US 3710280 A
A latching ferrite circulator utilizing deposited ferrite layers and operable without the requirement of a permanent magnet. A pair of separated ferrite layers respectively include a microstrip transmission line circuit and a ground plane on faces which oppose each other. The microstrip transmission line comprises at least one hub circuit portion and a plurality of circuit arm portions. At least two coplanar ferrite elements are deposited between the microstrip transmission line circuit and the ground plane. One ferrite element comprises the circulator element and is placed contiguous with the hub while the other ferrite element comprises a magnetic return path member which is located a predetermined distance from the circulator element. A latching conductor is located generally in the plane of the microstrip circuit intermediate the two ferrite elements so that when a DC current pulse is applied to the latching conductor, a closed magnetic circuit loop is provided through the two ferrite elements and the ferrite layers containing the microstrip circuit and the ground plane.
Claims available in
Description (OCR text may contain errors)
United States Patent 1191 Buck [111 3,710,280 1451 Jan. 9, 1973  DEPOSITED LATCHED JUNCTION CIRCULATOR HAVING MAGNETIC FLUX RETURN PATHS  Inventor: DanielC.Buck, Hanover, Md.
[73} Assignee: Westinghouse Electric Corporation,
22 Filed: o1'.12,1971
21 'AppLNo; 188,077
521 0.8. Ci; ..333 1.1, 333/84 M. 51 1111.01. ..H0lp 1/32, HOlp 5/12 581 Field of Search ..333/1.1, 24.1, 24.2, 84 M  References Cited UNITED STATES PATENTS 3,350,663 10/1967 Liekanowicz et al "333/11 3,477,028 11/1969 Aslaksen ..333/24 1 X 3,614,670 10/1971 Wilson ..333/l.1
Primary Examiner-Paul L. Gensler Attorney-F. H. Henson et al.
 ABSTRACT A latching-ferrite circulator utilizing deposited ferrite layers and operable without the requirement of a permanent magnet. A pair of separated ferrite layers respectively include a microstrip transmission line circuit and aground planeon faces'which oppose each other. The microstrip transmission line comprises at least one hub circuit portion and a plurality of circuit arm portions. At least two coplanar ferrite elements are deposited between the microstrip transmission line circuit and the ground plane. One ferrite element comprises the circulator element and is placed contiguous'with the hub while the other ferrite element comprises a magnetic return path member which is located a predetermined distance from the circulator element. A latching conductor is located generally in the plane of the microstrip circuit intermediate the two ferrite elements so that when a DC current pulse is applied to the latching conductor, a closed magnetic circuit loop is provided through the two ferrite elements and the ferrite layers containing the microstrip circuit and the ground plane.
12 Claims, 5 Drawing Figures 48 REVERSIBLE 0 c SUPPLY MAGNETIC FLUX TURN PATH MICROSTRIP LINE I FERRITE SUBSTRATE 11 1. L 4 k 42 111 10 X 1:, CUXQJL 3: 1 i a "1 7 FERRlTEPUCK30 1e 20 12-EERR1TE SUBSTRATE- snouuo PLANE DEPOSITED LATCIIED JUNCTION CIRCULATOR HAVING MAGNETIC FLUX RETURN PATHS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to means for controlling the transfer of microwave energy between two or more transmission lines and more particularly to a circulator which utilizes a gyromagnetic material such as ferrite to cause a switching action from one transmission line to another.
2. Description of the Prior Art Latching circulators employ one or more ferrite samples or pucks which are latched to remanence by means of a suitably positioned DC field provided either by a permanent magnet or electromagnet. The ferrite is latched by passing a pulse of DC current through a magnetizing loop so that upon termination of the pulse the ferrite will operate at the remanent flux density. Thus the internal DC magnetic flux density required for circulator operation is provided by the remanence flux state (latched state) of the ferrite puck.
