US5570099A — TDOA/FDOA technique for locating a transmitter

Claim 1

Independent Claim 197 words

A process for locating a transmitter, said process comprising the steps of: receiving at a first receiver a signal transmitted by said transmitter; analog to digital converting the signal received by said first receiver to yield a first digital signal; compressing the first digital signal or another digital signal derived from said first digital signal; receiving at a second receiver the signal transmitted by said transmitter, wherein there is relative motion between said first or second receiver and said transmitter; analog to digital converting the signal received by said second receiver to yield a second digital signal; transmitting the compressed signal to a cross-correlation unit local to said second receiver and coupled also to receive said second digital signal or another digital signal derived from said second digital signal; using said cross-correlation unit to generate and solve a cross-correlation function based on said compressed signal and said second digital signal or other digital signal derived from said second digital signal; and determining, locally to said first receiver, correction factors for the solution to the cross-correlation function, and transmitting said correction factors to a correction unit which applies said correction factors to the solution of said cross-correlation function.

Claim 2

Dependent Claim 197 words

A process for locating a transmitter, said process comprising the steps of: receiving at a first receiver a signal transmitted by said transmitter; analog to digital converting the signal received by said first receiver to yield a first digital signal; compressing the first digital signal or another digital signal derived from said first digital signal; receiving at a second receiver the signal transmitted by said transmitter, wherein there is relative motion between said first or second receiver and said transmitter; analog to digital converting the signal received by said second receiver to yield a second digital signal; transmitting the compressed signal to a cross-correlation unit local to said second receiver and coupled also to receive said second digital signal or another digital signal derived from said second digital signal; using said cross-correlation unit to generate and solve a cross-correlation function based on said compressed signal and said second digital signal or other digital signal derived from said second digital signal; and determining, locally to said first receiver, correction factors for the solution to the cross-correlation function, and transmitting said correction factors to a correction unit which applies said correction factors to the solution of said cross-correlation function.

Claim 3

Dependent Claim 43 words

A process as set forth in claim 1 wherein said compressing step represents said first digital signal or said other digital signal derived from said first digital signal by phase information comprising substantially fewer bits than the phase information before the compressing step.

Claim 4

Dependent Claim 52 words

A process as set forth in claim 1 further comprising the steps of: finite impulse response filtering said first digital signal or said other digital signal derived from said first digital signal; and finite impulse response filtering said second digital signal or said other digital signal derived from said second digital signal.

Claim 5

Dependent Claim 84 words

A process as set forth in claim 3 wherein said cross-correlation function is defined by ##EQU19## where e j (θ(n)π/2.spsp.M.sup.θ.spsp.-1.sup.) is the quantized phase representation of the compressed signal, s 2 represents the conjugate of the output of the finite impulse response filtering step of said second digital signal or said other digital signal derived from said second digital signal, n is the complex sample index, k is the τ index, Δ is the Fourier Transform angle increment and l is the ν index.

Claim 6

Dependent Claim 85 words

A process as set forth in claim 3 wherein said correction factors are defined by ##EQU20## where e j (θ(n)π/2.spsp.M.sup.θ.spsp.-1.sup.) is the quantized phase representation of the compressed signal, s 1 represents the conjugate of the output of the finite impulse response filtering of said first digital signal or said other digital signal derived from said first digital signal, n is the complex sample index, k is the τ index (-2≦k≦2), Δ is the Fourier Transform angle increment and l is the ν index (-2≦l≦2).

Claim 7

Dependent Claim 29 words

A process as set forth in claim 1 wherein said compressing step is performed by ##EQU21## where M.sub.θ (≧1) is the number of bits used to represent each θ.

Claim 8

Dependent Claim 82 words

A process as set forth in claim 3 wherein said cross-correlation step is defined by ##EQU22## is the quantized magnitude and phase representation of the compressed signal, s 2 represents the conjugate of the output of the finite impulse response filtering step of said second digital signal or said other digital signal derived from said second digital signal, n is the complex sample index, k is the τ index, Δ is the Fourier Transform angle increment and l is the ν index.

Claim 9

Dependent Claim 83 words

A process as set forth in claim 3 wherein said correction factors are defined by ##EQU23## is the quantized magnitude and phase representation of the compressed signal, s 1 represents the conjugate of the output of the finite impulse response filtering of said first digital signal or said other digital signal derived from said first digital signal, n is the complex sample index, k is the τ index (-2≦k≦2), Δ is the Fourier Transform angle increment and l is the ν index (-2≦l≦2).

