Classifications

• • 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
  • H01P1/387—Strip line circulators

Definitions

• This invention is directed to the field of RF circulators of the type commonly used in RF communication systems and devices.
• Circulators are commonly used in microwave systems to interconnect multiple devices so as to inhibit unwanted reflections between the devices. See, for example, the article by Knerr entitled “A Microwave Circulator That's Smaller Than a Quarter," Bell Laboratories Record, March 1973, pp 79 - 84.
• the physical construction of a conventional RF circulator of the type to which the invention is addressed is shown schematically in Figure 1.
• the illustrated circulator 10 includes a ferrite substrate 12 whose upper surface 14 (shown greatly enlarged) carries a conductive pattern. That pattern typically includes three conductive strips connected to a central circular pattern which defines a circulator junction. The three strips are usually attached to the junction at points 120 degrees apart around its circumference to provide input/output ports to the junction. The junction itself couples RF energy among the input/output ports.
• the bottom surface of the substrate 12 carries a ground plane 16 (shown greatly enlarged).
• a magnet 18 Disposed above the surface 14 is a magnet 18 which is separated from the surface 14 by a spacer 20 to prevent the magnet 18 from interfering with the RF field associated with the circulator junction.
• Another magnet 22 is situated beneath the ground plane 16 and in vertical alignment with the upper magnet 18. With this arrangement, the magnets 18 and 22 serve to provide a magnetic bias which induces proper operation of the circulator junction.
• the type of two-magnet circulator shown in Figure 1 is well known and is discussed in the literature. See, for example, the article by Ho entitled “Design Techniques for Low Loss, Miniature Microwave Microstrip Circulator at L-Band," Proceedings of the
• Figure 1 is a schematic side view of a conventional RF circulator.
• Figure 2 is a schematic side view of an RF circulator according to the invention.
• Figure 3 is a top view of the conductive pattern which is disposed on the upper surface of the substrate shown in Figure 2.
• Figure 4 depicts the equivalent magnetic structure of the circulator shown in Figure 2.
• the circulator described herein includes a conductive pattern which is arranged to form a circulator junction, and a magnet disposed above the conductive pattern.
• a ferrimagnetic substrate is disposed beneath the conductive pattern and preferably carries the pattern on its upper surface.
• An electrically conductive ground plane is preferably carried by or on the lower surface of the substrate.
• a magnetic layer preferably of cold rolled steel, is disposed in relation to the magnet so as to induce an image magnet in the magnetic layer, thereby eliminating the need for a second magnet. With this image magnet, closely confined and concentrated lines of magnetic flux are established through and perpendicular to the plane of the circulator junction.
• the improved circulator eliminates the need for a second conventional magnet, permits the magnetic layer to act as a support for the circulator (or for more than one circulator mounted thereon) and eliminates costly or bulky steel housings associated with some conventional circulators.
• the improved circulator 24 preferably includes a suitable ferrimagnetic substrate 26 of ferrite or garnet, for example.
• a conductive pattern 28 (shown greatly enlarged) which is arranged to form a circulator junction and a plurality of strips connecting the junction to input/output ports.
• the conductive pattern is formed directly on the upper surface of the substrate 26.
• the conductive pattern 28, typically formed of silver or copper, is shown as forming a circular circulator junction 30 to which three conductive strips 32, 34, and 36 are connected. The function of these strips is to couple the junction 30 to three input/output ports.
• a suitable magnetic bias is directed through the junction 30 and the underlying substrate 26, RF energy coupled to one of the strips is passed via the junction 30 to another strip with little loss and with minimum reflections.
• Fay and Co stock entitled "Operation of the Ferrite Junction Circulator," IEEE Transactions on Microwave Theory and Techniques, January, 1965, pp. 15 - 27.
• an electrically conductive ground plane 38 (shown greatly enlarged) is disposed immediately below the substrate 26 and is preferably formed of silver or copper on the bottom surface of the substrate 26. This ground plane provides a termination plane for electric lines of force and the return path for currents as is typical in microstrip circuitry.
• a magnet 40 is disposed above the conductive pattern 28 and is preferably separated therefrom by an insulating spacer 42 which preferably has a relative permeability of one.
• the magnet 40 may be a cast Alnico 8 magnet from Indiana General Corp. of Valparaiso, Indiana.
• I substitute for the conventional second magnet a magnetic layer 44 and dispose the layer 44 in relation to the magnet 40 so as to induce an image magnet in the magnetic layer 44.
• the layer 44 is preferably located immediately below and abutting the . ground plane 38 to ensure that an effective image magnet is induced therein by the magnet 40.
• the North (N) and South (S) poles of the magnet 40 induce in the layer 44 an image magnet 46 having the illustrated N and S poles.
• the polarity of the magnet 40 may be reversed, and a similar reversal will occur in the polarity of the image magnet.
• the effect of this image magnet, in cooperation with the magnet 40, is to establish closely confined and concentrated lines 48 of magnetic flux through the circulator junction 30 and perpendicular to the plane of the circulator junction. As shown by the dashed lines 48, the lines of flux do not diverge substantially, but are highly concentrated to induce an appropriate magnetic field in the substrate below the circulator junction for orienting the magnetic domains therein in a fashion to develop proper junction operation.
• the layer 44 is made of cold rolled steel and may extend horizontally beyond what is shown in Figures 2 and 4 to form another magnetic layer for an adjacent circulator.
• the layer 44 provides the only needed support for the circulator and may, indeed, support adjacent circulators (not shown) which may be identical to the illustrated construction.

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• 1984
  • 1984-02-03 EP EP19840901036 patent/EP0136328A1/de not_active Withdrawn
  • 1984-02-03 WO PCT/US1984/000153 patent/WO1984003392A1/en unknown

Non-Patent Citations (1)

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