Input impedance arrangement for RF transponder

摘要

A transponder 14.1 for a radio frequency (RF) identification system comprises an antenna 22.1 having an antenna impedance (Z A ) having a real part (R A ) connected to transponder circuitry presenting a load impedance (Z L ) having a real pan (R L ), a ratio R L R A of the real part (R L ) of the load impedance and the real part (R A ) of the antenna impedance having a first value that is bigger than one when the transponder is not transmitting data. During transmission of data the ratio is switched between the first value and a second smaller value.