Microstrip dual-mode filters with miniaturized size and broadened stopband using meander-shaped stepped-impedance ring resonator

An improved class of microstrip dual-mode bandpass filter is proposed using the meander-shaped stepped-impedance ring resonator (SIRR). This meander SIRR, together with a uniform impedance ring resonator (UIRR), is at first studied to demonstrate its attractive features of harmonic-resonance suppression and overall-size miniaturization. A pair of squared notches is then etched out on the corners along either of diagonal lines of this symmetrical SIRR that is capacitively driven by the two perpendicular feed lines. Two SIRR-based dual-mode filters are therefore designed, simulated and fabricated. The overall size of this filter finds to be reduced by about 50% in area. The 1st harmonic passband of this filter is raised to 5.30GHz that exceeds the three times of its fundamental passband at 1.52GHz as verified by experiment.

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