利用耦合係數法設計介電波導濾波器

Abstract

本篇論文藉由高介電 (εr=90) 材質、低溫共燒陶瓷 (LTCC) 與高介電 (εr=10.2) 印刷電路板 (PCB) 三種微波材料，設計出尺寸微小同時兼顧成本低廉，不同架構，不同頻率響應，適用於無線區域網路5至6 GHz (Hyper LAN 5.3 GHz) ，24GHz或毫米波 (millimeter wave) 頻段 30 GHz 的波導式帶通濾波器。 文中將簡介耦合係數法 (coupling coefficient method)，並利用此法分析外部品質因數 (external quality value) 與內部耦合係數(internal coupling coefficient)，再透過現有的商用EM模擬軟體 (如：Sonnet, IE3D, HFSS)，找出相對應的濾波器共振腔尺寸，整個複雜的濾波器設計流程將變的簡單又快速。論文中，藉由二階、三階式的濾波器設計與量測來實現三種柴式 (Chebyshev) 響應波導結構帶通濾波器。最後，探討交錯耦合 (cross coupling) 路徑產生傳輸零點 (transmission zero) 對濾波器截止頻段的高拒斥效應。

Three kinds of microwave materials, high dielectric constant (εr=90) materials, low temperature co-fired ceramic (LTCC) and high dielectric constant (εr=10.2) print circuit board (PCB), would be used in this paper to make small-size, low-price, varied structures and different frequency responses band-pass filters. These kinds of filters are suitable for application in 802.11a WLAN band 5 to 6 GHz (Hyper LAN 5.3 GHz), 24 GHz or millimeter wave frequency 30 GHz. Coupling coefficient method would be introduced in the paper. The method can analyze the external quality factors and the internal coupling coefficients. Then, utilizing EM simulation software obtain relative resonator dimensions corresponding to previously determined external quality factors and internal coupling coefficients. The whole filter design procedure is simple and concise. Three kinds of Chebyshev response waveguide band pass filters (two-pole and three-pole) are implemented. Finally, investigating the added cross coupling and the produced transmission zeros would illustrate high rejection at stop band.