A Reconfigurable Dual-Polarization Slot-Ring Antenna Element With Wide Bandwidth for Array Applications

A reconfigurable dual-polarized slot-ring antenna/array, switching between S-and C-band with wide bandwidth in each operating state is presented. By simultaneously switching eight p-i-n diode switches, a 2 x 2 C-band antenna array can be reconfigured to an S-band antenna unit cell, and vice versa. Fractal shapes are incorporated into the antenna structure to significantly enhance bandwidth. In the S-/C-band operating state, this antenna shows 69.1%/58.3% fractional bandwidth with a measured maximum realized gain of 2.4/3.1 dBi. For the 2 x 2 C-band array, the spacing between the elements is less than 0.5 lambda(0) over the frequency band which enables grating-lobe-free beam scanning. A unidirectional version of this antenna/array with more than 12/16 dB front-to-back ratio at 3.5/8 GHz is also demonstrated. This wideband antenna/array can be used as a unit cell of a larger array with element spacing of half wavelength at the center frequency of both frequency bands.