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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mm; hence, both elements can be easily integrated in embedded systems or in large planar-array configurations.The measured radiation patterns in both cases are in reasonable agreement with the simulated results, approximating typical dipole behavior with moderate absolute gain (3 to 5 dBi) at lower frequencies (below 4 GHz). At higher frequencies, both antenna designs exhibit unidirectional radiation characteristics, with higher gain (over 7.5 dBi) as compared to a conventional dipole performance. The front-to-back ratio is better than 10 dB and beamwidth is approximately 120°in the azimuth and 45°in the elevation plane. As a consequence, both radiators can be used at higher frequencies as directive base-station antennas (for example, in access points) to form sectors or backbone links of a wireless network. Due to higher gain, even single elements can be used (depending on the application needs), thus leading to an attractive, cost-effective, and easily fabricated alternative to larger arrays. ACKNOWLEDGMENT

A method of image formation through inhomogeneities is proposed and demonstrated. The imaging system, including inhomogeneity, is in one branch of an interferometer that produces broad-source fringes. The imaging system aperture is stopped to a small point. The effective aperture is in the other branch, which is otherwise empty.

Abstract-The improved configurations with dual-mode doublesquare-loop resonators (DMDSLR) for tri-band application are proposed in this paper. Two sets of loops including double-squareloop and G-shaped loop are involved in the resonators. The resonant frequency equations related to DMDSLR geometries are introduced for simply designing tri-band bandpass filter (BPF). Resonant frequencies and transmission zeroes can be controlled by tuning the perimeter ratio of the square rings and the couples. To obtain lower insertion loss, higher out-of-band rejection level, wider bandwidth of tri-band, and compact applications, the miniaturized DMDSLR structure is designed. The effective design procedure is provided. The proposed filter is successfully simulated and measured. It can be applied to WLAN (2.45, 5.20 and 5.80 GHz) and WiMAX (3.50 GHz) systems.