JP2017187395A - Watching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a watching device capable of identifying an azimuth and a position of a watching object, with a simple structure.SOLUTION: A watching device comprises: a transmission antenna 2; plural reception antennas 3A-3D; a selection circuit 4; an FM-CW radar unit 1; an A/D converter 7; and a signal processing part 5. The selection circuit 4 selects one reception antenna out of the plural reception antennas 3A-3D. The signal processing part 5 switches the selection circuit 4 so as to obtain a beat signal corresponding to each of the plural reception antennas 3A-3D, and causes the FM-CW radar unit 1 to transmit a transmission signal and receive a reception signal. The signal processing part 5 performs correction processing of a phase according to the reception antenna corresponding to the beat signal converted into a digital signal, and synthesizes beat signals whose phases have been corrected, obtained by the plural reception antennas 3A-3D, for detecting an azimuth and distance of a watching object.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a watching device, and more particularly, to a watching device using radio waves for watching a trend of a living body (animal such as a sick person, an elderly person, and a pet).

  Conventionally, a monitoring device using a radar that uses radio waves is known. Japanese Patent Laying-Open No. 2016-19584 (Patent Document 1) discloses a watching device for watching a sick person or the like on a bed. The monitoring device detects a first sensor (pyroelectric human sensor) including a plurality of detection units that detect movements of a sick person or the like in a plurality of regions on the bed and the presence or absence of a sick person or the like on the bed. A second sensor (millimeter wave Doppler radar) and a control unit for determining the state of a sick person or the like based on the output signals of these sensors are provided.

JP 2016-199584 A JP 11-133142 A

  The watching device disclosed in Japanese Patent Laying-Open No. 2016-19584 (Patent Document 1) uses a radar (second sensor) to detect the presence / absence of a watching target, and is focused on detecting motion. There is a problem that the electric human sensor (first sensor) is separately provided and the cost is high. Further, since radar is used only in a narrow area such as a bed, it is not possible to specify the azimuth and position where the watching target exists in a wide area.

  On the other hand, as a technique for detecting an object using only a radar, a technique using a frequency modulated continuous wave radar (FM-CW radar) is known. Japanese Patent Laid-Open No. 11-133142 (Patent Document 2) discloses an FM-CW radar that can detect the azimuth, distance, and speed of a target while performing beam scanning.

  FIG. 11 is a diagram illustrating a configuration example of an in-vehicle FM-CW radar. FIG. 12 is a diagram showing temporal changes in the transmission / reception frequency and beat frequency of the in-vehicle FM-CW radar. As shown in FIG. 11, the in-vehicle FM-CW radar is provided with a plurality of amplifiers, mixers, filters, and A / D converters, respectively, on a plurality of receiving antennas. Also, as shown in FIG. 12, the transmission signal is swept alternately in the frequency up direction and the frequency down direction as indicated by the solid line, and beat frequencies fb1 and fb2 corresponding to the frequency difference from the reception signal indicated by the broken line are obtained. ing.

  However, the FM-CW radar disclosed in Japanese Patent Application Laid-Open No. 11-133142 (Patent Document 2) is for vehicle use and is not suitable for watching a sick person or the like. Since in-vehicle radars are required to have higher speed than watching applications, an amplifier, mixer, filter, A / A for each receiving antenna is added to a high-frequency circuit portion that handles microwaves and millimeter waves as shown in FIG. In many cases, a D converter is provided, and a phase shifter is also provided in the high-frequency circuit portion for each individual receiving antenna. Therefore, it becomes an extremely expensive device, and it is difficult to disseminate it for use in a monitoring device. Further, in-vehicle radar needs to detect the vehicle speed of an approaching vehicle, and an up-down alternating sweep waveform as shown in FIG. 12 is used, and processing takes time. (DSP) is required.

  An object of the present invention is to provide a watching device capable of specifying the orientation and position of a watching target such as a sick person with a simple configuration.

  In summary, the present invention is a monitoring device for monitoring a biological trend, and includes a transmission antenna, a plurality of reception antennas, a selection circuit, a frequency modulation continuous wave (FM-CW) radar unit, and an A / D. A converter and a signal processing unit are provided.

