De-icing installation for an antenna system

Abstract

An antenna system (10) comprises an antenna (12) for transmitting and / or receiving radio signals, an enclosure (16) (preferably a self-supporting weatherproof enclosure, such as, e.g., a radome) defining a cavity (18) for protecting therein at least parts of the antenna from weather, and a de-icing installation (20). The de-icing installation includes a low-frequency-sound generator (22) connected to the cavity for generating acoustic waves therein and thereby induce mechanical oscillations in the enclosure capable of shaking off ice and / or snow buildup on the weather-exposed side of the enclosure. In further aspects, the invention relates to a weatherproof enclosure defining a cavity therein for protecting antenna components from weather, comprising a de-icing installation and to a method of retrofitting an antenna system.

Description

DE-ICING INSTALLATION FOR AN ANTENNA SYSTEMBackground of the Invention

[0001] The invention generally relates to a de-icing installation for an antenna system, in particular an antenna system comprising an enclosure that protects therein at least parts of the antenna from weather (e.g., a radome).

[0002] Satellite communication requires the use of ground stations to transfer data from one location to another. Radio frequency (RF) free space communication is a widely used technology to transport information.

[0003] A ground station can be located anywhere on Earth and subjected to very different environmental conditions, which can affect its performance. In particular, snow and / or ice accretion can strongly attenuate RF signals. Thermal de-icing systems are currently the most widespread, but they involve high operation costs and have a large CO2 footprint. Therefore, there is constant research on (more) efficient de-icing systems.

[0004] US 2019 / 379101 A1 discloses an ice-inhibiting radome system. A radome bladder spans over an antenna aperture. An air supply provides an oscillating flow of air at a predetermined flow rate over a plurality of pressurization / depressurization cycles. The radome bladder is fluidly connected to the air supply to receive the oscillating flow of air. A mechanical tensioning assembly is coupled to the radome bladder so as to provide adjustable tensioning of the inner and outer stretched membranes. The outer membrane forms the outer surface of the radome, on which snow or ice may build up. Pressurization of the radome bladder curves and stretches at least the outer membrane, which can shatter any ice or snow built up on the outer surface. The cyclic pressurization / depressurization operations may prevent ice or snow adhesion to the outer surface.

[0005] EP 2 382 685 A1 relates to a system and a method for clearing water from dish antenna covers. The system comprises a cover that is positioned on the outer surface of a dish antenna so as to cover the concave opening of the dish antenna. The cover thereby inhibits the accumulation of water, either frozen or liquid, on the inner concave surface of the antenna. The system further includes a mechanical vibration structure that is engaged with the cover that can be selectively activated to induce the cover tovibrate. By vibrating the cover, the accumulation of both frozen and liquid water or moisture on the outer surface of the cover can be reduced.

[0006] JP H05175715 A discloses a method and structure for preventing snow deposition on a reflector antenna. A sheet radome spans over the antenna. The driven member of an actuator is coupled to the sheet radome to impart vibrations to the sheet radome. Thanks to the vibrations, snow deposited on the sheet radome surface is shaken off.

[0007] US 5 172 024 A discloses a device for the removal of the ice formed on the surface of a wall, notably an optical or radio-electrical window. The device comprises a piezoelectric actuator.

[0008] DE 4031035 A1 relates to an antenna reflector cleaning and deicing system. The cleaning and de-icing system uses a mechanical shaking device for imparting vibrations to all or part of the reflector relative to its mounting, for dislodging deposited dirt or ice.

[0009] US 8 207 900 B1 discloses an ice-inhibition system for a communication or a radar antenna. The system includes a membrane placed before the antenna aperture and secured to the antenna along the antenna's perimeter. The membrane has one or more membrane excitation points identified thereon and when an outward membrane excitation force is delivered to the one or more excitation points, a shock wave is generated at each of the one or more membrane excitation points and propagates away from the membrane excitation points along the membrane toward the perimeter region removing any ice crystals formed on the outer surface of the membrane.

