Showing papers on "Phased array published in 1974"

Microwave theory of phased-array antennas—A review

Abstract: The microwave theory of phased-array antennas is reviewed, emphasizing large planar arrays suitable for phased-array radar. The review looks in detail at the three major parts of the antenna, namely, the element array, the phase shifters, and the feed system. The element array is studied by first modeling it as being infinite in extent and the concept of the per element absorption cross section and gain versus angle is developed. The technique of modal analysis using plane waves is explained and used to calculate the aforementioned quantities for waveguide and dipole elements. The review proceeds first through an analysis which applies to small elements, using a single element mode, and then to a more accurate solution containing the first higher mode in addition. The author has added new research to the review which explains the blindness effect for waveguide arrays. A necessary and sufficient condition for array blindness has been derived which removes a major uncertainty about the blindness effect. A result is that a blindness angle will always occur in E and H plane scanning of rectangular waveguide elements for any waveguide size, provided the array lattice is such as to permit a grating-lobe singularity by the simple one-element-mode theory. Elements large than some critical size are not required to produce blindness but the large size has the effect of producing greater shift of the blindness angle towards broadside from the grating lobe angle. The singularity in element admittance right at the grating lobe angle, which is a well-known milestone in the analysis of elements which have been modeled to support only one mode, is in reality a fiction. When higher modes are added to the solution, as is necessary for any physical element, the grating-lobe singularity is found to disappear. Thus for any real physical element, there is no grating lobe blindness, but the blindness angle is shifted inside of this angle by an amount which depends upon the element size. A review of element design calculations using many higher element modes is presented, and element configurations are shown which produce a good impedance match over a wide scan angle as well as a wide-frequency band. The application of the aforementioned results obtained from the infinite-array model to a practical, finite array are discussed. The theory of the most useful phase-shifter types for phased arrays is discussed, including those using both ferrite and semiconductor diodes. The ferrite toroid in a waveguide is a very effective design and the results of an optimization analysis for this configuration are presented. Choices of ferrite material parameters for low loss at both small and large signal levels are discussed. A method of reducing the temperature sensitivity of phase shift by means of the driver circuit is also reviewed. Semiconductor diode phase shifters have a greatly increased potential due to an improvement in diode reliability that has produced an expected mean life of 109h. The theory of phase-shifter operation using diodes in a balanced hybrid circuit is discussed and relations are given for bandwidth, loss, and power capability. The high-power limitation of the phase shifters is due to a nonlinear loss effect in the reverse biased state and is caused by the large RF voltages. The loss can be reduced by circuit techniques and by employing the new diodes of improved design, which are discussed. Feed systems for phased arrays are synthesized from a number of basic techniques according to the antenna applications. A few of the important techniques are reviewed here. Feed systems are required to produce an optimum aperture distribution for two types of patterns simultaneously, the sum pattern (Taylor distribution) and the difference pattern (Bayliss distribution). For the constrained feed, which uses transmission line throughout, two alternatives are presented for accomplishing the aforesaid. It is shown that the feed network can prevent reflections from the element array, which are always present to some degree, from adding an error component to the desired aperture distribution by employing 4-port power dividers which are provided with a reflection absorbing termination. An approximate method of wide-band beam steering is discussed in which a small number of time delay devices are used to feed subarrays of elements steered by conventional phase shifters. The subarray feeding technique is also employed in another application with the Butler beam forming matrix to form simultaneous multiple beams in an approximate manner that reduces the size of the beam forming matrix required. The space feed is an alternative to the constrained feed and distributes energy to the elements by free-space propagation. This method possesses great flexibility and may approach the capability of the constrained feed in secondary aperture performance by using a large number of feed elements. A design method of accounting for the near-field diffraction produced by the large feed is given.

Diode Phase Shifters for Array Antennas

Abstract: This paper contains considerations for diode phase shifters used for phased array antenna control. The categories are: 1) areas in which ferrite and diode phase shifters differ, 2) diode phase-shifter circuits, 3) the nature and typical performance of p-i-n diodes, 4) the requirements of a driver and a typical circuit, and 5) measured performance of phase shifters in L, S, C, and X bands.

Radar auroral echo characteristics as seen by a 398-MHz phased array radar operated at Homer, Alaska

Abstract: In this paper we present the first results of the mapping of the spatial distribution of auroral echoes by a 398-MHz phased array radar recently installed at Homer, Alaska. The results are shown in the form of two-dimensional spatial maps of auroral echoes. These maps are classified into types that are extensions of the ‘diffuse’ and ‘discrete’ echo types introduced by Leadabrand et al. (1959) and Presnell et al. (1959) for narrow beam radars. The auroral echo signatures typically seen during the afternoon and evening sectors are then described and discussed in relation to radar auroral echo characteristics found by previous investigations and other auroral processes. We show that interpretation of the occurrence of auroral echoes in terms of control by an electric field and by electron density in the radar scattering volume produces a consistent morphology of the radar aurora in relation to the other observed auroral processes. Finally, we include a dynamic auroral echo signature that may be related to the growth phase of an auroral substorm.

