Pulse radar apparatus

A target tracking pulse radar apparatus for producing angular error data representing deviations of gun-fired projectiles from a target position line, at ranges including those corresponding to a target range gate, characterized in that said radar apparatus includes a low frequency signal processor for detecting and processing echo signals in an auxiliary range gate situated within the target range gate, said low frequency signal processor comprising:

• (a) a signal analyser having a FFT filter bank for determining Doppler spectral components of low-frequency-detected echo signals received from the projectiles within the target range gate;
• (b) means for producing selection data about the spectral channels related to fixed clutter and clutter-free spectral channels;
• (c) means for selecting, from the selection data of the clutter-free spectral channels, the spectral values available in said clutter-free spectral channels and for determining a noise threshold value from the selected spectral values;
• (d) a threshold circuit for recording selection data about the spectral channels related to fixed clutter and the clutter-free spectral channels with the noise threshold value;
• (e) means for selecting the projectile Doppler spectral components from the signal analyser using the outputs of the clutter-free spectral channels for comparison of the output values in the latter channels with the noise threshold value;
• and
• (f) an angular error generator for generating said angular error data from the Doppler spectral components selected by the selection means to effect gun aiming correction.

A target tracking pulse radar apparatus for producing angular error data representing deviations of gun-fired projectiles from a target position line, at ranges including those corresponding to a target range gate, characterized in that said radar apparatus includes a low frequency signal processor for detecting and processing echo signals in an auxiliary range gate situated within the target range gate, said low frequency signal processor comprising:

• (a) a signal analyser having a FFT filter bank for determining Doppler spectral components of low-frequency-detected echo signals received from the projectiles within the target range gate;
• (b) computing means for determining, upon the supply of data representing the gun's own motion, selection data about spectral channels related to fixed clutter, spectral channels related to rain clutter, and clutter-free spectral channels;
• (c) first means for selecting, from the selection data of the clutter-free spectral channels, the spectral values available in said clutter-free spectral channels and for determining a noise threshold value from the selected spectral values;
• (d) means for comparing the spectral values from the spectral channels, related to rain clutter and determined by the selection data, with said threshold value to obtain selection data about the true spectral channels related to rain clutter;
• and
• (e) a threshold circuit for recording selection data about the spectral channels related to fixed clutter, the true spectral channels related to rain clutter with the associated threshold value, and the clutter-free spectral channels with the noise threshold value;
• (f) second means for selecting the projectile Doppler spectral components from the signal analyser using the outputs of the clutter-free spectral channels for comparison of the output values of the latter channels with the noise threshold value;
• and
• (g) an angular error generator for generating said angular error data from the Doppler spectral components selected by the second means to effect gun aiming correction.