應用於無人機防撞雷達之具360°同平面覆蓋及前向180°半平面覆蓋之波束切換平面天線模組

Abstract

本論文提出一種應用於無人機防撞雷達之波束可切換之平面圓形天線模組架構，並介紹其兩款不同覆蓋角度範圍之原型設計。首先是一款提供完整360°同平面覆蓋的波束切換平面天線模組，該模組整合了新型的雙模式單刀多擲開關、新型的圓形波束形成網路、一位元相移器，以及類八木天線。 我們所提出之雙模式開關能將輸入功率導向單一輸出端口（單開模式，類似傳統單刀多擲開關），或同時等量導向兩個相鄰的輸出端口（雙開模式），有效地將可用的波束數量加倍。圓形波束形成網路由多個子矩陣以圓形排列而成，相鄰的子矩陣共用其邊緣元件。每個子矩陣作為一個功率分配器，其邊緣元件以三路功率分配器取代。這些邊緣元件能有效地將功率從開關分配至相鄰的子矩陣以及下一級的邊緣元件，實現場型相似、增益相近且平順的波束切換。 為了驗證設計，我們製作並測試一款工作在5.8 GHz具12個可切換波束的天線模組原型。實測結果與模擬結果相吻合，並展現出12個一致的輻射場型，其旁波瓣位準皆低於−13 dB，且兩種開關模式下的增益差異小於1 dB。此外，每個波束都具有30°的半功率波束寬，確保水平方向上的全覆蓋，且相鄰波束間重疊極小。 其次是一款工作於24 GHz具備7個可切換波束以達到前向180°水平覆蓋之天線模組，並與市售之調頻連續波雷達模組整合。我們的天線模組包含一顆雙模式開關晶片、半平面覆蓋之平面圓形波束形成器、9個反射式相移器，以及9個改良的類八木天線。整個防撞雷達系統整合了前述之前向半平面覆蓋之波束切換天線模組、24-GHz雷達收發模組、微控制器，以及具中頻訊號放大器的電源控制電路。 實驗結果顯示，該天線模組原型得以在水平面上透過7個波束實現前向180°半平面的場型覆蓋能力，且每個波束場型高度相似，皆具有小於0.2 dB的增益差異、27°的半功率波束寬、以及−9 dB的旁波瓣位準。此外，透過天線模組中的反射式相移器可實現連續的相位調整，可進一步實現切換波束之間小範圍的波束掃描，以達到更準確的障礙物定位。

In this dissertation, we proposed a configuration for a planar and circular antenna module for collision avoidance radars to be deployed on drones or unmanned aerial vehicles (UAVs) and presented two different prototype module designs. First, a beam-switching antenna module offering complete 360° horizontal coverage is introduced. This module integrates a novel dual-mode single-pole-multiple-throw (SPMT) switch, a novel circular beamforming network (CBFN), one-bit phase shifters, and quasi-Yagi antennas. The dual-mode switch is capable of routing input power either to a single output port as a traditional SPMT switch (single-ON mode) or equally to two adjacent output ports (dual-ON mode), effectively doubling the number of available beam directions. The CBFN is formed by arranging modified sub-matrices (MSMs) in a circular layout, where adjacent MSMs share edge components (ECs). Each MSM functions as a binomial power divider, with the ECs replaced by three-way power dividers. These ECs enable efficient power distribution from the switch to adjacent MSMs and to downstream ECs, facilitating seamless beam transitions. For verification, a 12-beam beam-switching prototype module operating at 5.8 GHz was fabricated and tested. The measured results closely align with simulations, demonstrating 12 consistent beam patterns with sidelobe levels (SLLs) below −13 dB and gain variations under 1 dB between the two switch modes. Each beam exhibits a 30° half-power beamwidth (HPBW), ensuring full in-plane coverage with minimal overlap between adjacent beams. Second, a 24-GHz 7-beam beam-switching prototype module with forward-looking 180° in-plane coverage is presented. Its integration with a commercially available 24-GHz radar module is also presented. The antenna module is composed of a dual-mode switch chip with circulator function, a circular beamformer for half-plane coverage, reflection-type phase shifters (RTPSs), and metamaterial (MTM)-loaded quasi-Yagi antennas. Besides, a power supply module and a control circuitry, including an IF signal amplifier, were also designed and integrated with a microcontroller to realize the beam-switching function. The experimental results show that the antenna module is capable of achieving forward-looking 180° in-plane coverage with seven beams exhibiting similar beam patterns, less than 0.2 dB gain variation, 27° HPBW, and −9 dB SLL. On top of that, with the aid of the RTPSs, this prototype module can achieve continuous beam scanning between adjacent beam patterns, rendering it possible to achieve a more accurate localization of obstacles.