Claim 10

Dependent Claim 46 words

A process as set forth in claim 1 wherein said compressing step is performed by ##EQU24## and M a , (≧1) is the number of bits used to represent each a; and ##EQU25## where M.sub.θ (≧1) is the number of bits used to represent each θ.

Claim 11

Dependent Claim 82 words

A process as set forth in claim 3 wherein said cross-correlation step is defined by ##EQU26## is the quantized real and imaginary representation of the compressed signal, s 2 represents the conjugate of the output of the finite impulse response filtering step of said second digital signal or said other digital signal derived from said second digital signal, n is the complex sample index, k is the τ index, Δ is the Fourier Transform angle increment and l is the ν index.

Claim 12

Dependent Claim 83 words

A process as set forth in claim 3 wherein said correction factors are defined by ##EQU27## is the quantized real and imaginary representation of the compressed signal, s 1 represents the conjugate of the output of the finite impulse response filtering of said first digital signal or said other digital signal derived from said first distal signal, n is the complex sample index, k is the τ index (-2≦k≦2), Δ is the Fourier Transform angle increment and l is the ν index (-2≦l≦2).

Claim 13

Dependent Claim 46 words

A process as set forth in claim 1 wherein said compressing step is performed by ##EQU28## and M R is the number of bits used to represent the real part; and ##EQU29## and M Q is the number of bits used to represent the imaginary part.

Claim 14

Dependent Claim 74 words

A process as set forth in claim 1 further comprising the steps of: converting said first digital signal to a complex baseband signal, the compressing step being performed using said complex baseband signal or a digital signal derived from said complex baseband signal; and converting said second digital signal to a complex baseband signal, the cross-correlation function being performed using said complex baseband signal or a digital signal derived from said complex baseband signal.

Claim 15

Dependent Claim 71 words

A process as set forth in claim 13 further comprising the steps of: finite impulse response filtering said complex baseband signal derived from said first digital signal and performing the compression step and correction computation using the finite impulse response filtered signal; and finite impulse response filtering said complex baseband signal derived from said second digital signal and performing the cross-correlation function generating step using the finite impulse response filtered signal.

Claim 16

Dependent Claim 43 words

A process as set forth in claim 1 wherein said cross-correlation function generating step yields a difference in time delay, difference in frequency and difference in phase between the signal received at said first receiver and the signal received at said second receiver.

Claim 17

Dependent Claim 29 words

A process as set forth in claim 15 further comprising the subsequent steps of determining the location of said transmitter based on the corrected solution to said cross-correlation function.

Claim 18

Dependent Claim 36 words

A process as set forth in claim 16 wherein the determining step is performed by determining the difference in range between said transmitter and each of said receivers and the difference in velocity between said receivers.

Claim 19

Dependent Claim 30 words

A process as set forth in claim 1 wherein said transmitter transmits radio or microwave signals, and said receivers receives said radio or microwave signals with an antenna and amplifier.

Claim 20

Dependent Claim 18 words

A process as set forth in claim 1 wherein said correction unit is local to said second receiver.

Claim 21

Dependent Claim 15 words

A process as set forth in claim 1 wherein both of said receivers are moving.

Claim 22

Dependent Claim 34 words

A process as set forth in claim 1 wherein said transmitter transmits acoustic, sonic or ultrasonic waves and each of said receivers transduces said acoustic, sonic or ultrasonic waves to a corresponding electrical signal.

Claim 23

Dependent Claim 29 words

A process as set forth in claim 1 wherein said phase information indicates only a quadrant in a complex plane in which the phase of each digital sample resides.

Claim 24

Dependent Claim 33 words

A process as set forth in claim 16 further comprising the subsequent step of supplying said location information to a weapon control system and processing said location information by said weapon control system.

