W頻段衰減器研製

Abstract

本論文運用微帶線(microstrip line)與共面波導(coplanar waveguide or CPW)的結構，研製W頻帶之3、6、10、與20分貝之衰減器。首先，利用前後兩個阻抗反轉器(K-inverter)將3分貝與6分貝T型衰減器之並聯到地電阻(shunt resistor)轉成串聯電阻(series resistor)以改善衰減器之性能與降低製作困難度。至於10分貝與20分貝衰減器並不適合用阻抗反轉器來轉換並聯電阻，仍以傳統之T-型結構做設計。此時，微帶線並聯電阻之接地會有問題，本論文採用了扇形接地的設計以解決困難。對於微帶線衰減器是採用厚度5 mil介電常數9.8之三氧化二鋁陶瓷基板(Al2O3 ceramic substrate，εr = 9.8)，而CPW是使用15 mil厚之相同基板。最後，接上特別設計扇形探針轉換器進行W頻段探針的實作量測。所有衰減器與轉換器之模擬是使用有限元素法(finite element method or FEM)的電磁模擬軟體HFSS來執行三度空間電磁模擬。

The purpose of thesis is to realize the W band attenuators with 3 dB, 6 dB, 10 dB, and 20 dB of attenuation. The attenuators are implemented in microstrip and coplanar waveguide (CPW) circuit forms both with Al2O3 substrate of r=9.8 and thickness of 5 mil for microstrip and 15 mil for CPW respectively. For both microstrip and CPW 3 dB, and 6dB attenuators, the shunt resistor of the T-attenuator is transformed to a series resistor and two K-inverters. The 10 dB microstrip T-attenuator uses two fan stubs for grounding the shunt resistors in the T-attenuator. Cascading two of the microstrip 10 dB attenuators forms a 20 dB attenuator. The CPW attenuators are similar to that of the microstrip attenuators except the fan stubs for grounding the shunt resistors are not needed. At last, the fan-shaped transitions are designed for probe measurement in W band. The HFSS simulator is used to do the simulation.