Doherty Amplifier Output Combiner Using IPDs to Shrink PCB Size

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Solution Overview

Problem

Doherty amplifiers used in 5G Massive MIMO systems face challenges in circuit size and cost due to complex output combiners and matching networks, which are not suitable for compact designs required by multiple channels.

Innovation Solution

A Doherty amplifier design incorporating integrated passive devices (IPDs) and bond wires to replace traditional quarter-wave transmission lines, with phase-shift networks using C-L-C-L-C circuits to achieve 90-degree phase delays, reducing PCB size and cost while maintaining high efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If traditional quarter-wave transmission lines and complex output combiners are used in 3-way Doherty amplifiers, then high efficiency at low traffic state is achieved, but PCB size and circuit complexity increase significantly

Engineering Contradiction:

Improveefficiency at low traffic stateVSAvoidPCB size

Core Design Contradiction:

Loss of energyVSArea of stationary object

Solution Approach 1:

The patent replaces traditional mechanical/transmission line-based quarter-wave transmission lines with electrical equivalent circuits consisting of inductors and capacitors. This substitution allows the same phase-shifting function to be achieved with much smaller footprint components on the PCB, directly resolving the contradiction between maintaining high efficiency and reducing PCB size.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical parameters of the phase-shifting networks by using lumped element LC circuits instead of distributed transmission lines. This parameter change enables the same electrical function (90-degree phase shift) to be achieved with significantly reduced physical dimensions, allowing high efficiency performance to be maintained while PCB area is reduced.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If 3-way Doherty amplifier circuits with complex output combiners are implemented, then high efficiency is achieved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improveefficiency at normal operational output powerVSAvoidoutput combiner complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent replaces complex transmission line-based output combiners with simplified LC circuit equivalents. This substitution maintains the necessary signal combining functionality while dramatically reducing circuit complexity and making the design more suitable for integration and manufacturing, directly addressing the contradiction between efficiency and complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If traditional transmission line-based phase shift networks are used, then proper phase alignment is achieved, but PCB area and manufacturing cost increase

Engineering Contradiction:

Improvephase alignment accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent substitutes traditional transmission line phase shifters with LC circuit equivalents that provide the same phase-shifting function. This substitution maintains phase alignment accuracy while using smaller, more cost-effective components that are easier to manufacture and integrate, directly resolving the contradiction between reliability and ease of manufacture.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The design achieves high efficiency at both deep back-off and normal output power levels, with reduced PCB size and lower costs, enhancing flexibility and market readiness.

Implementation Method 1

the first output network imparts a phase delay of 90 degrees between an input of the first output network and an output of the first output network

Methodology Applied

Scientific EffectPhase delay:

Implementation Method 2

the first output network comprises a first inductive element coupled between the first amplifier output and a first intermediate node

Methodology Applied

Scientific EffectInductance: Inductor

Implementation Method 3

a first capacitor integrated within a first integrated passive device (IPD) and coupled between the first intermediate node and ground

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS12413187B2Doherty amplifiers

Publication Date: 2025.09.09 NXP USA INC

AI summary

A Doherty amplifier includes first and second input terminals, first and second amplifiers, and an output combiner circuit. The first amplifier includes a first amplifier input coupled to the first input terminal, and a first amplifier output. The second amplifier includes a second amplifier input coupled to the second input terminal, and a second amplifier output. The output combiner circuit is coupled between the first amplifier output, the second amplifier output, and a final summing node. The output combiner circuit includes a first inductive element, a first capacitor integrated within an integrated passive device (IPD), and a second inductive element. The first inductive element is coupled between the first amplifier output and a first terminal of the first capacitor, and the second inductive element is coupled between a combining node and the first terminal of the first capacitor. A second terminal of the first capacitor is coupled to ground.