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US3979752A
Expired / Lapsed
US
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Pulse-type radar with modulated carrier frequency
Assignee: Thales SA
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Filing: 1975-07-11
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Granted: 1976-09-07
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Expires: 1995-07-11
Abstract
Abstract A radar system emitting a recurrent sequence of n equispaced bursts of carrier frequency, varying from one burst to the next, has a transmitter including a carrier-frequency generator with a frequency-varying motor driven by a synchronizing circuit to produce a repetitive frequency pattern recurring a whole number of times in a program cycle of n pulse periods. An associated receiver includes a local oscillator whose frequency is incremented, from one pulse period to the next, by a feedback circuit comprising a modulator with inputs connected to the output of this oscillator and to a coupler picking up the instantaneous carrier frequency from the transmitter output; this modulator works into a frequency discriminator, tuned to a predetermined intermediate frequency, returning an error signal to a control input of the oscillator via a multiple integrator concurrently storing all the error signals for the several pulse periods; an adder superposes these error signals upon a monitoring signal extracted at the beginning of each pulse period from the carrier-frequency generator. The multiple integrator includes an operational amplifier with n parallel capacitors in respective feedback paths which are normally open-circuited and are sequentially connected in circuit under the control of a shift register restarted at the beginning of each program cycle. A similar multiple integrator may be inserted in an automatic-gain-control circuit for an intermediate-frequency amplifier in the output of a mixer which heterodynes the received echoes with the local-oscillator output.
Inventors
- 👤 Jean-Claude Charlot
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:39
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S13/24
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
279 words
In a radar system, in combination: a generator of periodic bursts of carrier frequency separated by pulse periods of predetermined duration, said generator having an outgoing channel for the transmission of said bursts of carrier frequency; frequency-varying means in said generator for changing said carrier frequency from one pulse period to the next; an incoming channel for the reception of echoes of said carrier frequency reflected by a target; synchronizing means connected to said frequency-varying means for establishing a repetitive modulation pattern for said carrier frequency having a whole number of repetition periods in a program cycle of n pulse periods; a local oscillator having an operating frequency variable in a range offset from the range of said carrier frequencies by a predetermined intermediate frequency, said incoming channel including mixer means connected to said local oscillator for heterodyning said operating frequency with received echoes to produce an output signal of said intermediate frequency for delivery to a utilization circuit; modulating means with input connections to said outgoing channel and to said local oscillator for deriving a difference frequency from said operating frequency and said carrier frequency; discriminating means connected to said modulating means for converting said difference frequency into a feedback signal having a predetermined mean value upon said difference frequency equaling said intermediate frequency; multiple integrating means connected to said discriminating means for simultaneously storing feedback signals from different pulse periods over a plurality of program cycles; and control means for said local oscillator connected to said multiple integrating means for individually changing said operating frequency during each pulse period according to the stored feedback signal thereof to make said difference frequency substantially equal to said intermediate frequency.
Claim 2
Dependent Claim
279 words
In a radar system, in combination: a generator of periodic bursts of carrier frequency separated by pulse periods of predetermined duration, said generator having an outgoing channel for the transmission of said bursts of carrier frequency; frequency-varying means in said generator for changing said carrier frequency from one pulse period to the next; an incoming channel for the reception of echoes of said carrier frequency reflected by a target; synchronizing means connected to said frequency-varying means for establishing a repetitive modulation pattern for said carrier frequency having a whole number of repetition periods in a program cycle of n pulse periods; a local oscillator having an operating frequency variable in a range offset from the range of said carrier frequencies by a predetermined intermediate frequency, said incoming channel including mixer means connected to said local oscillator for heterodyning said operating frequency with received echoes to produce an output signal of said intermediate frequency for delivery to a utilization circuit; modulating means with input connections to said outgoing channel and to said local oscillator for deriving a difference frequency from said operating frequency and said carrier frequency; discriminating means connected to said modulating means for converting said difference frequency into a feedback signal having a predetermined mean value upon said difference frequency equaling said intermediate frequency; multiple integrating means connected to said discriminating means for simultaneously storing feedback signals from different pulse periods over a plurality of program cycles; and control means for said local oscillator connected to said multiple integrating means for individually changing said operating frequency during each pulse period according to the stored feedback signal thereof to make said difference frequency substantially equal to said intermediate frequency.
