Abstract: An improvement in monopulse radar achieves nulling of multiple mainlobe jammers while maintaining the angle measurement accuracy of the monopulse ratio by using multiple simultaneous beams, thereby obtaining the additional degrees of freedom necessary for cancelling more than one mainlobe jammer (MLJ). The beams are placed one null beamwidth apart in order to maintain orthogonality. The MLJs are nulled in the orthogonal direction of the angle estimate giving undistorted monopulse ratios.

Abstract: A method of operating a radar system is shown to include the steps of transmitting a plurality of signals, each signal having a different frequency, and receiving, if existing, a corresponding return signal for each one of the plurality of signals. The method further includes ascertaining an angle off beam cross-over of a target from each existing return signal, selecting the angle off beam cross-over having the largest magnitude, ascertaining a reduction factor appropriate for the selected angle and reducing the magnitude of the selected angle by the reduction factor. With such an arrangement, a radar system is provided having improved elevation measurement accuracy.

Abstract: A system for cancelling jammer signals entering the mainlobe of a monopulse adar and providing target locations with respect to the jammer position comprising for a sequential lobing embodiment: measuring the angular position of the jammer in the radar's mainlobe via the use of monopulse sum and difference signals, pointing the radar antenna so that the jammer is positioned within the 3 dB points of the mainlobe of the monopulse antenna, converting the sum and difference echo signals received with the antenna in this position from the next radar transmission into a second set sum and difference signals, applying this second set of sum and second set of difference signals to the inputs of an adaptive canceller to cancel the jamming signal therein and storing these signals in time sequential order, changing the orientation of the radar antenna by a small arbitrary elevation angle, converting the sum and difference echo signals received with the antenna in this new position from a third radar transmission into a

Abstract: In a method for tracking a radar target the imaginary part of the complex elevation error signal is utilized and the value of the complex elevation error signal is calculated for a plurality of frequencies in a repeated sequence. The value change between the different frequencies is used for determining the position within an unambiguous interval and the values calculated at the zero crossing are utilized as measure of the inclination which in turn is compared with inclinations calculated for zero crossings in a general case, whereby a single-valued (unambiguous) interval and position can be determined and thereby the associated elevation angle or target height can be calculated. The method is specifically useful for tracking at low height where multi-path propagation poses a problem in tracking according to known methods.

Abstract: In a method for the detection of the garbling of pulses received by a secondary radar, the secondary radar comprises a monopulse antenna that can be used to obtain a pulse power signal and a pulse difference measurement signal synchronous with the received pulses. The method consists in detecting, at the same time, ripples superimposed on the power signal and ripples superimposed on the difference measurement signal, the presence of at least two garbled pulses being detected by the presence of ripples on at least one of the two signals. Application to the reception circuits of secondary radars.

Abstract: A direction finding method and system for locating the direction of a transmission source based on an electromagnetic wave which is transmitted from the transmission source and is received by an antenna means at a receiving end apparatus. The transmission source transmits an angle-modulated wave. Meanwhile, the receiving end apparatus receives the transmitted wave, converts into electrical signals a beat frequency signal which is caused by direct and reflected waves contained in the received wave, and time-averaging the electrical signals, thus minimizing a angle error due to a multipass interference.

Abstract: Disclosed are a method and a device to detect the intermingling, hence the garbling, of pulses received by a secondary radar by phase analysis. The monopulse reception antenna of a secondary radar delivering a sum signal given by its sum channel and a difference signal given by its difference channel, the method according to the invention consists in analyzing the phase difference between the sum signal and the difference signal, the garbling of at least two received pulses being detected by a phase difference with a value that is substantially different from 0.degree. or 180.degree.. Application to the detection of garbled pulses received when the working frequencies of the transponders are very close to one another.

Abstract: A nonrectangular antenna aperture is provided comprising four quadrants for receiving electromagnetic signals. The aperture has the capability to form a predetermined sum beam, a predetermined first difference beam, a predetermined second difference beam, and a predetermined double difference beam so that the product of the first and second difference beams is substantially equal to the product of the sum and the double difference beams.

