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 cylindrical cavity-backed multipole antenna system for high frequency applications is disclosed. The antenna system comprises a plurality N of planar radiation elements disposed on a dielectric disc mounted on the top surface of a conductive cylindrical cavity and equally spaced about its axis. A network circuit is adapted to introduce, for the system sum signal, progressive phase shifts of 360.degree./N to signals associated with adjacent elements and, for the difference signal, progressive phase shifts of 720.degree./N. The antenna system may be used to both transmit and receive electromagnetic radiation. The antenna sum and difference patterns are substantially symmetric in space about the antenna boresight.

Abstract: The invention of this disclosure comprises a system that simultaneously determines the frequency and direction of arrival of incoming signals. The apparatus of this invention comprises a layered half space dispersive delay line which is utilized as a beam forming element in a device that performs a two-dimensional Fourier transform on a function which is both time and space dependent.A pulse appears at the end of the delay line at a time which corresponds to the frequency of the incoming signal and the position of the pulse along the edge of the delay line is related to the direction of arrival of the incoming signals.

Abstract: The detection and warning of microbursts, low level wind shear, and other weather disturbances, which are hazardous to aircraft operations and to the public at large, are accomplished with either an airport surveillance radar (ASR) or a multi-beam Doppler radar. ASR Doppler systems normally operate to receive one of two relatively large vertical fan beams having different elevation angles but which overlap one another so that they have equal gains at an elevation angle, called the null, at a relatively low angle, for example 5.degree.. Below this null, the low beam antenna gain exceeds that of the high beam, and conversely above it. Accordingly, by subtracting the high beam Doppler spectrum from that on the low beam, a Difference Doppler Spectrum (DDS) is produced which is positive below the null and negative above. The velocity bounds of the positive portion of the DDS provide the wind speed components at the null and at heights near the surface.

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.

Abstract: A radar having a multiplicity of receive beams stacked in elevation and a target height extractor especially for use therein are disclosed. In operation, a set of range sweeps corresponding to an azimuth scan of the stacked receive beams across a detected target is established. A range cell interval corresponding to the detected target is estimated for each range sweep of the set. A target range measurement is computed from a set of estimated range intervals. Only the radar receive beam echo information corresponding to the estimated range cell interval for each range sweep of the established set is used by the height extractor to compute a corresponding set of elevation angles. A target elevation angle is formed as the weighted average of this computed set. Only one height computation is performed for each established set of range sweeps based on a function of factors including the computed target elevation angle and computed range measurement of the corresponding established set of range sweeps.

Abstract: An identification system comprising one or more tags and an interrogator. A tag is responsive to a radio frequency signal transmitted from the interrogator for phase modulating the signal alternately with a first frequency and a second frequency depending on a preselected code and for re-radiating the phase modulated signal back to the interrogator.

Abstract: Circuitry is disclosed for processing Doppler-shifted radar signals or ot noisy signals which fluctuate widely in frequency. The circuitry includes a dual channel discriminator including a voltage controlled oscillator as part of a feedback loop for frequency tracking of said signals. The discriminator further includes a frequency pass circuit in one channel thereof and a frequency stop circuit in the other channel thereof, with the outputs of these circuits applied to a multiplier. The multiplier output controls the frequency of the voltage controlled oscillator. The voltage controlled oscillator output is heterodyned with the input signals to obtain the heterodyned signals for application to the aforementioned two channels of the discriminator.

Abstract: In a continuous wave electromagnetic positioning or distance measuring system of the Wadley type (see U.S. Pat. No. 2,907,999) a number of secondary phase measurements are obtained from a number of successively produced primary phase measurements in such a manner that any instrumental errors incorporated in the primary phase measurements are eliminated. Each secondary phase measurement represents the fractional part of the phase delay that would be experienced by a signal of accurately known measuring frequency when propagated electromagnetically along a propagation path corresponding in length to the distance to be measured. The measuring frequency is determined by the frequencies of pattern and auxiliary pattern signals used in obtaining the primary phase measurements.

Abstract: Discrimination between sidelobe and main beam reception of interference signals in a lobe on receive only radar is accomplished by a method of operation in which interference signals are stored and averaged for the radar receive beam positions of boresight, up, down, left and right. Interference signals received at boresight are compared with interference signals received at each off-boresight beam position. Interference signals received at boresight are also differenced with interference signals received at the off-boresight beam positions and the results are compared with beam width defining threshold factors. The determined values are applied to logic functions that indicate reception of interference signals outside of the main beam pattern.

Abstract: An improved monopulse radar system wherein target return signals received by a plurality of antenna elements are corrected with correction signals derived within the system in response to pilot pulses. The improvement comprises a plurality of receiver channels, each receiver channel being coupled to a single one of the plurality of antenna elements. The improvement also comprises means for generating a first set of quadrature components of video signals developed in the plurality of receiver channels in response to the pilot pulses received by the plurality of antenna elements, and for generating a second set of quadrature components of video signals developed in the plurality of receiver channels in response to return signals from the target received by the plurality of antenna elements. Digital signals representative of the first and second sets of quadrature components of video signals are generated.

