A new technique for designing dual-band reconfigurable slot antennas is introduced The technique is based on loading a slot antenna with a lumped capacitor (or varactor) at a certain location along the slot Given a fixed capacitor location along the slot, decreasing the capacitance results in increasing the first and second resonant frequencies of the slot antenna However, the changes in the resonant frequencies are significantly different for the first and second resonances and, hence, a dual-band antenna with considerable frequency ratio tuning range can be obtained Based on this technique, an electronically tunable dual-band antenna with a frequency ratio in the range of 12-165 is designed and fabricated using a single varactor with a capacitance range of 05-22 pF The antenna has similar radiation patterns with low cross-polarization levels at both bands and across the entire tunable frequency range

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A varactor-tuned dual-band slot antenna

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A convenient procedure to obtain the radiation pattern of slot antennas consists of assuming that the conducting ground plane containing the slot is infinitely long. While this may be adequate for obtaining the radiation pattern in the half space of the aperture, for obtaining the complete radiation pattern of the antenna the proper dimensions of the ground plane have to be considered. The effect of the ground plane thickness on the radiation pattern for aperture antennas with the slots assumed as sources of cylindrical or spherical waves is examined using the geometrical theory of diffraction (GTD). The diffraction from the upper and lower edges of the ground plane was calculated considering the multiple diffractions between the edges. Numerical results are presented and discussed. >

R.M. DeFelice Souza

Papers

Effect of a finite ground plane thickness on the radiation pattern of an aperture antenna