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A mechanically-steerable dielectric lens antenna, suitable for installation in an ENF airborne MILSATCOM terminal on high performance aircraft, was designed and tested. The antenna system consists of a six-inch diameter plano/convex lens with a dual frequency feed (43.5-45.5 GHz for the uplink and 20.2-21.2 GHz for the downlink). The measured gain and half-power beamwidths of the antenna system are 35.5 dB and a 3.2 deg. for the uplink (44.5 GHz) and 29.5 dB and 6.0 deg. for the downlink (20.7 GHz), corresponding to overall aperture efficiencies of 71% and 81%, respectively. The first sidelobes are -18 dB for the downlink and -20 dB for the uplink while the corresponding far-out sidelobes are less than -26 dB and -34 dB, respectively, for all angles beyond 18 deg. These characteristics are compatible with a high ECCM capability for an antenna of this size in an aircraft.

The dimensions of a multiple-beam antenna designed to optimize some desirable characteristics of a synchronous communication satellite are derived. The multiple-beam antenna is an X-band waveguide lens with a cluster of feeds in its focal plane. Two antenna systems are considered: (1) an antenna system radiating pencil beams for area coverage, and (2) an antenna system radiating an earth-coverage beam with nulls in prescribed directions. The characteristics of the optimum configurations are studied over a band of frequency and for practical values of feed excitation errors.

A new antenna architecture has been investigated to assess its usefulness for limited scan systems. It consists of a passive lens with a few small subarrays spaced evenly across its focal surface. Between the lens and the focl surface is a phase shift layer, or 'mask', comprised of oppositely-facing planar arrays interconnected by phase shifters (similiar to a phased array lens). The mask redirects a focusing wave from an arbitrary angle onto one of the subarrays. It is shown that a system with only 19 small subarrays, and a mask containing about 4500 elments could provide complete earth coverage with as many as 19 simultaneous 0.3 deg beams. The pattern quality of those beams is good, provided that no two are steered to within a few beamwidths of each other. Keywords include: Microwave lens, Lens antennas, Multiple-beam antennas, Electronically-scanned antenna, and Satellite communications.

Feed deformations in a space fed lens may seriously degrade the antenna's far field pattern. The errors in the far field pattern due to the deformations may be reduced by appropriately adjusting the phase shifters in the feed and/or lens. A linear model was used to determine and correct for feed tilt, fold, lateral far field pattern distortions due to displacement, perpendicular displacement, and any combination of these errors. Lens corrections align the main beam on boresite, while feed corrections restore gain and sidelobe levels. Combining the feed and lens corrections almost totally restores the original far field pattern.

The note describes a waveguide lens antenna system excited by a variable beam-forming network capable of producing a wide range of radiation patterns. These patterns vary from a narrow high-gain beam, equivalent to that of a steerable paraboloid, to the earth-coverage pattern of a wide-coverage communication satellite.

A comparison between experimental and calculated radiation pattern data for a multiple-beam antenna is presented. The antenna consists of a waveguide lens aperture excited by a 19-element feed horn array and variable beam-forming network. The pattern data presented varies from a narrow high-gain beam, equivalent to that of a steerable paraboloid, to the earth-coverage pattern of a wide coverage communication satellite. Also discussed are the results of the earth-coverage measurements when either one or two feeds are turned off so as to produce nulls in the earth-coverage pattern., See also report dated 28 Jan 1975, ADA006405.

General objectives of this research are conception, experimentation and realization of new and novel guided-wave AO device modules in LiNbO3 and GaAs with applications to wideband multichannel optical information processing, and study of relevant physical mechanisms. This report presents the major accomplishments that were made in the last program year. These include: 1) Realization of single-mode TIPE microlenses and lens arrays in LiNbO3 waveguide and high-packing density multichannel integrated optic modules; 2) In-depth analysis on guided-wave acoustooptic bragg diffraction in ZnO-GaAs composite waveguides; 3) Realization of high-performance GaAs guided-wave acoustooptic Bragg Cells at GHz frequencies; and 4) Formation of microlenses and lens array in GaAs waveguide using ion milling. Keywords: TIPE(Titanium Indiffusion Proton Exchange); Lithium niobates; Acoustooptics; Zinc-oxide gallium-arsenide composite waveguides; Modules electronics.

