Design of an Electrically Small, Circularly Polarized, Parasitic Array Antenna for an Active 433.92-MHz RFID Handheld Reader

An electrically small, two-element, parasitic array (Yagi) antenna is proposed for an active 433.92-MHz RFID handheld reader. The antenna is composed of a square-shaped driver and director. The circular polarization is achieved by pulling the driver and pushing the director at one side. The sense of the antenna can be changed easily by pushing the driver and pulling the director at the same side. The total volume of the antenna is 115 mm × 115 mm × 13.8 mm (0.166 λ × 0.166 λ × 0.02 λ), and the electrical size is a kr of 0.75. The maximum measured realized gain is 3.5 dBic.