Echo location systems

Abstract

This invention generally relates to echo location or ranging systems in which the individual properties of targets or reflectors (such as range, bearing, elevation angle, relative velocity, impedance contrast, etc.) in a field of targets within some propagation medium are identified by the emission of signals into the propagation medium and processing of the detected reflections from the target field.

What is claimed is: 
     
       1. A method of using a transmitter member and an arrangement of receivers having at least one receiver member, all members being at locations referred to a coordinate system of fixed origin and in a medium having a known signal propagation velocity function, for ascertaining, for a field containing one or more reflecting targets, information about the targets' .[.relfectivity.]. .Iadd.reflectivity .Iaddend.strengths, positions and velocities as referred to said coorinate system, comprising the steps of: producing a signal pattern having at least two individual member signals having preassigned time intervals, said time intervals and the durations of the member signals being short relative to a period over which velocity vectors describing motions of the transmitter, receivers and targets are approximately constants;   forming said individual member signals as a weighted sum of a design base signal pair, a pair of base signals approximately sharing a common smooth and essentially .[.unimodel.]. .Iadd.unimodal .Iaddend.amplitude spectrum occupying a contiguous band of frequencies, said base signals being in mutual quadrature;   propagating said signal pattern with defined polarization character;   developing return signal patterns by reflection from the target field to each receiver;   processing reflected return signal patterns from each receiver by cross-correlating replicas of these return signal patterns with a detection base signal pair, thereby producing a pair of correlation component functions, said detection base signals having properties analogous to said design base signals, but with an amplitude spectrum overlapping that of the design base signal pair by an interval of frequency greater than any Doppler shift attributable to propagation toward and refelection from moving targets, the difference in phase angle between counterpart design and detection base signals at any common frequency component being described, in good approximation, mathematically by a constant and a term linear with frequency;   forming for each received return signal pattern a correlation amplitude function, formed from term-by-term sums of the absolute values of the correlation component functions raised to a like power not less than one, said sums then raised to a like power greater than zero but not greater than one;   identifying from the significant maxima of the correlation amplitude function return signal patterns corresponding to individual target reflections;   estimating for each detected target at each receiver a relative velocity component using the known signal propagation velocity function and the extension or compression of the initially preassigned time intervals between member signals in the return signal pattern for the target at the particular receiver, as determined from significant maxima of the correlation amplitude function;   estimating for each detected target at each receiver initial relative range information using an effective signal propagation velocity developed from the target's relative velocity estimate and known medium velocity function along with the elapsed signal travel time for onset of the return signal pattern identifying a target;   calculating final relative range information by introducing timing corrections to the elapsed signal travel time, such corrections representing linear elements of phase distortions arising from propagation, such corrections being dependent upon empirical tests using targets of known parameters, these corrections being catalogued according to initial range estimates, the conversion to final range information using the effective signal propagation velocity with the corrected elapsed time;   referring all estimates of target ranges and velocities to the fixed coordinate system; and   characterizing each member of the target field according to reflectivity, magnitudes being estimated from magnitudes of particular target correlation amplitude functions, accounting for losses associated with propagation and other observable and controllable signal amplitude modifications which are obtainable from empirical tests using targets of known parameters, and reflectivity polarities being determined from return signal pattern polarities as compared with the initial outgoing signal polarities.   
     
     
       2. The method according to claim 1 wherein more than one transmitter is used concurrently, and producing outgoing signal patterns from each transmitter separable by a combination of any distinction according to polarization character and the frequency filtering produced by said cross-correlating.   
     
