The invention generally relates to radomes and more specifically to aircraft radomes having localized areas with different radio signal attenuation properties.
A radome is a structural, weather proof enclosure that protects a radar or radio antenna. Radomes protect antenna surfaces from weather and/or conceal antenna electronic equipment from view. Radomes also protect personnel from being injured from moving parts of the antenna. Radomes also improve the aerodynamic profile of an aircraft in the vicinity of the radome.
Radomes may have different shapes, such as spherical, geodesic, planar, etc., based on the intended use. Radomes are often made from fiberglass, PTFE coated fabrics, plastics, or other low weight, but structurally strong materials.
Fixed wing aircraft often use radomes to protect radar or radio antennas that are disposed on the aircraft body. For example, many aircraft include radomes that take the form of a nose cone on the forward end of the aircraft body to protect forward looking radar antennas, such as weather radar antennas. Radomes may also be found on the top, bottom, or aft parts of the aircraft body when the radome is protecting a radio communications antenna (e.g., a satellite communications antenna), or on the bottom of aircraft when protecting radio antennas for ground based communication. In these cases, the radomes may look like blisters or small domes on the aircraft body.
Generally, radomes must be large enough to allow free movement of the radar or radio antenna parts. For example, most weather radar antennas are gimbaled for movement about multiple axes. As a result, the weather radar antenna can be pointed in virtually any direction to look for weather in the vicinity of the aircraft. Thus, the radome must have uniform signal transmission and reception properties in all directions so that the radar antenna may be properly calibrated. Additionally, it may be desirable to produce radomes having structural properties that allow them to maintain their shape (so as not to change aerodynamic characteristics of the airframe) even when hit by foreign objects (such as birds) during flight. Because the radome must have uniform signal transmission and reception properties combined with structural strength aircraft radomes the signal transmission and reception properties are often compromised to ensure that the strength requirements are met.
Further features and advantages of the invention can be gathered from the claims, the following description, and the attached diagrammatic drawings, wherein:
Turning now to the Figures,
Each of the radomes 22, 26, and 30 may house an antenna that performs a different function. In one example the first radome 22 may house a communications antenna that transmits radio signals to a communications satellite and receives radio signals from a communications satellite. Similarly, in one example, the second radome 26 may house a communications antenna that transmits radio signals to a ground based radio facility and receives radio signals from a ground based radio facility. On the other hand, in one example, the third radome 30 may house a radar antenna that transmits radar energy and receives a reflected portion of the transmitted radar energy to locate weather formations ahead of the aircraft 10. Each of these radomes 22, 26, 30 may have different structural and transmit/receive characteristics. Regardless, each of the radomes 22, 26, and 30 must comply with local regulations, such as FAR Part 25.571, which is hereby incorporated by reference as of the filing date of this application, before being certified for use on aircraft.
Generally, the third radome 30, which houses a radar antenna, is uniform in construction, to allow the radar antenna (which is likely gimbaled), to transmit and receive radar signals with uniform attenuation through the third radome 30 at any point on the third radome 30. In other words, the third radome 30 must have uniform properties at all locations through which radar energy will be transmitted or received. Because the third radome must comply with local regulations governing aircraft damage, the transmission properties of the third radome 30 may be reduced by mechanical strength requirements dictated by these damage regulations. Said another way, mechanical strength requirements and radio signal attenuation properties are often at odds with one another in radome design.
Hereinafter, characteristics attributed to the first radome 22 and to the second radome 26 may be used interchangeably with either radome. For example, characteristics attributed to the first radome 22 may be equally attributable to the second radome 26 and vice versa. Furthermore, characteristics of the first and second radomes 22, 26, may be combined with one another.
In contrast to the third radome 30, the first and second radomes 22, 26, which are constructed in accordance with the teachings of the disclosure, may have decoupled mechanical and radio wave attenuation properties. In other words, the first and second radomes 22, 26, may have localized areas that differ from one another in mechanical strength characteristics and/or in radio wave attenuation characteristics. For example, the first radome 22 may have a first portion that is strong enough to satisfy local damage regulations while having a second portion that has better radio wave attenuation characteristics than the first portion. Said another way, the first radome 22 may have a first portion that is structurally capable of withstanding foreign object impact damage (such as a bird strike) without becoming structurally compromised (i.e., a stronger portion) and a second portion that is structurally weaker than the first portion (because it is located in an area that is not likely to be struck by a foreign object or in a location that requires less physical strength), but that has better radio signal attenuation properties than the first portion.
Turning now to
In one embodiment, the antenna 44 may be a phased array antenna that is mechanically steered. Phased array antennas generally include localized transmission areas and localized reception areas that are electronically or mechanically manipulated to synthesize an electromagnetic beam of radio energy in a desired direction. As a result, a phased array antenna may be located very close to the fuselage 14 of the aircraft 10 and the outer shell 40 may be located very close to the antenna 44 (because the antenna is not significantly moved during operation). Thus, the profile of the outer shell 40 may be minimized.
