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A method may include generating for transmission a repeating sequence of N constant-frequency pulses of width t seconds at interpulse intervals of T seconds, with each pulse in the sequence having a particular constant phase according to a quadratic phase sequence, which phase is applied to each pul

A method may include generating for transmission a repeating sequence of N constant-frequency pulses of width t seconds at interpulse intervals of T seconds, with each pulse in the sequence having a particular constant phase according to a quadratic phase sequence, which phase is applied to each pulse in a first sense of modulation. The method may further include modulating the phase of echo energy received from one or more objects reflecting the transmitted repeating sequence of N constant-frequency pulses with a second sense of modulation opposite to the first sense of modulation. The method may further include producing from the modulated received echo energy N unique and discrete frequency translations of the received echo energy as a function of range r of the reflecting objects, of magnitude equal to multiples of 1/NT Hz, which may preserve the spectrum of the received echo energy, forming in combination a composite signal frequency spectrum.

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1. A method for using reflections of wave energy from one or more reflecting objects to characterize certain properties of these objects through the spectral characteristics of the reflections from them, the method comprising: generating for transmission a repeating sequence of N constant-frequency

1. A method for using reflections of wave energy from one or more reflecting objects to characterize certain properties of these objects through the spectral characteristics of the reflections from them, the method comprising: generating for transmission a repeating sequence of N constant-frequency pulses of width t seconds at interpulse intervals of T seconds, with each pulse in the sequence having a particular constant phase according to a quadratic phase sequence, which phase is applied to each pulse in a first sense of modulation;modulating the phase of echo energy received from one or more objects reflecting the transmitted repeating sequence of N constant-frequency pulses during each receiving subinterval by the identical quadratic phase sequence used for the transmitted repeating sequence of N constant-frequency pulses, with a second sense of modulation opposite to the first sense of modulation, so that the net phase modulation applied to echo energy reflected from a particular reflecting object at a particular range r, measured in discrete units of T of round-trip echo time, is a difference between the phase of the transmitted pulses at the time of their transmission and the phase applied to the received echo energy from range r, in either sense of the difference; andproducing from the modulated received echo energy N unique and discrete frequency translations of the received echo energy as a function of range r of the reflecting objects, of magnitude equal to multiples of 1/NT Hz, which frequency translations preserve the spectrum of the received echo energy, forming in combination a composite signal frequency spectrum. 2. The method of claim 1, wherein the quadratic phase sequence is represented by φ(n)=M(an^2+bn+c), where φ(n) is the phase applied to a pulse having pulse index n, M is an integer constant having no common factors with N; n is the index of pulses in the repeating sequence in the range 1 to N; a is a constant defining the repeating interval of the phase sequence, when considered modulo one rotation of phase, set to π/N for phase units of radians; b and c are constants of any value; wherein producing N frequency translations includes producing a frequency translation of the received echo energy as a function of range r of the form Ma(r−i)/NT Hz modulo 1/T Hz, where the index i represents any index offset in n between the application of φ(n) to the generated pulse, and the application of φ(n) to the received echo energy. 3. The method of claim 2, further comprising: determining that one or more spectral features of the received echo energy for a sequence of transmitted pulses having phases generated using a single value of the constant M fall within a spectral interval of 1/NT Hz for each respective range r, without spectral overlap;characterizing unambiguously spectral features of the corresponding received echo energy from each range r; andassigning the characterized spectral features to a particular range. 4. The method of claim 2, further comprising determining that the spectral features of the received echo energy from one or more of the at least one or more reflecting objects fall outside a spectral interval of 1/NT Hz for one or more of the respective ranges, or spectral features of the received echo energy from differing ranges overlap, producing an ambiguity in the assignment of range to spectral features in the echo energy spectrum, wherein generating a repeating sequence of N constant-frequency pulses includes generating a repeating sequence of N constant-frequency pulses using plural values of the constant M, the method further comprising determining parameters of spectral features of the corresponding received echo energy to disambiguate shifted or overlapping spectral features by finding, for each range r, at least one value of the constant M for which any such shift or overlap is resolved through permutations of spectral range order produced by differing values of M; characterizing spectral features of the received echo energy from each range r having overlapping or shifted spectral features; and assigning the characterized spectral features to a particular range. 