Inverted Doherty Output Network for Broadband Power Transfer

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Solution Overview

Problem

Conventional Doherty amplifiers have limited RF fractional bandwidth due to their circuit topology, which restricts their performance in high-speed, high-power, and broad-bandwidth applications, particularly in future RF communication systems.

Innovation Solution

The design of an inverted Doherty amplifier with specific impedance-matching components, an impedance inverter, and a combining node configuration that transforms input impedance to optimize power transfer and phase delay, enhancing RF fractional bandwidth and signal bandwidth by up to 25% and 23% respectively, compared to conventional Doherty amplifiers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional Doherty amplifier topology is used, then power amplification is achieved, but RF fractional bandwidth is limited

Engineering Contradiction:

ImproveRF fractional bandwidthVSAvoidcircuit topology complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional Doherty amplifier topology by placing the impedance inverter at the input side rather than the output side. This inversion allows the main amplifier and peaking amplifier to operate with different impedance transformations, enabling broader RF fractional bandwidth while maintaining the power amplification function. The inverted configuration changes the phase and impedance relationships between the two amplifier paths, resolving the bandwidth limitation of the conventional topology.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent modifies key impedance parameters in the Doherty amplifier circuit, specifically using an impedance inverter with a characteristic impedance different from the standard 50 ohms. By optimizing the impedance values at different nodes (input, output, and combining point) and adjusting the phase delay of the impedance inverter, the amplifier achieves extended bandwidth. These parameter changes transform the fixed-bandwidth conventional design into a broad-bandwidth inverted configuration.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If bandwidth is increased in conventional Doherty amplifiers, then RF fractional bandwidth improves, but signal bandwidth and instantaneous bandwidth are restricted

Engineering Contradiction:

Improvesignal bandwidthVSAvoidperformance consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

By inverting the topology and placing the impedance inverter at the input, the patent simultaneously improves RF fractional bandwidth, signal bandwidth, and instantaneous bandwidth. The inverted configuration allows both amplifiers to contribute effectively across a wider frequency range, enhancing performance consistency. The main amplifier handles lower frequencies while the peaking amplifier activates at higher frequencies, maintaining reliable amplification across the extended bandwidth without the restrictions of conventional topology.

Inventive Principle:

Principle #13The other way round (Inversion)

3Power

If impedance matching is optimized for maximum power transfer, then power efficiency improves, but bandwidth is reduced

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidbandwidth

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The patent optimizes power transfer efficiency by carefully selecting impedance values at different circuit nodes while maintaining broad bandwidth. The impedance inverter is designed with a specific characteristic impedance that transforms the load impedance appropriately across a wide frequency range. By adjusting the impedance parameters and phase delay of the inverter, the system achieves near-maximum power transfer efficiency without sacrificing bandwidth, unlike conventional designs where impedance matching narrows the bandwidth.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The inverted Doherty amplifier dynamically adapts the impedance transformation ratio between the main and peaking amplifiers across the frequency spectrum. The impedance inverter provides frequency-dependent impedance transformation that maintains optimal power transfer at different frequencies, enabling both high efficiency and broad bandwidth. This dynamic impedance adaptation resolves the trade-off between power transfer optimization and bandwidth preservation.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11159125B2Inverted Doherty power amplifier with large RF fractional and instantaneous bandwidths

Publication Date: 2021.10.26 MACOM TECH SOLUTIONS HLDG INC

AI summary

Apparatus and methods for an inverted Doherty amplifier operating at gigahertz frequencies are described. RF fractional bandwidth and signal bandwidth may be increased over a conventional Doherty amplifier configuration when impedance-matching components and an impedance inverter in an output network of the inverted Doherty amplifier are designed based on characteristics of the main and peaking amplifier and asymmetry factor of the amplifier.