The planar annular varactor and its application to millimeter parametric transducers

The parametric amplifier and parametric harmonic generator arts have not advanced into the millimeter wave region. A study of conventional pill and mesa varactors shows that the Q deteriorates rapidly in the millimeter wave region due to the overwhelming effect of skin losses. A new varactor structure containing a planar annulus is disclosed. An order of magnitude improvement of Q is realized from the planar annular varactor, thus making possible the extension of the low noise parametric amplifier art and pump harmonic generator art further into the millimeter wave region. The varactor structure incorporates advances of photolithography which permit the waveguide circuit conductive walls to be brought into close proximity to the diode junction. The planar annulus outside diameter is 12 microns and the inside diameter is 5 microns. The varactor diode and its package parameters and their influence upon transducer design are discussed.