RF Shielding is a key term used in electronics. If you are designing, testing, manufacturing an electronic product, RF shielding would be a part of your business. Without RF shielding, you cannot fulfil some product or test site requirements. Thus, depending on the application, RF shielding products vary. A small gasket used in an IT equipment or a huge test chamber are both used for RF shielding. On this post, you will find every aspect of RF shielding.
What is RF shielding?
RF shielding means blocking the radio frequency signals. It is used for keeping RF energy within an enclosure or material and minimizing emissions outside that enclosure or material. For RF shielding there are three items:
1) Inner space of enclosure/material
2) RF Shielding material
3) Outer space of enclosure/material
RF shielding material is used to block or minimize RF signal interaction between inner and outer spaces. Shielding material cannot block the RF signals %100, thus shielding performance is defined by shielding effectiveness.
What is RF shielding effectiveness?
Hence the shielding material cannot block all energy, the shielding or screening performance is shown by shielding effectiveness or screening effectiveness parameter. It shows how much of RF energy can be blocked at a specified frequency. For instance, if an RF shielding material can shield RF signals 100dB at 80MHz, this means if the level of a 80MHz RF source is 30dBm and it will allow -70dBm. RF Shielding Effectiveness of a material measured by some measurement techniques defined on international standards. For measuring RF shielding effectiveness, you will basically need these three items on your setup:
1) RF Source (Signal source/generator)
2) RF Shielding Material
3) Measurement Receiver
RF Shielding Materials
For RF Shielding copper, steel and aluminum are mostly used materials. Silver, beryllium, nickel, polyamide and some other raw materials are also used depending on the application and the form of structure. Structure of RF shielding varies different forms of RF shielding materials like:
Gaskets, Foil Tapes, Conductive Tapes, Shielding Fabrics, Fingerstock Gaskets, Conductive Elostomers, Wire Mesh and Knitted Gaskets, Metal RF Gaskets, EMI Gaskets, Shielding Panels and Shielding Enclosures.Stainless Steel RF Shielding Mesh, Shielding Fabric (with and without adhesive backing), custom-made RF Shielding clothing, Magnetic Shielding Foil
Where RF shielding is used?
RF shielding is a technique used in many fields that require RF protection. Some of the application areas are listed below
- Electromagnetic Compatibility (EMC) measurements and tests of electronic products/systems
- Electromagnetic Interference (EMI) measurements and tests of electronic products/systems
- Radio Frequency (RF) and Microwave measurements
- Antenna measurements
- Anechoic Chambers used for acoustics, EMC, RF measurements
Official and Governmental Organizations
- Security rooms especially for official buildings like hospitals and police offices
- Security rooms for banks and financial organizations
- Intellegince security
- Safe rooms
- Developing new electronic products and systems used in any industry (defense, automotive, communications, iot, radio devices, space, railway, avionics, consumer electronics and etc.)
- Developing electrical cables
- Developing cabinets and racks
Hospitals and Health Organizations
- EEG (ElectroEncephaloGraphy) measurements
- EMG (ElectroMyoGraphy) measurements
- ECG (ElectroCardioGraphy) measurements
- MEG (MagnetoEncephaloGraphy) measurements
- Magnetic resonance imaging (MRI) rooms of hospitals
- Hospital shielding
- Wearable shielded clothes
- Credit card pouches
- Cell phones pouches
- e-Passport e-Covers and Inlays
- Electronic toll pass pouches
- Shielded Tents
- Magnetic Active Cancellation System
- Faraday Cage
- Passive Magnetic Shielding
- EMF Shielding of electrical substations, switch rooms and cable trays
- RF Doors
- RF Shielded Shipping Containers
Which measurements are performed for RF shielding?
RF shielding quality is determined by performing some measurements before and after RF shielding. These measurements are listed below:
Ambient Measurements (Magnetic Field and Electric Field)
RF Shielding Effectiveness
Performance measurements before RF shielding
Performance measurements before RF shielding
Each product might have its own specific RF shielding performance criteria or standard. Measurements shall be performed with appropriate and standard compliant equipments. Frequency(Hz), field strength(dBuV/m) and shielding effectiveness (dB) are essential parameters that shall exist on the measurement reports.
RF Shielded Cameras, Audio and Video Systems
RF Shielded cameras, audio and video systems are used at EMC and RF test facilities, laboratories, anechoic chambers. RF shielded cameras and microphones ensure that test environment is monitored and recorded without any interaction between applied RF signals and without limited emissions levels. EMC hardened cameras can work under an electric field up to 3000 V/m. If you want to learn more about RF Shielded Audio and Video Systems click the link below:
RF Shielded Rooms or Enclosures
RF Shielding is used to create an RF isolated test or measurement environments. By using RF shielding materials, environment can be easily isolated from RF signals. Since the disturbing signals are minimized, RF shielded rooms or enclosures allow noise-free or disturbance-free test and measurement environment. For EMC, RF, Antenna, Microwave, EEG measurements RF shielded rooms and enclosures are used and required by standards. Performing measurements in an RF shielded room or enclosure will ensure accurate measurement results.
What is the relationship between RF Shielded Room and Anechoic Chamber?
RF Shielding does not deal with reflections, it is only for shielding and blocking the RF.
If a reflection occurs on inner surface, absorbing materials are added on the reflective surfaces to make space anechoic. Thus anechoic chambers require both RF shielding and absorbing materials. As below illustration shows, outer walls are for RF shielding, inner walls are covered by absorbing materials like ferrite tiles and/or RF absorbers.
RF Shielding Performance of Rooms or Chambers
There regional and international standards regarding RF shielding performance of a chamber or room. IEEE 299 and EN 50147-1 are the well known ones. Definition of Shielding Effectiveness (SE) is
the ratio of the signal received from a transmitter without the shield, to the signal received inside the shield when the shield is placed between the transmitting antenna and the receiving antenna.
Prior to compliance measurements, during installation basic instruments can be used to check whether the installation is proper or not. After installation completed, independent and third party measurements are done by calibration lab’s on-site team.
Are you looking for any RF Shielding Product or Service?
We are offering RF shielding products and services with our collabrative partners. Get Quote from us for these products or services:
- Metallic Panels
- Enclosures and Cabinets
- Anechoic Chambers
- Honeycomb Air Vents
- RFI Traps
- On-site installation
- On-site validation