With Variable Pulse Repetition Frequency (prf) Or Pulse Width Patents (Class 342/137)
  • Patent number: 4894660
    Abstract: A swept-frequency radar system transmits pulses consisting of swept-frequency subpulses of nonuniform duration separated by short nontransmitting periods during which an array antenna is resteered. The pulses reflected from a target are processed by a method including estimating the target ranges, producing a reference signal at the time at which the pulse reflected from the target is expected to return. The reflected pulse is phase detected by means of the reference pulse to produce phase detected signals which include information relating to the error between the actual range and the estimated range. The phase detected signals are Fourier transformed to produce range error information. The nonuniform subpulse durations reduce the magnitude of range sidelobes.
    Type: Grant
    Filed: October 12, 1988
    Date of Patent: January 16, 1990
    Assignee: General Electric Company
    Inventors: Don N. Thomson, David E. Maron
  • Patent number: 4847622
    Abstract: A coherent pulse radar is activated successively according to at least two pulse repetition frequencies. These frequencies are of values such that (a) the received signal is ambiguous both with regard to distance and with regard to velocity, and (b) their ratio is reducible to the quotient of two integers which are preferably adjacent and have no common factors. For the frequency analysis, a number of samples is taken which depends upon the pulse repetition frequency, the numbers of samples associated with the two pulse repetition frequencies being, in relation to one another, in the ratio of the two integers. The distance/velocity resolution cell is then invariant with respect to the pulse repetition frequency; this permits removal of the ambiguity concerning mean information items appertaining to a long integration time.
    Type: Grant
    Filed: February 26, 1988
    Date of Patent: July 11, 1989
    Assignee: Electronique Serge Dassault
    Inventors: Bernard Maitre, Marie-Francoise Schaub
  • Patent number: 4746922
    Abstract: This invention relates to a method of and a device for removing range ambiguity in a pulse Doppler radar and to a radar including such a device especially for missile guidance. On tracking operation at a high pulse repetition frequency the method consists in switching the repetition frequency f.sub.R (k) for each time interval .DELTA.t, over a new value f.sub.R (k+1) obtained in a circuit from the measured ambiguous range y(k) and from the ambiguity number n(k), as estimated in a circuit from radar information supplied by the radar, in order to remove eclipsing, to maintain the ambiguity number constant and to estimate the range with a growing accuracy in the course of the tracking operation.
    Type: Grant
    Filed: May 6, 1982
    Date of Patent: May 24, 1988
    Assignee: Thomson- CSF
    Inventor: Michel Prenat
  • Patent number: 4730189
    Abstract: A pulse Doppler radar system with variable pulse repetition frequency has a coherent integrator to which the reflected pulses are supplied in order to avoid deterioration of the indication of a moving target given over-the-horizon reception. The coherent integrator subjects the reflected pulses to a simplified vectorial addition by the use of a number of filters. A precondition for the modified coherent integration is a staggering of the pulse repetition periods such that their sums formed over successive pulse repetition periods are constant, and a phase reference for the signal amplitudes is obtained such that the phase difference is equal to zero after every second pulse repetition.
    Type: Grant
    Filed: May 24, 1984
    Date of Patent: March 8, 1988
    Assignee: Siemens Aktiengesellschaft
    Inventors: Harald Siegel, Rudolf Hauptmann
  • Patent number: 4727375
    Abstract: The invention relates to a process for adapting the post integration in a switched pulse repetition frequency radar and a circuit implementing this process. For that, the post integration of the detected signals is effected as a function of the signal received from the Doppler filter. For that, switches are used controlled by comparator circuits.The invention is useful in frequency ambiguous coherent Doppler radars using recurrence frequency switching by blocks.
    Type: Grant
    Filed: December 18, 1985
    Date of Patent: February 23, 1988
    Assignee: Thomson-CSF
    Inventor: Philippe Lacomme
  • Patent number: 4724418
    Abstract: An extended depth-of-focus synthetic aperture radar (SAR) system (13) mounted on a moving platform, including a controller (120), pulse timer (83), synthesizer (105) and modulator (17) for varying the pulse rate interval (PRI) and/or the radar carrier frequency of radar pulses produced, in order to establish a radar return which, when conventionally processed, results in a SAR terrain map exhibiting extended depth-of-focus under conditions of platform acceleration. Depth of focus is established by ensuring the establishment of two or three separate, independently selected focal points in a target region of interest.
    Type: Grant
    Filed: March 24, 1986
    Date of Patent: February 9, 1988
    Assignee: United Technologies Corporation
    Inventor: Frederik Weindling
  • Patent number: 4717917
    Abstract: Disclosed is an alien radio ranging transmitter rejection technique utilizing random PRF to eliminate the possibility of lock-on between two coherent R/T units in close proximity. If one, or both, are utilizing the random PRF technique taught herein, the alien signal is rejected utilizing standard noise suppression techniques. The random PRF is selected utilizing noise or angle data computed from the received return signal and is thereafter utilized to designate which one of a set number of PRF delays is utilized on a substantially random basis.
    Type: Grant
    Filed: June 26, 1985
    Date of Patent: January 5, 1988
    Assignee: Rockwell International Corporation
    Inventor: Orville J. Alitz
  • Patent number: 4706088
    Abstract: An extended depth-of-focus synthetic aperture radar (SAR) system (13) mounted on a moving platform, including a controller (120), pulse timer (83), synthesizer (105) and modulator (17) for varying the pulse rate interval (PRI) and/or the radar carrier frequency of radar pulses produced, in order to establish a radar return which, when conventionally processed, results in a SAR terrain map exhibiting extended depth-of-focus under conditions of platform acceleration. Depth of focus is established by ensuring the establishment of two or three separate, independently selected focal points in a target region of interest.
    Type: Grant
    Filed: March 24, 1986
    Date of Patent: November 10, 1987
    Assignee: United Technologies Corporation
    Inventor: Frederik Weindling
  • Patent number: 4679050
    Abstract: Described is a pulse radar apparatus having a repetition period containing m wobbles. The pulse radar apparatus is provided with: a transmitting and receiving unit (2), whereby the received target echoes are sampled and digitized; an n-point DFT processing unit (3); a threshold circuit (4); and a cluster combiner circuit (5) comprising means to form a cluster covering one single target using the signals obtained from the threshold circuit (4). Due to the wobbles, additional information arises in the DFT spectra. From the range, azimuth, local maximum values of the DFT spectrum and the associated output channel number of the DFT processing unit (3), a classification unit (6) determines whether a target is a multiple-time-around target. The classification unit (6) is also able to determine the target doppler frequency, even if this frequency exceeds the average pulse repetition frequency.
    Type: Grant
    Filed: November 25, 1985
    Date of Patent: July 7, 1987
    Assignee: Hollandse Signaalapparaten B.V.
    Inventor: Jan Bergman