Dual synthetic aperture radar system

• US 6,633,253 B2
• Filed: 04/01/2002
• Issued: 10/14/2003
• Est. Priority Date: 04/02/2001
• Status: Expired due to Fees

• Current Assignee: Thomas J. Cataldo
• Original Assignee: Thomas J. Cataldo
• Inventors: Cataldo, Thomas J.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US10/114,156
• Time in Patent Office: 561 Days
• Field of Search: 342/25, 342/159, 342/160, 342/195, 342/196
• US Class Current: 342/25.00R
• CPC Class Codes: G01S 13/5244 Adaptive clutter cancellation specially adapted for airborne MTI, G01S13/5242
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
• CPC Class Codes: G01S 2013/0245 Radar with phased array antenna

Abstract

The dual synthetic aperture array system processes returns from the receiving arrays. The two identical receiving arrays employing displaced phase center antenna techniques subtract the corresponding spectrally processed data to cancel clutter. It is further processed that a moving target is detected and its velocity, angular position and range is measured, in or out of the presence of clutter. There are many techniques presented in the disclosure. These techniques are basically independent but are related based on common set of fundamental set of mathematical equations, understanding of radar principles and the implementations involved. These many techniques may be employed singly and/or in combination depending on the application and accuracy required. They are supported by a system that includes, optimization of the number of apertures, pulse repetition frequencies, DPCA techniques to cancel clutter, adaptive techniques to cancel clutter, motion compensation, weighting function for clutter and target, and controlling the system in most optimum fashion to attain the objective of the disclosure.

Claims

1. A method for locating a moving target mover by processing radar signals to determine 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,

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 and a time delay of array 1 data points and array 2 data points and subtracting corresponding filters from said first array filters;

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 mover 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) said method determining that a moving target mover change value of Y are equal in D delay data and D+1 delay data for time 1 and time 2,

h) wherein all variables in said determinations are known except said clutter change value of x;

i) said method substituting said clutter change value of x in said equation for said mover change value of Y in which all variables are known and from this said determination said moving target mover change value of Y is determined and a peak of said moving target mover is determined;

j) said method solving for said clutter value of X in said delay equal to D data and said equal to D+1 data;

k) said method substituting all candidate determinations for Φ

_R in both of said equations and observing where solutions for said clutter value of X are calculated to be equal, this being determined to be a correct solution, there is a limited number of candidate possible solutions and said correct solution for candidate Φ

_R and consequently for Φ

_A;

l) said method equating said clutter value of X and solving in terms of Φ

_R and consequently using said determination to determine said radial and azimuth of said moving target mover;

m) said method correlating with said results of said above determination;

n) said method performing operations for other range Doppler bins where said moving target mover is detected and said results are correlated;

o) said method performing operations with other predetermined delays pairs, D and D−

1, etc, which are obtained to be at least one of being the same and being close to same results, and;

p) said method correlating other signals of a pulsatory nature constituting Pulse Repetition Frequencies (PRFs) at an identical antenna position and in a time frame which is close in time.

2. The method as in claim 1 for processing signals to determine range, velocity and azimuth of a moving target mover, said signals emanating from a transmit array and receiving said signals by dual receive arrays 1 and 2 mounted on a moving platform in line with said platform'"'"'s motion relative to terrain, said system employing a modified classical Displaced Phase Center Antenna (DPCA) system, detecting said MTI signals in said signals received in said receive array 1 and receive array 2 signals, detecting said MTI signal at at least one of its peak and an estimating peak of said MTI signals;

wherein said above detection calculation is performed for a predetermined delay equal to D and D+1 data, wherein a predetermined value of X defines a clutter change in amplitude and phase from a first designated time and wherein a predetermined value of Y defines a mover change in amplitude and phase from said first designated time to said second designated time, and wherein said value of Y is determined to be predetermined change in target designated as Y is determined to be the same in said predetermined D and D+1 delay data being equated and solved for said clutter change value of x;

wherein further since said determined clutter change values of Xs are equal also, thereafter said method substitutes all in the candidate Φ

