非标准配置条件下超短波多天线共址布局设计

本文针对超短波通信台站场地受限条件下的天线架设问题,分析研究对空通信设备特点及超短波传输特性,计算水平排列、垂直排列、组合排列方式下天线最小隔离度,基于超短波系统隔离度、发射接收馈线损耗、天线增益及滤波器特性曲线等研究天线架设间隔距离,制定超短波电台多天线共址优化布局方案,有效降低邻频互扰影响,对狭小空间等费标准配置条...     

基于蜂群算法任意平面阵最大信干噪比研究

针对复杂战场环境下超短波电台天线接收低信噪比信号能力弱和易受定向干扰的缺陷,结合战场超短波电台不规则分布和位置不能任意改变的特点,提出任意结构天线阵信号接收模型,采用蜂群算法优化阵元相位使得天线阵输出信干噪比最大。假设信噪比为0 dB,干噪比为60 dB,且在平面内随机选取8个阵元,采用蜂群算法优化后输出信干噪比为8.633 dB。与改进差分进化算法、遗传算法和粒子群优化算法相比,分别提高了0.577 dB、1.124 dB和1.543 dB。研究成果可为超短波电台组阵通信提供参考。     

基于相关干涉仪的超短波测向技术中有效频点比的研究

相关干涉仪算法作为一种快速的无线电测向方法,具有算法简单、灵敏度高、系统结构简单等优点,因此被广泛应用在超短波测向系统中。对于测向精度评价常采用均方根误差的方法,但该方法无法直观显示各角度满足测向精度要求频点个数。本文研究了相关干涉仪算法的原理,及其在一种5阵元天线的超短波测向接收机上的工程应用,提出了有效频点比的概念对测向效果进一步分析,并且通过提高天线基线长度解决了短基线低频下测向精度低、有效频点比低的问题,在工程上对相关干涉仪算法进行了验证。     

自制业余电台定向谐振天线

用于业余无线电的接收——发射天线,较多地采用大型的双极天线,其效果好。但架设天线占地大且不能随意移动。鞭状天线简单、轻便,但接收效果不好。单方面加长天线,尽管可以增大接收信号电平,但噪声同时也增大,因此,信噪比并未得到明显改善。众所周知,通常接收到的业余电台信号场强只有短波广播电台的千分之一甚至更弱。有时反而因加长天线感应了较多的噪波而淹没了有用的业余电台信号。用定向的     

车载超短波电台维修数字化训练系统的设计与实现

针对陆军某新型车载超短波电台原理和结构复杂,采用实装或半实物仿真训练成本高、训练效益低的实际问题,采用嵌入式技术、数字化样机、无线网络通信等技术,开发车载超短波电台维修数字化训练系统。系统采用“主控机+电台数字样机”模式,通过对“数字样机”面板模块及内部模块电路的数字化设计,实现采用“电台数字样机”对车载超短波电台工况的模拟,通过主控机控制“电台数字样机”完成超短波电台的正常工作状态检查、分解组合、故障判排等训练,以期解决陆军部队车载超短波电台维修训练手段不足、维修保障能力落后的问题。     

收音机的灵敏度和选择性

灵敏度和选择性是表明收音机性能的两项重要指标。灵敏度:是指收音机接收弱信号电台的能力。灵敏度高的收音机,接收远地电台和弱信号电台的能力就强。采用磁性天线的收音机,是以天线所接收的信号场强来表示灵敏度的,其单位是毫伏/米(mV/m);用外接天线(包括拉杆天线)的收音机,用天线上所加的信号电压来表示灵敏度,其单位为微伏,用μV表示。一台收音机在输出功率和信噪比(信号与噪音之比)一定     

电子线路应用实例及其技法(三)

环形天线抑制噪声干扰在周围受到计算机和电视机等设备电磁干扰的情况下,本设计可以使接收机正常的接收长波和中波电台的节目。这里采用环形天线及天线放大器,环形天线最大约一平方米的面积,可以将噪声衰减到相当于所接收波段的背景干扰的数量级。     

机载超短波通信系统建模与仿真

超短波电台是航空通信、作战指挥的重要设备,主要用于飞机与地面台站、飞机与飞机之间的双向话音和数据通信联络。因此在对超短波电台仿真时,考虑电波传播过程中受到各种干扰和地形遮蔽等因素影响,对在接收话音中有杂音或通信不上的情况进行模拟是很有现实意义的。本文在系统中加入电波传播损耗模型,并采用GIS技术,采集地形数据对通信有效性进行动态仿真,逼真地模拟了超短波电台在地空通信中的使用效果。     

