Abstract:
An energy detection apparatus and method for detecting energy is disclosed. The energy detection apparatus and method in the present invention obtains a new energy detection value by subtracting a previously sample-averaged value from a current output energy detection value and then adding an absolute sampled value. Thus, the apparatus and method of energy detection in the present invention is capable not only of saving cost due to no demand for memories but also of providing real-time detection with no time delay.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 94112830, filed on Apr. 22, 2005. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an energy detection apparatus and an energy detection method. More particularly, the present invention relates to an energy detection apparatus and an energy detection method that operates with no time delay.  
         [0004]     2. Description of the Related Art  
         [0005]     Digital signals play an important role in the processing of multimedia data. One of the applications of digital signals is in the transmission of one-dimensional digital sound information. The integration of audio and digital signal processing is indispensable for telecommunication.  
         [0006]     In audio data signaling, a large quantity of data is continuously transmitted and it may include considerably incorrect noise signals and interferences. To capture correct signals, the signals must be checked to determine if they are correct or not. Conventionally, the process of determining whether a signal should be captured includes detecting the strength of the signal energy. Briefly, when the energy level detected at a definite time point is higher than a preset energy threshold, the signal at the next time point can be captured and used. On the contrary, if the energy level is lower than the threshold value, the signal at the next time point is regarded as a noise signal so that capturing is stopped. Typically, the energy detection involves sampling the initial input signal to obtain an input analogue signal. After the processes of dispersing and converting the analogue signal into digital signal, a number of samples are used for finding an average energy value for a definite time interval. This average energy value is served as the basis for recognizing the energy level for the energy detection. In the following, the conventional energy detection method is briefly discussed.  
         [0007]      FIGS. 1A, 1B  and  1 C schematically show an input signal sampling diagram, an output waveform diagram of energy detection result, and an output diagram of the signaling sample captured and processed according to the energy detection result.  FIG. 1A  is an input signal sampling diagram. As shown in  FIG. 1A , a number of input signals is sampled in sequence and converted into absolute values. In a common energy detection method, to be effective in estimating, computing and detecting the energy values, a detection window is often defined. The detection window serves as a standard in the computation for determining the energy values, that is, defining the length of sampling period and the number of samples as a base for energy detection. For example, as shown in  FIG. 1A , the detection window has a time length of 8 samples. In  FIG. 1A , the sampling for the n th  time block and the (n+1) th  time block according to the aforementioned detection window size is sketched.  
         [0008]      FIG. 1B  shows the output waveform of the energy detection result. To carry out the energy detection, the sampled input signal data for a time block is registered and stored in a memory. After using the data to compute the energy values, whether to process or capture and output the sampled data stored in the memory is determined according to the computed energy values.  FIG. 1C  shows the output diagram of capturing the signal samples according to the energy detection result. From  FIGS. 1A through 1C , it can be easily seen that the sampling operation is still progressing sequentially during the n th  time block (see the n th  time block in  FIG. 1A ). However, the output of the energy detection result and the sample output according to the energy detection result are the values obtained in the (n−1) th  time block. In other words, the energy detection in any time block is based on the values obtained from the previous time block stored in the memory. It means the current energy detection has to depend on the previously collected samples. Since there is a time delay in the energy detection, a real-time detection of the energy values is impossible and cost of memories for registering and storing data is required. Thus, the major defects of this type of energy detection method are time delay in energy detection and additional cost of memories.  
         [0009]      FIGS. 2A, 2B  and  2 C schematically show an input signal sampling diagram, an output waveform diagram of energy detection result and an output diagram of the signaling samples captured and processed according to the energy detection result, for another method of energy detection in the prior art.  FIG. 2A  is an input signal sampling diagram similar to the one in  FIG. 1A . As shown in  FIG. 2A , a number of input signals is sampled in sequence and converted into absolute values.  