[0010] A low-tech example of a de-icing system is a snow rope, which is attached with one end to the top of a radome, and which may be manually swept over the radome by drawing on the lower end along the radome basis.Summary of the Invention

[0011] According to an aspect of the invention, an antenna system comprises an antenna for transmitting and / or receiving radio signals, an enclosure, such as, e g., a radome (preferably a self-supporting weatherproof enclosure, in particular a structural self-supporting weatherproof enclosure) defining a cavity for protecting therein at least parts of the antenna from weather, and a de-icing installation. As used herein, de-icingdesignates the process of removing ice, e.g., snow or frost, from a surface. The deicing installation includes a low-frequency-sound generator connected to the cavity for generating acoustic waves therein and thereby induce mechanical oscillations in the enclosure capable of shaking off ice and / or snow buildup on the weather-exposed side of the enclosure. If necessary, plural low-frequency-sound generators may be connected to the cavity for generating acoustic waves therein.

[0012] In a further aspect, the invention relates to a weatherproof enclosure, e.g., a radome, defining a cavity therein for protecting antenna components (e.g., one or more reflective surface and / or one or more feed antennas) from weather, comprising a deicing installation including a low-frequency-sound generator connected to the cavity for generating acoustic waves therein and thereby induce mechanical oscillations in the enclosure.

[0013] In yet a further aspect, the invention relates to a method of retrofitting an antenna system. The antenna system may comprise an antenna for transmitting and / or receiving radio signals and a weatherproof enclosure defining a cavity for protecting therein at least parts of the antenna from weather. The retrofitting method comprises installing a de-icing installation, including connecting a low-frequency-sound generator to the cavity, the low-frequency-sound generator being configured for generating acoustic waves with a frequency in the range from 5 Hz to 100 Hz in the cavity. If the antenna system does not comprise a weatherproof enclosure, the retrofitting method may comprise the installation of such an enclosure as well.

[0014] As used herein, the expression “low-frequency sound” refers to sound with frequencies in the range from 5 Hz to 100 Hz. “Infrasound” generally refers to sound with frequencies below the lower limit of the human hearing range, which is often given as 20 Hz to 20 kHz. However, other boundary values can be found in the literature, due to the fact that there is considerable variation between individuals. In the present document, the term “infrasound” is used to designate acoustic waves with frequencies in the range from 5 Hz to 30 Hz. The low-frequency sound generator may comprise or consist of an infrasound generator configured to produce acoustic waves with frequencies in the range from 5 Hz to 30 Hz.

[0015] The de-icing installation may include a controller connected to the low- frequency-sound generator. The controller may be configured to control the amplitude, the acoustic pressure and / or the frequencies, i.e., the spectrum, of the acoustic waves.Such control may be dynamic, e.g., in reaction to input provided to the controller (input entered by a user via a human-machine interface and / or data provided by one or more external sources, e.g., sensors). The controller may, for instance, be configured to adjust the amplitude, the acoustic pressure and / or the frequencies (spectrum) of the acoustic waves in such a way as to excite one or more normal modes of the enclosure.

[0016] The controller may also be configured to control operation of the low- frequency-sound generator taking into account on-site weather data. The expression “on-site weather data” means weather data relating to the installation site of the antenna system.

[0017] On-site weather data may include at least one of temperature, atmospheric pressure, relative or absolute humidity, dew point, wind speed, wind direction, solar radiation, precipitation, rainfall, and snowfall.

[0018] The de-icing installation may comprise a local weather station connected to the controller for providing at least part of the on-site weather data.

[0019] Additionally, or alternatively, the controller may be connected (e.g., over the Internet) to a meteorological service network for sourcing at least part of the on-site weather data.

