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 (ZA) having a real part (RA) connected to transponder circuitry presenting a load impedance (ZL) having a real part (RL), a ratio (Ra/Rl) of the real part (RL) of the load impedance and the real part (RA) 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.