Surface Acoustic Wave Filter Layout Without Multilevel Wiring Crossings
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Solution Overview
Problem
Existing longitudinally-coupled-resonator-type surface acoustic wave filters face challenges in reducing the area occupied by wiring lines, particularly in unbalanced-balanced filters used in mobile communication devices, due to multilevel crossing portions that hinder size reduction and high-density wiring layout.
Innovation Solution
The design includes a single unbalanced terminal, a pair of balanced terminals, and strategically arranged interstage and ground wiring lines that branch and connect to specific electrodes, allowing the ground wiring to be positioned outside the interstage wiring lines, eliminating the need for multilevel crossings and reducing the overall area occupied by wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If ground wiring lines are positioned inside interstage wiring lines, then electrical connections are achieved, but the area occupied by wiring lines increases due to multilevel crossing portions
Solution Approach 1:
The patent repositions ground wiring lines from inside to outside the interstage wiring lines, utilizing the lateral dimension rather than vertical layering. This dimensional rearrangement eliminates the need for multilevel crossing portions and through-holes, reducing wiring area while maintaining electrical connectivity.
Solution Approach 2:
The ground wiring lines are extracted from the interior region between interstage wiring lines and relocated to the exterior region. This extraction eliminates the complex multilevel crossing structure and reduces the overall wiring area occupied by the filter.
2Ease of operation
If multilevel crossing portions are used for wiring intersections, then electrical connections are established, but the number of through-holes and wiring complexity increases
Solution Approach 1:
The ground wiring lines are extracted from the interior region between interstage wiring lines and relocated to the exterior region. This extraction eliminates the complex multilevel crossing structure and reduces the overall wiring area occupied by the filter.
3Volume of moving object
If filter size is reduced, then miniaturization is achieved, but wiring density and crossing complexity increase
Solution Approach 1:
The patent repositions ground wiring lines from inside to outside the interstage wiring lines, utilizing the lateral dimension rather than vertical layering. This dimensional rearrangement eliminates the need for multilevel crossing portions and through-holes, reducing wiring area while maintaining electrical connectivity.
Solution Approach 2:
The ground wiring lines are extracted from the interior region between interstage wiring lines and relocated to the exterior region. This extraction eliminates the complex multilevel crossing structure and reduces the overall wiring area occupied by the filter.
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 enables a smaller-sized surface acoustic wave filter with reduced wiring area, allowing for efficient conversion between unbalanced and balanced signals without the need for complex crossing portions, thereby enhancing the filter's size reduction and performance.
Implementation Method 1
The longitudinally-coupled-resonator-type surface acoustic wave filter is formed on a main surface of a piezoelectric substrate
Implementation Method 2
a first central interdigital transducer (IDT) that is arranged on a central axis x that is orthogonal to the propagation direction of surface acoustic waves
Data Source
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AI summary
A longitudinally-coupled-resonator-type surface acoustic wave filter includes an unbalanced terminal (10), balanced terminals (20), a piezoelectric substrate, a first surface acoustic wave filter unit (11), a second surface acoustic wave filter unit (12), an unbalanced signal wiring line, balanced signal wiring lines, a pair of interstage wiring lines that connect the first surface acoustic wave filter unit (11) and the second surface acoustic wave filter unit (12) to each other, and ground wiring lines. The first surface acoustic wave filter unit (11) includes a first IDT (111) and a pair of a second IDT and a third IDT (112). The first IDT (111) includes a pair of first divided comb tooth shaped electrodes (111a) obtained by dividing a comb tooth shaped electrode on the side far from the unbalanced terminal (10) along a central axis x. The pair of first divided comb tooth shaped electrodes (111a) are connected by the interstage wiring lines to the second surface acoustic wave filter unit (12). A comb tooth shaped electrode of the second IDT and a comb tooth shaped electrode of the third IDT (112) on the side far from the unbalanced terminal (10) are respectively connected to ground wiring lines that are routed outside of the interstage wiring lines.