CN107028589B

CN107028589B - Systems and computer-implemented methods for biosignal recording

Info

Publication number: CN107028589B
Application number: CN201611001638.2A
Authority: CN
Inventors: K·C·冯; T·J·迪克; C·W·小霍尔
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2015-12-07
Filing date: 2016-11-14
Publication date: 2021-02-26
Anticipated expiration: 2036-11-14
Also published as: DE102016223919A1; JP2017104539A; CN107028589A

Abstract

A system and computer-implemented method for bio-signal recording. The method includes modulating the sampled evoked biosignal with a carrier sequence code to produce a modulated evoked biosignal. The carrier sequence code has an autocorrelation function. The method includes demodulating the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with the carrier sequence code, thereby producing an evoked biosignal spectrum. The evoked biosignal spectra have a peak sideband ratio as a function of the carrier sequence code. The method includes calculating a deviation between each element of the sampled evoked biological signals and the peak sideband ratio, and filtering noise artifacts from the sampled evoked biological signals based on the deviation. The peak sideband ratio can also be optimized by changing the sampling rate.

Description

System and computer-implemented method for bio-signal recording

RELATED APPLICATIONS

This application is related to U.S. patent application serial No. 14/697593 filed on 27.4.2015 and now published as US 2015/0229341, which patent application US 2015/0229341 is expressly incorporated herein by reference. Additionally, U.S. patent application serial No. 14/697593 relates to U.S. patent application serial No. 13/858038, filed on 6.4.2013 and now published as US2014/0303899, which is also expressly incorporated herein by reference as well as US 2014/0303899.

Technical Field

The present invention relates to biological signal processing.

Background

Since the amplitude of the bio-signal is low relative to the amplitude of the surrounding noise signal, it is difficult to record the bio-signal when measuring the bio-signal non-invasively from the body surface. Potential noise sources that can mask the measurement of biological signals from a body surface include broadcast electromagnetic radiation from electrical or electronic devices, scattered electromagnetic radiation from neutral sources moving through static fields, mechanical vibrations transmitted to the source in the environment and movement of the source itself, among others.

The impact of noise sources on the bio-signal recording can be minimized by electromechanically isolating the subject from potential interference using electrical shielding and vibration isolation. However, in real world applications, such control measurements are not feasible and low signal recordings must be done in high noise environments. In addition, the power spectrum of real-world noise sources often overlaps with the power spectrum of biological signals, and therefore conventional filtering techniques (such as band-pass filtering) are not applicable.

Disclosure of Invention

According to one aspect, a computer-implemented method for bio-signal recording includes: the control signal from the transmitter of the sensor is transmitted to the transmission source. The transmission source transmits energy to the object in accordance with the control signal. The method includes receiving an evoked bio-signal at a receiver of a sensor in response to energy reflections returned from an object. The induced biological signal is an analog signal. The method comprises calculating a sampled evoked biosignal by sampling the evoked biosignal at a predetermined sampling rate. The method includes modulating the sampled evoked biosignal with a carrier sequence code to produce a modulated evoked biosignal. The carrier sequence code has an autocorrelation function. The method includes demodulating the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with a carrier sequence code, thereby producing an evoked biosignal spectrum. The evoked biosignal spectra have peak sideband ratios as a function of carrier sequence code. The method includes calculating a deviation between each element of the sampled evoked biological signals and a peak sideband ratio, and filtering noise artifacts from the sampled evoked biological signals based on the deviation. In addition, the method includes outputting the true evoked biosignal based on the filtering.

According to another aspect, a computer-implemented method for bio-signal recording includes: the control signal from the transmitter of the sensor is transmitted to the transmission source. The control signal is transmitted according to a carrier sequence code, and the transmission source transmits energy to the object according to the carrier sequence code. The carrier sequence code has an autocorrelation function. The method includes receiving an evoked bio-signal at a receiver of a sensor in response to energy reflections returned from an object. The evoked biosignals are analog signals and are modulated according to a carrier sequence code. The method includes demodulating the evoked biosignal by calculating a convolution of the evoked biosignal with a carrier sequence code, thereby producing an evoked biosignal spectrum. The induced biosignal spectrum has a signal-to-noise ratio proportional to a peak sideband ratio. The peak sideband ratio is a function of the carrier sequence code. In addition, the method includes generating the real evoked biosignal by extracting the real evoked biosignal from the modulated evoked biosignal based on the peak sideband ratio.

According to another aspect, a system for bio-signal recording includes a sensor including a transmitter for transmitting a control signal to a transmission source. The transmission source transmits energy to the object in accordance with the control signal. The sensor also includes a receiver for receiving an evoked biological signal in response to a reflection of energy returned from the object. The induced biological signal is an analog signal. The system also includes a system clock communicatively coupled to the sensor to generate the sample induced bio-signal at a predetermined sample rate. The system also includes a modulator communicatively coupled to the sensor to receive the sampled induced biosignal and modulate the sampled induced biosignal with a carrier sequence code having an autocorrelation function. The system includes a demodulator communicatively coupled to the sensor to receive the modulated evoked biosignal and demodulate the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with the carrier sequence code to produce an evoked biosignal spectrum. The evoked biosignal spectra have peak sideband ratios as a function of carrier sequence code. In addition, the system includes a filter communicatively coupled to the sensor to calculate a deviation between the sampled evoked biosignal and the peak sideband ratio, filter noise artifacts from the sampled evoked biosignal based on the deviation, and output a true evoked biosignal based on the filtering.

According to another aspect, a system for bio-signal recording includes a sensor including a transmitter that transmits a control signal to a transmission source according to a carrier sequence code. The transmission source transmits energy to an object according to a carrier sequence code, and the carrier sequence code has an autocorrelation function. The sensor also includes a receiver for receiving an evoked biological signal in response to a reflection of energy returned from the object. The evoked biosignals are analog signals and are modulated according to a carrier sequence code. The system includes a demodulator communicatively coupled to the sensor to receive the modulated evoked biosignal and demodulate the modulated evoked biosignal by calculating a convolution of the evoked biosignal with the carrier sequence code to produce an evoked biosignal spectrum. The evoked biosignal spectra have a signal-to-noise ratio proportional to a peak sideband ratio, and the peak sideband ratio is a function of the carrier sequence code. The demodulator generates a real evoked biosignal by extracting the real evoked biosignal from the modulated evoked biosignal based on the peak sideband ratio.