Abstract: A method and apparatus to determine angles .theta..sub.1 and .theta..sub.2 between paths of two sets of reflected radar waves and a radar boresight utilizes the electrical angles .beta..sub.1 or .beta..sub.2 and two successive radar target observations. One set of radar waves may travel a path from a target and the second set may travel a multipath from the same target. Alternatively, the two sets of radar waves may follow direct paths from two targets. For coherent radar hardware, signals from two halves of an array are processed through a linear coherent receiver, analog-to-digital converter and processing unit with associated memory. The memory contains a database and program which calculates the electrical angles .beta..sub.1 and .beta..sub.2 and angles .theta..sub.1, and .theta..sub.2. For non-coherent radar hardware, mixers, a phase detector and two magnitude detectors are substituted for the linear coherent receiver.

Abstract: After each received signal in the same two antennas of the monopulse power feed system are inputted into a hybrid circuit, a sum signal .SIGMA. and a difference signal .DELTA. are formed, and they are demodulated in detection circuits, zero is outputted if the value of the sum signal .SIGMA. is equal to or smaller than the value of the difference signal .DELTA., otherwise the value subtracted the difference signal .DELTA. from the sum signal .SIGMA. outputted, in a signal processing section. Thus, beam compression and reduction of a side lobe are performed.

Abstract: A tracking radar system comprising an aerial arrangement having a plurality of outputs, means for deriving from the aerial outputs a sum signal representative of the sum of the aerial outputs and a difference signal representative of the direction of a target relative to the aerial, a receiver for processing said sum and difference signals to produce corresponding intermediate frequency sum and difference signals, means for comparing the intermediate frequency sum signal with the output of an oscillator in a first phase-locked loop and using the resulting signal to control the oscillator frequency so as to cause the oscillator to lock on to the frequency of the intermediate frequency sum signal, a phase-sensitive detector for comparing the intermediate frequency difference signal with the output of the oscillator to produce an output signal representative of the phase difference between the sum and difference signals, and bandwidth alteration means responsive to the sum signal to alter the bandwidth of the fi

Abstract: A method for processing an antenna pattern in which a first antenna system is placed to correspond with a first direction in relation to the beam width to be compressed, a second antenna system of the monopulse power feed system is placed to correspond with a second direction lying at a right angle to the first direction, in which an antenna beam of the first and the second antenna systems is scanned in a direction other than the first and the second directions. A sum signal .SIGMA.1, a difference signal .DELTA.1 and sum signal .SIGMA.2, difference signal .notident.2 are formed in hybrid circuits, and an output signal two-dimensionally compressed are obtained as a result of adding a signal resulting from the subtraction of the difference signal .DELTA.1 from the sum signal .SIGMA.1 to a signal resulting from the subtraction of the difference signal .DELTA.2 from the sum signal .SIGMA.2 in a signal processing section.

Abstract: An AWTSS is shown to be made up of an improved synthetic aperture radar (SAR) for generating radar maps with various degrees of resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter. The SAR consists, in effect, of four frequency-agile radars sharing quadrants of a single array antenna mounted within a radome on a "four axis" gimbal with a sidelobe cancelling subarray mounted at the phase center of each quadrant. Motion sensors are also mounted on the single array antenna to provide signals for compensating for vibration and stored compensating signals are used to compensate for radomeinduced errors. In addition, a signal processor is shown which is selectively operable to generate radar maps of any one of a number of desired degrees of resolution, such processor being adapted to operate in the presence of clutter or jamming signals.

Abstract: The invention relates to an apparatus and method for generating target range, azimuth angle, or elevation angle output signals corresponding to an apparent beam in a multiple-feed monopulse radar system. The multiple-feed monopulse radar system according to the present invention includes a transmitter/receiver unit, an adder/subtracter unit and a video comparator/adder unit. The transmitter/receiver unit is used to generate first and second actual antenna beams. Echoes caused by such actual beams are received and processed to provide first sum and first difference signals and second sum and second difference signals corresponding to the first and second actual beams, respectively. These signals are then supplied to the adder/subtracter unit which adds the first sum and first difference signals to provide a result .SIGMA..sub.1 +K.DELTA..sub.1, subtracts the first sum and first difference signals to provide a result .SIGMA..sub.1 -K.DELTA.

