Abstract: A burst tone range processing system for determining the distance between a ranging station and a signal re-transmitting target device, generates a burst tone signal of finite duration and transmits the signal along a delay transmission path from the ranging station to the target and along a reference transmission path within the ranging station. The transmitted signals are received from the reference and delay paths and assigned time tags. The signals are then correlated and the time tags assigned to correlated signals are compared.

Abstract: A method for determination of positions of measurement objects from a number of measurements of the directions to the measurement objects made at separate points in time. During the initial measurements of the directions to the measurement objects, a number of assumed areas, within which the measurement objects are assumed to be located, are established along the direction to each measurement object. Subsequent measurements of the directions to the measurement objects are performed from at least two different measurement stations, which between the points in time are moved along different paths. In connection with the measurement of the directions to the measurement objects, the positions of the assumed areas are compared with the expected appearances of the measurement objects, and the assumed areas which exhibit the best correlation to the expected appearances of the corresponding measurement object are assumed to represent the positions of the measurement objects.

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 terrain height radar system and processing method comprising a high resolution synthetic aperture radar (SAR) mounted on an air vehicle and a SAR signal processor containing a signal processing algorithm or method for computing terrain height and radar backscatter power. The system contains motion sensing and navigation functions that also provide data to the signal processor to provide motion compensation. Signal processing algorithms in the method compensate for planar motion of the air vehicle for variations of terrain height in the field of view. The algorithms also compensate for nonplanar motion of the radar, and for scatterers in or very near to a reference plane in the field of view. The algorithms exploit defocusing due to displacement from the reference plane to estimate the terrain height above the reference plane. The algorithm is computationally efficient because the bulk of the radar signal processing is common to both the SAR function and the terrain height estimation function.

Abstract: A method of co-ordinate registration for Over-the-Horizon Radar comprising he steps of generating a geographic auto correlation function to determine one or more geographic beacons in a coverage area of the Over-the-Horizon Radar, the auto correlation function being in polar co-ordinates, comparing the return radar signal with the geographical map of the coverage area in the general region of the one or more geographic beacons and finding the best fit of the geographic map with return radar signal to enable registration of co-ordinates of the return radar signal. The auto correlation function indicates the amount of correlation between a neighbourhood and a slight displacement from that neighbourhood. A geographic beacon is an area in which there is a substantial difference between the neighbourhood and its surroundings thereby producing a low auto correlation function.

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 rotating antenna synthetic aperture radar apparatus having a module in the processor circuit in which are stored image definition values for reducing image errors. The module acts upon process circuits to subdivide the distance range illuminated by the antenna into individual distance intervals and to determine the reference functions in these distance intervals.

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.

Abstract: A random binary modulated sensor transmits a continuous wave r.f. signal ulated by a binary random bit pair code signal which is transmitted by an antenna. A return signal reflected from a target is received by the antenna. A receiver mixer modulates the return signal with the r.f. signal and a delay circuit delays the binary random bit pair code. A coorelator receives the modulated return signal and delayed binary random bit pair code for producing a doppler output signal. A separate r.f. path in which a portion of the modulated r.f. signal is variably attenuated and variably phase shifted is present to cancel noise signals generated by antenna mismatch in transmission.

Abstract: A method for allowing a correlation function to be applied to binary codes f length 3 to length 128. A user may specify the desired length of the binary codes for correlation processing; whether the binary code is to use a phase sidelobe level as the threshold or a sidelobe amplitude as the threshold. The user will also be asked to specify the threshold as well as an in phase coefficient referred to as alpha and an out of phase coefficient referred to as a beta. The user may also specify that the codes be expanded which results in correlated compounds having a length twice that of the specified length being displayed to the user. When the user has specified the parameters for correlation processing of the binary code length selected by the user, the program of the present invention will process the binary codes eliminating allomorphic and symmetrical forms of the codes from correlation and then display the results to the user.

Abstract: The invention provides a method of determining the range of a radar signal reflecting object by utilizing a radar frequency carrier wave modulated by a first short code having a first repetition rate and a second code having a bit rate equal to the first code repetition rate. A received echo is first passed to an analogue correlator for correlation against a delayed version of the first code, and the output of the analogue correlator is fed to a digital correlator for correlation therein against the second code. In this way, the high bandwidth (greater range resolution) of analogue correlation can be combined with the lower bandwidth (longer ambiguity function) of digital correlation to provide high resolution target detection without ambiguity and at a fast rate without the need for a very large number of correlators.

Abstract: The distance between the target and the measurement means is segmented into adjacent distance compartments, the first one of which starts at the zero distance. Each distance compartment has an associated energy level obtained by the demodulation of the delay measurement signal resulting from the product of correlation between the emitted signal and the received signal reflected by the target. The disclosed method consists in creating two distinct aliasings of the spectrum of the signal measurement signal, the energy level of which corresponds to the first distance compartment, these aliasings being achieved on the part of the spectrum corresponding to negative distances. This two distinct aliasings make it possible to obtain two distinct energy levels on the totality of the first distance compartment, and thus enable the measurement of all the distances on this first distance compartment, including the very small distances, even almost zero distances, by comparisons and analyses of the two energy levels.

