A dual-polarized directional backtracking millimeter-wave health monitoring system and its application method

Abstract

This invention discloses a dual-polarized directional backtracking millimeter-wave health monitoring system, characterized by: a dual-polarized passive directional backtracking antenna and a millimeter-wave continuous-wave frequency-modulated radar. The dual-polarized passive directional backtracking antenna is attached to the chest at the patient's heart location, and can forward the received electromagnetic waves back to the direction of origin in an orthogonal polarization. The millimeter-wave continuous-wave radar includes a millimeter-wave transceiver circuit, a transmitting antenna, and a receiving antenna array. The millimeter-wave transceiver circuit includes a frequency sweep source, a transmitting channel, an MCU circuit, a DSP circuit, and a receiving channel. This invention's health monitoring system has a simple structure, high sensitivity, and low cost. In large-scale application scenarios, a single millimeter-wave radar terminal can monitor all patients within the area.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave health monitoring technology, and in particular to a dual-polarization directional backtracking millimeter-wave health monitoring system and its usage method. Background Technology

[0002] In recent years, with the increasing aging of the global population, the demand for health monitoring of elderly patients with chronic underlying diseases has become increasingly strong. Current health monitoring methods mainly rely on intelligent sensing devices that come into contact with the human body. These devices mostly operate in an active manner, which means they have limited battery power and cannot monitor the body for extended periods. Furthermore, a complete set of intelligent sensing devices is required for each patient, resulting in extremely high costs.

[0003] In addition to close-range monitoring, there are also wireless long-range heart rate and respiration monitoring solutions based on frequency modulated continuous wave (FMCW) radar. Millimeter waves have extremely high resolution, which can accurately identify respiratory and heartbeat characteristics. At the same time, FMCW radar is inexpensive and can monitor multiple targets, further reducing costs.

[0004] However, commercial silicon-based millimeter-wave monolithic radar has low output power and high noise figure, thus limiting its detection range. At the same time, since heart rate and respiratory signals are hidden in body movement signals, extracting these weak signals requires more sensitive receivers and complex digital processing algorithms, which limits the large-scale application of this technology.

[0005] Current millimeter-wave health monitoring systems primarily employ the FMCW (Frequency Multi-Channel Wave) architecture, using high-gain antennas and co-polarized transmit and receive signals. The basic principle is that the transmitting antenna emits a swept-frequency signal, which is reflected back to the receiving antenna by the target. The reflected signal is then mixed with the frequency of the swept-frequency source at that moment, and the frequency and phase of the intermediate frequency (IF) signal contain the target's position information. Since heartbeats and respiration are periodic signals, the phase of the target's position reflected in the IF signal fluctuates periodically. Because the movement levels of respiration and heartbeat are at the millimeter and sub-millimeter levels, even small random bodily fluctuations can cause severe distortion in respiration and heartbeat.

[0006] Currently, methods such as energy thresholding and outlier detection are mainly used to identify abnormal fluctuations in the body and exclude monitoring data from these states to reduce errors. However, this strategy reduces the system's temporal coverage and cannot guarantee real-time monitoring. Furthermore, when the target is in a complex environment, obstacles and multipath effects severely degrade signal quality, leading to a decrease in the signal-to-noise ratio of the detected physiological signals. In everyday home environments, obstacles are ubiquitous, causing significant attenuation in the millimeter-wave frequency band. Therefore, researching monitoring systems that are resistant to attenuation and multipath effects is crucial for the commercialization of millimeter-wave health monitoring systems.

[0007] Common methods to increase detection sensitivity mainly involve increasing signal transmission power and receiver sensitivity. However, in the millimeter-wave band, these methods lead to a sharp increase in hardware costs, hindering large-scale commercial applications and impeding industry development. From a signal processing perspective, increasing algorithm complexity and using big data prediction can also be employed, but this primarily compromises the real-time performance of monitoring.

