A Compact Single-Feed Circularly Polarized Microstrip Antenna with Symmetric and Wide-Beamwidth Radiation Pattern

Abstract

A compact single-feed circularly polarized microstrip antenna is proposed to achieve symmetric radiation pattern over a wide range of observation angles. In order to reduce the radiation aperture and consequently broaden the circular polarization (CP) and the half power beamwidth (HPBW) of the antenna, a partially etched superstrate and a conducting cavity are employed in the design. Further, reasonable axial ratio (AR) and impedance bandwidths are realized within the compact structure by using a simple series crossed-slot aperture coupled feeding. As a consequence, the overall dimension of the fabricated prototype is 0.32λ0× 0.32λ0× 0.12λ0at the center operating frequency of 1.56 GHz, and a 3.0% overlapped bandwidth of 10 dB return loss (RL) and 3 dB AR is obtained. Within the bandwidth, symmetric CP radiation pattern over almost the entire upper hemisphere is observed and the HPBW is also increased from 60° to 106°.

An Electrical Model to U-Slot Patch Antenna with Circular Polarization

“…This low value comes from the use of truncated corners. Sharma [1] showed that this type of antenna could not provide a large bandwidth at the axial ratio. Figure 7 shows the 3D radiation pattern of the proposed antenna for the resonant frequency 2.45GHz.…”

“…Either by cutting two of its corners or by making a diagonal opening in its metallization. These three topologies have been studied by Sharma et al [1].…”

“…The latter can vary in length and width while the truncation is symmetrical. According to Sharma [1], the antenna with truncated corners provides the lowest axial ratio. But has a slightly smaller bandwidth (axial ratio) than the other topologies [2]- [4].…”

Dual-Frequency Circularly Polarized Truncated Square Aperture Patch Antenna with Slant Strip and L-Shaped Slot for WLAN Applications

“…The wider adoption of CP technology is attributable to alignment variability (i.e., horizontal, vertical, and diagonal) of the receiving antenna with reliable performance [1]. Previous research has experimented with diverse antenna structures to produce circular polarization (CP) [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…However, the complexity of two feeding ports can be adjusted into one feeding port with an unequally split feeding structure [6,7], modifying the feeding structure into an S-shape [8], or using sequential rotation feeding structure [9] instead. Nevertheless, instead of changing the feeding structure of the antenna, there are many different methods that could also result in the antenna being circularly polarized such as the modification of the slot structure using various shape slits [10], adding a pair of inverted L [11], implementing truncated corners [12], introducing a parasitic patch [13,14], placing a parasitic unequal linear slots [15], T-shaped slot [16], or S-shaped slot [17], using two-diode controlled slot [18], and changing the main slot structure into a set of small square slots with multiple rectangular arms [19].…”