Calculating Volumetric Site Voltage Standing Wave Ratio in Hybrid Chambers
Volumetric site voltage standing wave ratio in hybrid chambers isolates 3D quiet zone reflections by converting normalized spatial field ripples into linear ratios.
Volumetric Site Voltage Standing Wave Ratio
Meaning
Measurement techniques used to evaluate the suitability of a test site for high-frequency radiated emissions testing check the presence of standing waves. Evaluating the volumetric site voltage standing wave ratio determines if the chamber is suitable for testing above one gigahertz. This evaluation is required to ensure that the test results from different laboratories are comparable.
Site Validation
Multi-point measurements must cover a cylinder of different heights within the quiet zone of the chamber. When calculating the volumetric site voltage standing wave ratio, the system measures the interference between the direct and reflected waves. This procedure is defined in the CISPR standards and is necessary for lab accreditation.
It provides a detailed map of the internal reflections of the room.
Scan Execution
Automating the positioning of the antenna is done to reduce the time needed to complete the multi-point sweep. The calculation of the volumetric site voltage standing wave ratio requires a series of sweeps across different path lengths. This scan is repeated with different antenna polarizations and at different test volumes.
The resulting values are saved to the laboratory compliance logbook. High-performance software helps compile these sweeps into a unified validation report.
Test Threshold
Limit values for this parameter are specified as a maximum ratio of six decibels to pass certification. If the volumetric site voltage standing wave ratio is too high, the test site cannot be used for certified emission testing. This failure requires the installation of additional foam absorbers on the floor of the chamber.