Dielectric lens antennas are applicable to the design of multiple-beam antenna (MBA) systems on EHF communication satellites. Advantages include excellent wide angle scanning properties and elimination of feed blockage. This report describes an experimental 90 lambda dia. zoned dielectric lens, operating at 44 GHz, which was fabricated and tested in order to estimate the performance of a dielectric lens MBA. Measurements showed that the lens generated a beam with a half-power beamwidth (HPBW) of 0.7 deg which could be steered over a total scan angle of 18 deg (corresponding to the earth's field-of-view from a geosynchronous satellite) with a scanning loss of less than 1 dB and a gain in excess of 47 dBi measured at the sub-satellite point over a 5% bandwidth. A theoretical analysis of the radiation characteristics of the lens antenna, using ray tracing and geometric optics techniques, gave excellent agreement with the measurements. Simplified design equations were developed to facilitate evaluation and development of lens antenna systems of this type.

A 3-D Dome/Rotman Lens Antenna system is described which offers the capability for greater than hemisphere scan coverage from a single feed array, greater than octave bandwidth, and multiple simultaneous beams. The history and selected results of related programs are included. Results of the analysis performed show peak phase errors of 15 degrees for scanning in the major axis planes. This error level would produce about 28 dB peak sidelobe levels for low sidelobe distributions. Complete descriptions of the analysis, computer programs and results are included.

The subject of this paper is a novel phased array antenna which is capable of providing 360 degree continuous scanning with low side lobes over a wide band. The antenna consists of a ring of feed elements coupling energy through a coaxial conical waveguide to a circular radiating aperture. Rays from the feed ring are constrained within the conical coaxial waveguide and propagate along geodesic paths in such a way as to be focused in the far field. A paper presenting a preliminary design of a Geodesic Lens Antenna was presented at this symposium in 1981. Since that time, evaluation has shown performance equivalent to a linear aperture illuminated with a Tchebyshev distribution. Progress achieved in computer aided design and analysis allows tailoring a Geodesic Cone Antenna to the specific needs and constraints of given applications. A brief explanation of the function of the Geodesic Cone Waveguide using geometric optics is presented. Design and analysis techniques utilizing geometric optics and modal analysis are described. A half octave demonstration model of a Geodesic cone Antenna has been built and tested and showed good correspondence with predicted performance., This article is from 'Proceedings of the Antenna Applications Symposium Held at Monticello, Illinois on 21-23 September 1983. Volume 1,' ADA142003, p165-189.

The Proceedings of the 1985 Antenna Applications Symposium is a collection of state-of-the-art papers relating to phased array antennas, multibeam antennas, satellite antennas, microstrip antennas, reflectors antennas, HF, VHF, UHF an various other antennas. Keywords: Satellite antennas; Lenses; Feeds; and Multiband antennas., See also Volume 2, AD-A165 535.

This report describes the fabrication and testing of a lens antenna that is designed to have wideband scanning capabilities for wide angle scanning in any plane. The lens has a 30 by 40 wavelength aperture. Far field patterns were measured in both azimuth and elevation planes over and eleven percent bandwidth. The azimuth scan angles were 0 deg, 15 deg, 30 deg and 45 deg and the elevation angles 0 deg and 15 deg. The quality of the patterns is fairly good with the average power level from + 50 deg to - 50 deg close to 44 dB in the sidelobe region (excluding the 7 or 8 close in sidelobes). These lobes have peak values about 30 dB. (Author)

Millimeter wave antenna technology has had a long history of development, and as millimeter wave systems evolve through planning to implementation, a significant amount of additional development work will be required. Millimeter wave antennas play a key role in the rationale for millimeter system designs because high spatial resolution can be achieved with modest physical dimensions. Reflector, lens, array, and horn technologies are surveyed. Multiple beam designs and adaptive processing antennas are described because these technologies afford high leverage opportunities to enhance electronic survivability and to extend communication capabilities. Ancillary components, such as radomes, are a necessary part of practical antenna designs and are discussed in some detail. Originator-supplied keywords include: Array Antennas, Lens antennas, Multiple beam antennas, and Reflector antennas.

