Magnetically-Coupled Filter Mitigates Resonator Flyback

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Solution Overview

Problem

Resonator-based filters, such as Bulk Acoustic Wave (BAW) and Surface Acoustic Wave (SAW) filters, experience 'flyback' or reduced rejection outside their passband, leading to excessive out-of-band noise or interference in high-frequency communication systems.

Innovation Solution

A filter circuit design that combines a resonator-based passband filter with a magnetically-coupled filter, where the magnetically-coupled filter has a low insertion loss and a wider passband, featuring two or more notches to attenuate frequencies outside the resonator-based filter's passband, thereby mitigating flyback by controlling frequency response at selected ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a resonator-based filter is used to achieve low insertion loss and compact size, then the filter performance is improved within the passband, but flyback occurs outside the passband leading to excessive out-of-band noise

Engineering Contradiction:

Improveinsertion lossVSAvoidout-of-band noise

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The filter is divided into two separate filter circuits: a resonator-based filter for the passband and a magnetically-coupled filter for out-of-band rejection. Each filter circuit is optimized for its specific function, with the resonator-based filter handling in-band signals and the magnetically-coupled filter handling out-of-band rejection, thereby resolving the flyback issue without compromising passband performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The magnetically-coupled filter acts as an intermediary element that specifically targets and attenuates out-of-band frequencies. This intermediate filter stage provides the necessary rejection for frequencies outside the passband while maintaining low insertion loss for in-band signals, effectively mediating between the resonator-based filter and the output

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the resonator-based filter provides high rejection near the passband, then out-of-band noise is reduced, but flyback occurs further outside the passband with lower rejection

Engineering Contradiction:

Improveout-of-band noiseVSAvoidfrequency response stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The frequency spectrum is segmented into two regions handled by different filter circuits: the resonator-based filter handles frequencies near the passband with high rejection, while the magnetically-coupled filter handles frequencies further outside the passband. This segmentation ensures consistent rejection performance across all out-of-band frequencies, eliminating flyback

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The magnetically-coupled filter uses variable coupling coefficients between its series and shunt inductors to create transmission zeros at specific frequencies. By adjusting these coupling parameters, the filter provides controllable attenuation at different out-of-band frequencies, ensuring stable and reliable frequency response characteristics

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If a magnetically-coupled filter is added to mitigate flyback, then out-of-band rejection is improved, but device complexity increases

Engineering Contradiction:

Improveout-of-band noiseVSAvoidfilter circuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The magnetically-coupled filter replaces complex resonator-based structures with a simpler inductor-based magnetic coupling mechanism. This substitution achieves the same out-of-band rejection function with fewer components and simpler topology, reducing overall device complexity while maintaining effective flyback mitigation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The magnetically-coupled filter provides multiple functions: it attenuates out-of-band frequencies, creates transmission zeros for enhanced rejection, and works in conjunction with the resonator-based filter to provide comprehensive frequency selectivity. This multi-functionality reduces the need for additional separate components, simplifying the overall device structure

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 combined filter circuit reduces out-of-band noise and interference by maintaining low insertion loss within the passband while providing high rejection regions both below and above the passband, effectively addressing the flyback issue through controllable frequency attenuation.

Implementation Method 1

a first shunt inductor magnetically coupled to a second shunt inductor

Methodology Applied

Scientific EffectMagnetic coupling: Electromagnetic Induction

Data Source

PatentUS10931263B2Filter circuits having a resonator-based filter and a magnetically-coupled filter

Publication Date: 2021.02.23 QORVO US INC

AI summary

Filter circuits having a resonator-based filter and a magnetically-coupled filter are disclosed. A filter circuit is deployed with a resonator-based passband filter connected to a magnetically-coupled filter which mitigates or reduces flyback of the resonator-based filter. The magnetically-coupled filter can be a passband filter with a relatively low insertion loss. The magnetically-coupled filter can be designed to mitigate flyback of the resonator-based filter by attenuating frequency response at selected frequency ranges.