Multiplexer Filter Layout to Suppress SAW Spurious Interference
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Solution Overview
Problem
In multiplexers, higher-order modes in surface acoustic wave filters can lead to increased return loss and degradation of bandpass characteristics, especially when spurious waves from one filter fall within the pass band of another, affecting the overall performance of multi-band and multi-mode cellular devices.
Innovation Solution
The placement of elastic wave filters with different pass bands, where the first filter generating a spurious wave is positioned nearest to the common connection terminal, and the use of a multilayer substrate with reduced wiring line length and specific resonator configurations, such as series and parallel arm resonators, to minimize inductance and maximize capacitance, thereby reducing spurious wave impact on adjacent filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If surface acoustic wave filters are connected to a common antenna terminal, then multi-band and multi-mode functionality is achieved, but spurious waves from one filter can fall within the pass band of another filter causing degradation of bandpass characteristics
Solution Approach 1:
The patent introduces a spatial dimension solution by mounting filters on opposite surfaces of a substrate. The first elastic wave filter is mounted on a first surface nearest to the common connection terminal, while the second elastic wave filter is mounted on a second surface opposite to the first surface. This three-dimensional spatial separation effectively isolates the spurious waves from the first filter from affecting the pass band of the second filter, thereby resolving the interference issue while maintaining multi-band functionality.
2Ease of manufacture
If the first elastic wave filter is positioned nearest to the common connection terminal, then the inductance component is reduced, but the spurious wave generation frequency may still overlap with other filter pass bands
Solution Approach 1:
The patent uses the substrate itself as an intermediary barrier. By mounting the first filter on the first surface and the second filter on the opposite second surface, the substrate acts as a physical mediator that blocks and isolates the spurious waves generated by the first filter from reaching the second filter's pass band, thus preventing interference while maintaining the low-inductance configuration.
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 effectively prevents the degradation of bandpass characteristics by reducing spurious wave effects, maintaining low insertion loss and improving the overall performance of the multiplexer across multiple frequency bands.
Implementation Method 1
In a surface acoustic wave filter including a piezoelectric layer, energy of a high-frequency power is confined within the piezoelectric layer
Implementation Method 2
In a surface acoustic wave filter including a piezoelectric layer, energy of a high-frequency power is confined within the piezoelectric layer
Data Source
AI summary
A multiplexer includes a common connection terminal on a first surface of a substrate and to be connected to an antenna element, and transmission-side and reception-side elastic wave filters of Band25 and Band66 mounted on a second surface of the substrate opposite the first surface, that are connected to the common connection terminal, and that have pass bands different from each other. The transmission-side elastic wave filter of Band66 is located nearest on the substrate to the common connection terminal among the elastic wave filters.