This method considers a multi-antenna MIMO receiver that receives signals from a single or multi-antenna transmitter node. At least one of the antennas of the receiver can either translate or rotate, while at least one other antenna remains static. The receiver measures the wireless channels from the transmitter node to these antennas over time. The inventors show that the ratio of the channels from any single transmit antenna to the receiver’s moving antenna and static antennas is independent of frequency offset. This ratio can therefore be used instead of the wireless channels themselves to perform SAR. As a consequence, this system allows a wireless receiver to calculate the relative power of the signals it receives from any particular wireless transmitter along any given direction. Further, it does not require any additional modification to or feedback from the transmitter nodes.
To perform SAR, a wireless receiver must periodically estimate the wireless channel from a transmitter node. As a result, the receiver needs to be aware of the actual signal transmitted by the wireless transmitter. However, if the transmitter is a single-antenna device, this system offers the additional advantage of not requiring prior knowledge of the actual signal transmitted by the transmitter node. In other words, the receiver can perform SAR from a single-antenna transmitter, purely from the received signals, without actually estimating the wireless channels from this transmitter to its receiver antennas.