Claim 25

Dependent Claim 253 words

A process for locating a transmitter, said process comprising the steps of: receiving at a first receiver a signal transmitted by said transmitter; analog to digital converting the signal received by said first receiver to yield a first digital signal; compressing said first digital signal or another digital signal derived from said first digital signal; receiving at a second receiver the signal transmitted by said transmitter; analog to digital converting the signal received by said second receiver to yield a second digital signal; receiving at a third receiver a signal transmitted by said transmitter; analog to digital converting the signal received by said third receiver to yield a third digital signal; transmitting the compressed signal to a convolution unit local to said second receiver and convolving said compressed signal with said second digital signal or another digital signal derived from said second digital signal; transmitting said compressed signal to a convolution unit local to said third receiver and convolving said compressed signal with said third digital signal or another digital signal derived from said third digital signal; determining, locally to said first receiver, correction factors for the solution to both convolution units, transmitting said correction factors to a correction unit local to said second receiver which applies said correction factors to an output of the convolution unit local to said second receiver, and transmitting said correction factors to a correction unit local to said third receiver which applies said correction factors to an output of the convolution unit local to said third receiver.

Claim 26

Dependent Claim 253 words

A process for locating a transmitter, said process comprising the steps of: receiving at a first receiver a signal transmitted by said transmitter; analog to digital converting the signal received by said first receiver to yield a first digital signal; compressing said first digital signal or another digital signal derived from said first digital signal; receiving at a second receiver the signal transmitted by said transmitter; analog to digital converting the signal received by said second receiver to yield a second digital signal; receiving at a third receiver a signal transmitted by said transmitter; analog to digital converting the signal received by said third receiver to yield a third digital signal; transmitting the compressed signal to a convolution unit local to said second receiver and convolving said compressed signal with said second digital signal or another digital signal derived from said second digital signal; transmitting said compressed signal to a convolution unit local to said third receiver and convolving said compressed signal with said third digital signal or another digital signal derived from said third digital signal; determining, locally to said first receiver, correction factors for the solution to both convolution units, transmitting said correction factors to a correction unit local to said second receiver which applies said correction factors to an output of the convolution unit local to said second receiver, and transmitting said correction factors to a correction unit local to said third receiver which applies said correction factors to an output of the convolution unit local to said third receiver.

Claim 27

Dependent Claim 76 words

A process as set forth in claim 24 further comprising the steps of: determining a time difference of arrival between the signals received at said first and third receivers based on the output of said correction unit which is local to said third receiver; and determining a time difference of arrival between the signals received at said first and second receivers based on the output of said correction unit which is local to said second receiver.

Claim 28

Dependent Claim 28 words

A process as set forth in claim 25 further comprising the step of determining the location of the transmitter based on the two time difference of arrival measurements.

Claim 29

Dependent Claim 41 words

A process as set forth in claim 24 wherein said compressing step represents said first digital signal or said other digital signal derived from said first digital signal by information comprising substantially fewer bits than the information before the compressing step.

Claim 30

Dependent Claim 24 words

A process as set forth in claim 24 further comprising the steps of: filtering said first digital signal; and filtering said second digital signal.

Claim 31

Dependent Claim 66 words

A process as set forth in claim 28 wherein each of said convolution units performs the function of ##EQU30## is the quantized representation of the compressed signal, s i represents the output of the filtering step of the ith (second or third) digital signal or said other digital signal derived from said ith digital signal, n is the sample index, and k is the τ index.

Claim 32

Dependent Claim 60 words

A process as set forth in claim 28 wherein said correction factors are defined by ##EQU31## is the quantized representation of the compressed signal, s i represents the output of the filtering of said first distal signal or said other digital signal derived from said first digital signal, n is the sample index, and k is the τ index (-2≦k≦2).

Claim 33

Dependent Claim 30 words

A process as set forth in claim 24 wherein said compressing step is performed by ##EQU32## where M s (≧1) is the number of bits used to represent each s.

Claim 34

Dependent Claim 33 words

A process as set forth in claim 26 further comprising the subsequent step of supplying said location information to a weapon control system and processing said location information by said weapon control system.

Claim 35

Independent Claim 211 words

A system for locating a transmitter, said system comprising: a first receiver for receiving a signal transmitted by said transmitter; a first analog to digital converter for converting the signal received by said first receiver to yield a first digital signal; means for compressing the first digital signal or another digital signal derived from said first digital signal; a second receiver for receiving the signal transmitted by said transmitter, wherein there is relative motion between said first or second receiver and said transmitter; a second analog to digital converter for converting the signal received by said second receiver to yield a second digital signal; a cross-correlation unit local to said second receiver and coupled to receive said second digital signal or another digital signal derived from said second digital signal; means for transmitting the compressed signal to said cross-correlation unit, said cross-correlation unit generating and solving a cross-correlation function based on said compressed signal and said second digital signal or other distal signal derived from said second digital signal; a correction unit; and means for determining, locally to said first receiver, correction factors for the solution to the cross-correlation function, and transmitting said correction factors to said correction unit which applies said correction factors to the solution of said cross-correlation function.

