With Variable Pulse Repetition Frequency (prf) Or Pulse Width Patents (Class 342/137)
  • Publication number: 20040004905
    Abstract: A calibration module and methods for a time-of-flight ranging system. The calibration module may be built into the circuitry of the time-of-flight ranging system and allows various operating parameters to be measured and evaluated. The calibration modes include amplitude calibration, frequency calibration, and time delay calibration. The calibration mode also includes an electronic noise measurement mode. The calibration modes may be initiated on power-up or reset, or in response to user input or time-based trigger.
    Type: Application
    Filed: May 29, 2003
    Publication date: January 8, 2004
    Inventors: Quinton Lyon, Claude Mercier
  • Publication number: 20040004567
    Abstract: Radar systems are used for ascertaining the range to at least one reflecting object present in an observation area and/or for ascertaining the speed of the at least one reflecting object. Such a radar system emits into the observation area successive transmitter pulses having a determined pulse duration, with a determined pulse-repetition frequency as a transmitted signal. The system receives transmitted pulses reflected by the at least one reflecting object of the transmitted signal as a received signal. The disadvantage thereby is, that the method has high signal dynamics, which has an unfavorable effect on the price of the circuit components required for the signal processing. The new method for operating a radar system shall be performable with cost effective means.
    Type: Application
    Filed: June 16, 2003
    Publication date: January 8, 2004
    Inventors: Jens Kroeger, Ralph Mende, Karsten Schumann
  • Patent number: 6646587
    Abstract: A Doppler radar apparatus includes a first oscillator for generating a first sweep signal to repeatedly sweep a predetermined frequency range periodically; a second oscillator for generating a second sweep signal having sweep properties identical to those of the first sweep signal, the second oscillator 41b starting sweep before the first oscillator finishes frequency sweep; a power combiner for combining the first and second sweep signals to generate a transmission signal; a switch for receiving, as inputs, the first and second sweep signals, and switching an output between the first and second sweep signals synchronously with the timing when sweep with each of the first and second sweep signals is terminated; and a mixer for mixing a reception signal coming from a part of the transmission signal reflected in a target and received, and an output signal from the switch with each other to produce an output signal from the mixer.
    Type: Grant
    Filed: June 14, 2002
    Date of Patent: November 11, 2003
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventor: Mikio Funai
  • Patent number: 6639546
    Abstract: A radar system provides unambiguous and uneclipsed range by virtue of pulse-to-pulse frequency diversity, in combination with alternating interpulse intervals and processing which “fills in” target information in the ranges which would otherwise be eclipsed by transmitted pulses.
    Type: Grant
    Filed: October 10, 2002
    Date of Patent: October 28, 2003
    Assignee: Lockheed Martin Corporation
    Inventors: David Ronald Ott, Fotis Koubiadis
  • Patent number: 6621450
    Abstract: A method for selecting a pulse repetition frequency to detect, track or search for a target that includes identifying a first feature representative interval of each pulse repetition frequency within a set of pulse repetition frequencies, choosing a selected pulse repetition frequency from the set of pulse repetition frequencies based on cost assigned to each pulse repetition frequency, wherein the cost assigned to a first pulse repetition frequency is at least based on a first cost function of a first position of a first target feature in relation to a first feature assessment interval of the first pulse repetition frequency, and emitting pulsed energy from the emitter using the selected pulse repetition frequency.
    Type: Grant
    Filed: July 12, 2002
    Date of Patent: September 16, 2003
    Assignee: Lockheed Martin Corporation
    Inventor: Bradford E. Carter
  • Patent number: 6614388
    Abstract: A sensor array with a pulse echo radar system with which a carrier signal of a microwave transmitter oscillator is transmitted in the form of pulses with a specified pulse repetition frequency in a transmission window. This radar signal is reflected from a target object and the position of the target object is calculated in a mixer from the times of transmission of the pulse to the arrival of the reflected radiation. An array of several transmitter and receiver units with switches are constructed in which the stochastic pulse sequences of each transmission window in each receiver branch are known and the transmitter and receiver units are linked to one another so that in each of the receiver branches the stochastic pulse sequences of each transmission window are detected separately and thereby the cross echoes may also be analyzed.
    Type: Grant
    Filed: October 10, 2001
    Date of Patent: September 2, 2003
    Assignee: Robert Bosch GmbH
    Inventors: Roland Klinnert, Klaus Voigtlaender, Hauke Schmidt
  • Publication number: 20030156057
    Abstract: In a method for HPRF-radar measurement of the range and Doppler frequency of at least one target, a transmit signal is generated which consists of two pulse sequences that are interleaved on a pulse to pulse basis, and have the same pulse repetition frequency PRF and the same transmit frequency. The pulses of a first one of the two pulse sequences have a linearly increasing phase value with a fixed phase difference &phgr;1n (greater than zero) from pulse to pulse with &phgr;1n≧0, while the pulses of the second pulse sequence have a linear increasing phase value with a fixed phase difference &phgr;2n which differs from &phgr;1n. The two received base band signals of each individual pulse sequence are Fourier transformed, and the amplitude peaks of the resulting two Fourier spectra are determined.
