PHASE-DEPENDENT RCS MEASUREMENTS

摘要

Free space, coherent radar cross section measurements on a moving target trace a circle centered on the origin of the complex (I, Q) plane. Noise introduces only small random variations in the radius of the circle. In real measurement configurations, additional signals are present due to background, clutter, target-mount interaction, instrumentation and the average of the time-dependent system drift. Such signals are important contributors to the uncertainty in radar cross section measurements. These tune-independent complex signals will translate the origin of the circle to a complex point (I_0,Q_0)- Such data are then defined by the three parameters (I_0,Q_0), the center of the circle, and σ_t, the radar cross section of the target. Data obtained when a target is moved relative to its support pylon can be separated into phase-dependent and phase-independent components using the techniques of (1) three-parameter numerical optimization, (2) least-median-squares fit, (3) adaptive forward-backward finite-impulse response procedure, and (4) orthogonal distance regression applied to a circle fit. We determine three parameters with known and acceptable uncertainties. However, the contribution of systematic errors due to unwanted in-phase electric signals must still be carefully evaluated.