Envelope Tracker Switch Layout for Magnetic Field Cancellation

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Solution Overview

Problem

Existing power amplifiers in radio systems face challenges with high power consumption and inefficiency due to parasitic inductance and load capacitance in voltage multiplexers, limiting the ability to quickly change bias voltages in response to control signals.

Innovation Solution

Implementing magnetic field cancellation in power amplifier systems through pairs of switches and bypass capacitors that generate opposing magnetic fields, reducing parasitic inductance and load capacitance, allowing for rapid adjustment of bias voltages that track the envelope of radio frequency signals on a symbol-by-symbol basis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional voltage modulator circuits are used to generate bias voltage for power amplifier, then the circuit can provide bias voltage, but parasitic inductance and load capacitance limit the ability to quickly change bias voltage, leading to power dissipation and RF signal integrity issues

Engineering Contradiction:

Improvebias voltage change speedVSAvoidpower dissipation

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent applies magnetic field cancellation by configuring current loops to generate opposing magnetic fields that neutralize each other. This counteracts the parasitic inductance effects, enabling faster bias voltage transitions without excessive power dissipation. The opposing magnetic fields from symmetrically arranged current loops create a net reduction in effective inductance, directly addressing the speed-energy loss contradiction.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Productivity

If parasitic inductance is present in the voltage modulator circuit, then the circuit structure is simpler, but the ability to track envelope quickly is limited, causing power dissipation

Engineering Contradiction:

Improveenvelope tracking speedVSAvoidpower dissipation

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The voltage modulator circuit employs multiple current loops arranged to produce opposing magnetic fields. This magnetic field cancellation technique effectively reduces the net parasitic inductance, allowing the envelope tracking to proceed at higher speeds without the penalty of excessive power dissipation that would otherwise result from rapid switching through inductive elements.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Reliability

If rapid changes in bias voltage are implemented to track envelope quickly, then envelope tracking performance improves, but parasitic inductance causes overshooting and RF signal integrity issues

Engineering Contradiction:

ImproveRF signal integrityVSAvoidenvelope tracking speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

By configuring current loops to generate opposing magnetic fields, the circuit cancels parasitic inductance effects. This enables rapid bias voltage changes for accurate envelope tracking while preventing the overshooting and RF signal integrity degradation that would normally accompany such fast transitions through inductive circuits.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The patent converts the harmful effect of parasitic inductance into a beneficial cancellation mechanism. By deliberately introducing symmetric current loops that generate opposing magnetic fields, the circuit transforms what would be a limiting factor (parasitic inductance) into a self-canceling phenomenon, enabling high-speed operation with maintained signal integrity.

Inventive Principle:

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

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 reduces power dissipation and minimizes parasitic inductance, enabling efficient and rapid modulation of bias voltages, thereby improving the integrity and efficiency of radio frequency signal transmission.

Implementation Method 1

the first current loop and the second current loop are configured to generate magnetic fields having opposite directions

Methodology Applied

Scientific EffectMagnetic field cancellation: Magnetic Field

Data Source

PatentUS12620939B2Magnetic field cancellation in radio frequency power amplifier envelope trackers

Publication Date: 2026.05.05 ANALOG DEVICES INT UNLTD CO

AI summary

Aspects of this disclosure relate to generating a bias signal with magnetic field cancellation. A voltage modulator circuit can generate a bias voltage that tracks an envelope of a radio frequency signal. For example, the bias signal can track the envelope of the radio frequency signal that is amplified by a power amplifier on a symbol-by-symbol basis. The voltage modulator circuit includes one or more pairs of switches with magnetic field cancellation.