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 encoding multi-bit features into sinusoidal waveforms at selected phase angles. The method includes receiving input digital data and encoding the input digital data in a sinusoidal waveform by modulating the sinusoidal waveform at selected phase angles within a period of the sinusoidal waveform, thereby creating a modulated sinusoidal waveform. An encoded analog waveform is generated, using a digital-to-analog converter, from a digital representation of the modulated sinusoidal waveform. The modulating includes forming a first data notch at a first phase angle of the selected phase angles wherein the first data notch includes a first plurality of transition features and subtends a first phase angle range about the first phase angle, the first plurality of transition features being representative of a first plurality of bit values included within the input digital data.

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 multi-carrier data communications system and method having high spectral efficiency. The method includes encoding input digital data at selected phase angles of a plurality of sinusoidal waveforms to create a plurality of modulated sinusoidal waveforms. An output analog waveform is generated where the output analog waveform includes a plurality of encoded analog communication signals corresponding to a plurality of digital representations of the plurality of modulated sinusoidal waveforms. The encoding is performed so that adjacent ones of the plurality of modulated sinusoidal waveforms are separated in frequency by less than 15 Hz and any sideband included within the output analog waveform is of a power at least 50 dB below a power of the encoded analog communication signal associated with the sideband.

A fully integrated power amplifier (PA) employing a transformer combiner with enhanced back-off efficiency includes a first PA to amplify a first radio frequency (RF) signal and a second PA to amplify a second RF signal. A first variable capacitor is coupled between differential output nodes of the first PA. A second variable capacitor is coupled between differential output nodes of the second PA. The differential outputs of the first PA and the second PA are coupled via respective first and second transformers to a load. Capacitance values associated with the first and second variable capacitors are dynamically adjustable based on an amplitude of the RF signal to achieve a desired power efficiency at an output power level.

A fully integrated power amplifier (PA) employing a transformer combiner with enhanced back-off efficiency includes a first PA to amplify a first radio frequency (RF) signal and a second PA to amplify a second RF signal. A first variable capacitor is coupled between differential output nodes of the first PA. A second variable capacitor is coupled between differential output nodes of the second PA. The differential outputs of the first PA and the second PA are coupled via respective first and second transformers to a load. Capacitance values associated with the first and second variable capacitors are dynamically adjustable based on an amplitude of the RF signal to achieve a desired power efficiency at an output power level.

The invention provides a sigma-delta modulator (SDM) and associated system improving spectrum efficiency of wired interconnection. The SDM may comprise a main circuit for transferring an aggregated signal by a signal transfer function, and a noise shaping circuit for shaping noise away from a low-pass band by a modified noise transfer function. A frequency response of the modified noise transfer function may have a notch at a passband, and the passband may not overlap with the low-pass band.

A level shift circuit lowers a voltage of a first differential signal by a second voltage value and outputs a lowered first differential signal as a second differential signal. A first differential circuit receives the first differential signal and outputs a third differential signal. A second emitter follower circuit receives the third differential signal at a base of a pair of second transistors. A second differential circuit receives the second differential signal at a base of a pair of third transistors. An output terminal is electrically connected to one of a first output node electrically connected to an emitter of the one of the second transistors and a collector of the one of the third transistors and a second output node electrically connected to an emitter of the another of the second transistors and a collector of the another of the third transistors and outputs a driving signal.

A level shift circuit lowers a voltage of a first differential signal by a second voltage value and outputs a lowered first differential signal as a second differential signal. A first differential circuit receives the first differential signal and outputs a third differential signal. A second emitter follower circuit receives the third differential signal at a base of a pair of second transistors. A second differential circuit receives the second differential signal at a base of a pair of third transistors. An output terminal is electrically connected to one of a first output node electrically connected to an emitter of the one of the second transistors and a collector of the one of the third transistors and a second output node electrically connected to an emitter of the another of the second transistors and a collector of the another of the third transistors and outputs a driving signal.

Disclosed herein is a method including receiving a stream of packets into a buffer, each packet having a processed video data portion and a page count portion, the processed video data portion being a result of a modulo operation performed on a word of video data, and the page count portion being a data page number on which the word of video data is to be placed. Each packet is read from the buffer, and an output packet including the video data portion and a data tag portion is generated therefrom. The data tag portion is associated with, but does not directly represent, the data page number where the word of video data of the processed video data portion or of video data of a processed video data portion of a next packet, is to be placed. Each data tag portion contains fewer bits than each corresponding page count portion.