JP2005136666A - Radio communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the transmission rate of data transmission of a back scatter system by introducing modulation processing of higher bit rate such as QPSK modulation. <P>SOLUTION: Phase shifters 354, 357, 360 are inserted into second-fourth signal paths respectively to form phase differences of 90°, 180° and 270° compared to carriers inputted into a first signal path respectively. Accordingly, a transmission data are segmented into two bits, the data are switched into signal paths corresponding to combinations of 0, 1 of two bits by combinations of ONs and OFFs of high-frequency switches 351, 352 and so on, and four kinds of phase differences are assigned to the carrier, thereby attaining the QPSK modulation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radio communication apparatus using a radio wave communication system using microwaves of a specific frequency band, and more particularly to a radio communication apparatus that realizes low power consumption between devices that are limited to a very short distance.

  More particularly, the present invention relates to a wireless communication apparatus that performs ultra-short-range data communication using a back scatter method using absorption and reflection of received radio waves based on antenna termination operation, and more particularly, modulation of higher bit rate. The present invention relates to a wireless communication apparatus that incorporates processing to improve the transmission rate of back-scatter data communication.

  As an example of wireless communication means that can be applied only locally, RFID can be cited. The RFID is a system composed of a tag and a reader, and is a system that reads information stored in the tag in a contactless manner with a reader. Other names include "ID system, data carrier system", etc., but this RFID system is common worldwide. For short, it may be called RFID. Translated into Japanese, it becomes “a recognition system using high frequency (wireless)”. Examples of the communication method between the tag and the reader / writer include an electromagnetic coupling method, an electromagnetic induction method, and a radio wave communication method (for example, see Non-Patent Document 1).

  An RFID tag is a device that includes unique identification information, and has an operating characteristic that oscillates a radio wave of a modulation frequency corresponding to the identification information in response to reception of a radio wave of a specific frequency. Based on the oscillation frequency, it is possible to specify what it is. Therefore, in a system using RFID, it is possible to perform identification of an article, identification of an owner, and the like using a unique ID written in an RFID tag. Currently, RFID systems are used in many systems, such as systems that manage entrance and exit, goods identification systems in logistics, fee clearing systems in restaurants, etc., and unauthorized removal prevention systems at stores such as CDs and software. ing.

  For example, an IC chip having transmission / reception and memory functions, a driving source of the chip, and an antenna can be packaged to manufacture a wireless identification device in a small size (see, for example, Patent Document 1). According to this wireless identification device, various data relating to articles and the like are transmitted to the receiving means of the IC chip via the antenna, the output is stored in the memory, and the data in the memory is read as necessary, It can be supplied to the outside wirelessly through an antenna. Accordingly, it is possible to quickly and easily confirm or track the presence or position of an article or the like.

  FIG. 6 shows a configuration example of a conventional RFID system. Reference numeral 101 corresponds to the tag side of the RFID, and includes a tag chip 102 and an antenna 103. As the antenna 103, a half-wave dipole antenna or the like is used. The tag chip 102 includes a modulation unit 110, a rectification / demodulation unit 112, and a memory unit 113.

The radio wave f _o transmitted from the tag reader 100 is received by the antenna 103 and input to the rectifying / demodulating unit 110. Here, the received radio wave f _o is rectified, and at the same time is converted into a DC power source, the demodulation function by the DC power supply starts operating, that for the tag 101 is a read signal is recognized. The power generated by receiving the radio wave f _o is also supplied to the memory unit 113 and the modulation unit 110.

  The memory unit 113 reads ID information stored therein in advance and sends it to the modulation unit 110 as transmission data. The modulation unit 110 includes a diode switch 111, and repeats the on / off operation of the diode switch 111 according to the bit image of the transmission data. That is, if the data is 1, the switch is turned on and the antenna is terminated with antenna impedance (eg, 50 ohms). At this time, radio waves from the tag reader 100 are absorbed. When the data is 0, the switch is turned off, the diode switch 111 is opened, and at the same time, the end of the antenna is opened. At this time, the radio wave from the tag reader 100 is reflected and returns to the transmission source. A communication method that expresses data by a reflection or absorption pattern of an incoming radio wave is called a “back scatter method”. In this way, the tag 101 can send internal information to the reader side with no power supply.

  One tag reader 100 includes a host device 106 such as a portable information terminal, a tag reader module 104, and an antenna 105 connected to the tag reader module 104.

