Varactor-loaded microstrip patch antenna with frequency-tuning capability and complete polarization diversity

A novel design of frequency and polarization reconfigurable microstrip patch antenna is presented. The resonating microstrip structure consists of multiple smaller patches interconnected by varactors. Four groups of varactors biased by four independent bias voltages allow independent control of antenna resonant frequency and polarization state while maintaining good impedance matching. The antenna design does not include any critical “via” connections to the microstrip ground layer, which could aggravate the fabrication process. The proposed design was verified on prototype fabricated for the L-band frequency range. The obtained frequency-tuning range was up to 50% of the central frequency (890 MHz to 1500 MHz) with return loss better than −15 dB within the whole range. The polarization could be adjusted either linear in an arbitrary direction or circular (left- or right-hand) with 180° phase-reversal option.