FR2729010A1 - ANTENNA FOR A MOTOR VEHICLE CAPABLE OF RECEIVING AN ACTIVE IMPEDANCE ADAPTER AND ASSEMBLY ACTIVE IMPEDANCE ADAPTER FOR SUCH ANTENNA - Google Patents

Abstract

Antenna for a motor vehicle having a base (30) fixed to a bodywork element (40) and receiving an antenna strand and an end piece (20) of coaxial cable (27) made up of a stack of annular parts: an annular element mass (21, 22), an annular insulating piece (23), and an annular core piece (24), the annular mass member (21, 22) being in contact with the body member (40) and connected to the braid (25) of the coaxial cable (27), the annular core part (24) being connected to the core (26) of said cable (27), the signal supplied by the antenna strand being received by a threaded rod (31) and receiving a nut (32) for holding the base (30) and the end piece (20) on the bodywork element (40), the rod (31) passing through an opening (41) of the bodywork element (40) and the end piece (20) through its central passage; the annular insulating part (23) of the end piece comprises, around the central passage of said end piece (20), a centering bearing surface (44) cooperating with an element (42) integral with the male element (31), the orifice formed in the annular core part (24) having a contour circumscribed with respect to that of the male element, so as to provide an isolation space between the two contours.

Description

ANTENNA FOR A MOTOR VEHICLE CAPABLE OF

  RECEIVE AN ACTIVE IMPEDANCE ADAPTER AND

  ACTIVE IMPEDANCE ADAPTER ASSEMBLY FOR A

SUCH ANTENNA.

  The present invention relates to an antenna for a motor vehicle capable of receiving an active impedance adapter as well as an active impedance adapter assembly for such an antenna. It is known that, for the reception of radio waves in amplitude modulation lo, short, small and large waves, the strand of an antenna must have a certain length adapted to this reception; when it is desirable, for implantation reasons, to limit the length of the antenna strand, use is made of an active antenna impedance adapter, that is to say a powered impedance adapter in electrical power, the role of which is to reinforce the signal received by the antenna to compensate for this reduction in length; indeed, an antenna that is too long is not without problems: difficulties in maneuvering in individual garages with generally low ceilings, difficulties during automatic vehicle washing operations,

  whistling at high speed, or other.

  The antenna strand is generally supported by a base; so far, the active antenna impedance adapter is in an independent box placed in the vicinity of the radio receiver or the base, or inside the base itself; such an arrangement, which requires a particular assembly, is bulky and inconvenient

  when the antenna is intended to equip a motor vehicle.

  When the active impedance adapter is inside the base, it is necessary that it has a height suitable for receiving it; such a height then leads to a base that is too high when it is not decided to add an active impedance adapter to the antenna; in addition, the base being placed outside the passenger compartment of the vehicle, the active impedance adapter is subjected to thermal stresses

that are detrimental to him.

  To date, there is no antenna capable, without any modification of the base, of allowing the addition, if it is

  desire, an active antenna impedance adapter.

  The present invention aims to avoid the above drawbacks and relates to an antenna capable of receiving, or not, an active adapter of space-saving impedance, associated with the base

classic antenna.

  Thus, according to the invention, an antenna for a motor vehicle comprising an antenna base intended to be fixed to a bodywork element, said base receiving, on the one hand, an antenna strand and, on the other hand, a end of coaxial cable connected to a radio receiver, said end being made up of a stack of annular 0 0 pieces comprising, around a same central passage: - at least one annular element of mass, - an annular insulating piece, and - a annular core part, the annular mass element being in contact with the bodywork element and being connected to the ground braid that the coaxial cable comprises, the annular core part being connected to the core of said coaxial cable , the signal supplied by the antenna strand being received by a threaded connection member, which comprises a male element and a female element and which ensures the mechanical retention of the base and of the endpiece relative to the element of bodywork, said element male ment of said threaded connecting member passing through an opening of the bodywork element and passing through the end piece through its central passage, a contact means being integral with one of the elements of the threaded connecting member to conduct the signal supplied by the antenna strand in the direction of the annular core part, is characterized in that the insulating annular part of the end piece comprises, around the central passage of said end piece, a centering surface cooperating with the male element or an element which is integral therewith, the orifice made in the annular core part for the passage of said male element having, in the plane of said annular core part, a contour circumscribed with respect to that of the male element, so as to provide an isolation space between the two contours. Advantageously, the element integral with the male element is an insulating ring carried by the base, and the centering surface of the annular insulating part is a cylindrical recess formed in the

insulating annular piece.

