Compact Filter Layout Using Recessed Grounded Substrate

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Solution Overview

Problem

Existing filter devices are required to be further reduced in size.

Innovation Solution

The filter device incorporates a substrate with recessed portions on one main surface that overlap strip-shaped conductors, allowing for a ground conductor layer to cover these recessed portions, and conductor posts to short-circuit the strip-shaped conductors to the ground conductor layer, reducing the distance between adjacent conductors and enabling a smaller device design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If recessed portions are provided in areas of the substrate that do not overlap the strip-shaped conductors to reduce electromagnetic coupling, then the degree of electromagnetic coupling between adjacent strip-shaped conductors is reduced, but the device size cannot be sufficiently reduced

Engineering Contradiction:
Improveelectromagnetic coupling controlVSAvoiddevice size
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The invention applies different structures to different locations: recessed portions are provided only in areas where they overlap strip-shaped conductors in plan view, rather than uniformly across the substrate. This localized approach optimizes electromagnetic coupling control where needed while minimizing impact on device size

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The invention transitions from a two-dimensional planar substrate to a three-dimensional structure with recessed portions. By creating depth variations in the substrate, the invention achieves better electromagnetic coupling control without proportionally increasing the device footprint, thus reducing overall device size

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If the distance between adjacent strip-shaped conductors is reduced to decrease device size, then the device can be reduced in size, but the electromagnetic coupling between adjacent conductors changes

Engineering Contradiction:
Improvedevice sizeVSAvoidelectromagnetic coupling
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The invention changes the physical parameters of the substrate by introducing recessed portions with specific depths and dimensions. These parameter changes allow the substrate to provide both electrical and mechanical functions, enabling closer spacing of conductors while maintaining proper electromagnetic coupling characteristics

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The substrate serves multiple functions simultaneously: as an electrical insulator, mechanical support, and electromagnetic coupling controller. This multi-functional composite approach allows the substrate to maintain proper coupling even when conductors are spaced closer together, enabling device size reduction

Inventive Principle:
Principle #40Composite materials

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 allows for a reduction in the size of the filter device while maintaining electromagnetic coupling, facilitating compact design without compromising performance.

Implementation Method 1

a ground conductor layer which is provided at least to a second main surface and which has a portion covering each of the recessed portions

Methodology Applied
Scientific EffectElectromagnetic shielding: Faraday Cage

Implementation Method 2

strip-shaped conductors which are provided to a first main surface and adjacent ones of which are electromagnetically coupled to each other

Methodology Applied
Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Data Source

PatentEP4207482B1Filter device
Publication Date: 2026.03.25 FUJIKURA LTD
  • EP4207482B1 patent drawingFigure 1(a)~1(c)
  • EP4207482B1 patent drawingFigure 2~3(b)
  • EP4207482B1 patent drawingFigure 4~5

AI summary

An object of this invention is to reduce the size of a filter device. Provided is a filter device (1) including: a substrate (11) including a first main surface and a second main surface (111, 112); strip-shaped conductors (12a1 to 12a5) provided to the first main surface (111); and a ground conductor layer (13) provided at least to the second main surface (112), the second main surface (112) having a recessed portion (11ai) provided for each strip-shaped conductor (12ai), the recessed portion (11ai) overlapping the strip-shaped conductor (12ai) in plan view and having a surface covered with the ground conductor layer (13).