JP2009204572A - Position measuring device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position measuring device and a position measuring method for measuring the position of an object with a single transmitting antenna and a single receiving antenna. <P>SOLUTION: This position measuring device 1 for measuring the position of the object comprises the single transmitting antenna A<SB>1</SB>for radiating a transmitted signal to space, the single receiving antenna A<SB>2</SB>for receiving, as a received signal, scattered wave that is scattered by the object, propagates through a plurality of propagation routes, and arises from the transmitted signal, and an arithmetic processing section 13 for calculating the object position by a period reversing method based on the waveform of the received signal received by the receiving antenna A<SB>2</SB>. The plurality of propagation routes include at least one propagation route via an electric wave scattering object that can scatter the electric wave and has known shape and position. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a position measurement apparatus that measures the position of an object by radio waves, and in particular, by using multiple scattering by an object (scatterer) different from the object using a single transmission antenna and a single reception antenna. The present invention relates to a position measuring device for measuring the position of the object.

  Conventionally, a technique for measuring the position of an object by radiating a radio wave toward the object and measuring the reflected wave is known as a radar. In this radar field, in recent years, it has been proposed to use multiple scattering of an object, for example, disclosed in Non-Patent Document 1. In the technique disclosed in Non-Patent Document 1, a plurality of transmission antennas and reception antennas are used, and the position of an object is obtained by a so-called MUSIC method based on multiple scattered waves from a target object (target).

On the other hand, in the field of wireless communication, for example, as disclosed in Non-Patent Document 2, there is a communication technique using a time inversion method, and communication performance is improved. This is because when a signal propagated from a transmission antenna through multiple scattering paths is received by an array antenna and a signal obtained by reversing the signal is transmitted from the array antenna, the transmission signal is reproduced at the position of the original transmission antenna. Is used.
AJDevaney, “Time reversal imaging of obscured target from multistatic data”, IEEE Trans.on Ant. & Prop.vol.53, no.5, pp.1600-1610 May 2005. BEHenty, DDStancil, “Multipath-enabled super-resolution for rf and microwave communication using phase-conjugate arrays”, Physical Review Letters, vol. 93, no. 24, Art. No. 243904, Dec. 2004.

  By the way, in the above-mentioned Non-Patent Document 1 and Non-Patent Document 2, a plurality of transmitting antennas and a plurality of receiving antennas are used. In order to measure the position of an object with a desired accuracy using such a plurality of transmission antennas and a plurality of reception antennas, the position (distance) between the plurality of transmission antennas and the position (distance) between the plurality of reception antennas Must be fixed correctly. In addition, it is necessary to set the distance between the multiple transmitting antennas and the distance between the multiple receiving antennas appropriately according to the wavelength of the radio wave used and the desired distance resolution, which increases the size of the multiple transmitting antennas and the multiple receiving antennas. May end up. In addition, a transmission circuit corresponding to the number of transmission antennas and a reception circuit corresponding to the number of reception antennas are required, which hinders downsizing and cost reduction of the position measurement device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a position measuring apparatus and a position measuring method capable of measuring the position of an object with a single transmitting antenna and a single receiving antenna. Is to provide.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, according to one aspect of the present invention, in a position measurement device that measures the position of an object, a single transmission antenna that radiates a transmission signal to space and a scattered wave caused by the transmission signal scattered by the object. A single reception antenna that receives a scattered wave propagated through a plurality of propagation paths as a reception signal, and a position calculation that calculates the position of the object by a time inversion method based on the waveform of the reception signal received by the reception antenna The plurality of propagation paths include at least one propagation path through a radio wave scatterer capable of scattering radio waves and having a known shape and position. In another aspect of the present invention, in a position measurement method for measuring the position of an object, a transmission step of radiating a transmission signal from a single transmission antenna to space, and the transmission signal scattered by the object A reception step of receiving a scattered wave caused by a plurality of propagation paths as a reception signal with a single reception antenna, and a time reversal method based on a waveform of the reception signal received in the reception step. A position calculation step for calculating the position of the object, and the plurality of propagation paths include at least one propagation path through a radio wave scatterer capable of scattering radio waves and having a known shape and position. It is characterized by.

  In the position measuring apparatus and the position measuring method having such a configuration, a transmission signal is radiated into space by a single transmission antenna, and a reception signal is received by a single reception antenna. In addition to the target object, the received signal includes a scattered wave of a propagation path via a radio wave scatterer whose shape and position are known. Therefore, the position of the object can be calculated by the time inversion method based on the waveform of the received signal. Therefore, the position measuring apparatus and position measuring method having such a configuration can measure the position of an object using a single transmission antenna and a single reception antenna.

  Hereinafter, the basic concept of the present invention will be described more specifically. 1 and 2 are diagrams for explaining the basic idea of the present invention. 1A shows the configuration of the position measurement system, FIG. 1B shows the waveform of the transmitted radio wave, and FIG. 1C shows the waveform f (t) of the received radio wave. FIG. 2A shows a waveform f (−t) of a received radio wave that has been time-reversed, and FIG. 2B shows a waveform in which the received radio wave that has been time-reversed is reversely propagated from a predetermined antenna through a first path. FIG. 2 (C) shows a waveform in which the time-reversed received radio wave is reversely propagated from the predetermined antenna through the second path, and FIG. 2 (D) shows the time-reversed received radio wave from the predetermined antenna to the third path. FIG. 2E shows a waveform obtained by superimposing FIGS. 2B to 2D. FIG. The horizontal axis in FIGS. 1B and 1C and FIGS. 2A to 2E is time, and the vertical axis is amplitude (intensity).

  As shown in FIG. 1A, the position measurement system S includes a position measurement device 1 and a radio wave scatterer K, and measures the position of an object T. The radio wave scatterer K is composed of a member that scatters radio waves, and its shape and position are known.

