A novel ring-wide bandpass filter by using orthogonal feed structure

In this article, a simple method to design a high‐performance ring‐wideband bandpass filter centered at 4 GHz without the perturbation element is presented. The coupling between the two orthogonal modes is accomplished by combining the resonant mode of the ring resonator and the resonant mode of the coupling line having a length about λg/4 with respect to 4 GHz. This fabricated filter at center frequency f0 of 4 GHz has showed very good measured characteristics, including a 3‐dB fractional bandwidth of 40%, a very low insertion loss of 0.3 ± 0.1 dB, a stopband from 6 to 10 GHz, and a very high selectivity. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2025–2027, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23577