[0008] Limited by current technology, commercially available millimeter-wave radar health monitoring systems, such as Texas Instruments' AWR1642 and Vayyar's devices, can only monitor in resting, unobstructed scenarios such as driving and sleeping. Chinese patent CN202111460385 discloses a "robust millimeter-wave radar vital sign measurement method" that employs multi-location evaluation and optimization, using the location with the best signal as the heartbeat measurement location. However, this method requires significant computational power and real-time processing. Summary of the Invention

[0009] To address the shortcomings of the existing technology, this invention provides a dual-polarization directional backtracking millimeter-wave health monitoring system and its usage method.

[0010] To achieve the above technical objectives, the technical solution of the present invention is as follows:

[0011] A dual-polarized directional backtracking millimeter-wave health monitoring system comprises a dual-polarized passive directional backtracking antenna and a millimeter-wave continuous-wave frequency-modulated radar. The dual-polarized passive directional backtracking antenna is attached to the chest at the patient's heart position and can forward the received electromagnetic waves back to the direction of origin in an orthogonal polarization. The millimeter-wave continuous-wave radar includes a millimeter-wave transceiver circuit, a transmitting antenna, and a receiving antenna array. The millimeter-wave transceiver circuit includes a frequency sweep source, a transmitting channel, a circuit, a DSP circuit, and a receiving channel.

[0012] Furthermore, the dual-polarized passive directional backtracking antenna consists of three metal layers and two dielectric layers, namely a radiating layer, a metal ground layer, and a feed line layer.

[0013] Furthermore, the two dielectric layers are a first dielectric layer and a second dielectric layer, respectively.

[0014] Furthermore, the radiating layer is composed of multiple square metal radiating patches, each with two feed ports: a horizontally polarized feed port and a vertically polarized feed port. The metal radiating patches are centrally symmetrically distributed, consisting of a central antenna array and three pairs of symmetrical antenna arrays.

[0015] Furthermore, the radiating patch is interconnected by metallized vias passing through the first dielectric layer and the second dielectric layer, and by feed lines.

[0016] Furthermore, the feeder lines include a first feeder line, a second feeder line, a third feeder line, a fourth feeder line, a fifth feeder line, a sixth feeder line, and a seventh feeder line.

[0017] Furthermore, the second and third feed lines are paired to form antenna pair 2, the fourth and fifth feed lines are paired to form antenna pair 3, and the sixth and seventh feed lines are paired to form antenna pair 4, with the two feed lines of each antenna pair being of equal length.

[0018] Furthermore, the metal floor layer is etched with power-feed vias, the diameter of which is slightly larger than that of the metallized vias.

[0019] Furthermore, the feed line and the radiating patch together constitute a passive directional backtracking antenna of the VAN-ATTA configuration.

[0020] This invention also provides a method for using a dual-polarization directional backtracking millimeter-wave health monitoring system, comprising the following steps:

[0021] (1) The patient places the dual-polarized passive directional backtracking antenna on his chest using a surface patch or other means;

[0022] (2) The millimeter-wave frequency modulated continuous wave radar is turned on and emits electromagnetic waves outward;

[0023] (3) The dual-polarized passive directional backtracking antenna receives electromagnetic signals and forwards a beam of orthogonally polarized waves pointing in the direction of the radar.

[0024] (4) The radar receives and relays signals containing information on the patient's heart rate, respiration, and distance.

[0025] (5) The radar receiver demodulates the signal and performs digital processing to calculate and output the patient's physiological parameters such as heart rate and respiration.

[0026] Compared with the prior art, the present invention has the following technical advantages:

[0027] (1) The direction backtracking antenna can intercept most of the incoming wave signal and reflect it in the direction of the incoming wave, which greatly increases the power of the reflected signal, increases the detection distance, and reduces the requirements for receiving performance.

[0028] (2) The directional backtracking antenna is attached to the chest where the patient’s heartbeat and breathing characteristics are strongest. Therefore, the signal received by the radar naturally contains the optimal position signal, and no additional algorithm is needed to determine the optimal position.

[0029] (3) The dual-polarized passive directional backtracking antenna forwards the orthogonal polarization of the target, while the signal that does not illuminate the patient's chest is transmitted in the same polarization as the transmitted signal. The polarization of the radar's receiving antenna is orthogonal to that of the transmitting antenna, so it only receives the signal forwarded by the directional backtracking antenna, avoiding interference from other clutter reflections and multipath effects, and reducing the requirements for digital processing algorithms and hardware.

