Broadband waveguide mixer

Abstract

A broadband waveguide mixer suitable for the microwave and millimeter wave regions is described. The mixer is characterized by having a unique dual-guide mixer mount through which extends two parallel and spaced waveguides. The RF wave and the local oscillator wave are respectively impressed on the two waveguides via a hybrid coupler. A pair of crossbars extend through each waveguide. A pair of diodes connected back-to-back are disposed in each waveguide and are connected to the respective crossbars. Each pair of diodes has a polarity opposite to that of the other pair. The output is derived from a coaxial cable connected to the adjacent ends of the two crossbars. The input signals may be applied by a folded hybrid tee or a short slot hybrid coupler to simplify the input structure. The mixer has low noise and broadband performance.

What is claimed is: 
     
       1. A broadband waveguide mixer suitable for use in the microwave and millimeter wave regions comprising: a. a first waveguide;   b. a second waveguide, said waveguides being disposed substantially parallel .Iadd.to .Iaddend.and spaced from each other;   c. a first elongated conductive element extending transversely through said .Iadd.first .Iaddend.waveguide;   d. a second elongated conductive element extending transversely through said second waveguide, said elements being disposed substantially on a common axis and being spaced from each other;   e. a first pair of diodes arranged back-to-back and disposed in said first waveguide and in contact with said first element;   f. a second pair of diodes arranged back-to-back and disposed in said second waveguide and in contact with said second element, said first pair of diodes having a polarity opposite to that of said second pair of diodes; and   g. a coaxial conductor connected to the adjacent ends of said elements, whereby when .[.a first wave is impressed on said first waveguide and a second wave of different frequency is impressed on said waveguide, the difference frequency wave is derived from said coaxial conductor.]. .Iadd.first and second waves of different frequencies are impressed on each of said first and second waveguides with one of said first and second waves out of phase with the corresponding other first or second wave, a wave having a frequency equal to the difference in frequencies of said first and second waves is derived from said coaxial conductor. .Iaddend.   
     
     
       2. A mixer as defined in claim 1 wherein means is provided for insulating each of said elements from its respective waveguide. 
     
     
       3. A mixer as defined in claim 2 wherein a capacitor is connected to the adjacent ends of each of said elements to provide coupling and direct current isolation. 
     
     
       4. A mixer as defined in claim 3 wherein means is provided for individually biasing said diodes. 
     
     
       5. A mixer as defined in claim 1 wherein means is provided for impressing a radio frequency wave .[.on one of said waveguides.]. .Iadd.constituting said first wave .Iaddend.and .[.additional means.]. for impressing a local oscillator wave .Iadd.constituting said second wave .Iaddend.on .[.the other waveguide, said waves being out of phase.]. .Iadd.each of said first and second waveguides, .Iaddend.whereby .[.the.]. .Iadd.an .Iaddend.intermediate frequency wave .Iadd.constituting said difference frequency wave .Iaddend.is derived from said coaxial .[.cable.]. .Iadd.conductor. .Iaddend. 
     
     
       6. A mixer as defined in claim 5 wherein a waveguide adaptor is connected to said waveguides. 
     
     
       7. A broadband waveguide mixer suitable for use in the microwave and millimeter wave regions comprising: a. a mixer mount;   b. a first waveguide extending through said mount;   c. a second waveguide extending through said mount and disposed substantially parallel to and spaced from said first waveguide;   d. a first elongated conductive element extending transversely through said mount and said first waveguide;   e. a second elongated conductive element extending transversely through said mount and said second waveguide, said elements being disposed substantially on a common axis and having their adjacent ends spaced from each other;   f. means for insulating said conductive elements from said mount;   g. a first pair of diodes arranged back-to-back and disposed in said first waveguide and in contact with said first element;   h. a second pair of diodes arranged back-to-back and disposed in said second waveguide and in contact with said second element, said first pair of diodes having a polarity opposite to that of said second pair of diodes; and   i. a coaxial conductor connected to the adjacent ends of said elements, whereby when .[.a first wave is impressed on said first waveguide and a second wave of different frequency is impressed on said second waveguide, the difference frequency wave is derived from said coaxial conductor.]. .Iadd.first and second waves of different frequencies are impressed on each of said first and second waveguides, a wave having a frequency equal to the difference in frequencies of said first and second waves is derived from said coaxial conductor. .Iaddend.   
     
     
       8. A mixer as defined in claim 7 wherein a conductive member is provided for each of said diodes, each of said conductive members extending through said mixer mounts, and means for insulating each of said members from said mount. 
     
     
       9. A waveguide mixer as defined in claim 8 wherein a capacitor is connected between each of the adjacent ends of said elements and said coaxial conductor. 
     
     
       10. A mixer as defined in claim 9 wherein means is connected betweeen each of said conductive elements and an associated one of said conductive members for individually biasing said diodes. 
     
     
       11. A mixer as defined in claim 7 wherein an opening is provided through said mixer mount through which said coaxial conductor extends.