JP5834409B2 - IC tag distance measuring device and IC tag - Google Patents

Description

  The present invention relates to an IC tag distance measuring device and an IC tag.

  An IC tag has an IC (integrated circuit) in which information such as its identification code is recorded and an antenna, and transmits and receives information with a reader / writer (hereinafter referred to as R / W) using radio waves. It is a device that performs. An IC tag is usually attached to an article such as a product and is used for management of the attached article. In recent years, it has been proposed to use an IC tag for purposes other than management of an object by measuring the distance between the IC tag and the R / W.

JP 2005-107772 A Japanese Patent Application Laid-Open No. 2001-92985 Special Table 2002-525640

  A conventional IC tag distance measurement method is, for example, that an IC tag measures the intensity of a radio wave transmitted by an R / W and specifies the distance between the IC tag and the R / W from the intensity. Therefore, the conventional distance measurement method has a problem that the accuracy of distance measurement is low. An object of the present invention is to solve such a problem.

  In order to solve the above problem, according to one aspect of the present apparatus, a transmission signal is supplied to an antenna to generate a ranging radio wave, and the ranging radio wave is transmitted to a target IC tag and another IC tag. And a first reflected wave generated by the target IC tag reflecting the distance measurement radio wave with a first reflectance and the other IC tag reflected by the distance measurement radio wave. The first combined reflected wave with the second reflected wave is received by the antenna to generate a first received signal, and the target IC tag has a second reflectance different from the first reflectance. A second combined reflected wave of the third reflected wave generated by reflecting the distance measuring radio wave and the fourth reflected wave generated by the other IC tag reflecting the distance measuring radio wave is the antenna. A radio wave receiving unit that receives the first received signal and generates a second received signal; and The distance of the IC tag having a phase difference calculation unit that obtains a phase difference between the signal component corresponding to the first reflected wave in the first reception signal and the transmission signal based on the second reception signal A measuring device is provided.

  According to the present embodiment, the distance between the distance measuring device and the IC tag can be measured with high accuracy.

It is a figure explaining the structure and operation | movement of the distance measuring device of Embodiment 1 (the 1). It is a figure explaining the structure and operation | movement of the distance measuring device of Embodiment 1 (the 2). It is a figure explaining the structure and operation | movement of the distance measuring device of Embodiment 1 (the 3). It is a block diagram of the distance measuring device of Embodiment 2. It is an example of the circuit diagram of an amplitude detector. It is a block diagram explaining the structure of a target IC tag and another IC tag. 10 is a flowchart for explaining the operation of the distance measuring apparatus according to the second embodiment. It is a figure explaining an example of the command signal which the distance measuring device of Embodiment 2 transmits. It is a figure explaining the time change of the output of an amplitude detector. It is an equivalent circuit diagram explaining the operation of the IC tag. It is a figure explaining an example of a distance measurement system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof. In addition, the same code | symbol is attached | subjected to the corresponding part even if drawings differ, and the description is abbreviate | omitted.

(Embodiment 1)
1-3 is a figure explaining the structure and operation | movement of the distance measuring apparatus 2 of this Embodiment. As shown in FIG. 1, the distance measuring device 2 includes a radio wave transmission unit 4, a radio wave reception unit 6, and a phase difference calculation unit 8.

  The radio wave transmission unit 4 includes an oscillator 10, a radio wave transmission circuit 12, and an antenna 14. The oscillator 10 generates a transmission signal having a predetermined frequency (for example, 1 GHz) and supplies the transmission signal to the radio wave transmission circuit 12. The radio wave transmission circuit 12 amplifies this transmission signal and supplies it to the antenna 14. The transmission signal supplied to the antenna 14 generates a distance measurement radio wave 16, and the distance measurement radio wave 16 is transmitted to a target IC tag 18 (an IC tag for distance measurement) and another IC tag 20.

  As shown in FIG. 2, the target IC tag 18 reflects the received ranging radio wave 16 with a first reflectance to generate a first reflected wave 22. On the other hand, the other IC tag 20 reflects the distance measuring radio wave 16 with a predetermined reflectance (for example, the first reflectance) to generate a second reflected wave 24. The first reflected wave 22 and the second reflected wave 24 are overlapped to become a first combined reflected wave 26.

  Further, as shown in FIG. 3, the target IC tag 18 transmits the distance measuring radio wave 16 with a second reflectance different from the first reflectance (for example, a reflectance of 25% of the first reflectance). The third reflected wave 28 is generated by reflection. Similarly, the other IC tag 20 generates the fourth reflected wave 30 by reflecting the distance measuring radio wave 16 with the predetermined reflectance. The third reflected wave 28 and the fourth reflected wave 30 are overlapped to become a second combined reflected wave 32.

  As shown in FIG. 2, the radio wave receiver 6 includes an antenna 14 and a radio wave receiver circuit 22. The antenna 14 receives the first combined reflected wave 26 and generates a first received signal. The generated first reception signal is supplied to the radio wave reception circuit 22 and amplified. Similarly, as shown in FIG. 3, the antenna 14 receives the second combined reflected wave 32 and generates a second received signal. The generated second reception signal is supplied to the radio wave reception circuit 22 and amplified.

  Based on the amplified first received signal and the amplified second received signal, the phase difference calculation unit 8 generates a signal component corresponding to the first reflected wave in the first received signal and the transmission signal. Find the phase difference. This phase difference corresponds to the distance between the antenna 14 and the target IC tag 18.

By the way, the transmission signal S ₀ (t) generated by the oscillator 10 can be expressed by the following equation.

  Here, A is the amplitude. ω is the angular frequency. t is the time.

On the other hand, the first received signal S ₁ (t) corresponding to the first combined reflected wave 26 can be expressed by the following equation.

Here, the first term on the right side of Equation (2) is a signal component corresponding to the first reflected wave 22. R ₁ and φ ₁ are the amplitude and phase (phase difference from the transmission signal) of this signal component. The second term on the right side of Equation (2) is a signal component corresponding to the second reflected wave 24. R ₂ and φ ₂ are the amplitude and phase of the signal component corresponding to the second reflected wave 24 (phase difference from the transmission signal).

Similarly, the second received signal S ₂ (t) corresponding to the second combined reflected wave 32 can be expressed by the following equation.

Here, the first term on the right side of Equation (3) is a signal component corresponding to the third reflected wave 28. R ₃ and φ ₃ are the amplitude and phase of this signal component (phase difference from the transmission signal). The second term on the right side of Equation (3) is a signal component corresponding to the fourth reflected wave 30. R ₄ and φ ₄ are the amplitude and phase of this signal component (phase difference from the transmission signal).

  Now, it is assumed that the distance measuring device 2, the target IC tag 18, and the other IC tags 20 do not move during distance measurement. Then, the following relational expression is established between the phase and amplitude of each signal component.

The target IC tag 18 generates the first reflected wave by reflecting the distance measuring radio wave with the first reflectance, and generates the third reflected wave by reflecting the distance measuring radio wave with the second reflectance. To do. Therefore, the amplitude R ₁ of the signal component corresponding to the first reflected wave is not equal to the amplitude R _{3 of the} signal component corresponding to the second reflected wave.

On the other hand, the other IC target 20 reflects the distance measurement radio wave with a predetermined reflectance (a constant value) to generate the second reflected wave and the fourth reflected wave. Therefore, the third amplitude R ₄ of the corresponding signal component to the amplitude R ₂ and fourth reflected wave signal component corresponding to the reflected waves are equal.

As described above, since the target IC tag 18 and the distance measuring device 2 do not move during the distance measurement, the distance between both devices is constant. Therefore, φ ₁ = φ ₃ is obtained. Similarly, during the distance measurement, the other IC tags 18 and the distance measuring device 2 do not move, so φ ₂ = φ ₄ .

Therefore, by obtaining the difference between the first received signal S ₁ (t) and the second received signal S ₂ (t), only the signal corresponding to the reflected wave from the target IC tag 18 can be extracted.

However, the first received signal S ₁ (t) and the second received signal S ₂ (t) are received at different times. For example, the first reception signal S ₁ (t) is received in the reception period [t ₁ , t ₁ + Δt]. On the other hand, the second reception signal S ₂ (t) is received in the reception period [t ₂ , t ₂ + Δt] (t ₁ and t ₂ are different). Accordingly, the first reception signal S ₁ (t) and the second reception signal S ₂ ((2) are shifted after the origin of one reception period is shifted by an integral multiple of (2π / ω) so that the reception periods of both signals overlap. Find the difference of t). However, even in this way, the calculation result is the same as S ₁ (t) −S ₂ (t). Therefore, thereafter, the difference (for example, S ₁ (t) −S ₂ (t−2πn / ω); n is an integer) obtained by shifting the origin of one reception time t in this way is expressed as S _1. (T) −S ₂ (t).

Equation (5) is the difference between the _first received signal S ₁ (t) and the second received signal S ₂ (t) obtained in this way (hereinafter referred to as a calculation signal). Equation (5) indicates that the arithmetic signal has the same phase as the signal component R ₁ sin (ωt ₁ + φ ₁ ) corresponding to the first reflected wave 28 in the first received signal S ₁ (t). Show. The phase phi ₁ can be expressed by the following equation.

Here, d is a distance between the target IC tag 18 and the distance measuring device 2 (more precisely, the antenna 14). λ is the wavelength of the distance measuring radio wave (= 2πc / ω, c is the speed of light). The unit of phi ₁ is rad.

As is clear from the equation (6), the phase φ ₁ corresponds to the distance d between the target IC tag 18 and the distance measuring device 2. Therefore, if the phase φ ₁ is known, the distance d between the target IC tag 18 and the distance measuring device 2 can be calculated. The following formula is used to calculate the distance d.

Formula (7) shows a calculation formula when the unit of phase φ ₁ is (rad) and a calculation formula when the unit of phase φ ₁ is degree (°).

When the phase φ ₁ is 90 ° and the frequency f of the transmission signal is 1 GHz, the distance d is 3.75 cm from the equation (7). Here, the measurement accuracy of the phase φ ₁ is about several degrees. Therefore, the measurement accuracy of the distance d is about 1 mm.

The distance measuring device 2 measures the distance to the target IC tag 18 based on the phase difference between the received signal and the transmitted signal generated by the reflected wave of the distance measuring radio wave 16. For this reason, if reflected waves from other IC tags 20 and radio wave reflectors are mixed in the received radio wave, it becomes an obstacle to distance measurement. However, the distance measuring apparatus 2 according to the present embodiment solves such a problem by obtaining a difference between the _first received signal S ₁ (t and the second received signal S ₂ (t).

By the way, when the frequency of the transmission signal is low, the first reception signal S ₁ (t) and the second reception signal S ₂ (t) are converted from analog to digital, respectively, and an arithmetic signal (= S ₁ (t ) -S ₂ (t)) is easy to find. However, if the frequency f of the transmission signal is increased to increase the measurement accuracy of the distance d, analog / digital conversion of the reception signal becomes difficult.

Therefore, in the present embodiment, the amplitude and phase of each of the first reception signal S ₁ (t) and the second reception signal S ₂ (t) are measured, and the phase of the calculation signal is determined based on these measurement values. to calculate the φ _1.

Expression (8) is an expression representing the first reception signal S ₁ (t) using the phase difference θ ₁ of the transmission signal. P ₁ is the amplitude of the first received signal S ₁ (t). Similarly, Expression (9) is an expression that represents the second reception signal S ₂ (t) using the phase difference θ ₂ of the transmission signal. P ₂ is the amplitude of the second received signal S ₂ (t).

  Using equations (8) and (9), the arithmetic signal can be expressed as:

Here, P _cal and θ _cal are parameters calculated by the following equations.

The phase calculation unit 8 of the present embodiment _first measures the amplitude P ₁ and the phase θ ₁ of the first reception signal S ₁ (t). Furthermore, the phase calculation unit 8 measures the amplitude P ₂ and the phase θ ₂ of the second reception signal S ₂ (t).

Thereafter, the phase calculation unit 8 calculates the phase θ _cal of the calculation signal based on Expression (12). This phase θ _cal corresponds to the distance to the target IC tag 18 as described above.

  By the way, the measurement of the amplitude and phase of the received signal is easy even in a high frequency band (for example, GH band). Therefore, according to the distance measuring device 2, the measurement accuracy of the distance to the target IC tag 18 can be increased.

Incidentally, the phase of the calculation signal is not only the phase of the reception signal corresponding to the first reflected wave 22, but also the phase difference between the signal component corresponding to the third reflected wave 28 and the transmission signal. Therefore, the phase difference calculation unit 8 uses the second received wave 28 in the second received signal based on the amplified first received signal S ₁ (t) and second received signal S ₂ (t). It is also a device for obtaining the phase difference between the signal component corresponding to the transmission signal and the transmission signal.

(Embodiment 2)
(1) Configuration FIG. 4 is a configuration diagram of the distance measuring device 2a of the present embodiment. This distance measuring device 2a is R / W provided in a portable terminal, for example.

  As shown in FIG. 4, the distance measuring device 2 a includes an oscillator 10, a processor 34, a reception-side filter 36 a, a transmission-side quadrature mixer 38 a, a transmission-side amplifier 40 a, a circulator 42, and an antenna 14. The oscillator 10 and the antenna 14 have the same functions as the oscillator and antenna of the first embodiment, respectively. The processor 34, the transmission-side filter 36a, the transmission-side orthogonal mixer 38a, the transmission-side amplifier 40a, and the circulator 42 function as the radio wave transmission circuit 12 of the first embodiment. The processor 34 has a CPU (Central Processing Unit) and a memory. In this memory, a program for causing the CPU to realize the functions described below is recorded. This memory is used for calculations performed by the CPU.

