垂直堆疊式高階雙通帶帶通濾波器設計

Abstract

本論文利用步階阻抗共振腔以垂直堆疊的方式，設計具有雙通帶的高階帶通濾波器。藉由改變步階阻抗共振腔的幾何參數，調整其諧振頻率，以得到兩個通帶的中心頻率，再經由相鄰共振腔之間耦合量與長度及間距關係的設計圖，選定兩個通帶可實現的比例頻寬完成設計。為達高階設計，且使每一對相鄰共振腔均有適當的耦合量，必須靈活調整共振腔之幾何參數，以達到設計高階電路的目的。最後，實作電路的量測結果與電磁模擬結果比較，兩者相當一致。

A rigorous synthesis method is presented for higher order microstrip bandpass filters with a dual-passband response in vertical stack configuration. The building block of the circuit is stepped-impedance resonator (SIR) of which resonant frequencies can be tuned by simply adjusting its structure parameters. Fractional bandwidth design graphs are established for determining offset and space between adjacent resonators. The impedance and length ratios of the SIR should be properly chosen so that all couplings between any two adjacent resonators can fulfill the design figures given by the element values of the lowpass prototype. Second-, sixth- and eighth-order bandpass filters are designed and fabricated. Measured results of the three fabricated circuits show good agreement with the simulated responses.