Drawings

FIG. 1 is an exemplary block diagram of a system for bio-signal processing using highly auto-correlated carrier sequence codes (HACS) according to an exemplary embodiment;

FIG. 2 is an exemplary schematic diagram for modulation and demodulation for bio-signal processing using HACS, according to an exemplary embodiment;

FIG. 3A is a schematic diagram of an exemplary bio-signal convolution using a HACS AND a logical AND (AND) gate, according to an exemplary embodiment;

FIG. 3B is a schematic diagram of an exemplary bio-signal convolution using a HACS and a logical OR gate, according to an exemplary embodiment;

FIG. 4 is a schematic diagram of an exemplary bio-signal trace modulated and demodulated using a HACS, according to an exemplary embodiment;

FIG. 5 is a schematic diagram of an exemplary bio-signal trace with the addition of analog "spike" noise modulated and demodulated using HACS, according to another exemplary embodiment;

FIG. 6A illustrates an exemplary graphical output of measuring evoked biosignals in a real world application without using a HACS;

fig. 6B shows an exemplary graphical output of measuring evoked biosignals in real world applications by using HACS and varying a predetermined sampling rate.

FIG. 7 is a schematic diagram of an exemplary bio-signal convolution using two's complement HACS and a logical exclusive OR (XOR) gate, according to an exemplary embodiment;

FIG. 8 is a schematic diagram of an exemplary bio-signal trace with a sinusoidal noise source modulated and demodulated using HACS, where the sidebands of the noise overlap with the sidebands of the signal, according to another exemplary embodiment;

FIG. 9 is a flow diagram of an exemplary method for bio-signal processing using highly auto-correlated carrier sequence codes (HACS) according to an exemplary embodiment;

FIG. 10 is a flow diagram of an exemplary method for filtering a modulation-induced biosignal, according to an exemplary embodiment; and

fig. 11 is a flow diagram of a different exemplary method for bio-signal processing using highly auto-correlated carrier sequence codes (HACS) according to an exemplary embodiment.

Detailed Description

The following includes definitions of selected terms employed herein. The definitions include various examples and/or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. In addition, components discussed herein may be combined, omitted, or organized with other components or into different architectures.

"computer communication," as used herein, refers to communication between two or more computing devices (e.g., computers, personal digital assistants, cellular telephones, network devices) and may be, for example, a network transmission, a file transmission, an applet transmission, an email, a hypertext transfer protocol (HTTP) transmission, and the like. Computer communications may occur, for example, through wireless systems (e.g., IEEE 802.11), Ethernet systems (e.g., IEEE 802.3), token ring systems (e.g., IEEE802.5), Local Area Networks (LANs), Wide Area Networks (WANs), point-to-point systems, circuit switched systems, packet switched systems, and others.

As used herein, "computer-readable medium" refers to a non-transitory medium that stores instructions and/or data. Computer readable media can take the form of non-volatile media and volatile media, including but not limited to. Non-volatile media may include, for example, optical disks, magnetic disks, and the like. Volatile media may include, for example, semiconductor memory, dynamic memory, and the like. Common forms of computer-readable media may include, but are not limited to, floppy disks, flexible disks, hard disks, magnetic tape, other magnetic media, ASICs, CDs, other optical media, RAMs, ROMs, memory chips or cards, memory sticks, and other media from which a computer, processor, or other electronic device may read.

As used herein, a "disk" may be, for example, a magnetic disk drive, a solid state disk drive, a floppy disk drive, a tape drive, a Zip drive, a flash memory card, and/or a memory stick. Further, the disk can be a CD-ROM (compact disk ROM), a CD recordable drive (CD-R drive), a CD rewritable drive (CD-RW drive) and/or a digital video ROM drive (DVD ROM). The disk may store an operating system that controls or allocates resources of the computing device.

As used herein, a "database" may refer to a table, a set of tables, a set of data storage devices (e.g., disks), and/or a method for accessing and/or manipulating those data storage devices.

As used herein, "memory" may include volatile memory and/or non-volatile memory. Non-volatile memory can include, for example, ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable PROM), and EEPROM (electrically erasable PROM). Volatile memory may include, for example, RAM (random access memory), Synchronous RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), and direct RAM bus RAM (DRRAM). The memory may store an operating system that controls or allocates resources of the computing device.

As used herein, a "processor" processes signals and performs general-purpose calculations and algorithmic functions. Signals processed by a processor may include digital signals, data signals, computer instructions, processor instructions, messages, bits, bit streams, those that may be received, transmitted, and/or detected. In general, the processors may be a variety of different processors, including multiple single-core and multi-core processors and co-processors and other multiple single-core and multi-core processor and co-processor architectures. A processor may include various modules for performing various functions.

As used herein, "vehicle" refers to any type of mobile vehicle capable of carrying one or more human users and powered by any form of energy. The term "vehicle" includes, but is not limited to, automobiles, trucks, vans, minivans, SUVs, motorcycles, scooters, boats, personal watercraft, and aircraft. In some cases, the motor vehicle includes one or more engines. Additionally, the term "vehicle" may refer to an Electric Vehicle (EV) capable of carrying one or more human users and being powered, in whole or in part, by one or more electric motors powered by a battery. EVs may include electric-only vehicles (BEVs) and plug-in hybrid vehicles (PHEVs). Additionally, the term "vehicle" may refer to an autonomous vehicle and/or an autonomous vehicle powered by any form of energy. The autonomous vehicle may or may not carry one or more human users.

Referring now to the drawings, wherein the showings are for the purpose of illustrating one or more exemplary embodiments and not for the purpose of limiting the same, fig. 1 is a block diagram of a system 100 for bio-signal recording using highly auto-correlated carrier sequence codes (HACS) according to an exemplary embodiment. The components of fig. 1, as well as the components of other systems discussed herein, hardware architectures, and software architectures may be combined, omitted, or organized into different architectures for the various embodiments. In some embodiments, the components of the system 100 may be implemented in a vehicle 102, for example, as discussed in U.S. patent application serial No. 14/697593, now published as u.s.2015/0229341, which is expressly incorporated herein by reference.