An overlapped subarray for limited scan application

Abstract: This paper describes a new technique for producing an overlapped subarray pattern by higher order mode coupling between nearest neighbor phased array elements. Theoretical and experimental results are compared and practical circuits are described for one plane of scan.

A new wideband, fully steerable, decametric array at Clark Lake

Abstract: A fully steerable, decametric array for radio astronomy is under construction at the Clark Lake Radio Observatory near Borrego Springs, California. This array will be a T of 720 conical spiral antennas (teepee-shaped antennas, hence the array is called the TPT), 3.0 km by 1.8 km capable of operating between 15 and 125 MHz. Both its operating frequency and beam position will be adjustable in less than one millisecond, and the TPT will provide a 49-element picture around the central beam position for extended source observations. Considerable experience was gained in the operation of completed portions of the array, and successful operation of the final array is assured. The results are described of the tests which were conducted with the conical spirals, and the planned electronics and data processing systems are described.

Element patterns and active reflection coefficient in uniform phased arrays

Abstract: Several fundamental element pattern-active reflection coefficient interrelationships in uniform phased arrays are summarized, extended, and integrated. For central elements of sufficiently large arrays the results provide the basis for attractive measurement schemes of array parameters.

A Phase-Locking Method for Beam Steering in Active Array Antennas

Abstract: A new principle for phase shifting, and hence beam steering, on an active array antenna is described. Each individual RF source is phase locked by a stable locking signal which is close in frequency to the nth harmonic of its free-running frequency. Pulses of appropriate amplitude and duration applied to the dc circuitry cause the fundamental output frequency of the RF source to shift in phase by increments of 2/spl pi//n. The construction and testing of a four-element L-band (1-GHz) array using transistor oscillators locked at S-band (4 GHz) to give 90/spl deg/ phase increments is described.

Shared pointing for offset target of an adaptive phased array

Abstract: A coherent optical adaptive system employs phase conjugation for locking the beam of a phased array of laser transmitter to a target, focusing the beam on the target and compensating for distortion and disturbances both within the system and in the propagating medium between the system and the target. A first diffraction-limited lobe of the beam is locked on a real target to track the real target. Simultaneously a second diffraction-limited lobe is directed to a location having a predetermined offset with respect to the target and relative energy of the two lobes is selectively adjusted. A signal component representing a fictitious target that is offset by a predetermined amount from the real target is summed with the signal received from the real target, the phase of the sum is compared with the phase of a reference, and the phase of the transmitted signal is adjusted so as to null the difference between the sum and the reference phases for each of a number of channels.

Relation of radar range resolution and signal-to-noise ratio to phased-array bandwidth

Abstract: Phased-array radar systems using wide-band linear-FM pulses suffer from array dispersion. This causes a loss in signal-to-noise (S/N) ratio and in radar range resolution (a broadening of the compressed-pulse width). Depending on the choice of the receiver matched filter (MF) and weighting filter (WF) one or the other of these effects may be minimized. The effects of dispersion in a square planar array with either a parallel feed or a center-fed series feed are studied. Loss in S/N ratio and in range resolution are determined for typical cases, and general curves are given for arrays with arbitrary size, scan range, and signal bandwidth. It is shown that there is an optimum or maximum-useful signal bandwidth for each array, for which the minimum S/N-loss MF-WF design is the same as the ideal-compressed-pulse-shape MF-WF design. For pulses having greater signal bandwidths, time delay steering should be used in the array.

A cylindrical array for the TACAN system

Abstract: A new cylindrical array has been developed for the TACAN ground antenna application. The technical requirements are unique since the circumferential radiation pattern is quasi-omnidirectional with multiple lobes and must be rotated at a precise rate. This is accomplished by electronically modulating the azimuth aperture distribution. Thus the antenna is a system including a specialized cylindrical array, a modulating RF feed network, and the associated electronic generator providing the required modulation and reference signals. Theoretical and practical design considerations are presented using a mathematical model of the antenna. This model describes the characteristic behavior and actual performance of the cylindrical array. The antenna's physical characteristics and design features are described, and measured array performance is presented in detail and compared to the system requirements. Operational performance data accumulated during actual flight test evaluation is presented briefly.

