S-band Radar Altimeter Signal Source Based On The Ad9854 Chip Design Technology

The radar altimeter with specific S-band LMF signals waveform has preferable detecting performance in specific application. Based on the requirements of this kind of radar altimeter, the thesis studied and realized its signal source. Because of the difficulty of realizing special signal by traditional means, the thesis exploits DDS chip of AD9854.The direct digital synthesis (DDS) technology is a new frequency synthesis technique. It has the advantages of fine frequency resolution, short frequency conversion time, wide modulation bandwidth and controlling facility, and has capability of generating the different waveforms. And the AD9854 chip produced by AD Company in 1999 is an excellent chip. Since AD9854 can generate only five fixed mode waveforms and can not satisfy extensive application requirements, the crux of research here are focused on how to exploit the chip of AD9854 based on the CPLD device to generate the specific signal waveform and turn it to S-band by up-conversion.The thesis consists of five chapters. In the first chapter, the thesis preliminarily determines the design method of the S-band radar altimeter signal source using DDS technology. In the second chapter, the design principle of system is proposed. Especially, this chapter describes the principle of DDS, and the technology of how to control the AD9854 of the PCB, and the technique of the microwave hairpin resonator filter of the up-conversion circuit. In the third chapter, the thesis studied the technique of how to realize the signal source, including how to programme the CPLD chip with VHDL to control the AD9854 and the designs of PCB. And moreover, the emulation and the result of the microwave hairpin resonator filter are given. In the fourth chapter, a lot of experiments have been done. The experimental results validate the technique proposed here, and show that can provide the signal which can satisfy the specific S- band radar altimeter requirements. In the last chapter, the thesis developed some improvement method to solve the problems which appeared when testing circuit of intermediate frequency.