Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/04—Adaptation for subterranean or subaqueous use
• • 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
  • H01Q13/28—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave comprising elements constituting electric discontinuities and spaced in direction of wave propagation, e.g. dielectric elements or conductive elements forming artificial dielectric
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
  • H01Q19/28—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using a secondary device in the form of two or more substantially straight conductive elements

Definitions

• the present invention relates to an inductive surface element, which is adapted to modify propagation conditions of electromagnetic radiation. It also relates to a surface wave generation assembly and a surface wave detection assembly each comprising such an inductive surface element.
• a surface wave is a mode of propagation of electromagnetic radiation, which is linked to a separation interface between two different media.
• the two media may differ from each other by their respective values of dielectric permittivity and / or electrical conductivity.
• a surface wave has the following characteristics:
• the wave vector that characterizes the propagation parallel to the interface is connected to the attenuation coefficient in the perpendicular direction and to the electromagnetic impedance of the interface.
• Such a mode of propagation on the surface is opposed to the mode of propagation in free space, which is sometimes called propagation in sky wave.
• Surface waves are used in various applications, including radar systems or communication systems for which the transmitted waves implemented are surface waves.
• the interface that is used is the boundary between the ground and the air environment above the ground.
• a wave of The surface can then be produced using a conversion element that couples some of the free-space propagation waves, as produced by the source, to surface waves.
• the following difficulties affect the existing conversion elements: free space propagation waves remain despite the conversion element, which constitutes a loss of efficiency between the power radiated by the source and the power that is actually diffused as surface waves; and
• the surface waves that are produced by the conversion element have propagation directions dispersed parallel to the ground, so that only a portion of the energy that is transported by these surface waves is transmitted in a desired direction.
• the conversion element when such a conversion element is used in association with a detector for receiving a surface wave transmission communication, the conversion element also transmits to the detector free space propagation waves, more than the received surface wave. The detection of the signal that is carried by the surface wave is then scrambled and disturbed by the free space propagation waves which are transmitted involuntarily.
• GB 788,824 discloses an antenna element which is adapted to transmit a wave which is focused perpendicularly to a base plate of this element, according to the free space propagation mode.
• EP 1 594 186 discloses an antenna which is formed by an open loop above a ground plane, the latter being intended to be buried. Two confined waves are formed between the loop and the ground plane, and the peripheral edge of the ground plane produces surface wave radiation to the outside. However, this system also produces a free space propagation wave.
• WO 03/007426 discloses an antenna with a low form factor radiating element, which is disposed above a high impedance surface itself located on a metal ground plane. But Horizontal polarized surface waves of the electric field appear in the high impedance surface and then transform into free-space propagation waves.
• a first object of the present invention is to produce surface waves with a minimum amount of power that is radiated as free-space propagation waves.
• a second object of the invention is to produce surface waves which are concentrated in azimuth around a desired direction of propagation, parallel to the surface of the ground.
• a third object of the invention is to provide a surface wave production system, which can use the available radiation sources to produce free-space propagation waves, in particular wired antennas.
• a fourth object of the invention is to provide a surface wave production system that is compact, inexpensive and easy to implement.
• a fifth object of the invention is to propose a surface wave production system which is adapted to operate in the frequency range between 0.2 MHz (MHz) and 3000 MHz, and in particular in the band of high frequencies, called HF band, between about 3 MHz and 30 MHz.
• an inductive surface element for electromagnetic radiation which element comprises: an electrically conductive base plate, which extends in a plane not parallel to the electric field component of the electromagnetic radiation;
• the secondary plates have the same height within ⁇ 10%, this height being between 0.035 x ⁇ and 0.35 x ⁇ , where ⁇ is a sizing parameter of the surface element inductive.
• the distance between the base plate and the edges of the secondary plates opposite is between a zero value and half the height of the secondary plates concerned.
• the secondary plates are arranged parallel to each other in a period such that the product of the height of the secondary plates by the period is between 0.001 x ⁇ 2 and 0.15 x ⁇ 2 to ⁇ 10 % near.
• the secondary plates each extend over a total length of at least 0.0003 x ⁇ perpendicular to the sensitive direction.
• Such an inductive surface element is then adapted to modify conditions of propagation, in the half-space, of a projection of the electric field component which is perpendicular to the base plate, when a wavelength of the radiation electromagnetic energy is between ⁇ - 10% and ⁇ + 10%.
• the wavelength of the electromagnetic radiation that is considered is that which is associated with the propagation in the medium where the inductive surface element is located, and which is equal to the speed of light in that medium divided by the frequency of the radiation.
• the inductive surface element makes it possible to produce or detect surface waves which are concentrated in azimuth around a direction of propagation parallel to a ground surface, when this element is placed on the ground or semi-buried near the ground surface, the base plate being parallel to an average boundary surface between the ground and the half airspace.
