ into the ceramics, altering the processing temperature, resistivity, and dielectric constant significantly increased. The substituted ceramics showed a higher dielectric constant at applied frequencies of 100‒100 000 Hz and did not vary at bias voltages of 50‒1000 mV, indicating no breakdown of the ceramics.

An autoregressive adaptive Kalman filter carrier tracking approach for mitigating ionospheric scintillation effects in GNSS receivers

Abstract Ionospheric scintillation causes a serious threat to the accuracy, integrity, and reliability of Global Navigation Satellite System (GNSS) receivers, leading to significant amplitude fading, and rapid phase fluctuations. The GNSS receivers with traditional carrier-tracking loops may sometimes fail to retain signal integrity during high scintillation scenarios, leading to degraded positioning performance or even loss of lock and can seriously affect the dynamic systems and safety of life-critical applications. We present an Autoregressive Adaptive Kalman Filter (AR-KF) based tracking approach to enhance the robustness of the GNSS receivers under scintillation conditions. The adaptive KF algorithm in the proposed framework dynamically adjusts the time-varying characteristics of the parameters in its tracking loop by leveraging insights gained from a sophisticated and high rate software defined radio-frequency (RF) system collocated by a specialized ionospheric monitoring GNSS receiver whereas the succeeding AR algorithm plays a crucial role by intelligently predicting and refining the carrier phase estimates, thereby mitigating the distortions and enhancing the GNSS tracking loop resiliences. The efficacy of the proposed filtering algorithm is evaluated using real-time GNSS signals affected by weak, moderate, and strong scintillation conditions. Experimental results demonstrate that the combined approach in this work can ensure relatively robust navigation and timing performance by effectively tracking even in severe scintillation conditions. The analysis revealed minimal intervention of the algorithm during weak scintillation but intelligently improving the performance in moderate, and strong scintillation scenarios. The findings from this study suggest the effectiveness of integrating adaptive KF and AR architecture through advanced signal processing methodologies into GNSS receivers, offering a consistent solution for navigational applications during strong scintillation conditions.

Qibosoq: an open-source framework for quantum circuit RFSoC programming

Abstract We present Qibosoq, an open-source server-side software package designed for radio frequency system on chip (RFSoC) for executing arbitrary pulse sequences and algorithms on self-hosted quantum processing units using only open-source software. Qibosoq connects the RFSoC firmware provided by Qick, a Quantum Instrumentation Control Kit, with Qibo, a quantum computing middleware framework that enables both experimental and gate-based applications.
It simplifies the work of experimentalists and developers by managing client-server communication protocols, implementing tests, and validation procedures, thereby reducing the complexity of experimental setups.
The client-side integration is achieved with dedicated drivers implemented in Qibolab, the specialized software module of Qibo for quantum hardware control. Therefore, this setup provides a seamless mechanism to deploy circuit-based algorithms on custom self-hosted quantum hardware platforms controlled by RFSoC electronics.

Flip-GFDM complexity reduction for a power-efficient visible light communication system

Visible light communication (VLC) has emerged as a promising solution to the limitations of traditional radio frequency systems, leveraging LEDs for high-speed, interference-free data transmission. However, optical orthogonal frequency division multiplexing (OFDM) techniques such as Flip-OFDM face challenges including high peak-to-average power ratio (PAPR) and spectral inefficiency. This study introduces what we believe to be a novel flip-generalized frequency division multiplexing waveform (Flip-GFDM), named non-Hermitian Flip-GFDM (NH-Flip-GFDM), designed to reduce complexity. By eliminating Hermitian symmetry and halving the IFFT/FFT size, the proposed approach achieves significant computational savings, with about a 50% reduction in complexity. Simulation results reveal that NH-Flip-GFDM maintains comparable symbol error rate (SER) and bit error rate (BER) performance to traditional Flip-GFDM while reducing PAPR by approximately 2 dB over Flip-OFDM. These improvements position NH-Flip-GFDM as a power-efficient and cost-effective solution for next-generation VLC systems.

Lesioning Through a Directional Deep Brain Stimulation Lead in the Subthalamic Nucleus.

