Single- and Dual-Polarized Tunable Slot-Ring Antennas

Single-and dual-polarized slot-ring antennas with wideband tuning using varactor diodes have been demonstrated. The single-polarized antenna tunes from 0.95 to 1.8 GHz with better than -13 dB return loss. Both polarizations of the dual-polarized antenna tune from 0.93 to 1.6 GHz independently with better than -10 dB return loss and > 20 dB port-to-port isolation over most of the tuning range. The capacitance of the varactor diodes varies from 0.45 to 2.5 pF, and the antennas are printed on 70times70 times0.787 mm3 substrates with epsivr = 2.2. The dual-polarized slot-ring antenna can either be made both frequency- and polarization-agile simultaneously, or can operate at two independent frequencies on two orthogonal polarizations. To our knowledge, this is the first dual-polarized tunable antenna with independent control of both polarizations over a 1.7:1 frequency range.