In fig. 1, the system 100 includes a sensor 104 for measuring a bio-signal from a subject. In one embodiment, sensor 104 is a sensor for detecting plethysmograph (PPG) measurements from the body surface of subject 106. In particular, the sensor 104 may measure changes in transmission or diffuse reflection from a body surface (e.g., body tissue) of the subject 106 under active illumination. More specifically, the sensor 104 may include a transmitter 108, a transmission source 110, and a receiver 112. The sensor 104 may also include a processor 114 and/or be communicatively coupled to the processor 114. The processor 114 may include other components that facilitate bio-signal recording as will be discussed in more detail herein.

It should be understood that the system 100 may include more than one sensor 104. Additionally, as discussed above and detailed in U.S. patent application serial No. 14/697593, in some embodiments, the sensor 104 may be located in the vehicle 102. For example, in some embodiments, one or more sensors may be part of one or more sensor components. Additionally, one or more sensors may be mechanically coupled to a vehicle seat of the vehicle 102. In other embodiments, the sensor 104 and/or the processor 114 may be integrated with a vehicle computing device (e.g., head unit) (not shown).

Referring again to the sensor 104 of FIG. 1, the transmitter 108 controls the transmission source 110. More specifically, the transmitter 108 sends a control signal (not shown) to the transmission source 110 and the transmission source 110 sends energy (e.g., an energy signal) to the object 106 in accordance with the control signal. It is understood that the energy transmitted by the transmission source 110 may include, but is not limited to, light, ultrasound, sonic and acoustic waves, magnetic resonance imaging using magnetic waves, electromagnetic waves, millimeter wave radar, computed tomography, and X-ray devices using gamma rays, among others. For example, in one implementation that will be used herein as an illustrative example, the transmission source 110 may include at least one Light Emitting Diode (LED) that can send light of a particular wavelength.

In some embodiments, the processor 114 may include a driver 118 that controls the transmitter 108 and/or the transmission source 110. In other embodiments, the driver 118 may be a component of the sensor 104 and/or the transmitter 108. The transmitter 108 and/or driver 118 may include drive circuitry and a controller to drive control signals to the transmission source 110 to drive energy (e.g., transmit energy (e.g., energy waves) to the object 106) as needed. For example, the transmitter and/or driver 118 may cause the transmission source 110 to drive energy on a pulsed basis or a continuous basis. In one embodiment discussed herein, the illumination may be pulsed (e.g., blinking) according to a carrier sequence code having an autocorrelation function. In fig. 1, the energy waves transmitted to the object 106 are indicated by a dashed line 120.

Upon transmission of energy waves 120 to object 106, energy is reflected from object 106 and received by receiver 112 to generate a data signal therefrom. In fig. 1, it is the reflected energy that induces the bio-signal that is indicated by the dashed line 122. The receiver 112 captures the reflected energy as an electrical signal in analog form. More specifically, the receiver 112 receives an evoked biosignal 122 representative of a biometric measurement (e.g., PPG measurement) of the subject 106. As will be discussed herein, the receiver 112 may process these analog signals and/or send the analog signals to, for example, the processor 114 for processing.

With respect to the processor 114, the sensor 104 may include the processor 114 and/or the processor 114 may be included as part of another system communicatively coupled to the sensor 104. For example, the processor 114 may be part of a monitoring system (not shown) integrated with the vehicle 102. In addition to the driver 118, the processor 114 may include a modulator 124, a demodulator 126, a filter 128, and a system clock 130. It should be understood that the processor 114 may include other components not shown, such as memory, data storage, a communication interface, and others. It should also be understood that some or all of the components of the processor 114 may be integrated with the sensor 104 and/or components of the sensor 104. It should also be understood that the highly auto-correlated carrier sequence codes (HACS) discussed herein for modulation and demodulation may be stored at one or more components of the system 100.

As will be described in greater detail herein, the modulator 124 facilitates the modulation of the induced bio-signal 122. The demodulator 126 facilitates demodulation of the evoked biological signals 122. In addition, the demodulator 126 and/or the filter 128 may generate a true biosignal from the evoked biosignal 122 that is free of noise artifacts that may contaminate the evoked biosignal 122. The system clock 130 controls the sampling of the evoked biological signals at different sampling rates. Each of these components will be described in greater detail herein.

An exemplary operation of the system 100 will now be described with reference to fig. 1 according to an exemplary embodiment. As discussed above, in one embodiment, the system 100 includes a sensor 104 having a transmitter 108. The transmitter 108 transmits a control signal to the transmission source 110. The transmission source transmits energy (i.e., energy waves 120) to the object 106 in accordance with the control signal. In addition, the sensor 104 includes a receiver 112 for receiving the evoked biosignal 122 in response to energy reflections returning from the object 106. The induced bio-signal 122 may be a data signal in electrical form. More specifically, the induced biosignal 122 is an analog signal.

The induced bio-signals 122 may be contaminated by noise and motion artifacts from sources surrounding the sensor 104 and the object 106. For example, in a vehicle setting, vibrations from the vehicle 102 and other noise inside and outside the vehicle 102 may contaminate the evoked biosignal 122. In some cases, the frequency and/or power spectrum of the noise and motion artifact may overlap with the frequency and/or power spectrum of the induced bio-signal 122. Such overlap can cause problems in obtaining a true biological signal free of noise and motion artifacts.

Thus, in one embodiment, the system clock 130 communicatively coupled to the sensor 104 may generate the sampling induced biosignal at a predetermined sampling rate. For example, the predetermined sampling rate may be 4ms or less. The sample-induced biosignal can be expressed in vector form as a ═ a (a)₁、a₂、a₃、a₄、a₅、a₆、a₇...), wherein A represents the evoked biological signals 122, and each element in A represents A (i)_t) Where t is the sampling rate and/or sampling interval. The modulation based on the sampled evoked biosignals may be configured to increase the amplitude of the evoked biosignals 122 relative to noise and motion artifacts that may contaminate the evoked biosignals.

