Propagation Parameter Estimation, Modeling and Measurements for Ultrawideband MIMO Radar

• Published in: IEEE transactions on antennas and propagation Vol. 59; no. 11; pp. 4257 - 4267
• Main Authors: Salmi, J., Molisch, A. F.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.11.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna arrays; Antenna measurements; Antennas; Applied sciences; Array signal processing; Arrays; Breathing; Delay; Exact sciences and technology; Frequency measurement; Human; Human subjects; Humans; Mathematical models; multipath channels; parameter estimation; Position (location); position measurement; propagation measurements; Radiocommunications; Radiolocalization and radionavigation; Receivers & amplifiers; Services and terminals of telecommunications; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Telemetry. Remote supervision. Telewarning. Remote control; Tracking; Transmitters. Receivers; Ultra wideband antennas; ultrawideband antennas; ultrawideband radar; virtual antenna array; Line of sight propagation; Magnetooptical effect; Parameter estimation; High resolution; Array signal processing; virtual antenna array; Iterative method; Broadband antennas; Modeling; Remote sensing; Accuracy; propagation measurements; Radar; Delay time; Localization; Antenna array; position measurement; MIMO system; ultrawideband radar; Target tracking; multipath channels; Vector method; Algorithm; Narrow band; ultrawideband antennas; Ultra wide band; Transmitting antenna; Maximum likelihood; Remote supervision
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2011.2164214

Ultrawideband (UWB) radar is a promising method for reliable remote monitoring of vital signs. The use of multiple antennas at transmitter and receiver (MIMO) allows not only improved reliability, but also better accuracy in localization and tracking of humans and their various types of movement. This paper describes an experimental demonstration of localizing a test subject and tracking his breathing under ideal conditions. The UWB MIMO channel, which includes the test subject as well as other objects, is modeled as a superposition of multipath components (MPCs). From the measured data one can extract the parameters of the MPCs, including their directions and delays, which allows localization of the test subject as well as tracking the breathing motion. Since the breathing pattern of the test subject induces delay variations of the diaphragm-reflected MPC that are much smaller than the Fourier resolution limits, the high-resolution RIMAX algorithm (iterative maximum-likelihood estimation scheme) is employed together with a path detection scheme for determining and tracking the MPC parameters. Furthermore, it is illustrated that with a wideband array model, the requirements for antenna spacing are not as limited as for conventional narrowband array processing. Through controlled experiments with a vector network analyzer and a virtual antenna array observing both an artificial "breathing" object as well as a human subject, it is shown that one can accurately estimate the small scale movement from human respiratory activity. This is achieved both for line-of-sight between transmitter, receiver, and objects, as well as for non-line-of sight.