90-Degree Doherty Impedance Inverter With Post-Combining Matching

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Solution Overview

Problem

Conventional Doherty amplifiers face limitations in bandwidth performance due to impedance-matching components placed between the outputs of the main and peaking amplifiers and the impedance inverter, which add electrical path length and constrain the rated RF fractional bandwidth.

Innovation Solution

Rearranging the order of signal combining and impedance matching by removing impedance-matching elements before the impedance inverter and using an impedance inverter with an integrated distributed inductive element, such as a microstrip line, to reduce the compensating phase rotation and enhance bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If impedance-matching components are placed between the outputs of the main and peaking amplifiers and the impedance inverter, then impedance matching is achieved, but the electrical path length increases and bandwidth is constrained

Engineering Contradiction:

Improveimpedance matchingVSAvoidelectrical path length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent removes the impedance-matching components from their conventional position between the amplifier outputs and the impedance inverter. By extracting these components and relocating them to the output of the impedance inverter, the electrical path length in the critical signal combining path is reduced, thereby improving bandwidth while maintaining impedance matching functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent inverts the conventional order of operations by performing impedance matching after signal combining rather than before. The impedance-matching components are placed at the output of the impedance inverter instead of before it, reversing the traditional architecture to achieve both bandwidth improvement and impedance matching.

Inventive Principle:

Principle #13The other way round (Inversion)

2Power

If conventional Doherty amplifier architecture is used with impedance-matching components before the impedance inverter, then signal combining is achieved, but bandwidth performance is limited

Engineering Contradiction:

Improvesignal amplificationVSAvoidbandwidth

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The patent applies inversion by reversing the sequence of signal combining and impedance matching. Instead of matching impedances before combining signals, the invention combines signals first through the impedance inverter and then applies impedance matching at the output, thereby expanding bandwidth while preserving power amplification capability.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent performs signal combining as a preliminary action before impedance matching. By having the impedance inverter perform the signal combining function first and then applying impedance matching at the output, the architecture achieves broader bandwidth performance while maintaining the power amplification function.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If impedance-matching elements are removed before the impedance inverter, then bandwidth is improved, but impedance matching may be affected

Engineering Contradiction:

ImprovebandwidthVSAvoidimpedance matching

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent extracts the impedance-matching elements from their conventional position before the impedance inverter and relocates them to the output of the impedance inverter. This extraction and relocation maintains the impedance matching function while removing the constraint on bandwidth that existed in the conventional architecture.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

By inverting the order of operations and placing impedance-matching elements after the impedance inverter rather than before, the patent achieves both goals: bandwidth is improved by removing the electrical path length constraint, and impedance matching is maintained by ensuring the matching elements are still present in the signal path, just in a different location.

Inventive Principle:

Principle #13The other way round (Inversion)

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 significantly improves the RF fractional bandwidth of Doherty amplifiers, allowing for scalability of signal amplification to higher powers while maintaining operating frequency performance.

Implementation Method 1

using an impedance inverter that comprises an integrated distributed inductive element in the form of a microstrip line

Methodology Applied

Scientific EffectDistributed inductance: Inductor

Data Source

PatentEP3577758B190-degree lumped and distributed doherty impedance inverter

Publication Date: 2024.04.03 MACOM TECH SOLUTIONS HLDG INC

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Figure 5A~5B

AI summary

Apparatus and methods for a modified Doherty amplifier operating at gigahertz frequencies are described. The combining of signals from a main amplifier (132) and a peaking amplifier (138) occur at a combining node prior to impedance matching of the amplifier's output to a load. An impedance inverter (410) comprises a first integrated distributed inductor and a second integrated distributed inductor connected by a capacitor (580), wherein the impedance inverter (410) is connected between an output of the main amplifier (132) and the combining node.