Gain-enhanced electronically tunable microstrip patch antenna

This paper presents an electronically tunable microstrip parch antenna with improved radiation characteristics. The directive gain of the antenna is i mproved by as much as 5.5 dB, by the addition of a high dielectric superstr ate, with a thin air gap interspeed between the dielectric layers. Three di fferent high-dielectric sheets have been tested, ann it is observed that th e gain improvement is the maximum for the highest dielectric. The air-gap i s experimentally adjusted to optimize for the best gain of the antenna, wit hout degrading its input characteristics. The total addition to the thickne ss is only 3.2 nm for an antenna operating at about 850 MHz. The resonant f requency of the antenna shifts toward low with the addition of the superstr ate layers. (C) 1999 John Wiley & Sons, Inc.