US2867803A

US2867803A - Circular cavity slot antenna

Info

Publication number: US2867803A
Application number: US621972A
Authority: US
Inventors: Paul L Kerley
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-11-13
Filing date: 1956-11-13
Publication date: 1959-01-06
Anticipated expiration: 1976-01-06

Description

Jan. 6, 1959 P. L. KERLEY CIRCULAR CAVITY SLOT ANTENNA U F. ll'vvl/li Ill,

Filed Nov. 13, 1956 OSCILLATOR FIG. 2

TRANSMISSION LINE OSCILLATOR INVENTOR, PAUL L. KERLEY.

ATTORNE X in airborne equipment.

United States Patent 2,867,803 CIRCULAR CAVITY SLOT ANTENNA Paul L. Kerley, Albuquerque, N. Mex., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application November 13, 1956, Serial No. 621,972

5 Claims. (Cl. 343-769) The present invention relates to antennas and more specifically to a type of antenna known as a slot antenna which has incorporated therein a resonant cavity.

The increase in the utilization of radio Waves in aircraft for the purposes of communication, direction and distance determination and the like has ca'used a corresponding increase in the number andtypes of antennas carried by modern aircraft. The reduction of the number of antennas by utilization of one to perform more than one function and the suitable design of antennas to 'frequency control for the transmitting oscillator, thus eliminating the need for an anode tuned impedance or tank circuit as a distinct element. In this connection a cavity resonator can be used adjacent to the slot as an additional or alternate tuning device.

An object of the invention is to provide an antenna of small size andwith a field pattern suitable for use Another object of the invention is to provide a novel antenna having a doughnut shaped field pattern and which can act both as an antenna and a resonant circuit. The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

Figure 1 shows one embodiment of the invention with an adjustable center element.

Figure 2 shows an embodiment of the invention adapted to transmit over a transmission-line.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts, there is shown in Figure 1 one embodiment of the antenna excited by an oscillator 18, as shown. Energy from oscillator 18 is supplied by means of a suitable transmission line 19 to a cylindrical cavity 20 which is shown in longitudinal section as bounded by ABCDEFGH, which includes inner and outer

cylindrical walls

17 and 21, respectively and lower'and

upper walls

23 and 24 respectively. The lower wall contains suitable opening and insulating means as at 25 to allow the transmission line to enter the cavity. It is understood, of course, that any other desired entrance means may be used.

The upper wall contains a circular slot 11 which extends into the cavity 20 by means of

cylinders

13 and 14 as shown. The transmission line is connected to

cylinders

13 and 14 at 26 and 27. In operation, cylindrical cavity 20 will resonate at a particular frequency when suitably excited by oscillator 18 and circular slot 11 allows radiation of the electro-magnetic wave in a direction outward from ground plane 10 in a doughnutshaped field pattern, the exact shape of which is determined by the shape of center element 12.

The loading of the antenna is controlled 'by moving center element 12 in and out perpendicularly to ground plane 10. Conicalcenter element 12 and

elements

15 and 16 are contiguous and mechanically rigid so, that movement of e1ement12 will occasion relative sliding motion between surfaces 16'and 17.

The antenna may be utilized as either an additional or an alternate tuning device for the oscillator. When it serves as the primary tuning device or resonant tank circuit of the oscillator, the areas of

cylinders

13 and 14 are made proportional to the desired capacity of the tank circuit and the length of path ABCDEFGH is made proportional to the inductance. The transmission line 19 will then be connected from 26 to 27 to the other elements of. the oscillator directly. This manner of connection does not form a part of this invention but is given as one illustration of possible use.

The embodiment in Figure 2 shows another use of the antenna. As can 'be seen from this figure, the center element 12 and

elements

15 and 16 have been eliminated and the antenna is made concentric with, but not touching, a single wire transmission line. In all other respects.

the structureof Fig. 2 is'identical with that of Fig. 1. In this way the radio frequency signal can be propagated down a line carrying-another current, for example. A specific application could be in power line telemetering systems, where one wire carries both sixty-cycle power and a high-frequency signaling circuit.

It may be noted that the antenna will not work efficiently without some sort of a center conductor, such as the. center elementll of Figure l or the transmission line of Figure 2. This is due to the fact that the radiated signal has a radial electric field which tends to cancel itself unless the center conductor is present to act as a shield between diametrically opposite portions of the It is thus seen that the antenna disclosed having incorporated therein a resonant cavity has a suitable field pattern and can be fabricated in a size suitable for airborne applications.

Obviously many modifications present invention are possible in light of the above teachings.- It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced other-wise than as specifically described.

What is claimed is:

l. A cavity slot antenna comprising first and second conducting coaxial cylinders, two conducting plates, said cylinders being joined at one end by one of said conducting plates, the other plate having a circular slot therein forming inner and outer portions, said slot being concentric with said cylinders, the other ends'of said cylinders being joined respectively to said inner and outer portions conducting flanges extending from said slot toward but not touching said one of the plates, and a cylindrical conductor placed coaxially within said cylinders and extending outwardly from said plates.

2. A cavity slot antenna comprising first and second conducting coaxial cylinders, the space between said cylinders being bounded on two ends by conducting plates, the plate on one end being formed with a circular slot therein, said slot being concentric with said cylinders, flanges extending from said slot toward the plate on the other end, and a conductor placed coaxially within said and variations of the asevgsos firstand second cylinders and extending outwardly past said conducting plates.

3. A conducting circular cavity slot antenna comprising a. cylindrical resonant cavity bounded by: a first cylinder, a second cylinder coaxial with and smaller in cross-sectional area than the first cylinder, at first plate normal to the first and second cylinders and joining one end of each of said cylinders, a second plate parallel to the first plate and extending inwardly from the other end of the first cylinder, at third plate parallel to the first plate and coplanar with the second plate extending outwardly from the other end of the second cylinder, and two concentric cylinders each extending from the second and third plates partly toward the first plate; said two concentric cylinders together defining a slot in communication with the cylindrical resonant cavity on one end of the slot, and a cylindrical conductor coaxially placed within said second cylinder and extending outward past thefirst, second, and third plates.

4. A conducting circular cavity slot antenna comprising a first cylinder, at second cylinder coaxially within the first, a plate connecting said first and second cylinders at one end thereof, an outwardly projecting flange on the other end of the second cylinder, an inwardly projecting flange on the other end of the first cylinder, said inwardly and outwardly projecting flanges being coplanar but and second cylindrical walls, a cylindrical slot contained. within said walls, said slot being formed by flanges ex- 4 spaced from each other, a end to the inwardly projecting flange coaxially within the first cylinder and projecting toward but not touching the connecting plate, a fourth cylinder attached at one end to the outwardly projecting flange and coaxially within the third cylinder and projecting toward but not touching the connecting plate, and a conductor placed coaxially within the second cylinder and extending outward past the projecting flanges.

5. A coupler for coupling high frequency currents from an oscillator to a transmission line comprising a cylindrical resonant cavity coaxial with and surrounding a. transmission line, said cylindrical cavity having first tending from one end of said walls inwardly from the outer wall and outwardly from the inner all and then' coaxially with the transmission line and said walls, and

an oscillator connected to said resonant cavity at the flange-formed slot, whereby electromagnetic radiation radiated through said slot will coact with andbe transmitted by said transmission line.

References Cited in the file of this patent UNITED STATES PATENTS 2,834,959 Dorne May 13, 1958 third cylinder attached atone I