Abstract: A multi-mode seeker which comprises a stationary antenna and electronic circuitry responsive to signals received by the antenna to cause the antenna to scan a field of view determined by the signals received by the antenna. The seeker has a nose region positioned at the forward portion thereof and an adjunct sensor disposed in the nose region ahead of the antenna. The electronic circuitry includes circuitry for performing a Sum/Delta monopulse processing technique on the signals received by the antenna the Sum/Delta monopulse processing including calculating each of a standard Sum signal, Delta-Azimuth signal and Delta-Elevation signal. The seeker has a boresight axis, the center of the field of view being off boresight, in general. The seeker has a field of regard, the field of regard having plural sectors, each of the sectors having separate predefined compensation.

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 weather radar system is operable in an automatic mode for positioning the radar system antenna beam to scan an elevation axis between upper and lower scan limits in incremental steps as selected by a user while continuously scanning an azimuth axis for enhancing the analysis of weather conditions.

Abstract: Linear array antenna systems are used in X-scan aircraft location systems and methods able to avoid disabling azimuth error conditions caused by multipath reflections under roll and pitch conditions during aircraft carrier landing operations. Aircraft azimuth and elevation data is derived based upon time of incidence at an aircraft location of two transverse, diagonally oriented, scanned antenna beams. The aircraft location data is derived by comparing time of incidence data with data on known timing of scanning of the beams, which have diagonally-oriented fan beam patterns. A plurality of vertically oriented radiating elements are typically positioned along a line diagonal to the vertical to produce a diagonally oriented fan beam pattern. Beam scanning results from relative adjustment of signal portions supplied to the radiating elements.

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 multifunction antenna system is provided which has adaptive beam forming capabilities for transmitting and receiving signals having various beam patterns over a hemispherical field of view. The antenna system includes a beamformer having an array of N spiral arm elements for transmitting and receiving a radiating beam. N analytic voltage signals are produced by the N cylindrically symmetric spiral arm elements in relation to the radiating beam. A beam processor is further provided for selecting the appropriate combination of vector weight coefficients in response to input data. The beam processor loads the selected N vector weights into a vector weighter. In the transmit mode, the vector weighter multiplies the selected vector weights by an input signal to produce the N analytic signals which are then applied to the multiple arm spiral antenna and transmitted therefrom.

Abstract: A search radar system, is provided which includes at least one search radar device (1) having a primary antenna (2) and at least one secondary radar device (3) having an SSR/IFF antenna (4). The radar devices (1, 3) independently supply plot data from which signals are derived that are each suitable for presentation on a radar display. The antennas (2, 4) are oriented in opposite directions so that the said signals are derived from individual plot data representing successive detections by the respective antennas of the same target which can be individually presented. Hence, the data rate of the radar system is doubled relative to a conventional radar system having a conventional secondary radar device and a conventional antenna system.

Abstract: This invention concerns a secondary radar antenna operating in S mode.The antenna comprises a row of columns (1) of radiating elements powered by a hyperfrequency distribution circuit (2) containing a summing channel (.SIGMA.), a difference channel (.DELTA.) and a secondary lobe suppression channel (.OMEGA.), each producing a radiation diagram. The antenna end columns (L, R) each produce at least one auxiliary radiation diagram offset with respect to the diagram produced by the summing channel and contributing with the other antenna columns (1) to the creation of the other three diagrams.Application: secondary radars in S modes in communication with a large number of aircraft per antenna revolution.

Abstract: An optical control system for a phased-array antenna system employs a time-multiplexed optical control architecture to provide very fast (a few hundred beams per second) antenna beam scanning using slow (milliseconds) response spatial light modulators in two optical signal processing channels. In each channel a cascade of relatively slow switching speed nematic liquid crystal cell spatial light modulators and associated free space delay units or fiber optic delay cables are disposed to receive transmit or receive optical input signals comprising a plurality of light beams. The control voltages applied to the spatial light modulators determine the paths of the light beams through the cascade and the differential time delay imparted to the light beams in the input optical signal. High speed 90.degree.

Abstract: A pulse chasing-type bistatic radar system is provided with a cluster of multiple narrow receive beams that covers the angle corresponding to the receive beam width required by the conventional pulse chasing mode, i.e., the required receive angle width, and scans in steps in accordance with the propagation of the transmit signals in the transmit beam. As the receive time-frame ends for the last narrow beam making up the cluster, it advances to a new position at the head of the cluster. Adopting this arrangement, the required number of receive beams can be reduced to the minimum.

