Analysis of the Synthesis Method for Broadband Oversized TE₀₁-to-TE₁₁ Mode Converter

An investigation of the single-frequency iteration method for synthesizing mode converter is taken, and the results show that the synthesized structure has an almost constant perturbation period, which limits the bandwidth of the mode converter. Therefore, a multifrequency iteration method based on variable perturbation periods is proposed to design a broadband oversized TE 01 -to-TE 11 mode converter in this article. To avoid the interference among the perturbation periods corresponding to different frequencies, a weight function is introduced to separate these periods from each other. Using the proposed method, a TE 01 -to-TE 11 mode converter is designed with the conversion efficiency over 95% in the range of 32.5–36.2 GHz (the relative bandwidth of 10.77%). To validate the performance of the proposed mode converter, a prototype is manufactured and measured. In the S-parameters measurement, an average conversion efficiency exceeding 93% and an average ohmic loss near 3% are obtained in the range of 32.3–36.2 GHz. The high purity of circular TE 11 mode is demonstrated at the output of the fabricated mode converter according to the measured field patterns.