Filter Multiplexer Resonator Bandwidth Optimization

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Solution Overview

Problem

Existing filters in multiplexers face challenges in achieving a wide pass band with small insertion loss and steep attenuation characteristics, especially as frequency bands narrow and gaps between them become smaller, leading to increased insertion loss and inadequate return loss within the pass band.

Innovation Solution

A filter design incorporating a series arm resonator with a larger relative band width than a parallel arm resonator, where the series arm resonator's resonant frequency is moved away from the high-frequency end of the pass band, and the parallel arm resonator provides a steep attenuation characteristic using a substrate with lithium niobate and Rayleigh or Love wave propagation, along with high-Q multilayer chip inductors for improved matching and reduced insertion loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the pass band is widened to accommodate narrow frequency bands, then the coverage range is improved, but the insertion loss increases and return loss deteriorates

Engineering Contradiction:

Improvepass band widthVSAvoidinsertion loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent applies local quality by differentiating the relative band widths of series arm and parallel arm resonators. The series arm resonator has a larger relative band width than the parallel arm resonator, creating localized functional differences that optimize both wide pass band coverage and low insertion loss simultaneously

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of relative band width differently for series arm and parallel arm resonators. By setting the series arm resonator's relative band width larger than the parallel arm resonator's, the patent achieves improved return loss and reduced insertion loss across the wide pass band

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If the resonant frequency is positioned closer to the pass band edge for compact design, then the filter size is reduced, but the attenuation characteristic becomes less steep

Engineering Contradiction:

Improvefilter sizeVSAvoidattenuation characteristic

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent uses local quality by assigning different relative band width characteristics to series arm and parallel arm resonators. The parallel arm resonator with smaller relative band width provides steep attenuation at the pass band edge, while the series arm resonator with larger relative band width maintains wide pass band coverage

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by having the parallel arm resonator specifically responsible for providing steep attenuation characteristics at the pass band edge, while the series arm resonator handles the wide pass band coverage, dividing functions to achieve both compact size and steep attenuation

Inventive Principle:

Principle #16Partial or excessive action

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 enhances return loss and reduces insertion loss within the pass band while maintaining steep attenuation at the low-frequency end, enabling filters with wide pass bands and small insertion loss, suitable for multiplexers handling multiple frequency bands with minimal signal interference.

Implementation Method 1

a parallel arm resonator including one end that is grounded; a first inductor including one end that is connected to one end of the series arm resonator and another end that is connected to another end of the parallel arm resonator; and a second inductor including one end that is connected to another end of the series arm resonator and another end that is connected to the another end of the parallel arm resonator

Methodology Applied

Scientific EffectElastic wave propagation: Surface Acoustic Wave

Implementation Method 2

a first inductor including one end that is connected to one end of the series arm resonator and another end that is connected to another end of the parallel arm resonator; and a second inductor including one end that is connected to another end of the series arm resonator and another end that is connected to the another end of the parallel arm resonator

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11509290B2Filter and multiplexer

Publication Date: 2022.11.22 MURATA MFG CO LTD

AI summary

A filter includes a series arm resonator that defines at least a portion of a signal path connected between first and second terminals, a parallel arm resonator including one end that is grounded, a first inductor including one end that is connected to one end of the series arm resonator and another end that is connected to another end of the parallel arm resonator, and a second inductor including one end that is connected to another end of the series arm resonator and another end that is connected to the other end of the parallel arm resonator. A relative band width of the parallel arm resonator is smaller than a relative band width of the series arm resonator.