UHF-band inductively-coupled RFID antenna with near-isotropic radar cross section patterns

This paper presents a RFID tag antenna at 911 MHz which has near-isotropic radiation patterns and easy conjugate impedance matching property by adopting an inductively- coupled feeding. With a typical antenna impedance of 2+j146Omega, the proposed tag of compact size 40 x 46 mm(0.12x0.14lambda) has the simulated maximum and minimum RCS´ of -16.75 dBm² and -21.47dBm², respectively, depending on the incident angles. The difference of about 4.7 dB (3.0 in measurement) is very small compared with that (about 70dB~80dB) of dipole-type tags. The designed antenna has been fabricated and its RCS´ have been measured varying the angles of incidence. The measured RCS´ have been found to have good agreement with the simulated ones.