Dual-band polarisation reconfigurable grounded fractal slot antenna

A polarisation reconfigurable fractal slot antenna with dual-band performance is proposed in this study. The antenna consists of a Minkowski Island fractal inspired slot in the ground plane, which is excited by a microstrip line. The input match of the antenna is improved by placing two protruding horizontal stubs inside the two corners of the fractal slot. Four p-i-n diodes are placed within the grounded fractal structure to realise polarisation reconfigurability. Based on the switching states of the p-i-n didoes, the proposed antenna can produce right-hand circular polarisation or left-hand circular polarisation. A novel biasing network is used, which uses only two wires for polarisation switching. A prototype of the proposed antenna is fabricated and tested. When the antenna is configured to radiate circular polarisation, the measured reflection coefficient bandwidths (corresponding to vertical bar S-11 vertical bar = - 10 dB) for the two bands are 15.44 and 13.16% and the measured axial ratio bandwidths (corresponding to AR <= 3 dB) are 17.61 and 8.69%, respectively.