US3038133A - Non-reciprocal electric coupling device - Google Patents

Description

June 5, 1962 G. DE VRIES 3,038,133

NON-RECIPROCAL ELECTRIC COUPLING DEVICE C0 U PIJNG FACTOR Filed Oct. 15, 1957 l 250 300 MEGA c YCLES/SEC.

INVENTOR GERRIT DE VR ES BY W AGEfi:

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-; tates atent 3,038,133 Patented June 5, I962 This invention relates to non-reciprocal electric coupling devices, in which the transmission of energy in one direction is nil.

Such devices are used, for example, as a microwave insulator, for example in a connection between a generator and a load in order to suppress the reaction of the load upon the generator. A plurality of devices of this kind are already known in which a piece of pre-polarized high-frequency magnetic material, for example of ferrite, is arranged at a given area in a wave guide so that waves in the wave guide are passed substantially unhindered in one direction and materially damped in the other direction. However, such devices are not usable for comparatively low frequencies, for example of the order of 500 mc./s., since the dimensions of the wave guide would become too large for practical use.

Furthermore, a non-reciprocal electric coupling device is already known which comprises two crossing coils having their winding surfaces arranged at right angles to each other and surrounding a common core of high-frequency magnetic material which is pre-polarized in a direction parallel to the intersecting line of the winding surfaces. Such a coupling device is indicated in certain cases by the name of gyrator. In such a gyrator, transmission of energy from one coil to the other may be eliminated by means of an external resistance coupling between the two coils. In the reverse direction, however, transmission of energy can take place. This device is not particularly suitable for waves having a wavelength of the order of 50 cms.

The non-reciprocal electric coupling device according to the invention likewise comprises two crossing windings surrounding a common core of high-frequency magnetic material which is pro-polarized in a direction parallel to the intersecting line of the winding surfaces. However, in the device according to the invention, the winding surfaces are at an angle between and 90 and the prepolarization has a value such that for a given frequency the transmission coeificient between the windings is nil. This device thus has no external coupling between the windings. If desired, the windings may each comprise a single turn.

In order that the invention may be more readily carried into effect, it will now be described more fully, by way of example, with reference to the accompanying drawing.

FIG. 1 shows two crossing Lecher lines 1 and 2, which are each short-circuited at one end to form a single turn and which surround a core 3 of high-frequency magnetic material. The planes in which the conductors of the Lecher lines 1 and 2 are situated are at an angle of (p to each other. The core is pro-polarized in a direction parallel to the intersecting line of said planes, as indicated by arrow H, by means (not shown), for example an electromagnet. Experiments have revealed that an angle (p between 0 and 90 corresponds to a field strength H, with which at a given frequency there is no transmission of energy from coil 1 to coil 2, but such transmission is possible in the reverse direction.

FIG. 2 shows the relationship between the coupling factor S between the coils 1 and 2 and the frequency f for different values H H H and H; of the pre-polarizing field. From the figure it may be seen that the coupling factor S corresponding to the field strength H becomes nil for a frequency of 250 mc./s.

The foregoing may also be recognized theoretically as follows. The relationship between the components Bxand By of the magnetic inductance in directions at right angles to the magnetic pre-polarization and the corresponding components Hx and Hy of the magnetic field strength may in general be expressed by the relations:

y=uz +m y wherein m and indicate complex permeabilities. From the condition that the Lecher line 2 does not surround a magnetic field produced by current in the Lecher line 1, it follows that tan (p must be equal to ,u iltz. From the fact that #1 and #2 are complex values, it follows that two conditions must be fulfilled. The permeabilities a and [Q may approximately be expressed by the relations:

res

wherein 0: indicates the angular frequency, co the angular frequency at which for the given value of the prepolarizing field H magnetic resonance of the high-frequency material occurs, and w the angular frequency at which the magnetic material is in anti-resonance, that is to say at which the real part of the permeability ,u which indicates the relationship between a component of the mag netic inductance in a direction at right angles to the prepolarization and the component of the magnetic field in the same direction, is nil. In the above-mentioned formulae, ,8 indicates a magnitude which is proportional to the magnetic losses of the material, and j is equal to the root of 1. Upon substitution of the above-mentioned relations of ,u and 1. in the condition tan p= #2 we have w=w and tan gr P es 2 ar ies From this it follows that, in order to suppress transmission of energy from the Lecher line 1 to the Lecher line 2, the pre-polarizing field for a given frequency to must be adjusted to a value such that the magnetic material of the core 3- is in magnetic anti-resonance for this frequency.

What is claimed is:

A non-reciprocal electrical coupling device comprising a core of high-frequency magnetic material, a first winding positioned to surround said core and lying substantially in a first plane, a second winding positioned to surround said core and lying substantially in a second plane, said windings being oriented with respect to each other so that said first and second planes intersect each other at an angle lying between the values of zero and ninety degrees, and means for pre-polarizing said core in a direction parallel to the line of intersection of said first and second planes, said pre-polarization having a value to cause said core material to be substantially in magnetic anti-resonance at a predetermined frequency whereby the signal transmission coefiicient between said windings is substantially zero in one direction at said frequency determined by the value of said pre-polarization.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Bloch et al. July 24, 1951 Hershber'ger Mar. 18, 1952 Engelmann July 17, 1956 Anderson et a1. July 31, 1956 45 Hogan July 2, 1957 Grisdale et al. May 13, 1958 FOREIGN PATENTS Great Britain July 2, 1952 Great Britain Sept. 29, 1954

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