    Type: Application
    Filed: November 25, 2002
    Publication date: August 21, 2003
    Inventors: Hermann Rohling, Wilhelm Guener, Hans Hommel, Dieter Nagel
  • Publication number: 20030151542
    Abstract: The present invention relates to a radar system having means (12) for producing a code, means (18) for modulating a transmission signal in a transmit branch, using the code, means (32) for delaying the code, means (20) for modulating a signal in a receive branch, using the delayed code, and means (26) for mixing a reference signal with a receiving signal, the modulation of one of the signals being performed by an amplitude modulation (ASK; “amplitude shift keying”) and the modulation of the other signal by a phase modulation (PSK; “phase shift keying”). Furthermore, a radar system is proposed in which blanking of phase transitions is provided. The present invention also relates to methods which may advantageously be carried out, using the radar systems according to the present invention.
    Type: Application
    Filed: March 26, 2003
    Publication date: August 14, 2003
    Inventors: Siegbert Steinlechner, Thomas Brosche
  • Publication number: 20030128152
    Abstract: A sensor front end is disclosed that is able to discriminate objects based on their range from the sensor. The sensor includes an antenna that transmits a sensor signal and, if an object is present receives a reflected signal therefrom. A pulsed oscillator provides a pulsed first signal having a first frequency and phase, and wherein the pulsed oscillator provides the pulsed first signal for a predetermined pulse duration and with a predetermined pulse repetition frequency. The pulsed oscillator provides the pulsed first signal to a first input port of a dual mode mixer that is further coupled to the antenna via a second port. The dual mode mixer transmits a portion of the pulsed first signal from the first input port to the second port and thus to the antenna to be transmitted as the sensor signal. In addition, the dual mode mixer uses a portion of the first signal to mix with the received reflected signal. The dual mode mixer then provides a mixed signal as an output at a third port.
    Type: Application
    Filed: January 9, 2002
    Publication date: July 10, 2003
    Applicant: TYCO ELECTRONICS CORPORATION
    Inventor: Kenneth V. Puglia
  • Patent number: 6509864
    Abstract: The invention relates to a distance measuring device. A transmitting part (E) for electromagnetic radiation especially radar radiation, emits measuring pulses (A, B) which are controlled by a pulse generator (1), and a receiving part (8) is switched to a ready-to-receive mode after a certain, adjustable delay (TDELAY, before a next measuring pulse is emitted, for receiving a reflected pulse during a time gate (18). The aim of the invention is to provide a calibration process taking into account all practical defects. To this end, the pulse generator (1) produces pulses with a multiple of the frequency with which the measuring pulses are repeated and a calibrating cycle in which calibrating pulses (&tgr;0 to &tgr;9) are produced with pulses generated by the pulse generator (1), controlled by the transmitting part (5), is carried out at longer intervals in time.
    Type: Grant
    Filed: March 6, 2002
    Date of Patent: January 21, 2003
    Assignee: s. m. s. smart microwave sensors GmbH
    Inventors: Ralph Mende, Hermann Rohling
  • Patent number: 6480142
    Abstract: A method and apparatus for measuring the parameters of atmospheric turbulent flows utilizes the Doppler shifted frequencies of received radar signals backscattered from sound generated aerodynamically by atmospheric turbulent flows. Doppler frequency bandwidths of the received backscattered signals are used to estimate the atmospheric flow turbulence and the mean frequency within a bandwidth is processed to estimate its radial flow velocity. Total flow velocity and the flow velocity angle with respect to the antenna boresight of the atmospheric turbulent flow may be estimated by estimating the radial flow velocity at two radial positions and processing these radial velocities. Processing of the Doppler data is initiated when the total signal power within the Doppler frequency band exceeds a predetermined power level.
    Type: Grant
    Filed: May 17, 2001
    Date of Patent: November 12, 2002
    Inventor: William L. Rubin
  • Patent number: 6476758
    Abstract: Systems and methods that may be used to determine the distance between an orbiting satellite and a ground station. A master clock divider circuit generates clock signals derived from a master clock. A transmit code generation circuit generates pseudo-random number codes and processes the pseudo-random number codes to produce a composite signal having positive and negative correlation peaks that is transmitted to the satellite as an analog signal. A digitizing circuit receives the analog signal transmitted from the satellite, and digitizes the analog signal. A frequency domain matched filter match filters the digitized analog signal to produce correlation peaks contained in the digitized analog signal.
