Point clutter threshold determination for radar systems

An adaptive detection threshold system for a radar having a scanning antenna system, said threshold system comprising:

• means for obtaining data corresponding to the amplitude of clutter signals received by the radar for different azimuths of the radar antenna;
• means for selecting at least first, second and third values of said data, with said first value being representative of the clutter amplitude received by the radar when its antenna is positioned in a first direction, said second value being representative of the clutter amplitude received by the radar when its antenna is positioned in a second direction, and said third value being representative of the clutter amplitude received by the radar when its antenna is positioned in a third direction, said second direction being located angularly between said first and third directions;
• means for combining said first, second and third values;
• and
• means for controlling the detection threshold level for signals received when the radar antenna is in said second direction, with the controlling means being dependent upon a combined value derived from combining said first, second and third values, said controlling means including means for compensating the detection threshold level for changes in the scan rate of the radar antenna system.

An adaptive detection threshold system for a radar having a scanning antenna system, said threshold system comprising:

• means for obtaining data corresponding to the amplitude of clutter signals received by the radar for different azimuths of the radar antenna;
• means for selecting at least first, second and third values of said data, with said first value being representative of the clutter amplitude received by the radar when its antenna is positioned in a first direction, said second value being representative of the clutter amplitude received by the radar when its antenna is positioned in a second direction, and said third value being representative of the clutter amplitude received by the radar when its antenna is positioned in a third direction, said second direction being located angularly between said first and third directions;
• means for combining said first, second and third values;
• and
• means for controlling the detection threshold level for signals received when the radar antenna is in said second direction, with the controlling means being dependent upon a combined value derived from combining said first, second and third values, said controlling means including means for compensating the detection threshold level for changes in the interpulse period of the radar.

An adaptive detection threshold system for a radar having a scanning antenna system, said threshold system comprising:

• means for obtaining data corresponding to the amplitude of clutter signals received by the radar for different azimuths of the radar antenna;
• means for selecting at least first, second and third values of said data, with said first value being representative of the clutter amplitude received by the radar when its antenna is positioned in a first direction, said second value being representative of the clutter amplitude received by the radar when its antenna is positioned in a second direction, and said third value being representative of the clutter amplitude received by the radar when its antenna is positioned in a third direction, said second direction being located angularly between said first and third directions;
• means for combining said first, second and third values;
• and
• means for controlling the detection threshold level for signals received when the radar antenna is in said second direction, with the controlling means being dependent upon a combined value derived from combining said first, second and third values, said controlling means including means for compensating the detection threshold level for the variable interpulse period in a moving target indicator radar system.

An adaptive detection threshold system for a radar having a scanning antenna system, said threshold system comprising:

• means for obtaining data corresponding to the amplitude of clutter signals received by the radar for different azimuths of the radar antenna;
• means for selecting at least first, second and third values of said data, with said first value being representative of the clutter amplitude received by the radar when its antenna is positioned in a first direction, said second value being representative of the clutter amplitude received by the radar when its antenna is positioned in a second direction, and said third value being representative of the clutter amplitude received by the radar when its antenna is positioned in a third direction, said second direction being located angularly between said first and third directions;
• means for combining said first, second and third values;
• and
• means for controlling the detection threshold level for signals received when the radar antenna is in said second direction, with the controlling means being dependent upon a combined value derived from combining said first, second and third values, said controlling means including means for compensating the detection clutter threshold level for radar instability.

An adaptive detection threshold system for a moving target detector radar having a scanning antenna system, said threshold system comprising the combination of:

• a clutter map containing integrated values corresponding to the mean amplitude of echo signals received by the radar for different azimuths of the radar antenna;
• means for comparing three clutter map values corresponding to first, second and third adjacent azimuth locations of the map, with said second azimuth location being between said first and third azimuth locations, and said comparing means providing a first residue estimate value equal to the largest of said three map values at a time when the radar is obtaining new echo signal data for the second azimuth location;
• means for providing a second clutter residue estimate value derived from said new echo signal data;
• means for compensating the second clutter residue estimate value for changes in the scan rate of the radar antenna system;
• means for providing a third clutter residue estimate value derived from conventional constant false alarm rate signal processing;
• means for combining the first, second and third clutter residue estimate values to provide an estimated interference value;
• means for adding a fixed value to said estimated interference value to obtain a combined threshold value;
• and
• means for inhibiting the signalling of an alarm when more than one of the clutter map values exceeds a saturation limit.

A method of setting the alarm threshold limit for a radar having a scanning antenna system, said method comprising the steps of:

• obtaining echo data values from a present azimuth, from an aximuth leading the present azimuth, and from an azimuth lagging the present azimuth;
• selecting the largest value of said three azimuths;
• shifting the selected largest value a fixed level to establish the threshold level effective for data during the present azimuth;
• adjusting the established threshold level based upon the change in rate of scanning of the radar antenna;
• and
• repeating the steps of the method for each subsequent azimuth of the radar.