[0020] The de-icing installation may comprise one or more vibration monitoring devices for monitoring the mechanical oscillations of the enclosure, e.g., the amplitude and / or the frequency of these oscillations. The one or more vibration monitoring devices may be connected to the controller, which may be configured to control operation of the low-frequency-sound generator taking into account vibration data provided by the one or more vibration monitoring devices.

[0021] The one or more vibration monitoring devices may comprise one or more of the following: motion sensors (e.g., laser-based contactless motion sensors), accelerometers (fixed to one or more locations on the enclosure), strain gauges, and ultrasonic transducers. However, other types of motion sensors are not excluded. The de-icing installation may comprise plural vibration monitoring devices for detecting different normal modes that are excited by the acoustic waves.

[0022] The antenna system may comprise a reflector antenna, e.g., a parabolic antenna or a parabolic torus reflector antenna. Such a reflector antenna may include one or plural reflectors, e.g., a main reflector and one or more subreflectors. Examplesof reflector antennas include: prime focus feed parabolic antenna, offset feed antenna, Cassegrain antenna, or Gregorian antenna. However, the antenna system could also comprise one or more antennas of a different type. The antenna system preferably includes an antenna with a diameter of at least 2 m.

[0023] The antenna system may comprise an antenna mount for pointing the antenna into different directions, e.g., for tracking a satellite, an airplane, a missile, an astronomical radio source, etc.

[0024] The enclosure is transparent to the radio waves the antenna transmits or receives. The enclosure preferably comprises a radome. Such radome may be of various shapes, e.g., spherical, planar, curved, geodesic, etc., and may be made from various RF-transparent materials, e.g., fiberglass, composite panels, fabric, etc. The radome may enclose the antenna and the antenna mount. Alternatively, the enclosure may be mounted on the antenna mount in such a way as to enclose at least part of the antenna but not the antenna mount. In particular, if the antenna system comprises a reflector antenna, the enclosure may be mounted on the reflector so as to enclose the reflective surface(s) of the reflector antenna and, optionally, the feed antenna.

[0025] It is worthwhile noting that the antenna system according to the invention allows for reduced heating, which has several advantages: reduced power consumption (operation costs reduction), less deformation of the antenna geometry (in particular of the reflective surfaces) due to thermal expansion and reduced infrared signature of the antenna system (this may be relevant, in particular, for military or astronomical applications).

[0026] Inducing oscillations of the enclosure by acoustic waves has the advantage that local excitation using small-sized actuators can be avoided or at least largely reduced. Furthermore, by generating acoustic waves in the cavity of the enclosure, no interference with functional areas of the antenna (in particular in its field of view) is necessary. The connection between the low-frequency-sound generator and the cavity of the enclosure can be made outside of the field of view of the antenna.

[0027] The de-icing installation has comparatively low energy consumption and can be scaled to different cavity (i.e. , enclosure) sizes. Furthermore, in certain applications the de-icing installation may be activated while the antenna is in operation.

[0028] In the present document, the verb “to comprise” and the expression “to be comprised of” are used as open transitional phrases meaning “to include” or “to consist at least of”. Unless otherwise implied by context, the use of singular word form is intended to encompass the plural, except when the cardinal number “one” is used: “one” herein means “exactly one”. Ordinal numbers (“first”, “second”, etc.) are used herein to differentiate between different instances of a generic object; no particular order, importance or hierarchy is intended to be implied by the use of these expressions. Furthermore, when plural instances of an object are referred to by ordinal numbers, this does not necessarily mean that no other instances of that object are present (unless this follows clearly from context). When this description refers to “an embodiment”, “one embodiment”, “embodiments”, etc., this means that the features of those embodiments can be used in the combination explicitly presented but also that the features can be combined across embodiments without departing from the invention, unless it follows from context that features cannot be combined.

[0029] As used herein, the expression “at least one of’ followed by a list of items means any one of the listed items or any combination of any plural items from the list. The conjunction “and” possibly preceding an item from the list (e.g., typically, the last item) shall not be construed as an exclusion of combinations that do not include the item(s) preceded by “and” or that do not include all items from the list.

