A dual frequency antenna for RSSI-based DOA estimation - from theory to prototype

Wildlife monitoring, e.g. tracking bats, is one of many emerging applications applying wireless sensor networks. In this paper, a dual band antenna for field strength-based direction finding is presented. The complete design process including theoretical considerations and simulations towards a working prototype is shown. To meet the networks crucial requirements of robustness and low-cost fabrication, the design of the antenna pursues a passive approach to realize a set of two orthogonal radiation patterns without side-lobes. The antenna is influenced by the small element separation, i.e. additional side-lobes and impedance transformation. The effects are compensated by an optimized element arrangement, as well as a dual-band matching and decoupling of the antenna elements. The proposed directional antenna array provides a gain pattern suitable for precise field strength-based direction of arrival estimation.