Miniaturized dual-mode quasi-elliptic function bandpass filter with wide rejection bandwidth

A novel miniaturized ring resonator is presented to achieve a dual-mode bandpass filter with wide rejection bandwidth. By utilizing periodical loadings inside the square ring resonator, it not only can compact size of 48%, raise the first spurious to 2.4 times of its fundamental passband, but facilitate the practical realization of dual-mode bandpass filter, simultaneously. The fractional bandwidth of 6% is achieved. The designed structure is quite simple. Moreover, both simulated and measured results demonstrate good agreement.