    Type: Grant
    Filed: March 6, 2001
    Date of Patent: November 5, 2002
    Assignee: Lockheed Martin Corporation
    Inventors: Christopher Chaput, Kenneth Ehlers, Robert Pierson, David Rowe, Jackson Ma
  • Patent number: 6446005
    Abstract: A system is disclosed for determining precise locations of the golf carts on a golf course in real time as the carts are in use during play of the course. Each cart is outfitted with a dead reckoning navigation (DRN) system for determining speed and direction, and a compass for determining heading of the cart during play. With these parameters and a known origin of the cart to which the DRN system has been calibrated, such as location of a tee box, the location of the cart relative to a known feature of the course such as a cup or hazard may be calculated. The DRN system uses a magnetic wheel sensor assembly having a magnetic strip with spaced alternating opposite magnetic poles affixed to the rim of an inside wheel well or mounting fixture therefor of the cart, mounted to confront a Hall effect sensor. During rotation of the wheel and the strip when the cart is moving, the sensor detects passage of the alternating poles, to measure speed and forward or backward direction of the cart.
    Type: Grant
    Filed: August 13, 1999
    Date of Patent: September 3, 2002
    Assignee: Prolink, Inc.
    Inventors: Kirk Bingeman, Richard Velasquez, William Tekniepe
  • Patent number: 6373427
    Abstract: The invention relates to a radar distance measuring device. An especially linear frequency-modulated high frequency signal is emitted via an antenna and mixed with an echo signal reflected by a target object whose distance is to be determined. The distance of said target object can then be calculated by analyzing the frequency of the mix result. The aim of the invention is to improve the distance resolution or increase the accuracy of measurement. To this end, a first frequency analysis is first carried out to obtain a rough analysis result. Said rough analysis result is used to control a filtering device which then restricts the mix result in its time range to a segment around the frequency of the target object. A discrete Fourier transformation is then carried out for this segment in order to produce an analysis result with a more refined scanning step than the first frequency analysis.
    Type: Grant
    Filed: May 12, 2000
    Date of Patent: April 16, 2002
    Assignee: Mikrowellen-Technologie und Sensoren GmbH
    Inventor: Felix Hohne
  • Patent number: 6326917
    Abstract: A scanner-control device for scanning an echo signal formed by returning transmit pulses, includes a clock generator, which triggers a pulse shaper for the transmit pulses and a further pulse shaper for scanning pulses. The scanner-control device also includes setting member for modifying a delay time of the scanning pulses, so that the echo signal can gradually be reconstructed from the returning transmit pulses.
    Type: Grant
    Filed: May 15, 2000
    Date of Patent: December 4, 2001
    Assignee: Robert Bosch GmbH
    Inventors: Thomas Pfendler, Siegbert Steinlechner
  • Patent number: 6232912
    Abstract: The invention particularly relates to the detection of fast-flying targets by means of an HPRF radar system that operates with a plurality of switchable pulse-repetition frequencies (PRFs). In the method, a high velocity resolution is attained, which permits a reliable detection of a multiple-target situation. At the same time, a precise range determination is attained with a high range resolution by means of a pure transit-time measurement of the pulses. The length of the used range gates is selected to correspond to the anticipated target length.
    Type: Grant
    Filed: November 16, 1998
    Date of Patent: May 15, 2001
    Assignee: Daimler-Benz Aerospace AG
    Inventor: Dieter Nagel
  • Patent number: 6232913
    Abstract: Characteristics of a target are measured by a radar or sonar. Pulses (101, 102, 103) are transmitted and in between (X) the transmissions of pulses a signal is received which depends on the transmitted pulses and on the distribution of the characteristics measured at different ranges. The distribution at different ranges of the characteristics measured is determined by representing it by means of a substantially linear system of equations in which the variables are the values of the characteristics measured at desired ranges, and by solving the system of equations for the variables. The transmitted pulses form a cyclically repeated pulse code or a continuously changing pulse train.
    Type: Grant
    Filed: March 24, 1999
    Date of Patent: May 15, 2001
    Inventor: Markku Sakari Lehtinen
  • Patent number: 6225943
    Abstract: A method, and exemplary apparatus for practicing the method, is shown for operating a pulse radar to allow the radar ambiguity function of such radar to be modified by controlling the range and Doppler ambiguities due to the pulse waveform of such radar.
    Type: Grant
    Filed: May 1, 1978
    Date of Patent: May 1, 2001
    Assignee: Raytheon Company
    Inventors: John J. Curley, Edward J. Sheldon, Nathan Slawsby
  • Patent number: 6111537
    Abstract: Method for reducing false target echo indications in a pulse Doppler radar having at least two different pulse repetition frequencies during the period in which the main beam of the radar illuminates a target. A target which is detected gives rise to a number of primary detections in each PRF. The method includes use of at least one variable criterion and a final criterion, which are both of the M/N type. The factor M in the variable criterion is initially greater than the factor M in the final criterion. The method also includes the feature that primary detections which are all to be found in the same range gate in a number of PRF's, which number is equal to the factor M in the variable criterion, are approved as targets in this range gate.
