Abstract: A radar system is designed to allow switched use of a pulse radar mode for detecting a target at a long distance away and a phase-difference radar mode for detecting a target at a short distance away, whereby target detection can be performed from a very close range to a long range with high accuracy. Also, the pulse radar mode enables detection of a plurality of targets in different ranges.

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).

Abstract: An automatic noise threshold circuit and method automatically sets an operating threshold for a signal receiving section of a laser pulse transmitting device such that a constant noise pulse firing rate is output from a detector to provide maximum return signal sensitivity and enable detection of the weakest possible laser pulse in order to obtain maximum performance out of a laser range finder. The circuit sets the noise pulse rate at that point at which, in conjunction with a firmware based process, the actual return signals from the target can be discrimintated from the accompanying noise.

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 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: Disclosed is a distance measuring equipment comprising: a light emitting element for generating a pulse beam; and a light receiving element for receiving a reflected pulse beam from an object under measurement with respect to the pulse beam generated from the light emitting element and converting the reflected pulse beam into an electric light receiving signal.

Abstract: Discernible frequency characteristics regarding BPSK and CW signals are dved from consecutive transform outputs of a dual channel chirp-Z processor. Physically separated antennas direct the signals to the chirp-Z channels and concurrently occurring transforms are directed from those channels to a particular phase detector in accordance with the type of signal to which such transforms relate. The selection of phase detector is made through switches which are controlled by logic circuitry in accordance with the discernible frequency characteristics.

Abstract: A pulse compression control system uses a code sequence having a larger self correlation side lobe level compared with an ideal code sequence as a transmission code sequence and includes a modulating unit for modulating a pulse by the transmission code sequence in a first order modulation unit. The pulse is received in a demodulating unit where it is demodulated. A reception code sequence from the demodulation unit is modulated by a key code sequence in a second order modulation unit so as to convert it to the ideal code sequence. A self correlation processing unit processes the ideal code sequence for pulse compression.

Abstract: A radar system simultaneously transmits first and second signals toward a target at higher and lower carrier frequencies, respectively. Each carrier is phase-modulated by a set of pulses. The first set of pulses is dispersed in time, and the second set of pulses is mutually complementary thereto. The transmitted pulses are reflected by the target and received simultaneously. The received signals are processed separately by Doppler filtering. Each Doppler-filtered return is code-matched filtered, and the filtered signals in each Doppler channel are summed with the corresponding Doppler-and-code-matched-filtered signals originating from the other transmitted frequency, to form range signals. Each range signal has its main lobe enhanced and its sidelobes suppressed by the summing of the code-matched-filtered mutually complementary echoes.

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 radar generates first and second mutually complementary binary code sequences. The autocorrelation functions of the first and second pulse sequences are selected so that, in the sum of their autocorrelation functions, the main lobes add, and the sidelobes are of equal amplitude and opposite polarity, and therefore cancel. The radar sequentially transmits dispersed pulses in which the chips are phase modulated with the two codes. The received pulses are applied uncompressed to the input of a Doppler filter bank, which filters them into various Doppler channels, each representative of a particular radial velocity of the target. Within each channel, the received signals modulated by the first code are matched-filtered by a filter matched to the first code, to produce a first time-compressed pulse, and those modulated by the second code are matched-filtered by a filter matched to the second code, to produce a second time compressed pulse.

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.

Abstract: A radar system is disclosed which includes a transmitter which produces a long coded radar pulse. The return of the long coded radar pulse is compressed by a long pulse compression filter to produce a short coded pulse and the short coded pulse is compressed by a short pulse compression filter to produce a return pulse for processing by an existing processor designed to process return coded pulses of a particular format. The long pulse transmitter can also transmit a short coded precursor pulse, to improve radar range coverage, along with the long coded pulse by the provision of a switching bypass device which routes the short coded pulse return signal around the long pulse compression filter.

Abstract: A method and apparatus are disclosed for providing optimum radar beam patterns to provide complete radar coverage at both short ranges and long ranges in a radar system using solid state transmitters. Long pulses for covering long ranges are generated and split into a pair of signals with a specific amplitude and phase relationship. These signals are provided to a transmit beam forming matrix of an array antenna to generate an optimum pattern for long range coverage. Short pulses are generated for providing short range coverage and are split into a pair of signals which are phase shifted differently from the long pulses. These signals are then provided to the transmit beam forming matrix to generate a different beam pattern for providing short range detection. The short range beam pattern has a sufficient amount of energy to provide coverage to maximum desired altitude over a range extending to where echoes from the long pulses may be received undistorted.