[0030] (4) The dual-polarized directional backtracking array antenna of this invention adopts a passive VAN-ATTA array architecture, is attached to the patient's chest, and has the function of forwarding the orthogonally polarized wave of the incoming wave in the direction of the incoming wave. Its self-focusing characteristic greatly enhances the detection range of traditional millimeter-wave health monitoring systems and reduces the requirements for back-end algorithms and receiver dynamic range. At the same time, its structure is simple, its sensitivity is high, and its cost is low. In large-scale application scenarios, a single millimeter-wave radar terminal can monitor all patients in the area. Attached Figure Description

[0031] Figure 1 This is a diagram illustrating the overall application scenario of the dual-polarization directional backtracking millimeter-wave health monitoring system of the present invention.

[0032] Figure 2 This is a schematic diagram of the dual-polarized passive directional backtracking antenna structure of the present invention;

[0033] Figure 3 This is a front view of the dual-polarized passive directional backtracking antenna of the present invention;

[0034] Figure 4 This is a back view of the dual-polarized passive directional backtracking antenna of the present invention;

[0035] Figure 5 This is a block diagram of the millimeter-wave continuous-wave frequency-modulated radar of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] Figure 1 A diagram illustrating the overall application scenario of a dual-polarized directional backtracking millimeter-wave health monitoring system is provided. This invention employs a dual-polarized passive directional backtracking antenna 1 and a millimeter-wave continuous-wave frequency-modulated radar 2 to monitor a patient's heart rate and respiration. The dual-polarized passive directional backtracking antenna 1 is attached to the patient's chest at the location of their heart, and its function is to relay the received electromagnetic waves back to the direction of origin in an orthogonally polarized manner. This achieves three main benefits.

[0038] Firstly, the directional backtracking antenna can intercept most of the incoming wave signal and directionally reflect it in the direction of the incoming wave, which greatly increases the power of the reflected signal, increases the detection range, and reduces the requirements for receiving performance.

[0039] Secondly, the directional backtracking antenna is attached to the chest where the patient's heartbeat and breathing characteristics are strongest. Therefore, the signal received by the radar naturally contains the optimal position signal, and no additional algorithm is needed to determine the optimal position.

[0040] Thirdly, the dual-polarized passive directional backtracking antenna relays the orthogonal polarization of the target signal, while signals not illuminating the patient's chest are transmitted in the same polarization as the transmitted signal. Since the radar's receiving antenna polarization is orthogonal to the transmitting antenna, it only receives signals relayed by the directional backtracking antenna, avoiding interference from other clutter reflections and multipath effects, and reducing the requirements for digital processing algorithms and hardware.

[0041] The above three advantages are the core ideas and innovations of this invention; the rest of the discussion revolves around how to implement them specifically. However, protection of the invention should not be limited to the specific implementation examples given.

[0042] The radar's transmitting antenna first omnidirectionally transmits a high-energy millimeter-wave signal into space. The electromagnetic waves illuminating the patient's chest are then orthogonally polarized by a dual-polarized passive directional backtracking antenna (meaning the direction of the electromagnetic wave's electric field vibration is perpendicular to the direction of the electromagnetic wave's electric field vibration emitted by the transmitting antenna) and directed towards the radar position. The radar receiver uses a multi-antenna array to receive the signal. The receiving array can estimate the angle of arrival to determine the target's azimuth, thus enabling multi-target heart rate monitoring. After reception, the signal is converted to intermediate frequency (IF) via a low-noise amplifier and downconverter. The IF frequency and phase contain the target's heart rate and respiratory information. The IF signal is then directly digitized by an ADC and fed into a DSP to calculate the heart rate and respiratory rate, and the data is output.

[0043] 2. Dual-polarized passive directional backtracking antenna

[0044] The dual-polarized passive directional backtracking antenna adopts a VAN-ATTA array architecture, such as... Figure 2-4 An example of implementation using a patch antenna is given, but the specific implementation can be any antenna form.

