Further Investigating Antenna Extrapolation Through Direct Higher Order Fitting

In a previous study, direct higher order fitting was introduced to process measurement data from the antenna extrapolation range. Direct fitting method fits the measured response to a more complete generalized antenna response equation, which includes antenna-to-antenna multiple reflections, thus the terms responsible for the fast oscillating ripples. This approach is especially effective for moderate- and high-gain antennas, where chamber reflections are relatively small compared to multiple antenna-to-antenna reflections. In the earlier paper, this method was applied to high-gain antennas with long ring-down time and produced results comparable to those obtained using spectrum domain filtering. The advantage of this approach lies in its simplicity, as it is a one-step process and much easier to implement than spectrum filtering, which requires domain transformation, Spectrum Extension Edgeless Gating (SEEG), and curve fitting. However, in the previous study, the fit between the measurement data and the generalized response equation was not ideal. In this paper, we propose a new scheme for using the direct higher order method to improve fitting accuracy, resulting in a more precise far-field gain calibration. Additionally, the improved method provides amplitude center information for the antenna under test, without requiring additional measurements.