本論文介紹一種使用了基板合成波導(Substrate Integrated Waveguide)電路結構的三階濾波型環形耦合器(Filtering rat-race coupler)，中心頻設計在10.2 GHz，此電路將帶通濾波器與環形耦合器兩種元件合併成一個，相較於傳統環形耦合器需要與帶通濾波器串接，面積能夠大幅度的縮小，整體電路大約為4.6 mm 5.17 mm。另外使用兩種提升通帶外側頻率選擇度的方法。 第一個電路由外圍四個TM010 mode的共振腔與中心一個TM110 mode共振腔所組成，利用水平TM 110模態與垂直TM 110模態互相正交與電場分布的特性，並且將四個輸入輸出端口以及耦合窗擺放位置特別設計，如此便可實現環形耦合器所需的高隔離度與輸出訊號相同相位與相反相位的架構。 第二個電路為在三階基板合成波導濾波型環形耦合器之第一與第三共振腔間增加一個耦合窗(coupling window)，使輸入訊號分成兩路訊號，一路訊號為原有路徑，另外一路訊號由第一個共振腔經由新加的耦合窗耦合至輸出端口，兩路訊號大小相同，相位呈現180度的相位差，因此在通帶右側(10.91 GHz)產生一個傳輸零點，使高頻的選擇度更好。 第三個電路運用具有地平面的共面波導(Grounded coplanar line, GCPW)結構，將原有透過耦合窗的磁耦合，改變為混和耦合，使得原有的傳輸零點能夠在通帶左側，以增加低頻選擇度。藉由改變共面波導的參數與耦合窗的大小，可以使傳輸零點位置自由改變，以增加電路設計的自由度。 ;This thesis introduces a substrate integrated waveguide third-order filtering rat-race coupler. The center frequency of passband is 10.2 GHz. To miniaturize the circuit size, a better design is to integrate the rat-race and BPFs into a single component. The overall circuit size is 4.6 5.17 mm2 . In addition, two methods to improve the frequency selectivity are proposed. The first circuit consists of four TM010 mode resonators and a TM110 mode resonator. Using the characteristics of the E-fields at horizontal TM110 and the vertical TM 110 orthogonal degenerate modes. The four input / output ports and the location of the coupling window are specially designed. Thus high isolation and in-phase and out-of-phase signal can be realized. The second circuit adds a coupling window between the first and third resonant cavity of the substrate integrated waveguide third-order filtering rat-race coupler. Therefore, the input signal is divided into two. The signal through original path cancels out the signal through the new coupling window. Therefore, a transmission zero located at 10.91 GHz, which makes the high frequency selectivity better. The third circuit is a substrate integrated waveguide third-order filtering rat-race coupler using a grounded-coplanar line (GCPW) etched on the upper face. Therefore, a transmission zero located at 9.97 GHz, which makes the low frequency selectivity better and allows more possibilities of design.
