JP2008271443A - Radio transmitter and radio communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter that achieves high-sensitivity communication regardless of a relative position relation with a communication target. <P>SOLUTION: The transmitter includes: a transmission antenna 20, including a plurality of feeding points 52, for transmitting a transmission signal; a variable attenuator 24 for changing a ratio of power, at the transmission antenna 20, to be supplied to the feeding points 52; and a transmission polarization direction control section 26 for controlling a polarization direction of the transmission signal to be transmitted from the transmission antenna 20. Thus, the polarization direction of the transmission signal to be transmitted from the transmission antenna 20 can be arbitrarily changed in simple configuration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless transmission device for transmitting a predetermined transmission signal toward a communication target and a wireless communication device for performing information communication wirelessly with a predetermined communication target, and in particular, a polarization direction of a transmission signal. The present invention relates to an improvement for controlling.

  A wireless transmission device for transmitting a predetermined transmission signal toward a communication target is used for various types of wireless communication. As an example of a wireless communication system using such a wireless transmission device, information is read out in a non-contact manner by a predetermined wireless tag communication device (interrogator) from a small wireless tag (responder) storing predetermined information. An RFID (Radio Frequency Identification) system to perform is known. This RFID system is capable of reading information stored in a wireless tag by communication with the wireless tag communication device even when the wireless tag is dirty or disposed at an invisible position. Therefore, practical use is expected in various fields such as merchandise management and inspection processes.

  By the way, normally, the wireless tag communication device transmits a predetermined transmission signal (question wave) toward the wireless tag by a transmission antenna, and a reply signal (response wave) returned from the wireless tag that has received the transmission signal. ) Is received by the receiving antenna (there is also a mode common to the transmitting antenna), but information is communicated with the wireless tag. However, depending on the relative positional relationship with the wireless tag, the communication sensitivity is significantly reduced. There was a bug. In other words, depending on the polarization plane of the radio wave for communication (surface on which the electric field component vibrates), it has not been possible to realize suitable communication with the wireless tag that is the communication target. In order to solve this problem, a wireless communication device having an antenna corresponding to a plurality of polarization planes has been proposed. For example, this is the mobile object identification device described in Patent Document 1. According to this technique, one of the two feeding points in the macrostrip antenna provided at a position where the lines extending from the two feeding points extending toward the center of the radiating element are orthogonal to each other and the transmitting unit. By alternately connecting the vertical polarization signals, vertical polarization signals and horizontal polarization signals can be alternately transmitted while the polarization planes of the signals are alternately inclined by 90 °.

JP 2000-307466 A

  However, since the conventional technology can only select one of two types of polarization directions orthogonal to each other, the relative position between the RFID tag communication apparatus and the RFID tag to be communicated with Depending on the relationship, the transmission rate of radio waves has dropped to about 70% of the case where the polarization direction is suitably determined, and as a result, there is a possibility that the communication sensitivity can be only about half of the maximum value. In other words, the above-described problem cannot be solved depending on such a configuration. Therefore, it is necessary to develop a wireless transmission device and a wireless communication device that realize high-sensitivity communication regardless of the relative positional relationship with the wireless tag. It was done.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a wireless transmission device and a wireless communication device that realize high-sensitivity communication regardless of the relative positional relationship with a communication target. There is to do.

  In order to achieve such an object, the gist of the first aspect of the present invention is a wireless transmission device for transmitting a predetermined transmission signal toward a communication target, the transmission device having a plurality of feeding points. An antenna for transmitting a signal, a feed rate changing unit for changing the ratio of power supplied to each feed point in the antenna, and a feed rate changing unit for feeding to each feed point in the antenna via the feed rate changing unit And a transmission polarization direction control unit that controls the polarization direction of the transmission signal transmitted from the antenna by controlling the ratio of the power to be transmitted.

  In order to achieve the above object, the gist of the second invention is that the wireless transmission device of the first invention transmits a predetermined transmission signal toward a communication target and according to the transmission signal. A wireless communication apparatus is characterized in that information is communicated with a communication target by receiving a reply signal returned from the communication target.

  Thus, according to the first aspect of the present invention, the antenna for transmitting the transmission signal, which has a plurality of feeding points, and the feeding rate for changing the proportion of power supplied to each feeding point in the antenna. Transmission polarization direction control for controlling the polarization direction of the transmission signal transmitted from the antenna by controlling the ratio of power supplied to each feeding point in the antenna via the changing unit and the feeding ratio changing unit Therefore, the polarization direction of the transmission signal transmitted from the antenna can be arbitrarily changed with a simple configuration. That is, it is possible to provide a wireless transmission device that realizes highly sensitive communication regardless of the relative positional relationship with the communication target.

  Here, in the first aspect of the present invention, preferably, the power supply ratio changing unit includes a variable attenuator corresponding to at least one of the plurality of power supply points. If it does in this way, the ratio of the electric power supplied to each feeding point in the antenna can be controlled in a practical manner.

  Preferably, the power supply ratio changing unit includes a variable gain amplifier corresponding to at least one of the plurality of power supply points. If it does in this way, the ratio of the electric power supplied to each feeding point in the antenna can be controlled in a practical manner.

