用STEL-2000A实现直接序列扩频收发系统

本文介绍了全数字式直接序列扩频芯片STEL－2000A的主要性能和用法,并以STEL－2000A为核心,辅以若干外围器件,构成了一个可用于野战信息传输的扩频收发系统。     

STEL-2000A 芯片在一种专用扩频通信系统中的应用

介绍使用STEL－2000A芯片设计一种工作在902－928MHz频率范围，适合多种环境，体积较小的扩频通信系统。着重介绍应用该芯片的专用扩频系统的一些性能指标。     

一种基于STEL-2000A的扩频数据链的实现

介绍STEL-2000A和PIC系列MCU实现一种灵活的全双工扩频数据链。文章包括硬件设计和软件设计两部分,硬件部分着重论述STEL-2000A的接121设计,软件部分着重论述PICMCU对STEL-2000A初始化和通信编程。     

基于径向函数的通信智能抗干扰系统设计

目前设计的通信抗干扰系统抗干扰能力较低,导致通信过程稳定性较差.为此,设计一种基于径向函数的通信智能抗干扰系统.系统硬件主要包括处理器、显示器和扩频器模块.处理器选用高性能PA576芯片缩短信号的计算时间,扩频器选用YU1768芯片;系统软件部分,利用A/D转换将检测信号进行数字化处理后,构造神经网络,进行系统优化,提升系统的抗干扰性能.实验结果表明,基于径向函数设计的通信智能抗干扰系统可以提高通信系统的抗干扰能力和通信稳定性.     

IEEE802.11直接序列扩频物理层特性

介绍了IEEE802.11物理层特性。简单介绍了ISM频段、扩频技术的背景及各国相应的标准,规范。重点描述了直接序列扩频技术指标规范。着重阐述免许可证审批2.4GHz ISM频段IEEE802.11的技术规范。     

直序扩频芯片的原理与应用

阐述了直接序列扩频的实现原理和Zilog公司生产的Z87200单片直接序列数字脉冲调制解调扩频芯片的硬件结构特点，该芯片将扩频通信收发主要电路的各个部分都集成于一块100个引脚的芯片中，工作方式为全双工或半双工，支持多种不同的工作模式。提出了将该扩频收发芯片应用到直接序列扩频系统中的具体方案，该方案包括发射部分、接收部分和控制部分，工作频段为800MHz；并进行了数据部分的调制与解调实验，实验结果表明：信息码经差分编码、扩频、解扩、译码后可恢复出信息码序列。     

FT2000A处理器嵌入式操作系统适配技术研究

文章介绍了一种嵌入式操作系统在国产FT2000A处理器上的适配方案。适配中解决的主要问题包括,系统引导程序开发、处理器体系结构适配和设备驱动开发三部分。文章以国产嵌入式操作系统天脉1为例,对该方案进行了验证,证明了方案的可行性。     

用于数字视频传输的直接序列扩频基带处理器

本文介绍了一种用STEL - 2 0 0 0A实现直接序列扩频 (DSSS)通信系统的方法 ,可用来传输压缩过的数字视频信号。与其它常用的传输方式相比 ,扩频传输能提供较强的抗干扰性能 ,十分适合抗干扰能力弱的压缩信息。     

GSMR射频通信接收机的设计

本文分析了一种可应用于GSMR频段的接收机方案和部分实现。采用二次变频宽中频接收机的技术,结构明了,实用性强。文中叙述了接收机总体方案的考虑和设计。并结合实际硬件电路对该方案进行了分析和讨论。     

基于STEL-2000A的基带扩频系统的设计

针对无线通信系统抗干扰性差、抗多径性能弱的缺点,设计了一个抗干扰性强的的高速基带扩频收发系统.该系统以专用扩频芯片STEL-2000A为核心,以EP3C10E芯片为外围控制芯片,辅以高速A/D、D/A芯片,从而实现了系统功能.首先给出了系统总体原理图,并对硬件设计部分进行详细的讨论,其次,在软件设计部分给出了算法总体设...     

