一种全数字QPSK解调器的Matlab仿真及设计

Design and Matlab simulation of an all-digital QPSK demodulator

QPSK作为一种抑制载波的抗干扰能力较强的四相移键控调制方式,被广泛应用于无线卫星通信中.同步(载波同步和符号同步)是解调过程中最核心的问题之一.采用基于软件无线电的思想,把尽可能多的通信功能用可升级、可替换的软件来实现.载波同步采用数字Costas环的方式,符号同步采用模平方谱线估计法来完成,并通过Matlab仿真验证结果的可行性.将仿真获得的参数结合硬件平台,最终在工程上实现了一款基于FPGA(现场可编程逻辑门阵列)的气象卫星解调器的设计.

As a modulation with relatively strong anti-interference capacity,quadrature phase shift keying（ QPSK） has been extensively used in wireless satellite communication.This paper describes the Matlab simulation of QPSK demodulation,and designs an all-digital QPSK demodulation with FPGA. The core of demodulation is synchronization,which includes carrier synchronization and signal synchronization. The carrier synchronization is completed through numerical Costas loop,while signal synchronization through modulus square spectrum analysis,and the re-sults are simulated on Matlab. The communication functions are implemented by upgradable or substitutable softwares as many as possible,based on the idea of software radio communication.The parameter values through Mat-lab simulation,combined with appropriate hardware system,technically realize the design of the proposed all-digital meteorological satellite demodulator based on FPGA.