多數飛機都依賴全球衛星定位系統（GNSS）所提供的定位、導航和時間（PNT）。但是GNSS系統可能因為訊號干擾或是造假等影響導致系統本身無法提供PNT服務。為了讓飛機可以不間斷地獲取PNT訊息，我們需要發展替代定位，導航和時間（APNT）系統。本篇論文提供一種利用1090MHz廣播式自動回報監視（ADS-B）系統訊號的都卜勒頻移量和飛機速度來計算飛機位置的方法。我們使用軟體定義無線電接收機（SDR）系統來記錄現實世界中飛機的ADS-B訊號以及解碼ADS-B訊號來獲得像是位置、速度、航向、以及高度等飛機的狀態資訊。接著我們使用快速傅立葉轉換（FFT）來計算每段ADS-B訊號的都卜勒頻移量。我們使用擴展式卡爾曼濾波器（EKF）系統來處理ADS-B訊號中來自飛機訊號發射器的頻率偏差，並利用訊號的都卜勒頻移量以及飛機速度這兩項作為系統輸入來進行計算。本篇論文的結果顯示使用都卜勒頻移量以及飛機速度最為EKF系統的輸入項可以成功計算出飛機位置並且符合APNT系統在終端區域的1浬導航精確度要求。

Most aircrafts rely on the Global Navigation Satellite System (GNSS) for positioning, navigation, and timing (PNT). However, GNSS are vulnerable to interference threats such as signal jamming and spoofing, which can disrupt their service. To ensure continuous PNT availability in aircraft, an Alternative Positioning, Navigation, and Timing (APNT) system is required. This thesis proposes a method that uses Doppler shift measurements and aircraft velocity data from 1090 MHz automatic dependent surveillance-broadcast (ADS-B) signals to determine aircraft positions. A software-defined-radio (SDR) system with a single antenna was used to record real world aircraft ADS-B signals and decode ADS-B messages to obtain aircraft status such as position, velocity, heading, and altitude. The Doppler shift value for each ADS-B message frame was calculated by Fast Fourier Transform (FFT). Extended Kalman filter (EKF) system was then used to process types of inputs, Doppler shift measurements of the ADS-B signal and aircraft velocity, while addressing the frequency bias in the ADS-B signal from the aircraft transmitter. The positioning results demonstrate that the EKF system using Doppler shift measurements and aircraft velocity as inputs, can accurately calculate aircraft positions and meet the accuracy requirements of the APNT system for navigation, which is 1 nm in terminal area.

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