Dynamic Phase Modulation in Dual-Input Doherty Amplifiers

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Solution Overview

Problem

Doherty amplifiers face challenges in achieving high efficiency and linearity due to load modulation and static phase differences between carrier and peaking amplifiers, leading to non-linear distortions and inefficiencies.

Innovation Solution

A phase-reconfigurable circuit with dynamic phase modulation is introduced, which dynamically adjusts the phase difference between the carrier and peaking amplifiers based on the input signal power, using vector-sum phase shifters and envelope detection to improve linearity and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a power amplifier is biased for good efficiency at the average power of the transmitted signal, then efficiency is improved, but linearity deteriorates because the amplifier clips or saturates during peak power moments

Engineering Contradiction:

Improveamplifier efficiencyVSAvoidsignal linearity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The amplifier is divided into two independent amplifiers (carrier amplifier and peaking amplifier) that operate at different power levels. The carrier amplifier handles average power operations with high efficiency biasing, while the peaking amplifier handles peak power operations to maintain linearity, thus resolving the contradiction between efficiency and linearity through functional segmentation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between carrier amplifier and peaking amplifier based on the instantaneous power level of the input signal. An envelope detector monitors the signal power and controls the switching mechanism, allowing the system to adapt its operating mode in real-time to maintain both efficiency and linearity under varying signal conditions.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If a power amplifier is biased for good efficiency at the peak power, then efficiency is improved, but linearity deteriorates because the amplifier is inefficient at average power level

Engineering Contradiction:

Improveamplifier efficiencyVSAvoidsignal linearity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each amplifier is biased optimally for its specific operating range: the carrier amplifier is biased for high efficiency at average power levels, while the peaking amplifier is biased for linearity at peak power levels. This local optimization of biasing conditions allows each component to perform its specific function with high effectiveness.

Inventive Principle:

Principle #3Local quality

3Device complexity

If a traditional Doherty amplifier uses a fixed phase difference of −90° between carrier and peaking amplifiers, then the amplifier structure is simple, but performance deteriorates because it cannot adapt to varying signal conditions

Engineering Contradiction:

Improvephase-shifter complexityVSAvoidamplifier performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The phase-shifter is transformed from a static fixed-phase component to a dynamic variable-phase component that can adjust the phase difference between carrier and peaking amplifier inputs based on the instantaneous power level. This dynamic adjustment capability allows the amplifier to maintain optimal performance across different operating conditions while managing complexity through controlled adaptability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

An envelope detector monitors the instantaneous power level of the input signal and provides feedback to the variable phase-shifter. This feedback mechanism enables the phase difference to be automatically adjusted in response to signal conditions, optimizing amplifier performance without requiring complex manual tuning or control systems.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20250096734A1Phase-Reconfigurable Circuits with Dynamic Phase Modulation for Wideband Dual-Input Power Amplifiers

Publication Date: 2025.03.20 QUALCOMM INC

AI summary

A phase-reconfigurable circuit for a dual-input power amplifier is provided. The circuit includes an envelope detector configured to process an envelope of an RF input signal into an envelope signal. A first vector-sum phase-shifter and a second vector-sum phase-shifter processes an in-phase and a quadrature-phase version of the RF input signal with the envelope signal to produce a first differential output signal having a dynamically-modulated phase difference with a second differential output signal.