EP0275303A1 - Low sidelobe solid state phased array antenna apparatus. - Google Patents

Low sidelobe solid state phased array antenna apparatus.

Info

Publication number
EP0275303A1
EP0275303A1 EP19870905342 EP87905342A EP0275303A1 EP 0275303 A1 EP0275303 A1 EP 0275303A1 EP 19870905342 EP19870905342 EP 19870905342 EP 87905342 A EP87905342 A EP 87905342A EP 0275303 A1 EP0275303 A1 EP 0275303A1
Authority
EP
European Patent Office
Prior art keywords
groups
power modules
modules
far field
array antenna
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP19870905342
Other languages
German (de)
French (fr)
Other versions
EP0275303B1 (en
Inventor
Jar Jueh Lee
Raymond Tang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Co
Original Assignee
Hughes Aircraft Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hughes Aircraft Co filed Critical Hughes Aircraft Co
Publication of EP0275303A1 publication Critical patent/EP0275303A1/en
Application granted granted Critical
Publication of EP0275303B1 publication Critical patent/EP0275303B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00Antenna arrays or systems
    • H01Q21/06Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/22Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00Antenna arrays or systems
    • H01Q21/0006Particular feeding systems
    • H01Q21/0025Modular arrays

Definitions

  • the present invention relates generally to the field of solid state, active aperture array antennas for radar, and more particularly to apparatus and methods for reducing sidelobe radiation by such antennas .
  • the mainlobe is the central lobe of a directional antenna's radiation pattern, the sidelobes referring to the lesser lobes of progressively decreasing amplitude on both sides of the mainlobe and often extending rearwardly of the mainlobe.
  • Radar antenna aperture configuration generally determines the extent and relative magnitude of the associated sidelobes; however, the gain of the strongest one of the sidelobes is typically only about 1/64 that of the mainlobe. In terms of decibels, the strongest sidelobe gain is typically down about 18dB from the associated mainlobe gain. Gains of the other sidelobes are usually considerably smaller than that of the strongest sidelobe. Although sidelobe gain is typically much smaller than mainlobe gain, because of the large solid angle into which sidelobes radiate, as compared to the small solid angle into which the mainlobe radiates, typically about 25 percent of the total power radiated by a uniformly illuminated radar antenna in the sidelobes.
  • sidelobe radiation- provides no useful function and in addition to representing wasted radiating power has other serious disadvantages.
  • radar clutter from sidelobe returns increases the difficultly of discriminating targets from background.
  • Another very significant disadvantage of sidelobe radiation is that such radiation can, in a military environment, be utilized by hostile forces for electronically jamming the radar and can also be used for positionally locating and for guiding munitions to the radar.
  • mainlobe radiation is ordinarily much greater than sidelobe radiation, its relatively small solid angle of radiation and its directionality makes mainlobe jamming, radar location and munitions direction more difficult.
  • passive types in which each radiating element in the array is provided power from a large, common power source.
  • tapering of the radiation output or, as it is sometimes termed, tapering of array illumination, is comparatively easy to implement by the use of restrictive branching from the power source to the radiating elements, such that progressively lower power is provided to elements further from the array center.
  • Active arrays have numerous actual and potential advantages over passive arrays.
  • the power modules of the active arrays being physically dispersed across the array, can be cooled more efficiently and effectively than the single, high power source of a corresponding passive array.
  • a comparative large number of power modules can fail or malfunction without substantially impairing effectiveness of the antenna.
  • failure or malfunction of the common power source in a passive array incapacitates the entire antenna.
  • the providing of very smoothly tapered illumination of passive array antennas should be possibly by the use of many (about 20 or more) different groups of power modules, each group having a different power output.
  • the use of many different power groups of modules is not practical because such construction adds substantially to the cost of producing the arrays and causes subsequent maintenance and logistical support problems.
  • supplies of all twenty different type modules would have to be stocked wherever any array maintenance and repair activities are expected to be needed.
  • a low sidelobe solid state, phased array antenna apparatus having a far field mainlobe and sidelobe radiation pattern, comprises an antenna aperture formed of a large number, N, of small, closely spaced radiating apertures; N small, linerly polarized radiating elements, each operatively associated with a corresponding small radiating aperture for radiating microwave energy therethrough; and a number, preferably equal to the number, N, of solid state power modules, each operatively associated with at least one corresponding radiating element for providing power thereto.
  • the power modules are divided into a number, M, of specifically arranged groups of modules, the number M preferably being between 3 and about 10, being more preferably between 3 and about 7 and being most preferably equal to about 5.
  • the output voltage amplitude of each of the power modules is the same in any group of modules, but is substantially different in different groups of modules.
  • the voltages amplitudes of the power modules for the different module groups and the boundaries of the M groups of modules are selected so as to cause the far field sidelobe peak gain to be down at least about 30dB from the associated far field mainlobe gain of the array.
  • the M groups of power modules are concentrically arranged around a central point of the array so that the voltage amplitudes of the power modules in the groups of modules decrease with increasing distance from the array central point.
  • the outer boundary of each group of modules is elliptically shaped, having respective semi-major and semi-minor axes a i and b i . It should be pointed out that a circular boundary is just a special case of this analysis wherein the aspect ratio a i /b i is equal to one. Also, without loss of generality, the shape of each elliptical boundary can be chosen to have the same aspect ratio for convenience of design.
  • the output voltage amplitudes and the arrangement of the groups of power modules are selected by treating the module groups as being formed of, or comprising, a superposition of M overlapping, elliptically-shaped zones, each such zone having the same boundary as a corresponding one of the module groups.
  • Each of the M zones has associated therewith a voltage amplitude, E i .
  • the voltage amplitude of the power modules in each group of modules is determined by treating the M module voltage amplitudes as a superposition of the voltage amplitudes, E i , of the corresponding overlapped zones.
  • the zone voltage amplitudes, E i , and the group boundary semi-major and semi-minor axes, a i and b i are selected by application of the following expression for the far field.
  • a corresponding process for configuring low sidelobe array antennas, the process comprising forming an array antenna aperture from a large number, N, of small radiating apertures, providing for each radiating aperture a radiating element and a power module for supplying power to the radiating element, dividing the power modules into M different output voltage level groups and selecting the configuration of the groups of power modules and the output voltages amplitudes thereof so as to cause the far field sidelobe gain to be down at least about 30dB from the corresponding far field mainlobe gain.
  • the process includes treating the arrangement of the M groups of modules as a superposition of M overlapping, elliptical radiating zones having the same boundaries as the power module groups, the output voltages amplitude for any group of modules being equal to the sum of the voltage amplitudes, E i , of the superimposed radiating zones, the semi-major and semi-minor axes a i and b i of the zones and the voltage amplitude levels E i thereof being selected in accordance with the above equation to provide a far field sidelobe gain which is at least about 30dB down from the associated far field mainlobe gain.
