FSK信号非相干解调的数字实现

Non-coherent demodulation is usually used for FSK signal,where narrowband filter with good selectivity is necessary for extraction of both signal enveloping and timing.The comb-spectrum IIR filter is used here.In this paper,an introduction is given about the implementation principle of the all digital 2FSK demodulator,with an emphasis on the technology scheme of the infinitely circular comb- spectrum filter used for the extraction of signal enveloping and timing,whose practicality has already been validated in many projects.

BPSK信号直接数字下变频的算法与仿真

GPS的导航电文(50 Hz)先是由伪随机码(1.023 MHz)进行扩频,再对1 575.42 MHz的载波进行二 进制移相键控(BPSK)调制.对于高达1 575.42 MHz的载波信号,接收机不可能直接对其处理,因此必 须进行下变频.由于载波频率与扩频码的频率相差太大,因此GPS接收机一般采用多级下变频的超外差 结构[1]完成信号的下变频.这种方法结构复杂,所需器件多,且所需的模拟器件功耗远高于数字器件.与 之相比,数字器件有着更高的集成工艺,更低的功耗和更低的成本.因此数字下变频较模拟混频方法具有 体积、成本和功耗上的巨大优势.数字下变频方法是将较高频率的经A/D转换的信号,利用算法如数字 混频和梳状滤波[2,3]、重抽样算法[4,5]完成信号的下变频.当然数字下变频不可能直接处理1 575.42 MHz 的载波,本文提出的算法是在经过一级模拟下变频基础上,用压缩抽取的方法完成数字化的中频信号的下 变频,较之数字混频的方法需要更少的运算量,只用加法即可完成,节省时间开销和CPU占用开销.

Matlab数字信号处理PPT1

matlab数字信号处理教程ppt讲述了基本MAtlab开发规则，使用移动，是个不错的选择

Software Defined LFM CW SAR Receiver

Abstract There is an increasing demand for a low cost, day-night, all weather spaceborne imaging capability using synthetic aperture radar (SAR) on small satellites. Traditional pulsed SAR payloads have been too expensive and too power demanding to be employed on low-cost microsatellite platforms. Recent developments based on Continuous Wave (CW) techniques have proved successful in minimizing the cost, mass and power of SARs for small airborne platforms (UAVs). However, when considering the use of CW techniques for space based SARs, other considerations come into place: A major one being need of high isolation between transmit and receive antennas, in short, a bi-static configuration. Conventional receiver designs based on analogue demodulation techniques remain inflexible and are complicated to change to suit changing operational requirements in a dynamic bi-static satellite formation. This chapter focuses on the research being carried out in the Surrey Space Centre (SSC) on the design and development of a software defined linear frequency modulated (LFM) CW SAR receiver that can be used on bi-/multi-static microsatellites for remote sensing.

SABRINA-A SAR Bistatic Receiver for

This letter discusses the implementation of SABRINA, Synthetic Aperture radar Bistatic Receiver for Interferometric Applications. The ground resolution of a fixedreceiver bistatic system is studied, showing that it is comparable to that of a monostatic system. Due to the short distance from target to receiver, large sensitivity is obtained. The noncooperative nature of the bistatic system forces a conservative data-acquisition strategy based on continuously sampling the scattered signal during a temporal window around the predicted satellite overpass time. Also, to be able to synchronize the system in time and in frequency, sampling of a direct signal obtained through an antenna pointed at the satellite is required. Besides the signal processing required to phase-lock the received signal, the bistatic synthetic aperture radar processing needs to take into account the azimuth-dependent phase history. First focused images obtained with the SABRINA–ENVISAT combination are discussed.