Abstract: The present invention relates to a method and system for determining target elevation angle, altitude and range and the like in a monopulse radar system with reduced multipath errors. A transmitter/receiver unit receives monopulse sum and difference signals caused by echoes from targets. The sum and difference signals are then logarithmically-amplified in a logarithmic amplifier unit. A selector selects one of the sum and difference signals having the largest amplitude, and generates a selection signal indicating which of the sum and difference signals has the largest amplitude. The selection signal is provided to a search radar target tracking unit which determines whether a target at a given range interval and azimuth interval, for example, has been selected for tracking by an operator.

Abstract: A frequency modulated-continuous wave (FM-CW) radar system for detecting a range, relative speed, and direction to a target. To this end, a beat signal generator, first and second signal distributors, a beat signal frequency detector, a beat signal amplitude level detector, and at least one pair of antennas are provided. Each antenna of each pair has the same directivity, is set to radiate a beam in a slightly different direction from the beam radiated by the other antenna, and is set to receive a return beam from a target. The first signal distributor distributes an FM signal having a frequency varying with time to each of said antennas successively and repeatedly. The second signal distributor distributes a reference FM signal to a first set of input terminals of the beat signal generator successively and repeatedly.

Abstract: A method of detecting the division of a radar target can detect a target, for instance caused by the release of a weapon from an aircraft which is tracked by a monopulse radar whose antenna is aligned onto the target with the aid of azimuth and/or elevation difference signals. Division of the radar target can be detected irrespective of whether the target is equipped with and uses an interference transmitter, by establishing a search channel in the radar difference channels. This channel has a sensitivity which is very low in a direction towards the tracked target, but which increases rapidly in directions which deviate somewhat from the direction towards the target. The search channel can be established by comparison of the absolute values of the signal levels in the difference channels with a threshold value.

Abstract: An RF circuit includes an RF power divider circuit having an input port and a plurality of output ports the RF power divider circuit providing in response to a signal fed to the input port an output signal at each output port each output signal having known amplitude and known phase. The RF circuit further includes means for selectively coupling at least a portion of a signal fed to an input port of the RF circuit to the input port of the RF power divider circuit and a like plurality of directional coupler circuits each of the coupler circuits having an input port and a coupled port with each input port coupled to a corresponding one of the plurality of output ports of the power divider circuit and each coupled port corresponding to an output port of the RF circuit.

Abstract: A target tracking system and methods that can isolate and maintain stable track on a selected target in multiple-target environment. In multiple-target environments, the signal returns received at the sum and difference channels are composites of individual targets. By decomposing received signals into individual components, angle measurements to each target are computed, and consequently, a specified target is isolated and accurately tracked in a stable manner. The present invention provides for apparatus and methods that compute angle measurements to each individual airborne target in a multiple target environment. The composite return signals from a number of targets that are closely spaced in Doppler are decomposed into their individual components, and hence, tracking measurements to each target are obtained without interference from other targets. The present invention may be used to determine the angular position of individual airborne targets within a multiple target environment.

Abstract: A system which receives a pseudonoise sequence signal quantizes the phase of the received signal in digital form as in-phase and quadrature digital signals. A digital correlator correlates the digital signals against the stored pseudonoise code sequence and separately accumulates the results. The accumulated results are vector added and a peak detector is utilized to determine the time of arrival of the signal. At the same time, the accumulated results are used by an arctangent calculator to derive a phase signal, which is gated as an output when the time of arrival is determined. An embodiment in a phase monopulse radar system collects the signals from four antennas spaced as pairs in both azimuth and elevation to determine the azimuth and elevation phase differences of the received signal. In this embodiment, a single digital correlator is utilized, the inputs to which are time multiplexed.

