Low-pass filter for common-mode and differential-mode interferences

The technology is based on constructive modifications of electrical conductors by means of conductive layers with structured surfaces for absorptive low-pass filter applications.

Challenge

Power electronics comprises, among other things, the conversion of electrical energy using switching elements. Rapid switching operations can cause conducted interference, which can be mitigated with suitable materials and by switching inductance and capacity. Effective coating of the inner conductor, which is often made of copper, can reduce conduction losses. Incorporating metal alloys between the inner and outer conductors can reduce differential-mode interference. Differential-mode interference can be mitigated by addressing the skin and proximity effects. However, efficient filtering of common-mode and differential-mode interferences still remains a challenge.

Our Solution

The present invention describes the modification of electrical conductors by means of conductive layers with structured slots and channels. The increased specific surface area and rerouting of the current path result in higher Ohmic losses and a vertical current component, which increases the inductive component of the layer, leading to a more effective damping of interferences. For common-mode interference, the low-pass filter layer is provided with slots running transversely or perpendicular to the current direction. These slots can be arranged across the entire layer or a portion of it. This increases the frequency-dependent resistance for common-mode currents, while largely preserving the useful signal on the differential line. For differential-mode interference, the structured layer is positioned between two conductors or wrapped around both conductors as an adhesive strip. Depending on the winding direction, the slots are oriented parallel or perpendicular to the current direction, allowing common-mode and differential-mode attenuation to be combined in a single design.

Figure 1: Modification of two-conductor transmission lines by means of layers with structured slots and channels.

Figure 2: Low-pass filter implementation on ground planes, whereby the surface is contoured using an orthogonal pattern.

Advantages

Integrated common-mode and differential-mode filter functionality without additional components
Enhanced damping by selective adsorption
Surface structuring with established production and printing processes possible
Reduced space requirements, weight and costs

Applications

Power electronics and drive technology
High-speed data transmission lines and interfaces
EMC-optimized cable and connection systems
Integration on flexible foils or adhesive tapes
Intelligent, functionalized surfaces

Development Status

Proof-of-Concept successfully shown via computer simulations. Experimental evaluation planned.

Patent Status

European patent application filed.

Patent holder: Ostfalia University of Applied Sciences (Wolfenbüttel, Germany)

Contact

Dr. Mirza Mackovic
Patent & Innovation Manager Technology
E-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Tel.: +49 551 30724 153
Reference: CPA-2643-FHBW

Published: January 8, 2026.

Tags: Measurement and analysis technology, Physics and Technology & Software