Reliant EMC

Cells & Chambers

 

Summeries of EMC Chambers and Cells are provided below:
  • Automotive Chambers
    Compact Chambers
    Fully Anechoic Chambers
    GTEM Cells
    LaplaCells
    Mil-STD Chambers
    Semi Anechoic
    Striplines
    TEM Cells
    TEM Cells - Open
    TEM Cells - Closed
    Ultra Compact Chambers
  • There is a LaplaCell vs GTEM matrix below.
    There is also a quick overview of the LapaCells products below.
    Reliant EMC also offers Environmental Chambers from Sanwood.

    Each technology has its positive features to consider:
    Automotive Chambers – were developed for radiation testing of automotive components according to the standard DIN/ISO 11452-2 and EN 55025 (CISPR 25), and for radiated emission and immunity testing on vehicles and components according to CISPR 12 / 25 and ISO 11451-2 / ISO 11452-2. The standard version of the Automotive Component Testing Chamber (ACTC) is qualified for measurements in the frequency range from 30 MHz to 18 GHz.
    The standard version of the Automotive Vehicle Testing Chamber (AVTC) is qualified for measurements in the frequency range from 20 MHz to 18 GHz. The AVTC can be upgraded for emission measurement according to EN 55022 (CISPR 16-1-14) and immunity testing according to IEC/EN 61000-4-3 with the optional addition of floor absorbers.
     
    Compact Chambers - is a solution for immunity tests according to IEC/EN 61000-4-3 for a measuring distance of 3.0 m and offers for its size the best characteristics for pre-acceptance emission measurements. The Compact Chamber is qualified for measurement in the frequency range from 30 MHz to at least 18 GHz. The Compact Chamber can be delivered as a semi-anechoic or as a fully anechoic chamber.
     
    Fully Anechoic Chambers – are defined in CISPR 16-1-4 as “Test site without ground plane”. The advantage of FAC´s is mainly, that reflections from the floor cannot occur and therefore an antenna height scan is no longer necessary, what may save a lot of measuring time. Anechoic chambers for 10 meter measuring distance are planned exclusively at customers´ requirements. 
     
    GTEM Cells – Takes co-axial input feed and gradually expands the section. It uses absorbers on the end wall to prevent reflections. A Co-axial core feeds a spectrum plate which is used as the antenna and offset at an angle with the ground plane to increase the size of the DUT with the size of the cell.  GTEM is an efficient design which requires relatively low power input in order to generate the field needed for immunity testing inside the cell.  The cells upper frequency limits are quoted up to 20 GHz but it must be noted that there are resonances above 1GHz range.  For bigger size DUT some assembly may be required.

     

  • Open TEM Cell – Radiated emission tests are typically carried out in anechoic chambers, using antennas to pick up the radiated signals. Due to bandwidth limitations, several antennas are required to cover the complete frequency range. A TEM cell is the right piece of equipment for desktop testing of radiated emissions. Open TEM cells cover the complete frequency range up to 2GHz and with usability even at frequencies beyond. Combined with a spectrum analyzer, products can be tested before and after EMC related design modifications.
    A TEM cell is a stripline device for radiated emissions and immunity testing of electronic devices.
    A TEM cell consists of a septum, the conductive strip in the centre section and walls which are connected to ground. The geometry is designed to present a 50Ω stripline. The device under test (DUT) is placed in between the bottom wall and the septum.
    Open TEM cells which have no side walls for convenient placement of the DUT.

     

Closed TEM Cell – Transverse electromagnetic (TEM) transmission-line cells are devices used for establishing standard electromagnetic (EM) fields in a shielded environment. The cell consists of a section of rectangular coaxial transmission line tapered at each end to adapt to standard coaxial connectors (Figure 1). You use TEM cells for emission testing of small equipment, for calibration of RF probes, and for biomedical experiments. The wave travelling through the cell has essentially a free-space impedance (377 W), thus providing a close approximation to a far-field plane propagating in free-space. The cell also has limitations, among which is that the upper useful frequency is bound by its physical dimensions which, in turn, constrain the size of an item you can test with the cell.
Figure 1: TEM-cell diagram.
 

  •  
    LaplaCells – Revolutionary design which brings the best of TEM and GTEM Cell technologies into one product. Consider this as two GTEM cells put back-to-back to each other. The use of dual septum technology achieves the field uniformity in a GTEM like cell and it allows maximum DUT size volumetric room for the given size of the cell.  The LaplaCell Includes sensors for field measurement inside the LaplaCell for real time feedback signal to be used by the Immunity Test System supplied by Laplace Instruments to achieve IEC61000-4-3 testing.  All LaplaCell's comes calibrated for both Emission and Immunity.  A Full size door allows greater accessibility to the DUT room area. Impedance match balun used for balancing the septum's and converts the 50 Ohm co-axial input impedance to 200 Ohm characteristic impedance inside the cell bring this cell closer to the free space impedance of 377 Ohm. Absorbers at the end of the cell eliminate reflections and filtered ancillary cabling room eliminates any signals from the outside of the cell from influencing the testing inside the cell.  No on-site assembly required. 
     
    MIL- STD Chambers – is designed to fulfill the requirements for radiated emission and immunity testing according to MIL-STD 461E. The standard version does already include the contact, the testing table, and it is qualified for measurements in the frequency range from 30 MHz to 18 GHz.
     