     
       3. The method according to claim 2 wherein for at least one received return signal train, positional information in the form of one angle for each target is encoded, and differentiating reflecting targets additionally by using amplitude spectral modifications of the member signals of the received return signal train; employing for transmitters and receivers related to said encoding, impulse-like design and detection base signals, individual base signals having the further property that the phase angles for all significant frequencies are described mathematically, in good approximation, by a constant and a term linear in frequency;   encoding the angular positional information for each target as a phase modification, which is alike for each member signal of the signal train to be received, by interposing a phase adjustment element into the signal propagation path such that targets distinctive in their angular positional information will have distinctive phase modifications, any phase modification being described, in good approximation mathematically, by a constant and a term linear in frequency for all significant frequencies, the angular positional information being functionally related to the constant phase modifications by single valued functions determined by empirical tests using targets of known parameters, the linear phase modification with frequency being determined and catalogued according to the constant phase modification as a timing correction;   forming an initial constant phase modification estimate for individual member signals of the received return signal train and the correlation components, wherein member signals are identified at time origins corresponding to the times of the significant maxima of the correlation amplitude function;   compensating the initial constant phase modification for the initial constant value of the design base signal, for the phase difference between the design and detection base signals, and for any constant phase distortion approximating effects of propagation, said distortion due to propagation being determined by empirical tests using targets of known parameters and catalogued according to initial target range estimates;   calculating final relative range information, including an additional timing correction to the elapsed signal travel time, such corrections representing linear elements of phase distortion arising from said phase adjustment element, said distortions being determined from the catalogued values corresponding to the compensated initial constant phase modification estimate;   forming the angular positional information from the compensated initial constant phase modification estimates using said single-valued functions;   incorporating angular positional information with other estimated target positional and velocity information in the fixed coordinate system; and   differentiating reflecting targets by using amplitude spectra of returning member signals for each target, adjusting said spectra for known modifications resulting from signal propagation and accompanying phase adjustment element effects, determined from empirical tests using targets of known parameters.   
     
     
       4. The method according to claim 3 wherein the initial constant phase modification estimate is formed from calculations of phase spectra for individual member signals of the received return signal train and the correlation components. 
     
     
       5. The method according to claim 3 wherein initial constant phase modification estimates for individual member signals are derived from the arctangent functions of ratios formed from values of the correlation components at times corresponding to time origins for member signals appertaining to reflection from a particular target, any pair of said values being appropriate to forming a ratio when their corresponding member signals are in quadrature; and developing additional ratios from values of said reflected return signal pattern at times corresponding to member signal origins appertaining to a particular target, whose numerator is derived from a member signal in quadrature with the denominator.   
     
     
       6. The method of claim 3 wherein for at least one received return signal train, positional information in the form of at least one angle for each target is encoded, such that for each target different phase encodings are imparted for the same angular information in different member signals, interposing for each transmitter and receiver related to said encoding a second phase adjustment element into the signal propagation path, changing at least one phase adjustment element for at least one member signal of the train to be received the total number of said changes being no less than one less than the number of positional information angles desired for each target;   designating phase encodings having independence such that the compensated constant phase modifications estimated from individual member signals and the known functional relationships between the phase adjustment element encodings and the desired angles develop a set of equations having as unknowns the target positional information, the number of equations being at least equal to the number of unknowns thereby allowing their solutions, and   applying timing corrections to individual member signals to compensate also for linear phase effects of phase adjustment elements, such corrections now modifying also final relative velocity component estimates as well as relative range information.   
     
     
       7. The method according to claim 6 wherein for at least one received return signal train, constant phase distortions approximating the properties of each reflecting target are estimated, developing at least one set of equations for the desired angular positional information for each target having at least one more equation than unknowns and including as an additional unknown variable the constant phase distortion introduced by the target, phase encodings having been selected to allow at least as many independent equations as the total of unknowns, and   incorporating phase distortion properties of each target as an additional target identifier.   
     
     
       8. The method according to claim 6 wherein for at least one received return signal train a constant phase distortion approximating uncompensated properties of the propagation medium is estimated, and developing at least one set of equations for the desired angular positional information for each target having at least one more equation than unknowns and including as an additional unknown variable the constant phase distortion approximating properties of the propagation medium, phase encodings having been selected to allow at least as many independent equations as the total of unknowns. .Iadd. 9. The method according to claim 1 wherein for at least one received return signal train, positional information in the form of one angle for each target is encoded, and differentiating reflecting targets additionally by using amplitude spectral modifications of the member signals of the received return signal train;   employing for transmitters and receivers related to said encoding, impulse-like design and detection base signals, individual base signals having the further property that the phase angles for all significant freqencies are described mathematically, in good approximation, by a constant and a term linear in frequency;   encoding the angular positional information for each target as a phase modification, which is alike for each member signal of the signal train to be received, by interposing a phase adjustment element into the signal propagation path such that targets distinctive in their angular positional information will have distinctive phase modifications, any phase modification being described, in good approximation mathematically, by a constant and a term linear in frequency for all significant frequencies, the angular positional information being functionally related to the constant phase modifications by single value functions determined by empirical tests using targets of known parameters, the linear phase modification with frequency being determined and catalogued according to the constant phase modification as a timing correction;   forming an initial constant phase modification estimate for individual member signals of the received return signal train and the correlation components, wherein member signals are identified at time origins corresponding to the times of the significant maxima of the correlation amplitude function;   compensating the initial constant phase modification for the initial constant value of the design base signal, for the phase difference between the design and detection base signals, and for any constant phase distortion approximating effects of propagation, said distortion due to propagation being determined by empirical tests using targets of known parameters and catalogued according to initial target range estimates;   calculating final relative range information, including an additional timing correction to the elapsed signal travel time, such corrections representing linear elements of phase distortion arising from said phase adjustment element, said distortions being determined from the catalogues values corresponding to the compensated initial constant phase modification estimate;   forming the angular positional information from the compensated initial constant phase modification estimates using said single-valued functions;   incorporating angular positional information with other estimated target positional and velocity information in the fixed coordinate system; and   differentiating reflecting targets by using amplitude spectra of returning member signal for each target, adjusting said spectra for known modifications resulting from signal propagation and accompanying phase adjustment element effects determined from empirical tests using targets   
     