5. The method of claim 4, wherein characterizing spectral features of the received echo energy having overlapping or shifted spectral features includes: acquiring spectra for m plural values of the constant M;characterizing for any ranges r those spectral features which can be assigned unambiguously as to range from any of the m spectra;subtracting the spectral features so characterized for each corresponding range r from each of the m spectra, at the respective spectral location for the feature for each value of M; andrepeating the preceding two steps with the modified spectra for remaining spectral features. 6. The method of claim 4, wherein characterizing spectral features of the received echo energy having overlapping or shifted spectral features from differing range intervals r includes: acquiring spectra for m plural values of the constant M, and performing the following steps for each range r:(a) shifting the acquired m spectra circularly, so that they align at the point in each spectrum where received echo energy at zero Doppler velocity from that range r would lie;(b) creating a minimum spectrum by taking, for each frequency in the aligned spectra, the minimum value at that frequency from an ensemble of aligned spectra; and(c) characterizing any spectral features in the minimum spectrum exceeding a preset threshold value and located within a predetermined frequency window as representing the spectral features for one or more objects at range r. 7. The method of claim 4, wherein characterizing spectral features of the received echo energy having overlapping or shifted spectral features from differing range intervals r includes acquiring spectra for m plural values of the constant M, and performing the following steps until one or more spectral features at each range r with received echo energy exceeding a preset threshold value is characterized: (a) performing the following steps 1-3 for each range r:(1) shifting the m spectra in circular fashion, so that they coincide at the point in each spectrum where a reflection at zero Doppler velocity from that range r would lie; and(2) creating for each range r a minimum spectrum by taking, for each frequency in the spectrum, the minimum value of the spectral energy at that frequency from an ensemble of the shifted spectra; and(3) determining a value representative of the energy in the spectral peak of the minimum spectrum for each range r;(b) selecting the range r which produces the largest such peak energy value;(c) characterizing one or more spectral features for this selected range r, from the minimum spectrum computed for range r,(d) removing the one or more spectral feature so characterized for this range r from all m spectra by subtraction, at the corresponding spectral location or locations; and(e) repeating steps (a)-(d), using the m modified spectra to characterize the next highest spectral component. 8. The method of claim 2, wherein generating a repeating sequence of N constant-frequency pulses includes generating a repeating sequence of N constant-frequency pulses for two or more values of the constant M (a) sequentially in time, (b) simultaneously using orthogonal wave polarizations, (c) simultaneously through the use of multiple-frequency carriers separately phase modulated, or (d) by any combination of the foregoing. 9. The method of claim 1, where there is only one receiving subinterval range gate per transmitted pulse, wherein receiving echo energy includes receiving all echo energy from all ranges, the method further comprising producing only one time series and spectrum. 10. The method of claim 1, where there are two or more receiving subinterval range gates per transmitted pulse, and wherein the phase modulation of the received echo energy is applied separately to the energy in the two or more range gates, the method further comprising producing two or more time series and spectra. 11. The method of claim 1, where t is equal to T, which is the case of contiguous pulses with 100% duty cycle, and the method further comprises transmitting the generated repeating sequence of N constant-frequency pulses, and during the step of transmitting, receiving echo energy from objects reflecting the transmitted energy by a receiver isolated from the transmitter signal through one or both of physical separation and electromagnetic isolation. 12. The method of claim 1, wherein generating a repeating sequence of N constant-frequency pulses is performed by a transmitter, and the method further comprises receiving echo energy from objects reflecting the transmitted energy by a receiver co-located with the transmitter for mono-static operation. 13. The method of claim 1, wherein generating a repeating sequence of N constant-frequency pulses is performed by one or more transmitters continuously transmitting the repeating sequence of N constant-frequency pulses, and the method further comprises receiving echo energy from objects reflecting the transmitted energy by one or more remote receivers for bistatic or multi-static operation. 14. The method of claim 1, further comprising transmitting the generated repeating sequence of N constant-frequency pulses as electromagnetic waves, at audio, radio, optical, or other wavelengths, as acoustic waves, or as vibrational waves. 