JP2009174971A - Radio-frequency tag and distance measuring apparatus of same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid interferences with response signals transmitted from a plurality of radio-frequency tags in a distances measuring system of radio-frequency tags and measure the distances to the plurality of radio-frequency tags at the same distance from a distance measuring apparatus. <P>SOLUTION: The distance measuring apparatus 10B of radio-frequency tags diffuses pulse modulation signals by PN codes uniquely allocated to radio-frequency tags, objects of distance measurement, and transmits diffused pulse modulation signals. The radio-frequency tags that have PN codes uniquely allocated to themselves matched with the PN codes used for the diffusion processing of the diffused pulse modulation signals transmit restored pulse modulation signals acquired by applying back-modulation to received diffused pulse modulation signals. When the distance measuring apparatus 10B of radio-frequency tags has received restored pulse modulation signals, the distance measuring apparatus 10B computes the distances to the radio-frequency tags, objects of distance measurement, on the basis of the time between the transmission of the diffused pulse modulation signals and the reception of the restored pulse modulation signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless tag distance measuring device that measures a distance to a wireless tag, and a wireless tag that is a distance measurement target.

  In a mass production factory or the like, a storage position is determined for each production process or product type, and product management is often performed. In order to perform such product management, the RFID tag distance measurement system is widely used. In the wireless tag distance measuring system, the distance measuring device measures the distance to the wireless tag by wireless transmission / reception between the wireless tag attached to the managed product and the distance measuring device.

  When measuring the distance to the wireless tag, the distance measuring device transmits a pulse signal. The wireless tag that has received the pulse signal modulates the received pulse signal with a uniquely assigned code and transmits it as a response pulse signal. The distance measuring device that has received the response pulse signal identifies the wireless tag that has transmitted the response pulse signal by identifying the original code that modulated the response pulse signal. Then, the distance to the specified wireless tag is measured based on the time from when the pulse signal is transmitted until the response pulse signal is received.

  According to such processing, it is possible to measure the distance to a specific wireless tag among a plurality of wireless tags, and to measure the distance from the distance measuring device to the product to which the specific wireless tag is attached. .

  The wireless tag distance measurement system can be used for product management in factories, retail stores that sell daily necessities, accessories, etc., event venues that need to manage the location of event participants, and the like.

JP-T-2006-505018 JP-T-2005-513629

  In the above-described wireless tag distance measuring system, when there are a plurality of wireless tags having the same distance from the distance measuring device, response pulse signals transmitted from these wireless tags are temporally overlapped and received by the distance measuring device. At this time, there is a problem that it becomes difficult to measure the distance to each wireless tag because a plurality of response pulse signals interfere with each other.

  The present invention has been made for such a problem. That is, in the wireless tag distance measurement system, it is possible to avoid interference of response signals respectively transmitted from a plurality of wireless tags, and to measure distances to a plurality of wireless tags having the same distance from the distance measuring device. To do.

  The present invention relates to a wireless tag that is a target of a distance measuring device that performs target distance measurement by wireless transmission and reception, a wireless reception means for receiving an incoming signal, and a signal included in the signal received by the wireless reception means Among them, a correlation processing unit that performs despreading processing on a signal that has been subjected to spreading processing based on a uniquely assigned PN code of the wireless tag, and outputs a despreading signal, and a wireless transmission unit that transmits the despreading signal, It is characterized by providing.

  Further, the present invention provides a wireless transmission unit that transmits a distance measurement signal for measuring a target distance, a wireless reception unit that receives an incoming signal that has arrived after transmission of the distance measurement signal, and transmission of the distance measurement signal A distance calculation unit that calculates a distance to a target wireless tag based on the timing and the reception timing of the incoming signal, the wireless tag distance measuring device comprising: A spread processing unit that generates a spread signal by spread processing based on the wireless transmission unit, the wireless transmission unit transmits the spread signal as the distance measurement signal, and the wireless reception unit reverses the spread signal by the wireless tag. A despread signal that has been subjected to spreading processing is received as the incoming signal, and the distance calculating unit receives a time from when the spread signal is transmitted until the despread signal is received. Based on, and calculates the distance to the wireless tag.

