A single-element high gain compact microstrip antenna has been experimentally demonstrated to operate over a wireless band covering 8 percent impedance bandwidth. As much as 11 dBi peak gain with linearly polarized radiation has been achieved using a prototype designed for personal communication systems (PCS: 1850 to 1990 MHz). The prototype occupies only 0.15λ0 by 1.0λ02 space, λ0 being the wavelength corresponding to the center frequency. This antenna is aimed to communicating with the wireless base stations as a booster/repeater device to serve a microcell in a weak signal zone.
by Debatosh Guha, University of Calcutta, India; Yahia M.M. Antar, Royal Military College of Canada Kingston, Ontario, Canada; P. Béland and M. Roper, Spotwave Wireless Inc. Ottawa, Ontario, Canada
In view of the compact and portable nature of the wireless equipment, their compact size and configuration have been a big issue to the wireless industry. Some challenges in realizing miniaturized wireless antennas have been discussed by Cantrell1 and some new useful candidates using dielectric resonators and microstrips have been recently reported.2-4
Of all the possible structures investigated so far, microstrip appears to be the most advantageous for various reasons, including simplicity, cost, weight and fabrication. However, a microstrip patch having a rectangular or circular shape suffers from an inherent limitation of narrow impedance bandwidth (≈2 to 3 percent with VSWR < 2) and the peak gain is limited to 6 to 7 dBi. Several techniques are known to increase the impedance bandwidth of a microstrip antenna, but they usually reduce the antenna gain. Several gain enhancement techniques like using a planar array or superstrate layers are also known, but they could significantly reduce the antenna bandwidth.
In this work, the combination of some useful techniques have been explored to demonstrate a small size, high gain antenna with a considerably large impedance bandwidth accommodating a commercial wireless band. The techniques employed here were studied earlier by different groups individually to investigate a mechanically tunable patch,5,6 to compensate probe reactance7 and to study improved radiation properties using a shaped ground plane.8-11
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