Standardized Field Uniformity Verification in Radiated Immunity Pre Scanning Enclosures
Standardized field uniformity verification prevents pre-scanning errors by mapping spatial grid power profiles inside compact immunity enclosures.
GTEM Cell
Meaning
Test chambers that expand the geometry of a traditional transverse electromagnetic cell allow for the evaluation of larger electronic assemblies. An engineer uses a gtem cell to perform radiated immunity and emissions testing within a shielded environment. The flared shape of the cell acts as a transmission line that transitions into a termination load, creating a predictable electromagnetic field inside.
This setup replaces the need for a large anechoic chamber for many types of pre compliance and full compliance testing.
Field Uniformity
Accuracy in these measurements relies on the creation of a uniform field within a defined volume known as the quiet zone. Inside a gtem cell, the septum and the outer walls maintain a constant characteristic impedance to prevent reflections from disturbing the wave front. This allows for consistent testing of mobile phones, printed circuit boards and small industrial controllers.
The field distribution is calculated based on the input power and the distance from the septum to the floor of the cell.
Equipment Integration
Setup time for a test is reduced because the cell is a closed system that does not require the extensive calibration of an open area site. When using a gtem cell, the device under test is placed on a dielectric support and rotated to measure emissions from different angles. Connection to a spectrum analyzer or signal generator occurs through filtered ports that maintain the shielding integrity of the enclosure.
This configuration protects the laboratory environment from high intensity signals and prevents ambient noise from entering the measurement.
Testing Capacity
Limits on the size of the equipment are dictated by the physical dimensions of the cell and the requirement for field uniformity. While a gtem cell is ideal for small to medium devices, very large systems still require a full anechoic chamber.