Dual synthetic aperture radar system

A method for locating a moving target mover by processing radar signals and determining range, velocity and azimuth of a moving target mover from a transmit array and dual receive arrays mounted on a moving platform in line with said platform motion relative to terrain, wherein a classical Displaced Phase Center Antenna (DPCA) system is employed, said DPCA system simulating an antenna to be receiving signals as if stationary while said antenna is in fact mounted on a moving carrier;

• said Displaced Phase Center Antenna (DPCA) system selectively using a cancellation of clutter signals determining a target mover azimuth measurement from two spaced-apart array measurements of a moving target mover, by
• a) transmitting signals from said transmit array toward a moving target mover;
• b) receiving signals of a pulsatory nature from said first receive array and said second receive array at delay equal D and D+1;
• c) mathematically multiplying said received signals of said first and said second receive arrays by a weighting function to reduce affects of adjacent clutter and spectral leakage of said signals;
• d) calculating a phase correction for time mismatch and antenna mismatch and further multiplying frequency components of said signal data by a weighting function for clutter to make said signal components equal in said receive array 2 to that of said receive array 1 and of said second delay pulses in comparison with said first delay pulses, and subtracting said second array 2 corresponding filters,
• e) said method further placing another filter close to said placed filter but sufficiently separated to be two distinct set of filters,
• f) said method processing data determined to be of low clutter area by measuring phase between resultant vectors as phase proportional to radial velocity for determining an azimuth of said target mover;
• g) if test for low clutter shows significant clutter is detected then the significant clutter processing will proceed;
• wherein the improvement comprises:
• h) equating the equations for YF in said delay equal to D data and said delay equal to D+1 data for filter 1 and filter 2
• where further all variables in said above equations are known except x location of peak of clutter, which is solved for x,—as follows:
• i) substituting YF for x in said above determination in which all variables are known, and from this determination a value of YF is determined and said peak of target mover is determined,
• Where D and D+1 is the Number of data points the second subarray is delayed,
• C—Clutter vector
• M—Mover vector
• WC1—Clutter weighting function for filter 1 data
• WM1—Mover weighting function for filter 1 data
• ΦR—Phase shift proportional to relative radial velocity of the mover
• ΦD—Phase change of the target mover proportional due to its angular position plus its relative radial velocity;
• ΦA—Phase change of the target mover proportional to its angular position off bore sight of the antenna;
• ΦC—Phase change of clutter due to its angular position in the beam of the antenna;
• V″11—Measured vector in subarray 1 at filter 1 and delay=D+1
• T′11—Measured vector in subarray 1 at filter 1 and delay=D+1
• T′12—Measured vector in subarray 2 at filter 1 and delay=D
• T′12—Measured vector in subarray 2 at filter 2 and delay=D+1
