数字集群系统中电路级失真的建模与仿真

Modeling and Simulation of Circuit Level Distortions in Digital Trunked Systems

在设计低功率数字集群通信终端时,系统中的电路级失真效应是一个不容忽视的问题。文中以基于调制方式的TET-RA数字集群系统为例,首先简略介绍了调制和基带差分解调的原理,然后通过理论分析对电路级失真效应进行建模,重点分析了增益和相位不平衡以及直流偏移效应对系统误码性能的影响。通过对整个通信系统进行计算机仿真,定量地研究了电路级失真效应对系统误码性能的影响。仿真结果证明,电路级失真效应对数字集群系统误码性能的影响不容忽视。在实际系统的设计中,必须考虑采取合适的数字补偿措施对其进行补偿。

The effect of circuit level distortions is an important issue in the design of low power terminals in digital trunked systems. In this paper, TETRA systems using π/4 - DQPSK is taken as an example. First, the π/4 DQPSK modulation and baseband differential demodulation are introduced briefly. Then, the effect of circuit level distortions （gain and phase imbalance and DC offset） on system BER performance is investigated quantitatively based on theoretical analysis, modeling of these distortions and computer simulation. The results reveal that the effect of circuit level distortions should not be neglected in system design, and it is necessary to compensate those distortions properly.