radar cross section
Article describes technique of precision antenna gain measurements through calibration reflectors radar cross section (RCS) value.
Absolutely gain measurements are based on the physical correlation between two antennas during energy transmission from one space point to another. In the very simple case antenna gain for the system of two electrically identical antennas is calculated by Frice equation.
The main task of this article is developing of antenna gain measurement method which is became an alternative to classical methods, based on Frice equation and provides the same or better accuracy.
The most similar to microwave antenna gain measurements techniques is RCS measurements. Correlation between object RCS value and antenna gain provides opportunity to measure this physical units one through another using main radiolocation equation.
For the simple reflectors RCS value uncertainties is less than 0,1 dB that could be compared with uncertainties of precision antenna gain measurements by extrapolation technique. Squared correlation between RCS and gain values give an advantage on traditional methods.
The technique suggested is based on using vector network analyzers (VNA) and provides clearly monostatic measurement scheme. During the measurements the VNA is established in a mode of complex reflection coefficient (S11) measurements. The signal reflected from the antenna input will repeatedly exceed reflections from calibration reflector. Therefore measurements are necessary to run in two stages – the reflected signal measurement with presence of a reflector in a working volume (signal + background) and with its absence (background). The subsequent processing is closed to subtraction of measured complex signals. Decreasing the influence of multipath reflections from calibration reflector can be provide by using methods witch realize capability of time gating of signals.
Measurement procedure, result processing and experimental verification are shown.