         [0010]      FIG. 2B  shows the output waveform of the energy detection result. The method is slightly different from the previous one because the input signal sampled data is not stored in the memory. Instead, a hardware having a capability similar to a digital signal-processing program is used to perform the accumulation and computation for obtaining the energy value of the previous time block. According to the obtained energy value, whether to process or capture the currently sampled data is determined. As shown in  FIGS. 2A through 2C , although the hardware can immediately output the values obtained from the sampled data, that is, it can immediately output the value after the value of the n th  time block has been input (the output diagram in  FIG. 1C ), the energy detection result of the (n−1) th  time block is still used. Therefore, there is still a time delay between the energy detection result and the sampled data output in this energy detection method.  
         [0011]     Accordingly, the conventional energy detection methods not only require additional memory cost for registering and storing the input data, but also fail to dynamically compute and output the energy values in real time that causes a time delay. In other words, these methods can hardly meet the demands for rapid and accurate energy value detection.  
         [0012]     In view of this, the present invention provides an energy detection apparatus and a method thereof which not only eliminates the additional memory cost and the time delay but also provides a real-time dynamic energy detection.  
       SUMMARY OF THE INVENTION  
       [0013]     Accordingly, at least one objective of the present invention is to provide an energy detection apparatus that can be used for carrying out energy detection computation without requirement of extra memories as in a conventional energy detection apparatus. Thus, the cost is reduced and energy detection with no time delay can be achieved.  
         [0014]     At least a second objective of the present invention is to provide an energy detection method that obtains a new energy detection value by subtracting a previously sample-averaged value from a current output energy detection value and then adding an absolute sample value. Thus, the energy detection method is able to resolve the problem of having to use the previous old value that results in a time delay in the conventional method of energy detection.  
         [0015]     At least a third objective of the present invention is to provide an energy detection method that obtains the energy detection value of the next period of the clock signal with a period T 1  by subtracting a previous sample-averaged value from a current output energy detection value and then adding an absolute sample value. In addition, one another clock signal with a period T 2  is used to compute the sample-averaged value. Thus, the energy detection apparatus and method is able to resolve the problem of having a time delay in the conventional energy detection method and the computation of the sample-averaged value obtained is more representative.  
         [0016]     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an energy detection apparatus. The energy detection apparatus comprises an absolute value extractor, a first adder, a first flip-flop, a second adder and an algorithmic unit. The absolute value extractor receives a plurality of sampled values in sequence and outputs respective absolute values by extracting their absolute values. The first adder is coupled to the absolute value extractor for adding a first computational intermediate value to the output of the absolute value extractor. The first flip-flop is coupled to the first adder. According to a first clock signal, the first adder produces an output to obtain an energy detection value, where the period of the first clock signal is T 1 . The second adder is coupled to the first flip-flop and the first adder. The second adder subtracts a sample-averaged value from the energy detection value to output a first computational intermediate value. The algorithmic unit is coupled to the absolute value extractor and the second adder. According to a second clock signal, an average value of all the outputs from the absolute value extractor within each period of the second clock signal is computed to output the aforementioned sample-averaged value. Here, the period of the second clock signal is T 2 , and T 2 =T 1 *k where k is a natural number.  
         [0017]     The present invention also provides an energy detection method. First, according to a clock signal, a sampled value P(t) is input in sequence. The period of the clock signal is T. After extracting the absolute value of the input sampled value P(t), an absolute sampled value |P(t)| is output. Then, after computing the summation value of all the absolute sampled values within the time period from t-k*T to t-T, Sum (|P(t−i*T)|, and dividing the summation value by k, a previous sample-averaged value is output. Here, k is a natural number and i is a value ranging from 1 to k. Lastly, after subtracting the aforementioned previous sample-averaged value from an energy detection value and then adding the absolute sampled value |P(t)|, the energy detection value of the next period of the clock signal is obtained.  
         [0018]     The present invention further provides an energy detection method. First, a plurality of sampled values is sequentially read. After converting the sampled values into absolute sampled values, the absolute sampled values are output. According to a first clock signal, the energy detection value in the next period of the first clock signal is obtained by subtracting a sample-averaged value from an energy detection value and then adding the current absolute sampled value. The period of the first clock signal is T 1 . Meanwhile, according to a second clock signal, after computing the summation value of all the absolute sampled values in the previous period of the current second clock signal and finding an average, the aforementioned sample-averaged value is output. The period of the second clock signal is T 2 , where T 2 =T 1 *k and k is a natural number.  
