Abstract: A CW radar range measuring system having a transmitter adapted to transmit a continuous wave radar signal phase encoded in accordance with a code and a receiver adapted to receive a radar return from the transmitted radar signal. The receiver includes an analog to digital converter section for converting a sequence of samples of the radar return into a corresponding sequence of digital words. A digital correlator/integrator is fed by the digital words and the code for providing an indication of radar return energy as a function of range from the transmitter. A processor is fed by the digital correlator/integrator for determining, from the indicated energy, target range. The system includes a frequency spectrum analyzer for determining a frequency spectrum of the digital words and wherein the processor determines the target Doppler frequency from such determined frequency spectrum.

Abstract: A radar system capable of identifying discriminatively multiple reflected waves generated between the radar system and a target (6) to thereby identify discriminatively a first echo indicating a real image from a target (6). The system includes a range finding unit (8) for determining arithmetically distance (R) to the target (6), a distance data processing unit (9) for selecting from plural distance data as obtained a set of distance data indicating the distances which bear an integral multiple relation to one another, a detecting unit (10) for comparing reception amplitude levels (Pr) for individual distance data of data sets with a predetermined threshold level (S) to thereby detect a set of distance data having the reception amplitude levels (Pr) exceeding the threshold level (S), and an identifying unit (11) for identifying discriminatively the distance data based on the first echo from the distance data ascribable to the succeeding multiple reflected waves in the distance data set detected.

Abstract: An automotive radar incorporates a repetitive randomized equivalent LFM sequence of frequencies for improved immunity to jamming from other automotive radars. Each frequency in the sequence is of sufficient duration to travel round trip over the detection range of the radar. The Doppler shift in the received signal is estimated by performing a spectral analysis on similar frequency components of the received signal, and is then removed from the entire received signal. The received signal is then reordered so as to form an equivalent LFM received signal, and is compared with a similarly reordered image of the transmitted signal so as to estimate the range to the target. The randomization sequence, initial start frequency, or initial start time of the repetitive sequence are varied to minimize the effects of jamming by other radars, and this variation can be directionally dependent.

Abstract: A low cost, real time, remote sensor device for accurately measuring distance to an object with a resolution of 1 millimeter or better using phase information from either electromagnetic or acoustic energy. The device repetitiously transmits a swept frequency and decodes the resulting echo to produce a phase gate which is then converted to an accurate measurement of the range from each sweep. A method for measuring the time between two known phase points on a return signal is employed to determine the range measurement. Since the phase of the signal is used to determine range, the resolution is not dependent on bandwidth.

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: A distance measuring apparatus measures the time an emitted optical pulse requires to go and return the distance to a target before being received by using the emission time and the reception time of the optical pulse, and obtains the distance to the target from the measured time. A converter converts an optical pulse received by a photodetector into an electrical signal. A divider divides the electrical signal pulse into two signal pulses. A delay element delays only one signal pulse. Both the undelayed and delayed pulses are applied to a threshold generator. The threshold generator generates and holds the value of signal intensity at the intersection of waveforms of the two pulses as a threshold value of the received signal pulse. A comparator generates a digital signal pulse indicating the reception time from the received signal pulse by using the generated threshold value.

Abstract: Disclosed herein is a distance measuring apparatus comprising an irradiation unit for generating an electromagnetic wave, a receiving unit for receiving a reflected wave of the electromagnetic wave reflected by an object of measurement and generating a reception signal, and a propagation delay time measuring unit for measuring a propagation delay time by counting the number of pulses of a pulse train having a predetermined frequency. The propagation delay time is the time between the time that the irradiation unit irradiates the electromagnetic wave and the time that the reflected wave is received by the receiving unit.

Abstract: A radar apparatus provided with a transmitting unit, antenna unit and a receiver unit. The transmitting unit transmits pulses having a modulation for enabling pulse compression on reception. As an ECCM feature, the radar apparatus is further provided with a blanking circuit. The blanking circuit includes two filters, one filter being responsive to the first half of the transmitting pulse only and the other filter being responsive to the second half of the transmitting pulse only. Blanking occurs if both filters simultaneously produce an output.

Abstract: A CW radar range measuring system having a transmitter adapted to transmit a continuous wave radar signal phase encoded in accordance with a code and a receiver adapted to receive a radar return from the transmitted radar signal. The receiver includes an analog to digital converter section for converting a sequence of samples of the radar return into a corresponding sequence of digital words. A digital correlator/integrator is fed by the digital words and the code for providing an indication of radar return energy as a function of range from the transmitter. A processor is fed by the digital correlator/integrator for determining, from the indicated energy, target range. The system includes a frequency spectrum analyzer for determining a frequency spectrum of the digital words and wherein the processor determines the target Doppler frequency from such determined frequency spectrum.

