US3350664A - Nonreciprocal ferrite device having a thin dielectric layer encircling the ferrite elment - Google Patents

Nonreciprocal ferrite device having a thin dielectric layer encircling the ferrite elment Download PDF

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Publication number
US3350664A
US3350664A US526844A US52684466A US3350664A US 3350664 A US3350664 A US 3350664A US 526844 A US526844 A US 526844A US 52684466 A US52684466 A US 52684466A US 3350664 A US3350664 A US 3350664A
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ferrite
waveguide
core
layer
dielectric layer
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US526844A
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English (en)
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Pistilli Angelo
Susin Pietro
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Italtel SpA
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Societa Italiana Telecomunicazioni Siemens SpA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/32—Non-reciprocal transmission devices
    • H01P1/38—Circulators
    • H01P1/383—Junction circulators, e.g. Y-circulators
    • H01P1/39—Hollow waveguide circulators

Definitions

  • ABSTRACT OF THE DISCLOSURE Circulator with at least three waveguide sections and a ferrite core of polygonal profile at the junction thereof, the core being enveloped by a dielectric layer whose thickness is a minor fraction (preferably between 10% and 30%) of the largest transverse core dimension and which is integral with a pair of polygonal dielectric end plates projecting on all sides beyond the core, resulting in an improved circulation ratio as compared with uncoated ferrite cores.
  • Our present invention relates to a nonreciprocal transmitter of microwave energy comprising a waveguide wherein a gyrotropic body (i.e. a nonreciprocal gyromagnetic compound) is disposed in the path of the transmitted microwaves in the region of a unidirectional magnetic field transverse to the direction of propagation.
  • a gyrotropic body i.e. a nonreciprocal gyromagnetic compound
  • the nonisotropic effect of the gyrotropic body determines the energy ratio between waves transmitted in the desired or forward direction and waves traveling in the undesired or reverse direction.
  • the general object of our invention is to provide means in such waveguide for improving this energy ratio.
  • a more particular object of this invention is to provide means in a circulator for minimizing reflections at the gyrotropic body by creating a proper impedance match between this body and the confronting waveguide branches.
  • a further object of our invention is to provide a highly compact gyrotropic structure satisfying the aforestated desiderata.
  • a gyrotropic body which comprises, in addition to the usual ferrite core of substantially constant transverse profile perpendicular to the applied magnetic field, a dielectric layer which encircles the profile of the core and which 3,350,664 Patented Oct. 31, 1367 has a thickness equal to a minor fraction of the largest transverse core dimension.
  • the thickness of this layer should have a lower limit of approximately 10% and an upper limit of approximately 30% of the largest transverse core dimension. Larger thicknesses may give rise to undesirable waveform modifications unless the dielectric constant is smaller than 2.
  • the gyrotropic body may include a pair of insulating end plates which project beyond the core and are integral with the dielectric layers surrounding same, thereby forming a continuous nonmagnetic casing around the core.
  • Suitable dielectric materials include Teflon as well as quartz, porcelain, polystyrene and other ceramic and polymeric substances such as, for example, those marketed under the names of Rexolite and Ray-K.
  • the gyrotropic body and its core may assume either cylindrical or prismatic shapes.
  • an advantageous profile is an n-sided polygon confronting with its corners the several branches, i.e. a preferably equilateral triangle in the case of a Y-type circulator.
  • FIG. 1 illustrates in isometric view (parts broken away) a Y-type waveguide circulator including a gyrotropic body according to the invention
  • FIG. 2 is a set of graphs illustrating the dependency of the pass band of the circulator upon the thickness of a dielectric laver forming part of the gyrotropic body.
  • FIG. 1 we have shown a conventional Y-type waveguide 10 having three coplanar branches 5, 6 and 7 spaced apart. At the junction of these branches there is located a gyrotropic body 8 which includes a ferrite core 1 having a constant equilateral triangular profile in the common magnetic plane of the waveguide branches.
  • a steady magnetic field symbolized by an arrow H, is applied perpendicularly to this magnetic plane at the junction of the three branches to permeate the ferrite core 1.
  • the polarity and intensity of this field H may be so chosen, for example, that wave energy entering the guide 10 at the input end of branch 5 is perferentially directed into branch 6 and that, similarly, waves entering at branches 6 and 7 leave at branches 7 and 5, respectively.
  • a dielectric layer 4 of uniform thickness s covers all three sides of the triangular ferrite core 1.
  • the circulation ratio is defined as the ratio of proportion of energy transmitted in the forward direction and proportion of energy transmitted in the reverse direction and, with Tefion and other dielectric materials referred to above, may attain a value on the order of 40 db at the rnidfrequency of the band if the layer thickness lies within the range specified.
  • the transmitted wave energy lies in a range of about 7000 to 8000 megacycles, the midfrequency f decreasing progressively from approximately 7600 me. to about 7350 me. as the thickness ratio s/a varies from to 30%.
  • the lower and upper limiting frequencies f, f" similarly decrease but with a slight broadening of the band toward the higher thickness ratios.
  • the layer thickness s should be proportionately reduced, if the frequency band is to be maintained substantially unchanged.
  • a gyrotropic body 1 as shown in FIG. 1, stripped of its dielectric layer 4, has a circulation ratio of only about 17 db at its midfrequency, compared with a corresponding ratio of 35 to 40 db measured in a device according to the invention as described more particularly with reference to FIG. 2.
  • a system for the nonreciprocal transmission of microwave energy from an input end of a waveguide to an out-put end thereof the combination with said waveguide of a source of a unidirectional magnetic field transverse to the direction of wave propagation from said input end to said output end and a gyrotropic body disposed in said waveguide in the region of said magnetic field for intercepting transmitted microwaves, said body comprising a solid ferrite core having an axis aligned with said field and a substantially uniform cross-section perpendicular to said axis, and a dielectric layer on said core encircling said axis, said layer having a dielectric constant ranging between substantially 2 to 10, the thickness of said layer ranging between substantially 10% and 30% of the largest dimension of said cross-section.
  • said waveguide has n coplanar branches including a first branch forming said inlet and a second branch forming said outlet, 11 being greater than 2, said branches having a junction in the region of said magnetic field, said core having an n-sided polygonal profile with corners confronting the respective branches.
  • a circulator comprising a waveguide structure with n coplanar sections converging at a central junction, n being greater than 2, the combination therewith of a source of unidirectional magnetic field transverse to the plane of said sections and a gyrotropic body disposed in said waveguide structure at said junction for intercepting microwaves traveling through any of said sections toward said junction; said body comprising a solid ferrite core having an axis aligned with said field and a substantially uniform cross-secton in the form of an n-sided polygon perpendicular to said axis, a dielectric layer on said core encircling said axis, the thickness of said layer being a minor fraction of the largest dimension of said cross-section, and a pair of nonconductive end plates with n-sided polygonal outline geometrically similar to but larger than said profile and projecting laterally on all sidesbeyond said layer, said end plates being integral with said layer and extending parallel to said plane within said structure.

