Abstract: A system for detecting a predictable time varying signal within a noisy environment. Rather than merely comparing the output of a matched filter implementation to a threshold, a parallel reference is also generated by autocorrelating the weighting function from the matched filter. The original output and this reference are both acted upon by a mathematical operator and the two then compared for closeness of fit using a Chi-Square Goodness of Fit Test, a Mean Square Error Test, or some other test for closeness of fit. A value indicates the closeness of the two curves and is then compared to a threshold to determine whether the signal of interest is present or not.

Abstract: Individual objects are located according to a coordinate system in time-successive patterns and correlated between patterns. The objects are correlated by assigning identifiers to each in both patterns. The locations are transformed by reorientation to their centroid. The average of the transformed coordinate differences is used to adjust the centroid of the objects in a subsequent pattern and the transformed coordinate differences adjusted for the centroid displacement. A figure of merit is taken as the root-mean-square of the adjusted differences and used to determine which possible combination of correlated objects between two patterns is most likely.

Abstract: A method of detecting, by means of a SAR radar, objects that change with time within a ground area. The SAR radar is supported by a platform in essentially rectilinear motion during a synthetic aperture and the ground area is reproduced at least twice in succession from different synthetic apertures. A two-dimensional SAR image is generated from each synthetic aperture. The SAR images are matched with each other by a method in which each image position in one image is associated with the same ground area in the other image, the images being filtered, knowing location data for the antennae and based on the fact that the cylinder geometry of the SAR images is projected onto the ground surface, so that only common spectral components of the reflectivity of the ground are extracted and used in the matching.

Abstract: In a method for operating a rotating synthetic aperture radar system that works with pulse frequency or in FM-CW operation in order to detect, penetrate and evaluate objects that are located vertically below the helicopter carrying the ROSAR device, pixels are determined using their own specific doppler histories.

Abstract: A ROSAR wire detection method is based upon ROSAR focusing of entire segments of wire. By generating a wire reference signal comprised of a sum of coherent reference signals, the basis for reliable wire detectability is provided.

Abstract: A method for estimation of Doppler spectrum, its moments, and polarimetric variables on pulsed weather radars which uses over sampled echo components at a rate several times larger than the reciprocal of transmitted pulse length. The variables are estimated by suitably combining weighted averages of the over sampled signals in range with usual processing of samples at a fixed range location. The invention may be Used on pulsed weather radar, lidars, sonars and accoustic flow meters.

Abstract: Individual objects are located according to a coordinate system in time-successive patterns and correlated between patterns. The objects are correlated by assigning identifiers to each in both patterns. The locations are transformed by reorientation to their centroid. The average of the transformed coordinate differences is used to adjust the centroid of the objects in a subsequent pattern and the transformed coordinate differences adjusted for the centroid displacement. A figure of merit is taken as the root-mean-square of the adjusted differences and used to determine which possible combination of correlated objects between two patterns is most likely.

Abstract: A Doppler-based radar system and related method are provided for determining the direction and speed of at least one selected target traveling in the same lane as a moving patrol vehicle supporting the radar system independent of the direction of the target relative to the platform. The radar system includes an oscillator to generate a signal, an antenna to transmit the signal toward the at least one target and to receive a return signal reflected from the at least one target, a turnstile in communication with the antenna for receiving the return signal and forming processing signals which are different in phase, and circuitry for determining the direction of the at least one target relative to the platform. In particular, samples of the processing signals are transformed into the frequency domain and cross-correlated forming cross-correlation components.

Abstract: A multifrequency phase-coded signal structure is presented for use in a system like a radar or sonar or detecting a remote target. The signal structure comprises at least one pulse signal in the form of a mutually complementary set of M sequences, each sequence being composed of M phase-modulated bits. Each two adjacent sequences are modulated on subcarriers separated by a frequency fs such that fs=1/tb, tb being a bit duration, and a the subcarriers are transmitted simultaneously.

