Reduced Sampling in NF Antenna Measurement Using Numerical Defined Expansion Functions

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This paper presents an advanced RF test methodology for time efficient antenna testing. The measured field is projected over precomputed basis functions obtained
with simulations of the antenna platform using fast ray-tracing methods [1], [2]. The source antenna is treated as a black box and no material or dimensional information is needed. As the number of basis functions is significantly reduced with respect to the Nyquist criteria, the number of NF measurement points is equally reduced, or down-sampled, leading to a significant saving in overall measurement time. The methodology is particular efficient for relatively small antennas installed on large platforms. The new methodology performs faster antenna measurements, while maintaining a certain level of confidence. It can be directly implemented, without hardware changes in existing spherical near field (SNF) measurements range.
In this paper we introduce the new methodology for the first time. The method has been validated using actual measurements of a small X-band antenna on a large satellite mock-up. The achievable measurement accuracy is investigated by determining the correlation with traditional measurements through the calculation of the Equivalent Noise Level (ENL).
The new methodology achieves a sampling reduction, or down sampling factor of 5-9 in the tested scenarios, maintaining good accuracy levels with respect to standard measurement. The new methodology is highly applicable for verification testing due to the significant measurement time savings, with a moderate trade-off on measurement accuracy.

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