Power transfer efficiency in an air-breathing radio frequency ion thruster

Due to a series of challenges such as low-orbit maintenance of satellites, the air-breathing electric propulsion has got widespread attention. Commonly, the radio frequency ion thruster is favored by low-orbit missions due to its high specific impulse and efficiency. In this paper, the power transfer efficiency of the radio frequency ion thruster with different gas compositions is studied experimentally, which is obtained by measuring the radio frequency power and current of the antenna coil with and without discharge operation. The results show that increasing the turns of antenna coils can effectively improve the radio frequency power transfer efficiency, which is due to the improvement of Q factor. In pure N_2 discharge,with the increase of radio frequency power, the radio frequency power transfer efficiency first rises rapidly and then exhibits a less steep increasing trend. The radio frequency power transfer efficiency increases with the increase of gas pressure at relatively high power, while declines rapidly at relatively low power. In N_(2)/O_(2) discharge, increasing the N_(2) content at high power can improve the radio frequency power transfer efficiency, but the opposite was observed at low power. In order to give a better understanding of these trends, an analytic solution in limit cases is utilized, and a Langmuir probe was employed to measure the electron density. It is found that the evolution of radio frequency power transfer efficiency can be well explained by the variation of plasma resistance, which is related to the electron density and the effective electron collision frequency.

Experimental results of a magnetic field modification to the radio frequency driver of a negative ion source

A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However, the magnetic field diffused into the driver has some influence on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver, a circular ring(absorber) of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around it and improve plasma outflowing. With the application of the absorber, the electron density is increased by about 35%, and the extraction current measured from the extraction grid is increased from 1.02 A to 1.29 A. The results of the extraction experiment with cesium injection show that both the extraction grid(EG) current and H-current are increased when the absorber is introduced.

Hollow cathode effect in radio frequency hollow electrode discharge in argon

Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the plasma density.In this work,the variations of the HCE in one RF period are investigated by using a two-dimensional particle-in-cell/Monte-Carlo collision(PIC/MCC)model.The results show that the sheath electric field,the sheath potential drop,the sheath thickness,the radial plasma bulk width,the electron energy distribution function(EEDF),and the average electron energy in the cavity vary in one RF period.During the hollow electrode sheath's expansion phase,the secondary electron heating and sheath oscillation heating in the cavity are gradually enhanced,and the frequency of the electron pendular motion in the cavity gradually increases,hence the HCE is gradually enhanced.However,during the hollow electrode sheath's collapse phase,the secondary electron heating is gradually attenuated.In addition,when interacting with the gradually collapsed hollow electrode sheaths,high-energy plasma bulk electrons in the cavity will lose some energy.Furthermore,the frequency of the electron pendular motion in the cavity gradually decreases.Therefore,during the hollow electrode sheath's collapse phase,the HCE is gradually attenuated.

用于油气井RFID扶正器激活的阅读器共形天线设计

基于油气井井下环境的特点,为实现井下扶正器的远程控制,同时改正射频识别(RFID)阅读器天线电磁波强度衰减过大、辐射性能差等缺陷,设计一种共形于井下管道的RFID扶正器阅读器偶极子天线。依据天线设计的基本理论,利用天线弯折技术,将该天线结构设计为倒“U”型,实现与套管相共形;通过仿真扫频分析优化天线参数,分析天线主要结构对性能的影响。结果表明,设计的天线最终的中心频率为860 MHz,在该频率下天线输入端口反射系数为-21.05 dB,增益为2.2 dB,天线尺寸为11 mm×148.44 mm,天线的性能满足设计需求,可用于套管扶正器等井下工具的无线控制。

DRFM干扰在OFDM新体制雷达中的研究

新体制雷达以正交频分复用(OFDM)数字调制方式作为雷达信号源,具有高频谱效率、高分辨能力等优点。本文首先介绍了新体制雷达系统的基本组成部分,主要包括OFDM信号源、发射模块、环境模块、接收模块和信号处理模块。其次介绍了数字射频存储器(DRFM)干扰的主要组成部分以及工作原理,其中主要包括假目标干扰。最后将DRFM干扰与新体制雷达结合,在加干扰和不加干扰两种情况下对仿真目标进行测距和测速,结果验证了新体制雷达测量目标的准确性以及DRFM干扰的可行性。对新体制雷达及DRFM干扰研究具有参考意义。

