三頻陷波蕈狀結構應用於超寬頻系統

Abstract

本論文提出一三頻陷波之蕈狀結構。利用蕈狀結構原有的帶止特性，我們利用在蕈狀結構的金屬面上加上三個有開口的環狀方型槽以及多根接地鉚釘的方式，得以實現三個高選擇度且高阻隔訊號程度的陷波，進而消除一些像WiMAX或是衛星通訊系統的射頻訊號所造成的干擾。由於此蕈狀結構可以提供獨立且可調的電流路徑，對於三個陷波皆可以有很高的頻率敏捷度，使得其在電路應用上將可以有更高的可朔性。另一方面，本論文亦設計一超寬頻帶通濾波器之結構，其方法為利用指叉電容以及並聯短路殘段創造出高通濾波器，並在高頻段的帶通頻帶中，加上缺陷地結構以抑制高頻的帶通頻帶，借而達到帶通濾波器的效果。該超寬頻帶通濾波器與論文前述之三頻帶止濾波器以串接的方式做結合，順利的呈現高選擇度的通帶邊緣，且在三個陷波頻帶3.53 GHz、5.49 GHz、8.21 GHz在超寬頻帶通濾波器的通帶中的植入損耗分別為23.2 dB、19.33 dB與18.43 dB。

In this thesis, a tri-notch (rejection) bands mushroom-like structure is designed and fabricated. By utilizing the characteristic of bandstop of mushroom-like structure, a tri-notch bands (TNB) bandstop resonator (BSR) with high selectivity and rejection level is realized by three etched square ring slots and numerous embedded vias on the metallic patch of mushroom to eliminate the interference of radio frequencies, such as WiMAX bands and some satellite communication system. Moreover, since the TNB BSR provides flexible and independent current paths to possess frequency agility to the three rejection bands, it has more adoptability in the circuit implementations. The designed TNB BSR is cascaded with the proposed ultra-wideband (UWB) bandpass filter (BPF), which is also presented in this thesis, composed of a series interdigital capacitor and two shunted shorting stubs and four dumbbell-shaped defective ground structures (DGS) to create a highpass filter cascaded with a bandstop filter in higher passband. The cascaded structure reveal high-selectivity of passband edges and three narrow stopbands at 3.53 GHz, 5.49 GHz and 8.21 GHz in the passband of UWB BPF with rejection level of 23.2 dB, 19.33 dB and 18.43 dB, respectively.