Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
  • H01Q9/40—Element having extended radiating surface
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
  • H01Q9/42—Resonant antennas with feed to end of elongated active element, e.g. unipole with folded element, the folded parts being spaced apart a small fraction of the operating wavelength
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/44—Resonant antennas with a plurality of divergent straight elements, e.g. V-dipole, X-antenna; with a plurality of elements having mutually inclined substantially straight portions

Definitions

• the present invention relates to omnidirectional resonant antennas and more particularly to omnidirectional resonant antennas in a half-space or the whole of the space. It is known in the prior art to produce resonant antennas, that is to say, antennas whose dimensions have been determined so that they exhibit a resonance phenomenon for multiples of a frequency predetermined. These antennas use the resonance phenomenon to increase the energy of the radiation emitted and / or received at the predetermined frequency and thus have a limited bandwidth. These antennas also have the advantage of having a small footprint compared to non-resonant antennas, that is to say antennas which do not exhibit a resonance phenomenon for multiples of a predetermined frequency.
• antennas can be produced using a single electrical conductor forming a dipole or a monopole, most often of the wired type. They are, for example, produced using a metal roof printed on a dielectric substrate, these latter antennas being known by the name of "patch antennas". Another embodiment consists in cutting slots in a ground plane, these antennas being known by the name of "slot antennas".
• omnidirectional resonant antennas in a space plane, that is to say that the electromagnetic radiation emitted or received is substantially uniform whatever the direction in this plan.
• the present invention therefore aims to fill this gap by creating an omnidirectional resonant antenna in a half-space or in the whole of the space.
• an omnidirectional resonant antenna in a half-space or the whole of the space comprising a single radiating electrical conductor formed by at least three strands placed end to end, the length of each strand and the orientation of the strands relative to each other helping to determine the overall radiation of the electrical conductor, characterized in that the strands are oriented in at least three different directions of space and in that the lengths of the strands are determined to obtain a global radiation of the omnidirectional electric conductor in a half-space or the whole space.
• the radiating electrical conductor has two parts symmetrical with respect to a plane of symmetry to obtain radiation from the electrical conductor, omnidirectional throughout the space;
• the radiating electric conductor is composed of a first, a second, a third, a fourth and a fifth strand, the fourth and the fifth strand being respectively the images by symmetry of the second and the first strands with respect to the median plane of symmetry of the third strand;
• a strand at the end of the radiating electrical conductor is positioned perpendicular to a ground plane
• the dimensions of the ground plane are less than the wavelength ⁇ to obtain radiation from the omnidirectional electrical conductor throughout the space; - the dimensions of the ground plane are several times greater than the wavelength ⁇ to obtain radiation from the omnidirectional electrical conductor in a half-space;
• the radiating electrical conductor has a first end connected to a wave emitter / receiver and a second end connected to the ground plane;
• the radiating electrical conductor has a first end connected to a wave transmitter / receiver and a second end connected to the ground elements;
• the radiating electrical conductor is connected to the wave emitter / receiver via an electromagnetic coupling zone; - the dimensions of the electromagnetic coupling zone partly determine the actual impedance of the antenna;
• the radiating electrical conductor consists of a first, a second and a third strand
• the strands are each formed by a band whose width is determined to adapt, at least in part, the actual impedance of the antenna to the impedance of a wave transmitter / receiver intended to be connected to the antenna;
• the radiating electrical conductor is made up of wire strands;
• the radiating electrical conductor has a first end connected to a wave transmitter / receiver and a second free end;
• the radiating electrical conductor is associated with a dielectric material reducing the dimensions of the antenna; - the radiating electrical conductor is embedded in a dielectric material reducing the dimensions of the antenna; and - the radiating electrical conductor is positioned on the surface of a dielectric material reducing the dimensions of the antenna.
• the invention also relates to a device for receiving and transmitting electromagnetic radiation in a half-space or in the whole of the space, characterized in that it comprises several omnidirectional resonant antennas according to any one of previous claims.
• FIG. 1 schematically shows an electrical conductor connected by a first end to a transmitter / receiver of waves and by a second end to a ground, as well as a graph illustrating the distribution of the surface density of current along this conductor .
• FIG. 2 shows schematically, in perspective, a first embodiment of an omnidirectional resonant antenna in space according to the invention, dimensioned from the graph of Figure 1.
• FIG. 3 shows in perspective a second embodiment of an omnidirectional resonant antenna in space according to the invention.
