US3017587A - Radio-frequency coaxial-transmission phase shifter - Google Patents

Description

Jan. 16, 1962 D. B. KERN ET AL RADIO-FREQUENCY COAXIAL-TRANSMISSION PHASE SHIFTER Filed NOV. 17, 1959 3 Sheets-Sheet 1 INVENTORS. ROBERT L. CONGER BY DALE B. KERN DRIVE MECHANISM .ikW

Jan. 16, 1962 B. KERN ET AL RADIO-FREQUENCY COAXIAL-TRANSMISSION PHASE SHIFTER 3 Sheets-Sheet 2 Filed NOV. 17, 1959 Jan. 16, 1962 D. B. KERN ETAL 3,017,537

RADIO-FREQUENCY COAXIAL-TRANSMISSION PHASE SHIFTER Filed Nov. 17, 1959 3 Sheets-Sheet 3 FIG. 4

INVENTORS.

ROBERT L. CONGER BY DALE B. KERN 3%? fan United States Patent 3,017,587 RADlU-FREQUENCY CUAXIAL-TRANSMESHON PHASE SHHFTER Dale Kern, Corona, and Robert L. Conger, Riverside,

Calm, assignors to the United States of America as represented by the Secretary of the Navy Filed Nov. 17, 1959, Ser. No. 353,662

' 9 Claims. (Cl. 333 3l) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to the transmission of electromagnetic-waves and more particularly to phase shifting apparatus for use in microwave frequency transmission systems utilizing coaxial lines as the transmission means.

The present invention is a small phase shifter for microwave frequencies in which a dielectric disk cam is inserted between the two conductors of a transmission line. With this arrangement of the dielectric disk cam, rotation of the disk will cause a phase shift to occur in the line, and the present device will operate at a phase shift rate of one hundred cycles per second or higher.

Previous phase shifters are known in the prior art that are compact and will operate at microwave frequencies; however, these phase shifters cannot be operated at high phase shifting rates. Other prior art phase shifters exist that can operate at a phase shifting rate of one hundred cycles per second, but they are only for S-band (10 cm.) and longer wave length microwaves, and are too large for use in'many'apparatus where compactness is required. The present invention overcomes these disadvantages of the prior art.

In this invention a dielectric cam is moved into a transmission line formed of a cylindrical rod conductor placed beside a metal plate or between two parallel metal plates. This type of transmission line is similar to coaxial transmission line in operation, and like the coaxial line there is no long wave-length cut-off and therefore long wavelength microwaves can be transmitted through a small line. Therefore, the present phase shifter can be quite compact as compared to other phase shifters which move dielectric plates inside wave guide. For example, cylindrical wave guide for S-band microwaves must be about three inches in diameter while coaxial transmission line and the transmission line described above can be as small as desired.

' When a dielectric plate is inserted between the center conductor and the outer metal plates of such a transmission line, as described previously, a phase shift will be produced, but the discontinuity at the edges of the dielectric plate will cause undesired reflections of the transmitted wave. These undesired reflections are overcome in the present invention by placing the dielectric plate in a recession in the outer metal plates so that the increased induction of the transmission line at this point resulting from the recession will balance the increase in capacitance caused by the dielectric plate.

It is an object of the invention, therefore, to provide a novel microwave phase shifter that is small and has a high phase shift rate.

Another object of the present invention is to provide a novel and simple phase shifting device for use in coaxial wave-guide transmission systems.

Still another object of the invention is to provide a novel and simple phase shifting device for use in coaxial wave guide transmission systems for quickly and continuously varying the phase shift of the energy with the wave guide.

A further object of the present invention is to provide a novel and compact phase shifting device for use with transmission lines of an open type having no cutoff frequency.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGURE 1 is a cross-sectional elevation of the phase shifter of the present invention, taken along line ltl of FIGURE 2;

FIGURE 2 is a cross-sectional view of the phase shifter taken along line 22 of FIGURE 1;

FIGURE 3 is an enlarged cross-sectional view of a small area of FIGURE 1;

FIGURE 4 is an elevational View of the rotated cylindrical metal plate showing one form of dielectric cam carried thereby.

