Broadband, low‐cost and low cross‐polarisation dual linearly polarised reflectarray antenna

Abstract

This study attempts to attain a broad bandwidth (BW) from a simple and low cost dual linearly polarised structure. The unit cell is a patch loaded with three concentric slots: a square, a vertical cross and a slant cross, printed on a foam backed dielectric. Required phases can be adjusted by both vertical and slant crosses which provides an extra degree of freedom in phase error and phase sensitivity reduction. The slant cross also improves angular stability of gain and cross-polarisation. Four reflectarrays (RAs) were designed at 10.7 GHz frequency. RA1 and RA2 utilised only the vertical and slant crosses, respectively, whereas RA2 achieved broader BW due to less sensitivity of slant cross. RA3 used both crosses to get lower phase error. However, due to dissimilarity among cells and uncontrolled phase sensitivity, it was poor in terms of gain and BW. To overcome this issue, in RA4, in addition to phase error and phase sensitivity control diversity, a local similarity is enforced. This array shows 23 dB gain and 3 dB gain BW of 17%. In 3 dB BW, its cross-polarisation level is −24 dB at boresight and also satisfactory in non-principal planes.