A 59-year-old woman with a previous subthalamic nucleus deep brain stimulation (DBS) implanted for Parkinson's disease developed a hardware related infection. Wound dehiscence and infection developed and necessitated removal of the DBS system. The patient experienced excellent therapeutic benefit from her DBS and expressed concern about device removal. The patient was offered the option of a lesioning procedure which could be performed during hardware explantation. An operative procedure was conducted where the intracranial DBS lead was connected to a radiofrequency system in a deliberate effort to create a targeted subthalamotomy through the existing DBS lead. A multilevel lesion was generated using the contacts on the directional DBS lead. Following the lesion the DBS lead and hardware were removed. Creating a lesion through a DBS lead using radiofrequency ablation is a therapeutic option for patients not interested in later re-implantation or for those with a history of multiple DBS related infections. Lesioning through segmented leads introduces more complexity into the procedure.

A Near-Field Radio Frequency System for Continuous Left and Right Lung Volume Sensing

A Near-Field Radio Frequency System for Continuous Left and Right Lung Volume Sensing

Development of a photoelectric hybrid phase reference line system for super tau-charm facility-beam test platform.

The Super Tau-Charm Facility-Beam Test Platform (STCF-BTP) is a platform developed to validate and optimize the design and feasibility of the Super Tau-Charm Facility. It requires precise synchronization of accelerating fields to achieve the desired high beam luminosity. We propose a novel phase reference line system that incorporates a phase reference distribution system based on a photoelectric hybrid approach and a control measurement system leveraging low-level radio-frequency systems. In the distribution system, phase-compensated signals are transmitted through optical fibers for drift stability, while low-noise microwave signals are delivered via coaxial cables. The receiver modules perform phase calibration between these dual paths to output optimized reference signals. Laboratory tests over a 50-m transmission path demonstrated that the system achieves <15fs additional jitter (10Hz to 10MHz) and maintains phase drift of below 20fs RMS over 24h across all receivers, meeting stringent requirements of the STCF-BTP. This hybrid approach offers a robust solution for precise phase reference distribution in accelerator facilities requiring femtosecond-level synchronization across multiple stations.

Drone Detection in Restricted Areas Using Deep Learning

As the use of drones becomes more widespread, the corresponding rise in drone-related intrusions poses a growing threat to public safety and privacy. Traditional anti-drone systems typically rely on radio-frequency sensors for drone tracking. This paper investigates the fusion of deep learning-based detection algorithms with surveillance cameras within the framework of radio-frequency anti-drone systems. The primary aim is to assess the efficacy of contemporary models and training methodologies in achieving precise and real-time drone detection. One of the central challenges addressed in this paper is the detection of small drones at extended distances, coupled with the demand for real-time performance. To overcome the scarcity of small drone datasets, the research team constructed a real-world dataset for comprehensive evaluations. Various iterations of the YOLO (You Only Look Once) models were compared using this dataset, with specific modifications implemented to enhance small object detection. Additionally, the image sources are diversified for training, incorporating bird images to mitigate false positives and enhance model robustness. Among the YOLO models tested, YOLOv5 exhibited superior precision, recall, and F1 score. The work delves into the impact of additional detection layers on precision, recall, and F1 score, revealing trade-offs between these metrics. The inclusion of bird images in the background training process demonstrated improvements in accuracy and recall, underlining the importance of diverse training data. An intriguing finding was observed when excluding extremely small drones and birds from the analysis, resulting in heightened precision but diminished recall. This highlights the delicate balance required in optimizing detection algorithms for different scenarios. The paper also acknowledges the need for further investigation into the generalizability of the proposed approach across various drone types.

A ground-to-GEO-to-LEO satellite optical wireless communication link based on a spectrally efficient and secure modulation scheme

Optical wireless communication (OWC) offers significant advantages over traditional radio frequency systems due to its high bandwidth, ease of deployment, license-free operation, immunity to electromagnetic interference, and inherent security benefits. This research presents a novel all-optical technique for transmitting multiple data channels over an optical link, employing Differential Phase-Shift Keying (DPSK) and Pulse Position Modulation (PPM) schemes. Notably, the combination of DPSK and PPM enhances both data security and spectral efficiency compared to conventional methods. The proposed technique demonstrably achieves error-free transmission of three data channels, each at a data rate of 10 Gbps, as validated through simulation results. Furthermore, the study explores the applicability of this technique to inter-satellite links. By integrating with a geostationary Earth orbit (GEO) data relay satellite, this technique can improve link availability for low-Earth orbit (LEO) satellites. Our novel approach holds significant promise for practical deployment and seamless integration into future high-speed and secure communication networks, catering to the ever-growing demand for robust data transmission.

A Ka-band self-packaged transition from groove gap waveguide to CBCPW using PCB supersede metal lid

This article introduces a novel transition that utilizes a printed circuit board (PCB) to replace the traditional metal lid of the groove gap waveguide (GGW). An efficient conversion from the GGW to the reflection cavity, consisting of a plated-blind groove and a shorting back, is achieved using the wedge. The tapered wide-slot probe is positioned at the bottom of the PCB to couple the electric field and simultaneously convert the TE 10 mode in the GGW to the quasi-TEM mode in the conductor-backed coplanar waveguide. The operational mechanism of the transition is investigated, the design procedure with good operability is proposed, and the key dimensions are analyzed. Additionally, a back-to-back transition prototype is developed and experimentally investigated. The prototype demonstrates an insertion loss of less than 2.05 dB in the Ka-band and a 50.5% 10-dB return loss fractional bandwidth. It should give prominence that the configuration of the transition offers a dedicated layer for peripheral circuit placement. This unique advantage can address the inconvenience of integrating peripheral circuits with the GGW and provide a viable solution to applying the GGW in more complex radio frequency modules or systems.

Design and development of a variable frequency high-power RF tetrode amplifier for high-energy compact proton cyclotron accelerators

The paper presents the design of a tetrode radio frequency (RF) amplifier system for high-current proton cyclotron accelerators used in the production of medical isotopes, targeting cyclotrons of different energy levels. The system is based on a variable frequency design with a tuning mechanism, making it adaptable to cyclotron devices operating at various energy levels and frequencies. The wideband tetrode amplifier design covers the typical cyclotron operating frequency range of 30–90 MHz, with a power output range from 50 kW to 150 kW. Based on this design, the system performance testing was conducted, and the RF system was successfully tuned and commissioned on the 50 MeV accelerator of the State Power Investment Corporation (SPIC), achieving satisfactory results. The design and testing procedures of the variable frequency RF amplifier will be discussed in this paper.

Multiple Sensor Scheduling in a Dual-Hop Underwater-Acoustic/Terrestrial-RF System

In this paper, we consider a dual-hop heterogeneous underwater acoustic/terrestrial radio frequency system. To accommodate multiple underwater sensors, we employ two multi-sensor scheduling techniques: generalised order sensor scheduling and round-robin scheduling. The underwater acoustic network is connected to the terrestrial radio frequency link through a decode and forward relay, serving as an acoustic-radio frequency communication node. This node is associated with the floating vehicle which is present on the water surface. Each underwater acoustic channel is considered to have Rayleigh fading with outdated channel state information. For the radio frequency link, we adopt Nakagami-m fading. For the presented dual-hop system, the closed-form analytical expressions of outage probability, average bit error rate, and effective capacity are derived. For better understanding, the asymptotic results for outage probability and average bit error rate are also derived. The diversity order and coding gain are also yielded for both the scheduling methods. Also, the analytical result is verified by Monte-Carlo simulations. Furthermore, the average fairness is evaluated for underwater multi-sensor networks.

In-House Design, Manufacturing, and Testing of a 2.856 GHz Combline Microwave Cavity Filter for the Low-Level RF Systems of Linear Particle Accelerators

A combline microwave cavity filter has been developed to generate the 2.856 GHz radio frequency (RF) tone to be used as the master reference of SPARC_LAB electron linac facility at the Frascati National Laboratories of the National Institute for Nuclear Physics (LNF-INFN). The filter must select the 36th harmonic from a frequency comb with a repetition frequency of 79.33MHz and reject the other harmonics. The comb is generated by the electric conversion of the laser pulse train from the oscillator of the photocathode laser. Since a filter for this very specific application is off-the-shelf, it was designed, manufactured, and tested in-house at LNF-INFN. The measured insertion loss at the center frequency is 2.2 dB, the bandwidth is 30MHz (percentage fractional bandwidth is 1.1 %). This narrow bandwidth is required to ensure effective rejection (insertion loss &gt; 65 dB) of adjacent harmonics in the frequency comb, specifically at frequencies of 2.77633 GHz and 2.93533 GHz. The purpose of filtering is to ensure that the tone, distributed in the low-level RF system, remains clean and can be used to synchronize the most crucial machine subsystems, such as RF power units, accelerating cavities, diagnostic systems, and lasers.

Operator learning curve with a novel dual-energy lattice-tip ablation system.

Operator learning curve with a novel dual-energy lattice-tip ablation system.

