670 GHz Schottky diode based subharmonic mixer with CPW circuits and 70 GHz IF

A mixer circuit, comprising:

• a LO input configured to receive an input LO signal having a frequency fLO, said LO input signal provided by an first coplanar waveguide;
• a LO matching network configured to match said input coplanar waveguide to an antiparallel diode pair, said antiparallel diode pair configured to provide a signal at a frequency 2fLO;
• an IF input configured to receive an IF input signal having a frequency fIF, said IF input signal provided by a second coplanar waveguide;
• an IF matching network configured to match said second input coplanar waveguide to said diode pair;
• said mixer configured to generate sum and difference signals, said sum signal having a frequency fOUT+=2fLO+fIF and said difference signal having a frequency fOUT−=|2fLO−fIF|, where the difference frequency is always understood to be a frequency that is measured by the absolute value of the difference between the two input frequencies;
• an RF matching network configured to match the output circuitry to a coplanar waveguide and a filter configured to allow one of said sum signal and said difference signal to pass;
• and
• an RF output connected to a third coplanar waveguide.

A method of fabricating a mixer circuit, comprising the steps of:

• on a surface of a semiconductor substrate:
• growing a first etch-stop layer;
• growing a layer of semi-insulating semiconductor;
• growing an second etch-stop layer on said layer of semi-insulating semiconductor;
• growing a contact layer on said etch stop layer;
• growing a Schottky layer on said contact layer;
• patterning and etching said Schottky layer to form diodes;
• metalizing said diodes;
• providing interconnects for said diodes, said diodes being connected in an antiparallel configuration;
• providing coplanar waveguides, input/output coupling probes, and IF output structures;
• fabricating on chip capacitors;
• providing vias to connect frontside and backside structures;
• and
• fabricating backside ground plane structures.