Parametric amplifier with thermoelectric refrigeration

The noise figure of a variable-capacitance parametric amplifier can be greatly improved by refrigerating the diode. A thermoelectric refrigerator can be used for this purpose without losing the advantage of system simplicity. A two-stage thermoelectric refrigerator has been built into a 6-Gc parametric amplifier. With no load this refrigerator has produced a temperature difference of 101°C below room temperature. In the amplifier it cooled the diode to 213°K. The effective noise temperature of the amplifier was reduced from 170°K when the GaAs diode was at room temperature to 108°K when the diode was cooled to 213°K. The design, construction and characteristics of the amplifier and the thermoelectric refrigerator are described.