EP4020700B1 - Antenne et système d'antenne pour communications par satellite - Google Patents

Antenne et système d'antenne pour communications par satellite

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Publication number
EP4020700B1
EP4020700B1 EP21216311.7A EP21216311A EP4020700B1 EP 4020700 B1 EP4020700 B1 EP 4020700B1 EP 21216311 A EP21216311 A EP 21216311A EP 4020700 B1 EP4020700 B1 EP 4020700B1
Authority
EP
European Patent Office
Prior art keywords
antenna
array antenna
waveguide
waveguide array
grid
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.)
Active
Application number
EP21216311.7A
Other languages
German (de)
English (en)
Other versions
EP4020700A1 (fr
EP4020700C0 (fr
Inventor
Marco FORMAGGI
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.)
ADS International Srl
Original Assignee
ADS International Srl
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Filing date
Publication date
Application filed by ADS International Srl filed Critical ADS International Srl
Publication of EP4020700A1 publication Critical patent/EP4020700A1/fr
Application granted granted Critical
Publication of EP4020700B1 publication Critical patent/EP4020700B1/fr
Publication of EP4020700C0 publication Critical patent/EP4020700C0/fr
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/16—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion
    • H01P1/162—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion absorbing spurious or unwanted modes of propagation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/28—Adaptation for use in or on aircraft, missiles, satellites, or balloons
    • H01Q1/288—Satellite antennas
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/02—Waveguide horns
    • H01Q13/0275—Ridged horns
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/006—Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/24—Polarising devices; Polarisation filters 
    • H01Q15/242—Polarisation converters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/24—Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction

Definitions

  • the present invention relates to the field of antennas and antenna systems for satellite communications.
  • the present invention relates to the field of waveguide array antennas and systems for satellite communications.
  • waveguide array antennas have gained attention thanks to their aspect ratio and their modular design.
  • EP 2 493 018 B1 discloses a mode filter for an antenna having at least one element aperture.
  • the mode filter includes at least one waveguide extension to extend the at least one element aperture, and at least one two-by-two (2 x 2) array of quad-ridged waveguide sections connected to a respective at least one waveguide extension.
  • the at least one waveguide extension is positioned between the at least one element aperture and the at least one two-by-two (2 x 2) array of quad-ridged waveguide sections, undesired electromagnetic modes of the antenna are suppressed.
  • US 6,650,291 B1 discloses a multi-band phased array antenna for radiating low frequency band signals and high frequency band signals.
  • the multiband phased array antenna is formed from unit cells having waveguides for radiating high frequency band signals and end-fire radiating elements for radiating low frequency band signals.
  • the unit cells have four walls with an open input end and an open radiating end. End-fire radiating elements are disposed on inner surfaces and outer surfaces of the four walls and radiate out the radiating end.
  • Four waveguides are disposed together to radiate into the input end of the low frequency assembly.
  • US 2020/161735 A1 discloses a method of producing a waveguide-to-coaxial adapter array includes applying solder paste to inner surfaces of throughholes of an electrical conductor, inserting coaxial connectors respectively in the throughholes from a first surface of the conductor so that cores of the throughholes respectively become located at the inner surfaces of the throughholes, inserting one or more fixtures including a flat surface in the throughholes from a second surface of the conductor that is opposite to the first surface, so that the flat surface of the fixture(s) contacts the cores of the coaxial connectors and that the cores of the coaxial connectors are held against the inner surfaces of the throughholes, connecting the cores of the coaxial connectors respectively to the inner surfaces of the throughholes by melting the solder paste, and disengaging the fixture(s) from the throughholes.
  • KR101566449 B1 and US3560976 A also disclose waveguide array antennas comprising sum and difference patterns and a mode filter
  • the radiating element size determines the cut-off frequency of the fundamental mode of propagation (namely, mode TE10 in rectangular waveguides, modes TE10 and TE01 in square waveguides).
  • each radiating element of the antenna in order to allow propagation of the fundamental mode, must have a size higher than half the wavelength at the lowest frequency of operation.