  Preferably, the power supply is performed without passing through an attenuator provided corresponding to at least one of the plurality of power supply points and a circuit that supplies power to the power supply point via the attenuator. A circuit switching unit that switches between circuits is provided as the power supply ratio changing unit. If it does in this way, the ratio of the electric power supplied to each feeding point in the antenna can be controlled in a practical manner.

  Preferably, power is supplied without passing through a delay line provided corresponding to at least one of the plurality of power supply points and a circuit for supplying power to the power supply point via the delay line. And a circuit switching unit that switches between circuits that perform the above. In this way, the polarization direction of the transmission signal transmitted from the antenna can be controlled in a practical manner.

  Preferably, the delay line changes the phase of a signal fed by a circuit passing through the delay line by approximately 180 ° compared to a phase of a signal fed by a circuit not passing through the delay line. It is. In this way, the polarization direction of the transmission signal transmitted from the antenna can be controlled in a practical manner.

  Preferably, the antenna is composed of two sets of dipole antennas arranged so as to be orthogonal to each other, and each dipole antenna is provided with one feeding point. In this way, the polarization direction of a transmission signal transmitted from a practical antenna including two sets of dipole antennas can be arbitrarily changed.

  Preferably, the antenna is a two-feed patch antenna, and two feed points are provided in a portion other than the center point of the patch antenna. In this way, the polarization direction of the transmission signal transmitted from a practical patch antenna can be arbitrarily changed.

  Preferably, the transmission polarization direction control unit is configured to supply each feeding point in the antenna via the feeding ratio changing unit so that the polarization direction of the transmission signal transmitted from the antenna changes every predetermined angle. The ratio of the electric power supplied to is controlled. In this way, transmission signals can be transmitted continuously for a predetermined time for each polarization direction, and suitable communication with the communication target can be realized.

  According to the second aspect of the invention, the wireless transmission device of the first aspect of the invention transmits a predetermined transmission signal toward the communication target and receives a reply signal returned from the communication target according to the transmission signal. As a result, information is communicated with the communication target, so that the polarization direction of the transmission signal transmitted from the antenna can be arbitrarily changed with a simple configuration. That is, it is possible to provide a wireless communication device that realizes highly sensitive communication regardless of the relative positional relationship with the communication target.

  Here, in the second invention, preferably, the antenna is a transmission / reception shared antenna that transmits the transmission signal and receives a return signal returned from the communication target according to the transmission signal. In this way, the configuration of the apparatus can be made as simple as possible.

  Preferably, a reception signal combining unit that combines the reception signals received corresponding to each feeding point in the antenna, and a reception signal processing unit that processes the reception signal combined by the reception signal combining unit. , Which is provided. In this way, the configuration of the receiving circuit can be made as simple as possible.

  Preferably, the apparatus further includes a plurality of reception signal processing units for individually processing reception signals received corresponding to the respective feeding points in the antenna. In this way, the received signal can be processed for each feeding point in the antenna. For example, the received signal input from each feeding point corresponding to the polarization direction of the transmission signal is weighted. Processing is possible.

  Preferably, the wireless communication device transmits a predetermined transmission signal by the antenna toward a wireless tag that is a communication target, and transmits a reply signal returned from the wireless tag in response to the transmission signal. The wireless tag communication device performs communication of information with the wireless tag by receiving. In this way, it is possible to provide a wireless tag communication device that realizes highly sensitive communication regardless of the relative positional relationship with the wireless tag that is the communication target.

  Preferably, the transmission polarization direction control unit is configured to change each polarization point of the antenna via the power supply ratio changing unit so as to change the polarization direction of the transmission signal every time a predetermined communication process is completed. The ratio of the electric power supplied to is controlled. In this way, it is possible to transmit a transmission signal under a certain condition during a predetermined communication process, and it is possible to realize suitable communication with a wireless tag that is a communication target.

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

FIG. 1 is a diagram illustrating a radio tag communication system 10 to which the present invention is preferably applied. The wireless tag communication system 10 includes a wireless tag communication device 12 which is an embodiment of the wireless transmission device or wireless communication device of the present invention, and a single or a plurality of communication targets of the wireless tag communication device 12 (FIG. 1). Is a so-called RFID (Radio Frequency Identification) system composed of a single wireless tag 14, and the wireless tag communication device 12 functions as an interrogator of the RFID system, and the wireless tag 14 functions as a responder. That is, when the interrogation wave F _c (transmission signal) is transmitted from the radio tag communication device 12 toward the radio tag 14, a predetermined information signal (data) is received in the radio tag 14 that has received the interrogation wave F _c. As a result, the interrogation wave F _c is modulated and sent back as a response wave F _r (reply signal) to the RFID tag communication apparatus 12, so that information is transmitted between the RFID tag communication apparatus 12 and the RFID tag 14. Communication takes place. The wireless tag communication system 10 is used, for example, for managing articles in a predetermined communication area. The wireless tag 14 is preferably attached to an article to be managed, for example. And are provided integrally.

