WO2004038452A1 - Antenne adaptative - Google Patents

Antenne adaptative Download PDF

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Publication number
WO2004038452A1
WO2004038452A1 PCT/SE2002/001944 SE0201944W WO2004038452A1 WO 2004038452 A1 WO2004038452 A1 WO 2004038452A1 SE 0201944 W SE0201944 W SE 0201944W WO 2004038452 A1 WO2004038452 A1 WO 2004038452A1
Authority
WO
WIPO (PCT)
Prior art keywords
antenna
array
phase
feed line
elements
Prior art date
Application number
PCT/SE2002/001944
Other languages
English (en)
Inventor
Lars Josefsson
Original Assignee
Telefonaktiebolaget Lm Ericsson
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 Telefonaktiebolaget Lm Ericsson filed Critical Telefonaktiebolaget Lm Ericsson
Priority to AU2002353684A priority Critical patent/AU2002353684A1/en
Priority to PCT/SE2002/001944 priority patent/WO2004038452A1/fr
Publication of WO2004038452A1 publication Critical patent/WO2004038452A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/38—Jamming means, e.g. producing false echoes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/44—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element

Definitions

  • the present invention relates to antennas, and more specifically how to effectively reduce radar cross section for enabling stealth performance.
  • a well-known problem within antenna techniques is how to effectively reduce the radar cross section of an antenna with a minimum effect on antenna performance to thereby enable a stealth performance.
  • On way to circumvent the problem of course is to use no antennas at all, like for instance the known F117 aircraft.
  • Another possibility is shielding the antenna by means of external frequency selective surfaces (FSS).
  • FSS external frequency selective surfaces
  • a third possibility would be to turn away the antenna. However, a turned away antenna can not be used until it is turned back again to the proper direction, which gives an unwanted important negative time factor.
  • Prior art also mentions switched curtains or radomes to be placed in front of an antenna.
  • U.S. Patent No. 4,684,952 describes a passive array of resonantly-dimensioned micro-strip antenna radiator patches, which are closely spaced above a ground-plane and individually associated with transmission line segments terminated to cause the overall array to receive an incident RF energy electromagnetic field.
  • the received field is converted into RF electrical currents, which flow along the transmission lines and are absorbed by the termination or reflected therefrom. In the latter case the reflected RF energy is re-transmitted in a predetermined direction as a redirected RF electromagnetic field.
  • WO 02/ 11239 discloses a multiple band re- configurable reflecting antenna array and a method for multiple band operation and beam steering.
  • An array of dipole antennas is disposed on a multiple band high impedance surface.
  • the antenna array is re-configured by changing the length of the dipole elements, to thereby change the resonant frequency of the dipoles.
  • small changes in dipole length allow to steer the reflected beam in a selected direction, while large changes in dipole length result in a switch of operating frequency band.
  • a U.S. Patent No. 3,568, 194 from 1967 discusses a way in which a return signal can be degraded by using a variable transmission load connected to the reflector.
  • the disclosed method and system comprise phase and/ or amplitude modulation of the radar signal by one or more "scattering" sources positioned on a target vehicle, thus causing the return target signal to appear as an incoherent object.
  • Another U.S. Patent No. 5,036,323 discusses an active radar stealth device for minimizing the radar cross-section of a host platform.
  • a coating which is essentially transparent for microwaves, is attached to the surface of the host platform and is exposed to an incident microwave field.
  • a plurality of detector/ emitter pairs contained within the coating detect and actively cancel, respectively, the microwave field at each respective detector/ emitter pair.
  • U.S. Patent No. 5,153,594 discloses an electronic counter-measure system for installation on an aircraft.
  • the system includes an interferometer transmitter comprising a plurality of repeater amplifier circuits connected in parallel.
  • the plurality of repeater amplifier circuits generate out of phase signals of different amplitudes, which respectively are transmitted by associated spaced transmitting antennas on the aircraft as a response to an incoming radar signal.
  • the method is particularly applied to an array of radiating elements. It is not necessary for the scattering from each element to be reduced. Instead the loading is controlled such that each element scatters with an amplitude and phase such that the combined backscattering from the complete array in a particular direction is minimized. This particular direction is typically towards the external (threat) source.
  • the signal is received by the main beam of the antenna and the sidelobes are shaped such that a null appears in the direction of the interference.
  • the sidelobes are of no concern in the present context. Instead a second pattern, namely the scattered pattern, which results from the external illumination from another external source, is shaped such that a null appears in the direction of the external illuminating source.
  • a method according to the present invention is set forth by the independent claim 1, and further embodiments of the invention are set forth by the dependent claims 2 to 7.
  • FIG. 1 illustrates an array antenna with control signals
  • FIG. 2 illustrates a radar antenna array irradiated by an external undesired radar source
  • FIG. 3 illustrates with a solid line a regular transmit/ receive antenna pattern and with a broken line the backscatter radiation pattern for the array according to the present invention
  • FIG. 4 illustrates the principle of the present invention using microstrip feeders each provided with a discontinuity in form of a stub for affecting the backscatter radiation pattern;
  • FIG. 5 illustrates a wave-guide feeder incorporating a discontinuity in form of an iris at a location corresponding to a phase ⁇ for a scattered signal
  • FIG. 6 illustrates an array corresponding to the array of Figure 3 but provided with additional dummy elements for obtaining a controlled scattering for reducing RCS of the array.
  • a phased array antenna has typically matched phase shifters (and/ or TR modules) to control the radiation pattern and the beam direction.
  • the scattering pattern is static and independent of the phase shifter settings (provided that the phase shifters and the feeding networks are well matched).
