A Compact Diplexer Using Coupled π-CRLH Zeroth Resonators

This paper presents a new diplexer design of a new-coupled composite right/left-handed (CRLH) resonator to serve the LTE applications. The realization of the diplexer is designed as coupled two zeroth order pi-CRLH resonators to represent with zero electrical length and hence attaining a significant size reduction. The filters are designed to achieve a desired frequency bandwidth of 4% similar to 16.7 Q-factor and similar to 0.066 coupling coefficient at a centre frequency of 2.1 and 2.6 GHz with transmission zeros. The diplexer exhibits a rejection level of 15-20 dB while maintaining insertion loss of 1 dB for the Tx and Rx bands. The circuit design concepts are verified using equivalent circuit simulations, full electromagnetic simulations and experimental measurements. In conclusion, a good agreement is perceived between the measured and simulated data with size compactness of 30 x 60 mm(2).