超宽带通信同步的研究

针对TH调制PPM超宽带(IJWB)系统,给出一种解决IR-UWB通信系统信号捕获和定时同步方法.这种方法基于导频脉冲序列,接收机使用与导频脉冲序列相匹配的相关滤波器,通过观察相关器的输出信号,可以估计导频序列的存在,此外,相关器输出的峰值可以使接收机与发射机时间对齐,从而达到同步.采用仿真与理论分析相结合的方法,详细分析了AWGN和多径信道下的同步性能,结果表明,理论分析和仿真结果相吻合,利用导频脉冲序列在各种信道下均可获得很好的同步.     

WCDMA系统中导频符号辅助的空时二维RAKE接收机

针对WCDMA上行链路的时分导频和复扩频方式的特点 ,提出了一种适用于WCDMA系统的线性自适应空时二维RAKE接收机 .利用导频符号进行信道估计 ,并作为空间波束成型器的参考信号 .理论分析和在多用户时变频率选择性衰落信道下的仿真研究表明 ,对导频信号的充分利用可以降低空时二维接收机的实现复杂度 ,所提的接收机能明显提高接收机的输出信干噪比 ,降低误码率     

一种应用于军事图像通信的UWB接收机

提出了一种改进型的基于前向自适应方式的TR接收机结构,并对其性能进行了理论论证和仿真分析．证明该接收机在特定的信道模型下有着可以与完全Rake相差不大的BER性能,硬件实现复杂度低,而且其特殊的信号结构设计特别适合用于脉冲同步的导频信号的接收。     

噪声环境下Nakagami-m参数估计方法研究

多径衰落信道估计是移动通信系统在实际环境中为了提高接收机性能而迫切需要解决的问题。Nakagami-m参数估计方法主要有盲估计和基于导频信号的信道参数估计方法,重点研究了基于最大似然的Nakagami-m参数盲估计方法,该方法充分利用了最大似然估计是一种最优选择原理,当其概率密度函数取最大值时,可以把m的期望值作为其参数估计值,由此无需导频信号而直接估计出系统的信道系数。理论分析和仿真试验均证明了该方法在噪声环境下的可行性和适用性。     

相关Nakagami信道下信道估计器对RAKE接收机性能影响研究

在实际环境中RAKE接收机在接收信号时都要进行信道系数估计,以便进行相干合并。文章研究了不采用导频信号与采用导频信号两种估计器,具有估计误差情况下,在相关Nakagami信道下的RAKE接收机的性能,并且通过特征函数法得到了误码率公式的闭合表达式。比较了两种估计器对系统性能的影响,最后给出了数值结果,可以看出,当导频信号能量与信号能量相等,且导频数目比较多时（大于5）,采用导频信号的系统性能优于直接估计信道系数的系统。直接估计信道系数的系统性能在信噪比大于5dB后,其性能远远优于导频信号的估计系统。     

基于多相滤波的数字接收机的FPGA实现

给出了一种基于多相滤波的数字信道化接收机的实现方法,系统的处理带宽为875MHz,解决了高速ADC与FPGA处理速度之间的矛盾。为了克服信道化接收机的接收盲区,采用信道重叠的方法,连续覆盖瞬时带宽。在信道化处理后接测频模块,可以消除虚假信号的输出和提高测频精度。整个接收机在单片FPGA中实现,能够检测同时到达的两个信号,并实时输出脉冲描述字（PDW）,经FPGA时序仿真结果验证了算法模型的正确性和有效性。     

基于椭圆球面波的非正弦通信系统同步方法

针对基于椭圆球面波的非正弦通信系统同步困难问题,提出了基于训练序列和导频信号的同步方法。该同步方法在发信端利用训练序列调制椭圆球面波脉冲信号作为同步头,并在调制信号中加入导频信号;在收信端利用导频信号,通过锁相环技术使本地采样时钟与发信端采样时钟同步,本地模板信号与接收的调制信号滑动相关,通过检测最大相关值,获取同步信号。理论分析和仿真结果表明:在加性高斯白噪声信道中,该方法在低信噪比的情况下,仍能获得良好的同步性能。     