[0030] Specific preferred embodiments include the following Numbered Embodiments (“NEs”):

[0031] NE 1 : An antenna system, comprising an antenna for transmitting and / or receiving radio signals; a weatherproof enclosure defining a cavity for protecting therein at least parts of the antenna from weather; and a de-icing installation including a low-frequency-sound generator connected to the cavity for generating therein acoustic waves with a frequency in the range from 5 Hz to 100 Hz and thereby inducing mechanical oscillations in the enclosure.

[0032] NE 2: The antenna system according to NE 1 , wherein the low-frequency- sound generator is configured to produce acoustic waves with a frequency in the range from 5 Hz to 30 Hz.

[0033] NE 3: The antenna system according to NE 1 or 2, wherein the de-icing installation includes a controller connected to the low-frequency-sound generator, thecontroller configured to control operation of the low-frequency-sound generator taking into account on-site weather data.

[0034] NE 4: The antenna system according to NE 3, wherein the on-site weather data include at least one of temperature, atmospheric pressure, relative or absolute humidity, dew point, wind speed, wind direction, solar radiation, precipitation, rainfall, and snowfall.

[0035] NE 5: The antenna system according to NE 3 or 4, wherein the de-icing installation comprises a local weather station connected to the controller for providing at least part of the on-site weather data.

[0036] NE 6: The antenna system according to NEs 3 to 5, wherein the controller is connected to a meteorological service network for sourcing at least part of the on-site weather data.

[0037] NE 7: The antenna system according to NEs 1 to 6, wherein the de-icing installation comprises one or more vibration monitoring devices for monitoring the mechanical oscillations of the enclosure.

[0038] NE 8: The antenna system according to NE 7, wherein the one or more vibration monitoring devices are connected to the controller, and wherein the controller is configured to control operation of the low-frequency-sound generator taking into account vibration data provided by the one or more vibration monitoring devices.

[0039] NE 9: The antenna system according to NE 7 or 8, wherein one or more vibration monitoring devices comprise one or more of the following: motion sensors, accelerometers, strain gauges, and ultrasonic transducers.

[0040] NE 10: The antenna system as claimed according to any one of NEs 1 to 9, wherein the antenna system comprises a reflector antenna, e.g., a parabolic antenna.

[0041] NE 11 : The antenna system according to any one of NEs 1 to 10, wherein the antenna system comprises an antenna mount for pointing the antenna into different directions, e.g., for tracking a satellite.

[0042] NE 12: The antenna system according to any one of NEs 1 to 11 , wherein the enclosure comprises a radome.

[0043] NE 13: The antenna system according to NEs 11 and 12 in combination, wherein the radome encloses the antenna and the antenna mount.

[0044] NE 14: The antenna system according to NE 11 , wherein the enclosure is mounted on the antenna mount so as to enclose at least part of the antenna but not the antenna mount.

[0045] NE 15: The antenna system according to NE 14 in combination with NE 10, wherein the enclosure is mounted on the reflector so as to enclose the one or more reflective surfaces of the antenna and, optionally, the feed antenna.

[0046] NE 16: A weatherproof enclosure, e.g., a radome, defining a cavity therein for protecting antenna components from weather, comprising a de-icing installation including a low-frequency-sound generator connected to the cavity for generating acoustic waves therein and thereby induce mechanical oscillations in the enclosure.

[0047] NE 16: A method of retrofitting an antenna system comprising an antenna for transmitting and / or receiving radio signals and a weatherproof enclosure defining a cavity for protecting therein at least parts of the antenna from weather, the method comprising installing a de-icing installation including connecting a low-frequency- sound generator to the cavity for generating therein acoustic waves with a frequency in the range from 5 Hz to 100 Hz.

