Abstract: An array antenna for direction-finding includes antenna elements which define a triangular outline well-suited for meeting space constraints or reducing reflections from mounting conditions associated with the array antenna. The actual geometric configuration of the antenna elements is limited to certain triangular configurations with corresponding geometric correction factors to maintain the accuracy of estimating the angle of arrival. A processing system determines the appropriate angle of arrival based upon differential phases received in the antenna elements and the appropriate geometric correction factor.

Abstract: A method for steering a beam of an antenna array minimizes a least squares approximation of an error function of a desired radiation pattern relative to an antenna array pattern calculated from a known radiation pattern for each antenna element.

Abstract: A multiple-beam electronic scanning antenna including an array of phase-shifters (2, Dij). The N simultaneous beams are obtained in N directions by a law of excitation (fij) applied to each computed phase-shifter (Dij) by summing the phase laws &psgr;1, &psgr;2, . . . &psgr;k, . . . &psgr;N associated respectively with each 1, 2, . . . k, . . . N order direction and by applying the resultant phase-shift (&psgr;tij) to the phase-shifter, without applying the resultant amplitude modulation (&rgr;ij). The multiple-beam electronic scanning antenna especially is applicable to uniquely phase-controlled antennas in satellite or terrestrial communications requiring simultaneous communications with several variable sites.

Abstract: A method and apparatus for improving the performance of Synthetic Aperture Radar (SAR) systems by reducing the effect of “edge losses” associated with nonuniform receiver antenna gain. By moving the receiver antenna pattern in synchrony with the apparent motion of the transmitted pulse along the ground, the maximum available receiver antenna gain can be used at all times. Also, the receiver antenna gain for range-ambiguous return signals may be reduced, in some cases, by a large factor. The beam motion can be implemented by real-time adjustment of phase shifters in an electronically-steered phased-array antenna or by electronic switching of feed horns in a reflector antenna system.

Abstract: A slow speed pulse chase apparatus in a bistatic radar system, wherein the receive antenna follows the transmit pulse out in space. The receive beam comprises many parallel beams that overlap all the possible positions of the transmit pulse as it travels into space. Slow speed chase apparatus provides a small group of beams which are held in a fixed location as the transmit pulse travels by and then is jumped in one large step to continue to the next position to remain there until the transmit pulse travels by.

Abstract: A scatterometer orbiting around the earth globe comprises a single fanbeam radar antenna which is rotated around a vertical axis, at a slow rotation rate. The antenna foot-print sweeps a circular disc. The slow conical sweep combined with the motion of the satellite on which the scatterometer is mounted results in highly overlapping successive sweeps such that an image pixel is revisited many times during an overpass. The pixels in the radial direction are resolved by range-gating the radar echo. The radar operates in the C-band. The scatterometer is intended, in particular, to determine wind speed and direction over the ocean.

Abstract: A switching unit for a photonic phased array for use in the microwave frequency bands uses lasers and other photonic devices to perform various functions in the phased array such that signals can be carried to the antenna elements on a single optical fiber. In one embodiment of the invention, a set of fixed phase shifters generates signals each having different phases. In the switching unit, each resulting signal, which is of a particular phase, modulates a laser of a different color. Each different laser color is thus associated with a given phase. Alternatively, time-delay units produce signals of different time-delay states which signals are then associated with lasers of different colors. The lasers are then used for selection of the signals to be applied to each element in the array. The laser signals are combined and carried on a single optical fiber to an optical network of tunable optical filters which can be located at the element level.

Abstract: A Forward Looking Sensor (FLS) alignment system includes a transmit antenna adapted to provide multiple beams, a receive antenna adapted to provide multiple beams, a transmitter coupled to said transmit antenna and adapted to radiate an electromagnetic signal through selected ones of the multiple antenna beams of said transmit antenna and a receiver coupled to said receive antenna and adapted to receive through selected ones of the multiple antenna beams of predetermined antenna beams of a receive antenna having multiple antenna beams reflections from the radiated electromagnetic signal and processing the received electromagnetic signal reflections to generate an alignment offset signal.