  Alternatively, the centering surface of the insulating annular part is an annular spacer which is pressed against the inner face of the annular core part and which cooperates with the male element. Advantageously, the annular spacer is molded with the insulating annular part; the annular spacer has an axial annular extension on which the annular core piece is centered. Preferably, the annular mass element consists of an annular grounding piece and an annular piece of

mass.

  According to one embodiment, the male element of the connecting member is a threaded rod integral with the base, and the female element

  is a nut carrying the contact means and screwed onto the rod.

  According to another embodiment, the male element of the connecting member is the threaded rod of a head screw and the female element is a thread which comprises the base, the contact means being

formed by the head of the screw.

  The contact means rests directly on the part

ring finger.

  Advantageously, between the contact means and the annular core part is inserted an active antenna impedance adapter consisting of a plate in the form of a flat washer, one of the faces of the plate carrying an annular conductive track of output coming into abutment against the annular core part and the other face carrying an annular conductive entry track on which abuts the contact means, the face of the plate which carries the entry track also carrying the means electrical adapters of an adapter circuit supplied electrically by a power supply terminal carried by said wafer, the output track being connected to the output terminal of the adapter circuit by means of a metallized through hole the plate, a ground terminal of said adaptation circuit being

  electrically connected to the annular mass element of the nozzle.

  Preferably, the active adapter is placed in a housing consisting of a cylindrical skirt held by clipping by the annular mass element of the end piece; the adapter ground terminal

  active is connected to ground by a pin secured to the housing.

  The housing is closed by a cover.

  Advantageously, the base carries clipping pins for clipping the base on the edges of an opening of the bodywork element. Preferably, the insulating annular piece carries at least one column; the column is adapted to be received in a chimney provided in the base, the chimney comprising ribs or beads to increase the effect of holding the clipping pins

on the body element.

  o10 The present invention also relates to an assembly consisting of an active adapter, a housing, a protector and a cover, these constituents being as used in the antenna having the

  characteristics mentioned above.

  To better understand the object of the invention, we will now describe it by way of purely illustrative example and not

  limiting, the embodiments shown in the accompanying drawings.

  In these drawings: - Figure 1 is an exploded view partially in section of an antenna according to the invention without active impedance adapter; - Figure 2 is an exploded view partially in section of the antenna of Figure 1 provided with an active impedance adapter; - Figure 3 shows the assembly according to Figure 2, the components of the assembly being assembled and mounted; - Figure 4 is a sectional view along the line IV-IV of Figure 5, of a variant of one of the pieces of the nozzle according to Figure 2; - Figure 5 is a view along V- V of Figure 4; - Figure 6 is a view similar to Figure 2 but shows another embodiment of the invention; - Figure 7 is a view along VII-VII of Figure 6; - Figure 8 is a partial sectional view of a variant of the base of Figure 6;

  - Figure 9 is a view along IX-IX of Figure 8.

