Research coding side lobe characteristics and the presence of side lobe suppression when the carrier Doppler
|School||National University of Defense Science and Technology|
|Course||Information and Communication Engineering|
|Keywords||m-sequence perfect/odd-perfect periodical sequence complementary sequences sets of periodic complementary sequences sidelobe surppression carrier doppler|
The channel capacity and the interference of multi-beams and multiusers are mostly determined by the magnitude of the sidelobes in spread spectrum communication and satellite-based navigation-position systems. The optimization of the codes are usually quoted for the autocorrelation sidelobes,namely,the outputs are the autocorrelation sidelobes of codes which are not moudulated by the signals. When modulated by the signals,the periodicity of the input codes is distroyed as a result that the outputs of the matched filter is greatly different to the codes which are not mudulated. The sidelobes characters of the PN codes modulated by signals are discussed taken m-sequence and Kasami sequence as examples in this dissertation. It can raise the mainlobe-sidelobes ratio when the initial phase is properly chosen. The mainlobe-sidelobes ratio can even be further improved when mismatched filters are adopted.The mainlobe-sidelobe characters of the PN codes are also discussed when modulated by the signals and carrier-doppler exsists in chapter 3. The non-coherent and coherent sidclobe suppression filters are also discussed in chaper 3.