Abstract:
There is disclosed a signal processing device including a reception part which receives a signal from outside, a preliminary detection part, a main processing part whose power consumption is larger than that of the preliminary detection part, and a power supply part which supplies power to the main processing part. The preliminary detection part collates bit values of bit information constituted of a combination of bit values included in the signal received by the reception part and those of collation key information constituted of a combination of preset bit values. Moreover, the power is supplied to the main processing part from the power supply part in a case where all the bit values agree with each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The entire disclosure of Japanese Application No. 2004-4315 including specification, claims, drawings, and abstract is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a signal processing device, a signal processing method and a signal processing program, having a function of collating bit information included in a transmitted signal.  
         [0004]     2. Description of the Related Art  
         [0005]     A keyless entry technique has been broadly used to remotely unlock an automobile door using a signal of an infrared ray or the like without using a conventional cylinder key. In this keyless entry technique, a key registers collation key information represented by a predetermined bit stringbeforehand, receives a signal transmitted from an automobile, and judges whether or not bit information included in the signal agrees with the collation key information to thereby control the unlocking of the door.  
         [0006]      FIG. 8  shows a signal processing device  100  disposed in a key. The signal processing device  100  comprises a reception part  10 , a preliminary detection part  12 , a main processing part  14 , a power supply control part  16 , a power supply part  18 , and a transmission part  20 . Usually, in order to suppress the power consumption, no power is supplied from the power supply part  18  to the main processing part  14  whose power consumption is large, and the power is supplied to the preliminary detection part  12  whose power consumption is small in a standby state.  
         [0007]     As shown in  FIG. 9 , a preliminary signal indicating that a signal is starting, and a subsequent vehicle transmission signal including the bit information are repeatedly transmitted from the automobile. The reception part  10  receives the vehicle transmission signal from the outside of the device, rectifies and detects the signal, and thereafter transmits the signal to the preliminary detection part  12  and the main processing part  14 . The preliminary detection part  12  receives the signal from the reception part  10 , and judges whether or not a pulse amplitude is not less than a predetermined threshold value α. When an intensity of the vehicle transmission signal is larger than the threshold value α, it is assumed that the preliminary signal has been received, and a power supply start signal is sent to the power supply control part  16 . On receiving the supply start signal, the power supply control part  16  starts the supply of the power to the main processing part  14  from the power supply part  18 . Accordingly, the main processing part  14  is brought into an on-state, and the bit information following the preliminary signal is received from the reception part  10  to thereby collate the information with the collation key information registered beforehand. When the bit information included in the vehicle transmission signal agrees with the bit information of the collation key information, a response signal is transmitted from the transmission part  20 . When this response signal is received on the automobile side, the door is unlocked.  
         [0008]     It is to be noted that a technique to collate the vehicle transmission signal with a collation key has been described in Japanese Patent Application Laid-Open Nos. Hei 8-62327 and Hei 8-62328.  
         [0009]     However, in the above-described conventional technique, it is judged whether or not the received signal is a signal transmitted from the automobile depending on whether the amplitude of the preliminary signal is not less than the predetermined threshold value α. Therefore, when noise having an intensity not less than the threshold value α is received, it is judged by mistake that the signal transmitted from the automobile has been input, the supply of the power to the main processing part  14  is started, and a problem that the power consumption in the signal processing device  100  increases has occurred.  
       SUMMARY OF THE INVENTION  
       [0010]     According to the present invention, there is provided a signal processing device including a reception part which receives a signal from the outside, a preliminary detection part, a main processing part whose power consumption is larger than that of the preliminary detection part, and a power supply part which supplies power to the main processing part, wherein the preliminary detection part collates bit values of bit information constituted of a combination of bit values included in the signal received by the reception part and those of collation key information constituted of a combination of preset bit values, to supply the power from the power supply part to the main processing part only in a case where at least some bit values agree with each other.  
