Abstract: Device and method for permanently checking the integrity of a transmission affected by parameters not directly accessible to measurement and whose influence on the modulus and phase of the field radiated in space can be determined by utilizing a mathematic model, the transmission being from an antenna array. Each antenna is supplied with one or more Hf carrier frequencies, each being modulated in a known way by one or more sinusoidal low frequency signals. First, a recording is made, at least at one point and during a time period T, of the amplitude of the combination of the signal received at this point and of a reference signal, having a fundamental frequency equal to one of the HF frequencies of the signal to be analyzed. Then, the amplitude of low frequency components of the signal thus obtained is extracted and memorized.

Abstract: A detector beamformer array system having a sparse array and a reference ay. The reference array is adapted, according to known principles, to have an output response with one main lobe significantly larger than all other side lobes, and with a substantially flat response. Signals received by both arrays are cross-correlated with one another, and only signals sufficiently correlated are annunciated. The resulting adaptive array system has a resolution even better than that of the sparse array's aperture, and with directional sector selectivity corresponding to the angular width of the reference array's mainlobe, providing a system having high resolution and directional selectivity, but with far fewer sensors than with filled arrays used for this purpose.

Abstract: The apparatus is an antenna system for autoadaptive direction and polarization filtering of radio waves traveling through an HF ionospheric channel and generating an output signal for coupling to a receiver. First and second crossed loop antenna elements having first and second output terminals, respectively, are disposed around a common axis. A filar antenna element has a longitudinal axis along the common axis. The filar antenna element has a first end terminal situated at the same phase center as the first and second output terminals. A multiplier circuit multiplies each value output from the first and second output terminals and the first end terminal by a corresponding complex weighting coefficient. The complex weighting coefficients are adjustable as a function of variations of polarization of a radio wave, and azimuthal and site arrival directions of the radio wave.

Abstract: To eliminate the complexity and the weight involved in the use of a Butler matrix, the present invention matrix antenna array uses a combination of processors and analog multipliers for weighting the signals, either to be transmitted or received, from the corresponding antenna element of the array. Since the analog multipliers are adaptable to operate in the microwave frequency, the control signals can be multiplied with the radar signal directly so that complexity of construction, bulkiness and heavy weight are eliminated from the matrix antenna array of the present invention.

Abstract: An efficient digital beam-forming network (100) utilizing a relatively few small-scale A/D converters is disclosed herein. The inventive beam-forming network (100) is disposed to generate an output beam B in response to a set of N input signals. The set of input signals is provided by an antenna array (110) having N elements, upon which is incident an electromagnetic wavefront of a first carrier frequency. The present invention includes an orthogonal encoder circuit (170) for generating a set of N orthogonal voltage waveforms. A set of biphase modulators (162-168) modulates the phase of each of the input signals in response to one of the orthogonal voltage waveforms, thereby generating a set of N phase modulated input signals. The N phase modulated input signals are combined within an adder (180) to form a composite input signal. The inventive network (100) further includes a downconverting mixer (184) for generating an IF input signal in response to the composite input signal.

Abstract: An off-line processor arrangement for a broadband accelerated convergence adaptive antenna array wherein signals from a plurality of antenna elements are applied to respective identical tapped delay lines (T) the outputs of which are fed through individual signal weighting means to a beamforming network (BFN), the arrangement including one or more lattice filter means (LF) to which the auxiliary antenna element signals are applied together with the output response of the beamforming network to compute sets of weight correction vectors (* W) with which to update weight coefficients and means for storing said updated coefficients, said stored coefficients being applied to the individual signal weighting means to weight the outputs of the tapped delay lines.

Abstract: A system for adaptively positioning nulls in the pattern of an antenna utilizing an auxiliary antenna in conjunction with a correlation receiver to determine the gain in amplitude and phase of the antenna pattern at the location of the interfering source. This gain is then utilized with the known gain at the peak of the main lobe of the antenna to compute coefficients of sinusoidal perturbation functions applied to the phase function of the antenna to establish a null in the direction of the interfering source.

Abstract: A transceiver interference cancellation system having an adaptive processor for receiving signals from a number of antennas and for suppressing particular signals from the antennas. The system includes a code generator which controls a switch to provide transmitted signals with a predetermined pulse code. Means including a code correlator are provided for detecting the pulse code in received signals and for controlling the operation of the adaptive processor such that wanted signals when identified are not suppressed.

Abstract: A method of and an arrangement for the combined correction of I/Q phase and amplitude imbalances within channels and interchannel phase and amplitude mismatches in arrays of signal channels. The I and Q channels of a reference channel are orthogonalized while simultaneously commencing the correction of an auxiliary channel. Optimum correction is obtained with reduction in hardware in comparison with a cascaded correction method, the auxiliary channel I and Q components being transformed only once.

