TWI739204B - System and method for signal sensing - Google Patents

Abstract

A system and a method for signal sensing are provided. The system for signal sensing includes a processor, a transmitter, a receiver, and an oscillator. The oscillator is coupled to the transmitter and the receiver. The oscillator generates a clock signal. The transmitter sends a plurality of output signals according to the clock signal. The receiver receives at least one first output signal reflected by an object according to the clock signal, and obtains channel state information according to the at least one first output signal. The processor identifies a state of the object according to the channel status information and outputs the state of the object.

Description

Signal sensing system and method

The present invention relates to a signal sensing system and method, and more particularly to a signal sensing system and method based on ODFM technology.

Radar sensing technology is widely used in various non-contact sensing fields, such as health care, safety monitoring, smart home, food safety inspection and other applications. Existing radar sensing devices (such as Doppler radar, millimeter wave (mmWave) radar, etc.) are too expensive. Considering that consumers will hesitate to purchase due to price considerations, use cheap orthogonal The use of Orthogonal Frequency-Division Multiplexing (OFDM) devices (for example, devices using WiFi, LTE, 5G and other technologies) as non-contact sensing has become one of the most popular research technologies in recent years.

The non-contact sensing principle of the OFDM device is a sonar system similar to a bat. The nature of the object to be measured (for example, the movement of the body or the type of liquid) will cause changes in radio waves. For example, after the transmitter sends out a signal, the signal will interact with the subject’s body After the collision, it is received by the receiver. Finally, the receiver device will analyze the received signal to identify the nature of the object under test. However, the above-mentioned method still has the following two key problems to be overcome.

[Question 1: A single OFDM device cannot sense the signal sent by itself]

Unlike existing radar sensing devices, the transmitter and receiver of the OFDM device belong to two different devices. After a device with a transmitter (also called a transmitting device) sends a signal, the device with a transmitter (also called a receiving device) cannot sense the signal sent by the device itself. In particular, due to the problem of frequency offset between the transmitting device and the receiving device, this problem may cause noise in the sensing of the receiving device, which makes signal sensing prone to errors (for example, errors in phase or amplitude).

[Question 2: Fresnel zone effect of electromagnetic waves]

Generally speaking, an elliptical area with the transceiver as the focal point is formed between the radio transceivers. This area is the area where the intensity of wireless electromagnetic waves is concentrated, accounting for about 80% of the entire wireless electromagnetic wave energy. If the object to be measured is farther away from the Fresnel wave zone, the sensed signal change is more susceptible to the influence of electromagnetic wave energy in the Fresnel wave zone.

In particular, the transmitter of the OFDM device needs to select the frequency of the subcarrier before transmitting the signal. In the conventional technology, when the receiver receives the signal reflected by the object under test, it usually uses only a single characteristic of the signal (for example, only frequency or only phase) for analysis to obtain the object under test. relevant information. However, in some sub-carriers with specific frequencies, the signal received by the receiver has a clearer amplitude. The change in phase is obvious, but the change in phase is less obvious. These frequencies are not easy to use in techniques that only use phase for analysis. In addition, in some sub-carriers of specific frequencies, the signal received by the receiver has obvious changes in phase but less obvious changes in amplitude. These frequencies are not easy to use in techniques that only use amplitude for analysis. middle.

Therefore, the present invention provides a signal sensing system and method, which can solve the noise problem caused by the frequency offset between the transmitter and the receiver, and effectively reduce the effect of the Fresnel band effect, thereby improving the OFDM radar The sensing distance.

The present invention provides a signal sensing system including: a sensing device and a processor coupled to the sensing device. The sensing device includes a transmitter, a receiver, and an oscillator. The oscillator is coupled to the transmitter and the receiver and used to generate a clock signal. The transmitter generates multiple sub-carriers orthogonal to each other, modulates multiple sub-signals of a signal according to the multiple sub-carriers to generate multiple output signals, and sends the multiple output signals according to the clock signal . The receiver receives at least one first output signal reflected by an object among the plurality of output signals according to the clock signal, and obtains channel status information according to the first output signal. The processor recognizes a state of the object according to the channel state information, and outputs the state of the object.

