Slot-line Circulator

Abstract

A slot-line circulator having a ferrite disc either coated on or embedded d integral with a dielectric substrate on one surface of which there is provided a narrow gap in a conductive coating to form a slot line adapted to propagate microwave energy. The energy-propagating slot line extends substantially halfway across the surface of the ferrite disc at which point the conductors forming the slot-line gap are branched outwardly to form an angle of substantially 120.degree.. Respective conductive coatings are provided parallel to and spaced from each of the branched conductors to form two slot-line arms, or channels, which connect to the wave-propagating slot line to form a Y-junction. The width of the conductive coatings and the spacing or gap therebetween for each of the Y-junction channels is identical. A current-carrying latching wire is provided through the center of the ferrite disc and is connected to a reversible DC source of to establish a circumferential DC magnetic bias field in the ferrite in either of two directions.

Description

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION

This invention relates to circulators and more particularly to slot-line circulators.

Heretofore, so-called junction circulators have made use of ferrite elements at the junction of three or more transmission lines. These junction circulators usually consist of a disc of ferrite material located at the junction of three strip transmission lines. Since for relatively broadband operation a rather large ferrite disc is required, such strip-line circulators have not proved feasible for use in miniaturized circuitry. This is especially the case where it is necessary to utilize circulators which are compatible to integrated microwave circuit requirements.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a junction circulator which overcomes the above-noted limitations.

It is another object of the present invention to provide a circulator which is compact and simple in construction.

It is another object of the present invention to provide a circulator adapted for miniaturized circuitry requirements and which eliminates the necessity of holding current.

In accordance with the present invention there is provided a slot-line circulator having a microwave energy-propagating slot line on one surface of a dielectric substrate and further including a ferrite disc which may be coated on or embedded in and integral with the dielectric substrate. The microwave energy-propagating slot line extends across substantially half the ferrite disc, at which point the spaced conductive coatings forming the slot-line angle outwardly in opposite directions at an angle substantially 120.degree. across the surface of ferrite disc and extend beyond the ferrite disc to continue along the surface of the dielectric substrate. A slot-line Y-junction is formed at substantially the center of the ferrite disc by means of conductive coatings parallel to and spaced from the conductive angled portions of the microwave energy-propagating slot line. The spacing of the conductive coatings forming the Y-junction are of uniform width as are the gaps forming the Y-channels. Also included is a current-carrying latching wire which extends through an aperture positioned therefor through the center of the disc and which is connected to a reversible DC source. The latching current produces a circumferential DC magnetic bias field in either one of two directions.

