Three-Resonator Filter Circuit With Dual Attenuation Poles
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Solution Overview
Problem
Existing band pass filters require four or more resonators to generate attenuation poles in both sides of the pass band, which hinders their miniaturization for use in small communication devices like smartphones and cellular phones.
Innovation Solution
A filter circuit and device utilizing three resonators, including a first and third resonator magnetically coupled and capacitively coupled, with a second resonator of a both-ends open type, to generate attenuation poles on both sides of the pass band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four or more resonators are used to generate attenuation poles in both sides of the pass band, then the attenuation characteristics are improved, but the device size increases
Solution Approach 1:
The patent combines magnetic coupling and capacitive coupling between resonators to achieve dual attenuation poles. Specifically, the first and third resonators are magnetically coupled while also being capacitively coupled through a capacitor, allowing three resonators to generate attenuation poles in both frequency regions, thereby reducing device size while maintaining attenuation characteristics
Solution Approach 2:
The patent changes the coupling parameters by introducing both magnetic coupling (through adjacent resonator positioning) and capacitive coupling (through explicit capacitors). This dual coupling mechanism alters the system's electrical characteristics, enabling attenuation pole generation with fewer resonators and thus reducing device volume
2Volume of moving object
If the number of resonators is reduced to less than four, then the device size is reduced, but attenuation poles cannot be generated in both sides of the pass band
Solution Approach 1:
The patent merges magnetic coupling and capacitive coupling mechanisms in a three-resonator configuration. The first and third resonators are positioned for magnetic coupling while capacitors provide capacitive coupling, creating multiple signal paths that generate attenuation poles in both frequency regions despite using fewer resonators
Solution Approach 2:
Capacitors are introduced as intermediary elements between resonators to provide capacitive coupling. These capacitors act as mediators that enable additional signal paths and coupling mechanisms, allowing the three-resonator system to achieve attenuation pole generation in both sides of the pass band
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 three-resonator structure allows for symmetrical design and reduced size while maintaining effective attenuation characteristics, enabling the filter to function as a band pass filter with improved insertion loss and return loss in both frequency regions.
Implementation Method 1
The first resonator and the third resonator are magnetically coupled with each other
Implementation Method 2
The first resonator and the third resonator are magnetically coupled with each other and capacitively coupled with each other
Data Source
AI summary
A filter device includes first and second terminals, a ground terminal, a first resonator connected to the first and second terminals, and a third resonator connected to the second terminal. A second resonator is coupled with the first and third resonators. The first and third resonators are magnetically and capacitively coupled with each other. The first resonator includes a first inductor and a first capacitor connected in parallel between the first terminal and the ground terminal. The third resonator includes a second inductor and a second capacitor connected in parallel between the second terminal and the ground terminal. The second resonator includes a third inductor including first and second end portions, a third capacitor including a first end connected to the first end portion of the third inductor, and a fourth capacitor including a first end connected to the second end portion of the third inductor.