Distance calculation device and distance calculation method

Abstract

To provide a distance calculation device capable of calculating a distance to a detected object using a single frequency radio wave.SOLUTION: A distance calculation device 1 includes an oscillator 11 which generates a high frequency signal; an antenna 12 which outputs the high frequency signal from the oscillator 11; a voltage acquisition part 13 which acquires a reflection voltage of the reflected signal flowing from the antenna 12 to the oscillator side; and a distance calculation part 14 which calculates a distance to a detection object using a relation expression showing relationship between the reflection voltage obtained in presence of the detection object, the reflection voltage obtained in absence of the detection object, the detection object reflection voltage being the reflection signal voltage corresponding to the reflected wave reflected by the detection object, and the distance to the detection object.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distance calculation device that calculates the distance to a detected object. [Background technology]

[0002] Conventionally, various technologies for detecting objects without contact have been developed (see, for example, Patent Documents 1 to 3). For example, methods for detecting objects without contact include an infrared method, a method using changes in capacitance, a method using radar, and an induction method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-146024 [Patent Document 2] Japanese Patent Application Publication No. 2019-132586 [Patent Document 3] Japanese Patent Application Publication No. 2018-190580 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for not only non-contact detection of objects but also measurement of the distance to those objects. One method that can measure distance is FMCW, which is used in automotive radar, but this method requires a certain frequency band because it requires changing the transmission frequency.

[0005] The present invention has been made in response to the above circumstances, and has an object to provide a distance calculation device or the like that can calculate the distance to a detected object using radio waves of a single frequency. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a distance calculation device according to one aspect of the present invention comprises an oscillator that generates a high-frequency signal, an antenna that outputs the high-frequency signal from the oscillator, a voltage acquisition unit that acquires the reflected voltage of a reflected signal flowing from the antenna to the oscillator, and a distance calculation unit that calculates the distance to the detected object using a relational equation that shows the relationship between the reflected voltage acquired when a detected object is present, the reflected voltage acquired when a detected object is not present, and the detected object reflected voltage, which is the voltage of the reflected signal corresponding to the reflected wave reflected by the detected object, and the distance to the detected object. With this configuration, it is possible to measure the distance to a detected object by calculating the distance to the detected object using radio waves of a single frequency.

[0007] In the distance calculation device according to an aspect of the present invention, the relational expression may represent the relationship between the magnitude of the voltage reflected from the detected object and the distance to the detected object. Such a configuration makes it possible to calculate distances over a wider range.

[0008] In addition, in the distance calculation device according to one aspect of the present invention, the relational expression may represent the relationship between the phase of the reflected voltage of the detected object, based on the reflected voltage of the detected object at a predetermined distance, and the distance to the detected object. With this configuration, it becomes possible to calculate the distance more accurately.

[0009] In addition, in a distance calculation device according to one aspect of the present invention, the distance calculation unit calculates a tentative distance to the detected object using a relational expression that indicates the relationship between the magnitude of the reflected voltage of the detected object and the distance to the detected object, and specifies a value of k (k is an integer) related to the arbitrariness of 2πk in the phase of the relational expression using the tentative distance and the relational expression that indicates the relationship between the phase of the reflected voltage of the detected object based on the reflected voltage of the detected object at a predetermined distance, and the distance to the detected object, according to the specified value of k, and calculates the distance to the detected object using the relational expression that indicates the relationship between the phase of the reflected voltage of the detected object based on the reflected voltage of the detected object at a predetermined distance, according to the specified value of k. This configuration allows for more accurate calculation of distances over a wider range.

[0010] In addition, in a distance calculation device according to one aspect of the present invention, the voltage acquisition unit may include a demodulator that demodulates a reflected signal from the antenna into an I-channel signal and a Q-channel signal using a high-frequency signal from an oscillator, first and second low-pass filters that extract low-frequency components of the I-channel signal and the Q-channel signal, respectively, and first and second AD converters that AD-convert output signals of the first and second low-pass filters, respectively. With this configuration, it is possible to obtain baseband signals of the I and Q channels, which can be used to calculate the distance.