BRIEF DESCRIPTION OF THE DRAWING

For a better understanding of the invention, together with other and further objects thereof reference is made to the single FIGURE in the drawing which illustrates a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing, at 10 there is shown a conventional slot-line arrangement for propagating microwave energy. Slot line 10 comprises a narrow gap between two spaced-parallel metallic strips 12 and 14 coated on one side of a dielectric substrate 16, the other side of the substrate being open to the surrounding air. The electrical parameters, design and operating characteristics of such slot lines are known and are described in an article entitled "Slot Line, An Alternative Transmission Medium for Integrated Circuits," page 104 of G-MTTTT, International Microwave Symposium (May 20, 21, 22, 1968), a publication of IEEE. In brief, slot line 10 utilizes a high permittivity substrate which causes the slot-mode wavelength, .lambda.', to be small compared to the free-space wavelength .lambda., and thereby results in the fields being closely confined to the slot with negligible radiation loss. The basic electrical parameters of the slot line are the characteristic impedance Z.sub.o and the phase velocity v. Relative velocity and wavelength are v/c=.lambda.'/.lambda., where c is velocity of light, .lambda.' is slot-line wavelength, and .lambda. is free-space wavelength. Because of the nonTEM nature of the slot-line mode, these relative parameters are not constant, but vary with frequency at a rather slow rate per octave. This behavior contrasts with quasi-TEM microstrip line, whose Z.sub.o and v/c are very nearly independent of frequency from DC to the highest frequency of ordinary interest. On the other hand, slot line differs from waveguide in that it has no cutoff frequency. Propagation along the slot occurs at all frequencies down to f=0, where, if the metal-coated substrate is assumed infinite in length and width, v/c approaches unity and Z.sub.o approaches zero. Other important parameters are the ratio of phase velocity to group velocity v/v.sub.g, the effect of adjacent walls on the basic parameters, and the minimum allowable spacing of such walls from the slot for negligible effect. As a further example of the slot line 10 and particularly to means of coupling energy into and out of such slot lines, reference is made to copending application, Ser. No. 826,314 for "Slot Line" filed May 21, 1969. Embedded in substrate 16 is a disc 18 made of a suitable ferrite material which extends through the thickness of substrate 16 from top to bottom so that the top and bottom exposed surfaces of ferrite disc 18 are coplanar with the top and bottom exposed surfaces of substrate 16. As shown, ferrite disc 18 is completely surrounded by the substrate material so that the substrate 16 and ferrite disc 18 form an integrated structure. However, if desired, the ferrite disc 18 may be merely coated on the surface of the dielectric substrate 16 which includes the slot line 10. The metallic strips, or coatings, 12 and 14 extended in parallel arrangement across ferrite disc 18 for a distance substantially equal to the radius of ferrite disc 18, at which point the strips 12 and 14 are flared outwardly as at 20 and 22 at an angle of approximately 120.degree. . The parallel portions of strips 12 and 14 on disc 18 are symmetrically arranged with respect to the center of ferrite disc 18 such that there is equal spacing between each of the strips 12 and 14 and a diametrical line drawn across ferrite disc 18. To form a Y-junction on disc 18, metallic strips or conductive coatings 24 and 26 are arranged parallel to flared conductive strip portions 20 and 22 respectively and extend across ferrite disc 18 to the substrate portion 16. The spacing or gaps between conductive strips 20 and 24 and conductive strips 22 and 26 is the same as the gaps between metallic strips 12 and 14 forming the energy-propagating slot line 10. By such an arrangement, three microwave energy-propagating channels of the Y-junction are formed as at 28, 30 and 32, with the three arms of the junction in ferrite disc 18 being symmetrical about the center thereof. The center of ferrite disc 18 is provided with a central orifice as at 34 which extends through substrate 16 and through which extends a current-latching wire 36. Latching wire 36 is connected to a reversible DC current pulse source 38 which energizes latching wire 36 in either one of two directions. In one direction, the current in wire 36 is directed inwardly towards ferrite disc 18, or into the paper, and in the other direction the current in wire 36 is in the opposite direction or out of the paper. In both cases a circumferential DC magnetic bias field will be established in ferrite disc 18.

The operation of the circulator is analogous to an E-plane waveguide circulator. As is well known, the electric field of a propagated electromagnetic wave extends across the slot formed by the parallel arranged metallic strips 12 and 14. In the air regions of the slot, the magnetic field lines curve and return to the slot at half-wavelength intervals. Thus the field possesses magnetic circulator polarized regions. If the bias energy from latching wire 36 is in one direction, energy entering channel 28 may be directed to channel 30, while if the latching or bias energy is reversed, the propagated wave or electromagnetic energy may be directed to channel 32. Thus the unit can function as a circulator or switch.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Claims

What I claim is:

1. A slot-line circulator comprising

a ferrite disc having a central aperture,

a slot-line Y-junction on one surface of said disc and symmetrical about said aperture,

and a current-carrying latching wire extending through said aperture and separate from said disc.

2. The slot-line circulator in accordance with claim 1 and further including

a dielectric substrate having thereon a microwave energy-propagating slot line,

said ferrite disc being integral with and surrounded by said dielectric substrate and said aperture extending through said dielectric substrate,

the slot line in said substrate being connected to one of the Y-forming slot-line junctions on said ferrite disc.

3. The circulator in accordance with claim 2 wherein the gap spacing between the conductors forming said Y-junction on said ferrite disc is the same as the gap spacing between the energy-propagating slot line on said dielectric substrate.

4. The circulator in accordance with claim 2 and wherein said disc is a surface ferrite coating on the propagating surface of said substrate.

5. The circulator in accordance with claim 3 and wherein said disc is a surface ferrite coating on the propagating surface of said substrate.