A Novel TM₀1–TE₁1Circularly Polarized (CP) Mode Converter

A novel mode converter that converts a TM01mode to a CP TE11mode was developed. In the converter, the TM01mode is transformed into a coaxial transverse electric and magnetic (TEM) mode first, then the coaxial TEM mode is split in space into multiple TE11sector waveguide modes by eight plates in the coaxial waveguide, which further subject the TE11sector waveguide modes to different signal paths and hence effectively convert the TEM mode into a CP TE11mode. A mode converter at 4GHz was designed. The conversion efficiency of TM01-to-TE11is 99% at center frequency with an axial ratio of 0.7dB. Over the frequency range of 3.8-4.3GHz, the conversion efficiency exceeds 90%, and the axial ratio is less than 2.7dB. A good agreement between experiments and simulations was observed