JP6165870B2 - Wireless sensor device - Google Patents

Description

  The present invention relates to a wireless sensor device, and more particularly to a wireless sensor device that can stably detect a detection target.

  2. Description of the Related Art Conventionally, sensors that measure the distance to an object using radio waves, sensors that detect movement of the object and detect the presence or proximity of the object, and the like have been proposed.

  In recent years, a sensor capable of detecting vital signs such as heartbeat and respiration in a non-contact manner with less burden on the subject has been strongly demanded due to an increase in health awareness.

  In the wireless sensor device 900 described in Patent Document 1 (conventional example 1), as shown in FIG. 4, an antenna 901, a transmission circuit 902, a detection circuit 903, a signal processing circuit 904, and a control circuit 905 are provided. I have. Further, a plurality of transmission lines (906, 907) having different line lengths, a switch 908, and a switch 909 are switched between the antenna 901 and an output terminal 902a provided in the transmission circuit 902, and the plurality of transmission lines are switched. Switching means for connecting the antenna 901 and the output terminal 902a is provided. The difference between the line lengths of the plurality of transmission lines is set to less than a quarter of the wavelength of the transmission signal.

  Control that selects and switches transmission lines with different line lengths when the detection output decreases when the phase difference of the reflected wave with respect to the transmission output approaches the null point where the sensitivity decreases due to a change in the distance to the detection target, etc. I do. For this reason, a technique is disclosed in which a phase difference between a transmission output and a reflected wave can be changed, and a minute variation is detected while avoiding a deterioration in sensitivity for detecting a motion of a detection target.

Japanese Patent Application No. 2012-213344

  In the above-described conventional wireless sensor device, the amplitude of the reflected wave is very small with respect to the amplitude of the transmission signal. In addition, the change of the reflected wave with respect to the minute displacement is also minute. In order to capture the minute change of the reflected wave having a small amplitude, the signal processing circuit 904 needs to use an amplifier having a large amplification factor. When an amplifier with a large amplification factor is used, if a direct current is applied to the input, the output of the amplifier will be in a state where it has been swung to the upper limit or lower limit of the amplitude. Must be prevented from entering the amplifier. Also, if the movement to be detected from the detection target is a low frequency change such as body movements associated with heartbeat or breathing, etc., and a low frequency change of about several Hz or less, the low frequency signal is not attenuated. It is necessary to use a capacitor having a large capacity.

  However, when a large capacity capacitor is used, the following operation may be performed. When the signal output for detecting the detection target decreases and the transmission line is switched, the phase of the signal input to the detection circuit 903 changes by π / 2 (rad) along with the switching. For this reason, the DC voltage output from the detection circuit 903 greatly fluctuates, and this fluctuation is input to the amplifier through a capacitor having a large capacitance. Due to the fluctuation of the DC voltage, the output of the amplifier may be in a state where it has been swung to the upper limit or the lower limit of the amplitude. In addition, since the capacitance of the capacitor is large, the time constant of the entire circuit including the capacitor becomes large, and it takes a long time to follow the fluctuation of the DC voltage and output the fluctuation of the low frequency again. There was a problem that the detection target could not be detected.

  The present invention solves the above-described problems, and an object of the present invention is to provide a wireless sensor device that can stably detect a detection target.

In order to solve this problem, a wireless sensor device of the present invention includes an antenna that radiates a transmission signal, receives a reflected signal reflected by a detection target, and a transmission circuit that generates the transmission signal. A first switching for selecting one transmission line, a second transmission line having a different line length from the first transmission line, one end of the first transmission line, and one end of the second transmission line, and connecting to the antenna Means, a second switching means for selecting and connecting the other end of the first transmission line and the other end of the second transmission line to the transmission circuit, and during transmission of the transmission signal from the transmission circuit, A detection circuit that receives and detects a part of the transmission signal and the reflected signal received by the antenna, and a signal processing circuit that is connected to the detection circuit and processes a signal output from the detection circuit; , The transmission circuit and the first switch And a control circuit for controlling the second switching means, wherein the control circuit connects a transmission line connecting the antenna and the transmission circuit from the first transmission line or the second transmission line. In the wireless sensor device that performs control to select and switch, the detection circuit and the signal processing circuit are connected to the other ends of the first transmission line and the second transmission line, respectively . The transmission signal is multiplied by the reflection signal .

