Multi-Way Doherty Amplifier Without Input Power Splitters

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Solution Overview

Problem

Existing Doherty power amplifiers face efficiency degradation when operating below peak powers due to high Peak-to-Average Power Ratio (PAPR) signals, and they require bulky input power splitters which increase circuit size and loss, leading to non-uniform power gain and insufficient load modulation.

Innovation Solution

A multi-way Doherty amplifier configuration that eliminates the need for input power splitters by using impedance converters and adaptive power distribution, allowing for proper load impedance modulation across the dynamic range and enabling uniform power gain without additional couplers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If traditional class-AB amplifiers are used for high PAPR signals, then the amplifier can handle the peak power requirements, but efficiency is seriously degraded when operating below peak powers

Engineering Contradiction:

Improveamplifier efficiencyVSAvoidoperating power range

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The amplifier is segmented into multiple parallel paths with different amplifier stages (e.g., Class C, Class AB, Class A) that operate at different power levels. Each path handles specific power ranges, allowing the system to maintain high efficiency across the entire operating range by selecting the appropriate path for the current signal level.

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If Doherty amplifier structure is used to improve efficiency, then efficiency is improved over extended input signal range, but the structure requires bulky input power splitters which increase circuit size and loss

Engineering Contradiction:

Improveamplifier efficiencyVSAvoidcircuit structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The input power splitter is extracted and replaced with a simplified input distribution network that uses impedance transformation and direct signal routing. This eliminates the need for bulky hybrid couplers while maintaining the essential function of distributing input power to multiple amplifier paths.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using a traditional power splitter at the input to divide power among amplifiers, the invention inverts the approach by using a power combiner at the output to combine signals from amplifiers that receive the full input signal. This reverses the signal flow architecture and eliminates the need for input power division.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of operation

If input power splitters are used to distribute input power to main and peak amplifiers, then power distribution is achieved, but circuit size increases and power gain becomes non-uniform

Engineering Contradiction:

Improvepower distributionVSAvoidpower gain uniformity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The power distribution is made dynamic through automatic level control (ALC) or envelope tracking that adjusts the operating point of amplifiers based on the instantaneous signal level. This dynamic adjustment ensures uniform power gain across different operating conditions without requiring precise fixed power splitting ratios.

Inventive Principle:

Principle #15Dynamics

4Use of energy by moving object

If multiple peak amplifiers are added to create multi-way Doherty configuration, then efficiency at different back-off power levels is improved, but device complexity and circuit size increase

Engineering Contradiction:

Improveefficiency at back-off power levelsVSAvoidnumber of amplifiers

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

Multiple amplifier paths serve multiple functions: they provide both power amplification and automatic load modulation. Each amplifier path can operate independently or in combination with others, allowing the system to achieve multiple efficiency peaks at different back-off power levels while using the same hardware infrastructure for both power generation and efficiency optimization.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8988147B2Multi-way Doherty amplifier

Publication Date: 2015.03.24 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The present disclosure provides a multi-way Doherty amplifier that includes an amplifier input, an amplifier output, a main amplifier having an input connected to the amplifier input, and at least a first and a second peak amplifier. In the Doherty amplifier, an input of the first peak amplifier is connected to the amplifier input or an output of the main amplifier, and an input of the second peak amplifier is connected to the amplifier input, the output of the main amplifier or an output of the first peak amplifier. The Doherty amplifier further comprises a first impedance converter connected between the output of the main amplifier and the amplifier output, a second impedance converter connected between the output of the first peak amplifier and an output of the second peak amplifier, and a third impedance converter connected between the output of the second peak amplifier and the amplifier output.