Multilayer Differential Filter for Common-Mode Signal Rejection
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Solution Overview
Problem
Existing filters with balanced and unbalanced inputs/outputs face issues such as inability to pass differential-mode signals without allowing common-mode signals, and large size due to λ/2 resonators, or allowing both modes to pass through.
Innovation Solution
A multilayer filter design with specific resonant circuits and capacitive-inductive configurations that include λ/2 and λ/4 resonators, connected in parallel and magnetically/capacitively coupled, to allow differential-mode signals while blocking common-mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If λ/2 resonators are used in the filter, then the filter can pass differential-mode signals, but the filter size becomes large
Solution Approach 1:
The patent combines λ/2 resonators and λ/4 resonators in a single filter structure, where the λ/2 resonators provide differential-mode signal transmission capability and the λ/4 resonators provide common-mode signal rejection. This merging allows the filter to achieve both functions simultaneously without requiring separate filter structures, thereby maintaining reliability while controlling size.
Solution Approach 2:
The filter structure is designed to perform multiple functions: λ/2 resonators handle differential-mode signals while λ/4 resonators handle common-mode signals. This multi-functionality allows a single filter to replace what would traditionally require separate components, reducing overall filter size while maintaining signal transmission reliability.
2Volume of moving object
If two low pass filters are formed in one multilayer body, then the filter size is reduced, but both differential-mode and common-mode signals pass through
Solution Approach 1:
Different regions of the multilayer filter body are assigned different functions: λ/2 resonator sections are optimized for differential-mode signal transmission while λ/4 resonator sections are optimized for common-mode signal rejection. This local differentiation allows each part to specialize in its function, achieving common-mode rejection reliability while maintaining compact size through the shared multilayer structure.
3Device complexity
If a filter with balanced and unbalanced inputs/outputs is used, then the structure is simplified, but differential-mode signals cannot pass through properly
Solution Approach 1:
The filter employs asymmetric resonator configurations where λ/2 resonators are specifically designed for differential-mode signal paths while λ/4 resonators are designed for common-mode signal paths. This asymmetric design allows the filter to properly handle differential-mode signals even with balanced input/output terminals, resolving the contradiction between structural simplicity and signal transmission reliability.
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 filter effectively passes differential-mode signals while preventing common-mode signals, and is compact in size by optimizing resonator lengths and conductor patterns.
Implementation Method 1
multiple λ/2 resonators are provided between an unbalanced input/output terminal and a pair of balanced input/output terminals
Implementation Method 2
The first stage resonant circuit and the final stage resonant circuit each include an inductor, and the at least one intermediate stage resonant circuit includes an inductor and a capacitor connected in parallel to each other
Implementation Method 3
the at least one intermediate stage resonant circuit includes an inductor and a capacitor connected in parallel to each other
Data Source
AI summary
A filter includes a first input/output terminal, a second input/output terminal, a third input/output terminal, a fourth input/output terminal, a first stage resonant circuit connected between the first input/output terminal and the second input/output terminal, at least one intermediate stage resonant circuit, and a final stage resonant circuit connected between the third input/output terminal and the fourth input/output terminal. The first stage resonant circuit and the final stage resonant circuit each include an inductor. The at least one intermediate stage resonant circuit includes an inductor and a capacitor connected in parallel to each other, and one end of the inductor and one end of the capacitor connected in parallel to the inductor are connected to a reference potential.