车载超短波电台维修检测系统的设计与实现

针对某新型车载超短波电台原理结构复杂、自检虚警率高、故障定位困难等问题,综合采用嵌入式技术、数据库软件、电路智能检测等技术,以车载超短波电台维修检测主机+模件测试夹具的架构构建硬件平台,研制开发车载超短波电台维修检测系统;该系统能够实现对车载超短波电台整机频率误差、输出功率、接收灵敏度等参数及电台内部模件性能指标的自动化测试,测试结果与标准特征值比对,实现电台整机技术状态评估和模件级故障定位,实现电台维修信息的实时存储与查询,从而解决陆军部队车载超短波电台维修检测手段不足、维修保障困难等实际问题。     

智能化超短波无线电中继站遥测遥控系统的开发研制

通过以单片机为核心的智能化遥控、遥测系统，对工作在高山无人值守恶劣条件下的超短波无线中继电台进行遥控切换和电台工作参数和状态的遥测，以提高高山超短波无线中继台的工作可靠性     

A broadband slant polarized cavity backed microstrip‐fed wide‐slot antenna array

This article deals with the design of a broadband cavity‐backed microstrip‐fed wide‐slot antenna array for L‐band applications. For verification purpose, a sample 1 × 4‐element antenna array has been designed, manufactured and tested. Experimental results have shown satisfactory agreement with the simulation. The proposed antenna array exhibits a measured impedance bandwidth of 1.4 GHz (90%) with frequency of 0.85 to 2.25 GHz and the gain is higher than 11 dBi. The designed antenna has small size and low weight and can be fabricated using a low‐cost fabrication process for easy integration with RF circuits and microwave components. This work is useful for some radar applications and radio frequency identification systems.     

Circularly polarized beam‐steering antenna array for ultra‐high frequency radio frequency identification applications

A circularly polarized beam‐steering antenna array with Butler matrix is designed in this letter for ultra‐high frequency radio frequency identification applications. To achieve the identification of the fast‐moving tag groups, a 3 × 4 Butler matrix is utilized to switch the radiation directions at ?25°, 0°, and +25°, respectively. Besides, series‐fed patch antenna element is designed and the 1 × 4 antenna array is built with element rotation for a good polarization performance. Finally, the proposed antenna system is fabricated and the identification area and radiation performance are tested.     

A miniaturized circularly polarized implantable RFID antenna for biomedical applications

A miniaturized circularly polarized implantable antenna operating at ultrahigh frequency band (902‐928 MHz) for radio frequency identification biomedical monitoring is first presented and experimentally validated in this article. The proposed antenna features a compact volume with a dimension of π × (6)² × 1.27 mm³ by employing an extended ring with meandered lines for size reduction. Moreover, adjusting the length of symmetrical meandered lines can introduce two orthogonal modes, which makes for good performance of circular polarization. Superb impedance matching between the chip and tag antenna is well implemented by applying a modified T‐match stub. In the simulation, the antenna achieves a ?10‐dB impedance bandwidth of 42 MHz (902‐944 MHz) and 3‐dB axial‐ratio bandwidth is 53 MHz (892‐945 MHz). Finally, the specific absorption rate is also calculated for human safety and the measured reading range reaches the maximum distance of about 87 cm.     

Multipolarization antenna design and analysis of on‐body communication

On‐body communications show highly polarization selectivity in both radio channels and antennas due to the complex body coupling and scattering effects, and full‐space dimension link distribution. To mitigate the polarization variation of on‐body communication links, multipolarization antennas are proposed to adaptively capture the on‐body channel polarization components. In this article, a tri‐polarization antenna design is introduced with its performance evaluated on a simplified three‐layered human chest model including skin, fat, and muscle tissues. The return loss, frequency response, and the radiation pattern of designed antenna are found to be affected by the relative orientation and distance between the antennas and the trunk, indicating the necessity of the antenna emplacement optimization for realistic on‐body communication devices.     

