RF Amplifier Bias Linearization for PVT-Stable Wideband Operation

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Solution Overview

Problem

Conventional adaptive/linearization biasing techniques for RF amplifiers are sensitive to process, voltage, and temperature variations, have limited envelope bandwidth, and are not suitable for power amplifiers using stacked transistors, particularly in modern communication systems like 5G.

Innovation Solution

A bias arrangement with separate bias and linearization circuits coupled by a coupling circuit, allowing for independent optimization of linearization and biasing operations, which improves linearity and stability while reducing sensitivity to PVT variations and envelope bandwidth limitations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional adaptive/linearization biasing techniques are used, then biasing is provided for the amplifier, but the system is sensitive to process, voltage, and temperature variations and has limited envelope bandwidth

Engineering Contradiction:

Improvesensitivity to PVT variationsVSAvoidenvelope bandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The bias arrangement is segmented into separate bias circuit and linearization circuit, each optimized for their specific function. The bias circuit generates the bias signal while the linearization circuit independently modifies it to compensate for PVT variations, thereby improving reliability without limiting envelope bandwidth

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The linearization circuit dynamically adjusts the bias signal based on real-time operating conditions, allowing the system to adapt to process, voltage, and temperature variations while maintaining wide envelope bandwidth capability

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If amplifiers operate in saturation to achieve highest efficiency, then efficiency is improved, but nonlinear behavior increases causing distorted output signals

Engineering Contradiction:

ImproveefficiencyVSAvoidnonlinear distortions

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The linearization circuit converts the harmful nonlinear effects of saturation operation into beneficial linearization by applying compensating signals, allowing the amplifier to operate in saturation for maximum efficiency while maintaining linear output signals

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The linearization circuit uses feedback mechanisms to detect and compensate for nonlinear distortions generated during saturation operation, enabling the amplifier to maintain both high efficiency and signal linearity simultaneously

Inventive Principle:

Principle #23Feedback

3Reliability

If separate bias and linearization circuits are used, then linearity and stability are improved, but device complexity increases

Engineering Contradiction:

Improvelinearity and stabilityVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

While maintaining functional separation for optimization, the bias circuit and linearization circuit are merged into a single integrated bias arrangement that shares common components and signal paths, reducing overall device complexity while preserving the linearity and stability benefits

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11264953B2Bias arrangements for improving linearity of amplifiers

Publication Date: 2022.03.01 ANALOG DEVICES INT UNLTD CO

AI summary

Bias arrangements for amplifiers are disclosed. An example bias arrangement for an amplifier includes a bias circuit, configured to produce a bias signal for the amplifier; a linearization circuit, configured to improve linearity of the amplifier by modifying the bias signal produced by the bias circuit to produce a modified bias signal to be provided to the amplifier; and a coupling circuit, configured to couple the bias circuit and the linearization circuit. Providing separate bias and linearization circuits coupled to one another by a coupling circuit allows separating a linearization operation from a biasing loop to overcome some drawbacks of prior art bias arrangements that utilize a single biasing loop.