Peaking Amplifier Pi-Network for Doherty Phase Distortion Compensation

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Solution Overview

Problem

Doherty amplifiers face challenges in achieving high efficiency and linearity due to significant non-linear input impedance variations in peaking amplifiers, leading to phase/amplitude mismatches and AM/PM distortion, which reduce overall efficiency and power performance.

Innovation Solution

A phase distortion compensation circuit, comprising a Pi-network and control load circuit, is coupled between the inputs of the peaking amplifiers to absorb non-linear input impedance variations, providing phase pre-distortion and maintaining phase alignment between carrier and peaking stages, thus enhancing efficiency and reducing AM/PM distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If Doherty amplifiers use transistors with high theoretical power efficiency, then power efficiency is improved, but linearity deteriorates due to significant non-linear input impedance variations

Engineering Contradiction:

Improvepower efficiencyVSAvoidlinearity

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by introducing a phase pre-distortion circuit that anticipates and compensates for the non-linear input impedance variations before they occur. The circuit pre-adjusts the phase of the input signal to counteract the expected phase distortion, thereby maintaining linearity while preserving the high efficiency of the Doherty amplifier configuration.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary element - a phase pre-distortion circuit comprising reactive components (inductors and capacitors) - that mediates between the input signal and the peaking amplifier. This intermediary circuit absorbs the non-linear input impedance variations and provides phase compensation, allowing the high-efficiency Doherty architecture to operate with improved linearity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If Doherty amplifiers operate at high power levels, then power output is improved, but phase alignment between carrier and peaking stages deteriorates due to input impedance variations

Engineering Contradiction:

Improvepower outputVSAvoidphase alignment

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The phase pre-distortion circuit performs preliminary phase adjustment based on the operating power level. By anticipating the phase shift that occurs at high power levels due to input impedance variations, the circuit pre-compensates the signal phase, ensuring that phase alignment between carrier and peaking stages is maintained throughout the power range.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs parameter changes by using reactive components whose impedance characteristics change with operating conditions. The phase pre-distortion circuit is designed with inductors and capacitors that provide varying phase compensation depending on the power level, dynamically adapting to maintain phase alignment as the amplifier operates across different power outputs.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If peaking amplifiers are designed for high efficiency operation, then overall amplifier efficiency is improved, but AM/PM distortion increases due to non-linear input impedance variations

Engineering Contradiction:

Improveamplifier efficiencyVSAvoidAM/PM distortion

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful non-linear input impedance variations into a beneficial effect by measuring and compensating for them. The phase pre-distortion circuit uses the known characteristics of the peaking amplifier's input impedance to create an equal and opposite phase distortion, thereby canceling out the harmful AM/PM distortion while preserving the efficiency benefits of the high-efficiency peaking amplifier design.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements a form of feedback by designing the phase pre-distortion circuit to account for the actual input impedance behavior of the peaking amplifier. The circuit parameters are selected based on measured or modeled impedance characteristics, creating a compensatory effect that reduces AM/PM distortion while maintaining the efficiency advantages of the Doherty configuration.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11146220B2Amplifier devices with phase distortion compensation and methods of manufacture thereof

Publication Date: 2021.10.12 NXP USA INC

AI summary

The embodiments described herein include amplifiers that are typically used in radio frequency (RF) applications. Specifically, the amplifiers described herein include a phase distortion compensation circuit that can compensate for input impedance variations that could otherwise lead to reduced efficiency and power performance. In one specific embodiment, the phase distortion compensation circuit is used to compensate for input impedance variations in the peaking amplifiers of a Doherty amplifier. In such embodiments, the phase distortion compensation circuit can absorb the non-linear input impedances of the peaking amplifiers in a way that may facilitate improved phase maintenance between the carrier and peaking stages of the Doherty amplifier.