    Type: Grant
    Filed: March 15, 1999
    Date of Patent: August 29, 2000
    Assignee: Telefonaktiebolaget LM Ericsson
    Inventor: Bengt Andersson
  • Patent number: 6081221
    Abstract: A method for resolving range ambiguities and separating overlaid signals in a Doppler weather radar is proposed. For uniform PRT transmission, it consists of a special deterministic code for phases of the transmitted pulsed, and associated decoding and processing of return signals. In the decoding process when the signal from one range interval is made coherent, the signal from the other range interval has a multiple split spectrum. The multiple spectra have the same shape but are offset from each other. Processing steps to separate the overlaid signals and a procedure to estimate the spectral moments are given. One crucial aspect in this procedure is the magnitude domain deconvolution. The magnitude domain deconvolution is also applied to a staggered PRT transmission scheme whereby it enables the estimation of spectral parameters with much lower standard error than the known methods.
    Type: Grant
    Filed: August 27, 1998
    Date of Patent: June 27, 2000
    Inventors: Dusan S. Zrnic, Mangalore Sachidananda
  • Patent number: 6072420
    Abstract: The present invention relates to an ultra wide band coherent radar system assessing the Doppler shift of the returned radar echoes, which radar system optimises the radio interference discrimination capability. The radar system comprises a control unit by which the transmit-receive process is partitioned into a number of consecutive sub-processes each of which consists of transmission followed by reception of a signal having a relative bandwidth of a fraction of an octave and where the received signals from the different narrow band transmissions are used to reconstruct broad band radar data by pulse compression techniques. Further, the control unit is arranged to determine the recurrence time, i.e. the time lapse between two consecutive transmissions, of a narrow band signal for a certain frequency step to be approximately inversely proportional to the frequency of this step and higher or equal to the Nyquist rate with respect to the Doppler bandwidth at this frequency.
    Type: Grant
    Filed: September 2, 1998
    Date of Patent: June 6, 2000
    Inventor: Hans Hellsten
  • Patent number: 6067040
    Abstract: A low-cost, high-resolution radar based detection system has a pulse repetition frequency generator connected to first and second narrow pulse modulators. A transmit channel is connected to the first narrow pulse modulator and emits pulse modulated carrier based transmit signals having a prescribed carrier frequency and a prescribed duration. A receive channel is connected to the second narrow pulse modulator. A time delay circuit delays the output of the second pulse modulator to the receive channel and a mixer mixes a portion of one of the pulse modulated carrier based transmit signals reflected from an object with the output of the second narrow pulse modulator.
    Type: Grant
    Filed: May 30, 1997
    Date of Patent: May 23, 2000
    Assignee: The Whitaker Corporation
    Inventor: Kenneth Vincent Puglia
  • Patent number: 6064331
    Abstract: The objectives of the invention are met by an improved radar tracking system and a process of radar tracking. In the improved system and process, an estimate of a target range and a range uncertainity swath from a first radar system is inputted into a second radar system along with a duty factor. The second radar system determines a set of zero eclipse intervals and respective ranges of range pulse repetition frequencies that solves a first set of equations. A usable range pulse repetition frequency is chosen from the results. Next, an estimated target Doppler frequency region and a Doppler uncertainity swath is inputted into the second radar system. The second radar system is instructed to determine a set of clear Doppler frequency region intervals, and respective ranges of Doppler frequency pulse repetition frequencies by solving a second set of equations.
    Type: Grant
    Filed: June 11, 1998
    Date of Patent: May 16, 2000
    Assignee: Boeing North American, Inc.
    Inventors: Louis J. Avila, Prentiss N. Robinson
  • Patent number: 6049302
    Abstract: A process and a system for selecting a pulse repetition frequency that causes clutter pulse repetition frequency lines from the negative carrier frequency and from the clutter harmonic frequencies to lay on top of clutter pulse repetition frequency lines from the positive carrier frequency. A pulsed Doppler radar receiver of the system has one or more channels each comprising of a radio frequency input section for receiving a radio frequency carrier. Following the radio frequency input section are one or more serially arranged intermediate frequency sections that terminate in a last intermediate frequency section. The last intermediate frequency section is followed by analog-to-digital conversion and down-conversion to baseband in-phase and quadrature channels. In-phase and quadrature data from the in-phase and quadrature channels is processible by a computational system to detect and track a target in the presence of clutter.
    Type: Grant
    Filed: May 4, 1999
    Date of Patent: April 11, 2000
    Assignee: Boeing North American
    Inventor: William L. Hinckley, Jr.
