Patent ID: 8315562

Claim:
A method comprising: transmitting an outgoing RF signal to an antenna through a directional device having a first terminal receiving the outgoing RF signal and having a second terminal transmitting most of the outgoing RF signal to the antenna; receiving a RF signal reflected by an RF tag from a third terminal of the directional device; generating a demodulated vector signal from a spurious RF signal and the RF signal received by the antenna; generating at least one attenuation control-parameter and at least one phase control-parameter from an error vector related to the demodulated vector signal based on a look up table containing a frequency dependent relationship between the control-parameters and the error vector; setting an attenuation of a controllable-variable-attenuation element of a controllable-variable-impedance element with the at least one attenuation control-parameter and setting a phase delay of a controllable-variable-phase element of the controllable-variable-impedance element with the at least one phase control-parameter; and reflecting the RF signal from the controllable-variable-impedance element to a fourth terminal of the directional device.