A Frequency Agile Microstrip Patch Phased Array Antenna With Polarization Reconfiguration

A novel multifunctional 1×4 phased array antenna employing wideband frequency agile microstrip patches with simultaneous polarization reconfiguration has been designed and experimentally verified. Each radiating element consists of a circular microstrip patch connected to an annular microstrip ring via four varactor diodes for achieving frequency agility between 1.5 and 2.4 GHz (frequency agility bandwidth ≈46%, S 11 ≤ -10 dB). Employing two feed points per radiator enables switching among four polarization senses (two linear and two circular polarizations) using a polarization feed network (PFN). For realizing beam steering, the optimum amplitude and phase excitation coefficients for each radiating element were calculated using projection matrix method based on active element pattern, which is then applied to each corresponding radiating element using programmable digital phase shifters, low noise amplifiers, and attenuators arranged in a beam forming network. Measurement shows ±52° beam peak steering at 1.5 GHz and ±28° beam peak steering at 2.4 GHz based on 3 dB gain variation criteria for both the linear and circular polarizations. The simulated and measured results agree reasonably well.