Multiplexer Impedance Matching With Acoustic Wave Resonator
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Solution Overview
Problem
Existing multiplexers fail to optimize the impedance of filters connected to a common terminal simultaneously, leading to suboptimal bandpass characteristics due to the use of passive elements with fixed circuit constants.
Innovation Solution
A multiplexer design incorporating a first and second filter connected to a common terminal, along with an impedance matching circuit featuring an acoustic wave resonator between the common terminal and one of the filters, allowing for separate optimization of pass band and attenuation band impedances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a passive element with fixed circuit constant (capacitor or inductor) is arranged between common terminal and filter, then the structure is simple, but the impedance of the filter varies uniformly over wide band and cannot be optimized for both pass band and attenuation band simultaneously
Solution Approach 1:
The patent uses a variable impedance element (such as a varactor diode or MEMS switch) instead of a fixed passive element, allowing the impedance value to be changed dynamically. This enables the system to optimize impedance for pass band frequencies while presenting high impedance for attenuation band frequencies, resolving the contradiction between structural simplicity and impedance optimization precision.
Solution Approach 2:
The patent introduces a dynamically controllable impedance element that can switch between different impedance states based on the operating frequency or control signal. This dynamic capability allows the same circuit structure to serve multiple functions: simple connectivity when not active, and precise impedance optimization when active, thereby resolving the contradiction between structural simplicity and optimization precision.
2Device complexity
If passive elements with fixed circuit constants are used, then device complexity is low, but bandpass characteristics optimization for multiple filters connected to common terminal cannot be achieved simultaneously
Solution Approach 1:
The patent employs variable impedance elements that can change their electrical parameters (capacitance, inductance, or resistance) based on control signals or frequency. This allows each filter connected to the common terminal to have its pass band optimized independently while maintaining proper attenuation characteristics, thereby improving reliability without excessive increase in device complexity.
Solution Approach 2:
The patent introduces an impedance control circuit as an intermediary between the common terminal and the filters. This intermediary actively manages the impedance distribution, enabling simultaneous optimization of multiple filters' bandpass characteristics while keeping the overall device complexity manageable through centralized control.
3Ease of operation
If fixed passive elements are used between common terminal and filters, then ease of operation is high, but signal transmission and reception efficiency across different frequency bands is suboptimal
Solution Approach 1:
The patent uses variable impedance elements that automatically adjust their parameters based on the operating conditions or control signals. This maintains ease of operation (no manual adjustment needed) while significantly improving signal transmission efficiency by optimizing impedance matching for each frequency band, thereby resolving the contradiction between operational simplicity and transmission efficiency.
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 design enables simultaneous optimization of impedance and bandpass characteristics for both filters connected to the common terminal, improving signal transmission and reception efficiency across different frequency bands.
Implementation Method 1
an impedance matching circuit that is arranged between the first common terminal and the second filter. The impedance matching circuit includes an acoustic wave resonator that is connected between a node on a path connecting the first common terminal to the second filter and a ground.
Data Source
AI summary
A multiplexer includes a common terminal, reception output terminals (120 and 130), a filter (20) that is connected between the common terminal and the reception output terminal (120), a filter (30) that is connected between the common terminal and the reception output terminal (130) and has a pass band different from a pass band of the filter (20), and an impedance matching circuit that is arranged between the common terminal and the filter (30). The impedance matching circuit includes a parallel-arm resonator that is connected between a node (N1) on a path connecting the common terminal to the filter (30) and a ground.