A MICROWAVE ANECHOIC CHAMBER FOR RADAR-CROSS SECTION MEASUREMENT

A microwave anechoic chamber has recently been developed at the Depart ment of Electrical Engineering, University of Malaya, for monostatic a nd bistatic radar-cross-section measurements. The structure of the cha mber is a quarter-section geodesic dome, with a 12 foot radius, and ra ised three feet above the floor. An antenna railing system is installe d inside the chamber. It consists of six rails, 30 degrees apart in az imuth angle around the dome. The antennas can be moved along the rails in the elevation direction, with the microwave beam pointing at the c enter of the dome where the target is located. This design enables a v ery large combination of incidence and scattering angles in bistatic m easurements. Four transmitting antennas are fixed at different elevati on angles next to one of the antenna rails. By using an azimuth-over e levation positioner as the pedestal for the target, and by positioning the movable antenna along that rail beside those fixed transmitting a ntennas, monostatic measurements with incidence angles ranging from 0 to 90 degrees can be accomplished. A vector network analyzer is utiliz ed to measure the amplitude and phase of the radar returns. An IEEE-48 8.2 interface bus is used to control various hardware components, as w ell as to perform data acquisition. A computer program was written to automate the measurement system. Data are stored in raw format, and pr ocessed later with dedicated software, so that different processing me thods and parameters can be applied. Calibrated measurement results wi th a precision of 0.5 dB can be achieved, when appropriate time-domain gating parameters are used. This paper highlights the design and cons truction of the microwave anechoic chamber, as well as the measurement -system configuration for scattering-cross-section measurements.