COMPACT DESIGNS OF A BAND-PASS FILTER WITH NOVEL OPEN-LOOP RESONATORS

摘要

In this article, several square open-loop resonators with transmission lines are proposed to design the optimized bandpass filters. A compact microstrip filter using an open-loop resonator was designed, fabricated and measured. At the center frequency f{sub}0 = 1.80 GHz, a 3-dB bandwidth of 5% can be varied from 1.76 to 1.85 GHz. The filter shows a maximum insertion loss in passband of 0.1 dB. A transmission zero is realized at about 3.1 GHz, and the attenuation at this frequency exceeds 70 dB. When compared with the conventional filters using coupled square open-loop resonators, the proposed filter has a size reduction of 30%. Good agreement between measurements and simulations are obtained.