  • FIG. 1 is an exploded perspective of an exemplary solid state, active array antenna with which the present invention may be used to advantage;
  • FIG. 2 is a pictorial drawing of the radiation pattern of a typical airborne radar, showing mainlobe and sidelobe portions of the radiation pattern;
  • FIG. 2 is a diagram depicting the coordinate system used to specify the coordinatee of the far field relative to an radiating antenna
  • FIG. 4 is a diagram depicting the manner in which a generally rectangular solid state active array antenna is divided into a series of M concentric, overlapping elliptical power module zones, each such zone having a different power level;
  • FIG. 5 is a diagram showing, relative to an array cross-section taken generally along line 5-5 of FIG. 4, how the aperature illumination taper is provided by superimposing different voltage levels of power modules in the different module zones of FIG. 4;
  • FIG. 6 is a diagram, similar to right hand portions of the diagram of FIG. 5, showing, for a particular array configuration and sidelobe radiation requirement, normalized power levels for five power module zones, the corresponding, normalized zone boundary dimensions being also indicated;
  • FIG. 7 is a graph plotting far field mainlobe and sidelobe gain va angle from broadside axis for the conditions shown in FIG. 6; idealized, elliptical aperture zones being assumed; and
  • FIG. 8 is a graph plotting far field mainlobe and sidelobe gain va angle from broadside axis for conditions in which stepped zone boundaries corresponding to actual module lattice configuration are assumed. DESCRIPTION OF THE PREFERRED EMBODIMENT
  • FIG. 1 there is shown in FIG. 1, in exploded form, an exemplary, solid state, active array antenna 10 of the general type with which the present invention may be used to advantage.
  • antenna 10 which is shown as an aircraft-mounted type, are an aperture assembly 12, a cooling liquid plate assembly 14, a solid state power module assembly 16 and a stripline feed assembly 18.
  • aperture assembly 12 Included in aperture assembly 12 is a large number of small radiating elements 24, each of which has disposed therein a dielectric filler 26.
  • a face 28 of aperture assembly 12 is a large number of openings 30, each of such openings being associated with one of radiating elements 24.
  • Mounted on cooling plate assembly 14 are a number of loop assemblies 32, each of which is also associated with one of radiating elements 24.
  • a large number of solid state power modules 34 comprise power module assembly 16, each such module preferably, but not necessarily, powering only a single associated radiating element 24.
  • the present invention is principally directed towards providing preselected voltage operating levels of power modules (corresponding to modules 34) and the physical arrangement of such modules in an assembly (corresponding to module assembly 16) so that the far field radiation from the antenna exhibits very low sidelobes.
  • FIG. 2 illustrates a typical radiation pattern 38 associated with a radar carried by an aircraft 40.
  • the airborne radar involved may, for example, comprise a solid state active array similar to array 10 depicted in FIG. 1. As shown in FIG.
  • radiation pattern 38 comprises a narrow, beam- shaped mainlobe 42 and smaller, fan-shaped sidelobes 44 on each side of the mainlobe.
  • Sidelobes 44 comprise several different lobes 46 which fan out at different angles, ⁇ , relative to a main beam axis 48; typically the sidelobes diminish in intensity as the angle, a increases. It can further be seen from FIG. 2 that some of lobes 46 extend rearwardly relative to mainlobe 42, the angles, ⁇ , associated therewith being greater than 90°.
  • the present invention relates to a process for configuring a solid state, active array so that the far field sidelobe gain is down a very substantial amount, preferably at least about 30dB down, from the far field mainlobe gain.
  • the reduced sidelobes provided by the present invention is accomplished by tapering the radiating illumination in a relatively few, precisely determined steps.
  • Array 60 corresponds generally to array 10 (FIG. 1), insofar as general construction is concerned.
  • array 60 has rectangular dimensions 2a and 2b, and has R rows and C columns of linearly polarized, rectangular radiating elements 62.
  • element 6z Associated with element 6z is a power module 64 (shown in phantom lines).
  • array 60 has an elliptically (instead of a rectangular) radiating aperture 66, it having been determined by the present inventors that array corner regions 68 contribute only negligibly to sidelobes.
  • the far field, G, associated with radiating aperture 66 is considered, the far field at any point defined by angles 0 and ⁇ being generally identified as G(0, ⁇ ) in FIG. 3.
  • a principal feature of the present invention is the dividing, for analysis purposes, of radiating aperture 66 into a relatively few, superimposed elliptical zones around a central point "A", and the selection of zone boundary axes a i , b i and the zone voltage amplitudes, E i , associated therewith in a manner providing a tapered illumination of the aperture which assures very low, far field sidelobes.
  • the number of elliptical zones selected varies between 3 and about 10 and more preferably between 3 and only about 7. Insufficient illumination tapering is considered to be provided using less than 3 zones and although smoother tapering can be provided by use of more than about 7 zones, the cost of using more than that number of different types of power modules is costly and has moreover, been found by the present inventors to be unnecessary for achieving very low sidelobes.
  • the number of zones shown and described is 5; however, any limitation to the use of about 5 zones is neither intended nor implied.
  • First through fifth concentric, progressively larger elliptical zones 74, 76, 78, 80 and 82, respectively, are thus selected, the zones having semi-major and semi-minor axes equal, respectively, to a 1 , a 2 , a 3 , a 4 , and a 5 and b 1 , b 2 b 3 , b 4 , and b 5 (FIG. 4).
  • First zone 74 is the smallest zone and fifth zone 82 is the largest zone and completely fills aperture 66, dimensions a 5 and b 5 being, therfore, respectfully equal to aperture dimensions a and b (FIG. 3).
  • zones 74, 76, 78, 80 and 82 are, for analysis purposes, considered as stacked (or superimposed) upon one another, with the fifth, largest zone 82 at the bottom and the first, smallest zone 74 at the top.
  • a different voltage amplitudes, E i amplitude E 1 being associated with zone 74, E 2 with zone 76, E 3 with zone 78, E 4 with zone 80 and E 5 with zone 82.
  • the voltage amplitudes, E i are added to establish power module voltage.
  • the combined voltage amplitude of the stacked zones 74-82 required to be provided by underlying power modules 60 is equal to E i + E 2 + E 3 + E 4 + E 5 .
  • the voltage amplitude required to be provided by underlying power modules 60 is equal to E 2 + E 3 + E 4 + E 5 ; in an annular region 88 of third zone 78 outside of second zone 74, the voltage amplitude required to be provided by the underlying power modules is equal to E 3 + E 4 + E 5 .
  • each zone 74-82 can be treated separately as providing only a single, corresponding voltage amplitude E 1 -E 5 .
  • the present process treats all zone axis dimensions, a i , b i , and zone voltage amplitudes, E i , as independent variables.
  • At least one set of values for these variables is computed which will provide, as may be required, either minimum sidelobes or a sidelobe gain which is a preselected number of dB less than the corresponding mainlobe gain.
  • These independent variables a i , b i and E i are computed, for numerous G(0, ⁇ ) points, by the equation:
  • a i , b i , E i standard techniques of gradient search can be employed.
  • an initial set of parameters is chosen as a starting point, and a present maximum sidelobe level (such as -30 dB) is selected as a performance criterion.
  • the antenna far field pattern with the initial set of input parameters can be calculated by using Equation (1).
  • the total power of all the sidelobes that exceed the present level, being defined as the error is computed. After this a small variation of one of the parameters, either a positive or negative increment, is introduced and the error is recomputed.
  • antenna pattern gain (in dB) against elevation angle, 0 as measured from the broadside axis. From FIG 7 it can be seen that the gains of all sidelobes 46 (shown shaded) are down at least about 36dB from the peak (0°) gain of mainlobe 42 over the entire visible radiation range.
  • FIG. 8 which shows that the highest sidelobe gain is down at least about 37 dB from the peak mainlobe gain.