     
        of known parameters. .Iaddend..Iadd. 10.  The method according to claim 9 wherein said step of forming an initial constant phase modification estimate comprises forming such initial constant phase modification from calculations of phase spectra for individual member signals of the received return signal train and the correlation components. .Iaddend..Iadd. 11. The method according to claim 9 wherein said step of forming an initial constant phase modification comprises forming estimates for individual member signals derived from the arctangent functions of ratios formed from values of the correlation components at times corresponding to time origins for member signals appertaining to reflection from a particular target, any pair of said values being appropriate to forming a ratio when their corresponding member signals are in quadrature; and developing additional ratios from values of said reflected return signal pattern, at times corresonding to member signal origins appertaining to a particular target, whose numerator is derived from a member signal in quadrature with the denominator. .Iaddend..Iadd. 12. The method of claim 9 wherein for at least one received return signal train, positional information in the form of at least one angle for each target is encoded, such that for each target different phase encodings are imparted for the same angular information is different member signals,   interposing for each transmitter and receiver related to said encoding a second phase adjustment element into the signal propagation path, changing at least one phase adjustment element for at least one member signal of the train to be received, the total number of said changes being no less than one less than the number of positional information angles desired for each target;   designating phase encodings having independence such that the compensated constant phase modifications estimated from individual member signals and the known functional relationships between the phase adjustment element encodings and the desired angles develop a set of equations having as unknowns the target positional information, the number of equations being at least equal to the number of unknowns thereby allowing thier solution, and   applying timing corrections to individual member signals to compensate also for linear phase effects of phase adjustment elements, such corrections now modifying alos final relative velocity component estimates as well as relative range information. .Iaddend..Iadd. 13. The method according to claim 12 wherein for at least one received return signal train, constant phase distortions approximating the properties of each reflecting target are estimated.   developing at least one set of equations for the desired angular positional information for each target having at least one more equation than unknowns and including as an additional unknown variable the constant phase distortion introduced by the target, phase encodings having been selected to allow at least as many independent equations as the total of unknowns, and   incorporating phase distortion properties of each target as an additional   
     
     
        target identifier. .Iaddend..Iadd. 14.  The method according to claim 12 wherein for at least one received return signal train a constant phase distortion approximating uncompensated properties of the propagation medium is estimated, and developing at least one set of equations for the desired angular positional information for each target having at least one moe equation than unknowns and including as an additional unknown variable the constant phase distortion approximating properties of the propagation medium, phase encodings having been selected to allow at least as many independent equations as the total of unknowns. .Iaddend..Iadd. 15. A method of determining the velocity of a signal reflecting object positioned in a medium of known signal-propagation characteristics, relative to a signal transmitter and a signal receiver, comprising the steps of:   (a) transmitting at two distinct instants of time at least two signals having a pedetermined time interval therebetween, each signal having a continuous amplitude spectrum between low and high frequency limits, for reflection of the signals by the object;   (b) receiving the reflected signals;   (c) measuring only the time interval between the received signals; and   (d) determining the relative velocity of the object based only upon the measured time interval between the received signals and the predetermined time interval between the transmitted signals. .Iaddend. .Iadd. 16. The method of claim 15, wherein said step of transmitting the signals comprises transmitting signals having an essentially short time duration. .Iaddend..Iadd. 17. The method of claim 16 wherein said step of transmitting the signals includes transmitting the signals in phase quadrature relative to each other. .Iaddend..Iadd. 18. The method of claim 16 wherein said steps of transmitting the signals comprises transmitting at least one signal which is transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency. .Iaddend..Iadd. 19. The method of claim 16 wherein said step of transmitting the signal comprises transmitting pulse signals, each of which is transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency. .Iaddend..Iadd. 20. The method of claim 15, wherein the two distinct instants of time are predetermined, and further including the steps of:   (a) measuring the arrival time of at least one reflected signal,   (b) determining the signal transit time from the measured arrival time and the predetermined time instant of its transmission;   (c) correcting the transit time as a function of the determined velocity; and   (d) determining the distance of said object relative to the transmitter and the receiver as a function of the corrected transit time and the   
     
