Showing papers on "Phased array published in 1975"

Fiber optic phased array antenna system for RF transmission

Abstract: A system for providing the plural variable phase RF signals required to control the beam pointing angle of a phased array A light energy source (shown as a laser generator) is modulated by an RF signal and fed to a plurality of channels in parallel Each of the said channels corresponds to one radiating element of the phased array and each channel includes as many selectively employed fiber optic delay lines of different lengths as are required to generate the discrete phases required at the corresponding antenna (radiator) element of the array A commutating programmer controls the selection of individual radiating element phases for each successive beam pointing position

Phase steered subarray antenna

Abstract: A phased array antenna which is adapted to provide electronic scanning over a limited scan range with a minimum number of control devices and yet maintain fairly low sidelobes is disclosed wherein the respective radiating elements are grouped into steerable subarrays. Phase steering of the subarrays is performed in discrete steps by means of phase shifters with one or two bits interspersed within the feed network. The phase state of these subarray phase shifters is selected to improve the antenna gain and suppress the grating lobes. Overlapping of the radiating elements of the subarrays is also employed to further suppress grating lobes throughout the limited scan range.

Phased array antenna with coarse/fine electronic scanning for ultra-low beam granularity

Abstract: An antenna and scanning means therefor particularly useful in an aircraft landing system operating in the microwave frequency range. The antenna is of the line phased array type which includes digitally controlled phase shifters for each of the radiating elements of the array. The beam formed by the antenna is steered by incrementing the phase shift applied at each of the array radiating elements by an amount of phase which is dependent in part upon the position of the radiating element in the array. Phase increments sufficient to shift the beam position by one coarse step (0.1°) are applied to symmetrically located radiating element pairs, pair by pair, until all elements have been incremented. The beam is thereby caused to move through one coarse step in a number of fine steps equaling the number of pairs of elements in the array. An additional feature of the scanning means is the application of phase increment to the array elements in a pseudo-random sequence.

π-Loop phase bit apparatus

Abstract: The use of electronically variable phase shifters is required in phased array radar systems. Diode phase shifters are particularly well suited for use in phased array radar systems because they have size and weight advantage over other types of phase shifting components such as ferrite devices and traveling wave tubes and, in addition, offer the potential of cost reductions through the application of batch processing techniques. In accordance with the present invention, a phase bit is provided by the appropriate forward or reverse biasing of one series and one shunt diode to switch between a π circuit and a loop transmission line circuit shunting the equivalent capacitance of the series diode when reverse biased.

Integrated Diode Phase-Shifter Elements for an X-Band Phased-Array Antenna (Short Papers)

Abstract: The design and production of 502 X-band P-I-N diode phase-shifter elements for a transmissive phased-array RADAR are presented. These elements consist of three phase-shifter states and two integrated dipole radiators formed using microwave integrated circuit techniques. The detailed design of loaded-line phase shifters and effects of circuit variations during production are examined in terms of measured performance. Finally, the performance of the phase shifters in the phased array is demonstrated through computed and measured antenna patterns giving quantitative results.

Heat pipe cooling of airborne phased array radar

Abstract: A system for controlling temperature in phased array radar modules where a combination support plate-heat exchanger allows a cooling fluid to circulate therethrough and a heat pipe extends the length of the module and into the support plate-heat exchanger where heat is taken to a remote heat exchanger. Heating elements are attached to the support plate-heat exchanger to facilitate initial system warmup.

Optical processing of pulsed Doppler and FM stepped radar signals.

Abstract: A real-time radar processor with an electron beam addressed KD(2)PO(4) light valve as the input electrical-to-optical transducer is described. The input format, output plane pattern, and the required optical processing of pulsed Doppler and FM stepped radar data on this system are discussed. Experimental output plane patterns with actual radar data are presented. Although these data are processed off-line, the processing is performed at real-time data rates.

Network-fed phased array antenna system with intrinsic RF phase shift capability

Abstract: An integral element/phase shifter for use in a phase scanned array. A non-resonant waveguide or stripline type transmission line, series force feeds the elements of an array. In the embodiments shown, four RF diodes are arranged in connection within the slots of a symmetrical slot pattern in the outer conductive wall of the transmission line to vary the coupling therefrom through the slots to the aperture of each individual antenna element. Each diode thus controls the contribution of energy from each of the slots (at a corresponding phase) to the individual element aperture and therefore determines the net phase of the said aperture. Three species of the invention are shown, the first and second involving RF diodes in the slots of waveguide broad and narrow walls respectively, and the third having slots through the shield plane of a stripline. The invention facilitates array phase scanning without the need for separate, and relatively more expensive, discrete phase shifters for each antenna element.

