Abstract:
An electro acoustic system built-in test and calibration method utilizes a built-in self-test module to send a test signal through a first circuit device to an audio transmitter, causing the audio transmitter to output a test signal, for enabling the test signal to be received by a audio receiver and then processed by a connected circuit device and converted into a feedback digital signal to the self-test module for comparing the linearity relative to the originally provided test signal so that the parameter values and conformity of circuit devices can be optimized subject to comparison result. The test and adjustment procedure is recycled for other parameter items, and a warning signal is produced when proper adjustment cannot be done. This built-in test and calibration module can be achieved in the form of an independent firmware code module, using the same DSP (digital signal processor) engine that drives the system for the self test purpose, in so doing, the function of self test can be called along the production line, in use, throughout the service life of the product, and virtually without any additional cost.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electro acoustic system and more particularly, to the built-in test and calibration method of such system, which enables the electro acoustic system to be self-tested and corrected at any place with ease.  
         [0003]     2. Description of the Prior Art  
         [0004]     With the development of various communication technologies, communication devices such as telephone have become part of our everyday life. Because regular home telephones are cheap, people usually buy a new one to replace the failed units. However, if one expensive communication device, for example, conference station has a communication problem or noises, the maintenance fee is very high, and the related examination apparatus is also expensive. It is a heavy cost burden to the user either to repair the conference station by oneself or to send the conference station to the distributor for repair.  
         [0005]     According to conventional techniques, the internal circuit of an expensive communication device must be tested during the semi-finished stage of the product, and the product is assembled and packed after test. However, some conditions such as signal interference and system instability may occur during assembly process or after a long period of use due to ageing or variation of parts and circuits. In this case, an expensive external test apparatus shall be used, or the product shall be detached for internal circuit examination, thereby resulting in waste of cost and manpower.  
         [0006]     Further, when the sampling test of one particular lot of products shows a high failure rate, the products of the whole lot must be wholly examined. It requires much time and labor to examine the products of the whole lot because of the accumulated man-hours and occupation of expensive test apparatus involved. In this case, the production line will be interrupted, and the manufacturing cost will be greatly increased.  
         [0007]     Therefore, it is desirable to provide an electro acoustic system built-in test and calibration method that eliminates the aforesaid problems.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide an electro acoustic system built-in test and calibration method, which provides a self-test module to enable the manufacturer or user to examine the electro acoustic system on the production line or in use without the requirement of an external test apparatus and major rework on the mechanicals.  
         [0009]     It is another object of the present invention to provide an electro acoustic system built-in test and calibration method, which enables the electro acoustic system to be self tested and corrected without disassembling the product, and also makes the system more tolerable to the variation of individual components, so that the manufacturing cost can be greatly reduced.  
         [0010]     It is still another object of the present invention to provide an electro acoustic system built-in test and calibration method, which greatly improves the stability and performance .of the electro acoustic system and prolongs its service life.  
         [0011]     To achieve these and other objects of the present invention, the electro acoustic system built-in test and calibration method utilizes a built-in self-test module to send a test signal through a first circuit device to an audio device such as a speaker, driving the audio device to emit a test signal, the test signal, in turn, will be picked up by a transceiver such as a microphone, and then processed by a connected circuit device and converted into a feedback digital signal to the self-test module for comparing relevant characteristics with the originally provided test signal so that the parameter values and conformity of circuit devices can be optimized subject to comparison result. The test and adjustment procedure is recycled for other parameter items. Therefore, the electro acoustic system can use the built-in self-test module for self test and calibration either on the production line or at home. A final objective is that, since most of the advance communication device such as a conference system, or feature phones, has built-in DSP (Digital Signal Process) as their main engine. Such component is a particularly powerful tool for generating test signals and analyzing the result. Hence this invention also has an objective that, the built-in self test and calibration module be embodied in the form of an independent firmware code running in the same DSP engine. In so doing, the test module consume little more than a few hundred lines of instructions only, so there is almost zero additional cost for the implementation, and since its an inherent part of the same DSP engine, it can be called into action while the product is still in the production line, and accompany the product throughout its service life. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a block diagram showing a built-in test and calibration method in an electro acoustic system with one speaker to one microphone according to the present invention.  
         [0013]      FIG. 2  is a block diagram showing a built-in test and calibration method in an electro acoustic system with one speaker to multiple microphones according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     The invention provides an electro acoustic system built-in test and calibration method. The electro acoustic system can be a one-to-one system of one speaker to one microphone as shown in  FIG. 1 , or one-to-multiple system of one speaker to multiple microphones as shown in  FIG. 2 .  
