Abstract: In an air traffic control radar system, a processor is described for correlating primary target data received from a target with a target report and a target track, wherein the processor has a search acquisition time that is adapted to the distance of the target from the radar site. The search acquisition time is shorter for more distant targets. The processor can employ a shorter cycle time (time quantum) to establish a correlation between target data and target reports than would otherwise be possible with conventional fixed search acquisition times. The average total dwell time may be reduced while complying with the mandated maximum processing time for more difficult radar reports.

Abstract: A search radar including the improvement of apparatus for enhancing the estimation of the target angle within a search scan of the radar is disclosed. More specifically, the improvement apparatus utilizes the generated scan angles and target amplitude measurements correspondingly associated therewith to generate intermediate signals which are representative of the natural logarithm of the target amplitude measurements plus the square of the corresponding scan angle multiplied by a predetermined constant. For each search scan, the apparatus computes separately signals representative of the moments of: the scan angles, the squares of the scan angles, the products of the scan angles and corresponding intermediate signals, and the intermediate signals. In turn, the apparatus operates on the computed moment representative signals in some prespecified mathematical relationship to effect an optimum estimation for the target angle in each search scan of the radar.

Abstract: The present invention provides a small-size image radar apparatus to be mounted on an aircraft, having a high resolution not only the flying direction but also in the direction vertical to the flying direction. The image radar apparatus comprises a transmission antenna 2, a plurality of independent reception antennas 5.sub.1, 5.sub.2, and a computer 10 for simultaneously executing a two-dimensional phase synthesis. The synthesis result is obtained as a two-dimensional image.

Abstract: Method and device for determining an azimuth angle and/or an elevation angle, based on a multibeam radar system, in which the echo signals of each radar target are recorded over at least two beams. The amplitude of an echo signal recorded in each receiving beam is normalized. For each receiving beam, the normalized amplitude is compared to the pattern values of an antenna pattern stored and normalized for this beam in order to determine the angle of a radar target. The comparison results from at least two receiving beams are combined to form an angle-dependent analysis quantity, and the angle whose angle-dependent analysis quantity meets a minimum and maximum criterion is determined to be the angle of the radar target. Included in the angle-dependent analysis quantity is a phase angle of at least two recorded echo signals. This operation can also be performed on the basis of a complex normalization operation.

Abstract: The process is used for suppressing the effect of signals that are received or sent via side lobes of an antenna (PA; HA) of an amplitude or phase monopulse radar device, in which for the purpose of position measurement of a first and, if need be, a second target (T1, T2) detected by the radar beam, three illumination functions Je(Lx), Jk(Lx) and Js(Lx) for the antenna (PA; HA) are provided for each measurement axis, as well as antenna functions Fe(X), Fk(X), and Fs(X) resulting from them. The first, second, and third illumination functions Je(Lx); Jk(Lx), and Js(Lx) are selected in this connection so that a quotient function Qe(X)=Fe(X)/Fs(X) or Qk(X)=Fk(X)/Fs(X), which is linearly or quadratically dependent on the target direction, is produced by normalizing the first and the second antenna functions Fe(X); Fk(X) with the third antenna function Fs(X). The power of this quotient is compared with at least one threshold value th.sub.e or th.sub.

Abstract: A method for finding a direction associated with a radiated electromagnetic wave, the method including the steps of: detecting the radiated electromagnetic wave; measuring at least one gain difference and at least one phase difference associated with the detected electromagnetic wave; estimating an elevational angle and an azimuthal angle associated with the detected electromagnetic wave using the at least one measured gain difference; determining a plurality of possible elevational and azimuthal angles associated with the detected electromagnetic wave using the at least one measured phase difference; and, respectively selecting one of the plurality of possible elevational and one of the plurality of possible azimuthal angles as elevational and azimuthal angles associated with the detected electromagnetic wave using the estimated elevational and azimuthal angles.

Abstract: Method and apparatus for the detection of a target receiver unit such as an enemy radar or radio receiver is disclosed. The surveillance system of this invention includes a transmitter unit coupled to an antenna to establish an electromagnetic surveillance field that includes signal components at two predetermined surveillance frequencies. When a target receiver is located within the surveillance field, the target receiver produces a second electromagnetic field having signal components at the intermodulation products of the surveillance field signal components due to a nonlinear mixing process that occurs within the target receiver. Signal components at predetermined intermodulation frequencies are detected by a receiver circuit within the surveillance system that has a passband excluding signal components at the two predetermined surveillance frequencies.

