Parallel Acoustic Wave Filter Layout for Low-Loss Multi-Band Coverage

Solution Overview

Problem

Existing acoustic wave filters face challenges in achieving wide band coverage with low insertion loss, particularly when multiple bands are required, as series resonators increase insertion loss and prevent downsizing.

Innovation Solution

The solution involves cascading acoustic wave filters with multimode filters of different aperture lengths, ensuring non-overlapping pass bands and using an inductor as a matching circuit to adjust impedances, eliminating the need for series resonators and minimizing insertion loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a series resonator is inserted between the acoustic wave filters and the input terminal to adjust impedance, then the filtering operation is realized, but the insertion loss increases and downsizing is prevented

Engineering Contradiction:

Improvefiltering operationVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent removes the series resonator from the filter structure. By extracting this component, the invention eliminates the source of insertion loss while maintaining the filtering function through alternative impedance adjustment methods using parallel connection and aperture length differentiation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the aperture lengths of the multimode filters in the parallel-connected acoustic wave filters. By differentiating the aperture length parameter between filters, the invention achieves impedance adjustment and filtering operation without requiring a series resonator, thus reducing insertion loss.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a series resonator is inserted between the acoustic wave filters and the input terminal to adjust impedance, then the filtering operation is realized, but the filter size increases

Engineering Contradiction:

Improvefiltering operationVSAvoidfilter size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent removes the series resonator from the filter structure. By extracting this component, the invention eliminates the source of insertion loss while maintaining the filtering function through alternative impedance adjustment methods using parallel connection and aperture length differentiation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the impedance adjustment function into the parallel-connected acoustic wave filters themselves by differentiating their aperture lengths. This integration eliminates the need for a separate series resonator component, achieving both filtering and impedance adjustment in a compact structure.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If multiple acoustic wave filters are connected in parallel to achieve wide band coverage, then the multi-band capability is improved, but the impedance matching becomes difficult

Engineering Contradiction:

Improvemulti-band capabilityVSAvoidimpedance matching

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies different aperture lengths to different acoustic wave filters in the parallel connection. This local differentiation of the aperture parameter enables each filter to contribute to different frequency bands with appropriate impedance characteristics, simplifying the overall impedance matching while achieving wide band coverage.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the aperture lengths of the multimode filters in the parallel-connected acoustic wave filters. By differentiating the aperture length parameter between filters, the invention achieves impedance adjustment and filtering operation without requiring a series resonator, thus reducing insertion loss.

Inventive Principle:

Principle #35Parameter changes

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 allows for improved impedance matching, reduced insertion loss, and downsizing of filters, enabling efficient multi-band coverage without the drawbacks of series resonators.

Implementation Method 1

acoustic wave filters such as surface acoustic wave (SAW) filters are used

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Implementation Method 2

The series resonator realizes an impedance adjustment such that one of the two filters has high impedance in the pass band of the other filter

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS7629864B2Filter including acoustic wave filters connected in parallel

Publication Date: 2009.12.08 TAIYO YUDEN KK

AI summary

A filter includes: a first acoustic wave filter having acoustic wave filters cascaded, an input stage of the acoustic wave filters including a first multimode filter; a second acoustic wave filter having acoustic wave filters cascaded, an input stage of these acoustic wave filters including a second multimode filter having an aperture length different from that of the first multimode filter, the second acoustic wave filter receiving an unbalanced in signal applied to the first acoustic wave filter, and having a pass band that does not overlap with that of the first acoustic wave filter.