         [0015]     In the one-to-one system as shown in  FIG. 1 , the built-in self-test module, referenced by  10 , tests may parameter items including Gain, Sensitivity, Phase delay, and Frequency response. In the one-to-multiple system as shown in  FIG. 2 , the built-in self-test module  10  tests many parameter items including Gain difference, Sensitivity difference, Phase delay difference, and Frequency response difference. Test of gain parameter keeps linear relationship of the circuits among the programmable gain amplifiers, assuring their parameter values to be within the accurate range. Test of frequency response controls stability of the speaker, the microphone(s) and the circuit.  
         [0016]     In the one-to-one system as shown in  FIG. 1 , the built-in self-test module  10  is installed in a digital signal processor or integrated circuit. The self-test module  10  sends a gain parameter test signal to a first circuit device, for enabling the first PGA (programmable gain amplifier)  18  in the first Codec  12  of the first circuit device to process the gain parameter test signal. The first Codec  12  can also convert the test signal into an analog signal. For easy matching, the signal is sent to an amplifier  14  for amplification, and then the amplified signal is sent to an audio device, namely, the speaker  16 , causing the speaker  16  to output a test audio signal, which is then received by an audio receiver, namely, the microphone  20 . After reception of the analog signal of the test signal by the microphone  20 , the analog signal is amplified by another amplifier  22  and then transmitted to a second PGA (programmable gain amplifier)  26  in a second Codec  24  of a second circuit device, which second Codec  24  converts the analog signal into a digital signal and sends the digital signal to the self-test module  10  for analysis on linearity or other related characteristics between the feedback digital signal and the original test signal. When the matching result exceeds a predetermined acceptable range, it will be necessary to adjust the parameter value of the first PGA (programmable gain amplifier)  18  or the second PGA (programmable gain amplifier)  26 . The predetermined acceptable range is built in the digital signal processor or EEPROM (not shown) of the respective embodiment of the electro acoustic system.  
         [0017]     When wishing to adjust the parameter value of the first PGA (programmable gain amplifier)  18  or the second PGA (programmable gain amplifier)  26  to the optimized parameter value, it is necessary to set up a predetermined median value for the second PGA (programmable gain amplifier)  26  and a predetermined maximum value for the first PGA (programmable gain amplifier)  18 . The predetermined median value and maximum value are obtained from the predetermined range in the respective embodiment of the electro acoustic system. After setting of the predetermined median value and the predetermined maximum value, the self-test module  10  sends out a test signal to repeat the loop between the first Codec  12  and the second Codec  24 , and uses a control signal to gradually lower the maximum value of the first PGA (programmable gain amplifier)  18  to the status that the linear relationship between the test signal sent by the self-test module  10  and the feedback digital signal obtained from the second Codec  24  is high enough, and the value at this status is the optimized parameter value for the first PGA (programmable gain amplifier)  18 . If there is an overload in the loop between the first Codec  12  and the second Codec  24 , the self-test module  10  will detect a nonlinear relationship between the original test signal and the feedback digital signal. Because the parameter value for the second PGA (programmable gain amplifier)  26  has been set to be the median value, a nonlinear relationship will occur only at the setting of the first PGA (programmable gain amplifier)  18 .  
         [0018]     After determination of the optimized parameter value for the first PGA (programmable gain amplifier)  18 , find out the optimized parameter value for the second PGA (programmable gain amplifier)  26 . At first, set the parameter value of the second PGA (programmable gain amplifier)  26  to be the maximum value. This maximum value is also built in the predetermined range in the respective embodiment of the electro acoustic system. Thereafter, the self-test module  10  sends out a test signal to repeat the loop between the first Codec  12  and the second Codec  24 , and uses a control signal to gradually lower the maximum value to the status that the linear relationship between the test signal sent by the self-test module  10  and the feedback digital signal obtained from the second Codec  24  is high enough, and the value at this status is the optimized parameter value for the second PGA (programmable gain amplifier)  26 . If there is an overload in the loop between the first Codec  12  and the second Codec  24 , the self-test module  10  will detect a nonlinear relationship between the original test signal and the feedback digital signal. Because the parameter value for the first PGA (programmable gain amplifier)  18  already has the accurate parameter value, a nonlinear relationship will occur only at the setting of the second PGA (programmable gain amplifier)  26 . The parameter values of the two PGAs  18  and  26  have a respective acceptable range recorded in the digital signal processor or EEPROM (not shown) of the respective embodiment of the electro acoustic system. If PGA minimum value&lt;optimized value&lt;PGA maximum value, send out the correcting message; furthermore, when the self-test module  10  is unable to adjust the parameter values of the first PGA (programmable gain amplifier)  18  and second PGA (programmable gain amplifier)  26  to the optimized status, it means that the internal circuit devices may be damaged. In this case, the self-test module  10  will output a warning signal to inform the user or examiner. When there is another parameter item to be tested after gain parameter test, the self-test module  10  will send a test signal again to repeat the aforesaid procedure until all circuit device parameters have been optimized.  
