Jam strobe resolution using a monopulse antenna

Claim 1

The method of resolving jammers in a radar system using a monopulse antenna, in which output signals from the monopulse antenna are combined to provide sum and difference signals, which are processed via coherent detector means to provide in-phase and quadrature values and converted to digital form, wherein a passive ECM pre-look operation comprises processing the in-phase and quadrature values to provide measurements for a plurality of data points for a dwell, in which the ECM pre-look operation includes a determination of whether or not main beam jamming is present; wherein said method of resolving jammers is operative in response to a determination during an ECM pre-look operation that main beam jamming is present, and comprises the steps: using said ECM pre-look measurements to compute real and imaginary parts for each data point of a set of said data points; and computing an average value of the imaginary difference-to-sum ratio Im(d/s) and comparing said average value against a first threshold value to detect whether there is a single source or multiple sources of the main beam jamming, with an indication that there are multiple sources being provided in response to exceeding the first threshold; responsive to said indication that there are multiple sources, forming a ratio of the imaginary and real parts of the difference/sum ratio (|Im(d/s)/Re(d/s)|), selecting a data subset for which said ratio of the imaginary and real parts of the difference/sum ratio is below a second threshold, the second threshold being different from the first threshold, and using the real part of the difference/sum ratio (re(d/s)) of that data subset as a selected subset of N data points; sorting the selected subset of N Re(d/s) data points in ascending numerical order; computing the integer part n of N/4, selecting the n upper and the n lower data points as upper and lower quartile subsets respectively; computing the average values of each of the upper and lower quartile subsets to provide estimated Re(d/s) values for two jammers; converting the average values for the two jammers to angular positions via a monopulse calibration relationship; and supplying data on said angular positions for generation of jam strobes.

Claim 2

The method of resolving jammers in a radar system using a monopulse antenna, in which output signals from the monopulse antenna are combined to provide sum and difference signals, which are processed via coherent detector means to provide in-phase and quadrature values and converted to digital form, wherein a passive ECM pre-look operation comprises processing the in-phase and quadrature values to provide measurements for a plurality of data points for a dwell, in which the ECM pre-look operation includes a determination of whether or not main beam jamming is present; wherein said method of resolving jammers is operative in response to a determination during an ECM pre-look operation that main beam jamming is present, and comprises the steps: using said ECM pre-look measurements to compute real and imaginary parts for each data point of a set of said data points; and computing an average value of the imaginary difference-to-sum ratio Im(d/s) and comparing said average value against a first threshold value to detect whether there is a single source or multiple sources of the main beam jamming, with an indication that there are multiple sources being provided in response to exceeding the first threshold; responsive to said indication that there are multiple sources, forming a ratio of the imaginary and real parts of the difference/sum ratio (|Im(d/s)/Re(d/s)|), selecting a data subset for which said ratio of the imaginary and real parts of the difference/sum ratio is below a second threshold, the second threshold being different from the first threshold, and using the real part of the difference/sum ratio (re(d/s)) of that data subset as a selected subset of N data points; sorting the selected subset of N Re(d/s) data points in ascending numerical order; computing the integer part n of N/4, selecting the n upper and the n lower data points as upper and lower quartile subsets respectively; computing the average values of each of the upper and lower quartile subsets to provide estimated Re(d/s) values for two jammers; converting the average values for the two jammers to angular positions via a monopulse calibration relationship; and supplying data on said angular positions for generation of jam strobes.

Claim 3

The method of resolving jammers in a radar system using a monopulse antenna, in which output signals from the monopulse antenna are combined to provide sum and difference signals, which are processed via coherent detector means to provide in-phase and quadrature values and converted to digital form, wherein a passive ECM pre-look operation comprises processing the in-phase and quadrature values to provide measurements for a plurality of data points for a dwell, in which the ECM pre-look operation includes a determination of whether or not main beam jamming is present; wherein said method of resolving jammers if operative in response to a determination during an ECM pre-look operation that main beam jamming is present, and comprises the steps: using said ECM pre-look measurements to compute real and imaginary parts for each data point of a set of said data points; and computing an average value of the imaginary difference-to-sum ratio Im(d/s) and comparing said average value against a first threshold value to detect whether there is a single source or multiple sources of the main beam jamming, with an indication that there are multiple sources being provided in response to exceeding the first threshold; responsive to said indication that there are multiple sources, using the imaginary part of the difference/sum ratio (Im(d/s)) to select a data subset below a second threshold, the second threshold being different from the first threshold, and using the real part of the difference/sum ratio (Re(d/s)) of that data subset as a selected subset of N data points: sorting the selected subset of N Re(d/s) data points in ascending numerical order; selecting upper and lower subsets as a given percentage of the N Re(d/s) data points respectively; computing the average values of each of the upper and lower subsets to provide estimated Re(d/s) values for two jammers; converting the average values for the two jammers to angular positions via a monopulse calibration relationship; and supplying data on said angular positions for generation of jam strobes.

Claim 4

The method of resolving jammers in a radar system using a monopulse antenna, in which output signals from the monopulse antenna are combined to provide sum and difference signals, which are processed via coherent detector means to provide in-phase and quadrature values and converted to digital form, wherein a passive ECM pre-look operation comprises processing the in-phase and quadrature values to provide measurements for a plurality of data points for a dwell, in which the ECM pre-look operation includes a determination of whether or not main beam jamming is present; wherein said method of resolving jammers if operative in response to a determination during an ECM pre-look operation that main beam jamming is present, and comprises the steps: using said ECM pre-look measurements to compute real and imaginary parts for each data point of a set of said data points; and computing an average value of the imaginary difference-to-sum ratio Im(d/s) and comparing said average value against a first threshold value to detect whether there is a single source or multiple sources of the main beam jamming, with an indication that there are multiple sources being provided in response to exceeding the first threshold; responsive to said indication that there are multiple sources, using the imaginary part of the difference/sum ratio (Im(d/s)) to select a data subset below a second threshold, the second threshold being different from the first threshold, and using the real part of the difference/sum ratio (Re(d/s)) of that data subset as a selected subset of N data points: sorting the selected subset of N Re(d/s) data points in ascending numerical order; selecting upper and lower subsets as a given percentage of the N Re(d/s) data points respectively; computing the average values of each of the upper and lower subsets to provide estimated Re(d/s) values for two jammers; converting the average values for the two jammers to angular positions via a monopulse calibration relationship; and supplying data on said angular positions for generation of jam strobes.