More specifically, a modulator 124 communicatively coupled to the sensor 104 may receive the sampled induced biosignal and modulate the sampled induced biosignal with a carrier sequence code having an autocorrelation function. The carrier sequence code may be a highly auto-correlated carrier sequence (HACS) to process the induced bio-signal 122. Exemplary HACS include, but are not limited to, Barker codes (Barker codes), Frank codes (Frank codes), gray codes (Golay codes), multi-time codes (poly-time codes), and others. Barker codes will be used in the exemplary embodiments disclosed herein, however the systems and methods discussed herein may be implemented with other types of HACS. Additionally, a barker code of length seven (7) will be discussed throughout the specification, although it should be understood that barker codes of different lengths and other carrier sequence codes may be implemented. Further, it should be understood that barker codes and other HACS of different lengths may be combined to produce a HACS that is also implementable in these methods and systems.

In one embodiment, the modulator 124 modulates the sampled evoked biosignal by code multiplying the sampled evoked biosignal with a carrier sequence. The number of samples in the sampling induced biosignal is equal to the length of the carrier sequence code. As an illustrative example, the seven (7) elements of the sampling-induced biosignal A discussed above may be associated with a Barker code B having a length of seven (7)₇Multiplication. Barker code B₇Can be represented as B₇(1, -1, -1). Thus, the induced biosignal and the Barker code B are sampled₇The multiplication results in a modulation of the sampled induced biosignal, which is expressed in vector form as AB₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇). The modulation of the sampled evoked biological signals may be calculated using a bit-by-bit shift of each sampling point of the sampled evoked biological signals with the carrier sequence code. For example, a ═ a₁、a₂、a₃、a₄、a₅、a₆、a₇) Can be multiplied by B using bit-by-bit shift from right₇Multiplication by (1, -1, -1).

Referring now to fig. 2, an exemplary schematic diagram for modulation and demodulation of bio-signal recordings using HACS is shown, according to an exemplary embodiment. In this example, the signal a202 (i.e., the evoked biosignal 122) has an amplitude of 1/2 of the noise N in the surrounding environment. Signal A202 is encoded by Barker code B ₇204 are modulated. For example, the signal A202 and the Barker code B ₇204 to produce a barker segment AB₇206 (example)E.g. AB₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇)). Thus, modulating the sampled induced biosignal produces a modulated induced biosignal having an amplitude proportional to the carrier sequence code. More specifically, as shown in FIG. 2, the bark section AB ₇206 has an amplitude ratio of +/-a.

Referring again to fig. 1, to reconstruct a true biosignal free of noise and/or motion artifacts, a demodulator 126 communicatively coupled to the sensor 104 receives the modulation induced biosignal and demodulates the modulation induced biosignal with a carrier sequence code. In one embodiment, the demodulator 126 calculates a convolution of the modulation induced biosignal with the carrier sequence code. Referring again to the illustrative examples discussed above and to fig. 2, the modulation-induced bio-signal is induced by the barker segment AB₇206 (i.e., AB)₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇) Is) is shown. Bark section AB ₇206 and original barker code B₇And (4) convolution. This convolution produces an evoked biosignal profile. Thus, in FIG. 2, AB ₇206 and barker code B ₇208 convolution, said barker code B ₇208 and the original barker code for modulation (barker code B)₇204) The same is true. The resulting induced biosignal spectrum is graphically illustrated as induced biosignal spectrum 210.

As shown in fig. 2, the evoked biosignal profile 210 has a code as a carrier sequence (i.e., barker code B in fig. 2)₇) The peak sideband ratio of the function of (c). Specifically, in fig. 2, the peak 212 has an amplitude of 7A, and there are six (6)

sidebands

214, 216 on each side of the peak 212. In this example, the signal-to-noise ratio of the demodulated evoked biosignals is 7A/N. As discussed above, in this example, the amplitude of signal a 204 is 1/2 of noise N in the environment. Therefore, after demodulation, the new signal-to-noise ratio is 7/2 ═ 3.5.

The evoked biosignal profile 210 shown in FIG. 2 is shown quantitatively in Table 1. Table 1 shows the results based on AB₇And B₇The convoluted evoked biosignal profile 210. Thus, as shown in Table 1At step 7, the amplitude is shown to be 7A. By calculating the sum at step 7 (i.e. a)₁+a₂+a₃+a₄+a₅+a₆+a₇) Divided by the sum at

steps

1, 3, 5, 9, 11 and 13 (i.e., a)₁+a₃+a₅+a₉+a₁₁+a₁₃) The absolute value of the peak sideband ratio. This results in a peak sideband ratio equal to 7A/-6A ═ 7/6.

Step (a)_i)	Measured (AB)₇ ^*B₇)_i	Theoretical (AB)₇ ^*B₇)_i
			(AB₇*B₇)₁	-a₇	-A
(AB₇*B₇)₂	a₆-a₇	0
			(AB₇*B₇)₃	-a₅+a₆-a₇	-A
(AB₇*B₇)₄	-a₄-a₅+a₆+a₇	0
			(AB₇*B₇)₅	a₃-a₄-a₅-a₆+a₇	-A
(AB₇*B₇)₆	a₂+a₃-a₄+a₅-a₆-a₇	0
			(AB₇*B₇)₇	a₁+a₂+a₃+a₄+a₅+a₆+a₇	7A
(AB₇*B₇)₈	a₁+a₂-a₃+a₄-a₅-a₆	0
			(AB₇*B₇)₉	a₁-a₂-a₃-a₄+a₅	-A
(AB₇*B₇)₁₀	-a₁-a₂+a₃+a₄	0
			(AB₇*B₇)₁₁	-a₁+a₂-a₃	-A
(AB₇*B₇)₁₂	a₁-a₂	0
			(AB₇*B₇)₁₃	-a₁	-A

TABLE 1

With respect to the convolution of the modulation-induced biosignal and the carrier sequence code, it should be understood that the demodulator 126 may calculate the convolution using a bit-by-bit shift with a logical and gate. Additionally, where the transmission source 110 is an LED or other flashing device, the carrier sequence code may be converted to a binary format. In particular, the carrier sequence code may be modified to account for the on (i.e., 1) or off (i.e., 0) state of the transmission source 110. Thus, in one embodiment, the modulator 124 may modulate the sampled evoked biosignal by converting the carrier sequence code into a binary format and modulating the sampled evoked biosignal with the carrier sequence code in the binary format. Referring again to the illustrative example, carrier sequence code B₇That (1, -1, -1) can be converted into a binary format such as B_7dThe term (1, 0, 1, 0). Thus, the modulator 124 may induce the biological signal by sampling with a modified carrier sequence code (i.e., B) in binary format_7dThe induced biosignals are modulated by multiplying by (1, 0, 1, 0)).

