Design of stacked circular/quasi-elliptical patch array for broadband CP applications

This paper presents a design of circularly polarised 4-element planar subarrays composed of low axial-ratio stacked patch elements in X-band. The wideband circular polarisation is excited using stacked circular disc and quasi-elliptical patch that printed on a superstrate with low dielectric constant (/spl epsi/ = 2.2) and a high dielectric constant (/spl epsi/ = 6.15) material as the substrate, respectively. The proposed element exhibits low mutual coupling in two principle planes that is comparable to a single-layer inside the subarray, a pair of microstrip-line fed elements was considered and arranged in four scenarios. Low sidelobe levels and 2-dB axial-ratio bandwidth of 19.5% in addition to a boresight axial-ratio of 0.15 are achieved. Variations in gain and axial ratio other than boresight (/spl theta/ /spl ne/ 0) in azimuth plane are also examined.