How does a Schottky diode mixer work at terahertz frequencies and what are its limitations?
Schottky Diode Mixer Technology for THz Receivers
Schottky diode mixers have been the backbone of terahertz heterodyne receiver technology since the 1970s, when they enabled the first ground-based and airborne astronomy observations at submillimeter wavelengths. Their ability to operate at ambient temperature makes them uniquely practical for many terahertz applications.
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Frequently Asked Questions
What is the highest frequency at which Schottky diode mixers have been demonstrated?
Schottky diode mixers have been demonstrated at frequencies up to about 5 THz in laboratory settings, with practical receivers operating routinely to 2.5 THz. Above 2 THz, hot electron bolometer (HEB) mixers generally provide better sensitivity.
Why do terahertz Schottky mixers need such small anode diameters?
The junction capacitance must be small enough that its impedance at the operating frequency is comparable to the diode series resistance. At 1 THz, a 1 fF capacitance has an impedance of about 160 ohms. Anodes larger than about 1 micrometer produce capacitances that short-circuit the terahertz signal.
Who manufactures terahertz Schottky diode mixers?
Virginia Diodes Inc. (VDI) is the leading commercial supplier of Schottky-based terahertz mixers and multiplier chains, producing both individual components and complete receiver front ends covering 75 GHz to 2.5 THz. JPL and LERMA have also developed advanced Schottky mixers for space science missions.