  • the spacing between two radiating elements must be lower that the wavelength corresponding to the highest frequency of operation, in order to avoid grating lobes.
  • Grating lobes are responsible for radiation into unwanted regions of space which leads to interference between neighbouring satellites.
  • the lowest frequency of the reception sub-band is 19.2 GHz, while the highest frequency of the transmission sub-band is 31 GHz.
  • the minimum radiating element size is about 7.8 mm in case of standard waveguide technology and the maximum spacing between two radiating elements is about 9.7 mm. This leaves in practice less than 1 mm of distance between the radiating elements, which, as the inventor noticed, is theoretically feasible but impractical and would result in a more complex and even less compact antenna.
  • TM11 and TE11 cut on at about 27.2 GHz and hence are propagating in the transmission sub-band, thus generating grating lobes and cross polarization.
  • the grating lobes phenomenon is regulated by international standards and by the satellite operators, who typically limit accordingly the amount of EIRP (Effective Isotropic Radiated Power) spectral density radiated by the ground antenna.
  • EIRP Effective Isotropic Radiated Power
  • the presence of higher grating lobes therefore results in lower EIRP spectral density and lower bit/Hz efficiency.
  • this reduction causes the end user to lease from the satellite operator more bandwidth and therefore to invest more funds to achieve the same satellite link performances.
  • the Applicant has tackled the problem of providing an antenna for satellite communications, in particular a waveguide array antenna, which allows achieving an efficient usage of the satellite communication bandwidth resources, for instance the Ka-band satellite communication bandwidth, while maintaining a certain degree of compactness and reduced complexity.
  • an antenna including an array of unit cells, each comprising a radiating element (e.g. a stepped horn), and a mode filter connected to the radiating element, the mode filter being configured to pass fundamental modes of propagation and to reject higher order modes of propagation.
  • a radiating element e.g. a stepped horn
  • a mode filter connected to the radiating element, the mode filter being configured to pass fundamental modes of propagation and to reject higher order modes of propagation.
  • the antenna may efficiently operate in wider satellite communication bands or in satellite communications bands with a wider separation between the reception and transmission bandwidth because the grating lobes are advantageously reduced. Also, the antenna compactness is not compromised, nor its complexity is increased.
  • the antenna components are designed and manufactured in waveguide technology.
  • one or more components of the antenna may be designed and manufactured in microstrip and stripline technology.
  • a design and manufacturing approach based on waveguide technology offers the advantage of avoiding dielectric materials which typically add losses and may vary their properties from one batch to another causing a shift of the optimal band of operation, which may require the tuning of the assembly by means of, for example, screws or shims.
  • waveguide array antenna will refer to an array antenna comprising components designed and manufactured in waveguide technology.
  • a “waveguide array antenna” according to the present invention is an array antenna partially or totally made in waveguide technology.
  • the present invention provides a waveguide array antenna for satellite communications, the antenna being configured to transmit and/or receive a first polarization signal and a second polarization signal, the second polarization being orthogonal to the first polarization, and comprising an array of unit cells, wherein each unit cell comprises:
  • the mode filter comprises a center portion and two end portions at the two sides of the center portion, wherein the center portion is a waveguide having a cross section with a Malta Cross shape, and wherein each of the end portions has the form of a square waveguide comprising hollow cylindrical (which may be called also "mouse ear shaped") elements at their corners.
  • the antenna further comprises a grid configured to divide each radiating element into a number of radiating sub-elements having an inter-element distance that is lower than or equal to the wavelength at a highest frequency of operation of the antenna, and an electromagnetic band gap layer configured to support the grid above the radiating elements.
  • the grid comprises a number of grid unit portions.
  • the electromagnetic band gap layer consists of a number of pins protruding from the walls of each grid portion.
  • the grid comprises an array of waveguide apertures.
  • each grid unit portion comprises a number of the waveguide apertures to be positioned above a corresponding radiating element.
  • each waveguide aperture has a quadridged shape.