Abstract: A target recognition system and method wherein only target amplitude data, i.e., coherent A-scan data, is interrogated for target recognition. Target aspect angle is ignored within the angular segmentation of the feature library without degrading classification performance. Observed signature characteristics are collected at various aspect angles and through unknown and arbitrary roll, pitch and yaw motions of each anticipated target and provided to a neural network as training sets. The neural network forms feature vectors for each target class which are useful for valid classification comparisons in all sea states, especially in calm and littoral waters. These feature vectors are useful for valid classification comparisons over at least 30 degrees of target aspect angle.

Abstract: The positions of moving targets in the azimuthal direction which result from the SAR processing are falsified by components of the vehicle movement in the Doppler spectrum of the received signal, so that without the implementation of additional signal processing, moving targets are imaged in the SAR image at a false azimuth position. A method of repositioning moving targets in SAR images which consist of multi-channel range/Doppler measurement data X with NND Doppler resolution cells, defines on the basis of the filtering coefficients of the STAP transformed into the frequency domain, a family of NDZ pattern functions M, and determines testing functions T assigned to the measurement data. The true azimuth position of a moving target is then computed on the basis of the position of the maximum of the correlation between the testing functions and the pattern functions.

Abstract: To suppress interfering stationary targets in radar source data, a STAP filtering method is used. Filtering coefficients are determined, and filtering of the data takes place, in the frequency domain; the process is therefore limited to a few computing operations per matrix element of the range/Doppler matrix. Since, by means of the STAP filter according to the invention, the optimal filtering characteristics can be implemented, the stationary target suppression also functions in the range of the minor lobes of the antenna.

Abstract: This invention features an improved technique for search and track surveillance. In this invention, distinct and random (in both space and time) signal beams are simultaneous transmitted from an array of transmitter source elements in a manner to cover all sectors about a source location. In addition, countermeasures against a system according to the invention are difficult because the signal waveforms for each beam are distinct and random, making prediction of any signal waveform for any beam very unlikely. An array of receiver sensor elements is provided to receive signals that are scattered from remote objects and may or may not be co-located with and share the elements of the source array element. The scattered signals are received and processed to yield the direction and range of the remote objects.

Abstract: An obstacle detection includes a transmission leakage transmission path, a receiving leakage transmission path opposite to the transmission leakage transmission path, a spread spectrum signal generation means connected to an end of the transmission leakage transmission path and generating a spread spectrum signal for detection of an obstacle for radiation from the transmission leakage transmission path. A correlation means is connected to an end of the receiving leakage transmission path so as to calculate a level of correlation between a reference spread spectrum signal and a spread spectrum signal received by the receiving leakage transmission path. A detecting means detects an obstacle in accordance with a change in the level of correlation calculated by the correlation means.

Abstract: A method and a system for detecting and ranging objects utilize summed and difference signals to determine whether a target is present at a predetermined distance from the system. The summed and difference signals represent corresponding points on two discriminator functions that are derived by summing and subtracting two autocorrelation functions. The two autocorrelation functions are identical functions, except that one has been shifted by a one-bit period. By analyzing the summed and difference signals, the system is able to detect objects that cross a boundary zone located at the predetermined distance from the system. In the preferred embodiment, an optical signal is transmitted by a transmitter of the system to detect a target. Preferably, the optical signal is modulated in accordance with a double concatenated eleventh order Barker-based code. The optical signal is received by an associated photodiode after being reflected by the target.

Abstract: A radar system (10) which transmits a random noise signal. The transmitted signal is embodied as an electromagnetic signal and is directed at an object or target. The object or target reflects at least a portion of the electromagnetic signal which is returned to the radar system. An image of the electromagnetic random noise signal is stored in memory (16) and compared with the returned modulated signal. Based on the correlation value, a determination is made regarding the object or target. In a particular implementation, the radar system is used in a target detection device (TDD) (10) in order to determine the distance from the target or object to the device and the relative velocity of the target or object and the device. When the target or object reaches a predetermined distance and also satisfies any other system requirements, the TDD (10) initiates a detonation signal which causes detonation of the missile or warhead.

