Narrowband passive differential tracking system (U)

Claim 1

A passive tracking system which tracks a target of known initial position from Doppler-shifted target signals, said passive differential tracking system comprising: a first and second illuminator of opportunity, each being an, independent electromagnetic signal transmitter, said first illuminator of opportunity transmitting a first signal which is reflected off said target to produce a first Doppler-shifted target return signal, and said second illuminator of opportunity transmitting a second signal which is reflected off of said target to produce a second Doppler-shifted target return signal wherein said first and second illuminators are selected from a group consisting of: UHF TV stations; Low VHF TV stations; and High VHF TV stations; an antenna which receives and conducts said first and second Doppler-shifted target return signals from said target; a receiver which produces a first and second digital output signal by receiving and respectively converting into digital said first and second Doppler-shifted return target signals from said antenna, and wherein said antenna and said receiver have frequency ranges selected from a group consisting of: 50-90 MHz for low band; 164-230 MHz for mid band; and 470-890 MHz for high band, and wherein said antenna includes antennas having a horizontal polarization with a minimum pain which ranges between 10 dB and 18 dB, said antenna having an azimuth beamwidth of between 30 and 40 degrees and an elevation beamwidth of between 20 and 90 degrees; an initial position determining means for measuring the initial position of said target; and a means for signal processing which receives said first and second digital output signals from said receiver, and combines said signals with said initial position of said target, said signal processing system thereby tracking said target by updating said target's changing in position with respect to said initial position; wherein said means for signal processing comprises a data processor which is programmed in BASIC with a two illuminator narrowband tracking program which enables said data processor to track said target by updating said target's location and said first and second illuminator of opportunity's location as well as Doppler and picture carrier frequency values for said first and second signal, said two illuminator narrowband tracking program comprising: 1 TWO ILLUMINATOR NARROW-BAND TRACKING PROGRAM 2 This program performs the 2 illuminator narrow-band tracking algorithm This program can artificially error the input dopplers in a Gaussian fashion 9 ′ FNDMS and FNDM{overscore (S)}I convert points on an x-y grid to lat-long and back again. 10 DEF FNDMS(X)=INT(X)+(INT(X*100+1/120)−INT(X)*100)/60+(X*10000−INT(X*100+1/120)*100)/3600 20 DEF FNDMSI(X)=SGN(X)*(ABS(INT(X)+ABS(INT((X−INT(X))*60+1/70)/100)+ABS(INT((X*60−INT(X*60−1/70))*60+1/70)/10000)) 21 N=VAL(RIGHT$(TIME$, 2 ) 22 RANDOMIZE N 25 LPRINT CHR$( 27 )+CHR$( 69 ):LPRINT DATE$:LPRINT 30 INPUT“LOC OF RECEIVER IN LAT,LONG(dd.mmss)”;LA( 0 ),LO( 0 ) 40 LPRINT“LOC OF RECEIVER IN LAT,LONG(dd.mmss)”LA( 0 ),LO( 0 ) 50 INPUT“LOC OF ILLUMINATOR 1 IN LAT,LONG(dd.mmss)”;LA( 1 ),LO( 1 ) 60 LPRINT“LOC OF ILLUMINATOR 1 IN LAT,LONG(dd.mmss)”LA( 1 ),LO( 1 ) 70 INPUT“LOC OF ILLUMINATOR 2 IN LAT,LONG(dd.mmss)”;LA( 2 ),LO( 2 ) 80 LPRINT“LOC OF ILLUMINATOR 2 IN LAT,LONG(dd.mmss)”LA( 2 ),LO( 2 ) 90 INPUT“INPUT CARRIER F AND ASSOCIATED DELTA F FOR ILLU. 1”;CAR( 1 ),DOP( 1 ) 100 LPRINT“INPUT CARRIER F AND ASSOCIATED DELTA F FOR ILLU. 1”CAR( 1 ),DOP( 1 ) 110 INPUT“INPUT CARRIER F AND ASSOCIATED DELTA F FOR ILLU. 2”;CAR( 2 ),DOP( 2 ) 120 LPRINT“INPUT CARRIER F AND ASSOCIATED DELTA F