In the position measurement system S having such a configuration, the position measurement apparatus 1 radiates a transmission signal from a single transmission antenna to the space, and uses a scattered wave scattered by the object T or the radio wave scatterer K as a reception signal. Receive with the receiving antenna. The single transmission antenna and the single reception antenna may be configured by separate antennas, respectively, or may be configured by a single antenna. “Single transmit antenna” and “single receive antenna” include not only the case where each is constituted by a separate antenna, but also the case where such a double antenna is constituted by a single antenna. . For example, if a single pulse Ws is radiated at time t ₀ as shown in FIG. 1B as the transmission signal Ws, the scattered wave caused by the object T and the radio wave scatterer K in the example shown in FIG. Since there are three propagation paths, the first to third paths P1 to P3, the first to third pulses Wr1 to Wr3 are received as the reception signal Wr. Note that the pulse Ws shown in FIG. 1B has a convenient waveform shape used to simplify the description, and the transmission signal Ws used in the actual position measurement apparatus 1 will be described later.

  The first path P1 is a propagation path from the position measurement device 1 to the object T and from the object T to the position measurement device 1. The second path P2 is a propagation path from the position measurement device 1 to the object T, from the object T to the radio wave scatterer K, and from the radio wave scatterer K to the position measurement device 1. The second route P2 includes the reverse route described above, and the second route P2 is degenerated. The third path P3 is a propagation path from the position measurement device 1 to the radio wave scatterer K, from the radio wave scatterer K to the object T, from the object T to the radio wave scatterer K, and from the radio wave scatterer K to the position measurement device 1. It is.

The distance between the position measuring device 1 and the object T is d1, the distance between the position measuring device 1 and the radio wave scatterer K is d2, and the distance between the object T and the radio wave scatterer K is d3. and in the case where the first pulse Wr1 of the received signal Wr received by propagating the first path P1 is received from the time t ₀ at 2d1 / c time elapsed time, to propagate the second path P2 second pulse Wr2 of the received signal Wr received by is received from the time _{t 0} in (d1 + d2 + d3) / c time elapsed time, and, of the received signal Wr received by propagating the third path P3 third pulse Wr3 is received from the time _{t 0} at 2 (d2 + d3) / c time elapsed time. Here, c is the propagation speed of the radio wave, is determined by the propagation medium of the radio wave, and is the speed of light when the radio wave propagation medium is a vacuum.

  Here, since the shape and position of the radio wave scatterer K are known, the distance d2 is known. The distance d1 and the distance d3 are unknown, and in order to obtain the position of the object T, the position measuring device 1 may obtain the distance d1 and the distance d3.

When the time reversal method is applied to obtain the distance d1 and the distance d3, the waveform f (-t) of the reception signal RWr obtained by time reversal of the waveform f (t) of the reception signal Wr is set to one antenna (identical to the same). The function g (t, r) obtained by superimposing the waveforms of the reception signals RWr that have been reversely propagated through the plurality of propagation paths and that have been time-reversed is true when the position of the object T is true. Only when the position is R _true (where R _true is a position vector), the phase becomes coherent at time t = −t ₀ , and g (t, r) strengthens.

  More specifically, first, the waveform f (t) of the reception signal Wr is time-reversed, and the waveform f (-t) of the reception signal RWr that is time-reversed is generated. For example, as shown in FIG. 1C, in the case of the reception signal Wr composed of the first pulse Wr1, the second pulse Wr2, and the third pulse Wr3 in the order of reception time, as shown in FIG. When reversed, the third pulse RWr3 obtained by time-reversing the third pulse Wr3, the second pulse RWr2 obtained by time-reversing the second pulse Wr2, and the first pulse RWr1 obtained by time-reversing the first pulse Wr1 are arranged in this order. In FIGS. 1 and 2, since the first to third pulses Wr1 to Wr3 are symmetrical with respect to the peak, the time-reversed first to third pulses RWr1 to Wr3 shown in FIG. Each of the third pulses Wr1 to Wr3 has the same shape.

  Next, this time-reversed reception signal RWr is propagated back from one antenna. For example, in the example shown in FIG. 1A, when the time-reversed reception signal RWr shown in FIG. 2A is propagated back in the first path P1, only 2d1 / c is obtained as shown in FIG. 2B. When time-shifted and back-propagated through the second path P2, as shown in FIG. 2C, it is time-shifted by (d1 + d2 + d3) / c and back-propagated through the third path P3, as shown in FIG. Thus, the time is shifted by 2 (d2 + d3) / c.

Then, a function g (t, r) = f (−t + (2d1 / c)) + f obtained by superimposing the waveforms of the reception signals RWr that have been reversely propagated through the first to third paths P1 to P3, respectively. (−t + ((d1 + d2 + d3) / c)) + f (−t + (2 (d2 + d3) / c)) is as shown in FIG. 2 (E) only when the position of the object T is the true position R _true . At the time t = −t ₀ , the phase becomes the same and the amplitude becomes maximum. Therefore, the position vector r may be varied to obtain the function g (t, r), and the position vector r that maximizes the function g (t, r) may be obtained. This position vector r is the position R _true of the object T and represents the position of the object T. The function g (t, r) is referred to as a position search function g (t, r).

  As described above, the position measuring apparatus 1 can measure the position of the object T with a single transmission antenna and a single reception antenna.

  Further, in the above-described position measuring apparatus, the position calculating unit calculates the position of the object by a time reversal method in which scattering by the radio wave scatterer is geometric optical scattering. According to this configuration, since the scattering by the radio wave scatterer is assumed to be geometric optical scattering, the calculation processing for calculating the position of the object is further simplified. For this reason, it is possible to reduce the cost of the apparatus for executing the arithmetic processing and shorten the arithmetic processing time.

  In the position measuring apparatus, the position calculating unit calculates the position of the object by a time reversal method using a solution of a scattered electric field by the radio wave scatterer. According to this configuration, since the solution of the scattered electric field by the radio wave scatterer is used, the position of the object can be calculated with higher accuracy. The solution of the scattered electric field may be an approximate solution, but in particular, when the radio wave scatterer is a conductor sphere, an exact solution has been obtained and the position of the object can be calculated with higher accuracy. It becomes.

  Further, in the above-described position measuring devices, the radio wave scatterers are plural. According to this configuration, since there are a plurality of radio wave scatterers, the multiple propagation paths include more multiple scattering paths, and the position of the object can be calculated with higher accuracy.

