FR2627015A1 - Multi-access omni-directional antenna - Google Patents

Abstract

The invention relates to a multi-access omni-directional antenna. The antenna includes a circular array RC which includes eight substantially omnidirectional radiating elements ERi distributed on the perimeter of a circle of diameter phi less than 0.75 gamma . The radiating elements ERi are diametrally opposed in pairs. A coupling circuit MAC includes seven access points Aj and enables the radiating elements ERi to be coupled to the access points Aj, the radiating elements ERi being supplied, from each access point, according to a phase-distribution law, onto these elements, which law is determined differently from one access point Aj in question to another, in order to generate a radiation pattern which is omnidirectional in azimuth. Application to wideband radio-frequency intercommunication systems and to intercommunication systems protected from sources of interference.

Description

 The present invention relates to an omnidirectional multi-access antenna.

 In the technical field of radiocommunications with mobiles in the frequency ranges HF, VHF or UHF, multi-access antennas are used. Indeed, the radiocommunication systems implemented for this purpose require relay stations with several transmission and reception channels, for example in mobile telephones. The omnidirectional nature of antenna radiation patterns in these systems makes them particularly vulnerable to sources of interference.

 In addition, the multiplication of the number of channels necessary for a very great flexibility of use of these systems to ensure the intercommunication between a central point such as a control station and a plurality of mobiles, a determined number of mobiles constituting a group can be assigned to a specific channel, can not be satisfied with the implementation of a plurality of superimposed elementary antennas having a limited number of access, the resulting antenna having a very large footprint.

 According to a first prior art, an omnidirectional antenna is used for each channel.

 Each dipole antenna constitutes a transmission or reception channel or a duplex transmission-reception channel. This technique requires a high mast height, on which the antennas are superimposed, since the decoupling between channels is obtained by the separation distance, of the order of the wavelength, separating the dipoles on the mast. This solution is particularly impracticable when each channel is constituted by a collinear network of directional dipoles in site.

According to a second prior solution, a single omnidirectional antenna is used. The access of the antenna is then connected to a network of hybrid junctions 00.900 to obtain a corresponding number of independent channels. This technique has the disadvantage of a large loss of power because each junction or coupler combines in phase quadrature two input signals to produce an output signal
half power, the other half of the power being dissipated in a load connected to the free terminal of the coupler. Thus, a system with two, four and eight ports implemented according to the aforementioned technique respectively causes a signal loss of 3, 6 and 9 dB.

 A third prior solution uses a single omnidirectional antenna whose access is connected to a battery of selective filters such as resonant cavities. There are as many filters as access desired, the decoupling between these accesses being provided by the filters.

However, a filter adjustment is necessary in case of frequency change of the channels and this technique is essentially narrow band.

According to a fourth prior solution described in the patent
No. 4,213,132, a circular array of four or eight dihedrals uniformly distributed around a central mast is associated with a multi-port coupling circuit comprising only 0 -90 hybrid junctions. These hybrid junctions are interconnected such that the signal on each dihedral element is in phase quadrature relative to the signals of the two adjacent elements. Although this solution offers the advantage of a system with four or eight broadband accesses, it does not meet the imperative of a good omnidirectionality required in the aforementioned applications. This omnidirectionality, however, has hollows of sensitivity of amplitude greater than 8 dB appearing on the radiation patterns for the radiating elements considered and is inherent in the structure of the coupling circuit used.

According to a fifth prior solution described in the French patent application No. 85 00445 filed on January 14, 1985 in the name of the
Applicant, a circular network of four dipoles distributed uniformly around a central mast is associated with a coupling circuit comprising a hybrid junction 0 "-900 and two hybrid junctions 0" -180 ".

This system has the advantages of good omnidirectionality and a wide frequency band. However, it is intrinsically limited to three accesses. Although the superimposition of several independent systems on the same mast can be considered, to obtain a multiple access number system of three, the height of the aerial or resulting antenna quickly becomes prohibitive, especially in the HF and VHF ranges , when the directivity of the system must be increased in site.

 The purpose of the omnidirectional multi-access antenna according to the invention is to overcome the drawbacks of the aforementioned solutions while at the same time using only simple technologies, in particular from passive components with low losses that are normally available commercially, using only a number of minimum phase shifting circuits.

 Another object of the present invention is the implementation of a radiofrequency intercommunication system using the aforementioned antenna and capable of locating sources of interference and providing communications protected against such interference.

The multi-access omnidirectional antenna of the invention is remarkable in that it comprises a circular array comprising eight substantially omnidirectional radiating elements regularly distributed at the periphery of a circle of diameter O less than 0.75 wavelength, 0 , 75X. The radiating elements are coupled by a coupling circuit having seven accesses. The radiating elements and the accesses of the coupling circuit are coupled according to the power phase matrix.

<tb><SEP> ELEMENTS <SEP> RADIANT
<tb> ACCES <SEP> ER1 <SEP> ER2 <SEP> ER3 <SEP> ER4 <SEP> ER5 <SEP> ER6 <SEP> ER7 <SEP> ER8
<tb> A1 <SEP> -45 <SEP> 1800 <SEP> 450 <SEP> -9oo <SEP> 1350 <SEP> O <SEP> -135 <SEP> 9O <SEP>
<tb> A2 <SEP> Oc <SEP> -90 <SEP> 1800 <SEP> 900 <SEP> 0 <SEP> -90 <SEP> 1800 <SEP> 90 <SEP>
<tb> A3 <SEP> OC <SEP> -45 <SEP> -90 <SEP> -135 <SEP> 1800 <SEP> 1350 <SEP> 90 <SEP>
<tb> A4 <SEP> Oo <SEP> OC <SEP> OC <SEP> OC <SEP> or <SEP> Oc <SEP><SEP> Ot <SEP> ot <SEP>
<tb> A5 <SEP> -135 <SEP> -90 <SEP> -45 <SEP> OC <SEP> 45 <SEP> 900 <SEQ> 1350 <SEP> 1800
<tb> A6 <SEP> -90 <SEP> OC <SEP> 900 <SEP> 180 <SEP> -90 <SEP> OC <SEP> 90 <SEP> 1800
<tb> A7 <SEP> .900 <SEP> 45 <SEP> 1800 <SEP> -45 <SEP> 90 <SEP> 225 <SEP> 0 <SEP> 1350
<tb> said radiating elements ERp, ERp + 4, for l <p44 being diametrically opposed on the circular network.

