.pdf version
NIST 18-Term Range Assessment


NSI's 18-term error assessment will provide a detailed evaluation of your antenna range performance. Error assessment can be compiled for antenna gain, side lobe level (SLL) at different levels and cross-polarization accuracy. Each error assessment is only valid for a particular antenna at a particular frequency in a particular facility. Some items may be generalized, but most items in the error assessment cannot. The validation does therefore not extend to all frequencies for any antenna to be tested in that facility. The error assessment, therefore, does not extend to other frequencies or antennas tested in that facility.

Three methods are used to estimate the magnitude of the following 18 error sources. The three methods are:

1. Mathematical analysis where the uncertainty in a given far-field quantity is given in terms of measurement errors and some information about the AUT.

2. Computer simulation for some error sources where the form of the error can be accurately simulated on the computer.

3. Self comparison measurements to obtain an experimental estimate of the error. In this approach a reference measurement is taken with the system in a known state with respect to a specific error source. The system is then changed to increase, decrease or change the sign of that specific error source and the measurement is repeated. A comparison of the far-field results from the two measurements gives an estimate of the effect of the specific error.

Error terms will be assessed based on the work described in the Allen Newell paper at http://www.nearfield.com/amta/ErrorAnalysis.pdf


- Checkout of range accuracy
- Using customer provided antenna
- Based on NIST 18-term model (detail below)
- Includes range assessment report
- Single frequency acquisition & analysis

  • Planar near-field case:
    - Full NIST 18-terms

  • Cylindrical near-field case:
    - NIST 18-terms as applicable
    - Assess theta/z axis orthogonality term
    - Assess theta/z axis intersection term
    Spherical near-field case:
    - NIST 18-terms as applicable
    - Assess theta/phi axis orthogonality term
    - Assess theta/phi axis intersection term

Typical Error Analysis Result




Please contact the NSI Sales department to order this product.

Nearfield Systems, Incorporated
19730 Magellan Drive, Torrance, CA 90502, USA, Tel: 310.525.7000, Fax: 310.525.7100
Email: sales@nearfield.com. Visit our website: www.nearfield.com