  The distance measuring device 2a includes a reception side amplifier 40b, an amplitude detector 44, and a phase comparator 46. The circulator 42 and the receiving side amplifier 40b function as the radio wave receiving circuit 22 of the first embodiment. The amplitude detector 44, the phase comparator 46, and the processor 34 function as the phase calculation unit 8 of the first embodiment.

  The distance measuring device 2a includes a reception side filter 36b, a reception side orthogonal mixer 38b, and a demodulator 48. These devices are used to demodulate data from the target IC tag 18 and other IC tags 20.

  The processor 34 also functions as part of a distance calculation unit and a command transmission unit described later. As shown in FIG. 4, the processor 34 is connected to a LAN (Local Area Network) 50. The LAN 50 is a network provided in a portable terminal, for example, and is connected to another CPU or the like. The processor 34 transmits / receives information to / from other CPUs via the LAN 50.

  FIG. 5 is an example of a circuit diagram of the amplitude detector 44. As shown in FIG. 5, the amplitude detector 44 includes an inverting amplifier 54 having an amplification factor of 0 dB, a first transistor 56a, a second transistor 56b, a load resistor 58, a capacitor 60, and an analog / digital converter 70. ing. The first transistor 56a and the second transistor 56b have substantially the same threshold value.

  The input signal input to the input terminal 72 is supplied to the gate of the first transistor 56a and the input of the inverting amplifier 56b. The inverting amplifier 56b inverts the polarity of the input signal and supplies it to the gate of the second transistor 56b.

  As shown in FIG. 5, one end of the capacitor 60 is grounded. The other end of the capacitor 60 is connected to the sources of the first transistor 56a and the second transistor 56b. The first transistor 56a charges the capacitor 60 until the sum of the voltage of the capacitor 60 and the threshold value of the first transistor 56a reaches the maximum value of the input signal. Similarly, the second transistor 56b charges the capacitor 60 until the sum of the voltage of the capacitor 60 and the threshold of the second transistor 56b reaches the maximum value of the output of the inverting amplifier 54. On the other hand, the load resistor 58 gradually discharges the capacitor 60.

  Therefore, a voltage lower than the maximum value of the input signal by the threshold value of the first and second transistors 56a and 56b is generated at both ends of the capacitor 60. The analog / digital converter 70 converts this voltage into a digital signal and outputs it. Therefore, the amplitude detector 44 outputs data approximately equal to the amplitude of the input signal from the output terminal 74.

  The phase detector 46 includes, for example, an analog multiplier that multiplies and outputs a pair of input signals and an analog-digital converter that converts the output from analog to digital. Accordingly, when a pair of input signals having substantially the same frequency is supplied, the phase detector 46 outputs a digital signal proportional to the phase difference between the input signals.

  With this configuration, the distance measuring device 2a transmits the distance measuring radio wave 16 to the target IC tag 18 and the other IC tag 20, and measures the phase difference corresponding to the distance from the target IC tag 18. (See FIG. 1).

  FIG. 6 is a configuration diagram illustrating the configuration of the target IC tag 18 and another IC tag 20 (hereinafter referred to as an IC tag). As shown in FIG. 6, the IC tags 18 and 20 include an antenna 76, a rectifier 78, a signal extraction circuit 80, a logic circuit 82, and a transistor 84.

  The antenna 76 receives the radio wave 86 transmitted by the distance measuring device 2 and supplies it to the rectifier 78 and the signal extraction circuit 80. The rectifier 78 rectifies the signal received by the antenna 76 to generate a DC voltage, and supplies the DC voltage to the signal extraction circuit 80, the logic circuit 82, and the transistor 84. The signal extraction circuit 80 demodulates the signal received by the antenna 76 to generate a digital signal, and inputs the digital signal to the logic circuit 82. The logic circuit 82 turns on / off the transistor 84 in response to a command and data included in the input digital signal. By this ON / OFF operation, the reflectance of the antenna 76 changes, and the reflected wave 88 is modulated.

(2) Operation FIG. 7 is a flowchart for explaining the operation of the distance measuring device 2a. The distance measuring device 2a first transmits a command signal to the target IC tag 18 (S2). FIG. 8 is a diagram for explaining an example of the command signal 90 transmitted by the distance measuring device 2a.

  The command signal 90 includes a synchronization signal 92, a delimiter signal 94, a data signal 96, and an error check signal (for example, a CRC signal) 98. The data signal 96 has a user ID (identification) area 100 and a data / command area 102.

  The distance measuring device 2a uses the user ID area 100 to transmit the user ID assigned to the target IC tag. In addition, the distance measuring apparatus 2 a transmits a command to the target IC tag 18 using the data / command area 102. The content of the command is to alternately change the reflectivity for the distance measuring radio wave between the first reflectivity and the second reflectivity. Further, the distance measuring device 2a transmits the number of times (for example, 100 times) of changing the reflectance alternately by using the data / command area 102. In the following description, it is assumed that the first reflectance is higher than the second reflectance.

  A digital signal corresponding to the command signal 90 is generated by the processor 34. The digital signal is smoothed by the transmission filter 36a and input to the transmission orthogonal mixer 38a. The transmission-side quadrature mixer 38a generates a command signal 90 by performing quadrature modulation on the high-frequency signal (for example, 1 GHz) generated by the oscillator 10 using this digital signal. The generated command signal 90 is converted into a radio wave by the transmission side amplifier 40a, the circulator 42, and the antenna 14, and transmitted to the IC tags 18 and 20.

  The target IC tag 18 that has received this radio wave first detects the user ID from the user ID area 100. The target IC tag 18 confirms that the detected user ID matches its own ID, and then changes the reflectivity for the distance measuring radio wave 16 to the first reflectivity and the first reflectivity according to the command and data in the data / command area 102. The reflectance is alternately changed to 2. On the other hand, since the other IC tag 20 does not match the user ID detected from the user ID area 100 with its own ID, the reflectance for the distance measuring radio wave 16 is set to a predetermined reflectance (for example, the first reflectance). Hold.

  That is, the processor 34 or the like sets the reflectivity for the distance measurement radio wave to the first reflectivity, and then sets the reflectivity to the second reflectivity value different from the first reflectivity value. It functions as a command transmission unit that sends out a command for instructing. Here, the processor 34 and the like are the processor 34, the transmission side filter 36a, the transmission side orthogonal mixer 38a, the oscillator 10, the transmission side amplifier 40a, the circulator 42, and the antenna 14.

  Next, the processor 34 inputs a predetermined positive voltage and 0 V to the I channel (In-phase Channel, quadrature component) and the Q channel (Q-phase Channel, quadrature component) of the transmission-side quadrature mixer 38a, and the oscillator 10 Generates a sine wave signal in phase with the high-frequency signal (transmission signal) generated by. The transmission side amplifier 40a, the circulator 42, and the antenna 14 amplify the sine wave signal to generate the distance measuring radio wave 16. The generated distance measuring radio wave 16 is transmitted to the target IC tag 18 and the other IC tag 20 (S4).

  Next, the processor 34 determines whether or not the number of measurements of the received signal has reached a predetermined number (S6). If the number of measurements does not reach the predetermined number, the process proceeds to the next Hi signal detection step (S8). When the number of measurements reaches a predetermined number, the measurement is terminated and the process proceeds to the phase calculation step (S28). The predetermined number is equal to or less than the number of times that the target IC tag alternately changes the reflectance.

  As described above, the target IC tag 18 periodically increases or decreases the reflectance with respect to the distance measuring radio wave 16 in response to the command signal 90 in step S2. As the reflectance changes, the amplitude of the received signal of the distance measuring device 2a also periodically increases and decreases. In the Hi signal detection step S8, the processor 34 detects the timing at which the received signal level reaches a high state (Hi level) based on the output of the amplitude detector 44.

FIG. 9 is a diagram for explaining the time change of the output of the amplitude detector 44. The horizontal axis is time. The vertical axis represents voltage. FIG. 9 shows the voltage 104 across the capacitor 60 shown in FIG. 5, the voltage 106 of the received signal supplied to the gate of the transistor 56a, and the output voltage 108 of the inverting amplifier 54 supplied to the gate of the transistor 56b. ing. FIG. 9 also shows the threshold value _{Vth of} the first transistor 56a and the second transistor 56b. FIG. 9 also shows a Hi signal reception period in which the amplitude of the reception signal increases and a Low signal reception period in which the amplitude of the reception signal decreases.

The first transistor 56a conducts while the received signal 106 supplied to the gate exceeds the voltage 104 across the capacitor 60 and the threshold value _Vth of the first transistor 56a, and charges the capacitor 60. Similarly, the second transistor 56b conducts while the output voltage 108 of the inverting amplifier 54 supplied to the gate exceeds the voltage 104 across the capacitor 60 and the threshold _Vth of the second transistor 56b, and the capacitor 60 To charge. Here, as described above, the threshold value _Vth of the first transistor 56a and the second transistor 56b is substantially the same.

Accordingly, the voltage 104 across the capacitor 60 becomes a value smaller than the amplitude of the received signal 106 (or the amplitude of the output voltage 108 of the inverting amplifier 54) by the threshold _Vth . The amplitude detector 44 converts the voltage 104 across the capacitor 60 from analog to digital and outputs the result. The processor 34 monitors this output and detects the timing at which the received signal reaches a high state (Hi level) (S8).

  When detecting the timing at which the received signal reaches the Hi level, the processor 34 waits for a sufficient time (for example, 1 μs) for the amplitude of the received signal to stabilize (S10).

Thereafter, the processor 34 records the outputs of the amplitude detector 44 and the phase comparator 46 in a memory (not shown) (S12). The data recorded in the memory at this time is the amplitude P ₁ and phase θ ₁ (the phase difference between the high-frequency signal generated by the oscillator 10 and the Hi level received signal) of the received signal (Hi level received signal) at the Hi level.

When the amplitude P ₁ and the phase θ ₁ of the Hi signal are recorded, the processor 34 detects the output of the amplitude detector 44 again, and as shown in FIG. 9, the detected amplitude is a predetermined value from the amplitude at the Hi level. It is determined whether or not the number has decreased by 105 (for example, 3 steps) or more (S14, S16). If it is determined that the detected data has decreased by a predetermined value, the processor 34 proceeds to the next Low signal detection step S18. If it is determined that the value has not decreased by the predetermined value, the processor 34 returns to the amplitude detection step S14.

  During the Low signal detection step S18, the processor 34 monitors the output of the amplitude detector 44 and detects the timing when the reception signal level reaches a low state (Low level). Thereafter, the processor 34 waits for a sufficient time (for example, 1 μs) for the amplitude of the received signal to stabilize (S20).

When this standby time has elapsed, the processor 34 detects the outputs of the amplitude detector 44 and the phase comparator 46 and records them in a memory (not shown) (S22). The data recorded in the memory at this time is the amplitude P ₂ and the phase θ ₂ (the phase difference between the high-frequency signal generated by the oscillator 10 and the low level received signal) of the received signal (low level received signal) at the low level.

When the amplitude P ₂ and the phase θ ₂ of the Low signal are recorded, the processor 34 detects the output of the amplitude detector 44 again, and the detected amplitude is increased from the amplitude at the Low level by a predetermined value (for example, 3 steps) or more. Whether or not (S24, S26). If it is determined that the value has increased by a predetermined value, the processor 34 returns to step S6. If it is determined that it has not increased by a predetermined value, the processor 34 returns to the amplitude detection step S24.

Returning to step S6, if it is determined that the number of measurements has reached the predetermined number, the processor 34 proceeds to phase difference calculation step S28. In the phase calculation step S28, the processor 34 calculates the phase difference θ _cal of the calculation signal based on the equation (12) described in the first embodiment and the data recorded in the memory. At this time, the processor 34 averages the amplitudes P ₁ and P ₂ and the phases θ ₁ and θ ₂ recorded in the memory, and uses them in the calculation of Expression (12). Therefore, according to the present embodiment, the measurement accuracy is improved.

Further, the processor 34 calculates a distance corresponding to the phase difference θ _cal in the next distance calculation step S30. At this time, the processor 34 calculates the distance d by using θ _cal calculated in the phase difference calculation step S28 as φ ₁ in the equation (7). As described above, the processor 34 functions as a distance calculation unit that calculates a distance corresponding to the phase difference between the signal component corresponding to the first reflected wave in the first reception signal and the transmission signal.

By the way, the range of θ _cal calculated in the phase difference calculation step S28 is 0 to 360 °. Accordingly, the distance range calculated in the distance calculation step S30 is a range from 0 mm to λ / 2 (for example, 15 cm). When the target IC tag 18 is separated from the distance measuring device 2a by an integer multiple of λ / 2, the distance between the distance measuring device 2a and the target IC tag 18 is a distance smaller than the actual distance by an integral multiple of λ / 2. Is calculated as However, as described in the third embodiment, even if such a distance is calculated, there is often no problem in application.

  FIG. 10 is an equivalent circuit diagram for explaining the operation of the IC tags 18 and 20. As shown in FIG. 10, the IC tags 18 and 20 include an equivalent circuit 110 of an anten 76, an equivalent circuit 112 such as a rectifier 78, an equivalent circuit 114 of a transistor 84, and a logic circuit 82.

  The equivalent circuit 110 of the antenna 76 has an antenna impedance 116 (for example, 50Ω) and a signal source 118. The power consumed by the antenna impedance 116 is the reflected wave power. The equivalent circuit 112 is an equivalent circuit of the entire circuit excluding the antenna 76 and the transistor 84. The equivalent circuit 112 is simplified to one load resistor. The value of this load resistance is, for example, 50Ω. An equivalent circuit 114 of the transistor 84 includes an ON resistance 120 and a switch 122. The value of the ON resistance 120 is 1Ω, for example.

  Now, when the switch 122 is closed by the logic circuit 82, the load resistance 112 and the ON resistance 120 are connected in parallel to the equivalent circuit 110 of the antenna. At this time, a large current flows through the antenna impedance 116 via the low-resistance ON resistance 120. For this reason, the reflectance of the antenna 76 becomes high.

  On the other hand, when the switch 122 is opened by the logic circuit 82, only the load resistor 112 is connected to the equivalent circuit 110 of the antenna. At this time, a minute current flows through the antenna impedance 116 via the high resistance load resistor 112. For this reason, the reflectance of the antenna 76 becomes low. The IC tags 19 and 20 control the reflectance of the antenna 76 in this way.

(Embodiment 3)
FIG. 11 is a diagram illustrating an example of the distance measurement system 124. The distance measuring system 124 includes the distance measuring device 2a according to the second embodiment and a plurality of IC tags 126. The plurality of IC tags 126 are the IC tags described with reference to FIG.

  As shown in FIG. 11, the distance measuring device 2 a is provided in the mobile terminal 130. The plurality of IC tags 126 are attached to the user's finger and wrist of the mobile terminal 130.

  The distance measuring device 2 a transmits a command signal 90 to the plurality of IC tags 126 and sequentially selects target IC tags from the plurality of IC tags 126. Each time the distance measuring device 2a selects a target IC tag, the distance measuring device 2a obtains the phase difference of the calculation signal according to the procedure (S4 to S30) described with reference to FIG. The distance measuring device 2a calculates the distance between each of the plurality of IC tags 126 and the position (predetermined position) of the distance measuring device 2a based on this phase difference.

  The portable terminal 130 specifies a command corresponding to the movement or shape of the user's hand 128 based on the distance (or phase difference) measured by the distance measuring device 2a. The mobile terminal 130 operates in response to the specified command. Therefore, according to the distance measurement system 124, the mobile terminal 130 can be operated without using a keyboard or a touch panel.

  By the way, as described above, the distance calculated by the distance measurement system 124 may differ from the actual distance by an integral multiple of 1/2 of the wavelength of the distance measurement radio wave. However, the shape and movement of the hand is estimated from the relative distance between the IC tags. Therefore, there is no problem even if the measurement distance is different from the actual distance.

  In addition, as shown in FIG. 11, you may provide another distance measuring apparatus 2b in the portable terminal 130. FIG. Thus, by providing a plurality of distance measuring devices, the shape and movement of the user's hand can be specified more accurately.

  In the present embodiment, the target IC tag is selected from a plurality of IC tags 126. However, the target IC tag and the other IC tag may be fixed. In this case, only the target IC tag is programmed to respond to a command signal for changing the reflectivity.

  In the present embodiment, the distance measuring devices 2a and 2b are provided in the mobile terminal 130. However, the distance measuring devices 2a and 2b may be provided in other information processing devices (for example, personal computers).

  In the above embodiment, a voltage having a constant intensity is input from the processor 34 to the transmission-side orthogonal mixer 38a to generate a sine wave having a constant frequency and amplitude. However, a signal obtained by amplitude-modulating the sine wave signal generated by the oscillator 10 by the quadrature mixer 38a may be used as the transmission signal. However, it is preferable that the cycle of the sine wave signal generated by the oscillator 10 is sufficiently longer than the cycle in which the target IC tag changes the reflectance.

  In the first and second embodiments, the number of other IC tags 20 is one. However, there may be a plurality of other IC tags 20.

  Regarding the above embodiment, the following additional notes are disclosed.

(Appendix 1)
A radio wave transmitter for supplying a transmission signal to an antenna to generate a radio wave for ranging, and transmitting the radio wave for ranging to a target IC tag and another IC tag;
A first reflected wave generated by the target IC tag reflecting the distance measuring radio wave with a first reflectance and a second reflected wave generated by the other IC tag reflecting the distance measuring radio wave. The first combined reflected wave is received by the antenna to generate a first received signal, and the target IC tag receives the distance measurement radio wave with a second reflectance different from the first reflectance. A second combined reflected wave of the third reflected wave generated by reflection and the fourth reflected wave generated by reflecting the distance measuring radio wave by the other IC tag is received by the antenna, and the second reflected wave is received. A radio wave receiver that generates a received signal of
A phase difference calculation unit that obtains a phase difference between a signal component corresponding to the first reflected wave in the first reception signal and the transmission signal based on the first reception signal and the second reception signal. An IC tag distance measuring device.

