Adaptive Bias Coupling for Amplifier Linearity and Efficiency

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Solution Overview

Problem

Conventional bias circuits for power amplifiers, including adaptive bias circuits, introduce nonlinearity that degrades the linearity of power amplifiers, and using fixed coupling components to mitigate this issue can degrade power and efficiency.

Innovation Solution

A bias network with an adaptive coupling circuit that modifies the bias signal by varying impedance based on the input power level, reducing nonlinearity introduced by the adaptive bias circuit and optimizing the bias signal for improved amplifier linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If an adaptive bias circuit is used to improve amplifier efficiency, then power efficiency is improved, but linearity degrades due to introduced nonlinearity

Engineering Contradiction:

Improvepower efficiencyVSAvoidlinearity

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

A coupling circuit is introduced as an intermediary component between the adaptive bias circuit and the amplifier. This coupling circuit modifies the bias signal to reduce nonlinearity while preserving the adaptive efficiency benefits, effectively mediating between the conflicting requirements of efficiency and linearity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If a fixed coupling component is used to reduce nonlinearity, then linearity is improved, but power and efficiency degrade

Engineering Contradiction:

ImprovelinearityVSAvoidpower efficiency

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The coupling circuit employs dynamic impedance adjustment based on the operating conditions of the amplifier. By varying the coupling impedance adaptively rather than using a fixed value, the system can optimize both linearity and efficiency across different power levels, avoiding the trade-off inherent in fixed coupling components

Inventive Principle:

Principle #15Dynamics

3Reliability

If the bias signal is strongly coupled to the amplifier, then bias effectiveness is improved, but nonlinearity increases

Engineering Contradiction:

Improvebias effectivenessVSAvoidlinearity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The coupling circuit changes the impedance parameter dynamically based on the amplifier's operating state. By adjusting the coupling impedance, the system can maintain effective biasing while controlling the amount of nonlinearity transferred to the amplifier, optimizing both bias effectiveness and linearity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3751732B1Coupling a bias circuit to an amplifier using an adaptive coupling arrangement

Publication Date: 2024.05.29 ANALOG DEVICES INT UNLTD CO

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Figure 2A~2B
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AI summary

Bias networks for amplifiers are disclosed. An example bias network includes an adaptive bias circuit, configured to generate a bias signal for an amplifier, and further includes a coupling circuit, configured to couple the adaptive bias circuit to the amplifier. The coupling circuit is made adaptive in that its' impedance depends on a power level of an input signal to be amplified by the amplifier. By configuring the coupling circuit to have a variable impedance that depends on the power level of the input signal, the coupling circuit may adapt to the input power level and, thereby, may modify the bias signal to reduce/optimize at least some of the nonlinearity that may be introduced to the bias signal by the adaptive bias circuit.