基于RFID技术的医疗器械信息化追溯系统

为了增强医疗器械系统的整体追溯性能,设计了基于RFID技术的医疗器械信息化追溯系统。在医疗器械信息化追溯系统整体架构下,设计系统硬件部分,包括读写器管理模块、基于RFID技术的数据采集及传输模块、追溯数据处理模块、追溯数据管理模块等,通过上述模块完成对医疗器械信息追溯数据的采集、传输、处理、调用及管理;系统的软件部分,在生产、流通、责任等3个追溯环节下,通过LANDMARC算法和VIRE算法对医疗器械信息追溯,获取追溯标签的最终位置坐标。通过系统CPU内存占用率测试、存储时间测试和追溯效率测试验证了该系统的有效性。

基于RFID的仓储自动化与智能化技术应用

随着全球供应链的不断发展及复杂化,仓储自动化与智能化技术成为提高效率及准确性的关键手段。探讨了射频识别(RFID)在仓储管理中的应用,利用RFID技术可实时追踪商品,减少库存错误,降低人工操作需求,提高整体物流速度。将传统的条形码系统与RFID系统进行对比,揭示RFID在准确性、可靠性及数据收集速度等方面的优势,为未来的仓储自动化与智能化发展提供参考。

基于RFID技术的消毒供应追溯系统的应用研究

文章深入研究了基于射频识别(radio frequency identification,RFID)技术的消毒供应追溯系统的应用,探讨了RFID技术在医疗器械管理中的应用潜力和实际效果。文章详细分析了RFID技术在提高消毒供应追溯系统效率和准确性方面的优势,同时指出了在实际应用过程中所面临的挑战和解决方案。通过本医院系统的应用和实施,展示了RFID技术在优化医疗资源管理、提升医疗服务质量以及保障患者安全方面的重要作用。

基于STC8H的USB接口RFID读卡器设计

设计了一种具有HID接口的RFID读卡器,该读卡器采用带硬件USB接口的STC8H单片机作为主控,采用多协议射频芯片FM1722作为读卡芯片,读卡器具有接口方便、读写速度快、性价比高、支持卡类型多等优点,可以用在物流、交通、身份识别、安全控制等领域。

Radio Frequency Fingerprinting Identification Using Semi-Supervised Learning with Meta Labels

Radio frequency fingerprinting(RFF)is a remarkable lightweight authentication scheme to support rapid and scalable identification in the internet of things(IoT)systems.Deep learning(DL)is a critical enabler of RFF identification by leveraging the hardware-level features.However,traditional supervised learning methods require huge labeled training samples.Therefore,how to establish a highperformance supervised learning model with few labels under practical application is still challenging.To address this issue,we in this paper propose a novel RFF semi-supervised learning(RFFSSL)model which can obtain a better performance with few meta labels.Specifically,the proposed RFFSSL model is constituted by a teacher-student network,in which the student network learns from the pseudo label predicted by the teacher.Then,the output of the student model will be exploited to improve the performance of teacher among the labeled data.Furthermore,a comprehensive evaluation on the accuracy is conducted.We derive about 50 GB real long-term evolution(LTE)mobile phone’s raw signal datasets,which is used to evaluate various models.Experimental results demonstrate that the proposed RFFSSL scheme can achieve up to 97%experimental testing accuracy over a noisy environment only with 10%labeled samples when training samples equal to 2700.

基于RFID技术的公共交通自动到站播报系统设计

随着城市公共交通的迅速发展,如何提升乘客乘车的体验与提高交通系统的管理效率变得愈发重要。本文研究基于射频识别技术(RFID),设计智能化的公共交通自动到站播报系统,经过需求分析、架构设计及硬件和软件实现等步骤,助力创建出一个高效可靠的自动到站播报系统。该系统能够准确实时定位车辆并触发到站播报,让乘客出行变得更加便捷,并有利于将整个公共交通体系推向更高程度的智能化阶段。

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.

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.

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.

