Method of generating accurate estimates of azimuth and elevation angles of a target for a phased-phased array rotating radar
First Claim
1. A method for generating accurate estimates of a radar target'"'"'s azimuth and elevation angles for a rotating monopulse radar comprising the steps of:
- measuring an antenna'"'"'s one-way transmit pattern and three receive antenna patterns;
generating two-way Sum, Delta-Azimuth and Delta-Elevation antenna patterns;
translating the coordinates of two-way Sum, Delta-Azimuth and Delta-Elevation antenna patterns to center on a sine-space beam steer;
sampling uniformly the two-way antenna patterns at mid-CPI points of numerous target returns;
coherently integrating over the sine-space trajectories of said target returns;
averaging coherent integration sums of said target returns and plotting said averages at their respective mid-CPI points to produce average gain antenna patterns;
generating U-offset and V-offset scan modulated coherently integrated (SMCI) monopulse curves from average gain patterns;
coherently integrating said two-way Sum, Delta-Azimuth and Delta-Elevation target returns of said antenna patterns;
calculating the target'"'"'s monopulse ratios from said coherently integrated target return measurements;
calculating the target'"'"'s U-offset and V-offset monopulse angles in sine-space using said SMCI monopulse curves;
adding said U-offset and V-offset monopulse angles to a sine-space beam steer to obtain an improved estimate of a target'"'"'s sine-space position denoted as Utgt and Vtgt; and
transforming said Utgt and Vtgt to azimuth and elevation angles in a non-rotating coordinate system using coordinate system transformations.
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Abstract
A method and apparatus for generating accurate estimates of a radar target'"'"'s azimuth and elevation angles for a phased-phased array rotating radar. Scan modulated coherently integrated (SMCI) monopulse curves are generated from a measured one-way transmit antenna pattern and three receive antenna patterns. The SMCI monopulse curves are calculated in advance for the expected beam steers. To utilize the SMCI monopulse curves, two-way Sum, Delta-Azimuth and Delta-Elevation target returns are coherently integrated, the target'"'"'s monopulse ratios calculated, and the SMCI monopulse curves or polynomials used to calculate the target'"'"'s U-offset and V-offset sine-space angles, which are added to the radar'"'"'s beam steer to get an improved estimate of the target'"'"'s sine-space angular position denoted as Utgt and Vtgt. A coordinate system transformation transforms Utgt and Vtgt to azimuth and elevation angles in a non-rotating coordinate system.
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Citations
14 Claims
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1. A method for generating accurate estimates of a radar target'"'"'s azimuth and elevation angles for a rotating monopulse radar comprising the steps of:
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measuring an antenna'"'"'s one-way transmit pattern and three receive antenna patterns;
generating two-way Sum, Delta-Azimuth and Delta-Elevation antenna patterns;
translating the coordinates of two-way Sum, Delta-Azimuth and Delta-Elevation antenna patterns to center on a sine-space beam steer;
sampling uniformly the two-way antenna patterns at mid-CPI points of numerous target returns;
coherently integrating over the sine-space trajectories of said target returns;
averaging coherent integration sums of said target returns and plotting said averages at their respective mid-CPI points to produce average gain antenna patterns;
generating U-offset and V-offset scan modulated coherently integrated (SMCI) monopulse curves from average gain patterns;
coherently integrating said two-way Sum, Delta-Azimuth and Delta-Elevation target returns of said antenna patterns;
calculating the target'"'"'s monopulse ratios from said coherently integrated target return measurements;
calculating the target'"'"'s U-offset and V-offset monopulse angles in sine-space using said SMCI monopulse curves;
adding said U-offset and V-offset monopulse angles to a sine-space beam steer to obtain an improved estimate of a target'"'"'s sine-space position denoted as Utgt and Vtgt; and
transforming said Utgt and Vtgt to azimuth and elevation angles in a non-rotating coordinate system using coordinate system transformations. - View Dependent Claims (2, 3, 4, 5)
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6. A method for generating scan modulated coherently integrated (SMCI) monopulse curves comprising the steps of:
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measuring an antenna'"'"'s one-way transmit pattern and three receive antenna patterns;
