QPSK非平衡性调制技术

正交相移键控(QPSK)调制技术已经在工程中得到了广泛应用,然而随着电子对抗技术的发展,QPSK的非平衡调制技术水平也得到了相应的提高,以专门针对通信或定位中的QPSK调制进行干扰.介绍一种实用的QPSK非平衡性调制技术及其系统构成,并对单片DDS调制芯片进行分析,对系统配置及软件开发的主要步骤分别说明.采用该技术可以有效解决干扰信号形成,并且与计算机接口兼容性好,可靠性高,具有较强的工程实用性.     

浅谈QPSK调制技术

介绍QPSK原理,给出QPSK矢量图和逻辑编码表,重点概述PHILIPS公司半导体芯片TDA8050A的参数.     

浅谈QPSK调制技术

介绍QPSK原理 ,给出QPSK矢量图和逻辑编码表 ,重点概述PHILIPS公司半导体芯片TDA80 5 0A的参数     

多电平PAM系统的最佳均衡理论

详细论述了多电平ＰＡＭ（脉冲幅度调制）系统的最佳均衡理论。首先建立了多电平ＰＡＭ系统的一种二进制码间干扰等效模型，将之视为二进制多路系统，从而说明其均稀可以用多个独立的二进制均衡器联事完成。在将均衡问题视为分类判决问题的基础上，根据贝叶斯准则导出了多电平ＰＡＭ系统的最佳均衡有达式和所能取得的最小符号概率的计算公式和近似计算公式。从最佳均衡解可以看到，无论是二进制通信系统还是多电平ＰＡＭ系统，其最佳     

Spectral Analysis of Pulse Frequency Modulation in the Nervous Systems

Spectral analysis is one of the more important design and evaluation tools available to the communications engineer and it could also be a key to increased understanding of the nervous system. Some results of an analysis of the spectrum of the frequency modulated pulses of the nervous system show that 1) change in average pulse frequency is the likely information-carrying parameter of a neural pulse train, since distortion-free recovery of this variable is possible by simple low-pass filtering, and 2) phase relationships existing between signal components and distortion components of a neural pulse train imply unusual distortion attenuating properties of multiple or duplicate information channels. These results are discussed in light of some known nervous system structures.     

An Upper Bound on the Performance of Pulse Modulation Systems

A lower bound is found on the mean square error achievable by any nonlinear pulse modulation system without memory. This bound differs by 6 dB from the limit given by Shannon theorems, at high signal-to-noise ratios. The bound is obtained by finding the signal locus which minimizes a simple lower bound on mean square error, for a given average signal energy and without bandwidth constraints. For the locus that we have found, an upper bound on error shows that the degradation with respect to Shannon's limit is within 8 to 9 dB. The locus, however, does not seem of practical interest.     

Optimum Demodulation in Pulse Communication Systems Employing Secondary Frequency Modulation

In this paper we examine the problem of optimum demodulation of a class of pulse modulation schemes that employ Secondary frequency modulation-frequently used in satellite data transmission and remote control systems. We develop approximate zero-lag and finite-lag receivers using approximate nonlinear filtering and smoothing techniques and study their steady-state behavior for various pulse modulation schemes. Comparisons of performance are also presented, between the zero-lag and finite-lag receivers on the one hand and between various primary modulation schemes on the other.     

QPSK调制方案下的干扰特性分析

通过求出QPSK解调输出干扰信号的均值和方差来研究其干扰特性,并且分析了锁相环相位相同和发生抖动两种情况下的干扰特性。     

微波高速QPSK 调制电路设计

介绍了微波高速正交相移键控(QPSK)调制器电路的设计和制作。电路采用环形调制电路形式,由环形肖特基二极管堆和微波宽带巴伦结构组成。利用高速发射极耦合逻辑(ECL)差分电路驱动,在误差矢量幅度(EVM)为5%时,在X 波段可实现调制码速率达500 Mbit/ s。通过电路优化以及补偿设计,可实现较高的电路性能。经产品测试,在X 波段,转换损耗小于12 dB,幅度和相位一致性小于±0. 25 dB 和±2°,载波抑制优于-38 dBc。该设计结构简单、精度高、可靠性高,对微波高速调制电路工程应用具有一定的参考意义。     

On Improving Bit Error Probability of QPSK and 4-Level Amplitude Modulation Systems by Convolutional Coding

We consider Amplitude Modulation (AM) systems, PhaseShift-Keying (PSK) and Amplitude-Phase-Keying (APK) systems in which each symbol can take 2ⁿvalues. After a systematic search of(n, n - 1)binary convolutional codes with large values of free distance and minimal number of code words at that distance, simulations have been performed with an 8-symbol modulation system (n = 3). For a bit error probability of less2 times 10^{-4}, the saving in average power signal-signal-to-noise ratio over that required for an uncoded system with the same channel symbol rate was more than 2 dB with PSK and APK, and 1.5 dB with AM.     

