US2848688A

US2848688A - Microwave switching circuit

Info

Publication number: US2848688A
Application number: US577022A
Authority: US
Inventors: Julius T Fraser
Original assignee: General Precision Laboratory Inc
Current assignee: General Precision Laboratory Inc
Priority date: 1956-04-09
Filing date: 1956-04-09
Publication date: 1958-08-19
Anticipated expiration: 1975-08-19

Description

Aug. 19, 198

.3. T. FRASER MICROWAVE SWITCHING CIRCUIT Filed April 9, 1955 INVENTOR.

JUL/U5 TF/Q/i-Sf/Q United States Patent Ofihce 2,848,688 Patented Aug. 19, 1958 MICROWAVE SWITCHING CIRCUIT Julius T. Fraser, Ossining, N. Y., assignor to General Precision Laboratory Incorporated, a corporation of New York Application April 9, 1956, Serial No. 577,022

5 Claims. (Cl. 333-7) This invention relates to apparatus for switching microwave energy from one to another transmission path.

In the past there have been known microwave switching devices which depend for their action upon the ionization of gases under low pressure. Such switches are usually arranged to be actuated by the presence of a predetermined power level within the waveguide and, although this kind of actuation is suitable for some purposes, it is frequently desirable to switch the wave energy regardless of the amount of power being transmitted. To meet this need, switches involving the movement of mechanical elements have been devised but these are inherently slow in operation, the speed being limited by the Another object is to provide a microwave switch which is compact.

In accordance with the invention, two short slot" hybrid junctions are axially aligned. In to the coupling space in one of the hybrid junctions is placed an element which is active in the Faraday magneto optical sense. A magnetic field is applied to this element and variation in its strength and direction causes a corresponding variation in the division of power between the two output arms.

For a clearer understanding of the invention reference may be made to the following detailed description and the accompanying drawing in which: 7

Figure l is an isometric View of a preferred embodiment of the invention; and

Figure 2 is a horizontal cross sectional view taken on the plane 22 of Figure 1.

Referring now to the drawing, there is shown a structure comprising basically two standard rectangular waveguides arranged side by side and having a common narrow wall or side 11. A portion of the common wall is cut away to form a coupling space 12 within the structure, beyond which the wall reappears as shown at.13. Thus there are defined four waveguide arms A, B, C and D. In the region of the coupling space 12 the outer

narrow walls

14 and 15 are drawn slightly toward each other as shown somewhat exaggerated at 16 and 17. Each

broad side

18 and 19 has a small protuberance, one of which is shown at 21, in the center of the coupling space to aid in matching the discontinuity.

The apparatus so far described has come to be called in the absence of the coupling space 12, while the energy in arm D will be advanced in phase by 135 with respect to its original phase. The junction is symmetrical and a similar division of energy would take place if microwave energy were introduced into any other arm. This hybrid junction per se has been described in the literature and is not the subject of the present invention. For further details reference may be made to an article by Henry J. Riblet entitled The Short Slot Hybrid Junction, published in the Proceedings of the I. R. E., volume 40, No. 2, February 1952, page 180, and to an article by Harold Heins entitled Radar Duplexer Uses Dual TR Tubes, published in Electronics for August 1954, page 149.

Referring again to the drawing, the common wall 13 is continued along the axis of the structure for a short distance and then is again cut away so as to form another coupling space 23 which space, together with the remaining walls, defines a second short slot hybrid junction having arms, C, D, E and F. As before, the outer narrow walls are drawn together slightly and two protuberances, one of which is shown at 24, are provided on the broad faces of the structure. In approximately the geometric center of the coupling space 23 there is placed a small rod 25 of a material which is active in the Faradaymagueto optical sense. Such materials include polyirons' and ferrites and are often referred to simply as ferrites and will be so designated in the present specification and claims. These materials, and their polarization rotation capabilities, are more fully described in the Luhrs and Tull Patent No. 2,644,930, issued July 7, 1953.