  The present invention is also a wireless tag that is a target of a distance measuring device that performs target distance measurement by wireless transmission / reception, based on wireless reception means for receiving an incoming signal, and a uniquely assigned PN code of the wireless tag It comprises correlation processing means for performing spread processing on the signal received by the wireless reception means by spreading processing and outputting the spread signal; and wireless transmission means for transmitting the spread signal.

  Further, the present invention provides a wireless transmission unit that transmits a distance measurement signal for measuring a target distance, a wireless reception unit that receives an incoming signal that has arrived after transmission of the distance measurement signal, and transmission of the distance measurement signal A distance calculation unit that calculates a distance to a wireless tag as a target based on the timing and the reception timing of the arrival signal, the wireless tag distance measurement device comprising: a signal included in the arrival signal; A despreading unit that generates a despread signal by performing a despread process on the signal that has been spread based on the PN code uniquely assigned to the wireless tag, and transmits the despread signal after the distance measurement signal is transmitted A distance to the wireless tag is calculated based on a time until a signal that is a source for generating a signal is received.

  According to the wireless tag distance measuring device according to the present invention, interference of response signals respectively transmitted from a plurality of wireless tags is avoided, and distances to a plurality of wireless tags having the same distance from the wireless tag distance measuring device are measured. be able to.

  FIG. 1 shows the configuration of the RFID tag distance measuring system according to the first embodiment of the present invention. In this system, the wireless tag distance measuring device 10A measures the distance to a wireless tag as a distance measurement target by transmitting and receiving wireless signals. A unique PN code (PN is an abbreviation of Pseudo Noise) is assigned to the wireless tags 12-1 to 12-4. In FIG. 1, “01001...”, “10011...”, “01111...” And “10001. "Is assigned. The wireless tag distance measuring device 10A specifies a wireless tag that is a distance measurement target using a PN code.

  In general, a PN code indicates a pseudo-noise pattern due to 1 and 0. By associating the signal values “1” and “−1” with the values “1” and “0” of the PN code, respectively, it is possible to generate a PN signal whose value changes with the pattern of the PN code. When the diffusion process for performing the convolution operation between the PN signal and the processing target signal is performed, the time length of the processing target signal is spread according to the time length of the PN signal. For such a spread signal, the original signal can be reproduced by performing a despreading process that performs a convolution operation with the PN signal used in the spreading process. In addition, an original signal can be extracted by despreading processing from a signal obtained by adding a plurality of spread signals subjected to spreading processing using different PN codes. The RFID tag distance measurement system according to the embodiment of the present invention utilizes such orthogonality of the PN code.

  When measuring the distance to the wireless tag to be measured, the wireless tag distance measuring device 10A transmits a pulse modulation signal. The pulse modulation signal is obtained by multiplying a sine wave signal by a pulse signal such as a rectangular single pulse signal. Each wireless tag receives the pulse modulation signal transmitted from the wireless tag distance measuring device 10A. Then, the pulse modulation signal is spread by a PN code uniquely assigned to itself, and the spread signal is transmitted as a spread pulse modulation signal.

  When the wireless tag distance measurement device 10A receives the spread pulse modulation signal, the wireless tag distance measurement device 10A performs despreading processing on the spread pulse modulation signal using the unique assignment PN code of the wireless tag that is the distance measurement target, and generates a restored pulse modulation signal. The wireless tag distance measuring device 10A calculates the distance to the wireless tag to be measured based on the time from when the pulse modulated signal is transmitted until the restored pulse modulated signal is generated.

