DSC based Dual-Resunet for radio frequency interference identification

Radio frequency interference(RFI)will pollute the weak astronomical signals received by radio telescopes,which in return will seriously affect the time-domain astronomical observation and research.In this paper,we use a deep learning method to identify RFI in frequency spectrum data,and propose a neural network based on Unet that combines the principles of depthwise separable convolution and residual,named DSC Based Dual-Resunet.Compared with the existing Unet network,DSC Based Dual-Resunet performs better in terms of accuracy,F1 score,and MIoU,and is also better in terms of computation cost where the model size and parameter amount are 12.5%of Unet and the amount of computation is 38%of Unet.The experimental results show that the proposed network is a high-performance and lightweight network,and it is hopeful to be applied to RFI identification of radio telescopes on a large scale.

Multi-Frequency Interference Detection and Mitigation Using Multiple Adaptive IIR Notch Filter with Lattice Structure

Radio Frequency Interferences (RFI), such as strong Continuous Wave Interferences (CWI), can influence the Quality of Service (QoS) of communications, increasing the Bit Error Rate (BER) and decreasing the Signal-to-Noise Ratio (SNR) in any wireless transmission, including in a Digital Video Broadcasting (DVB-S2) receiver. Therefore, this paper presents an algorithm for detecting and mitigating a Multi-tone Continuous Wave Interference (MCWI) using a Multiple Adaptive Notch Filter (MANF), based on the lattice form structure. The Adaptive Notch Filter (ANF) is constructed using the second-order IIR NF. The approach consists in developing a robust low-complexity algorithm for removing unknown MCWI. The MANF model is a multistage model, with each stage consisting of two ANFs: the adaptive IIR notch filter Hl(z) and the adaptive IIR notch filter HN(z), which can detect and mitigate CWI. In this model, the ANF is used for estimating the Jamming-to-Signal Ratio (JSR) and the frequency of the interference (w(0)) by using an LMS-based algorithm. The depth of the notch is then adjusted based on the estimation of the JSR. In contrast, the ANF HN(z) is used to mitigate the CW interference. Simulation results show that the proposed ANF is an effective method for eliminating/reducing the effects of MCWI, and yields better system performance than full suppression (kN=1) for low JSR values, and mostly the same performance for high JSR values. Moreover, the proposed can detect low and high JSR and track hopping frequency interference and provides better Bit error ratio (BER) performance compared to the case without an IIR notch filter.

On Normalized Least Mean Square Based Interference Cancellation Algorithm for Integrated Sensing and Communication Systems

Integrated sensing and communication(ISAC)technology is a promising candidate for next-generation communication systems.However,severe co-site interference in existing ISAC systems limits the communication and sensing performance,posing significant challenges for ISAC interference management.In this work,we propose a novel interference management scheme based on the normalized least mean square(NLMS)algorithm,which mitigates the impact of co-site interference by reconstructing the interference from the local transmitter and canceling it from the received signal.Simulation results demonstrate that,compared to typical adaptive interference management schemes based on recursive least square(RLS)and stochastic gradient descent(SGD)algorithms,the proposed NLMS algorithm effectively cancels co-site interference and achieves a good balance between computational complexity and convergence performance.

Fabrication and properties of high performance YBa_2Cu_3O_(7-δ) radio frequency SQUIDs with step-edge Josephson junctions

We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by employing stepedge junctions （SEJs） and in flip-chip configuration with 12 mm×12 mm resonators. The step in the substrate was produced by Ar ion etching with step angles ranging from 47° to 61°, which is steep enough to ensure the formation of grain boundaries （GBs） at the step edges. The YBCO film was deposited using the pulsed laser deposition （PLD） technique with a film thickness half of the height of the substrate step. The inductance of the SQUID washer was designed to be about 157 pH. Under these circumstances, high performance YBCO RF SQUIDs were successfully fabricated with a typical flux-voltage transfer ratio of 83 mV/φ0, a white flux noise of 29 μφ0/√Hz, and the magnetic field sensitivity as high as 80 fT/√Hz. These devices have been applied in magnetocardiography and geological surveys.

Effects of back gate bias on radio-frequency performance in partially depleted silicon-on-inslator nMOSFETs

The effects of back gate bias(BGEs) on radio-frequency(RF) performances in PD SOI n MOSFETs are presented in this paper. Floating body(FB) device, T-gate body-contact(TB) device, and tunnel diode body-contact(TDBC) device, of which the supply voltages are all 1.2 V, are compared under different back gate biases by different figures of merit, such as cut-off frequency( fT), maximum frequency of oscillation( fmax), etc. Because of the lack of a back gate conducting channel, the drain conductance(gd) of TDBC transistor shows a smaller degradation than those of the others, and the trans-conductance(gm) of TDBC is almost independent of back gate bias. The values of fT of TDBC are also kept nearly constant under different back gate biases. However, RF performances of FB and TB each show a significant degradation when the back gate bias is larger than ～ 20 V. The results indicate that TDBC structures could effectively improve the back gate bias in RF performance.

Design of synthetic aperture radar low-intercept radio frequency stealth

Not confined to a certain point,such as waveform,this paper systematically studies the low-intercept radio frequency(RF)stealth design of synthetic aperture radar(SAR)from the system level.The study is carried out from two levels.In the first level,the maximum low-intercept range equation of the conventional SAR system is deduced firstly,and then the maximum low-intercept range equation of the multiple-input multiple-output SAR system is deduced.In the second level,the waveform design and imaging method of the low-intercept RF SAR system are given and verified by simulation.Finally,the main technical characteristics of the lowintercept RF stealth SAR system are given to guide the design of low-intercept RF stealth SAR system.

Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure

A one-dimensional（1D） fluid model on capacitively coupled radio frequency（RF） argon glow discharge between parallel-plates electrodes at low pressure is established to test the effect of the driving frequency on electron heating. The model is solved numerically by a finite difference method. The numerical results show that the discharge process may be divided into three stages： the growing rapidly stage, the growing slowly stage, and the steady stage. In the steady stage,the maximal electron density increases as the driving frequency increases. The results show that the discharge region has three parts： the powered electrode sheath region, the bulk plasma region and the grounded electrode sheath region. In the growing rapidly stage（at 18 μs）, the results of the cycle-averaged electric field, electron temperature, electron density, and electric potentials for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are compared, respectively. Furthermore,the results of cycle-averaged electron pressure cooling, electron ohmic heating, electron heating, and electron energy loss for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are discussed, respectively. It is also found that the effect of the cycle-averaged electron pressure cooling on the electrons is to ＂cool＂ the electrons; the effect of the electron ohmic heating on the electrons is always to ＂heat＂ the electrons; the effect of the cycle-averaged electron ohmic heating on the electrons is stronger than the effect of the cycle-averaged electron pressure cooling on the electrons in the discharge region except in the regions near the electrodes. Therefore, the effect of the cycle-averaged electron heating on the electrons is to ＂heat＂ the electrons in the discharge region except in the regions near the electrodes. However, in the regions near the electrodes, the effect of the cycle-averaged electron heating on the electron is to ＂cool＂ the electrons. Finally, the space distributions of the electron pressure cooling the electron ohmic heating and the electron heating at 1/4 T, 2/4 T, 3/4 T, and 4/4 T in one RF-cycle are presented and compared.

