Technology Research, Communication Signal Based On Dds Technology

The main task of communication combats is to get the opponents'information and disturb their normal communication. In the research of communication combats and investigates, the communication signal generators are very necessary to simulate true conditions. But the price of the communication signal generators is very expensive and the function is simple. There are less spread spectrum signal generators also. So, it's becoming a new subject to develop better communication signal generators.The Direct Digital Synthesis (DDS) is a new frequency synthesis method and a revolution in the frequency technique. The fully digital DDS technique has such advantages as high frequency resolution, fast frequency switching speed, low phase noise and high stability. And it outlines other frequency synthesis methods. With an intensive study of digital integrated circuit, microelectronics and EDA technology, DDS is developed at speed.This article develops a simple construction and high performance communication signal generator based on the DDS technique. It uses the AD9954 chip of the AD Inc. as the kernel and the ADuC842 chip of the AD Inc. as the control part, and it can generate many communication signals such as FSK signals, PSK signals, Chirp signals, Frequency Hopping signals (FH-SS), Direct Spread signals (DS-SS), Frequency Sweep signals, Phase Sweep signals, and so on. It is excellent in frequency accuracy, frequency stability, frequency resolution, fast frequency switching speed and multiple modulated types.The main work of this article is as this:(1) The theory of the DDS is gone into the paper firstly. According to the composition of the DDS, the time– domain expression is derived and the spectrum analysis is made in the frequency– domain under ideal conditions. The frequency– domain performance of phase and amplitude truncation is analyzed by means of Fourier series method. Analyze the error of DAC and present several methods to eliminate the stray.(2) Study the related theory of normal modulated signals such as ASK, FSK, PSK and spread signals such as DS-SS, FH-SS and so on. Some are simulated with Matlab.