*2.1. Used Devices*

The radar used in this paper is the Texas Instruments AWR 1642 [35], originally developed for the automotive market [36]. Being designed for industrial applications, it has reduced costs with respect to other types of radar, and its use in the context of interest of this work allows to verify if it is possible to classify people movements with a good accuracy also exploiting commercial devices. It exploits two bandwidths, in the frequency ranges of 76–77 GHz and 77–81 GHz with 1 and 4 GHz bandwidth, respectively. The former is used for long range applications (up to 150 metres) and the latter for short range applications (up to 30 metres). The radar considered in Reference [6] is an Ankortek SDR-Kit 2400AD, a Software Defined Radio (SDR) working in the frequency range 24–26 GHz, with a maximum bandwidth of 2 GHz and a chirp time and maximum ramp slope of 15.625 MHz/μs [37]. With respect to radar used in Reference [6], the higher frequency, the larger bandwidth and the steeper ramp allow to achieve an increase of twenty time in range performance and three times in speed.

An additional characteristic of AWR 1642 is the presence of multiple-input multiple output (MIMO) technology in the sensor [38], which, in case of radar systems, has the goal of improving performance in angular detection.
