一种针对UWB-PPM多径信号的加权非相干接收机设计方案

由于实现简单,基于能量检测的非相干超宽带(UWB:Ultra-Wideband)接收机对一些低速数据应用具有很大的吸引力,但另一方面,相对于相干接收机来说其误码性能一般较低.为了提高其误码性能,一种采用子分区积分加权合并的优化措施在文献[4]中被提出.本文针对加权非相干接收机在UWB-PPM多径信号下的情况进行了研究,推导了相应的闭式误码性能表达式,并进一步分析了该接收机的最佳和准最佳加权系数组合.通过计算机仿真对加权非相干接收机的误码性能分析和准最佳加权系数的有效性进行了验证,对子积分区间宽度的影响进行了分析.结果表明,加权非相干接收机在理想情况下至少具有3dB以上的性能提升,并对子积分区间宽度的影响具有一定的强健容忍能力.本文最后提出了一种简单灵活的加权非相干接收机结构设计方案,包括相应的加权系数估计算法和实现结构.     

PPM调制的超宽带差分接收机

提出一种PPM-DIFF-UWB调制方式及其接收机,该接收机采用三条具有不同延时特性的相关支路实现PPM-UWB信号的差分接收,提供了一种关于PPM调制的超宽带信号的低复杂度的接收方式,可用于实现在密集多径信道下的多径分集接收,且不需要复杂的信道估计以及发送额外的参考信号.理论分析和实验仿真结果表明该接收机的误码性能优于常规的PPM-TR-UWB接收机.     

多径信道下辅助矢量接收机性能分析

研究了在直接序列码分多址(DS-CDMA)系统中,多径环境下一种基于RAKE结构的辅助矢量接收机。该接收机在收集多径信号的同时抑制系统中的多址干扰,从收集的多径信号中估计出信道响应矢量,并利用估计出的信道响应矢量对多径信号进行合并,最后进行判决。仿真结果表明,辅助矢量接收机能够有效地去除DS-CDMA系统中的多址干扰,同时具备良好的抗多径衰落性能,误码性能明显优于RAKE接收机。     

UWB-TR接收机性能分析

在确定STR接收机模型的基础上,采用对接收机输出噪声进行高斯近似的方式对UWB-STR接收机性能进行了分析,得到UWB-STR接收机的误码性能表达式。表明该种接收机误码性能不仅与信噪比有关,而且与噪声输入带宽和积分时间有关,其特性可类推到其他类型的自相关接收机。最后与其他现有文献的结论进行了对比及修正,并提供了UWB-ATR的误码性能表达式。     

瑞利衰落信道下扩频信号隐分集性能分析

介绍了瑞利衰落信道下采用扩频信号的失真接收机获取隐分集增益机理.在多重分集通道和每个分集通道存在离散多径的瑞利信道模型基础上,分别详细分析推导了单重分集通道和多重分集通道情况下的隐分集性能表达式,给出了不同情况下的误码性能理论曲线,并在硬件系统测试平台上,对扩频信号的隐分集性能进行了实测.测试结果表明该分析方法可行,可用于指导工程实践.     

线性调频信号的多径隐分集性能分析

在中、低速率散射通信设备中,线性调频信号的失真自适应接收机因其可观的隐分 集效果而获得了工程应用。但目前仅能通过工程经验得出具体型号的近似分集重数。概述了 线性调频信号失真自适应接收机产生隐分集增益的机理,作为比较推导了显分集散射通信系 统的误码性能,然后对分离多径接收机的隐分集性能进行了理论分析,给出了已知散射信道多 径时延功率谱条件下的系统误码性能的理论公式和推导步骤。该方法可为工程实践提供理论 依据。     

光纤CDMA系统光接收机误码性能研究

光纤ＣＤＭＡ系统是一个扩频系统。本文首次对该系统中带扩频相关特点的光接收机噪声及误码性能进行了细致深入的研究,给出了误码率的计算公式,并进行了数值计算,作出了相应的曲线。研究结果表明其误码性能优于普通光接收机。     

应用分组编码调制的超宽带自相关接收机及其性能分析

由于实现简单,非相干传输参考接收机(TR)对于超宽带通信具有较大吸引力,但另一方面,由于需要发送参考脉冲,降低了系统的能量效率和数据传输率.为克服这一缺点,现有文献提出一种采用分组编码调制方案的码字匹配与信号汇聚(CMSA)接收机,但相关文献没有对 CMSA 接收机的最优性和误码性能进行理论分析.针对这一问题,本文基于广义最大似然比检验,提出一种针对分组编码调制超宽带信号的新型非相干接收机.该接收机与 CMSA 接收机的码字判决规则等价,即证明了 CMSA 接收机实质上是广义最大似然意义下的最优接收机.与 CMSA 接收机不同,新型接收机采用脉冲帧信号进行自相关的结构,具有实现更加简单和灵活的特点.同时文中对接收机的错误性能进行了理论分析,在推导成对差错概率的基础上得到接收机的误比特率理论上界,多径衰落信道下的仿真结果表明当误比特率小于 10-3 时,该理论上界是误比特率的一个很好近似.     

