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.
Phase Center Offset
Meaning
Spatial displacement between the physical center of an antenna and its electrical center represents the point from which radiation appears to originate. For high-precision positioning systems, the phase center offset varies with the operating frequency and the angle of the signal. This variation must be compensated for to ensure accurate distance measurements.
Antenna Design
Feed networks and patch configurations determine the location of the electrical center of the antenna. The magnitude of the phase center offset depends on the substrate thickness and the ground plane size. Designers try to minimize this distance to simplify the calibration algorithms of the receiver.
This task is especially important for dual-band antennas used in automotive navigation modules.
Positioning Correction
Software algorithms in global navigation satellite receivers use a correction table to adjust for antenna displacement. This correction table uses the phase center offset to calculate the true distance from the satellite to the board. If this step is omitted, the resulting coordinate calculations can have errors of several centimeters.
This error is unacceptable for industrial automation and surveying applications. High-precision boards rely on these sub-millimeter corrections to achieve centimeter-level accuracy in the field.
Calibration Accuracy
Chamber testing must map this offset across all operational frequencies during the antenna qualification phase. Standardized tables of the phase center offset are compiled by placing the antenna on a precision turntable. The recorded data is stored in the firmware of the wireless device to be used during field operation.