Abstract:
A data communication apparatus includes an antenna, an analog front-end circuit, and a controller. The analog front-end circuit is connected between the antenna and the controller and includes first and second modulators, a driver, a demodulator, and an input switch. The first modulator modulates data to be transmitted to a read-write device as a response to a request from said read-write device and sends the modulated data to the antenna. The second modulation circuit modulates data to be transmitted to other ID tags. The driver amplifies an output from the second modulator to drive the antenna. The demodulator demodulates data sent from the other ID tags and ID-tag read-write devices. The input switch selectively inputs the data to the first or second modulator. This abstract is provided to comply with rules requiring an abstract, and it is submitted with the intention that it will not be used to interpret or limit the scope or meaning of the claims.

Description:
BACKGROUND 
   1. Field 
   This patent specification describes a data communication apparatus, and more particularly a data communication apparatus capable of functioning as an ID tag and an ID-tag read-write device in a relatively compact structure. 
   2. Discussion 
   An electric identification tag has come into widespread use for identification of materials such as products in shops, for example, since it is smaller and less expensive and can contains an overwhelming amount of information in comparison with a barcode system. For example, in a second-hand car dealer, an identification tag (hereinafter referred to as an ID tag) is attached to each of cars for sale there. Each one of the ID tags attached to the cars in the shop has a memory in which various kinds of detailed information of the car are stored. All the information can be read wirelessly with a special tool called an ID-tag read-write device. With this system, a buyer who is interested in buying a specific car can read various kinds of detailed information about the car, such as its detailed technical specification and history, for example, only by bringing the ID-tag read-write device close to the ID tag of that specific car. 
   With an increasing use of such ID tags, the ID-tag read-write device has been combined with the function of the ID tag so that the ID-tag read-write device can also be used as an ID tag. 
   A background ID-tag read-write device that serves as the ID tag as well as the ID-tag read-write device includes a wireless communicator  1  which includes a passive communicator  2  and an active communicator  3 , as shown in  FIG. 1 . The passive communicator  2  serves as an ID tag to receive a command signal sent from an external apparatus and to return a response signal in response to the command signal. The active communicator  3  serves as an ID-tag read-write device to send a command signal to other apparatuses and to receive response signals from other apparatuses. 
   The passive communicator  2  is configured to receive signals of a sleep request and a sleep-termination request in addition to the read and write command signals sent from external apparatuses in order to prevent radio interferences caused by other ID tags and ID-tag read-write devices existing together in a wireless communications area. The passive communicator  2  falls into sleep upon receiving a sleep request signal and then it does not respond to the read and write command signals sent from external apparatuses. For example, when a plurality of passive communicators  2  are existing together in a wireless communications area, the plurality of passive communicators  2  except for a specific one are all set to a sleep mode so that the radio interferences caused by other passive communicators  2  can be prevented. 
   The passive communicator  2  includes a status holder  4  which holds a status of the sleep mode so that the passive communicator  2  is held in the sleep mode until the passive communicator  2  receives the sleep-termination request signal and terminates the sleep mode. 
   The active communicator  3  is configured to transmit signals of a sleep request and a sleep-termination request to external apparatuses, in addition to the read and write request signals, and to receive response signals from the external apparatuses in response to these sleep and sleep-termination request signals. That is, the active communicator  3  causes a counterpart of the communications to fall into sleep by transmitting the sleep request signal, and to terminate the sleep by transmitting the sleep-termination request signal. Further, before sending any request signals to external apparatuses, the active communicator  3  reads the status of the sleep mode stored in the status holder  4  of the passive communicator  2  and accordingly determines whether or not the passive communicator  2  is in the sleep mode. When the passive communicator  2  is determined as in the sleep mode, the active communicator  3  disables an output of the request signals. Thus, interferences among the request signals to each other can be prevented in a case where a plurality of active communicator  3  are existing together in a same wireless communications area. 
   BRIEF SUMMARY 
   This patent specification describes a novel data communication apparatus which is equipped with an ID-tag function and an ID-tag read-write function in a relatively compact configuration. In one example, a novel data communication apparatus includes an antenna, an analog front-end circuit, and a control circuit. The antenna is configured to receive a signal from other ID tags and to send a signal the apparatus. The control circuit is configured to generate data. The analog front-end circuit electrically is connected between the antenna and the control circuit and includes first and second modulation circuits, a driver circuit, a demodulation circuit, and an input switch. The first modulation circuit is configured to modulate data to be transmitted to a read-write device as a response to a request from said read-write device and to send the modulated data to the antenna. The second modulation circuit is configured to modulate data to be transmitted to other ID tags. The driver circuit is configured to amplify an output from the second modulation circuit to drive the antenna. The demodulation circuit is configured to demodulate data sent from the other ID tags and the other ID-tag read-write devices. The input switch is configured to selectively input data to one of the first and second modulation circuits, the data being sent from the control circuit to the analog front-end circuit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a block diagram of a background data communications apparatus; 
       FIG. 2  is a block diagram of a data communications apparatus according to an embodiment; 
       FIG. 3  is an illustration for explaining a serial data format used by the data communication apparatus of  FIG. 2 ; 
       FIG. 4  is a block diagram of a data communications apparatus according to another embodiment. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the description of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. 
   Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to  FIG. 2 , a wireless communications apparatus  100  according to an example embodiment is explained.  FIG. 2  illustrates a block diagram of the wireless communications apparatus  100  which has a wireless ID (identification)-tag function and a wireless ID-tag read-write function. The wireless ID-tag function is generally provided to a wireless ID tag to send information by radio to other wireless communications apparatuses in response to their requests transmitted on-air and to rewrite information previously recorded therein in response to the requests transmitted on-air from other wireless communications apparatuses. The wireless ID-tag read-write function is to read and write on-air information stored in other wireless ID tags provided to various kinds of materials such as products in shops, for example, to indicate their identifications. 
   Accordingly, when the wireless communications apparatus  100  of  FIG. 2  operates in a wireless network together with a plurality of wireless communications apparatuses similarly including the wireless ID-tag function and the wireless ID-tag read-write function, the wireless communications apparatus  100  selectively serves as a wireless ID tag or as a wireless ID-tag read-write apparatus. That is, the wireless communications apparatus  100  operates as a wireless ID tag when one of other wireless communications apparatuses and as a wireless ID-tag read-write apparatus when other wireless communications apparatuses operate as wireless ID-tags. 
   The wireless communications apparatus  100  is preferably made in a transportable form, such as a cellular phone, a portable type memory, a portable digital audio device, a digital camera, and a PDA (personal data assistance), for example. However, the wireless communications apparatus  100  is not limited to these examples but can be a device which is detachably installed in equipment fixed on the ground or an apparatus firmly or detachably mounted to a mobile facility such as a vehicle, for example. 
   As illustrated in  FIG. 2 , the wireless communications apparatus  100  includes an antenna  1 , an analog front end (AFE) circuit  10 , and a control circuit  20 . The AFE circuit  10  includes a front end controller  11 , an R/W (read and write) modulator  12 , an R/W tag demodulator  13 , an ID tag modulator  14 , a power detector  15 , a driver circuit  16 , and an input switch  17 . 
   The AFE circuit  10  is connected to the antenna  1  and to the control circuit  20  and is configured to modulate and demodulate data. The front end controller  11  controls the operations of the AFE circuit  10  and exchanges data with the control circuit  20 . The R/W modulator  12 , which may be referred to as a second modulator, modulates data to be transmitted to other wireless ID tags (not shown). The driver circuit  16  amplifies an output from the R/W modulator  12  and drives the antenna  1  with the amplified output. The ID tag modulator  14 , which may be referred to as a first modulator, modulates data to be transmitted as responses to the requests from other wireless ID tags (not shown). The R/W demodulator  13  demodulates data received as responses from other wireless ID tags and data received from other wireless ID-tag read-write apparatuses. The power detector  15  detects an event in which the antenna  1  receives data by radio waves from other wireless ID-tag read-write apparatuses. The input switch  17  switches back and forth between the R/W modulator  12  and the ID-tag modulator  14  for an entry of data transmitted from the control circuit  20 . 
   The control circuit  20  is connected with the AFE circuit  10  by a plurality of signal lines including a serial input line  31 , a serial output line  32 , and a wake line  33  to exchange digital signals therebetween. Digital signals from the control circuit  20  are transmitted to the AFE circuit  10  through the serial input line  31 . Each of the digital signals includes a command signal, an address signal, an error signal (ECC), and transmission data, as illustrated in  FIG. 3 . Each of the command signal and the address signal has an 8-bit length, for example, and the error signal has a 16-bit length, for example. The transmission data has a limitless length. 
   The input switch  17  is provided with terminals A, B, and C. The terminal A is connected to the R/W modulator  12 , the terminal B is connected to the ID-tag modulator  14 , and the terminal C is connected to the control circuit  20  through the serial input line  31 . The front end controller  11  is connected to the serial input line  31  so as to receive signals from the control circuit  20  through the serial input line  31 . The front end controller  11  is also connected to the input switch  17  which receives the same signal sent from the control circuit  20  to the front end controller  11  through the serial input line  31 . Upon receiving the signal from the control circuit  20 , the front end controller  11  analyzes commands included in the received signal. When the command signal is analyzed as a command for instructing the AFE circuit  10  to act as an ID-tag read-write device, the front end controller  11  selects the terminal A of the input switch  17  so as to connect the serial input line  31  to the input terminal of the R/W modulator  12 . Alternatively, when the command signal is analyzed as a command for instructing the AFE circuit  10  to act as an ID tag, the front end controller  11  selects the terminal B of the input switch  17  so as to connect the serial input line  31  to the input terminal of the ID-tag modulator  14 . Thus, the single line of serial input line  31  is sufficient to connect between the AFE circuit  10  and the control circuit  20 . In this way, this structure has an apparent effect of suppressing an increasing wiring space and cost, particularly in a case where a plurality of the AFE circuits  10  are provided to a single device of the control circuit  20  and, moreover, each of the plurality of the AFE circuits  10  is located away from the control circuit  20 . 
