太赫茲槽孔陣列天線之設計

Abstract

本論文講述太赫茲頻段之槽孔陣列天線設計，根據不同的實現方式分為兩部分，第一部分是利用PCB設計操作頻段位於WR-3.4之槽孔天線陣列，利用PCB製作天線具有低成本以及低剖面特性，使用Rogers RT/duroid 5880單層板，此基板之介電常數為2.2，損耗正切0.0026，其板材特性是利用太赫茲時域光譜測得。天線設計之中心頻率為290 GHz，藉由分析單一槽孔天線的阻抗設計天線陣列，其中包含轉接結構以及功率分配器，量測結果顯示8×8陣列天線其反射係數於273 GHz至296 GHz皆低於-10 dB，最大增益為16.7 dBi，量測場型與模擬十分相近，並加入表面粗糙度模擬比較，顯示其對於太赫茲頻段的影響。 第二部分為採用CNC工藝實現之槽孔陣列天線，將天線陣列設計於高階模態共振腔之上，此種架構相較於串聯式饋入較易於太赫茲頻段上實現，其設計過程可從串聯式饋入之槽孔陣列天線拓展，各層槽孔天線可利用其等效電路達到匹配，並探討此架構的濾波耦合矩陣，以及利用蝶型槽孔改善共振點匹配，反射係數可從-15 dB 改善至-25 dB。均勻分布之8×8天線陣列最大增益約22.3 dBi，模擬效率在頻寬內為90%以上。最後介紹了不均勻阻抗分布的8×8天線陣列，達到控制天線輻射場型的效果，其旁波瓣位準可達24.6 dB。

This thesis discusses the design of slot array antennas operating in the terahertz frequency band, which is divided into two parts based on different implementation methods. The first part focuses on a slot array antenna operating in the WR-3.4 band, designed using printed circuit board (PCB) technology. Antennas fabricated using PCB technology offer advantages such as low cost and low profile. The design utilizes a Rogers RT/duroid 5880 single-layer substrate, which has a dielectric constant of 2.2 and a loss tangent of 0.0026. The material properties were characterized using terahertz time-domain spectroscopy. The antenna is designed for a center frequency of 290 GHz, with the array design based on an analysis of the impedance of a single-slot antenna. The design incorporates a transition structure and a power divider. Measurement results show that the 8×8 array antenna achieves a reflection coefficient below -10 dB from 273 GHz to 296 GHz, with a maximum gain of 16.7 dBi. The measured radiation patterns align closely with simulations, and additional simulations incorporating surface roughness effects demonstrate its impact on terahertz performance. The second part involves the implementation of a slot array antenna using CNC machining. The antenna array is designed on a high-order mode resonator cavity, offering easier realization at terahertz frequencies compared to series-fed structures. The design process extends from series-fed slot array antennas, and equivalent circuits are utilized to achieve matching for each layer of slot antennas. The filtering coupling matrix of this structure is analyzed, and bowtie slots are employed to improve resonance matching, improving the reflection coefficient from -15 dB to -25 dB. A uniformly distributed 8×8 antenna array achieves a maximum gain of approximately 22.3 dBi, with a simulated efficiency of over 90% across the bandwidth. Finally, a non-uniform impedance distribution 8×8 antenna array is introduced to control the antenna's radiation pattern, achieving a sidelobe level of up to 24.6 dB.