 The intercom system object of the invention, comprising in particular an intercommunication system protected against sources of interference, comprises a multi-access antenna previously mentioned. I1 further comprises at least one frequency-phase receiver or goniometer connected to at least two first ports of the coupling circuit constituting the antenna, this receiver being intended for the location of interference, a control and command unit receiving receiver-goniometer the frequency and azimuth direction information of a wave incident on the circular array, and at least one interference-protected receiver connected to at least two adjacent second ports of the coupling circuit.

 The omnidirectional multi-access antenna and the interfering system protected against interference objects of the invention find application to the intercommunication between a plurality of fixed or mobile points such as a command post to operational vehicles, in any application .

The invention will be better understood on reading the description and on the observation of the drawings below in which
FIG. 1a represents a general diagram of the multi-access omnidirectional antenna which is the subject of the invention,
FIG. 1b is a schematic representation of a 0 "-900 hybrid junction used for implementing the antenna according to the invention shown in FIG.
FIG. 1c represents a 0 "-1800 hybrid junction used for the implementation of the antenna according to the invention represented in FIG.
FIG. 2 represents a perspective view of a circular array of radiating elements constituting the antenna according to the present invention,
FIG. 3 represents a view from above of a nonlimiting embodiment of a circular network constituting the antenna as represented in FIG. 2;
FIGS. 4 and 5 respectively represent the radiation diagrams in azimuth, curve A, and in site, curve B, of an antenna confrmed with the object of the present invention, for radiating elements constituted by half-wave dipoles. , respectively for A4 and
A7 of the aforementioned antenna,
FIGS. 6 and 7 respectively represent the radiation diagrams in azimuth, curve A, and in site, curve B, of an antenna according to the subject of the present invention for radiating elements constituted by dihedral reflector dipoles,
FIG. 8a represents a perspective view of the circular network of the antenna of an intercommunication system which is the subject of the invention and FIG. 8b represents a block diagram of the latter,
FIG. 9a represents a perspective view of the circular array of the antenna of a variant of a seven-channel intercommunication system, object of the invention and FIG. 9b a block diagram of the latter,
FIG. 10 represents another variant of a seven-channel intercommunication system according to the invention,
FIG. 11a represents, in perspective, an aerial constituted by two antennas according to the inverltion superimposed on a mast and FIG. 11b represents a corresponding twelve-channel intercommunication system,
FIG. 12a represents, in perspective, an aerial constituted by an antenna according to the invention and FIG. 12b represents an intercommunication system protected against sources of interference, according to a first nonlimiting embodiment,
FIG. 13 represents the theoretical curves of the phase of the signals collected on two accesses of the antenna, as a function of the arrival angle of an interference wave,
FIG. 14 represents representative diagrams of. the directional response of the interference-protected receivers according to FIG. 12b, and
FIG. 15a represents the aerial consisting of an antenna according to the invention, and FIG. 15b represents an intercommunication station with several reception channels protected against sources of interference.

 The omnidirectional multi-access antenna object of the invention will be described firstly in connection with the figures lb lb, lc.

 According to one aspect of the invention, the multi-access omnidirectional antenna comprises a circular network RC comprising eight radiating elements ERi, the index i being between 1 and 8. In FIG. 1a, the circular network RC is represented in developed form and a more detailed description of this network will be given in conjunction with FIG. 2 later in the description. The radiating elements ERi are substantially omnidirectional and regularly distributed around the periphery of a circle of diameter less than 0.75 where # -describes the wavelength of the radiofrequency signal emitted or received by the antenna which is the subject of the invention .

 The aforementioned radiating elements ERi are coupled together by means of a coupling circuit MAC to generate an omnidirectional radiation pattern.

 The coupling circuit MAC has seven accesses respectively Aj with j between I and 7.

The radiating elements ERi and the access Aj are coupled according to a power phase matrix hereinafter
BOARD. I

<tb><SEP> ELEMENTS <SEP> RADIANT
<tb> ACCES <SEP> ER1 <SEP> ER2 <SEP> ER3 <SEP> ER4 <SEP> ER5 <SEP> ER6 <SEP> ER7 <SEP> ER8
<tb> A1 <SEP> -45 <SEP> 1800 <SEP> 45 <SEP> -90 <SEP> 135 <SEP> OC <SEP> -1350 <SEP> 90 <SEP>
<tb> A2 <SEP> OC <SEP> -90 <SEP> 1800 <SEP> 90 <SEP> OC <SEP> -90 <SEP> 1800 <SEP> 900
<tb> A3 <SEP> 0 <SEP> -45 <SEP> -90 <SEP> -135 <SEP> 1800 <SEP> 1350 <SEP> 900 <SEP> 450
<tb> A4 <SEP> 0 <SEP> 0 <SEP> 0 <SEP>. <SEP> 00 <SEP> 00 <SEP> 0 <SEP> 0 <SEP>
<tb> A5 <SEP> 1350 <SEP> -90 <SEP> -45 <SEP> 00 <SEP> 450 <SEP> 90 <SEP> 135 <SEP> 180
<tb> A6 <SEP> -90 <SEP> OC <SEP> 90 <SEP> 1800 <SEP> -90 <SEP> OC <SEP> 90 <SEP> 180 <SEP>
<tb> A7 <SEP> -90 <SEP> 450 <SEP> 1800 <SEP> -45 <SEP> 900 <SEP> 225 <SEP> 0 <SEP> 135
<Tb>
Radiating elements for example ER and ER 4 for
p p + 4 lisp4 P <4 are diametrically opposed on the circular network RC.

