Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
  • H01Q21/0037—Particular feeding systems linear waveguide fed arrays
  • H01Q21/0043—Slotted waveguides
• • 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
  • H01Q13/20—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
  • H01Q21/0075—Stripline fed arrays
  • H01Q21/0081—Stripline fed arrays using suspended striplines
• • 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

Definitions

• the field of the invention is that of telecommunication antennas, and more particularly that of antennas for radio-relay systems (FH antennas).
• FH antennas radio-relay systems
• the invention more specifically relates to a flat antenna for microwave radio systems fed by a waveguide.
• FIG. 1a shows schematically a parabolic antenna 1 connected to a waveguide G.
• flat antennas are known to be generally as effective as parabolic antennas.
• Flat antennas are also characterized by their compactness and low wind resistance (especially because of a small thickness) and thus tend to be preferred to satellite dishes.
• An advantage of the printed technology exploited in the context of the flat antenna is its good ability to adapt to coaxial connections, for example those of the SMA-3, 5 mm type.
• FIG. 1b it is thus possible to connect a flat antenna 2 having a coaxial connector to a waveguide G via a guide-coaxial transition TGC.
• the flat antenna 2 comprises an array of radiating elements integrated in the dielectric substrate of the antenna.
• the antenna 2 more specifically comprises a set of linear subarrays a r 4 parallel to each other, each linear subarray a r 4 being constituted by a set of radiating elements 3.
• the radiating elements typically each consist of a conductive square surface having a corner connected to a brb subnetwork feeder line 4 (typically in the form of a micro-ribbon line).
• FIG. 2 more specifically represents an exemplary embodiment of the power supply of a flat antenna 2 via a guide-coaxial transition TGC.
• a supply line L (typically a micro-ribbon line) fed by the waveguide via the guide-coaxial transition TGC is arranged transversely to the linear subarray a to r 4 .
• This supply line L thus makes it possible to supply the power supply lines of sub-networks and consequently the radiating elements of all the sub-networks.
• the coaxial connection is effectively fragile and sensitive to galvanic cuts.
• the micro-ribbon feed line L has significant linear losses, generally greater than the losses of the waveguide.
• the object of the invention is to propose a flat antenna FH which does not have the drawbacks associated with the use of a coaxial guide transition, while allowing an equiphase supply of all the radiating elements of the same sub-network.
• the invention proposes a flat antenna system comprising at least one sub-array of radiating elements disposed on a face of a substrate superimposed on a ground plane, each sub-network consisting of a plurality radiating elements adapted to be fed by a sub-network supply line to which they are connected, a slot being formed in the ground plane opposite each sub-network supply line, the system comprising in addition to a power transmission line arranged with respect to the ground plane so as to effect electromagnetic coupling by slot between said power transmission line and each of the sub-network supply lines, the system being characterized in that that the power transmission line is arranged to extend obliquely with respect to the subnetwork supply lines.
• the energy transmission line is a rectangular waveguide, one side of which is pressed against the ground plane, and wave radiation slots are formed in said waveguide face so that the slits of the ground plane and the slits of the waveguide are superimposed;
• the energy transmission line is a waveguide having a U-shape in section, and said waveguide is arranged in such a way that the ground plane closes the space of the waveguide;
• the energy transmission line is a triplate line comprising a conductive line sandwiched between two ground planes of triplate line, wave radiation slots being made in the one of the plane planes of the triplate line which is pressed against said ground plane so that the slits of the ground plane and the slots of the triplate line are superimposed;
• the energy transmission line is a triplate line comprising a conductive line sandwiched between two plane planes of triplate line, and in that one of the ground planes of the triplate line coincides with said ground plane ;
• the system comprises a plurality of linear subarrays parallel to each other and in that the slots in the ground plane are positioned vertically to the supply lines;
• the slots in the transmission line are notches made obliquely in the length of the transmission line;
• each supply line with respect to the corresponding slot is performed so as to control the coupling ratio between the energy transmission line and the said supply line;
• each subnetwork supply line comprises means for weighting the amplitudes of radiation of the radiating elements of the sub-network
• the weighting means comprise impedance transformers interposed between the radiating elements;
• the size of the radiating elements of a sub-network is weighted so as to weight the radiation amplitudes of said radiating elements; the weighting of the size of a radiating element in the form of a conducting surface consists in reducing one of the characteristic dimensions of said surface; and
• the supply line of a sub-array of radiating elements is a micro-ribbon line.