  • extra loads or discontinuities are added within the feed lines and controlled in a systematic fashion, thus modifying the reflections in the feed lines of signals from an external source. Thereby a signal scattered off from the array can be controlled.
  • a particular systematic fashion can create a null in the direction of an external source such that the power scattered back towards that source is minimized.
  • the reduction of the radar cross section typically leads to an antenna gain reduction since the mismatch in the feed lines constitutes a loss.
  • the mismatch loads are chosen such that the antenna gain (in an intended direction) is maximized and the power scattered back towards the external source is minimized. The procedure can be understood from the analogy with signal/ interference optimization in communication systems.
  • reference 3 represents one radiating element in an array antenna (here shown with four elements altogether).
  • a phase shifter 1 or TR (transmit/ receive) module controls the radiating and receiving patterns of the array antenna.
  • TR transmit/ receive
  • An incoming plane wave 6 emanates from a distant external source 5.
  • Each element 3 will not only receive a part of the incoming signal 6 but also scatter back a portion thereof.
  • the received power and the scattered power are of the same magnitude.
  • a reflected portion 4 of the received signal is reflected from a discontinuity 2 in the feed line.
  • This portion can be controlled in amplitude and phase as indicated in Figure 1. Examples of realizations of the discontinuity 2 will be given later. All elements 3 will scatter equally, assuming those to be identical (thus for simplicity neglecting mutual coupling and other effects). Normalizing to this magnitude the total scattered field from one element can be written where T is the reflection from the discontinuity 2, as seen at the element port, and ⁇ is the phase determined by the location of the radiation element in the antenna array relative to the incoming plane wave. For a planar array most of the scattered field will be directed in the specular direction 7 as a concentrated beam.
  • this beam is part of the overall scattered pattern, which will have considerable amplitude also in the direction back towards the external source.
  • the inclusion of discontinuities 2 and their control according to the invention provides a means for minimizing this backward radiation and hence also reduces the monostatic radar cross section.
  • the number of (complex) variables is large (equals the number of radiating elements) while only one condition (null towards the external source 5) shall be fulfilled.
  • One preferred additional condition is to minimize the effect on the antenna performance, thus minimizing the total antenna reflection loss (example with a non- tapered array excitation):
  • the threat direction(s) may be roughly known or can be estimated for a certain mission. Then a broad null is aimed towards this direction. The number of degrees of freedom is actually enough for synthesizing very low levels scattered back in almost all directions (except close to the specular direction 7). Thus this could be a standard setting built into the antenna system.
  • Another embodiment is to make use of the described principle by not using all of the radiating elements in the array. Still another further variation is to add extra (dummy) elements to (the rim of) the array and employ the controlled scattering to those only.
  • the impedance elements used can be of any kind for instance a shunt or series reactance, a stub, an iris, a pin or a varactor diode etc.
  • the control could for instance be effected by biasing the diodes, or by utilizing MEMS (MicroElectroMechanical System) switches.
  • the phase value could be controlled by a phase shifter or by having several switched obstacles along the feed line.
  • a controlled reflection can also be realized by a rotating field ferrite device and a polarization sensitive obstacle. Also a static case with fixed irises etc could be used.
  • Figure 3 illustrates schematically an antenna radiation pattern for a transmitted/ received signal in a desired direction, shown as a solid line, and compared to a scattering pattern for an external signal, illustrated by a broken line.
  • the main lobe of the array is controlled according to the state of the art by controlling of the phase ⁇ of each phase shifter 1.
  • the scattering pattern could have a more or less pronouced null in the direction of an external source represented by the arrow 6.
  • To obtain the full beam steering capacity for transmit the phase ⁇ also has to compensate for an influence of each inserted discontinuity member 2 acting to assist in generating a scattering pattern according to the broken line for an external undesired irradiation indicated by the arrow 6.
  • Reference number 5 illustrates a possible amplifier in front of the phase shifter 1.
  • Figure 4 illustrates a method to generate desired discontinuities by means of an arrangement 2 connected to a respective micro-strip feeder.
  • This arrangement may for instance be a variable stub.
  • the value of _T can then be varied according to methods well known by a person skilled in the art.
  • the radiator 3 may in this case be for instance a patch antenna element.
  • a stub is illustrated as the discontinuity arrangement 2 but also other components, such as a pin or a varactor diode could well be utilized for arrangement 2.
  • the arrangement 2 may also be an impedance member presenting a shunt or series reactance. Control of a varactor diode can be effected by biasing the diode in a way well known by a person skilled in the art. Similarly control of a shunt or series reactance can be performed for instance by utilizing MEMS switches.
  • Figure 5 illustrates still another example of arrangement utilizing a waveguide with an iris inserted at a given distance giving the factor ⁇ along the wave-guide feeding for instance a horn radiator.
  • a number of such waveguides, each with a respective phase shifter 1, will form the array antenna.
  • Figure 6 is illustrated still a further embodiment utilizing the present invention. According to Figure 6 extra (dummy) elements are added, for instance to the rim of the array, to create a controlled scattering in those only or combined with all or part of the active elements of the array.
  • extra (dummy) elements are added, for instance to the rim of the array, to create a controlled scattering in those only or combined with all or part of the active elements of the array.
  • the system according to the present invention enables for instance a fighter or reconnaissance aircraft to operate without being easily observed by other radars. Still full use of the aircraft's own radar may take place.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)

