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The miniaturized dual-mode dual-band band-pass filters (BPF) using Minkowski-island-based (MIB) fractal patch resonators are proposed in this paper. The BPF is mainly formed by a square patch resonator in which a MIB fractal configuration with 2nd order iteration is embedded in the patch. By perturbation and interdigital coupling, the wide-band and dual-band responses are obtained respectively. For miniaturized wide-band design, at 2.41 GHz central frequency it has good measured characteristics including the wide bandwidth of 2.26-2.56 GHz (3-dB fractional bandwidth of 12.4%), low insertion loss of 0.72 dB, high rejection level (−52.5/−44.9 dB), and a patch size reduction with 60.6%. For compact dual-band design, the proposed filter covers the required bandwidths for WLAN bands . The patch size reduction of 78.1% is obtained. Two transmission zeros are placed between the two passbands and resulted in good isolation.

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A miniaturized dual‐mode band‐pass filter (BPF) using Minkowski‐island‐based (MIB) fractal patch resonator is presented in this article. The BPF is mainly formed by a λg/4 square patch resonator, which is a MIB fractal configuration with second order iteration is embedded in the patch. By tuning the perturbation, which resulted from the fractal patch, two resonant modes are excited and a pair of transmission zeros are generated to improve the BPF performance. The proposed filter at center frequency (f0) of 630 MHz has very good measured characteristics including the bandwidth of 552–708 MHz (3‐dB fractional bandwidth of 24.8%), low insertion loss of –1.38 dB and size reduction with 76.4%. The filter performance is characterized to verify the design concept. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:594–597, 2011; View this article at wileyonlinelibrary.com. DOI 10.1002/mop.25796

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A Fabry‐Perot resonator excited by a microstrip patch antenna that has a superstrate with a stepped dielectric constant is designed to operate at 5.8 GHz. The antenna is fabricated and is shown to provide enhanced directivity over that achievable using uniform dielectric slabs, with either εr = 4.4 or εr = 10.2 as superstrates. The measured maximum gain of the patch antenna with a step‐index dielectric constant superstrate with a dimension of 2λ0 × 2λ0 was found to be 13.44 dBi, whereas the corresponding values for the uniform dielectric superstrate are 11.25 (εr = 4.4) and 12.44 dBi (εr = 10.2). As shown in this article, the aperture efficiency of the step‐index dielectric is also higher than those of the other two. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:711–715, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26614