Wideband Electromagnetic Wave Absorption Sheet
Wideband Electromagnetic Wave Absorption Sheet (FJM Series) is the core product of the FJM Series, an EMC countermeasure material for absorbing and attenuating electromagnetic waves across a wide frequency band including microwave to millimeter-wave.
It is intended to address not only specific frequencies, but also
- Reflection waves that occur over a wide frequency range
- Unpredictable reflection waves
- Noise from actual usage environments that varies by device
"Cannot identify which frequency is causing the problem, want to attenuate electromagnetic waves at multiple frequencies"
Such situations are where wideband absorption sheets are used.
They demonstrate stable effects while reducing design burden in environments where frequency identification is difficult or overall noise reduction is required.
Why is "Wideband Absorption" Necessary?
Reality of Electronic and Automotive Devices
In actual device interiors,
- Electromagnetic waves at multiple frequencies have an impact
- Frequencies vary slightly between individual products
- Characteristics change with temperature, orientation, and wiring
Such situations are not uncommon.
Therefore,
- Narrowband (pinpoint) countermeasures may miss some issues
- Problems may recur at frequencies other than the measured frequency
Such cases occur.
"First, broadly suppress the whole range"
This is the role of wideband absorption sheets.
Mechanism of Wideband Absorption Sheet
Wideband absorption sheets attenuate electromagnetic waves by utilizing the loss characteristics of the material.
Basic Principle
- Electromagnetic waves enter the sheet
- Pass through the conductive resistive film
- Electromagnetic waves are converted to heat energy
- Weakened without reflection
For this reason, stable attenuation effects can be obtained over a wide frequency band, not just at specific peaks.
Basic Structure of FJM Wideband Absorption Sheet
Structural Features
Wideband absorption sheets
- Do not create specific attenuation peaks
- Effectiveness does not drop dramatically even when frequency changes
They have these characteristics.
It becomes easier to obtain "a certain level of attenuation effect" including the entire GHz band and millimeter-wave band.
Resistive Film Grades and Wideband Type
For wideband applications, the following are mainly used.
| S350 (Representative) |
"Wideband × High frequency" = Basic design concept Main applications: Situations where wideband is effective |
|---|---|
| Communication Devices / Wireless Modules |
An important advantage of wideband absorption is that it is less likely to degrade communication quality. |
Distinction from Narrowband Absorption Sheet
| Item | Wideband absorption | Narrowband absorption |
|---|---|---|
| Target Frequency | Wide range | Specific frequency |
| Design Freedom | General- purpose | Custom |
| When to Use | Overall | Pinpoint |
Benefits of Wideband Absorption Sheet
Design Aspect
- Frequency identification not required
- Less hit-or-miss during prototyping
- Easy to retrofit
Evaluation Aspect
- Easy to use as EMC test countermeasure
- High reproducibility