Abstract

L'invention concerne un procédé permettant de réduire efficacement la section transversale d'un radar à des fins d'irradiation externe d'un agencement d'antenne. Ledit procédé s'applique, en particulier, à un réseau d'éléments rayonnants. Il n'est pas nécessaire de réduire la dispersion provenant de chaque élément du réseau. Au lieu de cela, chaque élément est agencé afin d'être dispersé avec une phase et une amplitude telles qu'une rétrodiffusion combinée émanant de la totalité du réseau dans un sens particulier est réduite. Ce sens particulier est typiquement orienté vers la source externe (menace). L'invention concerne un agencement d'antenne dans lequel des signaux radar sont reçus par un lobe de réseau tout en mettant en forme un motif de dispersion réduite à antibrouillage dans le sens du radar extérieur et un motif de dispersion réduite pour un éclairage extérieur quelconque par introduction d'un élément d'impédance dans la ligne d'alimentation d'un certain nombre d'éléments de réseau. Selon l'invention cette charge d'impédance peut également varier systématiquement en fonction des exigences de chaque situation particulière.
PCT/SE2002/001944 2002-10-24 2002-10-24 Antenne adaptative WO2004038452A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2002353684A AU2002353684A1 (en) 2002-10-24 2002-10-24 Adaptive antenna
PCT/SE2002/001944 WO2004038452A1 (fr) 2002-10-24 2002-10-24 Antenne adaptative

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2002/001944 WO2004038452A1 (fr) 2002-10-24 2002-10-24 Antenne adaptative

Publications (1)

Publication Number Publication Date
WO2004038452A1 true WO2004038452A1 (fr) 2004-05-06

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PCT/SE2002/001944 WO2004038452A1 (fr) 2002-10-24 2002-10-24 Antenne adaptative

