BandSorb® ST Series

Thin, Flexible, Resonant Magnetically-Loaded Microwave Absorber

Product Description

BandSorb® ST is a series of resonant absorbers which reflect -20 dB or less of normally incident microwave energy at the design frequency in the range of 1.5 to 26 GHz. Designers can use it for applications requiring absorption at a specific frequency or in a narrow frequency band.


SEM supplies BandSorb® ST series materials in sheets and custom configurations. The standard sheet size is 300 mm x 300 mm. BandSorb®  ST has a varying thickness according to the desired resonant frequency. Grades are designated by a suffix corresponding to the resonant frequency.

Features and Benefits:

BandSorb® ST consists of a thin, flexible, high-loss, magnetically loaded, electrically non-conductive silicone rubber. Silicone absorbers have high service temperature capability (170°C continuous) and allow short exposure to higher temperatures.


BandSorb® ST series can be used to absorb at a specific frequency or in a narrow frequency band, including:

  • Attaching to masts of ships, walls, etc. to reduce reflections and echoes from nearby antennas
  • Attaching to vehicles to reduce radar signature.
  • Lining magnetron housings to prevent detuning.
  • Fabricating into tapered shapes for impedance matching in waveguide or microstrip applications.
  • Suppressing reflections, surface currents, and cavity resonances inside microwave modules.
  • Lining of cavity-backed and shrouded telecommunication antennas where narrowband performance is required, e.g., waveguide feeds.

For module interference, cavity resonance and surface current problems where no specular reflectivity performance is required, BandSorb® ST, is recommended due to its high magnetic loss properties.

Design Frequency Range GHz 1.5 to 18
Thicknesses mm (inch) 1.2 – 4.5 (0.047 – 0.177)
Typical Size mm (inch) 300 x 300 (11.8 x 11.8)
Elastomer Binder Silicone
Hardness ASTM D 2240 Shore A 50-95
Elongation ASTM D 412 % 10-180
Tensile Strength ASTM D 412 MPa (psi) 2-6 (479)
Maximum service Temperature °C (°F) 170 (338)
Flammability Rating UL94* V0
Colour Grey
Volume Resistivity ASTM D 991 Ω-cm (Ω-in) >10(10) (>4 x 10)(9)
Compliance 2015/863/EU (RoHS 2.0) Compliance, REACH SVHC Compliance, Halogen free

*Tested in accordance of UL94 specification
*The technical specification data is based on SEM tests and analysis that we believe to be reliable. SEM will not be held responsible for inaccuracies or omissions contained therein. In all cases – details and values should be verified by the customer.