Compact Quarter-Wave Resonator and Its Applications to Miniaturized Diplexer and Triplexer

Novel and compact composite right/left-handed (CRLH) quarter-wave type resonators are proposed in this paper. The resonator can resonate at the frequency where the electrical length is phase-leading or negative, which results in a smaller size as compared to the conventional phase-delayed microstrip-line resonator. Furthermore, it is only half the size of the CRLH half-wave resonator resonating at the same frequency. In addition, the proposed resonator is capable of engineering the multiresonances very close to each other, which makes it suitable to implement the miniaturized multiband microwave components such as diplexers and triplexers. A very compact diplexer and a very compact triplexer are proposed based on the proposed CRLH quarter-wave resonators in this paper and both of them have demonstrated very good performance. Specifically, compared to the referenced works based on the conventional microstrip resonators, the proposed diplexer and triplexer are 50% and 76% smaller than their microstrip counterparts, respectively.