Phase-Shifterless Power Controlled Combining Based on 20-kW S-Band Magnetrons With an Asymmetric Injection

A real-time phase-shifterless power controlled combining based on 20-kW S-band continuous-wave magnetrons with an asymmetric injection was proposed in this letter. A high-power-capacity combiner was designed, and the behaviors of the asymmetric injection magnetrons were qualitatively characterized. The system showed a nearly 3-MHz injection-locked bandwidth and an output power control range over 3 dB at an injection ratio of 0.07. An excellent spur suppression ratio of -65.0 dBc at 500 kHz, an output amplitude stability of 0.02 dB (peak to peak) and a phase stability of ±0.9° (peak to peak) were also demonstrated. To the best of our knowledge, the power output of 34.0 kW with a total combining efficiency of 86.7% sets a new performance record for an S-band continuous wave magnetron power combining system, which is one of the best spur suppressions among all reported S-band injection locked magnetrons with an output power of over 15 kW.