Editing Circulator (section)

====Waveguide junction circulators====
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[[File:WG Junction Circulator HP LC cropped.jpg|center|thumb|500px|High-Power Liquid-Cooled Waveguide Junction Circulator.  Image courtesy of [http://www.microwavetechniques.com Microwave Techniques]]]
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[[File:WR-112 Circulator with Bullets.jpg|thumb|400px|Internal construction of a WR-112 (WG 15; R 84) waveguide junction circulator.]]

A waveguide junction circulator contains a magnetized ferrite resonator, which is located at the junction of three [[Waveguide (radio frequency)|waveguides]].<ref name="Helszajn Waveguide Junction Circulators">{{Cite book|title=Waveguide Junction Circulators: Theory and Practice|first=Joseph|last=Helszajn|date=1998|publisher=John Wiley & Sons|isbn=0-471-98252-0}}</ref>  In contrast with a stripline junction circulator, the ferrite itself is the resonator, rather than the metal central portion of a stripline center conductor.  The ferrite resonator may have any shape that has three-fold [[Rotational symmetry]], such as a cylinder or [[Triangular prism]].  The resonator is often just one ferrite, but it is sometimes composed of two or more ferrites, which may be coupled to each other, in various geometrical configurations.  The geometry of the resonator is influenced by electrical and thermal performance considerations.  Waveguide junction circulators function in much the same way as stripline junction circulators, and their basic theory of operation is the same.

The internal geometry of a [[Waveguide (radio frequency)|waveguide]] junction circulator comprises a junction of three waveguides, the ferrite resonator, and impedance matching structures.  Many of these circulators contain pedestals located in the central junction, on which the ferrite resonator is located.  These pedestals effectively reduce the height of the waveguide, reducing its [[characteristic impedance]] in the resonator region to optimize electrical performance.  The reduced-height waveguide sections leading from the resonator to the full-height waveguides serve as impedance transformers.

The ferrite resonator is magnetized through its height, i.e., the static magnetic bias field is perpendicular to the plane of the device and the direction of signal propagation is transverse to the direction of the static magnetic field.  The static magnetic bias field is typically provided by permanent magnets that are external to the waveguide junction.

{{center|'''E-Field Plots Showing Electromagnetic Wave Propagation in Waveguide Junction Circulators'''}}
{|
| [[File:Wg scatter.ogg|thumb|400px|E-field scatter plot of an electromagnetic wave propagating through a waveguide junction circulator.]]

| [[File:Wg ferrite.ogg|thumb|400px|E-field plot of the rotating standing wave pattern in the ferrite of a waveguide junction circulator.  The direction of signal propagation is from bottom to upper right, and the upper left ferrite apex is nulled.]]
|}