Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/1242—Rigid masts specially adapted for supporting an aerial
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/52—Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure
  • H01Q1/528—Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure reducing the re-radiation of a support structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/28—Combinations of substantially independent non-interacting antenna units or systems

Definitions

• the field of the invention is that of co-located antenna systems, that is to say electronic systems comprising a plurality of active antennas grouped at the same point so as to have the same phase center.
• the invention relates to a sensor of the type comprising such a system of co-located antennas, as well as a mast, at the top end of which the antennas are placed, and down cables to one (or more) receiver (s), to which the antennas are connected.
• the invention has many applications, such as for example: single station direction finding. Indeed, the possibility of replacing, in algorithms for finding arrival angles (azimuth and elevation), the space dimension by knowing the antenna responses makes it possible to access the desired angle values; - jammer rejection; transmissions, using for example reception on several antennas (multi-channel reception); pseudo-spatial filtering (substitution of the space dimension by the diversity dimension of antennas); - beamforming ("beamforming" in English); etc.
• single station direction finding the possibility of replacing, in algorithms for finding arrival angles (azimuth and elevation), the space dimension by knowing the antenna responses makes it possible to access the desired angle values; - jammer rejection; transmissions, using for example reception on several antennas (multi-channel reception); pseudo-spatial filtering
• antenna response is meant in the context of the description presence a relationship (generally vector) between the electric (or magnetic) field incident to an antenna and the signal present at the output of this antenna.
• this response can be represented by a complex quantity depending on the type of antenna, its environment, its geographic position (at high frequencies, typically 3-30 MHz ) and its orientation.
• the responses of the antennas can be obtained either by calculation or simulation, or by various measurements carried out on the system of co-located antennas.
• antenna responses is only possible if these antennas are well electromagnetically decoupled from each other.
• this is not the case in the sensors currently offered by manufacturers.
• the inventors of the present invention have been able to determine that in known sensors, there is an electromagnetic coupling between the antennas induced by the existence of: a first type of coupling between current distributions present on the radiating parts of the antennas and current distributions which exist on the conductive mast; a second type of coupling between current distributions present on the radiating parts of the antennas and current distributions which exist on the down cables.
• the various distribution of the aforementioned currents are of surface type.
• the present invention is intended to overcome this major drawback of the prior art. More specifically, one of the objectives of the present invention is to provide a sensor of the aforementioned type (notably comprising a system of co-located antennas, a mast and down cables), but the antennas of which are electromagnetically decoupled from each other .
• the invention also aims to allow such decoupling, simply and inexpensively.
• Another object of the invention is to enable such a decoupling in a wide range of frequencies.
• a sensor of the type comprising an antenna system collocated. itself comprising at least two active antennas having the same phase center, said antennas being placed at a high end of a mast and being connected to down cables.
• the mast is made of a dielectric material
• the sensor comprises filtering means arranged on at least one of said down cables, so as to effect decoupling of said antennas.
• the general principle of the invention therefore consists in eliminating the first and second types of coupling mentioned above, using respectively a dielectric mast
• said filtering means comprise ferrite elements - preferably toroids or ferrite tubes - around which is wound at least one of said down cables.
• the characteristics of the ferrite elements are chosen so as to introduce the desired attenuation (typically 30 dB) of the surface currents at the frequencies considered.
• the toroids exhibit good efficiency due to the presence of a closed loop.
• the tubes facilitate assembly since the cables can be slid there easily.
• said ferrite elements are of at least two different types.
• filtering is carried out in a wide frequency band.
• the order of placement of the type of ferrite on the cables does not matter.
• said filtering means comprise at least two filters distributed over at least one of said down cables, and each of said filters comprises at least one ferrite element.
• Such spacing, regular or not, of filters aims to optimize the quality of the filtering over a given length of cables and for a given frequency band.
• At least one first filter is placed immediately at the outlet of the active parts of said antennas.
• the active parts of the antennas are sometimes also called electronic parts.
• at least one last filter, among said at least two filters is placed at ground level.
• surface (sheath) currents these tend to seek to reach the lowest possible potential (zero of the supply or earth).
• the invention makes it possible to prevent a current induced on an antenna from inducing a sheath current capable of joining a supply zero of another antenna or escaping towards the earth. Once the lines have reached the ground, the sheath currents are only weakly generated and tend to be naturally attracted to the ground. However, for safety, a few decoupling (filtering) devices are maintained at ground level, for example over a few centimeters.
• each of said antennas comprises an active part and a radiating part, and the active parts of said antennas are contained in metal cases electrically insulated from each other.
• said metal boxes are located immediately at the exit of the radiating parts of said antennas. This avoids the presence of a cable section forming an unwanted radiating part.
• the adaptation between the impedance of the radiating part and the input impedance of the metal cases is optimized.
• said filtering means comprise at least one optical cable forming at least one of said down cables.
• the length of the descent cable on which said filtering means are arranged is limited to the height at which said antennas are placed, at the high end of the mast.
