Development Of Digital Module For Digital Trank Communication Repeater

In the TETRA system of private network communication,the base station often has signal dead zone in the coverage area of the signal network,and the repeater plays an important role in extending the coverage of the base station network.The cost of the repeater is much lower than that of the base station,which can maximize the coverage of the signal network in the case of the fixed number of base stations.The repeater system mainly plays the role of relaying the transmission signal between the base station and the receiving terminal.As the repeater system itself has a high gain characteristics,so when the isolation between the transceiver antenna is not enough,the echo interference signal will often cause the system self-excited,seriously affecting the communication signal transmission.Traditional analog repeater in the use of engineering mostly from the system installation,shielding the point of view to solve the self-excited problem.Analog repeater can not fundamentally solve this problem of echo interference.It is necessary to study a new digital repeater with anti-echo interference.In this paper,from the perspective of engineering,through the development of the TETRA repeater digital IF part of the introduction of echo interference cancellation algorithm to directly and effectively solve the problem of self-excited repeater.This thesis first introduces the research background and significance of the TETRA digital repeater and the theoretical basis of the development of the digital IF module,and gives a detailed mathematical analysis;Then the key module in the digital intermediate frequency system(such as digital frequency conversion module,digital filter module,the module of vibration,etc.)on the basis of the principle and characteristics of the working principle of adaptive interference elimination module and the performance of several common interference elimination algorithm detailed mathematical analysis,overall design scheme of digital intermediate frequency module are given,and the entire system on FPGA platform,MODELSIM and ISE combined MATLAB simulation,the function of each module is proved to be correct.The simulation results show that the suppression capability of the digital IF system is greater than 25 dB and the noise cancellation capability is more than 20 dB.Finally,the digital module of the digital repeater is implemented and the parameters are tested.The test results are as follows: Suppression is greater than 18 dB,noise cancellation is greater than 20 dB.The test results show that the digital IF technology can effectively solve the self-excited problem in the traditional analog repeater.