US2814800A - Broadband pitot tube antenna - Google Patents

Description

Nov. 26, 1957 w. R. MARTIN ET AL BROADBAND PITOT TUBE ANTENNA Filed July 19, 1955 INVENTORS WILLIAM R. MARTIN FREDERIC R. ZBORIL GROUND LINE United States Patent 2,814,800 BROADBAND PITOT TUBE ANTENNA William R. Martin, Burbank, and Frederic R. Zboril, Sherman Oaks, Calif., assignors to Lockheed Aircraft Corporation, Burbank, Calif.

Application July 19, 1955, Serial No. 522,952 7 Claims. (Cl. 343-708) This invention relates, generally, to aircraft antennas and, more particularly, to a broadband Pitot tube antenna which is omnidirectional in the horizontal plane and which employs the externally mounted Pitot tube and its supporting mast as a part of the basic radiating structure.

The antenna requirements on both commercial and military aircraft can generally be met with conventional apparatus only by employing a plurality of separate special purpose antennas. This is due in part to the wide frequency bandwidth needed for the different transmitting and receiving equipment such as the ultra high frequency (U. H. F.) communication equipment, the distance measuring equipment (D. M. E.) and the identification friend or foe (I. F. F.) equipment. The normal requirement for using several special purpose antennas is also brought about by the demand for antenna configurations having low air drag characteristics. In order to comply with the above requirements it is usual practice to utilize flush mounted antennas since they create substantially no additional air drag and while they are not suitable for broadband operation, satisfactory results may be obtained using more than one such antenna. This is not desirable however because of the space and structural problems created. Obviously it would be much better if large areas of the fuselage were not needed for antenna installations.

An object of this invention is to provide an antenna which utilizes the Pitot tube and Pitot tube mast on an aircraft as a radiating element whereby substantially no increase in air drag is created, thus providing a design which is comparable on this basis to the conventional flush mounted antenna and yet is far superior insofar as its operating bandwidth capabilities are concerned.

Another object of this invention is to provide a Pitot tube antenna having an operating bandwidth including the range between 225 to 400 and 950 to 1230 megacycles while exhibiting a standing wave ratio of less than 2 to 1. These characteristics make the antenna suitable for use with any or all of the transmitting and receiving equipment normally found in aircraft. Hence it may serve as a combination U. H. F., D. M. E. and I. F. F. antenna to replace the plural antenna arrangements commonly used for the same purpose.

Another object of this invention is to provide a Pitot tube antenna for aircraft having a structural configuration and ruggedness making it suitable for use as an arrestor hook such as is required on carrier based aircraft.

Still another object of this invention is to provide a Pitot tube antenna which will no longer make it necessary to reserve large areas on the underside of the fuselage for antenna installations. Thus, a more efiicient, structural design of the airplane is made possible.

Further and other objects will become apparent from a reading of the following detailed description, especially when considered in combination with the accompanying drawing wherein like numerals refer to like parts.

In the drawing:

Figure 1 is a view showing a typical installation of the Pitot tube antenna on an aircraft;

Figure 2 is a fragmentary sectional side view of the antenna showing the details of construction;

Figure 3 is a side view of the antenna;

Figure 4 is a perspective view showing the antenna feed element;

Figure 5 is a front view of the antenna; and

- allel with the longitudinalaxis engage cap 8 2,814,300 Patented Nov. 26, 195? TCQ Figure 6 is a sectional view taken on line 6--6 of Figure 2.

Antenna 1, as best shown in Figure l, is secured to the underside of aircraft fuselage 2 adjacent the nose 3 thereof in the usual location of the dynamic pressure measuring Pitot tube installation. Pitot tube 4 extends outwardly and forwardly from the aircraft fuselage in conventional fashion, as shown in Figure 2, for receiving ram air through the tip end 5 which is aligned generally parof the aircraft. A mast 6, also projects outwardly and forwardly from the aircraft fuselage and encloses all but the tip end 5 of the Pitot tube to absorb the bending loads which would otherwise be applied to the Pitot tube by the slipstream air.

Mast 6 extends outwardly from fuselage 2 a distance preferably no greater than 9 inches, but in any event slightly beyond the tip end 5 of Pitot tube 4. The outer end '7 of mast 6 is generally flat and substantially parallel with Pitot tube tip' end 5 and with the longitudinal axis of the aircraft.

