Patent ID: 7538717

Claim:
An airborne radar device comprising: at least two antennas; wherein the radar device is arranged to send out, via the antennas, radar pulses focused in main lobes; wherein the antennas are arranged to receive reflected radar pulses, the antennas being separated from each other vertically; means for transforming the received radar pulses into signals in the form of sequences of bins (Rk), the signals being carried in a first channel (K 1 ) and a second channel (K 2 ); clutter-suppressing means arranged in such a way that a clutter component (e c ) of a certain bin (R k ) in the first channel (K 1 ) is also found in the second channel (K 2 ) multiplied by a complex constant (C(R k )), where the complex constant (C(R k )) is a quotient between complex antenna gain of the second channel (K 2 ) and of the first channel in a direction of ground for the current bin (R k ), the clutter-suppressing means being arranged to estimate a complex constant (Ĉ(R k )) which describes how the signals from the receiver antennas are weighted together separately for each bin (R k ) when the resultant output signal (Ψ) is formed, the estimated constant (Ĉ(R k )) serving to suppress the clutter component (e c ) in the resultant output signal (Ψ) by subtraction of the second channel (K 2 ) from the first channel (K 1 ) multiplied by the estimated constant (Ĉ(R k )).