Summary
International Symposium on Antennas and Propagation
2010
Session Number:2WC1
Session:
Number:2WC1-9
Single-feed Circularly Polarized Microstrip Antenna Loaded with a Periodic Structure Superstrate
Chawalit Rakluea, Sarawuth Chaimool, Kwok L. Chung, Prayoot Akkaraekthalin,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
Circularly polarized antennas (CPAs) are an interesting option for satellite and wireless communication systems. Microstrip patch antennas (MPAs) have been widely used as radiating elements in CPAs. There are two commonly used feeds for circularly polarized microstrip antennas (CP-MPAs), namely a single-feed and a dual-feed. Although the axial ratio (AR) bandwidth of single-feed CP-MPAs is narrow, they are very attractive because they allow a reduction in the complexity and RF loss of feeding network. There are many methods reports in the literature on single-feed CP-MPAs : square patch with truncated corners [1], U-slotted rectangular patch [2], and circular patch with slits [3]. Yo et al. [4] proposed an interesting method to get circular polarization by embedding two circular slots in the circular patch. However, the 10-dB return-loss and 3-dB AR bandwidths (ARBW) are only 5.6% and 1.3%, respectively. Therefore, many researchers are exploring methods and techniques to achieve wideband polarization characteristics, as well as wideband impedance bandwidth (ZBW) for CP-MPAs [5]-[6]. One technique for achieving wideband MPAs is the use of stacked elements or parasitic superstrate [5]. When the two or more layers are designed for the same frequency and polarization, an increase in bandwidth can be obtained. However, relatively few papers have provided detailed information for the CP-MPA. Most of the papers related to the studies of the superstrate effects are only for linearly polarized MPA (LP-MPA) and single-element of stacked patch. A combination of CP-MPAs with the periodic structures including frequency selective surface (FSS) [7] and electromagnetic bandgap (EBG) [8] has been fruitful. Using the filtering properties of such structures, it is possible to reduce surface wave, to achieve wide band and high gain. This has motivated us to study a periodic structure superstrate-loaded CP-MPA. As one half-wavelength (λ/2) separation between FSS and ground plane is required for high gain CP-MPA antenna, it inevitably increases the profile and stringently limits the operation bandwidth of the antenna. A first work of the authors of this paper [9] has explored the possibility of using a periodic structure in a CP-MPA to achieve simultaneously ZBW, ARBW and gain enhancement. That work proved that it was possible to get such enhancement. In this paper, the wideband and yet low-profile technique of periodic structure superstrate is proposed. The working bandwidth of a 2.45 GHz single-feed CP-MPA is significantly enhanced. The dimensions of antenna are optimized to achieve good ARBW and ZBW using CST and IE3D.