FIG. 2 is a diagram illustrating the configuration of the wireless tag communication device 12. As shown in FIG. 2, the wireless tag communication device 12 of this embodiment generates a command bit string (transmission bit string) corresponding to transmission data for the wireless tag 14, and encodes the command bit string by the FSK method or the like. And a transmission data output unit 16 for outputting and a high frequency for generating a predetermined frequency signal corresponding to the carrier wave of the interrogation wave F _c and modulating the carrier wave with the transmission data output from the transmission data output unit 16 A transmission circuit unit 18, a transmission antenna 20 having a plurality of feeding points for transmitting the signal output from the high-frequency transmission circuit unit 18 as the interrogation wave F _c toward the wireless tag 14, and the transmission antenna 20 A plurality (two in FIG. 2) of power supply ratio changing units for changing the ratio of the power supplied to each power supply point in FIG. By controlling the variable attenuators 24a and 24b (hereinafter simply referred to as the variable attenuator 24 unless otherwise distinguished) and the ratio of the power supplied to each feeding point in the transmitting antenna 20 via the variable attenuator 24. A transmission polarization direction control unit 26 that controls the polarization direction of a transmission signal transmitted from the transmission antenna 20 and a response returned from the wireless tag 14 in response to the interrogation wave F _c transmitted from the transmission antenna 20. A receiving antenna 28 for receiving the wave F _r , a high-frequency receiving circuit unit 29 that performs frequency conversion and demodulation processing of a received signal received by the receiving antenna 28, and a signal output from the high-frequency receiving circuit unit 29 A reception signal processing unit 30 that performs decoding processing of data included in the response wave returned from the wireless tag 14 It is configured.

FIG. 3 is a diagram for explaining the configuration of the RFID circuit element 34 provided in the RFID tag 14. As shown in FIG. 3, the wireless tag circuit element 34 includes an antenna unit 36 for transmitting and receiving signals to and from the wireless tag communication device 12, and the wireless tag connected to the antenna unit 36. An IC circuit unit 38 for performing information communication processing with the communication device 12 is provided. The IC circuit unit 38 rectifies the interrogation wave F _c received from the RFID tag communication device 12 received by the antenna unit 36, and the energy of the interrogation wave F _c rectified by the rectification unit 40. Functions as a power supply unit 42 for storing, a clock extraction unit 44 that extracts a clock signal from the carrier wave received by the antenna unit 36 and supplies the clock signal to the control unit 50, and an information storage unit that can store a predetermined information signal The RFID circuit element 38 via the memory unit 46, the modulation / demodulation unit 48 connected to the antenna unit 36 to modulate and demodulate signals, the rectification unit 40, the clock extraction unit 44, the modulation / demodulation unit 48, and the like. And a control unit 50 for controlling the operation of the function. The control unit 50 performs control to store the predetermined information in the memory unit 46 by communicating with the RFID tag communication device 12, and the modulation / demodulation unit 48 receives the interrogation wave F _c received by the antenna unit 36. In FIG. 5, basic control such as control for reflecting and returning the response wave F _r as the response wave F _r is performed after modulation based on the information signal stored in the memory unit 46.

FIG. 4 is a diagram illustrating a wireless transmission device (transmission circuit) provided in the wireless tag communication device 12. FIG. 5 is a diagram illustrating a specific configuration of the transmission antenna 20 provided in the wireless tag communication device 12. As shown in FIG. 5, the transmitting antenna 20 is preferably two sets of dipole antennas 22a and 22b arranged so as to be orthogonal to each other (hereinafter simply referred to as a dipole antenna 22 unless otherwise distinguished). Each of the dipole antennas 22 is provided with one feeding point 52a, 52b (hereinafter simply referred to as the feeding point 52 unless otherwise distinguished). Is. As shown in FIGS. 4 and 5, in the wireless transmission device provided in the wireless tag communication device 12, the power supply ratio change for changing the ratio of the power supplied to each power supply point 52 in the transmission antenna 20. A variable attenuator 24 is provided as a unit, and the transmission polarization direction control unit 26 controls the attenuation amount in each of the variable attenuators 24 to thereby control the ratio of the power supplied to each feeding point 52 in the transmission antenna 20. And the polarization direction of the interrogation wave F _c (transmission signal) transmitted from the transmission antenna 20 is thereby controlled.

Here, the transmission polarization direction control unit 26 preferably controls the attenuation amount in each variable attenuator 24 so that the polarization direction of the transmission signal transmitted from the transmission antenna 20 changes every predetermined angle. . Preferably, the attenuation amount in each variable attenuator 24 is controlled so that the polarization direction of the transmission signal is changed every time a series of communication processing such as ID acquisition and data reading of the wireless tag 14 is completed. . Further, a reception signal strength detection unit for detecting the signal strength of the reception signal received by the reception antenna 28 is provided, and attenuation in each variable attenuator 24 so that the signal strength detected by the reception signal strength detection unit is maximized. A mode of controlling the amount is also conceivable. The transmission polarization direction control unit 26 controls the polarization direction of the interrogation wave F _c (transmission signal) transmitted from the transmission antenna 20 as described above. Such control is similarly executed for other configurations of the present invention described below.

