本論文提出一個使用槽孔耦合架構之帶通濾波器設計，並且對於旁生通帶之諧波具有良好的抑制能力。文獻上，傳統槽孔耦合結構的等效電路能夠用來模擬通帶的發生，然而對於傳輸零點以及倍頻響應並不能提出準確的描述；在本文中先以傳統等效電路為基礎，接著觀察上下層饋入線之間的電場分布，利用耦合線段以及相關的電容來修正傳統的電路模型，此修正後之等效電路對於槽孔耦合架構的響應，在倍頻以及傳輸零點的預測上產生了準確的等效模擬。接著控制等效電路中耦合線的奇偶模態阻抗值，改變饋入線之間的耦合量來調整通帶內之頻寬。最後配合著修正後之等效電路，在槽孔之間加入T型分支，產生額外的傳輸零點來抑制旁生通帶的發生，使得止帶上限可以由原本的兩倍主頻提升至四點五倍主頻。在本論文中帶通濾波器應用於數位電視頻段( 430-710 MHz )，使用厚度為0.8 mm的FR-4基板。本論文製作之帶通濾波器量測結果在通帶內( 430-710 MHz )之插入損耗與反射損耗值分別為0.9 dB以及12 dB，在三倍頻產生之旁生通帶可以獲得17 dB之抑制。全波模擬與量測結果有相當良好的吻合度。 In this thesis, a design of the aperture-coupled filter and it's corresponding equivalent circuit will be presented. In the proposed filter, a back-to-back microstrip-slotline transition is used. Compared to the conventional equivalent circuit models of aperture-coupled structure, the proposed circuit model in this thesis has better characteristics in the locations of transmission zeros and harmonic frequency responses. By terminating microstrip lines with open stubs, the two ports of this circuit have 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 and size reduction. Applying a T-shaped open stub at common ground plane, the first spurious passband of proposed filter could be suppressed. A filter design for digital TV ( 430-710 MHz ) applications is designed. The measured insertion loss and return loss are 0.9 dB and 12 dB, respectively. Suppression of spurious passband is greater than 17 dB. All circuits are fabricated on FR-4 substrates. Simulation and measurement are in good agreement.
