UHF-Band Radar Cross Section Measurements With Single-Antenna Reflection Coefficient Results

This article discusses the challenges and advantages of measuring radar cross section (RCS) using reflection coefficient measurements from a single-antenna test setup. In practice, arranging two ultrahigh-frequency (UHF) antennas in a quasi-monostatic configuration is difficult due to their large physical size. In addition, the coupling power between the two antennas can be much larger than the signal of interest, imposing further limitations on this configuration. However, traditional RF measurement hardware and postprocessing algorithms are combined to extract RCS across frequency and azimuthal angle accurately with the S-11 values collected from a single antenna. This is made possible by using vector background subtraction and time-gating windowing techniques to suppress multipath reflections, clutter, and mismatch reflection while increasing the measurement's dynamic range. The test setup utilizes the National Instruments LabVIEW software for control and automation, a General Purpose Interface Bus (GPIB)-enabled vector network analyzer, and a rotary table allowing for experiments to be conducted in an anechoic chamber or an outdoor measurement range. Experiments are conducted at the University of Oklahoma in the far-field anechoic chamber and outdoors using the components mentioned above to validate the derived algorithms and measurement concepts. The chamber setup is calibrated using a metal sphere to extract the RCS of a smaller metal sphere. The initial RCS extraction had an average error of 4.9 dBsm over the 300-1000-MHz frequency range using only calibration and vector background subtraction. After applying time gating, the error is further reduced to 0.54 dBsm. The implemented test setup is accomplished using traditional measurement equipment and a single antenna allowing for a portable, flexible, and low-cost solution for RCS measurements in the UHF band.