Abstract: A data processing system for a phased array antenna consisting of an array of transmit/receive elements which result in a significant reduction in the data processing requirements for the received signals. In operation, the RF transmitted and received beams are formed and steered in a conventional manner with a phase shifter and amplitude weighting for each element. However, a simplifying approximation is made in the signal processing of the received signals for interference suppression, which results in minimal degradation of the system performance. In such a system, interference suppression is obtained by generating nulls in the receive antenna pattern in the direction of the interference. The nulls are produced by adjusting the phase and amplitude (weight) of the received signal from each array element just enough to null the interference with minimal impact on the rest of the antenna pattern.

Abstract: A microwave radiometer is formed of a set of frequency scanning antennas disposed parallel to each other and connected by a common microwave feeder. Signals of individual ones of the antennas are translated to different intermediate frequencies such that differences between the intermediate frequencies are proportional to baseline spacings between pairs of antennas of nested interferometers. A correlator containing parallel delay lines and a set of multiplier channels coupled to paired taps of the delay lines receives signals at the intermediate frequencies to produce a set of correlation signals. A two-dimensional Fourier transformation is applied to the correlation output signals to provide the power spectral density of microwave radiation incident upon the array of antennas.

Abstract: An adaptive array processor is disclosed for processing the signals from a main antenna and one or more auxiliary antennas to provide suppression of wideband interference. The outputs from the respective antennas are transformed into the frequency domain by synchronized chirp transformers conducted over a transform block length. The transformed auxiliary antenna signal is weighted by time varying, frequency dependent weights which are adaptively determined. The transformed main antenna and weighted auxiliary antenna signals are then combined. The combined signal is then transformed back to the frequency domain by an inverse chirp transformation.

Abstract: An adaptive antenna array arrangement for a receiver in a frequency hopped spread spectrum system. The arrangement includes an auxiliary local oscillator (lo.sub.a) which is hopped sequentially and pseudo-randomly across the spread system independently of the main frequency hopped oscillator (Lo.sub.m). The adaptive array processor (FUA, FM, PM) is digital, operates in an open loop configuration and evaluates the frequency bands during periods of time when the main oscillator is not operating in those bands. The processor derives null sterring weights for each band. The weights for each band are stored (WS) and subsequently used (W.sub.In -W.sub.Qn) when the main oscillator hops into the band and so cause the array of generate nulls directed towards sources of unwanted systems.

Abstract: A method and device for removing undesired jammer signals from desired signals which comprises forming a beam on the desired signal in an adaptive antenna array characterized by an orthogonalizer array (12) to receive digitized signals from the antennas, and pass signals to a beamforming array (14) and including a late jammer canceller array (16) and an intelligent controller (24) arranged to control weights (W) and select a row having the desired beamformed signal.

Abstract: A beamforming adaptive control loop is simultaneously employed in combination with a null-steering adaptive control loop to enhance the signal/interference ratio resulting in an increase in the messasge quality. The loops may employ temporal processing in which case on-epoch sample/hold filters and off-epoch sample/hold filters form separate loops which enhance the desired signal and cancel the undesired signal, respectively. The correlated output from the beamforming loop is added to the correlated output of the null-steering loop and mixed with the incoming signal.

Abstract: An adaptive depolarization-interference-compensator for a digital radio relay system using multi-level quadrature amplitude modulation (QAM) with co-channel operation of the orthogonally polarized signals which is not necessarily synchronous with the clock frequency and/or carrier frequency and produces good compensation of depolarization effects.The receiving branch of the two receivers (3, 4), which use the same RF-local oscillator (5) or separate RF-local oscillators are synchronized for the differently polarized signals and each contain a quadrature demodulator (8, 14) for two signal components (I- and Q-channel).

Abstract: The effects of multipath and other interference signals in communication receivers are reduced by implementing an adaptive array. The invention addresses a signal environment in which the directions of arrival and the time of arrival of the signal of interest and the unwanted multipath or interference signals are unknown. The feedback equation of the LMS adaptive array is changed so that a reference signal is not needed. The system uses the strongest received signal as the signal of interest and rejects the other received signals.