Abstract: Disclosed is a method for the processing of a signal received directly or indirectly from a transmitter, sending out pulses that are digitally encoded according to a transmission code of N instants; said processing comprising notably an operation of filtering that is matched with the transmitted signal and an operation of detection by the comparison of the post-filtering level of the signal with a so-called detection threshold; wherein the signal received is subjected to two processing operations A and B, the processing operation A comprising a self-correlation and the processing operation B comprising an intercorrelation with a mismatched code having a length at least equal to 3N, the function of intercorrelation of this mismatched code with the transmission code giving a major central lobe and at least N side lobes that are zero on either side of this major lobe; and wherein it is decided that there is a detection relating to one of the instants of the correlation or of the intercorrelation only if the leve

Abstract: A system which utilizes a digital correlator to determine the time of arrival of a received pseudonoise sequence. At the same time, the incoming pseudonoise sequence is quantized to higher resolution and passed through a digital delay line with a total delay of slightly greater than the duration of the pseudonoise sequence itself. From the time of arrival measurement, a clock strobe timing is established to do active correlation on the delayed received sequence as it emerges from the delay line. The results of the active correlation are accumulated and/or added to obtain the amplitude of the received signal.

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: An electromagnetic signal having originally the time variation of a rectangular pulse is radiated into a lossy medium with conductivity .sigma.. It is distorted by the medium to the distorted electromagnetic pulse f(.sigma.,y,t) when it travels the distance y/2, in time t/2, from a transmitter to a scattering or reflecting target and the same distance y/2, in time t/2, back to the receiver. The time variation f(.sigma.,y,t) of the distorted pulse can be calculated for any conductivity .sigma. and distance y using the conductivity .sigma. known from previous measurements to determine the range to the target distorted pulse f(.sigma.,y,t). Consequently, distorted pulses f(.sigma.,y.sub.n,t) can be computed and compared to the received distorted pulse f(.sigma.,y,t). The computed pulse f(.sigma.,y.sub.n, t) that is most similar to the received pulse f(.sigma.,y,t) determines the distance y.sub.n /2 to the scattering or reflecting object, which is the range to the target.

Abstract: An electromagnetic signal having originally the time variation of a rectangular pulse is transmitted into a medium with conductivity .sigma.. It is distorted by the medium to a signal f(.sigma.,d,t) if it traveled the distance d from a transmitter to a scattering or reflecting object and the same distance d back to the transmitter. The time variation f(.sigma.,d,t) of the distorted signal can be calculated for any conductivity .sigma. and distance d. Using the conductivity .sigma. known from previous measurements, the returned, distorted signal f(t) is compared with computed distorted signals f(.sigma.,d,t) for various distances d. The computed signal f(.sigma.,d,t) that is most similar to the actually received signal f(t) determines the distance d to the scattering or reflecting object. The comparison between the computed, distorted signals and the actually received signal is done by cross-correlations.

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: Disclosed is an in-furnace slag level measuring apparatus having a microwave radar for measuring a slag level in a convertor or the like. The level of a transmission signal or a reception signal is adjusted in accordance with the level of a detection signal so that the signal level in the microwave radar is adjusted to be constant. Further, the level measurement value and the detection signal are inputted and the level measurement values obtained in a predetermined time are subjected to averaging operation. In the averaging operation, when the detection signal is smaller than a set point, the averaging operation is performed while disregarding the level measurement value at that time.

Abstract: A radar system comprises a transmitter which essentially continuously transmits a modulated carrier wave signal and a receiver for receiving the carrier wave signal reflected at an object (echo signal). The carrier wave signal is modulated with a code-generating signal whose code frequency is determined for the range resolution of the radar. The code-generating signal is such that one bit in the code has a duration which is several times longer than the period of the carrier wave signal and several bits of the code form a block which is obtained by modulation of a carrier wave with constant frequency. The frequency of the carrier wave is changed between blocks so that the transmitter sends a block with a carrier wave frequency which is different from the carrier wave frequency or frequencies which the receiver is set up to receive. The receiver stores the transmitted code and correlates it with the received signal.

Abstract: An optimization method for sidelobe suppression filters, and a filter utilizing a binary coding waveform are formulated. The method comprises expanding the frequency transfer function of an ideal sidelobe suppression filter into a polynomial series; truncating the polynomial series into a finite-termed polynomial series with unknown weighting coefficients A,B,C,D . . . , using the inverse Fourier transform to convert the finite-termed polynomial series into the corresponding pulse response in the time domain; then using the LP algorithm to minimize the output peak sidelobes to determine all the weighting coefficients A, B, C, D . . . and inserting them back to the inverse transfer function of the optimized filter.

