A HIGH SENSITIVITY AND WIDE DYNAMIC RANGE ZERO-IF RF RECEIVER FOR COGNITIVE RADIO APPLICATION

This paper presents an RF receiver of zero-Intermediate Frequency(IF) architecture for Cognitive Radio(CR) communication systems.Zero-IF architecture reduce the image reject filter and IF filter,so it is excellent in low cost,compact volume,and low power dissipation.The receiver employs three digital attenuator and a high gain,high linearity low noise amplifier to achieve wide dynamic range of 70 dB and high receiving sensitivity of-81 dBm.A fully balanced I/Q demodulator and a differential Local Oscillator(LO) chips are used to minimize the negative effects caused by second-order distortion and LO leakage.In order to select an 8 MHz-channel from 14 continuous ones located in UHF band(694-806 MHz) accurately,approach of channel selectivity circuits is proposed.The RF receiver has been designed,fabricated,and test.The measured result shows that the noise figure is 3.4 dB,and the error vector magnitude is 7.5% when the input power is-81 dBm.

Receiver Detection Employing Semaphore in Cognitive Radio

Interference from secondary users to primary users should be avoided in cognitive radio. However, it is difficult to solve the interference problem if the secondary users cannot get the information of the primary receivers. Insufficient information of primary users would result in inaccurate spectrum detecting result. To deliver the information of primary users, Receiver Detection Employing Semaphore (ReDES) is proposed in this paper. Primary receiver informs secondary users of its licensed receive frequency according to semaphore architecture directly in ReDES. The semaphore is used to determine the spectrum holes by secondary users. Frequency mapping method is come up with as a realization of ReDES. The procedure and the detailed techniques are illustrated to make ReDES scheme reasonable and feasible. Simulation results show that the proposed scheme can effectively detect the frequencies of primary receivers, and improve the accuracy of spectrum detection.

Robust digital receiver for EPC sensor network

A robust digital receiver based on a matched filter （MF） is proposed for the radio frequency identification （RFID） reader system to enhance the reliability of signal processing in the electronic product code （EPC） sensor network （ESN）. The performance of the proposed receiver is investigated by examining the anti-collision algorithm in the EPC global Class1 Generation2 protocol. The validity and usefulness are demonstrated by both computer simulations and experiments. Based on the verification results, comparing with the conventional zero crossing detector （ZCD） based receiver, the proposed receiver is very robust against strong amplitude distortions and considerable frequency deviations happening on the backscattered signal from a passive tag.

某型射频接收机强电磁耦合的仿真预测

针对强电磁环境下射频接收机仿真预测的问题,开展强电磁脉冲信号构建、射频接收机建模、场路结合方式预测等研究,得到射频接收机内部监测点场强、壳体表面电流、接收机线缆耦合电压等仿真结果,实现对某型射频接收机电磁防护的优化设计,为射频接收机强电磁防护实施提供支撑。

高频雷达射频干扰抑制的自适应接收滤波设计

为抑制高频雷达中的射频干扰,本文提出了一种自适应滤波器设计方法。首先,基于海杂波和射频干扰的多普勒特性,设计了海杂波区域自适应检测算法,以有效地估计射频干扰特性。然后,对海杂波、噪声和射频干扰的功率谱进行分析,并采用连续均值剔除算法,以检测射频干扰是否存在及其频率范围。最后,引入基于相似度约束的接收滤波器算法,根据射频干扰频带自动计算约束参数,从而实现了接收滤波器的自适应设计,以稳健地抑制射频干扰。仿真结果表明,相比传统白化滤波器,本文所设计滤波器可以有效地抑制宽带和窄带射频干扰,提高雷达抗干扰能力。

