被動定位的優勢在於系統本身無須主動發射訊號，即可藉由接收外部電磁波反推發射源位置，因而具備低可偵測性，特別適用於高風險、通訊受限或敵方控制區域之任務。另一方面，低軌衛星具有重訪頻率高、延遲低與涵蓋範圍廣等特性，適合應用於戰術任務、全球監控與動態電磁訊號追蹤。因此，若能結合雙星架構與被動定位方法，將有機會在不暴露自身位置之情況下，建立具實務價值之廣域電磁發射源定位能力。
本研究以實驗室雙星任務架構為基礎，探討利用時間延遲差（TDOA）與都卜勒頻率差（FDOA）進行靜態發射源之被動定位分析。研究中以真實衛星錄製資料為主要分析對象，建立涵蓋訊號前處理、候選頻帶搜尋、同步偵測、雙星接收幾何分析及 TDOA/FDOA 理論量測敏感度評估之分析架構，並著重檢驗實測訊號是否具備進入後續定位解算之必要條件。除自定義訊號外，本文亦導入船舶自動識別系統（AIS）訊號作為替代檢驗對象，評估雙星接收架構應用於實際海事目標偵測與定位之可能性。為避免弱訊號分析中僅憑高峰值、窄帶譜線或模板命中數造成誤判，本文進一步設計多階段候選驗證機制，結合封包鏈結構、計數器連續性與格點一致性檢查，以提升弱訊號辨識之可信度。
實驗結果顯示，本研究所建立之多階段搜尋與驗證流程可於控制組資料上穩定辨識出具封包連續性之有效候選，顯示該流程能在所選 IRIS-F2 參考資料中辨識具連續封包結構之候選訊號；然而，在 IRIS-F3 衛星資料中，雖可觀察到部分近直流弱線、相關峰值增強與 AIS-like 偵測事件，但多數候選皆無法同時通過封包鏈與格點一致性驗證，AIS 測試亦未獲得可通過 CRC 之可靠解碼結果。此結果說明，弱訊號分析中單一偵測指標不足以作為成功解碼之依據，必須透過控制組對照與封包級驗證來區分真實訊號與高分誤判。綜合而言，本文雖未能在 IRIS-F3 資料中取得經可靠驗證之最終解碼結果，但成功建立並驗證了一套適用於雙星被動接收弱訊號之搜尋、篩選與誤判排除流程，可作為後續雙星定位實驗與真實任務資料分析之方法基礎。

This thesis investigates weak-signal, identification, and validation in real dual-satellite record-ings under a passive-reception framework. Unlike studies that focus mainly on simulated data or idealized signal conditions, this work addresses wideband satellite IQ recordings containing frequency drift, fixed narrowband interference, weak near-DC structures, and template-triggered false alarms. In this thesis, localization analysis refers to the assessment of signal availability, dual-satellite reception geometry, theoretical TDOA/FDOA measurement sensitivity, and front-end candidate validity. Because no IRIS-F3 packet was reliably verified, experimental TDOA/FDOA estimation and final position determination were not performed. The objective is therefore not merely to obtain high-scoring andidates, but to determine whether those candidates satisfy the prerequisites for subsequent localization.
The proposed workflow is built around a multistage procedure that includes candidate-band search, near-DC focused search, noncoherent accumulation, packet-chain validation, and lattice-consistency checks. The study also introduces duplicated counters, soft counter chains, independent non-edge chains, and lattice expansion as packet-level validation tools for distinguishing genuinely repeatable packet trains from high-scoring false candidates. In addition, an AIS-specific demodulation flow is incorporated as an alternative-hypothesis test to evaluate whether some observed narrowband structures may correspond to known aritime communication signals rather than the target packet source.
To verify the effectiveness of the proposed method, the thesis uses real IRIS-F2 satellite data as a control group and real IRIS-F3 satellite data as a test group. The control-group results show that authentic packet candidates exhibit a stable focused CFO, clearly extendable packet chains, and sustained lattice support across multiple predicted packet positions. These observations confirm that the proposed framework is capable of recognizing real and decodable packet structure in practical satellite recordings.
When applied to the real IRIS-F3 data, the analysis reveals several suspicious phenomena, including near-DC weak lines, partially integrable candidates, and AIS-like detections. However, most of these candidates remain at chain = 1 or show only very short chains during packet-level validation and fail to produce the stable lattice behavior observed in the control group. These results indicate that the IRIS-F3 data do contain weak RF structures, but the currently observed candidates still lack sufficient evidence to be interpreted as reliably verified target packets. The AIS tests also show that decoded count alone is not a trustworthy indicator, because AIS-like detections may still appear in the absence of CRC-passing packets and message consistency.
Overall, this thesis demonstrates that in real dual-satellite weak-signal analysis, the main challenge is not merely finding candidates, but proving that the candidates are real, repeatable, and structurally consistent. The primary contribution of this work is therefore a practical validation framework that distinguishes candidate structures from validated packet trains and clarifies the boundary between geometrically feasible localization and measurement-level feasibility in real dual-satellite data.

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