Design and analysis of multimode x-band wraparound mode converter and extractor for pulse compression systems

The characteristics of multimode X-band wraparound mode converter and extractor for RF pulse compression systems have been analyzed using a full 3D electromagnetic field inside a structure based on the finite element method (FEM). The converter performance is sensitive to the number of guide feeding and the feed of the WR90 rectangular waveguide while the extractor at two and seven guide feeding is sensitive to the feed of the WR90 rectangular waveguide and the circular output waveguide radius, which allow small reflection near 0.2 occurring at the input. The two output ports have transmission equal to unity at most X-band frequencies for the useful circular TE₀₁ mode. For the specific circular mode extractor, the transmission is large or is equal to 0.5 at most X-band frequencies. The converter and extractor characteristics at the first five modes TE₁₁, TE₂₁, TE₀₁, TE₁₂ and TE₂₂ such as reflection coefficient, transmission coefficient and the magnitude of electric field are obtained using numerical simulations.