动态双频跳频电台接收端FPGA设计

为解决动态双频跳频电台跳频信号解跳频这一关键技术的硬件实现,依照动态双频跳频同步方案,设计了跳频电台接收端的整体结构,研究了跳频电台接收端解跳频的数学模型,采用Verilog HDL语言在EP4CE6F17C8芯片上实现了两种解跳频器设计方案,分别为IP核乘法器解混频+带通滤波+BPSK解调方案和加法树乘法器解混频+带通滤波+改进型DPSK解调方案。测试结果表明,两种方案都能实现跳频电台接收端解跳频器功能,后一方案消耗硬件资源更少,更符合跳频电台接收端多通道并行运算要求,为下一步研制动态双频跳频电台样机提供了技术参考。

毫米波大气臭氧探测辐射计系统设计

平流层臭氧浓度对于地球气候变化和生态环境有着重要影响.具有谱分析能力的高光谱毫米波辐射计是一种用来探测大气痕量气体的被动式微波遥感器,能够有效探测大气臭氧垂直廓线,在空间地球科学领域中具有十分重要的应用价值.本文研制了一种探测平流层大气臭氧吸收谱线的新型高光谱毫米波臭氧辐射计系统,该系统结构包括射频接收机和数字后端谱分析仪.射频接收机部分采用超外差结构获取142.175 GHz±100 MHz带宽信号,数字后端谱分析部分采用高性能模数转换器对输入模拟信号进行5×108 sample·s^(–1)采样,14 bit量化,输入信号3 dB带宽200 MHz,通过高性能现场可编程门阵列(FPGA)获取信号功率谱,实现了探测通道数16384,谱分辨率12.2 kHz.根据辐射计系统关键模块的设计方案、器件选型和测试方法,开展大气探测实验,并将实验结果与大气辐射传输模拟软件(ARTS)仿真结果进行对比,得出系统灵敏度及各项指标可以满足大气臭氧反演需求,验证了系统设计的正确性,满足平流层臭氧浓度监测、预警及其导致的气候变化研究的应用需求.

阳江市应急广播系统建设方案

应急广播是通过广播、电视、网络视听等各种媒体向公众或特定地区公众传播突发事件消息的一种重要方式。当遭遇紧急情况或重大灾害时,该系统能够迅速、准确地向受灾人群传递现场情况,以便相关主体及时采取应对措施,从而有效减少人们的生命财产损失。简述应急广播系统的基本概念、总体架构和主要功能,以广东省阳江市阳江广播电视台阳春钩髻顶应急广播系统建设项目为例,提出几点具体的建设与执行策略,以供同行参考。

基于USRP的便携式接收机设计与实现

针对通信信号抵近接收的使用需求,进行了基于软件无线电外设(USRP)平台的便携式接收机研究。接收机以USRP作为射频前端,完成中频正交(IQ)数据的提取,在通用计算机上实现信号的检测、识别、解调。采用信号源注入和实际信号接收进行测试,结果表明该便携式接收机能够有效完成通信信号接收,对新信号检测时间小于1 s,在信噪比不小于15 dB条件下信号类型识别准确率达90%以上。

影响射频接收灵敏度测试的研究

随着移动通信技术的飞速发展,LTE技术已成为全球移动网络运营商的主流选择之一其高速数据传输、低延迟、高网络容量以及广域覆盖等特点备受青睐。然而,LTE系统的性能受到诸多因素影响,比如天线设计、信号波束宽度以及小区参数等。因此,如何有效测量LTE系统的灵敏度并深入理解相关影响因素,已成为网络性能测试与优化的重要课题。本文将测量LTE灵敏度的相关技术以及主要影响因素从理论和实验两个方面进行分析,希望能对LTE技术的应用与发展提供有益的参考。