  In the above-described position measurement devices, the transmission signal is a UWB pulse. According to this configuration, since the transmission signal is a UWB pulse, it is possible to provide a position measuring device with high distance resolution. For example, it is possible to provide a position measuring apparatus capable of measuring a position with an error of several tens cm. In order to measure the position with higher accuracy, it is preferable that the UWB pulse is a monocycle pulse composed of one cycle of pulses.

  The position measuring apparatus and the position measuring method according to the present invention can measure the position of an object with a single transmitting antenna and a single receiving antenna.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 3 is a block diagram illustrating a configuration of the position measurement apparatus according to the embodiment. In FIG. 3, the position measurement apparatus 1 includes a transmission antenna A ₁ , a reception antenna A ₂ , a signal generation unit 11, a signal reception unit 12, an arithmetic processing unit 13, an interface unit 14, an input unit 15, An output unit 16, a storage unit 17, and a bus 18 are provided.

The transmission antenna A ₁ is an omnidirectional antenna that converts the electric signal pulse generated by the signal generation unit 11 into a radio wave transmission pulse and radiates the transmission pulse as a transmission signal to space. The receiving antenna A ₂ receives scattered waves caused by a transmission signal scattered by the target object T and propagated through a plurality of propagation paths, converts them into received waves of electric signals, and converts the received waves to An antenna that outputs a received signal to the signal receiving unit 12.

Then, the transmitting antenna A ₁ is constituted by a single antenna, or receive antenna A ₂ consisting of a single antenna. In the example illustrated in FIG. 3, the transmission antenna A ₁ and the reception antenna A ₂ are each configured as separate antennas, but may also be configured as a single antenna.

The transmission pulse is a radio wave in which electromagnetic wave energy is concentrated in a predetermined time range. As the ratio band B ₀ / f _tr, which is the ratio of the occupied bandwidth B ₀ to the center frequency f _tr in the transmission pulse, increases, the measurement accuracy improves. Here, if the larger and smaller frequencies of −10 dB with respect to the maximum value of the power spectrum are f _H and f _L , respectively, the center frequency f _tr is (f _H + f _L ) / 2. The occupied bandwidth B ₀ is (f _H −f _L ). An example of such a transmission pulse is a UWB (Ultra Wide Band) pulse defined by the US FCC (Federal Communications Commission). The definition of the US FCC is, for example, “Subpart F-Ultra-Wideband Operation § 15.503 Definitions” [online], search on June 3, 2005, Internet <URL: http: // a257. g. akamaitech. net / 7/257/2422/12 feb20041500 / edocket. access. gpo. gov / cfr_2004 / octqtr / pdf / 47cfr15.503. pdf>. In addition, the transmission pulse is a monocycle pulse including, for example, a one-cycle pulse shown in FIG. 6 described later from the viewpoint of further improving measurement accuracy.

The scattered wave caused by the transmission signal includes not only the scattered wave that is transmitted from the transmission antenna A ₁ but reflected by the object T and received by the reception antenna A ₂ , and the transmission signal that is radiated from the transmission antenna A _1. A scattered wave that is reflected by one or a plurality of other objects other than the object T and then reflected by the object T and received by the receiving antenna A ₂ or a transmission signal radiated from the transmitting antenna A ₁ is reflected by the object T. Furthermore, the scattered wave reflected by one or more other objects except the object T and received by the receiving antenna A ₂ , or the transmission signal radiated from the transmitting antenna A ₁ is one or more other objects excluding the object T ( is reflected by the first object) reflected by the object T from the scattered waves also includes received by the reception antenna a ₂ was further reflected in one or more other objects except the object T (second object). The first object and the second object may be the same or different.

  The plurality of propagation paths include at least one propagation path via the radio wave scatterer K. The radio wave scatterer K is composed of a member that scatters radio waves, and its shape and position are known. The radio wave scatterer K may be any member as long as it scatters radio waves, but is preferably a conductor such as metal, for example, because it generates scattered radio waves with stronger intensity. In addition, the shape of the radio wave scatterer K is preferably a simple shape such as a sphere because the calculation processing of the position scanning unit 132 described later in the calculation processing unit 13 becomes easy.

Signal generating unit 11 generates a pulse of the electrical signal corresponding to the transmission pulses to be transmitted in accordance with the control of the processor 13 via the interface unit 14, and outputs to the transmission antenna A _1. The signal receiving unit 12 A / D-converts the received wave input from the receiving antenna A ₂ and stores it in the storage unit 17 as a received signal via the interface unit 14. The signal receiving unit 12, as necessary reception wave input from the reception antenna A _2, may be amplified. Further, since the direct wave directly received by the receiving antenna A ₂ from the radio wave radiated by the transmitting antenna A ₁ becomes an unnecessary interference wave in measuring the scattered wave, the signal receiving unit 12 is required to perform the A / D conversion before the A / D conversion. Alternatively, this direct wave may be removed after A / D conversion. In this direct wave removal processing, the waveform of the received signal d (t) when the target object T does not exist is stored in advance, and the direct wave is calculated by calculating f (t) −d (t + τ _a ). Remove. Here, f (t) is a received signal during measurement of scattered waves, and τ _a is a case where the correlation between f (t) and the signal d (t + τ _a ) is maximized. In addition, since the target object T is far from the reception antenna A ₂ compared to the transmission antenna A ₁ , the reception time zone of the direct wave and the reception time zone of the scattered wave can be separated in time. In some cases, the direct wave can be removed by not measuring or ignoring the received signal in the reception time zone of the direct wave.

  The interface unit 14 is an interface circuit for exchanging signals among the signal generation unit 11, the signal reception unit 12, the arithmetic processing unit 13, and the storage unit 17. The input unit 15 measures various commands such as a command for starting a position measurement program for measuring the position of the target object T, a command for instructing transmission / reception of transmission pulses, and the position of the target object T by the method of the present invention. For example, it is a device that inputs various data such as the position and shape of the radio wave scatterer K and the distance d2 between the position measurement device 1 and the radio wave scatterer K to the position measurement device 1, such as a keyboard and a mouse. It is. The output unit 16 is a device that outputs the command and data input from the input unit 15 and the position of the object measured by the position measurement apparatus 1, and includes, for example, a CRT display, LCD, organic EL display, plasma display, and the like. Display devices and printing devices such as printers.