[0048] Preferred embodiments are also defined in the claims.Brief Description of the Drawings

[0049] By way of example, preferred, non-limiting embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:Fig. 1 : is a schematic drawing of an antenna system according to a first embodiment of the invention, featuring a generally spherical radome;Fig. 2: is a schematic drawing of an antenna system according to a second embodiment of the invention, featuring a generally conical radome;Fig. 3: is a diagram of the simulated sound pressure distribution on the internal surface of a generally spherical radome;Fig. 4: is an illustration of the first natural mode oscillations of the radome of Fig. 3.Detailed Description of Preferred Embodiments

[0050] The invention uses sound waves, in particular low-frequency-sound, to excite systems exposed to snowfall and / or icing to prevent and remove accretions. Accordingto certain embodiments, a low-frequency-sound generator is attached to the structure of interest. It creates sound waves, which propagate inside enclosure cavity, at one or more specific frequencies. This results in an oscillating pressure distribution against the inner wall(s) of the enclosure, which will also start oscillating and cause snow / ice to slip off from the weather-exposed outer surface.

[0051] The working frequency of the system may be chosen close to the natural frequencies of the air cavity to generate a standing wave inside the cavity and to maximize the sound pressure. The spectrum of the generated sound may include frequencies from the infrasound to the ultrasound domain, including the audible domain. For the de-icing of antenna system enclosures, the generated sound spectrum will include infrasound frequencies and / or frequencies from the low-frequency audible range. Operation of the sound generator in a narrow frequency band at a resonance frequency of the cavity may be preferred. The excitation amplitude delivered by the generator can be adjusted to reach a suitable structure’s response for the application. The sound waves can be created from an infrasound generator, e.g., using compressed air, and / or a low-frequency sound generator (for example a loudspeaker).

[0052] The system can be adapted to any kind of cavity shape. The embodiments discussed hereinafter serve as illustrations of the working principle but shall not be interpreted as limiting the invention to any specific cavity or enclosure shape.

[0053] The low-frequency-sound generator can be operated continuously or in cycles. Cycle times can be adjusted based on structural response and environmental conditions.

[0054] Fig. 1 illustrates an antenna system 10 according to a preferred embodiment of the invention. The antenna system 10 may, e.g., be or be part of a radio telescope or a ground station, in particular, a satellite Earth station. The antenna system 10 comprises a parabolic antenna 12 for transmitting and / or receiving radio signals and an antenna mount 14 for pointing the antenna 12 into different directions and / or tracking an object (source or target of radio waves) that may not be stationary with respect to the antenna system. The antenna system comprises a radome 16, i.e., a self-supporting weatherproof enclosure, that protects the antenna 12 and the antenna mount 14 from weather. In the context of the present document, “self-supporting” means “capable of supporting its own weight”. The radome is preferably dimensionedand shaped in such a way that its internal cavity 18 does not impede the movement of the antenna 12.

[0055] The antenna system 10 comprises a de-icing installation 20 for removing accumulations of ice, e.g., snow or frost, from the outer surface of the radome 16. The de-icing installation 20 includes a low-frequency-sound generator 22 connected to the radome cavity 18 for generating acoustic waves therein and thereby induce mechanical oscillations in the radome 16 that shake off ice and / or snow buildup on the weather-exposed side of the radome 16. While only one low-frequency-sound generator 22 is shown, plural low-frequency-sound generators could be connected to the cavity 18 for generating acoustic waves therein.

[0056] The low-frequency-sound generator 22 may comprise an insonator 24, e g., operated with compressed air, connected to a resonance tube 26, which terminates into a diffusor 28. The diffusor 28 may be connected to the radome cavity via an attachment socket 30 at the base of the radome 16 or of the antenna system 10. The low-frequency-sound generator 22 may be generally of the type of low-frequency- sound generators used as infrasound soot cleaners in industrial installations, e.g., in chimneys, boilers, etc. It should be noted that the schematic drawing does not necessarily show the correct position of the low-frequency-sound generator 22. In a real implementation, the de-icing installation is arranged such that it does not interfere with operation of the antenna.

