A Reconfigurable 1 × 4 Circularly Polarized Patch Array Antenna With Frequency, Radiation Pattern, and Polarization Agility

In this communication, the design and experimental verification of a reconfigurable
$1 \times 4$
circularly polarized (CP) patch array antenna with frequency, radiation pattern, and polarization agility are reported. An orthohexagonal patch element antenna with three groups of parasitic patch and varactor diode is adopted to enable frequency and polarization reconfiguration. By properly adjusting the dc voltage applied on the three groups of varactor diode, the operating frequency can be tuned continuously, and the polarization can be switched simultaneously between left-handed CP (LHCP) and right-handed CP (RHCP). Four switchable feeding probes integrated with a designed single-pole four-throw (SPFT) switch are used to feed the element antenna for achieving different initial phase. Hence, by properly switching feeding probes for the four elements, the radiation beam of the array antenna can be dynamically reconfigured among five different beam states. To verify the proposed concept, a full functional prototype was fabricated and characterized for four different frequency bands with all polarization and beam states. A good agreement between the simulation and measurement is obtained, thus validating the multiple reconfigurable capability of the array antenna in frequency, pattern, and polarization.