Miniaturized dual-mode bandpass filter using meander square ring resonator

A dual-mode bandpass filter using the degenerate modes of a meander square ring structure printed on the high-permittivity substrate is proposed. The dual-mode resonator is based on a square ring loaded with two meander strips at the coupling sides. The filter is printed on the Al2O3 substrate with a permittivity of 9.8 and could be easily integrated with RF circuits. Besides its simple structure, the filter shows low insertion loss and small size, owing to the high-permittivity substrate used. The proposed filter shows a 7.2% bandwidth at 2416 MHz, and it also provides transmission zeros on both sides of the bandwidth. Experimental results are in good agreement with simulated values.