15. The method of claim 1, further comprising transmitting the generated repeating sequence of N constant-frequency pulses as phase-modulated coherent waves, or as incoherent wave carriers modulated by phase-modulated coherent waves. 16. A system, comprising: a sequence generator configured to generate for transmission a repeating sequence of N constant-frequency pulses of width t seconds at interpulse intervals of T seconds, with each pulse in the sequence having a particular constant phase according to a quadratic phase sequence, which phase is applied to each pulse in a first sense of modulation; anda modulator configured to modulate the phase of echo energy received from one or more objects reflecting the transmitted repeating sequence of N constant-frequency pulses during each receiving subinterval by the identical quadratic phase sequence used for the signal generated for transmission, with a second sense of modulation opposite to that of the first sense of modulation, so that the net phase modulation applied to echo energy reflected from a particular reflecting object at a particular range interval r, measured in discrete units of T of round-trip echo time, is a difference between the phase of the transmitted pulses at the time of their transmission and the phase applied to the received echo energy from range r, in either sense of the difference; anda signal processor configured to produce from the modulated received echo energy N unique and discrete frequency translations of the received echo energy as a function of range r of the reflecting objects, of magnitude equal to multiples of 1/NT Hz, which frequency translations preserve the spectrum of the received echo energy, forming in combination a composite signal frequency spectrum. 17. The system of claim 16, wherein the sequence generator is further configured to generate a quadratic phase sequence that is represented by φ(n)=M(an^2+bn+c), where φ(n) is the phase applied to a pulse having pulse index n, M is an integer constant having no common factors with N; n is the index of pulses in the repeating sequence in the range 1 to N; a is a constant defining the repeating interval of the phase sequence, when considered modulo one rotation of phase, set to π/N for phase units of radians; b and c are constants of any value; and the signal processor produces a frequency translation of modulated received echo energy as a function of range r of the form Ma(r−i)/NT Hz modulo 1/T Hz, where the index i represents any index offset in n between the application of φ(n) to the sequence generated for transmission, and the application of φ(n) to the received echo energy by the modulator. 18. The system of claim 17, wherein the signal processor is further configured to: determine that one or more spectral features of the received echo energy for a sequence of transmitted pulses having phases generated using a single value of the constant M fall within a spectral interval of 1/NT Hz for each respective range r, without spectral overlap;characterize unambiguously spectral features of the corresponding received echo energy from each range r; andassign the characterized spectral features to a particular range. 19. The system of claim 17, wherein the signal processor is further configured to determine that one or more spectral features of the received echo energy from one or more of the at least one or more reflecting objects falls outside a spectral interval of 1/NT Hz for the respective ranges, or spectral features of the received echo energy from differing ranges overlap, producing an ambiguity in the assignment of range to spectral features in the echo energy spectrum; the sequence generator is further configured to generate for transmission a repeating sequence of N constant-frequency pulses using plural values of the constant M, and the signal processor is configured to determine parameters of spectral features of the corresponding received echo energy to disambiguate shifted or overlapping spectral features by finding, for each range r, at least one value of the constant M for which any such shift or overlap is resolved through permutations of spectral range order produced by differing values of M, to characterize unambiguously the disambiguated spectral features of the echo energy for that range r, and assign the characterized spectral features to a particular range. 20. The system of claim 17, wherein the signal processor is further configured to determine that one or more spectral features of the received echo energy from one or more of the at least one or more reflecting objects falls outside a spectral interval of 1/NT Hz for the respective ranges, or spectral features of the received echo energy from differing ranges overlap, producing an ambiguity in the assignment of range to spectral features in the echo energy spectrum; the sequence generator is further configured to generate for transmission a repeating sequence of N constant-frequency pulses using plural values of the constant M; and the signal processor is configured to determine parameters of spectral features of the corresponding received echo energy resulting from transmission a repeating sequence of N constant-frequency pulses for plural values of the constant M; and to disambiguate and characterize overlapping or shifted spectral features at particular ranges r by: acquiring spectra for m plural values of the constant M;(a) characterizing for any ranges r those spectral features which can be assigned unambiguously as to range from any of the m spectra;(b) subtracting the spectral features so characterized for each corresponding range r from each of the m spectra, at the respective spectral location for the feature for each value of M; and(c) repeating steps (a) and (b) with the m spectra as modified by subtraction. 