Normally, radiated emission tests are carried out in anechoic chambers equipped with antennas to pick up the radiated signals. Due to bandwidth limitations, several antennas are required to cover the complete frequency range. Furthermore, it requires a lot of space and the cost of the equipment for a standard configuration setup is considerable. An engineer of a small or medium size enterprise usually has to rely on his experience and on best practice methods in order to design an EMC compliant product. Nevertheless, it is estimated that >50% of products fail EMC compliance tests at the first attempt. Every time an engineer sends a new product for compliance testing, it is a shot in the dark. Failing is very expensive. Not only is the cost of re-tests high, but also the project schedule and market introduction gets delayed.
What’s needed is a compact and affordable laboratory setup to measure radiated emissions, prior to submission for EMC compliance testing. A TEM cell is the right piece of equipment for desktop testing of radiated emissions.
TEKBOX has developed the TBTC3 to cover the complete frequency range up to 730MHz and with usability at even higher frequencies. Combined with a spectrum analyser, products can be tested before and after EMC related design modifications. A TEM cell based setup will not deliver exactly the same quantitative results as a measurement in a certified test house, however it will give an excellent indication on whether the design suffers from excessive radiated noise or not. An engineer will clearly see whether his modifications changed the EMC performance, for better or for worse. An open TEM cell eliminates the guesswork.
A TEM cell is a stripline device for radiated emissions and immunity testing of electronic devices. It is not a replacement, but due to its size and cost it is a convenient alternative to measurements in an anechoic chamber. 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. The TBTC3 is a so called open TEM cell which has no side walls for convenient placement of the DUT. It may pick up RF background noise, which can be taken into account by doing a measurement of the cell output signal before powering on the DUT.
TEKBOX TEM cells have a better frequency response compared with standard TEM cells of similar size. TEM cells suffer from higher order wave modes which limit the usable bandwidth. A unique design feature of TEKBOX TEM cells is the implementation of resistance perpendicular to the desired propagation direction of the wave. Consequently higher order wave modes and resonances are suppressed.
The device is supplied together with a 50Ω/25W RF termination and a DC block to protect the spectrum analyser or RF receiver input.
The TEKBOX TBTC3 open TEM cell is delivered as a kit that has to be self-assembled.