Abstract

Un appareil d'antenne à réseau à semi-conducteurs à faible rayonnement du lobe latéral comprend une grande ouverture de rayonnement divisée en un grand nombre N, de petites ouvertures de rayonnement étroitement espacées, chaque petite ouverture de rayonnement étant associée à un élément de rayonnement et à un module de puissance à semi-conducteurs polarisé linéairement. La grande ouverture de rayonnement est divisée en M, de préférence entre 3 et environ 10 zones de rayonnement concentriques, de forme elliptique et de dimensions différentes, superposées les unes sur les autres, à des fins d'analyse. Chacune de ces zones possède une amplitude de tension de sortie Ei, et des axes semi-majeurs et semi-mineurs de longueurs respectives, ai et bi, chaque zone étant considérée séparément dans l'équation du champ éloigné G(,PHI) = [f(,PHI) (â cos PHI - âg(F) sin PHI cos ) ]2, dans laquelle f(,PHI) = (I), ui = (II), J1(ui) est la fonction de Bessel de premier ordre, â et âPHI sont des vecteurs unitaires dans les coordonnés sphériques et Ko est le nombre d'ondes associées au champ de rayonnement. A l'aide de l'équation du champ éloigné, les valeurs de Ei, ai et bi pour chaque zone sont calculées, d'où il résulte un gain de crête du lobe latéral du champ éloigné qui se trouve à un minimum ou un nombre spécifique de dB, par exemple au moins 30dB, en dessous du gain du lob principal du champ éloigné. Les valeurs de Ei dans les zones de chevauchement sont aditionnées pour établir les amplitudes de tension requises des modules de puissance sous-jacents associés aux N ouvertures de rayonnement.A low-radiation side-lobe semiconductor array antenna apparatus includes a large radiation opening divided into a large number N, small closely spaced radiation openings, each small radiation opening being associated with a radiation element and a linearly polarized semiconductor power module. The large radiation opening is divided into M, preferably between 3 and about 10 concentric radiation zones, of elliptical shape and of different dimensions, superimposed on each other, for analysis purposes. Each of these zones has an amplitude of output voltage Ei, and semi-major and semi-minor axes of respective lengths, ai and bi, each zone being considered separately in the far field equation G (, PHI) = [ f (, PHI) (â cos PHI - âg (F) sin PHI cos)] 2, in which f (, PHI) = (I), ui = (II), J1 (ui) is the Bessel function of prime order, â and âPHI are unit vectors in spherical coordinates and Ko is the number of waves associated with the radiation field. Using the far field equation, the values of Ei, ai and bi for each area are calculated, resulting in a peak gain of the far field lateral lobe which is at a minimum or a number specific dB, for example at least 30dB, below the gain of the main far field lob. The values of Ei in the overlapping zones are added up to establish the required voltage amplitudes of the underlying power modules associated with the N radiation openings.