  The selection circuit selects one reception antenna from the plurality of reception antennas. The FM-CW radar unit radiates a transmission signal from the transmission antenna and outputs a beat signal indicating a beat frequency that is a difference between the frequency of the reception signal received by the reception antenna selected by the selection circuit and the frequency of the transmission signal. . The A / D converter converts the beat signal into a digital signal.

  The signal processing unit controls the selection circuit and the frequency modulation continuous wave radar unit, receives the beat signal converted into a digital signal, and performs digital signal processing. The signal processing unit causes the frequency modulation continuous wave radar unit to transmit the transmission signal and receive the reception signal while switching the selection circuit so as to obtain a beat signal corresponding to each of the plurality of reception antennas. The signal processing unit performs phase correction processing on the beat signal converted into the digital signal according to the corresponding antenna, and then synthesizes the beat signal after phase correction obtained by each of the plurality of receiving antennas. To detect the azimuth and distance of the object being watched over.

  Preferably, the signal processing unit shifts from the first sweep band, the first result of detecting the azimuth and distance of the watching target using the transmission signal of the first sweep band from the first frequency to the second frequency. The azimuth | direction and distance which show that both the azimuth | direction of a watch target and the 2nd result which detected the distance using the transmission signal of the 2nd sweep band from the 3rd frequency to the 4th frequency exist watch target Is displayed as the detection result.

  Preferably, the signal processing unit causes the frequency modulation continuous wave radar unit to sweep the frequency of the transmission signal from the first frequency to a second frequency higher than the first frequency over a predetermined sweep time and output a beat signal. The process is performed sequentially for a plurality of antennas, and the time for returning the frequency of the transmission signal from the second frequency to the first frequency after one sweep is shorter than the sweep time.

  Preferably, the frequency modulation continuous wave radar unit includes a variable frequency oscillator that generates a transmission signal, an amplifier that amplifies the reception signal, and a detection circuit. The detection circuit multiplies the reception signal output from the amplifier and the local signal corresponding to the transmission signal to generate a beat signal and detects the beat signal.

  ADVANTAGE OF THE INVENTION According to this invention, the monitoring apparatus which can pinpoint the direction and position of monitoring object is realizable by simple structure at low cost.

It is a figure which shows schematic structure of the monitoring apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the circuit structural example of the FM-CW radar unit used for the monitoring apparatus which concerns on this Embodiment. It is a figure for demonstrating the signal relationship of the FM-CW radar unit used for the monitoring apparatus which concerns on this Embodiment. It is a flowchart for demonstrating the process which a signal processing part performs. It is a figure which shows the human body position of the front direction used for the experiment for showing the signal processing effect of a monitoring apparatus. It is a figure which shows the example of an image | video which is a detection result of the front direction detected with the watching apparatus. It is a figure which shows the human body position of the diagonal direction used for the experiment for showing the signal processing effect of a watching device. It is a figure which shows the 1st example of an image | video which is the 1st detection result of the diagonal direction detected with the watching apparatus. It is a figure which shows the 2nd image example which is the 2nd detection result of the diagonal direction detected with the watching apparatus. It is a figure which shows the position of the true image detected by the product of the data shown by the image | video of FIG. 8 and FIG. It is the figure which showed the structural example of the vehicle-mounted FM-CW radar. It is the figure which showed the time change of the transmission / reception frequency and beat frequency of in-vehicle FM-CW radar.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a diagram showing a schematic configuration of a monitoring device according to an embodiment of the present invention. Referring to FIG. 1, a monitoring device 100 according to the present embodiment includes a transmission antenna 2, a reception unit 3 including a plurality of reception antennas 3A to 3D, a selection circuit 4, and a frequency modulation continuous wave (FM-CW). A radar unit 1, an A / D converter 7, a D / A converter 8, a signal processing unit 5, and a display unit 9 are provided.