The present invention provides a signal sensing method for a signal sensing system, the signal sensing system includes a sensing device and a processor, the sensing device includes a transmitter, a receiver and coupled to The transmitter and the receiver An oscillator, the method includes: generating a clock signal by the oscillator; generating a plurality of sub-carriers orthogonal to each other by the transmitter, and respectively modulating the multiplicity of a signal according to the plurality of sub-carriers Sub-signals to generate a plurality of output signals, and send the plurality of output signals according to the clock signal; at least one of the plurality of output signals reflected by an object is received by the receiver according to the clock signal A first output signal, and obtain a channel state information according to the first output signal; and the processor recognizes a state of the object according to the channel state information, and outputs the state of the object .

Based on the above, the signal sensing system and method of the present invention can integrate a transmitter and a receiver based on OFDM technology in the same device, and allow the transmitter and the receiver to share the same oscillator, thereby solving the problem of the transmitter and the receiver. Noise problems caused by frequency offset between receivers. In addition, the present invention also proposes a mechanism that can effectively reduce the influence of the Fresnel band effect, thereby increasing the sensing range of the OFDM radar.

1000: Signal Sensing System

101: Signal Sensing Module

102: Signal smoothing module

103: Frequency Analysis Module

104: feature detection module

201: Signal generation module

202: sensing device

203: Echo Cancellation Module

201a: Packet configuration module

201b: Packet processing module

202a: Transmitter

202b: receiver

202c: Oscillator

SGL, SGL_1: signal

OB: Object

OL: Outlier information

M1, M2: Maximum

400, 401: Chart

S601: Steps for oscillator to generate clock signal

S603: The transmitter generates multiple sub-carriers orthogonal to each other, modulates multiple sub-signals of a signal according to these sub-carriers to generate multiple output signals, and sends the output signals according to the clock signal.

S605: A step in which the receiver receives at least one first output signal reflected by the object according to the clock signal, and obtains channel status information according to the first output signal

S607: The processor recognizes the state of the object according to the channel state information, and outputs the state of the object

FIG. 1 is a schematic diagram of a signal sensing system according to an embodiment of the invention.

FIG. 2 is a schematic diagram of a signal sensing module according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a signal smoothing module according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a frequency analysis module according to an embodiment of the invention.

FIG. 5 is a schematic diagram of a feature detection module according to an embodiment of the invention.

FIG. 6 is a schematic diagram of a signal sensing method according to an embodiment of the invention.

FIG. 1 is a schematic diagram of a signal sensing system according to an embodiment of the invention.

1, the signal sensing system 1000 mainly includes a signal sensing module 101, a signal smoothing module 102, a frequency analysis module 103, and a feature detection module 104.

FIG. 2 is a schematic diagram of a signal sensing module according to an embodiment of the present invention.

Please refer to FIG. 2, the signal sensing module 101 in FIG. 1 includes a signal generating module 201, a sensing device 202 and an echo cancellation module 203. The signal generating module 201 includes a packet configuration module 201a and a packet processing module 201b. The sensing device 202 includes a transmitter 202a, a receiver 202b, and an oscillator 202c.

In this embodiment, the signal sensing system 1000 further includes a processor (not shown) and a storage circuit (not shown), and the processor is coupled to the storage circuit and the aforementioned sensing device 202. There are multiple programs stored in the storage circuit of the signal sensing system 1000 Code snippets, after the above-mentioned code snippets are installed, they will be executed by the processor. For example, the storage circuit includes a plurality of modules, and the packet configuration module 201a, the packet processing module 201b, the echo cancellation module 203, the signal smoothing module 102, the frequency analysis module 103, and the characteristics are executed by these modules. Each operation of the detection module 104, wherein each module is composed of one or more code fragments. However, the present invention is not limited to this. The various operations of the packet configuration module 201a, the packet processing module 201b, the echo cancellation module 203, the signal smoothing module 102, the frequency analysis module 103, and the feature detection module 104 can also be used It can be implemented in other hardware forms.