  According to this, since the detection circuit is provided for each transmission line, even when the transmission line is switched, the signal input to the detection circuit is not affected by the change in phase caused by the switching. Therefore, since the DC voltage of the output of the detection circuit does not fluctuate, the output of the amplifier of the signal processing circuit is not shaken off, and it does not take a long time to output a fluctuation of a low frequency. Therefore, it is possible to provide a wireless sensor device that can detect a detection target stably.

  In the wireless sensor device of the present invention, the control by the control circuit is performed at predetermined time intervals so as to select and switch between the first transmission line and the second transmission line, and the first transmission. The line and the second transmission line are alternately selected and switched.

  According to this, since the transmission operation is performed by alternately switching the first transmission line and the second transmission line having different line lengths, the components orthogonal to each other can be extracted, and the presence or absence of the reflected wave is reliably detected. Therefore, the detection target can be detected more stably.

  In the wireless sensor device of the present invention, a phase difference between the first transmission line and the second transmission line is π / 4 (rad).

  According to this, since the phase difference between the first transmission line and the second transmission line is different by π / 4 (rad), by switching the transmission line, the phase difference between the transmission signal and the reflected signal is π / Different signals can be obtained by 2 (rad). For this reason, it is possible to reliably avoid the null point where the sensitivity is remarkably lowered and to detect the detection target more stably.

  ADVANTAGE OF THE INVENTION According to this invention, the wireless sensor apparatus which can detect a detection target stably can be provided.

It is a figure which shows the operation | movement outline | summary of the wireless sensor apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the wireless sensor apparatus which concerns on embodiment of this invention. It is an operation | movement timing diagram of the wireless sensor apparatus which concerns on embodiment of this invention. 10 is a block diagram illustrating a configuration of a wireless sensor device described in Patent Document 1. FIG.

[First Embodiment]
The wireless sensor device 100 according to the first embodiment will be described below.

  First, an outline of the operation of the wireless sensor device 100 according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, the wireless sensor device 100 radiates a transmission signal, and detects the detection target 500 from the reflected signal that is reflected from the detection target 500.

  Next, the configuration of the wireless sensor device 100 will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the wireless sensor device 100.

  As shown in FIG. 2, the wireless sensor device 100 includes an antenna 10, a transmission circuit 20, a first transmission line 31, a second transmission line 32, a first switching unit 41, a second switching unit 42, A first detection circuit 51, a second detection circuit 52, a first signal processing circuit 61, a second signal processing circuit 62, and a control circuit 70 are provided.

  In addition, the wireless sensor device 100 has a power supply circuit (not shown), and supplies power necessary for operation to each part of the wireless sensor device 100.

  The antenna 10 radiates a transmission signal and receives a reflection signal obtained by reflecting the transmission signal at the detection target 500. The antenna 10 is connected to the first switching means 41.

  The transmission circuit 20 performs a transmission operation for generating and outputting a transmission signal. The transmission circuit 20 is connected to the second switching means 42 and the control circuit 70 and is controlled by the control circuit 70.

  The first transmission line 31 is a transmission line having a characteristic impedance substantially equal to the output impedance of the transmission circuit 20 and the impedance of the antenna 10 at the frequency of the transmission signal generated by the transmission circuit 20 and having a line length Le. One end of the first transmission line 31 is connected to the first switching means 41, and the other end is connected to the second switching means 42 and the first detection circuit 51.