The selection circuit 4 selects one reception antenna from the plurality of reception antennas 3A to 3D. FM-CW radar unit 1 radiates transmission signal e _t from the transmission antenna 2, is the difference between the frequency of the transmitted signal e _t of the received signal e _r received by the receiving antenna selected by the selection circuit 4 A beat signal SB indicating the beat frequency is output. The A / D converter 7 converts the beat signal SB into a digital signal. The D / A converter 8 converts the digital signal sent from the signal processing unit 5 into an analog signal, and the analog signal after being converted into the selection circuit 4 and the FW-CW radar unit 1 is used as a control signal (SA, SF). Output.

  The signal processing unit 5 controls the selection circuit 4 and the FM-CW radar unit 1 with the antenna switching signal SA and the frequency control signal SF from the D / A converter 8, and receives the beat signal converted into a digital signal and performs digital processing. Perform signal processing.

  The display unit 9 displays the position, azimuth, size, and the like of the watching target human body 6 obtained from the signal processing result of the signal processing unit 5.

  The monitoring device 100 is configured to analyze each beat signal SB obtained by a plurality of receiving antennas by the signal processing unit 5 so that the location (distance, direction) of the monitoring target human body 6 can be specified with high resolution. It is a feature.

  In other words, the signal processing method executed by the signal processing unit 5 of the watching device 100 is such that the presence location (distance, direction) of the person to be watched can be specified by arranging a small number of about four receiving antennas in an array. It is characterized by that. If this signal processing method is used, even if the interval between the antennas is narrow, the location of the person to be watched can be specified with high accuracy. That is, in general, the resolution for specifying the azimuth direction is improved as a large number of antennas are arranged in an array and the distance between the antennas is increased, but there is a problem that the apparatus becomes larger. However, the watching device 100 solves the problem of increasing the size of the device by devising a signal processing method that can specify the azimuth direction of the subject with high accuracy without requiring a wide interval between the receiving antennas.

  FIG. 2 is a diagram for explaining a circuit configuration example of an FM-CW radar unit used in the monitoring apparatus according to the present embodiment.

Referring to FIG. 2, FM-CW radar unit 1, transmission signal _{e t} a generated voltage controlled oscillator: and (VCO Voltage-controlled oscillator) 12 , a power divider (PD) 13, a received signal _{e r} An RF amplifier 14 for amplification and an I / Q detection circuit 15 are included.

The VCO 12 generates an FM-CW signal by the frequency control signal SF.
PD13 is divided into two FM-CW signal VCO12 occurs in local signal _{e L} and the transmission signal _{e t} of the I / Q detection circuit 15.

I / Q detection circuit 15, the multiplies the local signal e _L I and Q quadrature signals corresponding to the received signal e _r and the transmission signal e _t outputted from the RF amplifier 14 to generate a beat signal Detect.

  The FM-CW radar unit 1 further includes a low-pass filter (LPF) 16 and an amplifier 17. The LPF 16 removes noise included in the I and Q signals output from the I / Q detection circuit 15. The amplifier 17 amplifies each of the I and Q signal outputs of the LPF 16. A beat signal SB including two signals orthogonal to I and Q is output from the FM-CW radar unit 1 through the amplifier 17.

  FIG. 3 is a diagram for explaining the signal relationship of the FM-CW radar unit used in the monitoring apparatus according to the present embodiment.

Referring to FIGS. 1 and 3, the signal processing unit 5 sets the selection circuit 4 to receive antennas 3A to 3D in the period T1 to T4 so as to obtain beat signals SB corresponding to the respective receive antennas 3A to 3D. There causes the reception of the transmitted and received signals e _r of the transmission signal e _t while switching so are sequentially selected one by one in the FM-CW radar unit 1. The signal processing unit 5 performs phase correction processing on the beat signal SB converted into a digital signal in accordance with the corresponding reception antenna, and then performs phase correction obtained by each of the plurality of reception antennas 3A to 3D. The direction and distance of the watching target are detected by synthesizing the beat signals.