Strip line or microstrip latching ferrite circulators which operate without the need of permanent magnets for use for example as a three port circulator are also well known to those skilled in the art. Examples of such devices are taught in US. Pat. Nos. 3,341,789, P. C. Goodman, et al. and 3,350,663, W.W. Siekanowicz, et al. While the noted prior art purportedly operates as intended, it is an object of the present invention to provide an improved ferrite circulator utilizing microstrip transmission line means which is simpler in construction and which is particularly adapted to be fabricated by the deposition of ferrite layers in accordance with a well known chemical vapor transport process.
SUMMARY Briefly, the subject invention comprises a pair of opposing ferrite substrates with one substrate having a microstrip transmission line circuit deposited on its inner face while the other substrate has a ground plane deposited on its inner face. A plurality of ferrite magnetic circuit members are deposited in a common plane intermediate the microstrip circuit and the ground plane and are selectively separated in accordance with the configuration of the microstrip transmission line circuit. One or more latching conductors are located substantially in the plane of the microstrip transmission line circuit, running between pairs of ferrite members such that a DC current applied thereto establishes a magnetic field which forms a closed circuit around the ferrite member on either side of the conductor, the ground plane and the ferrite substrate containing the microstrip circuit.
BRIEF DESCRIPTION OF THE DRAWINGS shown in FIG. 1 taken along lines 2-2 thereof;
FIG. 3 is a similar top plan view of a four port circulator configured in accordance with the teachings of the subject invention;
FIG. 4 is a longitudinal cross-sectional view of the circulator shown in FIG. 3; and
FIG. 5 is a top plan view partially in section of another embodiment of a four port circulator.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and more particularly to FIGS. 1 and 2, reference numerals 10 and 12 refer to a pair of disc shaped ferrite substrates which respectively include a microstrip transmission line circuit 14 and a metallic ground plane 16 deposited by well known techniques e.g. chemical vapor transport on mutually opposing inner faces 18 and 20.
The term microstrip transmission line includes various transmission lines that propagate signal substantially in the TEM mode. It includes, for example, various parallel plate transmission lines whether or not dielectric material is used. The microstrip transmission line circuit 14 deposited on the face 18 is configured to provide a three port circulator and comprises a common region, hereinafter called a hub circuit portion 22 and three RF signal transmission line means, hereinafter referred to as arm circuit portions 24, 26 and 28 which intersect the hub 22 at substantially angles with respect to one another and which extend to the outer periphery of the substrate 10 as shown in FIG. 1. FIG. 1, moreover, is illustrative of the configuration of the microstrip circuit 14 with substrate 10 removed.
A generally circular ferrite layer member or puck 30 together with three separated arcuate ferrite layer members 32, 34 and 36 all of equal thickness comprise first and second ferrite means respectively which are deposited in a common plane on either the ferrite substrate 12 containing the metallic ground plane 16 or the substrate 10 containing the microstrip circuit 14.1-Iowever, the deposition of the ferrite members 30, 32, 34 and 36 is such that when the substrates l0 and 12 are sandwiched together such as shown in FIG. 2, the circular ferrite puck 30 is contiguous with and has its center aligned with the center of the hub 22 of the microstrip circuit 14. Moreover, the diameter of the ferrite puck 30 is adapted to be greater than the diameter of the hub circuit portion 22 so that it extends beyond the perimeter thereof. The arcuate ferrite members 32, 34 and 36 which are coplanar with the ferrite puck 30 are located equidis'tantly away from the perimeter of the puck 30 and between the circuit arm portions 24, 26 and 28 as shown in FIG. 1. The remainder of the space is occupied by a suitable dielectric 37 which can also be deposited by a chemical vapor transport process.