  Referring to Figure 1, we see that there is shown schematically an antenna base 30 for a motor vehicle; such a known base is generally made up of a hollow molded plastic part defined by a wall of generally frustoconical shape developed from a base in the general shape of an ellipse surrounded at its lower part by a sealing lip bearing on a body element 40; at the upper part of the base 30, a metal pin, for example made of brass, not shown, internally threaded, is intended to receive the externally threaded end of an antenna strand; this metal pin is in electrical contact with a metal support covered by the plastic material of the base 30 and comprising a male element in the form of a threaded rod 1o 31 intended to receive a female element in the form of a tightening nut 32; at its exit from the base 30, the threaded rod 31 is surrounded by plastic material constituting an insulating ring 42; when the base 30 is placed on the body element 40, the insulating ring 42 passes through an opening 41 of the body element 40; a positioning pin, not shown, allows the base 30 to be oriented relative to the vehicle body: the base having a frustoconical shape inclined relative to the axis of the threaded rod 31, the inclination must be oriented towards the rear of the vehicle. Such a base 30 is well known and will therefore not be described further; he

  suffice, for example, to refer to FR-A-2 632 779.

  For its connection to the antenna strand, a coaxial cable 27, also connected to the radio, with which the vehicle is equipped, and comprising in particular a core 26 and a ground braid 25, is provided with a

tip 20.

  The end piece 20 is produced by the assembly of annular parts: an annular mass-taking part 21 having raised teeth 43, an annular mass part 22, an insulating annular part 23, an annular core part 24; the annular parts for mass taking 21, mass 22 and core 24 are metallic, made of thin cut and folded sheet metal; the insulating annular piece 23 is made of plastic; the end piece 20 is assembled by crimping tabs, which have the metallic annular parts, in corresponding housings of the annular insulating plastic part 23: such housings are visible in FIG. 5 under the references 61, 62 although this FIG. 5, like FIG. 4, corresponds to a part 123 which is slightly different from the part 23 and which will be described below; the insulating part 23 also has notches 63 and 64, also visible in FIGS. 4 and 5; the notches 63, three in number arranged circumferentially at 120 degrees from each other, each receive an axial elastic tab of the annular mass piece 22, tab carrying a transverse boss 35 whose role will appear below; the notch 64 makes it possible to receive the end of the coaxial cable 27, more particularly the stripped end of the core 26 of said cable 27, and a tab 39 of the annular piece of core 24 to which is fixed, by 1o welding , said end of the core 26. The annular insulating part 23 also has in its center a cylindrical recess 44, of a diameter barely greater than that of the insulator 42 of the base 30. The annular grip part ground 21 is extended along a tail 34 crimped around a stripped part of the ground braid 25 of the cable 27

  as well as around the cable itself.

  Such a tip 20 is known and of the kind which is

  described, for example, in FR-A-2 563 946.

  The assembly of the assembly is carried out as follows. The base 30 being on the bodywork element 40 in the position shown in FIG. 1, the end piece 20 of the cable 27 is threaded on the threaded rod 31 and on the insulator 42, then a nut 32 is screwed onto the threaded rod 31. When the nut 32 is tightened, the teeth 43, of the annular grounding piece 21, scratch the underside of the bodywork element 40 which, as is known, is the electrical mass of the vehicle ; therefore, the ground braid 25 of the cable 27 is connected to said ground; in parallel, the antenna signal is transmitted by the threaded rod 31 to the nut 32, thanks to the tightening cooperation of their respective threads, which nut 32 transmits said antenna signal to the core 26 of the cable 27 thanks to the cooperation of the transverse face 33 of the nut 32 and of the annular core part 24, bearing one on the other. Taking into account the way in which the antenna signal is transmitted to the core 26 of the cable 27, it was not necessary to take special precautions regarding the circumferential clearance existing between the threaded rod 31 and the central hole 29 of the annular core part 24 through which it passes, said annular core part 24 being able to touch the threaded rod 31; according to the invention, such a tip 20 is arranged so as to allow the addition, if desired, of an active impedance adapter; in the case of an adaptation of the antenna signal, it is essential that the annular core part 24 of the end piece 20 does not touch the threaded rod 31, in which case the adaptation circuit would be short-circuited; to prevent manufacturing tolerances from leading to centering of the end piece 20, by cooperation of the insulator 42 of the base 30 with the cylindrical recess 44 of the annular insulating part 23, insufficient from this point of view, the central hole 29 of the annular core part 24 is provided large enough for this contact

be avoided for sure.

