A Miniaturized Metamaterial Absorber for Ultrahigh-Frequency RFID System

An ultrahigh-frequency (UHF) miniaturized metamaterial absorber (MMA) using incurved square loop loaded with lumped resistors is proposed in this letter. The size of the unit cell is miniaturized to be only 20 × 20 mm2, about 0.0036λ2at the center frequency (910 MHz), which is only a quarter of the size of a conventional UHF metamaterial absorber unit cell. Detailed simulations and experimental results show that the MMA covers the worldwide UHF radio frequency identification (RFID) operation band (860-960 MHz) with absorptivity more than 90% over a certain range of incident angles. Thus, the MMA can be used to improve performance of RFID systems, especially suitable for the use in restricted spaces.