應用於無人機之空間可重構相控陣列之三維融合超聲波及微波之相位同步系統

Abstract

在現今高度科技化的社會中，無人機因其高度機動性以及小巧的機型，使其成為了現今不管是軍事或是民生使用不可或缺的一環，也因此非常適合應用於下個世代行動通訊系統中，作為機動性更高的可調式空中基站之飛行載具。然而，因為無人機本身的尺寸及負重限制直接影響收發天線的孔徑尺寸大小，使其訊噪比及接收訊號強度指標無法滿足理想通訊品質之所需。 為了克服這個問題，我們實驗室先前提出了操作於無人機群上之空間可重構式相控陣列天線(SRPArray)的概念。藉由將天線單元搭載於多台無人機上，使每個天線單元可以隨著無人機移動而改變陣列的配置，搭配無人機之間的空間定位和對應的相位補償，即可實現可實時改變陣列空間配置的相控陣列天線。這種分散式的陣列架構提供了天線單元之間相對移動的可能性，為整個相控陣列的場型設計與整合提供了更高的空間自由度。 在此系統中，為了達到空間可重構性，無人機之間的相對定位機制至關重要，為此，我們提出了融合超聲波及微波之相位同步系統(UMPS)，藉由超聲波及微波訊號抵達的時間差，實現相對位置定位。我們將先前的研究成果 [20] 拓展成二維UMPS系統，其可達到在340 mm至740 mm的量測距離下，距離方均根誤差約9 mm以及相位補償誤差小於5.6度之結果。然而在實際應用中，無人機群在三維空間中飛行，因此本論文中我們進一步將UMPS系統拓展至三維架構，同時考量SRPArray中個別無人機操作模式的切換需求，將UMPS系統整合成可切換收發之架構，針對無人機群使用情境，更有彈性地進行計算模式切換。在三維UMPS量測架設中，其可達到在距離300 mm，theta為45至67.5度且phi為-90至90度之量測範圍，距離方均根誤差約21 mm的準確度。此外，為了提高三維空間定位的量測準確度，我們亦提出結合子領導者(Sub-leader)架構以及推拉定位法(Push and pull)的多重定位機制，藉由子領導者架構，延長定位的量測距離範圍和準確度，並透過無人機之間不斷交換定位資訊，可達到更好的定位準確度。

Unmanned aerial vehicles (UAVs) have become crucial assets in both military and civilian applications due to their maneuverability and compact size. They are particularly suitable as wireless communication nodes in sixth-generation (6G) mobile networks, serving as agile and adaptable airborne base stations. However, the limited payload capacity of UAVs restricts the aperture size of the antenna payloads, directly impacting signal quality metrics, such as signal-to-noise ratio (SNR) and received signal strength indication (RSSI). To address this issue, the concept of a spatially reconfigurable phased array (SRPArray) carried by a UAV fleet was proposed in our lab. This approach integrates antenna elements onto UAVs, allowing dynamic position adjustments via UAV movement. With the aid of positioning capability and phase compensation on each UAV, a real-time spatially reconfigurable phased array may be realized. This decentralized architecture results in an additional degree of freedom in the pattern design and synthesis in the phased array. To achieve spatial reconfigurability, robust relative positioning among UAVs is crucial. To this end, the ultrasonic-and-microwave-fused phase synchronization (UMPS) system was developed in our lab, in which relative positioning among UAVs is realized based on time-of-flight measurements of the ultrasonic and microwave positioning signals. Extending the previously achieved one-dimensional (1-D) UMPS to two-dimensional (2-D) measurements yields similar accuracy, with a root mean square (RMS) error of 9 mm in distance and a phase compensation RMS error under 5.6° within a 340 mm to 740 mm measurement distance. Given the three-dimensional nature of UAV operations, in this thesis, we extend UMPS to a comprehensive three-dimensional (3-D) framework. In the 3-D UMPS setup, it achieved an RMS error of approximately 21 mm in distance within a measurement distance of 300 mm, with theta ranging from 45° to 67.5° and phi ranging from -90° to 90°. Besides, we also integrate a novel hybrid multi-positioning mechanism, combining the sub-leader framework with push-and-pull strategies to enhance positioning accuracy. This method extends the range of positioning distance and enhances the positioning accuracy with the aid of inter-UAV communication.