Time-multiplexed AoA Estimation and Ranging.

A joint angle-of-arrival (AoA) and ranging estimation scheme for ultra-wideband devices is presented and experimentally evaluated. Instead of using N parallel receive chains, antenna elements are sequentially switched to the receiver, i.e., time-multiplexed. To obtain time-multiplexed measurements, a special messaging scheme is proposed that extends the conventional double-sided two-way-ranging scheme by a number of response packets that is equivalent to the number of antenna elements. Thereby, each response packet-switched through a different receive antenna-is used to record the complex-valued channel impulse response, which contains the phase information later utilized for AoA estimation. Ranging is jointly obtained through recorded receive and transmit timestamps. As the time-multiplexing introduces significant delays between phase measurements, even small synchronization errors would cause significant AoA errors. Hence, the critical building block is the clock drift compensation. The experimental evaluation with a DW1000 UWB chip and four switched lambda/2 spaced antennas shows an angular accuracy of 5.5 degrees RMSE and the capability of accurate 2-D localization.