Starting mode regime in an FEM oscillator with a Bragg resonator

In an FEM oscillator with a Bragg resonator excitation of an additional starting mode can be exploited as a source of an initial signal for the operating mode. In such a regime the starting mode has a rather small detuning from synchronism resulting in a high temporal gain but a rather small electron efficiency. With the starting mode growth the situation becomes favorable for excitation of the operating mode. Afterwards due to a non-linear competition mechanism the operating mode suppresses the starting mode and a single-mode regime of oscillations is realized with a rather high efficiency.