     
        propagation characteristics of the medium. .Iaddend..Iadd. 21.  A method of determining the direction of a signal reflecting object relative to a signal transmitter and a signal receiver, comprising the steps of: (a) transmitting a signal from the transmitter, such signal having a continuous amplitude spectrum between low and high frequency limits, for reflection from the object;   (b) receiving the reflected signal with the receiver;   (c) changing the phase of the transmitted signal in dependence upon the direction of its travel while propagating between the transmitter and the receiver, such phase change characterized other than by a simple time delay;   (d) measuring the phase of the received reflected signal; and   (e) determining the direction of the object based on the measured phase. .Iaddend..Iadd. 22. The method of claim 21 wherein said step of transmitting a signal comprises transmitting a signal having a phase change comprising a constant for each direction independent of frequency. .Iaddend. .Iadd. 23. The method of claim 22 wherein said step of changing the phase of the signal comprises:   propagating the signal through a medium having a dimension which varies in dependence upon the direction of travel of the signal. .Iaddend..Iadd. 24. The method of claim 21 wherein said step of changing the phase of the signal comprises:   propagating the signal through a medium having a dimension which varies in dependence upon the direction of travel of the signal. .Iaddend..Iadd. 25. A method of ascertaining the range of one or more reflecting targets in a target field referred to a coordinate system comprising the steps of:   (a) producing a signal having a linear combination of at least a pair of base signals such signals having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of said pair of base signals is zero;   (3) each base signal of such pair being in phase quadrature to the other member of the pair;     (b) transmitting the signal pattern into the target field;   (c) receiving reflections of the transmitted signal pattern from the target field; and   (d) processing the received reflections to ascertain the range of at least one of such targets in the target field. .Iaddend..Iadd. 26. A method of ascertaining the range and velocity of one or more reflecting targets in a target field referred to a coordinate system comprising the steps of:   (a) producing a signal pattern having at least two signals, each being a linear combination of at least a pair of base signals said base signals having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smootly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of said pair of base signals is zero;   (3) each base signal of such pair being in phase quadrature to the other member of the pair;     (b) transmitting the signal pattern into the target field during at least partially different time intervals for each signal of the signal pattern;   (c) receiving reflections of the transmitted signal pattern from the target field; and   (d) processing the received reflections to ascertain the range and velocity of at least one of such targets in the target field. .Iaddend. .Iadd. 27. A method of ascertaining the angular information of one or more reflecting targets in a target field referred to a coordinate system comprising the steps of:   (a) producing a signal being a linear combination of a pair of base signals such signals having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies   (2) having a finite time interval before and after which each signal of said pair of base signals is zero   (3) each base signal of such a pair being in phase quadrature to the other member of the pair; and   (4) each of such pair of base signals being transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency;     (b) transmitting the signal pattern;   (c) introducing a phase distortion, having a component independent of frequency, which varies in a known and single valued manner according to desired angular information into the signal propagation path;   (d) receiving reflections of the transmitted signal pattern from the target field; and   (e) processing the received reflections to ascertain the angular information for at least one of such targets in the target field. .Iaddend..Iadd. 28. The method of claim 27, further including the step of determining the range of at least one of the targets, comprising the step of:   processing the received reflections to ascertain the range of at least one   
     
