基於CNC及雷射加工技術之太赫茲被動元件

Abstract

本論文主要講述太赫茲頻段方向耦合器及濾波器的設計與實現，根據不同的製程方式將內容分成兩個部分，首先第一部分是採用CNC銑削工藝設計兩種位於WR-3.4頻段的波導正交分合波器(Quadrature hybrid)，其一為中心頻率300 GHz，具有帶通特性的共振腔方向耦合器，可於操作頻率上將功率做等分，並具有大於25 dB的良好匹配及隔離度，量測結果顯示其中心位置偏移至292.5 GHz，且插入損耗及耦合值增加至約6.4 dB。而另一項設計為四個分支所構成的E平面分支線方向耦合器，能夠達到240 GHz至324 GHz的寬頻操作，實測數據與預期有著高度的一致性，帶內振幅不平衡小於0.8 dB，相位不平衡則介於-2°到+4°之間，匹配及隔離度皆有大於15 dB。 接著是第二部分，基於雷射加工成本低及製造效率高等優勢，吾人也以該方式來製作真空基板合成波導(Empty substrate integrated waveguide, ESIW)形式的Riblet方向耦合器，同時搭配轉接夾具來進行量測，結果表明其在260 GHz至300 GHz的頻段內，匹配及隔離度都高於15 dB，耦合值約為7 dB，相較設計值多了約3 dB，而插入損耗則是提升至10 dB，與模擬存在明顯差異，後續也將探討影響結果的幾種可能因素，最後，吾人也嘗試以雷射加工製程來實現金屬波導元件，並與本實驗室過去以CNC方式製作的共振腔結構濾波器進行比較，期望能在維持元件性能的情況下，提升製作速度並降低成本，文中也會針對所使用的各項雷射參數做說明，以及討論雕刻過程中面臨到的問題。

This thesis primarily discusses the design and implementation of directional couplers and filters in the terahertz frequency range. The content is divided into two sections based on different manufacturing methods. In the first section, two types of waveguide orthogonal power dividers (Quadrature hybrids) located in the WR-3.4 frequency band are designed using CNC milling technology. One of them is a resonant cavity directional coupler with a center frequency of 300 GHz and a bandpass characteristic. This coupler equally splits power at the operational frequency and demonstrates strong matching and isolation properties exceeding 25 dB. Measurement results reveal a center position shift to 292.5 GHz, with insertion loss and coupling value increasing to around 6.4 dB. Another design consists of an E-plane branch-line directional coupler composed of four branches, enabling wideband operation from 240 GHz to 324 GHz. The measured data closely aligns with expectations, exhibiting an in-band amplitude imbalance of less than 0.8 dB. The phase imbalance falls within the range of -2° to +4°, and both matching and isolation values exceed 15 dB. Continuing to the second section, leveraging the advantages of low cost and high manufacturing efficiency inherent in laser processing technology, I also utilize this approach to fabricate a Riblet directional coupler in the form of an Empty Substrate Integrated Waveguide (ESIW), within a vacuum substrate. Simultaneously, I employ a fixture for the measurement process. The results indicate that within the frequency range of 260 GHz to 300 GHz, both matching and isolation exceed 15 dB. The coupling value measures around 7 dB, which is approximately 3 dB higher than the design value. On the other hand, the insertion loss increases to 10 dB, exhibiting a significant difference from the simulation. Subsequent discussions will delve into several potential factors that could influence these results. Finally, I also endeavor to realize metallic waveguide components through laser processing technology. A comparative analysis is conducted with the resonant cavity structure filters previously fashioned using CNC techniques in our laboratory. The aim is to enhance production speed and reduce costs while maintaining component performance. The article will also provide explanations for the various laser parameters used and address challenges encountered during the engraving process.