Doherty power amplifier with tunable impedance load

摘要

Radio frequency (RF) amplification devices are disclosed that include Doherty amplification circuits and control circuits along with methods of operating the same. In one embodiment, the Doherty amplification circuit includes a quadrature coupler having an isolation port and a tunable impedance load coupled to the isolation port and configured to provide a tunable impedance. The control circuit is configured to tune the tunable impedance of the tunable impedance load at the isolation port dynamically as a function of the RF power of the Doherty amplification circuit. In this manner, the control circuit can provide dynamic load modulation, thereby increasing the power efficiency of the Doherty amplification circuit, particularly at backed-off power levels. The load modulation provided by the control circuit also allows the Doherty amplification circuit to provide broadband amplification in various RF communication bands.

主权项

1. A radio frequency (RF) amplification device comprising:
a Doherty amplification circuit that functions as a Doherty amplifier and configured to amplify an RF signal, wherein the Doherty amplification circuit includes a main RF amplifier, a peaking RF amplifier, a quadrature coupler and a tunable impedance load configured to provide a tunable impedance, wherein the main RF amplifier is coupled to the quadrature coupler, the peaking RF amplifier is coupled to the quadrature coupler, the quadrature coupler has an isolation port and the tunable impedance load is coupled to the isolation port of the quadrature coupler, and wherein the peaking RF amplifier is configured to be deactivated while the RF signal is below a threshold level and is configured to be activated while the RF signal is above the threshold level and the main RF amplifier is configured to be activated while the RF signal is below the threshold level and above the threshold level; and a control circuit configured to dynamically detect RF power of the Doherty amplification circuit and dynamically tune the tunable impedance of the tunable impedance load as a function of the RF power of the Doherty amplification circuit such that a load impedance presented by the quadrature coupler to the main RF amplifier is approximately equal to double a characteristic amplifier impedance of the Doherty amplification circuit while the peaking RF amplifier is deactivated and the main RF amplifier is activated.