Target Range Selection of FMCW Radar for Accurate Vital Information Extraction

Abstract

Frequency modulated continuous wave (FMCW) radar, which can detect the range and small displacement of a target, has been used for contactless vital information extraction. For accurate vital sign (respiration and heartbeat) measurement, a precise selection of the target range bin, where vital information exists, is important. In this paper, an effective method for selecting the range bin with accurate vital information is proposed. The proposed method is based on the newly introduced magnitude-phase coherency (MPC) index. The experimental results show that the vital information extracted by the proposed method is more accurate than those by conventional methods, indicating that the proposed range bin selection based on MPC is an effective method for extracting accurate respiration and heartbeat rates.

Improved Heartbeat Detection by Exploiting Temporal Phase Coherency in FMCW Radar

“…where BW is bandwidth, c is speed of light, T c is chirp duration, and F s is sampling frequency. The M (t, r) is the extent of the radio wave reflected from the target at r. The P (t, r) is the time delay of the radio wave reflected from the target at r, and modeled as in (3) [24]- [26], [32]- [34].…”

“…2 shows the heartbeat-band filtered P (t, r) in the boundary of the human target, and the referenced heartbeat signal. According to conventional studies [32]- [34], [39], heartbeat signals exist in specific range bins corresponding to the body part where the skin is thin, such as the neck. As shown in Fig.…”

“…where σ P (r) is SD of P (t, r). The method in [34] selects the range bin by exploiting the coherency between the magnitude and phase at each range bin as The method in [35] selects the range bin with maximum magnitude as…”

“…Heartbeat, for which the displacement is smaller than that for respiration, is vulnerable to artifacts and harmonics of respiration [40], [41], which makes it difficult to select the range with a heartbeat signal. Conventional methods select the range bin using the coherency between phases in different range bins [33], the coherency between magnitude and phase [32], [34], extent of magnitude [35], fluctuation of phase [36], or the phase average [37]. However, conventional methods do not consider the characteristics of the heartbeat to select the range bin.…”

Single-Channel FMCW-Radar-Based Multi-Passenger Occupancy Detection Inside Vehicle

“…After mixing the transmitted and received signals and applying the low-pass filter, the instantaneous frequency (IF) signal x(t, n) is calculated. x(t, n) is composed of the beat frequency f r , magnitude M(t, r), and phase P(t, r), as follows [21,22]:…”