  The storage unit 17 functionally includes a reception waveform storage unit 171 that stores a waveform of the reception signal from the signal reception unit 12, and a waveform of the reception signal that is time-reversed from the reception signal stored in the reception waveform storage unit 171. A time reversal waveform storage unit 172 for storing and a scan result storage unit 173 for storing a scan result of the position search function g (t, r) are provided, and are necessary for executing various programs such as a position measurement program and various programs. Various data such as data and data generated during the execution are stored. The storage unit 17 is, for example, a volatile storage element such as a RAM (Random Access Memory) serving as a so-called working memory of the arithmetic processing unit 13, a ROM (Read Only Memory) or a rewritable EEPROM (Electrically Erasable Programmable Read Only Memory). And the like, and a hard disk for storing various programs and various data.

Processor 13, for example, is configured to include a microprocessor and its peripheral circuits, etc., calculates the position of the object T by the time reversing method on the basis of the waveform f (t) of the received signal received by the reception antenna A ₂ Is. In the present embodiment, the arithmetic processing unit 13 calculates the position of the object T by a time reversal method in which the scattering by the radio wave scatterer K is geometric optical scattering. The arithmetic processing unit 13, for example, functionally generates a time-reversed waveform generation unit 131 that generates a waveform f (−t) of the received signal that is time-reversed by time-reversing the waveform f (t) of the received signal, Assuming that the scattering by the radio wave scatterer K is geometric optical scattering, the position scanning unit 132 that searches for the position of the object T based on the waveform f (−t) of the reception signal that is time-reversed, and the search result of the position scanning unit 132 Is output to the output unit 16, and the signal generation unit 11, the signal reception unit 12, the interface unit 14, the input unit 15, the output unit 16, and the storage unit 17 are respectively set according to the function according to the control program. Control.

  The arithmetic processing unit 13, the interface unit 14, the input unit 15, the output unit 16, and the storage unit 17 are connected by a bus 18 so that signals can be exchanged with each other.

The arithmetic processing unit 13, the interface unit 14, the input unit 15, the output unit 16, the storage unit 17, and the bus 18 are configured by, for example, a computer, more specifically a personal computer such as a notebook type or a desktop type. Is possible. The signal generating unit 11, the transmitting antenna A _1, the receiving antennas A ₂ and the signal reception section 12 may also be formed by a known configuration used to radar.

  Note that the position measurement apparatus 1 may further include an external storage unit 19 as indicated by a broken line as necessary. The external storage unit 19 is, for example, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-R (Compact Disc Recordable), a DVD-R (Digital Versatile Disc Recordable), a Blu-ray Disc (Blu-ray Disc), or the like. An apparatus that reads data from and / or writes data to a recording medium, such as a flexible disk drive, a CD-ROM drive, a CD-R drive, a DVD-R drive, and a Blu-ray disk drive.

  Here, when a position measurement program or the like is not stored, the position measurement program or the like may be installed in the storage unit 17 via the external storage unit 19 from a recording medium on which the position measurement program or the like is recorded. Alternatively, data such as acquired reception signals and data representing the estimated shape of the object may be recorded on a recording medium via the external storage unit 19.

  Next, the operation of this embodiment will be described. FIG. 4 is a flowchart showing the operation of the position measurement apparatus according to the first embodiment. For example, when a position measurement program activation command is received from the input unit 15, the position measurement device 1 executes the position measurement program. When the position measurement program is executed, a time reversal waveform generation unit 131, a position scanning unit 132, and an output processing unit 133 are functionally configured in the arithmetic processing unit 13, and a reception waveform storage unit 171 functionally in the storage unit 17. A time reversal waveform storage unit 172 and a scanning result storage unit 173 are configured. When receiving a start command for starting the measurement of the position of the object T from the input unit 15, the position measurement device 1 starts measuring the position of the object T.

More specifically, in FIG. 4, first, the position measuring device 1 generates a pulse of an electric signal corresponding to the transmission pulse by the signal generation unit 11 under the control of the arithmetic processing unit 13, and this is transmitted by the transmission antenna A ₁ . The electric signal pulse is converted into a radio wave transmission pulse, and this transmission pulse is radiated to the space as a transmission signal (S11).

The transmission pulse radiated into the space propagates through the space with time and is scattered by the target object T and the radio wave scatterer K. Scattered waves reach the receiving antenna A ₂ follow a different propagation path.

The position measuring apparatus 1 receives the scattered wave by the receiving antenna A ₂ and converts it into a received wave of an electric signal under the control of the arithmetic processing unit 13, and A / D converts the received wave by the signal receiving unit 12, The received signal is stored in the received waveform storage unit 171 of the storage unit 17 through the interface unit 14 (S12). For example, the reception signal is sampled at a predetermined sampling period set in advance, and stored in the order of address in the storage area assigned as the reception waveform storage unit 171 in the sampled order. For example, the intensity of the sampled received signal at the sampling time ST _S (level) RP _S is stored in the address the add _S.

For example, when a predetermined time elapses after the transmission pulse is transmitted, the position measurement apparatus 1 determines the position of the object T by the time reversal method based on the waveform f (t) of the received signal (scattered wave). Calculate. The predetermined time is, for example, a sufficient time to receive the scattered wave, for example, according to the transmission power of the transmitted pulse, the receiving antenna A ₂ of the reception sensitivity and the position measuring apparatus 1 for searching an object T range, etc. Is set appropriately. Further, for example, when receiving an output command for instructing the output of the position of the object T from the input unit 15, the position measurement device 1 performs the time inversion method on the object T based on the waveform f (t) of the received signal (scattered wave). Calculate the position.

More specifically, first, the time reversal waveform generation unit 131 of the arithmetic processing unit 13 time-reverses the received signal waveform f (t) stored in the reception waveform storage unit 171 and time-reverses the received signal. Waveform f (-t) is generated, and the generated time-reversed received signal waveform f (-t) is stored in the time-reversed waveform storage unit 172 (S13). For example, when the received signal is stored in the received waveform storage unit 171 as described above, the time-reversed received signal is the address stored first from the address stored last in the storage area of the received waveform storage unit 171. Are generated by sequentially reading the received signals. For example, when each strength (level) RP _S (S = ₁ to _Q ) of the received signal is stored in order from the address add ₁ to the address add _Q , the received signal is sequentially transmitted from the address add _Q to the address add ₁ . By reading each intensity (level) RP _S (S = 1 to Q) (by reading in the reverse order from the storage order), the waveform f (−t) of the reception signal that is time-reversed is generated.