• XF—Clutter filter response changes in amplitude and phase from filter 1 to filter 2
• YF—Mover filter response changes in amplitude and phase from filter 1 to filter 2
• p—The distance filter 2 is from filter 1
• V′11—Measured vector in subarray 1 at filter 1 delay=D;
• V′11=V″11
• V′12—Measured vector in subarray 2 at filter 1 delay=D
• D+1 is the delay for the second set of data for subarray 2
• V′12—Measured vector in subarray 2 at filter 1 and delay (D+1)
• V″12—Measured vector in subarray 2 at filter 1 and delay (D+1)
• WC1—Clutter weighting function for subarray 2 at filter 1 and delay (D+1)
• WC2—Clutter weighting function for subarray 2 at filter 2 and delay (D+1)
• WC—Clutter weighting function for subarray 2 at filter 1 and delay D
• WC approximately equal clutter weighting function for subarray 2 at time 2 and delay (D+1);
• WC1 approximately=WC2=WC
• WM1—Mover weighting function for subarray 2 at filter 1 and delay D
• WM2—Mover weighting function for subarray 2 at filter 2 and delay (D+1)
• WM—Mover weighting function for subarray 2 at filter 1 and delay D equal mover weighting function for subarray 2 at filter 2 and delay (D+1)
• WM=WM2=WM1
• wherein the following additional parameters have not been defined previously:
• T′11—Measured vector in subarray 1 at filter 2 and delay=D or D+1
• T′12—Measured vector in subarray 2 at filter 2 and delay=D
• T′12—Measured vector in subarray 2 at filter 2 and delay=D+1
• XF—Clutter filter response changes in amplitude and phase from filter 1 to filter 2
• WC1—Clutter weighting function for subarray 1 at filter 1 and delay (D)
• WC2—Clutter weighting function for subarray 2 at filter 2 and delay (D)
• WC—Clutter weighting function for subarray 2 at filter 1 and 2 and delay D
• WC1≈WC2≈WC WC approximately equal clutter weighting function for subarray 2 at filter 1 and 2 and delay (D)
• WM1—Mover weighting function for subarray 2 at filter 1 and delay D
• WM2—Mover weighting function for subarray 2 at filter 2 and delay (D)
• WM—Mover weighting function for subarray 2 at filter 1 and 2 and delay D equal mover weighting function for subarray 2 at filter 2 and delay (D+1)
• WM1=WM2=WM=WM1=WM2=WM
• YF—Mover filter response changes in amplitude and phase from filter 1 to filter 2
• p—The distance filter 2 is from filter 1
• j) Solving for XF in said delay equal to D data and said delay equal to D+1 data, wherein there is determined two equations where XF are determined to be the same;
• k) substituting all candidate ΦR in both equations and observing where the XF solutions are equal, this being determined to be the correct solution, wherein there are a limited number of candidate possible solutions,
• l) equating X and solving in terms of ΦR, there being determined an equation in ΦR, and, with said solution for ΦR, consequently determining said radial velocity and azimuth of said moving target mover,
• m) correlating with said results above,
• n) performing said operations for other range Doppler bins where said target mover is detected and the results correlated
• o) correlating said results with performing same operations with other delays pairs, D and D−1, etc, wherein same or close to same results should be obtained, and,
• p) correlating with other signals of a pulsatory nature constituting Pulse Repetition Frequencies (PRFs) at said predetermined antenna position.

