Wide-band baseband 90 phase shifting circuit and FSK radio receiver having the same.

摘要

An FSK radio receiver of direct conversion type, which derives baseband in-phase and phase quadrature signals from a received FSK RF signal in respective mixers by applying local oscillator signals to the mixers differing in phase by 90<o>, in which wide-band baseband 90<o> phase shifting circuits formed of only digital logic elements (11, 14), (13, 12) phase shift the in-phase and phase quadrature signals to enable a demodulated digital data signal to be obtained by subsequent digital processing. In that processing, signals having a frequency that is double that of the in-phase and phase quadrature signals are derived and used to derive the demodulated data signal, ensuring high accuracy of detection and lowering the accuracy required for the local oscillator frequency.