  • the radiating element is a stepped horn.
  • the antenna further comprises a first diplexer and a second diplexer, the first diplexer being configured to separate a first polarization transmission signal and a first polarization reception signal and the second diplexer being configured to separate a second polarization transmission signal and a second polarization reception signal, the waveguide array antenna further comprising one or more beamforming networks connecting the first and second diplexers with the unit cells.
  • each unit cell further comprises a polarizer, the polarizer being a septum polarizer or an orthomode polarizer.
  • the antenna further comprises a distributed aperture polarizer positioned above the grid.
  • the antenna is configured to operate between 19.2 GHz and 21.2 GHz in reception and between 29 GHz and 31 GHz in transmission.
  • the antenna is manufactured as a layered assembly comprising a radiating layer comprising the radiating elements and a mode filter layer comprising the mode filters.
  • the layers are made of metal by using a computerized numerical control machining technology.
  • the metal may be, for example, aluminium, copper or magnesium alloy.
  • one or more of the layers are made of metalized plastic, or 3D printed metal, or cast metal.
  • the present invention provides an antenna system for satellite communications, the system being configured to be installed at a fixed location or on a land vehicle or on a vessel or on an aircraft, the system comprising a waveguide array antenna as set forth above, a radome, a positioner and a housing for an antenna control unit.
  • FIGS 1a and 1b are two views of an antenna system 100 for two-way satellite communications in accordance with embodiments of the present invention.
  • the antenna system 100 may be configured to communicate with a geostationary orbit satellite (GEO) or a non-geostationary orbit satellite (e.g. low earth orbit, LEO, or medium earth orbit, MEO).
  • GEO geostationary orbit satellite
  • LEO low earth orbit
  • MEO medium earth orbit
  • the antenna system 100 may be installed at a fixed location, on a land vehicle, on a vessel or on an aircraft.
  • the antenna system 100 includes a radome 110, an antenna 120, in particular a waveguide array antenna, a positioner 130 and a housing 140 for an antenna control unit (ACU) 141.
  • the housing 140 may also house sensors providing attitude and heading information, such as an attitude heading reference system (AHRS) 142.
  • AHRS attitude heading reference system
  • the ACU 141 may receive information on the strength of a received radiofrequency (RF) signal for example from a beacon receiver, a tracking receiver or a modem and use such information to optimise satellite pointing.
  • the AHRS 142 typically embeds gyroscopes and accelerometers and may cooperate with one or two GNSS antennas 150 to estimate the direction of true north, which is then used to accurately point to the satellite.
  • the positioner 130 may include rotary joints and sliprings and may have two or more degrees of freedom and implement direct drive servo motors and absolute digital encoders. Additionally suitable RF switches, low noise amplifiers (LNA) or low noise blockdown converters (LNB) and power amplifier (PA) or block up converter (BUC) may be connected to the antenna and/or system ports.
  • LNA low noise amplifiers
  • LNB low noise blockdown converters
  • PA power amplifier
  • BUC block up converter
  • the antenna 120 may be configured to operate in the Ka frequency band, in particular in the range between 17.3 GHz and 31 GHz, for instance between 19.2 GHz and 21.2 GHz in reception and between 29 GHz and 31 GHz in transmission.
  • the antenna 120 preferably comprises an array of unit cells, each comprising a radiating element and a mode filter located below the radiating element to filter higher order modes reaching the radiating element (namely, each unit cell comprises a respective mode filter connected to the radiating element).
  • the antenna 120 preferably comprises an array of unit cells, each comprising a radiating element and a mode filter located below the radiating element, and a grid positioned above the radiating elements.
  • the grid is preferably supported over the radiating elements by an electromagnetic band gap (EBG) structure or layer positioned between the radiating elements and the above grid.
  • ESG electromagnetic band gap
  • the antenna 120 may comprise a polarizer, e.g. in the form of a distributed element polarizer (namely, the antenna may comprise a respective polarizer in each unit cell).