Thus, the radiating elements ER1 and ER5, ER2 and ER6, ER3 and ER7,
ER4 and ER8 are diametrically opposed on the circular network RC above.

 According to an advantageous embodiment of the omnidirectional multi-access antenna object of the invention, the radiating elements ERi may be constituted by identical radiating elements. By way of nonlimiting example, these can in fact be made using half-wave dipoles, trombones, coaxial feed dipoles, asymmetrical dipoles, printed dipoles, doublets, or reflector dipoles. dihedral. The term "dihedral reflector dipole" usually refers to a dipole-type radiating element disposed in the plane of symmetry and parallel to the edge of a dihedral angle-of-aperture reflector 45 ".

 The MAC coupling circuit is an eight-input and eight-output multi-port circuit, seven of the inputs constituting the Aj accesses previously mentioned, these ports being able to be interconnected with transmission circuits, which can be constituted either by an emitter output either by a receiver input or by a simultaneous or alternating transmit transmission circuit operating in duplex or semiduplex. Of course, the eight outputs of the MAC coupling circuit are each connected to one of the aforementioned radiators ERi.

 According to a particularly advantageous characteristic of the multi-access omnidirectional antenna which is the subject of the invention, the seven access ports Aj of the coupling circuit MAC are indeed reciprocal and can be considered as antenna inputs or antenna outputs.

According to a preferred embodiment of the coupling circuit
MAC cited above, as shown in Figure la, it comprises a first stage formed of four hybrid junctions 0 -180, each coupling together a pair of diametrically opposite radiating elements ERi of the circular network RC and a second stage formed of two junctions hybrids 0 -180 and two hybrid junctions 0 -90. Each of the first hybrid O0180O junctions of the second stage together couple a pair of hybrid junctions 0-180 of the first stage and each of the second hybrid junctions 0-90 couples together the same pair of hybrid junctions O018O0 of the first stage that each of the hybrid junctions 0 - 180 of the second floor. The MAC coupling circuit finally comprises a third stage formed by a 0-180 hybrid junction, three 0 -90 hybrid junctions and two 45 "phase shifting circuits coupling the junctions of the second stage to the seven access ports Aj of the antenna system. .

A more detailed description of the performance of the coupling circuit
MAC as shown in Figure la will be given in connection with Figures lb and lc.

 In FIG. 1b, there is shown, in a conventional manner, a hybrid junction 0 -90. These hybrid junctions 0-90 are of conventional type and their input-output terminals are conventionally numbered 1, 2, 3, 4 as shown in FIG. 1b with respect to the center of symmetry c of the representation of the junction. By convention, and taking into account the mode of operation at the emission and / or the reception of each of the input-output terminals 1, 2, 3, 4, the terminals 1,3 and 2,4 are called terminals of Inputs-output symmetrical with respect to the center c, the output terminals output 1,2 and 3,4 are said antisymmetric input-output terminals with respect to the center c and the input-output terminals 1,4 and 2 , 3 are called asymmetric input-output terminals with respect to the center c. During the transmission-reception operation of the omnidirectional multi-access antenna which is the subject of the invention, the symmetrical input-output terminals 1, 3 and 2, 4 show for the corresponding signals the same first given phase relation depending on the construction mode of the hybrid junction considered, the antisymmetric input-output terminals 1, 2 and 3, or, more precisely, the signals passing through the terminals. antisymmetric, have the same second phase relationship detaches rminée, these terminals being normally dépéndantes but can play the same role in the emission, respectively in the reception, taking into account the reciprocity of the Hybrid junctions 0 -90 mentioned above, and asymmetrical output terminals of output 1,4 and 2,3 are such that, on transmission, the aforementioned terminals are either completely decoupled, these terminals acting as input terminals, or deliver signals transmitted phase-shifted by 90, these terminals acting as output terminals, and reciprocally at the reception for the same asymmetrical I / O terminals 1,4 and 2,3.

 As shown in FIG. 1b, a power signal P entering on the input-output terminal 1 is transmitted on the one hand to the corresponding antisymmetrical input / output terminal 2 with a power P / 2. and a given phase relation and on the other hand to the corresponding symmetrical input-output terminal 3 with a power P / 2 and a phase shift of -90 "with respect to the signal delivered by the input-output terminal 2 with this input-output terminal 3 constitutes an asymmetrical input-output terminal No useful signal is present on the input-output terminal 4.

 In the same way, as shown in FIG. 1c, a hybrid junction 0-180, which may be constituted by a hybrid junction 0-90 on one of the output terminals of which an additional phase shifter circuit DA of 90 is added, the input-output terminal 3 for example, is represented in the same way.

 Given the aforementioned convention, the first stage I of the MAC coupling circuit is formed of four 0-180 hybrid junctions, these four hybrid junctions being denoted by C1, C2, C3, C4 in FIG. Each hybrid junction couples together two radiating elements ERp and ER with 1 # p + 4 with 14 \ <p # 4 diametrically opposite on the circular network RC via two first symmetric input-output terminals, terminals 1 and 2. 3 for example.

The second stage II is formed by two hybrid junctions OOl800 and by two hybrid junctions 0-90, these junctions being respectively designated C5, C6, C7, C8. The hybrid junctions 0-180 C5, C6 of the second stage together couple two hybrid junctions 00-180a C1 and C3 respectively C2 and C4 of the first stage themselves coupling a pair of non-adjacent radiating elements ER p via two first symmetrical input-output terminals, the terminals I and 3 for example respectively connected to one of the second symmetrical input-output terminals, terminal 4 for example, of the hybrid junction 0 -180 considered C1, C3 or C2, C4 of the first stage.The hybrid junctions 0 -90
C7, C8 of the second stage together couple the two hybrid junctions 0 -180 C1, C3, respectively C2, C4, of the first stage, which couple a pair of non-adjacent ER radiating elements, via
p two asymmetrical first input-output terminals, terminals 2 and 3 for example connected to the other of the second symmetrical input-output terminals, terminal 2 for example of the hybrid junction 0 -180 considered C1, C3, respectively C2-C4 of the first stage.