generating two-way Sum, Delta-Azimuth and Delta-Elevation antenna patterns by performing a point by point multiplication of the antenna gain of the one-way transmit pattern with the antenna gains of the three receive patterns;
translating the coordinates of two-way Sum, Delta-Azimuth and Delta-Elevation antenna patterns to center on a sine-space beam steer;
sampling uniformly the two-way antenna patterns at mid-CPI points of numerous target returns;
coherently integrating over the trajectories of said target returns;
averaging coherent integration sums of said target returns and plotting said averages at their respective points; and
generating scan modulated coherently integrated (SMCI) monopulse curves from the Sum, Delta-Azimuth and Delta-Elevation average gain antenna patterns as follows;
generating a U-offset SMCI monopulse curve by taking the real parts of the Delta-Azimuth U-cardinal plane gains divided point-by-point by the Sum U-cardinal plane gains; and
generating a V-offset SMCI monopulse curve by taking the real parts of the Delta-Elevation V-cardinal plane gains divided point-by-point by the Sum V-cardinal plane gains. - View Dependent Claims (7, 8, 9)
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10. A method for applying SMCI monopulse polynomials to target returns and determining azimuth and elevation angles in a non-rotating coordinate system comprising the steps of:
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coherently integrating two-way Sum, Delta-Azimuth and Delta-Elevation target returns;
calculating the target'"'"'s U-offset and V-offset monopulse ratios from said coherently integrated target return measurements;
calculating the target'"'"'s U-offset and V-offset monopulse angles in sine-space using said SMCI monopulse polynomials;
adding said U-offset and V-offset monopulse angles to a sine-space beam steer to obtain an improved estimate of a target'"'"'s sine-space position denoted as Utgt and Vtgt; and
transforming said Utgt and Vtgt to azimuth and elevation angles in a non-rotating coordinate system using knowledge of the antenna'"'"'s yaw and tilt angles and coordinate system transformations. - View Dependent Claims (11)
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12. A method of producing an average gain pattern for a rotating radar employing coherent integration comprising the steps of:
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storing a measured two-way antenna pattern with U and V sine-space coordinates;
translating said antenna coordinates to center on a beam steer;
calculating a W component of said antenna pattern coordinates;
calculating the number of samples in a coherent processing interval (CPI);
calculating a yaw angle scanned in a sampling period;
calculating said yaw angle scanned in said CPI;
calculating a starting yaw angle with respect to the NWU X-axis;
calculating mid-CPI points of numerous target returns in a NWU frame;
coherently integrating over trajectories of said target returns for integration steps one to number of samples in a CPI; and
averaging said coherently integrated pattern of said target returns to obtain an average gain pattern. - View Dependent Claims (13)
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14. A phased-phased array rotating radar system comprising:
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a phased-phased array rotating antenna;
an antenna electronics unit for sending and receiving signals to and from said phased-phased array rotating antenna wherein the direction of radar beams transmitted by said antenna are electronically controlled;
means connected to said antenna electronics unit for processing target return signals and generating transmit command signals;
a signal and data processor for generating estimates of a target azimuth angle and elevation angle including means for pulse compression of target return signals;
means for coherent integration of compressed pulses;
means for detection processing of said coherently integrated compressed pulses;
means for monopulse processing of detected signals;
means for target tracking;
means for generating array beam steering commands;
a beam steering generator connected to said signal and data processor for generating beam steering commands for said antenna electronics unit;
said signal and data processor for generating estimates of a target azimuth angle and elevation angle comprises means for generating scan modulated monopulse curves from average gain patterns, means for calculating a target'"'"'s monopulse ratios, means for calculating said target'"'"'s U-offset and V-offset monopulse angles, means for adding said U-offset and said V-offset monopulse angles to a sine-space beam steer obtaining estimates of said target'"'"'s angular position (Utgt and Vtgt); and
means for transforming said estimates Utgt and Vtgt to said azimuth and elevation angles in a non-rotating coordinate system.
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Specification