Claim 3
Dependent Claim
36 words
The combination defined in claim 1, further comprising clamping means controlled by said synchronizing means and inserted between said discriminating means and said multiple integrating means for holding said feedback signal constant over each pulse period.
Claim 4
Dependent Claim
42 words
The combination defined in claim 2, further comprising a source of sawtooth voltage in step with said pulse periods and switchover means for connecting said source in lieu of said discriminating means to said multiple integrating means during a preliminary operating phase.
Claim 5
Dependent Claim
66 words
The combination defined in claim 3 wherein said discriminating means includes filter means in cascade with said modulating means for rejecting difference frequencies remote from said intermediate frequency, and a threshold detector connected to said filter means and controlling said switchover means for initially connecting said source to said multiple integrating means until the difference frequency passed by said filter means reaches a predetermined minimum amplitude.
Claim 6
Dependent Claim
60 words
The combination defined in claim 1 wherein said feedback signal has a zero value upon said difference frequency equaling said intermediate frequency, said control means including a summing circuit with additive inputs connected to said multiple integrating means and to said generator for superimposing said feedback signal as an error signal upon a monitoring signal representative of the carrier frequency.
Claim 7
Dependent Claim
113 words
The combination defined in claim 1 wherein said multiple integrating means comprises an operational amplifier with n capacitive feedback paths, and an n-stage shift register connected to said synchronizing means for receiving therefrom a recurrent switching signal appearing successively at respective stage outputs of said shift register substantially at the beginning of consecutive pulse periods, said feedback paths being provided with normally open circuit breakers respectively connected to said stage outputs for individual closure by said switching signal during corresponding pulse periods, said shift register further having a loading input connected to said synchronizing means for entry of said switching signal into the first register stage at the beginning of a program cycle.
Claim 8
Dependent Claim
51 words
The combination defined in claim 6 wherein said shift register is further provided with clearing inputs for at least its highest-ranking stages connected to said loading input for joint energization at the beginning of a program cycle, thereby enabling a changeover to a program cycle with less than n pulse periods.
Claim 9
Dependent Claim
84 words
The combination defined in claim 6 wherein said synchronizing means comprises a master oscillator, a harmonic frequency modifier connected to said master oscillator, a first pulse-shaping circuit connected to said master oscillator for energization thereby, and a second pulse-shaping circuit connected to said frequency modifier for energization thereby, one of said pulse-shaping circuits delivering said switching signal at a higher repetition frequency, the other of said pulse-shaping circuits energizing said loading input with a lower repetition frequency signal equaling 1/n times said higher frequency.
Claim 10
Dependent Claim
67 words
The combination defined in claim 1 wherein said incoming channel includes a variable-gain amplifier downstream of said mixer means for stabilizing the amplitude of said output signal, and automatic-gain-control means comprising a control loop with other multiple integrating means for storing corrective signals from different pulse periods over a plurality of program cycles, said automatic-gain-control means being connected to said variable-gain amplifier for stabilizing the gain thereof.
Claim 11
Dependent Claim
53 words
The combination defined in claim 9 wherein said control loop further includes sampling and holding means responsive to a gating signal received once per pulse period from said utilization circuit for making said other multiple integrating means responsive to the magnitude of said output signal in a selected fraction of a pulse period.
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) | 1979-09-07 | 1980-03-08 | 1980-09-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-07 | 1984-03-08 | 1984-09-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-07 | 1988-03-08 | 1988-09-07 | $7700.00 | Window Closed / Lapsed |