Abstract: A method is provided for the direction of arrival (DOA) tracking of at least one source, along a single azimuth axis or along both azimuth and elevation axes. The method includes the steps of selecting all the high peaks from a DOA function as potential track points, converting the potential track points into a plurality of tracks and selecting a true track from the plurality of tracks.

Abstract: A transmit/receive (T/R) module adapted for use in a radar system. The module has a unified structure including a layered substrate on and in which two T/R channel circuits are integrated. The channel circuits make use of power distribution, channel controller, and RF signal routing circuitry, partly on a channel shared basis. In the RF routing circuitry, respective coupler elements are employed to combine RF receive signals for output to an RF receive manifold and to split an RF transmit signal from a transmit manifold into separate RF transmit signals for input to the T/R channel circuits.

Abstract: A frequency modulated continuous wave (FMCW) phase shift radar system includes a transmitter, a receiver, and a linearly-tuned oscillator circuit arranged in the transmitter as a source of electromagnetic radiation. The linearly-tuned oscillator circuit has a voltage controlled oscillator (VCO); and a closed loop feedback circuit including a local oscillator and a harmonic mixer coupled to receive a stabilized local oscillator (LO) frequency signal from the local oscillator and a radio frequency (RF) signal from an output of the voltage controlled oscillator. The harmonic mixer mixes the LO frequency signal with the RF signal to produce an intermediate frequency (IF) signal, and a linear frequency discriminator is coupled to receive the IF signal and to produce an output voltage signal which is applied to an input of the VCO to stabilize the latter, thus completing the feedback circuit.

Abstract: A phased array radar system for target tracking having a track initiation unit, a track prediction unit, a scheduling unit, a track selection unit, and a transmitter/receiver unit. The track initiation unit initiates new tracks representing detected aircraft targets. The track prediction unit predicts the expected position and the calculated position uncertainty of the target as a function of time and the minimal, maximal and optimal time difference to the next measurement. The scheduling unit performs an independent calculation of a sequence of possible time intervals to the next measurement in accordance with specified conditions, and then performs an intersection operation between the calculated sequences of time intervals in order to calculate the optimal time interval to the next measurement. A track selection unit selects that track which has the shortest remaining time interval, K.sub.i, to the next measurement and decreases the time interval to the next measurement for all other tracks with K.sub.i.

Abstract: An active array radar system is controlled by photonic signals. The array of N antenna elements is divided into M subarrays, each having N/M antenna elements. Tunable lasers provide M optical wavelengths within non-overlapping bands. For reception, the microwave signals are optically modulated onto a single fiber for each subarray. Time delays are introduced for an offset between elements in a subarray and for an offset between subarrays. By using wavelength division multiplexing, a true time delay is attributed to each antenna element on the array. A non-coherent optical combiner having an array of N photodetectors demodulates the receive signals and recovers the coherent sum of the RF signals.

Abstract: A power distribution system (12) is provided in radar apparatus to distribute power from a 270 VDC source (60) through an intermediate power converter (70) and very high frequency (VHF) regulator/modulator units (80). Bus conductors (71,74) interconnect the source, the intermediate power converter, and the VHF units. Capacitors (71, 76) are connected to the bus conductors on the input and output sides of the intermediate power converter. Each VHF unit supplies modulating pulses to RF amplifiers (82) of an AESA array of the radar apparatus.

Abstract: A digitally beam formed phased array antenna capable of both transmitting and receiving signals is constructed from a series of digitally controlled antenna elements. To transmit signals, a series of direct digital synthesizers is used to drive the antenna elements forming the phased array. Each direct digital synthesizer is programmed from a common digital processor with specific time and phase delay information such that the signals from the array combine to form a desired antenna pattern. To receive signals, signals from each antenna element in the phased array are processed by analog to digital converter. The digitized signals are then pre-processed in a time and phase delay preprocessor which receives time and phase delay information from a corresponding direct digital synthesizer prior to signal combining in a common digital processor.