  • the antenna 120 may further comprise one or more diplexers for separating the transmission and reception signals, and one or more beamforming networks connecting the diplexer(s) to the unit cells.
  • the antenna components can be designed and manufactured in waveguide technology. According to other embodiments, it may also include components designed and manufactured in microstrip and stripline technology. As already mentioned above, such approach based on waveguide technology has the advantage of avoiding dielectric materials which add losses and may vary their properties from one batch to another, potentially requiring the tuning of the assembly.
  • the grid is suitable for dividing each radiating element into a number of radiating sub-elements so as to achieve an inter-element distance that is lower than or equal to the wavelength at the highest frequency of operation.
  • the grid is preferably supported above the radiating elements by an electromagnetic band gap (EBG) structure. The grid and the EBG structure will be better described herein after.
  • EBG electromagnetic band gap
  • the mode filter is capable of suppressing higher order modes which may be excited and propagate (in particular, for the standard Ka-band mentioned above, in the transmission sub-band) and which may increase the grating lobes and cross polarization interference.
  • square, or circular, waveguides may be used in the antenna components for supporting the propagation of two orthogonal modes.
  • square, or circular, waveguides are typically used for feeding the radiating elements.
  • Quadridged waveguides may also be used.
  • square, or circular, waveguides are typically used in, e.g., the polarizers to propagate the fundamental mode (namely, TE01, TE10 in square waveguides) of the dual polarization signals, and, as known, they may also support higher order modes (e.g.
  • TE11 and TM11 in square waveguides in case the band of operation is wide or in case of large separation between the transmission and reception sub-bands.
  • the higher order modes cut on at about 27.2 GHz and hence they may propagate in the transmission sub-band.
  • the mode filter of the present invention is specifically designed to filter the higher order modes with simultaneous E or H plane symmetry on two orthogonal planes that may reach the radiating element a feeding waveguide.
  • the higher order modes rejected by the mode filter of the present invention are in particular modes TE11 and TM11 in case of a square waveguide.
  • the mode filter may be designed to reject modes TM01 and TE21.
  • the mode filter may be configured to reject modes TE11 and TE20.
  • the mode filter structure will be better described herein after.
  • each unit cell of the array may comprise more than one radiating element.
  • FIG. 2 shows a block scheme of an antenna 200 according to first embodiments of the present invention.
  • the block scheme of Figure 2 may represent a dual polarized waveguide array antenna suitable for being employed in the system of Figure 1 .
  • the antenna may support transmission and reception of two signals in two independent polarizations, namely a first polarization and a second polarization, wherein the second polarization is orthogonal to the first polarization.
  • the first polarization may be a left hand circular polarization (LHCP) and the second polarization may be a right hand circular polarization (RHCP).
  • the antenna 200 may comprise two diplexers 220, 222.
  • Each diplexer 220, 222 may comprise two filters, e.g. a receive reject filter 221a, 223a and a transmit reject filter 221b, 223b. Each receive reject filter is used to provide rejection in the reception band while each transmit reject filter is used to provide rejection in the transmission band.
  • the two diplexers 220, 222 have four interface ports: a first port 211 for transmission of a first polarization signal, a second port 212 for transmission of a second polarization signal, a third port 213 for reception of the first polarization signal, and a fourth port 214 for reception of the second polarization signal.
  • the two diplexers 220, 222 may be connected to one or more beam forming networks 230.
  • the beam forming network(s) are connected to an array of unit cells 250.
  • the antenna 200 may comprise two beam forming networks, one respective beam forming network for each polarization.
  • each beam forming network may implement beamforming in both azimuth and elevation planes.
  • Figure 2 shows, for sake of non-limiting example, eight unit cells 250.
  • Each unit cell includes a radiating element 253 and a mode filter 252 located below the radiating element 253.
  • the radiating element may be for instance a stepped horn.
  • the antenna 200 preferably also comprises a polarizer.
  • the block representing the polarizer in Figure 2 is a dashed box.
  • the polarizer may be a distributed element polarizer 251b.
