Patent Grant
8045329
This disclosure generally relates to antennas, and more particularly, to a thermal dissipation mechanism that may be used to absorb heat from a radar absorbing member of an antenna.
Antennas operating in the microwave frequency range use various directing or reflecting elements with relatively precise physical characteristics. To protect these elements, a protective covering commonly referred to as a radome may be placed over the antenna. The radome separates the elements of the antenna from various environmental aspects, such as precipitation, humidity, solar radiation, or other forms of debris that may compromise the performance of the antenna.
According to one embodiment, a heat dissipation system includes an elongated radar absorbing member configured with a thermal dissipation mechanism. The radar absorbing member extends proximate a junction of a microwave antenna enclosure that houses an antenna and a radome that covers an opening in the microwave antenna enclosure. The radar absorbing member absorbs electro-magnetic energy incident upon the junction. The thermal dissipation mechanism absorbs heat generated by the absorbed electro-magnetic energy.
Some embodiments of the disclosure may provide numerous technical advantages. For example, one embodiment of the radar absorbing member configured with the thermal dissipation mechanism may allow increased output power density levels than may be provided by known radar absorbing member designs. Radar absorbing members are often used with radomes of microwave antennas to reduce its effective radar cross-section (RCS), reduce electro-magnetic interference, and/or improve the antenna's pattern. Because these radar absorbing members inherently absorb electro-magnetic radiation, they may limit the transmitted output power density generated by the microwave antenna. In some embodiments, the thermal dissipation mechanism actively cools the radar absorbing member during operation; thus, the output power density level generated by the microwave antenna may be increased without causing excessive heating of the radar absorbing member and/or other components adjacent to the radar absorbing member, such as the radome configured on the microwave antenna.
Some embodiments may benefit from some, none, or all of these advantages. Other technical advantages may be readily ascertained by one of ordinary skill in the art.
A more complete understanding of embodiments of the disclosure will be apparent from the detailed description taken in conjunction with the accompanying drawings in which:
Antennas used to propagate electro-magnetic radiation in the microwave frequency ranges are often covered with radomes for protection from damage due to operation in uncontrolled environments. For antennas having multiple radiating elements that operate in the microwave frequency range, radomes may be positioned over an opening of the microwave antenna enclosure such that electro-magnetic radiation passes through freely while shielding its relatively delicate elements and associated electronics from the ambient environment. Thus, radomes may typically include low radio-frequency (RF) loss materials to not unduly affect the radiation pattern of the antenna.
The transparency of some antennas to enemy radar, such as those used in military applications may be important. Although radomes may provide relatively good protection, their constituent materials may form an electrical discontinuity with adjacent antenna enclosures that house their respective antennas. The junction at the edge of the radome may be used to reduce the electro-magnetic interference (EMI) contribution to other co-located antennas by reducing the electro-magnetic energy trapped in the radome. It can also improve antenna pattern by reducing scattered contributions to sidelobe levels. It can also be used to reduce its radar cross-section (RCS). To remedy this problem, the junction may be covered by a radar absorbing material to absorb electro-magnetic radiation incident upon the junction. This radar absorbing material, however, may trap a significant amount of heat when used in conjunction with antennas that generate relatively high output power density signals.
Radiating elements 12 may be any type of physical structure that transmits and/or receives electro-magnetic radiation. Radiating elements 12 transmit electro-magnetic radiation with an output power density that may cause heat build-up inside radar absorbing member 22. In some cases, radiating elements 12 generate electro-magnetic radiation having an output power density that is greater than 5 Watts per square inch (W/in2) and may sometimes be many Watts per square inch (W/in2). Electro-magnetic radiation at these output power density levels may cause excessive heating within the radar absorbing member 22. In some cases, the radar absorbing member 22 may be helpful in improving the antenna performance or radar cross-section (RCS).
Although the radar absorbing member 22 may be useful for enhancing the transparency of microwave antenna 10 from detection by radar, its electro-magnetic absorbing characteristic also absorbs electro-magnetic radiation generated by radiating elements 12. Because radar absorbing member 22 may be made of a generally thermally insulative material, it may experience excessive heat build-up when radiating elements 12 transmit electro-magnetic radiation. In some cases, this excessive heat build-up in radar absorbing member 22 may cause various types of damage to radome 18, such as delamination of the various layers of radome 18 from one another.
Thermal spreader 26 may be thermally coupled to support frame 28 using any suitable approach. In one embodiment, thermal spreader 26 is maintained in physical contact with radar absorbing member 22 and support frame 28 using fasteners, such as bolts, or a suitable adhesive. In one embodiment, thermal coupling may be enhanced by a relatively thin layer of heat transfer compound, such as a ceramic-based thermal grease or a metal-based thermal grease that is sandwiched between thermal spreader 26 and support frame 28 and/or radar absorbing member 22.
Thermal spreader 26 may be made of any suitable type of material. In one embodiment, thermal spreader 26 is made of a metal, such as aluminum, that has a relatively high degree of thermal conductivity. In another embodiment, thermal spreader 26 has a shape that does not unduly affect the propagation pattern of antenna elements 12 or adversely affect the transparency of microwave antenna 10 to radar detection. Examples of suitable materials for this purpose may include, aluminum, copper, chemical vapor deposition (CVD) diamond, pyrolytic graphite, K-1100 carbon fibers and copper infiltrated carbon fibers.
