基于DPSK调制的自由空间光通信性能分析

介绍了相干DPSK(差分相移键控)的调制和解调原理,并对零差解调、外差解调和MZI(马赫-曾德干涉)解调三种相干解调方式进行了理论分析。利用Matlab和Optisystem仿真软件构建了基于DPSK调制的FSO(自由空间光通信)系统,得到不同条件下系统误码性能;对三种解调方式进行了仿真,仿真结果表明,零差相干解调方式具有更好的误码性能,更适合FSO。     

1b量化解调数字调制信号及其在单片机中的应用

通过对数字调制信号的硬件方式和软件方式解调比较，详细介绍了1b量化解调数字调制信号的技术原理及解调方法，指出了该方法基于单片机的应用背景及系统实现。     

CallerID信号解调的软件实现

针对于CallerID信号的解调方法主要分为硬件解调和软件解调.本文介绍了一种基于非相干解调原理的软件解调实现方法.在以往的码元判决中多采用抽样判决方式,与此不同,该实现中采用的正负幅值段时间长度判决大大提高了码元解调的准确率,增强了解调软件的健壮性.     

数字通信系统中的混沌调制解调

由于具有类噪声的宽带功率谱,在当今的宽带数字通信系统中,利用混沌信号进行调制解调正受到越来越多的瞩目。分析了混沌调制解调的原理,在此基础上介绍了现有的几种混沌调制技术：CSK、COOK、DCSK及FM－DCSK,并根据实际情况介绍了相应的非相干解调方式。最后,归纳了混沌调制解调技术中存在的问题及发展的方向。     

DVB-S零中频数字解调系统的实现

比较两种QPSK数字解调方式，提出适于DVB－S系统的零中频数字解调方案，简单分析其工作原理，重点介绍零中频数字解调系统的硬件组成和软件控制。     

信号饱和对遥测设备自跟踪影响的研究及应用

介绍了遥测设备中广泛采用的比相单通道单脉冲角跟踪原理,借助数学模型阐述了角误差的调制和解调的实现过程,分析了信号强度对于设备自跟踪的影响,并采取实测方式研究了信号饱和对角误差电压解调的影响,测试一定距离时影响角误差解调的遥测信号强度。该测试原理和方法对于遥测设备人员准确跟踪被测目标,避免因信号饱和影响设备自跟踪具有重要意义。     

利用FPGA芝现通用解调器

在通信侦察领域,有时需要用到通用解凋器。本文介绍了多模式通用解调器的原理和利用FPGA实现的具体方法,阐述了AM、FM、PSK、FSK四种调制信号的解调方法,给出了四种解调方式的抗噪声性能以及硬件电路实现的具体方法。     

光纤布喇格光栅应变传感技术

介绍了基于芯内布喇格光栅的光纤应变传感技术，讨论了它的传感原理、解调方法及其传感方式等相关技术，分析了其特点。     

L波段直接调制解调变频器与L波段变频器

本文介绍了L波段变频器和L波段直接调制解调变频器的工作原理，并就这两种变频方式进行了比较。     

基于e-Labsim平台的GMSK调制与相干解调研究

GMSK(高斯最小移频键控)是20世纪80年代提出的一种典型的连续相位调制方式,常应用在GSM、GPRS移动通信系统和WLN等多个领域。文章主要介绍了数字通信中GMSK调制与解调原理,采用e-Labsim仿真平台来实现GMSK调制与解调。     

Novel Optical Phase Demodulator Based on a Sampling Phase-Locked Loop

A novel phase-locked coherent demodulator, based on a sampling phase-locked loop, is presented and investigated theoretically. The demodulator is capable of operating at high frequencies, by using optical sampling to downconvert the high-frequency input radio-frequency signal to the frequency range of the baseband loop. We develop a detailed theoretical model of the (sampling) phase-locked coherent demodulator and perform detailed numerical simulations. The simulation results show that the operation of the sampling demodulator resembles the operation of the baseband demodulator for very short optical pulses (<2 ps). Furthermore, we investigate how the signal-to-noise ratio of the demodulator is affected by timing and amplitude jitter of the pulsed optical source     

