Bandpass Filter Realization Using Degenerate Dual-Modes of a New Type of Patch Resonator for Significant Size Reduction

A new type of dual mode patch resonator is proposed and dual-mode bandpass filters are designed by perturbing its degenerate modes using two slots which are orthogonal to each other. It has been shown that resonant frequencies of the degenerate modes can be varied independently by adjusting one slot length at a time. Geometrical size as well as radiation loss has been reduced further by using inductively loaded cross-slotted patch resonator. A bandpass filter operating at 2.98GHz with a fractional bandwidth of 4.69% is designed after miniaturization. A size reduction of approximately 30% is observed when compared with miniaturized triangular patch resonators, for the same center frequency.