The first-order behavior of separable oscillators

The first-order performance of oscillators satisfying Groszkowski's criterion of separability of linear and nonlinear elements can be predicted in the first order with a knowledge only of the Nyquist diagram of the linear portion of the circuit, the amplitude characteristic of the nonlinear portion, and the loop gain. The best form of nonlinear characteristic from the standpoint of frequency stability is one in which the odd-power terms are dominant.