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In this article, the design concept of an active reconfigurable reflectarray antenna has been proposed and tested. The elementary radiators are hollow patch element loaded with varactor-diode device in which the reflected phase can be varied. This phase alteration is based on the variation of the diode capacitance which can be achieved by varying the biasing voltage of the active varactor device. By activating these varactor devices, the phase of each antenna element in the array configuration can be adopted dynamically, and consequently, its radiation beam direction can be reconfigured. The advantage of the MEMS switches is the complexity of the integration and continuing beam scanning capability. The reflectarray incorporating active elements has been built and tested at 6.0 GHz. Narrow band multifrequency shared aperture is demonstrated theoretically and experimentally. The performance of the proposed active antenna is excellent, which pioneers the design of arbitrarily reconfigurable antennas. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 367–374, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24050 [ABSTRACT FROM AUTHOR]

In the past two years, extensive research has been carried out at IRCTR (International Research Centre for Telecommunication-Transmission and Radar) in order to analyze and model the reflection and transmission coefficients of a semiconductor, i.e., doped silicon, under illumination of light. It was found that the characteristics of the semiconductor material could substantially be changed once it is illuminated with light. This property of the semiconductor material can be used to realize a nonmechanical beam deflector that can form and scan a beam of millimeter-wave (MMW) radiation at a rapid rate. The preliminary measurements in a closed waveguide structure show that there is a total reflection of MMW and microwave (MW) power after the laser is turned on. The laser light causes a considerable change in the equivalent conductivity of the silicon wafer, changing it from an insulator to a good conductor. The reflection and transmission are modeled using the S–T matrix of the total microwave network. There is a good similarity in the behavior of the theoretical and measurement results. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 349–353, 2001. [ABSTRACT FROM AUTHOR]

A dual-polarized L-band microstrip antenna was designed, constructed, and tested. A new design procedure based on optimizing the orthogonal mode isolation is demonstrated experimentally to provide highly decoupled feedlines and radiated fields with low cross-polarization levels. Isolation between orthogonal ports of less than -36 dB across the operating band is reported. An impedance match of better than -10 dB over a 1% bandwidth centered around the resonant frequency was achieved. Cross-polarization levels were less than -40 dB on boresight, and typically less than -35 dB over the entire radiated field on the resonant frequency. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 252–255, 2000. [ABSTRACT FROM AUTHOR]

An X-band waveguide resonator is used to measure the complex permittivity of solid-state materials. The measurement technique uses the perturbation technique. The sample is inserted in the waveguide resonator in a cylindrical form. The sample shifts the resonance frequencies. The resonance frequencies and shift frequencies are measured using an HP network analyzer. Three different reference materials are used to check the accuracy of the measurement technique. The reference materials are: Rexolite, HYD-Cast, and RT/Duroid. A good agreement between the measured dielectric constant and the given values in the literature is observed. The advantage of such a technique is that a very small volume of the sample is needed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 269–272, 1999. [ABSTRACT FROM AUTHOR]

The aperture admittance is formulated for a slice dielectric-filled (εr ≥ 1) rectangular waveguide antenna. By considering the specific media discontinuity at the aperture, the formulation is able to predict aperture admittance of the waveguide with various dimension ratios and dielectrics. The summarized results are new in the sense that they have rarely been found in the literature. Calculations and supporting measurements show that the filled dielectric has an important influence, in addition to waveguide height, on the aperture admittance. The proposed approach permits a good simulation of aperture characteristics and impedance matching. [ABSTRACT FROM AUTHOR]

This article presents a theoretical and experimental study in which a transition between the microstrip-line end launcher and the microstriplike antenna (MLA) and from the coax line to the microstrip line has been realized. A sinusoidal current distribution in the conductor loop, responsible for coupling the energy from the microstrip end launcher to the MLA is assumed. A combination of short transformers and quarter-wave sections has been used as a matching network, in order to optimize and broaden the transition bandwidth. [ABSTRACT FROM AUTHOR]