Near-Field Pattern of Large Aperture Higher Order Mode Generator Using Backpropagated Fields in Free Space

This paper reports the estimation of the electric field from a large aperture cavity that generates a higher order mode by backpropagation of fields measured in free space. A higher order mode of a TE_6,2 mode at 94 GHz is designed and fabricated using a quasi-optical manner for the analysis. The backpropagating field at the aperture is compared with the measured field. The field estimated at the aperture is used to analyze the mode information, such as the amount of mode mixture of two different rotating fields and the phase difference between two modes. This paper provides a quantitative way to analyze the rotating cylindrical modes generated from an oversized cavity.