The third stage III is formed of a hybrid junction 0 -180, C9, and three hybrid junctions 0-90 respectively denoted Cl, Cil and C12. The hybrid junction 0 -180 C9 of the third stage couples together the two hybrid junctions 0 -180 C5-C6 of the second stage via two first symmetrical input-output terminals, terminals 1 and 3 for example, which are respectively connected to one of the second symmetrical input-output terminals, the terminals 4 for example hybrid junctions 0 -180 C5, C6 of the second stage.One of the hybrid junctions 0 -90 C10 of the third stage couples together the two hybrid junctions 0 -180 C5-C6 of the second stage via two first asymmetrical terminals, terminals 2 and 3 for example, respectively connected to the other of the second symmetrical input / output terminals, terminal 2, 0-180 C5-C6 hybrid junctions of the second stage.The other two hybrid junctions 0 -90 Cll-C12 of the third stage together couple the two hybrid junctions 0 -90 C7-C8 of the second stage via the first terminals ' asymmetrical input-output terminals 2 and 3 for example, which are respectively connected directly and via a phase-shifting circuit of 450 D1 to one of the second asymmetrical input-output terminals, the terminal 1 for example of each hybrid junction 00.900 C7, C8 of the second stage and vice versa for the hybrid junction 00.900 C12, with respect to the hybrid junction 00.900 Cl 1, which has its asymmetric input-output terminal 2 connected to the input terminal asymmetric output 4 of the hybrid junction C7 via a phase-shifting circuit of 45 D2, the asymmetrical input-output terminal 3 of this same hybrid junction C12 being connected directly to the asymmetrical input-output terminal 4 of the 00.900 C8 hybrid junction on the second floor. The input-output terminals of the hybrid junctions of the third stage not yet used make it possible to achieve the Aj accesses of the MAC coupling circuit. Thus, one of the second symmetrical terminals, terminal 4 for example, of the hybrid junction 00.1800
C9 of the third stage and the second asymmetric input-output terminals 1 and 4 of the hybrid junctions 0 "-90" C10, Cl1 and C12 of the third stage thus form respectively the accesses A4, A2, A6, A5, A7 and Al , A3. In addition, the other of the two second symmetrical terminals, the terminal 2 of the hybrid junction 00.1800 C5 of the third stage is loaded by a suitable dissipative impedance X.

 Thus, the hybrid junctions 00.1800 used respectively 00 0000 are identical each to each, this only condition being imposed to achieve the phase laws corresponding to the supply phase matrix of the radiating elements ERi from access Aj.

 Furthermore, as already mentioned previously and advantageously in order to unify the variety of components used for the realization of the MAC coupling circuit, each hybrid junction 0 "-180" can be constituted by a hybrid junction 00.900 to one of the asymmetric terminals of which is associated a 90 "phase shifter circuit.

Thus, the hybrid junctions C1 to C12 constituting the three stages of the MAC coupling circuit are reciprocal passive components and without loss of energy other than technological commonly covering a frequency band equal to the octave. The two phase shifters 45 D1 and D2 performing the corresponding phase shifts are also passive and reciprocal components with low energy loss. According to one nonlimiting embodiment, they may be formed for example by lengths of lines of length # / 8 where # denotes the wavelength of the radiofrequency signal transmitted or received over a 30% frequency band. As a corollary, the MAC coupling circuit offers the advantages of simple realization of low power loss and wide operating frequency bandwidth. In the same way, in order to simplify as much as possible
constraints of realization of the coupling circuit MAC, the hybrid junction
C9 can be achieved by means of a simple adapted tee.

By the only implementation of the coupling circuit MAC as represented in FIG. 1a, the power of each of the seven accesses Aj is
divides power equally in the eight radiating elements ERi of the
circular network RC with phase rule according to the following table
TABLE II

<tb><SEP> 1 <SEP> ELEMENTS <SEP> RADIANT <SEP>;<SEP> Modes
<tb> Access <SEP> ERl <SEP>: ER2 <SEP>; ER3 <SEP>: ER4: <SEP>EP5'ER6<SEP>: Ep <SEP>: ER8
<tb><SEP> A1 <SEP><SEP> -45 <SEP>: 180: <SEP> 45 <SEP>: -90 <SEP> 90 <SEP> 0 <SEP>: -1350: <SEQ> 90c <SEP>: <SEP> - <SEP> 3 <SEP>
<tb><SEP>:<SEP> O <SEP><SEP> .900 <SEP>: 1800 <SEP>: <SEP> 900 <SEP>: <SEP> 0 <SEP>: .9OC <SEP>: 1800 <SEP>: <SEP> 900 <SEP>: <SEP> - <SEP> 2
<tb><SEP> A3 <SEP>: <SEP> 0 <SEP>: -45 <SEP>: -900 <SEP>: -135: 180 <SEP>: 1350 <SEP>: <SEP> 900 <SEP > 45≈ <SEP> 45 <SEP>: <SEP> -1 <SEP>
<tb><SEP> A4 <SEP> 0: <SEP>: <SEP> 0 <SEP>: <SEP> 00 <SEP>: <SEP><SEP> 00 <SEP>: <SEP><SEP> 00 <SEP>: <SEP><SEP> 0 <SEP> 0 <SEP> 0 <SEP>: <SEP> 0
<tb><SEP> -135: -90 <SEP>: -050 <SEP>: <SEP><SEP> 00 <SEP>: <SEP> 450 <SEP>: <SEP> 900 <SEP> 135: 180 :
<tb><SEP>;::::; :: <SEP><SEP> 90 <SEP>: 180 <SEP>: -90: <SEP> 0: <SEP> :: <SEP><SEP>: 180 ::: <SEP> 2
<tb><SEP> A7 <SEP>: -90: <SEP> 45 <SEP>: 180 <SEP>: -45.: <SEP> 90 <SEP>: 225: <SEP>. <SEP> 0 <SEP> 135 <SEP> 3 <SEP>
<Tb>
On the board, it appears that each access Aj of the coupling circuit
MAC generates in addition to the phase values previously mentioned in Table 1, a distinct and independent phase mode such as the phase difference between two adjacent radiating elements ERi, ERi + 1 of the network
RC is equal to m. + with m = -3, -2, -1, G, 1, 2, 3 respectively corresponding to accesses AI, A2, A3, A4, A5, A6 and A7.

