Enhanced Gain Extrapolation Technique: A Third-Order Scattering Approach for High-Accuracy Antenna Gain With Sparse Sampling, at Fresnel Distances

Abstract

In this article, we describe an enhanced three-antenna gain extrapolation technique that allows one to determine antenna gain with significantly fewer data points and at closer distances than with the well-established traditional three-antenna gain extrapolation technique that has been in use for over five decades. As opposed to the traditional gain extrapolation technique, where higher order scattering is purposely ignored, so as to isolate only the direct antenna-to-antenna coupling, we show that by incorporating third-order scattering, the enhanced gain extrapolation technique can be obtained. The theoretical foundation using third-order scattering is developed, and experimental results are presented comparing the enhanced technique and traditional technique for two sets of internationally recognized NIST reference standard gain horn antennas at the X band and the Ku band. We show that with the enhanced technique, gain values for these antennas are readily obtained to within stated uncertainties of ±0.07 dB using as few as ten data points per antenna pair, as opposed to ≈4000–8000 data points per antenna pair that is needed with the traditional technique. Furthermore, with the described enhanced technique, antenna-to-antenna distances can be reduced by a factor of 3, and up to a factor of 6 in some cases, compared to the traditional technique, a significant reduction in the overall size requirement of facilities used to perform gain extrapolation measurements.