Noise Suppression Sheet
Noise Suppression Sheet (FJM Series) is a functional film of the FJM Series whose main purpose is to attenuate unwanted high-frequency noise (electromagnetic wave components) generated inside electronic devices and automotive systems.
It is designed with the concept of suppressing radiated noise generation rather than "completely blocking" or "reflecting" electromagnetic waves.
It contributes to stable operation and improved reliability of products by reducing noise levels while maintaining design flexibility.
Why is "Noise Suppression" Necessary?
Common Problems in Actual Equipment
- The design was supposed to pass EMC testing, but in reality, electromagnetic waves are leaking out at levels that would fail the test
- Noise conditions change with surrounding conditions (temperature, orientation, wiring)
- There are multiple noise sources, making it difficult to identify the cause
In such cases,
- Adding a shield case
- Adding a ferrite core
Point measures alone may be insufficient.
"Not completely stopping the noise, but lowering it to a level that is not a problem"
The material for this purpose is the noise suppression sheet.
Mechanism of Noise Suppression
Noise suppression sheets are materials that attenuate electromagnetic waves by acting on the impedance of the circuit.
Basic Principle
- Noise (electromagnetic waves) is generated
- By attaching the sheet, it acts on the impedance of the equipment
- Noise is weakened
This is the general basic principle.
The FJM Series uses the same principle.
Basic Structure of FJM Noise Suppression Sheet
Structural Features
- Very thin (under 50μm / with adhesive layer)
- Lightweight
- Flexible
- Can be applied to curved and narrow areas
It can be used by "attaching on top of the noise source" rather than "surrounding the component".
Resistive Film Grades and Noise Suppression Characteristics
The characteristics of FJM Series noise suppression sheets vary depending on the resistive film.
Transmission Attenuation Rate
Microstrip Line Method
| Resistive Film | Surface resistivity (Ω/□) | Features |
|---|---|---|
| S200 | Approx. 120 | Relatively high conductivity, for noise countermeasures |
| S250 | Approx. 260 | Balanced type |
| S350 | Approx. 380 | Effective for high-frequency bands |
Frequency Band Where Noise Suppression Sheet Excels
- GHz Band
- Circuit-derived noise
- Radiated noise from cables
Main Applications and Usage
| Common issues | Target | Effect | |
|---|---|---|---|
| Automotive ECU / Control Systems, Integrated Circuits, Boards, Cables | Board interference / Insufficient margin in EMC testing | Attachment to board Enclosure inner wall | Radiated noise reduction Improved stability during actual operation |
| General Electronic Devices | - | Around CPU/FPGA Near IC Around high-speed memory | A major advantage is the ability to make retrofit adjustments with minimal design changes. |
| Around communication / signal lines: | - | High-speed communication connectors Flex cables Internal module wiring | Crosstalk reduction Noise interference reduction * It is valued for not significantly weakening the signal itself. |
Difference Between Noise Suppression and Electromagnetic Wave Absorption
| Viewpoint | Noise suppression sheet | EMI absorption sheet |
|---|---|---|
| Purpose | Noise reduction | EMI absorption |
| Frequency | Wide | Wideband or narrowband |
| Intensity | Gentle | Strong |
| Main Use | ECU/Board | Radar / Radiation countermeasures |
- "Malfunction Prevention" = Noise Suppression
- "Radiation / Reflection Countermeasures" = Absorption Sheet
This is the basic distinction.
Benefits of Noise Suppression Sheet
Design Aspect
- Pinpoint countermeasures near noise sources
- Easy to use without frequency analysis
- Retrofit and fine adjustment possible
Implementation Aspect
- Thin and lightweight
- Compatible with curved and narrow areas
Evaluation Aspect
- Effective for securing EMC margin
- Easy to use as a market trouble countermeasure