  The second transmission line 32 has a characteristic impedance substantially equal to the output impedance of the transmission circuit 20 and the impedance of the antenna 10 at the frequency of the transmission signal generated by the transmission circuit 20. The second transmission line 32 is a transmission line having a line length that is different (delayed) from the first transmission line 31 by a phase difference of π / 4 (rad). One end of the second transmission line 32 is connected to the first switching means 41, and the other end is connected to the second switching means 42 and the second detection circuit 52.

  The first switching means 41 selects the antenna 10, the first transmission line 31, and the second transmission line so that either the first transmission line 31 or the second transmission line 32 can be selected and connected to the antenna 10. One end of 32 is connected.

  The second switching means 42 selects the transmission circuit 20, the first transmission line 31, and the second transmission line so that either the first transmission line 31 or the second transmission line 32 can be selected and connected to the transmission circuit 20. The other end of the transmission line 32 is connected.

  The first detection circuit 51 is connected to the other end of the first transmission line 31 and the second switching means 42. In the first detection circuit 51, the first switching means 41 and the second switching means 42 select the first transmission line 31 and the transmission circuit 20 is transmitting the transmission signal while the transmission circuit 20 is transmitting the transmission signal. A part of the signal and the reflected signal received by the antenna 10 are input. The first detection circuit 51 detects a part of the input transmission signal and the reflected signal received by the antenna 10.

  The second detection circuit 52 is connected to the other end of the second transmission line 32 and the second switching means 42. In the second detection circuit 52, the first switching means 41 and the second switching means 42 select the second transmission line 32, and the transmission output from the transmission circuit 20 while the transmission circuit 20 transmits the transmission signal. A part of the signal and the reflected signal received by the antenna 10 are input. The second detection circuit 52 detects a part of the input transmission signal and the reflected signal received by the antenna 10.

  The first signal processing circuit 61 is connected to the first detection circuit 51 and the control circuit 70. The first signal processing circuit 61 processes the detection output signal output from the first detection circuit 51 and outputs the result to the control circuit 70.

  The second signal processing circuit 62 is connected to the second detection circuit 52 and the control circuit 70. The second signal processing circuit 62 processes the detection output signal output from the second detection circuit 52 and outputs the result to the control circuit 70.

  That is, the first detection circuit 51 is connected to the other end of the first transmission line 31, and the second detection circuit 52 is connected to the other end of the second transmission line 32. The first signal processing circuit 61 and the first detection circuit 51 are connected to the first signal processing circuit 61.

  The control circuit 70 is connected to the transmission circuit 20, the first switching unit 41, the second switching unit 42, the first signal processing circuit 61, and the second signal processing circuit 62. The control circuit 70 controls the operation state of the transmission circuit 20. In addition, the control circuit 70 controls the first switching unit 41 and the second switching unit 42, and connects the transmission line connecting the antenna 10 and the transmission circuit 20 from the first transmission line 31 or the second transmission line 32. Control to select and switch. Further, the control circuit 70 acquires output signals from the first signal processing circuit 61 and the second signal processing circuit 62, and detects and detects body movements accompanying the breathing of the detection target 500, movements of the body surface accompanying the heartbeat, and the like. Judgment of presence or absence is performed.

  Next, the operation of the wireless sensor device 100 will be described with reference to FIGS.

  FIG. 3 is a diagram for explaining the operation timing of the wireless sensor device 100.

  As shown in FIG. 3, the control circuit 70 controls the first switching means 41 and the second switching means 42 at time T <b> 1, and sets the transmission line connecting the antenna 10 and the transmission circuit 20 as the first transmission line. Control to select and switch 31 is performed. Further, the control circuit 70 outputs a transmission output control signal during a time t1 from time T1 to T2, and controls the transmission circuit 20 so that the transmission signal is output. The transmission signal is output from the transmission circuit 20 and radiated from the antenna 10 through the second switching means 42, the first transmission line 31, and the first switching means 41.