电视与广播

TN941 2004041047滚降系数误差对M一P SK信号误码性能的影响/詹亚锋,曹志刚,马正新(清华大学)11通信学报.一2 003,24(10)一125一130滚降系数是M一P SK信号的一个重要参数,它刻画了信号的带宽和包络的起伏程度.从理论上分析了接收机中滚降的系数不匹配对M一P SK信号误码性能的影     

中频带宽对调频遥测解调性能的影响分析

接收机中频带宽是影响调频(FM)遥测解调误码性能的一个重要因素。根据FM信号的解调原理,对非相干鉴频和多符号检测2种解调方式下,中频带宽对解调误码率性能的影响进行了仿真分析,提出了最优误码性能下中频带宽参数的推荐值为1.2倍码速率,通过硬件实验对仿真分析结果进行了验证。     

Unification of MLSE receivers and extension to time-varyingchannels

Forney (1972) and Ungerboeck (1974) have each developed maximum-likelihood sequence estimation (MLSE) receivers for intersymbol interference (ISI) channels. The Forney receiver uses a whitened matched filter, followed by a sequence estimation algorithm using the Euclidean distance metric. The Ungerboeck receiver uses a matched filter, followed by a sequence estimation algorithm using a modified metric. A unified development of both receivers is given, in which each receiver is derived from the other. By deriving the Ungerboeck receiver from the Forney receiver, we show that the whitening operation is cancelled in the Euclidean distance metric, leaving the modified metric. In addition, the Ungerboeck receiver is extended to the case of a time-varying known channel. When the channel is unknown, decision-directed channel estimation is assumed, which requires channel prediction to account for the decision delay. It is shown that the Ungerboeck receiver requires additional channel prediction, degrading performance due to prediction uncertainty. To solve this problem, two alternative receiver forms are developed which do not require additional prediction, though the computational complexity is increased. Performance and complexity of the receiver forms are compared for the IS-136 digital cellular time-division multiple-access (TDMA) standard     

Random Correlation-Based Receiver for Impulse Radio Communications in UWB Channels

Impulse radio is a low-complexity ultra-wideband system which is suitable for highly dispersive multipath channel. In this paper, we propose a random correlation-based receiver for impulse radio communications. The proposed receiver correlates the received pilot symbols with the randomly generated base functions according to channel statistics and forms the detection template by combining several base functions which have larger correlation coefficients with the pilot symbols. The proposed receiver demodulates the received signal by employing a symbol rate sampling. Computer simulation results have shown that the proposed receiver outperforms the conventional correlator-based receiver, compressive sensing correlator-based receiver, weighted energy detector and autocorrelation receiver.     

Adaptive communication receivers

This paper describes the results of an investigation of some communication receivers whose response to an input signal changes in a manner determined by the input signal. The problem considered is the design of a communication receiver to receive a message which is coded intoMfixed unknown signal waveforms and transmitted through a noisy channel. An optimal (minimum probability of error at each time interval) receiver is derived which has an exponentially growing structure. It requires(M - 1)M^{n-1}subsystems to receive thenth message symbol. The derivation suggests forms of adaptive receivers which need a more practical amount of equipment to implement, which we call the gremlin and the decision-directed adaptive receiver. The gremlin receiver is a taught-learning machine since, after it makes a decision, a gremlin tells it what the correct decision was. The decision-directed receiver is a self-taught learning machine, using its own output instead of a gremlin's. It is shown that the gremlin receiver converges to a matched filter for the unknown signal and that, in any practical case, the decision-directed receiver performs almost as well. Finally, some results of an experimental simulation of the decision-directed receiver are presented. A plot of the relative frequency of error vs. time is given for a number of different signal-to-noise ratio's (SNR's).     

A low complexity reduced-rank MMSE receiver for DS/CDMA communications

The minimum mean squared error (MMSE) receiver is a linear filter which can achieve optimal near-far resistance in direct-sequence code-division multiple-access communications. However, one of the main problems of this receiver is the required number of filter taps, which is typically large. This is especially true in systems with a large processing gain in which case the receiver's computation burden becomes very high. As a result, methods for reducing the complexity of the MMSE receiver have been of great interest in recent years. We propose an efficient partitioned MMSE receiver based on a classification algorithm. It is shown that the computational complexity (in terms of the filter taps) of the proposed receiver can be reduced significantly while good performance is maintained. Based on the special structure of our proposed receiver, we also propose a release-merge adaptive partition algorithm which can update the partition and the receiver's coefficients simultaneously. In particular, it is demonstrated that the proposed receiver can perform much better than previously proposed reduced-rank MMSE receivers, such as the partial despreading MMSE receiver and the cyclically shifted filter bank receiver, with even a smaller number of taps.     