  The configuration of the RFID tag distance measuring device 10A for executing such processing is shown in FIG. The pulse modulation signal generation unit 14 generates a pulse modulation signal and outputs it to the wireless transmission unit 16 and the distance calculation unit 28. The wireless transmission unit 16 converts the pulse modulated signal into a wireless signal and transmits it via the measurement device antenna 18. The pulse modulation signal output from the pulse modulation signal generation unit 14 to the distance calculation unit 28 is used for measuring the distance to the wireless tag, as will be described later.

  The pulse modulation signal transmitted from the wireless tag distance measuring device 10A is received by each wireless tag. FIG. 3A shows the configuration of the wireless tag 12. The pulse modulated signal received by the wireless tag antenna 32 is input to the duplexer 34. The duplexer 34 inputs the pulse modulated signal to the correlation processing device 36. The duplexer 34 can be configured using a circulator, a directional coupler, or the like.

  As the correlation processing device 36 of the wireless tag 12, a device that performs spreading processing on an input signal by the PN code uniquely assigned to the wireless tag 12 and outputs the same is used. As such a device, a SAW device, a CCD (Charge Coupled Device) matched filter, a digital matched filter, or the like can be used. Some SAW devices require supply power (such as SAW convolvers) and others do not require supply power. When a SAW device that does not need to supply power is used, it is not necessary to mount a power supply source on the wireless tag 12.

  In addition, a digital matched filter, a SAW convolver, and the like can arbitrarily set a PN code when performing a spreading process. The configuration in this case is shown in FIG. Here, the case where the digital matched filter 36A is used is shown. When using a SAW convolver, the digital matched filter 36A may be replaced with a SAW convolver. The wireless tag 12 includes a PN code storage unit 38 that stores a PN code and a PN code setting circuit 40. The PN code storage unit 38 stores a plurality of different PN codes in advance. The PN code setting circuit 40 reads the PN code from the PN code storage unit 38, and sets the operation state of the digital matched filter 36A so that the digital matched filter 36A executes processing based on the PN code. Further, instead of providing the PN code storage unit 38 and the PN code setting circuit 40, a configuration may be adopted in which a PN code is set in the digital matched filter 36A by a device external to the wireless tag 12. According to the configuration of the wireless tag 12 using the digital matched filter 36A, it is possible to share hardware for a plurality of wireless tags 12 to which different PN codes are given.

  The correlation processing device 36 performs a spreading process on the pulse modulated signal input from the duplexer 34 using a unique assigned PN code of the wireless tag 12 to generate a spread pulse modulated signal and outputs the spread pulse modulated signal to the duplexer 34. The duplexer 34 outputs the spread pulse modulated signal to the RFID tag antenna 32. A spread pulse modulated signal is transmitted from the wireless tag antenna 32.

  With such a configuration, the wireless tag 12 receives the pulse modulated signal transmitted from the wireless tag distance measuring device 10 </ b> A, and transmits the spread pulse modulated signal that has been subjected to the spreading process using the unique assignment PN code of the wireless tag 12.

  Next, processing performed by the wireless tag distance measuring device 10A for the spread pulse modulated signal transmitted from each wireless tag will be described. The radio reception unit 20 receives the spread pulse modulation signal transmitted from each radio tag via the measurement device antenna 18, amplifies the signal until a predetermined signal level is obtained, and outputs the amplified signal to the despread processing unit 22.

  The PN code storage unit 24 stores a unique assignment PN code of a wireless tag used in the wireless tag distance measurement system. When a wireless tag to be measured for distance is specified by a user operation or a device provided separately, the code selection unit 26 reads a specific assigned PN code of the specified wireless tag from the PN code storage unit 24. Then, a PN signal is generated based on the read PN code and output to the despreading processing unit 22.

  The despreading processing unit 22 performs a convolution operation on the spread pulse modulated signal output from the wireless reception unit 20 using the PN signal output from the code selection unit 26, and outputs the calculation result to the distance calculation unit 28.