This report describes a 3-D Dome/Rotman Lens Antenna preliminary system design, and also a demonstration of the critical hardware is given. It offers the capability for (1) greater than hemisphere scan coverage from a single feed array, (2) greater than octave bandwidth, and (3) multiple simultaneous beams. The hisotry and selected results of related programs are included. (Author)

Scattering of an incident plane, or cylindrical, wave by a staggered parallel-plate waveguide is examined. Of particular interest are the modal coefficients of the unattenuated modes in the waveguide when the incident fields is an E-wave. Several past approaches based on ray techniques are critically examined. It is found that they are not applicable when the stagger is small or when the incident field is a cylindrical wave. For the latter incidence, we introduce here an aperture field method, in which the modal coefficients are calculated through the Fourier decomposition of the scattered field at the waveguide aperture. To determine this scattered field, we apply the uniform asymptotic theory for the primary contribution, and the spectral theory for the first interaction. Extensive numerical data show that the aperture field method gives accurate results in canonical problems whose exact solutions are known. As an application to the design of the constrained waveguide lens antenna, out method enables one to determine the field distributed over the lens in a more exact manner. (Author)

Voltage standing-wave ratio (VSWR) for a singly excited radiating probe element in a linear array in a parallel-plate waveguide is measured over the 8.0- to 10.0-GHz frequency band. The following parameters are varied: probe length, probe separation, and distance from probes to ground plane. (Author)

Edited trans. of Antenny (USSR) n6 p17-49, 106-162 1969

The present status of the space-based radar phased array lens simulator is discussed. Huge arrays of thin wire radiating elements on either side of a ground screen are modeled by the simulator. Also modeled are amplitude and phase adjust modules connecting radiating elements between arrays, feedline to radiator mismatch, and lens warping. A successive approximation method is employed. The first approximation is based on a plane wave expansion (infinite array) moment method especially suited to large array analysis. the first approximation results then facilitate higher approximation computations that account for effects of nonuniform periodicities (lens edge, lens section interfaces, failed modules, etc.). The programming to date is discussed via flow diagrams. An improved theory is presented in a consolidated development. the use of the simulator is illustrated by computing active impedances and radiating element current distributions for infinite planar arrays of straight and 'swept back' dipoles (arms inclined with respect to the array plane) with feedline scattering taken into account. (Author)

It is well known that a two dimensional (parallel plate configuration) bootlace lens can be designed to have more than one focal point. Wide angle scanning capabilities of these lenses in two dimensions is well established, being larger for higher number of focal points. However, no three dimensional bootlace lens having more than one focal point has been reported. It is the purpose here to report on three dimensional bootlace lenses having two, three, and four perfect focal points. Equations for lens surfaces are obtained for all three cases. An analysis shows that a lens with a larger number of focal points can be scanned to much larger angles in one plane at the expense of a modest decrease in scanning capability in the orthogonal plane. Computer simulations of radiation patterns for different scan angles are presented for all three lenses. These results also show that a lens with a higher number of focal points can be scanned to larger angles. (Author)

The simulation theory and software implementation for a space-based radar RF lens are described. Infinite array theory and moment methods are used to simulate the mutual coupling among the wire radiators on each lens array face, 'feedback' coupling from the nonilluminated array to the illuminated array, active progressively phased modules interconnecting the arrays, and arbitrarily shaped thin wire radiating elements. Edge effects are accounted for by iterative techniques. Active impedances, element currents, and power gain patterns are computed. (Author)

This brief analysis outlines the features of a subarraying system with amplitude control circuits at the feed array face. The analysis treats the idealization of the lens feed as a continuous aperture, and includes the assumption that the cylindrical lens back face is in the far field of the array feed. The analysis includes the effect of truncation at the main array, and demonstrates that the high sidelobes of the conventional sin x/x subarray illumination, when truncated, are primary contributors to high grating lobe levels under certain circumstances. The proposed correction for these truncation effects is to produce a low sidelobe subarray illumination at the main aperture by controlling the feed array taper. Numerical results show the effectiveness of this subarraying technique for controlling the array far sidelobes and grating lobe levels, and for producing wide band null troughs within the subarray pattern. (Author)

Contents: Structural Requirements and Constraints of High Gain Satellite Antennas for 30/20 GHz Communications; NASA Technology for Large Space Antennas; Typical Examples of European Technology for High Stability Space Structures. (Author), Presented at the Structures and Materials Panel Meeting (49th), Porz-Wahn, Germany, 7-12 Oct 79.