Abstract: The present invention is in general related to target type estimation in target tracking systems. The invention enables a low complexity estimation of target type, using, e.g. ESM sensor data, by the introduction of an ambiguity restoring procedure in certain likelihood calculations. The invention further enables the systematic use of target type probability information in the calculation of strobe track crosses and their associated quality which is particularly useful for deghosting purposes. Methods for utilisation of target type probability information in the processes of strobe tracking, association, track quality evaluation and multiple hypothesis tracking are also disclosed.

Abstract: A system and method tests the frequency response of a linear time-invariant unit-under-test, such as an antenna. A test signal is generated at a selected frequency and modulated with a spread spectrum input excitation signal to produce a broadband test signal that is substantially wider than the bandwidth of a device-under-test. The test signal is transmitted from one of either the unit-under-test or test device to a responsive test device or unit-under-test. The test signal is demodulated by mixing an input excitation signal that is delayed and increased in steps, such that the difference in time generates an estimate of the impulse response of the unit-under-test. The test signal is correlated and integrated to filter out unwanted interference and reflections.

Abstract: The present invention relates to a method of detecting and classifying objects using radar. The method means that a broadband radar signal comprising wavelengths that coincide with characteristic lengths of targets to be detected and classified is transmitted. Further, a returned echo signal is received and analysed, at which a signal analysis in a combined time-frequency domain is used, which comprises determining characteristic frequencies in the signal return and their mutual time relations. Finally, a comparison with the corresponding stored values of an analysis of possible targets is performed.

Abstract: In a radar system having a transmitter that produces pulses to be radiated by an antenna and a receiver that detects target information, complex demodulation is performed on an attenuated and limited waveform of the transmitter produced pulse. A matched filter is generated responsive to the complex demodulated waveform that is a time reversed conjugate image of the waveform corresponding to the produced pulse. Complex demodulation is performed on the return signal received by the receiver corresponding the produced pulse and the complex demodulated return signal is correlated with the matched filter that corresponds to the time reversed conjugate image of the waveform of the produced pulse.

Abstract: A reference-based autofocusing procedure is particularly suited to existing and future interferometric SAR systems, though the principles are generally applicable to signal processing systems for which there are two partially correlated data sets having relative spectral errors. In an airborne or spaceborne system, the technique only requires some additional steps in the ground processor functions. The invention takes advantage of the fact that in a bistatic system, one antenna phase center both transmits and receives with the usual common-mode cancellation, and can thus be expected to form a reasonably well-focused image. In the second system, with the degraded phase error response, the image provided by the first system is used as a coherent reference to aid the estimation and removal of the relative phase errors between the two.

Abstract: A method of determining the ability of a medium to absorb electromagnetic waves including placing antenna unit (10) having spaced transmitting and receiving antennas (2 and 3) on a limiting surface of a medium (13), emitting, with the transmitting antenna (2), a radar wave into the medium (13) which is detected as a cross-signal by the receiving antenna (3), pre-processing and digitalizing the cross-signal, and, thereafter, analyzing the cross-signal with an algorithm for determining the ability of the medium to absorb electromagnetic waves and, thereby, a type of the medium; and an electromagnetic sensor the operation of which is based on the method.

Abstract: A pseudo-noise-modulated spread spectrum is irradiated undirectedly--or, encoded by different modulation, into mutually displaced spatial sectors--and the energy (20) received after reflection at a potential target (13) is cross-correlated, using the pseudo-noise code which is predetermined at the transmission end, in order to provide a spherical monitoring effect which is continuous but which cannot be located in respect of its origin, to provide a warning in particular for marine craft, land vehicles and aircraft against an attacking guided missile as the target (13) to be repelled, and in order to be able to transfer to a target tracker (12) distance and speed information obtained from the correlation product, with the alarm signal, if the alarm sensor (11) is not itself also used as the tracking sensor.

Abstract: A global positioning system (GPS) ocean scatterometer with an adaptable spatial resolution for sensing and processing GPS signals reflected from an ocean surface for wind measurements in a wide range of altitudes and wind velocities. To increase wind sensitivity at low altitudes, the GPS ocean scatterometer employs a sub-chip GPS receiver which includes, inter alia, a signal correlator and a pair of code correlators for generating a sub-chip footprint to boost system resolution. To increase wind sensitivity at high altitudes, the GPS ocean scatterometer employs a multi-chip GPS receiver which includes, inter alia, a wide-band oscillator and a multi-chip generator for generating a multi-chip footprint to boost scattered energy.

