The Modified Series Model for an Abrupt-Junction Varactor Frequency Doubler

The theoretical performance of an abrupt-junction high-quality epitaxial varactor diode used as a harmonic frequency doubler is considered. The modified series model for the device, consisting of a nonlinear elastance (reciprocal of capacitance) and a nonlinear resistance, is presented. A comparison is made between the performance limits derived for the modified series model and similar results based on the conventional series model. In addition to dissipating some power, the charge-variable series resistance contributes to the frequency conversion of the device.