A High-Efficiency Dual-Cavity Extended Interaction Oscillator

A dual-cavity extended interaction oscillator (EIO) is proposed to overcome the efficiency limitation and circuit instability of the conventional EIO (i.e., the single-cavity, strong-coupling EIO), and its advantages in efficiency and stability are demonstrated by the study of a dual-cavity, Ka-band, EIO circuit. Circuit characteristics of the weak-coupling and strong-coupling circuits are studied and the key design issues are analyzed. Efficiency improvement from 14.2% to 20.2% and from 16.8% to 21.7% is predicted by the 3-D particle-in-cell (PIC) simulations performed in CST and CHIPIC, respectively. Not only a high-efficiency dual-cavity EIO circuit is achieved, but also the stability and robustness are analyzed and improved. This design provides an effective approach toward efficiency and stability improvement in the millimeter-wave range, and analyses on the weak-coupling and strong-coupling circuits are practical for the extended interaction structure study.