  Next, another configuration of the wireless transmission device suitably provided in the wireless tag communication device 12 as an alternative to the wireless transmission device shown in FIG. 4 will be exemplified. In the following description, portions common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

FIG. 6 is a diagram for explaining another example of the wireless transmission device suitably provided in the wireless tag communication device 12 as an alternative to the wireless transmission device shown in FIG. The radio transmission apparatus shown in FIG. 6 includes a delay line 54 provided corresponding to at least one feeding point 52 (the feeding point 52b of the dipole antenna 22b in FIG. 6) among the plurality of feeding points 52, and the delay thereof. A circuit switching unit 56 that switches between a circuit that feeds power to the feeding point 52 via the line 54 and a circuit that feeds power without going through the line 54 is provided. The delay line 54 preferably changes the phase of the signal fed by the circuit passing through the delay line 54 by approximately 180 ° compared to the phase of the signal fed by the circuit not passing through the delay line 54. It is a 180 ° phase shifter. In such a wireless transmission device, the transmission polarization direction control unit 26 controls the attenuation amount in each of the plurality of variable attenuators 24 and also supplies the power supply via the circuit switching unit 56 and the delay line 54. By switching between a circuit that supplies power to the point 52 and a circuit that supplies power without going through the point 52, the ratio of the power supplied to each power supply point 52 is controlled, whereby the interrogation wave F _c transmitted from the transmitting antenna 20 is controlled. Control the direction of polarization.

FIG. 7 is a diagram illustrating still another example of a wireless transmission device that is preferably included in the wireless tag communication device 12 as an alternative to the wireless transmission device shown in FIG. The wireless transmission device shown in FIG. 7 has an attenuation fixed amount (for example, −−) provided corresponding to at least one of the plurality of feeding points 52 (the feeding point 52b of the dipole antenna 22b in FIG. 7). 3 dB) attenuator 58, a second circuit switching unit 60 that switches between a circuit that feeds power to the feeding point 52 via the attenuator 58 and a circuit that feeds power without passing through the attenuator 58, and the high-frequency transmission circuit unit 18 A third circuit switching unit 62 that switches between a circuit that supplies an output signal to a power feeding unit 52 (the power feeding point 52a of the dipole antenna 22a in FIG. 7) that is different from the power feeding unit 52 corresponding to the attenuator 58 and a circuit that does not supply the signal. And a terminating resistor 64 provided between a terminal opposite to the side to which the dipole antenna 22a is connected in the third circuit switching unit 62 and a ground point. A, a. In such a wireless transmission device, the transmission polarization direction control unit 26 switches the circuit via the circuit switching unit 56, the second circuit switching unit 60, and the third circuit switching unit 62 to each feeding point 52. Control the rate of power supplied. Specifically, i) the circuit switching unit 56 does not pass through the delay line 54 (hereinafter referred to as the terminal a side), the second circuit switching unit 60 does not pass through the attenuator 58 (hereinafter referred to as the terminal a side), A circuit in which the third circuit switching unit 62 is on the dipole antenna 22a side (hereinafter referred to as the terminal a side), ii) the circuit switching unit 56 is on the terminal a side, and the second circuit switching unit 60 is on the side via the attenuator 58 (hereinafter referred to as “a”). A circuit having the third circuit switching unit 62 as the terminal a side, iii) a circuit switching unit 56 through the delay line 54 (hereinafter referred to as the terminal b side), and a second circuit switching unit 60. A circuit having the terminal a side, the third circuit switching unit 62 as the terminal a side, iv) the circuit switching unit 56 as the terminal b side, the second circuit switching unit 60 as the terminal b side, and the third circuit switching unit 62 as the terminal a side V) The circuit switching unit 54 is connected to the terminal a side, the second The circuit switching unit 56, the second circuit switching unit, and the like so as to selectively establish any one of the circuits having the circuit switching unit 60 on the terminal a side and the third circuit switching unit 62 on the termination resistor 64 side. 60 and the third circuit switching unit 62 are switched. With such control, the ratio of the power supplied to each feeding point 52 is controlled, and thereby the polarization direction of the interrogation wave F _c transmitted from the transmitting antenna 20 is controlled. When the attenuator 58 is set to −3 dB, it is possible to select three kinds of inclinations of 0 degrees, 60 degrees, and 120 degrees with respect to the dipole antenna 22a.

FIG. 8 is a diagram illustrating still another example of a wireless transmission device that is preferably included in the wireless tag communication device 12 as an alternative to the wireless transmission device shown in FIG. The radio transmission apparatus shown in FIG. 8 includes a variable phase shifter 66 corresponding to at least one feeding point 52 (the feeding point 52b of the dipole antenna 22b in FIG. 8) among the plurality of feeding points 52. In such a wireless transmission device, the transmission polarization direction control unit 26 controls the amount of phase shift in the variable phase shifter 66, and the circuit via the second circuit switching unit 60 and the third circuit switching unit 62. Is switched to control the ratio of the power supplied to each feeding point 52, thereby controlling the polarization direction of the interrogation wave F _c transmitted from the transmitting antenna 20.