Abstract: A pulse radar for operation at 94 GHz and higher frequencies is shown to include an antenna, a diplexer and first detector that are each optically fed so that radio frequency signals may be, when transmitting, passed through the diplexer to the antenna and, when receiving, from the antenna through the diplexer to the first detector.

Abstract: An enhanced performance Mode S interrogator that includes a matched channel receiver. The receiver includes equiripple-phase response filters with finite peaks of attenuation. This new class of filters provides a faster rise of attenuation than all-pole filter while extending the equiripple delay further into the stopband.

Abstract: A method of and an apparatus for measuring the null angle in the difference vs. sum pattern and in the difference pattern of a monopulse antenna. The null angle of the monopulse antenna in the radiation pattern is acquired by transmitting an RF signal from a plurality of antenna elements to the monopulse antenna, acquiring the sum signal and difference signals in the directions of the respective antenna elements and acquiring the null angle in accordance with the sum and difference signals. The apparatus comprises a rotator for changing the direction of the monopulse antenna and a transmitting antenna facing the monopulse antenna for transmitting a test signal to the monopulse antenna.

Abstract: An AWTSS is shown to be made up of an improved synthetic aperture radar (SAR) for generating radar maps with various degrees of resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter. The SAR consists, in effect, of four frequency-agile radars sharing quadrants of a single array antenna mounted within a radome on a "four axis" gimbal with a sidelobe cancelling subarray mounted at the phase center of each quadrant. Motion sensors are also mounted on the single array antenna to provide signals for compensating for vibration and stored compensating signals are used to compensate for radome-induced errors. In addition, a signal processor is shown which is selectively operable to generate radar maps of any one of a number of desired degrees of resolution, such processor being adapted to operate in the presence of clutter or jamming signals.

Abstract: A monopulse radar system includes sum and difference receivers, and an auxiliary receive beam offset from the sum and difference beam axis. The received sum and difference signals are processed to produce first and second weighting signals which, when multiplied by the auxiliary signal, produce first and second weighted auxiliary signals which are approximately equal to the magnitude of, and are in a particular phase with, the received sum and difference signals, respectively. In the presence of a jamming signal in the main lobe of the monopulse receiver, the weighted auxiliary signals are summed with the sum and difference signals to produce adapted sum and difference signals, in which the jammer signal is suppressed by a null in the effective receive antenna pattern. The null perturbs the sum and difference patterns, so that the ratios of the sum and difference signals no longer accurately represent the off-axis angle of the target.

Abstract: An AWTSS is shown to be made up of an improved synthetic aperture radar (SAR) for generating radar maps with various degrees of resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter. The SAR consists, in effect, of four frequency-agile radars sharing quadrants of a single array antenna mounted within a radome on a "four axis" gimbal with a sidelobe cancelling subarray mounted at the phase center of each quadrant. Motion sensors are also mounted on the single array antenna to provide signals for compensating for vibration and stored compensating signals are used to compensate for radome-induced errors. In addition, a signal processor is shown which is selectively operable to generate radar maps of any one of a number of desired degrees of resolution, such processor being adapted to operate in the presence of clutter or jamming signals.

Abstract: An AWTSS is shown to be made up of an improved synthetic aperture radar (SAR) for generating radar maps with various degrees of resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter. The SAR consists, in effect, of four frequency-agile radars sharing quadrants of a single array antenna mounted within a radome on a "four axis" gimbal with a sidelobe cancelling subarray mounted at the phase center of each quadrant. Motions sensors are also mounted on the single array antenna to provide signals for compensating for vibration and stored compensating signals are used to compensate for radome-induced errors. In addition, a signal processor is shown which is selectively operable to generate radar maps of any one of a number of desired degrees of resolution, such processor being adapted to operate in the presence of clutter or jamming signals.