Abstract: First and second phase control amount tables output to first and second vector multiply circuits phase control signals Sc1 and Sc2 representative of corresponding phase shift amounts with gains represented by input gain control signals Sg1 and Sg2 as arguments. The first and second vector multiply circuits shift the phases of in-phase components S13 and S23 and quadrature components S14 and S24 of an antenna 2 in opposite directions in accordance with the phase control signals Sc1 and Sc2. Consequently, the amount of phase shift caused by receiving amplifiers is corrected so that the phase difference at antenna terminals between the input signals to the antennas is maintained.

Abstract: A radar electronic scan apparatus 10 employs an array of transmit/receive phase-shift modules 14 with a plurality of ferrite phase-shift subarrays 16. Each ferrite phase-shift subarray has a pair of phase-shift ferrite substrates 32A and 32B mounted on a support with each substrate having four phase taps for connection to radiators of the electronic scan apparatus.

Abstract: This radar with a wide instantaneous angular field and a high instantaneous angular resolution, in particular for a missile homing head, includes essentially:a transmitting antenna with a relatively wide radiation pattern, transmitting a quasi-continuous wave;a receiving antenna including a plurality of radiating elements;means for formation of beams associated with said receiving antenna, to achieve a linear combination of the signals from the various radiating elements of said receiving antenna, in order to obtain a group of simultaneous reception beams allowing the instantaneous scanning of the airspace covered by said transmitting antenna.

Abstract: A phased array antenna element design and method of using same is disclosed wherein the antenna elements are each provided several signals containing phase, and amplitude information for controlling a beam transmitted or received. The signals are mixed within each antenna element to produce RF signals for transmission or for use as filtering signals for reception. The signals are selected such that some antenna elements receive a same signal and more particularly, such that a single signal is provided to each row of the array and to each column of the array. The row and column signals are combined at elements located at an intersection of the row and column.

Abstract: The disclosed broadening method consists in dividing the radar antenna into n groups of columns of active modules, applying, at transmission, a different linear phase law to each group and, at reception, forming n.sup.2 simultaneous beams, each having the nominal angular width of the complete antenna, and in shifting these beams as a whole to cover the angular domain in which the energy has been radiated at emission.

Abstract: In a phased array radar, simultaneous beam steering and single-sideband mlation is accomplished in the phase shifters in response to phase control signals produced by the beam steering controller and input to the phase shifters. The beam steering controller produces the phase control signals from a pre-selected beam steering angle, a pre-selected radar intermediate frequency and a voltage representing the frequency error from incomplete compensation of the target motion (doppler) of the previous cycle of the radar. Using the phase shifters thusly eliminates the need for an expensive separate component, the single sideband modulator.

Abstract: A digitally beam formed phased array antenna capable of both transmitting and receiving signals is constructed from a series of digitally controlled antenna elements. To transmit signals, a series of direct digital synthesizers is used to drive the antenna elements forming the phased array. Each direct digital synthesizer is programmed from a common digital processor with specific time and phase delay information such that the signals from the array combine to form a desired antenna pattern. To receive signals, signals from each antenna element in the phased array are processed by analog to digital converter. The digitized signals are then preprocessed in a time and phase delay preprocessor which receives time and phase delay information from a corresponding direct digital synthesizer prior to signal combining in a common digital processor.

Abstract: A signal manifold having a source signal converter coupled to an RF source for converting a source electronic signal from the RF source into an optical signal. The manifold has an optical coupler, having multiple optical fibers, coupled to the first signal converter; and a sink signal converter coupled to the optical coupler. The sink signal converter converts the optical signal from the coupler into a sink electronic signal and conveys that electronic signal to an RF sink.The manifold can be a transmit manifold, or a receive manifold. In addition, a transmit manifold and a receive manifold can be combined to provide a bi-directional signal manifold. The invention herein also provides low-loss asymmetric fiber-optic combiner which includes multiple optical fibers, each fiber having cladding removed from the respective fiber end, exposing the fiber core. The cores are joined together in a predefined configuration and each are optically coupled to a plenum optical fiber.

