A Millimeter-Wave Frequency Reconfigurable Circularly Polarized Antenna Array

This paper discusses the design of a high gain right-hand circularly polarized millimeter-wave frequency reconfigurable antenna array. The 16-element antenna array is designed to reconfigure its operating frequency over both K- and Ka-bands. More specifically, the reconfigurability is ensured through the integration of a modified ring resonator along with the array's sequentially rotated stacked feeding network. The ring resonator is designed to reconfigure its operating frequency over four distinct bands with center frequencies at 25 GHz, 26 GHz, 27.75 GHz and 29 GHz, respectively. Such integration enables the proposed millimeter-wave antenna array to exhibit unique radiation characteristics by maintaining circular polarization with an Axial Ratio (AR) <; 1 dB in a fractional bandwidth of 37.5% between 21.2 GHz and 31 GHz. A Figure of Merit that takes into account the array's axial ratio, sidelobe levels and fractional bandwidth is developed to highlight the unique performance of the presented millimeter-wave circularly polarized array in comparison to available work in the literature. The fabricated antenna array shows good agreement with the simulated data where it is found that the measured realized gain exceeds 12 dBic with sidelobe levels of less than -17.5 dB over the various frequency bands of the frequency reconfigurable antenna array.