Abstract: An iterative process to determine the wavelet function and combination of ales of the function which provides data where there is a large separability compared to the separability of the data set prior to processing. Wavelets are selected for inclusion in a library in accordance with predetermined criteria and then applied to a digitized signal by convolution to perform digital filtering. The convolution of each wavelet is performed for the number of times dictated by the coefficients of the wavelet for each of the input signal samples. Separability of the wavelet implemented digital filtration is calculated as a percentage for each wavelet. The separation data is stored in memory until the iterative process is applied to all wavelets. The separability data is then examined to identify the wavelet producing the greatest separation. The data separability is estimated using a likelihood ratio after the probability densities for each of two sets of profile data are estimated.

Abstract: A delay compensated Doppler radar altimeter which eliminates the relative delay curvature associated with the energy reflected by a scatterer located in the along-track direction of an aerial platform for which a most accurate estimation of scatterer elevation is desired. By Doppler shifting each return, the range indicated for each scatterer over its illumination history is equal to the minimum range x.sub.h experienced when the relative velocity between the aerial radar and the ground is effectively zero. Compensating each signal so that its entire along-track history can be used for elevation estimation leads to an advantage of more than 10 dB in gain improvement over existing systems, and less degradation from surface topography.

Abstract: A precision ranging radar system for use in parking and backup maneuvers by drivers of vehicles to avoid collisions. The radar system includes a noise code generator for generating a noise code, a data source for generating a data bit stream, and a local oscillator microwave source. A data mixing mechanism is coupled to the noise code generator and data source for embedding data derived from the data source into the noise code. Transmit and receive microwave antennas are provided. A transmit phase modulator is coupled to the data mixing mechanism, the local oscillator microwave source, and the transmit antenna. A receive phase modulator is coupled to the local oscillator microwave source, and a code delay unit is coupled to the noise code generator and the receive phase modulator. A downconverter mixer is coupled to the receive microwave antenna and to the receive phase modulator, and a baseband integrator and amplifier is coupled to the downconverter mixer for outputting data from the radar system.

Abstract: An improved circuit and method of making precise time of arrival measurements on optical pulse data of relatively varying widths. The invention provides an analog input pulse representing received optical pulse data, along with a delayed version of the analog input pulse. The time of delay is set such that the original analog pulse and the delayed analog pulse cross each other at a predetermined point. This cross-over consistently occurs at the same point on the signal independent of the size or shape of the analog pulse. Preferably, the cross-over occurs at approximately 70% of the analog pulse amplitude. The cross-over point between the original pulse and the delayed pulse triggers the generation of the leading edge of a time of arrival pulse.

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: A signal processor is described for object detection systems such as radar and sonar systems in which wave energy is transmitted and received as a train of discrete pulses of frequencies stepped in predetermined sequence. The received signal processor comprises a plurality of processing channels of number corresponding to the number of sub-pulses in the transmitted pulse train, each channel including frequency selective means such that signal returns of frequencies corresponding to but one of the transmitted sub-pulses are processed by that channel. Means are provided for simultaneously sampling the signal levels in all channels and indicating that channel in which the signal level is greatest, this sampling process being serially repeated at times related to each of the times of transmission of one sub-pulse of the train.

Abstract: A system for obtaining digitized samples of an analog signal at a selectable rate, R. The system includes: a timing generator for producing a train of sampling pulses at a predetermined sampling rate, f.sub.s ; an analog to digital converter for producing a digitized sample of the analog signal in response to each one of the sampling pulses; a processor; and, a selector, for passing each Nth one of the digitized samples produced by the analog to digital converter, where N=f.sub.s /R to the processor. The selector includes a decimator, responsive to a signal, N=f.sub.s /R, representative of the ratio of the sampling rate, f.sub.s, to the digitized signal obtaining rate, R, for producing pulses at the rate, R=f.sub.s /N; and, a register for storing each Nth one of the digitized samples produced by the analog to digital converter, each one of such digitized samples being stored in response to a corresponding one of the pulses produced by the decimator.

