A Circular Patch Fed by a Switch Line Balun With Printed L-Probes for Broadband CP Performance

A broadband circularly polarized (CP) patch antenna fed by a planar balun with a pair of printed probes is presented in this letter. Using switch line structure to design the balun, combined with two printed L-probes to supply dual feed with 90deg phase difference to the circular patch, the antenna achieves good performance in terms of large impedance and axial ratio (AR) band-widths. The measured results agree well with the simulations, indicating that the antenna possesses an impedance (S₁₁ < -10 dB) bandwidth of 45%, and axial ratio (AR < 3 dB) bandwidth of 41%. In addition, the 3-dB gain bandwidth and the peak gain are 44%, and 6 dBi, respectively.