遥感卫星地面站12米口径天线Ka频段G/T值测试方法综述

Ka频段G/T值是遥感卫星地面站12米口径天线最重要的指标之一,其测试方法与遥感站目前常用的X频段测试方法相比,适用条件更加严苛,因此如何选取最佳的测试方法成为本文研究的主要内容。首先介绍了Ka频段12米口径天线特点;然后分别论述了分段测试法、信标法、比较法和射电源法的原理及其优缺点,并提出了Ka频段对月测试的这一最方便简洁的测试方法及其修正系数的研究方向;最后通过实测结果进行比较,给出Ka频段G/T值测试方法选取建议,为工程师现场测试提供了科学的指导和参考。

A compact transmit/receive switch for 2.4 GHz reader-less active RFID tag transceiver

Radio frequency identification(RFID) is a ubiquitous identification technology nowadays. An on-chip high-performance transmit/receive(T/R) switch is designed and simulated in 0.13-μm CMOS technology for reader-less RFID tag. The switch utilizes only the transistor width and length(W/L) optimization, proper gate bias resistor and resistive body floating technique and therefore,exhibits 1 d B insertion loss, 31.5 d B isolation and 29.2 d Bm 1-d B compression point(P1d B). Moreover, the switch dissipates only786.7 n W power for 1.8/0 V control voltages and is capable of switching in 794 fs. Above all, as there is no inductor or capacitor used in the circuit, the size of the switch is 0.00208 mm2 only. This switch will be appropriate for reader-less RFID tag transceiver front-end as well as other wireless transceivers operated at 2.4 GHz band.

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.

Indoor Radio Propagation Model Based on Dominant Path

When there are bigger obstacles in the indoor environment such as elevator, the radio waves basically can not penetrate it. The contribution of received signal strength by transmission and reflection will be greatly reduced, and most of the time, the radio waves will reach the user by bypass diffraction. Therefore, the traditional path loss model is no longer applicable, and the improved model should be proposed. In this paper, we firstly proposed an indoor radio propagation model based on dominant path in which the received signal strength has nothing to do with the direct distance between user and access point, but is related to the length of dominant path. Then on the basis of dominant path model, the NLOS influence is considered in order to further improve the accuracy of dominant path model. Experimental results demonstrated that the proposed dominant path model can improve the accuracy of traditional path loss model remarkably.

Radio Coverage Mapping in Wireless Sensor Networks

Radio coverage directly affects the network connectivity, which is the foundational issue to ensure the normal operation of the network. Many efforts have been made to estimate the radio coverage of sensor nodes. The existing approaches (often RSSI measurement-based), however, suffer from heavy measurement cost and are not well suitable for the large-scale densely deployed WSNs. NRC-Map, a novel algorithm is put forward for sensor nodes radio coverage mapping. The algorithm is based on the RSSI values collected by the neighbor nodes. According to the spatial relationship, neighbor nodes are mapping to several overlapped sectors. By use of the least squares fitting method, a log-distance path loss model is established for each sector. Then, the max radius of each sector is computed according to the path loss model and the given signal attenuation threshold. Finally, all the sectors are overlapped to estimate the node radio coverage. Experimental results show that the method is simple and effectively improve the prediction accuracy of the sensor node radio coverage.

Analysis of RFID Based Positioning Technique Using Received Signal Strength and Directional Antenna

Automatic robot navigation is being utilized in many industries for the purpose of high speed work delivery. Color follower, fix path follower robots are current solution to this activities but dynamic path configuration is not possible in these robots. Hence new system proposes effective and fully dynamic path follower robots using RFID and directional antenna. Radio Frequency Identification (RFID) system permits automatic identification of objects with RFID tags using radio waves which have been widely used in mobile robot navigation, localization and mapping both in indoor and outdoor environment. This article presents a navigation strategy for autonomous mobile robot using passive RFID system. Proposed robot system is provided with RFID tag functionality which will load tag number and direction instruction. At some turning point, user will put RF tag, this tag will be read by RF reader which is placed on robot. As per direction instruction robot will change the direction and reach to the destination. Also as per the movement, robot will send its GPS location to PC (Personal Computer) which will be displayed on PC. Hence main goal is to provide more reliable and low energy consumption based indoor positioning system which will be achieved using directional antenna.

