Narrowband Interference Rejection to Aid PN Code Acquisition

• Main Authors: Yuh-Jiun Lin, 林裕鈞
• Other Authors: Yu T. Su
• Format: Others
• Language: en_US
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/75784325472430171320

碩士 === 國立交通大學 === 電信研究所 === 82 === Spread spectrum techniques have many applications, including interference rejection, multipath suppression, multiple access, low probability of intercept, and accurate ranging. Of all the potential applications, the ability of a spread spectrum system to withstand interference, both intentional and unintentional, is probably its greatest asset. Nevertheless, any spread spectrum receiver can only suppress a given amount of interference; if the level of interference becomes too great, the system will not function properly. Interference rejection techniques must therefore be used to sustain the system performance requirements. In this thesis, interference rejection filters are employed in both coherent mode and noncoherent mode to suppress narrowband interference. We consider both perfect acquisition and imperfect acquisition cases. In the coherent case, a nonlinear techniques, decision- directed Kalman (DDK) filter and a related nonlinear least mean square (LMS) filter, are introduced to perform interference rejection. For the noncoherent case, we consider complex Kalman filter, complex LMS algorithm and complex least mean fourth (LMF) algorithm. It is shown that the presence of the rejection filter can significantly improve the performance in both acquisition mode and tracking mode. Comparsions of various rejection filters are made and design considerations are addressed.