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US526844A 1965-02-15 1966-02-11 Nonreciprocal ferrite device having a thin dielectric layer encircling the ferrite elment Expired - Lifetime US3350664A (en)

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IT300565 1965-02-15

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US (1) US3350664A (2)
AT (1) AT263090B (2)
CH (1) CH440397A (2)
FR (1) FR1467627A (2)
GB (1) GB1127758A (2)
NL (1) NL6505908A (2)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851279A (en) * 1973-10-17 1974-11-26 Hughes Aircraft Co Tee junction waveguide circulator having dielectric matching posts at junction
US4016509A (en) * 1974-11-06 1977-04-05 National Research Development Corporation Waveguide circulators
US4122418A (en) * 1975-05-10 1978-10-24 Tsukasa Nagao Composite resonator
US4240049A (en) * 1979-09-24 1980-12-16 Bell Telephone Laboratories, Incorporated Waveguide junction circulator having spurious mode absorbing means
US4415871A (en) * 1981-10-13 1983-11-15 The United States Of America As Represented By The Secretary Of The Army Dielectric waveguide circulator

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3063028A (en) * 1960-05-05 1962-11-06 Bell Telephone Labor Inc Enhanced gyromagnetic effect in nonreciprocal wave transmission
US3104361A (en) * 1960-02-26 1963-09-17 Hughes Aircraft Co Ferrite circulator with conductive plate of uniform thickness having tapered angularapexes for broad banding

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3104361A (en) * 1960-02-26 1963-09-17 Hughes Aircraft Co Ferrite circulator with conductive plate of uniform thickness having tapered angularapexes for broad banding
US3063028A (en) * 1960-05-05 1962-11-06 Bell Telephone Labor Inc Enhanced gyromagnetic effect in nonreciprocal wave transmission

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851279A (en) * 1973-10-17 1974-11-26 Hughes Aircraft Co Tee junction waveguide circulator having dielectric matching posts at junction
US4016509A (en) * 1974-11-06 1977-04-05 National Research Development Corporation Waveguide circulators
US4122418A (en) * 1975-05-10 1978-10-24 Tsukasa Nagao Composite resonator
US4240049A (en) * 1979-09-24 1980-12-16 Bell Telephone Laboratories, Incorporated Waveguide junction circulator having spurious mode absorbing means
US4415871A (en) * 1981-10-13 1983-11-15 The United States Of America As Represented By The Secretary Of The Army Dielectric waveguide circulator

Also Published As

Publication number Publication date
AT263090B (de) 1968-07-10
FR1467627A (fr) 1967-01-27
NL6505908A (2) 1966-08-16
CH440397A (it) 1967-07-31
GB1127758A (en) 1968-09-18

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