Abstract: An array antenna (10) that can form and sweep a predicted radiation beam pattern in different directions by using a subharmonic frequency signal from each voltage controlled oscillator (VCO) (20) to control the array phasing. Each VCO (20) generates a radio frequency carrier signal that drives an antenna element (16). A subharmonic signal is generated from a portion of the signal from the VCO (20). The subharmonic signal is mixed with a constant frequency signal to produce an intermediate frequency (IF) signal. The frequency of the IF signal is compared to the frequency of a variable frequency signal in a phase locked loop (PLL) (40). Since the phase of a signal is dependent on its frequency, the variable frequency signal is generated to have a frequency corresponding to a certain phase. The PLL (40) generates an error signal as a function of the difference in frequencies between these two signals. In response to the error signal, the VCO (20) changes the frequency of the carrier output signal.

Abstract: Telecommunication systems and methods for driving a phased-array antenna ing a plurality of spaced antenna elements that radiate and receive a beam of radio frequency signals. Each of a plurality of ferroelectric phase shifters connect to a different one of the antenna elements. A signal processor system, having a receiver and a frequency synthesizer communicates with the phase shifters under the control of a data processor system. A joystick connects to the data processor system for permitting manual input of beam steering information thereto. The data processor system responds to the joystick inputs by controlling the relative phase shifts of the signals propagating in the ferroelectric phase shifters. The system further includes a temperature sensor circuit for sensing the temperature of each of the ferroelectric phase shifters.

Abstract: An apparatus for detecting illegal tampering with an electricity meter which is adapted to record the amount of electricity supplied to the meter through cables has a first signal generating sensing coil situated externally of, and upstream of, the meter which generates a first signal representative of the current flowing through one of the supply cables and a second signal generating second sensing coil, located within the meter, which generates a second signal representative of the amount of electricity to be recorded by the meter. A Monitoring device monitors the first and second signals and produces a third actuation signal when one of the first and second signals differs from its correct value as a result of tampering.

Abstract: A method for detecting fixed or moving objects within an angular zone, as may be used in vehicle anti-collision systems, employs separate and distinct transmission and reception patterns. The transmission pattern successively illuminates consecutive segments of the angular zone. The reception pattern receives echo signals in parallel from illuminated objects in each zone segment. The echo signals are then digitally beam formed into a total field signal. The angular positions of the detected objects are then derived from the total field signal.

Abstract: A phased-array antenna (18) for use with a frequency-hopping transmitter (16) includes a plurality of elemental antennas (210), each associated with a phase-shifter (212) which is controlled (20) to form a beam (216) in the desired direction at a base frequency. The antenna elements (210, 212) are formed into subarrays (408t, 408b) each of which is fed from a common port (310). A further phase-shifter (312) is associated with each subarray, for imposing a phase shift on a group of elements of the overall array. The further phase-shifters are controlled when the frequency of the transmitter is away from the base frequency, to cause a stepwise-continuous correction phase across the array, which maintains the desired beam direction.

Abstract: In an apparatus and method for controlling an array antenna comprising a plurality of antenna elements arranged so as to be adjacent to each other in a predetermined arrangement configuration, a plurality of received signals received by the antenna elements is transformed into respective pairs of quadrature baseband signals, using a common local oscillation signal, wherein each pair of quadrature baseband signals is orthogonal to each other. Then predetermined first and second data are calculated based on each pair of transformed quadrature baseband signals, and are filtered using a noise suppressing filter. Respective elements of a transformation matrix for in-phase combining are calculated based on the filtered first and second data, and the received signals obtained from the each two antenna elements are put in phase based on the calculated transformation matrix. Thereafter, a plurality of received signals which are put in phase are combined in phase, and an in-phase combined received signal is outputted.