  A part of the transmission signal radiated from the antenna 10 is reflected by the detection target 500 and received by the antenna 10 as a reflected signal.

  The reflected signal received by the antenna 10 is input to the first detection circuit 51 via the first switching means 41 and the first transmission line 31, and a part of the transmission signal and the reflected signal are detected.

  When the amplitude of the transmission signal Vo is A and the frequency is f, the angular frequency 2πf is ω time, and the transmission signal Vo is expressed by the equation (1). Further, the amplitude of the reflected signal Vr is B, and the reflected signal Vr is expressed by Expression (2), where θ1 is the phase shift angle (phase difference) of the reflected signal Vr with respect to the transmission signal Vo in the first period.

(Equation 1)
Vo = A · cosωt (1)
Vr = B · cos (ωt + θ1) (2)

  As described above, B is the amplitude of the reflected signal, and the transmission signal radiated from the antenna 10 with the amplitude A represented by the expression (1) is reflected by the detection target 500 and returns to the antenna 10 again. The amplitude of the reflected signal is attenuated to B and received by the attenuation (transmission loss) received by the transmission path between the transmission line and the attenuation (reflection loss) caused by the reflectance when the transmission signal is reflected by the detection object 500 It will be.

  When the reflected signal Vr is detected by the first detection circuit 51 using the transmission signal Vo as a reference signal, the detection output Vd represented by the expression (3) is output to the output of the first detection circuit 51.

(Equation 2)
Vd = Vo × Vr
= A · B {cosωt · cos (ωt + θ1)}
= (A · B / 2) cos (2ωt + θ1) + (A · B / 2) cosθ1 ·· Equation (3)

  In the first half of the equation (3), since the angular frequency is 2ωt, the frequency is twice the frequency of the transmission signal. Therefore, a bypass capacitor for removing a high frequency is provided in the first detection circuit 51. It can be easily removed by means. Assuming that the output signal Vp1 of the first detection circuit 51 from which the frequency component twice the transmission frequency is removed, Vp1 is expressed by Expression (4). Expression (4) is an output determined by the phase difference θ1 of the reflected signal Vr with respect to the transmission signal Vo.

(Equation 3)
Vp1 = (A · B / 2) cos θ1 (4)

  Θ1 representing the phase shift angle of the reflected signal Vr with respect to the transmission signal Vo is given by the path from the transmission signal Vo output from the transmission circuit 20 to the detection object 500 being reflected back to the first detection circuit 51. This is the total phase shift amount.

  When the phase difference θ1 between the transmission signal and the reflected signal is π / 2 (rad) depending on the distance between the wireless sensor device 100 and the detection target 500, the output signal Vp1 of the first detection circuit 51 is obtained from Equation (4). Becomes 0. When the phase difference θ1 between the transmission signal and the reflected signal becomes 0 (rad), the output signal Vp1 of the first detection circuit 51 becomes the maximum value (A · B / 2), and the phase difference θ1 becomes π ( rad), the minimum value is − (A · B / 2).

  Further, the detection sensitivity with respect to the movement of the detection target 500 is a ratio at which the output changes with respect to the change of θ1 due to the movement of the detection target 500, and therefore, the value obtained by differentiating Equation (4) by θ1 is Is done.

(Equation 4)
dVp1 / dθ1 = − (A · B / 2) sin θ1 (5)

Therefore, the maximum sensitivity is obtained when θ1 is π / 2 + nπ (rad), and θ1 is 0 + nπ (r
In the case of ad), the sensitivity is a so-called null point (where n is a natural number).

  When the first transmission line 31 is selected, the transmission signal is output from the transmission circuit 20, reflected by the detection target 500 through the antenna 10, and returned to the first detection circuit 51. The path length L1 is expressed as in equation (6). However, in Expression (6), the distance from the antenna 10 to the detection target 500 is Lx.

