A Compact Dual-Band Quasi-Elliptic Filter Employing Meander-Line- and CRLH-Based SIW Triplets

A compact dual-band quasi-elliptic filter with high selectivity is developed and investigated in this communication. It employs two hybrid-structure substrate integrated waveguide (SIW) triplets, which show completely inverse transfer responses under the same conditions of inductive cross coupling. The first meander-line-based triplet is able to produce a transmission zero (TZ) above the passband. Whereas the second SIW triplet,which is composed by a composite right/left-handed (CRLH) resonator, creates a TZ below the passband. By utilizing these features, a dual-band quasi-elliptic filter based on SIW dual-mode resonances (TE101 and TE201), whose operating frequencies are allocated at 8 GHz and 10 GHz, is designed for demonstration. The design process, principles, and experiments are carefully described in this communication. The measured and simulated results are in good agreement, indicating excellent electrical performance with low loss, compact device size and high selectivity. The most notable point is that a dual-band quasi-elliptic filter on SIW platforms is obtained with all inductive couplings for the first time, which shows a unique benefit in eliminating negative-coupling structures while permitting miniaturization for SIW dual-band filter design.