The host device 106 notifies the communication control unit 120 of a read instruction for the tag 101 via the host interface unit 121. Upon receiving the tag read command from the communication control unit 120, the baseband processing unit 119 performs a predetermined editing process on the transmission data, performs further filtering, and then sends the filtered data to the ASK modulation unit 117 as a baseband signal. send. ASK modulating unit 117, ASK with frequency f _o of the frequency synthesizer 116: performing (Amplitude Shift Keying amplitude shift keying) modulation.

  The frequency setting of the frequency synthesizer 116 is performed by the communication control unit 120. In general, the transmission frequency to the tag is used by hopping in order to reduce the standing wave of the signal from the RF tag and multipath. This hopping instruction is also given by the communication control unit 120. The transmission signal subjected to ASK modulation is radiated from the antenna 105 toward the tag 101 via the circulator 114.

A signal having the same frequency as the transmission signal from the tag reader 100 is returned from the tag 101 by reflection by the back scatter method (described above). This signal is received by the antenna 105 of the tag reader 100 and input to the mixer 115. Since the mixer 115 the same local frequency f _o and the transmission is inputted, so that the signal subjected to modulation by the tag 101 appears at the output of the mixer 115. The demodulator 118 demodulates 1/0 data from this signal and sends it to the communication controller 119. The communication control unit 119 decodes the data, extracts the data (ID) stored in the memory 113 in the tag 101, and transfers the data (ID) from the host interface unit 120 to the host device 106.

  The tag reader 100 can read information in the tag 101 by the mechanism as described above. In general, the tag reader can also be used as a tag writer, and can write specified data on the host device 106 side in the memory 113 in the tag 101.

  Conventionally, such a back-scatter wireless communication system is applied to identification and authentication of articles and people, as represented by RFID tags, because the communication range is limited to an extremely short distance. There were many.

  On the other hand, back-scatter wireless communication has a feature that a wireless transmission path with extremely low power consumption can be established if the communication distance is limited. Recently, with the improvement of mounting technology, IC chips equipped with a memory function have appeared, and the memory capacity has further increased. Therefore, there is a demand not only to perform communication of relatively short data such as identification / authentication information but also to adopt back-scatter communication for general data transmission.

  However, in the conventional back scatter communication systems, a modulation method having a relatively low bit rate such as ASK (Amplitude Shift Keying) or BPSK (Binary Phase Shift Keying) is adopted. There is a problem in terms.

JP-A-6-123773 Klaus Finkenzeller (Translated by Software Engineering Laboratory) "RFID Handbook Principles and Applications of Contactless IC Cards" (Nikkan Kogyo Shimbun)

  An object of the present invention is to provide an excellent wireless communication apparatus capable of suitably performing ultra-short-range data communication by a back scatter method using absorption and reflection of received radio waves based on an antenna termination operation. is there.

  It is a further object of the present invention to provide an excellent wireless communication apparatus that can incorporate a higher bit rate modulation process to improve the transmission rate of back-scatter data communication.

The present invention has been made in consideration of the above problems, and is a wireless communication device that performs data communication by a back scatter method using reflection of received radio waves, and a data transmission unit includes:
An antenna for receiving radio waves coming from the transfer destination;
An input terminal for inputting a radio wave received by the antenna and an output terminal for transmitting a reflected wave of the received radio wave;
n signal paths connected in parallel between the input terminal and the output terminal, where the k-th signal path gives a phase difference of (k−1) π / 2 ^n-1 (however, 1 ≦ k ≦ n),
A signal path selection unit that forms reflected waves having different phases in n by selecting any one of the signal paths according to transmission data,
Represents the transmission data with the phase difference pattern of the reflected wave relative to the received radio wave.
This is a wireless communication device.

Here, the k-th signal path gives a phase difference of (k−1) π / 2 ⁿ (where 1 ≦ k ≦ n). The signal path selection unit divides the transmission data into 2 ^n-1 bits, selects a signal path corresponding to a combination of 2 ^n-1 bits 0 and 1, assigns a phase to the reflected wave, and 2 ^n- phase PSK modulation can be performed.

  The wireless communication apparatus according to the present invention includes, for example, a first signal path that obtains a first reflected wave that directly reflects a received radio wave without passing through any phase shifter, and a phase shifter that provides a phase difference of λ / 4 Are connected in series, and a second signal path for obtaining a second reflected wave whose phase is shifted by π / 2 compared to the first reflected wave, and a phase shifter for providing a phase difference of λ / 2 are connected in series. A third signal path that obtains a third reflected wave whose phase is shifted by π compared to the first reflected wave and a phase shifter that provides a phase difference of 3λ / 4 are connected in series to form the first reflected wave. And a fourth signal path for obtaining a fourth reflected wave whose phase is shifted by 3π / 2 as compared with the above.

