US4373190A
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Efficient, precompression, bandwidth-tolerant, digital pulse expander-compressor
Assignee: United States Department of the Navy
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Filing: 1981-01-22
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Granted: 1983-02-08
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Expires: 2001-01-22
Abstract
Abstract A digital pulse expander-compressor for use in pulse compression radars and having the advantage of precompression bandwidth tolerance. The pulse expander-compressor exploys a discrete Fourier transform circuit and multi-stage delay line feeding inputs x(n) to the discrete Fourier transform circuit to generate outputs in accordance with the formula <IMAGE> where n is the sequence number of the clock pulse; N is the number of delay stages plus one; and k is the number of the output subpulse from the transform circuit. An arrangement of delay stages differentially delays the output subpulses from the discrete Fourier transform circuit, and a coherent summer adds the real and imaginary parts of the signals from the delay lines. The delay stages delay the subpulse s(k), O</=k</=N/2-1, by <IMAGE> clock pulse intervals, while delaying the subpulse s(k), N/2+1</=k</=N-1, by <IMAGE> clock pulse intervals. The subpulse s(k), k=N/2, is not used. The pulse expander-compressor generates and compresses a polyphase code pulse with a pulse compression ratio of M2 where M is an odd integer less than N. An odd integer is desired so that the code can be made to have conjugate symmetry about the zero modulation frequency code subsequence.
Inventors
- 👤 Bernard L. Lewis
- 👤 Frank F. Kretschmer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 17:52
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S13/26; G01S13/28; G01S13/284; G01S13/288
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
160 words
An efficient, pre-compression, bandwidth-tolerant, digital pulse expander-compressor comprising: transform means having N output terminals and responsive to an applied subpulse for successively generating N replicas x(n) of the subpulse, where n=0, 1, 2,-, N-1 and N is an integer, in a time which is N times the length of the subpulse, and for weighting the replicas x(n) in accordance with the formula ##EQU13## where k=0, 1, 2,-, N-1, to provide N weighted subpulses s(k), each at a respective one of the N output terminals, whenever one of the N replicas x(n) is generated; and delay-summation means connected to the transform means for delaying each of the N weighted supulses s(k) corresponding to any replica of the applied subpulse by a time which is ##EQU14## the length of the applied subpulse for 0≦k≦N/2-1, and by a time which is ##EQU15## the length of the applied subpulse for N/2+1≦k≦N-1, and for separately summing the real and imaginary parts of the delayed subpulses.
Claim 2
Dependent Claim
160 words
An efficient, pre-compression, bandwidth-tolerant, digital pulse expander-compressor comprising: transform means having N output terminals and responsive to an applied subpulse for successively generating N replicas x(n) of the subpulse, where n=0, 1, 2,-, N-1 and N is an integer, in a time which is N times the length of the subpulse, and for weighting the replicas x(n) in accordance with the formula ##EQU13## where k=0, 1, 2,-, N-1, to provide N weighted subpulses s(k), each at a respective one of the N output terminals, whenever one of the N replicas x(n) is generated; and delay-summation means connected to the transform means for delaying each of the N weighted supulses s(k) corresponding to any replica of the applied subpulse by a time which is ##EQU14## the length of the applied subpulse for 0≦k≦N/2-1, and by a time which is ##EQU15## the length of the applied subpulse for N/2+1≦k≦N-1, and for separately summing the real and imaginary parts of the delayed subpulses.
Claim 3
Dependent Claim
42 words
The pulse expander-compressor recited in claim 1 wherein the transform means includes: delay means having N distributed output terminals including the input terminal thereof for producing a uniform delay as long as the applied subpulse between adjacent ones of successive output terminals.
Claim 4
Dependent Claim
34 words
The pulse expander-compressor recited in claim 2 wherein the transform means includes: a fast Fourier transform circuit connected to the N distributed output terminals of the delay means for forming discrete Fourier transform signals.
Claim 5
Dependent Claim
15 words
The pulse expander-compressor recited in claim 1 wherein the delay-summation means includes: a coherent summer.
Claim 6
Dependent Claim
91 words
The pulse expander-compressor recited in claim 4 wherein the delay-summation means includes: a plurality of delay means, each delay means for producing a delay between the input and output thereof N times the length of the applied subpulse, ##EQU16## such delay means being serially connected between the coherent summer and the output terminal of the transform means for the weighted subpulse s(k) for 0≦k≦N/2-1, and ##EQU17## such delay means being serially connected between the coherent summer and the output terminal of the transform means for the weighted subpulse s(k) for N/2+1≦k≦N-1.
Claim 7
Dependent Claim
128 words
An efficient pre-compression, bandwidth-tolerant method of pulse expansion and compression comprising the steps of: generating N replicas x(n) of an applied subpulse, where n=0, 1, 2,-, N-1 and N is an integer, in a time which is N times the length of the subpulse; weighting the replicas in accordance with the formula ##EQU18## where k=0, 1, 2,-, N-1 to provide N weighted subpulses s(k) whenever one of the N replicas x(n) is generated; and separately summing the real and imaginary parts of the weighted subpulses s(k), where 0≦k≦N/2-1 and N/2+1≦k≦N-1, corresponding to any replica of the applied subpulse, after a delay time which is ##EQU19## the length of the applied subpulse for 0≦k≦N/2-1 and after a delay time which is ##EQU20## length of the applied supulse for N/2+1≦k≦N-1.
Claim 8
Dependent Claim
128 words
An efficient pre-compression, bandwidth-tolerant method of pulse expansion and compression comprising the steps of: generating N replicas x(n) of an applied subpulse, where n=0, 1, 2,-, N-1 and N is an integer, in a time which is N times the length of the subpulse; weighting the replicas in accordance with the formula ##EQU18## where k=0, 1, 2,-, N-1 to provide N weighted subpulses s(k) whenever one of the N replicas x(n) is generated; and separately summing the real and imaginary parts of the weighted subpulses s(k), where 0≦k≦N/2-1 and N/2+1≦k≦N-1, corresponding to any replica of the applied subpulse, after a delay time which is ##EQU19## the length of the applied subpulse for 0≦k≦N/2-1 and after a delay time which is ##EQU20## length of the applied supulse for N/2+1≦k≦N-1.
Claim 9
Dependent Claim
28 words
The pulse expansion and compression method recited in claim 6 wherein the generating step includes: successively delaying the subpulse by uniform delays as long as the applied subpulse.
Claim 10
Dependent Claim
26 words
The pulse expansion and compression method recited in claim 6 wherein the weighting step includes: forming discrete Fourier transform signals with a fast Fourier transform circuit.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-02-07 | 1986-08-09 | 1987-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-02-07 | 1990-08-09 | 1991-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-02-07 | 1994-08-09 | 1995-02-08 | $7700.00 | Window Closed / Lapsed |