In particular, the transmitter 202a and the receiver 202b of the present invention may be transceiver devices (or circuits) based on OFDM technology.

The oscillator 202c is coupled to the transmitter 202a and the receiver 202b. The oscillator 202c is used to generate a clock signal that meets the specifications, and at the same time provides the transmitter 202a and the receiver 202b as an oscillation source. In this embodiment, the transmitter 202a and the receiver 202b share the clock signal generated by the oscillator 202c.

In this embodiment, the signal generating module 201 is used to send multiple packets according to a piece of packet configuration information to generate a signal. In more detail, the packet configuration module 201a in the signal generation module 201 receives the packet configuration information set by the user or the device. The packet configuration information can be the sending rate of the packet. The packet processing module 201b may, for example, divide the data to be sent into multiple packets according to the packet configuration information and send these packets to generate a signal to be transmitted through the transmitter 202a.

After that, the transmitter 202a generates multiple subcarriers orthogonal to each other based on the operating principle of OFDM, and transfers the foregoing from the packet processing module 201b. The signal is divided into multiple sub-signals, and the multiple sub-signals are modulated according to the multiple sub-carriers to generate multiple output signals. After that, the transmitter 202a sends the output signal SGL according to the packet configuration information and the clock signal of the oscillator 202c.

After that, the receiver 202b receives at least one output signal SGL_1 (also referred to as the first output signal) reflected by the object OB in the output signal SGL according to the clock signal of the oscillator 202c. For example, the receiver 202b receives the output signal SGL_1 in the form of an analog signal according to the clock signal of the oscillator 202c and samples the output signal SGL_1 in the form of a digital signal.

After obtaining the output signal SGL_1, the receiver 202b obtains channel state information (CSI) according to the output signal SGL_1. The processor of the signal sensing system 1000 recognizes a state of the object OB according to the channel state information, and outputs the state of the object.

In more detail, in the operation of obtaining channel status information according to the output signal SGL_1, the echo cancellation module 203 can first eliminate the interference signal in the output signal SGL_1. In particular, the interference signal is transmitted through a path (also referred to as a first path) between the transmitter 202a and the receiver 202b, and the first path is not reflected by the object OB. In other words, due to the multipath problem of wireless transmission, some of the signals sent by the transmitter 202a will be directly transmitted from the transmitter 202a to the receiver 202b without reflection, and these signals will cause errors in judgment. , So these signals will be identified as interference signals. The echo cancellation module 203 can eliminate interference signals by using hardware, multiple reference active noise cancellation (Mutiple Reference Active Noise Control, Mutiple Reference ANC), and recursive minimum. Recursive Least Squares (RLS), Least Mean Square (LMS), or Filtered-X LMS (FxLMS) methods.

FIG. 3 is a schematic diagram of a signal smoothing module according to an embodiment of the present invention.

Referring to FIG. 3, after obtaining the output signal SGL_1 from which the interference signal has been removed, the signal smoothing module 102 uses a filter to filter the output signal SGL_1 from which the interference signal has been removed to delete at least one outlier data OL.

FIG. 4 is a schematic diagram of a frequency analysis module according to an embodiment of the invention.

Referring to FIG. 4, after removing the interference signal and outlier data OL in the output signal SGL_1, the frequency analysis module 103 obtains channel status information according to the output signal SGL_1 from which the interference signal and outlier data OL have been removed. After that, the frequency analysis module 103 obtains at least one complex number in the time domain according to the channel status information. How to obtain the channel status information and the complex number corresponding to the channel status information according to a signal can be known from the conventional OFDM technology, and will not be repeated here. As shown in the graph 400 in FIG. 4, the graph 400 is used to show the distribution of time, the real part of the obtained complex number and the imaginary part of the obtained complex number in a three-dimensional space. relation.

