Angle of Arrival Estimation via Small IoT Devices: Miniaturized Arrays vs. MIMO Antennas

This tutorial discusses the problem of angle of arrival (AoA) estimation from small Internet of Things devices. It reviews the limitations and challenges of existing miniaturization strategies, which involve classical antenna arrays. As larger distance between antennas is typically needed for increased precision, the miniaturization without loss of accuracy is a significant problem. The article demonstrates that the use of electrically small antennas does not directly solve the problem, since smaller antennas may require increased distance to avoid coupling between elements. Therefore, this work proposes a new technique to perform AoA estimation in small platforms: a multiple-input multi-ple-output (MIMO) antenna. MIMO antennas are commonly used to increase the communication throughput; however, few works have studied their usage for AoA estimation in line-of-sight environments. The proposed solution offers performance similar to state-of-the-art arrays, but at a substantially reduced size. A performance study is carried out to confirm and validate the proposed technique's accuracy and miniaturization efficacy. Size reduction up to 75 percent compared to linear arrays is achieved with mean absolute errors smaller than 0.11°. The method also demonstrates a resolution of 5° with peak mean absolute error of 0.3° for two simultaneous impinging signals. © 2018 IEEE.