An Optical/Digital Processor: Hardware and Applications

Abstract: A real-time two-dimensional hybrid processor consisting of a coherent optical system, an optical/digital interface, and a PDP-11/15 control minicomputer is described. The input electrical-to-optical transducer is an electron-beam addressed potassium dideuterium phosphate (KD 2 PO 4 ) light valve. The requirements and hardware for the output optical-to-digital interface, which is constructed from modular computer building blocks, are presented. Initial experimental results demonstrating the operation of this hybrid processor in phased array radar data processing, synthetic aperture image correlation, and text correlation are included. The applications chosen emphasize the role of the interface in the analysis of data from an optical processor and possible extensions to the digital feedback control of an optical processor.

180° phase shifting apparatus

Abstract: The use of electronically variable phase shifters is required in phased array radar systems. Diode phase shifters are particularly well suited for use in phased array radar systems because they have size and weight advantage over other types of phase shifting components such as ferrite devices and traveling wave tubes and, in addition, offer the potential of cost reductions through the application of batch processing techniques. In accordance with the present invention, a 180° phase bit is provided by two series diodes with three transmission line segments shunting each junction to ground through a common shunt diode. Operation is effected by the simultaneous forward or reverse biasing of the series and shunt diodes, thereby introducing a 180° phase difference in a signal transmittal therethrough.

A new technique for feeding a cylindrical array

Abstract: A new technique for exciting a cylindrical array is described. It uses a Butler matrix and a simple switching matrix for exciting only that sector of the array that contributes to formation of a desired radiation pattern. It accomplishes full circumferential coverage with fewer active components, reduced complexity, and better performance than other matrix methods for exciting cylindrical arrays. An array of N elements is configured so that N/M (M = 1, 2, 3, ...) contiguous elements spanning an active angular sector of 2\pi/M are excited simultaneously to form a radiation pattern. This paper considers the case M = 4 in which a quadrant array is excited by an N/4 -way power divider and an N/4 \times N/4 Buffer matrix. Pattern selection or rotation is accomplished by N/4 phasers and N/4 1P4T switches. Continuous full circle rotation of the radiation pattern requires N switching operations in addition to linear control of the phasers.

Phased-array antenna employing an electrically controlled lens

Abstract: A phased-array antenna in which transmitting energy from a primary feed system is radiated through free space as a primary wave to a plurality of first radiator elements, where they are received, and conducted over a plurality of phase shift elements, which may be electronically controlled, and which convert the primary wave into a planar wave and additionally effect a desired beam deflection, with such waves being radiated by a plurality of second radiator elements, in the form of a planar wave with received energy passing in the opposite direction along the same path, in which a second primary feed system is disposed at the second radiator elements and also supplied with transmitting energy which is radiated through free space, as a primary wave, to the second radiator elements where it is received, conducted over said phase shift elements and radiated by the first radiator elements in the form of a planar wave.

Hard Limiting in Synthetic Aperture Signal Processing

Abstract: In synthetic aperture radar a large linear phased array is formed from the rapid movement of a single element through each position in the array. Storage and coherent combining of the successive radar echoes are central to the array-forming process. Optical processing is the most common technique because of the efficiency with which Fourier transformation may be accomplished with simple optics. Real-time operation, however, requires all-electronic processing, which is difficult to accomplish because of the huge quantity of data to be manipulated. Dynamic range compression by hard limiting may ease the problem by reducing the number of bits per frame. The effects of hard limiting are analyzed in this paper. It is shown that large targets simultaneously illuminated by the radar antenna will produce image targets or ghosts displaced in angle. Statistically homogeneous clutter will "linearize" the hard-limited receiver and suppress the ghosts without loss in contrast, as does thermal noise if it is larger than the target echoes. Pulse compression reduces the probability of images from prominent targets. Judicious choice of the pulse-compression waveform is a powerful tool for destroying coherent buildup of images from all large targets not in the same range resolution cell. Linear FM, the most common choice, unfortunately does not exhibit this desirable property.

Waveguide-tuned phased array antenna

Abstract: A phased array radar antenna comprises an array of hollow, rectangular tubes, each tube having an opening therethrough. A tuning slug is positioned within each of the hollow tubes, and is mechanically coupled with a transducer for moving each tuning slug through the corresponding hollow tube responsive to an electrical input thereto. A feed horn is provided for radiating electromagnetic energy into the openings of the hollow tubes whereby the energy is reflected therefrom in a direction and in a beam width determined by the position of all of the slugs.

Polarization rotator for phase array antennas

Abstract: The polarization control of the antenna is obtained by space feeding the nals through a polarization control rotator to a monopulse feedhorn.