• FIG. 1 c schematically shows a flat antenna having a direct waveguide access
• FIG. 3 represents a possible embodiment of a flat antenna system
• FIGS. 4a and 4b illustrate different ways of weighting amplitudes of the radiating elements
• FIGS. 5a and 5b illustrate the slot coupling between a waveguide and a supply line as a function of the position of the line relative to the center of the slot;
• - Figure 6 shows an advantageous embodiment of a flat antenna system according to the invention.
• FIG. 3 shows a possible embodiment of a system 10. flat antenna.
• the same references have been used for the elements that are common to FIG.
• the system 10 comprises a flat antenna 20 as well as a waveguide G.
• the flat antenna 20 conventionally comprises in itself a flat metal conductive plate constituting a ground plane 5 (at the rear on FIG. 3), and a substrate in the form of a superimposed dielectric plate and substantially parallel to the ground plate
• a circuit is printed on the face of the substrate opposite to the ground plane 5 and comprises radiating elements 3.
• the antenna 20 comprises a set of linear subarray a r 4 arranged on the face of the substrate opposite to the ground plane, parallel to each other, each linear subarray a r 4 being constituted by a set of radiating elements 3 able to be fed by a subarray supply line b r b 4 to which they are connected.
• the supply line is typically a microstrip line ("microstrip" according to the English terminology) printed on the same substrate or on another layer.
• the radiating elements typically consist of a conductive square surface whose apex is connected to the corresponding subarray supply line b r b 4 , the diagonal of the square starting from this vertex being perpendicular to the supply line b r b 4 corresponding.
• the invention is not limited to a particular form of the radiating elements, nor to a particular connection to the corresponding supply line.
• the radiating elements may thus consist of a conductive surface having the shape of a polygon (for example a triangle or a rectangle) or even a circle.
• the radiating elements may also be supplied at other points of the conductive surface at one of the peaks of said surface, for example along one of the sides or inside the conductive surface.
• a slot F 1 -F 4 is formed in the ground plane 5 opposite each subarray supply line b r b 4 .
• the slots are preferentially identical. Each slot F 1 -F 4 is thus placed transversely to the corresponding supply line.
• the system 10 also comprises a power transmission line G arranged with respect to the ground plane 5 so as to achieve an electromagnetic coupling by slot between said transmission line and each of the subnetwork supply lines.
• the energy transmission line may be a waveguide, or any other type of transmission line, in particular a triplate line.
• the waveguide has for example a waveguide having a rectangular sectional shape. It may also be a waveguide having a U-shape in section.
• the electromagnetic fields propagate in the rectangular cavity of the waveguide from bottom to top in the example of FIG.
• a terminal resistor may be provided at an upper plate 1 1 of the waveguide G.
• wave radiation slots identical to the slots of the ground plane are made, for example by machining, in the body of the waveguide, in particular on one of the faces of the waveguide intended to be pressed against the ground plane 5 so that the slits of the ground plane and the slots of the waveguide are superimposed (for these reasons, we have taken the same references to designate all the slots).
• the electromagnetic fields propagating in the space of the guide then radiate, via the superimposed slots made in the ground plane of the antenna and in the face of the waveguide pressed against the ground plane, and come to excite the power lines of the subnetworks.
• the waveguide has a U-shaped section, the waveguide is arranged so that the ground plane 5 closes the waveguide space. The electromagnetic fields propagating in the space of the guide then radiate through the slots in the ground plane of the antenna.
