Non-linear dynamic filtering device for the angular measuring of noise

Abstract

To improve the accuracy of angular measurements in a radar or sonar system by suppressing noise due to target glint, an angular-deviation signal .epsilon. derived from the output signals .SIGMA. and .DELTA. of a sum channel and a difference channel is multiplied with a gain-control signal K(t) before being subjected to recursive filtering. Signal K(t) is obtained, also by recursive filtering, from a weighting function P(t) which goes to zero during periods when the measurement of the angular deviation is unreliable as determined from a low value of sum signal .SIGMA. and from a peaking of a quadrature deviation signal .epsilon.q, function P(t) being proportional to the product .SIGMA..sup.n .multidot.(S-.vertline..epsilon.q.vertline.) where the exponent n is at least equal to 1 and S is a predetermined threshold. The recursive filter processing the deviation signal .epsilon. has two cross-connected stages, both controlled by signal K(t), respectively emitting a corrected deviation measurement .epsilon. and an estimated time differential .tau.d.epsilon./dt, .tau. being a delay introduced in a recursive loop of each stage. Prior to being multiplied with gain-control signal K(t), the deviation signal .epsilon. may be additively combined with an angular-orientation signal .theta..sub.r of a radar antenna to yield an angular value .theta..sub.c which can then be multiplied by a measured target distance D to provide a transverse-deviation signal d; in that case the two filter stages respectively emit a corrected deviation signal d and a target-velocity estimate v.