More specifically, device 100 watch shown in Figure 1, FM-CW against a transmission signal e _t of the radar unit 1 to the body 6 of the subject watching and radiated by the transmitting antenna 2, the received reflected signal signal e _r Are received by the four receiving antennas 3A to 3D and input to the receiving end (Rx) of the FM-CW radar unit 1 through the selection circuit 4. Received signal e _r input is converted into a beat signal SB of the frequency f _b which is proportional to the reciprocal distance r _b to the body 6 of the target watching the FM-CW radar unit 1, via the A / D converter 7 Are taken into the signal processor 5. The signal processing unit 5 calculates the round-trip distance r _b to the body 6 of the target watching from the beat signal SB. Here, the selection circuit 4 is configured so that the four reception antennas 3A to 3D can be sequentially switched by the antenna switching signal SA.

  Preferably, the signal processing unit 5 causes the FM-CW radar unit 1 to sweep the frequency of the transmission signal from the first frequency f1 to the second frequency f2 higher than the first frequency f1 over a predetermined sweep time T. The time for returning the frequency of the transmission signal from the second frequency f2 to the first frequency f1 after one sweep is made longer than the sweep time T by performing processing for outputting the beat signal to the plurality of receiving antennas 3A to 3D in order. shorten. In the example shown in the waveform of FIG. 3, the time for returning the frequency from f2 to f1 is set to almost zero, and the waveform showing the change in frequency is like a sawtooth wave. It should be noted that the time for returning the frequency from f2 to f1 does not have to be zero. If the frequency is shorter than the sweep time T, there is an effect that it takes less time than the up / down sweep.

  In the example of the in-vehicle radar shown in FIG. 11 and FIG. 12, high speed is required and vehicle speed information of the monitoring target vehicle is also necessary. Therefore, the frequency sweep of the FM-CW radar is performed in the up (frequency increasing) direction and the down direction. (Frequency reduction) direction is necessary, and it is desirable to simultaneously receive all of the plurality of receiving antennas with one frequency sweep.

  On the other hand, the monitoring device 100 according to the present embodiment is limited to the purpose of watching a person who does not require high speed and the speed of the monitoring target does not need to be detected. There is no problem even if the frequency sweep is sequentially performed by selecting each and the frequency sweep is only increased. By selecting one of the receiving antennas and sequentially performing frequency sweeping, the elements of the high-frequency circuit portion can be reduced to one system. Further, by only increasing the frequency sweep, the sweep time per time can be halved, the processing amount processed by the signal processing unit 5 can be reduced, and the signal processing unit 5 is fast and expensive. It is not necessary to employ a DSP or the like. Therefore, it is possible to configure the watching device at a very low cost.

  FIG. 4 is a flowchart for explaining processing executed by the signal processing unit. Referring to FIGS. 1 and 4, when the processing is started, the signal processing unit 5 uses the frequency control signal SF to change the frequency sweep band BW of the FM-CW radar unit 1 to the first sweep band (BW = 1). ).

  The first sweep band is a frequency band from the sweep start frequency f1 to the sweep end frequency f2 (> f1). For example, the first sweep band (f1 = 24.5 GHz, f2 = 25.8 GHz: bandwidth B = 1300 MHz). ).

Subsequently, in step S2, a parameter n for selecting an antenna is set to an initial value 1. Further, in step S3, the signal processing unit 5 selects the nth antenna by the antenna switching signal SA. Subsequently, in step S4, the n-th frequency sweep in the set frequency sweep band BW is executed. In step S5, the beat signal is obtained from the received signal e _r of the n-th antenna. In step S6, it is determined whether n = 4 (whether the acquisition of the beat signal using the fourth antenna has been completed). If n = 4 is not satisfied, n is incremented in step S7 and steps S3 to S3 are performed again. The process of S5 is executed.

  By repeating the above steps S3 to S5 for the number of antennas n = 4, the transmission frequency is swept as shown in FIG. Hereinafter, the processes of steps S3 to S5 will be described in more detail.

From the circuit of the FM-CW radar unit 1 of FIG. 2, linearly swept at a period of sweep time T over the frequency f of the transmission signal e _t 3 the bandwidth B from f1 to f2 transmit signals When delivering e _t, the received signal e _r reflected by the human body 6 is received by the receiving antenna is delayed by tau _b. The transmission signal at this time is represented by the following expression (1).

  Then, the phase θ (t) is expressed by the following formula (2).

  The frequency f of Formula (2) is represented by the following Formula (3).