         [0019]     In brief, the energy detection apparatus and method in the present invention obtains a new energy detection value by subtracting a previous sample-averaged value from an output energy detection value and then adding an absolute sampled value. Thus, the apparatus and method of energy detection in the present invention is capable not only of saving cost due to no demand for memories, but also of providing a real time dynamic energy detection with no time delay.  
         [0020]     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0022]      FIG. 1A  is an input signal sampling diagram in a conventional energy detection method.  
         [0023]      FIG. 1B  is an output waveform diagram of the energy detection result of a conventional energy detection method.  
         [0024]      FIG. 1C  is an output diagram of captured or processed signal samples according to the energy detection result obtained from a conventional energy detection method.  
         [0025]      FIG. 2A  is an input signal sampling diagram in another conventional energy detection method.  
         [0026]      FIG. 2B  is an output waveform diagram of the energy detection result of another conventional energy detection method.  
         [0027]      FIG. 2C  is an output diagram of captured or processed signal samples according to the energy detection result obtained from another conventional energy detection method.  
         [0028]      FIGS. 3A and 3B  are block circuit diagrams showing the components of an energy detection apparatus according to one embodiment of the present invention.  
         [0029]      FIG. 4  is a flow diagram showing one energy detection method according to the present invention.  
         [0030]      FIG. 5  is a flow diagram showing another energy detection method according to the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0032]      FIGS. 3A and 3B  are block circuit diagrams schematically showing an energy detection apparatus and an algorithmic unit within the energy detection apparatus according to one embodiment of the present invention, respectively. As shown in  FIG. 3A , the energy detection apparatus  300  comprises an absolute value extractor  301 , a first adder  302 , a first flip flop  303 , a second adder  304  and an algorithmic unit  305 .  
         [0033]     First, the absolute value extractor  301  of the energy detection apparatus  300  receives a plurality of sampled values in sequence and converts the sampled values to obtain the absolute sampled values. Later, the absolute sampled values are output to the first adder  302  which is electrically connected with the absolute value extractor  301 . The first adder  302  receives the absolute sampled values and adds the output from the second adder  304 . The output from the second adder  304  is obtained by subtracting the computed output value of the algorithmic unit  305  from the output of the first flip-flop  303 . The first adder  302  outputs the summation result to the first flip-flop  303 . Lastly, the first flip-flop  303  outputs the output from the first adder  302  according to a clock signal with a period T 1 . The output value is the energy detection value of the energy detection apparatus  300 .  
         [0034]     The second adder  304  therein subtracts the sample-averaged value computed by the algorithmic unit  305  from the previously output energy detection value of the first flip-flop  303 , and then the value obtained is fed back to the first adder  302 . The value fed back to the first adder  302  has already had the previous sample-averaged value subtracted from the current energy detection value output of the apparatus  300 . This value is sent to the first adder  302  and added to the subsequently input absolute sampled value. Hence, the energy detection value for the next period of the energy detection apparatus  300  is provided. Therefore, the energy detection value output from the apparatus  300  not only accounts for the new absolute sampled value and the energy detection value output currently, but also puts into consideration of the previous sample-averaged value. As a result, the energy detection apparatus can operate without any time delay and output the new energy detection value of the next period in real time.  
         [0035]     In the following, the algorithmic unit  305  for computing the sample-averaged value in the embodiment of the present invention is described in more detail.  FIG. 3B  is a block circuit diagram of the algorithmic unit inside the energy detection apparatus shown in  FIG. 3A . The algorithmic unit  305  comprises a third adder  306 , a multiplexer  307 , a second flip-flop  308 , a third flip-flop  309  and a divider  310 .  
