Abstract: A phased array antenna includes an array of antenna elements configured to transmit signals that form an antenna beam. A corresponding set of amplifiers supplies a respective set of continuous wave (CW) signals to the antenna elements for transmission. The CW signals having respective different frequencies that are offset from each other by incremental offset frequencies such that the different frequencies are spaced over a frequency range at intervals. Phases of the set of CW signals are aligned such that, at periodic instants, all of the CW signals have simultaneous zero crossings. The frequency and phase relationships among the set of CW signals cause the antenna elements to radiate an antenna beam that scans a field of view in a raster pattern. The resulting ultra-fast scan rate effectively delivers short pulses to any given point within the field of view, making the radiated signal suitable for three-dimensional imaging.

Abstract: A technique for improving impedance matching in a phased array antenna involves placing a segmented fence around the antenna elements of the array. The antenna elements are arranged above a ground surface such as a ground plane. The segmented fence includes spaced-apart conductive projections electrically coupled to and extending from the ground surface, such that the segmented fence partially terminates electric fields traveling in directions parallel to the ground surface. The segmented fence lies in paths extending in at least two directions along the ground surface to define fence enclosures that surround individual antenna elements. With dual-polarization or multi-polarization dipole antenna elements, the fence enclosures partially terminate the electric field in each direction parallel to the ground surface to simplify impedance matching without unduly restricting the magnetic field.

Abstract: An antenna includes at least two planar conductors cooperatingly arranged in a planar configuration having a bifilar spiral winding structure, a log-periodic structure or a sinuous configuration and a frequency-independent reflective backing situated on one axial side of the planar configuration. The backing includes a solid, disk-shaped dielectric substrate having a relatively high dielectric constant, and three mutually perpendicular arrays of elongated dielectric elements at least partially embedded in the solid dielectric substrate. The elongated dielectric elements have a relatively low dielectric constant. The elongated dielectric elements of the three mutually perpendicular arrays are formed as rods, cones and rings.

Abstract: An Instantaneous Frequency Measurement (IFM) receiver that receives a signal from a target and determines the frequency of the signal. The IFM receiver includes delay lines selected in lengths forming relatively prime ratios or by using the preferred method of the present invention which minimizes the total number of different delays required to achieve a given accuracy in frequency measurement.

Abstract: An antenna includes at least two planar conductors cooperatingly arranged in a planar configuration having a bifilar spiral winding structure, a log-periodic structure or a sinuous configuration and a frequency-independent reflective backing situated on one axial side of the planar configuration. The backing includes a solid, disk-shaped dielectric substrate having a relatively high dielectric constant, and three mutually perpendicular arrays of elongated dielectric elements at least partially embedded in the solid dielectric substrate. The elongated dielectric elements have a relatively low dielectric constant. The elongated dielectric elements of the three mutually perpendicular arrays are formed as rods, cones and rings.

Abstract: An antenna includes at least two planar conductors cooperatingly arranged in a planar configuration having a bifilar spiral winding structure, a log-periodic structure or a sinuous configuration and a frequency-independent reflective backing situated on one axial side of the planar configuration. The backing includes a solid, disk-shaped dielectric substrate having a relatively high dielectric constant, and three mutually perpendicular arrays of elongated dielectric elements at least partially embedded in the solid dielectric substrate. The elongated dielectric elements have a relatively low dielectric constant. The elongated dielectric elements of the three mutually perpendicular arrays are formed as rods, cones and rings.

Abstract: A broadband impedance matching circuit employs active circuits featuring non-Foster reactance behavior, such as negative capacitor circuits and negative inductor circuits, to achieve extremely broadband matching of electrically small antennas. The matching circuit includes at least one non-Foster reactance circuit selected to neutralize the reactance exhibited by the antenna. The circuit further includes a dynamic dispersive impedance transformer circuit which compensates for the frequency dependent radiation resistance presented by the electrically small antenna. The dynamic dispersive impedance transformer is constructed using complementary Foster and non-Foster reactance circuits configured as an impedance transformer.

Abstract: An antenna and system for determining two-dimensional angle-of-arrival includes circular array interferometers for azimuth, linear interferometers for elevation, and a mast for positioning the interferometers in a vertically stacked orientation. The circular array interferometers exhibit azimuth constant-phase-difference contours orthogonal to elevation constant-phase-difference contours exhibited by the linear interferometers. An antenna and system for determining azimuth of input signals includes ambiguous and non-ambiguous circular array interferometers. The non-ambiguous circular array interferometer resolves ambiguities introduced by the ambiguous circular array interferometer, the at least one ambiguous circular array interferometer operatively coupled to a low-order Butler matrix and power divider/combiner such that a high order Butler matrix is not required to generate omnidirectional phase modes from the ambiguous circular array interferometer.

Abstract: A satellite based signal transmission and reception system which generates multiple beams with low side lobes and minimal crossover losses. The system includes a focusing device and an array of signal generator elements coupled to feed radiator elements. The feed radiator elements are assigned into overlapping beam sub-arrays characterized by a frequency and radiated beam polarization. Each overlapping sub-array generates a transmission beam signal which is orthogonally polarized with respect to the beam generated by the other overlapping sub-array. The use of beam orthogonality provides for physically overlapping beam sub-arrays without the use of analog combining networks which are inherently lossy structures. This allows beams to be generated having a highly tapered amplitude distribution to simultaneously achieve low side lobe levels and low beam cross over losses.