  The phase of the received signal delayed by the delay time τ from the equations (2) and (3) is expressed by the following equation (4).

  From the equations (2) and (4), the phase δθ (t) of the beat signal SB is expressed by the following equation (5).

The beat frequency fb is _expressed by the following equation (6).

Therefore, if the beat signal SB is e _b (t) (however, the amplitude term is omitted), the beat signal is expressed by the following equation (7).

  If the beat signal represented by Expression (7) is pulsed by FFT (Fast Fourier Transform), the result of Expression (8) below is obtained.

Equation (8) shows a pulse waveform taking a peak value represented by the following formula (9) in the omega = omega _b, the phase term [Phi (tau _b) is represented by the following formula (10) The

Here, fb corresponding to omega _b because the formula (6), the following equation (11) (12) is derived.

  Further, the following formula (13) is derived from the formulas (11) and (12).

  By transforming equation (13), the following equation (16) is obtained, and when substituting into equation (8) together with equation (17), ω is expressed as a function of the distance r, and among the four receiving antennas 3A to 3D: The magnitude of the signal from the i-th antenna is expressed by the following equation (18).

  The above is the processing up to beat signal acquisition executed for each antenna in steps S3 to S5 in FIG.

  When steps S3 to S5 are executed for four antennas (YES in step S6), the process of step S8 is executed. In step S8, the beat signals obtained from the reception signals of the four antennas are phase-corrected and combined to obtain a detection result.

The process of step S8 will be described in further detail. If r = r _bi (r _bi represents the distance from the transmitting antenna to the i-th receiving antenna after being reflected from the human body), the signals received by the four receiving antennas 3A to 3D are combined. The combined signal η1 of the reflected signal by is expressed by a vector sum as shown in the following equation (19).

However, since the distance r _bi is different for each receiving antenna, the vectors are directed in different directions, and there is a problem that the vector sum of Expression (19) does not converge. Therefore, in the present embodiment, in order to solve this problem, phase correction is executed by canceling the phase term as in the following equation (20) by multiplying equation (18) by the phase term e ^−jβ1r .

As in the case of deriving equation (19), if r = r _bi (r _bi represents the distance from the transmitting antenna to the i-th receiving antenna after being reflected from the human body), according to equation (20) The combined signal η2 when the reflected signal from the human body 6 is received by the four receiving antennas 3A to 3D is expressed by the following equation (21).

  According to Equation (21), it can be seen that the four vectors have the same value in the same direction (in this case, 1) and have a maximum value.

Thus, by using the equation (20), the vector of the four receiving antennas 3A to 3D is directed in the same direction (in this case, 1) where the human body exists, so that the combined signal η is the place where the human body exists. Shows the maximum peak power. On the other hand, in a place where a human body does not exist, r ≠ r _{bi and the} vector is directed in a disjoint direction, so that it rapidly attenuates. Therefore, the resolution in the azimuth direction is improved.

  Following step S8 in FIG. 4, in step S9, it is determined whether or not the second frequency sweep band (BW = 2) has been swept. If not executed yet in step S9 (NO in S9), the process proceeds to step S10, and the frequency sweep band BW of the FM-CW radar unit 1 is set to the second sweep band (BW = 2).

  The second sweep band is a frequency band from the sweep start frequency f3 to the sweep end frequency f4 (> f3). For example, the second sweep band is (f3 = 25.5 GHz, f4 = 26.8 GHz: bandwidth B = 1300 MHz).

  In step S10, after the frequency sweep band BW of the FM-CW radar unit 1 is set to the second sweep band (BW = 2), the processes in steps S2 to S7 are repeated.

  On the other hand, when the sweep of the second frequency sweep band (BW = 2) has been executed in step S9 (YES in S9), the process proceeds to step S11. In step S11, the frequency sweep band BW of the FM-CW radar unit 1 is executed in the first sweep band (BW = 1), and the frequency sweep band BW of the FM-CW radar unit 1 is converted into the second sweep band (BW = A process of multiplying the result executed in 2) is executed. This multiplication process will be described later.