  When the signal output from the radio reception unit 20 includes a spread pulse modulation signal that has been subjected to a spreading process using a unique assignment PN code of a radio tag to be measured for distance, the despreading processing unit 22 generates a pulse modulation signal. A restored pulse modulation signal having the same time waveform as the pulse modulation signal output from the unit 14 is output.

  The distance calculation unit 28 measures the difference between the timing at which the pulse modulation signal is output from the pulse modulation signal generation unit 14 and the timing at which the restored pulse modulation signal is output from the despreading processing unit 22. Then, based on the measured timing difference, a round-trip propagation time between the measuring device antenna 18 and the wireless tag is obtained, and a distance to the wireless tag is calculated based on the round-trip propagation time and the propagation speed of the wireless signal. The distance calculation unit 28 outputs the distance calculation result to the display unit 30. The display unit 30 displays the distance calculation result.

  When calculating the round-trip propagation time, the distance calculation unit 28 determines the delay time from when the signal is output from the pulse modulation signal generation unit 14 until it is transmitted from the measurement device antenna 18, and the signal at the measurement device antenna 18. The delay time from reception until output from the despreading processing unit 22 is subtracted from the timing difference. As a result, the distance to the wireless tag based on the position of the measurement apparatus antenna 18 can be calculated. These delay times are unique to the RFID tag distance measuring apparatus 10A, and can be obtained in advance at the design stage. Also, by measuring the timing difference between the pulse modulated signal and the restored pulse modulated signal using the phase difference of the modulated sine wave of each signal in addition to the rise timing of these signals, the accuracy of the calculated distance can be improved. Can be high.

  According to such a system configuration, it is possible to specify a wireless tag to be measured for distance and measure the distance from the wireless tag distance measuring device 10A to the specified wireless tag. For example, in the PN code assignment shown in FIG. 1, when the wireless tag 12-2 is designated as the distance measurement target, the despreading processing unit 22 is based on the unique assignment PN code “10011...” Of the wireless tag 12-2. A PN signal is output. As a result, the wireless tag 12 that has been spread by the PN code “10011...” From the spread pulse modulated signals transmitted from the wireless tags 12-1 to 12-4 from the despreading processing unit 22. -2 is output as a restored pulse modulated signal based on the spread pulse modulated signal transmitted from -2. Therefore, the wireless tag distance measuring device 10A can calculate the distance to the wireless tag 12-2.

  When there are a plurality of wireless tags having a small difference in distance from the wireless tag distance measuring device 10A, the spread pulse modulated signals transmitted from these wireless tags are received by the wireless tag distance measuring device 10A in a time-overlapping manner. . Even in such a case, according to the RFID tag distance measuring device 10A according to the present embodiment, based on the spread pulse modulation signal transmitted from the RFID tag to be measured by the orthogonality of the PN code described above. A restored pulse modulated signal is generated. Therefore, the spread pulse modulation signals transmitted from the plurality of wireless tags do not interfere with each other, and the distance to the distance measurement target wireless tag can be measured.

  Next, the RFID tag distance measuring system according to the second embodiment of the present invention will be described. FIG. 4 shows the configuration of the RFID tag distance measuring system according to the second embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In the wireless tag distance measuring system according to the first embodiment, the wireless tag distance measuring device 10A transmits a pulse modulated signal, and each wireless tag transmits a spread pulse modulated signal. On the other hand, in the RFID tag distance measuring system according to the second embodiment, the RFID tag distance measuring device 10B transmits a spread pulse modulation signal corresponding to the distance measurement object, and the RFID tag as the distance measurement object is the restored pulse modulation signal. That is, a pulse modulated signal that has not been subjected to spreading processing is transmitted.

  The wireless tag distance measuring device 10B performs a spreading process on the pulse modulated signal using a unique assigned PN code of the wireless tag to be measured for distance, and transmits the spread pulse modulated signal. Among the plurality of wireless tags that have received the spread pulse modulated signal, the wireless tag in which the PN code used for the spread processing of the spread pulse modulated signal and its own uniquely assigned PN code matches the received spread pulse modulated signal. Then, a restored pulse modulated signal subjected to despreading processing is transmitted.

  Upon receiving the restoration pulse modulation signal, the wireless tag distance measurement device 10B determines the distance to the distance measurement target radio tag based on the time from when the diffusion pulse modulation signal is transmitted until the restoration pulse modulation signal is received. calculate.

  FIG. 5 shows the configuration of the RFID tag distance measuring apparatus 10B for executing such processing. The same components as those of the RFID tag distance measuring device 10A shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  The pulse modulation signal generation unit 14 generates a pulse modulation signal and outputs it to the diffusion processing unit 42 and the distance calculation unit 28. When a wireless tag to be measured for distance is specified by a user operation or a device provided separately, the code selection unit 26 reads a specific assigned PN code of the specified wireless tag from the PN code storage unit 24. Then, a PN signal is generated based on the read PN code and output to the diffusion processing unit 42. The spread processing unit 42 outputs a spread pulse modulated signal obtained by performing spread processing on the pulse modulated signal using the PN signal output from the code selecting unit 26 to the wireless transmission unit 16. The radio transmission unit 16 converts the spread pulse modulated signal into a radio signal and transmits the radio signal via the measurement device antenna 18.

  The spread pulse modulated signal transmitted from the wireless tag distance measuring device 10B is received by each wireless tag. As the wireless tag, the same one as the wireless tag 12 according to the first embodiment shown in FIG. 2, that is, the one shown in FIG. 3A or 3B can be used. The spread pulse modulated signal received by the wireless tag antenna 32 is input to the duplexer 34. The duplexer 34 inputs the spread pulse modulated signal to the correlation processing device 36.

  In the above description, the correlation processing device 36 that uses a PN code that is uniquely assigned to the wireless tag 12 and that performs an output process on the input signal is described. When a signal that has been subjected to spreading processing using a uniquely assigned PN code is input to such a correlation processing device 36, a signal before spreading processing that has been subjected to despreading processing is output.

  When the spread pulse modulated signal that has been spread by the uniquely assigned PN code is output from the demultiplexer 34, the correlation processing device 36 performs a despreading process on the spread pulse modulated signal to restore the restored pulse modulated signal. Is output to the duplexer 34. The duplexer 34 outputs the restored pulse modulation signal to the RFID tag antenna 32. A restoration pulse modulation signal is transmitted from the wireless tag antenna 32.

  With such a configuration, among the plurality of wireless tags that have received the spread pulse modulated signal, the wireless tag in which the PN code used for the spread processing of the spread pulse modulated signal and its own uniquely assigned PN code are received. A restored pulse modulated signal obtained by performing despreading processing on the spread pulse modulated signal is transmitted.

  Next, processing performed by the wireless tag distance measuring device 10B with respect to the restored pulse modulation signal transmitted from the wireless tag will be described. The wireless reception unit 20 receives the restored pulse modulated signal transmitted from the wireless tag via the measurement device antenna 18, amplifies the signal until a predetermined signal level is obtained, and outputs the amplified signal to the distance calculation unit 28.

  The distance calculation unit 28 measures the difference between the timing at which the pulse modulation signal is output from the pulse modulation signal generation unit 14 and the timing at which the restored pulse modulation signal is output from the wireless reception unit 20. Then, based on the measured timing difference, a round-trip propagation time between the measuring device antenna 18 and the wireless tag is obtained, and the distance to the wireless tag of the distance measurement target is determined based on the round-trip propagation time and the propagation speed of the wireless signal. calculate. The distance calculation unit 28 outputs the distance calculation result to the display unit 30. The display unit 30 displays the distance calculation result.