  FIG. 9 is a diagram for explaining another example of the transmission / reception circuit suitably provided in the RFID tag communication apparatus 12 as an alternative to the transmission / reception circuit shown in FIG. The transmission / reception circuit shown in FIG. 9 includes a transmission / reception shared antenna 68 that transmits the transmission signal and receives a return signal returned from the wireless tag 14 according to the transmission signal. The antenna 68 includes two sets of dipole antennas 22 arranged so as to be orthogonal to each other, like the transmission antenna 20 described above with reference to FIG. 5, and one antenna is provided at the center of each dipole antenna 22. Each feeding point 52 is provided. Further, the transmission / reception circuit shown in FIG. 9 supplies a signal supplied from the high-frequency transmission circuit unit 18 via the third circuit switching unit 62 to each dipole antenna 22 and also receives a received signal received by each dipole antenna 22. A plurality of (two in FIG. 9) transmission / reception separators 70a and 70b (hereinafter simply referred to as transmission / reception separators 70 unless otherwise distinguished), and each feeding point in the antenna 68. A reception signal combining unit 72 that combines the reception signals received corresponding to 52 (dipole antenna 22) and supplied via the transmission / reception separating unit 70. Further, the high frequency reception circuit unit 29 and the reception signal processing unit 30 in the transmission / reception circuit shown in FIG. 9 perform demodulation processing and decoding processing of the reception signal combined (simple combination) by the reception signal combining unit 72.

  FIG. 10 is a diagram for explaining still another example of the transmission / reception circuit suitably provided in the RFID tag communication apparatus 12 as an alternative to the transmission / reception circuit shown in FIG. The transmission / reception circuit shown in FIG. 10 includes a plurality of (two in FIG. 10) high-frequency reception circuit units that individually process the reception signals received corresponding to the feeding points 52 of the antenna 68, that is, the dipole antennas 22. 29a and 29b (hereinafter simply referred to as a high frequency receiving circuit unit 29 unless otherwise distinguished) and received signal processing units 30a and 30b (hereinafter simply referred to as a received signal processing unit 30 unless otherwise distinguished). Is. In such a transmission / reception circuit, the individual high-frequency receiving circuit unit 29 and the reception signal processing unit 30 are provided corresponding to each feeding point 52, so that the received signal can be processed for each feeding point 52. In addition, by providing a configuration such as a reception weight processing unit (not shown in FIG. 10), it is possible to perform processing such as weighting the reception signal input from each feeding point 52 corresponding to the polarization direction of the transmission signal. .

FIG. 11 is a diagram for explaining still another example of the transmission / reception circuit suitably provided in the RFID tag communication apparatus 12 as an alternative to the transmission / reception circuit shown in FIG. The transmission / reception circuit shown in FIG. 11 includes a fixed amplification factor (for example, +3 dB) amplifier 74 provided corresponding to the dipole antenna 22a and a fixed amplification factor provided for the dipole antenna 22b (for example, And a fourth circuit switching unit 78 that switches between a circuit that supplies power to the power supply point 52b via the amplifier 76 and a circuit that supplies power without passing through the amplifier 76. In such a transmission / reception circuit, the transmission polarization direction control unit 26 controls the amount of phase shift in the variable phase shifter 66, and the circuit is connected via the third circuit switching unit 62 and the fourth circuit switching unit 78. By switching, the ratio of the electric power supplied to each feeding point 52 is controlled, and thereby the polarization direction of the interrogation wave F _c transmitted from the transmitting antenna 20 is controlled.

  FIG. 12 is a flowchart for explaining a main part of the RFID tag communication control by the RFID tag communication apparatus 12, and is repeatedly executed at a predetermined cycle.

First, in step (hereinafter, step is omitted) S1, θ corresponding to the transmission polarization plane direction of the transmission antenna 20 (antenna 68) is set to an initial value θ ₀ , so that the transmission polarization plane direction is the same. The amount of attenuation in the variable attenuator 24, the connection of the circuit switching unit 56, the second circuit switching unit 60, the third circuit switching unit 62, and the fourth circuit switching unit 78, the amount of phase shift in the variable phase shifter 66, and the like are controlled. . Next, in S2, a command corresponding to the transmission data of the transmission signal is set, and a command bit string (transmission bit string) corresponding to the command is generated. Next, in S3, the command bit string generated in S2 is encoded and output. Next, in S4, the carrier wave is modulated by the transmission data output in S3, and is output from the transmission antenna 20 (antenna 68) as a transmission signal. Next, in S5, it is determined whether or not there is a response from the wireless tag 14 (reply of a reply signal) according to the transmission signal transmitted in S4. If the determination in S5 is negative, the processes in and after S7 are executed. If the determination in S5 is affirmative, in S6 corresponding to the operation of the reception signal processing unit 30, the reception antenna Processing such as demodulation and decoding of the received signal received by the antenna 28 (antenna 68) is performed. Next, in S6 ′, it is determined whether or not a series of communication processing has been completed. If the determination at S6 'is negative, the command to be transmitted next is set at S2, and a command bit string corresponding to the command is generated. If the determination at S6' is affirmative, S7 In FIG. 4, it is determined whether or not θ corresponding to the transmission polarization plane direction is the maximum value θ _max . If the determination in S7 is negative, in S8, a predetermined value dθ is added to θ corresponding to the transmission polarization plane direction, and the attenuation amount and circuit in the variable attenuator 24 so as to be in the transmission polarization plane direction. After the connection of the switching unit 56, the second circuit switching unit 60, the third circuit switching unit 62, and the fourth circuit switching unit 78, the amount of phase shift in the variable phase shifter 66, and the like are controlled, the processing after S2 is performed again. If the determination in S7 is affirmative, the routine is terminated. In the above control, S2 and S3 correspond to the operation of the transmission data output unit 16, and S1 and S7 to S6 ′ correspond to the operation of the transmission polarization direction control unit 26, respectively.

