Compact UHF 3rd-Order Bandpass Filter with Sharp Skirt by Cascaded Triplet CRLH-ZORs

Abstract

We propose a novel bandpass filter miniaturized by the composite right- and left-handed (CRLH) zeroth order resonators (ZORs) which form a cascaded triplet (CT) to have a significantly sharp skirt for high frequency selectivity. A 3rd-order UHF bandpass case is tested. Therefore, firstly, we design an in-line ZOR bandpass filter whose total size is nearly 0.3 times the size of the paralleledge coupled filter. Secondly, we create a transmission zero (TZ) by changing the three in-line ZORs of the filter to a CT. As a result, with the insertion loss less than 1.1 dB and return loss less than −15 dB, the proposed filter has the size-reduction so that its size is smaller than 1/3 of a 3rd-order parallel-edge coupled filter, and its skirt is as steep as a 6th-order Chebyshev filter. The simulation and measurement validate the proposed design method, and the CRLH ZOR properties are proven by the no-phase variation electric field and dispersion diagram.