FOR ILLU. 2”CAR( 2 ),DOP( 2 ) 130 INPUT“INPUT TIME FROM LAST MEASUREMENT (IN SECONDS)”;T 140 LPRINT“INPUT TIME FROM LAST MEASUREMENT (IN SECONDS)”T 149 COUNT=0 150 INPUT“INITIAL LOC OF TARGET IN LAT,LONG(dd.mmss)”;LA( 3 ),LO( 3 ) 160 LPRINT“INITIAL LOC OF TARGET IN LAT,LONG(dd.mmss)”LA( 3 ),LO( 3 ) 170 FOR I=1 TO 2 171 XX=0 172 FOR J=1 TO 20:XX=XX+RND:NEXT 173 XX=(XX−10)*.7745967 174 DOP(I)=DOP(I)+DOP(I)*.002*XX 175 PRINT DOP(I) 176 NEXT 177 FOR A=0 TO 3 ′convert lat-long values to an x-y grid 180 LAA(A)=FNDMS(LA(A)) 190 LOO(A)=FNDMS(LO(A)) 200 X(A)=60* (LOO( 0 )−LOO(A))*COS(LAA( 0 )*3.14159/180) 210 Y(A)=60* (LAA(A)−LAA( 0 )) 220 NEXT 230 FOR A=1 TO 2 ′calculate range sum difference 240 RSD(A)=−(162000!)*DOP(A)*T/CAR(A) 250 NEXT 260 XG=X( 3 ):YG=Y( 3 ) 270 FOR A=1 TO 2 ′calculate values of simultaneous equations 280 RR(A)=RSD(A)+SQR((XG−X( 0 )){circumflex over ( )}2+(YG−Y( 0 )){circumflex over ( )}2)+SQR((XG−X(A)){circumflex over ( )}2+(YG−Y(A)){circumflex over ( )}2) 290 RRG(A)=RR(A)−RSD(A) 300 NEXT 310 WHILE SQR((RR( 1 )−RRG( 1 )){circumflex over ( )} 2 +(RR( 2 )−RRG( 2 )){circumflex over ( )} 2 )>.001 ′window of convergence 320 COUNT=COUNT+1 330 IF COUNT=50 THEN PRINT“DIVERGENCE”:GOTO 800 340 FOR A=0 TO 2 ′calculate values of Jacobian 350 DRDX(A)=((XG−X(A)){circumflex over ( )}2+(YG−Y(A)){circumflex over ( )}2)(−.5)*(XG−X(A)) 360 DRDY(A)=((XG−X(A)){circumflex over ( )}2+(YG−Y(A)){circumflex over ( )}2)(−.5)*(YG−Y(A)) 370 NEXT 380 J( 1 , 1 )=DRDX( 0 )+DRDX( 1 ) 390 J( 1 , 2 )=DRDY( 0 )+DRDY( 1 ) 400 J( 2 , 1 )=DRDX( 0 )+DRDX( 2 ) 410 J( 2 , 2 )=DRDY( 0 )+DRDY( 2 ) 420 D=J( 1 , 1 )*J( 2 , 2 )−J( 1 , 2 )*J( 2 , 1 ) ′determinant of Jacobian 430 IF D=0 THEN PRINT“J IS SINGULAR”:GOTO 800 440 IN( 1 , 1 )=( 1 /D)*J( 2 , 2 ) ′calculate inverse of Jacobian 450 IN( 1 , 2 ,)=−( 1 /D)*J( 1 , 2 ) 460 IN( 2 , 1 )=−( 1 /D)*J( 2 , 1 ) 470 IN( 2 , 2 )=( 1 /D)*J( 1 , 1 ) 480 XG=XG+(IN( 1 , 1 )*(RR( 1 )−RRG( 1 ))+IN( 1 , 2 )*(RR( 2 )−RRG( 2 ))) ′next guesses of 490 YG=YG+(IN( 2 , 1 )*(RR( 1 )−RRG( 1 ))+IN( 2 , 2 )*(RR( 2 )−RRG( 2 ))) ′new location 500 FOR A=1 TO 2 510 RRG(A)=SQR(XG−X( 0 )){circumflex over ( )} 2 +(YG−Y( 0 )){circumflex over ( )} 2 )+SQR ((XG−X(A)){circumflex over ( )} 2 +(YG−Y(A)){circumflex over ( )} 2 ) 520 NEXT 530 PRINT XG,YG 540 WEND 550 LAT=LAA( 0 )+YG/ 60 560 LOT=LOO( 0 )−XG/( 60 *COS(LAA( 0 )* 3 . 14159 / 180 )) 570 LAT=FNDMSI(LAT) ′convert back to lat-long 580 LOT=FNDMSI (LOT) 590 PRINT“NEW LOC IS“LAT”LAT, “LOT”LONG” 600 LPRINT“NEW LOC IS“LAT”LAT, “LOT”LONG” 610 PRINT“AVERAGE SPEED IS“ 3600 *SQR((X( 3 )−XG){circumflex over ( )}2+(Y( 3 )−YG){circumflex over ( )} 2 )/T“KNOTS” 620 LPRINT“AVERAGE SPEED IS” 3600 *SQR((X( 3 )−XG){circumflex over ( )}2+(Y( 3 )−YG){circumflex over ( )} 2 )/T“KNOTS” 625 IF XG−X( 3 )=0 THEN Z=1 630 IF Z=1 THEN IF YG−Y( 3 )>0 THEN HE=0 ELSE HE=180 ELSE HE=ATN((YG−Y( 3 ))/(XG−X( 3 )))*180/3.14139 640 IF XG−X( 3 )>0 THEN HE=90−HE 650 IF XG−X( 3 )<0 THEN HE=270−HE 660 PRINT“THE COURSE IS”HE“DEGREES” 670 LPRINT“THE COURSE IS”HE“DEGREES” 680 PRINT“DISTANCE TRAVELED IS”SQR((X( 3 )−XG){circumflex over ( )}2+(Y( 3 )−YG){circumflex over ( )}2)”NAUT. MILES 690 LPRINT“DISTANCE TRAVELED IS”SQR((X( 3 )−XG){circumflex over ( )} 2 +(Y( 3 )−YG){circumflex over ( )}2)”NAUT. MILES”:LPRINT 700 INPUT“INPUT A NEW SET OF DOPPLERS ( 1 =YES, 0 =NO)”;N 710 LPRINT“INPUT A NEW SET OF DOPPLERS ( 1 =YES, 0 =NO)”N 720 IF N=0 THEN GOTO 800 730 INPUT“NEXT DOPPLER FOR ILL. 1”;DOP( 1 ) 740 LPRINT“NEXT DOPPLER FOR ILL. 1:“DOP( 1 ) 750 INPUT“NEXT DOPPLER FOR ILL. 2”;DOP( 2 ) 760 LPRlNT“NEXT DOPPLER FOR ILL. 2: ”DOP( 2 ) 761 INPUT“INPUT NEW INITIAL LOC ( 1 =YES, 0 =NO)”;G 762 IF G=1 THEN GOTO 149 770 LA( 3 )=LAT:LO( 3 )=LOT 780 COUNT=0 790 GOTO 170 800 STOP.