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
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/0006—Particular feeding systems
- H01Q21/0025—Modular 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
Claims
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)
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)
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)
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 |
-
1987
- 1987-07-21 WO PCT/US1987/001755 patent/WO1988001106A1/en active IP Right Grant
- 1987-07-21 JP JP50480387A patent/JPH01500476A/en active Pending
- 1987-07-21 EP EP19870905342 patent/EP0275303B1/en not_active Expired - Lifetime
- 1987-07-21 DE DE87905342T patent/DE3787797T2/en not_active Expired - Fee Related
Non-Patent Citations (1)
Title |
---|
See references of WO8801106A1 * |
Cited By (2)
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 |
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