Unambiguous Direction Estimation Algorithm Using Dual Antennas in Cooperative Positioning

The realization of anchor-free collaborative positioning requires accurate estimation of the direction of the incident wave from the neighboring collaborative nodes. The traditional passive direction-finding system requires at least three antennas to form an array to receive signals to achieve a high angular resolution, and phase ambiguity must be considered, which makes the system structure complex and costly. In response to this, the letter proposes an unambiguous direction-finding algorithm that can achieve high accuracy with only two antennas. This method uses a similar idea to synthetic aperture radar (SAR) to detect the direction. First, the wireless channel ratio of the two antennas is used to eliminate the phase difference between independent transceiver devices, and then the SAR formula is used to spatially filter the received data, and finally the direction information is obtained from the peak of the spatial spectrum. Software simulation and experimental verification show that the algorithm can achieve unambiguous estimation of multiple incoming wave directions, while reducing the clock synchronization requirements, and the measured direction-finding accuracy is basically within 1°.