An All Circular Waveguide Four-Way Power Combiner With Ultrahigh-Power Capacity and High Combination Efficiency

The two-way power combiner consisting of two TM
₀₁
-TE
₁₁
serpentine mode converters with a common output has demonstrated high-power capacity and high combination efficiency for two phase-locked relativistic backward wave oscillators (RBWOs). To realize channel power combination for four phase-locked X-band RBWOs, we propose an all circular waveguide four-way power combiner based on the previous two-way power combiner. Four TM
₀₁
modes are first combined into two TE
₁₁
modes with two TM
₀₁
-TE
₁₁
mode two-way power combiners; then, through two separate 90° bending waveguides and tapered waveguides, the two TE
₁₁
modes are combined into one TE
₁₁
mode with a TE
₁₁
-TE
₁₁
mode two-way power combiner. Separate calculations show that at 9.22 GHz, the conversion efficiency of the TM
₀₁
-TE
₁₁
mode two-way power combiner is 95.4%, the transmission efficiencies of 90° bending waveguide and tapered waveguides, and the combination efficiency of the TE
₁₁
-TE
₁₁
mode two-way power combiner are close to 100%. Integrated simulations indicate that as four incident ports are fed with TM
₀₁
modes with power of 2.5 GW at each port and phase of 0°, 180°, 0°, and 180°, respectively, the total combination efficiency is 94.5%, and the maximum electric field in the four-way power combiner is 774 kV/cm.