Abstract: A stepped beam transmit antenna that comprises a feed array that includes a dielectric substrate and a plurality of radiating elements disposed on the substrate. The radiating elements each comprise two coplanar and coextensive fins that are separated by a narrow gap and that are tapered at their radiating end to form a linear tapered slot feed aperture. Beam position inputs are disposed at respective input ends of each of the radiating elements. A backshort is disposed adjacent the tapered slot feed aperture of each of the radiating elements. A low pass filter is disposed adjacent the backshort of each of the radiating elements. A switching diode is disposed between the backshort and the tapered slot feed aperture of each of the radiating elements. The antenna includes a power distribution network comprising a suspended printed line. A lens is disposed adjacent the feed array for projecting energy beams produced by the antenna.

Abstract: A radar device emits a wave beam into a given angular range outside a vehicle, and scans the given angular range by the wave beam. The radar device detects a reflected wave beam. A recognizing device is operative for recognizing an obstacle with respect to the vehicle on the basis of the result of detection of the reflected wave beam by the radar device. In the recognizing device, a point recognizing section recognizes obstacles as points, and a uniting section is operative for uniting adjacent points among the points provided by the point recognizing section. The uniting section provides sets each having adjacent points. A line-segment recognizing section is operative for detecting a specific set or specific sets of adjacent points among the adjacent-point sets provided by the uniting section, and for recognizing every detected specific set as a line segment having a length only along a width direction of the vehicle.

Abstract: Apparatus for calibrating a phased array antenna having a plurality of active modules and a test manifold. An RF antenna, which is both a transmitting and receiving antenna is positioned at a far field range from the antenna to be calibrated. A receiver is connected to the output of the far field receiving antenna and the output of the test manifold of the antenna to be calibrated for the transmit calibration and a transmitter is connected to the far field transmitting antenna and the test manifold for a receive calibration, a command phase and amplitude for each steering angle of each module of the antenna being calibrated. The phase and amplitude data from the test manifold is compared with the phase and amplitude data of the far field range to obtain an error signal, and the error signal is combined with the command amplitude and phase iteratively until the error signal is minimized for each module of the antenna.

Abstract: A system and method for polar digital beamforming of at least one independent transmit beam is disclosed. A computer generates a digital signal representing both pointing and modulation information which is communicated to a plurality of subarray controllers which generate the polar weighting signals corresponding to the appropriate antenna element for transmitting. The complex weighting signals may be generated by summing a sequence of complex multiplications or by simply inverting the real and imaginary components of the weighting signal for particular modulation schemes. A phasor may be used in conjunction with an attenuator to modulate a local carrier signal. Alternatively, phasors are utilized without attenuators to increase the efficiency of the power amplifiers. The antenna architecture disclosed permits a single set of phasors and attenuators to be utilized per antenna element regardless of the number of beams to be generated.

Abstract: A radar apparatus that is provided with auxiliary antennas (5, 10) of an omnidirectional nature. In addition to customary ECCM applications, such as side-lobe suppression and side-lobe blanking, the auxiliary antennas (5, 10) are also used for the emission of frequency-shifted pulses which are emitted simultaneously with radar transmitter pulses. To this effect, the radar apparatus is provided with auxiliary transmitters (8, 13). Furthermore, auxiliary receivers (6, 11) have been provided for analyzing the responses of jammers to the frequency-shifted pulses.

Abstract: A method of estimating the directions of radiating sources (56, 58, 60) with respect to an array (46) of a number of antenna elements (48), each of which elements has a separate gain/phase control (50). With nominal gain and phase selected a first estimte of the radiating sources directions (.theta.) is accompished by application of the MUSIC algorithm (2). The algorithm is iteratively applied to a microprocessor (54) using updated gain and phase values. Iteration is terminated at that iteration which produces the maximum difference values of the smallest eigenvalue pair of Q.sub.(i).