Abstract: An apparatus for measuring the distance of a target includes a circuit arrangement of a transmitting circuit, a first receiving circuit, a second receiving circuit, a charging/discharging circuit, a switching gate, an analog-to-digital converter, a microprocessor, and a monitor. A modulated pulse signal is emitted by the transmitting circuit, and will be received by the first receiving circuit which makes the charging/discharging circuit start being charged. When the modulated pulse signal is reflected from a reflective object, it will be received by the second receiving circuit and the second receiving circuit will send a stop signal to terminate the charge to the capacitor of the charging/discharging circuit. By calculating the time period of the charging time under the control of switching gate, analog-to-digital converter, microprocessor, the distance of a target object is measured.

Abstract: A coherent pulse radar system capable of eliminating a signal associated with a multiple time around path or capable of removing range ambiguity of this multiple time around signal. The radar system includes a device for changing phases of transmitted pulses, for phase detecting received radar pulses with respect to transmitted pulses associated with the present and preceding reception period, and for integrating phase detected signals in a coherent manner.

Abstract: A method and apparatus exploiting the discovery that the crosscorrelation of constantly spaced rows of the matrices representing certain pulse codes sum to zero. In a ranging system, such as a radar, pulses are coded according to the rows of a such a matrix, transmitted sequentially and each return processed sequentially through a filter matched to one of the coded pulses. (A different preselected filter is used for each return.) The sequence of filters is chosen so that for returns for a given range interval, each filter is matched to the returning pulse, resulting in outputs from the filters representing auto-correlations of the returned pulses. These outputs are time delayed added coherently to form the compressed pulse, and annunciated as a target hit. Should the filters and returns be mismatched, as with ambiguous stationary clutter returns, the outputs of the filters are cross-correlations which, according to said discovery, sum to zero.

Abstract: Times t.sub.1 and t.sub.2 required for two electromagnetic waves having different wavelengths to propagate from a reference point to a target point are measured. Necessary meteorological conditions along the path are also measured to determine refractivities N.sub.1 and N.sub.2 of the path for the two electromagnetic waves as:N.sub.1 =.alpha..sub.1 .multidot..rho..sub.s +.beta..sub.1 .multidot..rho..sub.wN.sub.2 =.alpha..sub.2 .multidot..rho..sub.s +.beta..sub.2 .multidot..rho..sub.wwhere .rho..sub.s and .rho..sub.w are densities of dry air and water vapor in the path, respectively. Length of the path D is calculated using the following formula:D=[t.sub.1 +{(.alpha..sub.1 +.beta..sub.1 .multidot..rho..sub.w /.rho..sub.s).multidot.(t.sub.2 -t.sub.1)}/{(.alpha..sub.1 +.beta..sub.1 .multidot..rho..sub.w /.rho..sub.s)-(.alpha..sub.2 +.beta..sub.2 .multidot..rho..sub.w /.rho..sub.s)}].multidot.C.where C is the speed of an electromagnetic wave in vacuum.

Abstract: A radar apparatus transmits a pulse and receives a corresponding return within the duration of the transmitted pulse. The returned pulse and a proportion of the energy of the transmitted pulse are mixed in a mixer to produce a demodulated pulse of duration equal to the overlap in time of the transmitted and received pulses. In order to render the apparatus insensitive to close targets a video gate prevents the portion of the demodulated pulse corresponding to e.g. 0 to 1/4 full range passing to a processing circuit. The processing circuit forms the ratio of the amplitudes of two frequency components of the spectrum of the demodulated pulse as a measure of range (FIG. 3) or forms the mean amplitude of the demodulated pulse weighted according to a weighting function (FIG. 4).

Abstract: Certain man-made structures located in a complex background, such as railroad ties, telephone poles, and fences are detected by a flying craft, using a low powered structure resonant radar system. The radar system transmits a radar signal which includes wavelengths of the same order of magnitude as twice the spacing of the elements of the man-made structure or grating multiples thereof, and transmits them in a plurality of different directions and frequencies. Reflections of the transmitted radar are received and structural resonance backscatter is detected wherein the backscatter amplitude at the resonant frequency is much higher than that at adjacent frequencies or that of the clutter background, indicating the presence of the search-for type of structure. The bright structural resonance backscatter can then be exploted by the structure resonant radar for guidance, homing, etc.

