Bistatic coherent radar receiving system

Claim 3

The method of claim 1 further including the step of normalizing the matrix range bin samples attending each pulse of said pulsed illumination to common matrix values representing said illuminating pulse.

Claim 4

The method of claim 1 further including the step of deleting low amplitude matrix values identified in accordance with a predetermined Hamming amplitude weighting criteria from the range bin values used in said transforming step.

Claim 5

The method of claim 1 wherein said matrix includes range bin values for a first number of radar illumination pulses and wherein said transforming step includes the processing of matrix range bin values from a smaller second number of radar pulses and wherein new digital values are received in matrix positions between said first and second numbers concurrently with the execution of said transforming step.

Claim 6

The method of claim 1 further including the step of correcting the range indication of said target with respect to the relative locations of the radar receiver and transmitter.

Claim 7

The method of claim 1 further including the step of summing adjacent pairs of range bin values from the range bins following each transmitter pulse occurrence to enhance targets represented in more than one range bin.

Claim 8

The method of claim 6 wherein said summing includes forming the summation of a range bin value with the preceding range bin value to form a first summed value and with the succeeding range bin value to form a second summed value.

Claim 9

The method of claim 1, wherein said pulsed radar target illumination is noncoherent in nature.

Claim 10

The method of claim 1 wherein said pulsed radar target illumination is coherent in nature.

Claim 11

In a passive radar receiver responsive to radar pulses located in the transmit and receive time portions of the pulse repetition interval of a remotely sourced illuminating radar signal, the method for real-time coherently processing received pulse information comprising the steps of: mixing the received radar signal with a first local oscillator signal to form a first phase intermediate frequency signal; multiplying said received radar signal with a quadrature phased second local oscillator signal to form a second phase intermediate frequency signal having quadrature phase relationship with said first phase intermediate frequency signal; integrating each said first and second phase intermediate frequency signals to form first and second integrated signals; sampling said first and second integrated signals periodically, once in each of a plurality of range bin time increments commencing at each said radar pulse and extending contiguously through the attending pulse repetition interval, each range bin sample including a pair of signal values related respectively to said first and second integrated signals; storing a first array of said digital signal pair values according to pulse repetition interval group order; summing adjacent range bin values in each said pulse repeitition interval group of said array, forming thereby a second array of digital signal pair values representing range bin straddling return radar pulse phase and amplitude; subtracting a predetermined one of said second array values, a value taken from the same range bin in each pulse repetition interval group, from each other array value in said pulse repetition interval group to form a third array of digital signal pair values having phase compensated, reduced, instability; modifying said third array values in accordance with Hamming amplitude weighting to form a fourth array of digital signal pair values of modified radar antenna side lobe content; generating the discrete Fourier transform for a predetermined number of corresponding range bin values in each said pulse repetition interval group of said array, forming thereby a doppler frequency fifth array of digital signal values; correcting said fifth array signal values to exclude predetermined low velocity weighted components thereof, forming thereby a sixth array of signal values; comparing array values in said sixth array with a predetermined amplitude signal threshold, storing a predetermined set of identification parameters for each sixth array value exceeding said threshold; adjusting said identification parameters in accordance with the relative physical locations of said radar receiver and radar transmitter; displaying said threshold exceeding sixth array values in PPI format in positions identified by said adjusted parameters.

