Research On Linear Frequency Modulation Source And Pulse Compression

From 1980s,with the development of modern digital technology and VLSI technology rapidly, the modern digital technology has been universalized. Combined the digital with the traditional frequency synthesis technology, direct digital frequency synthesis is generated. It is an important revolution in the area of frequency synthesis. DDS consists of phase accumulator, sine ROM, DAC and LPF. There are some advantages of DDS, such as frequency conversion fast, resolution high, keeping phase continuous during frequency conversion, implementing many modulated function and microprocessor controlling easily. Recently, with the rapid development, DDS is applied to the area of radar, communication, anti-electronics and instruments tested, and so on. One of an important application is radar signal. Based on DDS technology, LFM signal has good performance of pulse compression, anti-jamming capability and have a thick skin to Doppler shift. Now LFM signal is one of the most widely used pulse compression signal in radar.This paper sets about from the generation of the LFM signal, studies around the LFM signal technology to do some work on the theory and practice. This paper researches on the design and implementation of a LFM signal generator with high carrier frequency and wide band, for simulated the transmitter signal of radar. It simply introduces two digital generation methods which are DDWS and DDFS, then detailed describes the principle and design project of LFM signal based on DDFS. Finally the hardware circuit is designed and implemented with DDS chip AD9858 which is the product of AD Corporation. The part of control is achieved by single chip AT89C51. A lot of experiments and analysis are necessary. The purpose of this paper is that provides the theoretical basis and experimental data to the eventual realization of the program.