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: A method and apparatus for hybrid analog-digital pulse compression, as well as, a method of use and manufacture includes an analog intermediate frequency filter, a converter, and a digital correlator. The analog intermediate frequency filter filters and weights returned echo signals, and the digital correlator compresses the filtered and weighted echo signals. The frequency or impulse response of the digital correlator is set based on the frequency or impulse response of the analog intermediate frequency filter to obtain a pulse compressor with minimal mismatch loss and improved sidelobe suppression. The invention provides for the lowest possible sampling rate of analog-to-digital convertors used with the apparatus; thus, minimizing the cost of this device and all subsequent digital processing.

Abstract: An electronic vernier for a laser range finder enhances the resolution of the range finder to that of the vernier without increasing the frequency of the range clock. The range finder includes a range counter circuit for storing the total integer number of clock pulses produced by a range clock and counted by a range counter. The vernier includes a tapped delay line which subdivides the clock pulses into a predetermined plurality of equal increments. The contents of the tapped delay line at the time of transmission of the ranging pulse, and reception of the reflected ranging pulse identify the phase of the clock pulse. An electronic storage register of the vernier captures and stores the contents of the tapped delay line, and then transfers vernier transmission and reception fractions to a system controller for computing a corrected range measurement from the total integer number of clock pulses produced by the range clock and counted by the range counter.

Abstract: A system and method for determining the range between a receiver of a radio frequency signal and a transmitter of the signal includes transmission of a ranging signal having a grossly timed trigger followed by a chirp waveform. In response to receipt of the leading edge of the grossly timed trigger, the receiver of the ranging signal generates a first reference chirp at about the same time as the expected time of receipt of the chirp waveform, and thereafter compares the two chirps to provide a time correction signal (it being known that when two identical chirp signals, one time delayed from the other, are mixed, the resulting signal will have a frequency proportional to the amount of delay between the two chirp signals.) The time correction signal is used to correct the timing of an outgoing corrected chirp that is to be used to determine range between the transmitter and receiver based on a time of arrival.

Abstract: The present invention pertains to a radar range finder for high-precision, contactless range measurement, which is based on the FMCW principle and operates with digital signal processing at a limited frequency shift. One exemplary embodiment is described.

Abstract: An apparatus for measuring the transit time of electromagnetic waves operates with pulse frequencies (9, 10), conducted in a feedback loop (12) which are supplied after passing through a measurement path (13) or through a reference path (14) to a resonator (35). As a result of an 180.degree. phase-shift of the last pulse (10) of each pulse sequence (9, 10) the resonator oscillation collapses abruptly at a specific point in time. The directly preceding zero passage of the resonator oscillation defines the time of reception of the pulse sequence.

Abstract: A method and apparatus is disclosed for improved out-of-range rejection in pseudo-random noise (PN) coded systems by adjusting the relative phase difference between the two phase states of a bi-phase modulation. The energy in the spectral lines of the bi-phase modulated RF signal to generate a signal to be fedback to a voltage-controlled bi-phase modulator to adjust the relative phase difference between the two phase states. Sampled signals are mixed down to baseband using single sideband suppressed carrier modulation of the center frequency of the transmitted signal and the offset frequency. The offset frequency is chosen to be less than the PN code repetition frequency. The baseband signal is filtered and envelop detected producing a DC voltage proportional to the amplitude of the center line of the PN spectrum which is compared to either a fixed reference or to the amplitude of one or more of the remaining lines in the spectrum.

Abstract: A method and apparatus for identifying a remote target includes a transmitter for transmitting pulses of energy toward the target for generating echo signals, and a receiver for receiving the echo signals, and for generating received signals representing the target, noise and clutter. The received signals are applied through a plurality of cascaded channels, each including a Doppler filter cascaded with a multiplier, each also including range sidelobe suppression, for, in each of the cascaded channels, narrowband filtering the signals passing therethrough about a controllable center frequency, and for, if necessary, converting the signals passing therethrough to baseband, for thereby applying one of a plurality of Doppler filtered baseband signals to the input of each of the range sidelobe suppressors of each of the cascaded channels. The power of the Doppler filtered baseband signals in each range bin is evaluated for determining the frequency at which the spectral density is greatest.

Abstract: A phase modulated signal is split into quadrature components Savg+SaSin(.phi.(t)+kx(t)) and Cavg+CaCos((.phi.(t)+kx(t)). The average value for each signal is compared with the signal to produce a data bit whose meaning is that the average value was exceeded at a sampling instant. The bits at successive times (t.sub.0 and t.sub.1) are separated by an interval set by the Nyquist rate on the peak rate of change of the phase for the signal. Four bits at two sample times t.sub.0 and t.sub.1 are processed to determine the phase quadrants modulo 360 degrees to determine the direction of the phase change. The determination is used to produce a counter enable signal, counter direction control signal (up/down) and optionally an error signal if the phase change during one clock period is more than plus or minus one quadrant. A tracking counter counts the number of quadrants of change from those signals.

