Active Cancellation Circuit for Low-Frequency Power Line Emissions

Solution Overview

Problem

Conventional electronic systems, particularly RF power amplifiers, generate significant low-frequency emissions that are conducted back onto the power line, violating EMI/EMC standards and requiring large, heavy filters that are undesirable in airborne and mobile applications.

Innovation Solution

A radio system with an active cancellation circuit utilizing a bi-directional DC-DC converter to cancel low-frequency emissions from the power amplifier circuit, allowing for smaller capacitors and reducing weight and volume while maintaining effective filtering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional filters with large capacitors and inductors are used to reduce low-frequency emissions, then emission filtering effectiveness is improved, but weight and volume increase significantly

Engineering Contradiction:

Improvelow-frequency emissionsVSAvoidfilter weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of stationary object

Solution Approach 1:

The patent replaces the conventional passive mechanical filter system (large capacitors and inductors) with an active electronic cancellation system using DC-DC converters. This substitution uses electronic control to generate canceling currents that actively neutralize low-frequency emissions, achieving the same filtering effect without the heavy passive components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters by using high-frequency switching DC-DC converters (operating at kHz to MHz ranges) instead of low-frequency passive filters. This parameter change allows the use of much smaller capacitors and inductors while achieving equivalent or superior emission cancellation through active control mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If conventional filters with large capacitors and inductors are used to reduce low-frequency emissions, then emission filtering effectiveness is improved, but volume increases significantly

Engineering Contradiction:

Improvelow-frequency emissionsVSAvoidfilter volume

Core Design Contradiction:

Object-affected harmful factorsVSVolume of stationary object

Solution Approach 1:

The patent replaces the conventional passive mechanical filter system (large capacitors and inductors) with an active electronic cancellation system using DC-DC converters. This substitution uses electronic control to generate canceling currents that actively neutralize low-frequency emissions, achieving the same filtering effect without the heavy passive components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters by using high-frequency switching DC-DC converters (operating at kHz to MHz ranges) instead of low-frequency passive filters. This parameter change allows the use of much smaller capacitors and inductors while achieving equivalent or superior emission cancellation through active control mechanisms.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If passive filtering components are used to meet EMI/EMC standards, then emission compliance is achieved, but system efficiency is reduced due to power losses

Engineering Contradiction:

Improveconducted emissionsVSAvoidpower loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent replaces the conventional passive mechanical filter system (large capacitors and inductors) with an active electronic cancellation system using DC-DC converters. This substitution uses electronic control to generate canceling currents that actively neutralize low-frequency emissions, achieving the same filtering effect without the heavy passive components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the harmful power line emissions into a beneficial control signal. The DC-DC converter detects the emission currents and generates equal and opposite canceling currents, transforming the harmful emissions into an opportunity for active cancellation and improved overall system efficiency.

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

The active cancellation circuit achieves significant weight and volume reductions, with a 5× weight reduction factor and 4× size reduction, while maintaining effective low-frequency emission cancellation, improving system efficiency and compliance with EMI/EMC standards.

Implementation Method 1

The active cancellation circuit is configured to cancel low-frequency emissions from the power amplifier circuit on the power line

Methodology Applied

Scientific EffectActive cancellation:

Implementation Method 2

The active cancellation circuit comprises two DC-DC converters operating in parallel, one capable of charging an energy storage capacitor and the other capable of discharging the energy storage capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS7899415B1Low-frequency power line emissions reduction system and method

Publication Date: 2011.03.01 ROCKWELL COLLINS INC

AI summary

A radio system comprises a power source and a power amplifier circuit coupled to the power source on a power line. The radio system also comprises an active cancellation circuit. The active cancellation circuit comprises a bi-directional DC-DC converter. The active cancellation circuit is configured to cancel low-frequency emissions from the power amplifier circuit on the power line.