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Abstract-The performance of single feed truncated corner circularly polarized microstrip antennas with different substrate thickness is studied by simulation and experiment. It is found that the axial ratio bandwidth could be enhanced considerably when a thicker substrate is used, provided that a U-slot and/or L-probe is used to effect impedance matching. One of the configurations attains an axial ratio bandwidth (< 3 dB) of about 14% within the impedance matching band when the substrate thickness is about 0.2λ o .

The U-slot patch antenna, a single-layer single-patch antenna on a relatively thick substrate ( 0 08 0 ), is a wide-band antenna with an impedance bandwidth in a range of 20%-30%, which is about an order of magnitude larger than that of the regular patch antenna. Recently, it was shown that a half U-slot patch antenna, with half of one of the dimensions of the U-slot patch, maintains similar wide-band behavior. The half-structure was also successfully applied to the U-slot with shorting wall. In this paper, new results on half structures, not previously published, are presented. First, the shorting pin technique is used to reduce the size of the half U-slot patch antenna. By both simulation and experimental studies, it is concluded that the impedance bandwidths, radiation patterns, radiation efficiencies and gains of the halfstructures are comparable to the corresponding full structures. Bandwidth of 28.6% and radiation efficiencies exceeding 90% are obtained for the half U-slot patch with shorting pin. Radiation patterns are stable across the matching band. Second, it is shown that a structure obtained from halving the E-shaped patch, which is a derivative of the U-slot patch, also maintains its wide-band behavior.Index Terms-Broadband antennas, microstrip antennas.

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A wideband circularly polarized (CP) L-slot antenna single fed by L-shaped feed line is designed. Wideband CP is obtained by truncating one of the corners of the antenna element. This arrangement introduces orthogonal components with quadrature phase difference to excite circularly polarized wave. A bandwidth of 46.5% (2.18-3.5 GHz) is achieved with an axial ratio 3 dB and return loss 10 dB. Good agreement between measured and computed results is achieved. Moreover, parametric study results are presented.Index Terms-Broadband antennas, circular polarization, slot antennas.