Robustness of a new angular counter-measure

Presents an array processing scheme to protect an aerial target against an attacker (missile). The missile localizes the target's direction with an active phased array. To face this threat, an active phased array is deployed which "re-transmits" the attacker's emission and creates by an interference phenomenon, a field issuing from a false target at another location. In that manner, the angular measure is biased. The decoy system is made up of one central receiver and m aligned transmitters. The received signal is emitted towards the attacker simultaneously by the m transmitters with proper complex weights (phase and gain). These weights are determined such that the real and false targets fields match as much as possible along the attacker array. When the number of transmitters is large enough, this decoying technique is efficient even for large angular deviation requirements. Performance degrades significantly when facing dispersions on amplifiers and phase-shifters, which means that the m-emitters restore approximately phases and gain commands. The authors extend the previous command to a robuster version, which is less susceptible to emitter errors. These new weights are derived from the analysis of the sensitivity of the beam pattern maximum to the "field command" fluctuations. The new criterion to minimize tends to regularize the initial linear criterion. A quadratic penalty devoted to robustness is added. The robustness gain is quite significant: an additional mean deviation up to half a lobe can be reached.