Multiplexer High-Pass Filter Inductor Impedance Matching
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Solution Overview
Problem
The attenuation characteristic of high-pass filters (HPFs) in multiplexers deteriorates due to impedance matching issues, leading to increased loss and reduced performance in low-frequency regions.
Innovation Solution
Incorporating an additional inductor (L4) connected between the common terminal and the HPF, which allows for reduced capacitance of capacitors in the HPF, thereby improving impedance matching and attenuating characteristics in low-frequency regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If impedance matching is optimized for HPF passband, then transmission loss in HPF passband is reduced, but attenuation characteristic in low-frequency region deteriorates
Solution Approach 1:
The HPF is divided into two separate filter sections: a first HPF section (connected to common terminal) and a second HPF section (connected to output terminal). Each section is independently optimized for its specific function, allowing the first section to handle attenuation in low-frequency regions while the second section maintains transmission efficiency in the passband.
Solution Approach 2:
The first HPF section acts as an intermediary between the common terminal and the second HPF section. It pre-filters signals to improve attenuation characteristics before signals reach the second HPF section, thereby resolving the conflict between passband transmission and low-frequency attenuation.
2Reliability
If capacitor capacitance in HPF is reduced, then attenuation characteristic in low-frequency region is improved, but impedance matching in passband deteriorates
Solution Approach 1:
The HPF capacitor is segmented into two parts: a first capacitor in the first HPF section and a second capacitor in the second HPF section. This allows independent optimization of capacitance values for each section, enabling improved low-frequency attenuation while maintaining passband impedance matching.
Solution Approach 2:
Different capacitance characteristics are assigned to different sections of the HPF. The first capacitor is optimized for low-frequency attenuation characteristics, while the second capacitor is optimized for passband impedance matching, allowing each part to have the quality needed for its specific function.
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 solution enhances the attenuation characteristic of the HPF, reducing loss and improving performance in low-frequency regions, while maintaining or slightly increasing loss in other frequency bands compared to previous designs.
Implementation Method 1
Incorporating an additional inductor (L4) connected between the common terminal and the HPF, which allows for reduced capacitance of capacitors in the HPF, thereby improving impedance matching and attenuating characteristics in low-frequency regions.
Data Source
AI summary
A multiplexer includes: a low-pass filter that is connected between a common terminal and a first terminal and is formed of one or more first inductors and one or more first capacitors; a bandpass filter that is connected between the common terminal and a second terminal, has a passband higher than a passband of the low-pass filter, and is formed of one or more second inductors and one or more second capacitors; a high-pass filter that is connected between the common terminal and a third terminal, has a passband higher than the passband of the bandpass filter, and is formed of one or more third inductors and one or more third capacitors; and a fourth inductor that has a first end coupled to the common terminal and a second end coupled to the high-pass filter.