Method and apparatus for reducing FM audio artifacts in a receiver

摘要

An apparatus and method for reducing FM audio artifacts in a receiver are provided. A direct conversion radio frequency (RF) receiver converts an analog FM signal into a phase shifted digital low IF signal. A digital controller coupled to the analog FM receiver provides adaptive frequency translation for different channel spacing and provides adaptive low IF configuration through the different channel spacing, thereby suppressing audio artifacts.

主权项

1. A radio receiver, comprising:
an antenna for receiving a frequency modulated (FM) signal separated from other signals by a channel spacing; a radio frequency (RF) filter for filtering the FM signal into a filtered signal; a low noise amplifier (LNA) for amplifying the filtered signal into an amplified signal; a local oscillator for digitally generating a first LO injection signal and a second LO injection signal which are phase offset, the first and second LO injection signals also being frequency shifted based on the channel spacing; an analog quadrature mixer for generating low IF I/Q signals in response to the amplified signal being mixed with the frequency shifted LO injection signals; a first path for processing the low IF I signal through a low pass filter, an analog-to-digital converter and a digital filter to generate a low IF digital signal (ILIF); a second path for processing the low IF Q signal through a low pass filter, an analog-to-digital converter and a digital filter to generate a low IF digital signal (QLIF); an adaptive frequency translator for adaptively frequency offsetting the low IF digital signal (ILIF) and low IF digital signal (QLIF) into a baseband signal without amplitude and phase imbalance by: applying, to the low IF digital signal (ILIF) , a first predetermined frequency offset for 12.5 kHz channel spacing, applying a second predetermined frequency offset for 20 kHz channel spacing and by applying a third predetermined frequency offset for 25 kHz channel spacing; and applying, to the low IF digital signal (QLIF), the first predetermined frequency offset for 12.5 kHz channel spacing and by the second predetermined frequency offset for 25 kHz channel spacing.