WO2005076497A1

WO2005076497A1 - Wireless tag communication apparatus

Info

Publication number: WO2005076497A1
Application number: PCT/JP2005/000422
Authority: WO
Inventors: Katsuyuki Kuramoto
Original assignee: Brother Kogyo Kabushiki Kaisha
Priority date: 2004-02-06
Filing date: 2005-01-14
Publication date: 2005-08-18
Also published as: JP2005223730A

Abstract

A wireless tag communication apparatus capable of realizing a high-sensitivity communication irrespectively of a position relative to a wireless tag. A reception antenna (38) has a plurality of reception antenna elements (40) so oriented as to receive reflected waves (Frf) having their respective different polarization planes. The reception antenna (38), therefore, can realize high-sensitivity communication irrespectively of the relative angles of the polarization planes of the reflected waves (Frf) from a wireless tag (14). Additionally, the required number of the reception antenna elements (40) to be used is relatively small, so that the apparatus size can be advantageously reduced. That is, there can be provided a wireless tag communication apparatus (12) capable of realizing a high-sensitivity communication irrespectively of a position relative to a wireless tag (14).

Description

Specification

Wireless tag communication device

Technical field

The present invention relates to an improvement in a wireless tag communication device that performs communication with a wireless tag that can write and read information wirelessly.

Background art

[0002] RFID (Radio Frequency) that reads information from a small wireless tag (transponder) storing predetermined information in a non-contact manner by a predetermined wireless tag communication device (interrogator)

Identification) systems are known. This RFID system is capable of reading information stored in a wireless tag by communicating with the wireless tag communication device even when the wireless tag is dirty or invisible, is placed at a position, or is not visible. Because of this, practical applications are expected in various fields such as product management and inspection processes!

[0003] Generally, the wireless tag communication device transmits a predetermined transmission signal to the wireless tag.

(The carrier wave) is transmitted by the transmitting antenna, and the return signal (reflected wave) returned from the wireless tag that received the transmission signal is received by the receiving antenna (there is also a common mode with the transmission antenna), so that the wireless tag Although information communication is performed with the wireless tag, there is a problem that the communication sensitivity is significantly reduced depending on the relative positional relationship with the wireless tag. That is, when the plane of polarization (the plane on which the electric field component oscillates) of the receiving antenna provided in the wireless tag communication device is perpendicular to the plane of polarization of the reflected wave from the wireless tag, the reflected wave is almost completely lost. I could not receive it. As a configuration for solving such a problem, for example, a moving object identification device described in Patent Document 1 has been proposed. According to this configuration, since the plurality of planar array antennas are arranged at a predetermined arrangement and interval, the reflected wave of the RFID tag power is received by the planar array antennas, and the plane of polarization of the reflected wave is received. It is said that high-sensitivity communication is possible regardless of the relative angle of the communication.

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-177338

[0005] However, in the above-described conventional technique, the plane of polarization of the planar array antenna does not always have a suitable angle with respect to the plane of polarization of the reflected wave from the wireless tag, so that communication sensitivity is reduced. The ability to eliminate the possibility of doing. In addition, a large area is required to dispose a relatively large number of planar array antennas, which causes a new problem that the device becomes large. That is, a wireless tag communication device that realizes high-sensitivity communication regardless of the relative positional relationship with the wireless tag has been developed yet.

Disclosure of the invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wireless tag communication device that realizes high-sensitivity communication regardless of the relative positional relationship with the wireless tag. To provide.

Means for solving the problem

[0007] In order to achieve such an object, the gist of the present invention is to transmit a predetermined transmission signal to a wireless tag by a transmission antenna, and to transmit a predetermined signal to the wireless tag. A wireless tag communication device that communicates information with the wireless tag by receiving a reply signal received by a receiving antenna, wherein the receiving antenna can receive the reply signal having a different polarization plane. It is characterized by having a plurality of disposed antenna elements.

The invention's effect

[0008] According to this configuration, since the receiving antenna includes the plurality of antenna elements arranged so as to be able to receive the return signal having different polarization planes, the polarization of the reflected wave of the RFID tag is also increased. In addition to the fact that high-sensitivity communication is possible regardless of the relative angle of the wavefront, there is an advantage in that a relatively small number of antenna elements is sufficient and the device can be miniaturized. That is, it is possible to provide a wireless tag communication device that realizes high-sensitivity communication regardless of the relative positional relationship with the wireless tag.

[0009] Preferably, a weight value for controlling a weight value applied to the return signal supplied to each antenna element according to the strength and phase of each of the return signals received by the plurality of antenna elements It includes a control unit. With this configuration, the return signal supplied from the predetermined antenna element corresponding to the polarization plane of the reflected wave from the wireless tag By increasing the weight given, communication with as high a sensitivity as possible can be realized.

[0010] Preferably, the reception antenna includes a first antenna element as a base, a second antenna element having a polarization plane angle of 15 ° or more and 45 ° or less with respect to the first antenna element, and And at least a third antenna element. In this way, communication with as high a sensitivity as possible can be realized. Regarding the polarization plane angle of the second antenna element or the third antenna element with respect to the first antenna element, the angle range in which practical sensitivity can be guaranteed while the antenna installation area is as small as possible is 15 ° or more and 45 ° or less. The angle range over which the sensitivity attenuation can be ignored is 35 ° or more and 45 ° or less, and the optimal angle is 45 °.

[0011] Preferably, the transmission antenna has a plurality of antenna elements arranged so as to be able to transmit the transmission signals having different polarization planes. In this way, a suitable transmission signal can be transmitted according to the relative positional relationship with the wireless tag, and the return signal of the wireless tag power can be strengthened.

[0012] Preferably, the transmission antenna further includes a transmission polarization plane control unit that controls a polarization plane of the transmission antenna according to an intensity of the return signal received by the reception antenna. With this configuration, a suitable transmission signal can be transmitted according to the relative positional relationship with the wireless tag, and the return signal of the wireless tag can be strengthened.

[0013] Preferably, the transmission polarization control unit causes the transmission signal to be transmitted by any one of the plurality of antenna elements, and switches the antenna element to switch the transmission antenna. It controls the plane of polarization. In this way, the polarization plane of the transmitting antenna can be switched in a practical manner.