_R in said equations where said clutter change values of Xs are equal, said method equating equations for X and obtaining an equation for Φ

_R being an unknown and said method solving and correlating with said previous solution and therefore attaining said position of said moving target and wherein clutter and target vectors and their change are not required to be known in this technique, wherein the improvement in said method for processing signals comprises the steps of;

accurately attaining the radial velocity, Φ

_R proportional to radial velocity and Φ

_A, proportional to azimuth by no other two receive array system and more accurate delay line cancellor or monopulse system and-more accurate than a three antenna system comprising;

said steps of said method comprising the following;

a) providing a transmit array and dual receive arrays, said arrays employing DPCA methodology to detect moving target movers and measure their range, relative radial velocity and azimuth accurately;

b) wherein the best mode radar system of said method for processing signals comprises the further steps of providing a sidelooking electronic scanned system with said transmit array and a said dual receive arrays where -said transmit array is equal to an addition of said dual receive arrays, wherein said received signals include components representing signal returns from said terrain, which said signals returns have Doppler components caused by motion of said platform relative to said terrain;

c) said method for processing signals pointing said transmit array and said dual receive arrays at a same azimuth position and at a substantial part of plus or minus ninety degrees from the perpendicular of said moving platform, to determine delay equal D wherein said arrays are mounted in line with a motion of said moving platform;

d) said radar being operated as a said best mode modified DPCA system where an optimum distance traveled of said arrays is calculated to be equal to one half of a distance between phase centers of said dual receive arrays to effectively cancel clutter interfering with obtaining said signals;

e) said radar transmitting an N number of signals of pulsatory nature at precise intervals, wherein said signals are received by said dual receive arrays, wherein said first receive array comprises complex data from a first point one to said complex data point N, wherein said second array comprises said delay calculated to be equal to D data for an optimum cancellation of said signal interfering clutter, starting at said complex data point D and proceeding to said data point N and thence to said data point D−

1, this being recirculated data, said data being stored for a predetermined M number of range bins;

f) said method for processing signals multiplying said N data points from said array 1 and array 2 by a weighting function to reduce spectral leakage, affects of adjacent clutter and other detrimental affects of processing said signals, spectrally processed such as by Fast Fourier Transform (FFT) processing;

g) said method for processing signals conducting a phase correction 2Π

fr t where f r are all frequencies detected and time t being the time mismatch between said predetermined delay Ds and a Pulse Repetition Frequency (PRF) pulse and wherein further a phase correction, Φ

_co is defined, whereby if a travel of said platform was determined to be halfway between said D and D+1 delay, then Φ

_∞

=Π

K/N, phase correction factor K_CM=Dfr/2NV=Π

/N wherein further Φ

_CE=K_CMx where s=0K_CM=Dfr/2NV=Π

/N;

h) said method for processing signals further conducting a clutter weighting function where WC in the significant clutter region is as follows $\mathrm{Wc}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+K_{\mathrm{CM}}<br><br>\left(s-x\right)\right)\right)$

where A_CM e<sup>j(Ψ

_CM)</sup> is calculated to be said clutter at its peak, wherein said clutter change value of x is determined to be s−

x equal to zero, and also for a predetermined value of WM at said target azimuth position;

i) said method for processing signals applying phase correction and clutter weighting function to the appropriate filters of said array 2 and subtracting corresponding filters of said array 2 from said filters of said array 1;

j) said method for processing signals calculating a threshold and detecting where present said MTI signals;

k) wherein for delay equal to D+1, said signals are received by said dual receive arrays, wherein said first array comprises said predetermined first complex data point one to said predetermined complex data point N, wherein said second array comprises said delay equal to D+1 data for said optimum cancellation of said signal interfering clutter, starting at said complex data point D+1 to said data point N to said data point D, this being said recirculated data, said data being stored for M number of range bins;

l) said method for processing signals further multiplying said data points of said array 1 and array 2 by a weighting function to reduce spectral leakage, affects of adjacent clutter and other detrimental affects and spectrally processed such as Fast Fourier Transmit (FFT) processing;

m) said method for processing signals conducting a phase correction, Φ

_co, for delay equal D and for travel midway between the D and D+1 pulse, wherein for the following Φ