Intermediate the circular ferrite puck 30 and eachof the arcuate ferrite members 32, 34 and 36 is located an electrical latching conductor 38, 40 and 42 respectively which are commonly connected across the terminals 44 and 46 of a reversible DC voltage source 48 in such a sense so as to magnetize the arcuate members in the same direction. The latching conductors 38, Mind 42, moreover, are deposited on or attached to the face 18 of the ferrite substrate 10 such that they lie substantially in the same plane as the microstrip transmission line circuit 14 as shown in FIG. 2.
When a DC current is applied simultaneously to each of the latching conductors 38, 40 and 42, via terminals 44 and 46, a magnetic field H of predetermined polarity will be set up around the respective conductors depending on the relative polarity of the voltage at terminals 44 and 46 and a closed magnetic path or loop will be provided by the circular puck 30, the upper and lower ferrite substrates and 12 and the three ferrite members 32, 34 and 36. The magnetic loop associated with latching conductor 42 is shown in FIG. 2. When the DC excitation is removed the ferrite puck 30 will exhibit a remanence magnetic flux state due to the direction of flow of the DC current and thus will provide a latched direction of signal transfer of RF energy to and from selective microstrip arm circuit portions 24, 26 and 28. Upon the application of a reverse current the direction of magnetization would reverse, thereby latching the circulator in the opposite direction.
The ferrite members 32, 34 and 36 thus act to provide a respective return path for the magnetic loops established by the current flow in the conductors 38, 40 and 42. The degree of latch can be made equally as good as a machined toroid because the magnetic gaps between the ferrite layers are essentially non-existent due to the deposition process. Moreover, the substrate return path does not affect the circulator action because the ferrite behavior in the regions of the microstrip arms is reciprocal, that is, the DC magnetization is parallel to the direction of propagation of the RF signals. Thus, a latchable ferrite circulator comprised of deposited multilayers of ferrite material is provided which does not require the need for a magnet.
A second embodiment of the subject invention is disclosed in FIGS. 3 and 4 where, for example, a four port circulator is desired. As in the case of the previous embodiment considered above, a pair of ferrite substrates 48 and 50 respectively, include a microstrip transmission line circuit 52 and a microstrip ground plane 54 deposited on mutually opposing surfaces of the substrates. The microstrip transmission line 52 in the present embodiment comprises a double hub configuration with three circuit arms projecting therefrom. More particularly, it includes circuit hub portions 56 and 58 which share a common circuit arm portion 60. The hub 56 has circuit arms 62 and 64 projecting therefrom while the hub 58 includes arm circuit arms 66 and 68. Whereas in the previous embodiment a single circular ferrite layer or puck 30 was deposited so as to be in registration with the single hub 22, the present embodiment includes two coplanar circular ferrite pucks 70 and 72 which comprise first and second ferrite means respectively. These pucks are deposited in a manner heretofore described so that they are respectively contiguous with the microstrip circuit 52 and the ground plane 54. Intermediate the two circular pucks 70 and 72, in the plane of the microstrip circuit 52, is fabricated a single latching conductor 74 which is jumped over or under the common circuit arm 60 and which is adapted to be coupled to a reversible DC source such as shown in FIG. 1 by means of circuit leads 69 and 71. The space intermediate the substrates 48 and 50 not filled by the circular ferrite pucks 70 and 72 is preferably filled with a suitable dielectric material 73.
When a DC current is flowing in the latching conductor 74 as determined by the polarity of the voltage applied to the extremities thereof, a magnetic field H is produced and a closed magnetic path is provided by the combination of the substrates 48 and 50 and the two circular ferrite pucks and 72 (FIG. 4). The magnetization of the ferrite pucks provided by the direction of the magnetic field again determines the direction of transfer of RF signal energy flowing to or from the device by means of the circuit arm 62, 64, 66 and 68 with the latching feature being provided by the remanence magnetic state of the ferrite pucks 70 and 72 as noted earlier.
