Research And Design Of The Spread Spectrum Signal Generator Based On FPGA

The research that spread spectrum signal source on the spread spectrum technology has an extremely important effect. In recent days, our country is still in the blank in the field of spread spectrum signal generator and mainly takes advantage of specialized spread spectrum integrated circuit from some foreign companies to generate spread spectrum signal. However, most of the functions in these circuits have already solidified that limit the flexibility in development and design, and at the same time exist security hidden dangers in the field of national defense and other areas. Therefore, this subject will present a new method of generating spread spectrum signal which could replace foreign specialized spread spectrum integrated circuit so that provide flexible and reliable spread spectrum resource to the designers who are exploiting the spread spectrum products.The subject that utilizes FPGA as the core exploit tool, focus researches and designs on generation of pseudo random code and direct digital frequency synthesis as well as making use of hardware described language to realize and carry out simulation experiment. Simultaneously, it takes advantage of Micro Controller Unit to design a control system which transfers information code created by upper computer to FPGA as well as manages the spread spectrum modulation. In addition, in order to fulfill the index of spread spectrum signal generator, this subject also has analyzed and verified systematically on the selection of digital to analog converter and design of analog radio frequency filter.The index of spread spectrum signal generator are as follows: the way of direct sequence spread spectrum,m sequence with 13th degree spread spectrum code and mode rate at 200KHz,information rate with 20KHz,the way of radio frequency for BPSK and with the rate of carrier center for 4M±0.01Hz,frequency resolution is 0.01Hz,the spurious rejection ratio of phase truncation≥40dB,the spurious rejection ratio of amplitude quantification≥60dB.By emulation and practical tests, it can be seen that the spread spectrum signal generator could meet the design targets, and can be upgraded in accordance with software requirements which has a strong practicality and broad market prospects.