One embodiment of the invention will now be described with'reference to the drawings wherein like numerals refer to like parts in each of the figures.

This embodiment is for use with a phase scan antenna system, such as disclosed in copending application Serial No. 853,66lfiled November 17, 1959.

For use with a three rod antenna system, a phase shift of about one-quarter wave length must be introduced successively into the transmission lines from the three antenna elements, and the cycle of three successive phase shifts must repeat continuously, at a rate of from 20 to cycles per second, for example.

The phase shifter uses two metal plates, having high conductivity, formed into cylinders 10 and 12. Cylinder plate Ill is in a fixed position, whereas cylinder plate 12 may be rotated.

Plate 10 forms the outer-cylindrical walls of the phase shifter housing within which cylinder 12 may be rotated. Circular end walls 14 and 16, also of high conductance metal such as aluminun or brass for example, close the ends of the phase shifter housing. Circular end wall 14 has a plurality of coaxial connectors 18 mounted on the outside thereof, equidistantly spaced radially and cir curnferentially thereabout, to which coaxial transmission lines are connected. Circular end wall 16 has a plurality of coaxial connectors 19, determined by the number of antennas to be connected to the phase shifter, mounted on the outer surface thereof, directly opposite to and spaced the same as connectors 18 on end wall 14. The outside terminal of coaxial connectors 18 and 19 are conductivcly connected to the phase shifter housing. Solid metal rod conductors 2t? connect the central terminals of each pair of opposite coaxial connectors 18 and 19. Conductors 20 are insulated from the outside terminals of coaxial connectors 18 and 19, and from the end walls 14 and 16 of the phase shifter housing by an insulative material 25, such as Teflon for example, as

shown in FIGURE 1. End walls 14 and 16 have central apertures 22 and 24 therein, respectively. Apertures 22 and 24 each have a recess about their periphery on the outer surface of their respective walls and have bearings 26 and 28, respectively, mounted therein. Members 27 and 29 respectively, keep bearings 26 and 28 in place. Rotatable plate cylinder 12 is closed on opposite ends by portions 30 and 32, respectively, forming cylinder 12 into a drum which is mounted coaxially within cylinder 16. Portions 30 and 32 have shaft portions 34 and 36, respectively, protruding therefrom along the central axis of cylinder 12. Shaft portions 34 and 36 are mounted in bearings 26 and 28, respectively, for coaxial rotation of cylinder 12 within cylinder 10. Portions 3t) and 32 are provided with grooves 37 and 38, respectively, which operate as RF chokes. A drive mechanism 39 attached to shaft 34 is used to rotate cylinder 12.

Cylinder 12 has a dielectric plate 40, of polystyrene for example, partially recessed in recess 42 in the surface thereof. Dielectric plate 40 is in the form of an upright cylinder having the upper end cut off by a plane at 45 to the plane of the base, such that if the dielectric plate 40 were laid out flat one edge would be straight and the other edge would be in the form of a sine wave, forming a dielectric cam.

The surface of dielectric plate or cam 40 comes into close proximity with conductors and as the dielectric plate rotates with cylinder 12 within the phase shifter housing a varying amount of the surface of the dielectric plate will move successively past conductors 20. Microwave energy traveling between a conductor 20 and metal plate 12 will pass through dielectric 40 when the dielectric is between conductor 20 and plate 12. Microwave propogation velocity is decreased in proportion to the amount of dielectric 40 between a particular conductor 20 and cylindrical plate 12, and in such a manner that the phase of the energy traveling through the particular conductor 20 is retarded with respect to the energy traveling through the other conductors 20 which have different amounts of dielectric 40 between them and metal plate 12. The shape of dielectric 40 is such that from practically none to substantially all of a conductor will have dielectric between it and cylinder 12 in varying amounts as the cylinder and the dielectric thereon are rotated by drive mechanism 39. The dielectric plate 40 is placed in a recess in plate 12 so that line impedance will be constant through the phase shifter. As the movable cylinder plate 12 rotates the phase shift also changes at the same rate.