Abstract: An energy pulse capture system senses, receives, and processes signals reflected from a target. In an illustrative embodiment, light pulses are reflected off of a target, received by optical equipment, converted into analog electrical signals, and then processed to obtain information therefrom. The invention basically identifies targets by measuring the time delay between a transmitted signal and a received or "return" signal. The invention includes a windowing system to more efficiently process digitized electrical signals representing the return signals. The windowing system effectively defines a "window" in memory within which the return signal is stored, and "locks" on to this window to reduce time spent searching for the return pulses among other data. In another aspect of the invention, a real time return system is used to more efficiently process the electrical signals representing the return pulses.

Abstract: The present invention discloses a system and a method for transmitting data in a shield machine and for calculating the filling amount of a void by detecting the distance to the natural ground. The system and the method are capable of transmitting analogue signals or signals of relatively high frequencies with reliability, enabling an unskilled operator to accurately detect buried articles and accurately carry out the back-filling work. Therefore, an optical rotary joint (100) is disposed between a rotary cutter head (10) and a non-rotary shield body (2) to count time taken to detect the peak value of a reflected signal larger than a standard value or time taken to detect the zero cross position present prior to the peak value. In accordance with the counted time, the distance between the antenna and the natural ground is calculated and displayed. Then, the void volume is calculated in accordance with the distance so that a target value of the back-filling amount is set.

Abstract: A radar system (20) has a chaotic code source (22) with a chaotic code output (23), which generates a chaotic code according to a chaotic difference equation. The radar system (20) further includes a transmitter (24) with a carrier signal source (28) of a carrier signal (29), and an encoder (30) having as a first input the carrier signal (29) of the carrier signal source (28) and as a second input the chaotic code output (23) of the chaotic code source (22), and as an output a transmitted radar signal (36) having the chaotic code output (23) encoded onto the carrier signal (29). A radar system receiver (26) includes a correlator (46) having as a first input the chaotic code output (23) of the chaotic code source (22) and as a second input a received radar signal (44), and as an output an indication of the correlation of the first and second inputs. The correlation is used to determine the distance, speed, or other characteristic of an object that reflected the radar signal.

Abstract: A method and an apparatus for measuring the distance to a target according to the time-of-flight of laser pulses. The apparatus includes a transmitter of laser impulses toward the target and a receiver of laser impulses reflected from the target. A driver of the transmitter generates a first time signal corresponding to the transmission. The receiver generates a second time signal corresponding to the reception. A delay generator delays at least one of the first and second signals to compensate for time errors, and provides a third signal corresponding to the first signal and a fourth signal corresponding to the second signal, such that a time difference between the third and fourth signals is exactly equal to the time-of-flight of the transmitted pulses.

Abstract: A telemetric process for measuring short distances comprises emitting an electromagnetic signal modulated by a pseudo-random sequence having a number (n) of bits delivered at a clock frequency (fH), correlating the echo detected with the modulated signal time-delayed by known means, and varying the clock frequency, as a function of the correlation measurement, within an operational field divided into a plurality of operating ranges, the number of bits inthe pseudo-random sequence being modified accoridng to the operating range of the clock frequency. The process is particlualry useful for proximity measurement close to a reflecting surface.

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 sequenc of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time beacuse 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.

Abstract: The invention relates to time of flight telemetry and has application to detection and imaging systems. Determination takes place of a response time of an optoelectronic measuring chain or cascade (20, 34, 36) able to measure an outward and return time (flight time) of a first light pulse emitted in the direction of an object whose distance is to be determined. This response time, determined by means of a second light pulse emitted and then detected by the measuring chain or cascade, is subtracted from the previously determined outward and return time in order to obtain a corrected time used for calculating the sought distance.

Abstract: In order to improve the measuring accuracy in optical distance meters determining transit-time, the meters having optical senders emitting short pulses (11), optical receivers in which the reflected pulse received from the object to which the distance is being measured is converted to a corresponding electrical pulse (12), the signal received is repeatedly digitalized (13a, 13b, etc.) and these digital values are stored in a memory. Each of these stored values, is then fed from the memory one by one a predetermined number of times (14a, 14b, etc.) to a digital low-pass filter with deriving characteristic within its pass band. The number of computations of this filter before the output magnitude (15a, 15b, etc.) of the filter passes zero (16) constitutes a measurement (17) of the distance to the object being measured.

