FM stereo decoder incorporating Costas loop pilot to stereo component phase correction

A stereo MPX decoder, comprising:

• a pilot recovery phase locked loop (PLL) circuit operative to generate a pilot phase error from an input MPX signal;
• a pilot to stereo component phase recovery circuit operative to extract the phase difference between said MPX signal and a stereo carrier phase signal to yield a pilot to stereo component phase correction signal;
• an adder for summing said pilot to stereo component phase correction signal with a frequency doubled pilot phase error signal to yield said stereo carrier phase signal;
• and
• a mixer operative to multiply said MPX signal with the sine of said stereo carrier phase signal to yield a stereo output signal therefrom.

A stereo MPX decoder, comprising:

• a phase locked loop (PLL) circuit adapted to generate a pilot phase error from an input MPX signal;
• a Costas loop circuit coupled to said PLL and operative to generate a phase correction signal representing the phase difference between a received stereo pilot carrier signal and an expected stereo pilot carrier signal;
• compensating said received pilot carrier signal with said phase correction signal to yield a stereo carrier phase signal;
• and
• means for generating a stereo output signal as a function of said stereo carrier phase signal and said MPX signal.

A stereo MPX decoder, comprising:

• a phase locked loop circuit, comprising:
• a pilot tone phase locked loop (PLL) circuit adapted to generate a pilot phase error from an input MPX signal;
• a Costas loop circuit coupled to said PLL and operative to generate a phase correction signal representing the phase difference between a received stereo pilot carrier signal and an expected stereo pilot carrier signal;
• compensating said received pilot carrier signal with said phase correction signal to yield a stereo carrier phase signal;
• means for generating a stereo output signal as a function of said stereo carrier phase signal and said MPX signal;
• a filter operative to generate a mono output signal from said MPX signal;
• and
• a stereo blend circuit operative to generate a left output signal and a right output signal from said mono output signal and said stereo output signal.

A frequency modulation (FM) radio, comprising:

• an FM demodulator coupled to an antenna and operative to generate an MPX signal from an RF input signal received therefrom;
• a MPX stereo decoder coupled to said FM demodulator, said MPX stereo decoder, comprising:
• a phase locked loop (PLL) circuit adapted to generate a pilot phase error from an input MPX signal;
• a Costas loop circuit coupled to said PLL and operative to generate a phase correction signal representing the phase difference between a received stereo pilot carrier signal and an expected stereo pilot carrier signal;
• compensating said received pilot carrier signal with said phase correction signal to yield a stereo carrier phase signal;
• means for generating a stereo output signal as a function of said stereo carrier phase signal and said MPX signal;
• filter means for generating a mono output signal from said MPX signal;
• and
• a stereo blend circuit operative to generate a left output signal and a right output signal from said mono output signal and said stereo output signal.