DMS Filter Transition Region for Spurious Mode Suppression
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Solution Overview
Problem
Designing a compact double-mode surface-acoustic-wave filter that effectively suppresses spurious modes within a passband while maintaining an aspect ratio within process limits is challenging, especially in space-constrained devices.
Innovation Solution
Implementing a double-mode surface-acoustic-wave filter with a transition region featuring a partly uniform geometric property, such as a trapezoidal-shaped pitch and metallization ratio, to achieve spurious mode suppression without exceeding process limits, thereby allowing integration into smaller devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a double-mode surface-acoustic-wave filter is designed to suppress spurious modes within the passband, then filtering performance is improved, but the device footprint and complexity increase due to requiring additional resonators
Solution Approach 1:
The patent applies local quality by creating a transition region with specifically engineered geometric properties (trapezoidal pitch and metallization ratio profiles) at the boundaries between single-mode and double-mode sections. This localized structural modification enables spurious mode suppression without requiring additional resonators throughout the entire device, thereby reducing overall complexity while maintaining filtering performance.
2Reliability
If the filter is designed with sufficient spurious mode suppression, then filtering performance is improved, but the aspect ratio exceeds process limits
Solution Approach 1:
The patent employs parameter changes by systematically varying the pitch and metallization ratio across the transition region according to specific trapezoidal profiles. These controlled parameter transitions enable the filter to achieve adequate spurious mode suppression while maintaining an aspect ratio within manufacturing process limits, avoiding the need for excessive aspect ratios that would exceed process capabilities.
3Reliability
If additional resonators are added to suppress spurious modes, then filtering performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent reduces manufacturing cost by implementing spurious mode suppression through localized geometric modifications in the transition region rather than adding multiple resonators throughout the device. This approach minimizes the quantity of materials and fabrication steps required, thereby reducing manufacturing cost while achieving the necessary filtering performance.
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 filter achieves sufficient spurious mode suppression with a reduced footprint and lower cost, enabling integration into space-constrained devices with fewer additional resonators and minimal passband ripples.
Implementation Method 1
double-mode surface-acoustic-wave filter
Implementation Method 2
interdigital transducer
Data Source
AI summary
An apparatus for filtering is disclosed that implements a double-mode surface-acoustic-wave filter having a transition region with a partly uniform geometric property. In an example aspect, the double-mode surface-acoustic-wave filter includes at least one interdigital transducer with multiple fingers. The multiple fingers include a first set of fingers having a geometric property and a second set of fingers. The second set of fingers is positioned adjacent to the first set of fingers and is associated with an outer edge of the at least one interdigital transducer. The geometric property across a subset of the second set of fingers is substantially uniform. A value of the geometric property across the subset of the second set of fingers is different than a value of the geometric property across the first set of fingers.