         [0011]     According to another configuration of the present invention, there is provided a signal processing method executed in a signal processing device including, a reception part which receives a signal from the outside, a preliminary detection part, a main processing part whose power consumption is larger than that of the preliminary detection part, and a power supply part which supplies power to the main processing part, the method comprising a receiving step of receiving the signal from the outside using the reception part, a preliminary detecting step of collating bit values of bit information constituted of a combination of bit values received in the receiving step and those of collation key information constituted of a combination of preset bit values using the preliminary detection part, and a power supplying step of supplying the power to the main processing part from the power supply part only in a case where at least some bit values of the bit information agree with those of the collation key information in the preliminary detection step.  
         [0012]     According to still another configuration of the present invention, there is provided a signal processing program in a signal processing device including a computer, a reception part which receives a signal from the outside, a main processing part whose power consumption is larger than that of the computer, and a power supply part which supplies power to the main processing part, the program allowing the computer to function as preliminary detection means for collating bit values of bit information constituted of a combination of bit values included in the signal received by the reception part and those of collation key information constituted of a combination of preset bit values, and supplying the power to the main processing part from the power supply part only in a case where at least some bit values agree with each other. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a block diagram showing a constitution of a signal processing device in an embodiment of the present invention;  
         [0014]      FIG. 2  is a timing chart showing a function of the signal processing device in the embodiment of the present invention;  
         [0015]      FIG. 3  is a diagram showing an example of a circuit of a boundary detection part in the embodiment of the present invention;  
         [0016]      FIG. 4  is a timing chart showing production of a boundary signal by the boundary detection part in the embodiment of the present invention;  
         [0017]      FIG. 5  is a diagram showing an example of a circuit of an excess period signal production part in the embodiment of the present invention;  
         [0018]      FIG. 6  is a diagram showing an example of a circuit of a shift signal production part in the embodiment of the present invention;  
         [0019]      FIG. 7  is a diagram showing an example of a circuit of a demodulated data acquisition part and a bit comparison part in the embodiment of the present invention;  
         [0020]      FIG. 8  is a block diagram showing a constitution of a signal processing device in a background technique; and  
         [0021]      FIG. 9  is a diagram showing an example of a demodulated pulse signal including bit information in the background technique. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     As shown in  FIG. 1 , a signal processing device  200  in an embodiment of the present invention comprises a reception part  30 , a boundary detection part  32 , an excess period signal production part  34 , a shift signal production part  36 , a demodulated data acquisition part  38 , a bit comparison part  40 , a power supply control part  42 , a power supply part  44 , a main processing part  46 , and a transmission part  48 . The boundary detection part  32 , excess period signal production part  34 , shift signal production part  36 , demodulated data acquisition part  38 , and bit comparison part  40  constitute a preliminary detection unit  202  of the present embodiment. A function of the signal processing device  200  in the present embodiment will be described hereinafter with reference to a timing chart of  FIG. 2 .  
         [0023]     As shown in  FIG. 2 ( h ), an ASK signal superimposed on a carrier wave of hundred several ten kHz is transmitted from an object to be unlocked, such as an automobile. The reception part  30  receives this ASK signal, adjusts a signal level by auto gain control (AGC), and thereafter demodulates the signal into a demodulated pulse signal shown in  FIG. 2 ( a ) using a detector circuit. The reception part  30  transmits the demodulated pulse signal to the boundary detection part  32 .  
         [0024]     The demodulated pulse signal includes a preliminary signal indicating the start of the signal, and subsequent signals indicating bit information. The bit information is preferably frequency modulated. For example, it is assumed that to be capable of understanding the relation of FIGS.  2 ( a ) and ( b ), the bit information indicates “1 (H level)” in a case where a pulse period is longer than a time T for seven periods of a base clock, and indicates “0 (L level)” in a case where the pulse period is shorter than the time T for seven periods of the base clock. Additionally, the relation between the period of the pulse of the demodulated pulse signal and the period of the base clock is not limited to this relation, and may be such a relation that the bit information of the demodulated pulse signal can be judged.  
