Parametric amplification with a high-Q LC resonator

Our measurements at 0.15-4.2 K and at frequencies below 1 MHz show that vol tage biased varactor diodes can be used for the tuning of high-Q LC resonat ors. GaAs diodes with a variable capacitance in the range 1-13 pF are found to be adequate for circuitry with a Q value in the regime (1-4) x 10(4) an d a noise level below 2 nV/root Hz. We use the voltage-controlled varactor capacitance to obtain parametric gain from the resonator. (C) 2000 Elsevier Science B.V. All rights reserved.