Antenna module unit with a VLF antenna module

Abstract

Antenna module unit (10) for receiving VLF radio signals, comprising a first loop-shaped or curved rod-shaped antenna body (44) and a first signal amplification unit (38) electrically connected to the first antenna body (44), characterized in that the first antenna body (44) and the first signal amplification unit (38) are arranged within a cylindrical envelope (U) which has a length of at most 1300 mm, in particular at most 1215 mm, and a diameter of at most 200 mm, in particular at most 176 mm.

Description

[0001] The present invention relates to an antenna module unit for receiving VLF radio signals, comprising a first loop-shaped or curved rod-shaped antenna body and a first signal amplification unit electrically connected to the first antenna body.

[0002] In the field of maritime reconnaissance, particularly for submarines and naval vessels, the reception of signals in the Very Low Frequency (VLF) range plays a crucial role. VLF signals in the frequency range of approximately 3 kHz to 30 kHz are capable of penetrating seawater, which allows underwater communication between submarines without them having to surface or reveal their position through active transmission.

[0003] Receiving such signals, however, presents considerable technical challenges. Due to the extremely long wavelengths (10 km - 100 km), resonant antenna structures are not feasible. Instead, the maximum size is determined by the dimensions of the vessels. For submarines, for example, VLF loops are known to be used, wound around the outer diameter of the hull. However, such antenna structures not only involve a high degree of design complexity but also cause the problem that the VLF antenna is difficult to shield against electromagnetic radiation from inside the vessel. Furthermore, the installation, repair, and replacement of such a conventional loop antenna are very time-consuming and expensive.

[0004] Against this background, the object of the invention is to provide an antenna module unit that allows reliable detection of VLF signals while simultaneously reducing the effort required for manufacturing, installation, retrofitting and repair.

[0005] According to the present invention, this problem is solved by an antenna module unit for receiving VLF radio signals, comprising a first loop-shaped or curved rod-shaped antenna body and a first signal amplification unit electrically connected to the first antenna body, wherein the first antenna body and the first signal amplification unit are arranged within a cylindrical envelope which has a length of at most 1300 mm, in particular at most 1215 mm, and a diameter of at most 200 mm, in particular at most 176 mm.

[0006] According to an important feature of the invention, it is therefore proposed to significantly reduce the size of the first antenna body so that it fits within the cylindrical enclosure with the specified dimensions. Simultaneously, the reduction in efficiency or signal strength associated with the reduction in the size of the antenna body is compensated for by also arranging the associated first signal amplification unit within the cylindrical enclosure and thus in close proximity to the antenna body. Signal losses on the path from the antenna body to the signal amplification unit can therefore be significantly reduced.

[0007] It has been found that an acceptable antenna efficiency can be achieved in this way despite the significantly reduced size of the antenna element. One explanation for this effect is that both antenna elements with dimensions on the order of the dimensions of the watercraft and antenna elements with the reduced dimensions according to the present invention exhibit qualitatively comparable situations in that the antenna dimensions are very small compared to the wavelengths of the signals to be received. The inductance and radiation resistance of the antenna elements are then negligible, and the structural behavior approaches pure capacitance as the frequency of the signals approaches zero.The inventive contacting of the signal amplification unit directly on the antenna body (within the same relatively small envelope), in combination with a corresponding electrical matching of the antenna module unit, is then sufficient to receive VLF signals with sufficient quality.

[0008] The cylindrical enclosure according to the invention represents a geometric specification and can be understood as the virtual boundary of a space with the specified dimensions within which the antenna module unit, in particular the first antenna body and the first signal amplification unit, are housed, preferably completely housed. The cylindrical enclosure can, in particular, correspond to a space typically available on watercraft for accommodating antenna module units, for example, the interior of a radome, in which the antenna module unit can be housed and protected on the vehicle. The miniaturization of the antenna body and the specific dimensions of the enclosure thus contribute, both individually and especially in combination, to reducing the effort required for manufacturing, installation, retrofitting, and repair.

[0009] In one embodiment of the invention, an effective receiving area of ​​the first antenna body, or an antenna plane of the first antenna body defined by the loop shape or by the curvature of the curved rod shape, can be orthogonal to the longitudinal axis of the envelope. In this way, the effective receiving area can have an optimal spatial orientation relative to the vehicle when the antenna module unit is installed in a space on the vehicle corresponding to the cylindrical envelope, for example, a radome. The first antenna body can, in particular, have a substantially flat design, i.e., be arranged, for example, within a plate-shaped envelope, so that the antenna plane corresponds to the plane of the plate. For example, the first antenna body can have a ring shape with a ring diameter of a maximum of 200 mm, and in particular a maximum of 176 mm.

