Embedded Electrode Geometry for Compact Wideband Acoustic Filters
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Solution Overview
Problem
Designing an acoustic filter that can provide filtering for higher frequencies, fit within space-constrained devices, support high-frequency and wide-bandwidth applications, and maintain performance in terms of insertion loss, temperature stability, and spurious-mode suppression is challenging due to interdependencies between size, bandwidth, and spurious modes.
Innovation Solution
Implementing an acoustic filter with an embedded electrode structure having tailored geometric properties, including a metallization ratio greater than approximately 0.2, exterior angles between 50° to 120°, and a cross-sectional design that provides additional degrees of freedom for optimizing performance and ease of manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the acoustic filter is designed with conventional electrode structures, then the device can be manufactured with standard processes, but the filter cannot achieve optimal performance in insertion loss, temperature stability, and spurious-mode suppression simultaneously
Solution Approach 1:
The electrode structure is divided into multiple discrete fingers with specific geometric configurations. Each finger segment contributes to different aspects of filter performance, allowing independent optimization of insertion loss, temperature stability, and spurious-mode suppression through tailored segment geometries and arrangements.
Solution Approach 2:
Different regions of the electrode structure have different geometric properties optimized for specific functions. The metallization ratio, finger width, and spacing vary locally to achieve optimal performance characteristics in different frequency ranges and to suppress specific spurious modes while maintaining temperature stability.
2Adaptability or versatility
If the acoustic filter is designed to support high-frequency and wide-bandwidth applications, then the filter performance is improved, but the device size increases making it difficult to fit within space-constrained devices
Solution Approach 1:
The electrode fingers are extended in the vertical dimension by embedding them partially or fully within the piezoelectric layer thickness. This vertical dimensionality allows increasing the effective electrode area and improving frequency response without proportionally increasing the planar footprint, enabling high-frequency and wide-bandwidth performance in compact form factors.
Solution Approach 2:
The electrode structure is nested within the piezoelectric layer by embedding the electrodes partially or fully into the layer thickness. This nesting approach maximizes the use of available space within the piezoelectric substrate, allowing complex electrode geometries to be accommodated without increasing overall device volume.
3Reliability
If the metallization ratio is increased to improve spurious-mode suppression, then the filter performance is enhanced, but the manufacturing precision requirements become more stringent
Solution Approach 1:
The design specifies particular parameter ranges (metallization ratio greater than 0.2, exterior angles between 50° to 120°) that balance performance requirements with manufacturing capabilities. These parameter choices are optimized to achieve adequate spurious-mode suppression while remaining compatible with standard semiconductor fabrication tolerances and processes.
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 embedded electrode structure enhances the acoustic filter's performance in terms of insertion loss, temperature stability, and spurious-mode suppression, enabling it to be tuned for specific frequency ranges and bandwidths while fitting within space-constrained devices.
Implementation Method 1
The acoustic filter includes means for producing a formed acoustic wave. The means has two opposite surfaces that respectively form first and second planes. The acoustic filter also includes means for converting the radio-frequency signal to an acoustic wave and converting the formed acoustic wave into the filtered signal.
Implementation Method 2
An apparatus is disclosed that implements an acoustic filter having an embedded electrode structure with particular geometric properties. In an example aspect, the geometric properties of the embedded electrode structure can be tailored to enhance performance of the acoustic filter in terms of insertion loss, temperature stability, quality factor, and spurious-mode suppression.
Data Source
AI summary
An apparatus is disclosed for implementing an acoustic filter having an embedded electrode structure with particular geometric properties. In an example aspect, the geometric properties of the embedded electrode structure can be tailored to enhance performance of the acoustic filter in terms of insertion loss, temperature stability, quality factor, and spurious-mode suppression. Furthermore, the geometric properties can enable the acoustic filter to be tuned for a particular frequency range and/or bandwidth, to fit within space-constrained devices, and improve the ease of manufacturing. Various performance improvements and design requirements can be met using the embedded electrode structure because the geometric properties of the embedded electrode structure provide additional degrees of freedom in designing the acoustic filter. This design freedom enables a performance of the acoustic filter to be optimized in the presence of multiple complex interdependencies.