New Smaller TEMcell for Precompliance Testing

When it comes to pre-compliance EMC testing, radiated emission tests are typically carried out in expensive, dedicated anechoic chambers, using antennas to pick up the radiated signals.  Several antennas are needed to cover the complete required frequency range. Anechoic chambers require a large space commitment - and the equipment cost for a standard conformance setup is very large.

Engineers usually rely on past experience and on best practices in order to design products that are EMC-compliant. But maybe more than 50% of products fail their initial testing. When an engineer sends a new product for compliance testing, it is something of a guessing game and failure is very expensive. Not only are re-testing costs high, but project schedules and market introduction is expensively delayed. 

What is needed is an affordable, compact lab set-up to measure radiated emissions on your own premises, prior to compliance testing. A TEM cell is an excellent solution for desktop testing of radiated emissions. Tekbox has developed open TEM cells that cover the complete frequency range up to 2GHz and can even be used at frequencies above that.   Combining a TEM cell with an affordable benchtop spectrum analyzer, products can be tested before and after EMC-related design modifications.  A test set-up using a TEM cell may not deliver exactly the same quantitative results as certified test house measurements. However, it does provide excellent guidance on whether the product design is producing excessive radiated noise.  And engineers can clearly see how changes improve or degrade the EMC performance - or whether it remains unchanged. Using TekBox TEM cells eliminates the guesswork!

A TEM cell is a basically an RF stripline device, designed for evaluating radiated emissions and immunity testing of electronic devices. It is not a replacement for an anechoic chamber, but it is a convenient and compact first-line alternative. 

A TEM cell consists of a septum, the conductive strip in the center section and walls which are connected to ground. The geometry is designed to present as a 50ohm stripline. The device under test (DUT) is placed in between the bottom wall and the septum.

TBTC0 is a new TEM cell with dimensions 15.3" x 4.0" x 1.1".  TEM cell connectors: N-female

The four models TekBox TBTC0/1/2/3 are so called “open TEM cells” with no side walls, which allows for convenient placement of the DUT.  While it may pick up some RF background noise, this, however, can be taken into account by doing a “blank” measurement of the cell output signal before powering on the DUT.

Tekbox open TEM cells have a better frequency response compared to standard TEM cells of similar size. TEM cells normally suffer from higher order wave modes, which limits the usable bandwidth.  But a unique design feature of the Tekbox TEM cells implements resistance perpendicular to the desired propagation direction of the wave. Consequently higher order wave modes and resonances are suppressed.

All TEM cells are supplied with a 50ohm/25W RF termination, a DC block to protect the spectrum analyzer or RF receiver input, and a N-Male to N-Male coaxial cable.