Doherty-Chireix combined amplifier

A method of amplifying an RF signal, the method comprising:

• providing an amplifier circuit comprising, a first amplifier, a second amplifier, and a power combiner circuit connected to the first and second amplifiers, the power combiner circuit comprising a Chireix combiner that is configured to present a Chireix load modulated impedance response, and compensation elements;
• operating the amplifier circuit in a Doherty amplifier mode for amplitude values of the RF signal that are at or below a predefined threshold, wherein operating the amplifier circuit in the Doherty amplifier mode comprises:
• generating a first amplified version of the RF signal using the first amplifier while the second amplifier is turned off;
• applying the first amplified version of the RF signal to a first input port of the power combiner circuit;
• and
• compensating for a reactance of the Chireix combiner using the compensation elements;
• operating the amplifier circuit in a Chireix amplifier mode for amplitude values of the RF signal that are above the predefined threshold, wherein operating the amplifier circuit in the Chireix amplifier mode comprises:
• generating a first amplified version of the RF signal using the first amplifier;
• generating a second amplified version of the RF signal using the second amplifier, the second amplified version of the RF signal being out of phase with the first amplified version of the RF signal;
• and
• using the Chireix combiner to combine the first amplified version of the RF signal and the second amplified version of the RF signal and to modulate an impedance seen by the first and second amplifiers across varying power levels of the first and second amplified versions of the RF signal.

A method of amplifying an RF signal using an amplifier comprising first and second amplifier devices, and a power combiner circuit connected to the first and second amplifiers, the power combiner circuit comprising a Chireix combiner that is configured to present a Chireix load modulated impedance response, and compensation elements, the method comprising:

• operating the amplifier in a Doherty amplifier mode when an amplitude of the RF signal is at or below a predetermined threshold, wherein operating the amplifier circuit in the Doherty amplifier mode comprises:
• amplifying the RF signal using the first amplifier device while the second amplifier device is turned off;
• extracting a first amplified RF signal from the first amplifier device using the power combiner circuit;
• and
• compensating for an admittance of the Chireix combiner using the compensation elements so as to increase efficiency of the amplifier circuit;
• operating the amplifier in a Chireix amplifier mode when an amplitude of the RF signal is above the predetermined threshold, wherein operating the amplifier circuit in the Chireix amplifier mode comprises:
• amplifying the RF signal using the first amplifier device and the second amplifier device;
• extracting a first amplified RF signal from the first amplifier device and a second amplified RF signal from the second amplifier device using the power combiner circuit.