Abstract: A broadband transmitter element, located at a remote object, transmits a broadband signal at a prescribed transmission time. A broadband receiver element, located at a base platform spaced from the remote object, receives electromagnetic radiation during a reception search window. The broadband receiver element stores information characterizing the broadband signal. A synchronizer synchronizes the broadband transmitter element with the broadband receiver element for timing the transmission and reception. A processing device derives an estimated time of flight for the broadband signal to travel from the remote object to the base platform, and a correlation detector, located at the base platform, identifies the remote object and the arrival time of the broadband signal by correlating the stored information with signals received during the reception search window.

Abstract: An attitude determination system uses multiple antenna inputs which are time-multiplexed into a multi-channel receiver. Each channel tracks one incoming signal from a known or ascertainable source. For each of the incoming signals being tracked, digital processing can be used to determine range differences between the different antenna elements for that incoming signal, and to compute attitude based on the range differences and the known configuration of the attenna elements relative to each other.

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

Abstract: When an IFF system interrogates a target aircraft and receives IFF reply signals, monopulse processing of the reply signals can provide more accurate determination of target azimuth. However, when reply signals have amplitudes close to noise or jamming levels, azimuth processing by non-monopulse techniques such as beamsplitting or center of gravity analysis can provide better accuracy than monopulse azimuth processing. Methods are described to enable adaptive selection of the type of azimuth processing to be employed. Such selection is based on active comparison of received signal magnitudes against monopulse sum and difference signal threshold values and a noise threshold value. Monopulse azimuth processing can thus be used at all times, except when non-monopulse azimuth processing is chosen by such adaptive selection.

Abstract: An inertial navigation system (INS) and a monopulse radar system are mounted on a body. The inertial navigation system outputs at least a velocity of the body. Either a synthetic aperture radar (SAR) map or doppler beam sharpening (DBS) map is created using the outputs of the monopulse radar system. The monopulse radar system outputs at least a summation output, an azimuth difference and an elevation difference associated with an object detected in either the SAR or DBS map. The position processor of the system and method of the present invention, however, only inputs the summation output and one of the azimuth difference and election difference. The position processor determines the other of the azimuth difference and the elevation difference by converting the velocity output by the INS into a doppler angle .theta. (the angle between the velocity, a vector, and a line connecting the object and the body) and determining either the azimuth difference or the elevation difference from the doppler angle .theta..

Abstract: An electrical surveillance measures system for measuring direction of arrival (DOA), i.e., both azimuth and elevation, of a pulsed or continuous wave radar signal from a moving emitter. Either carrier frequency or pulse repetition interval (PARI) Doppler shift are used whereby the ratio of the Doppler shift is measured by a moving observer. The DOA is measured as a unit vector having basis vectors formed from a linearly independent set of observer's velocity vectors. The DOA unit vector has a linear part where the coefficients of the basis vectors are derived directly from the ratios of frequency or PARI measurements taken in three contiguous dwells. The DOA unit vector has a nonlinear part formed from the requirement that the DOA vector have unit magnitude. The unit vector is resolved in the system coordinates in which emitter azimuth and elevation are defined to allow computation of the latter two values.

Abstract: In a transmission mode, one repetition transmission pulse generated by a transmitter is divided into a plurality of subpulses having different frequencies by a variable distributor. The subpulses are assigned to a plurality of elevation angle directions by phase shifters, and the assigned subpulses are transmitted from an antenna device. In a reception mode, the reflected signals of the subpulses transmitted in the range of the plurality of elevation or inclination angles are captured from this range by the antenna device. The captured signals are simultaneously received by a plurality of receivers and EL synthesis units. The number of reception channels is set equal to or larger than the number of transmission subpulses.

Abstract: The volume of space, in range, azimuth and elevation, over which a conventional Tactical Ballistic Missile (TBM) early warning radar is required to search for incoming missiles is very large. This placed very heavy demands on the radar designer, resulting in large, very high power, low mobility radars, with subsequent vulnerability to ARMs and other defence suppression systems. This invention proposes an alternative approach to a TBM early earning radar which considerably reduces both the design and vulnerability problem, and permits effective TBM early warning radars to be constructed using current technology. This is achieved by moving the radar (1) beyond the front edge of the defended area (2). The increased elevation scan requirements are more than compensated for by a range-adaptive scanning technique which reduces the volume search time by more than 50% compared with a more conventional arrangement.