A swept back streamlined shaped cap 8 is secured to mast 6 on the outer. end thereof by means of a dielectric bolt 9 made of resin impregnated fibreglass, or the like. Bolt 9 extends through a bore 10 in mast 6 to threadedly while the head end 11 thereof rests on a bracket 12, carried within aircraft fuselage 2.

A dielectric spacer 13' of Teflon, or the like, is interposed between mast 6 and cap 8 to electrically isolate the cap from the Pitot tube, mast and aircraft structure. Space13 is generally uniform in'thickness, as indicated in Figure 2 A coaxial cable 14, supported by bracket 12, extends through a bore 15 in mast 6 and terminates at outer end 7 adjacent Teflon spacer'13". Outer conductor 16 of cable 14 is suitably electrically connected to mast 6 and Pitot tube 4, including tip end-5 thereof, by soldering end 17 of outer conductor 16 tothe surface of mast 6 within bore 15 The inner conductor 18 of coaxial cable 14, which'is separated from outer conductor 16 by a dielectric sleeve 19', extends slightly beyond the outer end 7 of mast 6- and into a cavity 2tl'formed in Teflon spacer 13.

The extremely broad band characteristic of the antenna is obtained principally because of a triangular feed 21, the base of which is electrically connected to cap 8 by means of solder, or the like, and the apex of which is suitably secured to inner conductor 18 of coaxial cable 14, as best shown in Figure 4. As shown, feed 21 actually includes a pair of triangular elements 22 and 23 arranged at to each other. However, it should be understood that a single triangular element may be employed as Well as more than two triangular elements if required for impedance matching purposes. The specific arrangement largely depends upon the desired impedance match.

By varying the'thickness of Teflon spacer 13 or by modifying the shape of cap 8, the impedance match can be adjusted as desired to meet the requirements of a particular application. With mast 6 sweeping rearwardly, the necessary electrical balance to obtain the desired control over the radiation pattern of the antenna is made possible by utilizing the tip end 5 of Pitot tube 4 as an integral part of the'basic radiating structure.

As shown in Figure 5, antenna. 1 is" itself generally symmetrical in the front view and .is attached to a portion of the fuselage which is also generally symmetrical to provide symmetry in the radiation pattern and aerodynamic drag characteristics.

The antenna operates in a manner similar to-that of a dipole antenna to provide nondirectio'nal' coverage in azimuth of the energy being propagated. The structural configuration of'the" antenna, asW'ell as the triangular feed connecting center conductor 18 with cap 8, result in producing an excellent radiation pattern with broad band operation. The side view V-shape of the combination mast and cap coupled with the electrically conductive Pitot tube which projects forwardly from a point near the apex of the V, as best shown in Figure 3, enables the structure to serve well as a combination Pitot tube and broadband, general purpose antenna. Because of its structural shape and ruggedness it may also be used as an arrestor hook for checking the forward motion of an aircraft in cooperation with a barrier cable, not shown, as required for carrier based aircraft, for example, to avoid overshooting the runway.

Mast 6 and cap 8 may either be of all metal construction, or, in order to conserve on weight, these parts may be formed from a suitable lightweight plastic material provided the outer surface thereof is coated with a conductor such as copper, or the like.

While a specific embodiment has been shown and described, it should be understood that certain alterations, modifications and substitutions may be made to the instant disclosure without departing from the spirit and scope of the invention as defined by the appended claims.

We claim:

1. An omnidirectional, broadband antenna for aircraft and the like comprising, a mast secured to the aircraft, a probe-like member secured to said mast adjacent the outer end thereof, said probe-like member electrically connecting with said mast and extending transversely therefrom, a cap member carried on the outer end of said mast, a dielectric spacer interposed between said cap member and said mast for electrically isolating one from the other, said cap member being swept back to extend transversely from said mast in a direction opposite to said probe-like member to control the electrical characteristics of the antenna in cooperation with the probelike member, a triangular blade carried within said dielectric material and having the base thereof secured to said cap member and the apex thereof terminating adjacent to, but spaced from the mast, and feed means, said feed means including an outer conductor electrically connected to said mast and an inner conductor extending through said mast and isolated therefrom to connect only with the cap member at the apex of said blade whereby to maintain the cap member at a different electrical potential from the mast and probe-like member whereby to effect electromagnetic radiation over a wide frequency band while maintaining a low standing wave ratio.