Abstract: In a continuous wave Doppler system in which a fixed transmitter transmits a continuous wave signal to be reflected by moving targets and by fixed structure, an aircraft receives the reflective signals at two spaced apart antennas. The signals reflected from moving targets are distinguished from ground clutter reflected from fixed structure by the phase difference between the Doppler signals receive by the two antennas. The signals reflected from moving targets are distinguished from the ground clutter in response to the phase difference between the Doppler signals received by the two antennas being not equal to a phase difference value determined to be the phase difference for clutter signals. The phase difference value for clutter signals is determined from a function expressing the phase difference value as a linear variation with the Doppler frequency of the signals.

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.

Abstract: The invention relates to methods which make it possible to measure the Doppler shift of the echoes of a detection system. That is, the present invention modulates the frequency of the pulses of the transmissions of this system by a pseudohyperbolic function such that a restricted number of copies of the transmission signal can be used to perform the correlation operations on reception and to have them followed by an interpolation operation.

Abstract: An apparatus and computer-implemented method of determining a probability that a first track and a second track represent the same physical object.

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.

Abstract: An along-track interferometric SAR (Synthetic Aperture Radar) of the present invention includes a single SAR line and observes a target only once. SAR data derived from a single observation are subjected to look division in order to reproduce two SAR images deviated in time from each other. Interference processing is executed with the two SAR images in order to determine a phase difference. The phase difference is converted to the velocity of the target. This can be done without resorting to any additional hardware.

Abstract: A local region image tracking apparatus continuously tracks an arbitrary local region within a search image that is described by search image data by comparing the search image data to be subjected to a tracking process out of input image data picked up by image pickup means with reference image data related to the arbitrary local region. The local region image tracking apparatus includes an image data bus transferring the input image data from the image pickup means, and a plurality of correlation tracking processors coupled in parallel to the image data bus and respectively capable of independently carrying out the tracking process with respect to at least one search image, where the tracking process with respect to one or a plurality of search images is distributively carried out by the correlation tracking processors.

Abstract: A method and apparatus for preventing the occurrence of range ambiguities and Doppler ambiguities in both a radar and sonar environment. A series of N pulses are produced, each of which contains a number of contagious subpulses. Each of the subpulses exhibit a different frequency than the remaining subpulses in that particular pulse. Furthermore, the order of appearance of the subpulses in each of the pulses is unique with respect to the remaining pulses in the series. A matched filter receiver and Doppler processor are used to provide auto correlations and cross correlations to prevent the range ambiguities and Doppler ambiguities.

Abstract: A radio range finding system includes a radio range finder and a plurality of remote mobile transponders. The radio range finder transmits a signal modulated with an address code identifying a particular mobile transponder. When a mobile transponder receives the modulated signal M.sub.s transmitted by the radio range finder and the modulated signal has been modulated with an address code that corresponds to the address assigned to that mobile transponder, the mobile transponder transponds a return signal R.sub.s to the radio range finder. A receiver in the radio range finder conveys the received signal to a mixer which also receives an internal carrier signal identical to the modulated signal output by transmitter. The output of the mixer is then filtered and demodulated to yield an output signal proportional to the distance between the mobile transponder and the radio range finder.

Abstract: For less expensive estimation the impulse response x.sub.MOS of a high-resolution, band-limited radar channel in a radar station operating with an expanded transmitted pulse a(t), from a received signal e, over which a correlated or uncorrelated additive interference signal n can be superimposed, with the use of knowledge about the spread code c and the use of a channel estimator with which a so-called linear, optimum unbiased estimation of the radar channel impulse response x.sub.MOS is performed in a time range covering M range gates of interest, the linear, optimum estimation in the unbiased channel estimator is modified in such a way that the pulse response x.sub.MOS of the band-limited radar channel is determined according to the basic principle of a multiplication of the sampled received signal e and an inverse estimation matrix A.sub.E.sup.-1. The matrix A.sub.E is formed by the extension of the rectangular matrix represented by the components c.sub.

