Enhanced hemispherical array antenna

Abstract

Improved Hemispherical Array Antenna The present invention relates to an array antenna (1) comprising: a hemispherical radome (10); a plurality of radiating elements (20) carried by the radome; a plurality of transmit / receive modules (30) carried by the radome, each radiating element being associated with and electrically connected to a transmit / receive module. It is characterized by a common radio communication module, equipped with a common antenna (44), located at the center of the radome and connected to the transmit / receive electronics of the common radio communication module, each transmit / receive module (30) comprising a communication module, equipped with an elementary antenna for bidirectional radio frequency communication with the common radio communication module (40). Figure for the abstract: Figure 1

Description

Title of the invention: Improved hemispherical array antenna

[0001] The present invention relates to three-dimensional array antennas and, more particularly, to hemispherical array antennas.

[0002] As for example presented in French patent application no. 22 05733, the radiating elements of an array antenna can be arranged on a curved support surface, in particular hemispherical.

[0003] Each radiating element is controlled by a transmit / receive module (or TR module). In what follows, for the sake of simplicity, a TR module is considered to be associated with a single radiating element. However, alternatively, a TR module can control a number of radiating elements.

[0004] A TR module is mounted immediately behind the associated radiating element, i.e. for example on an inner face of the support surface when the radiating elements are arranged on an outer face of this support surface.

[0005] Typically, each TR module is connected to low-level control electronics via a wired connection, such as a coaxial cable or optical fiber. This connection allows the TR module's transmission chain to receive the transmission signal and shape it (amplification and / or phase shifting) before applying it to the radiating element to emit an electromagnetic wave. This connection also transmits the reception signal, corresponding to an electromagnetic wave captured by the radiating element and processed (amplification and / or phase shifting) by the TR module's reception chain, to the control electronics. Furthermore, this connection enables the controllable components of the TR module to compensate for bias and / or participate in beamforming.

[0006] However, in the case of a hemispherical array antenna, such an arrangement presents various disadvantages.

[0007] In particular, the internal volume delimited by the support surface is reduced, making the wiring of the TR modules extremely difficult. This is a manual operation that cannot be automated. This limits productivity, but above all, the reproducibility of the manufactured network antennas. Each network antenna therefore requires a complex calibration operation.

[0008] The aim of the present invention is therefore to provide a network antenna that can overcome these problems.

[0009] To this end, the invention relates to an array antenna comprising: a hemispherical radome, with center C and radius R; a plurality of radiating elements, the radiating elements being supported by the radome; a plurality of transmit-receive modules, the transmit-receive modules being supported by the radome, each element radiating being associated with a transmit / receive module and electrically connected to it by one or more power link(s), characterized in that the array antenna further comprises: a common radio communication module, equipped with a common antenna, placed at the center C of the hemispherical radome and connected to transmit / receive electronics of the common radio communication module, each transmit / receive module comprising a communication module, equipped with an elementary antenna for bidirectional radio frequency communication with the common radio communication module.

[0010] According to other advantageous aspects of the invention, the network antenna comprises one or more of the following features, taken individually or in any technically possible combination:

[0011] - the radially facing inward of the radome is an insulating metallic layer electromagnetically a cavity inside the radome.

[0012] - the cavity is equipped with an electromagnetic wave absorption device for reduce background noise.

[0013] - the absorption device is a meta-material covering a floor of the cavity.

[0014] - the meta-material consists of the stacking of a reflective layer, a absorption layer and metallic plane, the metallic plane being perforated so as to present a periodic pattern suitable for trapping radio frequency waves in the thickness of the meta-material according to their polarization.

[0015] - the common antenna is an omnidirectional antenna, presenting in every plane passing through an axis of symmetry of the network antenna an opening of at least 170° for an attenuation of -12dB.

[0016] - the common antenna is a "patch" type antenna.

[0017] - the radiating elements are covered with an adaptation layer, itself covered with a protective layer.

[0018] - in transmission, the common antenna emits a transmission signal that each module of transmission, reception, collection in order to be issued.

[0019] - in reception, the elementary reception signal at the output of each module The transmission and reception signals are re-emitted into the cavity towards the common antenna, the different elementary reception signals overlapping in the cavity to form an overall reception signal, with the common antenna collecting the overall reception signal.

