US 3849746 A
A mounting assembly for mounting a rectangular ferrimagnetic toroid core longitudinally within a rectangular waveguide of a low-power-mode ferrite-core phase shifter comprising:
Description (OCR text may contain errors)
nited States Patent [191 Mason et a1.
[ NOV. 19, 1974 MOUNTING ASSEMBLY FOR I AJ N N AV GUJB L PHASE SHIFTER  Inventors: Robert J. Mason, Medford; Earl Dixon, Voorhees, both of NJ.
 Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.
22 Filed: Oct.l8, 1973 21 Appl. No.1 407,744
Attorney, Agent, or FirmR. S. Sciascia; P. Schneider; W. T. Ellis [5 7] ABSTRACT A mounting assembly for mounting a rectangular ferrimagnetic toroid core longitudinally within a rectangular waveguide of a low-power-mode ferrite-core phase shifter comprising:
a. four pegs inserted into four holes positioned in the waveguide walls so that one peg is positioned on each side of the waveguide at each end of the core and acting to restrict lateral movement of the core with respect to the waveguide;
b. dielectric transformers at each end of the core partially overlapping each of the four pegs and acting to restrict movement in the longitudinal direction of the core with respect to the pegs.
6 Claims, 6 Drawing Figures PATENTEL NOV 1 91974 sum 2 a? 21 MOUNTING ASSEMBLY FOR FERRIMAGNETIC w CORE IN WAVEGUIDE PHASE SHIFTER FIELD OF THE INVENTION The present invention relates generally to microwave phase shifters and more particularly ferrimagnetic cores.
DESCRIPTION OF THE PRIOR ART the space within the hollow ferrimagnetic toroid. The
phase is varied by sending a current pulse thorugh the wire which acts to induce a magnetic flux in the toroid. When thecurrent pulse hasdissipated and thus h= o,
there will still be s dne remanent magnetic flux density B in the toroid due to hysteresis effects, This remanent flux density change will cause a change in the propagation constants in the toroid. Thus the microwave signal will pass through the ferrimagnetic toroid either faster or slower depending on whether the flux density is increased or decreased from its last level. This change in the electrical length of the toroid will cause the phase shift in the microwave signal. The flux density is proportional to the size of the current pulse through the wire. Thus the phase shift can be varied by varying the size of the current pulse.
This invention concerns itself with mounting the toroid of ferrimagnetic material in the longitudinal center of a rectangular waveguide. Ferrimagnetic core materials are generally fragile and magnetostrictive and therefore must be attached to, and supported in the waveguide in a movement restricting manner, yet the stresses on the ferrimagnetic materials resulting from the differential thermal expansions of the different materials in the phase shifter must be limited to an acceptable level.
The prime problem in such phase shifters results from the fact that the thermal expansion of the metal of the waveguide is different from the thermal expansion of the ferrimagnetic toroid, thus during changes in the thermal environment the waveguide will expand a different amount than the toroids and thus the core will have a tendency to slip out of its mounting within the metal waveguide. A mounting that allows sufficient clearances for thermal and magnetostrictive expansion yet restricts the movement of this core is therefore desirable.
SUMMARY OF THE INVENTION Briefly the invention comprises a mounting to properly restrict the movement of a ferrimagnetic core of a phase shifter while allowing space for thermal and magnetostrictive expansion of the core.
Thus in a phase shifter where a toroid core of ferrimagnetic material is mounted longitudinally in a waveguide, movement of this core is restricted bya. support means, positioned on either side of the core, restricting lateral motion of the core and being restricted in its own longitudinal movement by pegs protruding outwardly from the support means and being inserted in the side-walls of the waveguide;
b. dielectric transfonners at each end of the core,
completely covering the ends of the core and overlapping the ends of the support means restricting longitudinal motion of the core with respect to the support means.
0. top and bottom walls of the waveguide restricting vertical motion of the core.
OBJECTS OF THE INVENTION An object of the present invention is to mount a ferriimagnetic core in a waveguide such that movement of this core will properly be restricted while still allowing space for thermal and magnetostrictive expansion.
A further object'is to prevent slipping of the ferrimagnetic core out of its mountings in a waveguide.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanyingdrawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top view of an embodiment of the mounting assembly of the present invention with the top removed.
FIG. 2 is a sectioned side view of an embodiment of the mounting assembly of the present invention with the top removed.
FIG. 3 is an end view of an embodiment of the mounting assembly of the present invention with the top removed.
FIG. 4 is a sectioned, perspective, end view of an embodiment of the mounting assembly of the present invention.
' FIG. 5 is a sectioned, perspective, end view of an embodiment of the mounting assembly of the-present invention with a heat-conducting element for high power mode operation.
FIG. 6 is a top view of an embodiment of the mounting assembly of the present invention with heatconducting elements for high-power-mode operation.
DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows the basic ferrimagnetic-core phaseshifter that will be used'to illustrate the present invention. The walls of the rectangular waveguide 14 are of metal. The rectangular, ferrimagnetic, toroid core 12 is positioned in the longitudinal center of the waveguide 14. The core consists of a bonded stack of one or more ferrimagnetic toroids. A wire 24, embedded in a coaxial dielectric insert 26, runs down the longitudinal center of the toroid core 12, as shown in 'FIG. 4. The wire 24 acts to conduct the pulse of current which will change the remanent flux density B, and thus change the phase of the phase shifter by making the toroid appear electrically longer or shorter to the microwave energy- On either side of the toroid core, a plurality of dielectric pegs 16 are inserted into holes drilled in the waveguide wall such that the peg-heads protrude out at the toroid core 12. These pegs 16 act to restrict lateral motion of the toroid core. Any number of pegs may be used on each side of the toroid core. The'only restriction is that there is a peg positioned in the waveguide at each end of the core. (This restriction will be explained later.) The pegs may be secured with epoxy if they fit too loosely in their respective holes.
