From The Crop Circle Ship Wiki
The Field Generator is a componenet of the crop circle ship which exists in the position between the bottom of the Watersphere and the Electrical Structures. It's exact connections or purpose are currently unknown, however it seems more likely to be related to gravity, and not energy (it is not shown in the Barbury Castle Tetrahedron).
personal gravity field generator - help from above?
The best examples of the Field Generator were provided in 2002.
The position of the Field Generator is indiciated in each of these examples. I feel that this is accurate.
Below, the Field Generator is shown inside or above the Electrical Structures. See the large structure image at the bottom of this page.
 Additonal information
The two formations below were created on the same night. Is it possible that the one on the right shows an effect that the Field Generator has on gravity?
Below, may be the field generator.