Study Of Digital IF Modulator-Demodulator Based On SOPC

With the emergence of software defined radio (SDR), the implementation of the connection between all kinds of communication systems could meet the needs of modern communication developement. The technology of IF (intermediate frequency) modulate-demodulate plays a very important rool in the system of SDR, determining the performance of communication system, where key point is.The paper focuses on the method of designing IF modulator-demodulator for SDR. Based on SOPC and DDS technology, digital base band signals are modulated to intermediate frequency, while the intermediate frequency signals are demodulated to recover the base band signals through using MATLAB/DSP Builder tool. On uniform hardware platform, Nios II processor controls the methods of modulation-demodulation, and the carrier wave frequencies to satisfy the requestment of software defined radio using Nios II IDE software development tool. Finally, the system achieves SOPC HW-SW (hardware-software) co-design. Based on SOPC technology, design of signal IF modulator-demodulator includes design of hardware platform, modulation module design, demodulation module design, hardware circuits' design about Nios II processor controller, and the modules of DDS, filters and bit synchronization designing, and so on.The paper puts forward the requests according to the standard of IF modem YD/T 634-1994, and gives a new thought and method through studying digital IF modem of SDR. The result medicates the design that satisfies the specification.