Isolating target return from reflections via Doppler differentiation

Abstract

It is shown that the direct radar return from a target has a higher Doppler shift when compared to any reflected component of this return from other nearby surfaces, if the angle of the direct return from the target to the velocity vector is smaller than that of the reflected component of the return. This is particularly the case in the common scenario of a target over a water surface which is targeted by an object at a higher elevation moving at a high speed. In this scenario, the spectrum of the return signal is evaluated and is judiciously divided in two frequency bands, the higher of which is caused only by the return from the target and not the reflection. By simply bandpass filtering the signal accordingly, the effect of the reflection is removed and the resolution of the antenna/phased array beam is improved. This approach could be combined with any of the existing methods of target return isolation and improve their performance.