A Novel Low-profile Broadband Circularly Polarized Compact Antenna Array

A novel low-profile broadband circularly polarized compact 2x2 array is presented in this paper. The array combines the advantages of stacked patch structure, sequential rotation method and a feed network composed of Wilkinson power divider and T-junction power splitter, exhibiting excellent performance. The dual feeds of the square patch are connected to output ports of Wilkinson power divider with a 90 degrees phase shifter to radiate circularly polarized wave. Then, a compact 2x2 array fed by sequential-rotation method to form phase 0 degrees, -90 degrees, -180 degrees and-270 degrees is proposed, with a low profile less than 0.1 wavelength. All of the radiation elements and feed network are printed on the lower substrate without the need of a separate substrate for feed network, while four parasitic patches are printed on the upper substrate. Experimental results show that the array can achieve an impedance bandwidth of 27.78% for the 10-dB return loss and a 3-dB axial ratio bandwidth of 52%. The antenna gain bandwidth, considering 1-dB gain variation within the impedance bandwidth, is about 16%, with the maximum gain about 14.19dBi.