Description

LOW SIDELOBE SOLID STATE ARRAY ANTENNA APPARATUS AND PROCESS FOR CONFIGURING AN ARRAY ANTENNA APERTURE
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of solid state, active aperture array antennas for radar, and more particularly to apparatus and methods for reducing sidelobe radiation by such antennas .
2. Discussion of the Background Radar antennas are well known to radiate microwave radiation in an braod pattern which, for directed antenna, includes a narrow mainlobe and wide sidelobes of radiation. By common definition, the mainlobe is the central lobe of a directional antenna's radiation pattern, the sidelobes referring to the lesser lobes of progressively decreasing amplitude on both sides of the mainlobe and often extending rearwardly of the mainlobe.
Radar antenna aperture configuration generally determines the extent and relative magnitude of the associated sidelobes; however, the gain of the strongest one of the sidelobes is typically only about 1/64 that of the mainlobe. In terms of decibels, the strongest sidelobe gain is typically down about 18dB from the associated mainlobe gain. Gains of the other sidelobes are usually considerably smaller than that of the strongest sidelobe. Although sidelobe gain is typically much smaller than mainlobe gain, because of the large solid angle into which sidelobes radiate, as compared to the small solid angle into which the mainlobe radiates, typically about 25 percent of the total power radiated by a uniformly illuminated radar antenna in the sidelobes.
Ordinarily, sidelobe radiation- provides no useful function and in addition to representing wasted radiating power has other serious disadvantages. For example, radar clutter from sidelobe returns increases the difficultly of discriminating targets from background. Another very significant disadvantage of sidelobe radiation is that such radiation can, in a military environment, be utilized by hostile forces for electronically jamming the radar and can also be used for positionally locating and for guiding munitions to the radar. In this regard, although mainlobe radiation is ordinarily much greater than sidelobe radiation, its relatively small solid angle of radiation and its directionality makes mainlobe jamming, radar location and munitions direction more difficult.
For these and other reasons, the reduction or suppression of radar sidelobe radiation is, particularly in military radar, important and military procurement documents establishing rigid limits on sidelobe radiation are not uncommon.
It is generally known that sidelobe radiation can be suppressed in array-type radar antennas by "tapering" the illumination over the aperture so that individual radiation-emitting elements near the side edges of the array radiate less energy do than other elements closer to the center of the array. Power may, for example, be individually applied to emitting elements of the array, so that the radiation energy distribution across the array, in at least one direction, is substantially Gaussian. Radar arrays have, until quite recently, been
"passive" types in which each radiating element in the array is provided power from a large, common power source. For such passive arrays, tapering of the radiation output, or, as it is sometimes termed, tapering of array illumination, is comparatively easy to implement by the use of restrictive branching from the power source to the radiating elements, such that progressively lower power is provided to elements further from the array center.
More recently, however, there has been great interest in developing active aperature arrays in which each radiating element, or a subgroup of elements, in the array is driven by a separate, small, solid state power supply or module. Active arrays have numerous actual and potential advantages over passive arrays. As an example, the power modules of the active arrays, being physically dispersed across the array, can be cooled more efficiently and effectively than the single, high power source of a corresponding passive array. Moreover, within a large active array, a comparative large number of power modules can fail or malfunction without substantially impairing effectiveness of the antenna. In contrast, failure or malfunction of the common power source in a passive array incapacitates the entire antenna.
According to theory, the providing of very smoothly tapered illumination of passive array antennas should be possibly by the use of many (about 20 or more) different groups of power modules, each group having a different power output. In reality, however, the use of many different power groups of modules is not practical because such construction adds substantially to the cost of producing the arrays and causes subsequent maintenance and logistical support problems. As an illustration, if twenty different power modules groups were to be used in an array, supplies of all twenty different type modules would have to be stocked wherever any array maintenance and repair activities are expected to be needed.
As a result of costs and problems involved with using a large number of different power module groups in active arrays, sidelobe reduction has generally been attempted using only a relatively few different power module groups which have heretofore provided only coarsely tapered array illumination and relatively poor side lobe reduction. The selection of power module operating levels and arrangement has, so far as is known to the present inventors, been previously mademerely by approximately fitting the resulting, staircase-shaped distribution, having only a few steps, to an optimal distribution which may, for example, be in the bell-shape of a Gaussian distribution. Such fitting of an actual, stepped distribution to an optimum distribution curve has not heretofar, also so far as is known to the present inventors, been based upon any rigorous, systematic analysis and has not, therefore, except possibly in isolated, accidental cases, resulted in minimal sidelobes. Nor have such heretofore used curve-fitting approaches enabled specific sidelobe radiation levels to be predicted or designed to, as is often required to meet procurement specifications. As a result, to satisfy present and anticipated, future low sidelobe requirements for solid state active array antennas, improvements are required in the design of such antennas, and specifically in processes for the systematic selection of power module operating levels and physical arrangements of power modules operating at different power levels so as to provide low sidelobes. It is to such a systematic approach for power module operating levels and arrangements that the present invention is directed.
SUMMARY OF THE INVENTION According to the present invention, a low sidelobe solid state, phased array antenna apparatus, having a far field mainlobe and sidelobe radiation pattern, comprises an antenna aperture formed of a large number, N, of small, closely spaced radiating apertures; N small, linerly polarized radiating elements, each operatively associated with a corresponding small radiating aperture for radiating microwave energy therethrough; and a number, preferably equal to the number, N, of solid state power modules, each operatively associated with at least one corresponding radiating element for providing power thereto. The power modules are divided into a number, M, of specifically arranged groups of modules, the number M preferably being between 3 and about 10, being more preferably between 3 and about 7 and being most preferably equal to about 5. The output voltage amplitude of each of the power modules is the same in any group of modules, but is substantially different in different groups of modules. The voltages amplitudes of the power modules for the different module groups and the boundaries of the M groups of modules are selected so as to cause the far field sidelobe peak gain to be down at least about 30dB from the associated far field mainlobe gain of the array. According to an embodiment, the M groups of power modules are concentrically arranged around a central point of the array so that the voltage amplitudes of the power modules in the groups of modules decrease with increasing distance from the array central point. Also, according to an embodiment, the outer boundary of each group of modules is elliptically shaped, having respective semi-major and semi-minor axes ai and bi. It should be pointed out that a circular boundary is just a special case of this analysis wherein the aspect ratio ai/bi is equal to one. Also, without loss of generality, the shape of each elliptical boundary can be chosen to have the same aspect ratio for convenience of design. The output voltage amplitudes and the arrangement of the groups of power modules are selected by treating the module groups as being formed of, or comprising, a superposition of M overlapping, elliptically-shaped zones, each such zone having the same boundary as a corresponding one of the module groups. Each of the M zones has associated therewith a voltage amplitude, Ei. The voltage amplitude of the power modules in each group of modules is determined by treating the M module voltage amplitudes as a superposition of the voltage amplitudes, Ei, of the corresponding overlapped zones. In conjunction therewith, the zone voltage amplitudes, Ei, and the group boundary semi-major and semi-minor axes, ai and bi, respectively, are selected by application of the following expression for the far field.
