Polyphase PDM amplifier

An amplifier for providing high fidelity amplification of an amplitude and frequency varying input signal, comprising:

• means for providing such amplitude and frequency varying input signal;
• means responsive to said amplitude and frequency varying input signal for converting said signal into a plurality of pulse trains of like frequencies, but differing in phase from one another by a fixed amount, said pulse trains having pulses which vary in duration in functional dependence upon the magnitude and polarity of said input signal, said functional dependence being common to at least two of said pulse trains;
• and,
• means for combining said plurality of pulse trains into a composite signal of increased magnitude and of substantially the same waveform as said amplitude and frequency varying input signal, whereby high fidelity amplification of said amplitude and frequency varying signal is provided.

A pulse duration modulation amplifier comprising:

• a plurality of pulse duration modulators, each responsive to a respective synchronizing signal and to a common input signal, for each providing a pulse train comprising periodically occurring pulses having pulse widths modulated in accordance with said common input signal;
• means for providing synchronizing signals to each of said plurality of pulse duration modulators for controlling the timing of operation thereof so that said pulse trains provided by said modulators all have substantially the same pulse repetition rate but have different relative phases whereby each of said pulse duration modulators effectively serves to sample said common input signal at different times;
• an output circuit;
• and
• a like plurality of switching circuits coupled to said output circuit, each of said switching circuits operative to control the supply of an incremental signal to said output circuit, and each responsive to a corresponding said pulse train for controlling the operation thereof so as to thereby combine said outputs signals to provide a composite signal, corresponding to an amplified said input signal, to said output circuit;
• wherein said switching circuits are connected in parallel with one another, and wherein said parallel connected switching circuits are connected in series with said output circuit across a DC power supply.

A high efficiency RF amplitude modulation system comprising:

• an RF carrier signal generator;
• an RF modulator responsive to said RF carrier signal and to an amplified signal for modulating said RF carrier signal in accordance therewith;
• and,
• amplifier means responsive to an input signal for supplying said amplified signal to said RF modulator, including at least two pulse modulators for each supplying an output signal comprising periodically occurring pulses which are modulated in accordance with said input signal, said output signals having substantially the same pulse repetition rate but differing in phase by a fixed amount, and means for amplifying and combining said output signals so as to thereby derive said amplified signal to be supplied to said RF modulator.

A method of amplifying an amplitude and frequency varying input signal comprising the steps of:

• providing a selected number of switching circuits;
• connecting said circuits to a load such that the operation of each circuit serves to control the supply of an incremental signal to said load;
• converting said amplitude and frequency varying input signal into a number of pulse trains corresponding to the number of said switching circuits, with each pulse train being composed of periodic pulses which vary in duration in functional dependence upon said input signal, said pulse trains having a common selected repetition rate, but having fixed discrete phase displacements therebetween and said functional dependence being common to at least two of said pulse trains;
• and,
• controlling the operation of each of said switching circuits with a corresponding said pulse train whereby said load is supplied with a composite signal comprised of a combination of said pulse trains, said composite signal having the same waveform as said input signal but of greater magnitude.