According to the embodiments discussed above, demodulator 126 may pass (e.g., using a logical AND gate)) The modulated evoked biosignals are demodulated by calculating a convolution of the modulated evoked biosignals with the carrier sequence code in binary format. Referring again to the illustrative example, the demodulator may calculate B using a logical AND gate_7d(1, 0, 1, 0) and AB₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇) The result of the convolution of (A) is (B)_7dac) (0, 1, 2, 4, 2, 1, 0). In this example, the induced biosignal spectrum produced had an amplitude of 4A, with 2 peak adjacent sidebands and 1 more distant sideband, and the peak sideband ratio was 4/12. Fig. 3A is an exemplary convolution of a bio-signal using a HACS and a logical and gate according to the example described above.

In another embodiment, and referring again to fig. 1, the system clock 130 may calculate the sampled evoked biosignals by sampling and holding the evoked biosignals at a predetermined rate. In this implementation, the modulator 124 may modulate the sampled induced biosignal by multiplying the sampled induced biosignal with a carrier sequence code using a logical exclusive or gate. In addition, the demodulator 126 may demodulate the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with the carrier sequence code. Referring again to the illustrative example, the demodulator may calculate B using a logical XOR gate_7d(1, 0, 1, 0) and AB₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇) The result of the convolution of (A) is (B)_7dac) (1, 2, 3, 4, 3, 2, 1). In this example, the induced biosignal spectrum produced has an amplitude of 4A, has 3, 2, or 1 sidebands, and has a peak sideband ratio of 4/26. Fig. 3B is a schematic diagram of an exemplary bio-signal convolution using HACS and a logical xor gate according to the above example.

The embodiment discussed in fig. 3B is shown graphically in fig. 4. Specifically, fig. 4 shows an exemplary bio-signal trace modulated and demodulated using a HACS according to an exemplary embodiment. Trace 402 shows a sinusoidal signal, such as an evoked biosignal. The sinusoidal signal is discretized by sampling and holding the signal according to the system clock at a predetermined rate shown in trace 404. The result is shown in trace 406. Trace 408 shows the modulation of the sampled evoked biosignal by multiplying it with the carrier sequence code using a logical xor gate. Trace 410 shows the demodulation of the modulated evoked biosignal by convolving the modulated evoked biosignal with the carrier sequence code. As can be seen in trace 410, the amplification is 4A.

Referring again to fig. 1, the true induced biosignal may be constructed based on the peak sideband proportion. Specifically, a filter 128 communicatively coupled to the sensor 104 may calculate a deviation between the sampled induced biosignal and the peak sideband ratio. The filter 128 may filter and/or tune noise artifacts from the sampled evoked biosignals based on the variance and output the true evoked biosignals based on the filtering. For example, the filter 128 may remove elements of the sample-induced bio-signal if the corresponding deviation satisfies a predetermined threshold outside of the peak sideband ratio. In one embodiment, the deviation of each element of the sampled induced biosignal is compared to a predetermined threshold. The filter 128 may filter the corresponding elements of the sampled evoked biosignal based on the comparison.

Referring again to the illustrative example shown in FIG. 2, the peak sideband ratio is-7/6. Thus, elements of the sampling induced bio-signal that deviate from the peak sideband ratio of-7/6 by more than a predetermined threshold are rejected and removed. For example, if an element of the sampling-induced biosignal deviates more than 1/1000 from the peak sideband ratio of-7/6, then this element is removed. In one embodiment, this element is removed or replaced with the last consecutive value in the sampled evoked biological signal. Thus, the true induced biosignal can be reconstructed by filtering out the deviations.

Referring now to fig. 5, an illustrative example of the use of HACS to filter noise using induced biosignal spectra is shown. Specifically, fig. 5 shows an exemplary bio-signal trace with the addition of analog "spike" noise modulated and demodulated using HACS, according to another exemplary embodiment. Trace 502 shows a sinusoidal signal, e.g., a true evoked biosignal with little noise. Trace 504 shows the evoked biosignal with noise and an amplitude close to 2. Trace 506 shows the induced biosignal spectrum with a peak sideband ratio of-7/6. Trace 508 shows the introduction of spiking random noise into the signal shown in trace 502, with a shift from the peak sideband ratio. Based on the shift from the peak sideband ratio, the noise shown in trace 508 is removed and the signal shown in trace 502 is reconstructed as shown in trace 510. Similar peak sideband deviation rejection criteria may be used with the logical and gate and logical xor gate of fig. 3A and 3B to similarly reject noise data points.

Fig. 6A and 6B illustrate the application of HACS in real world applications. In fig. 6A, trace 602 shows the evoked bio-signal, the PPG signal, measured in a real-world environment by direct skin contact with the sensor, which shows little noise. Trace 604 shows the recording of the PPG signal done simultaneously with trace 602 using a contactless sensor, thereby introducing a significant amount of ambient noise. In fig. 6B, trace 606 shows the evoked bio-signal, the PPG signal, measured in a real-world environment by direct skin contact with the sensor, which signal shows little noise as visible. Trace 608 shows the modulation and demodulation of the induced (non-contact) bio-signal using HACS at a sampling rate of 4 ms. Thus, the peak-to-sideband ratio can be optimized by varying the predetermined sampling rate, which produces less noise artifacts in the signal, e.g., see trace 608 compared to trace 604. Thus, using HACS for recording bio-signals as described herein shows a reduction of noise and/or motion artifacts in order to reconstruct the true bio-signal.