  As described above, according to the present embodiment, the transmission antenna 20 having a plurality of feeding points 52 for transmitting the transmission signal and the ratio of the power supplied to each feeding point 52 in the transmission antenna 20 are changed. A transmission ratio changing unit for controlling the ratio of power supplied to each feeding point 52 in the transmission antenna 20 via the power supply ratio changing unit. Since the transmission polarization direction control unit 26 (S1 and S7 to S9) for controlling the wave direction is provided, the polarization direction of the transmission signal transmitted from the transmission antenna 20 can be arbitrarily set with a simple configuration. Can be changed. That is, it is possible to provide a wireless transmission device that realizes highly sensitive communication regardless of the relative positional relationship with the communication target.

  Further, when either the transmission antenna 20a or the transmission antenna 20b is operated at the maximum output without using the variable attenuator 24, the transmission signal becomes a polarization plane corresponding to the transmission antenna 20a or the transmission antenna 20b. The communication object arranged in a 45 ° angle relationship with each of the transmission antennas 20a and 20b is approximately 70% stronger than the communication object arranged in the positional relationship parallel to the transmission antenna 20a or the transmission antenna 20b. Can only receive the transmitted signal. Further, by applying the same power to both the transmission antennas 20a and 20b to the communication objects arranged in a positional relationship of 45 ° with each of the transmission antennas 20a and 20b, the transmission antenna 20a or the transmission antenna A transmission signal having the same strength as that of a communication object arranged in a positional relationship parallel to 20b can be given. In this case, however, the power twice as much as that in the case of using either the transmission antenna 20a or 20b is used. It may radiate, and there may be cases where electric power exceeding the legal regulation value is required. On the other hand, in the method of the present embodiment, the polarization direction of the transmission signal can be arbitrarily changed, and communication corresponding to the inclination of the communication target becomes possible. That is, it is possible to provide a wireless transmission device that realizes highly sensitive communication without increasing radiated power.

  In addition, since the variable attenuator 24 is provided corresponding to at least one of the plurality of feeding points 52 as the feeding ratio changing unit, the feeding rate changing unit is supplied to each feeding point 52 in the transmission antenna 20. It is possible to control the ratio of electric power in a practical manner.

  Further, an attenuator 58 provided corresponding to at least one of the plurality of feeding points 52 and a circuit that feeds power to the feeding point 52 via the attenuator 58 are fed without feeding. Since the second circuit switching unit 60 that switches between the circuits to be performed is provided as the feeding ratio changing unit, the ratio of the power supplied to each feeding point 52 in the transmission antenna 20 is controlled in a practical manner. can do.

  In addition, a delay line 54 provided corresponding to at least one of the plurality of feeding points 52 and a circuit that feeds the feeding point 52 via the delay line 54 are bypassed. Since the circuit switching unit 56 for switching between the power feeding circuit and the circuit switching unit 56 is provided, the polarization direction of the transmission signal transmitted from the transmission antenna 20 can be selected in three or more directions and practical. It can be controlled in a manner.

  Further, the delay line 54 shifts the phase of a signal supplied by a circuit passing through the delay line 54 by 180 ° so as to change by 180 ° compared to the phase of a signal supplied by a circuit not passing through the delay line 54. Since it is a phase shifter, the polarization direction of the transmission signal transmitted from the transmission antenna 20 can be controlled in a practical manner.

  The transmission antenna 20 is composed of two sets of dipole antennas 22 arranged so as to be orthogonal to each other, and each dipole antenna 22 is provided with one feeding point 52. The polarization direction of the transmission signal transmitted from the practical transmission antenna 20 including the two sets of dipole antennas 22 can be arbitrarily changed.

  In addition, the transmission polarization direction control unit 26 supplies each power supply in the transmission antenna 20 via the power supply ratio changing unit so that the polarization direction of the transmission signal transmitted from the transmission antenna 20 changes every predetermined angle. Since the ratio of the power supplied to the point 52 is controlled, the transmission signal can be continuously transmitted for each predetermined direction in each polarization direction, and suitable communication with the communication target is realized. be able to.

  In addition, the wireless transmission device shown in FIG. 4 or the like transmits a predetermined transmission signal toward the communication target, and receives a reply signal returned from the communication target in response to the transmission signal. Since information is communicated between them, the polarization direction of the transmission signal transmitted from the transmission antenna 20 can be arbitrarily changed with a simple configuration. That is, it is possible to provide a wireless communication device that realizes highly sensitive communication regardless of the relative positional relationship with the communication target.

