Optically Modulated Scatterer Technique for Radiation Pattern Measurement of Small Antennas and RFID Tags

The optically modulated scatterer (OMS) technique is developed for the electromagnetic field distribution measurement with minimum disturbance to the field under test. In this letter, we present a novel method to measure the radiation pattern of unwired small dipole-like antennas such as radio frequency identification (RFID) tag antennas by OMS technique. The radiation pattern could be measured by this technique without any metallic feeding wire that would disturb the field pattern. The variation of the radiation pattern caused by the materials attached to an RFID tag antenna could also be evaluated with this technique.