Abstract
The paper presents overmoded circular waveguide mode converters (TE
01
into HE
11
with TE
11
as an intermediate mode) used in a 42 ± 0.2 GHz, 200 kW gyrotron transmission line system for plasma heating in electron cyclotron resonance heating application. To convert mode from TE
01
to TE
11
, we have used wriggle converter method with a deformation in the converter axis and for TE
11
to HE
11
mode converter the depth of corrugation decreases gradually from
to
. Both the converters are optimized in terms of design parameters using mode field matching technique. The TE
01
to TE
11
mode converter showed a conversion efficiency of 95% (predicted 99%) for a length of 1205 mm, while TE
11
to HE
11
mode converter gave conversion efficiency of 99% (predicted 99.98%) for a diameter of 32 mm. Cross-polarization isolation of 31.7 dB is obtained in TE
11
to HE
11
mode converter. Convergence of the theoretical values and the simulated results indicates that the converters meet the system requirements.