Digital ¦Ð/4-dqpsk Modem And Fpga Implementation

The aim of this thesis is to implement all digital modem of π/4 offset differentially encoded quadrature phase shift keying(π/4-DQPSK),which belongs to a part of the wireless communication systems.π/4-DQPSK modulation is a linear narrowband technolody,which possesses features of high spectrum utilization ratio,better spectrum specification, stronger anti-fading performance and applicability to noncoherent detection.The modem method has been employed in mobile communication system, satellite communication system. The paper firstly introduces the rationale of a FPGA-Based π/4-DQPSK modem and design & realization of each module,such as pulse shaping filter, NCO model,differential detection,bit synchronization.Secondly,author has done algorithm simulation with Matlab.Based on this,under the ISE5.2 of Xilinx company,Very High Speed Integrated Circuit Hardware Description Language (VHDL) has been adopted for designing and implementing every module.Via observing timing simulation,programme can implement right modem.Thirdly, analyses theoretical bit-error-rate (BER) for 1 bit differential detection in static AWGN channel,which is applied to realization process. When SNR equals to 16 dB, BER is 10-8.Lastly,designs PCB with Protel 99SE, completes programme down into FPGA chip,and debugs circuit.Here, bit rate is 200kbps,carrier frequency is 455kHz.Testing result validates the program is right. This π/4-DQPSK modem achieves scheduled object.