Mode analysis of a SAW delay-line oscillator

The stability of multimode delay-line oscillators is discussed using Van der Pol's approximation. It is shown that a nonlinear parameter does not appear in the stability conditions which involve only the open loop transfer function. It is also shown that multimode behavior appears in the case of concave transfer function. Experimental results obtained by means of a surface acoustic wave delay-line three-mode oscillator, including a tunable filter, are in good agreement with the theoretical predictions.