Depressed Acne Scars—Effective, Minimal Downtime Treatment with a Novel Smooth Motion Non-Insulated Microneedle Radiofrequency Technology

Background: The microneedle fractional RF handpiece used in our study (Intensif Handpiece, EndyMed Medical, Caesarea, Israel) is a novel handpiece that uses a tip with 25 non-insulated, gold plated microneedle electrodes. The needles are inserted into the skin by a specially designed electronically controlled, smooth motion motor minimizing patient discomfort. RF emission delivered over the whole dermal portion of the needle allows effective coagulation resulting in minimal or no bleeding, together with bulk volumetric heating. Study Design/Materials and Methods: The study included 20 patients, treated for depressed acne scars using the IntensifTM?Microneedles handpiece (EndyMed PRO Platform System, EndyMed Medical, Caesarea, Israel). The degree of clinical improvement was assessed by the global aesthetic improvement scale (GAIS) and subjects satisfaction by post treatment questionnaires. Results: The number of treatments per patient varied between 1 and 6 (average 3.3 treatments per patient). Eleven patients (55%) reported none to minimal pain, six (30%) moderate discomfort and only three (15%) reported significant pain. Objective evaluation of the improvement by a board certified dermatologist showed improvement in 95% of patients. 25% showed excellent improvement, 50% experienced good improvement, and the 20% showed minimal improvement. One patient showed no improvement. Conclusions: The presented results show that the tested electronically controlled motorized insertion, non-insulated microneedle treatment technology provides a minimal discomfort, minimal downtime, effective and safe treatment for depressed acne scars.

Rydberg electromagnetically induced transparency and Autler–Townes splitting in a weak radio-frequency electric field

We utilize an electromagnetically induced transparency(EIT) of a three-level cascade system involving Rydberg state in a room-temperature cell, formed with a cesium 6 S_(1/2)–6 P_(3/2)–66 S_(1/2) scheme, to investigate the Autler–Townes(AT)splitting resulting from a 15.21-GHz radio-frequency(RF) field that couples the |66 S_(1/2) → |65 P_(1/2) Rydberg transition.The radio-frequency electric field induced AT splitting, γAT, is defined as the peak-to-peak distance of an EIT-AT spectrum.The dependence of AT splitting γAT on the probe and coupling Rabi frequency, ?_p and ?_c, is investigated. It is found that the EIT-AT splitting strongly depends on the EIT linewidth that is related to the probe and coupling Rabi frequency in a weak RF-field regime. Using a narrow linewidth EIT spectrum would decrease the uncertainty of the RF field measurements.This work provides new experimental evidence for the theoretical framework in [J. Appl. Phys. 121, 233106(2017)].

A novel radio frequency coil for veterinary magnetic resonance imaging system

In this article, a novel designed radio frequency （RF） coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging （MRI） system. Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil. The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation. The size and the shape of the new coil are optimized and validated by simulation through using the finite element method （FEM）. Good magnetic resonance （MR） images are achieved on a shepherd dog.

Comparison of pulse-modulated and continuous operation modes of a radio-frequency inductive ion source

The paper describes an experimental study of the characteristics of a pulse-modulated radiofrequency(RF)discharge sustained at low pressures,typical of the operating modes of RF gridded ion sources.The motivation for the study is the question of whether the RF pulsemodulated mode can increase the efficiency of the ion source.The ion current values extracted from an RF inductive ion source operating in continuous and pulse-modulated modes were compared.The experimental data were also compared with the parameter calculations based on a0D numerical model of the discharge.The measurements showed that the pulse-modulated operation mode of the RF ion source had a noticeable advantage when the power of the RF generator was 140 W or lower.However,as the generator power increased,the advantage was lost because the pulse-modulated operation mode,having a higher RF power instant value,entered the region of existence sooner than the continuous mode,where the ion production cost begins to grow with RF power.

Preparation and Characterization of Transparent Conductive Zinc Doped Tin Oxide Thin Films Prepared by Radio-frequency Magnetron Sputtering

High transparent and conductive thin films of zinc doped tin oxide （ZTO） were deposited on quartz substrates by the radio-frequency （RF） magnetron sputtering using a 12 wt% ZnO doped with 88 wt% SnO2 ceramic target.The effect of substrate temperature on the structural,electrical and optical performances of ZTO films has been studied.X-ray diffraction （XRD） results show that ZTO films possess tetragonal rutile structure with the preferred orientation of （101）.The surface morphology and roughness of the films was investigated by the atomic force microscope （AFM）.The electrical characteristic （including carrier concentration,Hall mobility and resistivity） and optical transmittance were studied by the Hall tester and UV- VIS,respectively.The highest carrier concentration of -1.144×1020 cm-3 and the Hall mobility of 7.018 cm2（V ·sec）-1 for the film with an average transmittance of about 80.0% in the visible region and the lowest resistivity of 1.116×10-2 Ω·cm were obtained when the ZTO films deposited at 250 oC.