The outer shell 40 may have a first portion 50, which is at least partially oriented towards the front end 12 of the aircraft 10, a second portion 52, which is oriented aft of the first portion 50, and a third portion 54, which is oriented aft of the second portion 52. The first portion 50 may be the strongest portion structurally. The first portion 50 may be capable of withstanding foreign object damage while the aircraft 10 is in flight without becoming compromised. For example, the first portion 50 may be strong enough to withstand an impact from a four pound bird at the aircraft's maximum design cruise speed (Vc) at sea level or at 0.85 Vc at 8,000 feet without compromising the ability of the aircraft 10 to successfully complete a flight.
Due to the added strength, the first portion 50 has greater radio signal attenuation than the second and third portions 52, 54. The second portion 52, because it is angled with respect to a direction of flight (e.g., the second portion 52 is oriented at a more acute angle with respect to the actual flight path of the aircraft than the first portion 50), will not require the same structural strength as the first portion 50. Thus, the second portion 52 may be designed to reduce radio signal attenuation at the expense of structural strength or rigidity. For example, a transmission signal T transmitted through the second portion 52 may be less attenuated than the same transmission signal T when transmitted through the first portion 50 because the second portion 52 is made of materials (or structures) that allow better transmission of radio signals than the materials (or structures) of the first portion 50. As a result, the antenna 44 may require less power to perform its communication function than an antenna housed by a conventional uniformly constructed radome. While the overall attenuation reduction may depend on design constraints, in some cases, a signal may experience an attenuation reduction of 2 dB or more when transmitted through the second portion 52 than when transmitted through the first portion 50.
Similarly, the third portion 54, because it is on the rear side of the radome, will not require the same structural strength as the first portion 50 because the third portion 54 is protected from impacts by shadowing from the forward structure. Thus, the third portion 54 may be designed to reduce radio signal attenuation, similar to the second portion 52. For example, a receive signal R received through the third portion 54 may be less attenuated than the same receive signal R when received through the first portion 50. Similar to the second portion 52, in some cases, a signal received through the third portion 54 may experience an attenuation reduction of 2 dB or more when compared to the same signal received through the first portion 50. The second and third portions 52, 54 may be designed to reduce attenuation for either a transmission signal or a receive signal. Optionally, the second and third portions 52, 54 may be designed to reduce attenuation for both transmission signals and for receive signals.
A second embodiment of the radome 22 is illustrated in
Turning now to
Referring now to
The radome 122 may include a main body portion 170 that extends from the mounting assembly in a direction away from the aircraft fuselage 14, and a skirt portion 172. The skirt portion 172 aerodynamically connects the main body portion 170 to the aircraft fuselage. In one embodiment, the skirt portion may be formed of 3/32 inch thick aluminum sheeting. In other embodiments, the skirt portion 172 may be formed from 0.125 inch thick 6061-T6 aluminum sheeting.
The main body portion 170 may include a structurally strong first portion 150 near the front 161 of the radome 122, a reduced attenuation or second portion 152, aft of the front 161, another reduced attenuation or third portion 154 aft of the second portion 152, and another structurally strong first portion 150 aft of the third portion 154. The structurally strong first portion 150 may form a circumference of the main body portion 170, above the skirt portion 172. The second portion 152 and the third portion 154 may be separated by the first portion 150, or the second portion 152 and the third portion 154 may be joined to one another without any intermediate structures. In still other embodiments, the second portion 152 and the third portion 154 may be combined to form a single reduced attenuation portion.
A first antenna 144a may be disposed in the first mounting location 166 and a second antenna 144b may be disposed in the second mounting location 168, as illustrated in
In one embodiment, the first portion 250a, the first portion 250b, the second portion 252, and the third portion 254 may be formed from an A-sandwich, C-sandwich, laminate, or half-wave structure. Similarly, the edgeband 180 and the cross bridge 182 may be formed from an A-sandwich, C-sandwich, laminate, or half-wave structure.
In one embodiment, the cross bridge 282 may include a plurality of support posts 284 that extend inward from an inner surface of the radome 222, as illustrated in
The radome may also include a bulkhead plate 286 that extends from an inner surface of the first portion 250a. The bulkhead plate 286 structurally reinforces the first portion 152 without interfering with a line of sight transmission or reception to/from the antennas. In one embodiment, the bulkhead plate may be formed from 0.25 inch thick 6061-T651 aluminum, or other suitable material.
In other embodiments, the radomes may have first and second portions having reduced radio signal attenuation (for either transmit and receive bands or for different frequencies), without having a mechanically strong portion.
The disclosed radomes solve the problem of decoupling mechanical strength requirements from radio signal transmission and receiving attenuation requirements. The disclosed radomes also solve the problem of minimizing radio signal attenuation across different radio signal frequencies. As a result, the disclosed radomes are lighter weight with better performance than known homogeneous radomes.
The disclosure is not limited to aircraft radomes. The disclosure could be applied to virtually any radome having localized areas of reduced radio signal attenuation. For example, the disclosed radomes may be used on any type of vehicle (e.g., automobiles, trains, boats, submarines, etc.) or stationary radar facilities. The features of the invention disclosed in the description, drawings and claims can be individually or in various combinations for the implementation of the different embodiments of the invention.
This application is a non-provisional application that claims priority benefit of U.S. Provisional Patent Application No. 61/902,549, filed Nov. 11, 2013, the entirety of which is hereby incorporated by reference herein.
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Child | 15468808 | US |