  In step S12, the two-dimensional video obtained as a result of the process in step S11 is displayed on the display unit 9.

  Hereinafter, the detection result executed by the flowchart of FIG. 4 will be described in detail in the front direction and the diagonal direction.

  FIG. 5 is a diagram showing a human body position in the front direction used in an experiment for showing the signal processing effect of the watching device. FIG. 6 is a diagram illustrating a video example that is a detection result in the front direction detected by the watching device.

  As shown in FIG. 5, an image as a detection result when the positions of the human bodies for two persons are 3 m ahead and 6 m ahead on the y-axis is as shown in FIG. 6.

  Here, the transmitting antenna is arranged at the origin (0,0), and the receiving antenna is arranged at Rx1 (−0.0375,0), Rx2 (−0.0125,0), Rx3 (0.0125,0), Rx4 (0.0375,0). did. That is, four receiving antennas 3A to 3D are arranged at equal intervals of 2.5 cm. The human body positions of the two persons were Pa (0, 3) and Pb (0, 6), and the transmission frequency was 24.5 GHz to 25.8 GHz (B = 1300 MHz). At this time, the antenna interval between both ends of the four receiving antennas 3A to 3D is 7.5 cm, but a very good result was obtained.

  However, although the result of FIG. 6 is when the human body is on the y-axis, if there are two human bodies in an oblique direction, there may be cases where it cannot be detected correctly with a single sweep result.

  FIG. 7 is a diagram showing a human body position in an oblique direction used in an experiment for showing the signal processing effect of the watching device. FIG. 8 is a diagram illustrating a first video example which is a first detection result in an oblique direction detected by the watching device.

  If the two human bodies shown in FIG. 7 are at Pa (3, 3) and Pb (5, 6) in an oblique direction, the image is a true image Pa (3, 3), Pb ( 5 and 6), a number of false images F1 to F4 are generated.

  As a countermeasure against the generation of the false image, in the process of the flowchart of FIG. 4, another video whose frequency is shifted in steps S9 and S10 is created, and the two images are multiplied in step S11.

  FIG. 9 is a diagram illustrating a second video example that is the second detection result in the oblique direction detected by the watching device. In FIG. 9, an image is obtained in a sweep frequency band different from that in FIG. The video in FIG. 8 was a video when the transmission frequency was 24.5 GHz to 25.8 GHz (B = 1300 MHz), while the video in FIG. 9 was a video with a transmission frequency of 25.5 GHz to 26.8 GHz (15.5 GHz shifted from 25.5 GHz to 26.8 GHz). B = 1300MHz).

  Comparing FIG. 8 and FIG. 9, the positions Pa (3, 3) and Pb (5, 6) of the true image are hardly changed, but the positions where the false images (F1 to F4) are generated are different. I understand. Therefore, when the two detection results are multiplied so as to be executed in step S11, the true image appears at the same position and thus does not disappear, but the false images (F1 to F4) disappear because the generated positions are different. Therefore, the signal processing unit 5 shifts the sweep frequency band, performs detection twice, and determines that the position where the object is detected twice is the true image position.

  That is, the signal processing unit 5 detects the azimuth and distance of the watching target using the transmission signal in the first sweep band (24.5 GHz to 25.8 GHz: B = 1300 MHz) from the first frequency to the second frequency. Using the first result and the transmission signal of the second sweep band (25.5 GHz to 26.8 GHz: B = 1300 MHz) from the third frequency to the fourth frequency shifted from the first sweep band, the direction to be watched over And the second result of detecting the distance display the azimuth and distance indicating that the watching target is present as the monitoring target detection result.

  FIG. 10 is a diagram showing the position of the true image detected by the product of the data shown in the images of FIGS. 8 and 9. As shown in FIG. 10, when FIG. 8 × FIG. 9 is taken, it can be seen that the true image remains and the false images (F1 to F4) almost disappear. Although the false image F1 remains faint in FIG. 10, it is possible to display only the true image by performing an appropriate filter process.

