Design And Study Of Arbitrary Spectrum Generator Based On DSP

Signal generator is very important in modern electronic instruments. It is widely applied in many fields such as communication, navigation, radar, measure and control. Direct digital synthesizing is a new frequency synthesizing technology, which adopts phase increment controlled by digital. It has so many virtues such as high frequency resolving, fast frequency switching ability, continuous phase, low phase noise and integration easily for its digital operation that has been adopted wildly.After an analysis of the theory of popular signal generator and according to the target system, a signal generator with the brief structure and excellent performance is designed with adopting DDS, which is based on the AD Company's DDS chip- AD9857. The system structure, the design of software and hardware and the way to realize the circuitry of the signal generator is analyzed in detail.AD9857 is the core of the digital quadrate modulator based on DDS. The internal structure and operating principle of the up-converter (AD9857) are analyzed in this paper. In order to realize interpolation and low-pass filter high efficiently, the method of digital quadrate modulation based on cascade integral comb (CIC) filter used by AD9857 is analyzed by computer simulation. The hardware achieving principle and method of the digital quadrate modulator is presented in this paper, and then the eight-channel parallel digital quadrate modulation system based on DDS is developed. At the same time, in order to realize high-speed data exchange between PC and the eight-channel digital quadrate modulators, the USB2.0 data transfer system based on EZ-USB FX2 is developed in this paper, which reduces the electromagnetic interference between PC and digital signal processing system maximum, improves the reliability of the hardware system and the speed of data transfer in the signal processing system.