Research on Radio Frequency System Measurement Techniques for Microwave Testing

Abstract To address the inefficiencies and high costs associated with traditional radio frequency (RF) system performance testing, which often necessitates the use of a rotating platform to generate trigger signals, this paper introduces a novel testing system. This system is centered around an embedded signal trigger module, designed to revolutionize the testing process by eliminating the need for a rotating platform and consequently reducing the overall costs. The paper explores radar measurement techniques and validates the proposed system through practical testing. This involves an in-depth analysis of measurement technologies used in microwave testing of RF systems. The findings demonstrate the technical feasibility of the embedded signal trigger module-based testing method, proving its capability to perform on-site, cost-effective measurements of RF systems. Moreover, the study highlights the enhancement in measurement efficiency achieved through the innovative testing method. The results indicate that the embedded signal trigger module significantly improves the testing process for RF systems, offering a more efficient and economical alternative to conventional testing methods.

Characteristics of In Vivo Lesion Formation With a Temperature-Controlled Diamond-Tip Radiofrequency Ablation Catheter in the Ventricle: A Preclinical Model.

Power-controlled radiofrequency ablation with irrigated-tip catheters has been the norm for ventricular ablation for almost 2 decades. New catheter technology has recently integrated more accurate tissue temperature sensing enabling temperature-controlled irrigated ablation. We aimed to investigate the in vivo ablation parameters and lesion formation characteristics in ventricular myocardium using a novel temperature-controlled radiofrequency catheter. Twenty canines were divided into 3 groups: 4 noninfarcted, acute (phase I); 8 noninfarcted, chronic (phase II); and 8 infarcted, chronic (phase III). Lesions were delivered with a temperature-controlled radiofrequency system utilizing a chemical vapor deposit diamond for efficient thermal diffusivity. In phase I, 17 ablation settings were tested (temperature set points, 50/60/70 °C; ablation duration, 15/30/60/90/120 s; and power limit, 30/50 W). Four and one of these sets of parameters were further tested in phases II and III, respectively. Lesions were assessed by ex vivo contrast-enhanced magnetic resonance imaging and gross pathology 5 weeks after ablation in phases II/III. Across all phases, 111 ablation lesions were delivered. Ablation with the power limit of 50 W, the temperature set point of 60 °C, and the duration of 60 s produced significantly larger and deeper lesions (mean, 569.2 mm3; mean maximal depth, 9.8 mm) compared with 50 W/60 °C/30 s (mean, 340.4 mm3; mean maximal depth, 8.3 mm) and 50 W/50 °C/60 s (mean, 227 mm3; mean maximal depth, 6.9 mm), with P<0.05 for all pairwise comparisons. Ablation of infarcted myocardium in phase III (50 W/60 °C/30 s) resulted in smaller impedance and bipolar electrogram amplitude changes and lesion size compared with ablation in normal myocardium with the same settings. No steam pop, myocardial perforation, or char formation was observed in any of the 111 ablations across all phases. In vivo radiofrequency ablation in a canine model with a diamond-tip temperature-controlled catheter using a temperature set point of 60 °C and a power limit of 50 W created large lesions without steam pop risk in both normal and infarcted ventricular myocardia.

Laser Terminals on CubeSats: Developments for Telecommunications and Quantum Links

ABSTRACTSatellite‐based laser communication is an emerging technology that is finding its way from research to industry. Compared to radio frequency (RF) systems, it has a more efficient size, weight, and power budget and, furthermore, is license free. The required space laser terminals can be designed in different sizes, depending on the mission needs. Data rate requirements range from CubeSats with Mb/s to large satellites with Gb/s data rates and sometimes even Tb/s. This enables, for example, the use of high‐resolution imagers even in CubeSats or mega‐constellation networks with high‐rate intersatellite links. Space laser terminals are also necessary for satellite‐based Quantum Key Distribution (QKD), which is increasingly important for the development of future quantum‐safe networks. In contrast to classical optical links for data transmission, link budget constraints cannot be overcome by simply amplifying the power, but the end‐to‐end loss needs to be minimized. This is possible with high antenna gains defined by the transmit and receive optics size. Therefore, the optics size of the laser terminal is one of the most important parameters. Building optical terminals with large apertures for use in space is expensive and requires at least a small satellite platform, increasing the cost of development and launch. The New Space approach using a CubeSat platform is a cost‐effective alternative because many components can be selected off‐the‐shelf. This paper reviews developments of laser communication terminals for CubeSats in space to ground and intersatellite scenarios with applications in quantum communications and telecommunications. The systems are selected with respect to clear space deployment, and their core parameters are compared. Special focus and detailed insight are given for the development OSIRIS4CubeSat (O4C).