Digitally controlled analog flux sensing ferrite phase shifter driver

Abstract: The present invention relates to a digitally controlled phase shift network for an analog flux-sensing ferrite phase shifter driver, as would be applied in controlling the phase of individual antenna elements in phased array radar systems. The phase shift network described utilizes analog phase shifters while accepting a digital control input, and provides phase control without need for digital-to-analog converters between the analog phase shifters and their digital inputs. This is accomplished by integrating the volt-time product on the phase shifter secondary windings until the integral reaches a value corresponding to a phase shift increment of predetermined magnitude, dumping the integrator voltage between integrations, counting the number of integrate-and-dump operations to thus yield a digital measure of the phase shift achieved, and comparing such digital count against the digital control input. Nonlinearity of the differential phase-versus-flux characteristics of conventional phase shifters is compensated by causing the volt-time integration dump point to change upon reaching a predetermined point in the integrate-and-dump count.

A Modified Monopulse Technique for Radar Tracking with Low-Angle Multipath

Abstract: In this paper a new monopluse technique for reducing radar multipath angle-tracking errors is proposed. The solution is achieved by using two monopulse antennas at different heights. The available signals allow one to control the antenna-height diversity so that the elevation angle control signal is not affected by reflected-wave components. The size of the antenna system may be reduced by properly using phase shifters. A possible configuration of such a system is considered and some practical data on the antenna-height diversity are discussed.

Accuracy of hemispherical far-field patterns determined from near-field measurements

Abstract: This paper reports on the accuracy of far-field patterns determined from near-field measurements on a 499 element C-band phased array antenna. Hemispherical far-field patterns were determined from near-field measurements and principle plane cuts of these patterns were compared to the same cuts made on a farfield range. Comparisons are sheen for both the sum and azimuth difference patterns for three scan positions of the phased array.

A New Numerical Approach to Planar Phased Arrays

Abstract: In examining the directivity characteristics of planar phased arrays, an expression in the form of a double summation approximation to the double integration of the array pattern is conventionally used. This procedure is computing time-intensive. In this paper an exact closed-form expression for the directivity function for the case in which the radiation patterns of the elements are nonidentical and nonrotational symmetrical is proposed.

Ferroscan: Toward continuous-aperture scanning

Abstract: Work done severe years ago, which represents a step toward eliminating the necessity for subdividing a phased array aperture into many discrete elements, each with its own phase shifter, is reported on for the first time. A 5-wavelength, X band horn aperture, partially loaded with ferrite material, was designed and fabricated. The resulting antenna replaces at least 10 conventional phase shifter-element units and was successfully controlled by an external magnetic circuit to form sum and difference patterns and to scan the beam.

Optical technique for broadbanding phased arrays

Abstract: An optical method for broadbanding a phased array is considered. A narrow band feed-through aperture lens comprised of pick-up elements, radiating elements, and 360\deg type phase shifters is fed by a small feed array with an intervening passive lens. The lens has fixed frequency-sensitive properties. The feed array has variable time delay compensators which are selected in accordance with the desired scan angle in the far field. Using geometrical optics, design formulas are derived that relate bandwidth and scan angle to the minimum number of variable time delayers. To demonstrate performance, diffraction theory is used to calculate patterns, sidelobe levels, and efficiencies as a function of bandwidth and scan angle out to 50\deg scan for several aperture sizes. In the worst cases, the optical system provides somewhat less gain than the comparable constrained subarray antenna; however, it always provides much better sidelobe levels.

Phased array element retention

Abstract: A means for retaining radar elements in a structural configuration for a sed array. The elements are inserted in connectors and are held between two cap plates. The array face and retention configuration is to satisfy electrical and mechanical requirements in order to minimize surface-wave propagation and to predict scanning performance.

A decametric wavelength radio telescope for interplanetary scintillation observations

Abstract: A phased array, electrically steerable radio telescope (with a total collecting area of 18 acres), constructed for the purpose of remotely sensing electron density irregularity structure in the solar wind, is presented. The radio telescope is able to locate, map, and track large scale features of the solar wind, such as streams and blast waves, by monitoring a large grid of natural radio sources subject to rapid intensity fluctuation (interplanetary scintillation) caused by the irregularity structure. Observations verify the performance of the array, the receiver, and the scintillation signal processing circuitry of the telescope.

Wideband solid-state phased-array antenna development at UHF

Abstract: : Development of an experimental 16-element solid-state linear phased- array antenna that has an operating band from 06 to 095 GHz is described Radiating elements in the antenna are novel strip radiators made using printed circuit techniques The array aperture has been impedance matched to a VSWR<3 0:1 over the octave band from 05 to 10 GHz with beam scanning to plus or minus 60 degrees in the H plane Element patterns measured on a 10- by 10-element array aperture indicate that the aperture is also matched with beam scanning to plus or minus 60 degrees in the E plane Each of the radiators in the 16- element linear array was integrated with a microwave transistor amplifier with a nominal gain of 10 dB and efficiency of 50% at 3 watts output Bandwidths of the amplifiers limit the 16-element solid-state array to an operating band from 06 to 095 GHz Beam scanning in the H plane is accomplished by inserting lengths of coaxial delay lines between the integrated array and a 16:1 power divider network Techniques and methods used in this development are applicable at higher radar frequencies