Classifications

• • 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
  • H01Q21/20—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path
  • H01Q21/205—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path providing an omnidirectional coverage

Definitions

• the present invention relates to a cylindrical omnidirectional printed antenna and a maritime radar transponder which uses such antennas.
• a cylindrical antenna which is omnidirectional in a horizontal plane and which has a minimized diameter while presenting a fairly high gain. Its opening angle in a vertical plane can be of the order of 35 ° and, in this case, it can be used in a maritime radar transponder as a receiving antenna and transmitting antenna in the frequency band 9.2 GHz-9.5 GHz.
• the object of the invention is to produce an antenna which has these technical characteristics and the manufacture of which is easy to implement.
• a cylindrical antenna according to the invention consists of a cylindrical substrate of a dielectric material, the internal wall of which is covered with a layer of metallic material forming a ground plane and the external wall of which receives the radiating elements, these being arranged in a plurality of identical sub-networks parallel to each other and equidistant on a perimeter of the substrate, the sub-networks being supplied in phase, each sub-network consisting of a line of straight feed which, on the
• REPLACEMENT SHEET cylindrical substrate of the antenna is located on a generator of said cylinder and of a plurality of identical radiating elements located alternately on either side of said supply line and supplied by said supply line so as to be able emitting waves in phase, the distance on the perimeter of the cylinder which separates two neighboring sub-networks being at most equal to 2 times the maximum dimension on the perimeter of the cylinder of the radiating elements, the radiating elements on one side of a sub -network being interlaced with the radiating elements on the opposite side of a neighboring sub-network.
• each radiating element consists of a conductive patch of square shape, one corner of which is in galvanic contact with the supply line of the corresponding sub-network and whose diagonal is perpendicular to the line d at the feed point.
• the radiating elements of the same sub-network are distant from each other, on the supply line of said sub-network, by a half-wavelength guided by said line of food.
• the invention also relates to a maritime radar transponder comprising a cylindrical casing at least part of which forms a radome and which contains a wave receiver such as those emitted by a scanning radar system, a transmitter emitting such radar waves, a control circuit which controls the transmission of the transmitter when the receiver has received a radar wave from a radar system, the receiver and the transmitter respectively comprising a reception antenna and a transmission antenna.
• a maritime radar transponder comprising a cylindrical casing at least part of which forms a radome and which contains a wave receiver such as those emitted by a scanning radar system, a transmitter emitting such radar waves, a control circuit which controls the transmission of the transmitter when the receiver has received a radar wave from a radar system, the receiver and the transmitter respectively comprising a reception antenna and a transmission antenna.
• each antenna is a cylindrical antenna having the characteristics mentioned above and is mounted coaxially inside said part forming a radome.
• the transmitter, the receiver and the control circuit of this transponder are mounted on the same printed circuit board on which are threaded the cylindrical transmitting and receiving antennas, the transmitter located inside the transmitting antenna and the receiver inside the receiving antenna.
• the transmitter and the receiver are on one side while the control circuit is on the other side.
• FIG. . 1 is a perspective view of an antenna according to the invention
• FIG. 2 is a developed view on a plan of an array of radiating elements of an antenna according to the invention
• FIGS. 3a and 3b are characteristic curves of an antenna according to the invention
• FIG. 4 is a perspective view of a radar transponder according to the present invention which uses two antennas according to the invention.
• the cylindrical antenna shown in FIG. 1 consists of a cylindrical substrate of a dielectric material, the internal wall of which is covered with a layer 2 of a metallic material forming a ground plane and the internal wall of which receives radiating elements 3 supplied by lines of food 4.