  • Patent number: 5963677
    Abstract: A system to perform real time temporal correlation on pulsed and periodic signals. Application is to systems which perform PRI analysis of signals and provide signal gain as part of the correlation process. Correlation is performed in two stages, the first conditioning the signals for correlation using the zero mean, PW matched filter and the second performing temporal correlation using the difference minimization PRI correlator. The primary purpose of the filter is to minimize any DC signals before they reach the correlator. If DC signals reach the correlator, they correlate up at every PRI setting and on every temporal point, resulting in false detections and can block actual signals from detection. The filter also provides some gain for signals with pulse widths greater than one temporal cell. After conditioning with the filter, the data is correlated using a difference minimization correlator.
    Type: Grant
    Filed: November 17, 1997
    Date of Patent: October 5, 1999
    Assignee: Raytheon TI Systems, Inc.
    Inventors: Michael C. Schrick, Terry R. Altmayer
  • Patent number: 5943004
    Abstract: The invention relates to a method for realizing a radar transmission for a high-resolution radar. According to the method, a number of groups of pulses is transmitted with incremental frequencies, each group also comprising a number of pulses with incremental frequencies, which pulses are transmitted simultaneously or substantially simultaneously.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: August 24, 1999
    Assignee: Hollandse Signaalapparaten B.V.
    Inventors: Albert Groenenboom, Wietze Jan Hendrik Meijer
  • Patent number: 5907301
    Abstract: A procedure and a device for controlling, in a radar unit for the measurement of target data, the transmission of radar pulses and the reception of target echoes originating from the transmitted radar pulses, in such a way that the performance of the radar unit increases, in order thereby to gain a longer range during a period of time. The period of time is preferably repeated continually. The period of time is divided into a first and a second partial period of time where the first and the second partial periods of time are each at least twice as long as a pulse repetition interval which is used during the first partial period of time. During the first partial period of time the radar unit is controlled so that it transmits radar pulses for the measurement of target data with a higher energy content than what is possible in a steady state.
    Type: Grant
    Filed: January 16, 1998
    Date of Patent: May 25, 1999
    Assignee: Telefonaktiebolaget LM Ericsson
    Inventor: Bengt Andersson
  • Patent number: 5847677
    Abstract: A random number generator for generating a pseudo-random code for use with ittered pulse repetition interval radar systems has been disclosed in which the code generated by the random number generator possesses the five attributes desirable for a jittered radar PRI: a flat frequency spectrum, a nearly perfect spike for an autocorrelation function, a controllable absolute minimum and maximum interval, long sequences that do not repeat, and a reasonable average pulse rate. A method for analyzing the autocorrelation properties of the code generated by the random number generator is also disclosed. A means to generate a pulse signal with random pulse repetition jitter has been disclosed.
    Type: Grant
    Filed: July 7, 1997
    Date of Patent: December 8, 1998
    Assignee: The United States of America as represented by the Secretary of the Army
    Inventor: John W. McCorkle
  • Patent number: 5805110
    Abstract: A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna (10), so a background subtraction is not needed, simplifying the circuitry while improving performance. Techniques are used to reduce clutter in the receive signal, such as decoupling the receive (24) and transmit cavities (22) by placing a space between them, using conductive or radiative damping elements on the cavities, and using terminating plates on the sides of the openings.
    Type: Grant
    Filed: June 17, 1997
    Date of Patent: September 8, 1998
    Assignee: The Regents of the University of California
    Inventor: Thomas E. McEwan
  • Patent number: 5796364
    Abstract: A method of determining the velocity of a radar target wherein at least two different pulse repetition frequencies are used. Each pulse repetition frequency comprises a predetermined division into equidistant Doppler numbers. For an echo signal, a Doppler number associated with the echo signal is determined for each pulse repetition frequency. Out of two Doppler numbers associated with different pulse repetition frequencies, a nonambiguous Doppler number is subsequently determined which lies within a predetermined velocity nonambiguity range, and the velocity of the radar target is determined from this Doppler number.
    Type: Grant
    Filed: February 18, 1997
    Date of Patent: August 18, 1998
    Assignee: Daimler-Benz Aerospace AG
    Inventors: Norbert Fuchter, Franz-Xaver Hofele
  • Patent number: 5757320
    Abstract: A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna, so a background subtraction is not needed, simplifying the circuitry while improving performance. Uses of the invention include a replacement of ultrasound devices for fluid level sensing, automotive radar, such as cruise control and parking assistance, hidden object location, such as stud and rebar finding. Also, this technology can be used when positioned over a highway lane to collect vehicle count and speed data for traffic control.