Referring again to fig. 1, in some embodiments, the predetermined sampling rate controlled by the system clock 130 may be varied to reduce noise in the signal. In some embodiments, the sampling rate may be tuned such that the sampling frequency is increased and/or decreased. For example, a 2ms sampling interval may be tuned to a 4ms sampling rate. In addition, the predetermined sampling rate may be maintained by the system clock 130 according to the peak-to-sideband ratio. This results in minimized sideband bias.

Another exemplary operation of the system 100 shown in fig. 1 will now be described. As discussed above, in one embodiment, the system 100 includes a sensor 104 having a transmitter 108. The transmitter 108 transmits control signals to the transmission source 110 according to the carrier sequence code. Thus, transmission source 110 transmits energy (i.e., energy waves 120) to object 106 according to the carrier sequence code. The carrier sequence code has an autocorrelation function. In this implementation, the carrier sequence code may be converted to a binary format.

For example, carrier sequence code B₇(1, -1, -1) can be converted and/or modified to a binary format such as B_7dThe term (1, 0, 1, 0). The transmission source 110 is flashed (e.g., blinked) on (i.e., 1) and off (i.e., 0) according to the binary format of the carrier sequence code. In addition, the sensor 104 includes a receiver 112 for receiving the evoked biosignal 122 in response to energy reflections returning from the object 106. The evoked biosignal 122 is an analog signal and the evoked biosignal 122 is modulated according to a carrier sequence code. As use B_7dIf the transmission source 110 is on, the output is S + N, where S is the signal and N is noise. If the transmission source is off, the output is N. Thus, according to B_7dThe modulated evoked biosignal is equal to (S + N, S + N, S + N, N, N, S + N, N).

A demodulator 126 communicatively coupled to the sensor 104 receives the modulated evoked biosignal and demodulates the modulated evoked biosignal by calculating a convolution of the evoked biosignal with the carrier sequence code, thereby producing an evoked biosignal spectrum. In this example, the modulated biological signal is associated with B₇Which is (1, -1, -1) convolution. The evoked biosignal spectra have a signal-to-noise ratio proportional to a peak sideband ratio, and the peak sideband ratio is a function of the carrier sequence code. In this example, the peak sideband ratio is 4/-3, and can be expressed as 4(S + N) -3N ═ 4S + N.

In another embodiment, the transmission source 110 may be flashed and modulated using a carrier sequence codeThe generant signal may be convolved with the two's complement of the carrier sequence code. For example, modulating the bio-signal uses a logical exclusive OR gate and B₇Two's complement (is B) for (1, -1, -1)_7dWhich is (0, 1, 0, 1)) convolution. The resulting induced biological profile is B7_tc(0, 1, 2, 3, 7, 3, 2, 1, 0). Here, the amplification is 7A, with sidebands slightly greater than 2. Fig. 7 is a schematic circuit diagram of the demodulator 126 of fig. 1 using a logical xor gate according to the above example.

In another embodiment, the modulation of the carrier sequence codes may use a concatenation of two carrier sequence codes each having a different length. For example, a barker code with length seven (7) may be concatenated with a barker code of length 11. Conversion into binary format, which results in B_711dThe term (1, 0, 1, 0, 1, 0). Thus, the transmission source 110 may flash according to a concatenated carrier sequence code in binary format. The demodulator 126 calculates the modulation-induced biological signal and the concatenated carrier sequence code B₇₁₁A convolution of (1, -1, -1, -1). In this example, the peak sideband ratio is 9, and may be expressed as 9(S + N) -9N — 9S. Thus, in this example, the system noise is completely cancelled. This example is shown graphically in fig. 8. More specifically, fig. 8 shows an exemplary bio-signal trace with a sinusoidal noise source modulated and demodulated using HACS according to another exemplary embodiment, where the sidebands of the noise overlap with the sidebands of the signal. Trace 802 shows a sinusoidal signal, e.g., the evoked biosignal S ═ sin (x). Trace 804 shows noise and/or motion artifacts such as N ═ sin (.5x) + sin (1.5x) + sin (10 x). Trace 806 shows the signal S + N with noise. Trace 808 shows the spectrum of the convolution product of the induced biosignal with an amplification of 9. The demodulator 126 and/or the filter 128 may also process the modulated evoked biosignal by generating a real evoked biosignal, which is generated by extracting the real evoked biosignal from the modulated evoked biosignal based on the peak sideband ratio.

Referring now to fig. 9, an exemplary method for bio-signal recording using highly auto-correlated carrier sequence code (HACS) according to an exemplary embodiment will be described. Fig. 9 will be described with reference to the components of fig. 1, 2, 3A, 3B. The above-described system components and examples may contribute to the methods described herein. At block 902, the method includes transmitting a control signal from a transmitter of a sensor to a transmission source. The transmission source transmits energy to the object in accordance with the control signal. As discussed above with respect to fig. 1, the transmitter 108 controls the transmission source 110. More specifically, the transmitter 108 sends a control signal (not shown) to the transmission source 110 and the transmission source 110 sends energy (e.g., the energy signal 120) to the object 106 in accordance with the control signal.

At block 904, the method includes receiving an evoked bio-signal at a receiver of the sensor in response to energy reflections returned from the object. The induced biological signal is an analog signal. As discussed above with respect to fig. 1, the receiver 112 receives an induced biosignal 122 representative of a biometric measurement (e.g., a PPG measurement) of the subject 106. At block 906, the method includes calculating a sampled evoked biosignal by sampling the evoked biosignal at a predetermined sampling rate. The sample-induced biosignal can be expressed in vector form as a ═ a (a)₁、a₂、a₃、a₄、a₅、a₆、a₇...), wherein A represents the evoked biological signals 122, and each element in A represents A (i)_t) Where t is the sampling rate and/or sampling interval. The system clock 130 controls the sampling of the evoked biological signals at different sampling rates. In some embodiments, as discussed above, calculating the sampled evoked biosignal further includes sampling and holding the evoked biosignal at a predetermined rate by the system clock 130.

