在非理想環境下利用信號之週期穩態特性之陣列天線信號處理

Abstract

本論文提供了一個適當的方法來解決在強健式的可適性陣列天線信號處理上因為都卜勒效應所產生的誤差問題。藉由信號的週期性特性，我們可以有效率的接收需要的信號而不使用到信號的方位角（DOA）。傳統接收週期信號的方法，如LS-SCORE、CAB皆能良好接收，但相對而言，當在接收週期頻率時，所欲設定接收的週期頻率和信號發射的頻率有些微不同，便會造成嚴重的衰減，也因此使得理論無法正常運作。在過去文獻中提到使用不同的方法來解決週期頻率誤差（CFE）的問題，但除了收斂速度較慢外，複雜度也相對增加了不少。因此本論文中提出方法在修正週期誤差頻率時能夠較快速收斂，且效能相較之下也有較好的表現。其利用最大化設定的目標函數的方法，可以有效找尋到正確的週期頻率，使得基於信號週期性的可適性陣列天線能運作更良好。 此外，在電信領域的實際應用上，常常使用多信號的接收，被提出過的論文研究中皆是接收具有相同週期頻率的信號，故本研究提出一次接收多個週期頻率的信號方法，以期能更進一步降低硬體的負擔並節省更多的運算時間。

This essay aims to provide a proper method to solve the error problem of the cycle frequency caused by Doppler Effect while dealing with robust adaptive beamforming for cyclostationary signals. The desired signals with cyclostationarity can be received efficiently without requiring the direction of Arrival (DOA). It is argued that some traditional methods such as LS-SCORE [17] and CAB [27] algorithms can help in receiving signals properly. However, if there is a small mismatch in the cycle frequency of the desired signal, these algorithms could suffer from severe performance degradation. According to previous researches [2] [21], LS-SCORE and CAB were proved to solve the problem of the cycle frequency error (CFE), but they seem to suffer from slow convergence speed and complexity. Therefore, one possible solution of this issue is to consider using the method proposed in this essay that could find the correct frequency error faster. Also this method has been proved as an improvement with better performance comparing to LS-SCORE algorithm. In many practical applications of telecommunication, the system usually receives multiple signals at the same time. This essay also attempts to demonstrate a proper algorithm which allows receiving different cycle frequencies at the same time in order to release the loading of the hardware and save more processing time in adaptive array beamforming.