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.
Quiet Zone Measurement
Meaning
Verification of the test volume in an anechoic chamber ensures that the electromagnetic field is uniform and free from unwanted reflections. Through quiet zone measurement, test laboratories define the physical boundaries where a device under test can be placed for accurate measurement. This step guarantees that any variation in the results is caused by the device, not the room.
Spatial Uniformity
Evaluation of the test volume involves moving a calibrated antenna through a grid of pre-defined points. The data from the quiet zone measurement shows the spatial variations in the field strength across the designated region. These variations must remain below a specified decibel threshold to meet international standards.
Testing laboratories use these values to determine the maximum size of the product they can test. This measurement ensures that a wireless module placed anywhere within the designated cylinder is exposed to the same signal density.
Chamber Certification
Documenting the uniform region of the chamber is required for formal accreditation by regulatory bodies. The quiet zone measurement provides the objective evidence needed to prove that the testing environment is stable. This report is reviewed by auditors during the annual facility inspection.
Without this certification, the laboratory cannot issue compliant test reports to product developers.
Testing Procedure
Standard procedures require the sweeps to be repeated for different frequencies and antenna polarizations. If the quiet zone measurement shows a sudden degradation in performance, technicians must inspect the absorber wall for damage. This routine maintenance prevents testing delays and ensures consistency between different test runs.