Abstract: A beam forming apparatus is provided having a plurality of beam ports producing a corresponding plurality of differently directed beams, each one of such beams being associated with a corresponding one of the beam ports, one of such beams being directed at a desired signal source and at least one of the beams being directed at an interfering signal source. A processor is coupled to the beam ports, for combining signals at such beam ports into a composite signal with the ratio of the power of the desired signal component of such composite signal to the power of the interfering signal component of such composite signal being increased from the ratio of the power in such desired and interfering signal components at the one of the beam ports associated with the beam directed at the desired signal source. The beam forming apparatus directs one of the beams at a desired signal source and an additional beam at each one of a number of interfering signal sources.

Abstract: An adaptive antenna comprising at least two sensors for receiving electromagnetic signals and for producing first signals; the antenna further including divider means for dividing each first signal into respective second and third signals; weighting means for modifying each respective second signal according to a quantized weighting function; summing means for summing the respective second signals to provide a fourth signal; means for producing a system feedback signal in response to the fourth signal; limiter means for limiting the dynamic range of the system feedback signal; correlator means for correlating the respective third signals with the limited system feedback signal to produce respective correlator output signals; means for determining the signal environment power level of the far field sensed by the at least two sensors and for providing a fifth signal substantially corresponding to 1/.sqroot.

Abstract: Undesired signals from interfering satellites are separated from desired signals from a target satellite by using a sum beam and a difference beam as in a monopulse radar. Both desired and undesired signals are received by an antenna and separated by different mode couplers from a waveguide. The fundamental mode of the waveguide provides the desired signals along with components from the interfering signals. Both desired and undesired signals are picked up from the waveguide through a fundamental mode coupler. The higher order modes of the waveguide provide the interfering signals alone, representing the difference beam which will be aligned along the boresight. In a circular waveguide, the TM.sub.01.sup.o will yield a difference pattern for vertical polarization in any plane, and a TE.sub.21.sup.o or TE.sub.01.sup.o mode will result in a difference pattern for horizontal polarization. A square or a rectangular waveguide could be used instead of a circular waveguide to achieve the same result.

Abstract: This invention is directed to a modified monopulse comparator which includes two sum and difference hybrid junctions. The first hybrid junction produces a signal-free sample of any interference which is received by the datalink receiving antenna. The second hybrid junction is a standard monopulse comparator driven by amplified and filtered signals from the A and B antenna feeds after subtraction of the properly scaled and phased interference sample.

Abstract: A relatively narrow beamwidth (10.degree. or less) receiving antenna patt is formed at the receiver end of a radio frequency transmission link where a plurality of radiating sources are operating in a dense communications environment. The antenna pattern comprises the difference between two antenna receiving patterns where the beamwidth of one pattern is wider by a predetermined angular amount than the other pattern. In the preferred embodiment, a phased linear array of antenna elements is operated as two sets of elements wherein one set of elements comprising a number of elements less than the total number of elements provides a beamwidth that is broadened by a predetermined angular sector greater than the beamwidth formed by the entire array. The antenna elements are progressively phase shifted to provide overlapping beam patterns and the pattern of one set of elements is scanned so that one side of both patterns are substantially coincident.

Abstract: An adaptive antenna 10 embodying the present invention includes an array of sensors 12. Each sensor 12 has associated therewith a main channel 14, a feedthrough path 16 and a feedback path 18. Correlators 20 coprocess signals in the feedthrough path 16 and the feedback path 18; the result is transformed according to an algorithm by a computer 22 which controls a weighting circuit 24. The weighting circuit 24 thus progressively modifies the signal in the main channel 14 to minimize interference with a desired signal. Placement of a limiter 26 along the feedback path 18 simplifies correlator design relative to adaptive antennas without such limiters and improves performance relative to adaptive antennas with limiters in the feedthrough path.

Abstract: A narrow-band phase shift beamformer system is disclosed. The outputs from the elements in a transducer array are each divided into two components whose amplitudes are respectively proportional to the sine and cosine of the required phase shift, which are then processed so that the steered beam may be formed by coherent summation. The proportionalities of the respective sine and cosine components are achieved by switched capacitor circuits, which are preferably implemented by LSI circuits, permitting substantial hardware savings and yielding highly accurate component proportionalities.

Abstract: This invention relates to a mainlobe jamming cancellation system which can e used to allow a radar to detect targets even when relative motion exists between the jammer and the radar platform. In particular, this invention relates to a mainlobe canceller that utilizes a main antenna and one or more widely spaced auxiliary antennas in conjunction with one or more phase locked loops (PLL), to automatically align the jamming signals received by the several antennas. The alignment is necessary to realize a high degree of jammer cancellation.

Abstract: A radar ECCM system for degrading the effect that a standoff noise jammer has on a radar receiving site that is tracking an incoming aerial target. The system effectively removes from the mainlobe of the beam emanating from the site the component of random noise contained in the jamming signal.