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: A method of improving the amplitude-frequency characteristic when receiving a target echo (M) in a radar system installed on a satellite or an aircraft and carried at a given height (h) above the earth's surface. The method utilizes the known method of compressing a received pulse which contains a number of frequencies (f.sub.1 -f.sub.2) in order to obtain improved dissolution of the target. According to the method, the receiving lobe of the radar is swept, independently of frequency, over a given larger angular area (.theta..sub.b l-.theta..sub.a) within which the target (M) is located. Within the smaller angular area (.DELTA..theta.) occupied by the target as seen from the radar, i.e. the momentary width (.DELTA.w) of the target echo, however, the receiving lobe is controlled in dependence on the frequencies (f.sub.1 -f.sub.2) so as to obtain a number of optimally located receiving lobes for the smaller angular area (.DELTA..theta.).

Abstract: The invention relates to a surveillance sensor provided with at least one surveillance radar antenna 1 and at least one co-located and co-rotating electro-optical surveillance sensor 5 mechanically connected to said radar antenna. A combined panoramic picture is compiled by combining information from both sensors using a common track unit 30.

Abstract: Polystatic radar system and method for operating at relatively low power for a given coverage. The illumination power density of the transmit pattern is continuously varied as a function of the range to the receiver from each point within the receive beam coverage.

Abstract: A method of managing beams transmitted and received by a plurality of phased array antennas. In a search mode, the phased array antennas transmit searching pulses synchronously in a search mode. In a tracking mode, targets tracked by the phased array antennas are divided to a plurality of groups on the basis of pulsed repetition rate. Then, for the respective divided groups, transmission timings of tracking pulses to be sent form the phased array antennas are calculated by using ranges of the targets belonging to the respective groups so that transmission and reception operations do not occur simultaneously, thereby enabling the simultaneous usage of the phased array antennas.

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 sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because 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 restored range resolution, but the long pulse results in a large minimum range within which targets cannot be detected.

Abstract: A phased array antenna system has optical architecture comprising free space delay units and associated spatial light modulators compatible for operation with temporally incoherent or coherent laser light to produce signals having selected time delays to actuate antenna elements of an antenna array to transmit electromagnetic radiation at a selected beam angle from the phase array. The same optical architecture is used to process electromagnetic signals detected by the antenna array to produce an output signal for display or processing which corresponds to the radiation detected at the selected beam angle.

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 sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because 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: 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 sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because 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: 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 sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because 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: An azimuth-stacked radar method and apparatus of the type typically used for surveillance employs a mechanically-rotating antenna comprising horizontal end-fed rows of antenna radiating elements with phase shifter control on each row together with a monopulse elevation manifold to generate an elevation sum and difference beam pair. Additionally, this radar employs a waveform comprising multiple subpulses at different frequencies with sufficient separation between the subpulses at each frequency to spread them in azimuth to form a beam cluster and employs mechanical antenna rotation and phase-responsive elevation scanning. The scanning is accomplished in a way that will permit advantageous avoidance of ground clutter and other uninteresting radar reflectors.

Abstract: An array antenna system having a predetermined electric current distribution on an antenna aperture to form a desired shape of antenna beam. Active antenna elements arranged on the aperture transmit a signal for electronically scanning a predetermined region to detect a target and receive a signal reflected by the target. Passive antenna elements are also arranged on the aperture. The antenna system further includes a direction finding section including reception antenna elements which receive an incident signal. The active, passive and reception antenna elements are positioned to allow a predetermine electric current distribution to be established on the antenna aperture.

Abstract: A plurality of transmitting (14, 16, 18, 20) and receiving antenna elements (22, 24, 26, 28) are formed on a support member (12) which may be mounted on a corner of a vehicle for scanning a pattern including areas on opposite sides of the vehicle corner. In an automotive application, the pattern may include a rear area, and a blind spot on the side of the vehicle adjacent to the rear area. A transmitter (50) is connected to the transmitting antenna elements (14, 16, 18, 20) by a passive phased array (30) such as a planar microstrip Butler matrix, and an electronic switch (52) which sequentially connects the transmitter (50) to inputs of the transmitting array (30). A receiver (62) is similarly connected to the receiving antenna elements (22, 24, 26, 28) by a planar microstrip passive phased array (40), and an electronic switch (64) which sequentially connects the receiver (62) to outputs of the receiving array (40).

