JP2009281761A - Distance measuring device and system for radio tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate a prior processing for measuring a distance in a distance measuring device for a radio tag. <P>SOLUTION: This distance measuring device 10 for a radio tag transmits a pulse modulation signal to which diffusion processing is not applied. Each radio tag receives the pulse modulation signal transmitted from the distance measuring device 10 for a radio tag, applies the diffusion processing to the pulse modulation signal by a PN code assigned uniquely to itself, and transmits the signal to which the diffusion processing is applied as a diffused pulse modulation signal. The distance measuring device 10 for a radio tag detects a unique assigned PN code of each radio tag based on the diffused pulse modulation signal transmitted from each radio tag. The distance measuring device 10 for a radio tag measures a distance to the radio tag by using the PN code stored in a measuring object PN code storage part 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless tag distance measuring device that measures a distance to a wireless tag using a wireless tag unique assignment PN code, and a system including such a wireless tag distance measuring device and a wireless tag.

  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, a wireless tag distance measurement system is 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 pulse signal includes a unique assignment code of a wireless tag to be measured for distance. The wireless tag transmits a response pulse signal when a code uniquely assigned to the wireless tag is included in the received pulse signal. The distance measuring device that has received the response pulse signal measures the distance to the wireless tag 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, in order for the distance measuring device to perform distance measurement, it is necessary to acquire in advance a unique assignment code of the wireless tag to be measured. Therefore, it is necessary to perform processing for storing the unique assignment code of each wireless tag in the distance measuring device using an information input device or the like. However, in the wireless tag distance measurement system, the same wireless tag is not always used, and a wireless tag is newly added or a wireless tag that has been used until now is not used. Therefore, in such a configuration, it is necessary to change the stored contents of the distance measuring device every time the wireless tag used in the system changes, and there is a problem that labor is required for system management.

  The present invention has been made for such a problem. That is, an object of the present invention is to facilitate preprocessing for performing distance measurement in the RFID tag distance measuring device.

The present invention relates to a wireless tag distance measuring device that calculates a distance to a wireless tag as a distance measurement target based on a transmission timing and a reception timing of a wireless signal, and a pulse signal transmission unit that wirelessly transmits a pulse signal And a radio signal arriving after transmission of the pulse signal, acquiring a radio tag specific allocated PN code included in the received signal, and a radio tag specific allocated PN code acquired by the code acquiring unit A spread signal generation unit that generates a spread signal by spread processing, a spread signal transmission unit that wirelessly transmits the spread signal, and a reverse spread that has been despread on the spread signal and arrived after transmission of the spread signal Based on a despread signal receiving unit that receives a radio signal, a transmission timing of the spread signal, and a reception timing of the despread radio signal, the radio tag A distance calculating unit for calculating the distance, the
It is characterized by providing.

  The wireless tag distance measuring system according to the present invention includes the wireless tag distance measuring device and the wireless tag, wherein the wireless tag includes wireless receiving means for receiving an incoming signal, and the uniqueness of the wireless tag. A convolution operation unit that performs a convolution operation between a PN signal including an assigned PN code and a signal received by the wireless reception unit; and a wireless transmission unit that wirelessly transmits the signal obtained by the convolution operation unit. It is characterized by.

  According to the RFID tag distance measuring apparatus according to the present invention, it is possible to facilitate preprocessing for performing distance measurement.

  FIG. 1 shows a configuration of a wireless tag distance measuring system according to an embodiment of the present invention. In this system, the wireless tag distance measuring device 10 measures the distance to the wireless tag by transmitting and receiving wireless signals to and from the wireless tag. 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 10 specifies a wireless tag as a distance measurement target by 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. In the RFID tag distance measurement system according to the present embodiment, such orthogonality of the PN code is used.

  When measuring the distance to a wireless tag as a distance measurement target, the wireless tag distance measuring device 10 generates a pulse modulation signal obtained by multiplying a sine wave signal by a pulse signal such as a rectangular single pulse signal. Then, spreading processing is performed on the pulse modulated signal by using the uniquely assigned PN code of the wireless tag to be measured for distance, and the spread pulse modulated signal is transmitted.

  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 response pulse modulation signal subjected to despreading processing is transmitted.