(Appendix 2)
In the distance measuring device according to attachment 1,
The phase difference calculating unit includes amplitudes of the first reception signal and the second reception signal, a phase difference between the first reception signal and the transmission signal, and the second reception signal and the transmission signal. A distance measurement device for an IC tag, comprising: obtaining a phase difference between the signal component and the transmission signal based on a phase difference between the signal component and the transmission signal.

(Appendix 3)
In the distance measuring device according to appendix 1 or 2,
Furthermore, the distance measuring part of an IC tag characterized by having a distance calculation part which calculates the distance corresponding to the phase difference of the said signal component and the said transmission signal.

(Appendix 4)
In the distance measuring device according to any one of appendices 1 to 3,
Sending the distance measurement radio waves to a plurality of IC tags,
An IC tag distance measuring device, wherein an IC tag is sequentially selected from the plurality of IC tags, and a phase difference between the signal component and the transmission signal is sequentially obtained using the selected IC tag as the target IC tag. .

(Appendix 5)
A target IC tag that reflects a distance measurement radio wave with a first reflectance and then reflects the distance measurement radio wave with a second reflectance different from the first reflectance;
Another IC tag that reflects the distance measuring radio wave with a predetermined reflectance;
A transmission signal is supplied to an antenna to generate the ranging radio wave, and the radio wave transmitting unit that transmits the ranging radio wave to the target IC tag and the other IC tag; and the target IC tag includes the first IC tag. A first combined reflected wave of a first reflected wave generated by reflecting the distance measuring radio wave with a reflectance and a second reflected wave generated by the other IC tag reflecting the distance measuring radio wave. The third reflected wave generated by the target IC tag reflecting the distance measuring radio wave with the second reflectivity and the other IC tag Receives a second combined reflected wave with a fourth reflected wave generated by reflecting the distance measuring radio wave by the antenna and generates a second received signal, and the first reception A first signal in the first received signal based on the signal and the second received signal; Distance measuring device system of an IC tag and a distance measuring device of the IC tag and a phase difference calculating unit for obtaining a phase difference between the signal component and the transmission signal corresponding to the reflected wave.

(Appendix 6)
An IC tag that reflects a distance measurement radio wave with a first reflectance and then reflects the distance measurement radio wave with a second reflectance different from the first reflectance.

(Appendix 7)
Measure a value corresponding to the distance between each of a plurality of IC tags attached to a human hand and a predetermined position,
Based on a value corresponding to the distance, an instruction corresponding to the movement or shape of the person's hand is identified,
A method for operating an information processing apparatus, wherein the information processing apparatus is operated based on the specified command.

2 ... Distance measuring device 4 ... Radio wave transmitter 6 ... Radio wave receiver 8 ... Phase difference calculator 18 ... Target IC tag 20 ... Other IC tags

Claims (5)

A radio wave transmitter for supplying a transmission signal to an antenna to generate a ranging radio wave, and transmitting the ranging radio wave to the first target and the second target;
A first reflected wave generated by the first target reflecting the distance measuring radio wave with a first reflectance and a second reflection generated by the second target reflecting the distance measuring radio wave. A first combined reflected wave with a wave is received by the antenna to generate a first received signal, and the first target is used for ranging with a second reflectance different from the first reflectance. A second combined reflected wave of a third reflected wave generated by reflecting a radio wave and a fourth reflected wave generated by the second target reflecting the distance measuring radio wave is received by the antenna. A radio wave receiver that generates a second received signal;
Phase difference calculation for obtaining a phase difference between a signal component corresponding to the first reflected wave in the first received signal and the transmission signal based on the first received signal and the second received signal have a part and,
The distance corresponding to the phase difference obtained by the phase difference calculation unit is calculated.
Distance measuring device. The distance measuring device according to claim 1,
The phase difference calculation unit, and the amplitude of the first received signal and the second received signal, a first phase difference between the transmitted signal and the first reception signal, the second received signal and the transmission signal based on the second phase difference between the distance measuring apparatus characterized by determining the position phase difference between the transmitted signal and the signal component. Te distance measuring apparatus odor according to claim 1 or 2,
Distance measuring apparatus characterized by having a distance calculation unit configured to calculate the distance that corresponds to the phase difference the phase difference calculating unit is determined. In the distance measuring device according to any one of claims 1 to 3,
Furthermore, the radio waves for ranging are transmitted to a plurality of targets,
Wherein the plurality of the third target are sequentially selected from the target, and with the said selected third target first target, the distance measuring apparatus characterized by sequentially determining said phase difference. Each IC tag, if it matches the identifier ID is assigned included in the received command, in accordance with the modulation frequency of the distance measuring radio waves included in the command, the measurement距用wave at a first reflectance having a circuit repeating that you reflecting the distance measuring radio wave with a different second reflectance cyclically the first reflectance after reflection perilla
Multiple IC tags.

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