Meaning
A rule dictating that the distance between consecutive points in a near-field antenna scan must not exceed half of the operational wavelength guarantees that the measured field can be reconstructed without aliasing. In wireless device testing, spatial nyquist sampling determines the maximum step size for the robotic arm of the probe scanner. This restriction prevents high-frequency spatial details from being lost or folded into the measurements, ensuring the accuracy of the computed far-field patterns.
Calculation Constraint
The required measurement grid spacing depends on the highest frequency of operation.
Scanning Execution
Robotic test stands execute the measurement sweep by positioning the probe at coordinates calculated from the wavelength of the test signal. When spatial nyquist sampling is maintained, the resulting dataset holds sufficient information to execute the near-to-far-field transformation. If the spacing exceeds this threshold, the scanner generates a dataset that contains alias artifacts, forcing a repeat of the scan.
Mechanical Impact
Finer step sizes increase the total number of measurement points, extending the duration of the testing sequence. Engineers use the largest step size allowed by spatial nyquist sampling to minimize test time while preserving data integrity. This optimization helps to manage the throughput of high-volume electronics testing facilities.