_co=−

Π

K/N, phase correction error K_CM=Φ

_CE=−

π

D f_r/2NV=−

π

/2N is calculated;

n) said method for processing signals further calculating a clutter weighting function where W_C in the significant clutter region is as follows;

3. 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

W_C1—

Clutter weighting function for filter 1 data

W_M1—

Mover weighting function for filter 1 data

Φ

_R—

Phase shift proportional to relative radial velocity of the mover

Φ

_D—

Phase change of the target mover proportional due to its angular position plus its relative radial velocity;

Φ

_A—

Phase change of the target mover proportional to its angular position off bore sight of the antenna;

Φ

_C—

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

X_F—

Clutter filter response changes in amplitude and phase from filter 1 to filter 2

Y_F—

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)

W_C1—

Clutter weighting function for subarray 2 at filter 1 and delay (D+1)

W_C2—

Clutter weighting function for subarray 2 at filter 2 and delay (D+1)

W_C—

Clutter weighting function for subarray 2 at filter 1 and delay D

W_C approximately equal clutter weighting function for subarray 2 at time 2 and delay (D+1);

W_C1 approximately=W_C2=W_C

W_M1—

Mover weighting function for subarray 2 at filter 1 and delay D

W_M2—

Mover weighting function for subarray 2 at filter 2 and delay (D+1)

W_M—

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)

W_M=W_M2=W_M1

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

X_F—

Clutter filter response changes in amplitude and phase from filter 1 to filter 2

W_C1—

Clutter weighting function for subarray 1 at filter 1 and delay (D)

W_C2—

Clutter weighting function for subarray 2 at filter 2 and delay (D)

W_C—

Clutter weighting function for subarray 2 at filter 1 and 2 and delay D

W_C1≈

W_C2≈

W_C W_C approximately equal clutter weighting function for subarray 2 at filter 1 and 2 and delay (D)

W_M1—

Mover weighting function for subarray 2 at filter 1 and delay D

W_M2—

Mover weighting function for subarray 2 at filter 2 and delay (D)

W_M—

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)

W_M1=W_M2=W_M=W_M1=W_M2=W_M

Y_F—

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 X_F in said delay equal to D data and said delay equal to D+1 data, wherein there is determined two equations where X_F are determined to be the same;

k) substituting all candidate Φ

_R in both equations and observing where the X_F 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 Φ

_R, there being determined an equation in Φ

_R, and, with said solution for Φ

_R, 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.

4. The method as in claim 3 for processing signals to determine range, velocity and azimuth of a moving target mover, said signals emanating from a transmit array and receiving said signals by dual receive arrays 1 and 2 mounted on a moving platform in line with said platform'"'"'s motion relative to terrain, said system employing a modified classical Displaced Phase Center Antenna (DPCA) system, detecting said MTI signals in said signals received in said receive array 1 and array 2 signals, detecting said MTI signal at at least one of its peak and an estimating peak of said MTI signals;

wherein said detection calculation is performed for a plurality of delays equal to 1 and D data, wherein YF is determined to be the same in the D and D+1 data is equated and solved for XF, since XF S are equal also, said method solving for (Φ