21. The system of claim 17, wherein the signal processor is further configured to determine that one or more spectral features of the received echo energy from one or more of the at least one or more reflecting objects falls outside a spectral interval of 1/NT Hz for the respective ranges, or spectral features of the received echo energy from differing ranges overlap, producing an ambiguity in the assignment of range to spectral features in the echo energy spectrum; the sequence generator is further configured to generate for transmission a repeating sequence of N constant-frequency pulses using plural values of the constant M; and the signal processor is configured to determine parameters of spectral features of the corresponding received echo energy resulting from transmission a repeating sequence of N constant-frequency pulses for the plural values of the constant M; and to disambiguate and characterize overlapping or shifted spectral features at particular ranges r by acquiring spectra for m plural values of the constant M, and performing the following steps (a)-(c) for each range r: (a) shifting the acquired m spectra circularly, so that they align at the point in each spectrum where received echo energy at zero Doppler velocity from that range r would lie;(b) creating a minimum spectrum by taking, for each frequency in the aligned spectra, the minimum value at that frequency from an ensemble of aligned spectra; and(c) characterizing any spectral features exceeding a preset threshold value and located within a predetermined frequency window as representing the spectral features for one or more reflecting objects at range r. 22. The system of claim 17, wherein the signal processor is further configured to determine that one or more spectral features of the received echo energy from one or more of the at least one or more reflecting objects falls outside a spectral interval of 1/NT Hz for their respective ranges, or spectral features of the received echo energy from differing ranges overlap, producing an ambiguity in the assignment of range to spectral features in the echo energy spectrum; the sequence generator is further configured to generate for transmission a repeating sequence of N constant-frequency pulses using plural values of the constant M; and the signal processor is configured to determine parameters of spectral features of the corresponding received echo energy resulting from transmission of the repeating sequence of N constant-frequency pulses for the plural values of the constant M to disambiguate and characterize overlapping or shifted spectral features at particular ranges r by acquiring spectra for m plural values of the constant M, and performing the following steps to characterize spectral features in decreasing order of a measure of echo energy: (a) performing the following steps 1-3 for each range r:(1) shifting the m spectra in circular fashion, so that they coincide at the point in each spectrum where a reflection at zero Doppler velocity from that range r would lie;(2) creating for this range r a minimum spectrum by taking, for each frequency in the spectrum, the minimum value of the spectral energy at that frequency from an ensemble of the shifted spectra; and(3) determining a value representative of the energy in the spectral peak of the minimum spectrum for this range r;(b) selecting the range r which produces the largest such peak energy value;(c) characterizing one or more spectral features for this selected range r, from the minimum spectrum computed for range r,(d) removing the one or more spectral feature so characterized for this range r from all m spectra by subtraction, at the corresponding spectral location or locations; and(e) repeating steps (a)-(d), using the m modified spectra to characterize one or more additional spectral features in descending order of spectral energy. 23. The system of claim 17, wherein the sequence generator is configured to generate a repeating sequence of N constant-frequency pulses for two or more values of the constant M (a) sequentially in time, (b) simultaneously using orthogonal wave polarizations, (c) simultaneously through the use of multiple-frequency carriers separately phase modulated, or (d) by any combination of the foregoing. 24. The system of claim 16, where there is only one receiving subinterval range gate per transmitted pulse, and the signal processor produces one time series and spectrum. 25. The system of claim 16, where there are two or more receiving subinterval range gates per transmitted pulse, and wherein the phase modulation of the received echo energy is applied separately to the energy in the two or more range gates, and the signal processor produces two or more time series and spectra. 26. The echo ranging system of claim 16, where t is equal to T, which is the case of contiguous pulses with 100% duty cycle. 27. The system of claim 16, further comprising a transmitter configured to transmit the repeating sequence of N constant-frequency pulses as electromagnetic waves, at audio, radio, optical, or other wavelengths, as acoustic waves, or as vibrational waves. 28. The system of claim 16, wherein the sequence generator is further configured to generate a repeating sequence of N constant-frequency pulses that are phase-modulated coherent waves, or are incoherent wave carriers modulated by phase-modulated coherent waves.