Broadband high efficiency amplifier system

A method for generating a modulated radio frequency (RF) output signal representing a baseband input signal comprising:

• digitizing a sample of the baseband input signal to provide an N-bit digital signal representing an amplitude of the baseband input signal, where N is an integer greater than one;
• providing an RF carrier signal to each of N amplifier assemblies;
• operating each of the N amplifier assemblies according to the value of a corresponding bit within the N-bit word, such that a given amplifier assembly is active when its associated bit assumes a first value and mute when its associated bit assumes a second value;
• selectively applying a phase shift to the RF carrier signal provided to each of a first N−1 of the N amplifier assemblies, the applied phase shift associated with a given amplifier assembly being determined as a function of the values of all bits within the N-bit digital signal that are more significant than the bit associated with the given amplifier assembly;
• and
• combining the outputs of the N amplifier assemblies to construct the modulated RF output signal.

A system for generating a modulated radio frequency (RF) output signal representing a baseband input signal, the system comprising:

• a digitizer configured to sample the baseband input signal and produce a digital signal representing a linear function of the signal amplitude;
• an RF signal source configured to produce an RF carrier signal;
• a plurality of amplifier assemblies, each comprising at least one amplifier configured to receive the RF carrier signal as an input and amplify the RF carrier signal only when a corresponding bit of digital signal assumes a first value
• a plurality of continuous phase shifters configured to delay the RF carrier signal to account for differences in path length between the RF signal source and each of the plurality of amplifier paths;
• and
• a power combiner assembly configured to combine the output signals of the plurality of amplifier assemblies to provide the modulated RF output signal, the power combiner assembly comprising a series of hybrid combiners, an output port of each hybrid combiner in the series, other than a final hybrid combiner in the series, being connected to an isolation port of a subsequent hybrid combiner in the series.