基于扩频技术的低压电力线载波通讯系统

本文论述了基于扩频通讯技术的低压电力线载波通讯系统的算法设计、硬件实现和验证结果。作为低压电力线载波扩频通讯芯片的FPGA验证系统，本系统重点研究了如何用成熟的MCU技术和较少的硬件资源将复杂的扩频通讯技术应用于恶劣的低压电力线通讯环境中，以获得高可靠性的长距离数据通讯。本文论述的系统已经通过现场验证，收到了良好的效果。     

Spread-spectrum techniques in optical communication using transformdomain processing

A method of applying spread-spectrum techniques to optical communication is presented. The interference-suppression capability of spread-spectrum systems is shown to be enhanced by optical transform domain processing, and a design for spectral coding at optical frequencies is given. The encoding system is based on optical pulse compression and shaping. Several possible implementations of this system are suggested, and applications to fiber optics, laser radar, free-space optical communications, and other systems are discussed     

一种基于软件无线电技术的扩频通信系统

文章介绍了一种基于软件无线电技术的数字扩颊通信系统,包括扩频ASIC芯片的设计,发射机、接收机的设计等。着重描述了采用ESDA技术设计扩频ASIC信片的过程,给出了ASIC芯片的数学模型、仿真结果及系统性能分析。仿真及测试结果表明,该扩频通信系统具有较强的抗干扰能力。     

Exploiting the robust nature of spread-spectrum technology for future wireless applications

The attractiveness of spread-spectrum technology for future terrestrial mobile communication systems is shown. It is based on the robust nature of the spread-spectrum concept and its flexibility in the service design. The robustness of a spread-spectrum system is carried out and the corresponding benefits are listed and applied to future needs for communication systems.     

基于433M无线扩频技术在密闭空间的应用

针对密闭空间实时数据采集困难和信道利用率低的问题,提出一种基于433M无线扩频通信技术,将其运用于远程数据的通信。该设计采用STM8S103为主控芯片,用于对外设信号的调制解调,其数据传输率可达500kbs。无线收发模块对采集的实时数据进行433M扩频处理并发送至外部信号接收器,实现数据的传输。实验结果表明：当信号的最大发射功率为-132dBm时,功率损耗最低为100mW,密闭空间与外界通信距离达到2000米,可以满足通信的指标。该技术具有良好的应用前景。     

A digital DS spread-spectrum receiver with joint channel andDoppler shift estimation

A digital spread-spectrum receiver design is presented for communication over multipath channels with severe Doppler shifts. The characteristics of the underwater channel relevant to spread-spectrum system design are discussed, and a channel model for short-range communications (less than 10 km) is defined. The receiver considered uses a digital coherent RAKE combiner, coupled with an extended Kalman filter (EKF)-based estimator for channel parameters and pseudonoise code delay. Receiver performance is evaluated by computing average bit-error rate (BER) versus iterations of the EKF joint estimator, using both fixed and time-varying channels. It is shown that the BER obtained using the EKF joint estimator closely tracks the optimum BER obtained when the channel, delay, and Doppler parameters are known exactly. Finally, the Cramer-Rao lower bound for time-invariant joint channel, delay, and Doppler estimation is derived, and compared with the ensemble averaged mean-squared error of the EKF estimator     

Wavelet Notch Filter Design of Spread-Spectrum Communication Systems for High-Precision Wireless Positioning

Spread-spectrum communication systems are now commonly used in the field of cellular telephone positioning. However, wireless positioning systems by low-power spread-spectrum communication are extremely vulnerable to high-power interference, which limits achievable measurement precision. In this paper, a bandwidth variable wavelet notch filter design method is proposed to suppress a large number of jammers in multiple locations with noise interfering with spread-spectrum systems. The filter uses combinations of Gaussian wavelets with optimal time-frequency localization and computational efficiency for real-time operation of denoising. The performance of the adaptive filter has been evaluated by experiments associated with a spread-spectrum communication system model employing a reliable noise detector to locate the filter notch. Experimental results demonstrate that the proposed wavelet notch filter removes the narrow-band interference in accordance with the corrupted frequency contents while minimizing signal distortion and information loss, which leads to high-precision wireless positioning.     

Wide-Band Signal Processing Using the Two-Beam Surface Acoustic Wave Acoustooptic Time Integrating Correlator

A new acoustooptic architecture for performing real-time correlation of high-frequency wide-band signals has been developed. It uses a surface-acoustic-wave (SAW) delay line, and features the optical interference of two coherent light beams which have been Bragg-diffracted by SAW's propagating in the line. The signal multiplication, and subsequent time integration of the product formed, is performed by a photodiode array which detects the diffracted light. This architecture has achieved time-bandwidths products exceeding 10/sup 6/ (34 MHz X 30 ms), and has several attributes which make it particularly well suited for use as a spread-spectrum signal processor. These include linearity of operation, large dynamic range, a large time aperture over which the correlation can be observed, and the ability to determine the center frequency and bandwidth of the signals. A correlator with this architecture has been used to detect a number of wide-band spread-spectrum signals. Its suitability for use as a signal processor in several spread-spectrum systems is considered.