Microwave amplifier having cross-polarized cavities

Abstract

A multi-stage microwave gyrotwystron amplifier is disclosed having two or more stages comprising rectangular cavities to facilitate tuning. The first two stages comprise rectangular tuneable cavities that are oriented orthogonal to each other which produces a homogeneously modulated electron beam that is directed to a cylindrical output cavity which increases its power output as compared to prior art devices havig an output cylindrical cavity excited with a non-homogeneously modulated electron beam.

What we claim is: 
     
       1. A microwave amplifier having a cylindrical axis comprising: (a) a generator of an electron beam;   (b) an input waveguide for introducing a microwave signal into the amplifier;   (c) a first rectangular cavity having first means for accepting said electron beam so that said beam is guided parallel to said cylindrical axis and second means for accepting said microwave signal, said first rectangular cavity being dimensioned to have a first predetermined polarization of its enclosed fields, said first rectangular cavity modulating said electron beam by said microwave signal so as to provide an inhomogeneously modulated electron beam;   (d) a second rectangular cavity having means for accepting said inhomogeneously modulated electron beam, said second rectangular cavity being dimensioned to have a second predetermined polarization of its enclosed fields, said second predetermined polarization being orthogonal with respect to said first predetermined polarization, said second rectangular cavity further modulating said electron beam by said microwave signal to provide a homogeneously modulated electron beam; and   (e) a cylindrical waveguide having means for accepting said homogeneously modulated electron beam to produce a circularly polarized wave that is made available at an output of said cylindrical waveguide.   
     
     
       2. The microwave amplifier according to claim 1, wherein said first and second rectangular cavities are tuneable. 
     
     
       3. The microwave amplifier according to claim 2, wherein said first and second rectangular cavities are staggered tuned. 
     
     
       4. The microwave amplifier according to claim 3, wherein said first and second tuneable rectangular cavities each have a figure of merit, Q, of about 50. 
     
     
       5. The microwave amplifier according to claim 3, wherein said first and second rectangular cavities each have a figure of merit, Q, of about 100. 
     
     
       6. The microwave amplifier according to claim 1, wherein a cut-off drift tube is interposed between said first and second rectangular cavities and between said second rectangular cavity and said cylindrical waveguide. 
     
     
       7. The microwave amplifier according to claim 6 further comprising an output coupler. 
     
     
       8. The microwave amplifier according to claim 7 further comprising a transmission line terminator connected to said second end of said output coupler. 
     
     
       9. The microwave amplifier according to claim 1, wherein said cylindrical waveguide comprises; (a) a traveling wave tube having input and output flanges with the input flange connected to the output of said second rectangular cavity;   (b) a coaxial section serving as a dc break having first and second ends with the first end connected to the output flange of said traveling wave tube; and   (c) an electrode serving as a collector of said traveling wave tube having first and second ends with the first end connected to said second end of said dc break.   
     
     
       10. The microwave amplifier according to claim 1, wherein said electron beam generator comprises a magnetron injection gun that introduces said electron beam parallel to said cylindrical axis.