  Thus, the insulating annular part 23 of the end piece 20 has a centering surface defined by the recess 44 cooperating with a part integral with the male element or threaded rod 31, with the connecting member: the orifice made in the annular core part 24, for the passage of said male element 31, has, in the plane of the annular core part 24, a contour circumscribed with respect to that of the male element which is undoubtedly isolated of the annular core part 24; thanks to this arrangement, it is possible, if desired, o without any modification of the base or of the end piece, to allow, or not, the addition of an active impedance adapter; the addition of a

  such an adapter will be described below with reference to FIG. 2.

  The assembly of the antenna according to FIG. 1 ends with the fitting of a metal cover 36 which has a notch 38 for the passage of the cable 27 and the maintenance of which is ensured by three blocking passages 37 which it presents and in which the three bosses 35 of the legs of the annular mass piece 22 of the end piece 20 are placed elastically; thus, the metal cover 36 is connected to ground and

plays the role of armor.

  Referring to Figure 2, there is an active adapter according to the invention consisting of a plate 10, in the form of a flat washer, of double-sided printed circuit; one of the faces, the face 11 in the figure, carries an annular conductive track 12, called the exit track, and the other face, the face 13, carries an annular conductive track 14, called the entry track; the actual reinforcement of a signal is produced by electrical and electronic components connected by an adaptation circuit produced according to printed traces arranged on the input face 13 around the input track 14 which constitutes the terminal entry to this circuit; some of said components have been illustrated in the figure under the reference 15; such a circuit requiring for its operation an electrical supply, the supply terminal 16 of this circuit is connected by welding to a supply conductor 76; the output terminal of said supply circuit, located on the input face 13 of the wafer 10, is electrically connected to the output track 12, located on the opposite face 11, by means of a metallized hole 17 who

crosses the plate 10.

  The plate 10 is intended to be threaded onto the threaded rod 31 of the base 30; therefore, the insulating part of the double-sided printed circuit has a suitable central opening 19 having a diameter slightly greater than that of the threaded rod 31; for reasons which will appear more clearly below, the exit track 12 of annular shape has its small diameter which is larger than that of the central opening 19, while the small diameter of the entry track 14, also annular shape, is at most equal to the diameter of said

central opening 19.

  A metal box 50 is associated with the plate 10; the housing 50 consists of a cylindrical skirt 51 whose internal diameter is slightly greater than the external diameter of the wafer so as to receive said wafer 10 while it extends transversely relative to the longitudinal axis of the housing 50; the skirt 51 is extended at its upper part, with respect to FIG. 2, along a transverse shoulder 56 to which a cylindrical collar 59 is connected, having the same axis as that of the skirt 51 and extending, relative to the shoulder 56 , on the side opposite that of which extends the skirt 51; the housing 50 is adapted to be mounted on the end piece 20 in the manner of the cover 36 described with reference to FIG. 1; for this purpose, the flange 59 has a diameter suitable for this and has three blocking passages 57 and a notch 58, similar to the passages 37 and the notch

38 of cover 36.

  The adaptation circuit needing to receive the mass for its operation, and the housing 10 being grounded, the shoulder 56 of the housing 10 is used to bring the mass to the right of the adaptation circuit: the shoulder 56 carries a pin 52 directed towards the inside of the skirt 51 and adapted to pass through a notch 18 of the plate 10; when the latter is mounted in the skirt 51 until it touches the inside face of the shoulder 56, the end of the pin 52 is welded to the earth terminal of the adaptation circuit on the face 13

input of the plate 10.

  The housing 50 is adapted to receive a plastic protector 70 inside the skirt 51; the protector 70 comprises an annular dome 73, the concavity of which is directed towards the interior of the lo skirt 51 and which is surmounted in its center by a cylindrical chimney 74; at the outer periphery of the dome 73, at least one annular tooth 71 is adapted to come to cooperate with at least one transverse surface 67 formed on the inner face of the skirt 51, for holding the protector 70 in the skirt 51; the protector 70 includes a grommet 72 for the passage of the supply wire 76; when the plate 10 and the protector 70 are in place in the housing 50, the end of the chimney 74 participates in the maintenance of the plate 10, and the dome 73 defines a space for the components 15 of the circuit

adaptation that it protects.

