Design of a Tunable Absorber Based on Active Frequency-Selective Surface for UHF Applications

Area of Science:

• Electromagnetics
• Materials Science
• Metamaterials

Background:

• Conventional absorbers often lack tunability and are bulky.
• The ultrahigh frequency (UHF) band requires compact and adaptable electromagnetic wave absorption solutions.

Purpose of the Study:

• To develop an ultrathin, tunable absorber for the UHF band.
• To demonstrate control over reflectivity using active electronic components.

Main Methods:

• Designed a single-layer absorber based on a Salisbury screen topology.
• Replaced the resistive layer with an active frequency-selective surface (AFSS) loaded with resistors and varactors.
• Verified performance through simulations and experimental measurements.

Main Results:

• Achieved tunable reflectivity below -10 dB from 415 to 822 MHz.
• The absorber has a total thickness of 10 mm (λ/72 at the lower limit frequency).
• Simulated volume loss density distributions illustrated the absorption mechanism.

Conclusions:

• The proposed AFSS absorber offers effective and tunable absorption in the UHF band.
• The absorber's performance is sensitive to varactor bias voltage, AFSS design, and material properties.
• This technology enables compact, adaptable electromagnetic wave absorption for various applications.