A method for locating a moving target by processing radar signals to determine a range, velocity and azimuth of a moving target mover, said signals emanating from a transmit array and received by dual receive arrays 1 and 2 mounted on a moving platform in line with said platform motion relative to terrain, wherein a classical Displaced Phase Center Antenna (DPCA) system is employed, said DPCA system simulating an antenna to be receiving signals as if stationary while said antenna is in fact mounted on a moving carrier;

• said Displaced Phase Center Antenna (DPCA) system selectively using a cancellation of clutter signals determining a target azimuth measurement from two spaced-apart array measurements of a moving target, said method comprising:
• a) transmitting signals from said transmit array toward a moving target;
• b) receiving signals from said first receive array and said second receive array at delay equal D and D+1 and a time delay of array 1 data points and array 2 data points one said data point;
• c) mathematically multiplying said received signals of said first and said second receive arrays by a weighting function to reduce affects of adjacent clutter and spectral leakage of said signals;
• d) calculating a phase correction for time mismatch and antenna mismatch and further multiplying frequency components of said signal data by a weighting function for clutter to make said signal components equal in said receive array 2 to that of said receive array 1 and of said second delay pulses in comparison with said first delay pulses, and subtracting said second array 2 corresponding filters;
• wherein the improvement comprises:
• e) said method processing data determined to be of low clutter area by measuring predetermined phase between resultant vectors as a phase proportional to radial velocity and from that calculation a predetermined azimuth of said target is determined;
• wherein the improvement further comprises:
• f) if a test for low clutter shows that predetermined significant clutter is detected as in previous claims then said method proceeding to process said significant clutter;
• g) by suitable means determining peak of target or position of said peak of target relative to processed range Doppler bin,detecting all range-doppler bins said target and by suitable interpolation technique where said the location of said target and/or determined by where peak of target and forming a special filter that comprises the precise phase shift per said data point for that filter and/or for said N data points for said receive array 1 and said receive array 2 zero fill with a number of zeros with number of zeros to obtain said filter spacing as close as desired to said peak of target while the resolution of said filters remains the same and/or previous zero-fill process with a suitable interpolation technique for location of said peak of target, if necessary, if desired insert a special filter at said peak of target as described previously and placing a filter at at least one of any desired location and at said peak of target;
• h) By the previous ΔT and/or ΔF technique determine x, the position of the peak of clutter, and process the data at this point, at this point WC=WC and WM=WM determine the following;
• |(SIN(((D+1)(ΦR)/2))/(SIN(DΦR)/2)|=|(V′11−WCV′12)/(V′11−WCV′12)|
• where all parameters are known except ΦR and therefore solved for
• ΦR/2=phase of (V′11−WCV′12)/(V′11−WCV′12)
• where all parameters are known except ΦR and therefore solved for
• i) employing the same equations as for the previous solution for equating M and to equate C as follows:
• C=(V′11ejDΦR/WM1−V′12)/(ejDΦR/WM1−1/WC1) for delay=D
• C=(V′11ej(D+1)ΦR/WM1−V′12)/(ej(D+1)ΦR/WM1−1/WC1) for delay=D+1
• and equating C there is determined where the only unknown is ΦR but of D+1 th order and solving same since said solution is real and restricted to a range of values, and thereafter checking said determination with a previous solution equating M, as in the previous solution, and processing other doppler bins in a like manner such as on another side of said peak of target to obtain said peak of clutter, and utilizing other range bins to determine where said moving target mover is detected, and correlating same,
• j) correlating and performing said operational determinations with other delays pairs to obtain at least one of same results and results which are close to said same results,
• k) performing said operations for other range Doppler bins where said moving target mover is detected and said results are correlated,
• l) correlating with other Pulse Repetition Frequencies (PRFs) at said same antenna position and at a time which is close in time, wherein the following definitions are used:
• C—Clutter vector
• M—Mover vector
• WC1—Clutter weighting function for array 1 data
• WM1—Mover weighting function for array 1 data
• ΦR—Phase shift proportional to relative radial velocity of the mover
• ΦD—Phase change of the target proportional due to its angular position plus its relative radial velocity;
• ΦA—Phase change of the target proportional to its angular position off bore sight of the antenna;
• ΦC—Phase change of clutter due to its angular position in the beam of the antenna
• V″11—Measured vector in subarray 1 and delay=D+1
• V′11—Measured vector in subarray 1 at filter 1 delay=D;
• V′11=V″11
• V′12-Measured vector in subarray 2 at filter 1 delay=D
• D+1 is the delay for the second set of data for subarray 2
• V′12—Measured vector in subarray 2 at filter 1 and delay (D+1)
• V″12—Measured vector in subarray 2 at filter 1 and delay (D+1)
• WC1—Clutter weighting function for subarray 2 and delay (D+1)
• WC2—Clutter weighting function for subarray 2 and delay (D+1)
• WC—Clutter weighting function for subarray 2 and delay D+1
• WC—approximately equal clutter weighting function for subarray 2 for delay (D+1);
• WC1 approximately=WC2=Wc
• WM—Mover weighting function for subarray 2 and delay D
• WM2—Mover weighting function for subarray 2 and delay (D+1)
• WM—Mover weighting function for subarray 2 and delay D equal mover weighting function for subarray 2 and delay (D+1)
• WM=WM2=WM1
• WC1—Clutter weighting function for subarray 1 and delay (D)
• WC2—Clutter weighting function for subarray 2 and delay (D).

A method for locating a moving target by processing radar signals from a transmit array and dual receive arrays mounted on a moving platform in line with said platform motion relative to terrain, wherein a classical Displaced Phase Center Antenna (DPCA) system is employed, said DPCA system simulating an antenna to be receiving signals as if stationary while said antenna is in fact mounted on a moving carrier;