This final report summarizes the technical effort in the past years on reflector and lens antennas. In particular, this report studied the computation of dual-reflector patterns by series expansion method and by GTD, synthesis of shaped dual reflectors, and mutual coupling effect in lens.

Appendix A describes the design considerations that were applied to the Rotman lenses used in a Basic (Narrow) and a Small Community configuration for the Microwave Landing System. Appendices B thru E contain a detailed reliability and maintainability analysis of the two configurations including the airborne equipments. (Author), See also Volume 1, AD-A081 233.

A 36 GHz computer controlled airborne radar has been developed by NRL and NASA WFC which generates a false-color coded elevation map of the sea surface below the aircraft in realtime and can routinely produce ocean directional wave spectra with off-line data processing. (Author), Original contains color plates: All DTIC and NTIS reproductions will be in black and white.

The optimum parameters of an antenna whose beam is hopped to uniformly spaced directions within a circular coverage are derived for a phased array and for a multifeed lens antenna. The minimum directive gain, GMIN , within the coverage is the parameter optimized. The analysis shows that, for small bandwidth-diameter products, the two antenna configurations exhibit about the same GMIN, but the optimum aperture diameter is about 30% smaller with the phased array. However, as the bandwidth-diameter product increases, the GMIN of the lens antenna becomes progressively greater than that of the phased array.

A spherical constrained lens having two surfaces (a pickup surface and a radiating surface) of equal radii has been known to provide multiple beams in all planes. This lens is equivalent in performance to a spherical reflector antenna but has an advantages of generating multiple beams with true time delays and no feed blockage, since the feed surface is behind the pickup and radiating surfaces. An investigation has been made of a generalized bispherical constrained lens, with the radii of its two surfaces being allowd to vary. This additional degree of freedom allows flexibility in designing a multiple-beam antenna. It is shown that, for a specified radiating aperture and allowable maximum phase error, a lens with a smaller focal length F (or, equivalently, axial distance F between the feed and pickup surfaces), than that of the equal- radius lens can be obtained by increasing the radius of curvature of the radiating surface, resulting in a more compact lens. (Author)

An antenna technique which is capable of providing multiple independent beams over limited scan sections has been developed. This antenna design utilizes overlapping subarrays fed by a stacked-pillbox multiple beam lens. Beams generated by the multiple beam lens can be selected by a beam switching matrix. An antenna design has been worked out to provide 8 or 16 multiple simultaneous beams over an 8 degree half angle cone. The antenna depth is less than the aperture diameter so that it is compact. In this design, sidelobe level of -25 dB or lower is achieved with adjacent beams cross over at -2 dB. Multiple simultaneous beams with negligible beam coupling loss is accomplished by selecting beams which are more than one beam step apart. (Author)

As part of a study of the feasibility of a 140-GHz beamrider, measurements were made of the effect of multipath on the antenna power patterns of simulated missile capture antennas. The upper and lower lobes of two conically scanning capture antennas were simulated using 50.8-mm and 152.4-mm horn-lens antennas. Vertical field probes were made at a range of 100 m over high weeds, mowed grass and asphalt. A theoretical model for specular ground reflection compared favorably with the experimental results. On the basis of this model, it is concluded that the capture of a beamrider missile would be difficult at ranges greater than 200 m over some terrain. (Author)

This report acquaints the reader with a survey of the latest state-of-the-art technology that may be applicable to various types of ground signal collection systems. An overview of the performance parameters of both planar and lens fed arrays is presented. An extensive bibliography is a key feature of this report. (Author)

Limited-scan antennas are finding increasing use in satellite communications and airport approach radars. Earlier attempts to achieve limited scan involved the use of parabolic lenses, zoning, and movable or dual-focus feeds. In the method described here, the main beam is scanned electronically by using a circular-arc phased array. The microwave lens is designed so that its back face satisfies the scanning condition. The beam is focused by shaping the front face of the lens to meet the required focusing condition and by varying the phase propagation of the lens. Two of the lenses studied were dielectric-loaded. A waveguide lens designed to scan in one dimension yielded experimental results that were good agreement with the theoretical predictions. Representative plots, and computer-generated farfield patterns of two topographically unique cases, are given.

