Acoustic Wave Multiplexer Layout for Spurious Wave Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Surface acoustic wave filters in multiplexers often experience degradation in bandpass characteristic due to higher-order mode spurious waves, which increase return loss and ripple in adjacent filter passbands, affecting the overall performance of multi-band and multi-mode cellular devices.
Innovation Solution
Incorporating acoustic wave filters with series and parallel arm resonators connected to a common terminal, along with capacitance elements, to reduce spurious waves emitted at frequencies within other filters' passbands, thereby maintaining the bandpass characteristic of the multiplexer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If surface acoustic wave filters are connected to a common antenna terminal, then the multiplexer can support multiple frequency bands, but spurious waves at higher frequencies cause ripple and increase insertion loss in adjacent filter pass bands
Solution Approach 1:
A ground electrode is introduced as an intermediary structure between the piezoelectric layer and the substrate. This ground electrode selectively suppresses higher-order mode spurious waves while allowing the filter to maintain its pass band characteristics, thereby resolving the contradiction between multi-band support and bandpass characteristic reliability
Solution Approach 2:
The patent changes the physical parameters of the filter structure by adding a ground electrode at a specific position and orientation. This structural parameter change modifies the electromagnetic field distribution to suppress spurious modes without affecting the main pass band, enabling both multi-band operation and maintained bandpass characteristics
2Reliability
If the frequency of spurious waves falls within the pass band of another filter, then ripple occurs and insertion loss increases, but adding filtering structures increases device complexity
Solution Approach 1:
The ground electrode serves as a simple intermediary element that suppresses spurious waves without requiring complex additional filtering structures. This single structural modification achieves insertion loss reduction while maintaining device simplicity
Solution Approach 2:
The patent extracts and addresses only the specific problem of higher-order mode spurious waves by introducing a targeted ground electrode structure, rather than implementing comprehensive complex filtering solutions across all frequency bands
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 decreases the impact of spurious waves on adjacent filters, preventing bandpass characteristic degradation and maintaining low insertion loss across the multiplexer's frequency bands.
Implementation Method 1
In a surface acoustic wave filter having a piezoelectric layer, energy of a radio-frequency power is confined within the piezoelectric layer
Implementation Method 2
surface acoustic wave filters are connected to a common antenna terminal
Implementation Method 3
acoustic wave resonators that are electrically connected in series
Data Source
AI summary
A multiplexer includes acoustic wave filters that are electrically connected to a common connection terminal. In a first transmission-side filter of the acoustic wave filters, a series arm resonator closest to the common connection terminal includes acoustic wave resonators that are electrically connected in series and capacitance elements that are electrically connected between at least one of signal paths electrically connecting the acoustic wave resonators to each other and a reference terminal.