Varactor harmonic-generator chain as a pump source for a parametric amplifier

This letter gives the results of experiments on the pumping of an X band nondegenerate parametric amplifier with a Q band varactor harmonic-generator chain. It is shown that care must be taken to ensure efficient filtering in the first stage of the chain, and methods are given to obviate spurious responses in the tuning range of the parametric amplifier caused by additional harmonics from the solid-state pump source mixing in the varactor diode of the parametric amplifier.