         [0025]     The boundary detection part  32  has a function of detecting a boundary at which the demodulated pulse signal rises from “L level” to “H level”. As shown in  FIG. 3 , the boundary detection part  32  may comprise D flip flops (DFFs)  50   a ,  50   b  and a NAND element  52 . The demodulated pulse signal is supplied to an input terminal (D terminal) of the DFF  50   a  from the reception part  30 . The D terminal of the DFF  50   b  is connected to an output terminal (Q terminal) of the DFF  50   a . Base clocks CK are input into clock terminals (CK terminals) of the DFFs  50   a ,  50   b . Reset signals are input into reset terminals (R terminals) of the DFFs  50   a ,  50   b . The reset signal is usually maintained at the “H level”, and set to the “L level” only in a case where the signal processing device  200  is brought back into an initial state. Outputs from the Q terminal of the DFF  50   a  and a reverse output terminal (QB terminal) of the DFF  50   b  are input into the NAND element  52 .  
         [0026]     As shown in  FIG. 4 ( a ), after the demodulated pulse signal rises to the “H level” from the “L level”, and from when the base clock next turns to the “H level”, the “H level” continues to be output from the Q terminal of the DFF  50   a . After the demodulated pulse signal turns to the “L level” from the “H level”, and the base clock next turns to the “H level”, the “L level” continues to be output. As shown in  FIG. 4 ( b ), a signal which changes in reverse to the output of the Q terminal of the DFF  50   a  is output from the QB terminal of the DFF  50   b  delayed by one period of the base clock after the output of the Q terminal of the DFF  50   a  changes. As a result, as shown in  FIG. 4 ( c ), after the demodulated pulse signal rises to the “H level” from the “L level”, and from when the base clock next turns to the “H level”, a pulsed boundary signal indicating the “L level” is output from the NAND element  52  until the base clock next turns to the “H level”. Therefore, the boundary signal with respect to the demodulated pulse signal shown in  FIG. 2 ( a ) is as shown in  FIG. 2 ( c ).  
         [0027]     The excess period signal production part  34  has a function of producing an excess period signal indicating that the bit information included in the demodulated pulse signal is “1” or “0”. As shown in  FIG. 5 , the excess period signal production part  34  comprises D flip flops (DFFs)  54   a ,  54   b ,  54   c ,  54   d , NAND elements  56   a ,  56   b ,  56   c , OR elements  58   a ,  58   b ,  58   c , and NAND element  60 .  
         [0028]     The boundary signals produced by the boundary detection part  32  are input into reset terminals (R terminals) of the DFFs  54   a  to  54   d . A base clock is input into a clock terminal (CK terminal) of the DFF  54   a . Output signals from a reverse output terminal (QB terminal) of the DFF  54   a  are input into a CK terminal of the DFF  54   b , an input terminal (D terminal) of the DFF  54   a , and the NAND elements  56   a  to  56   c . Similarly, output signals from a QB terminal of the DFF  54   b  are input into a CK terminal of the DFF  54   c , a D terminal of the DFF  54   b , and the NAND element  56   b . Output signals from an output terminal (Q terminal) of the DFF  54   b  are input into the NAND elements  56   a ,  56   c . Output signals from a QB terminal of the DFF  54   c  are input into a CK terminal of the DFF  54   d , a D terminal of the DFF  54   c , and the NAND elements  56   a ,  56   b . An output signal from a Q terminal of the DFF  54   c  is input into the NAND element  56   c . Output signals from a QB terminal of the DFF  54   d  are input into a D terminal of the DFF  54   d  and the NAND element  56   c . Output signals from a Q terminal of the DFF  54   d  are input into the NAND elements  56   a ,  56   b.    
         [0029]     Output signals of the NAND elements  56   a ,  56   b ,  56   c  are input into the OR elements  58   a ,  58   b ,  58   c , respectively. Furthermore, threshold value control signals C 0 , C 1 , C 2  are input into the OR elements  58   a ,  58   b ,  58   c . Output signals of the OR elements  58   a ,  58   b ,  58   c  are input into the NAND element  60 .  
