Abstract: Monopulse radar operation is improved by nulling a single mainlobe jammer and multiple sidelobe jammers while maintaining the angle measurement accuracy of the monopulse ratio. A sidelobe jammer cancelling adaptive array is cascaded with a mainlobe jammer canceller, imposing a mainlobe maintenance technique or constrained adaptation during the sidelobe jammer cancellation process so that results of the sidelobe jammer cancellation process do not distort the subsequent mainlobe jammer cancellation process. The sidelobe jammers and the mainlobe jammer are thus cancelled sequentially in separate processes.

Abstract: Method and arrangement for an airborne radar system particularly adapted to detect large metal targets that are concealed from the air by camouflage or natural foliage. The arrangement includes an antenna that transmits a continuous wave electromagnetic signal having a selectable frequency that preferably has a wave length generally twice the length of an anticipated target and which is carried by a flying vehicle. The frequency of the transmitted signal is chosen to provide maximum penetration of the camouflage or natural foliage and maximum re-radiation from a metal target. Receivers connected to an in-line receiving antenna and to a crossed receiving antenna carried by a flying vehicle detect the radiation that is reflected from the terrain and a target with the same polarization as that transmitted. The co-linear antenna and receiver respond to the reflected radiation while the cross-polarized antenna does not detect this reflected radiation.

Abstract: A process for generating synthetic aperture radar interferograms comprises the following steps. First and a second radar images of a scene from a first and a second position spaced apart by a given baseline are generated. A first signal of said first image within a first radio frequency band of the spectrum is recorded. A second signal of said second image within a second radio frequency band of the spectrum having a frequency shift relatively to the first detecting band is recorded. The frequency shift being such that it ensures or maximizes correlation between the first and the second images. The first and second signals are combined for generating an interferogram of said scene.

Abstract: An electromagnetic energy absorbing structure provides a base structure having an electrically conductive ground plane positioned thereover. At least one dielectric and one impedance layer are positioned over the ground plane or surface on a side thereof opposite the base. An external most dielectric skin seals the structure. Additional alternating dielectric and impedance layers can be positioned over the first dielectric and impedance layers. The dielectric layer can be constructed from syntactic foam with impedance layers formed from patterns of conductive dipoles. The impedance layer, can alternatively, be formed from a resistive sheet formed into a broken pattern that may comprise a series of geometric shapes spaced from each other. The resistive sheet can be combined with a series of composite dielectric layers to form an integral composite structure.

Abstract: A method of processing a plurality of tracks representative of one or more target aircraft in a vicinity of a surveillance aircraft, where each track is generated in response to target reply signals provided by the target aircraft in response to interrogation signals transmitted by the surveillance aircraft, includes eliminating a portion of the plurality of tracks which are duplicate tracks of the same target aircraft. The remaining tracks are maintained and updated in response to the target reply signals provided by the target aircraft. A threat level for each of the remaining tracks is determined and two or more of the remaining tracks which are possibly representative of a same target aircraft are merged resulting in a composite track. The composite track is output to a display device utilizing information from a particular remaining track of the composite track having the greatest threat level to the surveillance aircraft while continuing to maintain and update all the remaining tracks.

Abstract: Measurement of the transfer function of a space fed lens array antenna membrane is achieved by utilizing a low power test illumination antenna opposite the feed side, while a probe antenna undergoes raster scanning of a test window on an opposite target side. The probe antenna measures near field distribution on the target side and data developed enables the transfer function of the membrane to be measured.

Abstract: An electronic counter countermeasure (ECCM) circuit for Automatic Gain Cool (AGC) electronic countermeasure (ECM) deception of conical scanning tracking radar receivers having a two position limiter in circuit with the AGC circuit to eliminate signal information enhancing the amplitude modulation of the error modulate signal to provide selectable values of dynamic range in a signal processor to render the ECM ineffective in target evaluation.

Abstract: Method and apparatus for measurement of the velocity of a moving target (20) in radio frequencies. From the measurement station (10) and from the target station (20), radio signals (S.sub.1,S.sub.2) are transmitted that are in different frequency ranges, as compared with each other, so that the receivers at the measurement station (10) and at the target station (20) are not subjected to interference. The radio signals (S.sub.1,S.sub.2) are received at stations (20,10) opposite to their transmission stations (10,20). The oscillator of the target station (20) is locked with the frequency transmitted by the measurement station (10) by means of a phase-locked loop (PLL). The frequency of said oscillator is passed to the transmitter part of the target station (20). The signal (S.sub.2) transmitted by the target station (20) is received at the measurement station (10). The Doppler shift (fd) of the frequency of the signal (S.sub.

Abstract: A compact radar sensor is provided. A monolithic millimeter wave integrated circuit (MMIC) transceiver is provided having a transmitter for transmitting a frequency modulated signal and a receiver for receiving reflected signals thereof. A microstrip patch antenna is provided for transmitting signals within a desired field and receiving the reflected signals from objects therein. A digital signal processor is further provided for analyzing the received signal and providing output signals therefrom.