  In addition, the antenna 68 is a transmission / reception shared antenna that transmits the transmission signal and receives a reply signal returned from the communication target in accordance with the transmission signal. Therefore, the configuration of the apparatus is as simple as possible. Can be.

  In addition, a reception signal combining unit 72 that combines the reception signals received corresponding to each feeding point 52 in the antenna 68, and a reception signal processing unit 30 that processes the reception signal combined by the reception signal combining unit 72, Therefore, the configuration of the receiving circuit can be made as simple as possible.

  In addition, since the antenna 68 includes a plurality of reception signal processing units 30a and 30b that individually process the reception signals received corresponding to the respective feeding points 52 in the antenna 68, each feeding point 52 in the antenna 68 is provided. The received signal can be processed every time. For example, the received signal input from each feeding point 52 can be weighted corresponding to the polarization direction of the transmitted signal.

  In addition, the wireless communication device transmits a predetermined transmission signal by the transmission antenna 20 toward the wireless tag 14 that is a communication target, and transmits a reply signal returned from the wireless tag 14 in response to the transmission signal. Since the wireless tag communication device 12 communicates information with the wireless tag 14 by receiving the wireless tag, the wireless tag realizes highly sensitive communication regardless of the relative positional relationship with the wireless tag 14 that is a communication target. A communication device 12 can be provided.

  In addition, the transmission polarization direction control unit 26 uses the transmission antenna 20 to change the polarization direction of the transmission signal every time the command included in the transmission signal is changed. Since the ratio of power supplied to each feeding point 52 is controlled, communication can be performed in the same polarization direction during a series of communication processes, and the polarization is switched and transmitted for each series of communication processes. Signals can be transmitted, and suitable communication can be realized with the wireless tag 14 that is a communication target.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, in the above-described embodiment, the RFID tag communication apparatus 12 includes the transmission antenna 20 (antenna 68) including two sets of dipole antennas 22 arranged so as to be orthogonal to each other. The invention is not limited to this, and for example, a square (rectangular) rectangular patch antenna 80 as shown in FIG. 13 or a circular patch antenna 82 as shown in FIG. 14 may be provided. . In the rectangular patch antenna 80, as shown in FIG. 13, two feeding points 84a and 84b are provided at portions other than the central point of the rectangular patch antenna 80 on a line connecting the central points of two opposite sides of the rectangular patch antenna 80. As in the above-described embodiment, the transmission polarization direction control unit 26 controls the ratio of the power supplied to the feed points 84a and 84b so that the transmission signal transmitted from the rectangular patch antenna 80 is transmitted. The polarization direction is controlled. Further, in the circular patch antenna 82, as shown in FIG. 14, two feeding points 84a and 84b are provided at portions other than the center point of the circular patch antenna 82 on two orthogonal diameters of the circular patch antenna 82. The polarization direction of the transmission signal transmitted from the circular patch antenna 82 is controlled by controlling the ratio of the power supplied to the feed points 84a and 84b by the transmission polarization direction control unit 26. . As described above, the present invention is applied to a wireless transmission device including the patch antennas 80 and 82 in which the two feeding points 84a and 84b are provided in a portion other than the center point of the planar antenna. The polarization direction of transmission signals transmitted from the antennas 80 and 82 can be arbitrarily changed.

  In the above-described embodiment, the RFID tag communication device 12 includes the variable attenuator 24 as the power supply ratio changing unit. As the power supply ratio changing unit, A variable gain amplifier corresponding to at least one feeding point 52 may be provided. Also with such a configuration, the ratio of power supplied to each feeding point 52 in the transmission antenna 20 or the like can be controlled in a practical manner.

  In the above-described embodiment, the RFID tag communication device 12 includes the transmission data output unit 16, the transmission polarization direction control unit 26, the reception signal processing unit 30, and the like as individual control devices. However, a function equivalent to these control devices may be functionally provided in a predetermined control device. The control by the transmission data output unit 16, the transmission polarization direction control unit 26, the reception signal processing unit 30, and the like described above may be digital signal processing or analog signal processing.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