     
        of such targets in the target field. .Iaddend..Iadd. 29.  The method of claim 27, further including the step of determining the range and velocity of at least one of the targets, comprising the steps of: producing a signal pattern comprising of at least two said signals,   transmitting the signal pattern into the target field during at least partially different time intervals for each signal of the signal pattern, and   processing the received reflections to ascertain the range and velocity of at least one of such targets in the target field. .Iaddend..Iadd. 30. The method of claim 27, wherein said step of producing a pair of base signals comprises producing signals with the property of:   one of each such pair of base signals being odd about a central coordinate value in its finite time interval and the other of each such pair being even with respect to its central coordinate value. .Iaddend..Iadd. 31. The method of claim 27, further including the step of ascertaining angular information regarding more than one angle of at least one of the targets, comprising the steps of:   (a) producing a signal pattern comprising at least two signals each said signal being a linear pair combination of base signals each having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of each said pair of base signals is zero;   (3) each base signal of such a pair being in phase quadrature to the other member of the pair;   (4) each of such pair of base signals being transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency; and   (5) each pair of such base signals occupying at least partially non-overlapping band of frequency from the other pairs;     (b) transmitting such signal pattern;   (c) introducing phase distortions having a component independent of frequency which vary in a known and single valued manner according to desired angular information into the signal propagation path, differing angular information being introduced in differing frequency bands;   (d) receiving reflections of the transmitted signal pattern from the target field; and   (e) processing the received reflections to ascertain the angular information for at least one of such targets in the target field.   
     
     
        .Iaddend..Iadd. 32.  The method of claim 27, further including the step of ascertaining angular information regarding more than one angle of at least one of the targets, comprising the steps of: (a) producing a signal pattern comprising at least two signals each said signal being a linear pair combination of base signals each having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of each said pair of base signals is zero;   (3) each base signal of such a pair being in phse quadrature to the other member of the pair;   (4) each of such pair of base signals being transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency; and   (5) each pair of such base signals occupying at least a partially overlapping band of frequency from the other pairs;     (b) transmitting such signal pattern;   (c) phase encoding positional information about plural angles in each signal;   (d) receiving reflections of the transmitted signal pattern from the target field; and   (e) processing the received reflections to ascertain the angular information for at least one of such targets in the target field.   
     
     
        .Iaddend..Iadd. 33.  The method of claim 32, wherein said step of phase encoding comprises the step of: introducing phase distortions having a component independent of frequency which vary in a known and single valued manner according to desired angular information into the signal propagation path, differing angular information being introduced into member signals of the signal pattern   
     