基于软判决的MMSE-OSIC接收机

串行干扰相消接收机是广泛应用于多输入多输出系统中的一种接收端信号处理与检测技术。在串行干扰相消接收机中,先检测的层的判决准确性会对后续层的检测产生影响。检测过程中产生的判决误差,将对后续层的检测引入残留干扰,进而影响后续层检测的正确性,造成差错传播。本文提出一种基于软判决的最小均方误差检测带排序串行干扰相消接收机,可以有效减轻基于硬判决方法的带排序串行干扰相消接收机的差错传播问题。在重构干扰信号时,该接收机使用根据软判决信息得到的符号期望,替代硬判决方法,能够有效降低干扰相消时各层之间由判决误差引起的残留干扰;该接收机还可以精确估计残留干扰的功率以及各层数据流的后处理信干噪比,改善了基于硬判决方法的串行干扰相消接收机存在的各层后处理信干噪比估计值偏大的问题。可靠性更高的软判决结果有效降低了残留干扰,更精确的各层后处理信干噪比抑制了残留干扰对后续数据流检测的影响,提高了判决结果和排序过程的准确性。仿真结果证明,基于软判决的最小均方误差检测带排序串行干扰相消接收机可以有效避免差错传播的产生,因而获得较大的性能提升。      

WCDMA下行链路接收机设计

根据下行链路的需求设计了可以满足实时性需要的接收机。在下行链路中,只有所希望的用户信号被解调,而抑制其他用户引起的干扰。针对这一特点,下行链路接收主要采用单用户接收机,在本文中对各种单用户接收算法进行了分析、仿真及性能比较,本文的单用户接收算法采用自适应LMMS单用户接收算法。采用的接收机是在自适应LMMSE接收机基础上提出的差分自适应接收机,该接收机运算量比较小,性能比较好,并且能够跟踪同步,能够在用户终端上使用。     

Adaptive detection of DS/CDMA signals in fading channels

This paper examines the behavior of the minimum mean-squared error (MMSE) receiver in frequency-nonselective-fading channels. It is noted that the MMSE receiver will often lose phase lock on the desired signal when the desired signal dips into a deep fade. A modification to the MMSE receiver is presented which is demonstrated to function quite nicely in flat-fading channels. Analytical results for the modified MMSE receiver are presented and found to agree very well with simulation results. These analytical results are then compared to the theoretical performance of the conventional (i.e., correlator) receiver in terms of both bit-error rate (BER) and capacity. As expected, the modified MMSE receiver was found to offer a substantial improvement in both BER and capacity. Finally, a simple empirically derived formula is given which will give a good approximation to the BER of the modified MMSE receiver in a Rayleigh-fading environment. This formula can also be used to determine the number of users a given system can support. It is noted that as E_b/N₀ grows, it is quite feasible to approach 100% channel utilization with the MMSE receiver, whereas a conventional receiver is typically limited to a utilization of 10%-20%     

基于Simulink的单比特数字接收机设计

瞬时测频接收机拥有大工作带宽以及高截获概率,是电子战系统的一个重要组成部分,然而它无法对同时到达的多个信号进行测频。单比特接收机是解决这个问题的一种方法,由于它采用了很低的ADC采样位数,以及直接射频采样能力和独特的测频算法,使它具有大带宽、实时测量双音信号频率信息的优异性能。相比于典型的数字接收机,自身结构也得到了极大的简化。提出了一种单比特接收机硬件设计架构,并基于Simulink工具搭建了模型,分析了这种设计的性能。该模型具有高度的灵活性,对于单比特接收机的设计与系统实现具有一定的指导意义。     

A Receiver with Memory for Fading Channels

In this paper, an adaptive receiver with memory for fading communication channels is considered. The receiver consists of an estimator and a detector. The estimator is a finite-memory MMSE estimator with decision-feedback which minimizes the probability of error of the receiver. Asymptotic approximations are employed to derive an adaptive decision role based on the estimate. An example is presented where the receiver with memory is shown to perform better than an optimum receiver without memory.     

Clocked power control circuit for inductively powered devices

Inductively powered devices are finding increasing use in many applications, such as biomedical implants and radio frequency identification (RFID) tags. In these systems, because of transmitter and receiver movements, the receiver coil may get close to the transmitter coil, which results in more than needed power delivered to the receiver load. This increases heat dissipated in the receiver circuit. In order to avoid overheating the receiver in such a high magnetic field (short coil separation distance) condition, the received power should be monitored and controlled. This paper introduces a clocked power control circuit integrated in the implant receiver, which is an independent, automatic power adjustment solution to limit heat dissipation with response to the coil separation distance. In this circuit, the rectified voltage across the load is monitored, and converted to a digital representation to selectively detune the receiver inductor-capacitor (LC) tank. To demonstrate this concept, a design example applied to inductively powered implants is given. Measurements on the prototype with a varied coil separation distance validate the desired power control functionality. Less power dissipation is achieved for the receiver compared to no power control condition.