• the inductive surface element of the invention is therefore an electromagnetic conversion element, which is capable of coupling free space propagation modes with surface waves. This coupling is particularly effective thanks to the geometry and sizing characteristics of the element that are introduced by the invention.
• the element makes it possible to efficiently transfer a portion of the radiated power of free-space propagation waves which reach the element, to surface waves. It can therefore be used with sources of electromagnetic radiation that are available, including wired sources whose cost is low and the use is easy to produce sky waves. These free-space propagation waves are then transformed, at least partially, into surface waves by the inductive surface element of the invention.
• the inductive surface element of the invention is effective in the electromagnetic radiation frequency range which is between 0.2 MHz and 3000 MHz, and especially in the HF band between 3 MHz and 30 MHz.
• the inductive surface element of the invention also makes it possible to effectively couple surface waves that reach this element with free-space propagation waves that can then be detected.
• the surface waves that are produced by the inductive surface element of the invention have propagation directions that are concentrated in azimuth around the sensitive direction of the element.
• the secondary plates are not necessarily flat. They can be adapted to modify the azimuth directionality of the element of inductive surface. For example, while remaining perpendicular to the base plate, they may have a circular curvature on both sides of the sensitive direction.
• the inductive surface element of the invention is simple, inexpensive and easy to implement. In particular, it can be manufactured separately from the source or the electromagnetic radiation detector with which it is intended to be used, which simplifies its method of manufacture.
• each series of secondary plates may comprise at least six secondary plates
• a width of at least one of the secondary plates can be between ⁇ / 2 and ⁇ , measured parallel to the base plate and perpendicular to the sensitive direction;
• the height of the secondary plates can be between ⁇ / 20 and ⁇ / 5, measured perpendicular to the base plate and from it;
• the inductive surface element may comprise a series of secondary plates, each secondary plate of which consists of a pair of ternary plates.
• the two ternary plates constituting a secondary plate are separated by a distance which is between ⁇ / 100 and ⁇ / 50, measured along the sensitive direction;
• At least one of the plates from the base plate and the secondary or ternary plates may comprise a portion of sheet metal or wire mesh, or a combination of at least one portion of sheet metal and at least one portion of mesh metallic.
• a portion (s) perforated or perforated sheet may be used (s), to reduce the weight of the element and the amount of material consumed; and at least some of the secondary or ternary plates can be electrically connected to the base plate.
• the invention also provides a surface wave generation assembly, which comprises: - a radiation source, which is adapted to produce at least one electromagnetic radiation having a free space propagation mode; and
• At least one inductive surface element as described above which is placed on the ground or semi-buried or buried near the ground surface, so that the base plate is parallel to an average boundary surface between the ground and a half airspace.
• the radiation source is oriented such that an electric field component of the electromagnetic radiation at the location of the inductive surface element is not parallel to the base plate.
• the radiation source is adapted so that a wavelength of the electromagnetic radiation is between ⁇ -10% and ⁇ + 10%, where ⁇ is the sizing parameter of the inductive surface element.
• the inductive surface element is buried near the ground surface when the distance between the base plate and the average boundary surface between the ground and the half airspace is less than ⁇ .
• the radiation source may in particular be adapted to produce the electromagnetic radiation with a radiation frequency which is between 0.2 MHz and 3000 MHz, and more particularly between 3 MHz and 30 MHz.
• the radiation source may comprise a wired antenna, the transmission efficiency of this type of antenna being particularly high.
• the strand is preferably oriented such that a straight antenna segment thereof is perpendicular to the base plate.
• the wired antenna can be advantageously positioned with respect to the inductive surface element in accordance with at least one of the following arrangement characteristics:
• the rectilinear antenna segment is separated from that of the secondary plates of the inductive surface element which is closest to the rectilinear antenna segment, by a distance which is less than or equal to 0.5 x ⁇ , measured according to the sensitive direction;
• a point of the rectilinear antenna segment which is closest to the base plate is located at a height which is less than 1.5 times the height of the secondary plates, these heights being measured from the base plate according to a direction perpendicular to the latter and the side of the secondary plates.
• the radiation source may comprise a loop-type wire antenna, the plane loop is oriented preferably parallel to the base plate.
• the requirement for the invention to operate is that electromagnetic radiation from the source has an electric field component not parallel to the base plate.
• the invention also proposes a set of surface wave detection, which comprises:
• a radiation detector which is adapted to detect at least one electromagnetic radiation
• the radiation detector is oriented to detect electromagnetic radiation when an electric field component of this radiation is non-parallel to the base plate, and is effective for detecting electromagnetic radiation when a wavelength of this radiation is included between ⁇ - 10% and ⁇ + 10%, where ⁇ is the sizing parameter of the inductive surface element.
