Dual-Sided SAW Filter Layout for Compact Multi-Band RF Filtering
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Solution Overview
Problem
There is a demand for miniaturized communication devices that can handle multiple frequency bands, and existing methods for stacking different chip sizes or bonding device wafers together face limitations in size reduction and yield.
Innovation Solution
A surface acoustic wave (SAW) filter is designed with SAW resonators on both front and back surfaces of a single chip substrate, forming separate radio frequency filters for different frequency bands, reducing the number of parts and downsizing wireless communication devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple frequency band filters are implemented using separate chips or stacked chips, then frequency filtering capabilities for multiple bands are achieved, but device size and part quantity increase
Solution Approach 1:
The patent combines multiple frequency band filters into a single chip by fabricating different filter circuits on opposite surfaces of the same substrate. The first filter circuit is formed on the front surface with its piezoelectric layer and electrodes, while the second filter circuit is formed on the back surface with its own piezoelectric layer and electrodes. This merging approach allows multiple frequency band filtering capabilities to be integrated into one compact device, reducing the overall device size and eliminating the need for separate chips or stacked configurations.
Solution Approach 2:
The patent utilizes the third dimension (depth/thickness) of the chip substrate to accommodate multiple filter circuits. By forming filter circuits on both the front and back surfaces of the substrate, the invention effectively uses the vertical dimension to pack more functionality into the same planar footprint. This dimensional approach allows frequency band filtering capabilities to be stacked in space rather than arranged side-by-side, thereby reducing the device area while maintaining multi-band adaptability.
2Adaptability or versatility
If multiple frequency band filters are implemented using separate chips or stacked chips, then frequency filtering capabilities for multiple bands are achieved, but the number of parts increases
Solution Approach 1:
The patent merges multiple frequency band filters into a single integrated chip structure. Instead of using separate chips for different frequency bands, the invention fabricates multiple filter circuits on opposite surfaces of one substrate, connecting them through conductive structures that pass through the substrate thickness. This consolidation reduces the number of discrete parts from multiple separate filters to a single multi-functional filter component, simplifying the overall system architecture and reducing assembly complexity.
3Adaptability or versatility
If device wafer bonding is used to combine multiple filters, then multi-band filtering is achieved, but manufacturing complexity and yield issues arise
Solution Approach 1:
The patent segments the manufacturing process into independent steps for forming filter circuits on the front and back surfaces of the substrate. Each surface can be processed separately through standard semiconductor fabrication techniques, including piezoelectric layer deposition, electrode patterning, and cavity formation. This segmentation allows each filter circuit to be manufactured using conventional processes without requiring complex wafer bonding steps, thereby simplifying the overall manufacturing process and improving production yield while achieving multi-band filtering capabilities.
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 SAW filter enables a single chip package to cover multiple frequency bands, reducing device size and parts, while maintaining efficient frequency filtering capabilities.
Implementation Method 1
a first piezoelectric layer, a plurality of surface acoustic wave resonators formed on a top surface of the first piezoelectric layer... a second piezoelectric layer, a plurality of surface acoustic wave resonators formed on a bottom surface of the second piezoelectric layer
Implementation Method 2
surface acoustic wave resonators formed on a top surface of the first piezoelectric layer... surface acoustic wave resonators and the wiring layer on the top surface of the second piezoelectric layer
Data Source
AI summary
A surface acoustic wave filter is disclosed. The surface acoustic wave filter includes a substrate, and first and second surface acoustic wave filter structures disposed on first and second main surfaces of the substrate, respectively. The first surface acoustic wave filter structure includes a first piezoelectric layer a plurality of first surface acoustic wave resonators formed on a top surface of the first piezoelectric layer, and a first wiring layer connecting the first surface acoustic wave resonators to each other. The second surface acoustic wave filter structure includes a second piezoelectric layer, a plurality of second surface acoustic wave resonators formed on a bottom surface of the second piezoelectric layer, and a second wiring layer connecting the second surface acoustic wave resonators to each other. A plurality of through electrodes extends through the substrate, the first piezoelectric layer, and the second piezoelectric layer. A circuit including the first surface acoustic wave resonators and the first wiring layer on the top surface of the first piezoelectric layer forms at least one first radio frequency filter, and a circuit including the plurality of second surface acoustic wave resonators and the second wiring layer on the bottom surface of the second piezoelectric layer forms at least one second radio frequency filter. The at least one first radio frequency filter and the at least one second radio frequency filter belong to different frequency bands.