Frequency Reconfigurable Antenna with Dual-Band and Dual-Mode Operation

A frequency reconfigurable antenna with dual-band operation is presented. The antenna has a circular radiating patch loaded with an annular slot, and the slotted patch is shorted to the ground plane with four conducting posts. The antenna has three feed ports. Two of the ports are used to excite the slot mode resonant at a lower frequency, and broadside radiation with dual orthogonal linear polarizations can be obtained. The other port is used to excite the monopolar-patch mode resonant at a higher frequency, and conical radiation with vertical polarization can be yielded. To reconfigure the operation frequencies, four varactors are symmetrically placed across the annular slot. The simulated results indicate that the resonant frequency of the slot mode can be tuned from 1.62 to 1.17 GHz when the capacitance of the varactors is varied from 0.6 to 1.8 pF; besides, for each capacitance value, the impedance bandwidth of the antenna operating in the monopolar-patch mode can cover the frequencies from 2.4 to 2.5 GHz. Experiments are also carried out to validate the simulated data.