Low‐profile UHF RFID reader antenna with CP radiation and coupled feeding technique

A low profile annular‐ring patch antenna with circularly polarized (CP) radiation for radio frequency identification (RFID) reader applications in the ultra‐high frequency (UHF) band (922‐928 MHz) is presented in this article. Perturbation method is applied by loading a pair of triangular open‐notch into the outer circumference of ring patch, and good impedance matching can be determined by using the coupled feeding technique. The overall size of this proposed antenna is 150 mm × 150 mm × 10.4 mm. The measured results show desirable 10‐dB impedance bandwidth and 3‐dB axial ratio (AR) bandwidth of 3.5% (908‐941 MHz) and 0.65% (922‐928 MHz), respectively. Stable antenna peak gain and efficiency of 7.2 dBic and 87% are also exhibited, respectively.     

Broadband circularly polarized antenna with moon‐shaped parasitic element

A broadband circularly polarized (CP) circular patch antenna with an L‐shaped ground plane and parasitic element is studied. The use of this L‐shaped ground is to achieve short probe feed connection to the circular patch, while maintaining a certain height between the circular patch and ground plane, so that good impedance matching and bandwidth enhancement can be attained. To achieve CP radiation, two notches are initially loaded diagonally into the circular patch, and to further enhance the CP bandwidth, a novel technique of loading a small size moon‐shaped parasitic element into the notched circular patch is proposed. By doing so, the CP bandwidth of proposed antenna can be tremendously increased by approximately 10%. The experimental results show that the proposed CP antenna can yield impedance bandwidth and CP bandwidth of 835–1150 MHz and 839–968 MHz, respectively, with good gain level of 7.6 dBic. Therefore, this proposed wideband CP antenna can be used for UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna that operates within the universal RFID bands (840 ? 960 MHz). © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:387–395, 2016     

Eccentric annular slot patch antenna with frequency agility for UHF RFID reader applications

The design of a simple ultrahigh frequency RFID (radio frequency identification) reader antenna that can operate within the North America RFID band (902–928 MHz) is studied. To generate circular polarization (CP) radiation in this band, a novel method of loading two narrow open‐ended slots (slits) into an eccentric annular slot patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the radiating patch is loaded to an L‐shaped ground plane. From the experimental results, the proposed antenna can yield an impedance bandwidth (10‐dB return loss) between 650 MHz to 1125 MHz, while good CP bandwidth (3‐dB axial ratio, AR) from 901 MHz to 930 MHz is also attained. Furthermore, gain level and efficiency of more than 7.8 dBic and 90%, respectively, were also measured. By simply removing one of the slits, this proposed antenna can also be modified to operate within the China (840–846 MHz) and European (865–868 MHz) RFID band.     

基于STM32的射电望远镜跟踪系统设计

为了满足天文爱好者的对射电天文学的探索,对于大型的射电望远镜天线,其指向精度要求高,观测的过程中需要做各种实时修正,造价昂贵,并不适合用于科普,因此设计了一种基于STM32微处理器的双轴射电望远镜控制系统。系统通过两台直流电机控制抛物面天线对太阳的运动轨迹进行跟踪并实时采集射电望远镜接收机电压,并将采集的数据利用TCP传输方式快速送至PC机用户监控软件进行显示和存储。该系统实现了时间分辨率为1ms的太阳射电数据采集与存储,提高了系统捕获持续时间很短的太阳爆发能力,为科普爱好者研究、分析太阳活动提供了数据支撑。     

基于AD9959的无线电罗盘天线信号产生器设计

为实现无线电罗盘的原位测试,设计一种基于DDS芯片AD9959的无线电罗盘天线信号产生器,该信号产生器输出信号可以程序控制,其频率及相位、幅度关系符合无线电罗盘天线输出信号的特征,能够满足无线电罗盘功能、性能测试及故障隔离对天线信号的需求.可以集成到ATE实现无线电罗盘的自动测试.     

无线电罗盘的天线信号模拟器的电路设计

根据无线电罗盘的工作原理,设计了此无线电罗盘的天线信号模拟器电路,它模拟无线电罗盘的组合天线对地面导航台无线电信号的接收功能,为无线电罗盘接收电路提供含有低频方位的高频信号;在该天线信号模拟器中,采用了单片机、GPIB等技术,重点解决了在不同频率上飞机纵轴与导航台之间的夹角可在一定的精度上的任意控制,从而实现对某型无线电罗盘的主要性能参数的自动测试任务。