• FIG. 4 shows an electrical conductor connected by a first end to a transmitter / receiver of waves and of which a second end is free, as well as a graph illustrating the distribution of the surface density of current along this conductor.
• FIG. 5 shows in perspective a third embodiment of an omnidirectional resonant antenna in space according to the invention, dimensioned from the graph of Figure 4;
• FIG. 6 shows in perspective a fourth embodiment of an omnidirectional resonant antenna in space according to the invention.
• Figure 1 shows extending along the x-axis of the graph, an electrical conductor 4 forming a monopole.
• an electrical conductor 4 is a “quarter wave” electrical conductor, that is to say an electrical conductor whose total length is equal to a quarter of a wavelength, denoted ⁇ , of a frequency predetermined.
• the predetermined frequency is hereinafter called the "working frequency”.
• a phenomenon of constructive resonance occurs in the electrical conductor 4 when one emits and / or receives an electromagnetic radiation whose wavelength is ⁇ .
• the electrical conductor 4 is here formed of a current conductive strip of constant width.
• the electrical conductor 4 has a first end 6 connected to a ground and a second end 8 connected to a wave transmitter / receiver 10 such as a conventional microwave transmitter / receiver.
• a wave transmitter / receiver is called a transmitter / receiver capable of transmitting and / or receiving electromagnetic radiation at a given frequency when it is connected to an electrical conductor.
• a curve 12 represents the distribution of the surface density of current along the electrical conductor at the working frequency. This curve is determined, for example, using conventional software for simulating electromagnetic radiation from electrical conductors.
• the area between the curve 12 and the electrical conductor 4 is divided into three areas 14, 16 and 18 of equal surface and whose interest will appear in the following description.
• a point 20 on the electrical conductor 4 marks the limit separating area 14 from area 16; similarly, a point 22 on the electrical conductor 4 marks the limit separating the area 16 from the area 18. The points 20 and 22 thus delimit three strands placed end to end on the electrical conductor 4.
• FIG. 2 represents a first embodiment of an omnidirectional resonant antenna in the dimensioned space from the graph of FIG. 1. This comprises an electrical conductor 26 forming a monopole similar to that of FIG. 1. The conductor electric 26 has thus a distribution of current surface density per unit of length similar to that of FIG. 1.
• the strand 28 has a length equal to that of the strand between the end 8 and the point 20 of Figure 1.
• the strand 30 has a length equal to that strand between the points 20 and 22 of Figure 1.
• the strand 32 has a length equal to that of the strand between point 22 and the end 6 of FIG. 1.
• the free end of the strand 28 is connected via an electromagnetic coupling zone 34 to a terminal 36 d a wave transmitter / receiver 37.
• the length of the coupling zone 34 that is to say the space between the free end of the strand 28 and the terminal 36 is determined by simulation or experimentally for adapt the real impedance of the antenna to the impedance of the wave transmitter / receiver 37.
• each strand of the electrical conductor 26 it is also possible to vary the width of each strand of the electrical conductor 26 to adapt the real impedance from the antenna to the impedance of the wave transmitter / receiver 37 so as to limit the phenomena nes of reflection at the interface of these two devices 26 and 37.
• the free end of the strand 32 is connected perpendicular to a ground plane 38 whose dimensions are less than the wavelength ⁇ of the working frequency. Under these conditions, the ground plane 38 does not form a screen to the radiation of the electrical conductor 26.
• the different parameters of the strands must be adjusted to compensate for the edge effects of the plane mass 38.
• the ground plane 38 is a plane whose width and length are several times greater than the wavelength ⁇ of the working frequency of the electrical conductor 26. It is then said that the ground plane is infinite. It will be noted that an infinite ground plane forms a screen with electromagnetic radiation from an electrical conductor such as conductor 26 and that consequently the resonant antenna is omnidirectional in a half-space.
• the lengths of the strands such as the strands 28, 30 and 32 are
• ⁇ is the wavelength of the o 10 80 working frequency.
• the lengths of each of the strands corresponding to the strands 28, 30 and 32 are respectively 53 mm, 30 mm and 3 mm.
• the width of the coupling zone such that the zone 34 is 1 mm, the terminal 36 has a length of 4 mm and the diameter of the wire with the transmitter / receiver is 0.2 mm.
• FIG. 3 represents a second embodiment of an omnidirectional resonant antenna in space according to the invention in which the resonant antenna is formed by an electrical conductor 50 forming a monopole.
• This electrical conductor has five strands 52, 54, 56, 58 and 60 placed end to end and arranged so as to form first and second image parts of one another with respect to a plane of symmetry 62.
