Patent ID: 9013268
Filing Date: 2015-04-21
Classification: A01K,E05F,G01V,G06K,G07C

Abstract:
1. An RFID tag reader, the reader comprising: a resonant circuit; an electromagnetic (EM) field generator for driving said resonant circuit to generate an electromagnetic (EM) field for modulation by a tag, said modulation comprising load modulation of said EM field by said tag; a detector system responsive to fluctuations in strength of said EM field at said reader; a negative feedback system responsive to said detector system to provide a control signal to control said EM field generator to reduce said detected fluctuations in strength of said EM field generated by said resonant circuit, wherein said negative feedback system operates on a per-cycle basis; and a demodulator responsive to said control signal to demodulate said EM field modulation by said tag, the reader further comprising a signal generator configured to drive said EM field generator, wherein said EM field generator has a power supply, and wherein said signal generator drives said EM field generator such that energy drawn per cycle of said EM field from said power supply varies to apply negative feedback, the tag reader further comprising a demand signal output circuit to provide a demand signal, wherein said demand signal is a signal responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generator, and wherein said demodulator is configured to interpret said demand signal to thereby demodulate said EM field modulation by said tag.