Defective ground structure loaded polarization reconfigurable ring-shaped patch antenna for multiband applications

A novel stub-loaded polarization-reconfigurable ring-shaped circular patch antenna designed for multi-band operation and switchable polarization is presented, having advantages such as ease in manufacturing and compact size (20 mm x 20 mm). The circular ring is segmented into four sectors, and two stubs are loaded on the inner side of the ring to disrupt the current distribution and create two orthogonal electric field vectors, generating circular polarization. The antenna supports it in switching three distinct polarization states: linear polarization, left-hand circular polarization, and right-hand circular polarization, selectable with different combinations of diodes. From the measured results, ARBW (<3 dB) is 32.12% and 6.06% for CP bands. Additionally, eight LP bands with IBW of 71.66%, 3.55%, 3.94%, 35.88%, 45%, 45.5%, 34.77%, and 8.2% are achieved. The antenna exhibits satisfactory stable gain across all frequency bands and excellent radiation performance, making it a promising candidate for modern wireless communication applications (C-band, ITS2 fixed, X-band, and Ku-band satellite downlink operations).