Stepped-impedance resonator bandpass diplexers with over-coupling structures

A stepped-impedance resonator (SIR) bandpass diplexer using over-coupling structures and tapped input/output (I/O) has been presented. The advantages of this construction are simple design and suppression of spurious response at twice the center frequency (2f0). The tapped I/O creates an extra transmission zero in each filter of the duplexer in order to improve stopband attenuation. The diplexer, designed at 0.9 and 1.8 GHz, is suitable for mobile communication and is easily fabricated in the packing surface. Experimental results of the designed duplexer are in good agreement with the theoretical predictions and simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 79–82, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20215