A compact bandpass filter using interdigital and step-impedance hairpin resonators

Abstract

A four-pole elliptic function bandpass filter is designed using miniaturized microstrip interdigital hairpin resonator and step-impedance hairpin resonator. Miniaturization hairpin resonators are realized by using interdigital structure and step-impedance structure having parallel coupled lines. The full-wave simulator IE3D is used to design the compact hairpin resonator and to calculate the coupling coefficient of the basic coupling strictures. The response of the fabricated filters using Al2O3 (εr = 9.7, Q × f = 350000 GHz) and 0.6Sm(Co1/2Ti1/2)O3-0.4CaTiO3 (εr = 37, Q × f = 43000 GHz) dielectric substrates are designed at a center frequency of 2 GHz. The compact size and the performance of this class of filter have been demonstrated. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1493–1495, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25231