GTEM 250 Emission and Immunity Testing for IEC/EN 61000-4-20

The GTEM 250 cell is a TEM waveguide with the upper frequency limit extended to the GHz range. It is a low-cost alternative measurement facility for both radiated emission and immunity measurements. It is included in the recently published standated IEC/EN 61000-4-20 "Emission and Immunity Testing in Transverse Electromagnetic (TEM) Waveguides”. Compared to other measuring methods like EMC test in anechoic chambers or OATS (Open Area Test Sites), GTEM-cells offer some significant advantages for the testing of small and medium sized EUT's.

(Equipment Under Test) up to a frequency range of 20 GHz. Quick turnarounds of the EUT as well as numerous testing variations are easy and fast to handle. Switching from emission to immunity testing requires only simple adjustments from receiver input to amplifier output. You are irrespective of long waiting times associated with off-site test labs or weather and ambient delays that can occur at OATS facilities. Whether you are at the design qualification, precompliance, compliance, or production sampling stage, the GTEM is the right choice for you!.

Apex	Locking System
Technical Panel	Multipoles Filter

Theory of operation

GTEM 250 cells (Giga-hertz Transversal Electro-Magnetic cells) are waveguide structures intended for electromagnetic compatibility measurements, as well as biomedical applications. The electromagnetic field distribution inside the cell is in TEM mode. With TEM mode propagation, there is no component of electric and magnetic field in the direction of propagation of electromagnetic wave. Therefore the field components are strictly perpendicular. Assuming the field distribution ideal TEM below the cut-off frequency of the cell (before the introduction of higher order modes), the electromagnetic field distribution can be considered static.

GTEM 250 Applications

• EMI and EMS devices
• Radiation and susceptibility test
• Specifically designed for telecom application
• Biomedical and dosimetrical applications
• Isotropic sensors calibration
• Receiver sensitivity test

GTEM 250 Installation Manual and General Safety Instructions

The GTEM GigaHertz Transverse Electromagnetic) cell is a precision electromagnetic compatibility (EMC) test instrument primarily intended for use as radiated immunity and radiated emission test facility without environmental electromagnetic interference. The cell is electrically similar to a coaxial cable with one side open (the apex) and other side closed on the impedance of the generator or receiver connected. In this case with a multimeter appears as 50 Ohm resistance.

Measurement Setup

The setup for emission measurements in a GTEM cell is shown below. The EUT is placed inside the GTEM and its radiation is measured with a receiver. The receiver can be software controlled and some software that includes the GTEM to OATS correlation is commercially available.