US2906974A - Microwave modulator and switch - Google Patents

Description

Sept. 29. 1959 F. REGGIA UAL 2,906,974

MICROWAVE MonuLAToR AND swITcH Filed Aug. 24, 1956 -Modulunq Signal Inpui ,IIIlII/IIA Frank Reggia lyoy Conway LeCraw yttorngys ...cc-Y

United States Patei't lee of jnerewaveenergy ynew.""lvlljmfeg1p'articnl'arnf-, the invennen provides nuegewave yswitching arrangement-fs" in 2,906,974 Patented. .Serb 29 1959 e resistor "z3," 'iev'nfg switch '24 ues'eaj if ne eier-ent through coil 2 0 risrof the correct 'n'` he effec- 2,906,974 A i T Betkesa-Md-,ssiguqrstuthelluited States, offAmerica as represented by the Secretary of the Army y Appiieuon August 24, -19s6-,fs`'ri No. "ses-,152

relatie. (Crass-98) (Granted under YTitle 35, USS. Code (1952), sec. 266) The invention described kherein maybe manufactured and used by orforh'rGovernrerit'for governmental purposes i epayrnleiit' to us oflaliyro'yaliy thereon.

This invention relates to yiihe"'control of the amplitude Y I gpiesefnuyvravailabieteintes,lilas larab, wijle rheswitch is "une: urge which ythe"lieu/"of microwav'eeiiergy-o'f a "frequency fo through a waveguide section may be controlled by the application of a magnetic eld to a ferrite body within waveguide 12 that is observed when current is applied the section; application of the magnetic field so affects to coil may be explained by the following theory. The the effective permeability of the ferrite as to change the fo linearly polarized energy entering the input end of effective cut-off frequency of the section from a value waveguide 12 may be considered to be the resultant of above fo to a value below fo, thereby permitting energy two circularly-polarized waves of equal amplitude, one ow to the output end of the section. negative and the other positive. With no applied mag- An object of the invention is to provide a device for netic field the effective permeability of the ferrite 18 controlling the amplitude of microwave energy flow that for both these waves is identical-typically, approxiaffords a wide range of attenuations, requires little energy mately 0.8. When a longitudinal magnetic field is apfor actuation, and is substantially non-dissipative, fastplied, however, the effective permeability of the ferrite acting, reliable, durable, and readily fabricated at low increases to approximately 1.7 for the negative wave, decost. creasing at the same time to approximately zero for the Other objects, aspects, uses and advantages of the inpositive wave. The effective electrical diameter of wavevention will become apparent from the following deguide 12 for the negative wave is thus increased suffiscription and the accompanying drawings, in which: ciently to permit propagation of the wave. Because of Fig. 1 is a simplified longitudinal sectional and schethe low insertion loss obtained, we believe that a conmatic representation :of a form. of microwave switch in version process occurs at the input and output of the accordance with the invention. switch whereby an 4appreciable percentage of the positive Fig. 2 is a simplified longitudinal section and schematic wave energy is converted to negative wave energy, and representation of another switch in accordance with the hence propagates. invention, mounted between two sections of flanged Wave- Fig. 2 shows an arrangment for conveniently mountguide. ing a switch in accordance with the invention between In Fig. 1 a circular waveguide section 12 is shown intwo conventional pieces of rectangular waveguide 32 tegral with an input waveguide section 14 and an out- 45 and 34 having anges 36. putwaveguide section 16. A coaxial ferrite rod 18 In Fig. 2 a switch subassembly 40 includes: a main is positioned within waveguide 12. A solenoid 20 is metallic plate 42, the length and width of which preferwound around waveguide 12. A battery 22 is connectably correspond to the outer dimensions of flanges 36; a able through a resistor 23 to solenoid 20 by means of metallic ground plate 44 the length and width of which a single-pole single-throw switch 24. are slightly less than the internal cross-sectional dimen- With switch 24 open, waveguide 12 has a certain cutsions of waveguides 32 and 34, plate 44 being parallel to oif frequency fel-Le., little or no energy of frequencies plate 42; a length of circular waveguide 46 having its less than fel will propagate through waveguide 12. Let axis perpendicular to plates 42 and 44 and extending bea microwave input signal of frequency fo, slightly less tween plates 42 and 44; a ferrite rod 48 extending cothan fel, be applied to input waveguide 14. With switch axially throughwaveguide 46 and through plates 42 and 24 open, little or none of the fo signal will reach output 44; a solenoid 50 wound coaxially around waveguide 46; waveguide 16. Now let switch 24 be closed. The rea wire lead 52 electrically grounding one end of solenoid sulting ow of current through solenoid 20 causes a 50 to main plate 42; and another wire lead S4 extendmagnetic field to be applied to ferrite 18 and lowers ing insulatedly from the other end of solenoid 50, through the eifective cut-olf frequency of waveguide 12 to a new 60 a passageway 5S in main plate 42, to a point beyond value feg that is lower than fel and that may be made the outer edge of plate 42. lower than fo. The fo energy in waveguide 14 thus be- Subassembly 40 is readily mounted by sandwiching comes coupled through waveguide 12 to output wavemain plate 42 between flanges 36 of waveguides 32 and guide 16. It will be understood that the fo output from 34. The complete assembly may be held together by waveguide 16 may be switched on and olf at very high 65 any usual or convenient means such as the screws 56 rates by switching on and olf the current applied to soleshown. noid 20. Various devices can be coupled to, or substi- From what has been said in connection with Fig. 1, tuted for, waveguide 16. Or waveguide 16 may be it will be understood that the coupling of microwave omitted; energy will then Ibe radiated from the output energy from waveguide 32 to waveguide 34 can be conend of rod 1S. 70 trolled, within a certain frequency range, by supplying If desired, a modulating signal may be applied across current to solenoid 50 by means of wire lead 54. i

g We believe that the lowering of cut-off frequency of It will be apparent that the embodiments shown are only exemplary andv that various rnodiications can be made in construction and arrangement within the scope of the invention as defined in the appended claim.

We claim:

A -microwave switch for mounting between two sections of standard anged rectangular waveguide and adapted for use at a frequency fo, comprising: a rectangular main metallic plate adapted to be mounted between the flanges of said two sections; a rectangular metallic ground plate parallel to said main plate and of lesser length and width than the interior dimensions of said lsections so as to be disposable therein; a length of reduced circular waveguide having its axis perpendicular to both of said plates and extending between said plates; a ferrite rod extending coaxially through said circular waveguide and through apertures in said plates and substantially lilling said waveguide; a coaxial solenoid around said circular waveguide; and means for applying an electrical current to said solenoid; the dimensions of the elements being selected so that the cut-off frequency of said reduced circular waveguide section with said ferrite rod extending therethrough is slightly higher than fo when no current is `applied to said solenoid, said means for applying an electrical current being adapted so that the application of current to the solenoid causes said cut-oil? frequency to fall below fo and thus permit the ow of fo energy between said two sections of rectangular waveguide.

References Cited in the tile of this patent UNITED STATES PATENTS OTHER REFERENCES Van Trier: Applied Scientilic Research, sec. B, vol. 3, No. 2, July 1953, pages 142-144.

Fox et al.: Behavior and Applications of Ferrites in the Microwave Region, The Bell System Technical J ournal,V vol. 34, No. 1, January 1955, pages 5-103.

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