  In such a case, the signal path selection means divides transmission data into 2 bits, selects a signal path corresponding to a combination of 0 and 1 of 2 bits, assigns a phase to the reflected wave, and performs QPSK modulation. be able to.

  According to the present invention, it is possible to provide an excellent wireless communication apparatus capable of suitably performing ultra-short-range data communication by a back scatter method using absorption and reflection of received radio waves based on an antenna termination operation. it can.

  Furthermore, according to the present invention, it is possible to provide an excellent wireless communication apparatus that can improve the transmission rate of back-scatter data communication by incorporating modulation processing with a higher bit rate such as QPSK modulation. .

  Further, according to the present invention, it is possible to realize low power consumption when wirelessly transmitting image data or the like from a portable device such as a digital camera or a mobile phone to a device such as a PC, a television, or a printer. A wireless communication system and a wireless communication apparatus can be provided.

  In addition, according to the present invention, an excellent wireless communication system and wireless communication capable of realizing low power consumption in a communication mode in which a transmission ratio occupies most of communication between devices limited to a very short distance. An apparatus can be provided.

  According to the present invention, it is possible to realize ultra-low-consumption image transmission that is orders of magnitude lower than that of a wireless LAN in a mobile device. This can greatly increase the battery life of the mobile device.

  Further, according to the present invention, the wireless transmission module of the mobile device as the data transmission side can easily realize cost reduction compared to the wireless LAN. In addition, since the wireless transmission module on the mobile side is not subject to a wireless station in the Radio Law, certification work such as conformity certification becomes unnecessary.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

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

  An object of the present invention is to realize low power consumption in a communication mode in which a transmission ratio occupies most of communication between devices limited to a very short distance. Wireless transmission is performed using reflected waves based on the scatter method. The RFID system itself is widely known in the art as an example of wireless communication means that can be applied only locally.

  An RFID tag is a system composed of a tag and a reader. The RFID tag, which is a system that reads information stored in the tag with a reader in a non-contact manner, is a device that includes unique identification information, and transmits radio waves of a specific frequency. In response to reception, it has an operating characteristic of oscillating a radio wave having a modulation frequency corresponding to the identification information, and the reader can identify what it is based on the oscillation frequency of the RFID tag. Examples of the communication method between the tag and the reader / writer include an electromagnetic coupling method, an electromagnetic induction method, and a radio wave communication method. The present invention relates to a radio wave communication system using a microwave such as a 2.4 GHz band.

  FIG. 1 schematically shows a hardware configuration of a wireless communication apparatus 300 according to an embodiment of the present invention. The illustrated wireless communication apparatus 300 corresponds to a device serving as a transmission source of image data such as a digital camera or a camera-equipped mobile phone, and is driven using, for example, a battery (not shown) as a main power source.

  A single digital camera includes a camera unit 302, a signal processing unit 303, a memory card interface unit 304, an operation / display unit 305, and a USB interface unit 306.

  The signal processing unit 303 converts the image data input from the camera unit 302 into image data of a predetermined format such as JPEG (Joint Photographic Experts Group), and the external memory card via the memory card interface unit 204. Stored in 307.

  The operation display unit 305 performs image display, various settings, and the like. A USB (Universal Serial Bus) interface unit 306 is used when an image is transferred to a PC using a USB interface.

  In the wireless communication apparatus 300 according to the present embodiment, an RFID tag based on a radio wave communication method is used as the wireless transmission module 308.

  The wireless transmission module 308 includes an antenna 309, a high frequency switch 310, a high frequency switch 311, a bandpass filter 312, and an ASK detection unit 313. In the present embodiment, the 2.4 GHz band is used as the frequency of the radio wave.

  When data transmission such as image transfer is performed, the high frequency switch 311 is controlled to be turned off together with the ASK detection unit 313 by the control signal from the signal processing unit 303 and is opened. When the wireless transmission module unit 308 receives the image data read from the memory card 307 by the signal processing unit 303, the wireless transmission module unit 308 performs on / off operation of the other high-frequency switch 310 connected to the antenna 309 according to the bit image of the data. Do. For example, the high frequency switch 310 is turned on when the data is 1, and is turned off when the data is 0.