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: A pulse radar apparatus is provided with a transmitting unit (4) for the transmission of a modulated transmitter pulse Y.sub.t, a mixer (9), an IF amplifier (11) and a quadrature detector (12) for the reception of signals Y.sub.r and the correlation of signals Y.sub.r with a replica X of the emitted modulated transmitter pulse Y.sub.t, to obtain an in time compressed correlation signal .sigma..sub.xy (.delta.). The pulse radar apparatus is also provided with a pulse discriminator (3) to enable, on the basis of at least one amplitude .vertline.Y.sub.r .vertline. of the received signal Y.sub.r and at least one amplitude .vertline..sigma..sub.xy (.delta.).vertline. of the correlation signal .sigma..sub.xy (.delta.), differentiation between the signals Y.sub.r, possessing modulation, and interference.

Abstract: Briefly, the range limiting system of the invention is capable of differentiating desired received signals having an amplitude above a predetermined threshold level and at least one other recognizable predetermined characteristic, from other received signals below that predetermined threshold amplitude. The system has a means for combining the received signal, which is of unknown amplitude which may be above or below the predetermined threshold amplitude, with a known signal of the predetermined threshold amplitude having at least one other predetermined characteristic which is distinguishable from the other recognizable characteristic of the received signal. The output of the combining means passes to a signal processing means which produces an output signal whose other recognizable characteristic is determined by the received signal only when the received signal is above the predetermined threshold amplitude, and by the known signal when the received signal is below the predetermined threshold amplitude.

Abstract: A digital range correlator is disclosed which provides a correlation scheme which can be mechanized and produced repeatedly with minimal need for offsets and reduced power supply sensitivity. CCDs are eliminated and the need for channel-to-channel matching is obviated. The digital correlator of the present invention includes an analog-to-digital converter for converting an input analog signal into a digital signal to provide a plurality of digital words one corresponding to each range gate. An accumulator is provided for summing the bits of each digital word to provide an accumulated sum for each range gate. The digital sums are compared in a processor to identify the range gate of the target. In a specific embodiment, the invention allows for the incorporation of a correlation code.

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.

Abstract: Post detection processing for a pulse doppler surveillance radar is disclosed wherein target reports having ambiguous ranges along with those containing unambiguous ranges are used for tracking targets. The tracking includes a maneuver recognition mechanism for adaptively weighting the range, range rate, and X and Y coordinate driving errors as a function of the maneuvering and non-maneuvering operations of the target.

Abstract: A method and device are provided for measuring the propagation time of a wave, wherein a wave is transmitted modulated in amplitude by a modulation signal. The wave reflected by an obstacle is received after a propagation time and the amplitude thereof is detected. The average value of the product of the detected signal and a reference signal is calculated and the delay with respect to the modulation signal is controlled so as to cancel out the average value. The modulation signal and the reference signal comprise a succession of elementary signals chosen so as to allow, in a single measurement, a long propagation time to be determined without ambiguity and with high accuracy.

Abstract: This device comprises a high-frequency signal generator (5) fitted with a modulation control input (10) to supply said pulses at its output in relation to a modulation signal applied to its modulation input and a modulation generator (15) to provide the modulation input with the modulation signal. This device also includes a replica circuit (18) to supply a replica of the pulse transmitted, a management circuit (25) to compare this replica wtih said pattern and to alter the modulation signal from the modulation generator so that the pattern complies with the replica.

Abstract: Stable measurement of terrain-height variations is provided by this radar system which employs a very low power spread spectrum transmitted signal which, after reception, is processed digitally for extremely stable and predictable performance. The system also includes an automatic power control circuit to maintain the transmitted power at the minimum required level.

Abstract: A circuit is provided for correlating both the phase and amplitude of received radar signals with the phase of a transmitted binary reference phase code, which enables implementation by off-the-shelf hardware. The received signal is demodulated and quadrature detected, and each segment of small duration of the received signal is converted to a three-bit data code word, with each data word defining both the phase and the amplitude of the demodulated received signal. Each bit of the same significance (e.g., most significant bit or least significant bit) of a series of data words is delivered to a different one of a group of one-bit correlators. Each correlator correlates the series of bits of the same significance from a sequence of data words, with the bits of the binary reference phase code. The outputs of the correlators whose bits represent the amplitude of the received signal, are multiplied according to the significance or position of the bit, and the products are added.

Abstract: Sets of group-complementary code arrays which have the property of being ually orthogonal over a subinterval of their total cross-correlation function have been identified. These group-orthogonal arrays are generated by a multiplication operation upon a given group-complementary array using a matrix which has diagonal elements from vectors which are orthogonal. Composite code arrays are synthesized by interleaving rows from the group-orthogonal set of arrays, and applying the resulting rows of codes to bi-phase modulate pulses in bursts. The resulting composite waveform has the desirable property of temporal (zero-Doppler) sidelobe cancellation in the maximum unambiguous range interval and response cancellation over one or more multiple-time-around range intervals of an equivalent uncoded pulse sequence.

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.