Abstract: A device for automatic correction of differential and deterministic errors in a radar receiver, preferably a monopulse radar receiver, which comprises a closed loop feedback system in which raw Off-Boresight Angle (OBA) data as well as current azimuth data are accumulated, averaged and linearized through linear aggression techniques. This linearized data is combined with data relating to pre-calibrated known antenna parameters. This combined data is fed back and combined with the raw OBA signal to produce a correction OBA signal. The corrected OBA signal is algebraically summed with the current known azimuth data produced by the radar receiver to produce a highly reliable error corrected instantaneous OBA value.

Abstract: A secondary surveillance radar system in which monopulse processing is used to obtain angle estimation of azimuth bearing, the improvement residing in a precision method, involving a monopulse qualifier signal, for identifying the maximum unambiguous off-boresight azimuth (OBA), while ensuring reduced sensitivity to Omni channel variations; the monopulse qualifier signal is developed from coherently combining the IF limited signals derived from the Sum+JDelta and Delta+jSum signals, such that two amplitude varying signals are created, such signals bearing a direct relationship to the Sum and Difference antenna pattern ratios and being independent of antenna signal power.

Abstract: Method and apparatus for instantaneous processing of the glint noise in a monopulse radar. The radar antenna receives a sum signal S and a difference signal .DELTA. whose phases vary as functions of time. Successive derivatives Q.sup.(k) of order k, are calculated as a function of time from k=0 to k=N'. Also, the scaler product Q=S.times..DELTA. of the sum signal and difference signals is calculated. Then, successive derivatives P.sup.(k) of order k are calculated as a function of time from k=0 up to k=N'. Also, the power P=.vertline.S.vertline..sup.2 of the signal received, which is equal to the square of the modulus of the sum signal S, is calculated. Next, a plurality of derived angle-error measurement operators (.epsilon..sub.k) are calculated such that a .epsilon..sub.k =Q.sup.(k) /P.sup.(k). Finally, a combined angle-error measurement operator .epsilon. is calculated such that ##EQU1## The weighting coefficients .beta..sub..kappa.

Abstract: An improved airborne target tracking monopulse radar system is disclosed which includes a null command generator, designed to provide an error signal which represents the angle between a target direction and the antenna's monopulse null direction. The generator is supplied with signals on sum and difference channels and a frequency which represents a selected target. The error signal is produced by first differentiating the sum channel signals and subtracting the differentiated output from the difference channel signals. The difference output is then multiplied with properly phased sum channel signals to produce the desired error signal.

Abstract: The invention is a radar system using sum and difference signals for tracking targets, wherein the system includes aperture means having a cross sectional area for transmitting energy toward a target and receiving return energy; and circuit means for generating sum and difference signals, the circuit means being selectively coupled to said aperture means, with the sum signal being generated using energy from the entire aperture means and with the difference signals being generated using return energy from the aperture means exclusive of energy from a predetermined area. The invention permits simultaneous optimization of the sum and difference signals and also suppresses the near-in sidelobes in the difference signals.

Abstract: A method of processing in a two-channel monopulse receiver and processor is shown to include the steps of: (a) forming composite signals equal to [S+(p+jy)] and [S-(p+jy)] where S in a monopulse sum signal and p and y are, respectively, pitch and yaw error signals; (b) alternately passing the composite signals through a two-channel amplifier; and (c) separating the components in the resulting amplified composite signals for conventional monopulse processing and smoothing to eliminate the effects of any imbalance (in phase or amplitude) between the channels in the two-channel amplifier.

Abstract: The invention relates to a method for improving the angular resolution of a monopulse radar.Starting from the sum signal S, a direction signal .theta..sub.b, and a signal representing the quadrature angle-error measurement .vertline..epsilon..sub.q .epsilon., the method consists of calculating in a first device 201 a signal .DELTA..theta. representing the wingspan of the target, then of calculating in a second device 202 two measuring signals .theta..sub.A and .theta..sub.B representing respectively the direction of the external limits of the target, as well as a signal Q representing the quality of these measurements and finally of carrying out an adaptive filtering operation on the measurements in a third device 203, in order to obtain filtered estimates for .DELTA..theta., .theta..sub.A and .theta..sub.B.

