Design of compact triple-mode bandpass filter using double center stubs-loaded resonator

A compact microstrip triple-mode bandpass filter using half-wavelength (lambda/2) open-ended microstrip line with double center loaded stubs is proposed in this article. Be introducing a radial-line stub to the traditional dual-mode resonator, a triple-mode resonator is realized and the mode characteristics of the resonator are discussed. Also, an equivalent lumped circuit is proposed and the method of parameters extracting is given. The proposed filter exhibits a quasi-elliptic function response with a compact circuit dimension. At last, an experimental filter is fabricated and a good agreement between simulations and measurements is reached. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2109-2111, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25364