[0010] In a further embodiment of the invention, the antenna module unit can also comprise a base body to which a first antenna body is mounted, wherein the first antenna body is electrically insulated from the base body. For example, the first antenna body can concentrically surround the base body and be connected to the base body circumferentially at at least one section by a retaining element. The base body can mechanically hold the first antenna body in position. Furthermore, the base body can provide structural stabilization and a mechanical connection between the first antenna body and the first signal amplification unit and / or hold possible further components of the antenna module unit.

[0011] In a further embodiment of the invention, the antenna module unit can comprise a radome in which the first antenna body and the first signal amplification unit are housed, the enclosing structure being defined by an internal geometry of the radome. Such a radome can protect the antenna module unit, including the first signal amplification unit, from mechanical influences, moisture, salt water, and other environmental influences. The radome is designed, in particular, to be largely transparent to electromagnetic waves.

[0012] In a further embodiment of the invention, the first antenna body and the first signal amplification unit can be part of a first antenna module, and the antenna module unit can further comprise at least one second antenna module with a second antenna body and a second signal amplification unit, the second antenna module also being arranged within the enclosure. The antenna module unit can thus be a multifunctional antenna that enables the reception, and optionally also the transmission, of radio signals in different frequency ranges in a common compact structure.

[0013] For example, the second antenna module can be selected from: - an antenna module for mobile and network services, which is configured to process the 2G / GSM standard, particularly in the 900 MHz and 1800 MHz bands, and / or 4G / LTE, particularly in the 850 MHz, 1800 MHz and 2600 MHz bands, and / or 5G, particularly in the sub-6 GHz band, and / or WLAN, particularly in the 2400 MHz and 5000 MHz bands, an antenna module for navigation and satellite-based services, which is configured to process frequencies for GPS, in particular L1 and L2, and / or Iridium, in particular in the range of 1610 MHz to 1626.5 MHz, and / or Inmarsat-C, in particular in the receive range of 1530 MHz to 1545 MHz and / or in the transmit range of 1626.5 MHz to 1646.5 MHz, an antenna module for tactical data links and identification, which is configured to process frequencies for Link-16, particularly in the range of 960 MHz to 1215 MHz, and / or IFF, particularly in the range of 980 MHz to 1150 MHz, and an antenna module for the VHF range, in particular from 30 MHz to 174 MHz, and / or the UHF range, in particular from 220 MHz to 512 MHz.

[0014] The examples of possible antenna modules given each extend the receiving capabilities and, where applicable, also the transmitting capabilities of the antenna module unit in frequency ranges important for communication on or under water.

[0015] In a further embodiment of the invention, the first antenna body can be electrically connected to an inner conductor of a coaxial cable, wherein the inner conductor can be electrically connected to a signal-carrying contact of the signal amplification unit. With such a configuration, insulation of the conductor from other metallic parts of the antenna module unit is unnecessary, and the structure is protected from interference by the outer sheath of the coaxial cable. The outer conductor of the coaxial cable can, in particular, be connected to ground. If the antenna module unit comprises a base body to which the first antenna body is held by means of a retaining element, the coaxial cable, or at least the inner conductor of the coaxial cable, can, in particular, run along or within the retaining element to contact the first antenna body.

[0016] The invention will now be described in greater detail using an exemplary embodiment and with reference to the accompanying drawings. These depict: Fig. 1 a side view of an antenna module unit according to an embodiment of the invention; Fig. 2 a side view of the antenna module unit Fig. 1, without radome; Fig. Figure 3 shows a schematic representation of the electronics module; and Fig. Figure 4 shows a section of the perspective view of the antenna module unit. Fig. 1 in the vicinity of the active antenna module for the VLF range.

[0017] In Fig. 1 is an antenna module unit according to the invention, generally designated by reference numeral 10. The antenna module unit 10 has a column-shaped structure extending along a central axis X. A radome 12 forms an outer protective shell of the antenna module unit 10. The antenna module unit 10 has a substantially circular cylindrical shape over a total length L. An electronic module 14 is arranged at a lower end of the structure.

[0018] Fig. Figure 2 shows the antenna module unit 10 in a view without the radome 12. A plurality of antenna bodies 16, 18, 20 are arranged distributed along the central axis X. In the embodiment shown here, the antenna module unit comprises a total of six antenna modules: an antenna module 21 for mobile communication and network services, an antenna module 22 for the VHF range, an antenna module 24 for the UHF range, an active antenna module 26 for the VLF range, an antenna module 28 for navigation and satellite-based services, and an antenna module 30 for tactical data links and identification. It is conceivable that the antenna module 21 for mobile communication and network services and the antenna module 30 for tactical data links and identification are implemented together in the form of a single antenna module.

