Frequency tunable dualmode microstrip patch antenna with polarization reconfiguration

A dual mode (TM₁₁ and TM₂₁) circular microstrip patch antenna combined with an annular ring is investigated for frequency tunability and polarization reconfiguration. Using varactor diodes, the resonant frequency of the both modes is tuned from 1.58 GHz down to 1.19 GHz which covers L-band communications with S₁₁ = -10dB. Each of the modes (patch and ring) employs two feed ports with 90° and 45° angular separation for TM₁₁ and TM₂₁ modes generation, respectively. By suitably exciting these ports, four different polarizations: linear vertical, linear horizontal, left hand circular polarization (LHCP) and right hand circular polarization (RHCP) can be generated simultaneously with the frequency tunability.