Abstract: A scanning method used by a laser radar for scanning a predetermined scanning region with a laser beam so that the whole of the scanning region is illuminated with the laser beam, is disclosed in which a laser beam makes a first spiral scanning outwardly or inwardly and then makes a second spiral scanning inwardly or outwardly so that the rotational direction of the second spiral scanning is the same as that of the first spiral scanning, and the first spiral scanning and the second spiral scanning are repeated. According to this scanning method, the output of drive means for driving an optical system which causes a laser beam to perform a scanning, can be reduced, since a maximum power necessary for causing a body large in inertia to make a curvilinear or rotational motion is far smaller than a maximum power necessary for causing the body to make a linear motion.

Abstract: A wheeled support assembly 10 is manually pushed over the ground and has a motor 22 rotating an antenna assembly 60 about a vertical axis 24. Encoders 28 on the antenna shaft 20 and on a wheel axle encode antenna angular position and position over the ground. Transmitted pulses and received data pass through a rotary microwave connector 26. For example, 400 sets of pulses are emitted at equal angular intervals in each revolution of the antenna assembly. The interval between pulses is e.g. 12 microseconds, with 256 pulses per set. Noise reduction is achieved by processing the received data accordingly. In a modification the rotary connector 26 is single channel with some electronic stages mounted on the rotating antenna assembly. Power is coupled to them via the microwave cable. An umbilical connects the assembly 10 to a support facility including a computer. Alternatively, battery power is used with data transferred radiatively.

Abstract: In a holographic radar having receivers (10) for amplifying, detecting, and A/D-converting the RF signals in all range bins received by antenna elements (1) and a digital beamformer (11) for performing digital operations on the outputs of these receivers to generate a number of beams equal to the number of antenna elements, three or four antenna arrays (D0 to D3), each array (2) being formed of a plurality of antenna elements (1), are oriented in different directions to provide 360.degree. coverage and switches (12) are provided to switch the connection between the antenna elements (1) and the receivers (10) according to pulse hit numbers and range bin numbers. Thus high-speed 360.degree. scan coverage can be attained with a small, inexpensive apparatus requiring as many receivers, memory elements and a digital beam former as needed for a single antenna array.

Abstract: An electronically scanned radar system has a serpentine antenna, with at least two ports. The antenna is physically rotated. Each port has a mixer, transmitter and local oscillator feeding signals to it, the signals of the transmitter and oscillator being synchronized with one another to take advantage of the physical rotation of the antenna. The radar system can be operated in various ways to produce two independent beams simultaneously in a surveillance mode and/or tracking mode at each port. Furthermore, with the use of coupling means, the system can be operated to produce four independent beams at two different frequencies simultaneously. The system can also be operated to produce one or more beams in a surveillance mode and/or one or more beams in a tracking mode at each port. Further, the system can be operated to compensate for the physical rotation of the antenna and can avoid jammers by hopping to another frequency.

Abstract: A signal processor for radar systems having phased array antenna structures. The processor determines the angle of arrival of the signal from a discrete energy source. The separate elements or output ports of the antenna structure are sampled to form a matrix of signal values. These values are converted into polynomial expressions consistent with one of the spectral estimating methods of maximum entropy, maximum likelihood, and thermal noise. The roots of the polynomial expressions are found and compared to the distance of the unit circle in a pole-zero diagram. Roots sufficiently close to the unit circle are selected as representative of the source signal peaks and the angular directions to such sources are determined by the corresponding angular location of the selected roots in the pole-zero diagram.

Abstract: A locating system employs a single-point device employing unique scanning patterns for generating peak signal data which can be used to calculate the position of a signal source within a scanned region. One preferred embodiment utilizes a satellite in high earth geosynchronous orbit and a simultaneous yaw and roll pattern to scan a substantial portion of the earth's surface. The point source being located may be virtually any form of transmitter of radiant energy such as infrared, electromagnetic, light or acoustical energy. The scanning device may also be positioned in a low earth orbit satellite, an aircraft, a missile or a helicopter. The single-point device re-radiates the signal source transmission to a computer command center which correlates single-point device scanning position data with received transmissions to accurately compute the location of the signal source. Beacons placed at precisely known locations may be used to interpret scan data.