基于导频序列信道缩短的超宽带信道估计

针对多频带超宽带系统,提出一种基于导频序列信道缩短的信道估计方法,解决了循环前缀长度小于信道最大多径延迟时难于估计信道参数的问题。首先在发送信号中插入块状导频,利用最小均方误差准则（MMSE）,在接收机前端设计信道缩短均衡器,然后根据均衡器输出序列估计出复合信道,最后通过反卷积解出原信道参数。仿真实验表明：该算法具有良好性能。     

宽带无线信道精细时延和响应联合估计方法

研究适用于无线信道测量的定时偏移和信道联合估计方法.发射机发送具有循环前缀结构的导频信号段.接收机根据粗同步信号确定快速傅里叶变换的窗口起始位置.利用改进时域最小二乘信道估计和变换域滤波,获得高精度的信道估计值.对频域接收导频信号段的定时偏移进行精细估计,对定时偏移量进行滤波并累加.最后,对频域接收导频信号段进行定时偏移补偿.信道估计器、定时延迟偏移精细估计器与补偿单元三者构成迭代相干延迟锁定环路.仿真结果表明:采用迭代相干联合估计方法进行精细定时延迟估计的性能明显优于非相干方法.     

数字信道化接收机信号处理技术

数字信道化接收机是一种比较优秀的电子战接收机。采用瞬时测频技术可以有效地消除相邻信道的虚假输出；利用非相干积累技术可以克服固定门限检测的缺点；跨信道信号的检测及恢复技术可以解决宽带信号的跨信道问题。仿真实验证明了以上方法的有效性，这些技术的采用可使数字信道化接收机早日实现实用化。     

Galileo/GPS双模相关器IP核设计

导航定位接收机中的相关器设计是导航定位接收机设计的一个关键技术,而相关器的设计将发展为基于SoC应用的IP核的设计。阐述了导航定位相关器的工作原理和结构,对构成相关器的各个模块进行了分析,并对Galileo/GPS的导航信号进行分析。在此基础上,采用基于SoC应用的IP核设计方法对Galileo/GPS双模相关器IP核进行设计,并进行了仿真验证和分析,可方便地应用于导航定位接收基带SoC的设计中。     

DS-CDMA中基于MMSE相关器的RAKE接收机

该文研究了DS-CDMA中用于频率选择性多径信道RAKE接收机的限阶MMSE相关器的性能,这种基于CSA(Correlations Subtractive Architecture)结构的MMSE相关器很适用于频率选择性多径信道。通过用MMSE柑关器取代普通多用户RAKE接收机的传统相关器,可以达到与扩展到多个码元的MMSE接收机相近的BER性能。CSA产生MMSE相关器不需要矩阵的逆变换,降低了运算复杂度,有利于直接取代普通RAKE接收机的相关器。     

Spread Spectrum PN Code Acquisition Using Hybrid Correlator Architectures

A hybrid correlator architecture is described which combines the serial structure of an active correlator with the parallel structure of a matched filter correlator. The mean PN code acquisition time performance of this hybrid serial-parallel correlator structure is analysed. Results are shown which compare the acquisition performance of the serial, parallel, and serial-parallel structures. The results are for a PN code length of 64 code chips and assumes a Gaussian channel with the receiver detection threshold set to obtain a constant false alarm rate. An enhancement to the serial-parallel acquisition algorithm is also described which can increase the acquisition time performance by about 15% for typical operating conditions. Overall the results demonstrate that the hybrid correlator can provide rapid code acquisition with a limited receiver complexity.     