         [0036]     As shown in  FIG. 3B , the algorithmic unit  305  utilizes the third adder  306  electrically connected with the absolute value extractor  301  (as shown in  FIG. 3A ) to receive a plurality of absolute sampled values in sequence. Then, the third adder  306  outputs the absolute sampled values to the multiplexer  307  electrically connected with the third adder  306 . According to a clock signal with a period T 2 , the multiplexer  307  outputs either the absolute sampled value of the third adder  306  or a ‘0’ value, which serves to reset the value and starts computing the value in the next period at the end of the period T 2 . Then, the multiplexer  307  is connected to the second flip-flop  308 , where T 2 =T 1 *k and k is a natural number.  
         [0037]     Within the period T 2  of a clock signal, the second flip-flop  308  sends the value at its input terminal to the third adder  306  after triggering of clock signal for each period T 1 . The third adder  306  adds the new absolute sampled value to the value submitted by the second adder  308 . After the summation operation, the value is sent to the second flip-flop  308  via the multiplexer  307 . Thus, the values are sequentially accumulated inside the second flip-flop  308 . At the end of the period T 2 , the second flip-flop  308  outputs an accumulated value to the third flip-flop  309  for temporary storage. In the meantime, the multiplexer  307  takes in the ‘0’ value (a reset value).  
         [0038]     Next, the accumulated value mentioned above is output by the third flip-flop  309  electrically connected with the second flip-flop  308  to the divider  310 . And the divider  310  performs the dividing of the accumulated value where division value k is a natural number for instance. It should be noted that the third flip-flop  309  is also controlled by the clock signal with a period T 2 .  
         [0039]     In one embodiment of the present invention, the divider  310  can be a shift register such as a 6-bit shift register for providing a division value  64 .  
         [0040]     Lastly, the algorithmic unit  305  outputs the value obtained by dividing the accumulated value through the divider  310 , and this value is the sample-averaged value for supplying the second adder  304  in  FIG. 3A .  
         [0041]      FIG. 4  is a flow diagram showing one energy detection method according to the present invention. As shown in  FIG. 4 , a sampled value P(t) is sequentially read according a clock signal with the period T in step S 401 . Then, the absolute value of the sampled value P(t) is extracted to produce an absolute sampled value |P(t)| in step S 402 . In step S 403 , a computation for obtaining a previous sample-averaged value is carried out. The computation includes accumulating all the absolute sampled values within the time period from t-k*T to t-T to produce a summation value, Sum (|P(t−i*T)|, and then dividing the summation value by k to produce the previous sample-averaged value required. Here, k is a natural number and i is a value ranging from 1 to k. Lastly, in step S 404 , after subtracting the previous sample-averaged value obtained in step S 403  from an energy detection value and then adding the absolute sampled value |P(t)|, the energy detection value of the next period of the clock signal is obtained.  
         [0042]      FIG. 5  is a flow diagram showing another energy detection method according to the present invention. As shown in  FIG. 5 , a plurality of sampled values is sequentially read in step S 501 . After converting the sampled values into absolute values, the absolute sampled values are output in step S 502 . Later, according to a clock signal of a period T 1 , the energy detection value of the next period is computed in step S 503 . The computation includes subtracting a sample-averaged value from an energy detection value and then adding the current absolute sampled value to obtain the energy detection value of the next period of the clock signal with a period T 1 .  
         [0043]     On the one hand, the energy detection value of the next period computed in step S 503  will be output for computation in step S 504 ; on the other hand, the values are output to step S 505  to complete the result of the energy detection method according to the present invention. In step S 504 , according to the clock signal with the period T 2 , after computing the summation of all the absolute sampled values in the previous period of the current clock signal and finding a sample-averaged average. This sample-averaged value is output as the step S 503  mentioned above. It should be noted that T 2 =T 1 *k and k is a natural number in the energy detection method of the present invention.  
         [0044]     In summary, the energy detection apparatus and method of the present invention provide a means of computing energy detection value without any need for additional memory. Thus, the cost is reduced and the energy detection can be carried out without any time delay.  
         [0045]     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.