Direct Digital Frequency Synthesis Technology And Its Spurious Analysis

The Direct Digital Frequency Synthesis(DDS) is a kind of new frequency synthesis method and also a revolution in the frequency synthesis techniques. With the development of digital integrated circuits and microelectronic techniques, DDS exhibits its advantages day by day.The direct digital frequency synthesizer is a kind of fully digitized frequency synthesizer, which consists of the phase accumulator, the sine look-up table, the digital to analog converter and the low band filter. It is of high frequency resolution, fast frequency switching speed, low phase noise, the ability to switch frequencies while maintaining constant phase, and the ability to producing arbitrary waveforms. Because of above features, DDS can be used in such fields as radar, communications, electronic warfare and electronic measurement instruments.In this dissertation, the direct digital frequency technique and its spurious are mainly studied. At first, introduces the development of frequency synthesis techniques and analyzes the spectrum characteristic of ideal direct digital frequency synthesizer output. Then the spectrum characteristics of the phase truncation error and amplitude quantization error are analyzed by the method of Fourier series. Basing on the analyzing of the spurious introduced by phase truncation which was made by Nicholas, the formula of the spurious location is deduced newly by using the mapping mathematics and number theory. A new simplifying algorithm is brought forward, which makes it possible to simulate the spurious location by computer. It's significant in estimating the spurious introduced by phase truncation in practical applications. At last researches the application of random dither technique and noise shaping technique in the reduction of DDS phase truncation error and amplitude quantization error, the computer simulation following.