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 radar tracking system 100 adapted for use with existing radar tracking systems. The inventive system includes a radar target detection system 106, 108 for detecting radar targets in clutter using magnitude and angular position information obtained from return signals. A tracking algorithm 104 is used to track and update the positions of said targets with respect to the position of the radar system. The tracking algorithm includes a true target angle estimator 110 for maintaining accurate target angle information when the target is clutter and when the target is out of clutter. The tracking algorithm maintains accurate target distance information when the target is in clutter and when the target is out of clutter. In a specific embodiment, accurate distance information is maintained in a track file 122 where the amplitudes of return signals are stored once a target is detected by the detection system 100.

Abstract: An arrangement for coordinating positional and angle information made on separate relatively moving platforms, such as aircraft, having independent coordinate systems, uses measurements of a common reference made on both platforms. The measurements are transmitted to a common location. Measurements made at a first time are processed to determine two of three coordinate transformation angles. After a period of time, a second set of measurements is used to determine the third coordinate transformation angle. In a particular embodiment of the invention, the direction of motion of one of the platforms is controlled to be orthogonal to a coordinate axis of the other platform. When the coordinate transformation is determined, it can be used to coordinate or align navigation instruments, weapons, or the like. In one embodiment of the invention, a missile is directed toward a target, in a situation in which the target is viewed from the missile and another moving vehicle.

Abstract: A radar system in which a frequency agile synthesizer is used to provide rapid frequency shifts and in which measures are taken to maintain phase coherency. The system is fully coherent such that all signals are derived from a common source and are capable of high pulse repetition rates in excess of 1 MHz. There are no inherent transmit duty cycle restrictions and the system is able to transmit complex phase and frequency modulated waveforms. A frequency interleaving scheme is used to resolve range ambiguities at high pulse repetition frequencies and the use of a complementary phase coding scheme allows a high range resolution processing with the transmitted waveforms.

Abstract: Apparatus for the automatic fuelling of vehicles. A robot head that carries a fuel filler tube is movable to enable it to be brought into position to engage with a vehicle fuel-tank pipe. The robot head carries an opening device for opening a fuel-tank cover plate of a vehicle. The positioning of the robot head is effected by a positioning system that includes a transceiver unit carried by the robot head and that preferably operates at microwave frequency. A passive transponder is carried by the vehicle and includes a simple code which the transponder is intended to modulate on a signal transmitted by the transceiver and is reflected by the transponder. The signal received by the transceiver from the transponder is decoded and is used to access a robot head movement plan that corresponds with that code, to automatically steer the robot head to the fuel tank pipe and thereby enable the vehicle to be fuelled.

Abstract: A moving target which is reflecting waves will give rise to the well known Doppler frequency shift. When the reflected signal can be compared with the transmitted signal in homodyne detection, the resulting signal is called the Doppler signal. Both frequency and phase of the Doppler signal carry information about the motion of the target.By observing a Doppler signal at several points in space, it is possible to determine the position, velocity and acceleration of a moving target. Systems employing this principle are-used to track acoustic emitters with sonar, as well as radio emitters with radar. While the prior an has relied on analyzing the Doppler shift frequency, the present invention introduces a method employing the analysis of the phase of the Doppler signal. The phase-based algorithm shows a better signal to noise ratio in applications where the ratio of velocity and distance to the point of closest approach is large.

Abstract: A ground based radar antenna system and method for determining the elevation angle .phi. of a tracked target having a shaped reflector and a pair of spaced feedhorns for transmitting radiated energy to and receiving returned signals from the tracked target T, the shaped reflector and feedhorns cooperating to increase the range of coverage of the elevation angle .phi. beyond the coverage previously available with a standard parabolic reflector and to increase the gain of the signals returned to the ground based radar antenna system while simultaneously eliminating elevation angle ambiguities over prior systems employing only feedhorns for collecting returned signals. The radar system includes a construction which approximates a cosecant-squared antenna pattern, permits the calculation of the target height and three-dimensional position, and is economical to manufacture.

Abstract: A radar arrangement has a transmitter/receiver unit which is rotatable and has an aerial projecting an elongate radar beam onto a reflector which rotates therewith. The reflected beam therefore scans the target area. Target reflections are reflected by the reflector on to the aerial for detection thereby. The reflector is switchable about the vertical axis through 90.degree. with respect to the aerial. In one position, the beam is therefore projected into, and scans, the target area with its elongate dimension vertical (so as to be best suited to detect rapidly approaching targets of small aspect such as aircraft or missiles), and in the other position the beam is projected into, and scans, the target area with its elongate dimension horizontal (so as to be best suited to detect intermittent targets appearing in relatively slow moving positions such as the rotor blades of a helicopter).