• At least one of said down cables is placed inside said mast. This improves the overall aesthetics of the sensor. It will be noted that this characteristic, made possible by the fact that the mast is made of dielectric material, does not constitute a constraint on proper operation.
• At least one of said antennas is an antenna of the active whip type, replacing an antenna of the vertical dipole type. This is to prevent a radiating element of an antenna (such as a strand of a vertical dipole) from being in the immediate vicinity of the down cables.
• said antennas are of different types and / or polarizations, so as to create a so-called antenna diversity. It will be noted that the use of different types of antennas is advantageous since the decorrelation of the signals received remains linked to the responses of the antennas. However, in the case of the use of antennas of the same type but arranged differently, these responses may prove to be too similar mathematically.
• said down cables are related to the power supplies of said antennas and / or to the transport of signals from said antennas.
• the antennas must be powered because they are active.
• the signals are transported from the antennas to the receiver (s).
• a single cable (power / signal transport), for example of the coaxial type, can be used to connect each antenna to the receiver.
• the invention also relates to a method of decoupling antennas within a co-located antenna system, of the type comprising at least two active antennas having the same phase center, said antennas being placed at an upper end of a mast and being connected to down cables.
• this method consists in making the mast in a dielectric material, and in having filtering means on at least one of said down cables.
• the invention therefore relates to a sensor of the type comprising a system of co-located antennas (cf. fig. 4), a mast (at the top end of which the antennas are placed), and down cables (from the antennas to one or more receivers).
• FIG. 1 only illustrates the connection, via a single down cable 3, between one 1 of the antennas of the system co-located antennas and a receiver 2.
• each antenna of the co-located antenna system is connected by a down cable to a receiver. Not all antennas are connected to the same receiver.
• Several antennas can use the same down cable (multiplexing technique).
• the antenna 1 is placed at the high end of the mast 4, at a height H from the ground.
• the active part 1a also called antenna preamplifier, is contained in a metal case. It is defined as a function of the radiation impedance of the antenna, so as to obtain the best possible adaptation between the radiating part lb and the down cable 3 (for example at 50 ⁇ ).
• the metal boxes of the active parts of the various co-located antennas are electrically isolated from each other and located immediately at the ends of the radiating parts.
• the single down cable 3 ensures both the supply and the transport of the signals coming from the antenna 1.
• the mast 4 is made of a dielectric material. In the example illustrated in Figure 1, it is hollow and the descent cables 3 are placed inside.
• each down cable 3 is associated with a plurality of filters 5 ,, 5 2 , ..., 5 n .
• the first filter 5 is placed immediately at the outlet of the active part lb of the antenna 1, from which extends the down cable 3.
• the last filter (s) 5 n is (are) placed at ground level. However, it is unnecessary to place filters along the entire length of the portion of the cable which rests on the ground, provided that the length of the portion of cable on which the filters are placed exceeds the height at which the antenna is placed.
• each filter 5 comprises six ferrite toroids 6 l to 6 6 , namely a torus 6 of type 4C65, three 6 ,, 6 2 and 6 6 , of type 4A1 1 and two 6 3 and 6 4 of type 3C85.
• a space D of about 4 cm exists between two successive tori.
• the filters are for example spaced a distance E of about 30 to 50 cm.
• the attenuations obtained by these filters vary from 45 dB at the frequency of 6 MHz to 40 dB at the frequency of 30 MHz.
• the down cable 3 is wound several times
• each ferrite core 6 (for example between eight and nine turns) around each ferrite core 6.
• It is for example a coaxial cable of the RG58 type.
• another type of cable such as for example a coaxial cable of the POPE HlOOO type, of low loss (1 dB per 100 m, from 3 MHz to 30 MHz) and with a large screen (outer sheath made of a copper strip).
• n turns in one direction then m turns in the opposite direction, crossing the ferrite along a diagonal (when changing direction).
• n is substantially equal to m.
• FIG. 4 a partial view of an example of a system with seven co-located antennas, comprising the following seven radiating parts: three frames placed orthogonally. two 41, 42 being perpendicular to each other in a vertical plane, the third 43 being placed horizontally; - two horizontal dipoles 44, 45, perpendicular to each other; a vertical dipole 46 (possibly replaced by an antenna of the active whip type (not shown), in order to prevent a strand of the vertical dipole being in the immediate vicinity of the down cables); an antenna 47 called XYZ.
• the sensor described above can be used in particular, but not exclusively, in HF (3 to 30 MHz), VHF (30 to 300 MHz) and UHF (300 MHz to 3 GHz). Filters must be made with ferrites adapted to the working frequencies.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)
• Details Of Aerials (AREA)
• Burglar Alarm Systems (AREA)
• Radar Systems Or Details Thereof (AREA)
• Radiation-Therapy Devices (AREA)
• Nitrogen And Oxygen Or Sulfur-Condensed Heterocyclic Ring Systems (AREA)
• Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=9553522

Family Applications (1)

Country Status (11)

Families Citing this family (4)

Family Cites Families (6)

• 1999
  • 1999-12-20 FR FR9916113A patent/FR2802711B1/fr not_active Expired - Fee Related
• 2000
  • 2000-12-14 PT PT00988923T patent/PT1240683E/pt unknown
  • 2000-12-14 AU AU25265/01A patent/AU772757B2/en not_active Ceased
  • 2000-12-14 US US10/168,767 patent/US20030090428A1/en not_active Abandoned
  • 2000-12-14 JP JP2001547689A patent/JP2003518790A/ja active Pending
  • 2000-12-14 AT AT00988923T patent/ATE243370T1/de not_active IP Right Cessation
  • 2000-12-14 CA CA002393570A patent/CA2393570A1/en not_active Abandoned
  • 2000-12-14 ES ES00988923T patent/ES2202213T3/es not_active Expired - Lifetime
  • 2000-12-14 WO PCT/FR2000/003544 patent/WO2001047057A1/fr active IP Right Grant
  • 2000-12-14 DE DE60003465T patent/DE60003465D1/de not_active Expired - Lifetime
  • 2000-12-14 EP EP00988923A patent/EP1240683B1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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