Particle-in-Cell Simulations on High-Efficiency Phase-Locking Millimeter-Wave Magnetrons with Unsynchronized High-Voltage Pulses

Abstract

Phase locking is an essential choice for building a coherent array, and a system of phase-locked magnetrons is relatively compact and cheaper than other microwave sources. Previous theoretical and experimental studies on phase locking are conducted using synchronized high-voltage pulses. Here, we investigate the characteristics of two phase-locked magnetrons using particle-in-cell (PIC) simulation software (CST STUDIO SUITE 2020) when two high-voltage pulses have delays. The results show that the magnetrons produced two-level RF signals because the operation could be divided into two stages. The first stage happened when one cathode emitted electrons; then, the electrons formed one spoke, traveling in synchronism with the 0-phase difference mode. Two output ports both produced half the output power of a free-running magnetron. The second stage happened after another cathode started to emit electrons, which were instantly pre-modulated by the electromagnetic field of the 0-phase difference mode produced during the first stage. In the second stage, simulations showed that pre-modulation accelerated the process of electron bunching. Eventually, two magnetrons were phase-locked, and the total output power of the two identical magnetrons nearly doubled the output power of the free-running magnetron, which demonstrated that the magnetrons were phase-locked in the high-efficiency phase-locking regime.