  When the distance calculation unit 28 calculates the round-trip propagation time, the delay time from when the signal is output from the pulse modulation signal generation unit 14 until it is transmitted from the measurement device antenna 18, and the signal is measured by the measurement device antenna 18. From the timing difference, the delay time from when the signal is received at the time until the signal is output from the wireless receiver 20 is subtracted. As a result, the distance to the wireless tag based on the position of the measurement apparatus antenna 18 can be calculated. These delay times are unique to the RFID tag distance measuring device 10B, and can be obtained in advance at the design stage. Also, by measuring the timing difference between the pulse modulated signal and the restored pulse modulated signal using the phase difference of the modulated sine wave of each signal in addition to the rise timing of these signals, the accuracy of the calculated distance can be improved. Can be high.

  According to such a system configuration, it is possible to specify a wireless tag to be measured for distance and measure the distance from the wireless tag distance measuring device 10B to the specified wireless tag. For example, in the code assignment shown in FIG. 4, when the wireless tag 12-2 is specified as the distance measurement target, the PN based on the unique assignment PN code “10011. A signal is output. As a result, a spread pulse modulated signal that has been spread by the PN code “10011...” Of the wireless tag 12-2 is transmitted from the wireless tag distance measuring device 10B. Among the wireless tags 12-1 to 12-4 that have received the spread pulse modulation signal, the wireless tag 12-2 to which the same uniquely assigned PN code as the uniquely assigned PN code “10011. Transmit a pulse modulated signal. Therefore, the wireless tag distance measuring device 10B can calculate the distance to the wireless tag 12-2.

  According to the wireless tag distance measurement system according to the present embodiment, only the wireless tag that is the distance measurement target performs despreading processing and transmits the restored pulse modulated signal due to the orthogonality of the PN code described above. Then, the restored pulse modulation signal is not transmitted from the wireless tag that is not the distance measurement target. Therefore, even when there are a plurality of wireless tags having a small difference in distance from the wireless tag distance measuring device 10B, signals transmitted from the plurality of wireless tags do not interfere with each other, and the wireless tag of the distance measurement target Can be calculated.

  As described above, the distance calculation unit 28 of the wireless tag distance measurement apparatus 10A or 10B calculates the distance to the wireless tag to be measured based on the restored pulse modulation signal. In order for the distance calculation unit 28 to calculate the distance, the signal level of the restored pulse modulation signal needs to exceed a predetermined value. Therefore, the maximum measurable distance of the RFID tag distance measuring device 10A or 10B can be increased by increasing the level of the signal transmitted by the RFID tag distance measuring device 10A or 10B. However, the wireless transmission unit 16 of the wireless tag distance measuring apparatus 10A or 10B cannot transmit a signal having a level exceeding the saturation level. Therefore, it can be said that the maximum measurable distance depends on the transmission saturation level of the wireless transmission unit 16.

  Here, in the wireless tag distance measurement system according to the first embodiment, the wireless tag distance measurement device 10A transmits a pulse modulation signal, and each wireless tag transmits a spread pulse modulation signal. Then, the wireless tag distance measuring device 10A calculates the distance to the wireless tag using the restored pulse modulated signal obtained by despreading the spread pulse modulated signal transmitted from the wireless tag. On the other hand, in the RFID tag distance measurement system according to the second embodiment, the RFID tag distance measurement device 10B transmits a spread pulse modulation signal, and the RFID tag for distance measurement transmits a restored pulse modulation signal. Then, the wireless tag distance measuring device 10B calculates the distance to the wireless tag using the received restoration pulse modulation signal.

  When the transmission saturation levels of the wireless transmission units 16 of the wireless tag distance measurement devices 10A and 10B are the same and the wireless tag distance measurement devices 10A and 10B transmit signals of transmission saturation levels, the distance calculation unit 28 calculates the distance. The level of the restoration pulse modulation signal used is higher in the RFID tag distance measuring device 10B. The reason is that the distance measurement target wireless tag of the wireless tag distance measurement device 10B transmits a restoration pulse modulation signal obtained by despreading the received spread pulse modulation signal to the wireless tag distance measurement device 10B. This is because the level of the signal transmitted by the wireless tag increases.

  Therefore, under the condition that the transmission saturation levels of the RFID tag distance measuring devices are the same, it can be said that the maximum measurable distance is longer in the second embodiment than in the first embodiment. Further, when the system is designed so that the maximum measurable distance is the same, the scale of the wireless transmission unit 16 of the wireless tag distance measuring device 10B of the second embodiment can be reduced.

  Further, the maximum measurable distance of the wireless tag distance measuring device 10A or 10B can be increased by reducing the noise figure of the wireless receiving unit 20 and increasing the amplification gain. Here, in the RFID tag distance measuring system according to the first embodiment, a diffusion process is performed on a signal from each RFID tag toward the RFID tag distance measuring device 10A. Therefore, it is desired that the wireless reception unit 20 of the wireless tag distance measuring device 10A has a small noise figure and a large amplification gain. On the other hand, in the wireless tag distance measuring system according to the second embodiment, a signal directed from the wireless tag to the wireless tag distance measuring device 10B is subjected to despreading processing in the wireless tag. Therefore, the received signal level at the RFID tag distance measuring device 10B increases as the spreading gain is obtained. For this reason, the wireless reception unit 20 of the wireless tag distance measurement device 10B is not required to have good noise figure characteristics and amplification gain characteristics as required by the wireless reception unit 20 of the wireless tag distance measurement device 10A. As a result, the second embodiment makes it easier to design the wireless receiving unit 20 than the first embodiment, and it is easy to increase the maximum measurable distance of the wireless tag distance measuring device 10B.

  Next, a radio tag positioning system to which the radio tag distance measurement system is applied will be described with reference to FIG. The wireless tag positioning system measures the position of the wireless tag by arranging a plurality of wireless tag distance measuring devices 10. FIG. 6 shows an example in which four RFID tag distance measuring devices 10 are arranged. As the RFID tag distance measuring device 10, the RFID tag distance measuring device 10A or 10B according to the first or second embodiment described above can be used.

  The information processing apparatus 44 outputs designation information for designating the distance measurement target wireless tag to the code selection unit 26 of each wireless tag distance measurement apparatus 10. The code selection unit 26 of each wireless tag distance measuring device 10 reads the unique assignment PN code of the wireless tag designated by the designation information from the PN code storage unit 24. Then, a PN signal is generated based on the read PN code, and is output to the despreading processing unit 22 or the spreading processing unit 42. Each RFID tag distance measuring device 10 executes processing based on the PN signal output from the code selection unit 26. Thus, the distance calculation unit 28 of each wireless tag distance measuring device 10 calculates the distance to the wireless tag designated by the information processing device 44 and outputs the distance to the information processing device 44.

  The information processing device 44 stores installation position information indicating the position where each wireless tag distance measuring device 10 is installed. The information processing device 44 obtains the position of the designated wireless tag based on the distance calculation result output from each wireless tag distance measuring device 10 and the installation position information of each wireless tag distance measuring device 10.

  The position of the wireless tag can be obtained as follows. The information processing device 44 obtains, for each RFID tag distance measuring device 10, an expression representing a calculated distance spherical surface 46 with the calculated distance as the length of the radius around the position of the RFID tag distance measuring device 10. The information processing device 44 calculates the position of the intersection 48 where the calculated distance spherical surfaces 46 obtained for each wireless tag distance measuring device 10 intersect as the position of the wireless tag 12.

  When the RFID tag distance measuring device 10 is arranged on a plane and the position of the RFID tag on the plane is measured, if three or more RFID tag distance measuring devices 10 that are not on the same straight line are arranged, 1 An intersection 48 of the points can be obtained, and this can be obtained as the position of the wireless tag. When measuring the position of the wireless tag in a three-dimensional space, four or more wireless tag distance measuring devices 10 that are not on the same plane may be arranged.