[0020] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0021] [Fig-1] [Fig. 1] is a perspective and partially exploded view of a preferred embodiment of a network antenna according to the invention;

[0022] [Fig.2] [Fig.2] is a partial cross-sectional representation of the radome structure of the array antenna of [Fig.1];

[0023] [Fig.3] [Fig.3] is a schematic representation in the form of functional blocks of the antenna of [Fig.1];

[0024] [Fig.4] [Fig.4] is a graph illustrating the radiation pattern of the central antenna of the array antenna of [Fig.1]; and,

[0025] [Fig.5] [Fig.5] is a perspective and partial cross-sectional representation of the absorption plane constituting the floor of the array antenna of [Fig.1]

[0026] The invention is based on the implementation of wireless communication, preferably radio frequency - RF, between each transmitting / receiving module of the network antenna and a central, common antenna connected to the low-level electronics for driving the network antenna.

[0027] In the embodiment of [Fig.1], the array antenna 1 comprises a hemispherical radome 10.

[0028] The radome 10 takes the general form of a hemisphere, with center C and radius R. It is delimited by a median plane P, constituting the floor of the antenna 1.

[0029] Axis A, normal to plane P at center C, is an axis of revolution symmetry of the array antenna 1.

[0030] The radome 10 is for example a polyhedron with triangular facets inscribed in the hemisphere of center C and radius R. Alternatively, it is hexagonal facets, or pentagonal facets, or the equivalent.

[0031] On [Fig.2], illustratively, three adjoining facets, 10, h 10; and 10i+i, of the radome 10 are shown in section along a plane passing through the axis A. i is an integer between 1 and N, the total number of facets, but also of radiating elements and of TR modules.

[0032] A facet 10; results from the superposition of several strata.

[0033] The junction of the strata of the different facets defines a plurality of layers in the radome, such as, for example, from the inside to the outside of the hemisphere, a metallized layer 12, a substrate 14, an adaptation layer 16, and a protection layer 18.

[0034] The continuous metallized layer 12 defines a hemisphere, which externally delimits a radiation space 2 of the array antenna 10 and internally, a cavity 4. The metallized layer makes it possible to electromagnetically isolate the volume of the cavity 4 from the space 2.

[0035] The metallized layer 12 is advantageously used to define a ground plane for the TR modules and radiating elements.

[0036] The substrate layer 14 is made of dielectric material whose relative permittivity is adjusted.

[0037] The adaptation layer 16 is, for example, made of a radiofrequency foam having a relative permittivity close to unity. This is, for example, the Rohacell® HF / WF material.

[0038] The outer layer 18 is, for example, made of a material having suitable mechanical properties to provide the desired mechanical resistance and protect the radiating elements from external aggressions. This is, for example, the FR-4 material.

[0039] The radome 10 carries a plurality of radiating elements 20 and a plurality of module TR 30, each module TR being associated with a radiating element in the present embodiment.

[0040] A radiating element 20 is for example a planar antenna (or "patch" antenna), single or multiport.

[0041] For example, each radiating element 20 of the array antenna 1 is carried by a facet. A radiating element 20 is, for example, disposed at the center of a facet. Advantageously, as shown in [Fig. 2], each radiating element 20 is mounted on an external face of the substrate 14 and is covered with the material constituting the matching layer 16.

[0042] Fig. 3 is a schematic electrical representation of the antenna 1. Each TR module, such as the TR module 30, is for example a printed circuit integrating a transmission chain 32 and a reception chain 33 connected, via a duplexer 3h, to the ports of the radiating element 20, by one or more supply lines.

[0043] Each TR module 30 is mounted behind the associated radiating element 20i. For example, it is mounted on an inner face of the metal layer 12, as shown in [Fig. 2]. It is therefore located inside the cavity 4.

[0044] Advantageously, an additional support layer is provided on the inner side of the metallized layer 12 to support the electronics, in particular the TR modules 30; and their power lines.

[0045] Vias are provided through the metallic layer 12 and the substrate 14 to allow the passage of the power lines electrically connecting the TR module 30; and the associated radiating element 20;.

[0046] According to the invention, each TR module 30; is provided with an elementary radio communication module 36; for communication, inside the cavity 4, with a common radio communication module 40. The module 36; is connected at the input of the transmission chain 32; and at the output of the reception chain 33; of the TR module 30i.

[0047] An elementary radio communication module 36; is equipped with an elementary radio frequency antenna - RF 34;.

[0048] As shown in [Fig.3], the network antenna 10 includes a common radio communication module 40.

[0049] It allows bidirectional radio frequency communication with each of the radio communication modules 36; of the TR modules 30;.