  As shown in the figure, when the high-frequency switch 310 is on, the antenna 309 is short-circuited to the ground, and radio waves (described later) coming from the transfer destination are absorbed. On the other hand, when the high-frequency switch 310 is off, the antenna 309 is open, and radio waves coming from the transfer destination are reflected. In this operation, a reflected wave having a phase difference of 180 degrees is generated by turning on and off the high frequency switch 310 with respect to the radio wave coming from the transfer destination. Therefore, a transmission data signal such as image data can be read at the transfer destination by detecting the reflection phase of the transmission radio wave.

  That is, the image data is basically a back scatter method as a PSK (Phase Shift Keying) modulated reflected wave of a radio wave from a transfer destination caused by a change in antenna load impedance caused by an on / off operation of a high frequency switch. Will be sent. The reflected wave signal from the wireless transmission module 308 is equivalent to a PSK modulated wave.

  The high-frequency switch 310 is generally composed of a gallium arsenide IC, and its power consumption is several tens of μW or less. Therefore, according to the communication method described above, wireless image transmission with ultra-low consumption can be realized.

  On the other hand, at the time of data reception, the high frequency switch 311 is turned on together with the ASK detection unit 313 by a control signal from the signal processing unit 311.

  The band-pass filter 312 and the ASK detection unit 313 are used when receiving an ASK-modulated delivery confirmation signal from the transfer destination, but these two blocks are not necessary if the transmission is one-way transmission without confirming transmission. Become. On the other hand, when delivery confirmation is performed, the control is performed by the signal processing unit 303.

  The bandpass filter 312 is used for the purpose of passing a frequency in the 2.4 GHz band and attenuating other frequency bands. The power consumption of the ASK detection unit 313 required when confirming delivery can be realized with 30 mW or less.

  Therefore, the average power when transmitting data such as image data in the wireless communication apparatus shown in FIG. 1 is 10 mW or less in the case of the delivery confirmation method, and data transmission is possible at several tens of μW in the one-way transmission. This is an overwhelming performance difference compared to the average power consumption in a general wireless LAN system.

In addition, the present invention relates to a wireless communication apparatus that performs data transmission with low power by a back scatter method that uses reflection of incoming radio waves. As another embodiment, the reflected wave of the wireless transmission module unit 308 A QPSK (Quadrature Phase Shift Keying) method can be applied as the modulation method. The purpose of changing from PSK to QPSK is to speed up data. In the PSK modulation method described above, 0 and 1 are assigned to the phase shifts shifted by 180 degrees, whereas in the QPSK modulation method, they are shifted to π / 2 by 0 phase, π / 2 phase, π phase, and 3π / 2 phase. Since (0,0), (0,1), (1,0), and (1,1) are allocated and transmitted, the bit rate is improved. If this is generalized, in the 2 ⁿ phase PSK modulation system, data is allocated to 2 ⁿ phases shifted by π / 2 ⁿ⁻¹ , so that the bit rate is improved if n is simply increased.

  FIG. 2 shows the configuration of the wireless communication apparatus according to this embodiment. The wireless transmission module 308 includes a circulator 350 having three ports C1, C2, and C3, an antenna 309 connected to the port C2 of the circulator 350, and a first signal path in which high-frequency switches 351 and 352 are connected in series. A second signal path in which a high-frequency switch 353, a phase shifter 354, and a high-frequency switch 355 are connected in series, a third signal path in which a high-frequency switch 356, a phase shifter 357, and a high-frequency switch 358 are connected in series; A switch 359, a phase shifter 360, and a fourth signal path formed by serially connecting a high frequency switch 361 are provided. Each phase shifter 354, 357, 360 has a 2.4 GHz band, an active phase whose phase can be varied by voltage control, such as a strip line such as λ / 4, λ / 2, 3λ / 4, respectively. Consists of containers.

  The first to fourth signal paths are connected in parallel to the ports C1 and C3 of the circulator 350. Further, the high frequency switches 351, 352,... Are turned on / off by the data coder 362 according to the transmission data.

  The circulator 350 has a directionality of transmitting signals in the directions of C1 → C2 and C2 → C3. By using this directivity, the antenna 309 is connected to C2, the input signal from C2 is taken out from C3, and processing for giving different phase differences in the first to fourth signal paths is performed and then returned to C1. , C2 is a reflected wave that has been subjected to phase shift processing.

  As described above, in the back scatter method, data transmission is realized by switching the absorption / reflection of the incoming radio wave by switching on / off the high frequency switch. Here, since the switching speed of the high-frequency switches 351, 352,... Is limited, in order to increase the speed, it is necessary to send a plurality of bit information in one switching.

