A Parametric Amplifier Using Lower-Frequency Pumping

The principle of parametric amplification using lower-frequency pumping has been verified in both a nonlinear inductance and a nonlinear capacitance system. In the former a ferrite core was used and a 30 per cent power gain was observed at a signal frequency of 10 mc and a pump frequency of 7 mc. The low gain is attributed to the small degree of nonlinearity. The nonlinear capacitance system gave much better results because of the larger degree of nonlinearity. Here a reversed-bias junction diode was used as the nonlinear coupling a signal circuit at 380 mc, an idling circuit at 220 mc, and a pumping circuit at 300 mc. A stable net gain of 20 db was obtained at 380 mc with a pump power of only 30 mw. Strong oscillations at 380 mc set in when the gain exceeded 40 db. The full percentage bandwidth is of the order of 0.3 per cent. The noise factor, with a nonisolated load, is in the order of 10 db.