[0050] The module 40 is equipped with a common antenna or source 44 and suitable electronics.

[0051] The communication must allow:

[0052] - in uplink communication, the transmission of the SE emission signal from the source 44 to each TR module 30; ;

[0053] - in downlink communication, the reception of the SR receive signal; of each TR module 30; to source 44; and

[0054] - advantageously, in uplink communication, the exchange of information complementary control of the TR modules, from the source 40 to each TR module 30; (phase shift q>; and gain A; of the controllable components of the transmission and reception chains to perform beamforming, bias compensation, etc.).

[0055] In the particular embodiment illustrated in [Fig.3], the electronics of the module 40 comprise a circulator 41 connecting transmitting means and receiving means, on the one hand, and the antenna 44, on the other hand.

[0056] In this embodiment, communication between module 40 and each TR module 30; takes place along a dedicated channel, characterized by a particular frequency F;.

[0057] Consequently, module 40 includes a transmit / receive unit 70; to address each TR module 30 in transmit and receive.

[0058] Each unit 70; includes a waveform generator 73;, suitable for generating an individual emission signal SE; adapted.

[0059] The different units 70; are connected to the input of a summing 43, the output of which is connected to the circulator 4L. The antenna 44 thus emits an overall signal SE resulting from the sum of the individual emission signals SE;.

[0060] The antenna 44 is connected to the input of a splitter 42, the output of which is connected to the input of each of the units 70; so as to apply to each module the global reception signal SR resulting from the sum of the individual reception signals SR; captured by the antenna 44.

[0061] The input of a module 70; includes a filter 72;, centered on the characteristic frequency F; of the corresponding channel, so as to isolate the individual received signal SR;.

[0062] A demodulator 74; then allows the SR; signal to be demodulated, possibly taking into account the waveform generated by the corresponding generator 73i.

[0063] The raw signal is then transmitted to a conventional processing chain.

[0064] During transmission, module 40 transmits to the receiving transmission module 30; at the beginning of a recurrence period, the SE emission signal; then, at the end of the recurrence period, various control signals so that module 30; sets the value of its operating parameters for the next recurrence period.

[0065] In reception, the elementary reception signal SR; at the output of each transmit-receive module 30; is re-emitted into the cavity 4 towards the common antenna 44, the different elementary reception signals superimposed in the cavity so as to form an overall reception signal, the common antenna 44 collecting the overall reception signal SR.

[0066] The common antenna 44 must allow the different elementary antennas 34; (which are located on the same sphere) to be addressed with an identical amplitude, phase and polarization.

[0067] Note that if it is planned to create only one type of beam, it is not necessary to provide for data transmission to adjust the phases and amplitudes at the level of the modules 30;, these values ​​can be fixed in the active modules.

[0068] In order to limit the number of electronic components downstream, i.e. at the level of the radiating elements, the phase and amplitude control devices can be located away from the TR module upstream of the waveform generator of module 40. The components of the signals which must be radiated by each radiating element are therefore created upstream and transmitted to the TR module, which then only has the function of stimulating the corresponding radiating element.

[0069] The common antenna 44 is placed in the vicinity of the center C of the network antenna 1.

[0070] Various antennas are known that exhibit, with varying degrees of precision, the desired hemispherical radiation properties, without phase shift or polarity perturbation. Those skilled in the art are familiar with dipole, monopole, collinear, helical, etc. antennas.

[0071] For example, in [Fig. 4], the radiation pattern of a patch antenna in an axial plane (i.e. containing axis A) is shown. If at -3dB the angular opening of the main lobe 45 is approximately 100°, at -6dB the angular opening is approximately 130° and at -9dB the angular opening is approximately 155°.

[0072] Thus, an antenna can approach an omnidirectional antenna provided that it works with high attenuations.

[0073] But, in return, it is necessary to lower the noise level.

[0074] However, inside the cavity 4, there is a problem of the reflection of radio frequency electromagnetic waves emitted either by the source 40, or by the elementary antennas 34; of the TR modules, insofar as it is a medium confined by the metallic layer 12.

[0075] These reflections must therefore be attenuated so that the signal-to-noise ratio inside cavity 4 is sufficient to allow communication between communication modules 40 and 36;.

[0076] This is why, advantageously, the network antenna 1 is equipped with an electromagnetic wave absorption device 50.

[0077] As illustrated in [Fig.1], this is for example an absorption plane 50 covering the plane P forming the floor of the cavity 4 of the array antenna 1.