Multiple relatively small hollow tubes 30a or a relatively larger, single hollow tube 30b may be used to convey fluid coolant through radar absorbing member 22. Hollow tubes 30a and 30b may have any suitable type of cross-sectional shape. In the particular embodiment shown, hollow tubes 30a have a generally circular cross-sectional shape while the single hollow tube 30b has a cross-sectional shape that is generally similar to the shape of radar absorbing member 22, which in this particular case is triangular in shape.
In operation, a fluid coolant flows through hollow tubes 30a and 30b to absorb heat generated inside radar absorbing member 22. This fluid coolant may operate as a two-phase fluid coolant in which the coolant enters hollow tubes 30a and 30b in liquid form and boils or vaporizes such that some or all of the fluid coolant leaves the hollow tubes 30a and 30b as a vapor. In other embodiments, the fluid coolant may operate as a single-phase coolant in which the coolant enters hollow tubes 30a and 30b as a liquid, increases in temperature, and exits again in all or mostly liquid form.
Heat absorbed by the fluid coolant may be removed in any suitable manner. In one embodiment, movement of the fluid coolant through hollow tubes 30a and 30b may be provided by convection. That is, the heating of fluid coolant within radar absorbing member 22 causes its movement to another location where it may be cooled. In this case, hollow tubes 30a and 30b may be thermally coupled to radar enclosure 14 for cooling of the fluid coolant. In the particular embodiment shown, hollow tubes 30a and 30b are coupled to antenna cooling system 33 that is also used to remove heat from other portions of microwave antenna 10. For example, antenna cooling system 33 may be configured to receive heated fluid coolant from an electrical circuit that is used to generate electro-magnetic energy through antenna elements 12.
The fluid coolant used in the embodiment of
Modifications, additions, or omissions may be made to microwave antenna 10 without departing from the scope of the invention. The components used to make radar absorbing member 22 may be integrated or separated. For example, hollow tubes 30a and/or 30b may be integrally formed with radar absorbing member 22 in which they are made of the same material from which radar absorbing material is made. Moreover, the operations of the thermal dissipation mechanism may be performed by more, fewer, or other components. For example, antenna cooling system 33 may also include a thermometer that is coupled to radar absorbing member 22 for monitoring its operating temperature and thus, controlling its operating temperature within a specified range. As used in this document, “each” refers to each member of a set or each member of a subset of a set.
Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformation, and modifications as they fall within the scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3818983 | Grandia | Jun 1974 | A |
| 4044396 | Haws et al. | Aug 1977 | A |
| 4057104 | Altoz | Nov 1977 | A |
| 4493010 | Morrison et al. | Jan 1985 | A |
| 4998181 | Haws et al. | Mar 1991 | A |
| 5276455 | Fitzsimmons et al. | Jan 1994 | A |
| 5423498 | Fluegel | Jun 1995 | A |
| 5488380 | Harvey et al. | Jan 1996 | A |
| 5570092 | Kohin-Nitzschelm | Oct 1996 | A |
| 5930117 | Gengel | Jul 1999 | A |
| 5960861 | Price et al. | Oct 1999 | A |
| 5977710 | Kuramoto et al. | Nov 1999 | A |
| 6059017 | Sayegh | May 2000 | A |
| 6084772 | Pell et al. | Jul 2000 | A |
| 6377219 | Smith | Apr 2002 | B2 |
| 6388317 | Reese | May 2002 | B1 |
| 6456224 | Cobb et al. | Sep 2002 | B1 |
| 6784837 | Revankar et al. | Aug 2004 | B2 |
| 6937471 | Haws et al. | Aug 2005 | B1 |
| 7017651 | Wilson et al. | Mar 2006 | B1 |
| 7061446 | Short, Jr. et al. | Jun 2006 | B1 |
| 7178586 | Goldman et al. | Feb 2007 | B2 |
| 7227753 | Weber et al. | Jun 2007 | B2 |
| 7416017 | Haws et al. | Aug 2008 | B2 |
| 7443354 | Navarro et al. | Oct 2008 | B2 |
| 7548424 | Altman et al. | Jun 2009 | B2 |
| 20040032275 | Cader et al. | Feb 2004 | A1 |
| 20040185906 | Iwahashi et al. | Sep 2004 | A1 |
| 20050190116 | Syed et al. | Sep 2005 | A1 |
| 20070096982 | Kalian et al. | May 2007 | A1 |
| 20080062650 | Wilson et al. | Mar 2008 | A1 |
| 20080106482 | Cherrette et al. | May 2008 | A1 |
| 20080150802 | Kalian et al. | Jun 2008 | A1 |
| 20090084527 | Rummel et al. | Apr 2009 | A1 |
| 20100194661 | Harokopus et al. | Aug 2010 | A1 |
| 20100206523 | Chen et al. | Aug 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 1 635 187 | Mar 2006 | EP |
| 870917 | Jun 1961 | GB |
| 10051213 | Feb 1998 | JP |
| 2003298270 | Oct 2003 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20100277867 A1 | Nov 2010 | US |