  • each unit cell 250 comprises a respective polarizer element, such as a septum polarizer or an orthomode polarizer, interposed between the beam forming network(s) and the mode filter connected to the radiating element.
  • a septum polarizer is a three port waveguide component comprising two rectangular ports, where the signals associated with two orthogonal linear polarizations propagate in the form of TE10 modes, and a common square port, where the signals associated with two circular polarizations propagate in the form of TE10 and TE01 orthogonal fundamental modes.
  • the transition from the two rectangular waveguides into the single square waveguide is achieved by means of a bisecting wall, called "septum", which generates a differential phase shift between the two fundamental modes in the square waveguide.
  • the septum is asymmetrical and may have a continuous or stepped shape over its length.
  • the polarizer may be a distributed aperture polarizer 251c.
  • the polarizer 251c is positioned above the grid 255.
  • distributed aperture polarizers are meander line polarizers, grid polarizers, parallel plate polarizers, and so on.
  • FIG. 3 shows a block diagram of an exemplary antenna 300 in accordance with second embodiments of the present invention.
  • the antenna comprises a grid above the radiating elements, as already described above, and each radiating element is connected to a respective mode filter located below the radiating element.
  • the block scheme shown in Figure 3 may represent a dual polarized waveguide array antenna suitable for being employed in the system of Figure 1 .
  • the antenna 300 may be a circularly polarized antenna.
  • the exemplary antenna 300 comprises two diplexers 320, 322, each optionally comprising a filter 321, 323, in particular a waveguide transmit reject filter.
  • the two diplexers 320, 322 have four interface ports: a first port 311 for transmission of the first polarization signal, namely, for instance a left hand circular polarization (LHCP) signal, a second port 312 for transmission of the second polarization signal, namely, for instance, a right hand circular (RHCP) signal, a third port 313 for reception of the first polarization signal, and a fourth port 314 for reception of the second polarization signal.
  • LHCP left hand circular polarization
  • RHCP right hand circular
  • the two diplexers 320, 322 are connected respectively to a first beam forming network 330 and to a second beam forming network 340, each one implementing beamforming in both azimuth and elevation planes respectively for the first and second polarization signals.
  • the first beam forming network 330 and the second beam forming network 340 are connected to an array of unit cells 350.
  • Figure 3 shows, for sake of non-limiting example, eight unit cells 350.
  • Each unit cell includes a polarizer 351, e.g. in the form of a septum polarizer, a mode filter 352, and a radiating element 353, e.g. in the form of a stepped horn.
  • the antenna 300 then preferably comprises a grid 355.
  • the grid 355 is preferably supported above the radiating elements 353 by an EBG structure 354.
  • Figures 4a and 4b are two views of an example of a layered assembly for a waveguide array antenna 400 in accordance with the embodiments of the present invention schematically represented in Figure 3 .
  • the layers are preferably made of metal by using a CNC (Computerized Numerical Control) machining technology.
  • the metal may be, for instance, aluminium, copper or magnesium alloy.
  • one or more of the layers of the assembly may be made of metalized plastic, or 3D printed metal, or cast metal.
  • Figures 5a and 5b are two exploded views (respectively, from the top and from the bottom) of the layered assembly for the dual polarised waveguide array antenna 400 shown in Figures 4a and 4b .
  • the antenna 400 comprises:
  • the radiating layer 402 preferably comprises radiating elements in the form of horns with a stepped structure (as shown in Figure 4b ) and a quadridged input waveguide (as shown in Figure 5b ), for increasing the bandwidth of operation.
  • optimal alignment of all the layers is required to minimise return loss and insertion loss and may be ensured by means of dowel pins.
  • optimal electric contact between all adjacent layers is required to avoid spillover from the waveguide walls and therefore minimise losses. This may be ensured by distributing the screws and fixing points throughout the whole surface of the layers.
  • the grid layer may comprise the last portion of the radiating layer below, e.g. the last portion of the stepped horn radiating elements.
