An improved field emission system and method. The invention pertains to field emission structures comprising 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 the field emission structures and the spatial force function. The spatial force function may be based on one or more codes. In various embodiments, the code may be modified or varied. The code may be combined with another code. One or more aspects of the code, including spacing and amplitude, may be modulated or dithered according to a predefined pattern. Multiple magnet arrays may be combined, each based on a different code or portion of a code, resulting in a combination spatial force function. Magnet structures having differing field patterns may be used to generate a desired spatial force function related to a cross correlation of the two field patterns.