  Next, the position scanning unit 132 of the arithmetic processing unit 13 searches for the position of the object T based on the waveform f (−t) of the reception signal that is time-reversed assuming that the scattering by the radio wave scatterer K is geometric optical scattering. To do.

More specifically, the position scanning unit 132 first generates a position search function g (t, r) based on the waveform f (−t) of the reception signal that is time-reversed (S14). The position search function g (t, r) is a time-reversed received signal waveform f for each of the plurality of propagation paths M used for calculating the position of the object T among the plurality of propagation paths L of the scattered wave. (−t) is shifted by the propagation time α _N (N = 1 to M) of the propagation path, and the sum of these shifted waveforms f (−t + α _N ) is obtained. Here, the plurality of propagation paths M used for calculating the position of the object T include at least one propagation path via the radio wave scatterer K. t is the time, is the transmitted pulse from the transmitting antenna A ₁ and time is radiated into space t0 (= 0), r is the position vector. In the case shown in FIG. 1, as described above, the position search function g (t, r) = f (−t + (2d1 / c)) + f (−t + ((d1 + d2 + d3) / c)) + f (−t + (2 (D2 + d3) / c)).

  Next, the position scanning unit 132 calculates the position search function g (t0, r) (t = t0 = 0) by changing r of the position vector to various values within a predetermined range set in advance. The result value is stored in the search result storage unit 173 of the storage unit 17 (S15). The predetermined range is appropriately set according to, for example, the range of the position measurement device 1 that searches for the object T.

  Next, the position scanning unit 132 determines whether or not the position search function g (t0, r) has been calculated for all position vectors r within the predetermined range (S16). If the position search function g (t0, r) is calculated for all position vectors r as a result of this determination (Yes), the process S17 is executed, while the position search function g (t0) for all position vectors r. , R) is not calculated (No), the process is returned to the process S14.

  In the processing S17, the output processing unit 133 of the arithmetic processing unit 13 outputs each value of the position search function g (t, r) stored in the scanning result storage unit 173 at each position in order to output the position of the object T. The data is output to the output unit 16 in association with the vector r. Then, the measurement process of the position of the object T is completed.

In the position measuring apparatus 1 according to this embodiment, since operating in this manner, it is possible to measure the position of the object T with a single transmit antenna A ₁ and a single receive antenna A _2. Further, in the position measuring apparatus 1, the position of the object T is calculated by a time reversal method in which the scattering by the radio wave scatterer K is geometric optical scattering. For this reason, the calculation processing for calculating the position of the object T is further simplified. Therefore, it is possible to reduce the cost of the arithmetic processing unit 13 that executes this arithmetic processing and to shorten the arithmetic processing time.

  One result of simulating the position measurement of the object T by the position measurement apparatus 1 according to the present embodiment will be described below.

  FIG. 5 is a diagram illustrating a radio wave scatterer and a target object in the simulation. FIG. 6 is a diagram illustrating a waveform of a transmission pulse in the simulation. The horizontal axis in FIG. 5 is time (wavelength) / wavelength (wavelength), and the vertical axis is amplitude. FIG. 7 is a diagram illustrating a waveform of a reception signal in the simulation. The horizontal axis in FIG. 7 is time (Time) expressed in nanoseconds (ns), and the vertical axis is amplitude. The same applies to FIGS. 10 and 14 described later. FIG. 8 is a diagram illustrating each value of the position search function in the xy plane. The horizontal axis in FIG. 8 is the x-axis, and the vertical axis is the y-axis. The size of the position search function is represented by gradation, and the size of the position search function increases as the color changes from white to black. In FIG. 11, the true position of the target object T is indicated by ●. In FIG. 8, the true position of the target object T is indicated by ●. The same applies to FIG. 11, FIG. 15, FIG. 17, and FIG.

In this simulation, as shown in FIG. 5, the radio wave scatterer K is a conductor sphere having a radius of 20 cm, and the center thereof is set to the coordinate origin (0, 0, 0). The target object T is a small conductor sphere having a radius of 1 cm, and is arranged so that the center thereof is the coordinates (40, 40, 0). For the position measuring device 1, these specifications of the target object T are unknown. Also, a single transmit antennas A ₁ and a single receive antenna A ₂ is also used, the same antenna (receiving antenna A) is used to transmit and receive (monostatic radar). The transmitting / receiving antenna A is arranged at coordinates (0, 45, 0). A radio wave medium is a vacuum free space.

  In this simulation, when the transmission / reception antenna A transmits a transmission pulse Ws, which is a monocycle pulse having a center frequency of 3 GHz and a wavelength of 10 cm, as shown in FIG. 6, the reception signal Wr having the waveform shown in FIG. 7 is received. The As described above, the propagation path of the scattered wave caused by the transmission pulse Ws has the three paths of the first to third paths P1 to P3. First to third pulses Wr1 to Wr3 respectively corresponding to the first to third paths P1 to P3 are included. This received signal was obtained by the FDTD method that is generally known as a numerical calculation method in the time domain of radio wave propagation. The FDTD method is a method of calculating the time change of an electromagnetic field by discretizing the Maxwell equation and alternately obtaining a magnetic field and an electric field.

  Based on the waveform f (t) of the received signal shown in FIG. 7, the result of calculating the position of the object T by the time reversal method assuming that the scattering by the radio wave scatterer K is geometric optical scattering is shown in FIG. FIG. 8 shows the value of each position search function g (0, r) in the xy plane obtained for each position vector r.

  As can be seen from FIG. 8, the peak of the position search function g (0, r) appears at the true position of the target object T, and the position of the target object T is determined by the position measuring apparatus 1 having the above-described configuration and operation. It is understood that it can be measured.

  Next, another embodiment will be described.

(Second Embodiment)
In the first embodiment, the position of the target object T is measured by using one radio scatterer K. In the second embodiment, the target object T is measured by using a plurality of radio scatterers K. The position is measured. As a result, the number of scattered wave propagation paths is increased as compared with the case of one radio wave scatterer K, and the position of the target object T can be calculated with higher accuracy.