  Upon receiving the response pulse modulation signal, the wireless tag distance measurement device 10 calculates the distance to the wireless tag to be measured based on the time from when the spread pulse modulation signal is transmitted until the response pulse modulation signal is received. calculate.

  FIG. 2 shows the configuration of the RFID tag distance measuring apparatus 10 for executing such processing. The wireless tag distance measuring device 10 detects a unique assignment PN code of a wireless tag capable of measuring the distance before executing the process of measuring the distance to the wireless tag. Here, the wireless tag capable of distance measurement refers to a wireless tag capable of transmitting and receiving wireless signals to and from the wireless tag distance measuring device 10. The wireless tag distance measuring device 10 stores the PN code detected by the code detection process in the measurement target PN code storage unit 20. Then, the distance to the wireless tag is measured using the stored PN code.

  Here, it is assumed that a unique assignment PN code of a wireless tag capable of distance measurement is stored in the measurement target PN code storage unit 20 by a code detection process described later, and a distance measurement process for measuring a distance to the wireless tag explain.

  When performing the distance measurement processing, the wireless tag distance measuring device 10 sets the transmission side switch 18 to the state of selecting the switch terminal 18B, and sets the reception side switch 42 to the state of selecting the switch terminal 42B. As a result, the output signal of the diffusion convolution calculator 16 is input to the wireless transmitter 24, and the output signal of the wireless receiver 40 is output to the distance calculator 44.

  The pulse modulation signal generation unit 14 generates a pulse modulation signal and outputs it to the diffusion convolution operation unit 16 and the distance calculation unit 44. The measurement target PN code storage unit 20 stores a uniquely assigned PN code of a wireless tag capable of measuring a distance. When a wireless tag to be measured for distance is designated by a user operation or a separately provided device or the like, the code selection unit 22 reads the specific assigned PN code of the designated wireless tag from the measurement target PN code storage unit 20. Then, a PN signal is generated based on the read PN code and output to the diffusion convolution unit 16.

  The spreading convolution operation unit 16 performs a convolution operation on the pulse modulation signal using the PN signal output from the code selection unit 22 and outputs the operation result to the wireless transmission unit 24 via the transmission-side switch 18 as a diffusion pulse modulation signal. . The wireless transmission unit 24 converts the spread pulse modulated signal into a wireless signal and transmits it through the measurement device antenna 26.

  The spread pulse modulated signal transmitted from the wireless tag distance measuring device 10 is received by each wireless tag. FIG. 3A shows the configuration of the wireless tag 12. The spread pulse modulated signal received by the wireless tag antenna 28 is input to the duplexer 30. The duplexer 30 outputs the pulse modulation signal to the convolution operation device 32. The duplexer 30 can be configured using a circulator, a directional coupler, or the like.

  The convolution operation device 32 of the wireless tag 12 uses a device that performs a convolution operation on the input signal using a PN code uniquely assigned to the wireless tag 12 and outputs the result. 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 convolution operation. The configuration in this case is shown in FIG. Here, the case where the digital matched filter 34 is used is shown. When using a SAW convolver, the digital matched filter 34 may be replaced with a SAW convolver. The wireless tag 12 is provided with an allocation code storage unit 36 for storing an allocation PN code and a PN code setting circuit 38. The allocation code storage unit 36 stores a plurality of different allocation PN codes in advance. The PN code setting circuit 38 reads the PN code from the assigned code storage unit 36, and sets the operation state of the digital matched filter 34 so that the digital matched filter 34 executes processing based on the PN code. Further, instead of providing the assigned code storage unit 36 and the PN code setting circuit 38, a configuration may be adopted in which a unique assigned PN code is set in the digital matched filter 34 by a device external to the wireless tag 12. According to the configuration of the wireless tag 12 using the digital matched filter 34, hardware can be shared for a plurality of wireless tags 12 having different unique assigned PN codes.

  The convolution operation device 32 performs a convolution operation on the signal output from the demultiplexer 30 using the unique assignment PN code of the wireless tag 12 and outputs the result to the demultiplexer 30. The duplexer 30 outputs the signal output from the convolution operation device 32 to the wireless tag antenna 28. A signal output from the duplexer 30 is transmitted from the wireless tag antenna 28.

  In the case where the signal input to the convolution operation device 32 is a spread signal that has been subjected to the spread processing using the uniquely assigned PN code, the convolution operation device 32 performs the spread processing in which the despread processing is performed on the input signal. The previous signal is output. On the other hand, when the signal input to the convolution operation device 32 is a spread signal that has been subjected to a spread process using a PN code different from the uniquely assigned PN code, the signal before the spread process is sent from the convolution operation device 32. Not output.

  Therefore, when the spread pulse modulated signal received by the RFID tag antenna 28 is a signal that has been spread by the uniquely assigned PN code, the convolution operation device 32 performs despread processing on the spread pulse modulated signal. The signal before spreading processing is output. As a result, among the plurality of wireless tags, the wireless tag in which the original PN code obtained by performing the spreading process on the received spread pulse modulated signal and the own unique assigned PN code match the spread pulse modulated signal. Then, the signal subjected to the despreading process is transmitted as a response pulse modulation signal.

  Next, processing performed by the wireless tag distance measuring device 10 for the response pulse modulation signal transmitted from the wireless tag will be described. The wireless reception unit 40 receives the response pulse modulation signal transmitted from the wireless tag via the measurement device antenna 26, amplifies it until a predetermined signal level is reached, and outputs it to the distance calculation unit 44 via the reception side switch 42. To do.

  The distance calculation unit 44 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 response pulse modulation signal is output from the wireless reception unit 40. Then, based on the measured timing difference, a round-trip propagation time between the measuring device antenna 26 and the wireless tag is obtained, and a distance to the distance measurement target wireless tag is determined based on the round-trip propagation time and the propagation speed of the wireless signal. calculate. The distance calculation unit 44 outputs the distance calculation result to the display unit 46 and the result storage unit 48. The display unit 46 displays the distance calculation result, and the result storage unit 48 stores the distance calculation result. The user can know the distance from the wireless tag distance measuring device 10 to the wireless tag by referring to the display unit 46. In addition, the storage contents of the result storage unit 48 can be acquired by a reading device configured by a personal computer or the like.

  When the distance calculation unit 44 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 26, and the signal is output from the measurement device antenna 26. From the timing difference, the delay time from when the signal is received until the signal is output from the wireless receiver 40 is subtracted. As a result, the distance to the wireless tag based on the position of the measuring device antenna 26 can be calculated. These delay times are unique to the RFID tag distance measuring apparatus 10 and can be obtained in advance at the design stage. Also, by measuring the timing difference between the pulse modulation signal and the response pulse modulation 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 as a distance measurement target and measure the distance from the wireless tag distance measuring device 10 to the specified wireless tag. For example, when the wireless tag 12-2 is designated as the distance measurement target in the unique PN code assignment shown in FIG. 1, the same PN code as the unique assignment PN code of the wireless tag 12-2 is given to the diffusion convolution operation unit 16. A PN signal based on “10011...” Is output. As a result, the wireless tag distance measuring device 10 transmits a spread pulse modulated signal that has been spread by the same PN code “10011...” As the unique assigned PN code of the wireless tag 12-2. Among the wireless tags 12-1 to 12-4 that have received the spread pulse modulated signal, the wireless tag 12-2 having the same uniquely assigned PN code as the PN code “10011...” Receives the response pulse modulated signal. Send. Thereby, the wireless tag distance measuring device 10 can calculate the distance to the wireless tag 12-2.

  Next, the code detection process will be described. In the code detection process, the RFID tag distance measuring device 10 transmits a pulse modulated signal that has not been subjected to the spreading process. Each wireless tag receives the pulse modulation signal transmitted from the wireless tag distance measuring device 10. 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. The wireless tag distance measuring device 10 detects the uniquely assigned PN code of each wireless tag based on the spread pulse modulation signal transmitted from each wireless tag.

  Details of the code detection process will be described. When performing the code detection process, the wireless tag distance measuring device 10 sets the transmission side switch 18 to the state of selecting the switch terminal 18A and sets the reception side switch 42 to the state of selecting the switch terminal 42A. As a result, the output signal of the pulse modulation signal generator 14 is input to the wireless transmitter 24, and the output signal of the wireless receiver 40 is output to the PN code detector 50.

  The pulse modulation signal generation unit 14 generates a pulse modulation signal and outputs the pulse modulation signal to the wireless transmission unit 24 via the transmission side switch 18. The wireless transmission unit 24 converts the pulse modulation signal into a wireless signal and transmits the wireless signal via the measurement device antenna 26.

  The pulse modulation signal transmitted from the wireless tag distance measuring device 10 is received by each wireless tag. The pulse modulated signal received by the wireless tag antenna 28 is input to the duplexer 30. The duplexer 30 inputs the pulse modulation signal to the convolution operation device 32.

  The convolution operation device 32 performs a convolution operation on the signal output from the demultiplexer 30 using the unique assignment PN code of the wireless tag 12 and outputs the result to the demultiplexer 30. The duplexer 30 outputs the signal output from the convolution operation device 32 to the wireless tag antenna 28.

  As described above, when a signal subjected to spreading processing using the same PN code as the uniquely assigned PN code is input to the convolution operation device 32, the signal before the diffusion processing of the input signal is output from the convolution operation device 32. The In the distance measurement process, the process of the convolution operation device 32 is used.

  On the other hand, when a pulse modulated signal that has not been subjected to spreading processing is input to the convolutional computing device 32, the convolutional computing device 32 outputs a spread pulse modulated signal that has been spread by the inherently assigned PN code. Such processing is used in the code detection processing.

  That is, the convolution operation device 32 generates a spread pulse modulated signal by performing a spreading process on the pulse modulated signal input from the duplexer 30 using the unique assignment PN code of the wireless tag 12 and outputs the spread pulse modulated signal to the duplexer 30. To do. The duplexer 30 outputs the spread pulse modulated signal to the RFID tag antenna 28. A spread pulse modulated signal is transmitted from the wireless tag antenna 28.

  Through such processing, each wireless tag receives the pulse modulated signal transmitted from the wireless tag distance measuring device 10 and transmits a spread pulse modulated signal that has been subjected to spreading processing using a uniquely assigned PN code. The wireless tag distance measuring device 10 receives the spread pulse modulated signal transmitted from each wireless tag. When spread pulse modulated signals are transmitted from a plurality of wireless tags, the wireless tag distance measurement device 10 receives a plurality of spread pulse modulated signals in a superimposed manner. In addition, a spread pulse modulated signal is not transmitted from a wireless tag that is not currently used or a wireless tag that exists at a position where the pulse modulated signal transmitted from the wireless tag distance measuring device 10 cannot be received. Therefore, the wireless tag distance measuring device 10 can receive the spread pulse modulated signal transmitted from the wireless tag capable of measuring the distance.

  Next, processing performed by the wireless tag distance measuring device 10 for the spread pulse modulated signal transmitted from each wireless tag will be described. The radio reception unit 40 receives the spread pulse modulated signal via the measurement device antenna 26. Then, the reception signal is amplified until a predetermined signal level is reached, and the amplified signal is output to the PN code detection unit 50 via the reception side switch 42.

  FIG. 4 shows the configuration of the PN code detection unit 50. The PN code detection unit 50 detects the unique assignment PN code of the wireless tag from the reception signal output from the wireless reception unit 40 and outputs it to the measurement target PN code storage unit 20.

  The reception signal storage unit 52 stores the reception signal output from the wireless reception unit 40. The total code determination unit 54 stores all PN codes employed in the wireless tag distance measurement system. Here, all the PN codes employed in the RFID tag distance measuring system are stored when the RFID tag distance measuring device 10 is manufactured, installed, or the like. The unique assignment PN code of the wireless tag used by the user corresponds to one of all the PN codes employed in the wireless tag distance measurement system.

  The total code determination unit 54 selects one of all the PN codes stored therein, and outputs a PN signal whose value changes with the pattern of the PN code to the despreading convolution unit 56. The despreading convolution operation unit 56 performs a convolution operation between the PN signal and the reception signal stored in the reception signal storage unit 52, and outputs the convolution signal to the level determination unit 58. The level determination unit 58 outputs level detection information to the total code determination unit 54 when the level of the convolution signal exceeds a predetermined threshold. When the level detection information is output from the level determination unit 58, the level determination unit 58 stores the PN code that is the source for generating the PN signal output to the despread convolution unit 56 in the measurement target PN code storage unit 20. Output. The measurement target PN code storage unit 20 stores the PN code output from the total code determination unit 54.

  The PN code detection unit 50 sequentially performs a convolution operation with the reception signal stored in the reception signal storage unit 52 and a level determination of the convolution signal for each of all the PN codes stored in the total code determination unit 54. Do. As a result, among all the PN codes stored in the total code determination unit 54, the one whose convolution signal level exceeds a predetermined threshold is output to the measurement target PN code storage unit 20.

  The level of the convolutional signal when the signal that has been spread by the PN code indicating the pattern of the PN signal output from the total code determination unit 54 is superimposed on the reception signal stored in the reception signal storage unit 52 Exceeds the threshold due to the orthogonality of the PN code. In this case, it can be said that the spread pulse modulated signal transmitted from the wireless tag having the PN code as a uniquely assigned PN code is received by the wireless tag distance measuring device 10. Therefore, by storing the PN code that is a source for generating the convolution signal exceeding the threshold value in the measurement target PN code storage unit 20, the unique allocation PN code of the wireless tag capable of distance measurement is stored in the measurement target PN code storage unit 20. Can be memorized.

  By such processing, the PN code detection unit 50 measures all the PN codes employed in the wireless tag distance measurement system that match the unique assigned PN code of the wireless tag capable of distance measurement. The data is output to the PN code storage unit 20. As a result, the measurement target PN code storage unit 20 stores the uniquely assigned PN code of the wireless tag capable of distance measurement. The wireless tag distance measurement device 10 measures the distance to the wireless tag using the PN code stored in the measurement target PN code storage unit 20 by the above-described distance measurement processing.

  For example, a case where the code detection process is executed in the PN code assignment shown in FIG. 1 will be described. As shown in FIG. 5, when the pulse modulation signal is transmitted from the wireless tag distance measuring device 10, the wireless tags 12-1 to 12-4 respectively receive the PN codes “01001. .. ”,“ 01111... ”, And“ 10001. As a result, the PN codes “01001...”, “10011...”, “01111...”, And “10001. Therefore, the wireless tag distance measuring device 10 can obtain each distance from the wireless tags 12-1 to 12-4 based on the distance measurement process.

  In the wireless tag distance measurement system according to the present embodiment, the wireless tag distance measurement device 10 acquires a unique assignment PN code of a wireless tag capable of distance measurement by executing a code detection process. Since the code detection process is a process based on transmission / reception of a wireless signal between the wireless tag distance measuring device 10 and the wireless tag, information for storing each unique assigned PN code of the wireless tag in the wireless tag distance measuring device 10 There is no need to provide an input device separately. Therefore, it is possible to easily perform pre-processing for performing distance measurement.

  Furthermore, according to the RFID tag distance measuring device system according to the embodiment of the present invention, the following effects can be obtained. As described above, when the wireless tag distance measuring device 10 measures the distance to the wireless tag, the unique assignment PN code of the wireless tag to be measured is used. Therefore, when performing distance measurement for all wireless tags capable of distance measurement, the wireless tag distance measurement device 10 uses each uniquely assigned PN code of all wireless tags capable of distance measurement.

  However, in the configuration in which the code detection process is not performed, among the PN codes adopted in the wireless tag distance measurement system, which PN code is assigned to the wireless tag capable of distance measurement is determined. The distance measuring device 10 does not recognize. Therefore, when performing distance measurement for all wireless tags capable of distance measurement, a spread pulse modulation signal is transmitted for each PN code employed in the wireless tag distance measurement system, and response pulse modulation is performed. The distance is measured for the wireless tag that has transmitted the signal. In such a process, since the process of transmitting the spread pulse modulation signal is performed for all of the adopted PN codes, there is a problem that the processing time becomes long.

  According to the wireless tag distance measuring apparatus 10 according to the embodiment of the present invention, the code detection process assigns the wireless tag capable of distance measurement among all the PN codes employed in the wireless tag distance measuring system. Can be stored in the measurement target PN code storage unit 20. Thus, when distance measurement is performed for all the wireless tags capable of distance measurement, it is only necessary to execute processing for each PN code stored in the measurement target PN code storage unit 20. Can be done quickly. In this process, the code selection unit 22 sequentially selects the PN codes stored in the measurement target PN code storage unit 20 and executes a distance measurement process based on the selection.