Abstract: An architecture for a monopulse, active aperture array is provided which functions as a high precision error compensation system correcting both the Sum and the Difference beams simultaneously. The architecture incorporates; a radiating antenna, a transmit-receiver, a -3.01 dB Wilkinson divider operable to split the signal received from the transmit-receiver, a Sum plus Difference network, a Sum minus Difference network both of which accept the split signal from the -3.01 dB Wilkinson divider and simultaneously error compensate the beams, and a four port magic tee operable to output the error compensated signals from the Sum plus Difference network and the Sum minus Difference network.

Abstract: Device for angle measurement for inclusion within a monopulse amplitude comparison radar receiver for particular application within secondary radars. In essence it consists of a log (.SIGMA.) signal comparator (9) against a detection threshold, which is meant to enable further processing; of two-analog-numerical converters (10, 11), a codes (12), receiving outputs .SIGMA. and .DELTA. from converters above, which provides the calculation of target azimuth.

Abstract: A radar search detection apparatus having a monopulse antenna to receive sum and difference beam signals which are applied to separate target detection channels to detect and identify target returns.

Abstract: Device for radar utilized to detect multiple-time-around echoes with the capability of transmitting in frequency agility and, besides the advantages due to this type of technique, further, capable of reading the ambiguity of distance directly by separating in frequency the multiple-time-around echoes. The device described is applicable to any pulses radar, such as for example, search or tracking, in which it is necessary to detect targets and recognize multiple-time-around echoes. Nevertheless its application is especially suited to a multifunctional radar (with phased-array antenna and monopulse capability).

Abstract: A processor adapted for use in conjunction with a monopulse radar system for discriminating between ground and airborne moving targets and comprising: Doppler filter circuits for detecting moving targets; angle measurement circuits which respond to the received sum and elevation difference signals so as to provide an indication of the relative angle of each moving target and of the ground; and means for identifying a detected target as a ground or an airborne target as a function of whether the angle of the target is substantially the same as or different from that of the ground.

Abstract: Two distinctly polarized monopulse signals are orthogonally superimposed using antennas spaced in pairs which are transversely aligned. Signals from the pairs are separately summed and differentiated. Signals from both pairs are summed in one system. A transmitter supplies pulses directly to one pair and through a 90.degree. phase shifter to the other pair.

Abstract: The radar is designed to identify and then eliminate rain clutter signals. For this, the radar works in circular polarization with alternately identical and opposite polarization directions at transmission and reception, from one recurrence to the next one. The signals are identified by a comparator which compares the sigma video signals relating to the same distance quanta for two successive recurrences, the identifying criterion being a major difference in the level of the signals compared, for rain clutter signals, and little difference for useful echo signals. A switch controlled by the comparator eliminates the parasite signals.

Abstract: Where reflection coefficient k of the surface of the sea is in a relatively wide range and as the ratio of the antenna height to the wavelength is larger, a radar system can eliminate ambiguities in measuring a target height of a low elevation angle on the sea surface. An antenna receives two beams, one beam having slightly different elevation angle from the other. An antenna direction adjusting mechanism adjusts, on the basis of tan.sup.-1 (ha/R), a direction in which receiving sensitivity of one of the beams is equal to receiving sensitivity of the other beam, so that this direction aims at mid point between the target and the image of the target. The phase difference between the two beams is obtained with respect to two different frequencies. Two series of data of the target height are obtained each on the basis of the respective phase difference.

Abstract: A method for producing antenna follow-up signals in which a sum signal and a difference signal are derived from a received beacon signal and an amplitude modulated signal is produced by superposition from these two signals. The amplitude modulated signal is converted into another frequency by means of a mixer which receives both the amplitude modulated signal and a mixing signal. The converted amplitude modulated signal is fed to an amplitude detector via a narrowband bandpass filter which permits only the signal frequency to pass. A voltage controlled oscillator is cyclically switched to produce a mixing signal which is fed to the mixer and which cyclically changes its frequency between two frequencies for the duration of each phase state of the difference signal. The converted signal at the output of the mixer changes its frequency between two further frequencies in response to the change of frequency of the mixing signal.