Claim 36

Independent Claim 211 words

A system for locating a transmitter, said system comprising: a first receiver for receiving a signal transmitted by said transmitter; a first analog to digital converter for converting the signal received by said first receiver to yield a first digital signal; means for compressing the first digital signal or another digital signal derived from said first digital signal; a second receiver for receiving the signal transmitted by said transmitter, wherein there is relative motion between said first or second receiver and said transmitter; a second analog to digital converter for converting the signal received by said second receiver to yield a second digital signal; a cross-correlation unit local to said second receiver and coupled to receive said second digital signal or another digital signal derived from said second digital signal; means for transmitting the compressed signal to said cross-correlation unit, said cross-correlation unit generating and solving a cross-correlation function based on said compressed signal and said second digital signal or other distal signal derived from said second digital signal; a correction unit; and means for determining, locally to said first receiver, correction factors for the solution to the cross-correlation function, and transmitting said correction factors to said correction unit which applies said correction factors to the solution of said cross-correlation function.

Claim 37

Independent Claim 282 words

A system for locating a transmitter, said system comprising: a first receiver for receiving a signal transmitted by said transmitter; a first analog to digital converter for converting the signal received by said first receiver to yield a first digital signal; means for compressing said first digital signal or another digital signal derived from said first digital signal; a second receiver for receiving the signal transmitted by said transmitter; a second analog to digital converter for converting the signal received by said second receiver to yield a second digital signal; a third receiver for receiving a signal transmitted by said transmitter; a third analog to digital converter for converting the signal received by said third receiver to yield a third digital signal; a first convolution unit local to said second receiver; means for transmitting the compressed signal to said first convolution unit and convolving said compressed signal with said second digital signal or another digital signal derived from said second digital signal; a second convolution unit local to said third receiver; means for transmitting said compressed signal to said second convolution unit and convolving said compressed signal with said third digital signal or another digital signal derived from said third digital signal; a first correction unit local to said second receiver; a second correction unit local to said third receiver; means for determining, locally to said first receiver, correction factors for the solution to both convolution units, transmitting said correction factors to said first correction unit which applies said correction factors to an output of said first convolution unit and transmitting said correction factors to said second correction unit which applies said correction factors to an output of said second convolution unit.

Claim 38

Independent Claim 282 words

A system for locating a transmitter, said system comprising: a first receiver for receiving a signal transmitted by said transmitter; a first analog to digital converter for converting the signal received by said first receiver to yield a first digital signal; means for compressing said first digital signal or another digital signal derived from said first digital signal; a second receiver for receiving the signal transmitted by said transmitter; a second analog to digital converter for converting the signal received by said second receiver to yield a second digital signal; a third receiver for receiving a signal transmitted by said transmitter; a third analog to digital converter for converting the signal received by said third receiver to yield a third digital signal; a first convolution unit local to said second receiver; means for transmitting the compressed signal to said first convolution unit and convolving said compressed signal with said second digital signal or another digital signal derived from said second digital signal; a second convolution unit local to said third receiver; means for transmitting said compressed signal to said second convolution unit and convolving said compressed signal with said third digital signal or another digital signal derived from said third digital signal; a first correction unit local to said second receiver; a second correction unit local to said third receiver; means for determining, locally to said first receiver, correction factors for the solution to both convolution units, transmitting said correction factors to said first correction unit which applies said correction factors to an output of said first convolution unit and transmitting said correction factors to said second correction unit which applies said correction factors to an output of said second convolution unit.

Claim 39

Dependent Claim 18 words

A system as set forth in claim 33 wherein the compressing means is local to said first receiver.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1999-10-29	2000-04-29	2000-10-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2003-10-29	2004-04-29	2004-10-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2007-10-29	2008-04-29	2008-10-29	$7700.00	Window Closed / Lapsed

TDOA/FDOA technique for locating a transmitter

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