Abstract: An active array antenna for use, for example, in a radar system, includes elemental antennas, each with a T/R module, distributed over a circular aperture. For lowest cost, the aperture is thinned. The T/R modules are operated at maximum output, to achieve maximum DC-to-RF efficiency, and for simplicity. A phase controller controls the phase shift which is imparted by each module to its signal, to form a main beam and its associated sidelobes. A perturbation phase generator portion of a phase controller adds a perturbation phase shift selected, in conjunction with a particular thinning distribution, to form a relatively wide null in the sidelobe structure, in which signal transduction is reduced. In a radar context, this null may be placed on a source of ground clutter or a jammer.

Abstract: In an apparatus for adaptively controlling an array antenna of M antenna elements, a multi-beam forming circuit calculates N beam field strengths in a known manner, and a beam selecting circuit selectively outputs beam field strengths not smaller than a predetermined threshold value by comparing the N beam field strengths with the threshold value. At least two adaptive control processors calculate N weight coefficients corresponding to N beams according to a constant modulus algorithm, respectively multiplies the calculated beam field strengths by the calculated N weight coefficients, and combines in phase respective signals of multiplication results, outputting the combined signal as a reception signal. In an initial state of one adaptive control processor, a weight coefficient thereof corresponding to the maximum beam field strength is set to a predetermined initial value not zero, and weight coefficients corresponding to the other beam field strengths are set to zero.

Abstract: A radar antenna includes a reception part constituted by elementary antennas, each elementary antenna delivering a reception signal to a computer for the formation of simultaneous radar beams by computation, and a transmission and reception part constituted by at least one elementary antenna. The computer uses the signals received by the elementary antennas of the reception part to form a set of radar beams within a solid angle radar beam formed by the elementary antennas of the transmission and reception part. The radar antenna finds particular application in the field of designation and trajectography radar.

Abstract: An antenna system comprises a main antenna for use of transmission and reception and a pair of sub-antennas use of only reception. The antenna beam of the system is scanned in the direction of a beam width to be compressed. Both received signals of the main antenna and the sub-antennas are fed to a signal processing circuit. The signal processing circuit converts these received signals to power signals and then performs signal processing on them. In this signal processing, the power signal received by the main antenna is output as a final output signal only if both double differential coefficients of the received signals received by the main antenna and the sub-antennas are equal to or less than corresponding predefined positive real number values, and if the phase difference between the power signal received by the main antenna and the power signal received by the sub-antennas is equal to or less than 90.degree.

Abstract: A phased array for transmitting to a microwave powered aircraft is focussed and steered by feedback from the aircraft. Each antenna of the array is phase modulated in turn, and the resulting amplitude modulation of the field at the aircraft is used to calculate a correction to the antenna phase, which is telemetered back to the array system and applied to the antenna phase shifter.

Abstract: In an apparatus and method for controlling an array antenna including a predetermined plurality of M antenna elements arranged in a predetermined arrangement configuration, beam electric field strengths of a plurality of N beams of transmitting signals are calculated, and then signals representing the calculated beam electric field strengths equal to or larger than a threshold value are outputted. Thereafter, based on the outputted signals, there are calculated a plurality of N weight coefficients for the receiving signals respectively corresponding to the plurality of N beams of transmitting signals, such that a main beam of the array antenna is directed toward an incoming direction of a desired radio wave and also a level of the receiving signal in an incoming direction of an unnecessary radio wave are made zero.

Abstract: A true time delay phased array is provided which includes a digital subarray interface in the transmit signal path. The digital transmit signal path interface includes a digital reference signal generation means and digital signal propagation means for supplying the digital reference signal to the subarray. Each subarray includes RF carrier signal generating means for generating an RF carrier signal phase coherent with the reference signal, a fiber optic true time delay circuit for applying an appropriate phase delay to the RF carrier and an appropriate true time delay to the modulation signal, and a waveform modulator for modulating the modulating signal onto the phase locked RF carrier signal to provide the transmit signal for the subarray. The present invention can be used in conjunction with existing digital interface technology for receive and control signal paths to provide an entirely digital subarray signal path interface.

