Reduced-size dual-mode slotted patch resonator for low-loss and narrowband bandpass filter applications

A compact, low-loss and narrowband dual-mode microstrip filter is proposed using degenerate modes of a microstrip patch resonator loaded with two narrow slots. The resonator structure is fed by inset lines connected directly to the centre of adjacent edges of a microstrip patch with two notches. The dual-mode filter is verified by both simulation and measurement.