Method and system for simultaneously broadcasting and receiving digital and analog signals

A method for simultaneously transmitting an analog FM signal and a digital signal comprising:

• generating the analog FM signal substantially centered about a center frequency of a predetermined broadcast band;
• generating a plurality of carrier signals within the predetermined broadcast band;
• modulating the plurality of carrier signals with the digital signal to produce digitally modulated waveforms, the digital signal forming a plurality of baud, each of the baud having a length greater than a maximum expected multipath delay;
• combining the analog FM signal and the digitally modulated waveforms to generate a composite signal;
• and
• transmitting the composite signal to at least one receiver.

A method for simultaneously transmitting an analog FM signal and a digital signal comprising:

• generating the analog FM signal substantially centered about a center frequency of a predetermined broadcast band;
• generating a plurality of carrier signals within the predetermined broadcast band;
• amplitude modulating the plurality of carrier signals with the digital signal to produce digitally modulated waveforms, the digital signal forming a plurality of baud, each of the baud having a length greater than a maximum expected multipath delay;
• combining the analog FM signal and the digitally modulated waveforms to generate a composite signal;
• and
• transmitting the composite signal to at least one receiver,
• wherein each of the carrier signals is a predetermined amplitude level below nominal amplitude of the analog FM signal, and wherein the carrier signals are distributed in spectrum around the analog FM signal.

A transmitter for generating a composite signal including an analog FM signal and a digitally modulated signal set, the transmitter comprising:

• an FM modulator for producing the analog FM signal, wherein the analog FM signal is substantially centered about a center frequency of a predetermined broadcast band;
• a signal generator for generating a plurality of carrier signals, wherein the carriers signals are spectrally disposed within the predetermined broadcast band;
• a data modulator coupled to the signal generator, the data modulator being operative to modulate the carrier signals by a digital signal to generate the digitally modulated signal set, the digital signal forming a plurality of baud, each of the baud having a length greater than a maximum expected multipath delay;
• and
• a combiner coupled to the FM modulator and the data modulator, for combining the analog FM signal and the digitally modulated signal set to yield the composite signal, wherein the composite signal is substantially disposed within the predetermined broadcast band.

A receiver for receiving a composite signal including an analog FM signal, a reference signal, and a digitally modulated signal, the composite signal being substantially disposed within a predetermined broadcast band, the receiver comprising:

• a receiver front end for receiving the composite signal;
• a signal separator coupled to the receiver front end, the signal separator being operative to separate the received digitally modulated signal from the received analog FM signal;
• means for averaging the reference signal over a plurality of signal bauds;
• an equalizer coupled to the signal separator for receiving the received digitally modulated signal, and for generating an equalized digital signal, the equalizer including a voltage controlled oscillator responsive to the averaged reference signal;
• and
• a demodulator coupled to the equalizer, the demodulator being operative to demodulate the equalized digital signal and to extract digital data from the equalized digital signal.

A method for producing a digital broadcast signal for transmission and reception comprising:

• frequency modulating a message to generate an FM signal;
• encoding a serial data message into a plurality of interrelated digital subchannel messages;
• generating digital subchannel signals from the digital subchannel messages;
• generating a reference signal having an amplitude less than an amplitude of the digital subchannel signals;
• combining the FM signal with the digital subchannel signals and the reference signal at a transmission point to generate the digital broadcast signal, wherein the digital broadcast signal and the FM signal are substantially disposed within a predetermined broadcast band;
• and
• transmitting the digital broadcast signal to at least one receiver suited to decode at least said serial data message.