    Type: Grant
    Filed: December 17, 1996
    Date of Patent: May 26, 1998
    Assignee: The Regents of the University of California
    Inventor: Thomas E. McEwan
  • Patent number: 5726657
    Abstract: A radar system in which a frequency agile synthesizer is used to provide rapid frequency shifts and in which measures are taken to maintain phase coherency. The system is fully coherent such that all signals are derived from a common source and are capable of high pulse repetition rates in excess of 1 MHz. There are no inherent transmit duty cycle restrictions and the system is able to transmit complex phase and frequency modulated waveforms. A frequency interleaving scheme is used to resolve range ambiguities at high pulse repetition frequencies and the use of a complementary phase coding scheme allows a high range resolution processing with the transmitted waveforms.
    Type: Grant
    Filed: March 22, 1996
    Date of Patent: March 10, 1998
    Assignee: Lockheed Martin Corporation
    Inventors: Albert N. Pergande, Daniel J. O'Donnell, Albert S. Sabin
  • Patent number: 5708437
    Abstract: A radar apparatus having a phased array antenna with a large number of transmit and receive modules, a control unit and a video processor. The control unit generates a number of pulse bursts per azimuth-elevation direction, all of which shows slight carrier frequency differences. The video processor determines a doppler spectrum and compared successive spectra for each pulse burst. As a result of the frequency differences, clutter does not show much of a shift while targets which are subject to fold-back in the frequency domain will show considerable shift. A threshold based on a mean spectrum therefore enables detection.
    Type: Grant
    Filed: March 7, 1996
    Date of Patent: January 13, 1998
    Assignee: Hollandse Signaalapparaten B.V.
    Inventor: Bernard Gellekink
  • Patent number: 5657022
    Abstract: Range-Doppler ambiguity is eliminated from an ultra-wideband radar system by transmitting an ultra-wideband chirped pulse towards a moving target, and mixing it with the doppler-shifted chirped pulse which is received as a target echo return signal. Multioctave radar tracing systems can potentiality track stealth aircraft without ambiguity since pulses containing many frequencies can defeat narrow-band radar absorbing material coatings. The unambiguous range-doppler signal processing method mixes the chirped pulse to yield an instantaneous Doppler frequency (which indicates target velocity) and a rate of change in the instantaneous Doppler frequency (which indicates target acceleration).
    Type: Grant
    Filed: November 17, 1992
    Date of Patent: August 12, 1997
    Assignee: The United States of America as represented by the Secretary of the Air Force
    Inventors: Paul Van Etten, Michael C. Wicks
  • Patent number: 5627545
    Abstract: The invention relates to a radar apparatus (1, 2, 3) provided with a doppler filterbank (4) and fast thresholds (5.i), for writing per pulse a range-doppler matrix in range-doppler memory (6) and the background level in background memory (7). By unfolding the range-doppler matrices and combining the unfolded range-doppler matrices for all the pulses in a burst in combination means (10), an incoherent combination of the pulses is obtained before an actual detection takes place. This cluster before detect scheme increases the detection probability for weak echoes, without increasing the false alarm rate.
    Type: Grant
    Filed: October 13, 1995
    Date of Patent: May 6, 1997
    Assignee: Hollandse Signaalapparaten B. V.
    Inventors: Pieter Van Genderen, Wietze J. H. Meijer
  • Patent number: 5598165
    Abstract: A method of controlling the transmission of a number of radio-frequency pulses having different frequencies in a radar device. The time interval between two consecutively transmitted pulses is determined by a pulse repetition frequency. The total number of radio-frequency pulses is distributed between at least two groups, each group comprising a number of pulses having different frequencies. Each group is repeatedly transmitted a number of times in succession. The time interval between two transmitted pulses having the same frequency in a group is determined by the number of pulses having different frequencies in the group.
    Type: Grant
    Filed: October 3, 1995
    Date of Patent: January 28, 1997
    Assignee: Telefonaktiebolaget LM Ericsson
    Inventors: H. P. Erik Winberg, S. Roland Jonsson
  • Patent number: 5543799
    Abstract: A cost-effective ultra-wideband radar system capable of locating nearby buried objects such as reinforcing steel rods, pipes, and other objects buried in concrete, soil, behind walls, or in the air. A sequence of ultra-wideband radar pulses are emitted without a carrier and the system detects deflected pulse energy caused by the transmitted pulse whenever encountering a change in the medium i.e. an air to metal change or concrete to metal change. This reflected energy is detected and visually displayed. The range gate delay is continuously varied, thus changing the distance from the unit to where the reflected energy would be potentially detected from the target. By continuously sweeping the "depth" of the scan, the operator need only move the unit in two dimensions across the surface to detect objects buried or hidden at varying depths interior to or behind the surface.