[0011] In addition, in a distance calculation device according to one aspect of the present invention, the voltage acquisition unit may include a local oscillator that generates a high-frequency signal having a frequency different from the high-frequency signal, a mixer that mixes a reflected signal from the antenna with the high-frequency signal from the local oscillator, a band-pass filter that extracts a specific frequency component from the output signal of the mixer, and an AD converter that performs AD conversion on the output signal of the band-pass filter. With this configuration, the reflected signal from the antenna can be down-converted using a high frequency signal from the local oscillator, and the sampling frequency of the AD converter can be lowered.

[0012] In addition, a distance calculation method according to one aspect of the present invention includes the steps of: acquiring, in a situation where a detected object is not present, a reflected voltage of a reflected signal flowing from an antenna that outputs a high-frequency signal from an oscillator that generates a high-frequency signal to the oscillator side; acquiring, in a situation where a detected object is present, a reflected voltage of a reflected signal flowing from the antenna to the oscillator side; and calculating the distance to the detected object using a relational equation showing the relationship between the reflected voltage acquired in a situation where a detected object is present, the reflected voltage acquired in a situation where a detected object is not present, and the detected object reflected voltage, which is the voltage of a reflected signal corresponding to a reflected wave reflected by the detected object, and the distance to the detected object. [Effects of the Invention]

[0013] According to the distance calculation device and the like according to one aspect of the present invention, the distance to a detected object can be measured using radio waves of a single frequency. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram showing the configuration of a distance calculation device according to an embodiment of the present invention. [Figure 2] A flowchart showing the operation of the distance calculation device according to the embodiment. [Figure 3] FIG. 10 is a diagram showing an example of the relationship between the distance to a detected object and the real part and imaginary part of a reflected voltage in the embodiment; [Figure 4] FIG. 2 is a block diagram showing an example of the configuration of a voltage acquisition unit according to the embodiment; [Figure 5] FIG. 2 is a block diagram showing an example of the configuration of a voltage acquisition unit according to the embodiment; [Figure 6] FIG. 2 is a block diagram showing an example of the configuration of a voltage acquisition unit according to the embodiment; [Figure 7] FIG. 2 is a block diagram showing an input receiving device using the distance calculation device according to the embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0015] A distance calculation device and a distance calculation method according to the present invention will be described below using embodiments. In the following embodiments, components and steps denoted by the same reference numerals are the same or equivalent, and repeated description may be omitted. The distance calculation device according to this embodiment calculates the distance to a detected object using a relational expression that indicates the relationship between the voltage of a reflected signal corresponding to radio waves reflected by a detected object out of radio waves output from an antenna, and the distance to the detected object.

[0016] 1 is a block diagram showing the configuration of a distance calculation device 1 according to this embodiment. The distance calculation device 1 according to this embodiment includes an oscillator 11, an antenna 12, a voltage acquisition unit 13, and a distance calculation unit .

[0017] The oscillator 11 generates a high-frequency signal. The oscillator 11 generates a high-frequency signal at a constant frequency. The frequency of the high-frequency signal may be determined depending on how close an object to be detected needs to be to the antenna 12. The higher the frequency (i.e., the shorter the wavelength), the closer the object can be detected to the antenna 12. The frequency of the high-frequency signal is not particularly limited, but may be, for example, 100 MHz or higher, or 1 GHz or higher. The frequency of the high-frequency signal may also be, for example, 50 GHz or lower, 30 GHz or lower, or 10 GHz or lower.

[0018] Antenna 12 outputs a high-frequency signal generated by oscillator 11. Antenna 12 typically transmits the high-frequency signal without modulation. Antenna 12 may or may not have directionality. In the former case, the distance to a detected object in a direction where the radiation intensity of the electromagnetic field is high according to the directionality can be measured. When an omnidirectional antenna 12 is used, the distance to a detected object around antenna 12 can be measured regardless of direction. The detected object is an object for which distance is to be calculated, and may be, for example, a human being, a part of a human being (e.g., a hand), a manufactured object, a transported object, a moving object such as a car, or any other object for which distance can be measured.

[0019] The voltage acquisition unit 13 acquires a reflected voltage of a reflected signal flowing from the antenna 12 to the oscillator 11. The specific configuration of the voltage acquisition unit 13 will be described later.

[0020] The distance calculation unit 14 calculates the distance to the detected object using a relational expression that shows the relationship between the reflected voltage acquired when the detected object is present, the reflected voltage acquired when the detected object is not present, and the detected object reflected voltage, which is the voltage of the reflected signal corresponding to the reflected wave reflected by the detected object, and the distance to the detected object.

[0021] A method for calculating the distance to the detected object will be described below. As shown in FIG. 1, the distance to the detected object 3 is, more strictly speaking, the distance from the antenna 12 to the detected object 3. This distance is designated as d. Also, as shown in FIG. 1, an input voltage v is applied from the voltage acquisition unit 13 to the antenna 12. i A high frequency signal of the above flows from the antenna 12 to the voltage acquisition unit 13, and a reflected voltage v r The reflected voltage v r has three components as follows:

number

[0022] where v a is the voltage of the reflected signal reflected at the end of the antenna 12 out of the high frequency signal transmitted from the voltage acquisition unit 13 to the antenna 12, and v b is the voltage of the reflected signal corresponding to the wave reflected by the surrounding environment such as a wall among the radio waves emitted from the antenna 12, and v c is the voltage of the reflected signal corresponding to the wave reflected by the detected object 3 among the radio waves emitted from the antenna 12. c is sometimes called the reflected voltage of the detected object.

[0023] If we assume that the reflected wave from the detected object 3 is a plane wave and only a direct wave, the voltage reflected from the detected object is expressed by the following equation: i is the input voltage mentioned above, d is the distance to the detected object 3, α is the attenuation coefficient, ω is the phase coefficient, and C is a coefficient determined by the antenna characteristics, circuit characteristics, and reflection characteristics of the detected object. Here, α and ω are both real numbers greater than 0.

number

[0024] By using the above formula, the reflected voltage v r is expressed as follows:

number

[0025] From the above equation, as d increases from d=0, the reflected voltage v r As shown in Figure 3, the vortex center converges to the center while rotating around it on the complex plane. a +v b The degree of rotation of the vortex is determined by the magnitude of ω, and the degree to which the vortex becomes smaller is determined by the magnitude of α. As is clear from this, when d is sufficiently large, that is, when there is no detected object 3, the vortex center v a +v b That is, the reflected voltage obtained in the absence of the object 3 can be measured as v a +v b This becomes:

number

[0026] The v measured in this way a +v b and the reflected voltage v when the object 3 is present. r By using this, the reflected voltage v of the detected object can be calculated as follows: c can be calculated.

number

[0027] In addition, the reflected voltage v when the detected object 3 is present at an arbitrary distance d1 r By measuring the input voltage v i and coefficient C can be removed. c '(d) is the reflected voltage v of the detected object at a given distance d1 c The reflected voltage v of the detected object is based on the distance d1 (d1), and can be considered as a normalized reflected voltage. c(d1) is the voltage of the reflected signal corresponding to the reflected wave reflected by a detected object located at a predetermined distance d1.

number

[0028] Substituting d2, which is different from d1, for d in the above equation gives the following equation.

number

[0029] Taking the absolute values ​​of both sides of the above equation gives the following equation:

number

[0030] From this equation, the damping coefficient α is given by the following equation, and the previously measured v a +v b , the reflected voltage v when the detection object 3 is placed at a distance d1, d2 r It is possible to calculate α using the above.

number

[0031] Also, the above v c Calculating the argument for both sides of equation (d2) gives the following equation: Note that the arg function is a function for calculating the argument at the principal value (-π,π).

number

[0032] However, the second term on the left side of the above equation is a term related to the arbitrariness of 2πk in the phase, where k is an arbitrary integer. Note that if d1 and d2 are sufficiently close compared to the wavelength λ of the high-frequency signal (for example, if the absolute value of the difference between them is λ / 4 or less), k can be set to 0, so the phase coefficient ω is expressed as follows, and the previously measured v a +v b , the reflected voltage v when the detection object 3 is placed at a distance d1, d2 r Using the above, ω can be calculated.

number

[0033] The distance calculation unit 14 may use the thus calculated attenuation coefficient α and phase coefficient ω to calculate the distance d to the detected object 3, for example, by one of the following methods (A) to (C).

[0034] (A) Calculation of distance using the first relational expression The above v c Taking the absolute values ​​of both sides of equation (d) gives the following equation:

number

[0035] By modifying this equation, the relational expression for the distance d can be obtained as follows:

number

[0036] On the right side of equation (2), the reflected voltage of the detected object, v c Since all values ​​except (d) are known, equation (2) is the distance d to the detected object 3 and the magnitude of the reflected voltage from the detected object |v c (d)|. This relational expression will be referred to as the first relational expression. The distance calculation unit 14 calculates the reflected voltage v acquired in a situation where the detected object 3 is not present. a +v band the reflected voltage v obtained when the object 3 is present. r By substituting into equation (1), the reflected voltage v c (d) is calculated, and the reflected voltage v c (d) Size│v c By substituting (d)| into the first relational expression, that is, expression (2), the distance d to the detected object 3 can be calculated.

[0037] In a real environment, the assumption that the reflected wave from the detected object 3 is a plane wave and that only direct waves exist is difficult to establish, so strictly speaking, the attenuation coefficient α will vary according to the distance d. Also, because the right-hand side of equation (2) is logarithmic, the variation in distance according to voltage error will also be large. Thus, although distance calculation using the first relational expression has the disadvantage of not being very accurate, it has the advantage of being able to measure a wider range of distances compared to distance calculation using the second relational expression, which will be described later.

[0038] (B) Calculating distance using the second relation The above v c 'Calculating the argument for both sides of equation (d) gives the following equation:

number

[0039] By modifying this equation, the relational expression for the distance d can be obtained as follows:

number

[0040] On the right side of equation (3), the integer k related to the arbitrariness of the phase and the reflected voltage v of the detected object are c Since all values ​​except (d) are known, equation (3) is the distance d to the detected object 3 and the reflected voltage v of the detected object at distance d1. c The reflected voltage v of the detected object based on (d1) c (d) / v cThis can be said to be a relational expression that shows the relationship between the phase of (d1) and the value k related to the arbitrariness of the phase. Note that if d and d1 are sufficiently close compared to the wavelength λ, k can be set to 0, so the relational expression for the distance d becomes the following equation.

number

[0041] On the right side of equation (4), the reflected voltage of the detected object, v c Since all values ​​except (d) are known, equation (4) is the distance d to the detected object 3 and the reflected voltage v of the detected object at distance d1. c The reflected voltage v of the detected object based on (d1) c (d) / v c This relational expression is called the second relational expression. Therefore, the distance calculation unit 14 calculates the reflected voltage v obtained when the object 3 is not present. a +v b and the reflected voltage v obtained when the object 3 is present. r By substituting into equation (1), the reflected voltage v c Calculate the reflected voltage v of the detected object c The reflected voltage V of the detected object at a distance d1 c v divided by (d1) c (d) / v c Phase argv of (d1) c (d) / v c By substituting (d1) into the second relational expression, that is, expression (4), the distance d to the detected object 3 can be calculated.

[0042] The phase coefficient ω is a coefficient that is roughly determined by the wavelength, and is not as affected by the surrounding environment as the attenuation coefficient α, so using the second relational expression has the advantage of being able to calculate distance more accurately.On the other hand, because the argument of a complex number is a multi-valued function, in order to be able to uniquely calculate distance, it can only be used within the range of one revolution of the vortex shown in Figure 3, and distance d must be close to distance d1, which has the disadvantage of narrowing the range of distances that can be measured.

[0043] Even if the distance d is far from the distance d1, if the value of k is known, the known value of k can be substituted into equation (3) and used as the second relational equation. In this way, it becomes possible to measure the distance at a position far from the distance d1. However, even in this case, the range in which the distance can be calculated is about λ / 2 (i.e., the range from -λ / 4 to +λ / 4 with respect to the reference distance). As mentioned above, λ is the wavelength of the high-frequency signal.

[0044] (C) Calculation of distance using both the first and second relational expressions Distance calculation unit 14 may calculate a tentative distance d' to the detected object 3 using a first relational expression, and then use the tentative distance d' and a relational expression that indicates the relationship between the phase of the detected object reflected voltage based on the detected object reflected voltage at a predetermined distance as a reference and the distance to the detected object, including the arbitrariness of the phase 2πk (k is an integer), to identify the value of k related to the arbitrariness of 2πk in the phase of that relational expression, and then calculate the distance to the detected object 3 using a second relational expression that corresponds to the identified value of k. A specific calculation method will be described below.

[0045] The distance calculation unit 14 first calculates the temporary distance d' using the first relational expression. That is, the distance calculation unit 14 sets the distance calculated using the expression (2) as the temporary distance d'. c By calculating the argument on both sides of equation '(d), we can obtain a relational expression that shows the relationship between the phase of the reflected voltage from an object relative to the reflected voltage from an object at a predetermined distance, including the arbitrariness of the phase 2πk, and the distance d to the object. Substituting the tentative distance d' for the distance d in this relational expression yields the following equation.

number

[0046] Transforming this formula yields the following formula: Note that since k is an integer, the round function is used to round off.

number

[0047] Therefore, the distance calculation unit 14 adds the reflected voltage v obtained when the detected object 3 is not present to the right side of the equation (5). a +v b and the reflected voltage v obtained when the object 3 is present. r The reflected voltage v of the detected object is calculated by substituting c The value of k can be calculated by substituting (d) and the temporary distance d'.

[0048] Next, the distance calculation unit 14 substitutes the value of k into equation (3) to obtain a second relational expression, and then calculates the reflected voltage v of the detected object calculated using equation (1). c By substituting (d), it is possible to calculate the distance d to the detected object 3. In this way, it is possible to obtain the advantage that it is possible to calculate distances over a wide range with higher accuracy.

[0049] As described above, it is assumed that the reflected wave from the detected object 3 is a plane wave and only a direct wave, and therefore it is generally assumed that the measurable distance is at least a certain distance (for example, about several wavelengths) away from the antenna 12, but in experiments, it was possible to properly measure even at a distance of about λ / 2 from the antenna 12. Therefore, it can be considered that there is no particular limitation on the shortest measurable distance.

[0050] Next, the operation of the distance calculation device 1 will be described with reference to the flowchart of FIG. (Step S101) The oscillator 11 starts generating a high-frequency signal. As a result, the high-frequency signal is output from the antenna 12. In addition, the voltage acquisition unit 13 starts acquiring the reflected voltage of the reflected signal from the antenna 12.

[0051] (Step S102) The distance calculation unit 14 calculates the reflected voltage v obtained when the detected object 3 is not present. a +v b The distance calculation unit 14 stores the reflected voltage v obtained when the detected object 3 is located at the distances d1 and d2.r These are also stored in a storage unit, and are used to calculate the attenuation coefficient α and phase coefficient ω required for the relational expressions used in calculating the distance. Furthermore, the attenuation coefficient α, phase coefficient ω, etc. are substituted into the relational expressions used in calculating the distance as appropriate.

[0052] (Step S103) Distance calculation unit 14 determines whether or not to calculate the distance to detected object 3. If the distance is to be calculated, the process proceeds to step S104, and if not, the process of step S103 is repeated until it is determined that the distance should be calculated. Note that distance calculation unit 14 may, for example, periodically determine that the distance should be calculated.

[0053] (Step S104) The voltage acquisition unit 13 acquires the reflected voltage v at that time. r Get.

[0054] (Step S105) The distance calculation unit 14 calculates the reflected voltage v obtained in step S104. r and the reflected voltage v obtained in step S102 in a situation where there is no detected object 3 accumulated in advance. a +v b By substituting into equation (1), the reflected voltage v c Calculate.

[0055] (Step S106) The distance calculation unit 14 calculates the reflected voltage v of the detected object calculated in step S105. c and a predetermined relational expression, the distance d to the detected object 3 is calculated by any one of the above methods (A) to (C). Then, the process returns to step S103. Note that this calculated distance d may be output, for example, by an output unit (not shown). This output may be, for example, displaying or transmitting the distance d, printing it, storing it in a recording medium, or transferring it to another component.

[0056] The order of the steps in the flowchart of Fig. 2 is an example, and the order of the steps may be changed as long as the same results are obtained. In the flowchart of Fig. 2, the processing ends when the power is turned off or an interrupt to end the processing occurs.

[0057] In addition, it is preferable that the pre-processing of step S102 in the flowchart of FIG. 2 be executed again, for example, when the environment around the distance calculation device 1 changes (for example, when the installation location of the distance calculation device 1 is changed) or when the configuration of the distance calculation device 1 changes (for example, when the antenna 12 is changed).

[0058] Next, some examples of the voltage acquisition unit 13 will be described with reference to FIGS. The voltage acquiring unit 13 shown in FIG. 4 includes a divider 21, a directional coupler 22, a demodulator 23, first and second low-pass filters 24a and 25b, and first and second AD converters 25a and 25b.

[0059] The distributor 21 distributes the high-frequency signal flowing from the oscillator 11 toward the antenna 12 into a first high-frequency signal and a second high-frequency signal. The first high-frequency signal is output to the directional coupler 22, and the second high-frequency signal is output to the demodulator 23. The directional coupler 22 outputs the first high-frequency signal input from the distributor 21 to the antenna 12, and outputs the reflected signal from the antenna 12 to the demodulator 23.

[0060] Demodulator 23 demodulates the reflected signal from antenna 12, i.e., the reflected signal from directional coupler 22, into an I-channel signal and a Q-channel signal using the high-frequency signal from oscillator 11, i.e., the second high-frequency signal from distributor 21. Note that this demodulation process is already known, and a detailed description thereof will be omitted.

[0061] The first and second low-pass filters 24a and 25b are low-pass filters that extract low-frequency components of the I-channel signal and the Q-channel signal from the demodulator 23, respectively. The output signals from the first and second low-pass filters 24a and 25b are AD-converted by the first and second AD converters 25a and 25b, respectively, and then passed to the distance calculation unit 14. In this case, the I-channel and Q-channel baseband signals are AD-converted, which means that signals with lower frequencies than high-frequency signals are AD-converted, making it possible to lower the sampling frequency. The output signals from the first and second AD converters 25a and 25b are respectively converted into the reflected voltage v r Therefore, the distance calculation unit 14 calculates the reflected voltage v r The distance d to the detected object 3 can be calculated using

[0062] The voltage acquiring unit 13 shown in Fig. 5 includes a directional coupler 22, a local oscillator 31, a mixer 32, a band-pass filter 33, and an AD converter 34. The directional coupler 22 is the same as in Fig. 4, and a description thereof will be omitted.

[0063] Local oscillator 31 generates a high-frequency signal with a different frequency from the high-frequency signal generated by oscillator 11. It is preferable that the frequency of the high-frequency signal generated by local oscillator 31 is close to the frequency of the high-frequency signal generated by oscillator 11. This is because the closer the two frequencies are, the greater the effect of down-conversion, which will be described later.

[0064] Mixer 32 is a mixer that mixes the reflected signal from antenna 12, i.e., the reflected signal from directional coupler 22, with the high-frequency signal from local oscillator 31. Both signals are multiplied in mixer 32. The signal resulting from this multiplication contains a component that is the sum of the frequencies of the two signals and a component that is the difference between them.

[0065] The band-pass filter 33 is a band-pass filter that extracts a specific frequency component from the output signal of the mixer 32. The specific frequency component of the band-pass filter 33 is preferably set to pass the difference component between the two signals output from the mixer. As described above, the closer the frequency of the high-frequency signal generated by the local oscillator 31 and the frequency of the high-frequency signal generated by the oscillator 11, the lower the frequency of the signal that passes through the band-pass filter 33, thereby enabling greater down-conversion to be achieved.

[0066] The AD converter 34 converts the output signal of the band-pass filter 33 into an AD signal. Since the output signal of the band-pass filter 33 has been down-converted, the AD converter 34 has the advantage of being able to perform AD conversion at a lower sampling frequency. The output signal of this AD converter 34 is converted into a reflected voltage v r Therefore, the distance calculation unit 14 calculates the reflected voltage v r The distance d to the detected object 3 can be calculated using

[0067] It goes without saying that the voltage acquisition unit 13 is not limited to the configuration shown in Fig. 4 and Fig. 5. The voltage acquisition unit 13 may, for example, directly AD convert the reflected signal from the antenna 12. In this case, sampling must be performed at a frequency higher than the high-frequency signal generated by the oscillator 11, but the reflected voltage v can also be obtained by directly AD converting the reflected signal. r can be obtained.

[0068] 4 and 5, the case where a single antenna 12 is used to output a high-frequency signal and receive a reflected wave has been described, but this is not necessarily the case. For example, as shown in FIG. 6, a transmitting antenna 12a and a receiving antenna 12b may be used. In this case, the directional coupler 22 is not required. Also, in FIG. 6, the distance calculation device 1 shown in FIG. 4 is configured using the transmitting antenna 12a and the receiving antenna 12b, but it goes without saying that a distance calculation device 1 with a different configuration, for example, the distance calculation device 1 shown in FIG. 5, may be configured using the transmitting antenna 12a and the receiving antenna 12b.

[0069] The distance calculation device 1 according to this embodiment can be used for any purpose, but as an example, it can be used as follows. The distance calculation device 1 according to this embodiment may be used, for example, to control the supply of flush water in a toilet. In this case, the toilet apparatus may include a toilet bowl, a water supply unit that supplies flush water to the toilet bowl, a control unit that controls the supply of flush water by the water supply unit, and the distance calculation device 1 according to this embodiment. The control unit may then control the water supply unit to supply flush water to the toilet bowl when the distance calculated by the distance calculation device 1 satisfies a predetermined condition. The distance is the distance to the person using the toilet. The predetermined condition may be, for example, that the calculated distance becomes shorter than a predetermined first threshold, and then the calculated distance becomes longer than a predetermined second threshold. The first and second thresholds may, for example, be the same value or different values. In the latter case, for example, the first threshold may be smaller than the second threshold. The toilet may be, for example, a men's urinal or a toilet such as a seated toilet.

[0070] Furthermore, the distance calculation device 1 according to this embodiment may be used, for example, in an interface that accepts input. In this case, for example, as shown in FIG. 7, the input acceptance device 2 may include the distance calculation device 1 and an input acceptance unit 16. Note that the distance calculation device 1 shown in FIG. 7 is similar to the distance calculation device 1 described above, except that it includes an antenna group 120 having four antennas 121 to 124 instead of the antenna 12, and further includes a switch 15 that switches between the antennas 121 to 124 connected to the voltage acquisition unit 13. The switch 15 sequentially switches between the antennas 121 to 124 connected to the voltage acquisition unit 13 in a time-division manner. As a result, the distance to the detected object is output from the distance calculation unit 14 using the reflected waves received by each of the antennas 121 to 124. The input receiving unit 16 can determine the distance to the detected object at the position of each of the antennas 121-124 based on the distance output from the distance calculation unit 14 and the connection relationship between the antennas 121-124 and the voltage acquisition unit 13 at the time the distance was output. Therefore, when a user makes a selection without contact using a hand or the like, the input receiving unit 16 may determine that a selection corresponding to a certain antenna has been input when the distance calculated using that antenna falls within a predetermined range, and output the selection result. In this way, the user can make a selection using a button or the like without contact. The input receiving device 2 may be a contactless input interface or a so-called contactless touch panel.

[0071] In order to accurately detect the position of the antenna where the user's hand is located, it is preferable that the antennas 121 to 124 have high directivity. The number of antennas included in the antenna group 120 is not important. It may be three or less, or five or more. In addition, although FIG. 7 illustrates a case where the distance to the detected object at the position of each of the antennas 121 to 124 is calculated by switching between them in a time-division manner, this is not necessarily the case. A voltage acquisition unit 13 and a distance calculation unit 14 may be provided for each antenna. The oscillator 11 may be provided for each antenna, or may be provided in common to multiple antennas.

[0072] As described above, the distance calculation device 1 according to this embodiment can calculate the distance to the detected object 3 using a single frequency. Furthermore, by calculating the distance using the method (C) above, it becomes possible to calculate the distance over a wider range with higher accuracy.

[0073] Furthermore, in the above embodiments, each process or function may be realized by centralized processing by a single device or a single system, or may be realized by distributed processing by multiple devices or multiple systems.

[0074] In the above embodiments, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component may be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. During execution, the program execution unit may execute the program while accessing a memory unit or recording medium.

[0075] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible, and it goes without saying that these modifications are also included within the scope of the present invention. [Explanation of symbols]

[0076] 1 Distance calculation device 3 Detected objects 11 Oscillators 12, 12a, 12b, 121-124 Antennas 13 Voltage acquisition unit 14 Distance calculation unit 21 Distributor 22 Directional coupler 23 Demodulator 24a First low-pass filter 24b Second low-pass filter 25a First AD converter 25b Second AD converter 31 Local oscillator 32 Mixer 33 Bandpass Filter 34 AD converter

Claims

1. an oscillator for generating a high frequency signal; an antenna that outputs a high-frequency signal from the oscillator; a voltage acquisition unit that acquires a reflected voltage of a reflected signal flowing from the antenna to the oscillator side; a distance calculation unit that calculates the distance to the detected object using a reflected voltage acquired when the detected object is present, a reflected voltage acquired when the detected object is not present, and a relational equation that shows the relationship between the detected object reflected voltage, which is the voltage of a reflected signal corresponding to a reflected wave reflected by the detected object, and the distance to the detected object.

2. 2. The distance calculation device according to claim 1, wherein the relational expression indicates the relationship between the magnitude of the reflected voltage from the detected object and the distance to the detected object.

3. 2. The distance calculation device according to claim 1, wherein the relational expression indicates the relationship between the phase of the reflected voltage from the detected object, with the reflected voltage from the detected object at a predetermined distance as a reference, and the distance to the detected object.

4. 2. The distance calculation device according to claim 1, wherein the distance calculation unit calculates a tentative distance to the detected object using a relational expression that indicates the relationship between the magnitude of the reflected voltage of the detected object and the distance to the detected object, specifies a value of k (k is an integer) related to the arbitrariness of 2πk in the phase of the relational expression that indicates the relationship between the phase of the reflected voltage of the detected object with the reflected voltage of the detected object at a predetermined distance as a reference, and the distance to the detected object, according to the specified value of k, and calculates the distance to the detected object using the relational expression that indicates the relationship between the phase of the reflected voltage of the detected object with the reflected voltage of the detected object at a predetermined distance as a reference, according to the specified value of k.

5. The voltage acquisition unit a demodulator that demodulates a reflected signal from the antenna into an I-channel signal and a Q-channel signal using a high-frequency signal from the oscillator; first and second low-pass filters for extracting low-frequency components of the I-channel signal and the Q-channel signal, respectively; 5. The distance calculation device according to claim 1, further comprising: first and second AD converters for AD-converting output signals of said first and second low-pass filters, respectively.

6. The voltage acquisition unit a local oscillator for generating a high frequency signal having a different frequency from the high frequency signal; a mixer that mixes a reflected signal from the antenna with a high-frequency signal from the local oscillator; a bandpass filter for extracting a specific frequency component from the output signal of the mixer; 5. The distance calculation device according to claim 1, further comprising: an AD converter that performs AD conversion on an output signal of said band-pass filter.

7. a step of acquiring a reflected voltage of a reflected signal flowing from an antenna that outputs a high frequency signal from an oscillator that generates a high frequency signal in a state where no object is present; acquiring a reflected voltage of a reflected signal flowing from the antenna to the oscillator in a situation where a detection object is present; and calculating the distance to the detected object using a reflected voltage acquired when the detected object is present, a reflected voltage acquired when the detected object is not present, and a relational equation showing the relationship between the detected object reflected voltage, which is the voltage of a reflected signal corresponding to a reflected wave reflected by the detected object, and the distance to the detected object.

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