Hybrid-fed microstrip loop resonator with capacitive meander lines

A compact wide-band bandpass filter (BPF) using the degenerate modes of a meander structure printed on the FR4 substrate is proposed. The resonator is based on a capacitive meander loop loaded with a perturbation strip at the center of the resonator for the coupling effects. Besides its simple structure, the filter shows low insertion loss and minified to small size, owing to the meander structure used for lengthening the resonant length. The effect of input/output symmetrically hybrid-fed lines located along a straight line on the proposed filter is studied for dual-mode filter. The proposed filter shows a 22.5% bandwidth at the central frequency of 2355MHz, and it also provides transmission zeros on both sides of the bandwidth. Experimental results are in good agreement with simulated values and bring into focus the problems and solutions of wide-band filter.