    Type: Grant
    Filed: September 2, 1994
    Date of Patent: August 6, 1996
    Assignee: Zircon Corporation
    Inventor: Charles E. Heger
  • Patent number: 5453932
    Abstract: An ultrasonic ranging device and method for positioning a working implement relative to a datum is disclosed. The ultrasonic ranging device is coupled to the implement and is capable of transmitting an ultrasonic ranging pulse toward the datum and further capable of detecting the occurrence of an echo of the ranging pulse. The ultrasonic ranging device periodically makes a ranging measurement by transmitting an ultrasonic pulse toward the datum and then detecting the occurrence of any echo within a time interval, and repeats this ranging step at a predetermined repetition rate. The ultrasonic ranging device also detects any spurious echoes by detecting the occurrence of an echo within the time interval following no transmission of an ultrasonic pulse. If a spurious echo is detected, then the predetermined repetition rate is changed so that the spurious echo will not interfere with a ranging interval.
    Type: Grant
    Filed: January 12, 1994
    Date of Patent: September 26, 1995
    Assignee: Advanced Grade Technology, Inc.
    Inventor: V. Joseph Brabec
  • Patent number: 5442359
    Abstract: A method and apparatus for resolving Doppler frequency shift ambiguities in pulse Doppler radar systems provides a radiated signal that is modulated with a periodic waveform having a plurality of pulses within a period, the interpulse intervals between pulses in the period being unequal. Radar target returns are autocorrelated for a plurality of lags, which may include the interpulse intervals and linear combinations thereof. The calculated arguments .theta..sub.Ci of the autocorrelation function are unwrapped by adding 2k.sub..pi., k=0, .+-.1, .+-.2, . . . , to the phase .theta..sub.C1 obtained for the shortest lag T.sub.1 and determining an integer m.sub.k2 from .vertline.(.theta..sub.C2 +2m.sub.k2 .pi.)-(T.sub.2 /T.sub.1).theta..sub.C1 .vertline. <.pi. and then setting .theta..sub.2 =.theta..sub.C2 +2m.sub.k2 .pi.. Phase angles .theta..sub.3, .theta..sub.4, . . . , .theta..sub.m are unwrapped in a similar manner, the integer m.sub.ki being determined from .vertline.(.theta..sub.Ci +2m.sub.ki .pi.)-(T.
    Type: Grant
    Filed: June 30, 1994
    Date of Patent: August 15, 1995
    Assignee: Unisys Corporation
    Inventor: William L. Rubin
  • Patent number: 5422646
    Abstract: An MTI radar based on a comparison of the Doppler shifts of the original signal and a phase-reversed signal using pulse compression wherein the received signal is phase detected for in-phase and quadrature components relative to the IF. A Doppler-corrected pulse compressor produces a magnitude signal for the Doppler shift of the received signal from the sequence of in-phase and quadrature components. Another Doppler-corrected pulse compressor produces a magnitude signal for the Doppler shift of the received signal from the conjugates of the sequence of in-phase and quadrature components. The magnitude signal of the same Doppler shift of the two compressors are compared and the difference is the output of the MTI.
    Type: Grant
    Filed: February 24, 1983
    Date of Patent: June 6, 1995
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Bernard L. Lewis
  • Patent number: 5347283
    Abstract: A radar transmitter in which a pseudo-random sequence of pulses are transmitted, each at a different frequency. Prior to the return of the first pulse, a receiver is retuned to the first transmit frequency, then the transmitter is retuned to the second transmit frequency and so on. The return pulses are integrated coherently across the sets at a each frequency to achieve the highest signal level. The pulses are integrated noncoherently within a set over all the frequencies transmitted to improve the signal-to-noise ratio.The technique of the present invention requires accurate knowledge of the range to the target. In a specific multi-line embodiment, the range calculation is provided by the centerline carrier frequency operating at a medium pulse repetition (prf) frequency. The retuning is then performed with the sidebands operating at a low prf.
    Type: Grant
    Filed: June 14, 1989
    Date of Patent: September 13, 1994
    Assignee: Hughes Aircraft Company
    Inventors: Howard J. Krizek, Gordon M. Johnsen
  • Patent number: 5150125
    Abstract: A pulse Doppler radar altimeter designed to resolve the ambiguous range problem associated with the use of a pulse repetition interval, which is less than the aircraft altitude, includes a radar transmitter configured to transmit first and second series of pulses where the first series has a pulse repetition interval slightly different from the pulse repetition interval of the second series. At a time when the first series is being transmitted, the receiver electronics including a range gate and a tracker searches for ground returns and positions the range gate in time coincidence with the detected ground return. Control then shifts so that the second series of pulses is transmitted and a determination is made whether overlap of the range gate with the ground return from the second series corresponds to the same altitude as when the first series was involved.
    Type: Grant
    Filed: December 24, 1990
    Date of Patent: September 22, 1992
    Assignee: Honeywell Inc.