  • FIG 6a schematically shows a unit cell 600 and a unit portion 601 of the grid layer 401 shown in Figures 5a and 5b (this unit portion is shown in more detail in Figures 9a, 9b and 9c ).
  • the unit cell 600 comprises a unit portion 602 of the radiating layer 402 (namely, a single stepped horn), a unit portion 603 of the two mode filter half-layers 403 (namely a single mode filter, which will be shown in more detail in Figures 7a and 7b ), and a unit portion 604 of the polarizer layer 404 (namely, a single septum polarizer).
  • Figure 6b shows the unit cell 600, the beam forming networks 605a, 605b comprised in the BFN half-layers 405, 406 and the diplexers 606a, 606b comprised in the diplexer half-layers 407 of the layered assembly of Figures 5a and 5b .
  • Figures 7a and 7b show, respectively, a top view and a isometric view of a waveguide mode filter 700 in accordance with embodiments of the present invention.
  • the mode filter comprised in each unit cell includes a center portion 710 and two end portions 720, 730 at the two sides of the center portion. All these portions are realized in waveguide technology.
  • the center portion 710 preferably has a length equal to about half the wavelength at a frequency corresponding to the center of the operational bandwidth.
  • the cross section of the center portion 710 has a shape suitable for achieving the reflection of the higher order modes.
  • Such a shape is the Malta Cross shape shown in Figures 7a and 7b . This corresponds to the cross section of a quadridged waveguide which is rotated by 45° with respect to the square cross section of the end portions 720, 730 and with respect to the square cross section of the waveguide at the output of the septum polarizer.
  • This particular shape has the advantage of filtering unwanted higher order modes (and in particular those that may be generated by the septum polarizer in the transmission sub-band, such as in the case of Ka-band).
  • the grid of the present invention may be realized in waveguide technology as an array of waveguide apertures.
  • the apertures may have a square, circular or polygonal (i.e. hexagonal or octagonal) shape.
  • the apertures may have a square quadridged, circular quadridged or polygonal quadridged shape.
  • the grid may be realized as a single or multi-layer PCB (Printed Circuit Board), where each layer is printed with an array of circular, square or, more generally, polygonal conductive loops.
  • PCB Print Circuit Board
  • Figures 9a, 9b and 9c show, respectively, a top view and two isometric views of a unit portion 900 of the grid of Figures 6a and 6b , in accordance with embodiments of the present invention.
  • the grid shown in Figures 9a, 9b and 9c is realized in waveguide technology.
  • the unit portion 900 of the waveguide grid schematically shown in Figures 9a, 9b and 9c comprises a cluster of waveguide apertures 910.
  • the array of waveguide apertures has the function of subdividing the radiating elements of the antenna into an array of radiating sub-elements (in the embodiment schematically shown in Figures 9a, 9b and 9c , each radiating element is subdivided into 2x2 radiating sub-elements) so as to minimise the inter-element distance and hence to minimise the grating lobes radiation.
  • Each aperture of the grid preferably has a quadridged shape, which advantageously allows to maximise the bandwidth of the radiated signal and to minimise insertion loss and return loss.
  • the quadridged apertures of the entire grid are preferably clustered in groups of four, each belonging to a single unit portion 900 of the grid.
  • the grid is preferably suspended at a predefined distance above the array of radiating elements by means of an electromagnetic band gap (EBG) structure, which allows placing the grid at an optimal distance from the radiating elements in order to minimise insertion and return loss and to avoid grating lobes.
  • EBG electromagnetic band gap
  • the EBG structure is positioned between the radiating elements and the grid above them.
  • the EBG structure allows for a broadband or dual band operation; it is designed to support the whole band of operation of the antenna and to prevent radiation outside of the boresight direction.
  • the EBG structure serves the dual purpose of structural support and prevention of side radiation from each of the radiating elements, thus further minimising losses and spurious radiation. It consists of a number of parallel, conductive pins protruding from the walls of the grid portions as it will be described herein below.
  • the structure supporting the grid 900 in the embodiment shown in Figures 9a, 9b and 9c comprises four pins 920 protruding from the walls of the unit portion 900 of the grid.