[0045] The dual-polarized passive directional backtracking antenna 1 is composed of three metal layers and two dielectric layers laminated together. The three metal layers are a radiating layer 11, a metal ground layer 12, and a feed line layer 13; the two dielectric layers are a first dielectric layer 14 and a second dielectric layer 15.

[0046] The radiating layer 11 is composed of multiple square metal radiating patches 111, each of which has two feed ports: a horizontally polarized feed port 1111 and a vertically polarized feed port 1112. The metal radiating patches are centrally symmetrically distributed and consist of a central antenna array and three pairs of symmetrical antenna arrays.

[0047] The radiating patch 111 is interconnected by a metallized via 141 passing through a first dielectric layer and a second dielectric layer and a feed line 131.

[0048] The feeder line 131 includes a first feeder line 1311 (antenna array 1), a second feeder line 1312, a third feeder line 1313, a fourth feeder line 1314, a fifth feeder line 1315, a sixth feeder line 1316, and a seventh feeder line 1317.

[0049] The second feed line 1312 and the third feed line 1313 are paired to form antenna pair 2, the fourth feed line 1314 and the fifth feed line 1315 are paired to form antenna pair 3, and the sixth feed line 1316 and the seventh feed line 1317 are paired to form antenna pair 4. The two feed lines of each antenna pair are of equal length. Their function is to interconnect the corresponding metal radiating patch antenna pairs and to complete the interconnection of the horizontal polarization feed port 1111 and the vertical polarization feed port 1112, so as to achieve the purpose of polarization reversal.

[0050] The first feeder line 1311, the second feeder line 1312, the fourth feeder line 1314, and the sixth feeder line 1316 satisfy the condition that the length difference between them is an integer multiple of the waveguide wavelength of the working signal at that frequency.

[0051] The metal floor layer 12 serves as the common floor for the feed line 131 and the radiating patch 111, and performs the function of signal isolation and shielding. Feed vias 121 are etched on it, with the aperture slightly larger than that of the metallized via 141.

[0052] The feed line 131 and the radiating patch 111 together constitute a passive directional backtracking antenna in VAN-ATTA configuration.

[0053] 3. Millimeter-wave frequency modulated continuous wave (FMCW) radar

[0054] The millimeter-wave continuous-wave radar includes a millimeter-wave transceiver circuit, a transmitting antenna, and a receiving antenna array. The millimeter-wave transceiver circuit includes a frequency sweep source, a transmitting channel, an MCU circuit, a DSP circuit, and a receiving channel. The radar uses active detection to monitor information such as the target's range, azimuth, and velocity. Radars generally have both electromagnetic wave receiving and transmitting capabilities. The basic process involves the radar first actively emitting a beam of electromagnetic waves. These waves are reflected upon contact with the target, and the reflected signal contains information about the target. A portion of the reflected energy (usually very weak) is intercepted by the radar receiver. By analyzing this signal, important parameters of the target can be calculated.

[0055] Millimeter-wave continuous wave radar monitors a patient's heart rate and respiration. Unlike other FMCW systems, it employs multi-channel reception, with the receiver link featuring angle-of-arrival estimation (AOA) to determine the target's direction and perform beam scanning.

[0056] Figure 5 A block diagram of a millimeter-wave continuous-wave frequency-modulated radar is given in the figure:

[0057] LNA: Low Noise Amplifier, used for pre-amplifying received signals.

[0058] Mixer: A frequency converter used to downconvert millimeter-wave signals to intermediate frequency signals.

[0059] IF: Intermediate frequency signal.

[0060] ADC: Digital-to-Analog Converter, which converts intermediate frequency signals into the digital domain for the calculation of physiological parameters.

[0061] Digital front end: Used to pre-filter the converted digital signal to facilitate further processing.

[0062] DSP: Digital Signal Processor, which calculates the filtered digital signal to obtain the required parameters such as heart rate and respiration.

[0063] MCU: Microcontroller, used to output final data and perform overall control of the radar.

[0064] Frequency sweep source: generates frequency-modulated continuous wave signals.

[0065] PA: Power amplifier, used to amplify the transmitted signal to the required power.