Additionally, at block 908, the method includes modulating the sampled evoked biosignal with a carrier sequence code, thereby producing a modulated evoked biosignal. The carrier sequence code has an autocorrelation function. The carrier sequence code may be a highly auto-correlated carrier sequence (HACS) to process the evoked biosignals. For example, as described in the exemplary embodiments herein, carrier orderingThe column code may be a barker code of length seven (7). As discussed above, in some embodiments, the modulator 124 may facilitate the modulation of the induced bio-signal from the sampling of the HACS. For example, sampling the induced biosignal with a Barker code B₇The multiplication results in a modulation of the sampled induced biosignal, which is expressed in vector form as AB₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇)。

As discussed above, in some embodiments, modulating the sampled induced biosignal further comprises converting the carrier sequence code to a binary format and modulating the sampled induced biosignal with the carrier sequence code in the binary format. Thus, the carrier sequence code B₇That (1, -1, -1) can be converted into a binary format such as B_7dThe term (1, 0, 1, 0). Additionally, in embodiments where the sampled induced biosignal is sampled and held, modulating the sampled induced biosignal may include multiplying the sampled induced biosignal with a carrier sequence code using a logical exclusive or gate. (see fig. 7 and 8).

At block 910, the method includes demodulating the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with a carrier sequence code, thereby producing an evoked biosignal spectrum. The evoked biosignal spectra have peak sideband ratios as a function of carrier sequence code. In other embodiments, the induced biosignal spectrum represents an induced biosignal having an amplitude that increases by a factor proportional to a peak sideband ratio. As discussed above, according to one illustrative example, demodulator 126 may couple AB₇＝(a₁、a₂、a₃、-a₄、-a₅、a₆、-a₇) With the original barker code used for modulation (e.g. barker code B)₇) Convolution, which produces an induced biosignal spectrum with a peak sideband ratio equal to 7A/-6.

In instances where the sampled evoked biosignal is modulated using a binary-formatted carrier sequence code, demodulating the modulated evoked biosignal further includes demodulating the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with the binary-formatted carrier sequence code using a logical and gate. For example, fig. 3A shows an exemplary convolution of a bio-signal using a HACS and a logical and gate.

At block 912, the method includes calculating a deviation between each element of the sampled induced biosignal and the peak sideband ratio. For example, the filter 128 may calculate the deviation between the sampled induced biosignal and the peak sideband ratio. At block 914, the method includes filtering noise artifacts from the sampled evoked biosignals based on the deviation, and outputting true evoked biosignals based on the filtering. Thus, in one embodiment, the filter 128 may filter noise artifacts from the sampled evoked biosignals based on the bias and output the true evoked biosignals based on the filtering.

Calculating the bias and filtering noise artifacts will now be described in more detail with reference to fig. 10. As mentioned above, for each element of the modulated bio-signal, a deviation between each element and the peak sideband ratio is determined at block 1002. At block 1004, the deviation is compared to a predetermined threshold. At block 1006, if the deviation meets and/or equals a predetermined threshold, then at block 1008, the corresponding element of the sampled evoked biological signal is removed. In one embodiment, this element is removed or replaced with the last consecutive value in the sampled evoked biological signal. Otherwise, at block 1010, the corresponding elements of the sampled induced biosignal are not removed.

Referring now to fig. 11, an exemplary method for bio-signal recording using highly auto-correlated carrier sequence code (HACS) according to another embodiment will be described. At block 1102, the method includes transmitting a control signal from a transmitter of a sensor to a transmission source. The control signal is transmitted according to a carrier sequence code, and the transmission source transmits energy to the object according to the carrier sequence code. The carrier sequence code has an autocorrelation function. Thus, in one embodiment, transmitting control signals from the transmitter 108 of the sensor 104 to the transmission source 110 includes the control signals driving execution and/or commands (e.g., on/off, blinking) of the transmission source 110 in accordance with the carrier sequence code. In some embodiments, as discussed above, the carrier sequence code is a concatenation of two carrier sequence codes each having a different length.

At block 1104, the method includes receiving an evoked bio-signal at a receiver of the sensor in response to energy reflections returned from the object. The evoked biosignals are analog signals and are modulated according to a carrier sequence code. Thus, the sensor 104 includes a receiver 112 for receiving the evoked biological signals 122 in response to energy reflections returning from the object 106.

At block 1106, the method includes demodulating the evoked biosignal by calculating a convolution of the evoked biosignal with the carrier sequence code, thereby producing an evoked biosignal spectrum. The induced biosignal spectrum has a signal-to-noise ratio proportional to a peak sideband ratio. The peak sideband ratio is a function of the carrier sequence code. In some embodiments, as discussed above, the carrier sequence code is a concatenation of two carrier sequence codes each having a different length. The demodulation is thus performed by convolving the modulated biosignal with a concatenation of two carrier sequence codes. In another embodiment, demodulating the modulated evoked biosignal further comprises demodulating the modulated evoked biosignal by calculating a convolution of the modulated evoked biosignal with a binary complement of the binary formatted carrier sequence code using a logical exclusive or gate. (see fig. 7). Further, at block 1108, the method includes generating a real evoked biosignal by extracting the real evoked biosignal from the modulated evoked biosignal based on the peak sideband ratio. Thus, a true bio-signal can be reconstructed from a noisy environment.

As discussed above, the embodiments discussed herein may also be described and implemented in the context of a non-transitory computer-readable medium storing computer-executable instructions. In addition, it will be appreciated that various of the implementations and other features and functions or alternatives disclosed above, or variations thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims

1. A computer-implemented method for bio-signal recording, comprising:

transmitting a control signal from a transmitter of a sensor to a transmission source, wherein the transmission source transmits energy to an object according to the control signal;

receiving an evoked bio-signal at a receiver of the sensor in response to energy reflections returned from the object, wherein the evoked bio-signal is an analog signal;

processing the sampled evoked biosignals by sampling the evoked biosignals at a predetermined sampling rate;

modulating the sampled evoked biosignal with a carrier sequence code to produce a modulated evoked biosignal, the carrier sequence code having an autocorrelation function;

demodulating the modulated evoked biosignal by processing a convolution of the modulated evoked biosignal with the carrier sequence code to produce an evoked biosignal spectrum having a peak sideband ratio as a function of the carrier sequence code;

processing a deviation between each element of the sampled induced bio-signal and the peak sideband ratio;

filtering noise artifacts from the sampled evoked biological signals based on the processed deviation; and

outputting a true evoked biosignal based on the filtering.