  To complete the shielding provided by the housing 50, the lower end of the skirt 51 is closed by a metal cover 53 which has a circular boss 54 adapted to be clipped into an annular groove 55 that the skirt 51 has on its outer surface; a hole 68 in the cover 53 allows the passage of the wire

supply 76.

  From the above description, it appears that the housing 50,

  the wafer 10 and the protector 70 constitute, once assembled, a

  easily adaptable active adapter sub-assembly.

  When it is desired to reinforce the antenna signal transmitted by the threaded rod 31, it suffices to clip this sub-assembly on the end piece 20 of the coaxial cable, to thread the assembly thus formed on the threaded rod 31 and to put in place and tighten nut 32; thus, the antenna signal transmitted by the threaded rod 31 passes through the nut 32, the bearing face 33 of which transmits it to the input track 14 of the wafer 10; the signal is then reinforced by the adaptation circuit and the signal thus processed is transmitted, thanks to the metallized hole 17, by the output track 12 in contact with the annular core part 24 of the end piece 20 which transmits it to blade

26 of the coaxial cable 27.

  Of course, after mounting the nut 32, the cover 53

  is placed on the housing 50.

  The assembled assembly is shown in FIG. 3. As can be seen, thanks to the invention, with the same base 30 and the same end piece 20, it is possible to have an overall arrangement without adaptation of the signal. antenna and a

layout with adaptation.

  In this FIG. 3, an alternative embodiment of the centering surface of the annular insulating part 23 has been shown, which makes it possible to provide an isolation space between the annular core part 24 and the male element or threaded rod 31; according to this variant, in the insulating annular part 23 of the end piece 20 is introduced a centering spacer, of insulating material, pressed against the inner face of the

  annular core piece 24, as shown at 28 in FIG. 2.

  According to another variant, this same object is achieved by bringing such a spacer in one piece with the rest of the annular insulating part; it then suffices, for the production of the end piece, to replace the insulating annular part 23 with an insulating annular part 123, shown in FIGS. 4 and 5, all other things being equal; the part 123 comprises a spacer 69 molded with the rest of the part and whose central passage 66 has a diameter less than that of the central hole 29 of the annular core part

24.

  Figures 6 and 7 relate to another type of antenna base which can receive, if desired, also an adapter

impedance asset.

  The base 130 of FIG. 6 is more particularly suitable

  to a vehicle roof antenna placed at the rear thereof.

  The base 130 consists of a hollow piece 134 molded in plastic material defined by a wall of generally frustoconical shape having at its lower part a sealing lip 146 for its support on the bodywork element 140; an internally threaded metal pin 135 is intended to receive the antenna strand; the metal pin 135 extends along a cylindrical tail 136, the axis of which it is inclined relative to the axis of the pin 135, internally hollowed out by a thread 155; the pin 135 and the tail 136, in one piece, are overmolded, inside the hollow piece 134, by a plastic material 137 of relatively low hardness, compressible, and the end of the tail 136 which projects beyond the hollow part 134 is overmolded with an insulator 142 of relatively low hardness also; the cross section of the insulator 142 is of generally rectangular shape, except for a protruding positioning appendage 144; when the base 130 is placed on the bodywork element 140, the end of the insulator 142 passes through an opening 141, of this element, of corresponding shape, the appendage 144 being received in a positioning notch 143 formed in the bodywork element 140 in

border of opening 141.

  The base 130 which has just been described is adapted to

  cooperate with a tip 120 of coaxial cable.

