The FPGA is widespread used in modern digital communication system. Especially the dealing with baseband signal and the total system control. The FPGA can not only reduce the length of circuit great, but also improve the stability of circuit, and the advanced development tool reduces the test period of overall system. In order to make the digital signal transmit in band-pass channel, it must to debug the carrier wave with digital signal. According to the differences of baseband signal number systems, it is divided into binary modulation or multi-system modulation (M number systems). Comparing with binary modulation, utilization rate of frequency spectrum of MPSK is higher which can transmit high speed data in limited band-pass channel. The combination of digital communication technology and FPGA is the inexorable trend of the development of modern digital communication system. This article describes the realization of a CPLD-based QPSK modulation system, including baseband signal generator circuit, QPSK modulation circuit, D/A converter circuits, the composition of the reconstruction filter. This paper introduces the hardware design, schematic drawing of the Protel system debugging and testing, and so on.