[0057] The de-icing installation 20 may include a controller 32 connected to the low- frequency-sound generator 22. The controller 32 may comprise a standalone microcontroller or be integrated, e.g., as a software application, in a general-purpose or special-purpose computer or server. The controller 32 may be configured to control the amplitude, the acoustic pressure and / or the frequencies, i.e., the spectrum, of the acoustic waves generated by the low-frequency-sound generator 22. The controller 32 preferably comprises a user interface (human machine interface, HMI). As shown in Fig. 1 , the controller 32 may be connected to sensors providing information about the on-site weather, vibration monitor devices 36 providing information about the oscillations of the radome 16 and the antenna control system for exchange of data between the de-icing installation 20 and the antenna control system.

[0058] The controller 32 is preferably configured to dynamically control the low- frequency-sound generator 22 depending on on-site weather data and / or vibration dataprovided by the one or more vibration monitoring devices 36, taking into account user- defined operation parameters. The controller 32 may, for instance, adjust the duration, the amplitude, the acoustic pressure and / or the frequencies (spectrum) of the acoustic waves. The low-frequency-sound generator 22 is preferably controlled in such a way as to excite one or more normal modes of the radome 16. The controller 32 may monitor whether the excitation of these modes is efficient based on the feedback received from the vibration monitoring devices 36. The controller 32 may adjust the operation parameters of the low-frequency-sound generator 22 to optimize the excitation of the normal modes of the radome. This may be helpful to compensate, e.g., for drifts (e.g., related to ageing of components) or other changes of the resonant frequencies of the radome structure. The controller 32 may also be configured to limit the oscillations of the enclosure by reducing the duration, the amplitude and / or the acoustic pressure of the acoustic waves and / or by detuning the frequencies (spectrum) of the acoustic excitation.

[0059] The de-icing installation 20 preferably comprises a local weather station 34 connected to the controller 32 for providing at least part of the on-site weather data. Additionally, or alternatively, the controller 32 may be connected (e.g., over the Internet) to a meteorological service network for sourcing at least part of the on-site weather data. Weather data used by the controller 32 may include temperature, atmospheric pressure, relative or absolute humidity, dew point, wind speed, wind direction, solar radiation, precipitation, rainfall, and / or snowfall. It will be appreciated that the controller 32 may normally be configured to operate the low-frequency-sound generator 22 only when needed, i.e., in wintry weather conditions with snowfall or risk of icing.

[0060] The de-icing installation 20 preferably comprises one or more vibration monitoring devices 36 for monitoring the mechanical oscillations of the radome 16.

[0061] The one or more vibration monitoring devices may comprise, e.g., motion sensors (e.g., laser-based contactless motion sensors), accelerometers (fixed to one or more locations on the enclosure), strain gauges, or ultrasonic transducers. Other types of motion sensors are not, but may be, excluded. The vibration monitoring devices 36 may be arranged so as to allow measurement of the different normal modes that are excited by the acoustic waves.

[0062] The infrasonic generator 22 may be attached at the base of the radome structure (riser) and transmits sound waves into the interior cavity of the radome. This excites the air volume, and an oscillating pressure distribution will result on the inner surfaces of the radome, as shown, for example, in Fig. 3. Consequently, the pressure distribution excites the radome structure which will start oscillating as well, as illustrated in Fig. 4. Snow / ice accumulation removal and / or prevention may be achieved by exciting modes with a high oscillation amplitude at the top of the radome.