  Therefore, in the second embodiment, only the position search function g (t, r) is different from that in the first embodiment, and the configuration and operation of the position measurement apparatus 1 according to the second embodiment are the same as those in the first embodiment. Since it is the same as that of the structure and operation | movement of the position measuring apparatus 1 concerning this, the description is abbreviate | omitted.

  One result of simulating the position measurement of the object T by the position measurement apparatus 1 according to the present embodiment will be described below.

  FIG. 9 is a diagram illustrating a plurality of radio wave scatterers and a target object in the simulation. FIG. 10 is a diagram illustrating a waveform of a reception signal in the simulation. FIG. 11 is a diagram illustrating each value of the position search function in the xy plane.

  In this simulation, as shown in FIG. 9, the radio wave scatterer K is constituted by first to fourth radio wave scatterers K1 to K4. The first to fourth radio wave scatterers K1 to K4 are conductor spheres having a radius of 5 cm. The center of the first radio wave scatterer K1 is set to the coordinates (30, 30, 10), and the center of the second radio wave scatterer K2 is arranged to be the coordinates (-10, -10, 30). The center of the scatterer K3 is arranged so as to have coordinates (50, 0, −20), and the center of the fourth radio wave scatterer K4 is arranged so as to have coordinates (−10, 10, −10). . The target object T is a small conductor sphere having a radius of 0.5 cm, and is arranged so that the center thereof is the coordinates (0, −10, 0). For the position measuring device 1, these specifications of the target object T are unknown. Similarly to the simulation of the first embodiment, monostatic radar is employed, and the transmission / reception antenna A is arranged at the coordinate origin (0, 0, 0). A radio wave medium is a vacuum free space.

  In the present specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

  Also in this simulation, when the transmission / reception antenna A transmits a transmission pulse Ws, which is a monocycle pulse having a center frequency of 3 GHz and a wavelength of 10 cm, shown in FIG. 6, the reception signal Wr having the waveform shown in FIG. 10 is received.

  The plurality of propagation paths include, for example, various paths such as paths that pass through the plurality of radio wave scatterers K. Of these, the first to fourth radio wave scatterers K1 to K4 are first to fourth. Third paths P1 to P3 (paths passing through one radio wave scatterer K) are adopted, and a total of 12 propagation paths are used for measuring the position of the target object T.

  Based on the waveform f (t) of the received signal shown in FIG. 10, the result of calculating the position of the object T by the time reversal method assuming that the scattering by the radio wave scatterer K is geometric optical scattering is shown in FIG. FIG. 11 shows the value of each position search function g (0, r) in the xy plane obtained for each position vector r.

  As can be seen from FIG. 11, the maximum peak of the position search function g (0, r) appears in the vicinity of the true position of the target object T, and the target object T is detected by the position measuring apparatus 1 having the above-described configuration and operation. It is understood that the position of can be measured.

  Further, in the first embodiment, as can be seen from FIG. 8, the peak of the position search function g (0, r) appears as a virtual image in addition to the true position of the target object T, and the position of the target object T In the second embodiment, the maximum peak of the position search function g (0, r) appears near the true position of the target object T, as can be seen from FIG. The erroneous estimation of the position is reduced, and the position of the target object T can be measured with higher accuracy.

  Next, another embodiment will be described.

(Third embodiment)
In the first and second embodiments, the position of the object T is calculated by the time reversal method in which the scattering by the radio wave scatterer K is geometric optical scattering, but in the third embodiment, the scattered electric field of the radio wave scatterer K is The position of the object T is calculated by the time reversal method using the solution. Therefore, the configuration and operation of the position measurement apparatus 1 according to the third embodiment are the same as those of the first and second embodiments except that the position scanning unit 132 of the arithmetic processing unit 13 is different from the position measurement apparatus 1 according to the first and second embodiments. Since it is the same as that of the structure and operation | movement of the position measuring apparatus 1 concerning 2nd Embodiment, the description is abbreviate | omitted.

  The calculation processing unit 13 in the position measurement apparatus 1 of the third embodiment calculates the position of the object T by the time reversal method using the solution of the scattered electric field by the radio wave scatterer K, and the position scanning unit 132 includes: The position of the object T is searched based on the waveform f (−t) of the reception signal that is time-reversed using the solution of the scattered electric field by the radio wave scatterer K. The solution of the scattered electric field may be an approximate solution. In particular, when the radio wave scatterer K is a conductor sphere, an exact solution is obtained, and the position of the object T is calculated with higher accuracy. Is possible.

  Next, the operation of this embodiment will be described. FIG. 12 is a flowchart showing the operation of the position measuring apparatus according to the third embodiment. For example, as in the first and second embodiments, when a start command for the position measurement program is received from the input unit 15 and a start command for starting the measurement of the position of the object T is received from the input unit 15, the position measurement device 1 starts measuring the position of the object T.

More specifically, in FIG. 12, first, the position measurement device 1 generates a pulse of an electric signal corresponding to the transmission pulse in the signal generation unit 11 under the control of the arithmetic processing unit 13, similarly to the processing S <b> 11. converts pulses of the electrical signal to the radio wave of the transmitted pulse at the transmission antennas a _1, it emits the transmitted pulse to the space as a transmission signal (S21).

The transmission pulse radiated into the space propagates through the space with the passage of time and is scattered by the target object T and one or more radio wave scatterers K. Scattered waves reach the receiving antenna A ₂ follow a different propagation path.

The position measuring device 1 receives the scattered wave by the receiving antenna A ₂ and converts it into a received wave of an electric signal under the control of the arithmetic processing unit 13 as in the process S 12, and the received signal is received by the signal receiving unit 12. A / D conversion is performed and the received signal is stored in the received waveform storage unit 171 of the storage unit 17 via the interface unit 14 (S22).

  Then, for example, as in the first and second embodiments, the position measuring device 1 performs time reversal based on the waveform f (t) of the received signal (scattered wave) by the passage of a predetermined time or the reception of an output command. The position of the object T is calculated by the method.

