Broadband Single-FED Single-Patch Circularly Polarized Microstrip Antenna

The paper demonstrates a novel antenna which can achieve a broad impedance bandwidth and circularly polarized bandwidth with a suspended corner-truncated square patch and a new probe-fed rectangular strip. By incorporating a probe-fed rectangular strip inside a high substantial cavity (~ 0.144λ), a broad impedance bandwidth (VSWR < 2.0) of 770 MHz (31.43%) is achieved. To obtain a good circularly polarized (CP) bandwidth overlap with the impedance bandwidth, two stubs with optimized lengths are loaded with the non-radiating edges of the corner-truncated square patch symmetrically. Measured results show that the CP antenna features a wide operating bandwidth of 10% ranging from 2.41 GHz to 2.66 GHz (VSWR < 1.5 and axial ratio < 3 dB) and that of 22.45% ranging from 2.31 GHz to 2.86 GHz (VSWR < 2 and axial ratio < 6 dB) and good radiation patterns with cross-polarization level (LHCP) lower than the co-polarization level (RHCP) by more than 20 dB at the broadside direction. The average gain of this antenna is recorded as about 8.16 dBi across the operating bandwidth.