基於數碼相關與載波相位的新式測距方法

Abstract

我們提出了一個新穎的測距方法，它結合數碼相關運算和載波相位偵測。載波相位偵測具有高精度的優勢，但是可量測的距離範圍卻被本身的波長所限制住，因此偵測到的實際載波相位會有未知的整數週期。因此我們利用數碼相關運算來幫忙尋找此整數值。如此的設計可以使得此測距系統同時具有偵測長距離以及保持高精度的優勢。除此之外，訊號是以半雙工(half-duplex)的機制傳送，如此可以消除兩個無線電收發器碼相位和載波相位的初始偏移量。而模擬的結果顯示，在數碼長度為63，載波頻率差3 MHz，取樣頻率20 MHz，以及訊號雜訊比為13分貝的情況下，可量測距離可到達2公里，量測距離的均方差(root mean square error)約為10公分。

In this thesis, we propose an integrated ranging methodology utilizing code correlation and carrier phase detection.The phase detection possesses high precision while it is sufferedby the problem of ambiguous integer cycles. We employ code correlation to aid the search of the integer. Hence the system is capable of ranging with high precision and long distance. Besides, the signal is transmitted with half-duplex mechanism to eliminate the code and phase offset between two transceivers. In our simulation, the measurable distance is up to 2km, with ranging root mean square (RMSE) approximately 10 cm under the following conditions: The code length is 63, the carrier frequency difference is 3 MHz, the sampling frequency is 20 MHz, and the signal to noise ratio (SNR) is 13 dB.