_R in said equations, wherein clutter and target vectors are not required to be known, wherein the improvement comprises;

said method accurately attaining radial velocity, Φ

_R proportional to radial velocity and Φ

_A, proportional to azimuth by no other two receive array system and more accurate delay line canceller or monopulse system and possibly more accurate than a three antenna system, said method comprising;

a) providing a transmit array and dual receive arrays 1 and 2 employing said DPCA methodology to accurately detect moving targets and measure there range, relative radial velocity and azimuth,

b) wherein the best mode radar system comprises providing a sidelooking electronic scanned system with a transmit array and a dual receive arrays where the said transmit array which is addition of said dual receive arrays, the received signals including components representing returns from the terrain, which are modified by Doppler components caused by motion of the platform relative to terrain

c) wherein for delay equal D said transmit array and said dual receive arrays 1 and 2 are pointed at the same azimuth and at a substantial part of plus or minus ninety degrees from the perpendicular of moving platform, the arrays are mounted in line with motion of said moving platform

d) said radar being operated as a best mode modified DPCA system where the optimum distance traveled of said arrays is determined to be one half of a distance between phase centers of said dual receive arrays 1 and 2 to cancel clutter most effectively

e) wherein said radar transmits N signals of pulsatory nature at precise intervals, said signals being received by said dual receive arrays 1 and 2, said first receive array 1 comprising a complex datapoint one to said complex data point N, said second receive array 2 comprising the delay equal to D data for the most optimum cancellation of clutter, starting at said complex data point D to said data point N to said data point D−

1, said data being recirculated data, said data being stored for M range bins,

f) said method multiplying said receive array 1 and said receive array 2 and said N data points being multiplied by a weighting function to reduce spectral leakage, affects of adjacent clutter and other affects, spectrally processed such as Fast Fourier Transmit (FFT) processing,

g) said method for processing signals conducting a phase correction 2Π

fr t where f r are all frequencies detected and time t being the time mismatch between said predetermined delay Ds and a Pulse Repetition Frequency (PRF) pulse and wherein further a phase correction, Φ

_CO is defined, whereby if a travel of said platform was determined to be halfway between said D and D+1 delay, then Φ

_COΠ

K/N, phase correction factor K_CM=Dfr/2NV=Π

/N wherein further Φ

_CE=K_CM x where s=0 K_CM=Dfr/2NV=Π

/N

h) said method determining a clutter weighting function where WC in the significant clutter region is determined as follows according to the following equation;

$\mathrm{Wc}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+K_{\mathrm{CM}}<br><br>\left(s-x\right)\right)\right)$

 

where A_CMe^j(Ψ

_CM⁾ is said clutter at its peak, x equal zero, also for WM at same said target azimuth position

i) said applying said phase correction and said clutter weighting function to the appropriate said array 2 filters and subtracting corresponding said filters of array 2 from filters of said array 1

j) determining a threshold and detecting where present said MTI signals,

k) determining at least one of said peak of target and said position of said peak of target relative to a processed range Doppler bin;

determining all range-doppler bins for detecting said target and by suitable interpolation technique where said location of at least one of said target and said peak of target and forming a special filter that comprises the precise phase shift per said data point for at least one of said filter and 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, place another filter very close to said placed filter but sufficiently separated to be two distinct set of filters

l) for delay equal to D+1, said signals are received by said dual receive arrays, the first array comprises complex data point one to said complex data point N, the second array comprises the delay equal to D+1 data for the most optimum cancellation of clutter, starting at said complex data point D+1 to said data point N to said data point D, this is recirculated data, said data is stored for M rang bins,

m) said array 1 and array 2 said N data points being multiplied by a weighting function to reduce spectral leakage, affects of adjacent clutter and other affects and spectrally processed such as Fast Fourier Transmit FFT processing,

n) wherein phase correction, Φ

_CO, for delay equal D and for travel midway between the D and D+1 pulse is the following Φ

_CO=−

Π

K/N, wherein further phase correction error K_CM=Φ

_CE=−

π

D f_r/2NV=−

π

/2N is calculated,

o) determining a clutter weighting function where W_C in the significant clutter region is as follows;