[0063] Fig. 2 illustrates an antenna system 110 according to a second preferred embodiment of the invention. Instead of a radome covering the antenna and its mount (cf. Fig. 1), the antenna system 110 comprises an enclosure 116 mounted on the edge of the parabolic reflector so as to enclose the reflector surface of the parabolic antenna 112 and the feed antenna, but not the antenna mount 114. The enclosure 116 is weatherproof so as to protect the enclosed antenna components from weather. It moves together with the antenna 112. It may be self-supporting or supported by other components of the antenna, e g., the supporting structure of a subreflector or the feed antenna. According to a preferred variant, the enclosure 116 comprises a weatherproof fabric fixed along the contour of the main reflector and spanned over the supporting structure of the subreflector or the feed antenna so as to form a generally conical radome.

[0064] Albeit not shown in the drawing, the antenna system 110 of Fig. 2 comprises a de-icing installation with a low-frequency-sound generator for removing accumulations of ice, e.g., snow or frost, from the outer surface of the enclosure 116. The de-icing installation includes a low-frequency-sound generator connected to the enclosure cavity 118 for generating acoustic waves therein and thereby induce mechanical oscillations that shake off ice and / or snow buildup on the weather-exposed side of the enclosure 116.

[0065] The de-icing installation of the antenna system 110 of Fig. 2 may further comprise the same components as the de-icing installation shown in Fig. 1 , e.g., a controller, a weather station, vibration monitor devices, etc.

[0066] Fig. 3 illustrates a (simulated) sound pressure distribution on the internal surface of a generally spherical radome (as in the embodiment of Fig. 1 ) obtained with a low-frequency-sound generator connected to the radome base. The pressure distribution inside the cavity was simulated based on the parameters of an infrasoundgenerator from Heat Management (a company specialized in the production of such generators). The frequency of the generator was chosen close to the natural frequency of the air volume (roughly equal to 8 Hz). The natural modes depend on the geometrical characteristics of the cavity. The simulation was based on finite element analysis of a large radome (25m in diameter), of known design, comprised of composite panels (Kevlar™ skins sandwiching a foam core) assembled with screws. The simulation results demonstrated that the first modes of the radome structure could be excited as their frequencies were close to the natural frequencies of the cavity (about 10 Hz for the 1ststructural mode and about 20 Hz for the second structural mode). In the simulations, high oscillations could be obtained at the top part of the radome, which is the most suitable location for de-icing / snow removal applications. After adjustment of the acoustic excitation to limit the stresses to a sufficiently low level to avoid any damage of the radome structure, an amplitude of about 12 mm could be achieved. Fig. 4 is a schematic illustration of the simulated oscillations. The rest position of the radome 16 is indicated by the continuous line. The dash-dotted lines show the extremal positions of the radome during the oscillation in an exaggerated fashion.

[0067] It will be appreciated that de-icing installations with low-frequency-sound generators may be retrofitted into existing antenna systems comprising an enclosure.

[0068] While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

Claims1 . An antenna system, comprising an antenna for transmitting and / or receiving radio signals; a weatherproof enclosure defining a cavity for protecting therein at least parts of the antenna from weather; and a de-icing installation including a low-frequency-sound generator connected to the cavity for generating therein acoustic waves with a frequency in the range from 5 Hz to 100 Hz and thereby inducing mechanical oscillations in the enclosure.

2. The antenna system as claimed in claim 1 , wherein the low-frequency-sound generator is configured to produce acoustic waves with a frequency in the range from 5 Hz to 30 Hz.

3. The antenna system as claimed in claim 1 or 2, wherein the de-icing installation includes a controller connected to the low-frequency-sound generator, the controller configured to control operation of the low-frequency-sound generator taking into account on-site weather data.

4. The antenna system as claimed in claim 3, wherein the on-site weather data include at least one of temperature, atmospheric pressure, relative or absolute humidity, dew point, wind speed, wind direction, solar radiation, precipitation, rainfall, and snowfall.

5. The antenna system as claimed in claim 3 or 4, wherein the de-icing installation comprises a local weather station connected to the controller for providing at least part of the on-site weather data.