Abstract: The monitoring assembly (10) monitors the location of mobile objects (12), i.e., personnel, within a structure (18). The object (12) carries a transponder (14) which periodically transmits status signals and receives command signals relating to audio control. Transceivers (16) are fixed at locations about the structure (18) for receiving the status signal producing the location signals, and transmitting commands to the transponders. The transmissions and reception occur during prescribed time windows. A controller (20) is connected to each transceiver (16) and monitors the location of transponders (14) and communication therethrough. The transponders (14) have audio capability of producing audio messages directly to the person thereof.

Abstract: The present invention is an airborne radar system which scans the flight path of an aircraft with two radar scans, an upper elevation pointing above local level and a lower elevation scan pointing below the glide slope. The radar returns from the upper elevation scan are used to detect the core of the microburst. The core and a model of the windshear which uses the core are used to select angles and range cell candidates, in a lower elevation scan, for hazard detection processing. The candidates in the lower scan, which is pointing at the ground, are used to create a hazard map tested against a predetermined hazard threshold. A threshold violation results in a pilot alert. The hazard map includes a vertical factor determined through model coefficients in the radial outflow as a function of altitude.

Abstract: Sensitivity time control (STC) data for an airborne weather radar system is provided as a function of aircraft altitude and radar system antenna tilt angle to normalize radar return signals at high as well as low aircraft altitudes. In one form of the invention the STC data is used to adjust the gain of a signal applied to a radar system received by a system antenna and in another form of the invention the STC data is used to establish a desired threshold for said signal.

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: A radar system includes a doppler/pulse compressor/range sidelobe suppressor filter bank (40), which separates received echo signals according to their frequency spectrum into doppler channels, and within each doppler channel performs pulse compression for reducing the duration of the received signals, and also performs range sidelobe suppression, for improving range resolution. It may be advantageous to perform certain types of processing in the time domain, such as determination of spectral moments for estimating velocity spread, mean closing velocity, and reflectivity of a diffuse target such as a weather phenomenon. An inverse (frequency-to-time) transform (50) is performed on the signals produced by the doppler/pulse compressor/range sidelobe suppressor filter bank (40), to produce a reconstructed version of the received signals. In these reconstructed signals, the pulses are compressed, and range sidelobes are reduced. The time-domain processing (62) is performed on the reconstructed signals.

Abstract: A segmented stretch waveform for wide band high duty cycle tracking application. The waveform is divided into multiples of two spaced segments as the tracking range closes. Target returns received during spaced segments are combined to correspond to the complete waveform; and range is determined in accordance with the combined waveform. Tracking range can be varied without changing bandwidth, FM slope, duty cycle or processing time.

Abstract: A low noise frequency synthesizer 10 that uses uses frequency dividers 13, 15, at least one of which(divider 15) is incrementable and decrementable in half integer steps, and analog gain compensation in a phase/frequency detector 14 to achieve lower noise, lower spurious levels and faster switching speed than traditional methods of frequency synthesis. The key features of the present invention are its half integer dividers 13, 15 and the ability to adjust the phase detector gain to compensate the loop for varying divide numbers. The synthesizer 10 comprises two dividers 13, 15 that provide two reference frequency signals that are a function of an input signal and an output signal of the synthesizer 10. A voltage controlled oscillator (VCO) 18 provides the output signal (f.sub.O) of the frequency synthesizer 10. A phase/frequency detector 14 compares the reference frequency signals and provides a phase error output signal that drives the VCO 18.

Abstract: An improved radar receiver having side lobe blanking and coherent side lobe cancellation circuits in the main receiver channel and a control arrangement that overcomes the conventional problem that the side lobe blanking circuit will also blank a noise jammer signal even after the coherent side lobe canceller circuits have acquired the jamming energy. In this system, the side lobe blanking circuits are mechanized with a logarithmic amplifier and with a fast time constant circuit in an auxiliary receiver channel. The fast time constant is selected to match or be slightly longer than the acquisition time constant of the coherent side lobe cancellers. This implementation allows the side lobe blanking circuits to be energized at all times, thus simplifying the operational control of the system. In some arrangements in accordance with the invention the fast time constant may be varied as a function of the amplitude of the jamming signal in the main channel.

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 loop simulator is provided for testing radar altimeter systems. Several accurately calibrated delay lines and attenuation elements can be switched into and out of the signal path. Using these elements, the loop simulator can be configured to provide several common tests for radar altimeters. Switching of the various elements is controlled by a microprocessor, which determines the appropriate configuration based upon a mode input, and automatically switches the correct elements into the signal path. The controller automatically compensates for attenuation of the various elements.

Abstract: A process for reducing the likelihood of runway incursions wherein the major components of an aircraft are individually tracked by radar instead of tracking only the overall image of the aircraft to more accurately predict possible runway incursions due to the rapid and accurate indication of any change in aircraft orientation during each sweep of the radar.