Design of an 11-Pole BPF Using Cascaded Triplets of TM010 Mode Dielectric Ring Resonators

An 11-pole high-performance bandpass filter (BPF) using TM
010
mode dielectric ring resonators is presented in this paper. The filter consists of three cascaded triplets (CT) of resonators with three cross-couplings which produce three controllable transmission zeros (TZs). Meanwhile, the sourceload coupling is intendedly avoided. As a result, a sharp roll-off rate of the passband skirt is achieved, and the ratio between the 40-dB bandwidth and the 3-dB bandwidth is as small as 1.18. The out-of-band rejections near the lower and upper side of the passband are as large as about 120 dB and 110 dB, respectively. The filter is compact, low-loss, and is a good candidate for wireless applications.