• the characteristic that the inductive surface element is buried near the ground surface further means that the distance between the base plate and the average boundary surface between the ground and the half air space is less than ⁇ .
• the radiation detector may then be placed within the surface wave detection assembly in a relative position with respect to the inductive surface element which is identical to that of the radiation source within the surface wave production set.
• FIG. 1a is a perspective view illustrating an implementation of an inductive surface element according to a first embodiment of the invention, in a surface wave production assembly;
• Figures 1b and 1c are respectively a plan view and a side view of the inductive surface element of Figure 1a;
• FIGS. 2a to 2c correspond respectively to FIGS. 1a to 1c for a second embodiment of the invention
• FIGS. 3a to 3c respectively illustrate three possible installations of the inductive surface element according to the invention
• FIGS. 4a and 4b are diagrams of transmission gain and of modification of the reflection coefficient, respectively, as a function of the frequency of the electromagnetic radiation, for an inductive surface element according to the invention.
• FIGS. 1a to 1c show an inductive surface element according to the invention which comprises a series of secondary plates, and the element of FIGS. 2a to 2c comprise a series of secondary plates constituted each by a pair of ternary plates.
• the references that are mentioned in the figures have the following meanings:
• Nbl, Nbdl number of secondary plates in each series preferably greater than or equal to six
• HF signal source denoted GEN.
• GEN HF Hant placement height of the antenna 3 above the plane of the base plate, measured for a lower point of the antenna 3
• All secondary 2 or ternary plates 2a, 2b may have dimensions that are identical. They are all perpendicular to the central line LS, and therefore all parallel to each other. In addition, they are all centered on the centerline LS, and the period P of the secondary plates is constant.
• the inductive surface element comprises a series of secondary plates of which each secondary plate consists of a pair of ternary plates, the period T is identical between the ternary plates of two adjacent pairs.
• the base plate 1 may be rectangular, as may each secondary or ternary plate 2a, 2b.
• the median line LS is the direction of emission of the surface wave OS which is produced by the inductive surface element from the electromagnetic wave OL, when the antenna 3 is placed itself. at the right of the center line LS.
• the inductive surface element produces a surface wave beam
• this beam is centered in azimuth about the center line LS, in a plane that is parallel to the base plate 1.
• the centerline LS is referred to as the sensitive direction in the general part of the present description.
• a surface wave generation assembly is formed by combining the inductive surface element of Figures 1a-1c or 2a-2c with a source of electromagnetic radiation.
• a radiation source comprises the transmitting antenna 3 and the signal source 4, which is connected to supply the antenna 3 as a transmission signal.
• the antenna 3 may be of the wired antenna type, and in particular a quarter-wave monopole antenna. Such an antenna is known to those skilled in the art. It comprises a rectilinear antenna segment capable of producing electromagnetic radiation that propagates initially in free space, from the antenna segment.
• the antenna 3 and the source 4 can be adapted so that the electromagnetic radiation has a frequency f in the HF band between 3 MHz and 30 MHz.
• the wavelength is then between 10 m (meter) and 100 m for the HF band mentioned above in the air.
• the arrangement of the production set of surface waves satisfies the following conditions:
• the inductive surface element is placed near the surface of the ground
• the dimensions of the inductive surface element are appropriately selected with respect to the wavelength of the electromagnetic radiation which is produced by the antenna 3; and - the rectilinear segment of the antenna 3 is positioned and oriented appropriately with respect to the inductive surface element.
• the inductive surface element can be either placed on the ground (FIG. 3a), or semi-buried (FIG. 3b), or completely buried (FIG. 3c).
• the base plate 1 is parallel or substantially parallel to an average surface S of boundary between the ground and the upper half airspace.
• the actual surface of the ground may be irregular, but the average surface S of the soil boundary is flat.
• the inductive surface element is further oriented with its secondary plates 2 which are vertical, and upwards above the base plate 1.
• the depth K of the base plate 1 below the average surface S of the soil boundary is preferably less than ⁇ , or even less than ⁇ / 2.
• the inductive surface element is placed on the ground ( Figure 3a).
• the inductive surface element used is in accordance with FIGS. 1a-1c with the following precise characteristics: the number Nbl of secondary plates 2 is equal to 21, the spacing P between two secondary plates 2 which are successive, is constant and equal to 0,0697 x ⁇ , the height H of each secondary plate 2 is equal to 0,1651 x ⁇ , the width L of each secondary plate 2 is equal to 0.6678 x ⁇ , the width Lpm of the base plate 1 is equal to the width L of the secondary plates 2 increased by 0.5 x ⁇ , and the length Lopm of the base plate 1 is equal to 1, 931 x ⁇ .
