Feasibility of heartbeat detection behind a wall using CW Doppler radar

Abstract

This paper presents a wireless measurement system for cardiopulmonary activity detection behind a wall. This system generates a continuous wave signal and is used at 2 different frequencies: 2.4 GHz and 10 GHz. The transmitted signal is directed toward the patient's chest situated at 1 m and then reflected. The radar system is based on a vector network analyzer, which measures the phase of S 21. The phase variation of S 21 contains information about heart and respiration activity. Measurements are carried out every 30 seconds, for a person sitting at a distance of 1 meter, directly in front of the system or behind a wall. Discrete wavelet transform is used as a processing technique to separate heartbeat signal from respiratory signal. The measurements were performed simultaneously with a PCbased electrocardiogram (ECG) which is used as a reference to validate the information extracted from the measured signals.

Evaluation Protocol for Analogue Intelligent Medical Radars: Towards a Systematic Approach Based on Theory and a State of the Art

“…In this section, we analyse more than 50 papers on medical radar experiments in order to extract from them interesting elements about their protocols [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 ...…”

“…These walls can also be anechoic [ 39 , 45 , 66 ]. Rarely, the experiment is carried out outside with no proximate walls [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ], or surrounded by ruins [ 24 , 74 ]. Ref.…”

“…For the last protocol information category, we deal with the ‘Measurements’ themselves. Details can be given about the sensors for measuring heart and respiration rates [ 7 , 8 , 27 , 30 , 40 , 48 , 57 , 65 , 76 ], the duration of the experiment [ 18 , 19 , 42 , 52 , 55 , 65 , 69 , 73 ], and the breathing style [ 22 , 36 , 48 , 56 , 60 , 65 , 75 ]. The Bland–Altman method to compare sensors and radar data is sometimes applied [ 34 , 76 ].…”

Innovative non-contact r-r intervals estimation using viterbi algorithm with Squared Branch Metric (VSBM)

“…Notably, the Doppler sensor-based method for heartbeat detection eliminates the need for device attachment, distinguishing it from traditional methods such as ECG or PPG (Nosrati & Tavassolian, 2018). A key advantage lies in the ability of transmitted microwaves to penetrate through the subject's clothes, rendering the Doppler sensor-based approach nonintrusive and eliminating the requirement for the subject to disrobe (El-Samad et al, 2016;Ohtsuki & Mogi, 2016;Sekine & Maeno, 2011;Yu et al, 2018;Zou et al, 2014). Nonetheless, achieving accurate heartbeat detection presents a challenge due to the low Signal-to-Noise Power Ratio (SNR) of heartbeat components within the reflected signal of a Doppler sensor, particularly when compared to the SNRs of respiration and minor body movements.…”