基于方形螺旋谐振器的紧凑型RFID标签天线

设计了一种小型化超高频(UHF,ultra-high frequency)射频识别(RFID,radio frequency identification)标签天线。该天线由内外两个方形螺旋谐振器短接构成,通过改变外圈螺旋谐振器的边长和内外圈螺旋谐振器的间距,可以有效调节标签天线的谐振频率。仿真结果表明,标签天线阻抗匹配良好,频带范围覆盖整个超高频频段(840~960 MHz),总尺寸为7.60 mm×7.60 mm×0.05 mm,比传统螺旋谐振器(SR,spiral resonator)天线小96%。测试结果表明,在4 W有效全向辐射功率条件下,标签天线在910 MHz处读取距离达到最大。所提小型化超高频射频识别标签天线具有尺寸小、频带宽、成本低和易于批量制作的特点,适用于对尺寸要求较小的应用环境。

Performance of a 4 cm iodine-fueled radio frequency ion thruster

The performance of an iodine radio ion thruster with a 4 cm diameter(IRIT4)was studied experimentally in this paper.Regulation of the mass flow rates of the iodine propellant is achieved by using a temperature control method of the iodine reservoir.Performance of the thruster using iodine as propellants is obtained at different total thruster powers of 40.6–128.8 W,different grid voltages of 1000–1800 V and the iodine flow rate of 100μgs^(-1).Results show that thrust and specific impulse increase approximately linearly with the increasing total thruster power and the screen grid voltage.The thrust of 2.32 mN and the specific impulse of 2361 s are obtained at the nominal total thruster power of 95.8 W and the screen grid voltage of 1800 V.It is also indicated that performance of the iodine propellant is comparable to that of the xenon propellant;and a difference between them is that the iodine thrust is slightly higher than xenon when the total thruster power is more than 62 W.At the nominal 95.8 W total thruster power,the thrust values of them are 2.32 m N and 2.15 mN respectively,and the thrust-to-power ratios of them are 24.2 mN kW^(-1)and 23.5 mN kW^(-1),respectively.

Application of Radio Frequency Identification (RFID) in Dairy Information Management

As a kind of brand-new technology, radio frequency identification management, data control and acquisition. This paper introduced food safety system construction, analyzed the advantages and problems in dairy modem suggestions for solution according to the practical situation. （RFID） plays an important role in dairy information tracing and culture function extension of managing breeding technology, and finally put forward some

基于GNU Radio和Hack RF的频谱感知与通信系统设计

针对传统的无线通信系统会导致频谱资源浪费与节点通信不稳定这一情况,提出一种基于GNU Radio和Hack RF的软件定义无线电通信平台,实现了在特定的频段具有频谱感知和稳定通信的功能。此系统可判断信道的空闲与否,并且在信道空闲时对此信道进行接入,从而更为高效地对信道资源进行利用。实验结果表明,所提方法不仅可以实现频谱资源的充分利用,减少频谱资源的浪费,而且可以克服USRP开发板价格较贵的缺点,从而使得认知无线收发系统更容易普及使用。

面向射电天文干扰监测的宽带频谱的周期RFI统计方法

随着无线电技术的发展,射频干扰(radio frequency interference,RFI)对射电天文观测的影响越来越大,尤其是周期性RFI对天文观测的影响越来越显著。本文围绕宽带、高时间分辨率频谱数据,采用阈值计算、噪声通道过滤、快速傅里叶变换、周期计算、通道合并、来源分析和模板库建立等步骤,提出一种面向宽带频谱序列的周期RFI统计方法。将该方法应用于新疆天文台南山观测站26 m射电望远镜(Nan Shan 26 m Radio Telescope,NSRT)脉冲星观测终端数据,有效地检测并提取出了频谱序列中的周期性RFI,可为进一步电磁干扰缓解提供数据支撑。

Three-dimensional numerical simulation of heating and melting behaviors of cerium oxide powders in radio frequency thermal plasma

The present study aims at the numerical simulations of the melting process of cerium oxide particles in RF thermal plasma.The physical model and the calculating method were described firstly;the interaction between cerium oxide particles and plasma was analyzed;specific attention was given to the effects of particle initial size,injection velocity on the particle melting and trajectory in plasma.The influence of the temperature field and velocity field distribution of the plasma around the particle trajectory on the melting effect is analyzed,and the relationship between the heat absorption efficiency of the particles and the particle size reduction process is further determined.It is also found that there exists an optimal particle initial injection velocity which led to a more concentrated final particle size distribution and a more significant reduction of particle size.The results could provide effective guidance for understanding the plasma spheroidization process of uranium dioxide and cerium dioxide powder particles.