Abstract: A decoy radar transmitter governed by a control signal derived from a main radar transmitter to emit radiation which is phase coherent with the carrier frequency of the main radar transmission is disclosed. A section of the main radar transmitter generates a control signal compositely formed by the combination of derived signals including a phase coherent subharmonic of the carrier frequency of the main radar, a frequency shift keyed signal and a signal having a power content. The frequency shift keyed signal is representative of a phase coded modulation sequence of the carrier frequency transmissions, each frequency fo the frequency shift keying corresponds to a phase polarity of the phase coding. A single coaxial cable conducts the composite control signal to the decoy radar transmitter. Upon receiving the composite control signal, a section of the decoy radar transmitter separates the power signal from the received control signal for use in energizing the decoy radar transmitter.

Abstract: In the standard DME system, an airborne station having transmitted a pair of interrogation pulses receives a plurality of pairs of space-coded reply pulses from which the pulse pairs intended for the airborne station are selected by a decoder (DK) and a correlator (KR).The invention uses the first pulse of the selected pulse pair for the distance measurement. A measuring counter (MZ) is provided whose count is transferred to a register file (SR) at the reception of every pulse. A reply signal intended for the airborne station stops the write operation, it being insured that the counts based on the two pulses of the reply signal intended for the airborne station are contained in the register file (SR). Starting from the last count based on the second pulse, an evaluating circuit calculates back to the first pulse, taking account of the decoded pulse spacing.

Abstract: A tag is receptive of two radio frequencies (RF signals) for mixing the two frequencies and radiating a signal which is either or both the sum and difference of the two RF frequencies. A uniquely identifiable tag includes, in addition to the mixer one or more filters for radiating a signal only when the sum or difference of the two signals is a pre-specified value or only when the RF signals are each of pre-selected values.

Abstract: A method of processing signals received by a four quadrant monopulse antenna to resolve the signals from two sources within the sum beam of such antenna is shown to comprise the steps of: (a) separately quadrature detecting each one of the signals (A, B, C and D) received at each one of the four quadrants to form corresponding complex signals having real (I) and imaginary (Q) terms, each one of such complex video signals being representative of a different one of the signals A, B, C and D; (b) forming the monopulse sum (A+B+C+D) signal, and monopulse difference signals [(A+B)-(C+D)], [(A+C)-(B+D)] and [(A+D)-(B+C)] and the corresponding monopulse ratios; and (c), calculating the monopulse ratios of the two signals that, when extant simultaneously, produce the corresponding monopulse ratios.

Abstract: The simulation of clutter echo return signals for a radar system is accomplished using two sets of diode noise sources, a frequency synthesizer for bandwidth control, multiplexing control, two D/A converters and mixers, a 90-degree sower splitter, and a summer; the output of the summer being the simulated clutter. The two sets of noise sources each produce a digital encoded controlled bandwidth Gaussian noise signal which is strobed by the multiplexing control unit firstly to the pulse repetition interval of the radar system and secondly to the data rate of the radar system. The two strobed D/A converters convert the two digital noise signals into their analog equivalents. The two separate video channels are required to obtain the Rayleigh noise distribution characteristic of clutter. This distribution results when the analog signals from the D/A converters are multiplied with in-phase and quadrature RF reference frequencies in the two mixers, then summed in the summer.

Abstract: A multichannel DME ranging circuit is described which is capable of simultaneous multistation operation. A microprocessor is coupled to control associated peripheral devices and the receiver/transmitter of a DME to produce a multiplexing for receiving frequency data input from up to three DME ground stations. The data received from each of the three DME stations is used to generate timing and interface signals to control the DME receiver/transmitter and associated video processing circuitry. The video processing circuitry is in turn used to provide signals to the ranging circuit to independently determine range, velocity, time-to-station, and the identity of each of the stations providing input to the DME. Each of the three channels is operated indpendently to produce a decoded identification of its respective ground station.

Abstract: An improved bracket decoder apparatus including an enhanced bracket decoder ortion and a regenerative bracket decoder portion operates to generate enhanced bracket decode signals and regenerative bracket decode signals. The foregoing combination of decoder portions will allow digital display systems which use IFF information to detect all targets that are replying regardless of the IFF train spacing, even overlapping replies. The enhanced bracket decoder portion of the apparatus can be operated alone to detect all reply conditions except the one of overlapping replies. The apparatus is configured to provide presently used signals also, i.e., the bracket decode, the degarbled bracket decode, and the range and code information for each video reply.

Abstract: A monopulse antenna system providing a pair of phase/amplitude related signals in response to the reception of a desire signal, having calibration correction means attached thereto which receive one of the output signals from the antenna system and produce a pair of output signals having equal amplitude and a 90 degree phase difference. The calibration correction circuitry supplies the pair of output signals to the two channels of the monopulse receiver which includes circuitry for comparing the amplitude of signals in each of the channels and standard monopulse circuitry which compares the phase of signals in the two channels. Gain and phase adjustments in at least one of the channels are adjusted in response to the pair of signals until the compared output signals are equal in amplitude and 90 degrees apart in phase.

Abstract: In a method of measuring the level of a flowing material kept in a container there is employed a microwave signal that is fed from a transmitter through a tubular waveguide (7) that extends vertically downwardly through the container and communicates therewith so that the surface (10) of the material in the waveguide follows the level of the surrounding material. The signal is reflected from the surface back up through the waveguide and is conducted to a receiver to be employed, after signal processing in an electronic unit, for determining the level of material in the container. The microwave signal is fed to the waveguide by way of a mode generator (11) that produces only one dominant propagation mode of the signal, the wavelength of which is smaller than the diameter of the waveguide (7).