Patent ID: 6725023
Filing Date: 2004-04-20
Classification: H03D,H03J,H04B

Abstract:
A radio FM receiver comprising:a receiver portion for converting received radio frequency signals into center frequency quadrature signals; a center frequency filter circuit connected to said receiver portion for suppressing undesirable image frequencies; and a quadrature PLL (phase-locked loop) demodulator having a VCO (voltage-controlled oscillator) for demodulating the obtained center frequency quadrature signals, said PLL being attuned to the carrier frequency within the selected frequency band, characterized in that said radio FM receiver further comprises: an error detector for detecting amplitude and phase errors in the quadrature channels; and a quadrature channel correction network coupled between said filter circuit and the quadrature PLL demodulator, said error detector, in response to the quadrature components of the center frequency signals, the quadrature signals of the VCO in the quadrature PLL demodulator, and the filtered difference of said quadrature components of the center frequency signals, supplying amplitude and phase correction signals to said quadrature channel correction network.