基于改进灰狼算法的共享仓储动态盘点方法

依据共享仓储货物定位精度准和盘点效率高的要求,提出了一种采用改进灰狼算法(Gray Wolf Optimization Algorithm)的货物动态盘点方法。通过射频识别技术和接收信号强度测距方法搭建了货物的三维定位模型;采用粒子群参数优化的灰狼算法对仓储货物的三维定位进行解算,实现共享仓储的自动盘点。仿真结果表明,改进的灰狼算法具有较好的定位精度和稳定的寻优性能,可以满足复杂动态环境下共享仓储货物盘点要求。

一种搭载FPGA和AD9361的软件无线电平台实现方法

为了解决传统无线电平台分立器件繁多、功能单一、开发周期长的问题,提出了一种搭载现场可编程门阵列(field programmable gate arrays,FPGA)和AD9361的软件无线电平台的实现方法。以FPGA(KINTEX-7)为主控芯片,表述了MicroBlaze嵌入式软核与相应串行外设接口(serial peripheral interface,SPI)、通用输入输出(general purpose input\output,GPIO)接口以及数据接口的设计思路,并对AD9361进行了芯片配置,实现了FPGA基带模块与AD9361之间的数据交互。功能测试结果表明,此平台能够根据需求更改数据调制方式与收发通道参数配置,且具有良好的收发性能。与传统无线电平台相比,此平台具有灵活性高、通用性强等特点,能够适用于多种应用场景。

一维天线阵列DOA估计实验系统设计与实现

设计了一套四阵元线阵DOA估计实验系统用于雷达对抗等课程实验。系统主要由宽带平面螺旋天线、四通道软件无线电接收机USRP-2955和数据处理计算机组成。平面螺旋天线放置在俯仰可调的一维支架上,可实现基于均匀或稀疏阵列的信号接收;计算机控制USRP实现四通道同步下变频及IQ数据采集。在微波暗室,利用标准增益喇叭天线发射信号,采用MUSIC超分辨算法实现了信号的正确估计。验证了提出的稀疏阵列原子范数最小化无网格和无监督深度学习等新理论、新方法DOA估计的可行性,提高了测角精度;验证了提出的利用仿真数据训练网络实现基于深度学习DOA估计的方法。实验系统具有良好的实验指导意义和现实应用意义。

10~50MHz地基低频射电天文数字接收机及上位机软件研制

低频段(<50 MHz)射电观测,是研究射电爆发、恒星形成、宇宙初期状态的重要手段,而我国对该频段相关仪器研究较少.本文从关键器件选型、仿真与设计、接口和通讯、功能模块等方面,对组成地基低频射电观测系统的核心部件——数字接收机与上位机软件进行论述.数字接收机由采集卡和工控机构成,采集卡配置包含AD9265芯片和K7系列现场可编程门阵列(Field Programmable Gate Array, FPGA).数字接收机探测频率覆盖1~62.5 MHz,接收功率范围-78~-6 dBm,拥有先进的频率分辨率(15.3 kHz)和时间分辨率(0.5~32 ms).为满足射电观测显示与存储需求,研发了具有针对性的上位机软件解决方案.软件支持高速串行计算机扩展总线标准(Peripheral Component Interconnect express, PCIe)数据传输协议,支持实时频谱显示、数据存储和交互操作,具有全频带内强度图显示与图像自动保存功能.自主研制的数字接收机与上位机软件已成功应用于新疆奇台观测站低频(10~50 MHz)射电观测设备,该设备自2021年6月投入运行,捕获多次太阳射电暴事件.将观测结果与澳大利亚Learmonth观测设备对比分析,结果表明,新疆奇台站低频射电观测系统探测精度更为精细、探测频率更低,性能指标位于国际前列.系统后期可开展星-地协同观测,推动我国低频段射电研究.