G(0,Φ) = [f(0,Φ) ( cos Φ - sin Φ cos 0)]2, wherein f(0,Φ ) = 2π ai bi Ei J1 (ui)/ui, ui = (ko ai sin 0) J1 (ui) is the first order Bessel function, 0 and are the unit vectors in the spherical coordinate system and ko is the wave number equal to 2π/λ, with λ being the wavelength associated with the radiated field.
A corresponding process is provided for configuring low sidelobe array antennas, the process comprising forming an array antenna aperture from a large number, N, of small radiating apertures, providing for each radiating aperture a radiating element and a power module for supplying power to the radiating element, dividing the power modules into M different output voltage level groups and selecting the configuration of the groups of power modules and the output voltages amplitudes thereof so as to cause the far field sidelobe gain to be down at least about 30dB from the corresponding far field mainlobe gain. The process includes treating the arrangement of the M groups of modules as a superposition of M overlapping, elliptical radiating zones having the same boundaries as the power module groups, the output voltages amplitude for any group of modules being equal to the sum of the voltage amplitudes, Ei, of the superimposed radiating zones, the semi-major and semi-minor axes ai and bi of the zones and the voltage amplitude levels Ei thereof being selected in accordance with the above equation to provide a far field sidelobe gain which is at least about 30dB down from the associated far field mainlobe gain.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the present invention may be had by considerating the accompanying drawings in which:
FIG. 1 is an exploded perspective of an exemplary solid state, active array antenna with which the present invention may be used to advantage; FIG. 2 is a pictorial drawing of the radiation pattern of a typical airborne radar, showing mainlobe and sidelobe portions of the radiation pattern;
FIG. 2 is a diagram depicting the coordinate system used to specify the coordinatee of the far field relative to an radiating antenna;
FIG. 4 is a diagram depicting the manner in which a generally rectangular solid state active array antenna is divided into a series of M concentric, overlapping elliptical power module zones, each such zone having a different power level;
FIG. 5 is a diagram showing, relative to an array cross-section taken generally along line 5-5 of FIG. 4, how the aperature illumination taper is provided by superimposing different voltage levels of power modules in the different module zones of FIG. 4;
FIG. 6 is a diagram, similar to right hand portions of the diagram of FIG. 5, showing, for a particular array configuration and sidelobe radiation requirement, normalized power levels for five power module zones, the corresponding, normalized zone boundary dimensions being also indicated;
FIG. 7 is a graph plotting far field mainlobe and sidelobe gain va angle from broadside axis for the conditions shown in FIG. 6; idealized, elliptical aperture zones being assumed; and
FIG. 8 is a graph plotting far field mainlobe and sidelobe gain va angle from broadside axis for conditions in which stepped zone boundaries corresponding to actual module lattice configuration are assumed. DESCRIPTION OF THE PREFERRED EMBODIMENT
There is shown in FIG. 1, in exploded form, an exemplary, solid state, active array antenna 10 of the general type with which the present invention may be used to advantage. Comprising antenna 10, which is shown as an aircraft-mounted type, are an aperture assembly 12, a cooling liquid plate assembly 14, a solid state power module assembly 16 and a stripline feed assembly 18. Included in aperture assembly 12 is a large number of small radiating elements 24, each of which has disposed therein a dielectric filler 26. Defined in a face 28 of aperture assembly 12 is a large number of openings 30, each of such openings being associated with one of radiating elements 24. Mounted on cooling plate assembly 14 are a number of loop assemblies 32, each of which is also associated with one of radiating elements 24. A large number of solid state power modules 34 comprise power module assembly 16, each such module preferably, but not necessarily, powering only a single associated radiating element 24. The present invention is principally directed towards providing preselected voltage operating levels of power modules (corresponding to modules 34) and the physical arrangement of such modules in an assembly (corresponding to module assembly 16) so that the far field radiation from the antenna exhibits very low sidelobes. With respect to sidelobes, FIG. 2 illustrates a typical radiation pattern 38 associated with a radar carried by an aircraft 40. The airborne radar involved may, for example, comprise a solid state active array similar to array 10 depicted in FIG. 1. As shown in FIG. 2, radiation pattern 38 comprises a narrow, beam- shaped mainlobe 42 and smaller, fan-shaped sidelobes 44 on each side of the mainlobe. Sidelobes 44 comprise several different lobes 46 which fan out at different angles, α, relative to a main beam axis 48; typically the sidelobes diminish in intensity as the angle, a increases. It can further be seen from FIG. 2 that some of lobes 46 extend rearwardly relative to mainlobe 42, the angles, α, associated therewith being greater than 90°.
As more particularly described below, the present invention relates to a process for configuring a solid state, active array so that the far field sidelobe gain is down a very substantial amount, preferably at least about 30dB down, from the far field mainlobe gain. In general, the reduced sidelobes provided by the present invention is accomplished by tapering the radiating illumination in a relatively few, precisely determined steps. For purposes of further describing the invention, the more general case of a rectangular, solid state active array 60, depicted in FIGS. 3-5; is considered. Array 60 corresponds generally to array 10 (FIG. 1), insofar as general construction is concerned. Also, for purposes of illustrating the invention, it may be assumed that array 60 has rectangular dimensions 2a and 2b, and has R rows and C columns of linearly polarized, rectangular radiating elements 62. Associated with element 6z is a power module 64 (shown in phantom lines).
It is, however, assumed, for purposes of simplifying the following computations, that array 60 has an elliptically (instead of a rectangular) radiating aperture 66, it having been determined by the present inventors that array corner regions 68 contribute only negligibly to sidelobes. For purposes of the following description, the far field, G, associated with radiating aperture 66 is considered, the far field at any point defined by angles 0 and Φ being generally identified as G(0,Φ) in FIG. 3. A principal feature of the present invention is the dividing, for analysis purposes, of radiating aperture 66 into a relatively few, superimposed elliptical zones around a central point "A", and the selection of zone boundary axes ai , bi and the zone voltage amplitudes, Ei, associated therewith in a manner providing a tapered illumination of the aperture which assures very low, far field sidelobes.