  More specifically, first, the time reversal waveform generation unit 131 of the arithmetic processing unit 13 performs time reversal on the waveform f (t) of the reception signal stored in the reception waveform storage unit 171 in the same manner as the processing S13. The time-reversed received signal waveform f (-t) is generated, and the generated time-reversed received signal waveform f (-t) is stored in the time-reversed waveform storage unit 172 (S23).

  Next, the position scanning unit 132 of the arithmetic processing unit 13 uses the solution of the scattered electric field by the radio wave scatterer K to search for the position of the object T based on the waveform f (−t) of the reception signal that is time-reversed. To do.

  This calculation may be performed in the time domain t, but in the present embodiment, this calculation is performed in the frequency domain ω as follows in order to simplify the calculation, shorten the calculation time, and the like. The

  More specifically, the position scanning unit 132 first performs Fourier transform on the time-reversed received signal waveform f (−t) to generate a time-reversed received signal waveform F (ω) in the frequency domain ω. (S24).

  Next, the position scanning unit 132 uses the solution of the scattered electric field by the radio wave scatterer K for each of the plurality of propagation paths M used for calculating the position of the object T in the plurality of propagation paths L of the scattered wave. As a result, a transfer function H (ω, r) is generated (S25). Here, the plurality of propagation paths M used for calculating the position of the object T include at least one propagation path via the radio wave scatterer K.

  Next, the position scanning unit 132 uses a plurality of reception signal waveforms F (ω) time-reversed in the frequency domain ω and a plurality of positions used for calculating the position of the object T in the plurality of propagation paths L of the scattered wave. By multiplying each transfer function H (ω, r) of the propagation path M, a position search function G (ω, r) = F (ω) · H (ω, r) in the frequency domain ω is generated ( S26).

Next, in order to return from the frequency domain ω to the time domain t, the position scanning unit 132 performs an inverse Fourier transform on the position search function G (ω, r) in the frequency domain ω to obtain a position search function g (t, r) is generated (S27). t is the time, is the transmitted pulse from the transmitting antenna A ₁ and time is radiated into space t0 (= 0), r is the position vector.

  Next, as in the process S15, the position scanning unit 132 shifts the position vector r to various values within a predetermined range set in advance, and the position search function G (t0, r) (t = t0 = 0). And the value of the calculation result is stored in the search result storage unit 173 of the storage unit 17 (S28).

  Next, the position scanning unit 132 determines whether or not the position search function g (t0, r) has been calculated for all the position vectors r within the predetermined range, similarly to the process S16 (S29). If the position search function g (t0, r) is calculated for all position vectors r as a result of this determination (Yes), the process S30 is executed, while the position search function g (t0) for all position vectors r. , R) is not calculated (No), the process is returned to the process S25.

  In the processing S30, as in the processing S17, the output processing unit 133 of the arithmetic processing unit 13 outputs the position search function g (t, r) stored in the scanning result storage unit 173 in order to output the position of the object T. Each value is output to the output unit 16 in association with each position vector r. Then, the measurement process of the position of the object T is completed.

In the position measuring apparatus 1 according to this embodiment, since the work such, it is possible to measure the position of the object T with a single transmit antenna A ₁ and a single receive antenna A _2. Further, in this position measuring apparatus 1, a solution of the scattered electric field by the radio wave scatterer K is used. For this reason, the position of the object T can be calculated with higher accuracy. In addition, when the radio wave scatterer K is a conductor sphere, the exact solution is obtained, so that the position of the object T can be calculated with higher accuracy.

  One result of simulating the position measurement of the object T by the position measurement apparatus 1 according to the present embodiment will be described below.

  FIG. 13 is a diagram illustrating a plurality of radio wave scatterers and a target object in the simulation. FIG. 14 is a diagram illustrating a waveform of a reception signal of a simulation when there is a target object at the first coordinate. FIG. 15 is a diagram illustrating each value of the position search function in the xy plane. FIG. 15A shows the result when the target object T is at the first coordinate C1, and FIG. 15B shows the result when the target object T is at the second coordinate C2. FIG. 15C shows the result when the target object T is at the third coordinate C3, FIG. 15D shows the result when the target object T is at the fourth coordinate C4, and FIG. (E) shows the result when the target object T is at the fifth coordinate C5.

  In this simulation, as shown in FIG. 13, the radio wave scatterer K is composed of first to third radio scatterers K1 to K3. The first to third radio wave scatterers K1 to K3 are conductor spheres having a radius of 3 cm. The center of the first radio wave scatterer K1 is set to the coordinate origin (−7, 2, 0), the center of the second radio wave scatterer K2 is arranged to be the coordinate (2, −7, 0), and It arrange | positions so that the center of the 3rd electromagnetic wave scatterer K3 may become a coordinate (8, -4, 0). The target object T is a small conductor sphere having a radius of 0.5 cm. In the first case, the target object T is arranged so that the center thereof is the coordinate C1 (−35, 60, 0). In the second case, the target object T is arranged so that the center thereof is the coordinate C2 (−15, 50, 0). In the third case, the target object T is arranged so that the center thereof is the coordinate C3 (2, 69, 0). In the fourth case, the target object T is arranged so that the center thereof is the coordinate C4 (35, 60, 0). In the fifth case, the target object T is arranged so that the center thereof is the coordinate C5 (40, 33, 0). For the position measuring device 1, these specifications of the target object T are unknown. Similarly to the simulation of the first embodiment, monostatic radar is employed, and the transmission / reception antenna A is arranged at the coordinate origin (0, 0, 0). A radio wave medium is a vacuum free space.

  In this simulation as well, when the transmission / reception antenna A transmits the transmission pulse Ws, which is a monocycle pulse with a center frequency of 3 GHz and a wavelength of 10 cm shown in FIG. 6, for example, in the first case, the reception signal having the waveform shown in FIG. Wr is received.

  The plurality of propagation paths include various paths such as paths passing through the plurality of radio wave scatterers K. Among them, the first to third radio wave scatterers K1 to K3 are first to third. Third paths P1 to P3 (paths passing through one radio wave scatterer K) are adopted, and a total of nine propagation paths are used for measuring the position of the target object T.

  FIG. 15 shows the result of calculating the position of the object T by the time reversal method using the solution of the scattered electric field by the radio wave scatterer K based on the waveform f (t) of the received signal for each of the first to fifth cases. Show. Each figure in FIG. 15 shows the value of each position search function g (0, r) in the xy plane obtained for each position vector r.

