Abstract:
A demodulating module includes: a processing unit, for generating a control signal; and a demodulator, coupled to the processing unit and stored with a plurality of correlative coefficient masks, for receiving a data signal, selecting one of the correlative coefficient masks according to the control signal, generating a demodulated signal according to the data signal and the selected correlative coefficient mask, and transmitting the demodulated signal to the processing unit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present relates to a demodulating module, an RFID (radio frequency identification) system utilizing the demodulating module, and a method thereof. More particularly, the present invention relates to a demodulating module utilizing a correlative coefficient mask for transforming data signals into corresponding data, an RFID system utilizing the demodulating module, and a method thereof. 
         [0003]    2. Description of the Prior Art 
         [0004]    In an RFID processing system, an RF signal received by an antenna needs to be decoded (or demodulated) after being processed by an RF front-end module. The decoding operation can be performed by means of software or hardware. One of the advantages of using software is that greater flexibility is available for coordinating with various kinds of communication protocols. However, when using software, there is a disadvantage that processing speed is slow and a powerful processor is required. Furthermore, if the RF signal has a poor duty cycle and the processing time is longer, a higher package error rate (PER) may occur as a result. 
         [0005]    In contrast, when performing the decoding operation by hardware means, although the processing speed can be increased, the hardware structure is fixed to provide little flexibility that the hardware is unable to coordinate with various communication protocols. 
       SUMMARY OF THE INVENTION 
       [0006]    Therefore, the present invention provides a demodulating module, which utilizes a plurality of correlative coefficient masks corresponding to different communication protocols to transform a data signal into corresponding data. Software and hardware can thereby be jointly used to demodulate a data signal. 
         [0007]    According to one embodiment of the present invention, a demodulating module is disclosed. The demodulating module comprises: a processing unit, for generating a control signal; and a demodulator, coupled to the processing unit and stored with a plurality of correlative coefficient masks, for receiving a data signal, selecting at least one of the correlative coefficient masks according to the control signal, generating a demodulated signal according to the data signal and the selected correlative coefficient mask, and transmitting the demodulated signal to the processing unit. 
         [0008]    According to another embodiment of the present invention, an RFID system is disclosed. The RFID system comprises: an antenna, for receiving an RF signal; an RFID front-end module, for transforming the RF signal into a data signal; a processing unit, for generating a control signal; and a demodulator, coupled to the processing unit and stored with a plurality of correlative coefficient masks, for receiving a data signal, selecting at least one of the correlative coefficient masks according to the control signal, generating a demodulated signal according to the data signal and the selected correlative coefficient mask, and transmitting the demodulated signal to the processing unit. 
         [0009]    According to another embodiment of the present invention, a demodulating method is disclosed. The method comprises step of: providing a plurality of correlative coefficient masks, receiving a data signal, selecting at least one of the correlative coefficient masks, and generating a demodulated signal according to the data signal and the selected correlative coefficient mask. 
         [0010]    Via the above-mentioned embodiment, the system is facilitated to coordinate with a plurality of communication protocols, and economical operation units can be implemented to decrease overall circuit costs. 
         [0011]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a block diagram of an RFID system according to an embodiment of the present invention. 
           [0013]      FIG. 2  illustrates a detailed configuration of a demodulator according to an embodiment of the present invention. 
           [0014]      FIG. 3  illustrates a schematic diagram of operations of a demodulator according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  illustrates a block diagram of an RFID system  100  according to an exemplary embodiment of the present invention. As shown in  FIG. 1 , the RFID system  100  comprises a demodulating module  101 , an antenna  103  and an RF front-end module  105 . The demodulating module  101  comprises a demodulator  107  and a processing unit  109 . The antenna  103  receives an RF signal RF, and the RF front-end module  105  transforms the RF signal RF into a data signal DS, which may be in a digital format. The processing unit  109  generates a control signal CS. The demodulator  107 , stored with a plurality of correlative coefficient masks, receives the data signal DS, and selects at least one of the correlative coefficient masks according to the control signal CS. Using the selected correlative coefficient mask for demodulating the data signal DS, the demodulator  107  generates a demodulated signal DMS, and transmits the demodulated signal DMS to the processing unit  109  for subsequent processes. In one embodiment, the plurality of correlative coefficient masks can respectively correspond to different encoding/decoding methods of different communication protocols, such as NRZ (Non-Return to Zero), Manchester, etc. 
         [0016]      FIG. 2  illustrates a detailed configuration of a demodulator  107  according to an embodiment of the present invention. As shown in  FIG. 2 , the demodulator  107  comprises a storage unit  201 , a latch  203 , a first correlation judging unit  205 , a second correlation judging unit  207 , and a comparator  209 . The storage unit  201  stores the correlative coefficient masks, and, according to the control signal CS, respectively provides a first correlative coefficient mask M 1  and a second correlative coefficient mask M 2  to the first correlation judging unit  205  and the second correlation judging unit  207 . The latch  203  latches all or a part of the data signal DS to form a first data group DG 1 . The first correlation judging unit  205  judges correlation between the first data group DG 1  and the first correlative coefficient mask M 1  according to the first correlative coefficient mask M 1  to output a first judging value CR 1 . The second correlation judging unit  207  judges correlation between the first data group DG 1  and the second correlative coefficient mask M 2  according to the second correlative coefficient mask M 2  to output a second judging value CR 2 . The comparator  209  compares the first judging value CR 1  and the second judging value CR 2  to generate corresponding data CD, which can be used as the demodulated signal DMS. 
