Abstract: A radio-frequency identification (RFID) tag reader interrogates a passive RFID tag by transmitting a signal to the tag, then detecting a much weaker reply at the same carrier frequency from the tag. Unfortunately, self-interference caused by signal leakage within the reader or crosstalk among the reader's antenna elements can make the reply more difficult to detect and limit the range at which the reader can sense tags. A self-interference cancellation circuit in the reader reduces or suppresses the effects of signal leakage and crosstalk, enabling detection of weaker tag replies. The self-interference cancellation circuit can calibrate itself before each transmission to ensure good performance. This improves the reader's sensitivity, increases the reader's range, reduces the reader's power consumption, and/or reduces the minimum required dynamic range of the analog-to-digital converters (ADCs) that digitize the received tag replies.