CN-122004805-A - FMCW radar vital sign detection method combining VMD and SSR

Abstract

The invention discloses an FMCW radar vital sign detection method combining VMD and SSR. The method comprises the steps of transmitting a chirp signal through an FMCW radar, capturing a radar echo signal, preprocessing the radar echo signal, extracting a human chest wall displacement signal, decomposing the human chest wall displacement signal through a VMD algorithm, determining optimal decomposition parameters through a vital sign distinguishing mode by means of variable step-length double-stage search, decomposing the human chest wall displacement signal through the optimal decomposition parameters to obtain a heartbeat signal and a respiratory signal modal component set, finally distinguishing respiratory harmonic modal components in the frequency range of the heartbeat signal, reconstructing the heartbeat signal, constructing an SSR model, carrying out sparse spectrum reconstruction on the heartbeat signal based on a ZA-EFRLS algorithm, solving the heartbeat signal, and extracting the heartbeat frequency. The method solves the problems of difficult extraction of the heartbeat signal, clutter interference, insufficient frequency resolution under a short-time observation window, long heartbeat frequency extraction time and the like.

Inventors

• GU JUNHUA
• LIU BOTAO
• YANG ZIKAI

Assignees

• 河北工业大学

Dates

Publication Date

20260512

Application Date

20260126

Claims (2)

1. 1. The FMCW radar vital sign detection method combining the VMD and the SSR is characterized by comprising the following steps: the first step, transmitting a chirp signal through an FMCW radar, capturing a radar echo signal, preprocessing the radar echo signal, and extracting a human chest wall displacement signal; Decomposing the human chest wall displacement signal by using a VMD algorithm, determining optimal decomposition parameters by using a variable step length double-stage search through a vital sign judging mode, and decomposing the human chest wall displacement signal by using the optimal decomposition parameters to obtain a heartbeat signal and a respiratory signal modal component set; Judging respiratory harmonic modal components in the frequency range of the heartbeat signal, and reconstructing the heartbeat signal; respiratory harmonic modal component set obtained through harmonic detection : (4) Wherein, the 、 Respectively a heartbeat signal modal component set and a respiratory signal modal component set, To take on an integer of 0 to 2, 、 Respectively the first 、 Center frequencies of the modal components; Acquiring an intersection of the breathing signal modal component set and the breathing harmonic modal component set to obtain a pure breathing signal modal component set, and taking a difference set of the heartbeat signal modal component set and the breathing harmonic modal component set to obtain a pure heartbeat signal modal component set; fourthly, constructing an SSR model, carrying out sparse spectrum reconstruction on the heartbeat signal based on a ZA-EFRLS algorithm, solving the heartbeat signal, and extracting the heartbeat frequency.
2. 2. FMCW radar vital sign detection method combining VMD and SSR according to claim 1 characterized in that in the second step the energy loss rate is calculated according to equation (6): (6) In the formula, For the total energy of all the modal components, Is the first Each modal component Is used for the total energy of the (a), Is the number of modal components; selecting the modal components belonging to the respiratory signal and the heartbeat signal according to the energy duty ratio of the respiratory signal and the heartbeat signal in each modal component to obtain a respiratory signal modal component set and a heartbeat signal modal component set; (7) (8) In the formula, Is the first The energy of the respiratory signal in the individual modal components, Is the first The energy of the center-hopped signal of each modal component, And A preset threshold value; and selecting the decomposition parameters with the minimum energy loss rate and neither the respiratory signal modal component set nor the heartbeat signal modal component set as the optimal decomposition parameters.

Description

FMCW radar vital sign detection method combining VMD and SSR Technical Field The invention belongs to the technical field of non-contact vital sign detection, and particularly relates to an FMCW radar vital sign detection method combining VMD and SSR. Background Cardiovascular disease has become a major cause of threat to human health, and electrocardiographic monitoring is considered as one of the criteria for clinical diagnosis of cardiovascular disease, with extremely high clinical value in early disease diagnosis and subsequent treatment. However, due to the inconvenience of conventional electrocardiographic monitoring, continuous monitoring for a long period of time in daily life is often difficult to implement, which may lead to a loss of abnormal electrocardiographic state records, delaying diagnosis of the disease. Wearable sensors or adhesive electrodes, such as respiratory tract, photoplethysmographic sensors, electrocardiographic sensors, and the like, may create uncomfortable experiences and additional burdens on the subject, particularly for some special patients with skin allergies and burns. In the non-contact vital sign detection method, although Wi-Fi-based non-contact sensing is receiving more and more attention in numerous applications such as respiratory detection, position estimation, gesture recognition and the like, performance is limited due to narrow bandwidth, small number of antennas and large wavelength, and particularly in HR detection, since 2.4-/5-GHz WiFi wavelength (60-120 mm) is far greater than chest wall displacement (0.2-0.5 mm) caused by heartbeat, tiny phase change caused by heartbeat is difficult to capture. Acoustic signals are another potential solution to vital sign detection, but their sensing range is limited. Furthermore, computer vision-based vital sign detection is sensitive to lighting and vision conditions, performs poorly in smoke, under-lighting or occlusion conditions, and may also lead to privacy leakage. Currently, continuous Wave (CW) doppler radar, ultra Wideband (UWB) pulse radar, and Frequency Modulated Continuous Wave (FMCW) radar are three types of radar commonly used for vital sign detection. The radio structure of the continuous wave doppler radar is simple, the power consumption is low, but the distance information of the target cannot be provided. Therefore, the performance is easily affected by clutter interference, resulting in poor vital sign detection accuracy. In contrast, UWB pulse radar and FMCW radar are capable of measuring the distance between the object under test and the device and occupy a wider bandwidth. However, for ultra wideband pulsed radar, the wider bandwidth depends on precise control of pulse width and radar peak signal strength, which results in higher hardware cost and system complexity. The millimeter wave radar is a radar technology with electromagnetic spectrum corresponding to 30-300 ghz frequency bands, and has the characteristics of wide bandwidth, narrow beam width, small volume and the like. The FMCW millimeter wave radar combines the advantages of FMCW and millimeter wave technologies, and the FMCW millimeter wave radar has significantly improved range resolution due to a wider bandwidth, thereby facilitating isolation of reflections from different objects. Meanwhile, the FMCW millimeter wave radar has potential for miniaturization due to higher carrier frequency. In addition, compared with cameras, wiFi routers, and acoustic sensors, the propagation of radar signals is neither susceptible to illumination/temperature/sound changes nor privacy-violating, so FMCW millimeter wave radar can be adopted for HR detection of targets. Radar senses the surrounding environment through chest wall displacement caused by respiration and heart activity, and various ambient noise mixed reflected signals, and does not observe the heart cycle directly in the radar signal, requiring appropriate algorithms to further extract potential heart features. However, HR is difficult to accurately detect due to interference of respiratory harmonics, noise, and noise. In particular, there may be a wide variety of objects in the environment (e.g., walls, doors, tables, and furniture), so the reflected signal contains many clutter and may mask the heartbeat signal. Furthermore, respiratory-induced chest wall displacement may be an order of magnitude higher than heart beat-induced chest wall displacement, and it is not a pure sine wave, containing several significant harmonic components. Breathing harmonics may approach or even mask the heartbeat signal, resulting in incorrect peak selection. Therefore, how to achieve accurate and reliable HR detection is a challenge. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide the FMCW radar vital sign detection method combining the VMD and the SSR, which aims to solve the problems of difficult heartbeat signal extraction, clutter interference, insufficient f