Design And Implementation Of QPSK Demodulation In Measurement And Control Communication

With the rapid development of modern digital signal processing technology,measurement and control communication technology has also undergone arevolutionary change, the modem plays a vital role in the high-speed datacommunication. As digital signal transmission has a good antijamming capability and alow error rate, digital demodulation technology has been widely applied in modernmeasurement and control communication.Paper describes the development and research status of modern measurement andcontrol communication, introduces the basic principle of QPSK digital modulationbriefly, studies deeply the QPSK digital demodulation principle and FPGA-baseddigital implementation. In this paper, the principle of digital Costas carriersynchronization loop and Gardner-based bit synchronization loop is analyzed andderived. With the help of ISE development software from Xilinx company, the designof QPSK digital demodulator is completed. The key technology modules includingdigital down-conversion module, carrier synchronization loop and bit synchronizationloop of QPSK demodulator are simulated and verified. The whole design of QPSKdigital demodulation circuit is completed ultimately.Finally, the online debugging of the carrier synchronization loop and the bitsynchronization loop is conducted with the homebrew circuit boards. After analyzed,the test error shows that the performance of the digital QPSK demodulator designed inthe paper could achieve the expected performance requirement.