A system and method for narrowband sinewave modulation. The system includes an input buffer for storing input digital data and a sub-periodic modulator for encoding the input digital data in a periodic waveform. The sub-periodic modulator encodes one or more bit values of the input digital data within each period of the periodic waveform. One or more digital-to-analog converters generate an encoded analog waveform from a digital representation of the periodic waveform wherein the encoded analog waveform is of a frequency f and a power P. The encoding is performed by the sub-periodic modulator such that any signal of frequency f resulting from the encoding is of a power P at least 50 dB less than power P, where f is offset from f by more than 25 Hz.

A system and method for narrowband sinewave modulation. The system includes an input buffer for storing input digital data and a sub-periodic modulator for encoding the input digital data in a periodic waveform. The sub-periodic modulator encodes one or more bit values of the input digital data within each period of the periodic waveform. One or more digital-to-analog converters generate an encoded analog waveform from a digital representation of the periodic waveform wherein the encoded analog waveform is of a frequency f and a power P. The encoding is performed by the sub-periodic modulator such that any signal of frequency f resulting from the encoding is of a power P at least 50 dB less than power P, where f is offset from f by more than 25 Hz.

A transmitter-receiver includes an electronic chip a mixer for mixing the frequency of a received radio frequency signal with that of an oscillating signal supplied by a first frequency synthesizer in, a switch having two inputs connected to an output of the mixer and to an auxiliary input terminal, a filter and gain stage connected to the output of the switch, and a modulator-demodulator connected to the output of the filter and gain stage. The first frequency synthesizer is connected between the output of the modulator-demodulator and radio frequency input and output terminal, and configured to supply a frequency-modulated signal to the radio frequency input and output terminal. The electronic chip further includes a second frequency synthesizer connected between the output of the modulator-demodulator and an auxiliary output terminal, and configured to synthesize a modulated low-frequency signal supplied by the auxiliary output terminal, whereby the center value of the low frequency is equal to the value of the intermediate frequency.

A transmitter-receiver includes an electronic chip a mixer for mixing the frequency of a received radio frequency signal with that of an oscillating signal supplied by a first frequency synthesizer in, a switch having two inputs connected to an output of the mixer and to an auxiliary input terminal, a filter and gain stage connected to the output of the switch, and a modulator-demodulator connected to the output of the filter and gain stage. The first frequency synthesizer is connected between the output of the modulator-demodulator and radio frequency input and output terminal, and configured to supply a frequency-modulated signal to the radio frequency input and output terminal. The electronic chip further includes a second frequency synthesizer connected between the output of the modulator-demodulator and an auxiliary output terminal, and configured to synthesize a modulated low-frequency signal supplied by the auxiliary output terminal, whereby the center value of the low frequency is equal to the value of the intermediate frequency.

A transmitter-receiver includes an electronic chip a mixer for mixing the frequency of a received radio frequency signal with that of an oscillating signal supplied by a first frequency synthesizer in, a switch having two inputs connected to an output of the mixer and to an auxiliary input terminal, a filter and gain stage connected to the output of the switch, and a modulator-demodulator connected to the output of the filter and gain stage. The first frequency synthesizer is connected between the output of the modulator-demodulator and radio frequency input and output terminal, and configured to supply a frequency-modulated signal to the radio frequency input and output terminal. The electronic chip further includes a second frequency synthesizer connected between the output of the modulator-demodulator and an auxiliary output terminal, and configured to synthesize a modulated low-frequency signal supplied by the auxiliary output terminal, whereby the center value of the low frequency is equal to the value of the intermediate frequency.

A transmitter-receiver includes an electronic chip a mixer for mixing the frequency of a received radio frequency signal with that of an oscillating signal supplied by a first frequency synthesizer in, a switch having two inputs connected to an output of the mixer and to an auxiliary input terminal, a filter and gain stage connected to the output of the switch, and a modulator-demodulator connected to the output of the filter and gain stage. The first frequency synthesizer is connected between the output of the modulator-demodulator and radio frequency input and output terminal, and configured to supply a frequency-modulated signal to the radio frequency input and output terminal. The electronic chip further includes a second frequency synthesizer connected between the output of the modulator-demodulator and an auxiliary output terminal, and configured to synthesize a modulated low-frequency signal supplied by the auxiliary output terminal, whereby the center value of the low frequency is equal to the value of the intermediate frequency.

A data communications system and method having high spectral efficiency. The method includes encoding input digital data using a plurality of symbol waveforms. Each symbol waveform occupies a period of a composite encoded waveform and represents one or more bits of the input digital data. Each symbol waveform has a first elliptical segment and a second elliptical segment of opposite polarity. The encoding includes defining each symbol waveform so that (i) a zero crossing from the first elliptical segment to the second elliptical segment of the symbol waveform is different for each of the symbol waveforms, and (ii) an energy of the first elliptical segment of the symbol waveform is substantially equal to an energy of the second elliptical segment of the symbol waveform. An encoded analog waveform is generated, using a digital-to-analog converter, from a digital representation of the composite encoded waveform.

A data communications system and method having high spectral efficiency. The method includes encoding input digital data using a plurality of symbol waveforms. Each symbol waveform occupies a period of a composite encoded waveform and represents one or more bits of the input digital data. Each symbol waveform has a first elliptical segment and a second elliptical segment of opposite polarity. The encoding includes defining each symbol waveform so that (i) a zero crossing from the first elliptical segment to the second elliptical segment of the symbol waveform is different for each of the symbol waveforms, and (ii) an energy of the first elliptical segment of the symbol waveform is substantially equal to an energy of the second elliptical segment of the symbol waveform. An encoded analog waveform is generated, using a digital-to-analog converter, from a digital representation of the composite encoded waveform.

A system and method for waveform modulation includes encoding input digital data at selected phase angles of an unmodulated sinusoidal waveform. The encoding includes selectively reducing a power of the unmodulated sinusoidal waveform at the selected phase angles in accordance with bit values of the input digital data so as to respectively define first, second, third and fourth data notches in the modulated sinusoidal waveform. An encoded analog waveform is then generated from a digital representation of the modulated sinusoidal waveform. The encoding is performed so that energies associated with the first and third data notches are balanced and energies associated with second and fourth data notches are also balanced. Each of the energies corresponds to a cumulative power difference between a power of the unmodulated sinusoidal waveform and a power of the modulated sinusoidal waveform over a phase angle range subtended by one of the data notches.

A system and method for waveform modulation includes encoding input digital data at selected phase angles of an unmodulated sinusoidal waveform. The encoding includes selectively reducing a power of the unmodulated sinusoidal waveform at the selected phase angles in accordance with bit values of the input digital data so as to respectively define first, second, third and fourth data notches in the modulated sinusoidal waveform. An encoded analog waveform is then generated from a digital representation of the modulated sinusoidal waveform. The encoding is performed so that energies associated with the first and third data notches are balanced and energies associated with second and fourth data notches are also balanced. Each of the energies corresponds to a cumulative power difference between a power of the unmodulated sinusoidal waveform and a power of the modulated sinusoidal waveform over a phase angle range subtended by one of the data notches.