Abstract: A shipboard search radar in which an antenna beam is stepped up and down in elevation to keep the beam pointed approximately toward the horizon even though the ship may be rolling and/or pitching.

Abstract: Improved radar apparatus includes a rotatable antenna structure which includes an antenna disposed within a housing which is rotatably driven. Also disposed within the rotatable housing are a unitary magnetron, microwave circulator and microwave limiter device which rotates when the housing is rotatably driven. Additionally, a transmitter, such as a modulator coupled to the unitary device and a receiver also coupled to the unitary device are disposed within the rotatable housing. Preferably, the antenna is formed as a slotted wave guide antenna. Radar signals transmitted from and reflected to the antenna pass through a slotted filter which is mounted in front of the antenna. A commutator, preferably formed of slip rings and brushes, serves to electronically connect the transmitter and receiver within the housing to signal processing circuitry fixedly disposed externally of the housing, thereby permitting the housing to rotate while coupling electrical signals to and from the transmitter and receiver.

Abstract: A multifunction active array system is disclosed, wherein the array aperture may be partitioned into a plurality of arbitrary subapertures. The array system includes N radiative elements, each coupled to a corresponding active module. Each module is in turn connected to an aperture partition selector, which includes an M-way power divider/combiner device, having a module port and M device ports. Each device port is coupled through an RF switch to a partition port of the device. M N-way manifolds are provided, having N manifold ports coupled to a respective one of said partition ports of each selector. The manifolds are coupled to a receiver and an excitation source. Each partition may be formed by the desired connection of a particular module to a manifold by the respective positions of the RF switches. The array system provides the capabilities of partitioning the array into M or less subapertures to simultaneously generate sum patterns, difference patterns, guard patterns, and adaptive nullings.

Abstract: A frequency agile radar system allows tracking of noncooperative targets with high accuracy. The system is particularly useful in an automatic landing system aboard an aircraft carrier. The radar employs an electronically steered planar array antenna system in which a symmetrical pencil beam of 1.degree. beamwidth is steered in 1/2.degree. steps in a raster scan. A space-stabilized acquisition window allows target acquisition, and target scanning modes are chosen as a function of target range. At far range, target scan is effected by those four beam raster positions which bracket the target whereas when the target is at near range where its cross section is larger than a single beamwidth, the raster is "ballooned" to paint or cover the target fully. The computed track of the target provides a continuing update of autopilot command signals radioed to the target to bring it to and hold it on a selected glideslope which effects the automatic landing.

Abstract: In a method and an apparatus for radar surveillance a multilobe antenna is commonly used for transmission as well as reception and distributes the power (P) to be radiated in several (n) simultaneous and uniform radiation lobes (L1-L7 ) which are swept across a zone to be surveyed.The antenna properties are maintained invariant while each signal transmitted or received by the antenna is coded by allocating a particular code element ({e.sub.i }.sub.1.sup.n) to each lobe (L1-L7 ). Each code element ({e.sub.i }.sub.1.sup.n) is fixed for forming, when the lobes (L1-L7) sweep, the received signals into a reception sequence ({S.sub.R .nu.)}.sub.1.sup.n) of elements ({.sigma..sub.o c.sub..nu. }.sub.1.sup.n) having predetermined mutual relations. The reception sequence is correlated by means of a correlation sequence of elements ({c.sub..nu..sup.* }.sub.1.sup.n) which are proportional to the conjugated elements of the reception sequence.

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 pulse radar apparatus is provided with a coherent transmitting and receiving unit with N juxtaposed receiving antennas and N receivers for the reception of echo signals and the processing thereof into two orthogonally phase-detected and digitized video signal components i.sub.r and q.sub.r, where r=0, 1, 2, . . . , N-1. A beamformer is provided to derive from these components the orthogonal components I.sub.k and Q.sub.k of the video signal determined jointly by the N receivers in accordance with a receiving beam pattern k corresponding with a specific elevation interval, where l=0, 1, 2, . . . ,N-1. The orthogonal components I.sub.n, Q.sub.n and I.sub.n+1, Q.sub.n+1 supplied through two adjoining beamformer output channels n and n+1, and derived from the video signals P.sub.n, P.sub.n+1 from echo signals of maximum amplitude received from moving targets, are used for determining the deviation (.DELTA..alpha.) of the elevation value .alpha.