This paper is about estimating the direction of arrival (DOA) of GNSS signals using two antennae for spoofing detection. There are many applications using two antennae. The DOA method could be useful to detect spoofing attack even though it can only provide 2-dimensional angle estimation result. Simulations show that using the difference of carrier phase measurement between the antennae, the direction of GNSS signals can be estimated with 180 degree ambiguity. Regarding this ambiguity, a tactical approach has been proposed. Assuming that all the spoofing signals come from a single transmitter, multiple authentic signals' and combined spoofing signals' paths are differentiable by checking 180 degree mirror images. And the estimation performance with respect to the measurement noise and geometry between satellites and user antennae has been analyzed. Also, the developed algorithm has been tested using live GPS signal gathered from the dual antenna RF front-end of IFEN SX-3 software receiver.

Keywords: GPS, GNSS, spoofing detection, anti-spoofing, DOA