  • Each pin 920 may be located at a position corresponding to the center of the respective wall.
  • the pins 920 form, together with their periodic replicas, an EBG layer.
  • the spacing D between the elements or replicas of the EBG layer is about 1.5 wavelengths at the highest frequency of operation.
  • the height H of each element may be equal to about 1/3 wavelength at the highest frequency of operation, while the size L of each element (as indicated in Figure 9b ) is preferably lower than 1/5 wavelength at the highest frequency of operation.
  • such layer not only serves the purpose of providing the required separation between the radiating elements and the above grid but also contributes to limiting the radiation into unwanted regions of space, thus improving overall antenna efficiency.
  • the inventor noticed that providing the EBG structure described above, as compared to an alternative approach such as providing metal walls, allows avoiding unwanted resonances.
  • the EBG structure advantageously removes any wave travelling parallel to the apertures of the radiating elements.
  • the EBG structure does not require tuning nor increases losses or excites unwanted resonances.
  • a dielectric spacer would have the disadvantage of requiring accurate tuning of its thickness for each production unit, as different batches may have slightly different dielectric constants.
  • it would cause additional losses and side radiation, which, in principle, can be avoided by adding metal walls that however may cause unwanted resonances.
  • the grid and the associated EBG structure described above may be configured to subdivide each radiating element in 2x2 (as shown in Figures 9a, 9b and 9c ), 3x3 or, more generically, NxN radiating sub-elements, where N is an integer number higher than 3. This allows covering several operating bands of frequency separated far apart.
  • Figure 10 shows a measured radiation pattern at 30 GHz for an exemplary waveguide array antenna according to the present invention, such as the antenna shown in Figures 4a and 4b .
  • the grating lobes are substantially absent.
  • Such grating lobes would have caused the EIRP spectral density allowed by the satellite operator to be reduced proportionally therefore requiring the end user to lease more bandwidth in order to achieve the same satellite link performance.

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  • Astronomy & Astrophysics (AREA)
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Claims (13)

  1. Antenne réseau à guides d'ondes (120, 200, 300, 400) pour des communications par satellite, l'antenne (120, 200, 300, 400) étant configurée pour transmettre et/ou recevoir un premier signal de polarisation et un deuxième signal de polarisation, ladite deuxième polarisation étant orthogonale à ladite première polarisation, et comprenant un réseau de cellules unitaires (250, 350, 600), dans laquelle chaque cellule unitaire (250, 350, 600) comprend :
    - un élément rayonnant (253, 353, 402, 602) ; et
    - sous ledit élément rayonnant (253, 353, 402, 602), un filtre de modes (252, 352, 403, 603, 700) relié audit élément rayonnant (253, 353, 402, 602), ledit filtre de modes (252, 352, 403, 603, 700) étant configuré pour laisser passer un mode fondamental de propagation dudit premier signal de polarisation et dudit deuxième signal de polarisation, et pour rejeter les modes de propagation d'ordre supérieur,
    dans laquelle ledit filtre de modes (252, 352, 403, 603, 700) comprend une portion centrale (710) et deux portions d'extrémité (720, 730) situées de part et d'autre de la portion centrale (710), dans laquelle la portion centrale (710) est un guide d'ondes présentant une section transversale en forme de croix de Malte, et dans laquelle chacune desdites portions d'extrémité (720, 730) présente la forme d'un guide d'ondes à section carré comprenant des éléments cylindriques creux (740) au niveau de ses coins.
  2. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon la revendication 1, dans laquelle elle comprend en outre une grille (255, 355, 401, 900) configurée pour diviser chaque élément rayonnant (253, 353, 402, 602) en un certain nombre de sous-éléments rayonnants présentant une distance entre les éléments qui est inférieure ou égale à la longueur d'onde à la fréquence de fonctionnement la plus élevée de ladite antenne, et une couche à bande interdite électromagnétique (254, 354, 920) configurée pour supporter ladite grille au-dessus desdits éléments rayonnants (253, 353, 402, 602).
