FM analog demodulator compatible with IBOC signals

摘要

A method includes: receiving an FM radio signal including an analog-modulated portion; digitally sampling an analog-modulated portion of the radio signal to produce a plurality of samples; using a ratio between an average magnitude and an RMS magnitude of a block of the samples to compute a signal quality metric; detecting sum and difference components of the baseband multiplex signal content; using the baseband content to produce an output signal; and blending the output signal from stereo to monaural as the signal quality metric falls below a threshold value.

主权项

1. A method comprising:
receiving an in-band on-channel radio signal including an analog-modulated portion and a digitally modulated portion; approximating a derivative of a phase of the radio signal by sampling the radio signal to produce a plurality of successive complex signal samples and determining a phase difference between successive ones of the complex signal samples representing the analog FM signal; using the phase difference to obtain an FM baseband multiplex signal, wherein approximating the derivative results in an error in a non-flat frequency response of a differentiator output; and compensating for gain loss in a stereo difference signal portion located in a bandwidth from 23 to 53 kHz of the FM baseband multiplex signal with a constant gain to correct for the error resulting from approximating the derivative of the phase of the radio signal.