Digital-to-analog Compatible Transmitter Module For Cluster Communication Design And Realization

Trunked System is widely used in the emergency communication system."every chanel in the system can be shared by all the users"is the most significant feature of Trunked System,thereby,channelized communication is so important in Trunked System, Trunked System achieves channel reuse by the technology of multi-stations swtiching, distributing the limited resources of frequency to the users dynamiclly. With the development of The Times, the limitation of the analog system has revealed. Digital trunking communication belong to vigorous development period. Due to the high cost and existing number of equipment,analog trunked communications system and digital trunking exist a longer combination transition.This paper introduces a kind of launch module meeting the real demand of the current situation. This module is compatible with the MPT1327 and DMR by a general software and hardware platform.The main content of this article is to introduce a use of DDS chip interoperate analog FM and digital simulation of 4 FSK practical modulation module method, the key technology includes Baseband data processing, the control of DDS chip and the emission signal circuit design. This paper firstly introduces the air interface and channel requirements of Simulation and digital trunked communications system,and then introduces ome key technology of 4FSK modulation method witch defined in the DMR agreement,mainly involves modulation parameters and shaping filter parameters.After then, make the analysis of the frequency domain of sampling frequency modulation signal(DDFM) with the characteristics of frequency sampling witch output by DDS chip. shows the way how to satisfy the damand in adjacent channel rejection of Trunked System. Finally, introduce the principle and method of realizing the circuit board of this equipment in every specific function module. Emphasis on baseband signal processing,whole net timing,times frequency circuit implementation and realization the control process design based on FPGA ,show the photos of the equipment .