| 摘要: | 中壢特高頻雷達位於機場附近，因其地理優勢可以觀測到多架飛機行經，本文以DBSCAN (Density-based spatial clustering of applications with noise) 為基礎，設計自動判讀飛機訊號的演算法，並參考[2020, 洪萱芸]，設計第二種以希爾伯特-黃轉換 (Hilbert-Huang Transform, HHT) 自動判讀飛機訊號的演算法，並利用2022年11月6號的干涉天線觀測資料來比較兩者的命中率與誤報率，接著使用誤報率較低且運算速率較快的DBSCAN演算法判讀結果進行雷達干涉法的運算，得到飛機在三維空間中的位置，並和民航機的廣播式自動相關監視 (Automatic Dependent Surveillance-Broadcast, ADS-B) 的飛機GPS定位進行推算，得到干涉天線的雷達初始系統相位偏差[0.3419, -0.2279, 1.0017, -1.5031] (單位: radian)，以此提升未來干涉天線觀測其他目標物的定位精準度，此外，在分析雷達的飛機回波訊號過程中，發現飛機回波訊號在頻譜圖零頻上會有頻寬增寬現象以及RTI (Range- Time-Intensity) 圖上有訊號不連續的狀況發生，經過模擬驗證後，當飛機的飛行速度越快、飛行高度越低以及處理資料時使用非同相積分次數越多時，飛機穿越雷達波束時的頻寬增寬現象越明顯，而訊號不連續的現象可能是由埤塘的二次回波形成的破壞性干涉所造成。;The Chung-Li VHF radar is located near the airport, and due to its geographic advantage, it can observe many airplanes traveling through it. In this paper, we design an algorithm based on DBSCAN (Density-based spatial clustering of applications with noise) to read the aircraft signals automatically, and the second algorithm for automatic reading of aircraft signals is based on the Hilbert-Huang Transform (HHT), which we refer to [2020, Hong Xuan-wan]. The algorithms′ positive and false positive rates are compared using interferometric antenna observation data from November 6, 2022. Subsequently, the algorithm with a lower false positive rate and faster computation rate, DBSCAN, is used to compute aircraft positions in three-dimensional space by radar interferometry. Then, the aircraft positions are estimated in comparison with aircraft GPS positions from Automatic Dependent Surveillance-Broadcast (ADS-B), obtaining the radar′s initial system phase deviation [0.3419, -0.2279, 1.0017, -1.5031] (unit: radians). This enhances the future positioning accuracy of other targets observed by the interferometric antenna. Furthermore, in the analysis of aircraft echo signals from the radar, it is found that the bandwidth widens at zero frequency in the spectrum and there are discontinuous signals on the RTI (Range-Time-Intensity) diagram. After simulation verification, it is concluded that as the aircraft′s speed increases, flight altitude decreases, and the number of non-coherent integration times used in data processing increases, the phenomenon of bandwidth widening when the aircraft crosses the radar beam becomes more significant. The discontinuous signal phenomenon may be caused by destructive interference from secondary echoes formed by ponds. |
