Antenna Near-Field Measurements
Goals
The Antenna Near-Field Measurements Project serves as a national resource by providing antenna measurement services and traceability through calibrations. It supports government and private industry programs, and maintains and develops the standards, methods, and instrumentation for antenna characterization of gain, polarization and pattern measurements.
Customer Needs
We continue to upgrade antenna metrology capability to meet evolving customer demands in the following areas:
Probe Characterization — Accurate probe characterization is fundamental to precise antenna measurements. We provide probe correction coefficients for use in planar, spherical and cylindrical near-field facilities.
Planar and Spherical Near-Field Measurements — These are required to accurately characterize large aperture, high-frequency antennas such as phased array and dish antennas used in satellite communications.
Antenna Standard Characterization — Industry and government require antenna standards for inhouse antenna measurements.
Measurement Traceability — Program specifications often require NIST traceability.
Independent Verification of Antenna Parameters — Government and industry request measurements to verify that their measurement and analysis procedures produce the predicted and correct results.
Technical Support — Assistance on measurement techniques and analysis algorithms for antenna facilities that are implementing near-field measurements.
 The NIST probe pattern range with the fixed probe located near the center of the photo and the moving probe located on the moving tower in the upper right. |
Technical Strategy
We currently maintain near-field antenna measurement standards and capabilities for frequencies from 1.5 to 110 gigahertz. The recent integration of a laser tracker system provides accurate information on probe position for use with position correction algorithms. These improvements will help maintain low uncertainties as measurement frequencies are increased in the future.
We have extended the frequency range of our extrapolation measurement capability. The new extrapolation range provides on-axis gain characterization capability to complement near-field antenna pattern measurements at millimeter-wave frequencies. Plans to provide polarization characterization up to 110 gigahertz are in process and will be available in the near future.
We are performing an internal comparison on all three of the NIST near-field ranges — planar, cylindrical, and spherical — to verify performance and refine uncertainties. Our capability with all three types of ranges is unique.
Accomplishments
- Antenna Calibrations — We perform antenna
calibrations for external customers. Examples
of recent measurements are:
- WR-28 — Open-ended Waveguide Probe
- WR-62 — 3 Standard Gain Horns
- WR-90 — 3 Standard Gain Horns and an Open-ended waveguide probe
- WR-42 — 2 Standard Gain Horns and 2 Dual-port Circularly Polarized Probes
- WR-22 — 2 Standard Gain Horns and 2 Dual-port Circularly Polarized Probes
- WR-62 — Cassegrain Dish Antenna
- A 60 to 110 gigahertz extrapolation range has been designed and installed. Antenna gain tests at 94 gigahertz show excellent performance. The new range significantly extends NIST antenna metrology capability.