  Phase shifters 354, 357, and 360 are inserted in the second to fourth signal paths described above, respectively, which are 90 degrees, 180 degrees, and 270 degrees compared to the carrier input to the first signal path. Create a phase difference. Therefore, the signal path through which the carrier passes can be switched by the combination of ON / OFF of the high frequency switches 351, 352, etc., and four kinds of phase differences can be given.

  For example, when only the high frequency switches 351 and 352 are turned on, the first signal path is selected. That is, the carriers input from the ports C2 and C3 of the circulator 350 are transmitted as they are as reflected waves from the antenna 309 through the ports C1 and C2.

  When only the high frequency switches 353 and 355 are turned on, the second signal path is selected. That is, carriers input from ports C2 and C3 of circulator 350 are shifted by λ / 4 by phase shifter 354, and are transmitted as reflected waves from antenna 309 through ports C1 and C2.

  When only the high frequency switches 356 and 358 are turned on, the third signal path is selected. That is, carriers input from ports C2 and C3 of circulator 350 are shifted by λ / 2 by phase shifter 357, and are transmitted as reflected waves from antenna 309 through ports C1 and C2.

  Further, when only the high frequency switches 359 and 361 are turned on, the third signal path is selected. That is, carriers input from ports C2 and C3 of circulator 350 are shifted by 3λ / 4 by phase shifter 360, and are transmitted as reflected waves from antenna 309 through ports C1 and C2.

  When data transmission such as image transfer is performed, the wireless transmission module unit 308 divides the data into two bits and assigns a phase corresponding to a combination of two bits of 0 and 1 to the carrier, thereby realizing QPSK modulation. It has become.

  Specifically, when receiving the image data read from the memory card 307 by the signal processing unit 303, the wireless transmission module unit 308 sends a bit image of the data to the data decoding unit 362. Then, the data decoding unit 362 divides the data into 2 bits, and when it is 00, turns on the high frequency switches 351 and 352 and turns off the other high frequency switches. At 01, the high frequency switches 353 and 355 are turned on, and the other high frequency switches are turned off. At 11, the high frequency switches 356 and 358 are turned on, and the other high frequency switches are turned off. When it is 10, the high frequency switches 359 and 361 are turned on and the other high frequency switches are turned off.

  Here, when the data is 00, since only the high frequency switches 351 and 352 are turned on, the first signal path is selected, and the phase of the carrier inputted from the ports C2 and C3 of the circulator 350 is shifted. Instead, it passes through the ports C1 and C2 and is transmitted as a reflected wave from the antenna 309.

  When the data is 01, only the high frequency switches 353 and 355 are turned on, so the second signal path is selected, and the carriers input from the ports C2 and C3 of the circulator 350 are compared with the data 00. Then, after being shifted by λ / 4 by the phase shifter 354, it is transmitted as a reflected wave from the antenna 309 through the ports C1 and C2.

  When the data is 11, only the high frequency switches 356 and 358 are turned on, so the third signal path is selected, and the carriers input from the ports C2 and C3 of the circulator 350 are compared with the data 00. Then, after being shifted by λ / 2 by the phase shifter 357, it is transmitted as a reflected wave from the antenna 309 through the ports C1 and C2.

  When the data is 10, only the high-frequency switches 359 and 361 are turned on, so the fourth signal path is selected, and the carriers input from the ports C2 and C3 of the circulator 350 are compared with the data 00. Then, after being shifted by 3λ / 4 by the phase shifter 360, it is transmitted as a reflected wave from the antenna 309 through the ports C1 and C2.

  In this embodiment, each combination of the high-frequency switches 351 and 352, 353 and 355, 356 and 358, 359 and 361 is disposed on the first to fourth signal paths. It is also possible to configure. However, since it is expected that there will be a slight phase shift in each high-frequency switch, it is up to the use of two so that all phase points have the same phase shift.

  In this way, according to the 2-bit value of data, it is possible to create reflected waves having four phases that are 90 degrees apart from each other, and a QPSK-modulated reflected wave can be created.

  Note that PSK modulation can also be performed in the wireless transmission module 308 shown in FIG. In this case, the high frequency switches 353 and 355 on the second signal path and the high frequency switches 359 and 361 on the fourth signal path are not controlled. When the data is 0, only the high frequency switches 351 and 352 on the first signal path are turned on. Further, when the data is 1, only the high-frequency switches 356 and 358 on the third signal path are turned on, and the phase of the reflected wave is shifted by 180 degrees as compared with the data 0. Therefore, the same circuit can support two modulation schemes, QPSK and PSK. This means that it can be changed dynamically during communication.