[0019] The dimensions of the circular cylindrical radome 12, in particular its internal dimensions, and its length L define a virtual envelope U within which the antenna modules 21, 22, 24, 26, 28, 30, in particular their antenna bodies, and the electronic module 14 are arranged. The envelope U preferably has a length L of approximately 1300 mm and a cylinder diameter of approximately 200 mm.

[0020] In the illustrated embodiment, a first antenna body 16 and a second antenna body 18 are at least partially assigned to the VHF antenna module 22, while the second antenna body 18 and the third antenna body 20 are at least partially assigned to the UHF antenna module 24. The third antenna body 20 can also be used for mobile communication and network services, as well as for tactical data links and identification. The VHF antenna module 22 and the UHF antenna module 24 can functionally share the second antenna body 18, resulting in two functionally separate antenna modules 22 and 24, each with a dipole antenna consisting of three antenna bodies 16, 18, and 20. This leads to a compact geometry, allowing a large number of antenna modules to be integrated into a small space. This allows the frequency bandwidth described above to be achieved using the majority of antenna modules.

[0021] It has been shown that shortening the respective antenna bodies 16, 18, 20 can result in, among other things, advantageous radiation characteristics by providing rounded sections at the axial longitudinal ends of the antenna bodies. Therefore, the antenna bodies 16, 18, 20 include a rounded section 16a, 18a, 20a at at least one axial longitudinal end, which has a convexly curved dome shape. In the illustrated embodiment, a further rounded section 18c is formed at the opposite axial longitudinal end of the second antenna body 18. Between the rounded sections 18a and 18c, the antenna body 18 has a circular cylindrical section 18b, which connects the rounded sections 18a and 18c, respectively. At one upper end of the antenna module unit 10, the antenna module 28 for navigation and satellite-based services is arranged.Furthermore, the antenna module for the VLF / HF range 26 is located at the upper end of the antenna module unit.

[0022] In Fig. Figure 3 schematically depicts the electronic module 14, which comprises a plurality of amplification units 32, 34, 36, 38, 40, and 42. In the illustrated embodiment, the electronic module 14 includes a corresponding amplification unit for each of the plurality of antenna modules mentioned above. It is also conceivable that at least some of the amplification units are combined into a single unit. This can further increase the level of integration. The respective amplification unit is configured to amplify received input signals for further processing. The outputs of at least some of the amplification units 32, 34, 36, 38, 40, and 42 can advantageously be queried and processed simultaneously. Alternatively, it is also conceivable that the outputs of the amplification units can be queried and processed temporarily in isolation from one another.

[0023] Fig.Figure 4 shows a section of the perspective view of the antenna module unit 10 in the vicinity of the active antenna module 26 for the VLF range. It can be seen that the antenna module 26 comprises an annular antenna body 44, for example, a wire ring, which concentrically surrounds a central longitudinal axis X of the antenna module unit 10. The antenna body 44 is preferably held on a base body 46 of the antenna module unit 10 by means of a plurality of retaining elements 48, such that the antenna body 44 surrounds the base body 46 at a radial distance. The base body 46 can be any structural element of the antenna module unit to which other antenna modules or the antenna bodies 16, 18, 20 described above are also attached. The antenna body 44 is preferably electrically insulated from the base body 46, for example by making the retaining elements 48 from an insulating material.

[0024] In the exemplary embodiment shown here, one of the retaining elements 48 can simultaneously be used to provide a feed point 50 to which the antenna body 44 is electrically contacted. A coaxial cable 52 is advantageously used for this purpose, the inner conductor of which can be connected to the antenna body 44 at the feed point 50. This has the advantage that the signal-carrying inner conductor is shielded by the outer conductor and the jacket of the coaxial cable 52 and can be easily routed in an insulating manner from other metallic parts of the antenna module unit. Shielding plays a particularly important role here due to the extremely low signal voltages. In the present example, the coaxial cable 52 can be routed through a central opening in the retaining element 48 to run from the antenna body 44 to a central section of the base body 46.

[0025] In the center of the antenna module unit 10, the coaxial cable 52 can then be guided along the central axis in a threading tube (not shown) to the VLF amplification unit 38 in the electronics module 14.

[0026] In the present embodiment, the VLF antenna module 26, in conjunction with the VLF amplification unit 38 of the electronic module 14, is preferably operated as an active VLF antenna (active antenna card). The antenna can be approximated as a pure capacitor and delivers a very high-impedance signal (in the megaohm range). To amplify the received signal, a correspondingly high-impedance amplifier can be used, or an impedance matching device can be employed to adapt the high input impedance to the input impedance typically required by a low-impedance amplifier (preferably 50 ohms).

