Wideband linear and circularly polarized patch antenna using a printed stepped T-feed

The inherent disadvantage of the narrow bandwidth of microstrip antennas is overcome by a wideband feed mechanism. A square patch excited by a stepped T-feed probe achieved an octave bandwidth (0.98 to 2.1 GHz) with a voltage standing wave ratio of <2. A similar return loss over an octave bandwidth (1.05 to 2.4 GHz) was measured when two orthogonal stepped T-feed probes fed by a log-periodic balun were used to generate circular polarization (CP). For CP, pattern symmetry is shown to occur over 50% of the band, and the CP 3 dB axial-ratio bandwidth is of the order of 30%