Abstract: A direct digital synthesizer circuit and method for reducing the harmonic content in a synthesized output signal. The direct digital synthesizer generates first and second address signals driving first and second sine look-up read only memory (sine ROM) circuits. The first and second sine ROMs generate first and second digital sine wave signals which are offset in phase from one another by 180 degrees. The first and second digital sine wave signals are converted to first and second analog sine wave signals. The first and second analog sine wave signals are combined in a subtractor circuit. As a result of the phase relationship between the first and second analog sine wave signals, the fundamental component of these signals are emphasized by subtraction while the second harmonic component of theses signals are simultaneously de-emphasized.

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: 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 phased array antenna system capable of scanning at rates faster than the information rate of signals being received to prevent the loss of information during the scanning process. The phased array is configured to add the capability to provide moderate multi-dimensional separation of multiple signals and to eliminate the sensitivity loss due to sampling usually encountered with such rapid-scan systems. The array antenna system is comprised of the means to form multiple, time sequenced responses, each response corresponding to a different beam of sensitivity. The beams scan the full coverage sector and together with each other form a contiguous set of beams that both fill the coverage sector at any one time and also synchronously scan the full coverage sector. The beams are differentially delayed to permit the beam responses from any particular incident signal to be added in unison, giving rise to a compressed pulse whose time of occurrence is related to the signal angle of incidence.

Abstract: A phased array antenna system capable of scanning at rates faster than the information rate of signals being received to prevent the loss of information during the scanning process. The sensitivity loss due to sampling usually encountered is avoided. The present invention is an improvement on a prior art system that avoids the sensitivity loss in that the present invention also avoids the frequency selectivity inherent in the prior art system.The array antenna system is comprised of the means to form multiple, time-sequenced outputs, each output corresponding to a different beam of sensitivity. The beams scan the full coverage sector and together with the other outputs form a contiguous set of beams that both fill the coverage sector at any one time and also synchronously scan the full coverage sector.

Abstract: A cylindrical phased array antenna system capable of scanning at rates faster than the information rate of signals being received so that no information is lost by the scanning process. The array is configured to add the capability to provide multidimensional separation of multiple signals and to eliminate the sensitivity loss due to sampling. The cylindrical phased array is comprised of the means to decompose the distribution of current on the radiator elements caused by wave incidence into component signals which are the Fourier spatial harmonics of the distribution, heterodyne means to differentially phase shift these component signals at rates exceeding 4 .pi. radians per cycle of the highest frequency present in the information content of the incident wave, and means to form multiple complex-weighted sums (beams) of the component signals.

Abstract: The invention applies to a cylindrical, electronically scanned antenna system wherein the scan occurs at rates more rapid than the information being processed, and wherein the invention comprises improvements in the distribution subsystem designed to achieve high values of gain by eliminating sampling losses and still assimilating and processing the information logically, fully and accurately, even though the antenna is scanning at a rapid rate. The multiple time sequenced outputs of multiple beams are themselves coherently summed, after being differentially delayed so that they all peak at the same time.

Abstract: A cylindrical phased array antenna system capable of scanning at rates faster than the information rate of signals being received so that no information is lost by the scanning process, and without sensitivity loss due to sampling and with reduced frequency selectivity. The cylindrical phased array is comprised of the means to decompose the distribution of current on the radiator elements caused by wave incidence into component signals which are the Fourier spatial harmonics of the distribution, heterodyne means to differentially phase shift these component signals at rates exceeding 4 radians per cycle of the highest frequency present in the information content of the incident wave, and means to form multiple complex-weighted sums of the component signals. The sums are multiple time sequenced responses, each response corresponding to a different beam of sensitivity.

Abstract: An ultra-widebandwidth compressive receiver includes a power divider for processing a composite input signal consisting of individual input signals. The power divider provides a plurality of power divided signals to corresponding nondispersive delay lines. Each nondispersive delay line generates a unique time delay for each power divided composite signal. The unique time delay is generated in accordance with an arithmetic progression. The unique time delay has the effect of altering the phase of a corresponding individual input signal. The time delayed composite signals are provided to a frequency converter which heterodyne mixes them with local oscillator signals of frequencies which are a base frequency plus multiples of a reference signal frequency. The result is provided to a power combiner which re-combines the time delayed and frequency converted individual input signals in order to generate a group of narrow signal pulses that are separated in time according to their frequency.

Abstract: A cylindrical phased array antenna system capable of scanning at rates faster than the information rate of signals being received so that no information is lost by the scanning process. The array is configured to add the capability to provide multi-dimensional separation of multiple signals and to eliminate the sensitivity loss due to sampling. The cylindrical phased array is comprised of the means to decompose the distribution of current on the radiator elements caused by wave incidence into component signals which are the Fourier spatial harmonics of the distribution, heterodyne means to differentially phase shift these component signals at rates exceeding 4.pi. radians per cycle of the highest frequency present in the information content of the incident wave, and means to form multiple complex-weighted sums of the component signals.

Abstract: A frequency divider includes a power divider which receives an input signal and divides the input signal into first and second signals. A frequency doubler receives the first signal and provides a third signal having a frequency which is twice the frequency of the first signal. A hybrid junction sums the second and third signals and provides a fourth signal which corresponds to the sum of the second and third signals and which has a low frequency modulation component which is substantially equal to one-half the frequency of the input signal, as well as a high frequency carrier component. An envelope detector and a band-pass filter, connected in series, receive the fourth signal and provide an output signal corresponding to the low frequency component of the fourth signal, which low frequency component is substantially equal to one-half the frequency of the input signal.