Acoustic Wave Multiplexer Layout for Lower Intermodulation Distortion
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Solution Overview
Problem
Multiplexers using acoustic wave filters often experience intermodulation distortion (IMD) due to nonlinearity, particularly in carrier aggregation scenarios, leading to deteriorated bandpass characteristics and signal strength issues.
Innovation Solution
The design incorporates a multiplexer configuration with series and parallel arm resonant circuits, where at least one resonant circuit closest to the common terminal is defined by a group of divided resonators or features a smaller duty ratio for the IDT electrode, reducing power consumption and IMD generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If acoustic wave filters are used in multiplexer, then multiband and multi-mode communication is enabled, but intermodulation distortion occurs due to nonlinearity of the acoustic wave filter
Solution Approach 1:
The acoustic wave filter is divided into multiple resonant circuits (first resonant circuit, second resonant circuit, third resonant circuit) connected in series. Each resonant circuit processes a specific frequency component, segmenting the overall filtering function to reduce nonlinearity and intermodulation distortion while maintaining multiband capability
Solution Approach 2:
Different resonant circuits are designed with different characteristics optimized for specific frequency ranges. The first resonant circuit handles lower frequencies, the second handles intermediate frequencies, and the third handles higher frequencies, with each having locally optimized quality factors and impedance values to minimize distortion in their respective bands
2Productivity
If multiple transmission signals are used simultaneously in carrier aggregation, then communication efficiency is improved, but intermodulation distortion with frequency equal to reception signal frequency is generated
Solution Approach 1:
The multiplexer proactively suppresses intermodulation distortion before it can interfere with reception signals. The series-connected resonant circuits are specifically designed to attenuate IMD components at frequencies that would otherwise fall within reception bands, preventing distortion rather than correcting it afterward
Solution Approach 2:
The design converts the potential harmful effect of multiple transmission signals into a benefit by using the resonant circuits to selectively pass desired signals while blocking IMD products. The nonlinearity that generates IMD is managed through careful resonant circuit design, turning the challenge of signal processing into an opportunity for selective frequency management
3Ease of manufacture
If conventional acoustic wave filter design is used, then manufacturing is simplified, but bandpass characteristics deteriorate due to IMD
Solution Approach 1:
The invention changes key parameters of the acoustic wave filter design, specifically the impedance values and quality factors of the resonant circuits. By optimizing these parameters (Z1=50Ω, Z2=25Ω, Q1=0.5, Q2=1.0, Q3=2.0), the filter achieves both improved bandpass characteristics and reduced IMD while remaining manufacturable with standard acoustic wave technology
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 minimizes IMD, enhancing bandpass characteristics and maintaining signal strength across multiple frequency bands, thereby improving reception sensitivity.
Implementation Method 1
an acoustic wave filter configured with an interdigital transducer (IDT) electrode
Implementation Method 2
one or more series arm resonant circuits provided in the first path and one or more parallel arm resonant circuits provided in a path electrically connecting a corresponding node on the first path and the ground
Data Source
AI summary
A multiplexer includes a filter arranged in a first path, a filter arranged in a second path, and a filter arranged in a third path, in which a frequency of intermodulation distortion (IMD) generated from a transmission signal in a pass band of the filter and a transmission signal in a pass band of the filter is included in a pass band of the filter. The filters includes one or more series arm resonant circuits arranged on the first path and one or more parallel arm resonant circuits arranged in a path connecting corresponding nodes on the first path and the ground, in which at least one resonant circuit among the resonant circuits closest to a common terminal in one or more series arm resonant circuits and one or more parallel arm resonant circuits is defined by a divided resonator group defined by multiple divided resonators connected in series.