         [0017]    The first correlation judging unit  205  or the second correlation judging unit  207  can be a correlator, which can be implemented by a multiplexer or an adder. As known by persons skilled in the art, a correlator compares input data by using comparison data in a specific data format (the correlative coefficient masks in this embodiment), and a larger result is produced if the input data matches the specific data format. Specifically, when the correlator is a multiplier, the correlative coefficient mask in a specific data format is multiplied with the input data. As known by persons skilled in the art, a maximum value representing highest correlation is produced when the input data and the correlative coefficient mask are exactly the same. When the correlator is an adder, the data of the correlative coefficient mask is an inverse of the specific data format; that is, if the specific data format is 1001, the correlative coefficient mask is 0110. In this case, as known by persons skilled in the art, a maximum sum value representing highest correlation is produced when the input data and the correlative coefficient mask are totally inverse. Therefore, when different encoding/decoding methods are used, a correlative coefficient mask corresponding to the encoding/decoding method can be used to judge correlation of the data and the correlative coefficient mask, and then the input data is transformed to another data format according to the correlation. 
         [0018]    The demodulator  107  may further comprise a data packer  211  for collecting a plurality of sets of the corresponding data to form a second data group DG 2  with a predetermined size, such as 8/16/32 bits, to be used as the demodulated signal DMS. The demodulator  107  also provides the second data group DG 2  to the processing unit  109 . Therefore, the second data group DG 2  is the demodulated signal DMS in the presence of the data packer  211 ; otherwise, the corresponding data CD is the demodulated signal DMS. 
         [0019]    Additionally, a data group usually has a data region and an auxiliary judging region. The auxiliary judging region, such as a frame sync region or a header region, is for recording a data amount or a starting point of data. Therefore, the storage unit  201  can further store a plurality of auxiliary judging masks FM, and the first correlation judging unit  205  or the second correlation judging unit  207  can judge correlation between the auxiliary judging region and a predetermined auxiliary judging mask according to the predetermined auxiliary judging mask selected from the auxiliary judging masks FM to help generate the first judging value CR 1  or the second judging value CR 2 . Specifically, when the correlator determines the auxiliary judging region according to the predetermined auxiliary judging mask, the position of the data region can be determined. In this way, what is being compared with the correlative coefficient mask is ensured to be the data region instead of a noise, and thus encoding/decoding errors can be avoided. 
         [0020]    The storage unit  201  further stores a threshold parameter FT. The first correlation judging unit  205  or the second correlation judging unit  207  generates the first judging value CR 1  or the second judging value CR 2  further depending on the threshold parameter FT. Specifically, the threshold parameter FT provides a threshold value. If the first judging value CR 1  or the second judging value CR 2  does not reach the threshold value, it is regarded as a noise or useless data to be invalidated, and therefore will not be used as a basis for data transformation. 
         [0021]    It should be noted that the demodulating module according to the embodiment of the present invention can be implemented in other systems besides an RFID system, and the data signal DS input into the demodulating module can be any other data signal. 
         [0022]      FIG. 3  illustrates a schematic diagram of operations of a demodulator according to one embodiment of the present invention. As shown in  FIG. 3 , a correlation judging unit (an adder in this embodiment) is utilized to compare a data group and a mask. A data group DG 11  corresponds to Data 0 , and thus has larger correlation with a correlative coefficient mask corresponding to Data 0  than a correlative coefficient mask corresponding to Data 1 . Also, once the comparator  209  gets a result that the data group DG 11  has larger correlation with a correlative coefficient mask corresponding to Data 0 , the data group DG 11  is transformed to Data 0  (i.e. the abovementioned corresponding data). Similarly, a data group DG 12  corresponds to Data 1 , and thus has larger correlation with a correlative coefficient mask corresponding to Data 1  than a correlative coefficient mask corresponding to Data 0 . Also, once the comparator  209  gets a result that the data group DG 12  has larger correlation with a correlative coefficient mask corresponding to Data 1 , the data group DG 12  is transformed to Data 1 . The auxiliary judging mask is compared with the auxiliary judging region to determine the position of the data region. In this embodiment, “64′” of the correlative coefficient mask or the auxiliary judging mask 64′h3333 — 3333_FFFF_FFFF indicates that the mask is 64-bits, and “h” indicates that the mask is represented in a 16-bit format. Thus, the mask that is used for comparison is the data 3333 — 3333_FFFF_FFFF. The mask examples 64′h3333 — 3333_FFFF_FFFF and 64′hFFFF_FFFF — 3333 — 3333 shown in  FIG. 3  follow the encoding/decoding standard of ISO14443A, but are not meant to be limitations on the scope of the present invention. 
         [0023]    Via the abovementioned embodiment, the system is facilitated to coordinate with a plurality of communication protocols, and economical operation units can be implemented to decrease overall circuit costs. 
         [0024]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.