• the antenna structure further comprises a power supply means of the transmission line (not shown), so as to supply electrical energy to said line, this energy propagating inside that and radiating through the slots F 1 -F 4 .
• slots are made on the same face of the waveguide (when a rectangular waveguide is used), and said face is arranged opposite the ground plane of the antenna 20, on the side opposite to the dielectric substrate of the antenna. In such a way, the guide access is secured to the ground plane of the antenna. Access is bein also understood solidarity with the ground plane when it comes close the space of the waveguide.
• a power supply line in the form of a triplate line comprising a conductive line sandwiched between two plane planes triplate line.
• one of the triplate line ground planes coincides with the ground plane of the antenna (in which the slots are made).
• wave radiation slots are formed in one of the triplate line ground planes which is pressed against the ground plane of the antenna so that the slits of the ground plane 5 and those of the ground plane of the triplate line are superimposed.
• the transmission line (here in the form of a waveguide, but this also applies to the embodiment with a triplate line ) is arranged so that it extends generally perpendicular to the subnetwork supply lines.
• the slots are made in the length of the transmission line (for example in the form of rectangular notches) so as to be positioned perpendicular to the supply lines. Due to this coupling, a transfer of energy takes place between power transmission lines, that is to say between the waveguide or the triplate line on the one hand and each of the power supply lines. subnet network on the other hand. In this way, each sub-network supply line is then excited by the energy radiated by the slots, and then supplies all the radiation elements connected to this line.
• the antenna structure of FIG. 2 provides for the supply of the sub-networks of radiating elements by a transverse supply line L
• the antenna structure according to the invention thus proposes to use a plurality of slots performed to achieve electromagnetic coupling between each sub-network and a portion of the power transmission line, on the opposite side to the dielectric substrate of the antenna.
• this document does not relate to the supply of an antenna having a circuit on which radiating elements are printed, and therefore does not deal with the supply of such elements.
• this document does not envisage exploiting the radiation of slots to form a coupling between two power transmission lines, and in particular a coupling of the waveguide with radiating element supply lines.
• the flat antenna is a network of radiating elements.
• the level of the side lobes is likely to be about -13 dB.
• the following description relates to two possible embodiments of a weighting of amplitudes of the radiating elements of the flat antenna, in particular for containing the level of secondary lobes, for example at about -20 dB. It will be appreciated that these embodiments are not limited to the scope of the present invention for direct waveguide access by electromagnetic slot coupling between the waveguide and the subnetwork feed lines. It will also be appreciated that these embodiments may be implemented separately or together.
• impedance transformers T are inserted between the radiating elements 3 of the same sub-network in the sub-network supply line bj.
• Transformers T are more precisely provided with transformation ratios corresponding to the progressive attenuations that one wishes to obtain.
• Transformers T are typically quarter-wave or half-wave transformers; they may also be transformers with so-called progressive laws (eg exponential or logarithmic laws).
• the weighting is "integrated" with the radiating elements 3 by varying the area of said elements.
• the reduction of the surface of a radiating element is accompanied by a reduction in the energy transfer capacity from the radiating element towards the outside, while nevertheless maintaining the same signal level.
• This second embodiment is advantageous in that it allows not to use transformers. These actually produce discontinuities on the subscriber line bj.
• the subnetwork supply line bj no longer has the discontinuities related to the use of transformers.
• the different radiating elements 3 of the sub-network are then equalized in that they are all fed in the same way by the supply line b
• the radiating elements generally have the form of square conductive plates, on the side 12, which represents the guided wavelength on the substrate of the printed circuit on which the radiating elements are formed and which corresponds to the main radiation frequency of the antenna .
• a radiating element in the form of a rectangular conductive plate having a length of / 2 and a width of / n, where n is greater than 2.
• the "integrated" weighting is preferably implemented by favoring the radiating elements 3i at the center of the sub-network (with respect to the excitation point P of the sub-feed line). network at the center of the line), and gradually reducing the size of the radiating elements 3 2 , 3 3 as one deviates from the excitation point P, symmetrically with respect to the point P.