Preferably the number of elliptical zones selected varies between 3 and about 10 and more preferably between 3 and only about 7. Insufficient illumination tapering is considered to be provided using less than 3 zones and although smoother tapering can be provided by use of more than about 7 zones, the cost of using more than that number of different types of power modules is costly and has moreover, been found by the present inventors to be unnecessary for achieving very low sidelobes. For specific purposes of illustrating the invention, the number of zones shown and described is 5; however, any limitation to the use of about 5 zones is neither intended nor implied.
First through fifth concentric, progressively larger elliptical zones 74, 76, 78, 80 and 82, respectively, are thus selected, the zones having semi-major and semi-minor axes equal, respectively, to a1, a2, a3, a4, and a5 and b1, b2 b3, b4, and b5 (FIG. 4). First zone 74 is the smallest zone and fifth zone 82 is the largest zone and completely fills aperture 66, dimensions a5 and b5 being, therfore, respectfully equal to aperture dimensions a and b (FIG. 3).
As can be seen from FIG. 5, which corresponds to a transverse output voltage cross-section of array 60, zones 74, 76, 78, 80 and 82 are, for analysis purposes, considered as stacked (or superimposed) upon one another, with the fifth, largest zone 82 at the bottom and the first, smallest zone 74 at the top. Associated with each zone 74, 76, 78 and 80 and 82 is a different voltage amplitudes, Ei, amplitude E1 being associated with zone 74, E2 with zone 76, E3 with zone 78, E4 with zone 80 and E5 with zone 82. In regions where two or more zones 74-82 overlap, the voltage amplitudes, Ei, are added to establish power module voltage. For example, in a central, elliptical region 84, defined by first zone 74, the combined voltage amplitude of the stacked zones 74-82 required to be provided by underlying power modules 60 is equal to Ei + E2 + E3 + E4 + E5. In an annular region 86 of second zone 76 outside of first zone 74, the voltage amplitude required to be provided by underlying power modules 60 is equal to E2 + E3 + E4 + E5; in an annular region 88 of third zone 78 outside of second zone 74, the voltage amplitude required to be provided by the underlying power modules is equal to E3 + E4 + E5. In turn, in an annular region 90 of fourth zone 80 outside of zone 78, the voltage required to be provided by underlying power modules 60 is E4 + E5; outside of zone 80, in an annular region 92 of fifth zone 82, underlying power modules 60 are required to provide a voltages amplitude equal only to E5. However, by known principles of superposition, each zone 74-82 can be treated separately as providing only a single, corresponding voltage amplitude E1-E5. The present process treats all zone axis dimensions, a i , bi, and zone voltage amplitudes, Ei, as independent variables. At least one set of values for these variables is computed which will provide, as may be required, either minimum sidelobes or a sidelobe gain which is a preselected number of dB less than the corresponding mainlobe gain. These independent variables ai, bi and Ei are computed, for numerous G(0, φ) points, by the equation:
G(0,Φ) = [f(0,Φ) (o cos 0 - âΦ sin Φ cos θ)]2, (1)
wherein f(0,Φ) 2π ai bi E i J 1 (ui ) /ui, (2) ui = (ko ai sin 0) and further wherein J1 (ui) is the first order Bessel function, ko is the wave number associated with the rad iation and θ and Φ are the unit vectors in the sperical coordinate system.
To determine the optimum set of parameters ( ai , bi, Ei) for low sidelobes, standard techniques of gradient search can be employed. In the optimization process an initial set of parameters is chosen as a starting point, and a present maximum sidelobe level (such as -30 dB) is selected as a performance criterion. Then the antenna far field pattern with the initial set of input parameters can be calculated by using Equation (1). Next the total power of all the sidelobes that exceed the present level, being defined as the error, is computed. After this a small variation of one of the parameters, either a positive or negative increment, is introduced and the error is recomputed. By examining the trend of the error, and hence the gradient (rate of change), one can decide which way the following step of variation should be implemented. The process is repeated for this parameter until a local minimum in the error is obtained. By the same procedure the iteration process is carried out for all other parameters until the error is reduced to an acceptable level. This optimization process can be readily accomplished by using a computer. By way of specific example, again with no limitations being thereby intended or implied, the present inventors have determined for M equal to 5 (that is, for five aperture zones), the optimum zone boundaries, ai, bi, and output voltage amplitudes, Ei. These values are shown below in Table 1, wherein a = a5 - 1.3 meters and b = b5 = .87 meters, the sum of E1 + E2 + E3 + E4 + E5 is normalized to 1.0 and the radiation frequency is
3.25 GHz. Furthermore, for simplicity of mathematical derivation, the aspect ratio, bi/ai , for each zone is identical to that of each other zone.
FIG. 6, directly corresponds to the righthand half of FIG. 5 and depicts, relatively to scale and for the bi dimensions normalized to b = b 5 = 1 , the corresponding, computed voltage amplitude, Ei, for each of the five zones 74, 76, 78, 80 and 82. Also shown in FIG. 6 is the dB value associated with the difference in power level across each boundary: 2.62 dB with zone 74, 3.06 dB with zone 76, 3.1 dB with zone 78 and 5.11 dB with zone 80.
For the computed ai, bi, Ei values listed in Table 1, there is plotted in FIG. 7 antenna pattern gain (in dB) against elevation angle, 0 as measured from the broadside axis. From FIG 7 it can be seen that the gains of all sidelobes 46 (shown shaded) are down at least about 36dB from the peak (0°) gain of mainlobe 42 over the entire visible radiation range.
In the foregoing, it has been assumed, for computations involving Equation 1, that the boundaries of the five elliptical zones 74, 76, 78, 80 and 82 are perfectly elliptical, as would be the case if there were an infinite number of infinitely small power modules 64 distributed over antenna elements 62. In reality, however, each radiating zone intersects a finite, though usually large, number of radiating elements 62 so that the zone boundaries are more accurately approximated by a discontinuous, stepped shape, (FIG. 4). The question then arises as to which of two adjacent zones the intersected radiating elements 62 (and corresponding power modules 64) should be allocated and also whether allocation to one zone or another makes any significant difference with respect to sidelobe gain reduction. To answer this question, a specific array pattern, with actual element spacing and lattice structure taken into account, was used by the present inventors to compute aperture zone parameters ai and bi and voltage amplitudes, Ei . For such purposed, the actual geometric configuration of a proposed solid state radar array, having an array size of 2.6 by 1.75 meters and having 1188 rectangular radiating elements, was assumed. It was futher assumed that the zone boundaries followed actual boundries of the radiating apertures. Values of ai, bi and Ei for minimum sidelobes were obtained for such an array configuration by operation of Equation 1. The computed gain VS elevation angle is plotted in FIG. 8 which shows that the highest sidelobe gain is down at least about 37 dB from the peak mainlobe gain. A comparison of FIGs. 7 and 8 thus reveals that although the sidelobe pattern is slightly different in actual conditions (FIG. 8) as compared to that of the idealized conditions (FIG. 7), the sidelobe gains are nevertheless about the same in both cases.
Although there has been described above apparatus and method for configuring a solid state, active array antenna aperature so as to provide about a -30 to -35dB peak sidelobe gain by using only a few different power module groups, for purposes of illustrating the manner in which the invention can be used to advantage, it is to be understood that the invention is not limited thereto. Accordingly, any and all variations and modifications which may occur to those skilled in the art are to be understood to be within the scope and spirit of the invention as defined in the appended claims.