   The front end controller  11  activates the driver circuit  16  to excite the antenna  1  upon a receipt of a command from the control circuit  20  for starting an output of carrier waves, and deactivates the driver circuit  16  to stop exciting the antenna  1  upon a receipt of a command from the control circuit  20  for stopping an output of the carrier waves. 
   The serial output line  32  connecting the R/W demodulator  13  of the AFE circuit  10  to the control circuit  20  transmits information sent from other read-write devices when the front end controller  11  is in an ID-tag mode and transmits information sent from other ID tags when the front end controller  11  is in a read-write device mode. 
   The power detector  15  detects an electromotive force to generate a signal WAKE and transmits the signal WAKE to the control circuit  20  through the wake line  33  when the antenna  1  is excited by radio waves sent from other read-write devices at a condition in which the AFE circuit  10  is not performing the read-write function. Upon receiving the signal WAKE from the power detector  15 , the control circuit  20  is activated even when the control circuit  20  is in a standby mode and transmits a command for instructing the AFE circuit  10  to act as the ID tag. 
   The R/W modulator  12  is connected to the terminal A of the input switch  17  and is activated in a case when the AFE circuit  10  acts as the ID-tag read-write device. The R/W modulator  12  modulates the data sent from the control circuit  20  with an amplitude shift keying (ASK) method and sends the modulated data to the driver circuit  16 . 
   The ID tag modulator  14  is connected to the terminal B of the input switch  17  and is activated in a case when the AFE circuit  10  acts as the ID tag. The ID tag modulator  14  modulates the data sent from the control circuit  20  with a load switching method (also referred to as a load modulation method) and sends the modulated data to the antenna  1 . 
   The R/W tag demodulator  13  is activated in both cases when the AFE circuit  10  acts as the ID-tag read-write device and as the ID tag. Upon receiving a signal from the antenna  1 , the R/W tag demodulator  13  demodulates and converts the signal into a digital signal and transmits the digital signal to the control circuit  20  via the serial output line  32 . In this example, the R/W tag modulator uses the ASK method for demodulation. That is, the wireless communications apparatus  100  is provided with a single demodulator (i.e., the R/W tag demodulator  13 ) for demodulating the signal in both cases when the AFE circuit  10  acts as the ID-tag read-write device and as the ID tag. With this configuration, the wireless communications apparatus  100  can be made in a relatively small size. The modulation methods of the ASK method and the load switching method are applied to the R/W modulator  12  and the ID-tag modulator  14 , respectively. In particular, the application of the load switching method which conforms to the ISO standards to the ID-tag modulator  14  expands the general versatility of the front end circuit portion (i.e., the AFE circuit  10 ) of the wireless communications apparatus  100 . As a result, the AFE circuit  10  can be used in a variety of different wireless communications systems. Moreover, the AFE circuit  10  can be integrated into a single integrated circuit which is generally suitable for mass production with a relatively low cost. 
   In this example, the control circuit  20  sends the signal for switching the input switch  17  to the front end controller  11  through the serial input line  31 . As an alternative to this, the control circuit  20  may send such a signal for switching the input switch  17  to the front end controller  11  through a communication line  34  which independently connects the front end controller  11  to the control circuit  20 . Upon receiving the signal for switching the input switch  17  from the control circuit  20 , the front end controller  11  sends this signal to the input switch  17  to switch between the terminals A and B of the input switch  17 . 
   Referring to  FIG. 4 , a wireless communications apparatus  101  according to another example embodiment is explained.  FIG. 4  illustrates the wireless communications apparatus  101  which is similar to the wireless communications apparatus  100  of  FIG. 2 , except for a signal line to the input switch  17  to switch between the terminal A and B of the input switch  17 . More specifically, the AFE circuit  10  is provided with a terminal  40  for connecting the communication line  34  from the control circuit  20  to the input switch  17  so that the control circuit  20  directly controls the selection of the terminals A and B. 
   Accordingly, the control circuit  20  sends the signal to connect the terminal C to the terminal A of the input switch  17  so as to connect the serial input line  31  to the R/W modulator  12  in a case when the AFE circuit  10  is caused to act as the ID-tag read-write device. Also, the control circuit  20  sends the signal to connect the terminal C to the terminal B of the input switch  17  so as to connect the serial input line  31  to the ID-tag demodulator  14  in a case when the AFE circuit  10  is caused to act as the ID tag. 
   The contents of this patent specification may be conveniently implemented using a conventional general purpose digital computer programmed according to the teachings of this patent specification, as will be apparent to those skilled in the computer art. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of this patent specification, as will be apparent to those skilled in the software art. This patent specification may also be implemented by the preparation of application specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art. 
   Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein. 
   This patent specification is based on Japanese patent application, No. JPAP2004-367279 filed on Dec. 20, 2004 in the Japan Patent Office, the entire contents of which are incorporated by reference herein.