適用於GPS接收機之時頻域抗干擾演算法設計

Abstract

隨著導航系統應用的逐漸普及，如車用導航、無人車甚至無人飛機等應用越趨熱門，對於導航系統的準確度和即時性之要求也就愈來愈高。而市售干擾器容易取得，其產生的掃頻訊號對衛星導航系統的定位品質危害甚鉅，因此吾人勢必要有一有效機制將干擾有效的消除。 本文目的為提出一可有效消除掃頻干擾的演算法，且其效能優於前人之相關研究，我們使用目前最普及的全球衛星導航系統GPS為驗證本研究成果的平台，在此我們使用時頻域方法消除干擾，提出一種利用minimax門檻值演算法進行小波包去噪，並將搭配後端的可適性濾波器進行干擾消除。 我們在不同強度的掃頻干擾下做模擬，並做消除效能的比較。根據模擬結果，我們的方法確能有效的消除掃頻干擾，且效能優於前人的小波包去噪演算法。

As applications of navigation systems become more widespread and popular (exemplified by the development of unmanned vehicles and unmanned aircraft etc.) more precise and reliable positioning and navigation become more and more important nowadays. Since people can easily obtain jammers to generate chirp-type jamming signals, which can cause a severe performance degradation to Global Positioning System(GPS) receivers, we, therefore require an effective scheme to mitigate these jamming signals. We propose an effective way of eliminating chirp-type jamming signals in this thesis, and it outperforms prior work. We use time-frequency domain method to do anti-jamming works. With minimax threshold algorithm, we can derive a threshold and use wavelet packet transform plus adaptive algorithms to prevent degradation of GPS receivers from such jammers. We compare the simulation results of our method with prior work under chirp-type jamming signals of different Jamming-to-Signal ratio(JSR)s. According to the simulation results, our method not only can mitigate chirp-type jamming effectively but also outperforms prior wavelet packet de-noising method.