Integrated Capacitor Acoustic Filter for Impedance Matching

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Solution Overview

Problem

Conventional acoustic filtering circuitry faces limitations in frequency range due to acoustic wave velocity constraints, requires significant space for external capacitors or interdigital transducers for impedance matching, and struggles with temperature dependence and spurious responses.

Innovation Solution

Integration of a capacitor within the acoustic filtering circuitry using a dielectric layer to separate capacitor plates, formed from the same layers as the transducers and waveguides, allowing for reduced size and no additional layers, enabling efficient impedance matching and improved filter responses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If external capacitors or interdigital transducers are used for impedance matching, then impedance matching is achieved, but device area increases significantly

Engineering Contradiction:

Improveimpedance matchingVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines the capacitor function with the existing interdigital transducer structure by using the same electrode fingers to serve both as acoustic wave transducers and as capacitor plates. This merging eliminates the need for separate external capacitors or additional interdigital transducers, achieving impedance matching while minimizing device area.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The interdigital transducer electrodes are designed to perform multiple functions: they act as acoustic wave transducers for signal processing and simultaneously serve as capacitor plates for impedance matching. This multi-functionality reduces the overall device complexity and area requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Speed

If acoustic wave devices operate at higher frequencies, then frequency capabilities are enhanced, but acoustic wave velocity constraints limit performance

Engineering Contradiction:

Improvefrequency capabilityVSAvoidperformance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent modifies the electrical parameters of the interdigital transducer, specifically the metallization ratio and electrode geometry, to optimize the electrical resonance frequency. By adjusting these parameters, the device achieves higher frequency capabilities while maintaining performance through improved electrical coupling and reduced capacitive effects.

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If device size is reduced, then space requirements are minimized, but manufacturing precision becomes more challenging

Engineering Contradiction:

Improvedevice sizeVSAvoidfabrication precision

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

By merging the capacitor function into the existing interdigital transducer structure, the patent eliminates the need for additional fabrication steps and structures. The same electrode patterns serve dual purposes, reducing device size without introducing additional manufacturing complexity or precision requirements.

Inventive Principle:

Principle #5Merging (Combining)

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 solution enables smaller, more efficient acoustic filtering circuitry with enhanced frequency capabilities, reduced space requirements, and improved temperature stability, addressing the limitations of conventional designs.

Implementation Method 1

Acoustic wave devices include a piezoelectric material in contact with one or more electrodes. Piezoelectric materials acquire a charge when compressed, twisted, or distorted, and similarly compress, twist, or distort when a charge is applied to them.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The capacitor includes a first plate on the surface of the piezoelectric layer such that the first plate is between the piezoelectric layer and the dielectric layer and a second plate over the first plate such that the second plate and the first plate are separated by at least a portion of the dielectric layer.

Methodology Applied

Scientific EffectDielectric insulation: Dielectric

Data Source

PatentUS10476481B2Acoustic filtering circuitry including capacitor

Publication Date: 2019.11.12 QORVO US INC

AI summary

Acoustic filtering circuitry includes a piezoelectric layer, a dielectric layer, a plurality of acoustic resonators, and a capacitor. The dielectric layer is over a surface of the piezoelectric layer. The plurality of acoustic resonators each includes a transducer on the surface of the piezoelectric layer such that the transducer is between the piezoelectric layer and the dielectric layer. The capacitor includes a first plate on the surface of the piezoelectric layer such that the first plate is between the piezoelectric layer and the dielectric layer and a second plate over the first plate such that the second plate and the first plate are separated by at least a portion of the dielectric layer.