RF System Advancements for Satellite and Space Communications: Integrating AI with High-Frequency and Hybrid Systems

With the rapid evolution of satellite communications, the use of advanced radio frequency (RF) systems has become pivotal in addressing emerging challenges. High-frequency bands, such as millimeter-wave (mmWave) and terahertz (THz), enable high-throughput data transmission but introduce new complexities such as Doppler shifts and signal degradation. Hybrid satellite-terrestrial networks are expanding the possibilities for 5G and 6G backhauls, while low Earth orbit (LEO) constellations improve latency- sensitive applications. This paper explores RF system advancements, including beamforming, MIMO, and AI-driven optimizations. Additionally, it discusses challenges like energy efficiency, atmospheric attenuation, and spectrum management. The paper concludes with insights into future trends such as quantum RF systems, deep- space communications, and reconfigurable intelligent surfaces. Keywords – Satellite Communications, RF Systems, Millimeter-Wave, Terahertz, Beamforming, AI-Driven Optimization, Hybrid Networks, Non-Terrestrial Networks (NTN), Cognitive Radios, Network Slicing, LEO Satellites, 5G/6G Backhaul, Doppler Mitigation, Energy-Efficient RF.

Liquid lenses for aerospace beam steering and communications: MOSAIC.

Laser communications (lasercom) can enable more efficient and higher bandwidth communications than conventional radio frequency (RF) systems, but requires more sophisticated pointing and tracking (PAT) systems to acquire and maintain links. Liquid lens arrays can provide compact, nonmechanical beam steering as an alternative to fast-steering mirrors and mechanical gimbals. An array of two liquid lenses offset in perpendicular axes along with a third on-axis lens in the array are used for beam steering and divergence control, respectively. The Miniature Optical Steered Antenna for Intersatellite Communications (MOSAIC) project applies liquid lens technology to create a transceiver for laser communications on spacecraft to enable wide field-of-view communications. This work provides analytical models of beam steering in order to inform subsystem sizing, and uses simulation studies along with previous work on space environment evaluation of liquid lenses to produce representative link budgets for a liquid lens based lasercom transceiver. A 25 Mbps link with 4 W transmit power at 1550 nm (optical C band) and 16-ary pulse position modulation (16-PPM) can be maintained up to 175 km separation with 3 dB margin, using larger pressure-actuated liquid lenses from Optotune arranged for hemispherical steering, potentially allowing for high speed optical links between formation flying swarms for applications such as interferometry.

The Efficacy and Safety of Synchronized Radiofrequency and High Intensity Facial Electrical Stimulationin Improving Facial Skin Laxity and Quality in Asians.

Noninvasive aesthetic procedures for facial rejuvenation are gaining popularity. Conventional treatments, such as radiofrequency (RF) and high-intensity focused ultrasound (HIFU), primarily improve skin quality but do not address the deeper musculoaponeurotic structures that affect facial laxity. A novel approach that delivers synchronized RF with high intensity facial electrical stimulation(HIFES) thought to target both the skin and underlying musculoaponeurotic framework to effectively enhance facial laxity has been investigated. To assess the long-term efficacy and safety of combined synchronous RF and HIFES therapies in treating facial skin laxity among Asian subjects. In this prospective, evaluator-blinded study, 15 participants aged 40-65 years with mild to moderate facial skin laxity were enrolled. Each underwent four weekly treatments using a synchronized RF and HIFES system using noninvasive electrode applicators on the forehead and cheeks. Objective assessments included forehead and cheek lifting measurements using a 3D photographic system, eyebrow lifting measurement using ImageJ software, skin texture and melanin levels using Antera 3D®, and skin elasticity using Cutometer® MPA 580. Additionally, patients provided self-assessments regarding their perceived level of improvement. Assessments were conducted at baseline, before the 3rd treatment, and at 1 month, 3 months, and 6 months after the last treatment. All participants completed the study. Significant improvements were observed in forehead and cheek lifting sustained at 6 months (p < 0.0001). A significant eyebrow lift of 1.39 mm was observed at 3 months (p = 0.0087), with a sustained lifting distance of 1.31 mm at 6 months (p = 0.0021). Skin firmness improved substantially (p < 0.0001), with R0 (skin firmness) increasing by 81.24% at 6 months. Skin texture improved notably in the crow's feet area (13.82% improvement at 3 months, p = 0.049). Melanin levels decreased significantly in the crow's feet and forehead regions. Treatment was well tolerated, with pain scores decreasing from 3.5 ± 1.8 to 1.6 ± 1.0 by the fourth session. No serious adverse events occurred. Combined synchronous RF and HIFES therapy is a safe and effective Noninvasive method of improving facial skin laxity and quality in Asian subjects. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.