ON THE MODELING AND OPTIMIZATION OF SCHOTTKY VARACTOR FREQUENCY-MULTIPLIERS AT SUBMILLIMETER WAVELENGTHS

Schottky varactor frequency multipliers are used to generate local osc illator power at millimeter and submillimeter wavelengths, The equival ent circuit of the Schottky varactor contains a junction capacitance, a junction conductance, a series resistance and a model for electron v elocity saturation, At millimeter wavelengths the equivalent circuit i s affected by the edge effects,,which are due to the small-area circul ar anode. The correction factors due to the edge effect for the juncti on capacitance and for the series resistance are available in the lite rature, In this work the electron velocity saturation is modeled by li miting the velocity of the transition front between the depleted and u ndepleted layer, By using this model the maximum current of the diode is given by the actual area of the transition front between depleted a nd undepleted layers, and is therefore related to the capacitance corr ection factor. The new model has been tested by analyzing a two diode balanced doubler for 160 GHz presented earlier in the literature. The agreement between the theoretical results and the measurements is exce llent, The new diode model is useful in optimization of varactors for high millimeter and submillimeter wave frequencies.