  In addition, it should be fully understood that the method for generating a polyphase modulated wave according to the present invention is effective as a general RFID having no power source other than the application to the data transmission of the present invention.

  Further, as a further development of the back scatter type radio communication apparatus to which the OPSK modulation shown in FIG. 2 is applied, 7 λ / 8 phase shifters and 16 high frequency switches are similarly connected to the port C1 of the circulator 350 and By connecting in parallel to C3, it is also possible to create an 8-phase PSK that assigns 45 degrees of phase to 8 kinds of data from 000 to data 111.

  FIG. 3 schematically illustrates a hardware configuration of a wireless communication apparatus that receives transmission data from the wireless communication apparatus illustrated in FIG. 2 in the present embodiment. The illustrated wireless communication apparatus corresponds to an image reproduction apparatus such as a PC or a television for displaying and outputting received image data, and a printer for printing out.

  In the present embodiment, since the image data is transmitted as a reflected wave, it is necessary to transmit an unmodulated carrier for generating a reflected wave from the wireless reception module 400. The wireless reception module 400 includes a 2.4 GHz band antenna 401, a circulator 402, a reception unit 403, a transmission unit 406, a frequency synthesizer 409, a communication control unit 410, and a host interface unit 411. Further, the reception unit 403 includes a quadrature detection unit 404 and an AGC (Auto Gain Control) amplifier 405. The transmission unit 406 includes a mixer 408 and a power amplifier 407. The host interface unit 411 is connected to a host device 412 such as a PC and transfers received image data.

  Transmission of an unmodulated carrier from the wireless reception module 400 is realized by applying a certain DC voltage from the communication control unit 410 to the mixer 408. The frequency of the non-modulated carrier to be transmitted is determined by the frequency of the frequency synthesizer controlled by the communication control unit 410. In the present embodiment, the 2.4 GHz band is used. The unmodulated carrier output from the mixer 408 is amplified to a predetermined level by the power amplifier 407 and transmitted from the antenna 401 via the circulator 402.

  The reflected wave from the image transmission device 300 is the same as the frequency transmitted from the wireless reception module 400 (described above). This reflected wave is received by the antenna 401 and input to the receiving unit 403 via the circulator 402. Since the same local frequency as the transmission is input to the quadrature detection unit 404, the PSK or QPSK modulated wave multiplied by the image transmission apparatus 300 appears at the output of the quadrature detection unit 404. However, since the received signal has a phase different from that of the local signal, a modulation signal corresponding to the phase difference appears in the I-axis signal and the Q-axis signal.

  In the AGC amplifier unit 405, the gain is controlled to an optimum value, and the output signal is passed to the communication control unit 410. The communication control unit 410 performs PSK or QPSK demodulation including carrier recovery and clock recovery from the I-axis and Q-axis signals. The correctly restored data is transferred to the host device 412 via the host interface unit 411.

  When confirming the delivery of data from the image transmission apparatus 300, the communication control unit 410 returns an acknowledgment ACK (Acknowledgement) if the received packet data is correct, or a negative acknowledgment NAK (Negative Acknowledgement) if the received packet data is incorrect. Each digital data is transferred to the mixer 408 and subjected to ASK modulation. Whether the data is correct or not is determined by a CRC (Cyclic Redundancy Check) code added to the image data packet.

  FIG. 4 shows a control sequence for performing wireless transmission between the wireless communication apparatus 300 as the image transmission apparatus shown in FIG. 2 and the wireless communication apparatus 400 as the image display apparatus shown in FIG. However, in the illustrated example, it is assumed that delivery confirmation is performed between both devices. Hereinafter, this control sequence will be described.

(Step 1)
On the image transmission apparatus side, for example, the user manually sets the data transmission mode.

(Step 2)
Similarly, on the image display device side, for example, the user manually sets the data reception waiting mode.

(Step 3)
The image display apparatus which is the image transfer destination transmits an unmodulated carrier for forming a reflected wave on the image transmission apparatus side.

(Step 4)
The image transmission apparatus that has received the non-modulated carrier makes a data transmission request using the reflected wave.

(Step 5)
The image display apparatus that has received the data transmission request transmits a transmission permission by ASK modulation.

(Step 6)
The image display device transmits an unmodulated carrier for forming a reflected wave.

(Step 7)
The image transmission apparatus that has received the unmodulated carrier transmits the packetized data using the reflected wave. At this time, the data is divided into 2 bits, and QPSK modulation is performed by assigning a phase corresponding to a combination of 0 and 1 of 2 bits (described above).