    Semi Anechoic Chambers – is used for Emission and Immunity test measurement at distance of 3 or 5 meters. It´s dome shaped roof as well as it´s optimized absorber layout, with ferrite and partial hybrid absorber lining for the frequency range from 26 MHz to 18 GHz, leads to minimized reflections. The SAC-3 / -5 Plus delivers outstanding performances for both, NSA (±3.5 dB) from 30 MHz to 1 GHz, and SVSWR (5 dB) from 1 GHz to 18 GHz conforming to the site validation standard CISPR 16-1-4 for SVSWR. The standard version does already include the antenna mast for 1-4 m height scan, the turntable as well as their controller.
     
    Stripline – a transverse electromagnetic transmission line. Unlike waveguide cells, Stripline has no lower cutoff frequency. Stripline requires a plain and rugged construction for mounting and operation. Stripline is made by etching DUT on a substrate that has a ground plane on the opposite faces. 
     
    TEM Cells – Simple, good field uniformity and efficient which requires low power to generate high field strength between the septum and ground plane of the cell.  DUT size influences upper frequency of the cell.  Upper limit frequency ranges from 200 MHz to 3000 MHz. Ready to be used off the box.

     

  • Ultra Compact Chambers – was manufactured as an alternative to GTEM for pre-compliance measurements as well as for the fields of research and science. Ultra Compact Chambers are qualified for measurements in the frequency range from 30 MHz to 18 GHz. The Ultra Compact Chamber can be used for pre-compliance radiated emission measurements and immunity tests according to the standard IEC/EN 61000-4-3 in 1.0 m measuring distance, DIN/ISO 11452-2 and EN 55025 (CISPR 25) standards.
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Laplace Instruments LaplaCell vs GTEM
LaplaCell
GTEM
Dual Septum - No resonances up to 3GHz
Single Septum - Resonances above 1GHz
Shielded and Filtered I/O compartment
No Shielded I/O compartment
Built in isotonic probe
isotonic probe required for immunity testing
Compact Size for equal EUT size
Requires 3 time the space
Free space impedance 200 Ohm
Free space impedance 50 Ohm
CE Certification self certification
CE Certification pre-compliance testing only
More efficient: A 10 Watt amplifier achieves 25V/m inside cell
GTEM requires a 35 Watt Amplifier to achieve a 10V/m inside the cell
 
Overview of the LaplaCell products from Laplace Instruments
Laplace Instruments LaplaCell
The LaplaCells are a modified form of GTEM cell, using a balanced dual septum design which maximizes EUT volume for a given external size of cell, and dramatically improves field linearity.
The EUT volume is fully lined in structural polycarbonate capable of supporting heavy products and access is via a large, full height door at the end of the cell.
Adjacent to the door is the I/O filter compartment which can be customized to suit the user’s requirements. USB, RS232, Parallel, Ethernet, co-ax and other product specific filters can be added at time of ordering.
1) The Laplace Instruments LaplaCell products (300 & 600) utilize a dual septum technology. This is like taking two GTEM Cells and putting them against each other and taking away the ground plain. Due to this technology, you get data from both septum's at the same time. This requires the use of a Balun for Balancing and Impedance matching, which is limited to 3GHz at this time.
2) The advantage of this technology is that with the LaplaCell you do not have resonances up to 3GHz whereas with GTEM you will have resonances influencing your testing above 1GHz. What this means is that a LaplaCell is usable for its specified range whereas GTEM can give problems if used above 1GHz. Most of the standards today do not go above 3GHz.
3) Please also note that with the LaplaCell products, I/O cables are brought in through an I/O filter compartment with shielded and filtered I/O ports so that cable signals do not influence testing within the cell. With GTEM products I/O feeds/cables are brought in through holes on the doors or a back panel.
4) There is no need for an isotonic probe for immunity testing with the Laplace LaplaCell products. This is a $10,000USD savings. An isotonic probe is needed for someone that purchases a GTEM and wants to perform Immunity testing. By using the isotonic probe the customer would know the field in V/m inside the cell. He would have to do this before every test. With the LaplaCell products, this is unnecessary because the probe is already inside the cell and is used in real time to insure the needed V/m inside the cell during the Immunity test.
5) Ambient noise shielding capabilities of LaplaCell600-3 don’t stop at 3GHz. The thickness of the metal case cover insures that ambient noise don't transfer inside the testing room.
6) The LaplaCell600-3 can sit on a 2x4 foot table and you would have room to put the instrumentation on the table also. Please also note that with GTEM you would need 3 times (10 feet long) more the space due to the overall size of the cell in order to achieve the same DUT test side room inside the cell. 
7) LaplaCells uniformity field up to 3GHz would give you information that would be closer to OATS. This is because the free space impedance of the LaplaCell is 200 Ohm. In a GTEM this value is 50 Ohm. OATS has it 377Ohm. The LaplaCell is much closer matched with OATS than GTEM. As a result, many LaplaCell users self-certification their EUT’s for CE Certification and as a pre-compliance cell for FCC Certification. GTEM has resonances above 1GHz which would mean that your harmonics may show higher than the fundamental for your product. This is one of the biggest reason why they only promote the GTEM cell as pre-compliance only device.
 
Key Points
· 30MHz to 3GHz frequency coverage
· Fully calibrated for Emissions (correlated to a 3M distanced test on OATS) and immunity (fully calibrated up to 27 points in accordance with IEC61000-4-20)
· Lc300/2: for EUT up to 30cm cube
· Field sensor for immunity testing is included
· Complies with IEC61000-4-20
· Excellent field uniformity
· Compact size
· Ready for immediate use upon delivery. No assembly required.
· Standard filtered I/O includes mains feed, fiber optic access and 12 individual connections.
 
For details on our complete line of Cells and Chambers, please see the links to the right.
 


Cells & chambers