How does near-field antenna measurement work?
Near-field measurement samples the amplitude and phase of an antenna’s field on a surface a few wavelengths away, typically planar, cylindrical or spherical, and mathematically transforms the data to the far field using modal expansions, with corrections for the probe’s own pattern. It allows accurate patterns and gain of large antennas in small chambers. Yaghjian’s 1986 overview remains a standard reference.[1][2]
Which scan geometry should be used?
| Scan | Best for | Notes |
|---|---|---|
| Planar | High-gain antennas (arrays, dishes) | Truncation limits valid angles |
| Cylindrical | Fan-beam antennas | Full azimuth coverage |
| Spherical | Low/medium-gain and omnidirectional antennas | Complete sphere; most general |
What sampling is required?
Sample spacing of at most λ/2 at the highest frequency in planar and cylindrical scans satisfies the sampling theorem for the propagating spectrum; spherical scans use angular steps based on the radius of the minimum sphere enclosing the AUT. Probe position accuracy of a small fraction of a wavelength is needed.[1][2]
What is probe correction?
The measured signal is the coupling between AUT and probe, so the probe’s receiving pattern is deconvolved during the transformation. Open-ended waveguides and small horns are common probes with well-characterized patterns.[1]
Frequently asked questions
Is near-field measurement accurate?
Yes; with proper sampling and probe correction it rivals far-field ranges.
Can near-field data diagnose array faults?
Yes; back-projecting to the aperture reveals failed elements.
Is phase needed?
Standard methods need phase; phaseless techniques exist with more complexity.
See also
References
Online sources accessed October 21, 2026; printed works cited by edition. See all sources.
- “An Overview of Near-Field Antenna Measurements”. A. D. Yaghjian, IEEE Transactions on Antennas and Propagation, vol. 34, no. 1, pp. 30-45. January 1986.
- “IEEE Recommended Practice for Antenna Measurements (IEEE Std 149-2021)”. IEEE Antennas and Propagation Society. 2022.