Abstract: An improved system is disclosed for controlling the operation of a transmit/receive module in a phased-array antenna system. The improved module control system of the invention is implemented in a simple integrated circuit chip and may be co-located with a transmit/receive module positioned at an antenna array element. Either fully distributed or row/column distributed beam steering architecture may be implemented by the improved module control system with both speed of operation and cost advantages realized over prior art systems.

Abstract: A transmit-receive module for a phased array radar comprises a phase shifter, high-power amplifier, low-noise amplifier, and duplexer which are constituted with field-effect transistors and a control circuit for processing negative-voltage signal data to control and drive the above RF devices.Therefore, a compact small-power-consumption transmit-receive module is obtained because a level conversion circuit for driving the RF devices is disused and the RF devices are directly driven by a control circuit. Moreover, the entire transmit-receive module can be downsized because a plurality of unit arrays are constituted with one control circuit.

Abstract: A transmit/receive element having a transmit/receive circuit that includes a variable frequency transmit phase lock loop and a variable frequency receive phase lock loop, and an output amplifier that receives a modulated transmit signal from the transmit phase lock loop for driving an antenna element. The transmit phase lock loop receives a feedback signal which is (a) the modulated transmit signal during receive intervals and (b) the output of the output amplifier during transmit intervals, such that the transmit phase lock loop is controlled by a feedback signal at all times.

Abstract: An improved phased array radar system has a plurality of bias binary fiber optic delay lines each connected between the transmit/receive cells and at least one of signal input means and signal processing means. A plurality of electronic binary delay lines are connected to at least one of the signal input means and the signal processing means and each bias binary fiber optic delay line.

Abstract: A low loss, fast switching, electronically tunable filter circuit which is microstrip compatible is obtained through the use of a resonant ring structure having two couplers, a low noise amplifier and a variable phase shifter. The tunable filter may advantageously be used in the receive channel of a transmit/receive module for phased arrays wherein the resonant frequency of the ring can be tuned anywhere in the operating frequency range so as to increase the dynamic range of the receiver.

Abstract: A transmission/reception module suitable for use in electronically phase-controlled antennas for a synthetic aperture radar includes a circulator provided for each individual radiator element terminal to achieve vertical and horizontal polarization. A low-noise amplifier is connected to the circulator in the reception path. A high-power amplifier is connected to the circulator in the transmission path. The two separate polarization reception channels each include a low-noise amplifier. The two separate polarization transmission channels each include a high-power amplifier. The reception channels and transmission channels are respectively connected to a polarization change-over. Switching arms of the polarization change-over are then connected to either the reception contact or the transmission contact of the transmission/reception switch.

Abstract: Prior art arrays of TR modules suffer from the disadvantage of requiring heavy and bulky waveguides or coaxial cables to provide controls therefore. In the present system, by using incoherent light to coherently synchronize the different TR modules of the array to produce a coherent phase array, the bulky waveguides and coaxial cables no longer are needed. To provide for the coherent synchronization of the phase array, oscillator and control signals are multiplexed onto different incoherent optical signals. The multiplexed optical signals are then summed and sent, via an optical fiber, to the TR modules of the array. At each of the TR modules, the oscillator signal and a corresponding control signal are separated from the summed optical signal and are used to weight the phase and amplitude of the radar signal to be transmitted from the TR module. When the properly synchronized and weighted modulated radar signal is sent from each of the TR modules, a coherently synchronized radar signal is produced.

Abstract: An unsupported, flexible, quasi-linear phased-array antenna within a space-based radar system which is tethered to a host satellite in free space. The antenna is formed by a plurality of antenna elements which are connected serially along a common axis. The antenna points in an Earth-pointing direction via gravity-gradient forces acting thereon. The phased-array antenna is capable of radiating a narrow electromagnetic beam in the end-fire direction along the array either in a spot or conical beam for detecting, identifying and tracking moving targets on or near the Earth's surface. According to one aspect of the invention, the phased-array antenna forms an elongated conductor which moves through a magnetic field in space for generating electrical power.