$\underset{\_}{\mathrm{Wc}}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+\underset{\_}{K_{\mathrm{CM}}}<br><br>\left(s-x\right)\right)\right)$

 

where A_CMe<sup>j(Ψ

_CM)</sup> is said clutter at its peak, x equal zero, also for W_M at same said target azimuth position,

p) said array 1 and array 2 data process the second filter very close to first filter

q) said data of claim P are processed as in claim F to I

r) subtract said array 2 corresponding filters from the corresponding filters of said array 1 and said filter where said target detected at or near its peak

s) test for said processed data to be low clutter with said delay equal D+1 data, measure amplitude of vectors V′

₁₁−

V′

₁₂, if they are equal or nearly equal and the perpendicular bisector of V′

₁₁−

V′

₁₂ passes close to the origin measured by a line perpendicular to the perpendicular bisector and going through the origin and |V′

₁₁ | divided by this amplitude will be potentially M/C would be high, also test for said processed data to be low clutter area with said delay equal D data, if V′

₁₂=V′

₁₂ or measure amplitude of vectors V′

₁₁−

V′

₁₂, if they are equal or nearly equal and the perpendicular bisector of V′

₁₁−

V′

₁₂ passes close to the origin measured by a line perpendicular to the perpendicular bisector and going through the origin and |V′

₁₁| divided by this amplitude will be potentially M/C would be high also not if significantly clutter present, then go to claim W

t) If a determination as in paragraph “

s”

meets the criteria of very low clutter then implement the equation

5. 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 Δ

T and/or Δ

F technique determine x, the position of the peak of clutter, and process the data at this point, at this point W_C=W_C and W_M=W_M determine the following;

6. The method as in claim 5 for processing signals to determine a range, velocity and azimuth of a moving target mover, said signals emanating from a transmit array and receiving said signals by dual receive arrays 1 and 2 mounted on a moving platform in line with said platform'"'"'s motion relative to terrain, said system employing a modified classical DPCA system, detecting said MTI signals in said signals received in said receive array 1 and receive array 2 signals, detecting said MTI signal at least one of its peak and an estimating peak of said MTI signals;

wherein said above detection calculation is performed for a predetermined delay equal to D and D+1 data, M is determined to be the same in said predetermined D and D+1 delay data being equated and solved, for Φ

_R in said equations;

wherein signal interfering clutter and target mover vectors are not required to be known in said method, wherein the improvement in said method of processing signals comprises attaining radial velocity, Φ

_R proportional to radial velocity and Φ

_A, proportional to azimuth accurately by no other two receive array system and more accurate delay line cancellor or monopulse system and possibly more accurate than a three antenna system, said method comprising the following;

a) providing a transmit array and a dual receive arrays, said arrays employing DPCA methodology to detect moving target movers and measure their range, relative radial velocity and azimuth accurately

b) wherein the best mode radar system of said method for processing signals comprises the further steps of providing a sidelooking electronic scanned system with said transmit array and said dual receive arrays where said transmit array is an addition of said dual receive arrays, wherein said received signals include components representing signal returns from said terrain, which said signals returns have modified Doppler components caused by motion of said platform relative to said terrain;

c) said method for processing signals pointing said transmit array and said dual receive arrays at a same azimuth position and at a substantial part of plus or minus ninety degrees, delay equal D wherein said arrays are mounted in line with a motion of said moving platform;

d) said radar being operated as said best mode modified DPCA system where an optimum distance traveled of said arrays is calculated to be equal to one half of a distance between phase centers of said dual receive arrays to effectively cancel clutter interfering with obtaining said signals;

e) said radar transmitting an N number of signals of pulsatory nature at precise intervals, wherein said signals are received by said dual receive arrays, wherein said first receive array comprises complex data from a first point one to said complex data point N, wherein said second array comprises said delay calculated to be equal to D data for an optimum cancellation of said signal interfering clutter, starting at said complex data point D and proceeding to said data point N and thence to said data point D−