• the substrate is, for example, in a dielectric material such as polypropylene or Teflon glass. Its relative permittivity is, for example, close to 2.2. For correct operation in a band centered on 9.4 GHz, its thickness is advantageously of the order of 800 microns.
• the radiating elements 3 are produced on the substrate 1 according to the technique of the printed circuit on a dielectric plate covered beforehand, on each of its two faces, with a layer metallic, for example, copper or aluminum and which is, after printing the radiating elements 3 on one of these two faces, rolled to form the cylindrical antenna shown in FIG. 1.
• Fig. 2 shows an array of radiating elements 3 according to an exemplary embodiment of the invention. This network is shown developed on a plan as it appears when printed on a plate, before rolling.
• It comprises four identical sub-networks RI, R2, R3, and R4, each of four identical radiating elements 3, the sub-networks Ri being mutually parallel and equidistant on the perimeter of the cylinder.
• the number of sub-arrays can be less than or greater than four, depending on the diameter of the antenna that one wishes to obtain.
• the Ri subnetworks are supplied in phase in a tree-like configuration.
• the sub-networks RI, R2, R3 and R4 are respectively supplied by conductive lines Ll, L2, L3 and L4 bent at 90 °
• the lines Ll and L2 have their common ends connected to a conductive line L12 bent at 90 °
• lines L3 and L4 have their common ends connected to a conductive line L34 bent at 90 °.
• the latter L12 and L34 have their common ends connected to a general supply line LA.
• Another supply mode could also be used as long as it provides a phase supply of the sub-networks RI to R4, for example, a supply in series.
• the lines L1 to L4 have lengths which are equal to a wavelength guided on the substrate at the operating frequency of the antenna. Their width is such that they have a characteristic impedance allowing the impedance adaptation with the sub-networks RI to R4.
• the lines L suspiciousand L have equal lengths and each have a characteristic impedance which allows impedance matching with lines L1 to L4 and the sub-networks which the latter supply. It should be noted that these impedance adaptations may nevertheless require quarter-wave transformers consisting of a widening sow supply lines over a length equal to a quarter of a guided wavelength on the substrate. Thus, in the case where more than four sub-networks are used, such transformers should be provided on the lines L1 to L4 and L12 and L34. Similarly, if more than four radiating elements per sub-network are used, it is necessary to provide transformers on the sections of line between the radiating elements.
• lines L and L have sections (horizontal in Fig. 2) which belong to the same perimeter of the cylinder. It is the same for lines L1 to L4 which also have sections belonging to the same perimeter of the cylinder.
• Each sub-network Ri consists of a rectilinear supply line L which, on the cylindrical substrate 1 of the antenna, happens to be on a generator of this cylinder.
• supply line L there are, supplied at points spaced on said line L of a half-wavelength guided on the substrate, four radiating elements 3.
• Each radiating element 3 advantageously consists of a conductive patch of square shape, a corner 31 of which is in galvanic contact with the supply line L R for its excitation and a diagonal d of which is perpendicular to the supply line L at the supply point is. tion 31.
• the radiating elements 3 could also consist of conductive pads of any shape, for example, circular, rectangular, etc. Square or rectangular in shape, they could also be fed from the middle of one side by means of an appropriate line section.
• the supply line L of each sub-network and the vertical section in FIG. 2 of the corresponding line L1 to L4 are collinear.
• the radiating elements 3g situated on one side of the supply line L D of a sub-network R. are interlaced with
• the radiating elements 3 interleaved are distant by a half wavelength guided on the substrate.
• the distance between the feed lines of two neighboring R and R sub-networks is an important parameter as regards the 1 1 + 1 omnidirectional characteristic of the antenna. This distance is more than 2 times the maximum dimension on the perimeter of the cylinder of the radiating elements, that is to say, in the case of radiating elements made up of pellets of square shape, the length of the diagonal of this pastille.
• Measurements were made on a cylindrical antenna having a substrate with a permittivity of 2.2 and whose radius is 15 mm.
• the distance on the line LR of each sub-network Ri between two radiating elements is substantially equal to 12.1 mm and the distance between two neighboring sub-networks is substantially equal to 2.40 mm.
