FM data-system radio receiver
AssigneeAllegro MicroSystems, LLC
InventorOliver L. Richards, Jr.
Life of this patent
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Abstract
An FM stereo radio data-system receiver has a front end including an FM discriminator that produces a composite signal composed of an AM stereo signal, including a 19 KHz pilot, and an AM digital-data signal. A dual-bandwidth phase locked loop (PLL) locks onto the pilot and serves both, as the decoder of the stereo portion of the composite signal, and as a generator of a strong stable 38 KHz carrier for use in regenerating the bit rate clock signal and for decoding the data-symbol signal of the digital-data portion of the composite signal. Advantages include economy of circuitry, a simpler and less costly high pass filter, and greater reliability in the decoding of the data signal.
Claims10
An FM radio data-system receiver having a radio-receiver front-end circuit means for receiving an FM broadcast signal modulated by an audio and digital-data signal, and for producing at a composite-signal output conductor, a composite signal including a pilot signal and a AM dual side band digital-data signal with a suppressed carrier, wherein the improvement comprises:
- a) a pilot-signal retrieval circuit means having an input connected to said composite-signal conductor, for generating at a first data-carrier output a first stable signal of frequency that is an exact multiple of the pilot signal frequency and corresponds to the frequency of the suppressed carrier, said first stable signal having a fixed phase relationship with the pilot signal;
- b) a demodulator means, connected to said pilot-signal retrieval circuit means and connected to said composite-signal conductor, for recovering and producing at a demodulator output, with respect to said first stable signal, the data-symbol signal from the data-signal portion of the composite signal;
- and
- c) a bit-rate clock recovery circuit means connected to said pilot-signal retrieval means, and connected to said demodulator output, for re-generating the bit-rate clock signal from the data-signal portion of the composite signal.
An FM radio data-system receiver comprising:
- a) a radio-receiver front-end circuit means for receiving a FM broadcast signal modulated by an audio and digital-data signal and for producing at a front-end output a composite signal including a 19 KHz pilot signal and a dual-side-band AM-modulated digital data signal with a suppressed 57 KHz carrier;
- b) a pilot-signal retrieval circuit means, connected to said front-end circuit means, for selectively retrieving the pilot signal and for generating at first and second outputs, respectively, a relatively noise-free 19 KHz signal and a stable 57 KHz signal both of which are in phase with said pilot signal;
- c) a 57 KHz demodulator means having a modulated-signal input connected to said front end output, and having a reference input connected to said second output of said pilot-signal retrieval circuit means, for recovering the data-symbol signal from the composite signal;
- d) a divider and phase-error detector means connected to the output of said demodulator means and to said first output of said pilot-signal retrieval circuit means, for frequency dividing the noise-free 19 KHz signal and for recovering and producing the bit-rate clock signal from the data-band portion of the composite signal.
An FM radio data-system receiver having a radio-receiver front-end circuit means for receiving an FM broadcast audio plus digital-data signal, and for producing at a composite-signal output conductor a composite signal including an audio pilot signal and a dual-side-band digital data signal with a suppressed carrier, wherein the improvement comprises:
- a) a pilot-signal retrieval circuit means having an input connected to said composite-signal conductor, for generating at a pilot output a relatively noise free pilot signal that is of the same frequency as, and in phase with, the pilot-signal part of said composite signal, and for generating at a first data-carrier output a first stable signal of frequency that is an exact multiple of the pilot signal and corresponds to the frequency of the suppressed carrier, said first stable signal having a fixed phase relationship with the noise free pilot signal;
- b) a demodulator means having a data-carrier input connected to said first data-carrier output of said pilot-signal retrieval circuit means, and having a data-signal input connected to said composite signal conductor, for recovering and producing at a demodulator output the data-symbol signal from the data-signal portion of the composite signal;
- and
- c) a bit-rate clock recovery circuit means having a pilot-reference input connected to the pilot output of said pilot-signal retrieval means, and having a data-symbol input connected to said demodulator output, for re-generating the bit-rate clock signal from the data-signal portion of the composite signal.
Dependencies are inferred from the claim text.