Abstract: A missile guidance system having means for deriving from a target angle tracking loop a signal indicative of an apparent movement of a target off a missile-to-target sight line caused by a change in missile attitude, and means for feeding said apparent movement signal into a space stabilization loop to adjust the position of the aerial to compensate for said apparent movement.

Abstract: To suppress rain echos in a terrain tracking radar with elevation monopulse devices, the signal in the difference channel is amplified by a predetermined factor. By comparing the level of the sum signal with the amplified difference signal, conclusion is reached about the presence of a ground echo or a rain echo. The factor should preferably be automatically adjustable according to the level in the sum channel.

Abstract: An angular scintillation reduction device used more especially in radar equipments making deviation measurements.It contains a circuit (60) receiving the video outputs of a radar receiver, the sum .SIGMA., range D and deviation measurement .epsilon. signals respectively on three terminals (3, 28 and 2). It delivers on a terminal (30) the values of the deviation measurement signal .epsilon. corresponding to the maximum values of the sum signal .SIGMA..It is applicable to all electromagnetic detection equipments which make deviation measurements.

Abstract: A radar system for tracking airborne targets, in which the transmitted pulse signal is swept over a predetermined frequency range (3). A local oscillator (15) in the receiver is swept over a similar frequency range the L.O. sweep modulation being initiated (20) by the first significant target return signal. Reflectors on the target at different ranges therefore produce different I.F.s in the receiver. Discrimination between the various target reflector features is thus achieved by filtering (25, 27, 29) the I.F. signals in a series of small bands, each band corresponding to a particular target-feature range. Azimuth, elevation and magnitude of a target feature can thus be obtained for each range cell.

Abstract: A single channel antenna tracking system for frequency-hopping communication systems. The tracking system utilizes the synchronization pulses accompanying the frequency-hopping data bursts. The receive antenna system includes an antenna feed network for providing sum and difference antenna receive signals. The tracking system comprises a tracking switch circuit which normally switches the antenna system sum signal to the receiver during reception of a frequency-hopping data burst. During the reception of an agile synchronization pulse, however, the switching system is adapted to timeshare between the antenna sum signal and the difference signal or signals. During the synchronization pulse duration, the receiver thus receives a single waveform which during one portion of the sync pulse represents the sum signal and during one or two other portions represents the difference signals. The respective sum and difference signals may then be processed to determine the antenna tracking error.

Abstract: A radar system for finding the location of a second flying object from a first flying object, comprises a nondirectional antenna for radiating a first radio wave from the first flying object, a second nondirectional antenna provided on the second flying object to receive the first radio wave and to radiate a second radio wave generated by modulating the received first radio wave and an array antenna provided on the first flying object to receive the second radio wave. The respective amplitudes of the signals given by the antenna elements of the array antenna are compared individually with a specified level and an operation for determining the direction of arrival of the second radio wave is executed using the signals given by all the antenna elements when either of the amplitudes of the signals given by the antenna elements is greater than the specified level.

Abstract: A system for detecting the approach of a vehicle toward the line of sight an antenna comprises an alerter for receiving an acoustic noise signal from the vehicle and determining whether the signal is increasing or decreasing. The increase of a noise signal indicates the approach of a vehicle and is used to activate a power supply to supply power to a digital signal processor. The digital signal processor receives the acoustic signal and performs a comparison to determine whether the signal in fact is noise produced by a vehicle. If so, the digital signal processor activates a radar based primary sensor which more accurately detects the approach of the vehicle and determines the instant at which the vehicle passes an antanna of the sensor. When the vehicle passes the antenna, the digital processor receives data and produces an output signal that can be used to activate a counter to count the passage of vehicles, surveillance equipment or to fuse a mine if the vehicle is assumed to be hostile.