Mitigation of multipath through the use of an artificial magnetic conductor for precision GPS surveying antennas

The Global Positioning System (GPS) allows surveyors to make static measurements with sub-centimeter accuracy. To achieve these levels of precision, however, requires the mitigation of multipath signals. While signal processing software in the receiver does a good job of correcting for multipath, further improvement can be gained by reducing such unwanted signals before they reach the antenna, such as with a ground plane. While conventional conducting ground planes can shield the antenna element from signals below the horizon, they can also propagate surface waves that can produce significant edge diffraction. Choke rings (circularly corrugated ground planes) provide excellent electrical performance, but are large, heavy, and very expensive. This paper shows that an artificial magnetic conductor (AMC) can provide a solution which has good electrical properties. An AMC is a periodic structure which simulates the boundary conditions of a magnetic conductor over a limited frequency band. AMCs are typically made from printed circuit board materials, hence they are relatively lightweight and inexpensive.