In order to ensure a phase law corresponding to the aforementioned tables between an access Aj and each radiating element ERi or between a radiating element ERi and each access Aj, on transmission and / or reception respectively, it is necessary to use , for the respective interconnection of the radiating elements ERi, hybrid junctions C1 to Cl2 and accesses
Aj, wiring circuits of equal electrical length for each floor considered.

 A more detailed description of the circular network RC will be given in connection with FIGS. 2 and 3.

 According to Figure 2, the radiating elements ERi may be constituted by dipoles disposed on a circle of diameter close to 0.5h where; denotes the radio frequency transmission-reception wavelength. The radiating elements thus formed are uniformly distributed, two adjacent radiating elements being separated by an angle of 45 ". The aerial constituted by the arrangement of dipoles or doublets as represented in FIG. 2 is mounted on a mast and, of course, an aerial may comprise one or more circular networks superimposed on the same mast as will be described later in the description.

 3 shows a top view of an aerial constituted by a plurality of dipoles provided with a dihedral reflector. In this case, the strands of the dipoles or doublets are oriented substantially parallel to the edge of each dihedron.

 The cylindrical symmetry of the circular network RC, its dimensions and the regularity of the supply phases of the radiating elements ERi make it possible to obtain radiation diagrams of very good omnidirectionality.

Figures 4 and 5 show the radiation patterns for a circular array of half-wave dipoles radiating at a frequency of 900 MHz, these dipoles being arranged around a mast as shown in Figure 2, Figure 4 being relating to the access A4 and FIG. 5 being on the contrary relating to the access A7 of the coupling circuit
MAC. In the above figures, the curve A corresponds to a radiation pattern in azimuth, horizontal plane, while the curves B correspond to the radiation pattern in the vertical plane of the site of the dipole, for example. As can be seen, the azimuthal radiation pattern A has a very good circularity to + 0.5 dB, all accesses combined. Radiation diagrams in site, curve
B, are similar to those of a single dipole although more or less flattened according to the access considered.

 FIGS. 6 and 7 are the counterparts of FIGS. 4 and 5 and illustrate radiation diagrams for a dipole array provided with dihedral reflectors, of the type as shown in FIG. 3, and arranged around a central mat. The degree of circularity of the azimuth radiation diagrams is here better than 2.2 dB for all accesses combined.

 As a result of the above performance, the average gain for each access of the omnidirectional multi-access antenna object of the invention is of the order of that which would be obtained with a single dipole. It differs from the latter by the technological losses in the MAC coupling circuit that can be estimated at 1 dB, for example, and by the losses due to the electromagnetic coupling and the mismatching of the antennas of the circular network RC, which are manifested by a transfer of energy between the accesses. As such, it should be noted that the A4 access is completely decoupled from the other six accesses, the latter being coupled only two by two. Moreover, the terminal of the hybrid junction C9 connected to the dissipative load X is completely decoupled from the seven ports A1 to A7.

The optimization of the impedance of the radiating elements makes it possible to bring the decoupling between two accesses to an acceptable level. An appropriate design of the hybrid junctions C5 to C6 also makes it possible to correctly adapt the impedance of the access A4 and to decouple the access between them.
A2 and A6. The use of dipole radiating elements provided with dihedral reflectors as described above substantially improves the decoupling between the accesses.

 Of course, a multichannel intercommunication system according to the subject of the invention will comprise at least one antenna as previously described. The description of such a system will be given in connection with FIGS. 8a and 8b.

 In FIG. 8a, there is shown the circular network RC of a multichannel intercommunication system comprising six channels.

 As shown in FIG. 8b, the corresponding intercommunication system is such that six of the ports A1, A2, A3, AS, A6, A7 are interconnected respectively at the output of a transmitter symbolized by E1, E2, E3, E4, E5, E6, one of the A4 accesses of the MAC interconnection circuit being interconnected to a six-port SEP separator circuit. Each access of the separator stage SEP is interconnected respectively to the input of a receiver R1 to R6 to form an intercommunication system with six transmission-reception channels. The separator stage SEP separates the six reception channels R1, R2, R3, R4, R5 and R6 by bandpass filtering.

 According to another embodiment of a multi-channel intercommunication system in FIGS. 9a and 9b, the circular network RC similar to that represented in FIG. 8a is completed by means of an omnidirectional antenna F disposed at the top of the mast for example. as shown in FIG. 9a. This auxiliary omnidirectional antenna F is an omnidirectional auxiliary reception antenna such as a whip antenna for example connected to a seven-port SEP separator circuit. The seven accesses Al to A7 of the interconnection circuit MAC are interconnected respectively on the output of an emitter E1 to E7 and each access of the separator stage SEP is interconnected respectively to the input of a receiver R1 to R7 to constitute a seven-channel transceiver system. The vertical auxiliary antenna F over the mast of the RC network provides reception of seven receive channels R1 through R7 through the SEP separator. The seven transmission channels E1 to E7 are provided by the MAC coupling circuit and the RC network.

 A nonlimiting variant embodiment of a seven-channel intercommunication station previously described in connection with FIGS. 9a and 9b will be described with reference to FIG.

According to the aforementioned figure, the seven accesses Al to A7 of the MAC coupling circuits are interconnected respectively to the output of a transmitter
E1, E2, E3, E4, E5, E6, one of the accesses, access A4 for example, being interconnected to the input-output terminal of a DPX duplexer circuit. The duplexer circuit comprises an access connected to the output of an emitter E7 and an output connected to a sepa separator stage with seven accesses SEP, each access of the separator stage SEP being respectively connected to the input of a receiver to constitute a seven-channel intercommunication circuit. The DPX duplexer connected to the A4 access provides both the transmission channel E7 and the reception channel of the seven channels R1 to R7.

