Compact microstrip bandpass filter using two-layer aperture-coupled resonator-embedded structure.

A two-layer microstrip bandpass filter using aperture-coupled topology is proposed in this article. The filter is composed of two uniform impedance resonators and two stepped impedance resonators located on two stacked microstrip layers, and the couplings between the resonators on the upper layer and those on the lower one are obtained by using three coupling apertures etched on a common ground plane placed between the two layers. With this two-layer configuration, the proposed filter becomes very compact. To demonstrate the design, a four-order bandpass filter is designed at 2.33 GHz. Compared with a single layer structure filter, a significant size reduction of about 50% is obtained. Furthermore, a stop-band is extended to 8 GHz (3.43 f0) with a rejection better than -20 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2357–2360, 2008; Published online in Wiley InerScience (www.interscience.wiley.com). DOI 10.1002/mop.23680 [ABSTRACT FROM AUTHOR]