A TM₀₁ to TE₁₁ Mode Converter Based on Step Waveguide Discontinuities for High Power Microwave Sources

High power microwave (HPM) systems using vacuum electron devices as source with TM01 circular waveguide output mode, often require a TM01 to TE11 mode converter for ease of coupling to the radiating system. Some novel cylindrical waveguide TM01 to TE11 mode converters using single and multiple cells of step waveguide discontinuities (SWDs) are proposed. It offers the advantages of high conversion efficiency, high power-handling, moderate bandwidth, and compact size. To validate the concept, the 3-GHz circular waveguide TM01 to TE11 mode converters with single-, dual-, and triple-SWD cells of discontinuities have been designed and simulated using a 3-D electromagnetic solver. It is observed that the bandwidth and power-handling capability increase as the number of SWD section increases. The dual-SWD cell-based mode converter (DSC-MC) was experimentally tested at low power using a network analyzer and by measuring its radiation pattern through a horn antenna. This mode converter demonstrated a bandwidth of 6.93%, a conversion efficiency of 91%, and a computed power-handling capability of 848 MW in a compact size of
$1.71\lambda _{{0}}$
.