Summary
International Symposium on Antennas and Propagation
2010
Session Number:2WB1
Session:
Number:2WB1-2
Wang-Shaped Patch Antenna Excited by H-Plane Oriented Wideband Feed-Networks
Chi-Ho Wong, Kwok L. Chung, Wai-Yip Tam, Sarawuth Chaimool,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
Over decades, impedance/return-loss bandwidth broadening of microstrip patch antennas has long been an essential objective in antenna society. Geometry complexity and cost effectiveness of many novel designs are the common yet essential trade-offs. Amongst the known techniques, the singly-fed slot-loaded single patch antennas with air substrate were the most simple and cost-effective designs [1]-[2]. When a U-slot [1] or a pair of parallel slots [3]-[4] is added onto a rectangular patch, additional current paths on the patch are extended so that nearby resonant modes can be generated. By merging of these adjacent resonant modes, a large 10-dB return-loss bandwidth (RLBW) of ~30% can be achieved [1]-[4]. However, both the geometries of U-slotted and E-shaped patches are inherently asymmetric. While a larger RLBW demands a higher antenna height, higher-order modes and probe radiation destroy radiation patterns and cause high cross-polar (x-pol) levels [5]-[6]. These, in turn, result in small pattern bandwidth and/or polarization bandwidth [5] in spite of the return-loss bandwidth was up to the order of 40-50% [7]. By the invention of Wang-shaped patch [8], which is differentially fed by a pair of mirrored L-probes, excited by an E-plane oriented wideband feed-network, the cross-polar levels have been suppressed below -20 dB over a bandwidth of 1.7 to 2.5 GHz. To avoid spurious radiation from the microstrip-lines [9] that interferes with co-polarization, feed networks are usually fabricated and printed below the antenna ground-plane. However, additional system ground-plane is required to be mounted at a distance from the feed-network, or otherwise, spurious radiation may interfere with the associated electronic circuits that share the same ground-plane. This paper illustrates the spurious effects of an H-plane oriented wideband feed-network, placed above and below the ground-plane, respectively. Impedance matching, radiation patterns, cross-polar levels, maximum gain and efficiency of the Wang-shaped antennas are all compared.