Abstract: A method and apparatus for use in a pulse-echo imaging or ranging system comprising means (32) for identifying the analytic signal from a received signal and means (34) for extracting ranging information from the analytic signal. The analytic signal can be obtained and processed by digital or by analog circuit means. One embodiment of the analog circuit means (32) includes means (90) for modulating the received signal on a carrier frequency, means (92) for obtaining a single sideband signal from the modulated signal and means (94) for envelope detecting the single sideband signal.

Abstract: The present invention relates to a process for measuring the ambiguous distance in a pulse Doppler radar of repetition frequency (f.sub.R).The device comprises means (3) for transposing the signal received R(t) by a signal of frequency p.multidot.f.sub.R, where p is a positive integer; first and second narrow band filtering means (2,5) isolating the principal line of the signal received R(t) and of the transposed signal d(t) respectively, and means (6) for measuring the phase difference (.DELTA..phi.) which exists between the two filtered signals and which is proportional to the ambiguous distance with a coefficient g.

Abstract: A rectilinear waveguide junction apparatus in which the input and output guides are parallel to the longitudinal axis of the apparatus. This apparatus is characterized in that it takes the form of a parallelipiped guide the internal volume of which is divided up by metal partitions which form two parallel input guides, two parallel output guides and a main intermediate guide of same section as the parallelipiped guide. This apparatus is used in very high frequency circuits, for example the supply circuits for satellite or radar antennae.

Abstract: A radar apparatus for detecting a distance from a radar antenna (13) to a buried object (1) underground.The radar apparatus calculates the distance based on Maxwell's equation relating to speed of propagation of electromagnetic waves using received signals of two or more different frequencies in the receiver (5) which were transmitted from the antenna (13), and thereafter reflected from the buried object (1).

Abstract: A precision distance measuring equipment (DME/P) receiver for detecting an RF signal including at least one interrogation pulse is described. The DME/P receiver includes first and second signal processing channels. The first processing channel includes a wideband filter, of bandwidth BW1, for receiving the processed RF signal and in response thereto generating a wideband (FA) mode signal proportional to the logarithm thereof. The second signal processing channel includes a narrowband filter, of bandwidth BW2, for receiving the processed RF signal and in response thereto generating a narrowband (IA) mode signal proportional to the logarithm thereof, the bandwidth BW2 of the narrowband filter being within the bandwidth BW1 of the wideband filter.

Abstract: From a first aspect this invention provides a missing pulse detector for determining the true termination time of a sequence of pulses in a signal of an assumed predetermined length having a rising edge and a trailing edge which may include pulses which do not reach a predetermined threshold, the detector including a counter connected to count pulses exceeding said threshold, up to a predetermined number, an oscillator for producing pulses at twice the frequency of the pulses in the signal and an enabling circuit for allowing pulses from the oscillator to pass to the counter only after the termination of a sequence of threshold-exceeding pulses from the signal.

Abstract: A high PRF pulse doppler radar for tracking moving targets is described wherein the PRF of the transmitted signal is varied within predetermined PRF limits to keep the target reflected high PRF signal centered within the receive gate of the radar and wherein spurious signals incidentally generated by the action of the receive gate are reduced below the receiver noise level. In the event of temporary target reflected signal loss, the PRF of the transmitted signal is varied within predetermined PRF limits based upon the velocity and range estimate of the target to keep subsequent target reflected signals centered within the receive gate of the radar.

Abstract: Improved signal to clutter response in a radar is achieved by transmitting broad bandwidth frequency modulated noise pulses. Utilization of millisecond pulse intervals enables the radar video processor to average the independent samples present in each echo pulse so that each pulse represents an estimate of the true average return from the background. The bandwidth of the IF processing circuit is equal to the RF circuit and transmitted pulse bandwidths.

Abstract: A method and apparatus exploiting the discovery that the cross-correlation of rows of Frank or P4 matrices of a given spacing sum to zero. In a ranging system, such as a radar, pulses are coded according to the rows of a Frank or P4 matrix, transmitted sequentially and each return processed sequentially through a filter matched to one of the coded pulses. (A different preselected filter is used for each return.) The sequence of filters is chosen so that for returns for a given range interval, each filter is matched to the returning pulse, resulting in outputs from the filters representing auto-correlations of the returned pulses. These outputs are time delayed added coherently to form the compressed pulse, and annunciated as a target hit. Should the filters and returns be mismatched, as with ambiguous stationary clutter returns, the outputs of the filters are cross-correlations which, according to said discovery, sum to zero.