Active phased array antenna for animal location with passive surface acoustic wave based tags

Passive transponders based on surface acoustic waves (SAW) working at 2.4 GHz can be used in animal location systems inside stables where GPS fails. For that kind of systems, a steerable antenna is needed. Due to the environmental conditions inside a stable, a phased array antenna system providing electronic steering and avoiding moving parts is favorable. The design of such an active phased array antenna is explained. Based on the requirements from the location application, the antenna elements are developed first. Two candidates (patch and helix) are evaluated using simulations and measurements. To be flexible, a modularized approach (control unit, backplane carrying RF and antenna module) is chosen for the antenna system. First measurements of a line array are shown and discussed. Currently, the system is completed to form a 2D array which allows scanning in two directions.