The technique by which particular area/space is restricted from Electro-magnetic (EM) or radio frequency waves is called RF shielding and the box designed for such purpose is called RF shield box.
The magnetic and conductive materials are used to do this task of shielding the RF waves. Copper is popular among all. Metal strip, metal foam and metal screen are also used.
This type of RF shield boxes are most commonly used in RF/wireless device testing to meet stringent RF compliance requirements along with nearby RF devices emitting EM waves.
The Skin depth is the one which determines absorption
characteristics of the shielding material. If it is small then the shielding material is also thin.
It depends on permeability, conductivity and frequency of operation.
Following materials are used in the development of RF shielding.
The metal needed to construct an RF shield is choosen based on level of shielding.
After the material is selected, steps should be taken to reduce seams as well as
penetrations. Also steps to prevent formation of oxidation & galvanic corrosion is also
Copper: It is widely used as RF shielding material and it is versatile. It is highly conductive. It does not oxidize immediately when exposed in the natural environmental conditions.
Aluminium: It is also one of the material used as RF shielding material like copper. For wall covering, heavier gauge aluminium is used compare to copper. Due to this it is more difficult to form and fabricate. Inspite of these demerits, aluminium is popular due to its non-ferous properties as well as strength to weight ratio. Morever is ability to extrude the desired custom shapes. As a non-ferous material it exhibits reduced lower frequency H field shielding.
Steel: It provides low frequency magnetic shielding features which are missing in copper and aluminium. It is a ferromagnetic material. Steel used as RF shielding is protected from environment till the duration of its use.
RF shield Box or RF shielding Test Enclosures
Following factors are considered before selecting or purchasing
an RF shielded enclosure:
➤The material selected should provide desired shielding level.
➤Reduce the amount of seams as well as penetrations in the shield enclosure to bring down potential points of deterioration.
➤Increase the quality of seams as well as penetrations for long term reliability and best performance.
The DUT (Device Under Test) is housed in a shield box and cables are run out from small openings to connect with test equipments to do the test.
Following are the popular RF shield box manufacturers/suppliers.
RF Test enclosures and shield boxes from Ramsey Electronics.
Solutions for all your RF Shielding and RF Shield Boxes for Wireless Testing are available
from Concentric Technology Solutions, Inc. Texas, US
Model: 5230 table top RF test enclosure
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