Electronic Design

Serious Talk About Parametric Amplifiers

The spotlight was on parametric amplifiers during three days of intensive microwave discussions at the National Symposium of the Professional Group on Microwave Theory and Techniques. In supporting roles were solid-state materials and the generation of millimetric waves. Masers, the center of microwave interest last year, were brought up only by way of odious comparison.

Improved system sensitivity, which R. Weglein of Hughes Research Laboratory said has exceeded 6 db, can be achieved in existing radars at low cost. There are thousands of such radars in the country, creating a ready market for such devices.

Further work at Bell Labs, using gallium arsenide, described by Dr. William Sharpless, has produced solid-state parametric amplifiers approaching masers as far as noise figures are concerned. Using multiple resonator filters such as coupling networks, according to George L. Matthaei of Stanford Research Institute, provides bandwidth as great as 27 % in non-degenerative parametric amplifiers. (Electronic Design, June 8, 1960, p. 7)

The parametric amplifier, with its transfer of energy from the pump frequency to the signal through the gallium arsenide diode's voltage-variable capacitance, was a formidable challenge to understanding—but it worked.

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