A spread-spectrum multiaccess system with cochannel interferencecancellation for multipath fading channels

The authors propose and analyze a direct-sequence spread-spectrum multiaccess (DS/SSMA) receiver that employs a cascade of cochannel interference (CCl) cancellers for communication over multipath fading channels. The receiver first coherently demodulates and despreads the received signal to produce correlator outputs and initial data estimates. Based on these estimates, the cancellation scheme essentially creates replicas of the contributions of the CCl embedded in the correlator outputs and removes them for a second improved hard data decision. By repeating this operation over and over, a cascade of CCl cancellers is derived. Through theoretical analysis and simulation, the authors investigate the canceller's bit error rate (BER) performance in both the absence and presence of errors in the amplitude and phase estimates of each user's received signal. Numerical results show the considerably large improvement in performance that can be attained by the cancellation scheme, even under partially degraded estimates     

Principles of high-resolution radar based on nonsinusoidal waves.I. Signal representation and pulse compression

Carrier-free coded waveforms that promise good clutter rejection and high-resolution capabilities for radar are represented as a sequence of positive and negative Gaussian pulses. On the basis of this signal representation, the matched-filter (or correlated receiver) response to carrier-free coded waveforms is analyzed and plotted for certain Barker and complementary codes, complementary-code pairs being the optimum codes for clutter rejection. The systematic design of a carrier-free, pulse-compression radar system is described. A correlator receiver that is specifically designed for the selective reception of complementary-code pairs is presented. Computer simulation results for the correlator receiver are also presented     

An adaptive correlator receiver for direct-sequence spread-spectrumcommunication

This paper presents a novel receiver for direct sequence spread-spectrum signals over channels containing interference and multipath. The receiver employs an adaptive correlator that jointly detects the transmitted data, removes interference, and compensates for multipath. The optimum correlation vector is derived by determining the Wiener vector that minimizes the mean squared error (MSE) between the transmitted data bit and the correlator output. For an additive white Gaussian noise (AWGN) channel, the optimal correlation vector is the spreading sequence used by the transmitter. For interference and multipath channels, the optimal correlation vector will suppress the interference and combine the multipath while optimizing the detection of the transmitted data bit. The paper presents analytical and simulation results which illustrate the bit-error rate (BER) performance of the receiver in multipath and narrowband interference. Additionally, simulation results are presented illustrating the convergence performance of the receiver when the tap weights are adjusted using either the least mean square (LMS) or recursive least squares (RLS) adaptive algorithms     

BPSK直扩接收的多相关解扩方法研究

在对直接扩频通信系统的信号及技术实现特点进行分析的基础之上,提出了采用多相关器实现BPSK直扩信号解扩的方法。采用多相关器进行BPSK直扩信号的解扩,改善了高动态变化条件下接收机的同步及跟踪性能;通过控制本地解扩序列的产生方式,提高了接收机对不同使用条件的适应能力,较之采用单相关器的解扩方法,其适应能力更强。通过仿真验证证明了该方法的有效性。     

确定信号情况下矢量水听器检测及估计性能研究

在某些场合,例如水下定位、编码通信,信号具有确知脉冲信号特性,声源相对于接收器的方位,可以采用矢量水听器处理来获得。对于确知脉冲信号,本文证明了在各向同性噪声场下,参考声压和振速的相关处理器的方向是声源方位的最大似然方位估计,以及方位估计的克拉美-罗界CRB(Cramer-Rao Bound)。给出了计算机的仿真结果。     

On optimum detection of linearly filtered CPM signals

A novel structure of the MLSE receiver for linearly filtered CPM (continuous phase modulation) signals is derived. It is shown that the correlator bank required in the works of Svensson (1987) can equivalently be replaced by a reduced correlator bank, preceded by a linear filter with impulse response h*(-t) [channel matched filter]. The reduced correlator bank only incorporates characteristics of the CPM signals and is independent of the channel impulse response. This implies that the complexity of the modified correlator bank depends only linearly on the channel filter impulse response length. The proposed receiver structure permits considerable complexity reduction when compared to the currently known solution     

Per-survivor processing sequence detection for DS/CDMA systems withpilot and traffic channels

A per-survivor processing (PSP) sequence detection receiver is proposed for DS/CDMA systems with pilot and traffic channels. The proposed receiver jointly estimates channel parameters and data symbols from pilot and traffic channels, and is derived by modifying the receiver of Choi (see IEEE Proc. Commun., vol.146, no.5, p.1-7, 1999). As a result, the new receiver can outperform the receiver of Choi in exchange for additional computation. Computer simulation results demonstrate the advantage of the proposed receiver over existing ones