[0014] Preferably, the transmission polarization control section causes the transmission signal to be transmitted by at least two of the plurality of antenna elements, and the transmission signal to be transmitted from each antenna element. By controlling each phase, the polarization plane of the transmitting antenna is controlled. In this way, the polarization plane of the transmitting antenna can be switched in a practical manner.

[0015] Preferably, the transmission antenna and the reception antenna share the plurality of antenna elements. By doing so, the size of the wireless tag communication device can be reduced as much as possible. [0016] Preferably, the antenna element is a rod-shaped array antenna. With this configuration, the transmitting antenna and the receiving antenna can be configured by the antenna element in a practical mode.

[0017] Preferably, the antenna element is a planar array antenna. With this configuration, the transmitting antenna and the receiving antenna can be configured by the antenna element in a practical mode.

Brief Description of Drawings

FIG. 1 is a diagram illustrating a configuration of a communication system to which the present invention is suitably applied.

FIG. 2 is a diagram illustrating an electrical configuration of the wireless tag communication device of FIG. 1.

FIG. 3 is a perspective view illustrating a transmitting antenna and a receiving antenna provided in the wireless tag communication device of FIG. 2 in detail.

4 is a diagram illustrating in detail the configuration of an adaptive processing unit provided in the wireless tag communication device of FIG. 2.

FIG. 5 is a block diagram illustrating a configuration of a wireless tag circuit provided in the wireless tag of FIG. 1, illustrating a configuration using a subcarrier.

FIG. 6 is a block diagram illustrating a configuration of a wireless tag circuit provided in the wireless tag of FIG. 1

, No subcarrier is used.

FIG. 7 is a plan view illustrating the appearance of the wireless tag of FIG. 1.

FIG. 8 is a diagram illustrating a polarization plane of a dipole antenna provided on the z-axis in FIG. 3.

[FIG. 9] Arranged so that the antenna element of FIG. 7 forms an angle に対して with respect to the z-axis in the yz plane of the reflected wave from the wireless tag arranged so as to be parallel to the y-axis in FIG. 7 is a graph illustrating a change in reception characteristics of the obtained receiving antenna element according to the angle Θ.

FIG. 10 is an enlarged graph showing a part corresponding to a part of the vertical axis in FIG.

[FIG. 11] With respect to the reflected wave of the RFID tag arranged so as to be parallel to the _z- axis, the antenna element force S shown in FIG. 7 is arranged so as to form an angle に対して with respect to the z-axis in the yz plane in FIG. FIG. 6 is a graph illustrating a change in reception characteristics according to the angle における of the installed receiving antenna element. is there.

12 is a flowchart illustrating a main part of a return signal demodulation control operation by an adaptive processing unit and a DSP of the wireless tag communication device in FIG. 2.

13 is a flowchart illustrating a main part of a transmission signal switching control operation performed by an adaptive processing unit and a DSP of the wireless tag communication device in FIG. 2;

14 is a diagram illustrating another electrical configuration of the wireless tag communication device in FIG. 1.

FIG. 15 is a perspective view illustrating in detail a transmitting antenna and a receiving antenna provided in the wireless tag communication device of FIG. 14.

FIG. 16 is a diagram illustrating still another electrical configuration of the wireless tag communication device in FIG. 1.

FIG. 17 is a perspective view illustrating in detail a transmitting antenna and a receiving antenna provided in the wireless tag communication device of FIG. 16;

FIG. 18 is a perspective view describing another example of the arrangement of the receiving antenna provided in the wireless tag communication device in FIG. 1 in detail.

FIG. 19 is a perspective view describing in detail an arrangement example of a receiving antenna having a plurality of planar array antennas provided in the wireless tag communication device of FIG. 1.

20 is a diagram illustrating a planar array antenna provided with a vertically polarized feed line and a horizontally polarized feed line provided in the wireless tag communication device of FIG. 1.

Explanation of symbols

10: Communication system, 12, 78, 86, 92: Wireless tag communication device, 14: Wireless tag, 16: DSP, 18: Transmission / reception circuit, 20: Adaptive processing unit, 22: Transmission digital signal output unit, 24: Modulation , 26: demodulation unit, 28: transmission signal DZA conversion unit, 30: frequency conversion signal output unit, 32: up converter, 34, 80: transmission antenna, 36: transmission antenna element, 36, 82: transmission antenna element , 36a, 82a: 1st antenna element for transmission, 36b, 82b: 2nd antenna element for transmission, 38: reception antenna, 40: antenna element for reception, 40a: 1st antenna element for reception, 40b: 1st antenna element for reception 2 antenna elements, 40c: third antenna element for reception, 42: down converter, 44: return signal AZD conversion section, 46: amplitude control section, 48: phase shift control section, 50: signal synthesis section, 52: weight value control , 53: Transmission polarization plane control unit, 54: Transmission / reception antenna, 56: Rod antenna element, 58: Modulation / demodulation unit, 60: IC circuit unit, 62: control unit, 64: subcarrier oscillation unit , 66: subcarrier modulation unit, 74: switch, 84, 94: transmission polarization control unit, 88, 94: transmission / reception antenna, 90, 96: transmission / reception antenna element, 90a, 96a: transmission / reception first antenna element, 90b, 96b: Second antenna element for transmission / reception, 90c, 96c: Third antenna element for transmission / reception, 92: Coupler

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

Example 1

FIG. 1 is a diagram illustrating a configuration of a communication system 10 to which the present invention is suitably applied. This communication system 10 includes a wireless tag communication device 12 according to an embodiment of the present invention and a plurality (four in FIG. 1) of wireless tags 14a, 14b, 14c, and 14d (hereinafter, unless otherwise distinguished, simply). Radio tags 14). The wireless tag communication device 12 functions as an interrogator of the communication system 10, and the wireless tag 14 functions as a transponder of the communication system 10. That is, when the carrier F, which is a transmission signal, is transmitted from the wireless tag communication device 12, the wireless tags 14a, 14b, 1 cl cl receiving the carrier F are transmitted.

In 4c and 14d, the carrier F is modulated based on the predetermined information signal and the return signal cl

The reflected waves are respectively returned as reflected waves F 1, F 2, F 3 and F 4 (hereinafter simply referred to as reflected waves F and rl r2 r3 r4 rf unless otherwise specified), and the reflected waves are received by the wireless tag communication device 12. Information is communicated with the wireless tag 14 by being rf-received and demodulated.

FIG. 2 is a diagram illustrating an electrical configuration of the wireless tag communication device 12. The wireless tag communication device 12 communicates information with the wireless tag 14 in order to perform at least one of reading and writing of information from and to the wireless tag 14, and generates a digital signal. DSP (Digital Signal Processor) 16 that performs digital signal processing such as modulating based on predetermined transmission information and outputting it as a transmission signal, or demodulating a return signal from the wireless tag 14 and reading the return information. And converts the transmission signal output from the DSP 16 into an analog signal and transmits it as a carrier wave F.

Rf that receives the reflected wave F of

Control the weight (weight) given to the reply signal provided from each receiving antenna element 40 described later provided on the receiving side of the transmitting / receiving circuit 18 And an adaptive processing unit 20 for executing the above processing.

The DSP 16 includes a CPU, a ROM, a RAM, and the like, and includes a so-called microcomputer system that performs signal processing according to a program stored in the ROM while using a temporary storage function of the RAM. A transmission digital signal output unit 22 that outputs a transmission signal to the wireless tag 14 as a digital signal, and a modulation unit that modulates the transmission digital signal output from the transmission digital signal output unit 22 based on predetermined transmission information. 24, and a demodulation unit 26 that demodulates a reply signal from the wireless tag 14 and reads out predetermined reply information.

The transmission / reception circuit 18 includes a transmission signal DZA conversion unit 28 that performs analog conversion of the transmission digital signal output from the modulation unit 24, a frequency conversion signal output unit 30 that outputs a predetermined frequency conversion signal, The upconverter 32 increases the frequency of the transmission signal analog-converted by the transmission signal DZA conversion unit 28 by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 30, and a plurality of transmission signals having different polarization planes (see FIG. 2, two transmission antenna elements 36a and 36b (hereinafter, simply referred to as transmission antenna elements 36 unless otherwise specified), and the transmission signal up-converted by the up-converter 32 is transmitted to the carrier F The transmitting antenna 3 for transmitting toward the wireless tag 14 as

cl

And a switch for switching the connection so as to supply the up-converted transmission signal output from the up-converter 32 to any one of the first transmitting antenna element 36a and the second transmitting antenna element 36b. (Switching switch) 33 and a plurality (three in FIG. 2) of receiving antenna elements 40a, 40b, and 40c having different polarization planes (hereinafter, simply referred to as receiving antenna element 40 unless otherwise specified). A receiving antenna 38 for receiving the reflected wave F from the wireless tag 14, and receiving rf signals from the receiving antenna elements 40a, 40b, 40c.

The downconverters 42a, 42b, 42c (hereinafter, not particularly distinguished) that lower the frequency of the supplied return signal by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 30 and supply the same to the adaptive processing unit 20 In some cases, this is simply referred to as a down-converter 42), and a return signal AZD conversion unit 44 that converts the return signal output from the adaptive processing unit 20 into a digital signal and supplies it to the DSP 16.

FIG. 3 shows a transmitting antenna 34 and a receiving antenna provided in the wireless tag communication device 12. FIG. 38 is a perspective view illustrating 38 in detail. As shown in FIG. 3, the first transmitting antenna element 36a, the second transmitting antenna element 36b, the first receiving antenna element 40a, the second receiving antenna element 40b, and the third receiving antenna element 40c Preferably, it is a rod-shaped array antenna such as a dipole antenna or the like, which is projected from the wireless tag communication device 12 to the outside and can individually transmit or receive a signal individually, each of which is shown in FIG. They are arranged in the same plane parallel to the yz plane. Here, the first transmitting antenna element 36a and the first receiving antenna element 40a are both arranged parallel to the z-axis shown in FIG. 3 so as to be parallel to each other. Further, the second transmitting antenna element 36b is disposed parallel to the y-axis shown in FIG. 3 so as to be perpendicular to the first transmitting antenna element 36a. Further, the second receiving antenna element 40b and the third receiving antenna element 40c are all disposed so as to form a predetermined angle に対して with respect to the first receiving antenna element 40a. This angle Θ is preferably in the range of 15 ° to 45 °, more preferably in the range of 35 ° to 45 °, and most preferably about 45 °. By taking such an angle Θ, the receiving antenna 38 composed of the first receiving antenna element 40a, the second receiving antenna element 40b, and the third receiving antenna element 40c is located in the same plane. The fan shape extends in the positive z-axis direction.

FIG. 4 is a diagram illustrating the configuration of the adaptive processing unit 20 in detail. As shown in FIG. 4, the adaptive processing unit 20 includes amplitude control units 46a, 46b, 46c (hereinafter, not particularly distinguished) that control the amplitudes of the return signals supplied from the down converters 42a, 42b, 42c. In this case, it is simply referred to as an amplitude control unit 46) and a phase control unit 48a, 48b, 48c for controlling the phase of each of the return signals output from the amplitude control units 46a, 46b, 46c (hereinafter, unless otherwise specified) Is simply referred to as a phase control unit 48) and a signal synthesizing unit 50 for synthesizing and outputting the return signals supplied from the phase control units 48a, 48b and 48c. It also includes a so-called microphone computer system which comprises a CPU, a ROM, a RAM, etc., and performs signal processing according to a program stored in the ROM while utilizing a temporary storage function of the RAM. The reply signal supplied from each receiving antenna element 40 according to the strength of the supplied reply signal, that is, the response signal received by the plurality of receiving antenna elements 40. A weight control unit 52 for controlling a weight given to the signal; and the transmitting antenna 34 according to the strength of the return signal received by the receiving antenna 38, that is, the strength of the combined signal output from the signal combining unit 50. And a transmission polarization plane control unit 53 for controlling the polarization plane of the above.