Ignition dynamics of radio frequency discharge in atmospheric pressure cascade glow discharge

A cascade glow discharge in atmospheric helium was excited by a microsecond voltage pulse and a pulse-modulated radio frequency(RF) voltage, in which the discharge ignition dynamics of the RF discharge burst was investigated experimentally. The spatio-temporal evolution of the discharge, the ignition time and optical emission intensities of plasma species of the RF discharge burst were investigated under different time intervals between the pulsed voltage and RF voltage in the experiment. The results show that by increasing the time interval between the pulsed discharge and RF discharge burst from 5 μs to 20 μs, the ignition time of the RF discharge burst is increased from 1.6 μs to 2.0 μs, and the discharge spatial profile of RF discharge in the ignition phase changes from a double-hump shape to a bell-shape. The light emission intensity at 706 nm and 777 nm at different time intervals indicates that the RF discharge burst ignition of the depends on the number of residual plasma species generated in the pulsed discharges.

Anti-interference method for HF radars by transmitting phase-modulated chirps

Radio frequency interference （RFI） is a major problem in high-frequency （HF） radars. Conventional filtering-involved RFI suppression methods may introduce distortions to the target signals of interest and often demand extra hardware costs. In this paper, a novel method for RFI suppression by using linearly or randomly phase-modulated （PM） chirps is proposed, which enables independent analyses of the target signal and the RFI. Furthermore, the directions of arrival （DOA） of the interference are used as constraints to ensure a better DOA estimation of the target. The effectiveness of the method is demonstrated by numerical simulation results. The method can greatly improve the anti-interference capabilities of HF radars and is extremely applicable in the portable and low-cost radar systems.

Radio Frequency Fingerprint-Based Satellite TT&C Ground Station Identification Method

This study presents a radio frequency(RF)fingerprint identification method combining a convolutional neural network(CNN)and gated recurrent unit(GRU)network to identify measurement and control signals.The proposed algorithm(CNN-GRU)uses a convolutional layer to extract the IQ-related learning timing features.A GRU network extracts timing features at a deeper level before outputting the final identification results.The number of parameters and the algorithm’s complexity are reduced by optimizing the convolutional layer structure and replacing multiple fully-connected layers with gated cyclic units.Simulation experiments show that the algorithm achieves an average identification accuracy of 84.74% at a -10 dB to 20 dB signal-to-noise ratio(SNR)with fewer parameters and less computation than a network model with the same identification rate in a software radio dataset containing multiple USRP X310s from the same manufacturer,with fewer parameters and less computation than a network model with the same identification rate.The algorithm is used to identify measurement and control signals and ensure the security of the measurement and control link with theoretical and engineering applications.

Designing Wireless Charger Circuit for Hearing Aids Using Radio Frequency Waves

In this paper, an attempt has been made to produce a recipient system of wireless charge for a simple hearing aid so that electrical signal would be generated through detecting and receiving radio frequency waves (RF). The purpose of this design is to receive wireless charge for hearing aids and basically for any electronic device which is not required to a high energy for being setup. In this study, it has been demonstrated that as the amount of radio receiving energy increases, distance of receiver from antenna should be decreased;otherwise, either maximum amount of the receiving energy, or signal power density of the transmitter should be increased. Since it is impossible to be performed, it is decided to set up an energy receiving system constructed by rectenna and charge Circuit and to adjust their parameters to provide energy requirements for a device with low-power consumption. In this paper, different components of an energy receiving system from radio frequency band have been mentioned and a diagram block has been suggested. Subsequently, input impedance of designed antenna has been adjusted by provided relations. This impedance should be adjusted with the total impedance of regarded hearing aid Circuit by which the highest amount of received signal power is transferred to the battery of hearing aids. Received signal is converted to a dc voltage by rectifier diode. Finally, by applying a voltage regulator which has been designed using a common-collector amplifier not only the output voltage is kept constant, but the power is also strengthened. The battery of the hearing aids will be charged using the obtained power and voltage.