An overview over the area of mm-wave antennas is presented with emphasis on possible avionics applications. For the purpose of the review, mm-wave radiating structures are grouped into two classes, i.e., antennas of conventional configuration and antennas based on new design concepts. The first class is composed of well known antennas such as reflector, lens, horn and slotted waveguide antennas. The design principles and performance characteristics of these antennas are well established at microwave and lower frequencies and scaling into the mm-wave region is straightforward in most cases. The reduction in size and the tighter fabrication tolerances associated with mm-wave region can be regarded as well understand. Most mm-wave antennas which are currently in use belong to this class of conventional antennas. The second class, consisting of antennas with significant features that are peculiar to the mm-wave region, is still under study. It includes radiating structures such as printed circuit mm-wave antennas; antennas derived from open mm-waveguides; and integrated antennas. Some of these antennas have microwave counterparts. Others are new with no microwave heritage., This article is from 'Microwave Antennas for Avionics. Lecture Series of the Avionics Panel and the Consultant and Exchange Programme Held in Rome, Italy on 7-8 May 1987; Guenzburg, Germany on 11-12 May 1987 and Ankara, Turkey on 14-15 May 1987,' AD-A185 152, p5-1-5-8.

A new design principle has been used to construct a three-dimensional constrained lens whose planar front and back faces are arrays of microstrip patches. The two arrays face in opposite directions and have a common ground plane. Each back face element is connected to a front face element by a short length of microstrip line and a feed-thru hole in the ground plane. The lengths of those transmission lines is a function of radius, with the longest in the center. Wide-angle focusing is achieved by the addition of a second geometric degree of freedom - the back face elements are not directly behind their corresponding front face elements, but are displaced radially, with the amount of displacement also varying as a function of radius., This article is from 'Proceedings of the Antenna Applications Symposium Held in Urbana, Illinois on 17-19 September 1986. Volume 1,' AD-A181 536, p343-365.

A parallel-plate waveguide microwave lens, constructed as part of the concept development of completely overlapped subarray antennas, was modified and tested. The lens' function is comparable to that of a Rotman lens with 16 inputs (beam ports) ands 60 outputs (antenna ports). However, the input face is linear with uniformly spaced monopole elements, and the output face is circular, with monopole elements spaced uniformly in angle. Using a four-way power divider at the center four inputs and the outputs connected to a line-source array, low sidelobe patterns were measured over a 22% bandwidth. Over the same 8.0 to 10.0 GHz band, total power loss in the lens was less than 2.3 dB including mismatch, spillover and reflectioon losses., This article is from 'Proceedings of the Antenna Applications Symposium Held at Urbana, Illinois on 19-21 September 1984. Volume 1,' AD-A153 257, p235-256.

A Bifocal Dielectric Lens Computer Model has been developed for the aid in the design analysis and performance evaluation for multiple-beam application. This type of lens antenna is very attractive at MN wave region where the feed network loss and size become problems. The model calculates and plots lens contour, the aperture distributions, and the corresponding radiation patterns and gain, with the feed located at any point on the focal arc. Several different approaches in lens contour designs were reported in the past. However an exact analytical solution is yet to come. Despite the lack of a closed-form solution, the Ray Lattice numerical method proposed by Holt and Mayer is very simple and attractive. The two surfaces of lens contour are determined through the ray path length constraints and Snell's refraction law., This article is from 'Proceedings of the Antenna Applications Symposium Held at Urbana, Illinois on 19-21 September 1984. Volume 1,' AD-A153 257, p257-273.

In order to determine the mechanical alignment requirements for the feed assembly for a large space fed microwave lens, an analysis was performed that predicts the effect of feed errors upon lens performance. The antenna model that was analyzed consists of a small linear array for the feed and a large linear array for the lens. Effects of both transverse and longitudinal feed displacement, tilt, and phase error upon lens rf performance are examined. Results show that sensitivity of antenna gain and sidelobe level to phase and amplitude errors in the lens illumination due to feed position error. Low sidelobe antennas are shown to be particularly sensitive to these errors. The results of this error study suggest the need for active feed and lens correction techniques for low sidelobe space fed lens antennas. Preliminary results of phase-only and phase-amplitude correction applied at the lens and at the feed and lens are given. (Author), This article is from 'Proceedings of the Antenna Applications Symposium (1983) Held at University of Illinois, Urbana on 21-23 September 1983. Volume 2', AD-A142 754, p265-283.

