A frequency reconfigurable antenna for high performance U-NII band radios

The present paper presents a frequency reconfigurable antenna, suitable for high performance U-NII band radios. The proposed antenna is capable of covering the Unlicensed National Information Infrastructure U-NII band either entirely (5.15 GHz-5.825 GHz) or in one of its three subbands (5.15-5.35 GHz, 5.47-5.725 GHz and 5.725-5.825 GHz), which allows using it for sensing the entire band and then adjust its bandwidth to select the suitable sub-band and filter-out the adjacent ones. To obtain a reasonably narrowband operation around the whole U-NII band, the antenna is composed of a radiating element in the form of an inverted U fed by a microstrip line on its upper side. In order to achieve the high-selective frequency reconfiguration that allows adjusting to the desired band and bandwidth, four horizontal slots with integrated switches are inserted in the ground plane to act as reconfigurable filter. Measurement results on a prototype antenna, with an ideal switch, fully demonstrate the performances of the proposed designs.