Peer-to-peer locking of magnetrons: Analysis and experiment

Summary form only given. The viability of coherent power combination of multiple high-efficiency, moderate power magnetrons requires a thorough understanding of frequency and phase control. Injection locking of conventional magnetrons, and other types of oscillators, employing a master-to-slave configuration has been studied theoretically and experimentally. We focus on peer-to-peer locking between two conventional magnetrons. Previous work on similar topics assumed equal power and free-running frequency among magnetrons. Such assumptions are removed in this analysis. The necessary condition under which two magnetrons may be locked to a common frequency is derived, with their coupling described by a general 2x2 matrix. Dependent on the degree of coupling, the frequency of oscillation when locking occurs was found to not necessarily lie between the two magnetrons´ free running frequencies. Likewise, when the locking condition was violated, the beat of the spectrum was not necessarily found to be equal to the difference between the free running frequencies. The beat frequency could be larger, as was observed in our experiments. The stability (accessibility) and temporal evolution of the two possible states in which the locking conditions of the two magnetrons are satisfied are being examined. The formulation was then extended to the locking of N magnetrons. Experimental results on the peer-to-peer phase-locking of two 1-kW magnetrons will be reported.