Analytical and Numerical Model Confrontation for Transfer Impedance Extraction in Three-Dimensional Radio Frequency Circuits

3D chip stacking is considered known to overcome conventional 2D-IC issues, using through silicon vias to ensure vertical signal transmission. From any point source, embedded or not, we calculate the impedance spread out;our ultimate goal will to study substrate noise via impedance field method. For this, our approach is twofold: a compact Green function or a Transmission Line Model over a multi-layered substrate is derived by solving Poisson’s equation analytically. The Discrete Cosine Transform (DCT) and its variations are used for rapid evaluation. Using this technique, the substrate coupling and loss in IC’s can be analyzed. We implement our algorithm in MATLAB;it permits to extract impedances between any pair of embedded contacts. Comparisons are performed using finite element methods.

Aerodynamic actuation characteristics of radio-frequency discharge plasma and control of supersonic flow

In this paper, aerodynamic actuation characteristics of radio-frequency(RF) discharge plasma are studied and a method is proposed for shock wave control based on RF discharge. Under the static condition, a RF diffuse glow discharge can be observed; under the supersonic inflow, the plasma is blown downstream but remains continuous and stable.Time-resolved schlieren is used for flow field visualization. It is found that RF discharge not only leads to continuous energy deposition on the electrode surface but also induces a compression wave. Under the supersonic inflow condition, a weak oblique shock wave is induced by discharge. Experimental results of the shock wave control indicate that the applied actuation can disperse the bottom structure of the ramp-induced oblique shock wave, which is also observed in the extracted shock wave structure after image processing. More importantly, this control effect can be maintained steadily due to the continuous high-frequency(MHz) discharge. Finally, correlations for schlieren images and numerical simulations are employed to further explore the flow control mechanism. It is observed that the vortex in the boundary layer increases after the application of actuation, meaning that the boundary layer in the downstream of the actuation position is thickened. This is equivalent to covering a layer of low-density smooth wall around the compression corner and on the ramp surface, thereby weakening the compressibility at the compression corner. Our results demonstrate the ability of RF plasma aerodynamic actuation to control the supersonic airflow.

Insights into Three-Dimensional Radiofrequency Circuits Connections

The authors state briefly the possibility of various simulators to handle propagation of electromagnetic waves along some interconnections, in 3D RF （Radio Frequency） circuits. The studies are first derived in the time domain： a Finite-Difference Time-Domain method is applied, taking spectra via FFTs （Fast Fourier Transform） as post-processors. Electric and magnetic field distributions, pulse propagations along stripline structures or vias are highlighted. The scattering parameters for various cases are extracted and compared. Some original issue of this work is an insight on crosstalk or shielding phenomena between lines.

Influence of Discharge Parameters on Tuned Substrate Self-Bias in an Radio-Frequency Inductively Coupled Plasma

The tuned substrate self-bias in an rf inductively coupled plasma source is controlled by means of varying the impedance of an external LC network inserted between the substrate and the ground. The influencing parameters such as the substrate axial position, different coupling coils and inserted resistance are experimentally studied. To get a better understanding of the experimental results, the axial distributions of the plasma density, electron temperature and plasma potential are measured with an rf compensated Langmuir probe; the coil rf peak-to-peak voltage is measured with a high voltage probe. As in the case of changing discharge power, it is found that continuity, instability and bi-stability of the tuned substrate bias can be obtained by means of changing the substrate axial position in the plasma source or the inserted resistance. Additionally, continuity can not transit directly into bi-stability, but evolves via instability. The inductance of the coupling coil has a substantial effect on the magnitude and the property of the tuned substrate bias.