  In addition, although the example using four receiving antennas 3A-3D as the receiving part 3 was shown, if it is two or more, it can operate | move similarly. Although the FM-CW radar unit 1 is shown as a configuration example of the radar, various radars such as a pulse radar, a chirp radar, and an encoding radar can also be used. The effect is the same even if data is acquired by scanning a pair of antennas of the transmission antenna and the reception antenna. Further, although the array antenna is placed on the receiving side in the configuration example of FIG. 1, the same effect can be obtained even if the antenna array is implemented on one or both of the transmitting side and the receiving side.

Finally, the effects of the monitoring device according to the present embodiment will be listed and described.
(1) The monitoring device 100 according to the present embodiment has an effect that the location (distance, direction) of the person to be monitored can be specified by arranging a small number of about four antennas in an array.

  (2) One of the features of the monitoring device 100 according to the present embodiment is that phase compensation is performed on the signal after the FFT of the received beat signal SB as shown in the equation (20). Thereby, even if the space | interval between antennas is narrow, there exists an effect that the location (distance, direction) of the target person to watch can be specified with high resolution.

  (3) Another feature of the watching device 100 according to the present embodiment is that two images obtained at different frequencies are multiplied together, thereby preventing a false image generated when the human body is in an oblique direction. Has the effect of counteracting.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

(1) The monitoring device using radio waves according to the present invention has utility as a monitoring sensor installed in a place that requires watching, such as an elderly person in a room, a person in a hospital bed, a resident on a bed in a facility or hospital. .
(2) Usability for watching an intruder in an answering house or an unattended place.
(3) Outside, it can be used for watching intruders around farms and important facilities.

  1 radar unit, 2 transmitting antenna, 3 receiving unit, 3A to 3D receiving antenna, 4 selection circuit, 5 signal processing unit, 6 human body, 7 A / D converter, 8 D / A converter, 9 display unit, 14 RF Amplifier, 17 Amplifier, 15 I / Q detection circuit, 100 Watching device.

Claims (4)

A monitoring device for watching the trend of a living body,
A transmitting antenna;
Multiple receive antennas;
A selection circuit for selecting one reception antenna from the plurality of reception antennas;
A frequency-modulated continuous wave that radiates a transmission signal from the transmission antenna and outputs a beat signal indicating a beat frequency that is a difference between the frequency of the reception signal received by the reception antenna selected by the selection circuit and the frequency of the transmission signal A radar unit;
An A / D converter for converting the beat signal into a digital signal;
A signal processing unit that controls the selection circuit and the frequency modulation continuous wave radar unit, receives the beat signal converted into a digital signal, and performs digital signal processing;
The signal processing unit causes the frequency modulation continuous wave radar unit to transmit a transmission signal and receive a reception signal while switching the selection circuit so as to obtain the beat signal corresponding to each of the plurality of reception antennas,
The signal processing unit performs a phase correction process on the beat signal converted into a digital signal in accordance with a corresponding reception antenna, and then performs the phase correction obtained by each of the plurality of reception antennas. Watching device that detects beat direction and distance by synthesizing beat signals.   The signal processing unit is shifted from the first sweep band, the first result of detecting the azimuth and distance of the watching target using the transmission signal of the first sweep band from the first frequency to the second frequency. The azimuth | direction and distance which show that the said monitoring object exists together with the 2nd result of having detected the azimuth | direction and distance of the said monitoring object using the transmission signal of the 2nd sweep band from the 3rd frequency to the 4th frequency. The watching device according to claim 1, wherein the watching device is displayed as a detection result of the watching target.   The signal processing unit sweeps the frequency of the transmission signal over a predetermined sweep time from the first frequency to a second frequency higher than the first frequency with respect to the frequency modulation continuous wave radar unit. The processing for outputting is performed sequentially for the plurality of reception antennas, and the time for returning the frequency of the transmission signal from the second frequency to the first frequency after one sweep is shorter than the sweep time. The watching device according to 1. The frequency modulation continuous wave radar unit comprises:
A variable frequency oscillator for generating the transmission signal;
An amplifier for amplifying the received signal;
The detection circuit according to claim 1, further comprising: a detection circuit that multiplies a reception signal output from the amplifier to generate the beat signal and a local signal corresponding to the transmission signal to detect the beat signal. Monitoring device.