Self-reconfigurable RFID reader antenna

This paper presents a self-reconfigurable switched beam RFID reader antenna concept and its experimental implementation. The specific antenna presented in this paper is a planar 2-element Yagi array with a parasitic element loaded with a self-oscillating switching circuit powered wirelessly, by the antenna signal itself. Once this reader antenna is fed with RF signal of sufficient power, the circuit starts oscillating, switching between the two complex impedance values, and thus changing the antenna radiation pattern. We describe a theory of operation, including modeling and simulation, and present a prototype of such an antenna operating at 900 MHz with two distinct switched beams and a peak gain of 4.5 dBi.