After obtaining at least one complex number in the time domain according to the channel status information, the frequency analysis module 103 converts these complex numbers into frequency domain signals in the frequency domain (as shown in the chart 401 of FIG. 4), and then according to this The frequency domain signal identifies the state of the object OB. In other words, the frequency analysis module 103 is described in the form of a complex number (for example, IQ Data) Transmit the channel (Channel), and convert the change of the channel in time to the frequency domain through the spectrum analysis method. The spectrum analysis method can be Fourier transform (Fourier transform, FT) or discrete wavelet transform (Discrete Wavelet Transform, DWT) and other methods.

FIG. 5 is a schematic diagram of a feature detection module according to an embodiment of the invention.

Referring to FIG. 5, after obtaining the frequency domain signal, the feature detection module 104 can determine the state of the object OB. Specifically, it is assumed that the object OB is a human body and the feature detection module 104 is used to detect the breathing frequency and heartbeat frequency of the human body. The chart 401 of FIG. 5 is an example of a continuation of the chart 401 of FIG. 4. In the chart 401, the dimension of the horizontal axis (also known as the first dimension) is used to represent the number of beats per minute (BPM), and the dimension of the vertical axis (also known as the second dimension) is used to represent the frequency . The feature detection module 104 will identify a certain range (also known as the first range) in the BPM (that is, the first dimension) of the frequency domain signal, and compare the frequency in the first range (that is, the aforementioned second The maximum value M1 (also referred to as the first maximum value) of the dimension) is identified as the first physiological information. For example, find the maximum value of the frequency in the BPM range between 6 and 25 in the frequency domain as the respiratory frequency (ie, the aforementioned first physiological information).

Similarly, the feature detection module 104 will identify another range of the BPM in the frequency domain signal (also referred to as the second range), and determine the maximum value M2 of the frequency in the second range (also referred to as the second range). The maximum value) is identified as the second physiological information. For example, find the maximum value of the frequency in the BPM range between 50 and 100 in the frequency domain as the heartbeat frequency (ie, the aforementioned first physiological information).

It should be noted that the aforementioned example is that the object OB is a human body and the aforementioned method is used to sense the respiration frequency and heartbeat frequency of the human body. However, the present invention is not limited to this. In one embodiment, the object OB to be sensed is a liquid, and the feature detection module 104 is used to determine the type of the liquid (for example, water or alcohol). In addition, in an embodiment, the feature detection module 104 may also be used to determine the position of the sensed object OB in a space for positioning.

In particular, Table 1 describes the difference in signal processing between the transmitter 202a and the receiver 202b that share the same oscillator 202c and the conventional transmitter and receiver that do not share the oscillator.

Please refer to Table 1 above. The example in Table 1 uses amplitude for analysis. The "signal flight distance" in Table 1 means that the signal arrives after being reflected by an object after being sent from the transmitter The length of the path traveled by the receiver. It can be clearly seen from Table 1 that when the object OB actually breathes at 12 BPM, the device that does not share the oscillator generates an error when the signal flight distance is 6 meters, while the device that shares the oscillator (that is, the present invention The signal sensing system 1000) produces an error when the signal flight distance is 10 meters.

Similarly, when the object OB actually breathes at 15 BPM, the device that does not share the oscillator generates an error when the signal flight distance is 8 meters, while the device that shares the oscillator (ie, the signal sensing system 1000 of the present invention) ) The error occurs when the signal flight distance is 14 meters.

Table 2 describes the difference in signal processing between the transmitter 202a and the receiver 202b that share the same oscillator 202c and the conventional transmitter and receiver that do not share the oscillator.

