Tunable Band-Pass Filters Based on Varactor-Loaded Complementary Split-Ring Resonators on Half-Mode Substrate Integrated Waveguide

Miniaturized band-pass filters (BPFs) using backward wave propagation in the left-handed (LH) band are proposed in this article. A half-mode substrate integrated waveguide (HMSIW), complementary split-ring resonators (CSRRs), and varactors are embedded on the same planar platform to implement the resonant-type approach of metamaterial transmission line and tuning capability. The tuning of the passband frequency is generated by simple and single direct current (DC) voltages from 0 to 36 V, which are applied to each varactor on CSRRs. Different capacitance values and resonant frequencies are produced while maintaining a nearly constant absolute bandwidth and quality factor. About 6.5% tunability and 11.30% of 3-dB fractional bandwidth is achieved around 2.30 GHz. The new electrically tunable BPFs are verified by a good agreement between the simulated and measured results. (c) 2013 Wiley Periodicals, Inc.