Ultrashort Wave Communication Terminal Demodulation Algorithm And The Fpga Implementation

VHF Communication has a wide application in the Command and DispatchSystem and production controlling system. For example, in some command system suchas transportation and public security dispatch, VHF Communication plays a major role.Especially when some unexpected disasters such as tsunamis, earthquakes occurredwith increasing frequency, and tradional communication systems like GSM which needthe supports of base station or wired backbone network may are not useful, so thecommunication equipments which can work without some infrastructure have becomean important means of communication and command.Developed countries like the United States and Japen have a very robustemergency communications systems.But after Wenchuan earthquake, Wenchuan almostbecame the island of imformation, which exposed the deficiencies of emergencycommunication of China. So this paper is focus on the design and implementation ofmodulation and demodulation about emergency communication terminal.This paper begins with generally introduction of VHF communications and digitalmodulation and demodulation techniques, then details the basic principles of the4-CPMmodulation techniques which adopted in this project, also analyzes and compares thefrequently-used demodulation algorithm of4-CPM. Finally PLL-based frequencydemodulation algorithm was designed for our project. And we did a simulation analysisof4-CPM modulation and demodulation algorithmusing with MATLAB, whichincluding data mapping, shaping filter, frequency modulation, phase-lockeddemodulator, matched filter.Secondly we proposed a digital Intermediate Frequency (IF) solution for thetransceiver of this terminal.and implemented all the modules of digital IF modulationand demodulation on FPGA hardware platform with Verilog HDL.In order to verify thecorrectness and feasibility of the module function, we had a functional simulation ofeach module with Modelsim.Finally, We programed the FPGA through JTAG interface, and tested and verifiedDACs, ADCs, GPMC interface, modulation and demodulation modules with onlinelogic analyzer (ChipScope Pro) on board-level.And the results proved that in additivewhite Gaussian noise channel, when Eb/No=10dB, the bit error rate is lower than103,and when Eb/No=14dB, the bit error rate dropped to104, So we had completed thedesired objectives.The VHF communication terminal we developed in this project supports datacommunication such as audio, SMS, and SD video. It is convenient for the transfer ofvarious kinds of information, and has a very important social and economicsignificance.