RF Front-End Filter Layout for Stopband Attenuation and Isolation
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Solution Overview
Problem
As communication devices become smaller and thinner, existing filter devices with multilayer LC resonators struggle to maintain sufficient attenuation characteristics outside the passband due to reduced size, leading to increased coupling between resonators and deteriorated isolation.
Innovation Solution
A filter device with a specific configuration of ground electrodes, capacitor electrodes, and vias that electromagnetically couple resonators, including a via connected between middle-stage resonators, adjusts the coupling degrees to improve attenuation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the filter device is reduced in size, then the device becomes smaller and thinner, but the attenuation characteristics outside the passband deteriorate
Solution Approach 1:
A via connected to ground electrodes is introduced as an intermediary element between the resonators. This via acts as a mediator to adjust the coupling strength between adjacent resonators, enabling control over attenuation characteristics without increasing the overall device size. The via provides an additional degree of freedom in designing the coupling mechanism while maintaining compact dimensions.
Solution Approach 2:
The coupling strength between resonators is adjusted by changing the parameters of the via (such as its position, dimensions, or connection points to ground electrodes). By modifying these parameters, the attenuation characteristics can be optimized for compact filter designs, allowing sufficient stopband rejection even when the device size is reduced.
2Volume of moving object
If the filter device is reduced in size, then the device becomes smaller, but the isolation between input and output terminals deteriorates
Solution Approach 1:
The via connected to ground electrodes serves as an intermediary that controls the electromagnetic coupling between resonators. By adjusting this coupling, the isolation between input and output terminals is improved, preventing harmful signal leakage while maintaining a compact device form factor.
Solution Approach 2:
The isolation characteristics are enhanced by optimizing the parameters of the via structure. By carefully selecting the via's position, size, and ground connection configuration, the coupling between input and output is suppressed, achieving better isolation in smaller filter devices.
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 configuration achieves enhanced attenuation characteristics with increased isolation between input and output terminals, even when the device is downsized, by adjusting the coupling between resonators using strategically placed vias.
Implementation Method 1
The plurality of resonators are between the first ground electrode and the second ground electrode in the normal direction and electromagnetically coupled to each other
Implementation Method 2
Each of the plurality of resonators includes a first capacitor electrode, a second capacitor electrode, and a first via
Data Source
AI summary
A filter device includes a main body, a ground terminal, ground electrodes, resonators, and a via. The ground electrodes are at different positions in a normal direction of the main body. The resonators are between the ground electrodes and electromagnetically coupled to each other. Each of the resonators includes two capacitor electrodes connected by a via. When the main body is viewed in plan view, each of the capacitor electrodes overlaps a respective one of the ground electrodes. The resonators include first resonators respectively connected to an input terminal and an output terminal, and second resonators between the first resonators. The via is between the second resonators when the main body is viewed in plan view from the normal direction, and is connected to the ground electrodes.