[0078] As illustrated in [Fig.5], the absorption plane 50 is for example a meta-material consisting of the superposition of a reflective layer 52, an electromagnetic wave absorbing layer 54 and a structured metallic layer 56.

[0079] A wave 60 originating from the cavity 4 and incident on the absorption plane 50 is transmitted by the structured metallic layer 56 provided that it has a first polarity compatible with the layer 56 so that the latter is transparent.

[0080] The transmitted wave 61 then propagates for the first time in the absorbing material 54.

[0081] At the interface with the reflective layer 52, the wave undergoes a change in its polarization while being reflected.

[0082] The reflected wave 62 propagates a second time in the absorbing material 54.

[0083] Its polarization having changed, the structured metallic layer 56 does not transmit it into the cavity 4, but reflects it.

[0084] The reflected wave 63 propagates a third time in the absorbing material 54.

[0085] At the interface with the reflective layer 52, it undergoes a change in its polarization, while being reflected.

[0086] The reflected wave 64 propagates a fourth time in the absorbing material 54.

[0087] Its polarization having changed a second time, the structured metallic layer 56 transmits it towards the cavity 4.

[0088] Wave 65 emerges in cavity 4 after four passes through the absorbing material. It is therefore strongly attenuated.

[0089] Thus, the background noise level can be greatly reduced in cavity 4.

[0090] With the implementation of a wireless link between the low-level electronics and With the front-end electronics (transmission and reception modules and radiating elements), we eliminate the need for cables and consequently the added weight they represent. This network antenna is therefore lightweight and compatible with carriers such as aerial drones.

[0091] Furthermore, the implementation of a wireless link avoids phase disparities. Indeed, electromagnetic radiation is homogeneous in phase regardless of its direction, whereas a multitude of cables will exhibit disparities in their lengths, and therefore in the phases of the signals they transmit.

[0092] The network antenna just presented finds applications in all applications requiring detection over a wide area. This is the case, for example, with airborne radar antennas, particularly for ground-to-air detection, electronic warfare systems, telecommunications antennas, etc.

Claims

Demands

1. Array antenna (1) comprising: - a hemispherical radome (10), of center C and radius R; - a plurality of radiating elements (20;), the radiating elements being carried by the radome; - a plurality of transmit-receive modules (30;), the transmit-receive modules being carried by the radome, each radiating element being associated with a transmit-receive module and electrically connected to it by one or more power supply links, characterized in that the array antenna further comprises: - a common radio communication module (40), equipped with a common antenna (44), placed at the center C of the hemispherical radome and connected to a transmit-receive electronics of the common radio communication module, each transmit-receive module (30i) comprising a communication module (36;), equipped with an elementary antenna (34;) for bidirectional radio frequency communication with the common radio communication module (40).

2. Array antenna according to claim 1, wherein the face radially inside the radome (10) is a metallic layer (12) electromagnetically insulating a cavity (4) inside the radome.

3. Antenna according to claim 2, wherein the cavity (4) is provided with an electromagnetic wave absorption device (50) to reduce background noise.

4. Antenna according to claim 3, wherein the absorption device is a meta-material covering a floor of the cavity (4).

5. Antenna according to claim 4, wherein the meta-material consists of the stacking of a reflection layer (52), an absorption layer (54) and a metallic plane (56), the metallic plane being perforated so as to present a periodic pattern suitable for trapping radio frequency waves in the thickness of the meta-material according to their polarization.

6. Antenna according to any one of claims 2 to 5, wherein, in reception, the elementary receive signal (SR) in output of each transmit receive module (30;) is re-emitted into the cavity (4) towards the common antenna (44), the different elementary receive signals superimposed in the cavity so as to form an overall receive signal (SR), the common antenna collecting the overall receive signal.

7. Antenna according to any one of the preceding claims, wherein the common antenna (44) is an omnidirectional antenna, having in any plane passing through an axis of symmetry (A) of the array antenna (1) an opening of at least 170° for an attenuation of -12dB.

8. Antenna according to claim 7, wherein the common antenna (44) is a "patch" type antenna.

9. Antenna according to any one of the preceding claims, wherein the radiating elements (20;) are covered with a matching layer (16), itself covered with a protective layer (18).

10. Antenna according to any one of the preceding claims, wherein, in transmit, the common antenna (44) emits a transmit signal (SE) which each transmit-receive module (30) collects for transmission.

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