6. The antenna system as claimed in any one of claims 3 to 5, wherein the controller is connected to a meteorological service network for sourcing at least part of the on-site weather data.

7. The antenna system as claimed in any one of claims 1 to 6, wherein the de-icing installation comprises one or more vibration monitoring devices for monitoring the mechanical oscillations of the enclosure.

8. The antenna system as claimed in claim 7, wherein the one or more vibration monitoring devices are connected to the controller, and wherein the controller isconfigured to control operation of the low-frequency-sound generator taking into account vibration data provided by the one or more vibration monitoring devices.

9. The antenna system as claimed in claim 7 or 8, wherein one or more vibration monitoring devices comprise one or more of the following: motion sensors, accelerometers, strain gauges, and ultrasonic transducers.

10. The antenna system as claimed in any one of claims 1 to 9, wherein the antenna system comprises a reflector antenna, e.g., a parabolic antenna.11 . The antenna system as claimed in any one of claims 1 to 10, wherein the antenna system comprises an antenna mount for pointing the antenna into different directions, e.g., for tracking a satellite.

12. The antenna system as claimed in any one of claims 1 to 11 , wherein the enclosure comprises a radome.

13. The antenna system as claimed in claims 11 and 12 taken in combination, wherein the radome encloses the antenna and the antenna mount.

14. The antenna system as claimed in claim 11 , wherein the enclosure is mounted on the antenna mount so as to enclose at least part of the antenna but not the antenna mount.

15. The antenna system as claimed in claim 10, wherein the antenna system comprises an antenna mount for pointing the antenna into different directions, e.g., for tracking a satellite, wherein the enclosure is mounted on the reflector so as to enclose the one or more reflective surfaces of the antenna and, optionally, the feed antenna, but not the antenna mount.

16. An antenna system, comprising an antenna, e.g., a reflector antenna, for transmitting and / or receiving radio signals; an antenna mount for pointing the antenna into different directions; a radome, the radome being a weatherproof enclosure defining a cavity for protecting therein at least parts of the antenna from weather, the radome enclosing the antenna and the antenna mount; and a de-icing installation including a low-frequency-sound generator connected to the cavity for generating therein acoustic waves with a frequency in the rangefrom 5 Hz to 100 Hz, preferably from 5 Hz to 30 Hz, and thereby inducing mechanical oscillations in the enclosure.

17. The antenna system as claimed in claim 16, wherein the de-icing installation includes a controller connected to the low-frequency-sound generator, the controller preferably being configured to control operation of the low-frequency- sound generator taking into account on-site weather data, wherein the on-site weather data preferably include at least one of temperature, atmospheric pressure, relative or absolute humidity, dew point, wind speed, wind direction, solar radiation, precipitation, rainfall, and snowfall.

18. The antenna system as claimed in claim 17, wherein the de-icing installation comprises a local weather station connected to the controller for providing at least part of the on-site weather data or wherein the controller is connected to a meteorological service network for sourcing at least part of the on-site weather data.

19. The antenna system as claimed in claim 17 or 18, wherein the de-icing installation comprises one or more vibration monitoring devices for monitoring the mechanical oscillations of the enclosure, wherein the one or more vibration monitoring devices are connected to the controller, and wherein the controller is configured to control operation of the low-frequency-sound generator taking into account vibration data provided by the one or more vibration monitoring devices, the one or more vibration monitoring devices preferably comprising one or more of the following: motion sensors, accelerometers, strain gauges, and ultrasonic transducers.

20. A method of retrofitting an antenna system comprising an antenna for transmitting and / or receiving radio signals, an antenna mount for pointing the antenna into different directions, and a radome, the radome being a weatherproof enclosure defining a cavity for protecting therein at least parts of the antenna from weather, the method comprising installing a de-icing installation including connecting a low-frequency-sound generator to the cavity for generating therein acoustic waves with a frequency in the range from 5 Hz to 100 Hz.

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