Design Of A DDS-based Signal Source And Research On The Relevant Key Technologies

Direct Digital frequency Synthesizer (DDS)is the devolving trend of signal source technology. This paper is based on the project from Engineering R&D center of Nanjing Collage of Information Technology, aiming to track the relevant technology home and abroad and shift this system gradually to commercial product.Firstly this paper introduces the home and abroad research background of DDS, and the task requirement of the project, then introduces the principle of DDS, give the theoretical analysis to all kinds of spurious waves, and derive the spurious value in the core chip AD9854introduced the phase truncation without consideration of the noise caused by quantization of amplitude; on basis of this the design method of system hardware and software are introduced.This system employs DDS chip AD9854as a core and EP1C6Q240FPGA as its control unit, communicates between MSP430F449MCU and PC and have the function of dual orthogonal output, frequency sweep, QPSK and FPSK modulation, and the agility of communication format which a typical source generator does not have. This system possesses such features as low power consumption, high stability and high ratio of performance to price.After system test, the main performance specifications are listed as follows:the highest frequency reaches120MHz, spurious component is as low as30dBc and the frequency resolution is0.1Hz. The system can be utilized as a detecting meters or systematic integration device in the current digital communication equipments, radars and other electronic equipments.