  3. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon la revendication 2, dans laquelle ladite grille (255, 355, 401, 900) comprend un certain nombre de portions unitaires de grille (900), et ladite couche à bande interdite électromagnétique est constituée d'un certain nombre de broches (920) faisant saillie depuis les parois de chaque portion de grille (900).
  4. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon la revendication 3, dans laquelle ladite grille (255, 355, 401, 900) comprend un réseau d'ouvertures de guide d'ondes (910) et dans laquelle chaque portion unitaire de grille (900) comprend un certain nombre desdites ouvertures de guide d'ondes (910) destinées à être positionnées au-dessus d'un élément rayonnant correspondant.
  5. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon la revendication 4, dans laquelle chaque ouverture présente une forme à quatre nervures.
  6. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon l'une quelconque des revendications précédentes, dans laquelle ledit élément rayonnant est un cornet à étages (stepped horn) (253, 353, 402, 602).
  7. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon l'une quelconque des revendications précédentes, dans laquelle ledit réseau d'antennes à guides d'ondes (120, 200, 300, 400) comprend en outre un premier diplexeur (220, 320) et un deuxième diplexeur (222, 322), le premier diplexeur (220, 320) étant configuré pour séparer un signal de transmission en première polarisation et un signal de réception en première polarisation, et le deuxième diplexeur (222, 322) étant configuré pour séparer un signal de transmission en deuxième polarisation et un signal de réception en deuxième polarisation, le réseau d'antennes à guides d'ondes (120, 200, 300, 400) comprenant en outre un ou plusieurs réseaux de formation de faisceau (230 ; 330, 340) reliant les premier et deuxième diplexeurs aux cellules unitaires (250, 350, 600).
  8. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon l'une quelconque des revendications précédentes, dans laquelle ladite chaque cellule unitaire (250, 350, 600) comprend en outre un polariseur (251b, 351), ledit polariseur (251b, 351) étant un polariseur à septum ou un polariseur orthomode.
  9. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon la revendication 7, dans laquelle ledit réseau d'antennes à guides d'ondes (120, 200, 300, 400) comprend en outre un polariseur discret (251a) interposé entre les premier et deuxième diplexeurs (220, 222) et un ou plusieurs réseaux de formation de faisceau (230).
  10. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon l'une quelconque des revendications 1 à 7, dans laquelle ledit réseau d'antennes à guides d'ondes (120, 200, 300, 400) comprend un polariseur à ouverture répartie (251c) positionné au-dessus de la grille (255).
  11. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon l'une quelconque des revendications précédentes, dans laquelle l'antenne est configurée pour fonctionner entre 19,2 GHz et 21,2 GHz en réception et entre 29 GHz et 31 GHz en transmission.
  12. Antenne réseau à guides d'ondes (120, 200, 300, 400) selon l'une quelconque des revendications précédentes, dans laquelle ledit réseau d'antennes à guides d'ondes (120, 200, 300, 400) est fabriqué sous forme d'un assemblage stratifié (400) comprenant une couche rayonnante comprenant lesdits éléments rayonnants et une couche de filtrage de modes comprenant lesdits filtres de modes, dans laquelle lesdites couches sont faites en métal à l'aide d'une machine d'usinage à commande numérique de l'aluminium.
  13. Système d'antenne (110) pour des communications par satellite, ledit système étant configuré pour être installé en position fixe ou sur un véhicule terrestre, ou sur un navire ou sur un aéronef, ledit système comprenant un réseau d'antennes à guides d'ondes (120) selon l'une quelconque des revendications précédentes, un radôme (110), un dispositif d'orientation (130) et un boîtier (140) pour une unité de commande d'antenne (141).
EP21216311.7A 2020-12-22 2021-12-21 Antenne et système d'antenne pour communications par satellite Active EP4020700B1 (fr)

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US9112279B2 (en) 2011-02-25 2015-08-18 Honeywell International Inc. Aperture mode filter
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