  The RFID tag positioning system to which the RFID tag distance measurement system according to the first or second embodiment of the present invention is applied is a product management in a factory, a retail store that sells daily necessities, accessories, etc., and the location of event participants It can be used for event venues that need to be performed.

It is a figure which shows the structure of the RFID tag distance measurement system which concerns on 1st Embodiment. It is a figure which shows the structure of the RFID tag distance measuring device which concerns on 1st Embodiment. It is a figure which shows the structure of a wireless tag. It is a figure which shows the structure of the RFID tag distance measurement system which concerns on 2nd Embodiment. It is a figure which shows the structure of the wireless tag distance measuring apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of a wireless tag positioning system.

Explanation of symbols

  10, 10A, 10B wireless tag distance measuring device, 12, 12-1 to 12-4 wireless tag, 14 pulse modulation signal generator, 16 wireless transmitter, 18 measuring device antenna, 20 wireless receiver, 22 despreading processor , 24 PN code storage unit, 26 code selection unit, 28 distance calculation unit, 30 display unit, 32 RFID tag antenna, 34 duplexer, 36 correlation processing device, 36A digital matched filter, 38 PN code storage unit, 40 PN code Setting circuit, 42 Diffusion processing unit, 44 Information processing device, 46 Calculation distance spherical surface, 48 Intersection point.

Claims (4)

A wireless tag that is a target of a distance measuring device that performs target distance measurement by wireless transmission and reception,
Wireless receiving means for receiving an incoming signal;
Correlation processing means for performing despreading processing on a signal subjected to spreading processing based on a uniquely assigned PN code of the wireless tag among signals included in the signal received by the wireless receiving means, and outputting a despreading signal; ,
Wireless transmission means for transmitting the despread signal;
A wireless tag comprising: A wireless transmission unit for transmitting a distance measurement signal for measuring a target distance;
A radio reception unit for receiving an incoming signal that has arrived after transmission of the distance measurement signal;
Based on the transmission timing of the distance measurement signal and the reception timing of the incoming signal, a distance calculation unit that calculates the distance to the wireless tag as a target;
A wireless tag distance measuring device comprising:
A spread processing unit that generates a spread signal by a spread process based on a unique assigned PN code of the wireless tag;
The wireless transmitter is
Transmitting the spread signal as the distance measurement signal;
The wireless receiver is
Receiving a despread signal that has been subjected to despread processing by the wireless tag for the spread signal as the incoming signal,
The distance calculation unit
A wireless tag distance measuring apparatus, comprising: calculating a distance to the wireless tag based on a time from when the spread signal is transmitted to when the despread signal is received. A wireless tag that is a target of a distance measuring device that performs target distance measurement by wireless transmission and reception,
Wireless receiving means for receiving an incoming signal;
Correlation processing means for performing spreading processing on a signal received by the wireless reception means by spreading processing based on a PN code uniquely assigned to the wireless tag, and outputting a spread signal;
Wireless transmission means for transmitting the spread signal;
A wireless tag comprising: A wireless transmitter for transmitting a distance measurement signal for measuring a target distance;
A radio reception unit for receiving an incoming signal that has arrived after transmission of the distance measurement signal;
Based on the transmission timing of the distance measurement signal and the reception timing of the incoming signal, a distance calculation unit that calculates the distance to the target wireless tag;
A wireless tag distance measuring device comprising:
A despreading unit that generates a despread signal by performing a despreading process on a signal subjected to a spreading process based on a unique allocation PN code of the wireless tag among the signals included in the incoming signal;
Radio tag distance measurement characterized in that a distance to the radio tag is calculated based on a time from when the distance measurement signal is transmitted until a signal that is a source for generating the despread signal is received. apparatus.

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