• the diagonal of the square of the pads 3 is substantially equal to 14 mm.
• the width of the supply lines L1 to L4, L12, L34, and LA was adjusted to a characteristic impedance of 80 ohms in the frequency band 9.2 GHz-9.5 GHz .
• Fig. 3a shows gain diagrams as a function of the azimuth angle which have been plotted with this antenna at an operating frequency of 9.4 GHz.
• the main axis of the cylinder of this antenna is vertical.
• the gain for the main polarization component is substantially constant and the gain ripples noted do not exceed 2.5 dB.
• the gain for the cross component is at least 10 dB lower than that of the main component. It can therefore be seen that the antenna emits a wave polarized substantially linearly in a horizontal plane.
• the standing wave ratio (ROS) is less than 1.5 in the band 9.2 GHz - 9.5 GHz.
• Fig. 3b the gain at an operating frequency of 9.4 GHz of an antenna according to the invention as a function of the angle formed by the direction of measurement with a horizontal plane, the antenna cylindrical having its main vertical axis. It can be seen that the opening angle at -3 dB as measured is + 18 ° and -18 ° relative to the horizontal.
• FIG. 4 There is shown in FIG. 4, a maritime rescue radar responder.
• the housing 10 shown here in thin dashed mixed lines, inside which are housed, coaxially, a cylindrical transmitting antenna 11 and a cylindrical receiving antenna 12.
• the housing 10 shown comprises a part 10a forming a radome transparent to radar waves and part 10b.
• the antennas 11 and 12 are inside the part 10a.
• the entire housing 10 can be a radome.
• a transmitter 14 housed inside the first cylindrical antenna 11, and, at the other end, a receiver 15 housed at the inside the second cylindrical antenna 12.
• a control circuit 16 is provided on the other face of the plate 13.
• Coaxial cables 17 and 18 are respectively provided for respectively connecting the high frequency signal output of the transmitter 14 at the transmit antenna 10 and the high frequency signal input from the receiver 15 at the receive antenna 11.
• An electrical supply device 19 is provided, in part 10b, for supplying direct current to the transmitter 14, the receiver 15 and the control circuit 16.
• this supply device 19 is separated from the rest of the responder and is located in a second housing separate from the housing 10. In this case, the part 10b of the housing 10 does not exist.
• the receiver 15 is of the type which can receive and demodulate signals transmitted by radar systems transmitting in the band of frequencies 9.2 GHz - 9.5 GHz. As for the transmitter 14, it emits, by frequency scanning, waves in the same frequency band.
• a radar responder is used as follows. It equips, for example, a buoy or a lifeboat.
• a second vessel has a rotating beam radar system which transmits, for example, on a frequency in the band 9.2 GHz - 9.5 GHz.
• the receiving antenna 11 of this transponder When it passes within range of a buoy or a boat whose maritime radar transponder is started, following for example a sinking, the receiving antenna 11 of this transponder periodically receives the signals transmitted by the radar system and the receiver 15, connected to the reception antenna 11, detects them. This has the effect of activating the control circuit 16 which then turns on the transmitter 14.
• the latter transmits, via the transmitting antenna 10 to which it is connected and by frequency scanning, radar waves in the same band which are then picked up by the radar system of the second boat. It is therefore possible to determine, on the screen of this system, the position of the buoy.
• the antennas according to the invention are particularly well suited to this particular application. Indeed, due to their shape, they are easily accommodated in a cylindrical housing. In the internal volume that each generates, it is possible to place the transmitter and receiver which, because of the ground plane on their internal walls of the antenna, are isolated from the ambient waves and parasites and which, consequently, do not require shields.

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• Variable-Direction Aerials And Aerial Arrays (AREA)
• Details Of Aerials (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=9411504

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• 1991
  • 1991-03-29 FR FR9104146A patent/FR2674689B1/fr not_active Expired - Fee Related
• 1992
  • 1992-03-23 DE DE69212471T patent/DE69212471T2/de not_active Expired - Fee Related
  • 1992-03-23 EP EP92908983A patent/EP0585250B1/de not_active Expired - Lifetime
  • 1992-03-23 WO PCT/FR1992/000263 patent/WO1992017915A1/fr active IP Right Grant

Non-Patent Citations (1)

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