Amplifier Feedback Circuit With Phase-Tuned IMD Cancellation

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Solution Overview

Problem

Wireless device designs face significant intermodulation distortion due to nonlinearities in amplifier systems, which increases bandwidth and causes channel interference, and existing solutions like intermodulation distortion sinks do not scale well over temperature and process variations.

Innovation Solution

An amplifier circuit with a feedback path incorporating a non-linear current generator and phase-shifting circuit, which applies a non-linear current based on the amplified signal to reduce intermodulation distortion by adjusting the phase and magnitude of the current, using a transistor and biasing circuit, and a phase-shifting circuit with a variable capacitor and resistor to improve linearity across various conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional amplifier architectures are used, then amplification is achieved, but intermodulation distortion increases due to nonlinearities

Engineering Contradiction:

Improvesignal linearityVSAvoidintermodulation distortion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent implements a feedback path that samples the amplified signal and feeds it back through a non-linear current generator. This feedback mechanism detects distortion components and generates corrective current that is subtracted from the input signal, creating a closed-loop system that actively reduces intermodulation distortion while maintaining amplification function.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent converts the harmful non-linear distortion generated by the amplifier into a useful signal. By sampling the distorted output and processing it through the non-linear current generator, the system transforms distortion components into corrective feedback current that, when subtracted from the input, eliminates the original distortion. This turns the amplifier's non-linearity from a defect into the mechanism for distortion cancellation.

Inventive Principle:

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

2Reliability

If existing distortion reduction solutions are implemented, then some distortion cancellation is achieved, but performance degrades over temperature and process variations

Engineering Contradiction:

Improvedistortion cancellationVSAvoidtemperature and process variation tolerance

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent employs variable capacitors and variable resistors in the feedback path that can be adjusted to compensate for temperature and process variations. These adjustable components allow the feedback network's transfer function to be tuned dynamically, maintaining optimal distortion cancellation performance across different operating conditions by changing circuit parameters rather than relying on fixed component values.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent transitions from static distortion cancellation to a dynamic system that adapts to changing conditions. The variable components enable the feedback network to dynamically adjust its characteristics in response to temperature drift and process variations, allowing the system to maintain linearity performance across a wide range of operating environments rather than being optimized for a single condition.

Inventive Principle:

Principle #15Dynamics

3Reliability

If feedback paths are added to reduce distortion, then linearity improves, but circuit complexity increases

Engineering Contradiction:

Improveamplifier linearityVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple functions into the feedback path: signal sampling, distortion detection, corrective current generation, and feedback injection all occur within the same feedback network. The non-linear current generator simultaneously processes the sampled signal and generates the corrective current, eliminating the need for separate distortion detection and correction circuits that would further increase complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The feedback network serves multiple purposes: it provides the necessary feedback for amplification stability, samples the output signal for distortion detection, and generates corrective current for distortion cancellation. This multi-functional design eliminates the need for additional dedicated distortion correction circuits, achieving linearity improvement without proportionally increasing circuit complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11038465B2Amplifier linearity boost circuits and methods for post distortion feedback cancelation

Publication Date: 2021.06.15 SKYWORKS SOLUTIONS INC

AI summary

An amplifier circuit is provided that includes an amplifier having a signal input and a signal output, the amplifier being configured to produce an amplified signal at the signal output, a feedback path coupled between the signal output and the signal input, and an amplifier linearity boost circuit positioned in the feedback path. The amplifier linearity boost circuit includes a non-linear current generator and a phase-shifting circuit, the non-linear current generator being configured to provide a non-linear current based on the amplified signal, and the phase-shifting circuit being configured to adjust a phase of the non-linear current to reduce an intermodulation distortion of the amplified signal.