Study On Compact Microwave Filters Using Ring/loop Structures

The main objective of the thesis is the planar ring/loop based microwave filter circuit,including bandpass filter, bandstop/band-reject filter and all-pass filter. The ring structure can bewidely found in microwave transmission line network, due to its low loss and compact size. In thefirst chapter, the dual mode bandpass filters using ring resonator are introduced. Then a novelequivalent circuit based on the multiple-mode resonance theory is proposed, for explaining theoperating mechanism of the transmission zeroes in the frequency response of a dual mode bandpassfilter. After the parameter extraction, the response of the dual mode bandpass filter can be obtainedfrom the equivalent model, which agrees well with the full-wave predictions. In the second chapter,the ring-based bandstop applications are concluded at first, and then a new ring configured bandstopfilter is proposed and developed. The new filter is advanced in low loss and wide range ofbandwidth tuning. In addition, a new transmission line equivalent network is given toexplain/analyze the bandstop behavior of the ring structure, two of which have the identicalresponse. In the last chapter, after overviewing the classic all-pass networks, a novel ring-based allpass filter is proposed. The ring-based all-pass filter is analyzed by using the odd/even method, andthen an explicit formulation is obtained on the all-pass condition. Furthermore, two types of thesecond order all-pass filter are discussed. In the last, a wideband90°differential phase shifter basedon the novel all-pass filter is designed and verified.