  The tip 120 is of the type of the tip 20 described above and produced by the assembly of annular parts 221, 222, 223, 224 similar to parts 21, 22, 123, 24, respectively, described above; the difference between the end piece 120 and the end piece 20 20 is that the annular parts 221, 222, 223 are of rectangular sections instead of circular ones; in addition, the insulating annular piece 223 carries, in one piece with it, four balusters 139 adapted to take place in four chimneys 138 provided in

the base 130.

  As in the previous version, can be associated with the end piece 120, a housing 150, a plate 100, a protector 170, a cover 153, similar, respectively, to the housing 50, to the plate, to the protector 70, to the cover 53, except their outer outline

  which is rectangular instead of circular.

  According to this variant, a threaded rod 131, which plays the role of the preceding threaded rod 31, is not carried by the base 130 but is the threaded rod 131 of a screw 151 having a head 132 provided with a face transverse support 133 for cooperation with the entry face of the plate 100, the screw 151 being adapted to be screwed into the internal thread

155 from base 130.

  The insulating annular part 223 also differs from the annular part 123 in that the centering surface is produced by an axial annular extension 169 on which the annular core part 224 is centered, the external face of the extension 169 being flush with the external face of the annular core piece 224; thus, it is the radial thickness of the extension 169 which physically defines the space

  isolation between the threaded rod 131 and the annular core piece 224.

  Thanks to the arrangement according to this variant, the assembly, when assembled and mounted, takes up little space axially under 1o the bodywork element 140, which is well suited to the rear of a vehicle o the space available for the interior of the vehicle between the vehicle roof and the interior trim is more reduced than at the front; for this reason also, the supply wire 76 is mounted transversely with respect to the wafer 100, as illustrated in

dashed lines in Figure 6.

  To facilitate the mounting of this variant by one and the same person, clipping pins 145 are provided at the edge of the insulation 142 of the base 130 for temporary clipping thereof on the edges of the opening 141 of the 'body element 140; from inside the vehicle, it is then possible to mount the sub-assembly constituted by the end piece 120, the housing 150, the plate 100 and the protector 170 on the base by introducing the balusters 139 in the chimneys 138 of the 'base 130; longitudinal ribs 147 are provided inside the chimneys 138, in line with the insulation 142, the balusters 139 being thus momentarily held by elastic clamping of the material, and it is possible to let go of the sub-assembly, to present and to screw the screw 151; the introduction of the balusters 139 in the chimneys 138 causes the material of the insulator 142 to swell, due to the ribs 147, which reinforces the retention effect of the

  clips 145 on the bodywork element 140.

  Instead of longitudinal ribs 147, it is possible to provide beads placed in line with the pins 145; such beads are shown at 247 in Figures 8 and 9; each bead 247 is at

  straight a picot 145; the beads 247 play the same role, described below

  above, than that of the balusters 139; the chimneys 138 may also have a slightly conical shape, as can be seen on the

figure 8.

Claims (17)