Please refer to Table 2 above. In the example of Table 2, the device that does not share the oscillator uses amplitude (for example, converting complex numbers into amplitude) for analysis, while the device that shares the oscillator (ie, the signal sensing system 1000 of the present invention) It is to directly observe the overall changes in the plural for analysis. It can be clearly seen from Table 2 that when the object OB actually breathes at 12 BPM, the device that does not share the oscillator generates an error when the signal flight distance is 6 meters, while the device that shares the oscillator (that is, the present invention The signal sensing system 1000) still has no error when the signal flight distance is 10 meters.

Similarly, when the object OB actually breathes at 15 BPM, the device that does not share the oscillator generates an error when the signal flight distance is 8 meters, while the device that shares the oscillator (ie, the signal sensing system 1000 of the present invention) ) The error occurs when the signal flight distance is 14 meters.

It can be seen from the above that the present invention can effectively reduce the mechanism of the Fresnel band effect, thereby increasing the sensing range of the OFDM radar. In particular, the present invention directly observes "the overall change of a complex number" instead of analyzing the single characteristic of converting the complex number into frequency or phase and using one of the two as in the conventional technology.

FIG. 6 is a schematic diagram of a signal sensing method according to an embodiment of the invention.

Please refer to FIG. 6, in step S601, the oscillator 202c generates a clock signal. In step S603, the transmitter 202a generates multiple sub-carriers orthogonal to each other, modulates the multiple sub-signals of a signal according to the sub-carriers to generate multiple output signals, and sends the output signals according to the clock signal. In step S605, the receiver 202b receives at least one first output signal reflected by the object according to the clock signal. Signal, and obtain channel status information according to the first output signal. In step S607, the processor recognizes the state of the object according to the channel state information, and outputs the state of the object.

In summary, the signal sensing system and method of the present invention can integrate a transmitter and receiver based on OFDM technology into the same device, and allow the transmitter and the receiver to share the same oscillator, thereby solving the problem of transmission The noise problem caused by the frequency offset between the receiver and the receiver. In addition, the present invention also proposes a mechanism that can effectively reduce the influence of the Fresnel band effect, thereby increasing the sensing range of the OFDM radar.

S601: Steps for oscillator to generate clock signal

S603: The transmitter generates multiple sub-carriers orthogonal to each other, modulates multiple sub-signals of a signal according to these sub-carriers to generate multiple output signals, and sends the output signals according to the clock signal.

S605: A step in which the receiver receives at least one first output signal reflected by the object according to the clock signal, and obtains channel status information according to the first output signal

S607: The processor recognizes the state of the object according to the channel state information, and outputs the state of the object

Claims (20)

