Abstract
A new small size non-degenerate dual-mode square patch filter is proposed. The proposed filter structure is based on a slotted square patch non-degenerate dual-mode resonator. The filter response is obtained by exciting the degenerate modes and the first higher order mode of the proposed resonator through asymmetrical feeding. The effect of etched slots is investigated, and design curves for the proposed structure are deduced. Fractional bandwidth from 4% to 25% with reduced harmonic response can be achieved. A bandpass filter is designed at 2.35 GHz with 7.6% fractional bandwidth on RT/Duroid 5880 material with 2.2 dielectric constant and 0.78 mm thickness. Simulations are performed using full wave IE3D simulator. Simulations agree well with the experimental results.