美国CUBIC车载测向设备的应用体会

我们使用CUBIC车载测向机已有半年多,结合日常及突发性的干扰查处工作,现对其性能作一个简单的评述。使用该设备给我们留下最深刻的印象就是其示向度较为稳定,这一点对于我们在城市环境中对无线电信号进行移动监测特别重要,因为在城市交错着各种高大建筑物,在这里,无线电波不断的发生反射和遮挡,一般的测向设备此时很容易产生示向度大范围摆动,即使使用测向精度和灵敏度较高的测向设备也很难避免这种情况的产生,从而无法判断正确的干扰来波方向。我们知道,在城市移动监测中我们主要关心的就是所测的电波来自相对于车体的那一个…     

依据ITU频谱监测手册选择测向机

测向机广泛应用于民用和军用无线电监测和定位领域的无线电发射机的位置确定,各国为了确保总的无线电传输质量,都根据相应标准对无线电频谱进行规范和监测,以免传输质量不良甚至产生严重事故.ITU针对民用无线电监测发布了多个建议,在技术上提供了通用的质量标准,这些建议汇总于《频谱监测手册》.     

Experiments on direction finder using RBF neural network with post-processing

Evaluation tests are carried out on the direction finder, which has an aperture comprising four monopoles on the circumference of 0.4 /spl lambda/. Radial bias function (RBF) neural network and a new post-processing procedure are used in the algorithm of DOA estimation. The estimation error was reduced to one-tenth that of MUSIC.     

Converting a small standard receiver into a hand-heldnarrow-aperture HF direction finder

Describes a compact HF-antenna accessory, designed for use with book-sized portable receivers. It converts the receiver for sky-wave-direction finding (DF), co-channel-interference reduction, and radio-frequency-interference (RFI) location, while being hand-carried by the user. When the system is operated in the DF mode while in motion, site-related errors in line of bearing (LOB) can be reduced by spatial averaging, and by over-sampling and excising "outliers." This approach is equivalent to increasing the effective aperture to improve resolution. Spatially averaging the LOBs permits useful DF measurements to be made in locations, so cluttered by scattering from nearby objects, as to be unsuitable with standard DF equipment. The receiving system has been designed to be as insensitive as possible to local reflections (including those from the operator's body)     

宽频带干涉仪测向圆阵中的互耦效应

运用相关处理方法对互耦情况下的宽频带干扰仪测向圆阵特性进行了分析,研究了互耦存在时的宽频带干扰仪测向圆阵设计原则。     

A DSP-based hearing instrument IC

This paper presents a digital signal processing IC, including AD/DA converters, for one-chip hearing instruments. An on-chip infrared remote control receiver is used to load a program Into the digital signal processor (DSP). The complete IC consumes 2 mW from a single cell battery and operates with supply voltages down to 0.9 V. The oversampling A/D and D/A converters show a dynamic range of 77 and 93 dBA, respectively. Only a few external capacitors are needed. The chip area is 35 mm² in a low-threshold 0.8-μm CMOS process     

Radiation analysis and errors associated with the monopulse operation of a satellite direction finder

This work describes the radiation performance of a novel concept for direction and location finding, using stationary satellite beacons. The received signals are processed with a monopulse four-element array. The monopulse mode is generated using the phase excitation of the radiating elements. For accurate processing the radiation phase should correspond with the bearing angle around the boresight direction. Phase deviations, however, occur in this phase pattern owing to the discrete excitation of the elements. Therefore, detailed analyses are presented for this phase pattern, its attainable gain and the depolarization effects, in order to select the kind of array elements, and their spacings, which minimize the phase pattern deviations. The dipoles and the slots, as array elements, yield better phase performance, smaller size and simpler structures than horn radiators, at the expense of worse depolarization.     

幅相不一致对沃森-瓦特测向的影响及解决方法

针对沃森-瓦特测向处理中幅相不一致对定单向及测向准确度的影响问题,分析了定单向法则失效的原因,提出了针对参考通道输出信号的全相位校正方法.利用该方法获取的最优相位修正量对参考通道输出信号进行移相处理,使测向通道与参考通道输出信号之间的相位关系满足定单向法则的要求,提高了定单向方法的稳健性.通过对测向误差特性的分析,给出了因测向通道间幅相误差导致的测向误差表达式,提出了利用最小二乘法计算误差曲线的拟合参数,从而可实现利用有限区域内的测向误差测量数据对全方位测向误差的估计,提高测向的准确度.通过仿真验证了提出方法的有效性.     

