Nonstationary phenomena in tapered gyro-backward-wave oscillators

Recently, it was found that a gyro-backward-wave oscillator (gyro-BWO) with a tapered waveguide can exhibit stationary oscillations at currents which exceed the starting current by more than 2 orders of magnitude. This result, at first glance, contradicts the theory of transients in untapered linear-beam BWO's, which predicts nonstationary oscillations at currents exceeding the start current by a factor of 3. To explain this behavior of the tapered gyro-BWO, its nonstationary theory is developed. The results obtained demonstrate the consistency of the tapered gyro-BWO operation with the known theory of transients and also show that the tapering may provide stationary oscillations at high currents.