Near-Field to Far-Field Transformation for Antenna Measurements (NF2FF)

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Near field (NF) ranges offer a convenient alternative to compact antenna test ranges (CATR) and anechoic far field ranges for the measurement of phased arrays [1,2,3,4,5,6,7,8,9]. NF sites allow for hologram analysis, low sidelobes characterization, and do not require a rotating pedestal capable of bearing the weight of the phased array. The primary objective of the NF2FF sourceforge project is to provide the phased array community with an open-source MATLAB alternative to proprietary NF measurement software. The code features planar near field to far field transforms with rectangular waveguide probe correction. The secondary objective of the project is to implement various functions for phased array hologram analysis. Phased array holograms allow for faulty element localization [5] and for measurement of active element amplitude and phase excitation, in transmit (Tx) as well as in receive (Rx) mode, which allows for insight in the difference between achieved and desired Tx and Rx array factor. In addition, active element Tx and Rx root mean square (RMS) amplitude and phase error can be measured which allows for insight in beam pointing error and side lobe level increase, and gain reduction, while scanning [10].

Hologram analysis can also be used to study near field communication (NFC) antennas.

Assumptions

The script assumes:

• Rectangular coordinate system with z axis normal to planar aperture
• exp(j*omega*t) time dependence convention. Please, substitute i with -j whenever implementing exp(-i*omega*t) time dependence convention based algorithms.

Datasets

The script uses near field datasets of a 94 GHz slotted waveguide (U.S. Patent No.: 7,994,969).

Wish list

Sought-after extensions are listed below. Please post them on the website, if you are willing to contribute:

• Cylindrical and spherical near field to far field transformation
• Graphical user interface

References

[1] W. Leach, Jr., D. Paris, "Probe compensated near-field measurements on a cylinder," IEEE Trans. Antennas Propagat., vol. 21, no. 4, pp. 435-445, July 1973.

[2] D. Paris, W. Leach, Jr., E. Joy, "Basic theory of probe-compensated near-field measurements," IEEE Trans. Antennas Propagat., vol. 26, no. 3, pp. 373-379, May 1978.

[3] A. D. Yaghjian, "Approximate formulas for the far field and gain of open-ended rectangular waveguide," IEEE Trans. Antennas Propagat., vol. 32, no. 4, pp. 378-384, April 1984.

[4] A. D. Yaghjian, "An overview of near-field antenna measurements," IEEE Trans. Antennas Propagat., vol. 34, no. 1, pp. 30-45, January 1986.

[5] J. J. Lee, E. M. Ferren, D. P. Woollen, and K. M. Lee, "Near-field probe used as a diagnostic tool to locate defective elements in an array antenna," IEEE Trans. Antennas Propagat., vol. 36, no. 6, pp. 884-889, June 1988.

[6] R. M. Goldstein, H. A. Zebken, and C. L. Werner, "Satellite radar interferometry: Two-dimensional phase unwrapping," Radio Sci., vol. 23, no. 4, pp. 713-720, July-August 1988.

[7] G. F. Masters, "Probe-correction coefficients derived from near-field measurements," in AMTA Symposium Digest, Oct. 7-11, 1991.

[8] C. A. Balanis, "Antenna Theory, Analysis and Design, 2nd Ed.," John Wiley & Sons, 1997.

[9] D. C. Ghiglia and M. D. Pritt, "Two-Dimensional Phase Unwrapping: Theory, Algorithms and Software," John Wiley & Sons, 1998.

[10] R. J. Mailloux, "Phased Array Antenna Handbook," Artech House, 2005.