Broadband TE01 to TE11 Mode Conversion Including Parasitic Input Modes

This article analyzes the effect of input parasitic modes on the broadband TE01 to TE11 mode converter, which is based on multifrequency phase matching. The interference mechanism of input parasitic modes on the output of broadband mode converter is studied by quantitatively investigating their input magnitude and phase. Further study is carried out to survey the effect caused by multiple parasitic modes, and an equivalent analysis model is established, of which results demonstrate the independence of parasitic modes’ interference on mode conversion. To eliminate the effect of parasitic modes, a method to design a mode converter with multiple modes input is adopted and verified by measurement. The test results show that the high purity of TE11 mode can be obtained at the output port with a conversion efficiency over −0.2 dB, when the power content of input parasitic modes content is up to 25%. The analysis of this article can be analogically extended to other devices based on the mode coupling theory of cylindrical waveguides, which helps to design high-efficient components, such as waveguide bends.