[0027] To achieve sufficient antenna efficiency and thus an acceptable signal-to-noise ratio, adjusting the antenna's capacitance plays a crucial role. For the VLF antenna of the exemplary embodiment, the general model consisting of a generator (antenna voltage U) and a capacitor (C) connected in series is used. The gain G of the VLF antenna (loop antenna) is given in this case by G = C × I, where l denotes the circumference of the antenna body. Since the size and thus the circumference of the antenna body 46 is predetermined by the miniaturization within the enclosure U according to the invention, the capacitance must be carefully adjusted or tuned to achieve sufficient gain or a sufficient signal-to-noise ratio.

[0028] For capacitive matching of the VLF amplifier unit 38, it can contain one or more capacitors to provide additional input capacitance. The optimal capacitance can be found by noise matching, by measuring the signal-to-noise ratio of a defined received signal for different input capacitances of the VLF amplifier unit 38. An optimally matched input capacitance is obtained at the maximum signal-to-noise ratio over the widest possible bandwidth of VLF frequencies. In this way, the capacitive coupling between the VLF antenna body 44 and the VLF amplifier unit 38 is optimized.

Claims

[1] Antenna module unit (10) for receiving VLF radio signals, comprising a first loop-shaped or curved rod-shaped antenna body (44) and a first signal amplification unit (38) electrically connected to the first antenna body (44), characterized by , that the first antenna body (44) and the first signal amplification unit (38) are arranged within a cylindrical envelope (U) which has a length of at most 1300 mm, in particular at most 1215 mm, and a diameter of at most 200 mm, in particular at most 176 mm. [2] Antenna module unit (10) according to claim 1, wherein an effective receiving area of ​​the first antenna body (44) or an antenna plane of the first antenna body (44) defined by the loop shape or by the curvature of the curved rod shape is orthogonal to the longitudinal axis (X) of the envelope (U). [3] Antenna module unit (10) according to claim 1 or claim 2, wherein the first antenna body (44) has a ring shape with a ring diameter of a maximum of 200 mm, in particular a maximum of 176 mm. [4] Antenna module unit (10) according to one of the preceding claims, furthermore characterized by a base body (46) to which a first antenna body (44) is held, wherein the first antenna body (44) is electrically insulated from the base body. [5] Antenna module unit (10) according to claim 3 or claim 4, characterized by , that the first antenna body (44) surrounds the base body (46) concentrically and is connected to the base body (46) in the circumferential direction at least at one section by a retaining element (48). [6] Antenna module unit (10) according to one of the preceding claims, furthermore characterized bya radome (12) in which the first antenna body (44) and the first signal amplification unit (38) are accommodated, wherein the envelope (U) is defined by an internal geometry of the radome (12). [7] Antenna module unit (10) according to any one of the preceding claims, characterized by , that the first antenna body (44) and the first signal amplification unit (38) are part of a first antenna module (26) and that the antenna module unit (10) further comprises at least a second antenna module (21, 22, 24, 28, 30) with a second antenna body (16, 18, 20) and a second signal amplification unit (32, 34, 36, 40, 42), wherein the second antenna module is also arranged within the envelope (U). [8] Antenna module unit (10) according to claim 7, wherein the second antenna module is selected from: ◯ an antenna module (21) for mobile communications and network services, which is configured to process the 2G / GSM standard, in particular in the 900 MHz and 1800 MHz bands, and / or 4G / LTE, in particular in the 850 MHz, 1800 MHz and 2600 MHz bands, and / or 5G, in particular in the sub-6 GHz band, and / or WLAN, in particular in the 2400 MHz and 5000 MHz bands, ◯ an antenna module (28) for navigation and satellite-based services, which is configured to process frequencies for GPS, in particular L1 and L2, and / or Iridium, in particular in the range from 1610 MHz to 1626.5 MHz, and / or Inmarsat-C, in particular in the receive range from 1530 MHz to 1545 MHz and / or in the transmit range from 1626.5 MHz to 1646.5 MHz, ◯ an antenna module (30) for tactical data links and identification, which is configured to process frequencies for Link-16, particularly in the range of 960 MHz to 1215 MHz, and / or IFF, particularly in the range of 980 MHz to 1150 MHz, and ◯ an antenna module (22, 24) for the VHF range, in particular from 30 MHz to 174 MHz, and / or the UHF range, in particular from 220 MHz to 512 MHz. [9] Antenna module unit (10) according to any one of the preceding claims, characterized by , that the antenna body (44) is electrically connected to an inner conductor of a coaxial cable (52), wherein the inner conductor is electrically connected to a signal-carrying contact of the signal amplification unit (38).

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