High-Efficiency Compact Millimeter-Wave Spatial Harmonic Magnetron with Axial Diffraction TEM Output

A compact Millimeter-Wave Spatial Harmonic Magnetron (SPHM) with Axially diffraction output (ADO) of the TEM mode is proposed. In this ADO configuration, a compact coupling structure is used to replace the cylindrical waveguide to decrease its radial dimension, to obtain an efficient output power extraction and to be more easily coupled to patch-microstrip systems with output TEM mode thereby facilitating large-scale integration. The RF field of the operating π/2-1 mode is extracted from every resonator cavity and guided to the coupling structure. The output RF field is further effectively converted to the TEM mode by a compact mode converter. Moreover, in the resonant system, a 16-cavity rising-sun slow wave structure (SWS) is applied to lower the phase velocity of the operating spatial harmonic and enhance interaction efficiency between the operating electrons and the high-frequency electric field. The particle-in-cell (PIC) simulations demonstrate that the practical SPHM could output a relatively pure TEM mode at the frequency of 37.7 GHz, and its total efficiency is up to 40.1% with 120kW radiation power for a diode voltage of 13kV.