用於偽亂碼信號獲取之多時段檢測法則

Abstract

雖然有偽亂碼調變的信號之獲取能夠利用偽亂碼匹配濾波器來快速的完成 ，然其相關的硬體複雜度及價格的限制使得此種設備不太適用限制使得此 種設備不太適用於高速率或長偽亂碼的獲取。在此種情形下，多時段檢測 和序列式檢測法不失為次佳之選擇。這篇論文主要考慮的是多時段循序偽 亂碼獲取系統之性能分析。由於我們感興趣的情形是在載波復原前完成偽 亂碼信號獲取，因此著重在非同相檢測環境。我們分析了多時段檢測系統 在加成性白高斯雜訊和相關性萊遜或者雷禮通道下的性能；此外，亦比較 同相和非同相兩種多時段檢測法之差異。我們所設定的性能分析準則包括 信號的獲取機率平均獲取時間以及獲取時間的變異數。另一方面，兩種不 同的信號利用法則也一併被考慮；第一種法則是使用分離的信號區段來檢 測，而第二法則則是使用重疊的信號區段；亦即，前一時段收到的信號會 被保留做為下次檢測參考。 Although PN signal acquisition can be rapidly accomplished by employing PN matched filters. Hardware complexity, speed and cost limitations might preclude such an implementations for long and/or high chip rate PN codes. Multiple dwell or sequential method is thus an attractive alternative under the said circumstances. This thesis concerns only about multiple dwell serial PN acquisition systems. Since we are interested in the case where the PN code is acquired before carrier recovery, noncoherent detections are assumed. Acquisition performance of noncoherent multiple dwell test (MDT) in both additive white Gaussian noise (AWGN) and correlated Rician or Rayleigh fading channels are investigated. Besides, Coherent MDT perfrmance is also presented for comparison's purpose. The performance measures under consideration are cumulative distribution, mean and variance of the acquisition time, respectively. Two multiple dwell detection schemes are studied. The first scheme uses disjoint received signal segments for detection test while the second scheme uses overlapped signal segments.