Appropriate clearances are provided between the troid core 12 and the protruding pegs to allow for thermal and magnetostrictive expansion. Thus, since the core is free to move within these clearances, the stresses in the core due to expansion are limited to an acceptable level.
A transformer is bonded to each end of the toroid core. This transformer 10 is a dielectric, impedancern atcl 1g1g transformer which acts to m atch the high impedance of the empty waveguide to thever yTcTwTmpedance of the ferrimagnetic core (dielectric constant e==l6).
Multi-step transformers have been found best suited to perform this matching function. The more steps used to provide intermediate steps between the two extremes, the better the broad-band matching characteristics.
In this particular embodiment a two-step impedancematching transformer 10 is used, though the invention is in no way limited to a two-step transformer. In fact any type of impedance-matching microwave transformer may be used.
The transfonner 10 may take any shape, the only restriction being that it completely cover the end of the toroid core and overlap the sides of the pegs positioned at the ends of the toroid core. The purpose of this overlap is to restrict the longitudinal movement of the toroid core 12 with respect to the pegs 16. The peg-heads may be flattened on the side coming in contact with the transformer 10 to provide more surface-area contact.
In the transformer 10 there is a small groove cut laterally across the transformer face that contacts the end of the toroid core 12. This groove 20 can be seen in the sectioned-side view of FIG. 2. The groove acts to feed the wire 24 into the center of the toroid core 12.
Due to the very high dielectric constant of the ferrimagnetic material of the core, if there is a low dielectric constant gap between the ferrimagnetic toroid core 12 and the waveguide ceiling, a number of unwanted modes would be set up in the waveguide. Furthermore, there would be unwanted absorptions and resonances such that the guide could not work over a proper bandwidth. Thus a very tight fit between the waveguide and the toroid core is desired. In order to accomplish this, a thin metallic sheet 18, for example of aluminum, extends completely from one sidewall of the waveguide to the other sidewall and acts as the top and bottom of the waveguide over and under the toroid.
The toroid core l2 i s h1ad e slightly higher than the adjacent waveguide sidewalls. Thus, when the thin metallic sheet 18 is placed over the core 12 and the waveguide walls 14, the toroid core 12 will push-up on the metallic sheet while the aluminum cover 22 pushes down on the sheet 18, thus giving a very tight contact between the waveguide metallic sheet 18 and the toroid core 12.
When no heat-conducting elements are fitted between the toroid core and the waveguide walls, as in FIGS. l-4 then the ferrimagnetic phase-shifter can 6 only be used in a low-power mode such as a receiving mode where very little heat builds up in the toroid core.
When a ferrimagnetic-core phase-shifter is used in a high-power mode, such as a transmitting mode, heatconducting elements are definitely needed to dissipate the large amounts of heat built up in the ferrimagnetic core. Thus, as in FIG. 5, a heat-conducting element could be positioned on each side of the ferrimagnetic core 12 with a peg 29 protruding out of the side of the 1 heat-conducting element facing the waveguide wall and fitting into a hole in the waveguide coinciding with the protruding peg. These pegs act to restrict the longitudinal movement of the elements 28 with respect to the waveguide walls. An appropriate clearance is allowed between the ferrimagnetic core 12 and the heatconducting elements 28 for thermal and magnetostrictive expansion while restricting lateral motion.
Again the toroid core 12 is made slightly higher than the heat-conducting elements 28 so that the core 12 will push-up on the metallic sheet 18 forming the waveguide ceiling and thus provide a tight contact between the waveguide ceiling l8 and the toroid core 12.
Thus the toroid core 12 is I l. restricted by either a heat-conducting element 28 or a peg 16 from lateral motion;
2. restricted by the top and bottom metallic from vertical motion;
3. restricted by the transformers 10 from longitudinal motion with respect to either the heat-conducting element 28 or the peg 16.
A top view of this mounting assembly with these heat-conducting elements 28 for high-power-mode operation is shown in FIG. 6. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
What is claimed is:
1. A mounting assembly for mounting a core of ferrimagnetic material within a waveguide of a low-power, microwave phase-shifter comprising:
a ferrimagnetic core mounted longitudinally within said waveguide;
a plurality of at least four dielectric pegs inserted in holes drilled in the waveguide walls with four of said holes lined up with the ends of said core and acting to hold said four outer pegs, one hole being positioned on each side of the waveguide at each end of the core, the heads of said pegs protruding toward said ferrimagnetic core but leaving an appropriate clearance between said ferrimagnetic core and the peg-heads to allow for thermal expansion and acting to restrict the lateral motion of said core; I
a plurality of dielectric transformers, one bonded to each end of said ferrimagnetic core and completely covering the ends of said core and overlapping the protruding heads of said four outer pegs so as to restrict longitudinal motion of said core with respect to said four outer pegs.
2.'A mounting assembly as in claim I wherein the side of each protruding head of said four outer pegs facing said transformer is flattened to provide more sheet 5 surface area contact between said transformers and by a thin metallic sheet, and further wherein the height dimension of said ferrimagnetic core is greater than the height dimension of the side walls of said waveguide such that said thin metallic sheet is stretched across the top of said core thus making a tight contact between the top and the bottom of said ferrimagnetic core and said waveguide walls.