This script helps the operator to improve the mechanical alignment of a spherical nearfield measurement system. It can analyze the existing system alignment based on previously measured near-field data, or it can acquire new alignment-specific data, and report the system alignment errors. It will then provide step by step instructions for making necessary alignment adjustments to improve the system accuracy.

It is based on technical papers published by NSI and posted on our website:

1997 - "The Alignment of a Spherical Near-Field Rotator using Electrical Measurements"
1998 - "Quantifying The Effect Of Position Errors In Spherical Near-Field"
1999 - "The Effect Of Measurement Geometry On Alignment Errors In Spherical Near-Field Measurements"

This script is normally used after you have done a complete system mechanical alignment similar to that done by NSI during installation.

- Convenient and quick check of spherical system alignment
- Fine tuning of the spherical system alignment for increased accuracy
- Fast and streamlined procedure
- Easy step by step guidance thru the process

The purpose of this script is to check and fine tune two parameters in the alignment - the Theta-zero angular error and the X-zero intersection error between the Phi and Theta axes (see figures below). The desired accuracy is dependent on many factors, including your expected RF measurement accuracy for the system, but here in this script we have included a recommendation to get the angular alignment error less than 0.05 degrees and intersection error less than 0.05 wavelengths at the highest test frequency.

Step by step procedure:

1. Overall system mechanical alignment
2. Run this script to optimize the Theta-zero and X-zero errors
3. Script will do automatic acquisition of alignment data
4. Script will then process the data and recommend alignment changes
5. The intersection error will require repositioning the Phi stage by translation or shimming
6. The script calculates the required Theta-zero adjustment which can be used as the Theta center offset for the next scan automatically
7. The script continues in a loop, acquiring and processing the data until you are satisfied with the results
8. Once completed, the script recommends you add the final Theta-zero error to your Theta stage index offset and then reindex
9. Following this, you should run a final alignment check and save the system state vector to the startup state.

Please contact the NSI Sales department to order this product.