Field emission structures comprising a plurality of electric or magnetic field sources having magnitudes, polarities, and positions corresponding to a desired spatial force function where a spatial force is created based upon the relative alignment of a field emission structure and a complementary field emission structure. The magnetic field sources may be arranged according to a code having a desired autocorrelation function. Specific exemplary embodiments are described with magnetic field sources arranged in a ring structure. The ring structure may include one or more concentric rings of component magnets. Additional magnets may be included. Magnet polarities and/or spacings may be defined by the code Mechanical constraints may be employed to limit lateral motion. Exemplary codes are described and applied to magnetic field source arrangements. Specific codes found by the inventors are described.