 In order to provide an intercommunication system having an access number greater than seven, it is naturally possible to superimpose on the same mast the circular arrays RC of a plurality of multi-access omnidirectional antennas which are the subject of the invention.

 A nonlimiting embodiment of such a multichannel system will be described in connection with Figures I la and 1 lob.

According to the aforementioned embodiment, the circular networks RC1 and
RC2 of each antenna are superimposed on the same mast and transmitters
E1 to E12 and the receivers R1 to R12 are selected to form a twelve channel intercommunication system. Thus, each circular network RC1 and RC2 is of course connected respectively to a coupling circuit MAC1 and MAC2. The circular networks are of any type, as previously described, and the coupling circuits MAC1 and MAC2 are of course identical to the MAC circuit as shown in FIG. 1a. Each coupling circuit MAC1 and MAC2 is coupled at the access level. A1, A2, A3, A5, A6, A7 to an emitter E1, E2, E3, E4, E5, E6, respectively E7, E8, E9, E1, E1, E12, the access A4 of each of the coupling circuits
MAC1 or MAC2 being connected to a separator stage SEP1, respectively
SEP2.

The accesses of the aforementioned splitter stages, six in number, are each coupled to the receiver inputs R1 to R6, R7 to R12 respectively. It can be seen that in such an embodiment as represented in FIGS. 11a and 11b, the total height occupied by the aerial constituted by the circular networks RC1 and RC2 is of the order of 1.5, where the length of transmission-reception wave of the radio frequency.

 In the same way, fourteen and twenty-four transmission-reception intercommunication stations may be formed by simply superimposing the configurations illustrated in FIGS. 9, 10 and 11 respectively. In the case of an intercommunication station with twenty-four transmission-reception channels, a total mast height of only 3.5X is necessary. This value is compared for example to the value of 23.5> necessary in the first solution of the prior art indicated in the introduction to the description.

 According to another characteristic of the intercommunication systems object of the invention implemented using one or more multi-access omnidirectional antennas as previously described, the multimode operation, the number of elementary antennas, the reduced dimensions and the symmetry of the revolution of the RC networks of radiating elements ERi confer on the antenna, object of the invention, potentialities of transmission protected against sources of interference and potentials for locating the direction of arrival of these signals interference.

In order to constitute a protected intercommunication system
against sources of interference as represented for example in
FIGS. 12a and 12b, FIG. 12a simply illustrating a
circular network RC likely to be used to realize a system
intercom protected against sources of interference, such as
represented in FIG. 12b, the aforementioned intercommunication system
further comprises at least one phase-frequency receiver or goniometer
GON connected to at least two first accesses, A4 and A5 accesses on the
Figure 12b of the MAC coupling circuit. The phase-frequency receiver receives
thus on the two input terminals the signals delivered by two consecutive accesses of the coupling circuit MAC and makes it possible to deliver a signal
representative of the frequency of the signal delivered by the source of interference and a signal relating to the azimuth direction of this source of interference.

This type of phase-frequency receiver or goniometer will not be described because
it can correspond to a type of goniometric receiver type
classical but without phase ambiguity over a 0-3600 phase range. In
In addition, the system also includes a decision and
UDC command receiving GON goniometer receiver. information from
frequency and direction in azimuth of the incident wave on the network
circular RC.

As further shown in FIG. 12b, at least one
receiver protected against interference, receiver noted RAI1 and RAI2 is
connected to at least two adjacent second ports of the coupling circuit
MAC. In FIG. 12b, the receiver RAI1 is connected to the ports A1 and A2.
while receiver RAI2 is connected to ports A6 and A7. Each
protected receiver has a basic receiver REC1 and REC2
connected to the aforementioned adjacent accesses via circuits of
gain 100 or adjustable attenuators and phase shifters 200 or
programmable. Adjustable gain or phase shift circuits or
programmable are interconnected to the decision and control unit
The adjustable gain and phase shift of the aforementioned circuits are determined and the signals transmitted by these latter are delivered to the elementary receiver REC or REC2 via a summing circuit 300 to generate a resulting signal whose variation as a function of the direction of the incident wave is a directional diagram, of the cardioid type for example, or a diagram comprising at least one preferential zone of minimum sensitivity.

 Thus, by determining the value of the frequency of the signal delivered by the interference source and the direction in azimuth thereof, by the GON receiver goniometer, the decision and control unit UDC allows an operator or a programmed central unit to make a corresponding adjustment of the attenuations and phase shifts of the combined signals by the summator 300 and delivered to the elementary receiver REC1 or REC2, the preferential zone of minimum sensitivity being thus oriented in the direction of the source of interference The process of calculating and determining the attenuation values of the attenuators 100 and of the phase shifters 200 as a function of the frequency and direction values in azimuth of the interference source will not be described because it corresponds to the techniques protection against spurious signals from radiofrequency intercommunication stations.

 It may also be noted that, in order to generate a directional diagram comprising a plurality N of zones of minimum sensitivity, the receiver protected against interference RAI1 or RAI2 may be connected to at least N + I adjacent accesses of the coupling circuit, the number N being at most equal to 6. In this case, the creation of the zones of minimum sensitivity substantially corresponds, by the principle of superposition of the states of physical equilibrium, to the superposition of a number of corresponding radiation patterns each comprising a zone of minimum sensitivity.

 The goniometric receiver GON may be calibrated to display the azimuth direction within a range 0 "-360" of an incident wave on the circular array RC. In a conventional manner, it may comprise for example a phase comparator detecting the phase difference between the signals coming from two adjacent accesses of the MAC coupling circuit, these two access being characterized by phase modes ml and m2 indicated in the preceding table II such that ml - m2 = +1 as for example the access pairs Al, A2 and A4, A5. It may also be provided with a frequency meter indicating the frequency of the incident wave as well as other devices for characterizing this incident wave.

