Harmonic Describing Function: Application to Microwave Oscillator's Design

A classic description of negative-resistance devices through the first harmonic approach (Describing Function, DF) yields to results that can be insufficiently accurate or even inexact since the harmonic content in the control signals cannot be avoided a priori by the designer, so the basic condition for the application of DF is not fulfilled. In this paper, the use of a new approach, the "Harmonic Describing Function" (HDF), is proposed to study the nonlinear device behaviour without restrictions in the harmonic content of signals involved in the analysis. HDF, evaluated by means of harmonic balance technique, describes the nonlinear device together with the linear network in which it is integrated, so the harmonic content of signals appears as a result of the analysis.