Design and Microwave Measurement of a Novel Compact TE $_{0n}$ /TE $_{1n'}$ -Mode Converter

Abstract

A novel method to generate a TE $_{0n}^{{{(\mathrm {C})}}}$ ( $n = 1$ , 2, 3) ( $C$ is circular for short) or TE $_{1n'}^{{{(\mathrm {C})}}}$ ( $n' = 2$ , 3, 4) mode via a TE $_{m0}^{{{(\mathrm {R})}}}$ ( $m = 2n$ or $m = 2n' - 1$ ) ( $R$ is rectangular for short) mode generator is proposed in this paper. Two main components, including a TE $_{10}^{{{(\mathrm {R})}}}$ –TE $_{m0}^{{{(\mathrm {R})}}}$ mode converter with multiple coupling apertures and matching steps and a TE $_{m0}^{{{(\mathrm {R})}}}$ –TE $_{0n}^{{{(\mathrm {C})}}}$ or TE $_{1n'}^{{{(\mathrm {C})}}}$ mode converter, were, respectively, demonstrated. Two novel compact mode converters, respectively, exciting the TE $_{01}^{{{(\mathrm {C})}}}$ and TE $_{13}^{{{(\mathrm {C})}}}$ modes at $Q$ - and $W$ -band based on the aforementioned methodology were designed and analyzed. In the TE $_{01}^{{{(\mathrm {C})}}}$ mode converter design, symmetric cylindrical ridges were introduced to improve the mode purity and suppress the unwanted TE $_{21}^{{{(\mathrm {C})}}}$ mode by cutting off its surface current on the metal wall. Such a mode converter operating at $Q$ -band was manufactured and vector network analyzer measurements showed excellent S-parameter performance (port reflection 90%), which agreed very well with our simulation. Besides, as an expansion of the TE $_{01}^{{{(\mathrm {C})}}}$ mode converter, the designed results of a high-order TE $_{13}^{{{(\mathrm {C})}}}$ mode converter excited by a similar methodology were also presented.