[0066] The millimeter-wave continuous wave radar includes a transmitting antenna and a receiving antenna array. The transmitting antenna consists of two series-fed high-gain patch antenna arrays, and the receiving antenna array consists of six parallel-fed four-element patch antenna arrays. The polarization directions of the transmitting and receiving antenna arrays are perpendicular to each other, and their phase centers are on a straight line to ensure accurate reception of the backtracking beam.

[0067] How to use the dual-polarization directional backtracking millimeter-wave health monitoring system of the present invention:

[0068] (1) The patient places the dual-polarized passive directional backtracking antenna on his chest using a surface patch or other means;

[0069] (2) The millimeter-wave frequency modulated continuous wave radar is turned on and emits electromagnetic waves outward;

[0070] (3) The dual-polarized passive directional backtracking antenna receives electromagnetic signals and forwards a beam of orthogonally polarized waves pointing in the direction of the radar.

[0071] (4) The radar receives and relays signals containing information on the patient's heart rate, respiration, and distance.

[0072] (5) The radar receiver demodulates the signal and performs digital processing to calculate and output the patient's physiological parameters such as heart rate and respiration.

[0073] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the scope of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A dual-polarization directional backtracking millimeter-wave health monitoring system, characterized in that: It consists of a dual-polarized passive directional backtracking antenna and a millimeter-wave continuous wave frequency-modulated radar. The dual-polarized passive directional backtracking antenna is attached to the chest at the patient's heart position and can forward the received electromagnetic waves back to the direction of the incoming wave in the form of orthogonal polarization. The millimeter-wave continuous wave frequency-modulated radar includes a millimeter-wave transceiver circuit, a transmitting antenna, and a receiving antenna array. The millimeter-wave transceiver circuit includes a frequency sweep source, a transmitting channel, an MCU circuit, a DSP circuit, and a receiving channel. The dual-polarized passive directional backtracking antenna consists of three metal layers and two dielectric layers, namely a radiating layer, a metal ground layer, and a feed line layer. The two dielectric layers are a first dielectric layer and a second dielectric layer, respectively. The radiating layer is composed of multiple square metal radiating patches. Each metal radiating patch has two feed ports, namely a horizontal polarization feed port and a vertical polarization feed port. Each metal radiating patch is centrally symmetrically distributed and consists of a central antenna array and three pairs of symmetrical antenna arrays. The metal radiating patch is interconnected by metallized vias passing through the first dielectric layer and the second dielectric layer, and by feed lines; The feeder lines include a first feeder line, a second feeder line, a third feeder line, a fourth feeder line, a fifth feeder line, a sixth feeder line, and a seventh feeder line. The first feeder line forms a central antenna array, and the second, third, fourth, fifth, sixth, and seventh feeder lines form three pairs of symmetrical antenna arrays. The second and third feed lines are paired to form a second antenna pair, the fourth and fifth feed lines are paired to form a third antenna pair, and the sixth and seventh feed lines are paired to form a fourth antenna pair. The two feed lines of each antenna pair are of equal length.

2. The dual-polarization directional backtracking millimeter-wave health monitoring system according to claim 1, characterized in that: The metal floor layer is etched with power feeding vias, the diameter of which is slightly larger than the diameter of the metallized via.

3. The dual-polarization directional backtracking millimeter-wave health monitoring system according to claim 1, characterized in that: The feed line and radiating patch together constitute a passive directional backtracking antenna of the VAN-ATTA configuration.

4. A method of using the dual-polarization directional backtracking millimeter-wave health monitoring system according to any one of claims 1-3, characterized in that, Includes the following steps: (1) The patient placed the dual-polarized passive directional backtracking antenna on his chest with a surface patch; (2) The millimeter-wave continuous wave frequency modulation radar is turned on and emits electromagnetic waves outward; (3) The dual-polarized passive directional backtracking antenna receives electromagnetic signals and forwards a beam of orthogonally polarized waves pointing in the direction of the radar. (4) The radar receives and relays signals containing information on the patient's heart rate, respiration, and distance. (5) The radar receiver demodulates the signal and performs digital processing to calculate and output the patient's heart rate and respiratory physiological parameters.

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