• it controls the transfer of energy between the two transmission lines (between the waveguide or the line triplate and a subnetwork supply line), i.e., the coupling rate is controlled, by varying the offset of the subnetwork supply line from the center of the subnetwork. slot.
• the slots are identical to each other (for example identical rectangular notches made both in the ground plane and in the body of the rectangular waveguide) and it will be noted that the control of the coupling ratio is performed within the scope of the invention without playing on the dimensions of the slots (that is to say in particular without providing different sizes of slots).
• This control of the coupling ratio is advantageous in that it makes it possible to compensate for the decrease in the power of the electromagnetic fields propagating inside the waveguide.
• FIG. 5a shows a slot F 1 of length L (actually two superimposed slits when using a rectangular section waveguide, or a triplate line whose ground plane is pressed against the plane of mass of the antenna) coming to excite a subscriber supply line bj. It is known that the distribution of currents along a half-wavelength slot has a maximum value at the center and decreasing towards the ends.
• FIG. 5b shows the coupling ratio between the slot and the feed line as a function of the longitudinal positioning of the line relative to the slot. It is found that the coupling is maximum when the line b ⁇ is placed perpendicular to the slot Fi at the center of the slot (point b). The coupling decreases as one moves away from the center of the slot (see points a and c, coupling at a greater than the coupling in c).
• FIG. 6 illustrates the advantageous embodiment of a flat antenna system according to the invention according to which a control of the coupling ratio between the energy transmission line and the various supply lines is carried out.
• the transmission line here waveguide G
• the transmission line has a series of oblique slots F 1 -F 4 , and is here arranged slightly obliquely with respect to the supply lines of the sub-networks so that the slots of the waveguide are superimposed on the slits of the ground plane and thus positioned perpendicularly to the supply lines, while gradually varying, from one subnetwork supply line to the other, the coupling ratio between the waveguide and power line.
• the coupling ratio increases from one supply line to the other in the incoming direction (from bottom to top in FIG.
• the arrangement according to the invention of the waveguide oblique with respect to the supply lines of the sub-networks, as illustrated by FIG. 6, is further adapted to allow a supply of all the radiating elements of a same subnet with the same phase (phase feed).
• the two types of transmission lines have different dielectric media.
• the wavelength in the substrate of low losses of the antenna is of the order of 0.7 to 0.8 times the wavelength in the free space.
• the wavelength in the free space is close to the wavelength in the waveguide.
• the gap between the radiating elements does not exceed about 0.8 length. wave in free space.
• said line which is 0.8 wavelength in the vacuum between two radiating elements, has an electric length of one wavelength in the dielectric between two radiating elements, allowing the supply of all elements with the same phase.
• the positioning of the waveguide obliquely with respect to the power supply lines of the sub-networks makes it possible to achieve at a gap of one wavelength in the vacuum, and therefore an equi-phase power supply between the sub-networks, while leaving a Vertical spacing between sub-array lines of approximately 0.8 wavelengths.
• the oblique positioning is further advantageous in that it allows to machine the body of the waveguide so as to practice oblique slots (the feed lines will then be perpendicular to the slots, as is schematically illustrated in FIG. 5a), which makes it possible to obtain an optimal distribution of the currents on the slots resulting from the propagation modes of the electromagnetic fields inside the waveguide.
• An application that will be made of the antenna system according to the invention relates to transmissions in the band of 22.1 to 23.1 GHz, but the invention is of course in no way limited to this particular range of frequencies.

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• 2005
  • 2005-11-14 FR FR0511527A patent/FR2893451B1/fr active Active
• 2006
  • 2006-11-14 EP EP06819455A patent/EP1949496B1/de not_active Not-in-force
  • 2006-11-14 ES ES06819455T patent/ES2384887T3/es active Active
  • 2006-11-14 KR KR1020087014216A patent/KR101166665B1/ko active IP Right Grant
  • 2006-11-14 WO PCT/EP2006/068430 patent/WO2007054582A1/fr active Application Filing
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