     
        with independent phase encoding. .Iaddend..Iadd. 34.  A system for determining the velocity of a signal reflecting object positioned in a medium of known signal-propagation characteristics comprising: (a) signal transmitter means for transmitting at two distinct instants of time at least two signals having a predetermined time interval therebetween, each signal having a continuous amplitude spectrum between low and high frequency limits, for reflection of the signals by the object;   (b) signal receiver means for receiving the reflected signals;   (c) processing sequencer means for measuring only the time interval between the received signals; and   (d) parameter estimator means for determining the relative velocity of the object based only upon the measured time interval between the received signals and the predetermined time interval between the transmitted signals. .Iaddend..Iadd. 35. The system of claim 34, wherein the two distinct instants of time are predetermined, and wherein:   (a) said processing sequencer means comprises means for measuring the arrival time of at least one reflected signal and determining the signal transit time from the measured arrival time and the time instant of its transmission, (b) said parameter estimator means comprises means for correcting the transit time as a function of the determined velocity, and determining the distnace of said object relative to said transmitter means and said receiver means as a function of the corrected transit time and the propagation characteristics of the medium. .Iaddend. .Iadd. 36. A system for determining the direction of a signal reflecting object, comprising:     (a) transmitter means for transmitting a signal having a continuous amplitude spectrum between low and high frequency limits, for reflection from the object;   (b) receiver means for receiving the reflected signal;   (c) phase lens means for changing the phase of the signal in dependence upon the direction of its travel while propagating between said transmitter means and said receiver means, such phase change characterized other than by a simple time delay;   (d) processing sequencer means for measuring the phase of the received reflected signal; and   (e) parameter estimator means for determining the direction of the object based on the measured phase. .Iaddend..Iadd. 37. The system of claim 36 wherein said phase lens means for changing the phase comprises means for changing the phase by a constant for each direction independent of frequency. .Iaddend. .Iadd. 38. The system of claim 37 wherein said phase lens means for changing the phase of the signal comprises:   a medium having a dimension which varies in dependence upon the direction of travel of the signal. .Iaddend..Iadd. 39. The system of claim 36 wherein said phase lens means for changing the phase of the signal comprises:   a medium having a dimension which varies in dependence upon the direction of travel of the signal. .Iaddend. .Iadd. 40. A system for ascertaining the range of one or more reflecting targets in a target field referred to a coordinate system, comprising:   (a) transmitter means for producing and transmitting into the target field a signal pattern having a linear combination of at least a pair of base signals, such signals having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of said pair of base signals is zero;   (3) each base signal of such pair being in phase quadrature to the other member of the pair;     (b) means for receiving reflections of the transmitted signal pattern from the target field; and   (c) means for processing the received reflections to ascertain the range of at least one of such targets in the target field. .Iaddend..Iadd. 41. A system for ascertaining the range and velocity of one or more reflecting targets in a target field referred to a coordinate system of fixed origin, comprising:   (a) transmitter means for producing and transmitting into the target field a signal pattern having at least two signals during at least partially different time intervals for each signal of the signal pattern, each signal being a linear combination of at least a pair of base signals, said base signals having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of said pair of base signals is zero;   (3) each base signal of such pair being in phase quadrature to the other member of the pair;     (b) means for receiving reflections of the transmitted signal pattern from the target field; and   (c) means for processing the received reflections to ascertain the range and velocity of at least one of such targets in the target field. .Iaddend..Iadd. 42. A system for ascertaining the angular information of one or more reflecting targets in a target field referred to a coordinate system, comprising:   (a) transmitter means for producing and transmitting into the target field a signal pattern being a linear combination of a pair of base signals, such signals having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of said pair of base signals is zero;   (3) each base signal of such a pair being in phase quadrature to the other member of the pair; and   (4) each of such pair of base signals being transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency;     (b) phase lens means for introducing a phase distortion, having a component independent of frequency, which varies in a known and single valued manner according to desired angular information into the signal propagation path;   (c) means for receiving reflections of the transmitted signal pattern from the target field; and   (d) means for processing the received reflections to ascertain the angular information for at least one of such targets in the target field.   
     
     
        .Iaddend..Iadd. 43.  The system of claim 42, wherein said means for processing comprises: means for processing the received reflections to ascertain the angular information and range for at least one of such targets in the target field. .Iaddend. .Iadd. 44. The system of claim 42, wherein:   said transmitter means comprises means for producing and transmitting into the target a signal pattern comprising at least two said signals during at least partially different time intervals for each signal of the signal pattern, and   said means for processing comprises means for processing the received reflections to ascertain the range and velocity of at least one of such targets in the target field. .Iaddend..Iadd. 45. The system of claim 42, wherein:   (a) said transmitter means comprises means for producing and transmitting into the target field a signal pattern comprising at least two signals each said signal being a linear combination of a pair of base signals, each having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of each said pair of base signals is zero;   (3) each base signal of such a pair being in phase quadrature to the other member of the pair;   (4) each of such pair of base signals being transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency; and   (5) each pair of such base signals occupying at least partially non-overlapping band of frequency from the other pairs;     (b) said phase lens means for introducing phase distortions comprises means introducing phase distortions having a component independent of frequency which varies in a known and single valued manner according to desired angular information into the signal propagation path, differing angular information being introduced in differing frequency bands;   (c) said means for processing comprises means for processing the received reflections to ascertain the angular information for at least one of such   
     
     
        targets in the target field. .Iaddend..Iadd. 46.  The system of claim 42, wherein: (a) said transmitter means comprises means for producing and transmitting into the target field a signal pattern comprising at least two signals, each said signal being a linear pair combination of base signals, each having the properties of: (1) sharing a common amplitude spectrum which is essentially flat or smoothly unimodal occupying a contiguous band of frequencies;   (2) having a finite time interval before and after which each signal of each said pair of base signals is zero;   (3) each base signal of such a pair being in phase quadrature to the other member of the pair;   (4) each of such pair of base signals being transformable to a symmetric signal relative to a time reference by adding a constant phase angle to the phase at each frequency; and   (5) each pair of such base signals occupying at least partially overlapping band of frequency from the other pairs;     (b) said phase lens means includes means for phase encoding positional information about plural angles in each signal; and   (c) said means for processing comprises means for processing the received reflections to ascertain the angular information for at least one of such targets in the target field. .Iaddend.