Claim 12

In a passive radar receiver responsive to radar pulses located in the transmit and receive time portions of the pulse repetition interval of a remotely sourced illuminating radar signal, the method for real-time coherently processing received pulse information comprising the steps of: mixing the received radar signal with a first local oscillator signal to form a first phase intermediate frequency signal; multiplying said received radar signal with a quadrature phased second local oscillator signal to form a second phase intermediate frequency signal having quadrature phase relationship with said first phase intermediate frequency signal; integrating each said first and second phase intermediate frequency signals to form first and second integrated signals; sampling said first and second integrated signals periodically, once in each of a plurality of range bin time increments commencing at each said radar pulse and extending contiguously through the attending pulse repetition interval, each range bin sample including a pair of signal values related respectively to said first and second integrated signals; storing a first array of said digital signal pair values according to pulse repetition interval group order; summing adjacent range bin values in each said pulse repeitition interval group of said array, forming thereby a second array of digital signal pair values representing range bin straddling return radar pulse phase and amplitude; subtracting a predetermined one of said second array values, a value taken from the same range bin in each pulse repetition interval group, from each other array value in said pulse repetition interval group to form a third array of digital signal pair values having phase compensated, reduced, instability; modifying said third array values in accordance with Hamming amplitude weighting to form a fourth array of digital signal pair values of modified radar antenna side lobe content; generating the discrete Fourier transform for a predetermined number of corresponding range bin values in each said pulse repetition interval group of said array, forming thereby a doppler frequency fifth array of digital signal values; correcting said fifth array signal values to exclude predetermined low velocity weighted components thereof, forming thereby a sixth array of signal values; comparing array values in said sixth array with a predetermined amplitude signal threshold, storing a predetermined set of identification parameters for each sixth array value exceeding said threshold; adjusting said identification parameters in accordance with the relative physical locations of said radar receiver and radar transmitter; displaying said threshold exceeding sixth array values in PPI format in positions identified by said adjusted parameters.

Claim 13

The method of claim 10 wherein said step of integrating said intermediate frequency signals includes mathematical integration over a time interval equal to the time of said sampling.

Claim 14

The method of claim 11 wherein said sampling time is one-half of the duration of each said illuminating radar pulse.

Claim 15

The method of claim 12 wherein said subtracted array value is the first array value in each said pulse repetition interval.

Claim 16

The method of claim 13 wherein said subtracted array value corresponds to the illuminating tramsitter pulse in each pulse repetition interval group of said second array.

Claim 17

The method of claim 14 wherein said Hamming amplitude weighting corrects the presence of sin x/x side lobes resulting from said transform generating step.

Claim 18

The method of claim 15 wherein the contents of said first array is continuously updated with newly-received signal information coincidentally with said transform generating.

Claim 19

Coherent passive radar receiver apparatus for use with targets illuminated by a remotely located, non-cooperative pulsed radar transmitter comprising: means generating from the signal received from said remote transmitter and radar targets a pair of intermediate frequency sine and cosine related quadrature phase signals; means for storing a matrix of digital values representing integrated periodic range bin samples of said sine and cosine intermediate frequency signals; means for correcting the matrix range bin sample values relating to each said transmitter pulse for the phase position of said transmitter pulse; means for transforming matrix values from corresponding range bins appending a predetermined number of said transmitter pulses to frequency domain Fourier transform signals; means for velocity weighting said Fourier transform signals to delete portions thereof representing predetermined doppler velocities; and means for displaying the remaining Fourier transform signal components, which also exceed a predetermined amplitude threshold, in organized relationship.

Claim 20

Coherent passive radar receiver apparatus for use with targets illuminated by a remotely located, non-cooperative pulsed radar transmitter comprising: means generating from the signal received from said remote transmitter and radar targets a pair of intermediate frequency sine and cosine related quadrature phase signals; means for storing a matrix of digital values representing integrated periodic range bin samples of said sine and cosine intermediate frequency signals; means for correcting the matrix range bin sample values relating to each said transmitter pulse for the phase position of said transmitter pulse; means for transforming matrix values from corresponding range bins appending a predetermined number of said transmitter pulses to frequency domain Fourier transform signals; means for velocity weighting said Fourier transform signals to delete portions thereof representing predetermined doppler velocities; and means for displaying the remaining Fourier transform signal components, which also exceed a predetermined amplitude threshold, in organized relationship.

Claim 21

The apparatus of claim 17 wherein said means for deleting selected portions includes means for deleting the transform signal portions representing near zero predetermined higher velocity components.

Claim 22

The apparatus of claim 17 wherein said means for correcting includes means for subtracting a transmitter pulse indicative signal from each range bin sample value appending each transmitter pulse in a group of transmitter pulses of predetermined length.

Claim 23

The apparatus of claim 17 wherein said means for displaying includes a PPI display.