Space feed receiver array

Abstract: A space feed phased array receiver system provides independent steering of discrimination and tracking clusters in the space feed by dividing each antenna cartridge into two channels. Each channel operates over a different portion of the RF band; each radiates a different sense of polarization to the focal region; and each is independently steered.

Mechanical multichannel phase shifter for phased array antenna - has triple-board strip-line rotating feeder coupling

Abstract: The mechanical multi-channel phase shifter has variable conduction paths lengths to supply a phased array antenna and has feeders constructed using triple-board strip-line techniques. The feeders are arranged partly on a rotor and partly on a stator concentrically such that the rotor's and stator's inner conductors for each feeder line overlap in a region whose length is proportional to the rotor angle. The stator board is arranged so that the space between its two parts accepts the rotor's overlap. All parts are pressed together by means of a spring so that good contact is made between the lobe conductors of the rotor and stator.

Phase array target amplifiers

Abstract: A phase array target amplifier for generating multiple channels of high frequency electromagnetic power. The amplifier comprises a plurality of spaced apart amplifier channels, each of which contains similar channel components. Thus, the amplifier includes a plurality of electron generating guns which generate a plurality of electron beams, and where each of the beams exists in a separate beam channel. Deflector plates to modulate the beams are located along the beam path for optionally and individually or simultaneously deflecting various of the electron beams. In addition, an electron drift region is established downstream from the deflector plates by means of a pair of opposed phase shift electrodes. The velocity of the various beams are modulated in these drift regions through the potential on the phase shift electrodes so that each of the beams are phase shifted in a time controlled manner with respect to each of the other beams. A semiconductor target device is also provided in each amplifier channel so that each target device is associated with an individual electron beam. These target devices are modulated responsive to the fraction of the beams current deflected on the active region of the target devices, to generate an array of amplified output signals with controlled phase relationship. In this way, it is possible to drive multiple power radiating arrays (e. g. phase array antennas).

Phased array antenna with array elements coupled to form a multiplicity of overlapped sub-arrays

Abstract: High gain limited scan operation of phased array antennas is accomplished with microwave circuitry by appropriately coupling the array elements into sub-arrays and establishing a 90° out of phase relationship between even and odd mode power at the aperture of each array element. Even and odd mode power from the feed circuit of each element is coupled to the feed circuit of each nearest adjacent element to form three element overlap subarrays in each plane of scan.

Random Signal Flaw Detection

Abstract: : This report describes four areas of work In the first area random signal beam forming techniques are developed which make it possible to transmit several independent beams from a phased array using the same number of incoherent noise sources Following this ultrasound beam scanning techniques are demonstrated in which random signal correlation systems and RF correlation systems using quadrature phase techniques are used in methods for scanning the intensity profile of ultrasound transducer beams using respectively broadband signals and narrow band signals In addition two types of deconvolution procedure are described and demonstrated which have been successful in improving the effective resolution of ultrasound correlation systems when viewing surface features Finally the design and construction of a random signal correlation system is described which uses an electronic delay line (Author)

A dual-reflector optical feed for wide-band phased arrays

Abstract: This paper contains a description of the fundamental performance characteristics of a new space feed suitable for wideband operation of phased-array antennas. A unique aspect of this feed is the combination of an active time-delayed small source array and a confocal passive two-reflector system in an offset Gregorian configuration to provide wide-band compensation to a scanning phased array antenna contaning only radiators and phase shifters. A two-dimensional model is analyzed using the plane wave spectrum representation of the near field. Calculations for bandwidths of up to 20 percent of center frequency are given. The good electrical performance of the feed as a function of bandwidth and scan angle establishes this system as an attractive candidate in space feed applications and as a tradeoff competitor or alternative to the conventional corporate feed.

Dual band phased array element

Abstract: A dual band phased array apparatus for exicting in a single microwave waveguide a phased array element with signals having a substantial frequency difference.

A Low Cost P-l-N Diode Phase Shifter for Airborne Phased-Array Antennas

Abstract: This paper presents a description of a p-i-n diode phase shifter that was designed for low cost production for use in X-band phased-array systems. The phase shifter is designed to make maximum use of photoetched circuit components and low cost materials, and is well suited for assembly on a fully automated assembly line. The salient features of this phase shifter are a printed-circuit transmission structure and inexpensive RF connectors that are integrated into the circuit package. The microwave performance characteristics are generally superior to those of equivalent devices; a useful bandwidth of 40 percent with an average insertion loss of 1.6 dB has been demonstrated with 3-bit units.