1, this being recirculated data, said data being stored for a predetermined M number of range bins;

f) said method for processing signals multiplying said N data points from said array 1 and array 2 by a weighting function to reduce spectral leakage, affects of adjacent clutter and other detrimental affects of processing said signals, spectrally processed such as by a Fast Transform Transmit (FFT) processing;

g) said method for processing signals conducting a phase correction 2Π

fr t where f r are all frequencies detected and time t being the time mismatch between said predetermined delay Ds and a Pulse Repetition Frequency (PRF) pulse and wherein further a phase correction, Φ

_co is defined, whereby if a travel of said platform was determined to be halfway between said D and D+1 delay, then Φ

_co=Π

K/N, phase correction factor K_CM=Dfr/2NV=Π

/N wherein further Φ

_CE=K_CM x where s=0 K_CM=Dfr/2NV=Π

/N

h) said method for processing signals further conducting a clutter weighting function where WC in the significant clutter region is as follows $\mathrm{Wc}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+K_{\mathrm{CM}}<br><br>\left(s-x\right)\right)\right)$

 

where A_CMe<sup>j(Ψ

_CM)</sup> is calculated to be said clutter at its peak, wherein x equal zero, and also for a predetermined value of WM at said target mover azimuth position;

i) said method for processing signals applying phase correction and clutter function to the appropriate filters of said array 2 and subtracting corresponding filters of said array 2 from said filters of said array 1;

j) said method for processing signals calculating a threshold and detecting where present said MTI signals;

k) said method for processing signals determining at least one of peak of target mover and position of said peak of target mover relative to processed range Doppler bin;

said method for processing signals determining all range-Doppler bins;

said target mover being detected and wherein by suitable interpolation technique where said location of said target mover is determined by the steps of paragraph j) where peak of target mover forms a special filter that comprises the precise phase shift per said data point for said 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 to obtain said filter spacing as close as desired to said peak of target while resolution of said filters remains the same and/or a previous zero-fill process with a suitable interpolation technique for location of said peak of target mover, if necessary, and if desired, inserting a special filter at said peak of target mover as described previously and locating and placing a filter at least one of any desired location and at said peak of target mover;

l) wherein for delay equal to D+1, said signals are received by said dual receive arrays, wherein said first array comprises said predetermined first complex data point one to said predetermined complex data point N, wherein said second array comprises said delay equal to D+1 data for said optimum cancellation of said signal interfering clutter, starting at said complex data point D+1 to said data point N to said data point D, this being said recirculated data, said data being stored for M number of range bins;

m) said method for processing signals multiplying said array 1 and array 2 N data points by a weighting function to reduce spectral leakage, affects of adjacent clutter and other detrimental affects and being spectrally processed such as Fast Transform Transmit (FFT) processing;

n) said method for processing signals conducting a phase correction, Φ

_CO, for delay equal D and for travel midway between the D and D+1 pulse wherein for the following Φ

_CO=−

Π

K/N, phase correction error K_CM=Φ

_CE=−

π

D f_r/2NV=−

π

/2N is calculated;

o) said method for processing signals further calculating a clutter weighting function where W_C in the significant clutter region is as follows;

$\underset{\_}{\mathrm{Wc}}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+\underset{\_}{K_{\mathrm{CM}}}<br><br>\left(s-x\right)\right)\right)$

 

where A_CM e<sup>j(Ψ

_CM)</sup> is said clutter at its peak, x equal zero, also for W_M at same said target mover azimuth position;

p) said method for processing signals testing for said processed data to be low clutter with said delay equal D+1 data, said method measuring amplitude of vectors V′

₁₁−

V′

₁₂, and if they are equal or nearly equal and a perpendicular bisector of V′

₁₁−

V′

₁₂ passes close to an origin measured by a line perpendicular to a perpendicular bisector and going thru said origin and |V′