2. The computer-implemented method of claim 1, wherein modulating the sampled evoked biosignal further comprises converting the carrier sequence code to a binary format and modulating the sampled evoked biosignal with the carrier sequence code in binary format.

3. The computer-implemented method of claim 2, wherein demodulating the modulated evoked biosignal further comprises demodulating the modulated evoked biosignal by processing the convolution of the modulated evoked biosignal with the carrier sequence code in binary format using a logical AND gate.

4. The computer-implemented method of claim 1, wherein processing the sampled evoked biosignal further comprises sampling and holding the evoked biosignal at a predetermined rate by a system clock.

5. The computer-implemented method of claim 4, wherein modulating the sampled induced biosignal further comprises multiplying the sampled induced biosignal with the carrier sequence code using a logical exclusive-or gate.

6. The computer-implemented method of claim 1, wherein the carrier sequence code is a barker sequence.

7. The computer-implemented method of claim 1, wherein filtering noise artifacts from the sampled evoked biosignal based on the processed deviations further comprises comparing the deviation for each element of the sampled evoked biosignal to a predetermined threshold and filtering the corresponding element of the sampled evoked biosignal based on the comparison.

8. The computer-implemented method of claim 1, wherein the induced biosignal spectrum represents the induced biosignal having an amplitude that increases by a factor proportional to the peak sideband ratio.

9. The computer-implemented method of claim 4, wherein processing the sampled evoked biosignal further comprises changing a predetermined rate of the system clock to optimize the peak sideband ratio in the evoked biosignal spectrum.

10. A computer-implemented method for bio-signal recording, comprising:

transmitting a control signal from a transmitter of a sensor to a transmission source, wherein the control signal is transmitted according to a carrier sequence code, and the transmission source transmits energy to an object according to the carrier sequence code, the carrier sequence code having an autocorrelation function;

receiving an evoked bio-signal at a receiver of the sensor in response to energy reflections returned from the object, wherein the evoked bio-signal is an analog signal and is modulated according to the carrier sequence code;

demodulating the evoked biosignal by processing convolution of the evoked biosignal with the carrier sequence code to produce an evoked biosignal spectrum having a signal-to-noise ratio proportional to a peak sideband ratio, wherein the peak sideband ratio is a function of the carrier sequence code;

outputting a real evoked biosignal by extracting the real evoked biosignal from the modulated evoked biosignal based on the peak sideband ratio.

11. The computer-implemented method of claim 10, wherein transmitting control signals from the transmitter of the sensor to the transmission source further comprises the control signals driving a flicker of the transmission source according to the carrier sequence code.

12. The computer-implemented method of claim 10, wherein the carrier sequence code is a concatenation of two carrier sequence codes each having a different length.

13. The computer-implemented method of claim 10, wherein demodulating the modulated evoked biosignal further comprises demodulating the modulated evoked biosignal by processing a convolution of the modulated evoked biosignal with a binary complement of the carrier sequence code in binary format using a logical exclusive or gate.

14. A system for bio-signal recording, comprising:

a memory holding instructions for execution by a processor, the processor comprising:

a sensor comprising a transmitter that transmits a control signal to a transmission source, wherein the transmission source transmits energy to an object in accordance with the control signal, the sensor further comprising a receiver for receiving an evoked bio-signal in response to a reflection of energy returned from the object, wherein the evoked bio-signal is an analog signal;

a system clock communicatively coupled to the sensor for processing the sample-induced biosignal at a predetermined sample rate;

a modulator communicatively coupled to the sensor to receive the sampled induced biosignal and modulate the sampled induced biosignal with a carrier sequence code having an autocorrelation function;

a demodulator communicatively coupled to the sensor to receive a modulated evoked biosignal and demodulate the modulated evoked biosignal by processing a convolution of the modulated evoked biosignal with the carrier sequence code to produce an evoked biosignal spectrum having a peak sideband ratio as a function of the carrier sequence code; and

a filter communicatively coupled to the sensor to process a deviation between the sampled evoked biosignal and the peak sideband ratio, filter noise artifacts from the sampled evoked biosignal based on the processed deviation, and output a true evoked biosignal based on the filtering.

15. The system of claim 14, wherein the demodulator further demodulates the modulated evoked biosignal by processing the convolution of the modulated evoked biosignal with the carrier sequence code in binary format using a logical and gate.

16. The system of claim 14, wherein the filter removes elements of the sample-induced biosignal if the corresponding deviation satisfies a predetermined threshold outside of the peak sideband ratio.

17. A system for bio-signal recording, comprising:

a sensor comprising a transmitter for transmitting control signals to a transmission source according to a carrier sequence code, wherein the transmission source transmits energy to an object according to the carrier sequence code, the carrier sequence code having an autocorrelation function,

wherein the sensor further comprises a receiver that receives an evoked biosignal in response to energy reflections returned from the object, wherein the evoked biosignal is an analog signal and is modulated according to the carrier sequence code; and

a demodulator communicatively coupled to the sensor to receive a modulated evoked biosignal and demodulate the modulated evoked biosignal by processing a convolution of the evoked biosignal with the carrier sequence code to produce an evoked biosignal spectrum having a signal-to-noise ratio proportional to a peak sideband ratio, wherein the peak sideband ratio is a function of the carrier sequence code,

wherein the demodulator outputs a real evoked biosignal by extracting the real evoked biosignal from the modulated evoked biosignal based on the peak sideband ratio.

18. The system of claim 17, wherein the carrier sequence code is a concatenation of two carrier sequence codes each having a different length.

19. The system of claim 17, wherein the demodulator further demodulates the modulated evoked biosignal by processing a convolution of the modulated evoked biosignal with a binary complement of the carrier sequence code in binary format using a logical exclusive or gate.

20. The system of claim 17, wherein the evoked biosignal includes a signal corresponding to the carrier sequence code in binary format and a noise element from sources surrounding the sensor and the object.

21. The system of claim 17, wherein the induced biosignal spectrum has an amplitude that increases by a factor proportional to the peak sideband ratio.