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AU (1) AU2002353684A1 (fr)
WO (1) WO2004038452A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1928056A1 (fr) 2006-11-28 2008-06-04 Saab AB Procédé de conception d'antennes réseau
GB2504396A (en) * 2012-07-23 2014-01-29 Secr Defence Phased array antenna with randomised impedance to reduce backscattered signal
JP2014173932A (ja) * 2013-03-07 2014-09-22 Mitsubishi Electric Corp アンテナ装置
CN104077498A (zh) * 2014-07-22 2014-10-01 西安电子科技大学 一种结合目标角度的外辐射源雷达多目标跟踪方法
CN104991240A (zh) * 2015-07-13 2015-10-21 西安电子科技大学 目标散射截面积的预测方法
WO2016141912A1 (fr) * 2015-03-09 2016-09-15 Sputnik24 Communication Systems GmbH Système d'antenne multifonction présentant un réflecteur pour radar
EP3128612A1 (fr) * 2015-08-04 2017-02-08 Alcatel Lucent Réseau d'antennes adaptatives et appareil et procédé pour fournir des signaux à un tel réseau
CN112882003A (zh) * 2021-01-12 2021-06-01 西安电子科技大学 一种雷达散射截面缩减方法、系统及应用

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4117485A (en) * 1971-01-05 1978-09-26 The United States Of America As Represented By The Secretary Of The Air Force Radar target cross section control method and means
US4684952A (en) * 1982-09-24 1987-08-04 Ball Corporation Microstrip reflectarray for satellite communication and radar cross-section enhancement or reduction
US5977925A (en) * 1997-07-11 1999-11-02 Telefonaktiebolaget Lm Ericsson Device for antenna systems
JP2001345624A (ja) * 2000-06-05 2001-12-14 Mitsubishi Electric Corp アレーアンテナ装置
WO2002011239A2 (fr) * 2000-08-01 2002-02-07 Hrl Laboratories, Llc Procede et dispositif relatifs a une surface d'impedance elevee

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4117485A (en) * 1971-01-05 1978-09-26 The United States Of America As Represented By The Secretary Of The Air Force Radar target cross section control method and means
US4684952A (en) * 1982-09-24 1987-08-04 Ball Corporation Microstrip reflectarray for satellite communication and radar cross-section enhancement or reduction
US5977925A (en) * 1997-07-11 1999-11-02 Telefonaktiebolaget Lm Ericsson Device for antenna systems
JP2001345624A (ja) * 2000-06-05 2001-12-14 Mitsubishi Electric Corp アレーアンテナ装置
WO2002011239A2 (fr) * 2000-08-01 2002-02-07 Hrl Laboratories, Llc Procede et dispositif relatifs a une surface d'impedance elevee

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
JENN DAVID C. ET AL.: "Inband scattering from arrays with series feed networks", IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 43, no. 8, August 1995 (1995-08-01), pages 867 - 873, XP000522598 *
PATENT ABSTRACTS OF JAPAN *
THORS ET AL.: "Conformal arrays: radiation vs scattering trade-off", IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM (IEEE CAT. NO. 02CH37313, vol. 3, 16 June 2002 (2002-06-16) - 21 June 2002 (2002-06-21), SAN ANTONIO, TX, USA, pages 86 - 89, XP010593088 *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1928056A1 (fr) 2006-11-28 2008-06-04 Saab AB Procédé de conception d'antennes réseau
US7913198B2 (en) 2006-11-28 2011-03-22 Saab Ab Method for designing array antennas
GB2504396B (en) * 2012-07-23 2015-02-18 Secr Defence Phased array antenna comprising impedance elements having random or pseudo-random values
WO2014016539A1 (fr) * 2012-07-23 2014-01-30 The Secretary Of State For Defence Antenne réseau à commande de phase
GB2504396A (en) * 2012-07-23 2014-01-29 Secr Defence Phased array antenna with randomised impedance to reduce backscattered signal
US9905923B2 (en) 2012-07-23 2018-02-27 The Secretary Of State For Defence Phased array antenna
JP2014173932A (ja) * 2013-03-07 2014-09-22 Mitsubishi Electric Corp アンテナ装置
CN104077498A (zh) * 2014-07-22 2014-10-01 西安电子科技大学 一种结合目标角度的外辐射源雷达多目标跟踪方法
WO2016141912A1 (fr) * 2015-03-09 2016-09-15 Sputnik24 Communication Systems GmbH Système d'antenne multifonction présentant un réflecteur pour radar
US10677911B2 (en) 2015-03-09 2020-06-09 Sputnik24 Communication Systems GmbH Multi-function antenna system with radar reflector
CN104991240A (zh) * 2015-07-13 2015-10-21 西安电子科技大学 目标散射截面积的预测方法
EP3128612A1 (fr) * 2015-08-04 2017-02-08 Alcatel Lucent Réseau d'antennes adaptatives et appareil et procédé pour fournir des signaux à un tel réseau
CN112882003A (zh) * 2021-01-12 2021-06-01 西安电子科技大学 一种雷达散射截面缩减方法、系统及应用

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