₁₁| being divided by said amplitude being potentially M/C being high;

said method also testing for said processed data to be low clutter with said delay equal D data, measuring amplitude of vectors V′

₁₁−

V′

₁₂, and if they are equal or nearly equal and a perpendicular bisector of V′

₁₁−

V′

₁₂ passes close to said origin measured by a line perpendicular to a perpendicular bisector and going thru said origin and |V′

₁₁| being divided by said amplitude being potentially M/C being high;

said method also testing also if it is not significantly clutter present, then said method proceeding to paragraph “

w”

herein;

q) If calculations of paragraph p) meets said criteria of very low clutter, then implementing the equation

7. 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 Δ

T and/or Δ

F technique determine x, the position of the peak of clutter, and process the data at this point, at this point W_C=W_C and W_M=W_M we have the following;

8. The method as in claim 7 for processing signals to determine range, velocity and azimuth of a moving target mover, said signals emanating from a transmit array and receiving said signals by dual receive arrays 1 and 2 mounted on a moving platform in line with said platform'"'"'s motion relative to terrain, said system employing a modified classical Displaced Phase Center Antenna (DPCA) system, detecting said MTI signals in said signals received in said receive array 1 and array 2 signals, detecting said MTI signal at at least one of its peak and an estimating peak of said MTI signals;

wherein said detection calculation is performed for a plurality of delays equal to 1 and D data, wherein a value of M is determined to be the same in all delay D data and is equated and solved, said method further solving for Φ

_R in said equations, wherein an increased number of delays allows approximately twice the equivalent return power without an increased number of said delays and wherein clutter and target vectors are not required to be known, and,

wherein the improvement comprises;

attaining radial velocity, Φ

_R proportional to radial velocity and Φ

_A, proportional to an azimuth of said target mover more accurately than determined by no other two receive array system and by a delay line canceller or monopulse system and by a three antenna system, said method comprising the following steps;

a) providing a transmit array and dual receive arrays employing said DPCA methodology to detect moving target movers and accurately measuring their respective range relative radial velocity and azimuth;

b) proving as a best mode radar system a sidelooking electronic scanned system with said transmit array and said dual receive arrays, where said transmit array is an addition of said dual receive arrays, wherein said received signals include components representing returns from the terrain, which are modified by Doppler components caused by motion of the platform relative to terrain;

c) wherein for any delay said transmit array and said dual receive arrays are pointed at the same azimuth and at a substantial part of plus or minus ninety degrees from the perpendicular of said moving platform, said arrays being mounted in line with a respective motion of said moving platform,

d) said radar being operated as a best mode modified DPCA system where an optimum distance traveled of said arrays is equal to one half of a distance between respective phase centers of said dual receive arrays to cancel clutter most effectively;

e) said radar transmitting N signals of pulsatory nature at precise intervals, said signals being received by said dual receive arrays 1 and 2, wherein said first array 1 comprises complex datapoint one to said complex data point N, wherein said second array 2 comprises the delay equal to any delay data for the most optimum cancellation of clutter, starting at said complex data point any delay D to said data point N to said data point D−

1, said calculated data being recirculated data, said data being stored for M range bins,

f) wherein said receive array 1 and said receive array 2, and said N data points are multiplied by a weighting function to reduce spectral leakage, affects of adjacent clutter and other affects, spectrally processed, such as Fast Fourier Transmit (FFT) processing,

g) said method for processing signals conducting a phase correction 2Π

fr t where f r are all frequencies detected and time t being the time mismatch between said predetermined delay Ds and a Pulse Repetition Frequency (PRF) pulse and wherein further a phase correction, Φ

_co is defined, whereby if a travel of said platform was determined to be halfway between said D and D+1 delay, then Φ