The rod 25 must be supplied with a magnetic field and this field may be obtained by various arrangements of coils or permanent magnets within or without the waveguide but for illustrative purposes is shown as being obtained from a coil 26 wound directly around the rod 25. The leads 27 and 28 support the coil 26 and rod 25 and pass through holes in the

walls

14 and 15. The leads are connected to a source of voltage 29.

In the absence of the rod 25 and coil 26, the wave energy in arm C would divide equally between arms E and F, the energy passing to arm E being shifted in phase an additional 45 or a total of while theenergy passing to arm F would be shifted an additional or a total of The energy in arm D would also divide equally between arms E and F, the portion passing to arm B being shifted an additional 135 or a total of 270 while that appearing in arm F would be shifted an additional 45 or a total of 180. The two components entering arm E would thus cancel since they would be of equal amplitude but opposite phase while the two components entering arm F would be in phase with each other and therefore additive. In other words, all of the power would appearin arm F, none of it appearing in arm E.

Applicant has discovered that the presence of the rod 25 and coil 26 without any current flowing in the coil 26 upsets the balance of the junction so that power appears in both arms E and F. Application of a D. C. voltage of one polarity to the

conductors

27 and 23 causes the power in arm E to increase while the power in arm F decreases. opposite effect, that is, the power in arm F increases while the power in arm E decreases.

The exact nature of the fields existing in the region of the coupling space 23 with the rod 25 magnetized is not fully understood. It is believed, however, that the polarization rotation caused by the ferrite rod 25 interacts with the complex modes introduced by the coupling space 23 to cause a resulting overall phase shift the magnitude of which depends upon the magnitude and polarity of the magnetic field passing through the rod 25. What- Reversal of the polarity causes the,

It isthusseenthat applicant has provided apparatus fordivertin'g microwave power from on'e'arm toanother regardless of whether the power level is low or-high. The

inductance ofthe small ferrite rod 25 'and the small coilf 26 are small enough that a rapid switching action may be;-

obtained by exciting the coil with' alternating curl-ent 'What is claimed is: V 1. A- microwave switch comprising twocollinear wave guide short slot" hybrid junctions axially aligned, eachof] said junctions including a couplingvspace, a ferrite ele-- ment in the coupling space in one of said junctions, and means for applying a magnetic fieldto said element perpendicularto the narrow waveguide walls.

2. A microwave switch comprising two waveguide short slot hybrid junctions axially aligned, each of said junctions including'a coupling space, a ferrite element occu pying a portion ofthe coupling space of one of's'aid junc' tions, and means for applying a magnetic field to said element perpendicular to the narrow waveguide walls.

A microwave switch'comprising, two waveguide short 'slot hybrid junctions axially aligned, each of said junctions including a coupling space, a ferrite element positioned approximately in the center of the coupling space of one'of; saidjunctions, a coil wound around said'element, the axis of said coil being perpendicular to the narrow waveguide walls, and a source of voltage 'connected' tosaid coil;

4. A microwave switch comprising, two collinear wave- 1 tionsincludinga coupling space, an element activein the guide short slot hybrid junctions, each of said junc- Faraday magneto optical sense positioned in approximately the geometric center of the coupling space of one of said junctions, a coil wound around said element and having its axis substantially parallel to the broad waveguide walls and perpendicular to the narrow waveguide walls, and a voltage source connected to said coil.

5. A microwave switch comprising, a pair of rectangular. waveguides having a common narrow wall, two intermediate portions of said [common wall being cut away thereby forming two coupling spaces in which microwave energy in said waveguides may interact, an element active in the Faraday magneto optical sense positioned in approximately the geometric center of one of said coupling spaces, a coil wound around said element and having its axis substantially parallel to the broad waveguide walls and perpendicular to the narrow waveguide Walls, two conductors connected respectively to opposite ends of' said coil and extending through holes in opposite outer narrow walls of said" waveguides, and a source of voltage connected to said conductors;

References Cited in the file of this patent UNITED STATES PATENTS 2,679,631 Korman May 25,, 1954 2,728,050 Van de Lindt Dec. 20, 1955 2,745,069 Hewitt May, 8, 1956 2,798,205 Hogan .i July 2, 1957 FOREIGN PATENTS 980,648 France. Dec. 27, 1950