在本論文中將介紹利用槽孔耦合結構之雙頻帶通濾波器設計，並針對此架構提出對應的等效電路，以便利於設計。在文獻上，槽孔耦合結構的傳統等效電路無法對共振器的傳輸零點與倍頻響應有良好的等效模擬，因此本文以傳統等效電路為基礎，修正電路中的共振與耦合元件，建立新式槽孔耦合結構的等效電路，此新型等效電路對結構的頻率響應有更精準的等效模擬。文中利用槽孔耦合架構的電路特性設計雙頻濾波器，並藉由電路彎折結構改善阻抗匹配，同時有效縮小電路面積。本文之雙頻帶通濾波器應用於數位電視(430 MHz~710 MHz)及GPS (1.575 GHz)頻段，使用板材厚度為0.4 mm的FR4基板。本論文實現之雙頻帶通濾波器量測結果在第一個通帶430MH~710MHz插入損耗值和反射損耗値分別為1.7dB及12dB，第二個通帶1.575 GHz則分別為3.5dB及20dB，全波模擬與量測結果有相當好的吻合度。 In this paper, we propose a dual-band filter design using aperture-coupled structure and the corresponding equivalent circuit to this structure. Compared to the conventional equivalent circuit of aperture-coupled structure, the proposed equivalent circuit model have better characterization in the locations of transmission zeros and harmonic frequency responses. This aperture-coupled structure is basically composed of two microstrip lines which couple through a rectangular slot on a common ground plane. By terminating two of the microstrip lines with stubs, the two-port form of this circuit has good application in filter design. Based on the equivalent circuit models, we can properly adjust the dimensions of the ground-plane slot and the open stub for impedance matching enhancement and effective circuit size reduction. A filter designed for digital TV (430-710MHz ) and GPS (1.575GHz) applications was fabricated. The measured insertion loss and return loss are 1.7dB and 12dB at 430MH~710MH, and 3.5 dB and 20dB at 1.575GHz, respectively. All circuits are fabricated on FR4 substrates, and are in good agreement with simulation.
