Coherent FM-CW millimeter-wave radar systems for radar cross-section measurements

Coherent instrumentation radars have been developed at 35 GHz and 94 GHz for use in radar-cross-section measurements at angles of incidence ranging from 0° to 60°. The systems are designed to measure the radar cross section of various targets, at like- and cross-polarizations, in an effort to better understand their scattering characteristics. Both are dual-antenna systems capable of operating in FM-CW (frequency-modulated, continuous wave) mode or as pulse or pulse-compression radars. Samples of the transmitted signal are provided for system calibration. The systems also include a phase-locked loop to linearize the sweep when operating in FM-CW mode. The use of quadrature mixers provides I and Q channels for phase-coherent measurement of the received signals. All hardware is mounted inside weatherproof, lightweight aluminum boxes with antennas protruding from one side. Multiconductor cables provide control signals and access to the received signals. General-purpose data-acquisition computers collect samples of the received signals that are later processed digitally