2. An omnidirectional, broadband Pitot tube antenna for aircraft and the like, comprising, a conductive mast secured to the underside of the aircraft and projecting forwardly and outwardly therefrom, a Pitot tube secured to said mast adjacent the outer end thereof and projecting forwardly to serve as an antenna conductive element, a second antenna conductive element carried by said mast on the outer end thereof, a dielectric spacer electrically isolating the second antenna conductive element from said Pitot tube and mast, said second antenna conductive element projecting rearwardly to electrically balance the Pitot tube and control the radiation characteristics of the antenna, and means for maintaining an electrical potential between the two antenna elements whereby electromagnetic energy is released, said means including a triangular shaped feed, the base of which connects with said second antenna conductive element for maintaining a low standing wave ratio over a wide frequency band.

3. An omnidirectional Pitot tube antenna for aircraft and the like comprising, a conductive mast secured to the underside of the aircraft and projecting forwardly and outwardly therefrom, a Pitot tube secured to said mast adjacent the outer end thereof and projecting forwardly to serve as one antenna conductive element, a second antenna conductive element carried by said mast on the outer end thereof, a dielectric spacer electrically isolating the second antenna conductive element from 75 said Pitot tube and mast, said second antenna conductive element projecting rearwardly to electrically balance the Pitot tube and control the radiation characteristics of the antenna, and means electrically coupled to said Pitot tube for maintaining an electrical potential between the two antenna elements whereby electromagnetic energy is released, said means including a low impedance electrical lead connecting with said second antenna element and isolated from said Pitot tube and mast.

4. An omnidirectional, broadband antenna for aircraft and the like comprising, a mast secured to the aircraft and extending outwardly therefrom, a cap carried by said mast on the outer end thereof, the outer surfaces of said mast and cap being conductive, a dielectric spacer interposed between said mast and cap and electrically isolating one from the other, a coaxial transmission line, the outer conductor of said transmission line being secured to the conductive surface of said mast and the inner conductor thereof terminating within said dielectric spacer, and a triangular shaped conductive feed having the base thereof secured to the conductive surface of said cap and the apex secured to the inner conductor of said transmission line whereby an electrical potential may be applied between the mast and cap for propagating radio energy there through.

5. An omnidirectional Pitot tube antenna for aircraft ,and the like comprising, a mast secured to the aircraft and extending outwardly therefrom, said mast being tilted forward relative to the aircraft, a Pitot tube extending from the mast in a forward direction relative to the aircraft, a cap secured to said mast on the outer end thereof, said cap projecting laterally outwardly from said mast in an aft direction to electrically balance said Pitot tube, a dielectric spacer interposed between said mast and cap for electrically insulating one from the other, and feed means connecting with said mast and cap whereby an electrical potential may be applied between the mast and cap for propagating radio energy therethrough.

6. An omnidirectional antenna for aircraft and the like comprising, a mast secured to the aircraft and extending outwardly therefrom, probe means extending transversely from the mast and being electrically integral therewith, a cap secured to said mast on the outer end thereof, said cap projecting laterally outwardly from said mast in a direction opposite said probe means for electrically balancing the latter, a dielectric spacer interposed between said mast and cap for electrically insulating one from the other, and feed means connecting with said mast and cap whereby an electrical potential may be applied between the mast and cap for propagating radio energy therethrough.

7. An omnidirectional, broadband antenna for aircraft, and the like comprising, a mast secured to the aircraft and extending outwardly and forwardly therefrom, an electrically conductive Pitot tube extending transversely from said mast adjacent the outer end thereof and aiming in a forward direction relative to the aircraft, a cap carried on the outer end of said mast and proiecting rearwardly to electrically balance said Pitot tube and provide the desired radiation pattern, the outer surfaces or" said mast and cap being conductive, said Pitot tube being electrically integral with said mast, a dielectric spacer interposed tween said mast and cap and electrically isolating one from the other, a two wire transmission line extending through said mast, one wire of the transmission line electrically connecting with said mast and Pitot tube, the other wire terminating within said dielectric spacer and being insulated from the mast, and a triangular feed sccured at the base thereof to said cap, the apex of said triangular feed electrically connecting with said other wire whereby an electrical potential may be applied between the mast and cap for propagating radio energy there through.

No references cited.

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