         [0030]     The threshold value control signals C 0 , C 1 , C 2  are set as three-bit binary values, and a magnification of the period of the pulse included in the demodulated pulse signal with respect to the period of the base clock, at which it is judged that the bit value is “1”, is determined by this binary value. For example, when “1”, “0”, “1” are set to C 0 , C 1 , C 2 , as shown in  FIG. 2 ( d ), the excess period signal indicates the “H level” in a case where the period of the pulse included in the demodulated pulse signal is the “H level” for a period seven or more times that of the base clock.  
         [0031]     The shift signal production part  36  has a function of expanding a pulse width of the excess period signal output from the excess period signal production part  34 . As shown in  FIG. 6 , the shift signal production part  36  comprises D flip flops (DFFs)  62   a ,  62   b ,  62   c ,  62   d , a NAND element  64 , and a D flip flop (DFF)  66 . A demodulated pulse signal is input into an input terminal (D terminal) of the DFF  62   a . Output signals from output terminals (Q terminals) of the DFFs  62   a ,  62   b ,  62   c  are input into D terminals of the DFFs  62   b ,  62   c ,  62   d , respectively. Base clocks and reset signals are input into clock terminals (CK terminals) and reset terminals (R terminals) of the DFFs  62   a  to  62   d . An output signal of the Q terminal of the DFF  62   c  is input into the NAND element  64 . An output signal of a reverse output terminal (QB terminal) of the DFF  62   d  is input into the NAND element  64 . An output signal of the NAND element  64  is input into an R terminal of the DFF  66 . Furthermore, “H level” is constantly input into a D terminal of the DFF  66 , and an excess period signal is input into a CK terminal thereof from the excess period signal production part  34 . A shift signal is output to the demodulated data acquisition part  38  from a Q terminal of the DFF  66 .  
         [0032]     The DFFs  62   a  to  62   d  and the NAND element  64  are constituted in such a manner that the DFFs  62   a ,  62   b  are further added on an input side of the boundary detection part  32 . Therefore, after elapse of a time for two periods of the base clock from when the boundary signal output from the boundary detection part  32  outputs a pulse of the “L level”, the signal outputs a pulse of “L level” to the R terminal of the DFF  66 . That is, a state of the output signal of the Q terminal of the DFF  66  is changed delayed by two periods of the base clock from when the boundary signal is set to the “L level”. The D terminal of the DFF  66  is constantly maintained at the “H level”, and the excess period signal is input to the CK terminal thereof from the excess period signal production part  34 . Therefore, as shown in  FIG. 2 ( e ), the shift signal output from the Q terminal turns to the “H level”, when the excess period signal turns to the “H level”, and maintains the “H level” from when the boundary signal is set to the “L level” until a time for two periods of the base clock elapses.  
         [0033]     The demodulated data acquisition part  38  receives the shift signal from the shift signal production part  36 , and demodulates and maintains the bit information included in the demodulated pulse signal. When the bit information included in the demodulated pulse signal is represented by four bits, as shown in  FIG. 7 , the demodulated data acquisition part  38  may comprise D flip flops (DFFs)  68   a ,  68   b ,  68   c ,  68   d . The shift signal is input into an input terminal (D terminal) of the DFF  68   a . Output signals from output terminals (Q terminals) of the DFFs  68   a  to  68   c  are input into D terminals of the DFFs  68   b  to  68   d , respectively. Clocks for demodulation, obtained by reversing the boundary signals, are input into clock terminals (CK terminals) of the DFFs  68   a  to  68   d , and reset signals are input into reset terminals (R terminals) thereof.  
         [0034]     Every time the boundary signal turns to the “H level”, the demodulated data acquisition part  38  shift output values of the Q terminals of the DFFs  68   a  to  68   c  to the DFFs  68   b  to  68   d , respectively, and holds a state of the shift signal input into the D terminal of the DFF  68   a  as an output value of the Q terminal of the DFF  68   a . That is, as shown in  FIG. 2 ( f ), the bit information of four bits included in the demodulated pulse signal is demodulated by the demodulated data acquisition part  38 , and lower to upper bits are held in order as the output signals of the Q terminals of the DFFs  68   a  to  68   d.    