[0027] The weight value control unit 52 is configured, for example, for the purpose included in the combined signal according to the strength of each of the return signals supplied from each down converter 42 and the strength of the combined signal output from the signal combining unit 50. The settings of each of the amplitude control unit 46 and the phase control unit 48 are changed so that the intensity of the return signal is as high as possible. That is, the weights are determined and combined so that the target return signals supplied from the respective receiving antenna elements 40 have the same phase, or the weights are determined such that the strength of the non-target signals is minimized. Thus, the directivity of the receiving antenna 38 is controlled so that the intended return signal (modulated signal by the wireless tag 14) is maximized and the weight given to each return signal is minimized so that unnecessary interference signals are minimized. I do.

The transmission polarization controller 53 controls the opening and closing of the switch 33, for example, so that the transmission signal is transmitted by any one of the plurality of transmission antenna elements 36. By transmitting and switching the transmitting antenna element 36 used for the transmission, the transmitted signal is transmitted from the transmitting antenna 34 so that the intensity of the composite signal output from the signal combining section 50 is as high as possible. Controls the polarization plane of carrier F.

cl

FIG. 5 is a block diagram illustrating a configuration of a wireless tag circuit 14 a provided in the wireless tag 14. The wireless tag circuit 14a receives a carrier F which is a transmission signal from the wireless tag communication device 12, and transmits and receives a reflected wave F which is a return signal.

cl rf

It comprises a tenner 54, a modulation / demodulation unit 58 connected to the transmission / reception antenna 54 for modulating and demodulating a signal, and an IC circuit unit 60 for performing digital signal processing. The IC circuit section 60 uses the carrier F received by the transmitting / receiving antenna 54 as an energy source.

cl

A control unit 62 for controlling the operation of the wireless tag circuit 14a, a sub-carrier oscillation unit 64 for generating a sub-carrier, and a sub-carrier generated by the sub-carrier oscillation unit 64 for the control unit 62. And a subcarrier modulating unit 66 that modulates based on a predetermined information signal input through the subcarrier modulation unit. The wireless tag 14 may have a configuration of a wireless tag circuit 14b that does not use a subcarrier, as shown in FIG. In this case, a reply signal from the wireless tag 14 and The signal passed from the controller 62b to the modem 58b must be modulated by FSK or PSK.

FIG. 7 is a plan view illustrating the appearance of the wireless tag 14. As shown in FIG. 7, the transmitting / receiving antenna 54 provided in the wireless tag 14 is preferably a dipole antenna composed of a pair of antenna elements 56 arranged linearly. Is connected to the IC circuit section 58.

FIG. 8 is a diagram illustrating a polarization plane of a dipole antenna arranged on the z-axis. Generally, in a dipole antenna, the polarization direction is determined according to the longitudinal direction. For example, with respect to the radio wave generated by the dipole antenna arranged on the z-axis and propagated in the X-axis direction shown in Fig. 8, the plane where the electric field component E (solid line) vibrates is a plane including the X-axis and the z-axis. The plane that vibrates the magnetic field component H (broken line) is an xy plane that is a plane that includes the X axis and is perpendicular to the z axis. Therefore, as in the case of the first transmitting antenna element 36a shown in FIG. The oscillating surface is a plane parallel to the xz plane

cl

. Here, when the transmitting / receiving antenna 54 of the wireless tag 14 is disposed so as to be parallel to the first transmitting antenna element 36a, that is, the antenna element 56 is disposed so as to be parallel to the z-axis. In this case, since the polarization planes coincide with each other, the carrier F transmitted from the transmitting first antenna element 36a is preferably received by the antenna element 56.

cl

However, when the antenna element 56 is disposed so as to be parallel to the y-axis, since the polarization planes are orthogonal to each other, the carrier F transmitted from the first transmitting antenna element 36a is It is hardly received by the antenna element 56.

cl

With respect to the wireless tag communication device 12 shown in FIG. 3, the polarization plane of the radio wave transmitted from the first transmitting antenna element 36a and propagated in the X-axis direction is parallel to the XZ plane, and

The polarization plane of the radio wave transmitted from the two antenna elements 36b and propagated in the X-axis direction is parallel to the xy plane. Therefore, with respect to the radio tag 14 in which the antenna element 56 is arranged parallel to the z-axis, the carrier F transmitted from the first transmitting antenna element 36a is

The power suitably received by the wireless tag 14 of cl The carrier F transmitted from the second transmitting antenna element 36b is hardly received by the wireless tag 14. On the other hand, Regarding the wireless tag 14 in which the antenna element 56 is arranged in parallel with the y-axis, the carrier F transmitted from the transmitting first antenna element 36a is transmitted by the wireless tag 14.

cl

However, the carrier F transmitted from the second transmitting antenna element 36b is suitably received by the wireless tag 14. Therefore, the transmission polarization controller 5 cl

By switching the opening and closing of the switch 33 so that the strength of the target return signal included in the synthesized signal output from the signal synthesizing unit 50 is as high as possible by 3, the relative position to the wireless tag 14 is A suitable transmission signal can be transmitted according to the positional relationship. Preferably, the transmission polarization control section 53 may switch the switch 33 between open and closed at a predetermined cycle. In this way, suitable communication can be performed between the wireless tag communication device 12 and the plurality of wireless tags 14 having respective individual positional relationships.

On the other hand, the reflected wave F from the wireless tag 14 in which the antenna element 56 is arranged so as to be parallel to the y-axis direction is, like the first receiving antenna element 40a shown in FIG. Parallel to axis

rf

However, the antenna is hardly received by the dipole antenna arranged so as to form the second antenna element 40b and the third antenna element 40c shown in FIG. The signal can be received by a dipole antenna arranged to form Θ. In particular, when the first receiving antenna element 40a, the second receiving antenna element 4 Ob, and the third receiving antenna element 40c are arranged so as to form a fan shape in a plane parallel to the yz plane, The reflected wave F returned from the wireless tag 14 and propagated in the X-axis direction, that is, the direction perpendicular to the plane stretched by the plurality of receiving antenna elements 40,

rf Good reception.

FIG. 9 shows an angle 0 (°) with respect to the z axis in the yz plane with respect to the reflected wave F from the wireless tag 14 in which the antenna element 56 is arranged in parallel with the y axis. To make

rf

FIG. 6 is a graph illustrating a change in reception characteristics according to the angle 0 of the disposed receiving antenna element 40, wherein the vertical axis represents the receiving antenna disposed at an angle of 0 = 45 ° with the z axis. The attenuation (dB) of the reception intensity for the element 40 is shown. In order to realize high-sensitivity reception irrespective of the relative positional relationship with the wireless tag 14, it is preferable that the receiving antenna element 40 be disposed at 45 ° to the z-axis, When a plurality of receiving antenna elements 40 are arranged in a fan shape as in a receiving antenna 38 shown in FIG. It is desirable that the angle Θ be as small as possible in order to reduce the size of the receiving antenna 38.

[0035] FIG. 10 shows the attenuation of the reception intensity 0 to 20 (dB) with respect to the reception antenna element 40 arranged so as to form an angle 0 = 45 ° on a part of the vertical axis, that is, the z-axis in FIG. It is a graph showing the corresponding part in an enlarged manner. As shown in FIG. 9, when the receiving antenna element 40 is disposed so as to form 0 ° with respect to the z axis, the receiving antenna element 40 is disposed so as to form 45 ° with respect to the z axis. In this case, the reception intensity is set to about −95 (dB), and the reflected wave F transmitted from the antenna element 56 is hardly received by the receiving antenna element 40.

rf

I can't believe it. Further, as shown in FIG. 10, when the receiving antenna element 40 is arranged so as to form 30 ° with respect to the z-axis, the antenna element 40 is arranged so as to form 45 ° with respect to the z-axis. Therefore, the receiving intensity (current value flowing through the element) is set to about 3 (dB) as compared with the case where the receiving antenna element 40 is arranged at 20 ° to the z-axis. The antenna is arranged so as to form an angle of 45 ° with respect to the z-axis. °, the receiving intensity is about 9 (dB) compared to the case where the antenna is arranged at 45 ° to the z-axis. When 40 is arranged at 10 ° to the z-axis, the reception intensity is about 12.5 compared to when arranged at 45 ° to the z-axis. (dB), when the receiving antenna element 40 is arranged so as to form 5 ° with respect to the z-axis, and when the receiving antenna element 40 is arranged so as to form 45 ° with respect to the z-axis. The received power is about 18.5 (dB). As described above, the reflected wave F from the wireless tag 14 disposed so that the antenna element 56 is parallel to the y-axis is efficiently received.

rf

In order to achieve this, the angle 0 of the antenna element 40 disposed in the yz plane with respect to the z-axis is preferably 15 ° or more.

FIG. 11 shows an angle 0 (°) with respect to the z-axis in the yz plane with respect to the reflected wave F from the wireless tag 14 in which the antenna element 56 is disposed parallel to the z-axis. To make

rf

FIG. 6 is a graph illustrating a change in reception characteristics according to the angle 0 of the disposed receiving antenna element 40, wherein the vertical axis represents the receiving antenna disposed so as to form an angle 0 = 0 ° with the X axis. The attenuation (dB) of the reception intensity for the element 40 is shown. As shown in this Figure 11, When the receiving antenna element 40 is arranged so as to form 30 ° with respect to the z axis, the receiving intensity is higher than when the receiving antenna element 40 is arranged so as to form 0 ° with respect to the z axis. Is about 0.6 (dB), and when the receiving antenna element 40 is arranged so as to form an angle of 45 ° with respect to the z-axis, the antenna element 40 is arranged so as to form an angle of 0 ° with respect to the z-axis. The received power is about -1.35 (dB) as compared to the case where it is installed. As described above, with respect to the reflected wave F from the wireless tag 14 arranged so that the antenna element 56 is parallel to the z-axis, before the antenna element 56 is arranged in the yz plane.

rf

Even if the angle of the antenna element 40 with respect to the z-axis changes within the range of 0 ° to 45 °, the reception characteristics thereof hardly change. Therefore, the angle に対する of the antenna element 40 with respect to the z-axis is optimally 45 °, but the reflected wave F from the wireless tag 14 in which the antenna element 56 is arranged so as to be parallel to the y-axis. In consideration of the above, the angle is preferably 45 ° or less.

rf

In other words, the first receiving antenna element 40a and the second receiving antenna element 40b and the third receiving element which form an angle of 15 ° or more and 45 ° or less with respect to the first receiving antenna element 40a, respectively. By providing the antenna element 40c, the force of the wireless tag 14 arranged so that the antenna element 56 is parallel to the y axis and the force of the wireless tag 14 arranged so as to be parallel to the z axis The reflected wave F can also be suitably received.

rf

Next, a communication operation of the communication system 10 configured as described above will be described. First, a transmission digital signal is output by the transmission digital signal output unit 22 of the wireless tag communication device 12. Next, the transmission digital signal output from the transmission digital signal output section 22 is modulated by the modulation section 24 based on predetermined transmission information. Next, the transmission digital signal modulated by the modulation unit 24 is converted into an analog signal by the transmission signal DZA conversion unit 28. Next, the frequency of the transmission signal analog-converted by the transmission signal DZA conversion unit 28 is increased by the up-converter 32 by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 30, and the transmission antenna To the carrier F from the transmitting antenna element 36 of the transmitting antenna 38.

cl and transmitted to the wireless tag 14.

The carrier F from the transmitting antenna 38 of the wireless tag communication device 12 is

cl

When the carrier F is received by the transmitting / receiving antenna 54, the carrier F is supplied to the modem 58.

cl

And demodulated. Next, the demodulated carrier F is supplied to the control unit 62, The sub-carrier is output from the sub-carrier oscillating section 64 using the carrier F as an energy source.

Is done. Next, the sub-carrier output from the sub-carrier oscillating section 64 is primary-modulated by the sub-carrier modulating section 66 based on a predetermined information signal input via the control section 62. Next, in the modulation / demodulation section 58, the carrier F power is modulated by the primary modulated subcarrier output from the subcarrier modulation section 66, and transmitted and received by the transmission / reception antenna 54.

cl

It is returned to the wireless tag communication device 12 as a reflected wave F.

rf

The reflected wave F from the transmitting / receiving antenna 54 of the wireless tag 14 is transmitted to the wireless tag communication device 1

rf

2, the reflected wave F is received by the first antenna element for reception.

rf

The downconverters 42a, 42b, and 42c are supplied from the antenna 40a, the second receiving antenna element 40b, and the third receiving antenna element 40c, and the frequency of each received signal is output from the frequency conversion signal output unit 30. After being lowered by the frequency of the converted signal, it is input to the adaptive processing unit 20.

FIG. 12 is a flowchart for explaining a main part of a response signal demodulation control operation performed by the adaptive processing unit 20 and the DSP 16 of the wireless tag communication device 12. The cycle time is as short as several msec to several tens ms ec. Is executed repeatedly.

First, at step (hereinafter, step is omitted), the received signals from the plurality of receiving antenna elements 40 downconverted by the downconverters 42 are read into the adaptive processing unit 20 at step SA1. It is. Next, in SA2, it is determined whether the weight given to each received signal has converged or not. If the determination of SA2 is affirmative, in SA6, the return signal (synthesized signal) output from the adaptive processing unit 20 and digitally converted by the return signal AZD conversion unit 44 is demodulated in the demodulation unit 26. After the predetermined reply information is read out, the present routine is terminated.If the determination of SA2 is denied, in SA3, the output signal from the adaptive processing unit 20, that is, the signal combining unit A composite signal output from 50 is detected. Next, in SA4, a difference between the intensity of the output signal from the adaptive processing unit 20 and the intensity of a predetermined reference signal is calculated. Next, in SA5 corresponding to the weight control unit 52, the weight given to the reply signal supplied from each receiving antenna element 40 is changed according to the polarization plane of each of the reply signals. For example, AAA (Adaptive Array Antenna) processing, the respective amplitude control units 46 so that the square of the difference between the intensity of the output signal from the adaptive processing unit 20 calculated in SA4 and the intensity of the predetermined reference signal becomes as small as possible. And the settings in the phase control unit 48 are changed. Then, in SA6, after the return signal output from the adaptive processing unit 20 and digitally converted by the return signal AZD conversion unit 44 is demodulated and predetermined return information is read, the routine ends. Let me do.

FIG. 13 is a flowchart for explaining a main part of a transmission signal switching control operation by the adaptive processing unit 20 and the DSP 16 of the wireless tag communication device 12, and an extremely short cycle time of about several msec to several tens ms ec. Is executed repeatedly.

First, in SB 1, a return signal output from the adaptive processing unit 20 and digitally converted by the return signal AZD conversion unit 44 is demodulated by the demodulation unit 26 and given a predetermined response. The information is read. Next, in SB2, it is determined whether or not suitable demodulation has been performed by the processing of SB1, that is, whether or not the response information has been read. If the determination of SB2 is affirmative, the force by which this routine is terminated is denied.If the determination of SB2 is denied, the signal combining in SB3 corresponding to the transmission polarization controller 53 is performed. The opening and closing of the switch 33 is switched so that the intensity of the target return signal included in the composite signal output from the unit 50 is as high as possible, so that the polarization plane of the transmitting antenna 34 is changed. . Then, in SB4, after the return signal output from the adaptive processing unit 20 and digitally converted by the return signal AZD conversion unit 44 is re-demodulated in the demodulation unit 26 and predetermined return information is read out, This routine is ended.

As described above, according to the present embodiment, the receiving antenna 38 has the plurality of receiving antenna elements 40 arranged so as to be able to receive the return signals having different polarization planes. High sensitivity regardless of the relative angle of the plane of polarization of the reflected wave F from the wireless tag 14.

rf

In addition to the fact that the communication is possible, it is sufficient to dispose a relatively small number of receiving antenna elements 40, so that there is an advantage that the device can be downsized. That is, it is possible to provide the wireless tag communication device 12 that realizes high-sensitivity communication regardless of the relative positional relationship with the wireless tag 14. [0045] Further, a weight value for controlling a weight value given to the return signal supplied from each receiving antenna element 40 according to the strength and phase of each of the return signals received by the plurality of receiving antenna elements 40 Since it includes the control unit 52 (SA5), it is supplied from a predetermined receiving antenna element 40 corresponding to the polarization plane of the reflected wave F from the wireless tag 14.

rf

By converging the weight given to the returned signal to the optimum value, communication with as high sensitivity as possible can be realized regardless of the direction in which the wireless tag 14 is arranged. In the above-described embodiment, the force described in the example in which the antenna element 56 of the wireless tag 14 is arranged so as to be parallel to the y-axis and the z-axis is also given to each return signal. By controlling the weights (amplitude and phase), highly sensitive communication can be realized.

Further, the receiving antenna 38 includes a basic first receiving antenna element 40a and a second receiving antenna that forms an angle of 15 ° or more and 45 ° or less with respect to the first receiving antenna element 40a. Since it has at least the element 40b and the third receiving antenna element 40c, communication with as high sensitivity as possible can be realized.

Further, since the transmission antenna 34 has a plurality of transmission antenna elements 36 arranged so as to be able to transmit the transmission signals having different polarization planes, the transmission tag 34 and the radio tag 14 are different from each other. A suitable transmission signal can be transmitted according to the relative positional relationship between the wireless tag and the return signal of the wireless tag 14 can be strengthened.

[0048] Further, since it includes a transmission polarization plane control unit 53 (SB3) for controlling the polarization plane of the transmission antenna 34 according to the strength of the return signal received by the reception antenna 38, the radio tag A suitable transmission signal can be transmitted in accordance with the relative positional relationship with the wireless tag 14, and the return signal from the wireless tag 14 can be strengthened.

[0049] Further, the transmission polarization plane controller 53 causes the transmission signal to be transmitted by any one of the plurality of transmission antenna elements 36 and transmits the transmission antenna element 36. Since the polarization plane of the transmission antenna 34 is controlled by switching, the polarization plane of the transmission antenna 34 can be switched in a practical manner.

[0050] Further, since the transmitting antenna element 36 and the receiving antenna element 40 are rod-shaped array antennas, the transmitting antenna 34 and the receiving antenna 38 can be configured by antenna elements in a practical mode. Next, second and third embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Example 2

FIG. 14 is a diagram illustrating an electrical configuration of a wireless tag communication device 78 according to a second embodiment of the present invention. FIG. 15 is a diagram illustrating a transmitting antenna 80 provided in the wireless tag communication device 78. 6 is a perspective view illustrating the receiving antenna 38 in detail. FIG. As shown in these figures, the transmission / reception circuit 18 of the wireless tag communication device 78 of the present embodiment has a plurality (two in FIG. 14) of transmission signals each having a different polarization plane. The transmitting antenna element 82, that is, the transmitting antenna 80 having the first transmitting antenna element 82a and the second transmitting antenna element 82b, and the frequency of the transmitting signal supplied to each of the plurality of transmitting antenna elements 82 (Two in FIG. 14) upconverters 32a and 32b (hereinafter referred to as the upconverter 32 unless otherwise specified) that increase the frequency by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 30. ), The transmission signal output from the DZA converter 28 is supplied to each up-converter 32, and the transmission signal supplied to each of the up-converters 32 And a transmission polarization control section 84 for controlling the phase. Preferably, the first transmitting antenna element 82a and the second transmitting antenna element 82b provided in the transmitting antenna 80 are approximately 45 ° each other in the same plane as the plurality of receiving antenna elements 40. It is arranged so as to form an angle.

When carrier wave F of the same phase is transmitted from each of first transmitting antenna element 82a and second transmitting antenna element 82b shown in FIG. 15, the polarization plane of the radio wave propagating in the X-axis direction is X

cl

When the carrier F of the opposite phase is transmitted from the first transmitting antenna element 82a and the second transmitting antenna element 82b in parallel with the z plane, the radio wave propagating in the X-axis direction.

cl

The polarization plane of is parallel to the xy plane. The transmission polarization plane control unit 84 provided in the wireless tag communication device 78 of the present embodiment is configured to control the phase of each of the transmission signals supplied to each of the up-converters 32 according to the above-described flowchart of FIG. The polarization plane of the transmission antenna 80 is controlled by controlling the phases of the transmission signals transmitted from the element 82a and the second transmitting antenna element 82b. Preferably, the signal sum The transmitting first antenna element 82a and the transmitting first antenna element 82a so that the intensity of the combined signal output from the component unit 50 is as high as possible, and thus, the demodulation unit 26 performs suitable demodulation. (2) The phase of the carrier F transmitted from each of the antenna elements 82b is

cl

By switching to the opposite phase, the polarization plane of the carrier F transmitted from the transmitting antenna 80 is changed.

cl

Control. Further, preferably, the transmission polarization plane controller 84 may switch the phase of the transmission signal supplied to each transmission antenna element 82 at a predetermined cycle. In this way, suitable communication can be performed between the wireless tag communication device 78 and the plurality of wireless tags 14 having respective individual positional relationships.

As described above, according to the present embodiment, the transmission polarization plane controller 84 causes the transmission signal to be transmitted by at least two transmission antenna elements 82 of the plurality of transmission antenna elements 82, Since the polarization plane of the transmission antenna 80 is controlled by controlling the phase of each transmission signal transmitted from each transmission antenna element 82, the polarization plane of the transmission antenna 80 is practically used. Can be switched.

Example 3

FIG. 16 is a diagram illustrating an electrical configuration of a wireless tag communication device 86 according to a third embodiment of the present invention. FIG. 17 is a diagram illustrating a transmitting / receiving antenna 88 provided in the wireless tag communication device 86. It is a perspective view explaining in detail. As shown in these figures, the transmission / reception circuit 18 of the wireless tag communication device 86 of this embodiment includes a plurality of (three in FIG. 16) transmission / reception antenna elements 90 having different polarization planes, that is, the first transmission / reception antenna element 90a. A transmission / reception antenna 88 having a transmission / reception second antenna element 90b and a transmission / reception third antenna element 90c; and a frequency conversion signal output section for converting the frequency of the transmission signal supplied to each of the plurality of transmission / reception antenna elements 90 to the frequency conversion signal output section. A plurality (three in FIG. 14) of upconverters 32a, 32b, and 32c (hereinafter, simply referred to as an upconverter 32 unless otherwise distinguished) which are increased by the frequency of the frequency conversion signal output from 30 and the plurality of The up-converted transmission signal output from each up-converter 32 provided for each transmission / reception antenna element 90 is transmitted to each transmission / reception antenna element. And a plurality of return signals received by the transmitting / receiving antenna elements 90 from the wireless tag 14 to the adaptive processing unit 20 via the plurality of down-converters 42 (3 in FIG. 16). Concatenation) (Transmitter / receiver separator) 92a, 92b, 92c and the transmission signal output from the DZA conversion unit 28 to each up-converter 32, and controls the transmission signal supplied to the up-converter 32. Thus, a transmission polarization plane control unit 94 for controlling the polarization plane of the carrier wave F transmitted from the transmission / reception antenna 88 is provided. Here, the above cl

The number of transmitting / receiving antenna elements 90 are preferably all arranged in the same plane. Further, both the second transmitting / receiving antenna element 90b and the third transmitting / receiving antenna element 90c are disposed so as to form a predetermined angle に対して with respect to the first transmitting / receiving antenna element 90a. The angle Θ is preferably in the range of 15 ° to 45 ° as described for the plurality of receiving antenna elements 40 in the first embodiment, and more preferably about 45 °. Angle.

The transmission polarization plane control unit 94 provided in the wireless tag communication device 86 of the present embodiment performs the amplitude and phase of each of the transmission signals supplied to each up-converter 32 according to the flowchart of FIG. The polarization plane of the transmission / reception antenna 88 is controlled by controlling the amplitude and phase of each of the transmission signals transmitted from the transmission / reception first antenna element 90a, the transmission / reception second antenna element 90b, and the transmission / reception third antenna element 90c. And control the directionality. Preferably, the signal is transmitted from the transmission / reception antenna 88 so that the intensity of the combined signal output from the signal combining unit 50 is as high as possible, and thus the demodulation unit 26 performs suitable demodulation. Control the polarization plane of the carrier F. Also suitable

cl

Alternatively, the transmission polarization plane control unit 94 may control the amplitude and phase of the transmission signal supplied to each transmitting / receiving antenna element 90 at a predetermined cycle. In this way, suitable communication can be performed between the wireless tag communication device 86 and the plurality of wireless tags 14 having respective individual positional relationships.

