TETRA Digital Trunking Communication Repeater Research

The Digital trunking communication has an important application in digital trunking private communication. The base station of the digital trunking communication usually has signal blind area which may lead to users to communication failure. As the compensation and extension to the network coverage of the tetra trunking base station, the tetra repeater is an effective scheme. The basic function of the digital trunking communication repeater is to amplify the power of the signal of the up and down link and complete the relay between the terminal and base station. The traditional repeater has a single mode, low ability for resisting interference, easy self-oscillation which will blind the communication network and such a defect is serious constraint the application of repeater. Point to the conditions above, design a repeater that has the Echo suppression ability is very important.Firstly,it introduces the research background and significance of develop the tetra repeater and carefully analyzes the system metrics and discusses the possible system architectures. For comprehensive consideration, it proposes one scheme that converting the RF signal to middle frequency first and then covert it to the RF signal after processing. It proposes one scheme that let there exist two modes which are digital and analogue band-choose processing. In this thesis, it carefully does the analysis and budget of the system performance index, allocate system performance meters to specific function modules, choose the components for each module according to the allocated system performance meters and do simulations for verification. It also design and manufacture the system printed circuit board and metal cavity.Secondly, it arguments the theories contained by the digital intermediate frequency technology which adopted by the project. It states the principles of multirate digital signal processing, band-limited sampling and digital covert in details. In view of the repeater self-oscillation caused by echo interference, it proposes an adaptive interference elimination scheme with a delay module. Besides this, it analysis the theory of LMS algorithm and use the MATLAB to simulate and verify the algorithm. The simulation results show that the adaptive interference elimination program with delay module can eliminate the echo effectively and reduce the self- oscillations risk of repeater.At last, it tests each RF characteristic of the repeater that work at analog band-choose mode and debug the system according to the test results for achieving the pre-set targets. The realization of the digital intermediate frequency system is based on the FPGA platform and use the MATLAB, MODELSIM and ISE to co-simulate the Verilog programs...