This invention results in the use of a transmission line of an open type consisting of an inner conductor of small cross-sectional area placed above a metal plate or between two metal plates being used as a phase shifter. Since this type of transmission line has no cutoff frequency, it can be as small as desired; the phase shift can be caused by introducing one or more dielectric plates into a transmission line as described herein and illustrated, by way of example, in the drawings.

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

What is claimed is:

1. A high speed phase shifter for use in microwave frequency transmission systems utilizing coaxial transmission lines comprising a substantially cylindrical dielectric cam inserted between the inner and outer condoctors of a section of a multiple coaxial transmission line, said section of a multiple transmission line being formed of a plurality of metal rods placed parallel to and spaced slightly away from a metal plate, each of said plurality of metal rods acting as one conductor of separate coaxial transmission lines and comprising the inner conductors thereof, said metal plate acting as the other conductor of said separate coaxial transmission lines and comprising the outer conductor thereof, means for rotating said cylindrical dielectric cam for passing varying amounts of dielectric material thereof between said metal rods and metal plate, a portion of the dielectric material of said dielectric cam being between each of said plurality of metal rods and said metal plate at all times, whereby the propogation velocity of microwave energy traveling between various metal rods of said plurality of metal rods and said metal plate will vary in proportion to the amount of said dielectric material therebetween and at a rate determined by the speed of said means for rotating said dielectric cam, and the phase of microwave energy traveling through a particular one of said metal rods is retarded with respect to the energy traveling through other of said metal rods having different amounts of said dielectric material between them and said metal plate.

2. A high speed phase shifter for use in microwave frequency transmission systems utilizing coaxial transmission lines comprising a substantially cylindrical dielectric cam inserted between inner and outer conductors of a section of multiple coaxial transmission line, said section of transmission line being formed of a plurality of metal rods equidistantly placed about and parallel to a metal cylinder, said metal rods being spaced from said metal cylinder such that said dielectric cam can be inserted therebetween, each of said plurality of metal rods acting as one conductor of separate coaxial transmission lines and comprising the inner conductors thereof, said metal cylinder acting as the other conductor of said separate coaxial transmission lines and comprising the outer conductor thereof, means for rotating said cylindrical dielectric cam for passing varying amounts of dielectric material thereof between the metal rods and metal cylinder, a portion of the dielectric material of said dielectric cam being between each of said plurality of metal rods and said metal cylinder at all times, whereby the propogation velocity of microwave energy traveling between various metal rods of said plurality of metal rods and said metal cylinder will vary in proportion to the amount of said dielectric material therebetween and at a rate determined by the means for rotating said dielectric cam, and the phase of microwave energy traveling through a particular one of said metal rods is retarded with respect to the energy traveling through other of said metal rods having different amounts of said dielectric material between them and said metal cylinder.

3. A device as in claim 2 wherein said cylindrical dielectric cam is in the form of a hollow upright cylinder Whose top end plane is at an angle of 45 to the plane of the base thereof and whose shortest sidewall height is very small in comparison to the maximum height, and is such that when the wall of the cylinder is laid out flat the base edge forms a straight line and the top edge forms a sine wave.

4. A device as in claim 2 wherein said cylindrical dielectric cam is carried on the surface of said metal cylinder.

5. A device as in claim 2 wherein said metal cylinder carries said cylindrical dielectric cam partially recessed in a recess formed in the outer surface of a portion thereof.

6. A device as in claim 2 wherein said plurality of metal rods and said metal cylinder are all housed within a hollow metal cylindrical housing, the ends of said housing being closed by flat disks each having a plurality coaxial connectors mounted thereon for connecting separate coaxial transmission lines thereto, equal in number to the number of said metal rods, the outer terminals of said coaxial connectors being conductively connected to said metal housing and the inner terminals of said coaxial connectors each being connected to one end of one of said plurality of metal rods and insulated from said housing.

7. A device as in claim 6 wherein said metal cylinder 9. A device as in claim 7 wherein said metal closure 10 2,336,314

portions each have a deep narrow circular groove therein which operates as an RF choke.

References Cited in the file of this patent UNITED STATES PATENTS 2,444.081 Willoughby June 29, 1948 2,445,793 Marchand July 27, 1948 2,831,169 Casal Apr. 15, 1958 Nail May 27, 1958

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