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 system (10) for reducing range sidelobes adapted for use with pulsed radar systems. The inventive system (10) includes a mismatched filter (90) for correlating a received signal (84) with a correlator signal (92) having a different length than the transmit signal (84) and for providing a predetermined number of reduced range sidelobes (97) at the output of the mismatched filter (90). The mismatched filter (90) has a first locally optimum sequence that is the correlator signal (92). The mismatched filter (90) has an input device (86) for receiving an extended locally optimum sequence (84) that is a received signal (84). The first locally optimum sequence (92) is a sub-sequence of the extended locally optimum sequence (84). In a specific embodiment the mismatched filter (90) has a Barker-based code that is the correlator signal (92). The mismatched filter (90) has an input device (86) for receiving an extended Barker-based code that is a received signal (84).

Abstract: A method and apparatus for enhancing resolution of range estimates in all echo location systems and, specifically, such systems as Radar, Sonar, and Synthetic Aperture Radar (SAR), for example. The invention utilizes high order signal processing to "sharpen" or contract the main lobe of the processing system ambiguity function and suppress its side lobes, for a given transmission pulse bandwidth. The method and apparatus may be implemented in the frequency domain or time domain. Enhanced resolution is achieved by using a filter (MSC filter), according to this invention, in the echo location data processing system so that the received echo data is processed by the MSC filter to produce a signal that exhibits enhanced range resolution. The MSC filter output, H(.omega.), which is specific to the transmitted pulse waveform, is the ratio of a high-order manipulation of the transmitted signal with its modified spectral profile.

Abstract: A network of localizers determines relative locations in three-dimensional space to within 1 cm by cooperatively measuring propagation times of pseudorandom sequences of electromagnetic impulses. Ranging transmissions may include encoded digital information to increase accuracy. The propagation time is determined from a correlator circuit which provides an analog pseudo-autocorrelation function sampled at discrete time bins. The correlator has a number of integrators, each integrator providing a signal proportional to the time integral of the product of the expected pulse sequence delayed by one of the discrete time bins, and the non-delayed received antenna signal. With the impulses organized as doublets the sampled correlator output can vary considerably in shape depending on where the autocorrelation function peak falls in relation to the nearest bin. Using pattern recognition the time of arrival of the received signal can be determined to within a time much smaller than the separation between bins.

Abstract: A signal processing system applies space-time adaptive processing ("STAP") to an airborne surveillance Doppler radar comprised of a single-channel, rotating antenna. The STAP substantially improves signal-to-interference-plus-noise ratio ("SINR"), thereby improving the detection of weak targets.

Abstract: A codeword generator produces codewords in the form of digital electronic signals which may be employed, for example, in spread spectrum communications system or RADAR systems. The generator effects a mixing ergodic transformation upon a suitable irrational number to produce a complex number sequence. The generator truncates the complex number sequence to a predetermined length, thus forming a codeword. The generator then forms other codewords within a family by permuting this first codeword. Other families of codewords may be generated by employing another mixing ergodic transform to transform the same irrational number or another suitable irrational number.

Abstract: A method and device of the pulse-compression radar or sonar type which makes it possible to determine the speed of a moving object is provided with a transmitter system, a receiver system, and a signal processing system. The transmitter system is capable of transmitting two associated pulses, one of which is modulated with an increasing variation law and the other of which is modulated with a decreasing variation law. The signal processing system includes two correlators, an adder, a subtractor, and a computer.

Abstract: A plurality of substantially interference-free radar systems, each comprising: means for generating pseudorandom waveforms for sequential transmission by radar; and a radar transmitting and receiving phased array antenna having a horizontal beamangle of a few milli-radians (mR), and a vertical beamangle of about 25 mR.

Abstract: The position of a periodic signal is determined in a number of steps. First, values that are related to the periodic signal are accumulated over a number of periods in a buffer. Then, an area with the lowest accumulated values in the buffer is detected for determining a zero position. A median position is determined with respect to the zero position, and the position of the periodic signal is calculated using this determined median position.

