Compact RCS Test Range Field Probing Using a Shorted Antenna as Target

A new compact range for RCS measurements has been qualified. It has a quiet zone of 3m diameter, 3m length and operates from 0.7 to 50 GHz. The range is oriented for RCS measurements, whereas antenna measurements are not foreseen. All RF equipment is integrated close to the feeds with highly integrated pulsed Tx/Rx-modules. Therefore, classical field probing by moving a probe antenna along a linear slide would require significant modification of the RF system. If one measures the RCS of a target on the linear slide, it is difficult to distinguish the target down range reflection from the reflection of the linear slide structure. A long stand-off between target and slide is not practical for mechanical reasons in regard to accuracy requirements at 50 GHz. More important, simply measuring a reflective plate will not give any cross-polarization information. A more advanced target is created by using an antenna with a short circuit after an RF cable to locate the reflection of the short well behind the scanner in down range. In addition, the antenna receives only nominal quiet zone co-polarization, consequently, only reflects co-polarization from the short, and the feed receives the compact range induced cross-polarization at the feed (one-way). The method has shown to be extremely effective. More important, it uses the RF instrumentation and RCS measurement methods as designed for regular operation without any modification, thus is the most realistic system level quality representation of the quiet zone, can be repeated at any time without elaborate range reconfiguration requirements and can serve as part of the commissioned RF system performance qualification. The paper will present the quiet zone field probe test setup, a calculation of antenna and RF cable requirements, an analysis of the down range profile of scanner and reflective antenna and field probing results.