Quadrature Doherty Amplifier Balancing for Load Mismatch Linearity

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Solution Overview

Problem

Doherty amplifiers face challenges in maintaining linearity and efficiency when driving mismatched loads, leading to increased adjacent channel leakage ratio (ACLR) and out-of-band emissions, particularly due to the imbalance between carrier and peaking amplification stages.

Innovation Solution

The implementation of a quadrature combined Doherty amplifier, which separates the RF input signal into pairs of input signal components with quadrature phase relationships and uses cascode amplification stages in both the carrier and peaking amplifiers, along with a combiner to generate an RF output signal, thereby achieving balanced amplification and reducing distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional Doherty amplifier configuration is used, then power amplification is achieved, but linearity and efficiency deteriorate when driving mismatched loads due to imbalance between carrier and peaking amplification stages

Engineering Contradiction:

ImprovelinearityVSAvoidamplification stage imbalance

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The amplifier is divided into two separate Doherty amplifier paths, each with its own carrier and peaking amplification stages. This segmentation allows independent optimization and balancing of each path, resolving the imbalance issue while maintaining power amplification capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Two Doherty amplifier paths are combined in parallel configuration with their outputs summed at the output node. This merging approach maintains the power amplification benefits while the balanced design of each individual path improves linearity and efficiency under mismatched load conditions.

Inventive Principle:

Principle #5Merging (Combining)

2Power

If traditional Doherty amplifier is used, then power amplification is provided, but adjacent channel leakage ratio and out-of-band emissions increase due to load mismatch distortion

Engineering Contradiction:

Improvepower amplificationVSAvoidadjacent channel leakage ratio

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

By segmenting the power amplification into two separate Doherty paths, each path can be independently optimized to minimize distortion. This reduces the generation of harmful spectral emissions while maintaining the required power amplification level.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the potential harm of load mismatch by using balanced amplifier paths that are less sensitive to mismatches. The dual-path configuration inherently provides distortion cancellation, transforming what would be a harmful effect into a benefit by reducing adjacent channel leakage and out-of-band emissions.

Inventive Principle:

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

3Reliability

If quadrature combined Doherty amplifier configuration is implemented, then distortion from load mismatch is reduced, but device complexity increases due to additional amplification stages and combiner

Engineering Contradiction:

Improvedistortion reductionVSAvoidamplification stages and combiner structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The complex function of distortion reduction is achieved by segmenting the amplifier into two independent Doherty paths, each handling specific signal components. This modular segmentation makes the complex function manageable and implementable with standardized amplifier building blocks.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each Doherty amplifier path serves multiple functions: power amplification, distortion reduction, and load mismatch compensation. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while achieving distortion reduction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Manufacturing precision

If balanced amplification stages are used in quadrature combined Doherty amplifier, then linearity improves, but manufacturing complexity increases

Engineering Contradiction:

Improveamplification balanceVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

By segmenting the amplifier into two identical Doherty paths, the manufacturing process can be standardized and replicated. This segmentation into modular units makes it easier to achieve consistent balance and linearity across production, as each module can be independently tested and calibrated.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses parameter changes in the amplifier design, specifically in the biasing and impedance matching networks of each Doherty path, to achieve balanced operation. These parameter adjustments are designed to be manufacturable with standard components and processes, balancing manufacturing precision requirements with ease of manufacture.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11502646B2Quadrature combined Doherty amplifiers

Publication Date: 2022.11.15 SKYWORKS SOLUTIONS INC

AI summary

Apparatus and methods for quadrature combined Doherty amplifiers are provided herein. In certain embodiments, a separator is used to separate a radio frequency (RF) input signal into a plurality of input signal components that are amplified by a pair of Doherty amplifiers operating in quadrature. Additionally, a combiner is used to combine a plurality of output signal components generated by the pair of Doherty amplifiers, thereby generating an RF output signal exhibiting quadrature balancing.