Scanning of surface acoustic wave phased array

Abstract: A multielement surface acoustic wave transducer array of very small aperture and separation has been fabricated on PZT substrates and the phase Scanning of the resultant acoustic beam from such a transducer array has been demonstrated. In addition to its use as an acoustic beam scanner, the transducer array may form a new type of signal processor, requiring no phase shifters or delay lines, for sonars and electromagnetic phased-array antenna applications.

An electronically scanned beacon antenna

Abstract: An electronically scanned cylindrical array having a minimum number of active devices has been designed. A saving of over 3 to 1 in diode elements as compared to conventional approaches has been achieved. In addition to providing instantaneous positioning to any azimuth direction, a constant azimuth beamwidth for an elevation fan beam has been realized. Extremely low azimuth sidelobes are obtained, and a straightforward synthesis procedure can provide elevation aperture designs to meet typical elevation pattern requirements. A modified Myer geodesic lens combined with a diode sequencing switch for coarse steering and a phased matrix feed for fine steering form the basis of the system. Sum and difference patterns show virtually no variation with scan or elevation angle and an omni-pattern is also available. Detailed pattern calculations as well as measured data on prototypes of key elements of the system are presented to verify the feasibility of the approach.

An X- Band Reflect-Array with Integrated PIN Diodes

Abstract: In classical reflect-arrays, radiating elements and phase-shifters are quite distinct. The transitions between these two parts and the shielding problems generally lead to complicated structures. In the array presented the phase shifter elements (PIN diodes) are integrated on the radiating surface. Scanning is then realized by changing the position of the reflection plane in open propagation.

Corrugated conical horn as a space feed for phased-array illumination

Abstract: The importance of corrugated conical horns in space-fed illumination of phased arrays is indicated. Design details pertaining to corrugated conical horns of optimum proportions for uniform illumination of a phased array with a prescribed area are also presented.

Scanning transients in phased-array antennas

Abstract: The effect of transients in phased arrays caused by the time variation of element phases is considered. The case in which the beam is continuously scanned is analyzed and the deterioration of main beam studied in some detail. For the linear scan, an upper limit on the scanning rate is found such that there is negligible effect on the pattern.

Optimized Cavity-Backed Slot Antennas for Phased Arrays

Abstract: The resonance frequency of a cavity-backed slot antenna and also the Q-factor are highly dependent of the dimensions of the cavity and of the dielectric filling of the cavity. A low Q-factor is desired for wideband frequency performance. Recently, the author published the values of the dimensions of the cavity which gave the lowest Q-factor of a slot antenna at prescribed resonance frequency, slot dimensions, and dielectric constant of the homogeneous cavity filling. However, the optimal cavity dimensions for the slot antenna are too big for using it in a wide scanning square lattice phased array. This paper presents design datas for slot antennas backed by a homogenous filled and optimized cavity where dimension restrictions have been considered. A new design with partially filled cavities will also be presented. Hereby several advantages have been obtained, for example, lower Q-factor, lower weight, better economy, and possibility for a more convenient feeding arrangement.

Practical Aspects of Phase-Shifter and Driver Design for a Tactical Multifunction Phased-Array RADAR System

Abstract: Three microwave garnet phase-shifter designs are used in the AEGIS weapons system. The microwave design is straight-forward except that the toroid assembly is potted with silicone rubber to increase its power-handling capability and the magnetizing wires are shielded with a spiral-wrapped wire to prevent the propagation of higher order modes. The driver circuit uses a new "flux-feedback" concept for improved accuracy and employs monolithic circuits, hybrid circuits, and discrete components. Mechanical and electrical design of the interfaces with mating components are important cost considerations and the chosen designs are described in detail. Several techniques for improving production yield are discussed and a table of production statistics is provided. Performance histograms and data averages as a function of time and operating frequency are also presented.

Far-Infrared-Submillimeter Phased Arrays and Applications

Abstract: The concept of a phased array of far-infrared (FIR) or submilliieter (SMM) waveguide lasers that can be scanned electronically is presented. Grating lobe reduction by computer analysis is shown. Possible applications of SMM arrays are considered.

A MIC Phase-Locked Loop Avalanche Oscillator in X Band (Short Papres)

Abstract: This short paper describes the design and performances of a MIC phase-locked loop X-band avalanche oscillator. The output power (500 mW/CW), the input reference level (1 mW), the locking time (80 ns), and the simplicity of digital phase control makes it very attractive as a primary element of an active phased array.

Phase-interpolation locking: new technique for beam-steered active antennas

Abstract: A new method of phase control for beam steering an active antenna array is suggested. Only half the normal number of phase shifters are needed, but there is a limit to he angle throught whih the beam ca be steered by this technique.