Compact mechanical frequency-tunable coaxial relativistic Cherenkov oscillator

A compact coaxial relativistic Cherenkov oscillator with mechanical frequency-tuning capability is proposed and numerically investigated. By axially adjusting the position of a tuning ring located at the end-reflective collector, phase modulation of the reflected electromagnetic waves enables frequency agility. The device demonstrates continuous frequency tuning from 9.04 to 9.66 GHz through a 9 mm axial displacement of the tuning ring, corresponding to a relative bandwidth of 6.6%. Numerical simulations reveal gigawatt-level output power with peak conversion efficiency reaching 35%. The device maintains compact dimensions of 140 mm in axial length and 45 mm in radial dimension, achieving frequency reconfiguration through a simple mechanical adjustment without requiring complex multi-segment synchronization mechanisms. This work provides a viable solution for balancing frequency-agile operation and structural simplicity in high-power microwave generation systems.