_co=Π

K/N, phase correction factor K_CM=Dfr/2NV=Π

N wherein further Φ

_CE=K_CMx where s=0 K_CM=Dfr/2NV=Π

/N

h) said method providing a clutter weighting function where WC in the significant clutter region is determined as follows according to the following equation;

$\mathrm{Wc}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+K_{\mathrm{CM}}<br><br>\left(s-x\right)\right)\right)$

 

where A_CM e<sup>j(Ψ

_CM)</sup> is said clutter at its peak, x equal zero, also for WM at same said target azimuth position,

i) said method applying said phase correction and said clutter weighting function to the appropriate array of said array 2 filters and subtracting corresponding filters of said receive array 2 from said filters of said receive array 1,

j) said method determining a threshold and detecting where present said MTI signals,

k) determining at least one of said peak of said target mover and said position of said peak of said target mover relative to a processed range Doppler bin; and

determining all range-doppler bins to detect said target mover and by interpolation determining at least one of where said location of said target is located and where said peak of target is located and forming a special filter comprising a precise phase shift per said data point for at least one of said filter and 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, wherein said determinations place a filter at any desired location or at said peak of target delay data where the two delay sets of data where the peak of target data is maximum and process said data,

l) receiving signals for delay equal to D+1, by said dual receive arrays, said first array comprises complex data point one to said complex data point N, the second array comprises the delay equal to D+1 data for the most optimum cancellation of clutter, starting at said complex data point D+1 to said data point N to said data point D, this is recirculated data, said data is stored for M range bins,

m) multiplying said array 1 and array 2 said N data points by a weighting function to reduce spectral leakage, affects of adjacent clutter and other affects and spectrally processed such as Fast Fourier Transmit (FFT) processing,

n) determining a phase correction, Φ

_CO, for delay equal D and for travel midway between the D and D+1 pulse being the following Φ

_CO=−

Π

K/N, wherein said phase correction error K_CM=Φ

_CE=−

π

D f_r/2NV=−

π

/2N is calculated, but which can be calculated for any delay data,

o) determining said clutter weighting function where W_C in the significant clutter region is as follows;

$\underset{\_}{\mathrm{Wc}}={\left(\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>{<br><br>\mathrm{Vnk}<br><br>}^2\right)}^{-1}<br><br>\underset{M}{\overset{M=1}{\sum <br><br>}}<br><br>U_{\mathrm{nk}}<br><br>{\mathrm{Vnk}}^{*}=<br><br>A_{\mathrm{CM}}<br><br><br><br>\text{\hspace{1em}<br><br>}<br><br>\exp <br><br>\left(j<br><br>\left({\mathrm{\Psi <br><br>}}_{\mathrm{CM}}+\underset{\_}{K_{\mathrm{CM}}}<br><br>\left(s-x\right)\right)\right)$

 

where A_CMe<sup>j(Ψ

_CM)</sup> is said clutter at its peak, x equal zero, also for W_M at same said target azimuth position,

p) testing for said processed data to be of a low clutter with said delay equal D+1 data, measuring amplitude of vectors V′

₁₁−

V′

₁₂, and if said vectors are at least one of being equal and being nearly equal, and determining that the perpendicular bisector of V′

₁₁−

V′

₁₂ passes close to the origin measured by a line perpendicular to the perpendicular bisector and going through the origin and |V′

₁₁| being divided by said amplitude being determined to be potentially M/C high, and testing for said processed data to be low clutter with said delay equal D data, measuring amplitude of vectors V′

₁₁−

V′

₁₂, and if said vectors are at least one of being equal and being nearly equal and the perpendicular bisector of V′

₁₁−

V′

₁₂ passes close to the origin measured by a line perpendicular to the perpendicular bisector and going through the origin and |V′

₁₁| being divided by said amplitude to be determined to be potentially M/C high, and also if determining that significantly clutter is not present, then proceeding to paragraph wherein,

q) if said determinations of paragraph p meets a criteria of being of very low clutter then implementing the equation

9. 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.