         [0019]     When wishing to test Gain difference in the one-to-multiple system as shown in  FIG. 2 , the built-in self-test module  10  sends a gain difference test signal to a first circuit device, for enabling the first PGA (programmable gain amplifier)  18  in the first Codec  12  of the first circuit device to process the gain difference test signal. The first Codec  12  converts the test signal into an analog signal, which is ten amplified by an amplifier  14  and then sent to an audio device, namely, the speaker  16 , causing the speaker  16  to output a test audio signal, which is then received by an audio receiver, namely, the microphone  20 . After reception of the analog signal of the signal by the microphone  20 , the analog signal is amplified by another amplifier  22  and then transmitted to a second PGA (programmable gain amplifier)  26  in a second Codec  24  of a second circuit device, which second Codec  24  converts the analog signal into a digital signal and sends the digital signal to the self-test module  10  for analysis on linear difference between the feedback digital signal and the original test signal. Thereafter, the parameter value of the first PGA (programmable gain amplifier)  18  and the parameter value of the second PGA (programmable gain amplifier)  26  are optimized subject to the first PGA (programmable gain amplifier)  18  and second PGA (programmable gain amplifier)  26  parameter value optimizing flow utilized in the afore the one-to-one system as shown in  FIG. 1 . When testing the gain parameters of the first and second PGA (programmable gain amplifier)  18  and  26 , test the gain parameters of the first PGA (programmable gain amplifier)  18  and third PGA (programmable gain amplifier)  36 . The test signal sent by the self-test module  10  for testing the gain parameters of the first PGA (programmable gain amplifier)  18  and third PGA (programmable gain amplifier)  36  passes through the first Codec  12  and the amplifier  14  to the speaker  16  for output, and the output signal from the speaker  16  is received by the second microphone  30 . The signal received by the second microphone  30  is then amplified by an amplifier  32  and then transmitted to a third circuit device, which comprises a third Codec  34  having therein the third PGA (programmable gain amplifier)  36 . The third Codec  34  converts the signal into a digital signal, and then feeds the digital signal back to the self-test module  10 , for enabling the parameter values of the first PGA (programmable gain amplifier)  18  and third PGA (programmable gain amplifier)  36  to be optimized subject to the first PGA (programmable gain amplifier)  18  and second PGA (programmable gain amplifier)  26  parameter value optimizing flow utilized in the afore mentioned one-to-one system as shown in  FIG. 1 . These three PGAs (programmable gain amplifiers)  18 ,  26  and  36  have respective acceptable range recorded in the digital signal processor or EEPROM (not shown) of the respective embodiment of the electro acoustic system. If PGA minimum value&lt;optimized parameter value&lt;PGA maximum value, send out the correct message; on the contrary, send out a failure-warning signal. Thereafter, compare the second PGA (programmable gain amplifier)  26  and the third PGA (programmable gain amplifier)  36  at the microphone side to check the conformity of their parameter values with the received signal, and then adjust the conformity to the optimized status so as to complete the gain test and adjustment. The self-test module  10  can repeat the aforesaid procedure to test the other parameter items and to adjust the parameter values of the other parameter items to be optimized parameter values. If the feedback digital signal between the second PGA (programmable gain amplifier)  26  and the third PGA (programmable gain amplifier)  36  is not in conformity, it means the respective parameter values are not optimized and a further correction is necessary. If the desired conformity is not achievable after repeated adjustment, it means a severe difference between the second PGA (programmable gain amplifier)  26  and the third PGA (programmable gain amplifier)  36 . At this time, the self-test module  10  will output a warning signal to inform the user or examiner.  
         [0020]     As indicated above, the invention provides an electro acoustic system built-in test and calibration method, which utilizes a built-in self-test module to send a test signal through a first circuit device to a audio transmitter, causing the audio transmitter to output a test signal, for enabling the test signal to be received by a audio receiver and then processed by at least one circuit device and converted into a feedback digital signal to the self-test module for checking the linearity relative to the originally provided test signal. Every circuit device has a respective parameter value. The parameter value of every circuit device may be adjustable subject to comparison result of the self-test module. The self-test module compares the linear relationship between the parameter values of the circuit device so as to optimize the related the parameter value. The self-test module also matches the conformity between the parameter value and the received feedback signal, and then optimizes the conformity. After test and adjustment of one parameter item, the self-test module proceeds to the test and adjustment of the next parameter item. Thus, by means of the built-in self-test module, the internal circuit is well examined without the use of an external test apparatus or the need of unwrapping the product. Therefore, the invention greatly saves the manufacturing cost, improves the stability and performance of the electro acoustic system, and prolongs the service life of the electro acoustic system.  
         [0021]     A prototype of electro acoustic system built-in test and calibration method has been constructed with the features of  FIGS. 1 and 2 . The light source assembly functions smoothly to provide all of the features discussed earlier.  
         [0022]     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention.