WO2016056383A1

WO2016056383A1 - Position detection device

Info

Publication number: WO2016056383A1
Application number: PCT/JP2015/076724
Authority: WO
Inventors: 井上　学
Original assignee: 株式会社村田製作所
Priority date: 2014-10-07
Filing date: 2015-09-18
Publication date: 2016-04-14

Abstract

Disclosed is a position detection device wherein a transmitter that radiates electromagnetic waves having a first frequency is disposed above a reflecting surface that reflects electromagnetic waves. A first reception device includes at least two reception antennas which are respectively disposed at positions that are identical to each other in the in-plane direction of the reflecting surface but are different from each other in the height direction of the reflecting surface. The electromagnetic waves having the first frequency are received by means of the reception antennas, said electromagnetic waves having been radiated from the transmitter. On the basis of the reception strengthes of the electromagnetic waves having the first frequency, said electromagnetic waves having been received by means of the reception antennas of the first reception device, a processing device calculates first distances from the reception antennas to the transmitter in the in-plane direction of the reflecting surface. Calculation accuracy of the distances from the reception device to the transmitter can be improved by taking into account electromagnetic wave multipath.

Description

Position detection device

The present invention relates to a position detection device that receives radio waves radiated from a transmitter and detects the position of the transmitter.

Patent Documents 1 and 2 disclose techniques for receiving radio waves radiated from a transmitter and detecting the position of the transmitter based on the intensity of a received signal.

According to the technology disclosed in Patent Document 1, radio waves transmitted by a slave attached to a moving body are received by three base stations. The distance from each base station to the handset is calculated from the radio field intensity received at each base station. The position of the slave unit can be specified based on the distance from each of the three base stations to the slave unit.

Also in the technique disclosed in Patent Document 2, the distance from the receiving device to the transmitter is calculated based on the radio wave intensity received by the plurality of receiving devices. Based on this distance, the position of the transmitter is detected. At this time, the environment variables of the transmitter and the receiver are defined, and the distance is corrected using the environment variables. The environment variable of the transmitter is an index of how much the sensitivity changes when the transmitter is placed in an ideal state. The environment variable of the receiving device is an index of how much the sensitivity changes when the receiving device is placed in an ideal state.

JP 09-159746 A JP 2004-053510 A

The radio field intensity received by the receiving device is generally affected by multipath. In the technique disclosed in Patent Document 1, the influence of multipath is not considered. For this reason, when affected by multipath, the accuracy of the calculation result of the distance from the base station to the slave unit is lowered. In the technique disclosed in Patent Document 2, the influence of an indirect wave is taken into account by introducing an environmental coefficient into the calculation of the distance from the receiving device to the transmitter. However, it is not specified what kind of mechanism the radio wave propagation depends on.

An object of the present invention is to provide a position detection device capable of improving the calculation accuracy of the distance from the receiving device to the transmitter in consideration of multipath of radio waves.

A position detection device according to a first aspect of the present invention provides:
A transmitter disposed above a reflecting surface for reflecting radio waves and emitting radio waves of a first frequency;
Including at least two receiving antennas arranged at the same position in the in-plane direction of the reflecting surface and at different positions in the height direction, and receiving the radio waves of the first frequency radiated from the transmitter by the receiving antenna. 1 receiving device;
A first distance in the in-plane direction of the reflecting surface from the receiving antenna to the transmitter based on the reception intensity of the radio wave of the first frequency received by the receiving antenna of the first receiving device. And a processing device for calculating.

Since multiple receiving antennas are arranged at different heights from the reflecting surface, the path length difference between the direct wave and the indirect wave is different for each receiving antenna. For this reason, the reception intensity obtained in consideration of the influence of multipath has different change characteristics with respect to the distance from the transmitter to the reception antenna. The distance estimation accuracy can be increased by obtaining the distance using a plurality of reception intensities having different change characteristics with respect to the distance.

In the position detection device according to the second aspect of the present invention, in addition to the position detection device according to the first aspect,
The processing device calculates the first distance based on a difference in reception intensity of radio waves received by the reception antenna.

The difference in reception strength has a region that varies greatly with changes in distance compared to the original reception strength. By using this area to obtain the distance from the transmitter to the receiving antenna, the distance estimation accuracy can be improved.

In the position detection device according to the third aspect of the present invention, in addition to the position detection device according to the first or second aspect,
The transmitter emits a radio wave of a second frequency different from the first frequency in addition to the radio wave of the first frequency;
In addition to the first frequency radio wave radiated from the transmitter, the first reception device receives the second frequency radio wave with the reception antenna,
In addition to the reception intensity of the radio wave of the first frequency received by the reception antenna of the first reception apparatus, the processing device performs the first based on the reception intensity of the radio wave of the second frequency. The distance is calculated.

By using two radio waves with different frequencies, it is possible to further improve the estimation accuracy of the distance from the transmitter to the receiving antenna.

In the position detection device according to the fourth aspect of the present invention, in addition to the position detection device according to the first to third aspects,
The receiving antenna of the first receiving device receives a direct wave from the transmitter and an indirect wave reflected by the reflecting surface.

The position detection device according to the fifth aspect of the present invention includes the position detection device according to the first to fourth aspects,
Including two receiving antennas arranged at the same position in the in-plane direction of the reflecting surface and at different positions in the height direction, and receiving the radio waves of the first frequency radiated from the transmitter by the two receiving antennas. A second receiving device;
Including two receiving antennas arranged at the same position in the in-plane direction of the reflecting surface and at different positions in the height direction, and receiving the radio waves of the first frequency radiated from the transmitter by the two receiving antennas. A third receiving device,
The reception antennas of the first reception device, the second reception device, and the third reception device are arranged at positions that do not line up in a straight line with respect to the in-plane direction of the reflection surface,
The processor is
Based on the reception strength of the radio waves of the first frequency received by the two reception antennas of the second reception device, the two reception antennas of the second reception device to the transmitter, Calculate a second distance for the in-plane direction of the reflecting surface;
Based on the reception strength of the radio waves of the first frequency received by the two receiving antennas of the third receiving device, the two receiving antennas of the third receiving device to the transmitter, Calculate a third distance in the in-plane direction of the reflecting surface;
The position of the two receiving antennas of each of the first receiving device, the second receiving device, and the third receiving device with respect to the in-plane direction of the reflecting surface, the first distance, and the second Based on the distance and the third distance, the position of the transmitter is calculated.

By arranging receiving antennas at three locations on the reflecting surface, it becomes possible to specify the position of the transmitter with respect to the in-plane direction of the reflecting surface.

FIG. 1 is a schematic diagram of a position detection apparatus according to the first embodiment. FIG. 2A is a block diagram of a processing device used in the position detection device according to the first embodiment. An example of the first received power-distance correspondence table and the second received power-distance correspondence table is shown in a graph format. It is the shown graph. FIG. 3A is a block diagram of a processing device of the position detection device according to the second embodiment, and FIG. 3B is a graph illustrating an example of a first received power difference-distance correspondence table in a graph format. FIG. 4 is a schematic diagram of a position detection apparatus according to the third embodiment. FIG. 5A is a block diagram of the processing device of the position detection device according to the third embodiment, and FIG. 5B is an example of a third received power-distance correspondence table and a fourth received power-distance correspondence table in a graph format. It is a graph to show. FIG. 6A is a block diagram of the processing device of the position detection device according to the fourth embodiment, and FIG. 6B is a graph illustrating an example of the first received power difference-distance correspondence table and the second received power difference-distance correspondence table. It is a graph shown in a format. FIG. 7 is a diagram illustrating an example of a planar arrangement of reception antennas of a reception device included in the position detection device according to the fifth embodiment. FIG. 8 is a schematic diagram of a position detection apparatus according to the sixth embodiment.

[Example 1]
FIG. 1 shows a schematic diagram of a position detection apparatus according to the first embodiment. A transmitter 15 is disposed above the reflecting surface 10 that reflects radio waves. The transmitter 15 radiates radio waves having a frequency f1. The reflective surface 10 is a floor surface of a store, for example, and the transmitter 15 is attached to the shopping cart 16. In addition, the transmitter 15 may be attached to the waist of a person who moves on the floor of the gymnasium.

The first receiving antenna 21 A and the second receiving antenna 21 B of the receiving device 20 are arranged above the reflecting surface 10. The first receiving antenna 21A and the second receiving antenna 21B are arranged at the same antenna installation position 13 with respect to the in-plane direction of the reflecting surface 10, and are arranged at different positions with respect to the height direction. Heights from the reflecting surface 10 to the first receiving antenna 21A and the second receiving antenna 21B are represented by H1 and H2, respectively. The first receiving antenna 21 A and the second receiving antenna 21 B are configured to receive a radio wave having a frequency f 1 radiated from the transmitter 15.

The reception device 20 transmits signals indicating the first reception power PA1 and the second reception power PB1 of the radio wave having the frequency f1 received by the first reception antenna 21A and the second reception antenna 21B to the processing device 30, respectively. To do. The signal indicating the first received power PA1 and the second received power PB1 is, for example, a voltage signal, and the voltage value represents the received power.

The processing device 30 calculates the distance D in the in-plane direction of the reflecting surface 10 from the antenna installation position 13 to the transmitter 15 based on the first received power PA1 and the second received power PB1. When calculating the distance D, the correspondence table between the received power and the distance stored in the memory 31 is referred to.

The processing executed by the processing device 30 will be described in detail with reference to FIGS. 2A and 2B.

FIG. 2A shows a block diagram of the processing device 30. The processing device 30 includes a distance calculation unit 35 and a distance selection unit 36. The memory 31 (FIG. 1) stores a first received power-distance correspondence table 32A and a second received power-distance correspondence table 32B. This correspondence table may be created by simulation, or may be created by actual measurement in an actual environment.

FIG. 2B shows an example of the first received power-distance correspondence table 32A and the second received power-distance correspondence table 32B in a graph format. The horizontal axis represents the distance D from the antenna installation position 13 to the transmitter 15 in the unit “m”, and the vertical axis represents the received power in the unit “dBm”. The solid line in FIG. 2B indicates the first received power PA1 by the first receiving antenna 21A, and the broken line indicates the second received power PB1 by the second receiving antenna 21B. The height H1 of the first receiving antenna 21A is 0.5 m, and the height H2 of the second receiving antenna 21B is 3.0 m. The frequency of the radio wave radiated from the transmitter 15 is 172 MHz.

2B, direct waves from the transmitter 15 to the first receiving antenna 21A and the second receiving antenna 21B and indirect waves reflected by the reflecting surface 10 are considered. The reflectance of the reflecting surface 10 was assumed to be 100%. It is assumed that the intensity of the radio wave passing through the propagation path other than the direct wave and the indirect wave reflected by the reflecting surface 10 is small enough to be ignored.

The first received power PA1 monotonously decreases with increasing distance D. The second received power PB1 increases as the distance D increases, and exhibits a maximum value when the distance D is about 5 m. In the range where the distance D is 5 m or more, the second received power PB1 monotonously decreases as the distance D increases. The reason why the two fluctuation characteristics with respect to the distance D are different is that the indirect wave reflected by the reflecting surface 10 is taken into consideration.

2A, the distance calculation unit 35 executes a first distance calculation process 35A and a second distance calculation process 35B. In the first distance calculating process 35A, the first candidate value D1 is obtained by applying the first received power PA1 to the first received power-distance correspondence table 32A. In the second distance calculating process 35B, the second candidate value D2 is obtained by applying the second received power PB1 to the second received power-distance correspondence table 32B.

As an example, a case will be described in which the first received power PA1 is about −74 dBm and the second received power PB1 is about −83 dBm. With the first distance calculation process 35A, about 3.5 m is obtained as the first candidate value D1. By the second distance calculation process 35B, two values of about 3.5 m and about 10 m are obtained as the second candidate value D2.

The distance selection unit 36 (FIG. 2A) selects the most probable candidate value as the estimated value of the distance D from the first candidate value D1 and the second candidate value D2. In the above example, the value of about 10 m obtained as the second candidate value D2 is excluded from the candidates for the distance D, and about 3 obtained with both the first candidate value D1 and the second candidate value D2. A value of .5 m is selected as an estimate of the distance D.

In the above example, the distance D cannot be uniquely determined from the second received power PB1. By calculating the distance D based on both the first received power PA1 and the second received power PB1, the estimated value of the distance D can be narrowed down to one value.

When the distance D is in the range of 0 m to 5 m, only the second received power PB1 determines one value from the range of 0 m to 5 m as the second candidate value D2, and further increases the value from within the range of 5 m or more. One value is obtained. By using the first received power PA1 in combination, one of the two values of the second candidate value D2 can be excluded from the distance D candidates.

When the distance D is in the range of 0 m to 3 m, the absolute value of the slope of the second received power PB1 is larger than the absolute value of the slope of the first received power PA1. Accordingly, when the first candidate value D1 obtained from the first received power PA1 is in the range of 0 m to 3 m, the second candidate value D2 obtained from the second received power PB1 is adopted as the distance D, The accuracy of the distance D can be increased.

As described above, when the first receiving antenna 21A and the second receiving antenna 21B are arranged at different heights, the path length between the direct wave and the indirect wave from the transmitter 15 to the first receiving antenna 21A. The difference is different from the path length difference between the direct wave and the indirect wave from the transmitter 15 to the second receiving antenna 21B. For this reason, the change characteristics with respect to the distance D of the first received power PA1 and the second received power PB1 are different. By estimating the distance D using both the first received power PA1 and the second received power PB1 having different change characteristics with respect to the distance D, the estimation accuracy can be improved.

[Example 2]
Next, Example 2 will be described with reference to FIGS. 3A and 3B. Hereinafter, differences from the first embodiment will be described, and description of the same configuration will be omitted.

FIG. 3A shows a block diagram of the processing device 30 (FIG. 1) of the position detection device according to the second embodiment. The processing device 30 includes a received power difference calculation unit 37 and a distance calculation unit 38. A first received power difference-distance correspondence table 33 is stored in the memory 31 (FIG. 1).

FIG. 3B shows an example of the first received power difference-distance correspondence table 33 in a graph format. The horizontal axis represents the distance D from the antenna installation position 13 to the transmitter 15 (FIG. 1) in the unit “m”, and the vertical axis represents the reception power difference in the unit “dBm”. The solid line in FIG. 3B indicates the difference PA1-PB1 between the first received power PA1 and the second received power PB1 shown in FIG. 2B.

The received power difference calculation unit 37 shown in FIG. 3A calculates a difference PA1-PB1 between the first received power PA1 and the second received power PB1. The distance calculation unit 38 obtains the distance D by applying the received power difference PA1-PB1 to the first received power difference-distance correspondence table 33.

As an example, when the first received power PA1 is -74 dBm and the second received power PB1 is -83 dBm, the received power difference PA1-PB1 is 9 dBm. By applying this difference PA1-PB1 = 9 dBm to the first received power difference-distance correspondence table 33 shown in FIG. 3B, the distance D is found to be about 3.5 m.

Comparing the first received power PA1 shown in FIG. 2B and the received power difference PA1-PB1 shown in FIG. 3B, the slope of the received power difference PA1-PB1 is within the range of 0 m to 5 m. It can be seen that the slope of the received power PA1 is greater than 1. Therefore, when the distance D is in the range of 0 m to 5 m, it is possible to increase the estimation accuracy of the distance D by using the received power difference PA1-PB1 rather than using the first received power PA1.

[Example 3]
Next, a distance detection apparatus according to the third embodiment will be described with reference to FIGS. 4 and 5A to 5B. Hereinafter, differences from the first embodiment will be described, and description of the same configuration will be omitted.

FIG. 4 shows a schematic diagram of a position detection apparatus according to the third embodiment. In the third embodiment, the transmitter 15 radiates a radio wave having a frequency f2 different from the frequency f1 in addition to the radio wave having the frequency f1. The first receiving antenna 21A and the second receiving antenna 21B are configured to receive a radio wave having a frequency f1 and a radio wave having a frequency f2. The frequency f1 is the same as the frequency of the radio wave radiated from the transmitter 15 (FIG. 1) of the first embodiment, and is 172 MHz, for example. The frequency f2 is 304.52 MHz, for example.

The receiving device 20 includes a first received power PA1 of a radio wave having a frequency f1 received by the first receiving antenna 21A, a second received power PB1 of a radio wave having a frequency f1 received by the second receiving antenna 21B, The third reception power PA2 of the radio wave of frequency f2 received by the first reception antenna 21A and the fourth reception power PB2 of the radio wave of frequency f2 received by the second reception antenna 21B are output. The first received power PA1, the second received power PB1, the third received power PA2, and the fourth received power PB2 are input to the processing device 30.

FIG. 5A shows a block diagram of the processing device 30 (FIG. 4) of the position detection device according to the third embodiment. The processing device 30 includes a distance calculation unit 35 and a distance selection unit 36. The distance calculation unit 35 executes a first distance calculation process 35A and a second distance calculation process 35B as in the first embodiment illustrated in FIG. 2A. Furthermore, the distance calculation unit 35 executes a third distance calculation process 35C and a fourth distance calculation process 35D.

As in the first embodiment shown in FIG. 2A, the memory 31 (FIG. 4) stores a first received power-distance correspondence table 32A and a second received power-distance correspondence table 32B. Further, a third received power-distance correspondence table 32C and a fourth received power-distance correspondence table 32D are stored.

FIG. 5B shows an example of the third received power-distance correspondence table 32C and the fourth received power-distance correspondence table 32D in a graph format. The horizontal axis represents the distance D from the antenna installation position 13 to the transmitter 15 (FIG. 4) in the unit “m”, and the vertical axis represents the received power in the unit “dBm”. The solid line in FIG. 5B indicates the third received power PA2, and the broken line indicates the fourth received power PB2. Also in the example shown in FIG. 5B, as in the example shown in FIG. 2B, the direct wave from the transmitter 15 to the first receiving antenna 21A and the second receiving antenna 21B and the indirect wave reflected by the reflecting surface 10 The effects of are taken into account. In the fourth received power PB2, a null point appears near the distance D of about 4 m. That is, the difference in path length between the direct wave and the indirect wave from the transmitter 15 to the second receiving antenna 21B corresponds to a phase difference of 180 degrees.

Also in the third embodiment, the first candidate value D1 and the second candidate value D2 are obtained in the same manner as in the first embodiment. In the third embodiment, the third candidate value D3 is obtained by applying the third received power PA2 to the third received power-distance correspondence table 32C in the third distance calculation process 35C. In the fourth distance calculation process 35D, the fourth candidate value D4 is obtained by applying the fourth received power PB2 to the fourth received power-distance correspondence table 32D.

The distance selection unit 36 selects the most probable candidate value as the estimated value of the distance D from the first candidate value D1 to the fourth candidate value D4. For example, when the received power is a value in the vicinity of the null point, the S / N ratio of the received power is lowered, so that the accuracy of the estimated value of the distance D obtained from the received power is lowered. Therefore, when the magnitude of the received power is in the vicinity of the null point, it is preferable to exclude the received power when estimating the distance D. In the example shown in FIG. 5B, when the magnitude of the fourth received power PB2 is in the vicinity of −90 dBm, the first candidate value D4 obtained from the fourth received power PB2 is excluded, and the first An estimated value of the distance D may be obtained from the candidate value D1, the second candidate value D2, and the third candidate value D3. As an example, an estimate of the distance D can be obtained by applying majority logic.

In Example 3, since radio waves of two different frequencies are used, an estimated value of the distance D can be obtained based on four received powers having different change characteristics with respect to the distance D. For this reason, the estimation precision of distance D can be raised more.

[Example 4]
Next, with reference to FIGS. 6A to 6B, a position detection apparatus according to Embodiment 4 will be described. Hereinafter, differences from the second embodiment shown in FIGS. 3A to 3B and the third embodiment shown in FIGS. 4 and 5A to 5B will be described, and description of the same configuration will be omitted.

FIG. 6A shows a block diagram of the processing device 30 (FIG. 4) of the position detection device according to the fourth embodiment. Similar to the second embodiment illustrated in FIG. 3A, the processing device 30 includes a received power difference calculation unit 37 and a distance calculation unit 38, and further includes a distance selection unit 41. The received power difference calculation unit 37 executes a first received power difference calculation process 37A and a second received power difference calculation process 37B. The distance calculation unit 38 executes a first distance calculation process 38A and a second distance calculation process 38B. The memory 31 (FIG. 4) stores a first received power difference-distance correspondence table 33 and a second received power-distance correspondence table 34.

FIG. 6B shows an example of the first received power difference-distance correspondence table 33 and the second received power difference-distance correspondence table 34 in a graph format. The horizontal axis represents the distance D from the antenna installation position 13 to the transmitter 15 (FIG. 4) in the unit “m”, and the vertical axis represents the difference in received power in the unit “dBm”. The solid line in FIG. 6B is the same as the difference PA1-PB1 between the first received power PA1 and the second received power PB1 shown in FIG. 3B. The broken line in FIG. 6B indicates the difference PA2-PB2 between the third received power PA2 and the fourth received power PB2 shown in FIG. 5B.

The first received power difference calculation process 37A is the same as the process of the received power difference calculation unit 37 (FIG. 3A) of the position detection apparatus according to the second embodiment. The first distance calculation process 38A is the same as the process of the distance calculation unit 38 (FIG. 3A) of the position detection device according to the second embodiment. By executing the first distance calculating process 38A, the fifth candidate value D5 (FIG. 6B) is obtained.

In the second received power difference calculation process 37B, a difference PA2-PB2 between the third received power PA2 and the fourth received power PB2 is obtained. In the second distance calculation process 38B, the sixth candidate value D6 (FIG. 6B) is obtained by applying the difference PA2-PB2 to the second received power difference-distance correspondence table 34. In the example shown in FIG. 6B, the fifth candidate value D5 and the sixth candidate value D6 are about 5.5 m and about 6 m, respectively.

The distance selection unit 41 obtains an estimated value of the distance D based on the fifth candidate value D5 and the sixth candidate value D6. For example, the distance near the null point of the received power is excluded from the distance D estimation process. For example, when about 4 m is obtained as the sixth candidate value D6, as shown in FIG. 5B, the sixth candidate value D6 is in the vicinity of the null point. For this reason, the sixth candidate value D6 obtained as about 4 m is excluded from the distance D estimation process.

In the example shown in FIG. 6B, neither the fifth candidate value D5 nor the sixth candidate value D6 is near the null point. In this case, for example, the larger change amount of the received power difference with respect to the distance change is adopted as the estimated value of the distance D. In the example shown in FIG. 6B, the absolute value of the slope of the difference PA2-PB2 is larger than the absolute value of the slope of the difference PA1-PB1 in the vicinity of the distance 6m. Therefore, the sixth candidate value D6 is adopted as the estimated value of the distance D.

Thus, by obtaining the estimated value of the distance D based on the difference with the larger absolute value of the slope, the estimation accuracy can be increased.

[Example 5]
Next, with reference to FIG. 7, a position detection apparatus according to Embodiment 5 will be described.

FIG. 7 shows an example of a planar arrangement of the receiving antennas of the receiving device included in the position detecting device according to the fifth embodiment. In the first to fourth embodiments, the first receiving antenna 21A and the second receiving antenna 21B are installed at one antenna installation position 13 (FIGS. 1 and 4) in the in-plane direction of the reflecting surface 10. It was.

The position detection device according to the fifth embodiment includes a first receiving device 20A, a second receiving device 20B, and a third receiving device 20C. Each of the first receiving device 20A, the second receiving device 20B, and the third receiving device 20C is the receiving device 20 (FIGS. 1 and 4) of the position detecting device according to any one of the first to fourth embodiments. It has the same configuration as. That is, the first receiving device 20A, the second receiving device 20B, and the third receiving device 20C are respectively the first antenna installation position 13A, the second antenna installation position 13B, and the third antenna installation position 13C. Have two receiving antennas. The two receiving antennas are arranged at different positions in the height direction. The first antenna installation position 13A, the second antenna installation position 13B, and the third antenna installation position 13C are positions that are not aligned in a straight line with respect to the most surface direction of the reflecting surface 10 (FIGS. 1 and 4), that is, It is arranged at a position corresponding to the apex of the triangle.

The processing device 30 reflects from the first antenna installation position 13A to the transmitter 15 (FIGS. 1 and 4) based on the reception strength of the radio waves received by the two receiving antennas of the first receiving device 20A. A distance DA in the in-plane direction of the surface 10 is calculated. As a method for calculating the distance DA, the distance calculation method of the position detection device according to the first to fourth embodiments is applied. Similarly, the processing device 30 calculates the distance DB from the second antenna installation position 13B to the transmitter 15 and the distance DC from the third antenna installation position 13C to the transmitter 15.

Further, the processing device 30 determines the position of the transmitter 15 based on the distance DA, the distance DB, the distance DC, the first antenna installation position 13A, the second antenna installation position 13B, and the third antenna installation position 13C. presume. For example, a first circumference 14A having a radius of a distance DA centered on the first antenna installation position 13A, and a second circumference 14B having a radius of a distance DB centered on the second antenna installation position 13B, It is estimated that the transmitter 15 is disposed at a position where the third circumference 14C having the radius of the distance DC intersects with the third antenna installation position 13C as the center.

When the first circumference 14A, the second circumference 14B, and the third circumference 14C do not intersect at one point, a straight line passing through the intersection of the first circumference 14A and the second circumference 14B It is estimated that the transmitter 15 is arranged at a position where a straight line passing through the intersection of the second circumference 14B and the third circumference 14C intersects.

[Example 6]
With reference to FIG. 8, a position detection apparatus according to Embodiment 6 will be described. Hereinafter, differences from the first embodiment will be described, and description of the same configuration will be omitted.

FIG. 8 is a schematic diagram of a position detection apparatus according to the sixth embodiment. In the sixth embodiment, the first receiving antenna 21A, the second receiving antenna 21B, and the third receiving antenna 21C are located at the antenna installation position 13 with respect to the in-plane direction of the reflecting surface 10 and at different positions with respect to the height direction. Is arranged. The processing device 30 is based on the first reception power PA1 of the first reception antenna 21A, the second reception power PB1 of the second reception antenna 21B, and the fifth reception power PC1 of the third reception antenna 21C. Then, an estimated value of the distance D from the antenna installation position 13 to the transmitter 15 is obtained.

In the sixth embodiment, in addition to the first received power PA1 and the second received power PB1 shown in FIG. 2B, a relationship between the fifth received power PC1 and the distance D is given. The change characteristic of the fifth received power PC1 with respect to the distance D is different from both the change characteristics of the first received power PA1 and the second received power PB1. By using three received powers having different change characteristics with respect to the distance D and obtaining an estimated value of the distance D, the estimation accuracy can be further improved.

Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 10 Reflecting surface 13 Antenna installation position 13A 1st antenna installation position 13B 2nd antenna installation position 13C 3rd antenna installation position 14A 1st circumference 14B 2nd circumference 14C 3rd circumference 15 Transmitter 16 Shopping cart 20 receiving device 20A first receiving device 20B second receiving device 20C third receiving device 21A first receiving antenna 21B second receiving antenna 21C third receiving antenna 30 processing device 31 memory 32A first Received power-distance correspondence table 32B Second received power-distance correspondence table 32C Third received power-distance correspondence table 32D Fourth received power-distance correspondence table 33 First received power difference-distance correspondence table 34 Received power difference-distance correspondence table 35 distance calculating unit 35A first distance calculating process 35B second distance calculating process 35C third distance calculating process 35D fourth Separation calculation process 36 Distance selection part 37 Reception power difference calculation part 37A First reception power difference calculation process 37B Second reception power difference calculation process 38 Distance calculation part 38A First distance calculation process 38B Second distance calculation process 41 Distance selection part D, DA, DB, DC Distance D1 1st candidate value D2 2nd candidate value D3 3rd candidate value D4 4th candidate value D5 5th candidate value D6 6th candidate value H1 1st Receiving antenna height H2 second receiving antenna height PA1 first received power PA2 third received power PB1 second received power PB2 fourth received power PC1 fifth received power

Claims

A transmitter disposed above a reflecting surface for reflecting radio waves and emitting radio waves of a first frequency;
Including at least two receiving antennas arranged at the same position in the in-plane direction of the reflecting surface and at different positions in the height direction, and receiving the radio waves of the first frequency radiated from the transmitter by the receiving antenna. 1 receiving device;
A first distance in the in-plane direction of the reflecting surface from the receiving antenna to the transmitter based on the reception intensity of the radio wave of the first frequency received by the receiving antenna of the first receiving device. And a processing device for calculating the position.
The position detection device according to claim 1, wherein the processing device calculates the first distance based on a difference in reception intensity of radio waves received by the reception antenna.
The transmitter radiates a radio wave having a second frequency different from the first frequency in addition to the radio wave having the first frequency,
In addition to the first frequency radio wave radiated from the transmitter, the first reception device receives the second frequency radio wave with the reception antenna,
In addition to the reception intensity of the radio wave of the first frequency received by the reception antenna of the first reception apparatus, the processing device is configured to perform the first based on the reception intensity of the radio wave of the second frequency. The position detection device according to claim 1, wherein the distance is calculated.
The position detection device according to any one of claims 1 to 3, wherein the reception antenna of the first reception device receives a direct wave from the transmitter and an indirect wave reflected by the reflection surface.
further,
Including two receiving antennas arranged at the same position in the in-plane direction of the reflecting surface and at different positions in the height direction, and receiving the radio waves of the first frequency radiated from the transmitter by the two receiving antennas. A second receiving device;
Including two receiving antennas arranged at the same position in the in-plane direction of the reflecting surface and at different positions in the height direction, and receiving the radio waves of the first frequency radiated from the transmitter by the two receiving antennas. A third receiving device,
The reception antennas of the first reception device, the second reception device, and the third reception device are arranged at positions that do not line up in a straight line with respect to the in-plane direction of the reflection surface,
The processor is
Based on the reception strength of the radio waves of the first frequency received by the two reception antennas of the second reception device, the two reception antennas of the second reception device to the transmitter, Calculate a second distance for the in-plane direction of the reflecting surface;
Based on the reception strength of the radio waves of the first frequency received by the two receiving antennas of the third receiving device, the two receiving antennas of the third receiving device to the transmitter, Calculate a third distance in the in-plane direction of the reflecting surface;
The position of the two receiving antennas of each of the first receiving device, the second receiving device, and the third receiving device with respect to the in-plane direction of the reflecting surface, the first distance, and the second The position detection apparatus according to claim 1, wherein the position of the transmitter is calculated based on a distance and the third distance.