Abstract: A method of measuring a distance to an object includes generating first signal pulses to be bounced off the object and receiving the first signal pulses, after the first signal pulses have been bounced off the object, as second signal pulses. When the amplitude of the second signal pulses is above a predetermined value, the second signal pulses are differentiated and then supplied as differentiated second signal pulses to an input of an analog-to-digital converter. When the amplitude of the second signal pulses is not above the predetermined value, the second signal pulses are passed through to the input of the analog-to-digital converter unchanged. Signal pulses at the input to the analog-to-digital converter are converted into digital signals. The digital signals are summed over a period of time to generate a sum. The sum is used to determine the time delay between generating the first signal pulses and receiving the second signal pulses. The time delay is proportional to the distance to the object.

Abstract: A method of signal processing for use in high duty factor radars for detecting targets at ranges both shorter and longer than a minimum range defined by a transmitted pulse having a defined pulse length. A coded pulse coherent array waveform is transmitted and a return signal which is a waveform reflected off a target is received. The reflected waveform is sampled and time shifted by adding data to its beginning and end. The vector is then processed (pulse compressed) to obtain target information. Target information can now be obtained which is normally in a "blind zone", because the distance of the target from the radar is such that it appears during an interval when sampling is not done because of waveform transmission.

Abstract: The method consists mainly in re-creating, from an incoming radar recurrence (R, R'), a corrected recurrence (R.sub.c, R'.sub.c) that has the same characteristics (notably the same sampling frequency and number of samples) but with the samples re-positioned temporally to make the necessary range correction.

Abstract: A pulsed coherent radar altimeter is described which employs a narrow band receiver and utilizes a novel digital coherent pulse generator. A coherent pulse radar transmits a pulse comprised of the sum of at least two phase related RF signals closely spaced in frequency. The phase shift due to platform motion and return surface irregularity of the return signal is approximately the same for each carrier. The receiver produces a signal representative of the difference of the two carriers which is substantially free of decorrelation effects, and which can be processed in a narrow band receiver to produce range information.

Abstract: An electronic signal synchronization apparatus useful with radars and other electronic systems requiring synchronizing signals provides, for a range of N pulses, M sets of synchronizing signals which occur at M different range event pulse counts. The signal synchronization apparatus comprises a microprocessor and a synchronizer, the latter including a range pulse counter, a range memory, an event counter and an event memory. The range memory, preferably a RAM, is connected for outputting an event count enabling signal each time the range counter reaches an event pulse count. The event counter increments one count each time a count enabling signal is received from the range memory. At each event count, the event memory outputs the corresponding set of synchronizing signals. At the Nth range pulse count, the event memory provides an END OF RANGE signal which resets the range and event counters to thereby enable the counters to repeat the counting as many times as is necessary.

Abstract: The distance of a target object is determined from the time of travel of a measuring light pulse which is emitted by a transmitter toward the target object, reflected thereby and received by a receiver. In timed relation with the instant of generation of the measuring light pulse, a start signal for beginning a measuring signal transit time measurement is generated, and, on receipt of the reflected measuring light pulse, a stop signal is generated for terminating this time measurement. A completely independent reference light pulse is generated and forwarded along a reference light path establishing a predetermined time of travel from the transmitter to the receiver, and the respective reference signal transit time is measured which contains the same undesirable additional time spans contained in the measured transit time of the measuring signal.

Abstract: Apparatus for measuring the time delay between pulse signals, particularly in conjunction with electro-optical range finders. A coarse measurement counter counts the output of a reference oscillator, while a fine measurement interpolator determines the residual time at the start and finish of a measuring interval. Both residual times are successively determined by the same fine measurement interpolator. A delay circuit only supplies the pulse transmitter with the trigger signal when the interpolation for the start signal in the interpolator is ended. An adjustable series of test pulses is produces by a clock generator, in order to form the average value from such a series of measurements in a logic circuit. Preferably, the clock generator is synchronized with the reference oscillator, which ensures the formation of a mean value with a narrow range of errors.

Abstract: An apparatus for measuring the delay time interval between electrical pulse signals, particularly in conjunction with electrooptical range finders. A coarse measuring counter counts clock pulses from a quartz oscillator during the interval and a fine measuring interpolator determines the residual time from the end of the interval to the next clock pulse. Residual time at the start of the measuring interval is avoided by exactly synchronizating the start of measurement with a timing pulse front (n+2) of the quartz oscillator.