Implementation of SDR Digital Beamformer-2次

Abstract—The hardware reconfiguration feature of a softwaredefined radio (SDR) architecture can support multiple modes of a digital beamformer (DBF) striving for compactness and efficient processing power, which are important issues for microsatellite synthetic aperture radar (SAR) systems. In this letter, based on the SDR architecture, a DBF system, consisting of multiple beam, direction-of-arrival (DOA) estimation, and null-steering operation modes, is realized using a field-programmable gate array (FPGA) processor. Since the hardware reconfiguration has to be processed with minimal delay, the FPGA hardware must be of modularized design. Different modes can share the common module during mode switching. Experimental results verify the performance of DOA, null steering, and mode switching. The processing time of each DBF mode is less than the cross-range pulse repetition interval of the microsatellite SAR system. Index Terms—Digital beamformer (DBF), microsatellite, software-defined radio (SDR), synthetic aperture radar (SAR).

基于软件无线电的数字信号接收技术的研究

软件无线电是近年来在无线通信领域提出的一种新的通信体系结构。这种通信体制 具有很好的通用性、灵活性和可配置性，并使系统互联和升级变得容易。软件无线电强 调以开放性的最简硬件为通用平台，尽可能地用可升级、可重新配置的应用软件来实现 各种无线电的设计。这样就可以在通用可扩展平台上，通过开发新的应用软件来满足用 户和市场的新需求，适应不断发展的技术进步。 软件无线电从1995 年美军的Speakeasy（易话通）计划开始发展，到现在已经取得 了许多成果。软件无线电涉及许多专业技术领域，如现代通信理论（含调制解调、信源 /信道编解码、均衡、加密解密等）、宽带天线理论、数字信号处理、微电子、计算机等。 本文主要研究了适合于用数字信号处理器(DSP)实现的全数字通信系统。该系统包括了 信道编码、解码；BPSK、QPSK 和GMSK 的调制和解调；在数字接收机中的同步技术。 本系统信道编解码采用的是“RS 码+交织+卷积码”的级联码，RS 码是最佳的线性 分组码，交织可以抵抗突发干扰，而卷积码可以利用各个码组的相关性提高编码的增益。 信号的调制解调本论文采用了正交调制解调的软件实现方法，其中GMSK 需要进 行近似变换才能使用正交线性的调制解调。在调制解调中需要注意的是减小码间串扰， 这需要使用合适的成形、匹配滤波器。而在相干解调中的关键问题是同步问题。同步主 要包括了载波同步和码元同步。同步的方法有很多，这里载波同步主要选用了Costas 环的方法，而码元同步使用了基于Gardner 算法的反馈插值同步的方法。

SAR with Digital Beamforming on Receive Only

Since their invention, the performance of Synthetic Aperture Radar (SAR) systems has improved considerably. Operation close to the theoretical limits of accuracy and resolution are possible using state of the art processing techniques and hardware components. Nevertheless, the principle is still the same: The SAR is a side-looking radar where resolution is achieved in range by bandwidth and in azimuth by Doppler processing. The price for improved performance is paid through systems which are more expensive, heavier and highly complicated.

Airborne bistatic SAR receiver

This paper describes the design and construction of a bistatic SAR receiver suitable for airborne applications, using orbital SAR systems (ENVISAT, ERS-2, RADARSAT, TerraSAR-X among others) as opportunity transmitters. The challenge of this design is to reduce the required data throughput of the recorded data. This is achieved storing data only in the time intervals when scattered signal from the target area appears. The task of detecting this time intervals is performed in real time using a matched filter of the signal received directly from the SAR transmitter.

Advanced Digital Beamforming Concepts for High Performance

This paper reviews advanced multi-channel SAR system concepts for the imaging of wide swaths with high resolution. Several novel system architectures employing both direct radiating arrays and reflector antennas fed by a digitial array are introduced and compared to each other with regard to their imaging performance. In addition, innovative operational SAR imaging modes are proposed which enable the mapping of ultra-wide swaths with high azimuth resolution. The new techniques and technologies introduced in this paper have the potential to enhance the imaging performance of future SAR systems by one order of magnitude if compared to state of the art SAR sensors like TerraSAR-X, ALOS, Radarsat-2 or Sentinel-1.