Implementation Of A π/4-dqpsk Modem Applied To Image Transmission For UAV

This paper focuses on the research of all-digital π/4offset differentially encoded quadrature phase shift keying (π/4-DQPSK) modem based on the image transmission for UAV. Then we use π/4-DQPSK digital modulation and baseband differential demodulation technology to implement digital signal transmission.π/4-DQPSK is a modification of QPSK modulation. It is a linear narrowband technology which has been widely employed in mobile communication system, satellite communication system. It possesses features of high spectrum utilization ratio, better spectrum specification, stronger anti-fading performance and applicability to non-coherent detection.This paper firstly introduces the rationale of each module in the system of π/4-DQPSK modem, such as match filter, bit synchronization and so on. Secondly, author has done algorithm simulation with Matlab. Based on this, under the ISE10.1of Xilinx company, Very High Speed Integrated Circuit Hardware Description Language (VHDL) has been adopted for designing and implementing every module. Through the way of downloading the program into FPGA chip and debugging circuit, the testing result proves that the π/4-DQPSK modem achieves a BER of10-6when SNR is15dB and it has the anti-frequency-offset capability of±10kHz.