Doherty Power Amplifier Using Even-Order Harmonic Load Modulation

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Solution Overview

Problem

Existing Doherty Power Amplifiers face limitations in power added efficiency due to the limited power level of odd order harmonic components and wastage of even order harmonic components, which are shorted to ground, and the degradation of efficiency caused by output parasitic effects.

Innovation Solution

A Doherty Power Amplifier design that realizes even order harmonic load modulation by feeding even order harmonic components to the drain of the amplifier, using quarter wavelength transmission lines and capacitors to short these components to ground, thereby increasing efficiency by utilizing higher power level even order harmonics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If even order harmonic components are shorted to ground in traditional Doherty PAs, then circuit simplicity is maintained, but power added efficiency deteriorates due to wastage of high power level even order harmonics

Engineering Contradiction:

Improvepower added efficiencyVSAvoidharmonic control circuitry complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

Instead of shorting even order harmonics to ground as in traditional designs, the patent inverts this approach by feeding even order harmonic components from one amplifier to the drain of the other amplifier. This inversion allows utilization of the high power level even order harmonics for improving power added efficiency while avoiding the need for complex harmonic control circuitry.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent employs self-service by using the amplifiers' own generated even order harmonic components to improve overall system efficiency. Each amplifier's even order harmonics are fed to the other amplifier's drain, allowing the system to utilize its own harmonic byproducts rather than discarding them, thereby improving power added efficiency without external harmonic control circuitry.

Inventive Principle:

Principle #25Self-service

2Loss of energy

If odd order harmonic load modulation is used, then some efficiency improvement is achieved, but power added efficiency is limited due to low power level of odd order harmonic components

Engineering Contradiction:

Improvepower added efficiencyVSAvoidpower level of harmonic components

Core Design Contradiction:

Loss of energyVSPower

Solution Approach 1:

The patent changes the parameter of which harmonic order is utilized for load modulation. Instead of using odd order harmonics with lower power levels, the patent switches to utilizing even order harmonics which have higher power levels. This parameter change from odd to even order harmonics directly addresses the limitation of low power level while achieving efficiency improvement.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If complex harmonic control circuitry is implemented, then precise harmonic termination is achieved, but development and verification efforts increase significantly

Engineering Contradiction:

Improveharmonic termination precisionVSAvoiddevelopment and verification effort

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts and eliminates the need for complex harmonic control circuitry by using a simplified topology where even order harmonics are directly fed between amplifiers through transmission lines. This extraction of the complex control circuitry maintains reliable harmonic termination through the inherent properties of the Doherty structure while significantly reducing development and verification efforts.

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the power added efficiency of the Doherty Power Amplifier by leveraging the higher power level of even order harmonic components, achieving higher efficiency compared to traditional odd order harmonic load modulation methods.

Implementation Method 1

a first quarter wave length transmission line TLd0 which is configured to couple the drain of the first amplifier and the drain of the second amplifier and feed the first even order harmonic components to the drain of the second amplifier

Methodology Applied

Scientific EffectElectromagnetic wave propagation: Electromagnetic Induction

Implementation Method 2

a third quarter wavelength transmission line TLp which is configured to couple the output terminal of the second amplifier and ground by connecting in series with a first capacitor C4. The first even order harmonic components are shorted to ground through a signal path via the first quarter wavelength transmission line TLd0, the second quarter wavelength transmission line TLmp, the third quarter wavelength transmission line TLp, and the first capacitor C4

Methodology Applied

Scientific EffectCapacitive reactance: Capacitance

Data Source

PatentUS11146215B2Doherty power amplifier, controlling method and device

Publication Date: 2021.10.12 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Disclosed are a Doherty power amplifier (2), a controlling method and a device. In the Doherty power amplifier (2), the even order harmonic components can be fed to the drain of the amplifier to realize even order harmonic modulation. The even order harmonic components have higher power level than the odd order harmonic components, therefore, higher efficiency could be achieved.