 Note that, to achieve at a protected receiver RAIl or RAI2 a directional diagram at a cardioid-shaped minimum sensitivity area for example, this receiver is connected to two adjacent accesses of the MAC coupling circuit. In this case, the attenuators or adjustable gain circuits 100 balance the amplitudes of the signals from the two ports and the phase shifter 200, for example a phase shifter 0 "-360", shifts one of the signals relative to the other and directs the hole of the cardiolde in the desired direction.

 The accuracy in locating the goniometric receiver GON depends mainly on the good linearity of the phase diagrams of the radiated field according to the accesses A1 to A7 of the antenna. The performances of each receiver RAI depend on the good linearity of the phase diagrams, on the good -circularity of the amplitude diagrams of the field radiated according to the accesses A1, A2 ..., A7 as well as the gain of the antenna following these access.

 In FIG. 12b, there is furthermore the existence of a REC5 emergency receiver connected to the access A3 of the MAC coupling circuit. This emergency receiver makes it possible to constitute an unprotected auxiliary communication channel.

 The performance in locating and in rejecting the interference of the antenna and the intercommunication system which is the subject of the invention, configured for example according to the diagram of FIGS. 12a and 12b, can be observed on the diagrams of FIGS. 13 and 14.

 FIG. 13 shows the phases of the signals received at the A4 curve A and A5 curve B accesses as a function of the arrival angle of a wave on the RC network. This is formed of eight half-wave dipoles distributed over a circle of 0.5 X diameter where 7 denotes the wavelength of the radiofrequency signal in transmission-reception around a central mast. It can be seen that the difference between the two phase curves A and B directly gives the azimuthal direction of arrival of the incident wave with a lower error or of the order of 1 ", which precedes a good location accuracy for the GON goniometer receiver.For the same RC network, Figure 14 shows the amplitude of the signal that would be collected on the REC2 receiver internal receiver RAI2 for a fixed setting attenuators 100 and for five values of the phase shift introduced by the phase shifter 200 corresponding to five directions of arrival of interference: 1350, 158, 1800, 2030, 2250. In these directions, the depth of the holes is greater than 30 dB and the angular widths of the holes at -27 dB of the maximum are less than 15 " . The calculated gain of the antenna is close to -1.5 dB relative to the isotropic. This good interference resolution means that the antenna and the intercommunication system object of the invention containing it can be used in a disturbed environment.

Figures 15a and 15b illustrate the schematic of a communication station with six independent reception channels protected against interference. In this case, the six-channel system thus comprises six receivers protected against interference, these receivers being noted
RAIl to RAI6. Each aforementioned receiver is connected to two adjacent accesses of the MAC coupling circuit, adjacent inputs of two adjacent receivers being interconnected to the same access of the coupling circuit via a dividing tee 500 and the non-adjacent extreme inputs of the receivers. end RAI1 and RAI6 are respectively connected to the extreme access A1 or A7 of the MAC coupling circuit via an attenuator circuit 600.

 A decision and control unit UDC interconnected to the interference-protected receiver RAI1 to RAI6 receives the frequency and azimuth direction information of the interference sources from an auxiliary goniometer receiver not shown in Fig. 15b. The control of the six RAI1 receivers RA16 is done manually or electronically by means of the Ubac control unit, which may comprise independent corresponding units or a microprocessor unit capable of ensuring the real time adjustment of each of the receivers protected against the interferences RAIl to RA16 above. It will be recalled that, by adjacent access, means two accesses of the MAC coupling circuit whose mode of phase m differ from one unit according to Table II previously described.

 By virtue of the reciprocity of the omnidirectional antenna which is the subject of the invention, the term intercommunication applies here as well to the transmission as to the reception of the radiofrequency signals concerned. It will also be noted that the more or less elaborate internal design of the goniometer receivers GON or protected against interference RAI and elementary receivers REC is within the domain of the normal skills of the person skilled in the art and does not alter in any way the operation or the structure of the the antenna and the intercommunication system object of the invention.

Claims (14)

