UHF RFID Reader With Reflected Power Canceller

Abstract

Reflected power imposes severe linearity problems to the receiver in radio frequency identification (RFID) readers. In this letter, the design and realization of a ultra high frequency RFID reader with a reflected power canceller circuit based on quadrature feedback are presented. Theory and measurements of the signal and noise in the receiver are presented as a function of incident carrier power. The receiver sensitivity is even better than without the canceller with high incident carrier power: A noise spectral density at the data band is -140 dBm/Hz at +12 dBm incident carrier power. At the same time, input compression point of +15 dBm is achieved. The dynamic range of the receiver is improved by 10 dB.