Adjustable filtering circuit for use in radio frequency identification reader device, has band-stop filter arranged in downstream side of one of the mixing stages, for suppressing carrier signal in intermediate frequency signal

摘要

The adjustable filtering circuit (300) has an adjustable oscillator (314) that generates an oscillator signal, and input mixing stages (318,320) that mix input signal with the oscillator signal, to generate an intermediate frequency signal. A band-stop filter (322) is arranged in the downstream side of one of the mixing stages, for suppressing carrier signal in the intermediate frequency signal. An independent claim is included for radio frequency identification (RFID) reader device.