  1. An antenna for a motor vehicle comprising an antenna base (30, 130) intended to be fixed to a body element (40, 140), said base receiving, on the one hand, an antenna strand and, on the other hand, a tip (20, 120) of coaxial cable (27) connected to a radio receiver, said tip (20, 120) consisting of a stack of annular parts comprising, around a same central passage: - at at least one annular mass element (21, 22; 221, 222), 1o - an insulating annular part (23, 123, 223), and - an annular core part (24, 224), the annular mass element (21, 22; 221, 222) being in contact with the bodywork element (40, 140) and being connected to the ground braid (25) which comprises the coaxial cable (27), the annular core part ( 24, 224) being connected to the core (26) of said coaxial cable (27), the signal supplied by the antenna strand being received by a threaded connection member, which comprises a male element (31, 131) and a elé female connector (32, 133) and which mechanically maintains the base (30, 130) and the end piece (20, 120) relative to the bodywork element (40, 140), said male element ( 31, 131) of said threaded connecting member passing through an opening (41, 141) of the body element (40, 140) and passing through the end piece (20, 120) through its central passage, a contact means (32, 132) being integral with one of the elements of the threaded connecting member to conduct the signal supplied by the antenna strand towards the annular core part (24, 224), characterized in that the part insulating annular (23, 123, 223) of the end piece comprises, around the central passage of said end piece (20, 120), a centering surface (44, 66) cooperating with the male element (31, 131) or an element which is integral therewith, the orifice made in the annular core part (24, 224) for the passage of said male element (31, 131) having, in the plane of said annular core part (24, 224), a contour circumscribed relative to that of the male element, so as to provide a space   isolation between the two contours.   2. Antenna according to claim 1, characterized in that the element integral with the male element is an insulating ring (42) carried by the base (30), and the centering surface of the annular insulating part (23 ) is a cylindrical recess (44) formed in the part insulating ring (23).   3. Antenna according to claim 1, characterized in that the centering surface of the insulating annular piece (23, 123, 223) is an annular spacer (28, 69) which is pressed against the inner face of the annular piece d soul (24, 224) and which cooperates with the male element (31, 131).   4. Antenna according to claim 3, characterized in that the annular spacer (69) is molded with the part 1o insulating ring (123, 223).   5. Antenna according to claim 4, characterized in that the annular spacer has an axial annular extension   (169) on which the annular core piece (224) is centered.   6. Antenna according to one of claims 1 to 5,   s15 characterized in that the annular mass element consists of an annular grounding piece (21, 221) and a piece mass annular (22, 222).   7. Antenna according to one of claims 1 to 6,   characterized in that the male element of the connecting member is a threaded rod (31) integral with the base (40), and the female element is a   nut (32) carrying the contact means (33) and screwed onto the rod (31).   8. Antenna according to one of claims 1 to 6,   characterized in that the male element of the connecting member is the threaded rod (131) of a head screw (151) and the female element is a thread (133) which comprises the base (130) , the means of contact   being constituted by the head (132) of the screw (151).   9. Antenna according to one of claims 1 to 8,   characterized in that the contact means (32, 132) is supported   directly on the annular core part (24, 224).   10. Antenna according to one of claims 1 to 8,   characterized in that between the contact means (32, 132) and the annular core part (24, 224) is inserted an active antenna impedance adapter (10, 100) consisting of a plate flat washer shape, one of the faces (11) of the plate carrying an annular conductive outlet track (12) bearing against the annular core part and the other face (13) carrying an annular conductive track d input on which the contact means (32, 132) come to bear, the face of the plate which carries the input track also carrying the electrical adaptation means of an adaptation circuit supplied electrically by a terminal d power supplied by said wafer, the output track (12) being connected to the output terminal of the adaptation circuit via a metallized hole (17) passing through the wafer (10), a ground terminal of said adaptation circuit being electrically connected to the annular ground element from the mouthpiece.   11. Antenna according to one of claims 1 to 10,   characterized in that the active adapter (10, 100) is placed in a housing (50, 150) consisting of a cylindrical skirt (51) held by   clipping by the annular mass element of the end piece (20, 120).   12. Antenna according to claim 11, characterized in that the earth terminal of the active adapter (10, 100) is connected to the   ground by a pin (52, 152) secured to the housing (50, 150).   13. Antenna according to one of claims 11 or 12,   characterized in that the housing (50, 150) is closed by a cover (53, 153).   14. Antenna according to one of claims 1 to 13,   characterized in that the base (130) carries clipping pins (145) for clipping the base (130) to the edges of an opening   (141) of the bodywork element (140).   15.Antenna according to claim 14, characterized in that the annular insulating part (223) carries at least one baluster (139).   16. Antenna according to claim 15, characterized in that the column (139) is adapted to be received in a chimney (138) provided in the base (130), the chimney (138) comprising ribs (147) or beads (247) to increase the holding effect   clipping pins (145) on the bodywork element (140).   17.An assembly consisting of an active adapter, a housing, a protector and a cover, characterized in that the active adapter (10, 100), the housing (50, 150), the protector (70, 170) and the cover (53, 153) are as used in the antenna according to the claims 1 to 16.