No abstract

An improved filter design of a dual‐mode double‐ring resonator with radial stub for ultra‐wideband (UWB) applications is presented in this paper. Based on the double‐ring resonator and adjusted voltage/current couplings, two radial stubs are added to the outer ring in order to construct the band‐pass filter. The dual‐mode double‐ring resonator exhibits wideband responses, and the radial stubs enhance the bandwidth of the operating‐frequency band. Thus, an alternative approach to improve the bandwidth of the conventional dual‐mode double‐ring resonator, is presented. The experimental and simulation results are given and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 219–222, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20593

ABSTRACT:The multiband and wideband performances of innovative fractal antennas constructed with circular patterns are proposed in this paper. By using the Descartes circle theorem and self-similar iteration design, the circular fractal antennas exhibit frequency-independent characteristics and multiband spectra. The simulated and experimental results with multiband/wideband spectra and radiation patterns are presented and discussed.

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

Construction of FSS screens coated with ferrite Ba(MnTi)Fe10O19 to implement broadband microwave absorbers is presented in this paper. The decrement method is used to measure the reflective response of the microwave absorber. Both reflectivity and absorption representations recognize the characterization of microwave absorbers for the X‐band. Two types of FSS screens, a square‐lattice screen and an equilateral‐triangle‐lattice screen, are introduced to obtain better bandwidth and absorption in this study. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 323–326, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20131

The precise determinations of innovative CPW‐fed slot antenna constructed with circular fractal patterns are introduced. By the Descartes circle theorem and self‐similar design of iteration, the CPW‐fed slot antenna is proposed. The practical design with multi‐band responses is presented. The first resonance exhibits the wide‐band operation with impedance bandwidth 66.4% (VSWR < 2). The radiation field presents array patterns, and the axial ratio is 1.18 dB at 1.8 GHz. Experimental results with iterative spectra and contour radiation patterns are presented and discussed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1586–1592, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21721

An X‐band rectangular waveguide partially filled with ferrite metamaterial exhibiting the transversal negative permeability is investigated in this article. Several kinds of the miniaturized waveguide loaded with the novel Sr(ZnTi)Fe10O19 ferrite in 7 GHz frequency band have been measured. The results reveal backward‐wave pass‐band located below the cutoff frequency. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 201–203, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22083

An innovative modified Sierpinski fractal monopole antenna with multiband performance is proposed in this paper. By using the Descartes circle theorem and a self‐similar iteration design, the antenna is constructed with circular fractal patterns. The resonances exhibit the log periodic characteristic, and the radiation field presents array patterns. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 909–911, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21515