US3725923A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Coherent digital pulse doppler radar system with improved signal handling capacity
Assignee: International Standard Electric Corp
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Filing: 1971-07-06
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Granted: 1973-04-03
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Expires: 1991-07-06
Abstract
Abstract A pulse Digital Doppler coherent MTI radar system in which sine and cosine phase detector outputs are both coded and stored in a plurality of range increments. A first channel stores digital codes for moving targets exceeding a minimum predetermined amplitude threshold. That information is used to control another MTI channel to reduce the number of target signals which must be processed in a second channel, thereby providing increased processing time. Storage of signal codes is effected in dual memories, one being read while real time storage is carried out in the other. The sine and cosine phase detector output processing facilitates derivation of target velocity and sense. A Fourier transform display depicts Doppler component content in selected signals, the latter being controlled by bearing as well as range increment data.
Inventors
- 👤 H Bosc
- 👤 M Castets
- 👤 J Debuisser
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 08:54
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/52; G01S13/522; G01S13/524; G01S13/5242; G01S13/53; G01S13/532; G01S13/58; G01S13/64
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
307 words
A coherent pulse Doppler radar system including an antenna scanning in the bearing coordinate and receiving means for derivation of sine and cosine receiver phase detector output signals comprising: sampling and coding means responsive to said sine and cosine phase detector outputs for digitally encoding the amplitude of signal in each of a plurality of range increments during each repetition period of said radar system; a first memory for discretely storing said range increment codes from said sampling and coding means for each of said sine and cosine signals; range selector means responsive to one of said sine and cosine outputs of said phase detectors, said means separately sampling the signal in each of said range increments, said range selectors including Doppler filtering to produce an output for each of said range increments in which the received signal includes a Doppler component corresponding to a moving target; a second memory for discretely storing said range selector outputs by range increment thereby to identify each range increment containing a moving target; column selection means for contemporaneously reading said first and second memories to produce selected output signals corresponding to each of said sine and cosine signals, said column selection means output signals thereby containing only said digital codes from said first memory in range increments identified in said second memory; a third memory for storing the output of said column selection means; canceller means for comparing said codes stored in said third memory for the same range increment over successive repetition periods of said radar system to provide a difference code varying as a function of corresponding target velocity in Each of said range increments; and a Fourier transform computer means responsive to said difference code for producing an output signal whose amplitude versus time represents the signal spectrum corresponding to at least one of said moving targets.
Claim 2
Dependent Claim
307 words
A coherent pulse Doppler radar system including an antenna scanning in the bearing coordinate and receiving means for derivation of sine and cosine receiver phase detector output signals comprising: sampling and coding means responsive to said sine and cosine phase detector outputs for digitally encoding the amplitude of signal in each of a plurality of range increments during each repetition period of said radar system; a first memory for discretely storing said range increment codes from said sampling and coding means for each of said sine and cosine signals; range selector means responsive to one of said sine and cosine outputs of said phase detectors, said means separately sampling the signal in each of said range increments, said range selectors including Doppler filtering to produce an output for each of said range increments in which the received signal includes a Doppler component corresponding to a moving target; a second memory for discretely storing said range selector outputs by range increment thereby to identify each range increment containing a moving target; column selection means for contemporaneously reading said first and second memories to produce selected output signals corresponding to each of said sine and cosine signals, said column selection means output signals thereby containing only said digital codes from said first memory in range increments identified in said second memory; a third memory for storing the output of said column selection means; canceller means for comparing said codes stored in said third memory for the same range increment over successive repetition periods of said radar system to provide a difference code varying as a function of corresponding target velocity in Each of said range increments; and a Fourier transform computer means responsive to said difference code for producing an output signal whose amplitude versus time represents the signal spectrum corresponding to at least one of said moving targets.
Claim 3
Dependent Claim
27 words
Apparatus according to claim 1 including display means operated synchronously with said Fourier transform computer to display the spectrum of at least one discrete moving target signal.
Claim 4
Dependent Claim
38 words
Apparatus according to claim 2 including a first threshold circuit connected between said Doppler filter in each of the outputs of said range selector means and the corresponding second memory input, to produce a predetermined signal-to-noise ratio improvement.
Claim 5
Dependent Claim
72 words
Apparatus according to claim 3 in which a second threshold circuit and a gating circuit is included between the output of said Fourier transform computer and said display, said second threshold circuit and said gate being interconnected to pass only signal amplitudes from said Fourier transform computer exceeding a predetermined amplitude level, the threshold levels of said first and second threshold circuits being selected to provide substantially equal theoretical probabilities of detection.
Claim 6
Dependent Claim
57 words
Apparatus according to claim 4 further defined in that means are applied to said column selection means for enabling said selector only during a predetermined sector of said antenna scan in the bearing coordinate, thereby limiting storage of signals in said third memory to those in a predetermined angular sector of the scan coverage of said antenna.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |