Microwave Absorbing Sheets: Principles and Common Frequency Ranges
Microwave absorbing sheets reduce the reflection and transmission of electromagnetic waves. By working principle they fall into three groups, and knowing which one applies helps when matching a sheet to the frequency band you care about.
Three working principles
- Absorption: the wave enters the material and its energy is dissipated, mainly as heat.
- Reflection: the wave (for example, radar) is reflected at the surface, reducing the radar cross section, and the reflection is directed toward non-critical areas so the receiver sees as little signal as possible.
- Interference: a surface structure or material design creates a path difference, so that waves along different paths cancel each other.
Typical sheet specifications
| Type | Thickness (mm) | Areal density (kg/m²) | Absorption band (GHz) | Shielding effectiveness (dB) |
|---|---|---|---|---|
| A | 1.6-1.7 | 4.6 | 8-40 | 20 |
| B | 0.96 | 2.6 | 8-40 | 15 |
| C | 0.56 | 1.24 | 8-40 | 10 |
| D | 0.55 | 1.27 | 30-100 | 25 |
| E | 0.71 | 3.16 | 30-100 | 20 |
| F | 3.8 | 10.1 | 2-8 | 15 |
| G | 0.2-1.5 | 0.5-3 | 0.05-10 | 15 |
Reading the table
- Thickness and weight vary widely with the band: type F, for 2-8 GHz, is 3.8 mm thick, while types D and E, for 30-100 GHz, are under 1 mm.
- Within the 8-40 GHz band, shielding effectiveness rises with thickness from type C to type A.
- Type G covers the widest range (50 MHz to 10 GHz) and is relatively thin.
To choose a sheet, fix the operating frequency first, then check the available space and weight limit, and finally confirm the attenuation you need.