Ring aperture with azimuthal gradient in phase shift

The rather simple idea is to use elctrodes on different potentials and arrange them annuarly around a ring shaped aperture hole such that the potential is steadily increased between the electrodes on the highest and smallest potential.

Due to the radial arrangement the electrodes on the highest and lowest potential are next to each other such that the phase shift makes one rather drastic jump.

Some simulation data

Scalar cutplane through simulated mesh