• Deviations of ⁇ 10% from these dimensions may be adopted, without the operation of the surface wave generation assembly being significantly altered, for the same frequency of the radiation that is produced by the antenna 3.
• the plates that compose it can be advantageously mesh or perforated sheet, to reduce the weight and the amount of raw material consumed.
• the thickness of the plates has no significant effect, as long as the plates can be considered as two-dimensional conductive surfaces.
• Each secondary plate is held fixed relative to the base plate 1, but it does not need to be electrically connected to the base plate 1. Thus each secondary plate can be electrically isolated from the base plate 1.
• the antenna 3 is preferably oriented so that the rectilinear antenna segment is vertical, and therefore perpendicular to the base plate 1.
• the distance Dant may be equal to 0.5 ⁇ ⁇ , and the height Hant of the antenna segment above the base plate 1 may be zero.
• An operating condition of the surface wave production assembly is that the component E z of the electric field E of the electromagnetic wave OL which is produced by the antenna 3, is not zero. In other words, the electric field E of the wave OL is not parallel to the base plate 1.
• the inductive surface element modifies the propagation conditions of the component E z , by converting a portion of the wave OL into the surface wave OS.
• the antenna 3 is placed plumb with the center line LS on one side of the inductive surface element, then the OS wave emerges above the inductive surface element, with a direction of propagation which is parallel to the centerline LS.
• the OS wave has a surface wave structure, with an amplitude of the electric field decreasing exponentially in the Z direction in the air half-space, from the average surface SI of the boundary of the inductive surface element.
• Figures 4a and 4b correspond to an inductive surface element as described above, which has been sized for a wavelength value of the OL wave equal to about 27.3 cm (centimeter). In other words, the dimensioning parameter ⁇ is equal to 27.3 cm. This wavelength value corresponds to a frequency f of electromagnetic radiation which is equal to 1.1 GHz (gigahertz).
• the solid line curve characterizes a transmission efficiency between the radiation source and a remote detector, using the inductive surface element in combination with the radiation source.
• the dashed line characterizes the same transmission efficiency, but in the absence of inductive surface element.
• the use of the inductive surface element allows a transmission gain of about 20 dB for the 1.1 GHz radiation frequency.
• FIG. 4b shows the modification of the energy reflection coefficient of the antenna 3, by comparing its operations with (continuous curve) and without the inductive surface element (dashed curve). A decrease in reflection of up to 10 dB is achieved at 1.1 GHz using the inductive surface element.
• a possible dimensioning for the inductive surface element of FIGS. 2a-2c can be: the number Nbdl of the ternary plates 2a and that of the ternary plates 2b are also equal to 21, the spacing P between two ternary plates 2a which are successive, or between two successive ternary plates 2b, is equal to 0.0953 x ⁇ , the shift D between the ternary plates 2a and 2b is 0.0229 x ⁇ , the height Hdl of each ternary plate 2a or 2b is equal to 0, 1074 x ⁇ , and the width Lpm of the base plate 1 is at least equal to the width Ldl of each ternary plate 2a or 2b, itself equal to 0.6678 x ⁇ .
• deviations of ⁇ 20% from these precise dimensions can be adopted without changing the source radiation frequency that is used with the inductive surface element.
• An inductive surface element according to the invention can also be used within a surface wave detection assembly.
• the inductive surface element is still placed on the ground, semi-buried or buried in the same way, but with its central line LS, or sensitive direction, which is oriented in a direction of reception of surface waves .
• a radiation detector can then be placed substantially in the same place as the antenna 3 with respect to the inductive surface element. Under these conditions, the inductive surface element partially transforms the received surface wave into a wave structure that converges on the radiation detector. The surface wave that is received can thus be detected with a high sensitivity. It is understood that the invention may be reproduced by modifying some of the features which have been described by way of example.
• an inductive surface element that is in accordance with the invention can be dimensioned simply for any radiation frequency, using the dimensioning rules that have been given.
• several inductive surface elements according to the invention may be arranged around the same source of electromagnetic radiation, in order to simultaneously transmit surface waves in several directions.

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• 2012
  • 2012-08-22 FR FR1202272A patent/FR2994773B1/fr not_active Expired - Fee Related
• 2013
  • 2013-08-20 WO PCT/FR2013/051953 patent/WO2014029947A1/fr active Application Filing
  • 2013-08-20 SG SG11201501306WA patent/SG11201501306WA/en unknown
  • 2013-08-20 EP EP13762177.7A patent/EP2888784B1/de active Active
  • 2013-08-20 JP JP2015527957A patent/JP6224104B2/ja active Active
  • 2013-08-20 ES ES13762177.7T patent/ES2588927T3/es active Active
  • 2013-08-20 BR BR112015003738-0A patent/BR112015003738B1/pt active IP Right Grant

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