Abstract: A monopulse thresholding processor and method for improving resolution by using the difference channel data to eliminate "excess" sum channel returns. The processor may be used with a radar system that comprises an antenna, a transminer, a receiver for processing transmitted radar signals to produce radar returns therefrom, a log compressor for converting radar returns to log values, and a display for displaying the radar returns. The signal processor comprises a left sum and right sum generator coupled to the receiver for computing a left sum and a right sum from radar returns generated by the receiver. A pseudo-difference generator is coupled to the left sum and fight sum generator for generating pseudo-difference channel data. A beam sharpener is coupled to the left sum and right sum generator and to the pseudo-difference generator for beam sharpening the radar returns.

Abstract: An apparatus for forming a latent image on a photoreceptor with a laser beam and for developing the latent image with a developer. A duty ratio of the laser beam is changed in accordance with the laps of using time of the developer.

Abstract: A radar system that includes an ultra wideband radar signal processor for electronically scanned arrays that utilizes frequency offset generation (FOG) to achieve beam steering as compared with phase shift and time delay techniques of conventional radars. The device comprises a transmit antenna, a chirp generator connected to the transmit antenna and a first summing circuit, a receiver antenna connected to the first summing circuit, a Doppler de-ramping chirp circuit connected to a second summing circuit, the output of the second summing circuit connected to an amplitude and weighting circuit and the output of the amplitude circuit connected to a spectrum analyzer of a Fast Fourier Transform (FFT) circuit. The signal processing consists of mixing the target returns with the transmitted signal to obtain a video beat note signal. This video beat note signal is mixed with a Doppler de-ramping chirp waveform which is matched to the desired target velocity.

Abstract: A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequenc of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time beacuse the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected.

Abstract: In a reflective angle of a radar, auxiliary elementary sources are positioned beneath the main source. By the division of the measurement signals of the measurement channel of the main source and of the auxiliary measurement channel, a monotonous characteristic is obtained, enabling the elevation angle to be measured with high precision. FIG. 1.

Abstract: A radar system for determining not only the azimuth and range of a target but also the target height over a predetermined range of elevation angles has separate receiving and signal processing channels coupled to a dual beam antenna for processing signals returned from a single target. The output of each signal processor is coupled to a height processor which divides the sum of the received signals into the difference of the two signals. The resulting ratio is used to access a look-up table to identify the elevation angle associated with the ratio from which the height of the target is calculated. The look-up table includes correction values to compensate for the antenna pattern nonlinearity.

Abstract: A fish school detecting method or apparatus radiates radio search signals with their carrier frequency in the S-band frequency range, successively in different azimuthal directions through a wide angular range, receives echo signals, and displays the echo signals on the screen of an indicator in such a manner that the echo signal reflected by a bird is clearly distinguished from the other objects, thereby locating the bird and detecting a fish school under the bird.

Abstract: A method for determining a mutual position between two objects, comprising transmitting a microwave signal from the first object towards the second object, causing the second object to receive the transmittal signal and re-transmit a signal, which is caused to be received by the first object. According to the invention the first object includes a transmitter/receiver unit (S/M-unit), which transmits the aforesaid signal (f.sub.o) from a transmitter antenna. The second object (T) is caused to re-transmit the aforesaid signal modulated with a signal (f.sub.m), the first object being caused to receive the transmitted signal through at least two antennae (M.sub.1, M.sub.2) placed symmetrically on a respective side of the transmitter antenna (S) and in an antenna plane common with the transmitter antenna (S). The angle (.theta.

Abstract: A single two dimension radar system having the capability of developing two dimensional data on all targets in its surveillance volume and three dimensional data for selected targets in its surveillance volume is disclosed. A single phased array antenna having two selectable elevation beam patterns, a wide beam and a narrow beam, is rotated in azimuth. In the two dimension mode, targets are detected and tracked in an azimuth and range position through use of the wide elevation beam. Upon selecting a particular target in track for three dimension data extraction, the radar system changes to the three dimension mode prior to the azimuth position of the selected target, and performs a sequential lobing process of the narrow beam in elevation angle. The power ratios of the target returns in the sequential lobes are analyzed and an elevation position of the selected target is determined. The radar system reverts to the two dimension mode after leaving the azimuth position of the selected target.

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.