A modification of the embodiment shown in FIGS. 3 and 4 whereby the need for a jumper configuration of the latching conductor 74 over or under the microstrip arm 60 is eliminated can be obtained so that the latching conductor lies entirely within the plane of the microstrip circuit 52 as shown in FIG. 5. The physical configuration is exactly as described with respect to the embodiment shown in FIGS. 3 and 4 with the exception that the latching conductor 74 includes microstrip elements 76 on either side of the intersection with the circuit arm 60 which act as low pass microwave filters which prevent RF signals from being coupled from the circuit arm 60 to the outer extremities of the latching conductor 74 to the circuit leads 69 and 71. The common circuit arm 60, moreover, include a pair of well known lumped microstrip capacitor blocks 78 located on either side of the junction with the latching conductor 74 for preventing DC current from flowing to the circuit hubs 56 and 58.
The embodiments shown in FIGS. 3, 4 and 5 have the advantage over the first embodiment disclosed in that no additional ferrite elements such as the arcuate members 32, 34 and 36 are required to close the magnetic loop. Moreover, this type of configuration can be logically extended to any number of circulators.
Having thus disclosed what is at present considered to be the preferred embodiments of the subject invention,
I claim as my invention:
1. A latching circulator comprising in combination:
a first and second substrate capable of providing a magnetic flux line path therethrough, separated by a predetermined distance and having a respective inner surface opposing one another;
at least three RF signal transmission line means coupled together at a common region, being contiguous with said inner surface of said first substrate;
an electrical ground plane contiguous with said inner surface of said second substrate;
first and second ferrite means of substantially equal thickness located in a common plane between said substrates, said first ferrite means being at least contiguous with said common region, said second ferrite means being separated a predetermined distance away from said first ferrite means such that said first and second substrates together with said first and second ferrite means define at least one closed magnetic circuit path; and
electrical conductor means passing between said first and second ferrite means and being located substantially in a plane common to an inner surface of one of said substrates, said conductor means being adapted to be connected to a. reversible DC voltage source which provides a current flow through said conductor means selectively in either of two directions to generate a magnetic field within said at least one closed magnetic circuit path whereby said first ferrite means controls RF signal flow between said at least three RF signal transmission line means.
2. The invention as defined by claim 1 wherein said first and second substrate are comprised of ferrite material.
3. The invention as defined by claim 2 wherein said at least three RF signal transmission line means comprises microstrip transmission line.
4, The invention as defined by claim 3 wherein said first ferrite means comprises a generally circular layer of ferrite material and said second ferrite means comprises three layer members respectively located between each of the three microstrip conductors.
5. The invention as defined by claim 4 wherein said three layer members comprises generally arcuate segments.
6. The invention as defined by claim 4 and wherein said electrical conductor means comprises a conductor being located in a plane common to the inner surface of said first substrate which plane is also common to said microstrip transmission line means.
7. The invention as defined by claim 1 and additionally including another at least three RF signal transmission line means coupled together at a common region and being contiguous with said inner surface of said first substrate, being separated from said previously cited at least three transmission line means by a predetermined distance and wherein one transmission line means of both form a common transmission line between the common regions thereof; and
wherein said second ferrite means is located contiguous with said common region of said another at least three signal transmission line means.
8. The invention as defined by claim 7 wherein all said transmission line means comprises microstrip transmission line means.
9. The invention as defined by claim 8 wherein said common regions comprise substantially circular hubs of microstrip conductor means and wherein said first and second ferrite means comprise generally circular ferrite layers capable of being magnetized in either of two states by current flow through said electrical conductor means.
10. The invention as defined by claim 9 wherein said electrical conductor means comprises a conductor located in a plane common to said RF signal transmission line means.
11. The invention as defined by claim 10 wherein said electrical conductor means intersects said common transmission line between said common regions, and additionally including isolation circuit means coupled at the junction thereof for preventing signal interaction between the two.
12. The invention as defined by claim 11 wherein said isolation circuit means comprises low pass filter means coupled to said latching conductor on either side of said junction and capacitor means coupled to said signal transmission line on either side of said junction.