(Equation 5)
L1 = 2 (Lx + Le) = 2Lx + 2Le Expression (6)

  Vp1 shown in Expression (4) changes when the detection target 500 moves, and θ1 changes as the distance between the antenna 10 and the detection target 500 changes due to the movement. Therefore, Vp1 changes due to the change in θ1. Therefore, the movement of the detection target 500 can be detected by detecting the change in Vp1.

  When the movement of the detection target 500 is slow, the change in the value of θ1 determined by the distance between the antenna 10 and the detection target 500 becomes gradual. For this reason, the signal output from the first detection circuit 51 during the time t1 from the time T1 to the time T2 is a signal including a direct current component as shown in the first detection circuit output of FIG. Become.

  The first signal processing circuit 61 performs amplification and AD conversion necessary for detecting the change amount from the signal output from the first detection circuit 51, and outputs the processing result to the control circuit 70.

  The control circuit 70 outputs a transmission output control signal for controlling the transmission circuit 20 so that the transmission signal is not output from the transmission circuit 20 at time T2, and stops the transmission operation for a time t2 until time T3.

  Next, the control circuit 70 controls the first switching means 41 and the second switching means 42 at time T3 and selects the second transmission line 32 as the transmission line connecting the antenna 10 and the transmission circuit 20. To perform switching control. Further, the control circuit 70 outputs a transmission output control signal during a time t1 from time T3 to T4, and controls the transmission circuit 20 so that the transmission signal is output. The transmission signal is output from the transmission circuit 20 and radiated from the antenna 10 through the second switching means 42, the second transmission line 32, and the first switching means 41.

  A part of the transmission signal radiated from the antenna 10 is reflected by the detection target 500 and received by the antenna 10 as a reflected signal.

  The reflected signal received by the antenna 10 is input to the second detection circuit 52 via the first switching means 41 and the second transmission line 32, and a part of the transmission signal and the reflected signal are detected.

  Similar to the above, the transmission signal Vo is expressed by equation (1), and the reflected signal Vr is expressed by equation (7). However, (theta) 2 represents the phase shift angle (phase difference) of the reflected signal Vr with respect to the transmission signal Vo of a 2nd period.

(Equation 6)
Vr = B · cos (ωt + θ2) (7)

  When the output Vd of the second detection circuit 52 is calculated in the same manner as the equation (3), the equation (8) is obtained.

(Equation 7)
Vd = Vo × Vr
= A · B {cosωt · cos (ωt + θ2)}
= (A · B / 2) cos (2ωt + θ2) + (A · B / 2) cosθ2 ·· Equation (8)

  Similarly to the above, assuming that the output signal Vp2 of the second detection circuit 52 from which the frequency component twice the transmission frequency has been removed, Vp2 is expressed by Expression (9). Expression (9) is an output determined by the phase difference θ2 of the reflected signal Vr with respect to the transmission signal Vo.

(Equation 8)
Vp2 = (A · B / 2) cos θ2 (9)

  Θ2 representing the phase shift angle of the reflected signal Vr with respect to the transmission signal Vo is given by the path from the transmission signal Vo output from the transmission circuit 20, reflected by the detection target 500, and returned to the second detection circuit 52. This is the total phase shift amount.

  When the phase difference θ2 between the transmission signal and the reflected signal becomes π / 2 (rad) depending on the distance between the wireless sensor device 100 and the detection target 500, the output signal Vp2 of the second detection circuit 52 is obtained from Equation (8). Becomes 0. When the phase difference θ2 between the transmission signal and the reflected signal becomes 0 (rad), the output signal Vp1 of the first detection circuit 51 becomes the maximum value (A · B / 2), and the phase difference θ2 becomes π ( rad), the minimum value is − (A · B / 2).

  Further, the detection sensitivity with respect to the movement of the detection target 500 is a ratio at which the output changes with respect to the change in θ2 due to the movement of the detection target 500, and therefore, the value obtained by differentiating the expression (9) by θ2 is Is done.

(Equation 9)
dVp2 / dθ2 = − (A · B / 2) sin θ2 Formula (10)

  Therefore, the maximum sensitivity is obtained when θ2 is π / 2 + nπ (rad), and the sensitivity becomes a so-called null point when θ2 is 0 + nπ (rad) (where n is a natural number).

  When the second transmission line 32 is selected, the transmission signal is output from the transmission circuit 20, reflected by the detection target 500 through the antenna 10, and returned to the first detection circuit 51. The path length L2 is expressed as shown in Expression (11). However, in Expression (11), the distance from the antenna 10 to the detection target 500 is Lx.

(Equation 10)
L2 = 2 (Lx + Le + π / 4) = 2Lx + 2Le + π / 2 Formula (11)

  Similarly to Vp1, Vp2 shown in Expression (9) also changes when θ2 changes due to the movement of the detection target 500, and thus the output changes according to the change of θ2. Therefore, the movement of the detection target 500 can also be detected by detecting a change in Vp2.

  Further, when the movement of the detection target 500 is slow, the change in the value of θ2 determined by the distance between the antenna 10 and the detection target 500 becomes gradual. For this reason, the signal output from the second detection circuit 52 during the time t1 from the time T3 to the time T4 is a signal including a direct current component as shown in the second detection circuit output of FIG. .

  The second signal processing circuit 62 performs amplification and AD conversion necessary to detect the amount of change from the signal output from the second detection circuit 52, and outputs the processing result to the control circuit 70.

  The control circuit 70 outputs a transmission output control signal so that the transmission signal is not output from the transmission circuit 20 at time T4, and stops the transmission operation during time t2 until time T5. After time T5, the operation from time T1 is repeated in the same manner.

  That is, the control by the control circuit 70 is performed at predetermined time intervals (t3 = t1 + t2) so as to select and switch between the first transmission line 31 and the second transmission line 32. The transmission lines 32 are alternately selected and switched.

  The difference ΔL between the path length L1 when the first transmission line 31 is selected and the path length L2 when the second transmission line 32 is selected is expressed by Equation (6) and Equation (11). Equation (12) is obtained.

(Equation 11)
ΔL = L2−L1 = π / 2 Formula (12)

  As described above, the phase difference is different by π / 4 (rad) when the first transmission line 31 is selected and when the second transmission line 32 is selected. When the second transmission line 32 is selected with respect to the phase difference, the phase of the reflected wave is delayed by π / 2 (rad) when the first transmission line 31 is selected.

  Therefore, by changing the selection of the first transmission line 31 and the second transmission line 32, the phase of the reflected signal input to the first detection circuit 51 and the second detection circuit 52 can be changed by π / 2 (rad). it can. For this reason, even when the phase difference θ1 between the transmission signal input to the first detection circuit 51 and the reflection signal becomes a null point where π (rad) is reached, the transmission signal and the reflection signal input to the second detection circuit 52 The phase difference θ2 of the phase difference is θ1 + π / 2 = 3π / 2 (rad). Accordingly, it is possible to detect a mutation in the detection target 500 while avoiding a null point at which the sensitivity for detecting the detection target 500 deteriorates.

  Hereinafter, the effect by having set it as this embodiment is demonstrated.

  In the wireless sensor device 100 of the present embodiment, the first detection circuit 51 is connected to the other end of the first transmission line 31, and the second detection circuit 52 is connected to the other end of the second transmission line 32. The first detection circuit 51 is connected to the first signal processing circuit 61, and the first detection circuit 51 is connected to the first signal processing circuit 61.

  As a result, even when the first transmission line 31 and the second transmission line 32 are switched, the signals input to the first detection circuit 51 and the second detection circuit 52 are affected by the change in phase associated with the switching. There is no. Therefore, since the DC voltage of the detection output appearing at the outputs of the first detection circuit 51 and the second detection circuit 52 does not fluctuate greatly, the outputs of the amplifiers of the first signal processing circuit 61 and the second signal processing circuit 62 may be shaken out. It does not take a long time to output low frequency fluctuations. Therefore, it is possible to provide a wireless sensor device that can detect a detection target stably.

  Further, in the wireless sensor device 100 of the present embodiment, the control by the control circuit 70 is performed at predetermined time intervals so as to select and switch between the first transmission line 31 and the second transmission line 32, and the first transmission. The line 31 and the second transmission line 32 are alternately selected and switched.

  Thereby, since the transmission operation is performed by alternately switching the first transmission line 31 and the second transmission line 32 having different line lengths, extracting the components orthogonal to each other reliably detects the presence or absence of the reflected wave. Therefore, the detection target can be detected more stably.

  In addition, the wireless sensor device 100 of the present embodiment is configured such that the phase difference between the first transmission line 31 and the second transmission line 32 is π / 4 (rad).

  Thereby, by switching between the first transmission line 31 and the second transmission line 32, it is possible to obtain signals in which the phase difference between the transmission signal and the reflected signal is different by π / 2 (rad). For this reason, it is possible to reliably avoid the null point where the sensitivity is remarkably lowered and to detect the detection target more stably.

  As described above, according to the wireless sensor device 100 of the present embodiment, it is possible to provide a wireless sensor device that can stably detect a detection target.

  As described above, the wireless sensor device 100 according to the embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Is possible. For example, the present invention can be modified as follows, and these embodiments also belong to the technical scope of the present invention.

  (1) In the present embodiment, the wireless sensor device 100 has been described with reference to a drawing away from the detection target 500. However, the wireless sensor device 100 may be carried or worn to detect body movement of the detection target 500. .

  (2) In the present embodiment, the first signal processing circuit 61 and the second signal processing circuit 62 will be described with reference to an example of performing amplification, AD conversion, and the like necessary to detect the amount of change from the detected signal. However, it may be configured to perform signal processing such as band limitation and sampling.

  (3) In the present embodiment, the example in which the first transmission line 31 and the second transmission line 32 are switched for each transmission has been described, but the switching may be performed for each of the plurality of transmission operations. .

DESCRIPTION OF SYMBOLS 10 Antenna 20 Transmission circuit 31 1st transmission line 32 2nd transmission line 41 1st switching means 42 2nd switching means 51 1st detection circuit 52 2nd detection circuit 61 1st signal processing circuit 62 2nd signal processing circuit 70 Control circuit 100 Wireless sensor device

Claims (3)

An antenna that radiates a transmission signal and receives a reflected signal that is reflected from the detection target;
A transmission circuit for generating the transmission signal; a first transmission line; a second transmission line having a different line length from the first transmission line;
A first switching means for selecting one end of the first transmission line and one end of the second transmission line and connecting to the antenna;
Second switching means for selecting the other end of the first transmission line and the other end of the second transmission line and connecting to the transmission circuit;
A detection circuit that receives and detects a part of the transmission signal and the reflected signal received by the antenna during transmission of the transmission signal from the transmission circuit;
A signal processing circuit connected to the detection circuit and processing a signal output from the detection circuit;
A control circuit that controls the transmission circuit, the first switching unit, and the second switching unit; and the control circuit includes a transmission line that connects the antenna and the transmission circuit, and the first transmission line. Alternatively, in the wireless sensor device that performs control to select and switch from the second transmission line,
The detection circuit and the signal processing circuit are connected to the other ends of the first transmission line and the second transmission line ,
The wireless sensor device , wherein the detection circuit multiplies the transmission signal and the reflection signal .   The control by the control circuit is performed at predetermined time intervals so as to select and switch between the first transmission line and the second transmission line, and the first transmission line and the second transmission line include: The wireless sensor device according to claim 1, wherein the wireless sensor device is alternately selected and switched. 3. The wireless sensor device according to claim 1, wherein a phase difference between the first transmission line and the second transmission line is π / 4 (rad). 4.

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