• the strands 52, 54, and 56 are rectilinear and orthogonal two by two between them.
• the first part consists of strands 52, 54 and a half-strand 64.
• the half-strand 64 represents the upper half of strand 56.
• the strands 52, 54 and 64 form an electrical conductor similar to the electrical conductor 26 described. with reference to FIG. 2.
• the total length of the electrical conductor formed by the strands 52, 54 and by the half-strand 64 is equal to the wavelength of the working frequency divided by four. More precisely, the length of the strand 52 is equal to that of the strand between the end 8 and point 20 of FIG. 1. The length of the strand 54 is equal to that of the strand between points 20 and 22 of the Figure 1. The length of the half-strand 64 is equal to that of the strand between point 22 and the end 6 of Figure 1.
• the second part of the electrical conductor 50 consists of strands 58, 60 and a half -strand 66. The half-strand 66 represents the lower half of the strand 56.
• the dimensions of the strands 58, 60 and of the half-strand 66 are respectively the same as those of the strands 54, 52 and of the half-strand 64.
• the second part of the electrical conductor 50 is intended to produce an electrical image of the first part so as to simulate the existence of a ground plane.
• the second part thus fulfills the functions of a ground plane such as the ground plane 38 of FIG. 2 for the first part, and vice versa. This is why the dimensions of the strands of the first part are determined in the same way as in the embodiment of FIG. 2.
• the free end of the strand 52 is connected to a first terminal of a wave transmitter / receiver 68 and the free end of strand 60 is connected to a second terminal of the wave transmitter / receiver 68.
• This first and this second terminals are also the image of each other with respect to the plane of symmetry 62 so as not to introduce phase shift between the signals transmitted / received by the wave transmitter / receiver 68.
• Figure 4 shows, extending along the x-axis of a graph, an electrical conductor 68 forming a monopole.
• This electrical conductor is here formed by a strip of constant width conducting current, however other shapes can be used in other embodiments.
• a first end of this electrical conductor is connected to a wave transmitter / receiver 69. The second end remains free.
• a curve 70 represents the surface density of current along the electrical conductor 68 at the working frequency. This curve is obtained, for example, using conventional simulation software. In this example, and similarly to what has been described with reference to FIG. 1, the area between the curve 12 and the electrical conductor 68 is divided into three areas 72, 74 and 76 of equal surface.
• a point 78 is placed on the electrical conductor 68 to mark the limit between the area 72 and the area 74.
• a point 80, on the electrical conductor 68 marks the limit between the area 74 and area 76.
• Points 78 and 80 cut the electrical conductor 68 into three strands of respective length L1, L2 and L3.
• the areas of areas 72, 74 and 76 are respectively proportional to the radiation levels of the strands of length L1, L2 and L3.
• FIG. 5 represents a resonant antenna dimensioned according to the graph in FIG. 4.
• This antenna comprises an electrical conductor 86 forming a monopole similar to the electrical conductor 68 of FIG. 4.
• the electrical conductor 86 is connected at one end to a terminal 87 of a wave transmitter / receiver 88. A second end of the electrical conductor 68 remains free.
• This electrical conductor 86 consists of three strands 90, 92 and 94 placed end to end. These strands are rectilinear and orthogonal two by two between them. The length of each of these strands is determined in accordance with FIG. 4, that is to say that the strand 94 has a length L1, the strand 92 has a length L2 and the strand 90 has a length L3.
• the free end of the strand 94 is connected to the transmitter / receiver of waves 88 while being perpendicular to a ground plane 96 whose dimensions are less than the wavelength ⁇ of the working frequency.
• the entire antenna constituted by the electrical conductor 86 and the ground plane 96 is embedded in a dielectric material 98 to reduce the dimensions of the antenna. Indeed, drowning the electrical conductor of an antenna in a dielectric material or placing it on the surface of a dielectric material makes it possible to reduce the dimensions required for the electrical conductor and therefore of the antenna.
• the resonant antenna of FIG. 6 comprises an electrical conductor 110 formed by a strip of current conducting material of constant width.
• This electrical conductor consists of three strands 112, 114 and 116 placed end to end and orthogonal two by two between them.
• the antenna also comprises two earth elements 120 and 122. These earth elements 120 and 122 are each formed by a strip of current conducting material of constant width.
• the first element 120 has three strands 124, 126 and 128 placed end to end.
• the second mass element 122 also has three strands 130, 132 and 134 placed end to end. These two ground elements 120 and 122 are respectively arranged on the right and on the left of the electrical conductor 110.
