便携式测向机所误差分析

便携式测向机体积小、携带方便、选址灵活，能方便地实现对无线电目标信号的多点定位和逼近式搜索、跟踪。其常与固定测向或移动车测向系统相结合，实现对目标信号的交叉定位。便携式测向机的机动性决定了其所处电磁环境的复杂性，这也相应增加了测向工作的难度。对测向机系统的测向误差分析，找出产生误差的原因，将有助于提高测向工作效率和测向的准确度。     

测向抗扰度及其测量中应注意的问题

在有干扰信号的情况下，无线电测向设备对主信号保持一定测向准确度的能力，称之为测向抗扰度。测向抗扰度是无线电测向设备的一个重要的技术指标，它用引起测向误差但该误差未超过某一许可值的最大干扰信号的场强来度量。显然，干扰信号的这个场强值越大，表示测向设备的测向抗扰度越佳。     

对无线电测向误差的分析与探讨

0 前言 无线电测向过程与其他测量手段一样,均存在误差。在实际工作中,许多因素都会使得测向结果与真实值产生偏差。深入了鹧造成无线电测向误差的原因,对于无线电测向技术人员来说具有较大的实际意义。测向误差大体可归纳为两类：系统误差和随机误差,具体又可分为：设备误差、电波传播环境与信号调制误差、噪声误差以及人为误差等。     

无线电通信测向中的极化误差分析

无线电通信测向中,因极化效应而产生测向误差不容忽视。通过论述测向中极化误差的各种相关因素,分析非正常极化波所引起的测向误差及地面反射波与直射波的相位滞后等问题,分析无线电测向中的极化误差产生基理,并结合实际应用提出减小极化误差的措施,提出采取取平均值法和相应的测向体制以解决在无线电测向中减小极化误差的方法。     

一种分析无线电测向准确度的方法

结合对无线电测向误差的分析,介绍了曲线拟合的基本概念和简单算法,及其在国家无线电监测中心上海监测站进行测向误差与频率对应关系研究时实际应用的结果。实验结果表明,曲线拟合是消除随机测向误差、寻找测向误差规律的有效方法。     

便携式测向机的误差分析

便携式测向机体积小、携带方便、选址灵活,能方便地实现对无线电目标信号的多点定位和逼近式搜索、跟踪.其常与固定测向或移动车测向系统相结合,实现对目标信号的交叉定位.便携式测向机的机动性决定了其所处电磁环境的复杂性,这也相应增加了测向工作的难度.对测向机系统的测向误差分析,找出产生误差的原因,将有助于提高测向工作效率和测向的准确度.Y9201BS超短波便携式测向机由成都圆通网络设备有限公司研制生产,性能稳定,本文以该测向机为例,探讨其在测向工作中的误差分析.     

探究空中无线电监测多站测向定位

为了保证无线频谱资源能够正常使用,空中无线电测向定位技术需要在信号侦查和抗干扰等方面不断进行改进。本文从无线电监测多站测向定位的角度出发,对空中无线电测向定位的特点进行分析,并对空中无线电监测多站测向定位系统进行分析,以求为以后的研究提供些许参考。     

多元固定站、车载移动台自动交叉监测监听测向定位网络

多元固定站、车载移动台自动交叉监测监听测向定位网络南京新兴电子系统公司俞惟铨一、任务的提出开展对空中无线电波的监测监听测向，迅速而又准确地或查找各种非法无线电辐射源，是加强无线电管理，合理使用频谱资源，促进无线电事业发展的一种重要手段。南京新兴电子系...     

灵活的移动无线电监测测向系统

R＆S公司的移动无线电监测测向系统是基于R＆S公司的成功经验,并为满足客户特定要求而设计的专业系统。R＆S公司提供完整的系统解决方案可实现无线电监测测向的所有任务：无线电监测、频谱管理、信号分析、测向和定位。     

测向数字化对确定测向质量的影响

测向数字化对确定测向质量的影响西南电子电信技术研究所余健在搜索、营救、识别有害干扰和监测频谱有效利用中，无线电测向是对无线电辐射源进行定位的一种有效手段。而在确定发射机位置和定位区域面积时，测向质量非常重要。通常情况下，我们用测向等级（或示向度等级）...     

Multiple signal DF using superresolution: a practical assessment

The location of radio transmitters through direction finding (DF) has been required almost since the earliest days of radio communications. The two world wars have, not unexpectedly, given impetus to major advances in DF technology. The only major advance in DF technology since World War II has been in the field of wavefront analysis and it is only now that the supporting technologies have made these techniques a practical proposition. Superresolution DF techniques potentially offer the user not only the capability to operate in multiple and unfriendly signal environments but also flexibility of antenna deployment and fast operation. The author attempts to explain how this enhanced DF performance is obtained aided by comparison with other DF techniques. Results obtained with the Siemens-Plessey SR DF demonstrator are also presented to outline the practical performance of superresolution DF techniques     

一种基于低成本软件无线电的二维测向系统设计

为解决现有测向系统体积大、运算量高、成本高、同步采集困难等问题,设计了一种低成本高精度二维测向系统,由五阵元十字型天线阵列及HackRF One同步采集子系统组成。该测向系统通过外接频率源、引入时间同步信号以及初始相位校准分别实现了接收设备间频率同步、时间同步、相位同步,然后将同步的采集信号采用多重信号分类（Multiple Signal Classification,MUSIC）算法进行处理,估计出二维波达方向。实验结果表明,系统的同步误差可控制在一个采样周期内,定位误差小于2°,可广泛应用于雷达、声呐、室内定位等多种领域。     