• said Displaced Phase Center Antenna (DPCA) system selectively using a cancellation of clutter signals determining a target azimuth measurement from two spaced-apart array measurements of a moving target, said method comprising:
• a) transmitting signals from said transmit array toward a moving target;
• b) receiving signals from said first receive array and said second receive array at all possible delays of array 2 data points from array 2 data points
• c) mathematically multiplying said received signals of said first and said second receive arrays by a weighting function to reduce affects of adjacent clutter and spectral leakage of said signals;
• d) calculating a phase correction for time mismatch and antenna mismatch and further multiplying frequency components of said signal data by a weighting function for clutter to make said signal components equal in said receive array 2 to that of said receive array 1 and of said second delay pulses in comparison with said first delay pulses, and subtracting said second array 2 corresponding filters,
• wherein the improvement comprises;
• e) said method processing data determined to be of low clutter area by measuring predetermined phase between resultant vectors as a phase proportional to radial velocity and from that calculation a predetermined azimuth of said target is determined;
• wherein the improvement further comprises:
• f) if a test for low clutter shows that predetermined significant clutter is detected as in previous claims then said method proceeding to process said significant clutter
• g) by suitable means determine peak of target or position of said peak of target for all possible delays relative to processed range Doppler bin;
• determine all range-doppler bins said target is detected and by suitable interpolation technique where said the location of said target and/or determined by where peak of target and form a special filter that comprises;
• the precise phase shift per said data point for that filter and/or for said N data points for said receive array 1 and said receive array 2 zero fill with a number of zeros with number of zeros to obtain said filter spacing as close as desired to said peak of target while the resolution of said filters remains the same and/or previous zero-fill process with a suitable interpolation technique for location of said peak of target, if necessary, if desired insert a special filter at said peak of target as described previously any or all above techniques will locate or place a filter at any desired location or at said peak of target at the two maximum peaks in delay=D and delay equal D+d
• h) By the previous ΔT and/or ΔF technique determine x, the position of the peak of clutter, and process the data at this point, at this point WC=WC and WM=WM we have the following;
• |(SIN(((D+d)ΦR)/2))/(SIN(DΦR)/2)|=|(V′11−WCV′12)/(V′11−WCV′12)|
• where all parameters are known except ΦR and therefore solved for
• dΦR/2=Phase of (V′11−WCV′12)/(V′11−WCV′12)
• where all parameters are known except ΦR and therefore solved for
• i) employing the same equations as for the previous solution for equating M we will equate C as follows:
• C=(V′11ejDΦR/WM1−V′12)/(ejDΦR/WM1−1/WC1) for delay=D
• C=(V′11ej(D+d)ΦR/WM1−V′12)/(ej(D+d)ΦR/WM1−1/WC1) for delay=D+d
• and equating C to determine an equation where the only unknown is ΦR but of D+d th order and difficult to solve but solvable since the solution is real and restricted to a range of values, thereafter checking with said previous solution equating M, and, as in the previous solution processing other doppler bins in a like manner such as on another side of said peak of target to obtain said peak of clutter, also there being other range bins where said target is detected, and correlating said determinations to obtain the best solution;
• j) correlating with performing said same operations with other delays pairs which are at least one of being the same and being close to said same results,
• k) performing said determinations for other range Doppler bins where said moving target mover is detected and said results are correlated;
• l) correlating said determinations with other signals of a pulsatory nature as Pulse Repetition Frequencies (PRFs) at a same antenna position and at a time which is close in time to said predetermined time, wherein said determinations are done according to the following definitions.
• C—Clutter vector
• M—Mover vector
• WC1—Clutter weighting function for array 1 data
• WM1—Mover weighting function for array 1 data
• ΦR—Phase shift proportional to relative radial velocity of the mover
• ΦD—Phase change of the target proportional due to its angular position plus its relative radial velocity;
• ΦA—Phase change of the target proportional to its angular position off bore sight of the antenna;
• Φc—Phase change of clutter due to its angular position in the beam of the antenna;
• V″11—Measured vector in subarray 1 and delay=D+d
• V′11—Measured vector in subarray 1 at filter 1 delay=D;
• V′11=V″11
• V′12—Measured vector in subarray 2 at filter 1 delay=D D+1 is the delay for the second set of data for subarray 2
• V′12—Measured vector in subarray 2 at filter 1 and delay (D+d)
• V″12—Measured vector in subarray 2 at filter 1 and delay (D+d)
• Clutter weighting function for subarray 2 and delay (D+d)
• WC2—Clutter weighting function for subarray 2 and delay (D+d)
• WC—Clutter weighting function for subarray 2 and delay D+d
• WC approximately equal clutter weighting function for subarray 2 for delay (D+1);
• WC1 X approximately=WC2=WC
• WM1—Mover weighting function for subarray 2 and delay D
• WM2—Mover weighting function for subarray 2 and delay (D+d)
• WM—Mover weighting function for subarray 2 and delay D equal mover weighting function for subarray 2 and delay (D+d)
• WM=WM2=WM1
• WC1—Clutter weighting function for subarray 1 and delay (D)
• WC2—Clutter weighting function for subarray 2 and delay (D).

In a transmission array with a dual receiving array synthetic aperture radar system, a method for detecting the position of a moving target, without the use of clutter and target vectors, comprising the steps of:

• positioning a first and second receiving array apart from the transmission array in a spaced relationship upon moving platform;
• utilizing a displaced phase center antenna methodology to detect a moving target, and measure data including but not limited to its range, relative radial velocity, and azimuth, wherein the improvement comprises the steps of:
• utilizing a clutter change value to determine a phase change of the target due to its relative radial velocity, and
• determining said phase change of said target proportional to its angular position off bore sight of said transmission array.