Inductive Cross-Coupling Reduction in RF Circuitry

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Solution Overview

Problem

Existing communication circuitries face challenges with mutual inductance coupling, which leads to undesirable degradation in filter rejection and increased solution size due to the need for shielding structures.

Innovation Solution

The implementation of a communication circuitry with input and output inductors configured to have negative mutual inductance, coupled with a compensation inductor having positive self-inductance, which substantially cancels the negative mutual inductance and achieves inductive decoupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If shielding structures are used to avoid inductive cross-coupling, then inductive cross-coupling is reduced, but the quality factor of inductors decreases due to ohmic losses and the solution size increases

Engineering Contradiction:

Improveinductive cross-couplingVSAvoidquality factor of inductors

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The harmful mutual inductance effect is extracted and separated from the inductor structure by introducing a compensation inductor that generates an opposing magnetic field, effectively removing the harmful coupling effect without requiring physical shielding structures

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A compensation inductor is introduced as an intermediary element between the input and output inductors. This compensation inductor creates a negative mutual inductance that acts as a mediator to cancel out the positive mutual inductance between the signal path inductors, thereby reducing inductive cross-coupling without shielding

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If shielding structures are used to avoid inductive cross-coupling, then inductive cross-coupling is reduced, but the solution size increases

Engineering Contradiction:

Improveinductive cross-couplingVSAvoidsolution size

Core Design Contradiction:

Object-affected harmful factorsVSVolume of stationary object

Solution Approach 1:

The shielding structure is extracted and replaced by a compensation inductor that generates an opposing magnetic field, removing the need for bulky physical shielding while maintaining the benefit of reduced inductive cross-coupling

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The approach changes from physical spatial separation (shielding) to parameter-based compensation (negative mutual inductance). By adjusting the compensation inductor value to create negative mutual inductance equal in magnitude to the positive mutual inductance, the harmful effect is canceled without increasing physical volume

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If inductors are confined within shielding structures, then inductive cross-coupling is reduced, but ohmic losses increase due to currents on the shields

Engineering Contradiction:

Improveinductive cross-couplingVSAvoidohmic losses

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The compensation inductor serves as an intermediary that creates a counteracting magnetic field to cancel harmful coupling, eliminating the need for shielding structures that generate ohmic losses through induced currents

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical/shielding approach (physical barriers) is replaced by an electromagnetic field-based approach (negative mutual inductance compensation), substituting a system that causes ohmic losses with one that operates through magnetic field interaction without resistive heating

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration effectively reduces mutual inductance coupling, enhancing filter rejection and maintaining high inductor quality factors without the need for additional shielding, thus optimizing circuit performance and size.

Implementation Method 1

the input inductor and the output inductor are configured to have a negative mutual inductance

Methodology Applied

Scientific EffectMutual inductance: Electromagnetic Induction

Implementation Method 2

the compensation inductor is configured to have a positive self-inductance that substantially cancels the negative mutual inductance

Methodology Applied

Scientific EffectSelf-inductance: Electromagnetic Induction

Data Source

PatentUS20250202516A1Communication circuitry with inductive cross-coupling reduction

Publication Date: 2025.06.19 QORVO US INC

AI summary

Communication circuitry is disclosed having radio frequency circuitry with an input terminal and an output terminal, wherein an input inductor is coupled between the input terminal and a common node. An output inductor is coupled between the output terminal and the common node, wherein the input inductor and the output inductor are configured to have a negative mutual inductance. A compensation inductor is coupled between the common node and a fixed voltage node, wherein the compensation inductor is configured to have a self-inductance that substantially cancels the negative mutual inductance between the input inductor and the output inductor.