A novel multibeam antenna concept is described. This antenna concept is a generalization of the R-2R lens to permit a full circle of simultaneous beams from a circular or cylindrical antenna array. The angular doubling which characterizes the R-2R geometry, and which ordinarily restricts its applicability to a limited angular sector, is accommodated through the mapping of a full circle of array elements onto two full circuits of the lens structure. In this mapping, the perfect phase focusing of the R-2R geometry is maintained. Recent progress on practical design problems is presented. (Author), This article is from 'Proceedings of the Antenna Applications Symposium (1983) Held at University of Illinois, Urbana on 21-23 September 1983. Volume 2', AD-A142 754, p209-238.

A space fed microwave lens antenna for deployment in outer space or other remote, hazardous or unattended location. Electronic means are provided for compensating for errors in the mechanical displacement of the phased array feed elements from the phased array lens elements. (Author), Supersedes PAT-APPL-606 325-84, AD-D011 155.

A frequency independent constant beamwidth lens antenna concept is described utilizing a point source to point focus nonspherical lens. The essential feature is that a twisted planar or hyperbolic paraboloidal phase or wave front is formed by the antenna which then in turn produces a frequency independent constant beamwidth beam in the far field of the antenna for radiation or reception of planar or nearly planar spherical waves. Moreover, the frequency independent constant beamwidth beam may be steered or scanned in azimuth without moving the lens antenna or a plurality of fixed beams in different directions may be formed simultaneously by the lens antenna. Patents. (RRH), Supersedes PAT-APPL-216 056-88.

A frequency independent constant beamwidth lens antenna concept is described utilizing a point source or point focus nonspherical lens. The essential feature is that a twisted planar or hyperbolic paraboloidal phase or wave front is formed by the antenna which then in turn produces a frequency independent constant beamwidth beam in the far field of the antenna for radiation or reception of planar or nearly planar spherical waves. Moreover, the frequency independent constant beamwidth beam may be steered or scanned in azimuth without moving the lens antenna or plurality of fixed beams in different directions may be formed simultaneously by the lens antenna. Patent applications. (RH)

A wide band, substantially constant beamwidth, frequency independent, scannable acoustic array uses a mosaic pattern acoustic lens arrangement of fully directive acoustic lens antennas as the primary array antenna elements. The lenses at the center of the array pass signals at all frequencies, the lenses near but not at the center pass all signals except those at the highest frequencies and the lenses on the outer periphery pass only those at the lowest frequencies. When used as a transmitter, a wide band source supplies a broad frequency signal to a plurality of filters, time delays, amplifiers, switches, and acoustic retinas for applying predetermined signals to the acoustic retinas act in a complimentary reciprocal fashion in the recovery of signals., Supersedes PAT-APPL-117 426-80.

A bootlace microwave lens antenna has orthogonal delay lines for reducing quadratic phase errors to improve focusing capability. The collector and radiator elements consists of mutually orthogonal pairs of subelements with one of the subelements oriented radially and the other oriented tangentially on the respective collector and radiator surfaces. Individual delay lines interconnect corresponding radial and tangential subelements on each surface thus allowing for phase corrections in the axial planes parallel to and perpendicular to the plane of scan by the introduction of an appropriate phase delay in each delay line. (Author), Supersedes PAT-APPL-562 336-83, AD-D011 020.

A phased array lens antenna which includes a lens having two faces disposed substantially at a right angle to each other. Transmit-receive modules which includes phase-shifter are shared between the two lense faces. Two lens antenna positioned in back-to-back relationship about a ship superstructure scan 260 deg. (Author), Supersedes PAT-APPL-505 570-83, AD-D010 381.

An antenna assembly configured by the combination of the high forward gain of a conventional planar phased array antenna with the wide angle scanning capability of a dome antenna. The invention includes an optically fed phased array, which may be structurally configured similar to a conventional lens array, but comprises a reflection/transmission switch and an electronic phase shifter at each radiating element. The switches facilitate operation of the phased array in two distinct modes; when the switches are set for the transmission mode, the phased array operates substantially as a conventional lens array to scan a + or - 60 deg conical sector; when the switches are set for the reflection mode, the phased array behaves like a reflect array to scan an additional + or - 60 deg to + or- 20 deg sector., Supersedes PAT-APPL-444 003-82, AD-D010 043.