 a coupling circuit (MAC) of said radiating elements comprising seven ports (Aj), said radiating elements (ERi) and said ports being coupled according to the following power phase matrix  a circular array (RC) comprising eight substantially omnidirectional radiating elements (ERi) regularly distributed at the periphery of a circle of diameter less than 0.75 wavelength (0.75 #),  An omnidirectional multi-access antenna, characterized in that it comprises <tb> said radiating elements ERp, ERp + 4, for l # p # 4 being diametrically opposed on the circular network (RC). <tb> A7 <SEP> -90 <SEP> 45 <SEP> 1800 <SEP> -45 <SEP> 90 <SEP> 225 <SEP> 0 <SEP> 135 <SEP> <tb> A6 <SEP> -90 <SEP> OC <SEP> 90 <SEP> 180 <SEP> -90 <SEP> OC <SEP> 90 <SEP> 1800 <tb> A5 <SEP> -1350 <SEP> -900 <SEP> -450 <SEP> 00 <SEP> 45 <SEP> 90 <SEP> 135 <SEP> 1800 <SEP> <tb> A4 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0 <SEP> <tb> A3 <SEP> 0 <SEP> -45 <SEP> ~ -90 <SEP> .1350 <SEP> 1800 <SEP> 1350 <SEP> 900 <SEP> 450 <SEP> <tb> A2 <SEP> OC <SEP> -90 <SEP> 1800 <SEP> 90 <SEP> OC <SEP> -90 <SEP> 1800 <SEP> 900 <SEP> <tb> A1 <SEP> -45 <SEP> 180 <SEP> 45o <SEP> <SEP> -9oo <SEP> <SEP> 135 <SEP> Oo <SEP> <SEP> -135 <SEP> 90 <SEP > <tb> ACCESS <SEP> ER1 <SEP> ER2 <SEE> ER3 <SEE> ER4 <SEE> <SEE> ERS <SEE> ER6 <SEE> ER7 <SEE> R8 <SEE> <tb> <SEP> ELEMENTS <SEP> RADIANT 2. Antenna according to claim 1, characterized in that said radiating elements (ERi) substantially omnidirectional are constituted by identical radiating elements such as half-wave dipole, trombone, dipole coaxial feed, asymmetric dipole, printed dipole, doublets, dipoles with dihedral reflector. Antenna according to one of the preceding claims, characterized in that said coupling circuit (MAC) comprises  a first stage formed of four hybrid junctions 0 "-180" (Cl C4), each of said hybrid junctions coupling together a pair of diametrically opposed dipoles of the array,  a second stage formed by two 0 "-180" hybrid junctions (C5, C6) and two 0 "-90" hybrid junctions (C7, C8), each of the 0 "-180" hybrid junctions (C5, C6) of said second stage coupling together a pair of hybrid junctions 00.1800 (C1, C3) respectively (C2, C4) of the first stage and each of hybrid junctions 0-90 (C7, C8) of said second stage coupling together the same pair of hybrid junctions 0 " -180 "(C1, C3) respectively (C2, C4) of the first stage, and  a third stage formed of a 0 "-180" hybrid junction (C9), of three hybrid junctions 00.900 (Cl0, Cl1, Cl2) and of two phase shifters (D1, D2) coupling the junctions of the second stage to the seven junctions of the antenna. 4. Antenna according to claim 3, characterized in that one (2) of the two symmetrical second terminals (2,4) of the hybrid junction 0 "-180" of said third jet is charged by a suitable impedance (X). 5. Antenna according to one of claims 3 and 4, characterized in that the hybrid junctions 0 "-180" respectively 0 -90 are identical each to each. 6. Antenna according to one of revendicati.ons 3 to 5, characterized in that each jπnction hybrid 00.1800 is constituted by a hybrid junction 0 -90 to one. asymmetrical terminals of which is associated a phase shifter circuit of 90.  7. multichannel intercommunication system, characterized in that it comprises at least one antenna according to one of the preceding claims. 8. System 4'intercommunication multichannel according to claim 7, characterized in that six of the accesses (A1, A2, A3, A5, A6, A7) are interconnected respectively to the output of a transmitter (E1, E2, E3, E4 , E5, E6), one of the ports (A4) being interconnected to a six-port separator circuit (SEP), each access of the separator stage (SEP) being interconnected respectively to the input of a receiver (R1 , R2 ...., R6) to form an intercommunication system with six transmission-reception channels. 9. multichannel intercommunication system according to claim 7, characterized in that the seven ports (A1 to A7) are interconnected respectively to the output of a transmitter (E1 to E7), said antenna being provided with a receiving antenna omnidirectional auxiliary (F) connected to a seven-port separator circuit (SEP), each access of the separator stage (SEP) being interconnected respectively to the input of a receiver (R1 'to R7) to constitute a system of intercommunication to. seven transmission-reception channels. Multichannel intercommunication system according to claim 7, characterized in that six of the seven ports (A1, A2, A3, A5, A6, A7) are respectively interconnected at the output of a transmitter (E1, E2, E3, E4, E5, E6), one of the ports (A4) being interconnected to the input-output terminal of a duplexer circuit (DPX), said duplexer circuit having an access connected to the output of a transmitter (E7) and an output connected to a seven-port splitter stage, each access of the splitter stage being respectively connected to the input of a receiver (R1 to R7) to form a seven-channel intercommunication circuit. 11. Intercommunication system according to the reyendications 7 and -8, characterized in that it comprises two antennas according to claims 1 to 6, the circular arrays (RC1 and RC2) of each antenna being superimposed on the same mast and transmitters (E1-E1) and the receivers (R1-R12) selected to form a twelve channel intercommunication system. 12. Intercommunication system according to claim 7, characterized in that, in order to constitute an intercom system protected against sources of interference, said system further comprises  at least one phase-frequency or goniometer receiver (GON) connected to at least two first access ports of the coupling circuit (MAC), at least one receiver being intended for the location of the interferences,  a decision and control unit (UDC) receiving from said goniometer receiver (GON) the frequency and azimuth direction information of an incident wave on the circular network,  - at least one receiver protected against interference (RAI1, RAI2) connected to at least two second adjacent accesses of the coupling circuit (MAC), each protected receiver having an elementary receiver (REC1, REC2) connected to said adjacent ports via gain (100) and phase shift (200) circuits. ) adjustable or programmable, said adjustable or programmable gain or phase-shifting circuits being interconnected to the decision-control unit (UDC), the adjustable gain and phase shift of said circuits being determined and the signals transmitted by them being determined delivered to said elementary receiver (REC1, REC2) via a summing circuit (300) for generating a resulting signal whose variation as a function of the azimuth direction of the incident wave is a cardioid-type directional diagram comprising at least one minus a preferential zone of minimum sensitivity, said preferential zone of minimum sensitivity being, by the adjustment of the gain circuits and adjustable phase shift, oriented in the direction of the source of interference. 13. System according to claim 12, characterized in that in order to generate a directional diagram comprising a plurality N of zones of minimum sensitivity, said interference-protected receiver (RAI1, RAI2) is connected to at least N + 1. adjacent access of the coupling circuit, the number N being at most equal to 6. 14. System according to claim 7, characterized in that in order to provide an intercommunication system protected against sources of interference to six channels, said system further comprises  six receivers protected against interference (RAI1 to RA16) each receiver being connected to two adjacent accesses of said coupling circuit (MAC), the adjacent inputs of two adjacent receivers being interconnected to one and the same access of the coupling circuit via a divider tee (500) and the non-adjacent extreme end-receiver inputs being respectively connected to the extreme access (A1) or (A7) of the coupling circuit (MAC) via an attenuator circuit ( 600)  a decision and control unit (UDC) interconnected to said interference-protected receivers and receiving the frequency and azimuth direction information of the interference sources from an auxiliary goniometer receiver.