一种可用于DVB-T的OFDM全数字解调器

OFDM是一种高效的数据调制方式，被广泛地应用于宽带数字通信领域。DVB-T就将它作为物理层的传输制式。本文提出了一种可用于DVB-T的OFDM全数字解调器。文章首先分析了各种因素对解调的影响，提出了全数字解调器的结构，然后介绍了符号同步、载波同步、时钟同步和信道补偿等模块在解调器中的全数字实现，最后给出了解调器的误码性能。结果表明，本文提出的全数字解调器具有较好的性能。     

全数字高速OQPSK信号解调技术分析

根据某侦察接收机的需要,基于软件无线电设计思想,分析了影响解调性能的主要因素以及解决方法,提出了一种偏移正交相移键控(OQPSK)解调器的全数字实现结构。介绍了数字下变频滤波抽取、符号同步和载波同步等模块的详细设计与实现。解调器结构简单,具有高度的稳定性、灵活性和可扩展空间,可以应用于通信、侦察接收机中。     

Likelihood-Based Demodulation in Multi-User Chaos Shift Keying Communication

This paper deals with the theory of multi-user chaos shift keying communication systems in the coherent case and in particular with bit error performance under near optimal demodulation. The new approximated likelihood and near optimal demodulator is based on the statistical likelihood of the received signal and is a theoretical generalization of the conventional correlation demodulator involving autocorrelations of the spreading. Near optimal theoretical results beginning from an exact analysis are derived for the bit error rate of a typical user; there is emphasis on their structure in regard to separating the effects of channel noise and interference from other users, and in comparison with single-user results. The new demodulator is shown under particular assumptions to be a form of rake demodulator in the sense that it involves autocorrelation-like terms at various lags. The results are illustrated by theoretical calculations and numerical simulations which point out the enhanced performance of the near optimal demodulator relative to the correlation demodulator.     

Demodulator for pal television signals with delay lines after the synchronous demodulator

A PAL demodulator which has a delay line after each synchronous demodulator is described. The error of the delay lines can be much greater, and their bandwidth can be smaller, than in the existing PAL demodulator.     

一种FSK反正切差分解调方法

针对频移键控在通信系统应用中其调制解调技术在一定程度上直接影响通信系统的性能,提出了一种FSK数字解调方法,称作反正切差分解调.该方法基于正交反正切算法,正交信号直接相除消除了幅度调制成分.新的方法适用于窄带和宽带的FSK信号并适合于数字接收机.仿真结果表明,该技术能有效解调FSK信号,并适合于多种制式的FSK信号.     

Reduction of AM-induced penalty in DPSK receivers by sum-squaredemodulation

A DPSK (differential phase shift keying) demodulator which is insensitive to the amplitude modulation induced by semiconductor optical amplifier phase modulators is proposed. The demodulator consists of only two additional power dividers/combiners, compared to a traditional DPSK demodulator. Analysis shows that the receiver penalty caused by amplitude modulation can be reduced from 2-4 dB to zero. The demodulator is demonstrated in a 2.5-Gb/s DPSK system experiment using an optical amplifier as phase modulator     

A low-complexity noncoherent iterative space-time demodulator

Turbo coded unitary space-time modulation (USTM) can provide large coding gain as compared to uncoded USTM. Because the noncoherent space-time maximum a posteriori demodulator is very complicated, in this letter, we propose a new low-complexity noncoherent iterative space-time demodulator for the USTM constructed from pilot symbol-assisted modulation. The proposed demodulator utilizes both hard and soft decisions from the turbo decoder to simplify the computational task as well as produce reliable soft outputs. Several examples demonstrate that this demodulator has both low complexity and good error performance.     

非相干解扩解调器频偏影响分析

频偏的存在相当于对带限信号的频谱进行了搬移，使解扩信号经过带限滤波器后能量受到损失，从而降低了系统的误码性能。本文首先详细分析了零中频非相干解扩解调器误码性能的影响，推导出误码率表达式，然后提出了改进型非相干解扩解调器，并分析了它的误码性能，最后对这两种解扩解调器误码特性进行了比较。     

Zero-crossing zero-IF demodulator

A new zero-IF digital demodulator which is applicable to M-ary narrowband digital FM signals is presented. This demodulator offers ease of integration and manufacturing and requires less power and size than conventional demodulators. The performance of this demodulator is comparable to that of conventional demodulators