Abstract: This invention relates to a method and apparatus for controlling a biphase modulator (602, 702) to improve autocorrelation in pseudorandom noise coded systems. The biphase modulator modulates a carrier frequency with one of two phase states responsive to a pseudorandom noise (PN) binary code sequence. The spectrum (610, 710) at the output of the biphase modulator comprises a plurality of spectral lines separated by the code repetition frequency, including a center spectral line (611, 711) and at least one adjacent spectral line (612-615, 712-717). The magnitude of the center spectral line is measured and compared to a reference to produce a control signal which is responsive to the magnitude of the center spectral line. This control signal is supplied to the biphase modulator for maintaining a predetermined magnitude of the center spectral line thereby achieving a desired spectrum output and improving autocorrelation of the system.

Abstract: A pseudorandom noise coded system (100) compensates for imperfections, improving out of range rejection, and includes a digital correlator (200) having a first complex multiplier (202) receiving a sequence of sampled data words and a sequence of precomputed complex data words and producing a sequence of first complex product words. A second complex multiplier (204) receives the sequence of first complex product words and a precomputed constant word and produces a sequence of second complex product words. A complex multiplexer (206) receives a sequence of binary code states, and the sequences of first and second complex product words and produces a sequence of complex multiplexer output words formed as a replica of either the first or the second complex product words, depending on the binary code. A complex accumulator (208) receives the sequence of complex multiplexer output words and produces a complex accumulated sum word formed as a complex sum of the complex multiplexer output words.

Abstract: An adaptive processor which uses the successive range and Doppler outputs of a conventional matched-filter to improve the signal-to-noise ratio for non white noise/clutter. The adaptive processor minimizes the output for a given range and Doppler cell with the constraint that the response to signals returning with specified range and Doppler offsets, with respect to the center of the range-Doppler cell, each have specified values. Weights are derived which can be applied to range-Doppler outputs in the neighborhood of the range-Doppler cell to minimize its output subject to the constraints. The weights depend on an estimate of the cross-covariance matrix of the various outputs of the range-Doppler cells that are to be weighted. The constraint parameters are specified in terms of the ambiguity function of the transmitted waveform.

Abstract: A radar pulse detection and classification system receives times-of-arrival of pulses from simultaneous emitters over a wide range of pulse repetition frequencies (PRF's). The pulses are deinterleaved into bands of pulse repetition intervals (PRI's) so that a fixed number of pulses are required for detection of an emitter regardless of the PRI of the emitter. The pulse periodicities of the pulses in a pulse stream are determined by autocorrelation, and candidate emitter PRI's are selected from the pulse periodicities which were determined by autocorrelation. The pulses of candidate emitters are time-integrated to obtain time-integrated signals, and emitters are detected from peaks in the time-integrated signals. The time-continuity of said pulses are measured to determine emitter existence. The system receives pulses from both jittered and non-jittered emitters.

Abstract: This radar incorporates a single channel, two-dimensional correlator, providing simultaneous correlation in the range/doppler plane. In conventional radar processors, separate channels are used to measure range and doppler. Range track is normally established first and the range signal is then used to enable, or correlate with the doppler channel. In this invention, this correlation is performed simultaneously in a single channel and truly represents the combined ambiguity function, rather than an attempt to merge two separate ambiguity functions. A purely random sequence of binary bits (+1 and -1's) is used to control the phase of each segment in the transmitted signal (either pulse or CW) as opposed to systems using pseudo-random sequences generated by various means such as linear shift register generators. A digital random number generator is used to produce a set of purely random numbers which, when applied to a rule, generates a random sequence of binary bits, plus or minus 1's (.+-.

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: A system which receives a pseudonoise sequence signal, quantizes the signal during a fixed increment of time, and passes the quantized signal to a single "split" correlator channel. The system utilizes sub-correlation products from that single "split" channel to calculate correlation outputs of other desired correlation channels. Specifically, the "split" correlator channel includes a pair of shift register strings, with the corresponding stages of each string being of equal length, and with a phase rotator being provided between consecutive stages of the shift register strings. In-phase and quadrature components of the received signal are each provided as inputs to a respective one of the shift register strings, and each shift register string stage is correlated with the pseudonoise sequence.