Communications: radio wave antennas – Antennas – With aircraft
Reexamination Certificate
1999-12-29
2001-03-06
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With aircraft
C343S872000, C343S895000
Reexamination Certificate
active
06198445
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to aircraft antennas and more particularly to an antenna component that is a structural member of the aircraft.
Modern aircraft have a need to provide radio communication over a variety of frequency ranges and communication modes. For example, radio communication may be in the VHF band using amplitude modulation (AM) and/or frequency modulation (FM) or in the UHF band. In order to communicate effectively, the aircraft must include multiple antennas dispersed on the aircraft. Typically, the aircraft will include antennas mounted behind the radio transparent skin of the aircraft, and/or include exterior blade antennas mounted to the skin of the aircraft.
For effective communication, the antenna dimensions should be in the same order of magnitude as the wavelength of the signal being propagated. In this respect, the wavelength for operation in the VHF/AM and UHF band (i.e., 0.150 to 2.0 GHz) is approximately 0.1 to 2 meters. Accordingly, for effective communication within this range, the antenna must have a size correspondingly large. However, this is not practical because an antenna of this size would be aerodynamically inefficient. Therefore, small blade antennas electrically matched through impedance tuning networks are used. The blade antenna is a small fin protruding from the skin of the aircraft that is used as the radiating element.
Blade antennas are aerodynamically inefficient because they protrude from the skin of the aircraft. Typically, multiple blade antennas are used on the aircraft for the multiple communications band (i.e., UHF, VHF/FM, VHF/AM). The blade antenna exhibits poor performance characteristics at lower frequencies (i.e., 30-88 MHz). The blade antenna is constructed to withstand the forces subjected to the antenna, however the blade antenna is still susceptible to impact damage (i.e., break off). The blade antenna does not add any structural strength to the aircraft, and interferes with the aerodynamic efficiency of the aircraft.
In the prior art, antenna radiating elements have been embedded within the skin of the aircraft. Such radiating elements provide an antenna structure for the aircraft that is structurally integrated within the skin thereof. However, these prior art antenna structures are typically difficult to manufacture and install. Additionally, the prior art antenna structures do not exhibit ideal gain characteristics and fatigue life of these prior art antenna structures is significantly reduced due to the configuration of the antenna radiating element.
Specifically, the prior art antenna structures consisted of a spiral center fed radiating element embedded within the structure of the aircraft. The spiral center fed radiating element was difficult to install and did not exhibit desired gain and/or power characteristics. Furthermore, the antenna structure with the spiral center fed radiating element is not adaptable for existing aircraft. In this respect, the prior art antenna structure would need to be integrated into the original design of the aircraft.
The present invention addresses the above-mentioned deficiencies in prior aircraft antenna design by providing an antenna that is a structural member of the aircraft. In this respect, the aircraft antenna of the present invention is a structural member of the aircraft that can be adapted for multiple uses. The antenna structure of the present invention provides improved gain, higher power, improved fatigue life, and lower signature over the prior art spiral center fed antenna structure by using an end fed radiating element. Accordingly, the antenna structure of the present invention provides an improvement over the prior art inasmuch as the antenna exhibits desired operating characteristics.
BRIEF SUMMARY OF THE INVENTION
A conformal load bearing antenna structure for attachment to an aircraft having an outer skin. The conformal load bearing antenna structure comprises a top face sheet and an end fed radiating element disposed thereon. Disposed adjacent to the top face sheet is a dielectric and a structural core disposed adjacent to the dielectric. In the preferred embodiment, a bottom face sheet is disposed adjacent to the structural core and an absorber is disposed adjacent to the structural core. An absorber pan is disposed adjacent to the absorber. Accordingly, the top face sheet, the dielectric, the structural core, and the bottom face sheet are configured to provide structural strength to the aircraft when the antenna is attached to the outer skin thereof.
In the preferred embodiment, the antenna structure further comprises a transmission mechanism disposed adjacent to the absorber and in electrical communication with the radiating element. The transmission mechanism comprises a center feed and at least one transmission strip radiating outwardly therefrom. Each of the transmission strips comprises an inner portion connected to the center feed and an outer portion having a contact. Each of the contacts is in electrical communication with the radiating element. In the preferred embodiment, the radiating element comprises four spirals, each of which are in electrical communication with respective ones of the contacts.
Typically, the top face sheet, the dielectric, the structural core, and the bottom face sheet are all bonded together with an appropriate adhesive. It will be recognized, that the top face sheet may be fabricated from a fiberglass material and the dielectric is fabricated from an epoxy loaded with titanium dioxide. The structural core of the antenna structure is fabricated from a honeycomb material, while the bottom face sheet is fabricated from fiberglass. The absorber is fabricated from a graphite loaded honeycomb material in order to provide the necessary dielectric characteristics. The antenna structure additionally can include an absorber pan. The absorber pan encloses the absorber and is fabricated from a graphite material.
In accordance with the present invention, there is provided a method of forming a conformal load bearing antenna structure for an aircraft from a top face sheet, an end fed radiating element, a dielectric, a structural core, a bottom face sheet, an absorber and an absorber pan. The method comprises bonding the end fed radiating element to the top face sheet and then bonding the top face sheet to the dielectric. Next, the structural core is bonded to the dielectric and the bottom face sheet is bonded to the structural core. Finally the absorber is bonded to the bottom face sheet in order to form the load bearing antenna structure. It will be recognized that the antenna structure may further comprise an absorber pan that is bonded to the absorber and the bottom face sheet. It will be recognized that the antenna structure may further comprise a transmission mechanism that is positioned in electrical communication with the radiating element. In this respect, the transmission mechanism is positioned beneath the absorber and has contacts which are placed through respective apertures of the absorber, bottom face sheet, structural core, and dielectric. Therefore, RF signals may be sent and received by the radiating element via the transmission mechanism and respective contacts.
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Alt Kevin Herman
Coughlin Daniel Patrick
Durham Michael David
Gath James Kenneth
Kudva Jayanth Nandalke
Anderson Terry J.
Boch, Jr. Karl J.
Northrop Grumman Corporation
Phan Tho
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