Research on Spread-Spectrum Modulation and Demodulation System Using Real-Valued Orthogonal Pseudonoise Sequences

本研究于1990年至1991年进行，目的是开发具有比m序列互相关性能更好的实值正交伪噪声序列的扩频调制解调系统，并推动该系统在高质量扩频通信系统中的实际应用。研究了从设计到实验的过程，使该领域的工程师能够理解。结果表明，从理论上讲，调幅码和脉宽调制码的同步或准同步扩频传输可以将多路干扰抑制到低水平。实验系统采用低频范围的数字信号处理，而高速专用处理器将实现高比特率的实用系统。本项目的成果如下：(1)调制解调系统的设计，设计了幅调制码、脉宽调制码以及相关处理，使同步或准同步扩频多址不产生多路干扰。通过分析和仿真，明确了量化误差、加性噪声和频带对相关器输出的影响。(2)调制解调系统的构建在构建的系统中，由于256长度的实值伪噪声序列而产生的调幅码或脉宽调制码通过带通传输通道，由基于快速傅里叶变换的前端或后端数字相关器解调。(3)估计调制解调系统的实验。当两种不同的码在加性噪声条件下进行复用解调时，相关器输出波形、过程增益、期望与非期望信号比的改进比和误码率的值都接近理论值。少

This research has been performed from 1990 to 1991, for the purpose of developing spread-spectrum modulation and demodulation system using real-valued orthogonal pseudonoise sequences with the better crosscorrelation properties than those of M-sequences and of urging the practical application of this system to high-quality spread-spectrum communication system. The process from design to experiment has been investigated to be understandable for the engineers in this field.It is shown that the synchronous or quasi-synchronous spread-spectrum transmission of the amplitude-modulated code and the pulse-width-modulated code enables multichannel interference suppressed to the low level according to theory. The experimental system adopts digital signal processing at a low frequency range, but a high-speed special processor will realize a practical system of high bit rate. The achievements of this project are the followings.(1)Design of modulation and demodulation systemAn amplitude-modulated c … More ode and a pulse-width-modulated code as well as correlation processing are designed so that multichannel interference does not occur in a synchronous or quasi-synchronous spread-spectrum multiple access. Effects of quantization error, additive noise and frequency band on correlator output are made clear through analysis and simulation.(2)Construction of modulation and demodulation systemIn the constructed system, the amplitude-modulated code or the pulse-width-modulated code due to the real-valued pseudonoise sequences of 256 length, passes through a band-pass transmission channel and is demodulated by a front- or back-end digital correlator based on the fast Fourier transform.(3)Experiment for estimating modulation and demodulation systemWhen two different codes are multiplexed and demodulated along with additive noise, correlator output waveform, process gain, improvement ratio of desired to undesired signal ratio and bit error rate show the high performance of the values close to theory. Less