    Inventor: James R. Hager
  • Patent number: 5150126
    Abstract: A transmitting and receiving part of a pulse Doppler radar, in which the transmitting oscillator, by frequency shifting, is at the same time used as a local (reception) oscillator, and the intermediate-frequency reference frequency is generated coherently with respect to the pulse repetition frequency. Since only one high-frequency oscillator is required, the quality of which does not have to meet very high requirements, a low-price pulse Doppler radar can be implemented.
    Type: Grant
    Filed: May 10, 1991
    Date of Patent: September 22, 1992
    Assignee: Dornier GmbH
    Inventors: Udo Knepper, Ralph Speck
  • Patent number: 5115243
    Abstract: A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected.
    Type: Grant
    Filed: April 16, 1991
    Date of Patent: May 19, 1992
    Assignee: General Electric Co.
    Inventors: Michael S. Perry, Jerome E. Freedman, John J. Gallagher
  • Patent number: 5115244
    Abstract: A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected.
    Type: Grant
    Filed: April 16, 1991
    Date of Patent: May 19, 1992
    Assignee: General Electric Company
    Inventors: Jerome E. Freedman, Michael S. Perry, John J. Gallagher
  • Patent number: 5057845
    Abstract: A radar apparatus which employs a pulse train containing an alternating sequence of first and second groups of pulses. The first group comprises a plurality of identical long pulses and the second group comprises a plurality of identical short pulses. The receiver has a single channel, the processing in which is successively adapted for the pulse returns of a group at any one time.
    Type: Grant
    Filed: October 18, 1990
    Date of Patent: October 15, 1991
    Assignee: Hollandse Signaalapparten, B.V.
    Inventor: Bernard Gellekink
  • Patent number: 5051749
    Abstract: A synthetic aperture radar assembly (1) locatable on a satellite (2) for radar imaging of a planet surface (3) in swaths, including means (8) for transmitting pulses (4) of electromagnetic radiation towards the planet surface (3) to be imaged, means (8) for receiving echoes of said pulses (4) returned by said planet surface (3), means for creating an image of a swath (5) of said planet surface (3) from said returned echoes and means for randomly varying the frequency of transmission of said pulses (4) to increase the width (11) of swath (5) imagable.
    Type: Grant
    Filed: March 8, 1990
    Date of Patent: September 24, 1991
    Assignee: British Aerospace Public Limited Company
    Inventor: Peter N. R. Stoyle
  • Patent number: 4973968
    Abstract: A radar system for determining first time around targets from multiple time around targets using two radar pulse trains of different pulse repetition intervals and thresholding means. Echos from pulses at each pulse repetition interval being compared to determine first time around targets from subsequent time around targets. The radar system uses thresholding levels to determine an echo and is less prone to problems of coincidence gate clashing with high duty cycles.
    Type: Grant
    Filed: February 22, 1989
    Date of Patent: November 27, 1990
    Assignee: Plessey Overseas Limited
    Inventor: David L. Hurd
  • Patent number: 4954830
    Abstract: A method is provided for calculating the unambiguous ranges of a radar target in a radar system employing multiple PRFs. The radar system provides digitized data items indicative of return signals in each of a plurality of range intervals for each PRF. A base PRF is selected and a range interval containing a target return signal is selected therefrom. This range interval is correlated with particular range intervals of the remining PRFs to find specific target return signals therefrom which satisfy a first predetermined relationship. This relationship generally provides that a target is identified if a preselected number of correlated range intervals of all PRFs have target return signals therein. If this relationship is satisfied, the target range is calculated from a range equation.
    Type: Grant
    Filed: September 14, 1979
    Date of Patent: September 4, 1990
    Assignee: Hughes Aircraft Company
    Inventors: Kapriel V. Krikorian, Robert A. Rosen, Frank K. Li
  • Patent number: 4924231
    Abstract: A device for removing ambiguities in the range and speed at the output of a Doppler-type radar in which all possible sets (p.sub.1, q.sub.1) and (p.sub.2, q.sub.2) corresponding to echoes at different repetition frequencies are stored in a first memory, p.sub.1 and p.sub.2 representing the number of the range quantum from which an echo signal is received and q.sub.1 and q.sub.2 the number of the filter at the output of which an echo signal is maximum. Pairs of signals are supplied in response to a first clock signal together with radar data in a second memory to two calculating circuits which carry out tests to determine of p.sub.1 and p.sub.2 and q.sub.1 and q.sub.2 respectively come from the same target and calculate the true target distance and true Doppler frequency. If both tests are positive the true distance and frequency are stored in a memory. If either is negative the first clock signal is produced to supply a new pair to the respective calculating circuits.
    Type: Grant
    Filed: October 31, 1988
    Date of Patent: May 8, 1990
    Assignee: Thomson-CSF
    Inventor: Michel Prenat