As described above, according to the present embodiment, the transmission / reception antenna 88 functions as a transmission antenna and a reception antenna, and has the plurality of transmission / reception antenna elements 90. The communication device 86 can be made as small as possible.

As described above, the preferred embodiment of the present invention has been described in detail with reference to the drawings. The present invention is not limited to this, and may be embodied in still another mode.

For example, in the above embodiment, the adaptive processing unit 20, the transmission polarization plane control unit 84, 94, etc., which are control devices provided separately from the DSP 16, may be functionally provided in the DSP 16.

In the above-described embodiment, the transmitting antenna element 36, the receiving antenna element 40, and the antenna element 56 of the wireless tag 14 of the wireless tag communication device 12 are all drawn linearly. However, some of them do not necessarily have to be perfectly linear, and some may be non-linear as long as they are antenna elements exhibiting a predetermined polarization direction.

In the above-described embodiment, the first receiving antenna element 40a, the second receiving antenna element 40b, and the third receiving antenna element 40c are arranged in the same plane so as to form a fan. For example, as shown in FIG. 18, the first receiving antenna element 40a and the second receiving antenna element 40b are arranged in a first plane (a plane parallel to the yz plane). It is also conceivable that the first antenna element 40a and the third receiving antenna element 40c are arranged in a second plane (a plane parallel to the xz plane) perpendicular to the first plane. Also in this mode, the second receiving antenna element 40b and the third receiving antenna element 40c preferably form an angle of 15 ° or more and 45 ° or less with respect to the first receiving antenna element 40a. It is arranged as follows. The reflected wave F of the wireless tag 14

When rf is propagated in a direction parallel to the first plane (for example, the y-axis direction) and the plane of polarization is perpendicular to the first plane, the reflected wave F is reflected by the first receiving antenna element 40a. And second for reception

rf

The signal is hardly received by the antenna element 40b, but can be received by the third receiving antenna element 40c. On the other hand, the reflected wave F from the wireless tag 14 is

rf

When the light is propagated in a direction parallel to the plane (for example, the X-axis direction) and its plane of polarization is perpendicular to the second plane, the reflected wave F is reflected by the first receiving antenna element 40a and the third receiving antenna.

rf

The signal is hardly received by the antenna element 40c, but can be received by the second receiving antenna element 40b. That is, according to this configuration, the reflected wave F force from the wireless tag 14 ¾60 ° Even when the reflected wave is propagated in any direction, the receiving antenna 3

rf

8, the reflected wave F can be suitably received.

rf

In the above-described embodiment, the transmitting antenna element 36 and the receiving antenna element 40 are rod-shaped array antennas such as dipole antennas. For example, a planar array antenna is used as an antenna element. It may be provided. Figure 19 shows each FIG. 11 is a perspective view illustrating a wireless tag communication device 92 including a transmitting / receiving antenna 94 having a plurality of transmitting / receiving antenna elements 96a, 96b, and 96c, which are planar array antennas having different polarization planes. A planar array antenna such as a microstrip antenna also exhibits a predetermined directivity similarly to a rod-shaped array antenna, and the plurality of transmitting / receiving antenna elements 96 are arranged so as to form a predetermined polarization plane angle with each other. This makes it possible to configure the transmission / reception antenna 94 in a practical mode. Further, as shown in FIG. 20, a planar array antenna having a vertical polarization feed line 98a and a horizontal polarization feed line 98b may be provided as a transmission antenna or the like. According to this planar array antenna, since the plane of polarization can be changed by switching between the vertical polarization feed line 98a and the horizontal polarization feed line 98b, the antenna arrangement area can be reduced as much as possible. is there.

In the above-described embodiment, the wireless tag communication device 12 is mainly used as an interrogator in the communication system 10 of FIG. 1. The present invention provides the wireless tag 14 with predetermined information. The present invention is also suitably applied to a wireless tag creating device for writing and a wireless tag reader / writer for reading and writing information.

[0064] Although not specifically exemplified, the present invention is embodied with various changes without departing from the spirit thereof.

Claims

The scope of the claims

[1] A predetermined transmission signal is transmitted to the wireless tag by a transmission antenna, and a return signal returned from the wireless tag that has received the transmission signal is received by the reception antenna, whereby information can be exchanged with the wireless tag. A wireless tag communication device that performs communication of

The wireless tag communication device, wherein the receiving antenna has a plurality of antenna elements arranged so as to be able to receive the return signals having different polarization planes.

[2] A weight control unit which controls a weight given to the return signal supplied from each antenna element according to an intensity and a phase of each of the return signals received by the plurality of antenna elements. 1 wireless tag communication device.

[3] The receiving antenna includes a basic first antenna element, and a second antenna element and a third antenna element each having a polarization plane angle of 15 ° or more and 45 ° or less with respect to the first antenna element. 3. The wireless tag communication device according to claim 1, wherein the wireless tag communication device has at least:

4. The radio tag communication device according to claim 1, wherein the transmission antenna has a plurality of antenna elements arranged so as to transmit the transmission signals having different polarization planes. .

5. The wireless tag communication device according to claim 4, further comprising a transmission polarization control unit that controls a polarization plane of the transmission antenna according to an intensity of the return signal received by the reception antenna.

[6] The transmission polarization control unit controls the polarization plane of the transmission antenna by transmitting the transmission signal using any one of the plurality of antenna elements and switching the antenna element. The wireless tag communication device according to claim 5, wherein

[7] The transmission polarization control section controls the transmission signal to be transmitted by at least two antenna elements of the plurality of antenna elements and controls the phase of each of the transmission signals transmitted from each antenna element. 6. The wireless tag communication device according to claim 5, wherein a polarization plane of the transmitting antenna is controlled by the controller.

[8] The wireless tag communication device according to any one of claims 1 to 7, wherein the transmitting antenna and the receiving antenna share the plurality of antenna elements.

9. The wireless tag according to claim 1, wherein the antenna element is a rod-shaped array antenna. Communication device.

9. The wireless tag communication device according to claim 1, wherein the antenna element is a planar array antenna.