         [0035]     The bit comparison part  40  has a function of outputting a collation agreement signal in a case where the bit information demodulated by the demodulated data acquisition part  38  is collated with the collation key information, and all bit values of the bit information included in the demodulated pulse signal agree with those of the collation key information. As shown in  FIG. 7 , the bit comparison part  40  may comprise XNOR elements  70   a ,  70   b ,  70   c ,  70   d , a NAND element  72 , a NOT element  74 , and a D flip flop (DFF)  76 .  
         [0036]     The output signal of the Q terminal of the DFF  68   a  in the demodulated data acquisition part  38 , and the lowermost bit value of the collation key information are input into the XNOR element  70   a . Therefore, when the output signal of the Q terminal of the DFF  68   a  agrees with the lowermost bit value of the collation key information, the “H level” is output to an output terminal of the XNOR element  70   a . When the signal does not agree, the “L level” is output. Similarly, the output signals of the Q terminals of the DFFs  68   b ,  68   c ,  68   d  in the demodulated data acquisition part  38 , and the second and the third bit values from the lowermost bit and the uppermost bit value of the collation key information are input into the XNOR elements  70   b ,  70   c ,  70   d . In the case of agreement of the input signals of the XNOR elements  70   b ,  70   c ,  70   d , the “H level” is output to the output terminal. When the signals do not agree, the “L level” is output.  
         [0037]     The output signals of the XNOR elements  70   a  to  70   d  are input into the NAND element  72 . When all the input signals of the NAND element  72  turn to the “H level”, the “L level” is output to the output terminal. In another case, the “H level” is output to the output terminal. That is, the “L level” is output to the output terminal of the NAND element  72  only in a case where all the bit values of the bit information detected from the demodulated pulse signal in the demodulated data acquisition part  38  agree with those of the collation key information. When even one bit value of the bit information detected from the demodulated pulse signal does not agree with that of the collation key information, the “H level” is output to the output terminal of the NAND element  72 .  
         [0038]     The output signal of the NAND element  72  is reversed by the NOT element  74 , and input into an input terminal (D terminal) of the DFF  76 . A data end signal indicating an end time of the demodulated pulse signal is input into a clock terminal (CK terminal) of the DFF  76 . Therefore, when all the bit values of the bit information detected from the demodulated pulse signal agree with those of the collation key information, an output terminal (Q terminal) of the DFF  76  is maintained at the “H level”. When even one bit value of the bit information detected from the demodulated pulse signal does not agree with that of the collation key information, the Q terminal of the DFF  76  is maintained at the “L level”. The output signal of the Q terminal of the DFF  76  is input as the collation agreement signal into the power supply control part  42 .  
         [0039]     The power supply control part  42  receives the collation agreement signal, and starts the supply of the power to the main processing part  46  from the power supply part  44 , when the collation agreement signal indicates the “H level”. On the other hand, when the collation agreement signal indicates the “L level”, no power is supplied to the main processing part  46 . When the power is supplied, the main processing part  46  is brought into an on-state, and a process of transmitting a response signal from the transmission part  48  or the like is executed. When this response signal is received, a process of unlocking the door or the like is performed on the automobile side.  
         [0040]     As described above, in the present embodiment, power is supplied to the main processing part  46  only in a case where all the bit values of the bit information included in the demodulated pulse signal agree with those of the collation key information. Therefore, when noise is received by the reception part  30 , an erroneous operation of starting the supply of the power to the main processing part  46  can be inhibited. As a result, an increase of power consumption can be suppressed. The present invention is highly effective especially in a small-sized signal processing device requiring portability, such as a portable key driven by a small-capacity power supply such as a battery.  
         [0041]     It is to be noted that the present invention is not limited to a concrete constitution in the above-described embodiment. That is, regardless of the unlocking process, the bit value of the bit information which has been transmitted from a process object and whose frequency has been modulated may be collated with that of the collation key information, and the supply of the power to a circuit having a larger power consumption may be started in accordance with the collation result. For example, when at least some bit values of the bit information of the demodulated pulse signal agree with those of the bit information of the collation key information, the power may be supplied to the main processing part.