Claims

CLAIMSWhat is claimed is;
1. A low sidelobe, solid state, phased array antenna apparatus having a far field mainlobe and sidelobe radiation pattern, the array antenna comprising: a) an antenna aperture formed of a large number, N, of small, closely spaced radiating apertures; b) a number, equal to the number N, of linearly polarized radiating elements, each of which is operatively associated with a corresponding one of the smsll radiating apertures for radiating microwave energy therethrough; and c) a number of solid state power modules, each of which is operatively associated with at least one of the radiating elements for providing power thereto, the number of power modules being divided into a number, M, of groups of power modules, the number M being between 3 and about 10 and being much less than the number N, the output voltage amplitudes of each of the power modules being substantially the same for any group of modules and being substantially different for different groups of modules; the Output voltage amplitudes of the power modules for the M different groups of modules and the boundaries of the M different groups of modules being selected so as to cause the far field sidelobe gain of the array to be down at least about 30dB from the associated far field mainlobe gain of the array.
2. The array antenna as claimed in Claim 1 wherein the number M is between 3 and about 7.
3. The array antenna as claimed in Claim 1 wherein the number M is about 5.
4. The array antenna as claimed in Claim 1 wherein the M groups of power modules are concentrically arranged around a central point of the array so that the voltage voltage amplitudes of the power modules in each of the M different groups of modules decrease with increasing distance of the groups from said central point.
5. The array antenna as claimed in Claim 4 wherein the outer boundary of each of the M groups of power modules is elliptically shaped, each said boundary having a semi-major axis of length ai and a semi-minor axis of length bi, wherein the subscript "i" refers to the ith boundary.
6. The array antenna as claimed in Claim 5 wherein the output voltage amplitudes and the arrangement of said M groups of power modules are selected by treating the M module group arrangements as comprising a superposition of M elliptically shaped, overlapping zones having the same boundaries as corresponding ones of the M groups of modules, each of said M zones having associated therewith a different voltage amplitude E i, the voltage amplitude of the power modules in each of said M groups being selected by adding the different voltage amplitudes, Ei, of the corresponding overlapping zones, wherein the subscript "i" refers to the ith zone.
7. The array antenna as claimed in Claim 6 wherein the voltage amplitudes, Ei, and semi-axis lengths, a i and bi, are selected by application of the following far field equation to cause the sidelobe gain to be down at least about 30dB from the mainlobe gain:
G(0,Φ) = [f(0,Φ) ( 0 cos Φ - sin Φ cos 0)]2, wherein f(0,Φ) = 2- ai bi Ei J1 (ui)/ui, ui = (ko ai sin 0) J1 (ui) is the first order Bessel function. and âΦ are unit vectors in the sperical coordinate system and ko is the wave number associated with the radiated field.
8. A low sidelobe, solid state phased array antenna apparatus having a far field mainlobe and sidelobe radiation pattern, the array antenna apparatus comprising: a) an antenna aperture formed of a large number,
N, of individual, closely spaced radiating apertures; b) a number, equal to the number N, of radiating elements, each of which is operatively associated with a corresponding one of the radiating apertures for radiating microwave energy therethrough; and c) a number of solid state power modules, each of which is operatively associated with at least one of the radiating elements for providing power thereto, the number of power modules being divided into a number, M, of groups of power modules, wherein the number M is between 3 and about 7 and is much less than the number N, the M groups of power modules being arranged in a concentric pattern around a central point of the array, the output voltage amplitude of each of the power modules being substantially the same in any one of the M groups of modules and being substantially different in different groups of the modules, the M groups of modules being arranged so that the voltage amplitudes of the power modules in the groups of modules decreases with increasing distance from the central point; the output voltage amplitudes of the power modules in the different groups of power modules and the boundaries of the different groups of power modules being selected, in combination, to cause the far field peak sidelobe gain of the array to be down at least about 30 dB from the corresponding far field mainlobe gain of the array.
9. The array antenna as claimed in Claim 8 wherein the outer boundary of each of the M groups of power modules is elliptical shaped, each said boundary having a semi-major axis of length ai and a semi-minor axis of length bi and wherein the M groups of modules are treated as comprising a superposition of M, elliptically-shaped zones having the same boundaries as corresponding ones of the groups of modules, each of the M zones having associated therewith a different voltage amplitude Ei, the voltages amplitude of the power modules in each of said groups of modules being a superposition of the different voltage amplitudes, Ei, of the overlapping zones associated with each of the groups, wherein the subscript "i" refers to the ith zone.
10. The array antenna as claimed in Claim 9 wherein the amplitudes Ei and the semi-major and semi-minor axis lengths ai and bi, respectively, are selected by application of the following far field equation so as to cause the sidelobe gain to be down at least about 30dB from the mainlobe gain:
G(0,Φ) = [f(0,φ) ( 0 cos Φ - sin Φ cos θ)]2, wherein f(θ,φ) = 2π ai bi Ei J1 (ui)/ui,
Ui = (ko ai sin 0)
J1 (ui) is the first order Bessel function, and are unit vectors in the sperical coordinate and ko is the wave number associated with the radiated field.
11. The array antenna as claimed in Claim 8 wherein the number M of groups of power modules is about 5.
12. A process for configuring a low sidelobe solid state, phased array antenna, the process comprising: a) forming an array antenna aperture of a large number, N, of small, closely spaced radiating apertures; b) providing for each of the small radiating aperatures a radiating element, N radiating elements being thereby provided; c) providing for each of the radiating elements a solid state power module; d) dividing the power modules into M different power module groups, the number M being between 3 and about 10, and being much less than the number N; e) selecting the configuration of the M groups of power modules and the output voltage amplitude of the power modules in each of the M groups of modules so as to cause the far field peak sidelobe gain to be down at least about 30dB from the corresponding far field mainlobe gain of the array.
13. The process as claimed in Claim 12 wherein the number M is between about 3 and about 7.
14. The process as claimed in Claim 12 wherein the number M is about 5.
15. The process as claimed in Claim 12 including arranging the M groups of power modules concentrically around a central point of the array and so that the voltage amplitudes of the power modules in the M groups of modules decreases with increasing distance from the central point.
16. The process as claimed in Claim 12 including arranging the M groups of power modules so that the outer boundaries thereof are substantially elliptically shaped, each boundary having a semi-major axis of length ai and a semi-minor axis of length bi, wherein the subscript "i" refers to the ith boundry.
17. The process as claimed in Claim 16 including treating the M groups of power modules as comprising a superposition of M elliptically shaped, overlapping zones having the same boundaries as corresponding ones of the M groups of modules, each of the M zones having associated therewith a voltage amplitude, Ei, and including treating the voltage amplitude of the power modules in each of the M groups of power modules as an additive superposition of the voltages amplitudes, E i , of the corresponding overlapping zones, wherein the subscript "i" refers to the ith zone.
18. The process as claimed in Claim 17 including using the following far field equation to obtain values for the zone voltages amplitudes, Ei, and the zone semi- major and semi-minor axis lengths, ai and bi, which cause the far field sidelobe gain to be down at least about 30dB from the corresponding far field mainlobe gain:
G(0,Φ) = [f(0,φ) ( 0 cos Φ - sin Φ cos θ)]2, wherein f(0,Φ) 2π ai bi E i J1 (ui)/ui, ui = (ko ai sin 0) J1 (ui) is the first order Bessel function. and are unit vectors in the sperical coordinate and ko is the wave number associated with the radiated field.
19. A process for configurating a low sidelobe, solid state, phased array antenna, the process comprising: a) providing, for an array antenna aperture, a large number, N, of small, closely spaced radiating apertures; b) providing for each of the small radiating apertures a radiating element, N radiating elements being thereby provided; c) providing for each of the N radiating elements a solid state power module; d) dividing the power modules into M different power module groups, the number M being between 3 and about 7 and being much less than the number N, the output voltage amplitude of all the power modules in any of the M groups of modules being substantially the same and the output voltage amplitudes of power modules in different groups of modules being different; e) arranging the M groups of power modules in a concentric pattern around a central point of the array so that the output voltage amplitudes of the M groups of power modules decrease with increasing distance from said central point; and f) selecting the output voltage amplitudes of the power modules of the M groups of power modules and the boundaries of the M groups of power modules so as to cause the far field sidelobe gain of the array to be down at least about 30dB from the corresponding far field mainlobe gain of the array.
20. The process claimed in Claim 19 including arranging the M groups of power modules so that the outer boundary of each said group is substantially elliptical in shape, each boundary having a semi-major axis of length ai and a semi-minor axis of length bi and including treating each of the M groups of power modules as a superposition of M elliptically shaped, overlapping zones having the same boundaries as corresponding ones of the M groups of power modules, each of the M zones having associated therewith a voltage amplitude, Ei, and including treating the voltage amplitude of each of the M groups of modules as an additive superposition of the voltage amplitudes, Ei, of the corresponding overlapping zones, wherein the subscript "i" refers to the ith zone.
21. The process as claimed in Claim 20 including using the following far field equation to obtain values of zone voltage amplitudes, Ei, and of the zone semimajor and semi-minor axis lengths, ai and bi, which cause the sidelobe gain to be down at least about 30dB from the mainlobe gain:
G(0,φ) = [f(0,φ) ( 0 cos Φ - sin Φ cos θ)]2,
wherein f(0,Φ) = 2π a i bi Ei. J1 (ui)/ui, ui = (ko ai sin θ)
J1 (ui) is the first order Bessel function, and are unit vectors in the sperical coordinate and ko is the wave number associated with the radiated field.
22. A process for configuring a low sidelobe, solid state phased array antenna, the process comprising: a) providing, for an array antenna aperture, a large number, N, of small, closely spaced radiating apertures; b) providing for each of the N small radiating apertures a radiating element and a solid state power module, a number N of radiating elements and N power modules being thereby provided; c ) dividing the array antenna aperture into a number , M , of differently s ized , overlapp ing concentric zones of ell iptical shape , each of said zones having a semimaj or axis of leng th, ai , and a semi-minor axis of length, b i; d) selecting, by use of the following far field equation, values of Ei, a i and bi which cause the far field sidelobe gain of the array to be down by at least about 30dB from the corresponding far field mainlobe gain;
G(0,φ) = [f(0,φ) ( cos Φ - sin Φ cos θ)]2, where in f (0 ,Φ ) 2π ai bi Ei J1 ( ui)/ui, ui = (ko ai sin θ) J1 (ui) is the first order Bessel function, and are unit vectors in the sperical coordinate, ko is the wave number associated with the radiated field and the subscript "i" refers to the ith zone; e) combining the Ei values for overlapping areas of said zones and selecting the output voltages amplitudes of power modules underlying the overlapped zones to be equal to said combined Ei values.
23. The process as claimed in Claim 22 wherein the number M is between 3 and about 10.
24. The process as claimed in Claim 22 wherein the number M is about 5.
EP19870905342 1986-07-29 1987-07-21 Low sidelobe solid state phased array antenna apparatus Expired - Lifetime EP0275303B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US89145686A 1986-07-29 1986-07-29
US891456 1997-07-11