(Step 8)
The image display device QPSK-demodulates the received packet data and restores the data. If the received data is correct, an acknowledgment ACK (Acknowledgement) is sent by ASK modulation. If wrong, a negative acknowledgment NAK (Negative Acknowledgment) is transmitted. Here, whether the data is correct or incorrect can be determined by a CRC (Cyclic Redundancy Check) code added to the data packet.

  When the image display apparatus transmits an acknowledgment signal of ACK or NAK, a command for the image transmission apparatus can be included in the same signal. For example, a case where a slide show is requested from the image display apparatus to the image transmission apparatus can be considered.

  This makes it possible to remotely control the image transmission apparatus from the image display apparatus. Furthermore, when an image display device such as a television can be operated with an infrared remote controller, the image transmission device can be indirectly controlled from the infrared remote controller by sending a command such as infrared remote control → image display device → image transmission device. It becomes possible.

  Thereafter, the processing of step 6 to step 8 is repeatedly executed until the end of data.

  In the above-described embodiment, since it is image transfer, bi-directional communication is used for confirmation of data delivery. However, when transferring streaming data such as a video camera, transmission in one direction may be performed. In this case, an ASK-modulated delivery confirmation signal is not required from the image display device, so that reception on the image transmission device side is also unnecessary, and further reduction in power consumption can be realized.

  In addition, it should be fully understood that it is not necessary to have an oscillator on the image transmission apparatus side in performing the control sequence as shown in FIG.

  In the example shown in FIG. 1, on the image transmission apparatus side, the wireless transmission module 308 is built in a photographing apparatus such as a digital camera. Of course, the gist of the present invention is not limited to this. The wireless transmission module may be configured by an external adapter or the like, and may be provided in a form in which the apparatus main body is externally connected based on USB (Universal Serial Bus) or other interface standards.

  FIG. 5 schematically shows a configuration example when the wireless transmission module is configured as an adapter type.

  As illustrated, the image transmission apparatus includes a camera unit 602, a signal processing unit 603, a memory card interface unit 604, an operation / display unit 605, a USB interface unit 606, and a memory card 607. . These components may be substantially the same as the components respectively indicated by reference numerals 202 to 207 of the conventional digital camera with a wireless LAN function shown in FIG.

  In general, the USB interface unit 606 functions as a slave, and transfers the target image data read from the memory card 607 by the signal processing unit 603 via the memory card interface unit 604 to a PC that is a USB host using a USB cable. Used when In the embodiment shown in FIG. 4, this USB interface works by being switched to the host, and connects to the wireless transmission module 601 of the slave device connected to the external USB to constitute an apparatus equivalent to FIG. Is possible.

  The wireless transmission module 601 can be considered as an adapter having an external shape with a USB connector and an antenna 609 as indicated by reference numeral 620, for example.

  The wireless transmission module 601 illustrated in FIG. 5 is substantially the same except that the USB interface unit 614 is added to the wireless transmission module 308 illustrated in FIG.

  When image transfer is performed, the high frequency switch 311 is controlled to be turned off together with the ASK detection unit 313 by the signal processing unit 303 and is in an open state. Further, the wireless transmission module unit 308 receives image data read from the memory card 607 via the host-side USB interface unit 606 and the slave-side USB interface unit 614. Then, according to the value of 2 bits of data, it becomes possible to create reflected waves having four phases different from each other by 90 degrees, and a reflected wave subjected to QPSK modulation is created (described above). For example, when the data is 01, the phase of the reflected wave is shifted by 90 degrees, when the data is 11, the phase of the reflected wave is shifted by 180 degrees, and when the data is 10, the phase of the reflected wave is shifted by 270 degrees.

  On the other hand, at the time of reception, the bandpass filter and the ASK detection unit are used to receive and process an ASK-modulated delivery confirmation signal from the transfer destination (described above). However, these two blocks are not necessary if the transmission is confirmed in one direction without confirmation of transmission. The delivery confirmation unit 608 controls the delivery confirmation. The bandpass filter 612 is used for the purpose of passing a frequency in the 2.4 GHz band and attenuating other frequency bands.

  Even with the configuration as shown in FIG. 5, it is possible to realize ultra-low-consumption image transmission, similar to the configuration of the apparatus shown in FIG. 1. The adapter type wireless transmission module like this embodiment is considered to be particularly effective in the miniaturization of the mobile device main body. In this embodiment, USB is used as an interface for connection with a device body such as a digital camera, but other interfaces may of course be used.