A DSP-based single-phase AC power source

This paper presents the development of a single-phase AC power source, which is capable of generating high-quality sinusoidal waveforms with adjustable amplitudes and frequencies over a wide range. Moreover, various types of arbitrary waveforms can also be generated. The system consists essentially of a well-controlled single-phase pulsewidth modulated inverter. To perform tight closed-loop control of the inverter, a digital controller based on the generalized predictive control approach has been developed. The controller gains are determined by minimizing a cost function that reduces both the tracking error and the control signals. To evaluate the proposed approach, a digital-signal-processor-based experimental prototype has been constructed. Experimental results under various loading conditions have demonstrated that the system performs well     

基于DSP的音频处理

在过去20年中音频技术已经取得了长足的进步。从20年前首先引入的激光唱盘(CD)开始,进而发展到超级音频CD(SACD)、DVD音频唱盘和MP3多媒体播放器,数字形式的音频技术越来越流行。可是一旦音频信号离开存储媒体,如何对它们进行处理呢?它们是如何到达系统的输出端的呢?现在所谓的“数字系统”完全达到数字化了吗?实际上很大多一部分音频系统都不是数字化的。 现在大多数音频处理仍然在模拟领域进行,因为早期的数字处理解决方案—基于通用的DSP和外部的模数转换器(ADC)和数模转换器(DAC)使得在硬件     

基于DSP的多方会议系统的混音方案

混音是多方会议系统中的一个关键环节,直接影响到用户之间的相互交流,而数字音频混音是音频会议中不可缺少的模块。文章通过对现有混音算法进行研究,分析了现有混音算法导致混音后音量忽大忽小的原因,在此基础上提出了一种改进的数字混音的算法,并且用定点数字信号处理（DSP）加以实现,实验结果表明,该算法具有合理性和可行性,可以应用于大规模的多方音频电话会议中。     

A DSP-based DS-CDMA multiuser receiver employing partial parallelinterference cancellation

The implementation of advanced DS-CDMA receivers based on multiuser detection principles is becoming a reality thanks to the combination of an improved understanding of the theoretical basis of multiuser detection and advances in digital, mixed-signal, and RF technologies. Due to their lower complexity, subtractive interference cancellation approaches are attractive for the practical implementation of multiuser detection. In a parallel interference cancellation receiver, it is practical to use the soft outputs of a matched filter bank for amplitude estimation. A bias arises in the decision statistics, however, due to imperfect estimation and interference cancellation. In this paper, the source of the bias is explicitly recognized, and a partial interference cancellation scheme that mitigates the negative effects of biased estimation and significantly improves system performance is proposed. A practical real-time algorithm that significantly reduces the implementation complexity of this scheme without sacrificing performance is then derived. To facilitate a software radio implementation, the signal processing complexity of the approach is characterized. The real-time processing algorithm is tested via implementation in software on a floating-point general-purpose DSP. The prototype includes a flexible software-based architecture which performs IF sampling and uses digital downconversion prior to baseband processing. The hardware test setup is described, and the results are presented and compared with simulation and analytical results. The experimental results confirm the simulation and analytical results which show large performance gains over the conventional matched filter     

A DSP-based adaptive controller for a smooth positioning system

The implementation of a self-tuning regulator for the positioning of a direct-drive servomotor is described. The servo motor is a permanent magnet DC motor in which no speed reducer is used. The auto-tuning regulator consists of two major loops. The inner loop contains a feedback (PD or PID) regulator with additional feedforward terms. The parameters of the feedforward compensation are adjusted by the outer loop, which contains an online parameter estimator. The estimator is based on a recursive least-squares equation, and the estimated parameters are the load inertia and viscous friction. This self-tuning regulator has been simulated with PC.MATLAB, and the results demonstrate the high performance of the scheme. Experimental results obtained with a small DC motor (Electrocraft E-576) are presented, and these results show good agreement with the digital simulation results. There are two innovative aspects to this work. First, parameter estimation is used to adapt the feedforward compensation terms instead of the gains of the feedback controller, as usually is the case in conventional indirect self-tuning regulators. Secondly, the complete adaptive controller has been implemented using a single-chip digital signal processor (DSP), which results in the reduction of system hardware and cost     

基于DSP实现的8状态turbo码译码器

国际电信联合会在UMTS/3GPP规范中推荐8状态turbo码作为数据纠错的方案。本文回顾了turbo码的MAX-LOG-MAP译码算法,并分析了输入量化方式对译码性能的影响。在100MHz的定点DSP芯片上实现该算法时,译码速度达到110kbps～300kbps。     

一种基于DSP的V.17Soft Modem实现方案

介绍了传真调制解调标准ITU-TV.17,分析了调制解调器的纯软件实现方法—SoftMo-dem的特点和关键技术,给出了一种基于TMS320C6201定点DSP的实现方案。该方案可以完全实现V.17的各项功能。     

An algorithm for eliminating the ambiguities of bearing measurement by a direction finder in a wide range of target distances

The paper describes a new algorithm for elimination of ambiguities in bearing measurements. The latter arise due to signal reception through background lobes of radiation pattern of the direction finder antenna. Based on a practical example, the estimates of bearing generation probability and of direction finding accuracy are obtained.     

基于DSP的海上目标跟踪系统

设计了一个以TMS320C6711数字信号处理器为主处理器,以FPGA为协处理器,并辅以采集、输出功能的系统.给出了系统中各部分的原理框图,分析了各部分的工作原理及信号流向.提出了一种基于阈值分割的目标跟踪方法,并应用于该系统当中.实验表明,该系统能够很好的对海上目标进行跟踪,并且实时性好、工作稳定可靠.     

一种新型的基于DSP的汉字及图形叠加设计

传统的字符叠加都是使用专用的OSD芯片,一般价格较高,故障率也较高,而且通常只能实现英文字母和数字的叠加.选用的一种新的字符叠加方案是基于TI的2000系列DSP的,通过调试验证效果良好,且实现了汉字及图形的叠加,并减小了故障率,降低了系统成本.