Doherty Power Amplifier Biasing for Peak Power and Backoff Efficiency

The patent applies dynamic biasing by transitioning the peaking amplifier from a fixed class C bias to a dynamic bias scheme where the bias voltage is adjusted in real-time based on the signal envelope. The bias voltage transitions from a lower class C bias during low-power operation to a higher class AB/BC bias during peak power operation, enabling the system to optimize power backoff efficiency at low power while achieving sufficient peak output power when needed.

The patent changes the bias voltage parameter dynamically based on operating conditions. By modifying the bias voltage from a fixed value to a time-varying parameter that adapts to the signal envelope, the system achieves both high power backoff efficiency (when bias is low in class C) and high peak output power (when bias is raised to class AB/BC during peaks).

Instead of using a static high bias (class AB) that degrades power backoff efficiency, the patent employs dynamic biasing where the peaking amplifier operates in class C during low-power conditions (maintaining high power backoff efficiency) and transitions to class AB/BC only during peak power conditions (providing sufficient peak output power). This dynamic adaptation eliminates the need for continuous high bias.

The bias voltage is modulated periodically or continuously according to the signal envelope characteristics. During most of the time (low-power regions), the bias remains at the efficient class C level, and during peak periods, it transitions to class AB/BC to provide adequate peak output power, thus achieving both goals through periodic/burst-mode operation.