  In Japanese Patent Laid-Open No. 10-209914, in a duplex wireless communication system configured with an interrogator and a plurality of tags positioned spatially separated from the interrogator, the interrogator is a continuous wave (CW). Proposals have been made for transmitting a radio signal to at least one tag in the system, which describes the point of QPSK modulating a subcarrier signal based on an information signal. However, in this publication, secondary modulation is further performed by the ASK modulation system using the subcarrier signal that has been primarily modulated by the QPSK modulation system (see, for example, FIG. 3 of the publication). In this case, the actual transmission rate is limited by the capability of the ASK modulation method, in other words, the QPSK modulation method adopted here does not contribute to the improvement of the transmission rate. There are also problems of DC offset and mixer noise. On the other hand, in the present invention, the main carrier wave is generated by switching the signal path through which the carrier passes according to the bit image of the transmission data with respect to the received radio wave from the transfer destination, and generating a reflected wave with a phase difference. Since the QPSK modulation is performed, the configuration is clearly different.

[Supplement]
The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.

FIG. 1 is a diagram schematically showing a configuration of a wireless communication apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a back scatter type wireless communication apparatus adopting QPSK modulation. FIG. 3 is a diagram schematically illustrating a hardware configuration of the wireless communication apparatus that receives transmission data from the wireless communication apparatus illustrated in FIG. 4 is a diagram showing a control sequence for performing wireless transmission between wireless communication apparatus 300 as the image transmission apparatus shown in FIG. 2 and wireless communication apparatus 400 as the image display apparatus shown in FIG. FIG. 5 is a diagram schematically illustrating a configuration example in the case where the wireless transmission module is configured as an adapter type. FIG. 6 is a diagram illustrating a configuration example of a conventional RFID system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 300 ... Wireless communication apparatus 302,602 ... Camera part 303,603 ... Signal processing part 304,604 ... Memory card interface part 305 ... Operation / display part 306,606 ... USB interface part 307,607 ... Memory card 308 ... Wireless transmission module 309, 609 ... Antenna 350 ... Circulator 351, 352, 353, 355, 356, 358, 359, 361 ... High frequency switch 610, 611 ... High frequency switch 354, 357, 360 ... Phase shifter 400 ... Wireless reception module 401 ... Antenna 402 ... circulator 403 ... receiver 404 ... orthogonal detector 405 ... AGC amplifier 406 ... transmitter
407 ... Power amplifier 408 ... Mixer 409 ... Frequency synthesizer 410 ... Communication control unit 411 ... Host interface unit 412 ... Host device 614 ... USB interface unit

Claims (3)

A wireless communication device that performs data communication by a back scatter method using reflection of received radio waves, and a data transmission unit,
An antenna for receiving radio waves coming from the transfer destination;
An input terminal for inputting a radio wave received by the antenna and an output terminal for transmitting a reflected wave of the received radio wave;
n signal paths connected in parallel between the input terminal and the output terminal, where the k-th signal path gives a phase difference of (k−1) π / 2 ^n-1 (however, 1 ≦ k ≦ n),
A signal path selection unit that forms reflected waves having different phases in n by selecting any one of the signal paths according to transmission data,
Represents the transmission data with the phase difference pattern of the reflected wave relative to the received radio wave.
A wireless communication apparatus. The k-th signal path gives a phase difference of (k−1) π / 2 ⁿ (where 1 ≦ k ≦ n),
The signal path selection means divides transmission data into 2 ^n-1 bits, selects a signal path corresponding to a combination of 2 ^n-1 bits 0 and 1, assigns a phase to the reflected wave, and 2 ⁿ phases Perform PSK modulation,
The wireless communication apparatus according to claim 1. A first signal path that obtains a first reflected wave that directly reflects the received radio wave without passing through any phase shifter, and a phase shifter that provides a phase difference of λ / 4 are connected in series, and the first reflected wave A second signal path for obtaining a second reflected wave whose phase is shifted by π / 2 in comparison with a phase shifter for providing a phase difference of λ / 2 is connected in series, and compared with the first reflected wave, π A third signal path that obtains a third reflected wave whose phase is shifted by a phase shifter that gives a phase difference of 3λ / 4 in series is connected in series, and the phase is shifted by 3π / 2 compared to the first reflected wave. A fourth signal path for obtaining the fourth reflected wave,
The signal path selection unit divides transmission data into 2 bits, selects a signal path corresponding to a combination of 0 and 1 of 2 bits, assigns a phase to the reflected wave, and performs QPSK modulation.
The wireless communication apparatus according to claim 1.

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