• the strands 124 and 130 of the ground elements are parallel and coplanar with the strand 112 of the electrical conductor 110.
• the strands 126 and 132 and the strands 128 and 134 are respectively parallel and coplanar with the strands 114 and 116 of the electrical conductor 110.
• the ends of the strands 128, 116 and 134 opposite the strands 126, 114 and 132 are connected together by a current conducting element 136.
• L the free end of the strand 112 is connected to a wave transmitter / receiver 138.
• the lengths of the strands 112, 114 and 116 are determined as a function of the distribution of the current surface density along the electrical conductor 110 in a similar manner to which has been described with reference to FIGS. 1 and 2.
• Such an antenna is typically produced by cutting out constant width slots in a sheet which is then folded at right angles. The operation of the omnidirectional resonant antenna in space will now be described with the aid of FIGS. 1 and 2.
• the wave transmitter / receiver 37 When emitting electromagnetic radiation at the working frequency using the antenna of FIG. 2, the wave transmitter / receiver 37 generates by electromagnetic coupling in the electromagnetic coupling zone 34, a surface density of current in the electrical conductor 26. The surface density of current thus created is distributed along the electrical conductor 26 as illustrated in the graph of FIG. 1.
• the length of the strands 28, 30 and 32 is determined so that the areas 14, 16 and 18 have an equal surface. Consequently, the radiation levels of each of the strands of the electrical conductor 26 are the same.
• the level of radiation emitted at any point in any space is practically the vector sum of the radiation emitted by each of the strands 28, 30 and 32.
• These strands are orthogonal to each other and the radiation emitted by one strand being parallel to its direction, it is therefore understandable that the radiation emitted by one strand does not interfere with that of the others.
• orthogonal strands optimize the gain of the antenna by avoiding destructive interference phenomena.
• no particular direction of space is favored by this antenna, since the strands are orthogonal_ and that the radiation level of each strand is the same. Consequently, the antenna thus produced is - practically omnidirectional. It is considered here that the radiation is practically omnidirectional in a predetermined region of space, if the level of radiation emitted / received by the antenna, in any two directions of this region of space does not vary by more than 50% .
• ground plane 38 does not constitute a screen for electromagnetic radiation and that consequently the radiation from the previous antenna is omnidirectional throughout the space.
• the radiation levels received in the directions of the strands 28, 30 and 32 are respectively proportional to the areas 14, 16 and 18 and therefore determined by the respective lengths of each strand.
• the length of each strand was chosen so that areas 14, 16 and 18 were equal. Consequently, the level of radiation received for a given radiation parallel to a strand will be the same whether this radiation is parallel to the strands 28, 30 or 32. Radiation of any direction can always be broken down into three components respectively parallel to the three strands 28, 30 and 32 the overall level of radiation received by the antenna is therefore unchanged regardless of the direction of this radiation.
• the reception is not limited by the ground plane 38 to a half-space, if the dimensions in width and in length thereof are less than ⁇ .
• the operation of the antenna shown in Figure 3 follows from that which has just been described.
• the second part of the electrical conductor 50 of the antenna formed by the strands 58, 60 and the half-strand 66 fulfills the functions of a ground plane extending along the plane of symmetry 62 for the first part formed by the strands 52, 54 and the half-strand 64. Consequently, the study of the operation of the first part of the antenna boils down to the study of the operation of an electrical conductor connected perpendicularly to a ground plane. confusing with the plane of symmetry 62. The operation of such a structure has already been described with reference to FIG. 2. Conversely; the first part of the antenna fulfills the functions of ground plane merging with the plane of symmetry 62 for the second part of the antenna. Consequently, similarly to what has just been described above, the operation of the second part of the antenna boils down to the study of an antenna whose structure is similar to that described with regard to the figure 2.
• the electrical conductor of the previous exemplary embodiments consists of strands formed with wire elements instead of strands in the form of a strip.
• the diameter of the wire forming each strand is determined to adjust the real impedance of such an antenna to that of the wave transmitter / receiver.
• the electrical conductor of the previous embodiments is made up of strands of any shape for which it is known to calculate the distribution of the surface density of current at the working frequency.
• a device for receiving and transmitting electromagnetic radiation comprises several omnidirectional resonant antennas in a half-space or in the whole of the space such as those described above each adapted to receive and transmit a predetermined wavelength .
• the reception and transmission device is both omnidirectional in a half-space or in the whole of the space, and capable of receiving and transmitting at different wavelengths.

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• 2001
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