  FIG. 6 shows a configuration of a PN code detection unit 60 according to a modification. The same components as those of the PN code detector 50 in FIG. 4 are denoted by the same reference numerals and description thereof is omitted. The PN code detection unit 60 performs a convolution operation with the received signal and a level determination of the convolution signal in parallel for all the PN codes employed in the RFID tag distance measurement system.

  The single code determination unit 62, the despreading convolution operation unit 56, and the level determination unit 58 are provided by the number of PN codes employed in the RFID tag distance measurement system. Different single code determination units 62 store different PN codes, and output PN signals whose values change according to the stored PN code patterns to the corresponding despreading convolution operation units 56. The despreading convolution operation unit 56 performs a convolution operation between the reception signal stored in the reception signal storage unit 52 and the PN signal output from the corresponding single code determination unit 62, and the corresponding level determination unit 58. Outputs a convolution signal. The level determination unit 58 outputs level detection information to the corresponding single code determination unit 62 when the level of the convolution signal exceeds a predetermined threshold. When the level detection information is output from the level determination unit 58, the single code determination unit 62 outputs the PN code stored by itself to the measurement target PN code storage unit 20. The measurement target PN code storage unit 20 stores the PN code output from the single code determination unit 62.

  According to such a configuration, convolution calculation and level determination can be performed in parallel for all PN codes employed in the RFID tag distance measurement system. As a result, the code detection process can be performed quickly.

It is a figure which shows the structure of a radio | wireless tag distance measurement system. It is a figure which shows the structure of a wireless tag distance measuring apparatus. It is a figure which shows the structure of a wireless tag. It is a figure which shows the structure of a PN code | symbol detection part. It is a figure explaining the specific example of a code | symbol detection process. It is a figure which shows the structure of the PN code | symbol detection part which concerns on an application example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 RFID tag distance measuring apparatus, 12, 12-1 to 12-4 RFID tag, 14 pulse modulation signal generation part, 16 spreading | diffusion convolution operation part, 18 transmission side switch, 18A, 18B switch terminal, 20 measurement object PN code memory | storage Unit, 22 code selection unit, 24 wireless transmission unit, 26 measuring device antenna, 28 RFID tag antenna, 30 demultiplexer, 32 convolution operation device, 34 digital matched filter, 36 allocation code storage unit, 38 PN code setting circuit, 40 Wireless reception unit, 42 reception side switch, 42A, 42B switch terminal, 44 distance calculation unit, 46 display unit, 48 result storage unit, 50, 60 PN code detection unit, 52 reception signal storage unit, 54 total code determination unit, 56 Despreading convolution operation unit, 58 level determination unit, 62 single code determination unit.

Claims (2)

A wireless tag distance measuring device that calculates a distance to a wireless tag as a distance measurement target based on a transmission timing and a reception timing of a wireless signal,
A pulse signal transmitter for wirelessly transmitting a pulse signal;
A code acquisition unit that receives a radio signal that has arrived after transmission of the pulse signal and acquires a radio tag specific assignment PN code included in the received signal;
A spread signal generation unit that generates a spread signal by a spread process based on a wireless tag specific assignment PN code acquired by the code acquisition unit;
A spread signal transmitter for wirelessly transmitting the spread signal;
A despread signal receiving unit that receives a despread radio signal that has been subjected to despread processing on the spread signal and has arrived after transmission of the spread signal;
A distance calculation unit that calculates a distance to the radio tag based on the transmission timing of the spread signal and the reception timing of the despread radio signal;
A wireless tag distance measuring device comprising: The wireless tag distance measuring device according to claim 1,
The wireless tag;
With
The wireless tag is
Wireless receiving means for receiving an incoming signal;
A convolution operation unit that performs a convolution operation between the PN signal including the PN code uniquely assigned to the wireless tag and the signal received by the wireless reception unit;
Wireless transmission means for wirelessly transmitting the signal obtained by the convolution operation unit;
A wireless tag distance measuring system comprising:

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