A signal sensing system includes: A sensing device, including: A transmitter; A receiver; and An oscillator, coupled to the transmitter and the receiver and used to generate a clock signal; and A processor for coupling to the sensing device, wherein The transmitter generates a plurality of subcarriers orthogonal to each other, modulates the plurality of sub-signals of a signal according to the plurality of sub-carriers to generate a plurality of output signals, and transmits the plurality of subcarriers according to the clock signal. Output signals, The receiver receives at least one first output signal reflected by an object among the plurality of output signals according to the clock signal, and obtains a channel state information (CSI) according to the first output signal , The processor recognizes a state of the object according to the channel state information, and outputs the state of the object. The signal sensing system described in claim 1, wherein in the operation of identifying the state of the object based on the channel state information, The processor obtains at least one complex number in the time domain according to the channel state information, converts the complex number in the time domain into a frequency domain signal in the frequency domain, and according to the frequency domain The domain signal identifies the state of the object. The signal sensing system described in claim 2, wherein the frequency domain signal includes a first dimension and a second dimension, and in the operation of identifying the state of the object based on the frequency domain signal , The processor recognizes a first range of the first dimension in the frequency domain signal, and recognizes a first maximum value of the second dimension in the first range as a first physiological information; The processor recognizes a second range of the first dimension in the frequency domain signal, and recognizes a second maximum value of the second dimension in the second range as a second physiological information. The signal sensing system described in item 3 of the scope of patent application, wherein the first dimension is used to represent beats per minute (BPM), the second is degree used to represent frequency, and the The first physiological information is used to indicate a breathing rate, and the second physiological information is used to indicate a heartbeat rate. The signal sensing system described in item 1 of the scope of patent application further includes: An echo cancellation module, wherein in the operation of obtaining the channel status information according to the first output signal, The echo cancellation module is used to eliminate an interference signal in the first output signal, wherein the interference signal is transmitted through a first path between the transmitter and the receiver, and the The first path is not reflected by the object. The signal sensing system as described in item 5 of the scope of patent application, in which The processor uses a filter to filter the first output signal from which the interference signal has been removed to delete at least one outlier data. The signal sensing system described in item 1 of the scope of patent application further includes: A signal generating module is used to send a plurality of packets according to a piece of packet configuration information to generate the signal. The signal sensing system according to the first item of the patent application, wherein the object is a user, and the state of the object is the breathing rate of the user. The signal sensing system as described in item 1 of the scope of patent application, wherein the state of the object is the position of the object. The signal sensing system according to the first item of the patent application, wherein the object is a liquid, and the state of the object is the type of the liquid. A signal sensing method for a signal sensing system, the signal sensing system includes a sensing device and a processor, the sensing device includes a transmitter, a receiver and coupled to the transmitter And an oscillator of the receiver, the method includes: Generating a clock signal by the oscillator; The transmitter generates multiple sub-carriers orthogonal to each other, modulates multiple sub-signals of a signal according to the multiple sub-carriers to generate multiple output signals, and transmits the multiple sub-carriers according to the clock signal Output signal Receiving at least one first output signal reflected by an object among the plurality of output signals according to the clock signal by the receiver, and obtaining a channel state information according to the first output signal; and The processor recognizes a state of the object according to the channel state information, and outputs the state of the object. The signal sensing method according to claim 11, wherein the step of identifying the state of the object according to the channel state information includes: The processor obtains at least one complex number in the time domain according to the channel state information, converts the complex number in the time domain into a frequency domain signal in the frequency domain, and according to the frequency domain signal Identify the state of the object. The signal sensing method according to claim 12, wherein the frequency domain signal includes a first dimension and a second dimension, and the step of identifying the state of the object according to the frequency domain signal includes: Identifying a first range of the first dimension in the frequency domain signal by the processor, and identifying a first maximum value of the second dimension in the first range as a first physiological information ;as well as Identifying a second range of the first dimension in the frequency domain signal by the processor, and identifying a second maximum value of the second dimension in the second range as a second physiological information . The signal sensing method according to item 13 of the scope of the patent application, wherein the first dimension is used to represent beats per minute (BPM), the second is degree used to represent frequency, and the The first physiological information is used to indicate a respiratory rate, and the second physiological information is used to indicate a heartbeat rate. According to the signal sensing method described in claim 11, the step of obtaining the channel state information according to the first output signal includes: Eliminating an interference signal in the first output signal by an echo cancellation module, wherein the interference signal is transmitted through a first path between the transmitter and the receiver, and the first A path is not reflected by the object. The signal sensing method described in item 15 of the scope of patent application further includes: The processor uses a filter to filter the first output signal from which the interference signal has been removed to delete at least one outlier data. The signal sensing method described in item 11 of the scope of patent application further includes: A signal generating module sends multiple packets according to a piece of packet configuration information to generate the signal. The signal sensing method according to the eleventh patent application, wherein the object is a user, and the state of the object is the breathing rate of the user. The signal sensing method as described in item 11 of the scope of patent application, wherein the state of the object is the position of the object. In the signal sensing method described in claim 11, the object is a liquid, and the state of the object is the type of the liquid.

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