Patent ID: 7742751

Claim:
A method, comprising: transmitting radio frequency (RF) signals using a radio frequency identification (RFID) transceiver to an RFID tag; receiving from said RFID tag, radio frequency (RF) signals by a receiver of said RFID transceiver in response to said transmitted RF signals; converting said received RF signals; sampling converted signals using a filter circuit configured in a first mode to have a first bandwidth, to sample a DC offset value of a first portion of said converted signals; filtering a second portion of converted signals using said filter circuit configured in a second mode to have a second bandwidth narrower than said first bandwidth; canceling said sampled DC offset value from said second portion of converted signals using said filter circuit configured in said second mode; holding said sampled DC offset using said filter circuit configured in an intermediate mode after said first mode; wherein said sampling, holding and filtering uses an alternating current (AC) coupling capacitor; and wherein said filtering comprises high pass filtering to block a portion of converted signals and to bypass a portion of converted signals wherein the bypassed signals have frequencies higher than the frequencies of the blocked signals; wherein said sampling includes shunting one end of said capacitor to a first impedance using a shunt switch which is closed in said first mode; and wherein said filtering includes coupling said end of said capacitor to an output having a second impedance greater than that of said first impedance, using a series switch which is closed in said second mode wherein said shunt switch is open in said second mode.