Joint detection for OFDM-CDMA communications in multipath fading channels

This paper proposes and compares four block joint detection algorithms for the orthogonal frequency division multiplexing (OFDM)-code division multiple access (CDMA) communication systems. The performance of the proposed OFDM-CDMA joint detectors with orthogonal and non-orthogonal spreading sequences are investigated in mobile radio channels. The proposed OFDM-CDMA detectors are zero forcing (ZF) and minimum mean square error (MMSE) detectors with decision feedback (DF) structures. The proposed joint detectors do not require discrete Fourier transform (DFT) or fast Fourier transform (FFT) operations and can be used to compensate the channel distortion. Hence for hardware implementation, the proposed detectors are more efficient than the conventional methods. The channel sorting method offers approximately 2 dB gain for the DF joint detectors and reduces the impairing effect of error propagation. The bit error rate (BER) performance of orthogonal codes is better than that of non-orthogonal ones in time varying channels. Simulation examples are given to demonstrate the effectiveness of the proposed detectors.     

Decision feedback sequence estimation for continuous phasemodulation on a linear multipath channel

An approach to reduced-complexity detection of partial response continuous phase modulation (CPM) on a linear multipath channel is presented. The method, referred to as decision feedback sequence estimation (DFSE), is based on a conventional Viterbi algorithm (VA) using a reduced-state trellis combined with decision feedback (DF). By varying the number of states in the VA, the receiver structure can be changed gradually from a DF receiver to the optimal maximum-likelihood sequence estimator (MLSE). In this way different tradeoffs between performance and complexity can be obtained. Results on the receiver performance, based on minimum distance calculations and bit error rate simulations, are given for Gaussian minimum-shift keying modulation on typical mobile radio channels. It is shown that for channels with a long memory, a significant complexity reduction can be achieved at the cost of a moderate degradation in performance     

无线电测向设备测向误差与数据处理方法研究

通过对某型测向设备的测向精度试验获取的试验数据的分析处理发现，现行的标准和规范中采用的测向误差计算方法没有能够正确区分出设备的能力和试验环境的影响。不能完全客观公正地评价测向设备的真实性能。为了获得合理的测向结果，建议严格按照ITU的有关标准选择测向场地。并选择合适的误差计算方法。     

DF100A型100kW短波发射机中和电路的维护

DF100型100KW短波发射机是电台的重要设备,为维护发射稳定,电路维护工作应受到高度重视.本文先分析了不良极间电容的影响,并给出了解决方法,然后选择中和电路,针对DF100型100KW短波发射机出现的问题进行了分析.     

基于时间调制的单通道多基线相位干涉仪测向

基于时间调制理论,提出了一种单通道框架下的多基线相位干涉仪测向方法,其克服了传统相位干涉需要多个射频通道带来的系统复杂度高以及通道幅相不一致性问题.所提方法利用单刀多掷开关周期性接通多基线相位干涉的各天线单元,并从接收信号产生的谐波特征中同时估计多组基线产生的相位差.首先分析传统多基线相位干涉仪测向存在的局限性,然后提出基于时间调制的单通道多基线相位测量方法,最后结合2～8GHz宽带测向需求,设计四基线相位干涉仪并进行仿真.仿真结果显示,在2～8 GHz范围内,测向误差能达到0.1°以内,证明了本文方法的有效性.     

Estimating defibrillation efficacy using combined upper limit ofvulnerability and defibrillation testing

It is frequently necessary, both clinically and in the laboratory, to estimate how strong a stimulus is required to defibrillate. Current techniques for forming such estimates require the repeated induction of ventricular fibrillation (VF) and subsequent attempts at defibrillation (DF testing). DF testing can be time consuming and in the operating room may increase the patient risks. A novel scheme is presented which combines DF testing with upper limit of vulnerability (ULV) testing. ULV testing is a relatively safe procedure which yields data well correlated with defibrillation efficacy. A Bayesian statistical model of combined ULV/DF testing is presented which is both powerful and concise. The model is used in two examples to design minimum rms error protocols and estimators for the DF95 (the stimulus strength which defibrillates 95% of the time). A simulation for humans of one example solution shows that a single VF episode of combined ULV/DF testing (rms error=23% of the mean DF95) is better than two VF episodes with DF testing alone (25%). The simulation results for a second example are directly compared with laboratory results from six pigs, showing a less than 1.0% average difference between the simulated and measured rms errors     

Blind Adaptive and Iterative Algorithms for Decision-Feedback DS-CDMA Receivers in Frequency-Selective Channels

In this paper, we examine blind adaptive and iterative decision-feedback (DF) receivers for direct-sequence code-division multiple-access systems in frequency-selective channels. Code-constrained minimum variance and constant modulus design criteria for DF receivers based on constrained optimization techniques are investigated for scenarios subject to multipath. Computationally efficient blind adaptive stochastic gradient and recursive least squares algorithms are developed for estimating the parameters of DF detectors along with successive, parallel, and iterative DF structures. A novel successive parallel arbitrated DF scheme is presented and combined with iterative techniques for use with cascaded DF stages in order to mitigate the deleterious effects of error propagation. Simulation results for an uplink scenario assess the algorithms and the blind adaptive DF detectors against linear receivers and evaluate the effects of error propagation of the new cancellation techniques against previously reported approaches     

天线回转中心偏离阵列球心对测向的影响

在微波暗室内进行射频仿真试验时,必须保证被试装备天线回转中心和天线阵列的球心重合,否则就会引起测向误差,从而影响对被试装备性能的科学评估.分析了对心不准对装备测向测试结果的影响,建立了测向误差的分析模型,并且结合实例详细分析了偏心距离和测向误差的关系.相关分析模型和结论可以作为对心设备建设中对对心精度的指标论证的依据,也可以为仿真试验战情的设计提供科学的借鉴.