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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°.

A small-size 2 × 2 broadband circularly polarized microstrip antenna array is proposed in this article. The array has four broadband dual-feed U-slot patch antenna elements with circular polarization, and the sequential feeding technique is used to further enhance the 3 dB axial ratio bandwidth. The lateral size of the fabricated array is as small as 1 33λ 0 × 1 33λ 0 , and the profile is only 0 04λ 0 . Measured results show that the overlapped −10 dB reflection coefficient and the 3 dB AR bandwidth is 53%, and the variation of the measured realized gain is less than 1 dB for S-band satellite communications (1.98-2.2 GHz).

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A dual-band circularly-polarized double-layer U-slot microstrip patch antenna is proposed. The antenna is fed by a two-way Wilkinson power divider with different phase. The feed points are carefully chose to achieve a wide bandwidth. The antenna is printed on the substrate with high dielectric constant and simulated by HFSS and the simulation results are discussed. The impedance bandwidth (VSWR<1.5) of the lower band and higher band is 24.2% between 1.08GHz to 1.31GHz , and 5.7% between1.52GHz to 1.61GHz, respectively. The AR bandwidth (AR<6 dB) is 45% between 1.07GHz to 1.71GHz. The simulated results are in good agreement with the requirement of GPS applications.Index Terms-GPS, U-slot, dual-band, wide beamwidth.