It is a figure explaining the radio | wireless tag communication system to which this invention is applied suitably. It is a figure explaining the structure of the RFID tag communication apparatus which is one Example of this invention. It is a figure explaining the structure of the RFID circuit element with which the RFID tag which is a communication object of the RFID tag communication apparatus of FIG. 2 was equipped. It is a figure explaining an example of the radio | wireless transmitter of this invention with which the radio | wireless tag communication apparatus of FIG. 2 was equipped. It is a figure which illustrates the specific structure of the transmission antenna with which the RFID tag communication apparatus of FIG. 2 was equipped. FIG. 5 is a diagram illustrating another example of a wireless transmission device that is suitably provided in the wireless tag communication device of FIG. 2 as an alternative to the wireless transmission device shown in FIG. 4. FIG. 5 is a diagram illustrating still another example of a wireless transmission device that is preferably provided in the wireless tag communication device of FIG. 2 as an alternative to the wireless transmission device shown in FIG. 4. FIG. 5 is a diagram illustrating still another example of a wireless transmission device that is preferably provided in the wireless tag communication device of FIG. 2 as an alternative to the wireless transmission device shown in FIG. 4. It is a figure explaining another example of the transmission / reception circuit suitably provided in the RFID tag communication apparatus as an alternative to the transmission / reception circuit provided in the RFID tag communication apparatus of FIG. It is a figure explaining another example of the transmission / reception circuit suitably provided in the RFID tag communication apparatus as an alternative to the transmission / reception circuit provided in the RFID tag communication apparatus of FIG. It is a figure explaining another example of the transmission / reception circuit suitably provided in the RFID tag communication apparatus as an alternative to the transmission / reception circuit provided in the RFID tag communication apparatus of FIG. 3 is a flowchart for explaining a main part of RFID tag communication control by the RFID tag communication apparatus of FIG. 2. It is a figure which illustrates the structure of the square patch antenna suitably provided for the RFID tag communication apparatus of FIG. It is a figure which illustrates the structure of the circular patch antenna suitably provided for the RFID tag communication apparatus of FIG.

Explanation of symbols

12: Wireless tag communication device (wireless transmission device, wireless communication device)
14: Wireless tag (communication target)
20: Transmitting antenna 22: Dipole antenna 24: Variable attenuator (feed rate changing unit)
26: transmission polarization direction control unit 30: reception signal processing unit 52, 84: feeding point 54: delay line 56: circuit switching unit 58: attenuator 60: second circuit switching unit 62: third circuit switching unit 66: variable shift Phaser 68: Antenna 70: Transmission / reception separating unit 72: Received signal combining unit 78: Fourth circuit switching unit 80: Square patch antenna 82: Circular patch antenna

Claims (15)

A wireless transmission device for transmitting a predetermined transmission signal toward a communication target,
An antenna for transmitting the transmission signal having a plurality of feeding points;
A feed rate changing unit for changing the rate of power supplied to each feed point in the antenna;
A transmission polarization direction control unit that controls a polarization direction of a transmission signal transmitted from the antenna by controlling a ratio of power supplied to each feeding point in the antenna via the feeding ratio changing unit; A wireless transmission device comprising: a wireless transmission device;   The wireless transmission device according to claim 1, wherein the power supply ratio changing unit includes a variable attenuator corresponding to at least one of the plurality of power supply points.   The wireless transmission device according to claim 1, wherein the power supply ratio changing unit includes a variable gain amplifier corresponding to at least one of the plurality of power supply points. An attenuator provided corresponding to at least one of the plurality of feeding points;
A circuit switching unit that switches between a circuit that supplies power to the power supply point via the attenuator and a circuit that supplies power without going through the attenuator is provided as the power supply ratio changing unit. Wireless transmitter. A delay line provided corresponding to at least one of the plurality of feeding points;
5. The wireless transmission device according to claim 1, further comprising: a circuit switching unit that switches between a circuit that supplies power to the power supply point via the delay line and a circuit that supplies power without using the delay line. .   6. The delay line is configured to change a phase of a signal fed by a circuit passing through the delay line by approximately 180 ° as compared to a phase of a signal fed by a circuit not passing through the delay line. Wireless communication device.   7. The antenna according to claim 1, wherein the antenna is composed of two sets of dipole antennas arranged so as to be orthogonal to each other, and each dipole antenna is provided with one feeding point. Wireless transmitter.   The wireless transmission device according to claim 1, wherein the antenna is a two-feed patch antenna, and two feed points are provided in a portion other than the center point of the patch antenna.   The transmission polarization direction control unit is configured to control the power supplied to each feeding point in the antenna via the feeding ratio changing unit so that the polarization direction of a transmission signal transmitted from the antenna changes every predetermined angle. The wireless transmission device according to claim 1, which controls a ratio.   The wireless transmission device according to any one of claims 1 to 9 transmits a predetermined transmission signal toward a communication target, and receives a reply signal returned from the communication target in response to the transmission signal. A wireless communication device that performs information communication with a wireless communication device.   The radio communication apparatus according to claim 10, wherein the antenna is a transmission / reception shared antenna that transmits the transmission signal and receives a return signal returned from the communication target according to the transmission signal. A received signal synthesizer that synthesizes received signals corresponding to each feeding point in the antenna;
The wireless communication apparatus according to claim 11, further comprising: a reception signal processing unit that processes the reception signal combined by the reception signal combining unit.   The wireless communication apparatus according to claim 11, comprising a plurality of reception signal processing units that individually process reception signals received corresponding to the respective feeding points in the antenna.   The wireless communication device transmits a predetermined transmission signal by the antenna toward a wireless tag that is a communication target, and receives a reply signal returned from the wireless tag in response to the transmission signal. The wireless communication device according to claim 10, wherein the wireless communication device is a wireless tag communication device that communicates information with a tag.   The transmission polarization direction controller controls the power supplied to each feeding point in the antenna via the feeding ratio changing unit so as to change the polarization direction of the transmission signal every time a predetermined communication process is completed. The wireless communication apparatus according to claim 14, wherein the ratio is controlled.

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