Publications (2)

Publication Number Publication Date
EP0275303A1 true EP0275303A1 (en) 1988-07-27
EP0275303B1 EP0275303B1 (en) 1993-10-13

Family

ID=25398223

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870905342 Expired - Lifetime EP0275303B1 (en) 1986-07-29 1987-07-21 Low sidelobe solid state phased array antenna apparatus

Country Status (4)

Country Link
EP (1) EP0275303B1 (en)
JP (1) JPH01500476A (en)
DE (1) DE3787797T2 (en)
WO (1) WO1988001106A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0451497A1 (en) 1990-03-09 1991-10-16 Alcatel Espace Method for forming the radiation pattern of an active antenna for radar with electronic scanning, and antenna using this method

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5102620A (en) * 1989-04-03 1992-04-07 Olin Corporation Copper alloys with dispersed metal nitrides and method of manufacture
US5039478A (en) * 1989-07-26 1991-08-13 Olin Corporation Copper alloys having improved softening resistance and a method of manufacture thereof
GB2238176A (en) * 1989-10-21 1991-05-22 Ferranti Int Signal Microwave radar transmitting antenna
US5422647A (en) * 1993-05-07 1995-06-06 Space Systems/Loral, Inc. Mobile communication satellite payload
IL110896A0 (en) * 1994-01-31 1994-11-28 Loral Qualcomm Satellite Serv Active transmit phases array antenna with amplitude taper
US5539415A (en) * 1994-09-15 1996-07-23 Space Systems/Loral, Inc. Antenna feed and beamforming network
FR2783974B1 (en) * 1998-09-29 2002-11-29 Thomson Csf METHOD FOR ENLARGING THE RADIATION DIAGRAM OF AN ANTENNA, AND ANTENNA USING THE SAME
GB0213976D0 (en) 2002-06-18 2002-12-18 Bae Systems Plc Common aperture antenna
US7460077B2 (en) * 2006-12-21 2008-12-02 Raytheon Company Polarization control system and method for an antenna array

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3553706A (en) * 1968-07-25 1971-01-05 Hazeltine Research Inc Array antennas utilizing grouped radiating elements
US3760345A (en) * 1972-08-28 1973-09-18 Us Navy Adapting circular shading to a truncated array of square elements
US3811129A (en) * 1972-10-24 1974-05-14 Martin Marietta Corp Antenna array for grating lobe and sidelobe suppression
US4052723A (en) * 1976-04-26 1977-10-04 Westinghouse Electric Corporation Randomly agglomerated subarrays for phased array radars

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8801106A1 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0451497A1 (en) 1990-03-09 1991-10-16 Alcatel Espace Method for forming the radiation pattern of an active antenna for radar with electronic scanning, and antenna using this method
EP0451497B2 (en) 1990-03-09 2000-12-20 Alcatel Space Industries Method for forming the radiation pattern of an active antenna for radar with electronic scanning, and antenna using this method

Also Published As

Publication number Publication date
JPH01500476A (en) 1989-02-16
EP0275303B1 (en) 1993-10-13
WO1988001106A1 (en) 1988-02-11
DE3787797T2 (en) 1994-04-21
DE3787797D1 (en) 1993-11-18

Similar Documents

Publication Publication Date Title
US4090203A (en) Low sidelobe antenna system employing plural spaced feeds with amplitude control
US3045238A (en) Five aperture direction finding antenna
US3755815A (en) Phased array fed lens antenna
US4336543A (en) Electronically scanned aircraft antenna system having a linear array of yagi elements
US5187489A (en) Asymmetrically flared notch radiator
US5233356A (en) Low sidelobe solid state array antenna apparatus and process for configuring an array antenna aperture
US4912481A (en) Compact multi-frequency antenna array
US6919854B2 (en) Variable inclination continuous transverse stub array
IL221050A (en) Variable height radiating aperture
US4186400A (en) Aircraft scanning antenna system with inter-element isolators
US3653057A (en) Simplified multi-beam cylindrical array antenna with focused azimuth patterns over a wide range of elevation angles
US3553706A (en) Array antennas utilizing grouped radiating elements
EP0275303A1 (en) Low sidelobe solid state phased array antenna apparatus.
US5923302A (en) Full coverage antenna array including side looking and end-free antenna arrays having comparable gain
US3445850A (en) Dual frequency antenna employing parabolic reflector
Bornemann et al. Synthesis of spacecraft array antennas for intelsat frequency reuse multiple contoured beams
US3308467A (en) Waveguide antenna with non-resonant slots
JPH05129822A (en) High gain antenna with molding lobe
CN108682968B (en) Single-feed three-beam low-RCS super-surface included angle reflector antenna
KR20200132170A (en) Phased Array Antenna with Limited Beam Steering and Monopulse
US5142290A (en) Wideband shaped beam antenna
Rattan et al. Antenna Array Optimization using Evolutionary Approaches.
US4752781A (en) Side-locking airborne radar (SLAR) antenna
KR102215647B1 (en) Phased Array Antenna with Limited Beam Steering and Monopulse
KR102433667B1 (en) Active phased array antenna with mixed polyomino structure

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19880328

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB IT

17Q First examination report despatched

Effective date: 19910123

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB IT

REF Corresponds to:

Ref document number: 3787797

Country of ref document: DE

Date of ref document: 19931118

ET Fr: translation filed
ITF It: translation for a ep patent filed

Owner name: SOCIETA' ITALIANA BREVETTI S.P.A.

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19940609

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19940620

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19940627

Year of fee payment: 8

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19950721

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19950721

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19960402

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19960430

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20050721