  As can be seen from FIGS. 15A and 15B, the substantially maximum peak of the position search function g (0, r) appears in the vicinity of the true position of the target object T, and is determined by the position measuring apparatus 1 having the above-described configuration and operation. It will be appreciated that the position of the target object T can be measured.

  Further, as can be seen by comparing each diagram of FIG. 15 with FIGS. 8 and 11, the virtual image is reduced as compared with the first and second embodiments, and the erroneous estimation of the position is reduced, and the accuracy is increased. The position of the target object T can be measured.

  Next, a comparison result between the second and third embodiments and a comparative example will be described. FIG. 16 is a diagram illustrating a plurality of antennas and a target object in a comparative example. FIG. 17 is a diagram illustrating each value of the position search function on the xy plane when the target object T is at the first coordinate C1. FIG. 17A shows the case of the second embodiment, FIG. 17B shows the case of the third embodiment, and FIG. 17C shows the case of the comparative example. FIG. 18 is a diagram illustrating each value of the position search function on the xy plane when the target object T is at the second coordinate C2. 18A shows the case of the second embodiment, FIG. 18B shows the case of the third embodiment, and FIG. 18C shows the case of the comparative example.

  In the comparative example, as shown in FIG. 16, an antenna is placed in place of the plurality of radio wave scatterers K in the second and third embodiments, and a transmission / reception antenna is configured by four array antennas. Accordingly, the position measurement accuracy with respect to the target object T is expected to be “in the case of the second embodiment <in the case of the third embodiment <in the case of the comparative example”.

  As can be seen from FIGS. 17 and 18, the position measurement accuracy with respect to the target object T is “in the case of the second embodiment <in the case of the third embodiment”, but in the case of the third embodiment and the comparative example. When the third embodiment is compared, it can be seen that although the virtual image appears in the third embodiment, the position measurement accuracy with respect to the target object T is “the case of the third embodiment≈the case of the comparative example”.

As described above, the position measuring apparatus 1 according to the first to third embodiments, it is possible to measure the position of the object T with a single transmit antenna A ₁ and a single receive antenna A _2. Therefore, unlike the case of the array antenna, there is no need to accurately fix the position (distance) between the plurality of transmission antennas and the position (distance) between the plurality of reception antennas. The size can be reduced, and the position measuring device 1 can be reduced in size and cost. In particular, since the size can be reduced, the position measuring device 1 can be easily attached to a moving body such as a robot, a vehicle, a ship, and an aircraft. For this reason, the moving body can recognize the positions of surrounding objects, and is particularly advantageous when the moving body automatically travels.

  The calculation method used in the position scanning unit 132 of the arithmetic processing unit 13 is not limited to the calculation method used in the first to third embodiments, and other electromagnetic methods such as the FDTD method and the moment method are used. A field calculation technique may be used.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. It is interpreted that it is included in

It is FIG. (1) for demonstrating the fundamental view of this invention. It is FIG. (2) for demonstrating the fundamental view of this invention. It is a block diagram which shows the structure of the position measuring apparatus in embodiment. It is a flowchart which shows operation | movement of the position measuring apparatus in 1st Embodiment. It is a figure which shows the electromagnetic wave scatterer and target object in simulation. It is a figure which shows the waveform of the transmission pulse in simulation. It is a figure which shows the waveform of the received signal in simulation. It is a figure which shows each value of the position search function in xy plane. It is a figure which shows the several electromagnetic wave scatterer and target object in simulation. It is a figure which shows the waveform of the received signal in simulation. It is a figure which shows each value of the position search function in xy plane. It is a flowchart which shows operation | movement of the position measuring apparatus in 3rd Embodiment. It is a figure which shows the several electromagnetic wave scatterer and target object in simulation. It is a figure which shows the waveform of the received signal of the simulation in case there exists a target object in a 1st coordinate. It is a figure which shows each value of the position search function in xy plane. It is a figure which shows the some antenna and target object in a comparative example. It is a figure which shows each value of the position search function of xy plane in case the target object T exists in the 1st coordinate C1. It is a figure which shows each value of the position search function of xy plane in case the target object T exists in the 2nd coordinate C2.

Explanation of symbols

S Position measuring system A ₁ Transmitting antenna A ₂ Receiving antenna K Radio wave scatterer T Target object 1 Position measuring device 11 Signal generating unit 12 Signal receiving unit 13 Arithmetic processing unit 16 Output unit 17 Storage unit 131 Time reversal waveform generating unit 132 Position Scanning unit 133 Output processing unit 171 Reception waveform storage unit 172 Time reversal waveform storage unit 173 Scanning result storage unit

Claims (6)

In a position measuring device that measures the position of an object,
A single transmit antenna that radiates the transmitted signal into space;
A single reception antenna that receives, as a reception signal, a scattered wave caused by the transmission signal scattered by the object and propagated through a plurality of propagation paths;
A position calculator that calculates the position of the object by a time reversal method based on the waveform of the received signal received by the receiving antenna;
The position measuring apparatus characterized in that the plurality of propagation paths include at least one propagation path through a radio wave scatterer that can scatter radio waves and has a known shape and position. The position measurement device according to claim 1, wherein the position calculation unit calculates the position of the object by a time reversal method in which scattering by the radio wave scatterer is geometric optical scattering. The position measurement device according to claim 1, wherein the position calculation unit calculates the position of the object by a time reversal method using a solution of a scattered electric field by the radio wave scatterer. The position measuring device according to any one of claims 1 to 3, wherein there are a plurality of the radio wave scatterers. The position measurement device according to claim 1, wherein the transmission signal is a UWB pulse. In a position measurement method for measuring the position of an object,
A transmission step of radiating a transmission signal from a single transmission antenna into space;
A reception step of receiving a scattered wave caused by the transmission signal scattered by the object and propagated in a plurality of propagation paths as a reception signal with a single reception antenna;
A position calculation step of calculating the position of the object by a time reversal method based on the waveform of the reception signal received in the reception step,
The position measuring method characterized in that the plurality of propagation paths include at least one propagation path through a radio wave scatterer capable of scattering radio waves and having a known shape and position.