Low-noise nonreciprocal parametric amplifier with power matching at the input and output

The paper deals with the signal and noise performance of a parametric straight-through amplifier which comprises the cascade connection of a parametric diode up and down converter. By feeding the reactance diodes with pump voltages which are mutually shifted in phase by ±90° and by the additional insertion of a feedback admittance between input and output, complete decoupling is obtained in the backward direction. To obtain power matching on both sides, an idle circuit is arranged between the two converter stages which transmits voltages in both lower and upper sidebands. The practical design of an amplifier is described for a signal frequency of 200 Mc and a pump frequency of 940 Mc. The design of the idle circuit, the pump input and the adjustment of amount and phase angle of the pump voltages, as well as the neutralization, are explained in detail. Measuring results are given which were obtained with this test assembly that was designed in accordance with the rules given. At the mean signal frequency, power matching was achieved at the input and output and the forward transducer gain amounted to 8 db at a 3-db bandwidth of 6 Mc. The backward transducer gain amounted to -40 db, the excess noise figure Fxof only the preamplifier was 0.8, and the excess noise temperature Tz=240°K. The measurements confirmed the theory.