A method for filtering a received signal rfid reader and reader

The present invention discloses a method and a kind of RFID reader reader filtering the received signal, the method comprising: receiving RF signals from the RFID reader chip of the smart card, and the RF signal output of the quadrature demodulator quadrature Solutions modulated signal; filtered quadrature demodulated signal quadrature-demodulated signal by the first band-pass filter; after the first input signal with the quadrature demodulating pass filter to filter the first amplifier stage a first amplifying stage; quadrature demodulated signal is input to the first amplifying stage of the second band-pass filter, and again filtered by a second bandpass filter; and filtered again through a second bandpass filter quadrature demodulator signal is input to the second stage amplifier amplifying the second level. Embodiments of the present invention, the entire filtering effect by two more thorough filtering, to meet the requirements of the conventional RFID readers, to reduce high frequency noise and low frequency noise, keep useful 800KHz signal.