LDPC码在QPSK调制下的应用分析

对低密度奇偶校验码(LDPC)在QPSK调制下的对数似然比(LLR)算法进行了深入研究,分析了LDPC码在QPSK调制下初始消息的计算方法,推导了初始消息的计算公式。同时对该算法进行了程序仿真,仿真结果表明LDPC码在QPSK调制中具有良好的性能。当信噪比为3.5 dB时,误码率可达到10-6数量级。     

整形激光脉冲与激光探针同步技术

实现了应用于神光Ⅱ装置中的高精度整形激光脉冲与激光探针同步方案。在该方案中,激光探针经硅光导开关进行光电转换之后作为激光脉冲整形单元的触发信号,使激光脉冲整形单元,输出与激光探针同步的整形激光脉冲。为了降低由于触发信号不稳定引起的时间晃动,在光电转换之前放大激光探针,以调整激光脉冲整形单元触发信号的幅度。在神光Ⅱ装置中实现了整形激光脉冲与激光探针小于4.5 ps(均方根)的时间同步精度。     

Cochannel Interference in Nonlinear QPSK Satellite Systems

Increased frequency reuse in satellite systems will result in increased levels of cochannel interference. Such interference can in fact become the limiting factor affecting system performance. In this paper, the effects of cochannel interference on the bit error rate (BER) of a QPSK satellite system are analyzed. A nonlinear satellite transponder having a specified AM-AM and AM-PM transfer characteristic is assumed. An arbitrary number of up- and downlink interferers is considered. The theoretical results are compared with results obtained from time-domain computer simulations. Two facets of the cochannel interference problem which are of particular interest are investigated: the non-Gaussian nature of the interference and the small-signal suppression which may occur for uplink interferers.     

瑞利衰落信道下MPSK信号调制方式识别

调制识别是非协作通信系统接收机设计中的重要研究课题。在实际环境中,噪声和信道衰落是影响信号调制方式识别的重要因素。针对瑞利衰落信道上MPSK较难识别的情况,提了基于似然比的识别算法,并根据最大似然准则对瑞利信道的参数进行了估计完成对2种调制信号的识别。仿真结果表明:在存在高斯白噪声的瑞利衰落信道的环境下,以BPSK和QPSK为例,正确识别率达到90%。     

大型全数字QPSK调制技术的实验方案设计

CPLD（复杂可编程逻辑器件）技术的普及与应用已成为不可逆转的潮流。高等院校也开始逐步将CPLD技术纳入教学计划中,这必然要配有相应的实验课程。QPSK（正交相移键控）调制技术应用相当广泛,已成为许多大型系统的主要调制手段。在这样的情况下设计一种既能满足正常实验教学要求,成本又低且稳定的实验系统已成为迫切的需要。本文在MAXPLUS2环境下采用原理图输入和文本输入相结合的方法产生了QPSK的调制信号。文中不仅给出了QPSK的调制框图,并且完整描述了各个部件CPLD的实现方法,最后把整个系统下载测试,验证了该实验方案的正确性。     

基于FPGA的北斗QPSK调制实现与解调验证

为研制北斗卫星导航模拟信号源,设计实现了北斗QPSK信号调制器。文中在分析了北斗卫星导航系统B1频段信号的正交相移键控调制信号的基础上,基于软件无线电的思想,在FPGA 硬件平台上实现了QPSK信号调制器,通过功率谱测试,QPSK解调和简单串口信息传输,验证了调制解调硬件单元的正确性。     

New Signature Waveforms for Multi-rate QS-CDMA System with QPSK Modulation

This paper presents a multi-rate quasi-synchronous CDMA (QS-CDMA) system with QPSK modulation based on the new signature waveforms, namely GPZ-chip waveforms which are constructed by the generalized pairwise Z-complementary (GPZ) codes and optimal chip waveforms. According to the properties of GPZ-chip waveforms, the multiple access interference of different users can be reduced or eliminated. The interferences among different streams of the same user are handled by an optimal (or suboptimal) multi-stream detector(s). The performance of the proposed system is simulated and analyzed in a cellular communication environment consisting of multipath fading. The result shows that the proposed system has similar performance as compared to the single-rate QS-CDMA system employing GPZ codes with one chip waveform due to the properties of multi-stream detection. Also, the proposed system can achieve a significant interference reduction as compared to the multi-rate system employing concatenated WH/m sequence sets with one chip waveform due to the zero correlation zone properties of the GPZ-chip waveforms, thus resulting better BER performance.     

经符号成形的数字信号调制制式识别

提出了一种对经过符号成形的调制信号进行识别的新算法,利用特征参数提取与决策树分类器相结合对8种常用数字信号进行调制识别。首先详细介绍了符号成形对调制信号及信号瞬时参数提取的影响,然后选取特征参数通过决策树分类器进行识别分类,最后进行了计算机仿真,仿真表明该算法能够有效识别经符号成形的数字信号,且与无符号成形的数字信号调制识别方法相比。有着更好的识别性能。     

TD-SCDMA空中接口调制解调的研究实现与仿真

文章中提出了TD-SCOMA空中接口物理层的QPSK调制解调以及其滤波得主要实现在案。在复基带信号上进行建模进行仿真。通过对结果进行分析，符合TD-SCDMA的协议要求。     

在LabVIEW平台上实现QPSK调制解调电路的虚拟

虚拟仪器概念的出现，是对传统仪器概念的重大突破，美国国家仪器公司（NI）开发的LabVIEW软件平台，是一个基于图形化编程的虚拟仪器软件平台，用它来开发各种仪器及虚拟电路具有独到之处，本文介绍了一种在LabVIEW平台上实现WPSK调制解调电路的虚拟方法。