Patent Publication Number: US-2022221497-A1

Title: Prognostic method and apparatus for improving circuit health

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0003562, filed on Jan. 11, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     One or more embodiments relate to a method and an apparatus for improving circuit health, and more particularly, to a method and an apparatus for improving the health of a circuit to be analyzed based on an S-parameter plot. 
     2. Description of Related Art 
     In order to improve the reliability of circuits, parts, devices and systems, prognostics and health management (PHM) technique for estimating a target lifespan, a maintenance management cycle, and a remaining operating time is being used in various fields. In particular, it is very important to effectively apply such a PHM technique to weapon systems and communication equipment that may cause damage to a large number of people when operation is stopped due to a failure or a defect. For example, when a defect occurs in a radar operated by the military during a war and the operation thereof is stopped, the detection capability of the military is deteriorated and the overall operational performance may be significantly compromised. Therefore, it is necessary to improve the reliability of corresponding circuits, parts, device, and systems by using an effective PHM technique. 
     The PHM technique is a technique for preventing unexpected failures by diagnosing a failure of machine equipment in advance and determining an appropriate maintenance time. For example, when key parts dependent on overseas repair fail, it may take time to secure parts and repair personnel, and thus the repair time may be increased. However, by applying the PHM technique, it is possible to predict the expected failure time of key parts and to organize delivery of parts and repair personnel in advance, thereby reducing the repair time. Therefore, synergistic effects like system operation rate improvement, quality improvement, productivity improvement, and energy efficiency improvement may be expected. 
     The PHM technique includes four stages: a data obtaining stage, a characteristic factor extracting stage, a health estimating stage, and a decision-making stage. First, an optimal database may be built through analyses of system design characteristics, operating conditions, and maintenance history in the data obtaining stage. Also, atypical data may be collected based on experience-based and statistical approaches. In the characteristic factor extracting stage, unnecessary noise is removed from the previously obtained data, and factors highly correlated with system failure and health are extracted. A current system state and a future state (remaining life) are calculated by using the characteristic factors extracted earlier in the health estimating stage. 
     As a characteristic factor for estimating and managing the health of an electronic circuit, a resistance or impedance measured from a device or an interconnection is used previously. In the case of a method of measuring a resistance, since a change in resistance may be measured after a defect occurs, it is impossible to estimate and eliminate or prepare for a defect in advance. In the case of a method of measuring impedance, impedance is calculated by using a resistance, a capacitance, and an inductance, which shows a large change in a low frequency region. While the method is useful for detecting a defect of a relatively large circuit or system (e.g., an electric motor, a generator, a turbine, etc.), the method is not sensitive to small changes. Therefore, it is difficult to identify defects or damage occurring in small-sized circuits. 
     SUMMARY 
     One or more embodiments provide a method of improving health of a circuit based on an S-parameter plot. 
     One or more embodiments provide an apparatus for improving health of a circuit based on an S-parameter plot. 
     One or more embodiments provide an electronic device that determines the remaining lifespan of a circuit by using the apparatus for improving circuit health and replaces a circuit based on the remaining lifespan. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure. 
     According to one or more embodiments, a method of improving circuit health, the method includes obtaining an S-parameter plot of a circuit having an input port and an output port; determining a resonance frequency of the circuit based on the S-parameter plot; and estimating the health of the circuit based on the resonance frequency. 
     The method may further include obtaining a first resonance frequency when the circuit is in a fresh state; and obtaining a second resonance frequency when the circuit is in an old state, wherein the estimating of the health of the circuit may include estimating remaining lifespan of the circuit based on the first resonance frequency, the second resonance frequency, and the resonance frequency. 
     The remaining lifespan of the circuit to be analyzed may be estimated based on a ratio between a difference between the resonance frequency and the second resonance frequency and a difference between the first resonance frequency and the second resonance frequency. 
     The obtaining of the second resonance frequency when the circuit is in the old state may include obtaining a resonance frequency of the circuit after repeatedly applying a chemical, physical, or thermal stimulation to the circuit a pre-set number of times. 
     The obtaining of the S-parameter plot of the circuit may include obtaining a plot regarding a reflection coefficient, which is a ratio between a reflected wave and an incident wave of the input port, obtaining a plot regarding a reverse transfer coefficient, which is a ratio between the reflected wave of the input port and an incident wave of the output port, obtaining a plot regarding a transfer coefficient, which is a ratio between a reflected wave of the output port and an incident wave of the input port, or obtaining a plot regarding a reflection coefficient, which is a ratio between the reflected wave and the incident wave of the output port. 
     The determining of the resonance frequency of the circuit may include determining a frequency having a maximum value or a minimum value in a pre-set frequency band in the S-parameter plot as the resonance frequency. 
     According to one or more embodiments, an apparatus for estimating health of a circuit to be analyzed by using an S-parameter plot analysis. The apparatus includes a memory; an S-parameter measurer configured to obtain an S-parameter plot of a circuit to be analyzed having an input port and an output port and store data regarding the S-parameter plot in the memory; and at least one processor configured to determine a resonance frequency of the circuit to be analyzed based on the data regarding the S-parameter plot stored in the memory and estimate health of the circuit to be analyzed based on the resonance frequency. 
     The processor may be configured to estimate the remaining lifespan of the circuit to be analyzed based on a first resonance frequency when the circuit to be analyzed is in a fresh state, a second resonance frequency when the circuit to be analyzed is in an old state, and the resonance frequency. 
     The remaining lifespan of the circuit to be analyzed may be estimated based on a ratio between a difference between the resonance frequency and the second resonance frequency and a difference between the first resonance frequency and the second resonance frequency. 
     The second resonance frequency Fp 2  may be a resonance frequency of the circuit to be analyzed obtained by repeatedly applying a chemical, physical, or thermal stimulation to the circuit for a pre-set number of times. 
     The resonance frequency of the circuit to be analyzed may be a frequency having a maximum value or a minimum value in a pre-set frequency band in the S-parameter plot of the circuit to be analyzed. 
     According to one or more embodiments, an electronic device includes a plurality of circuits connected in parallel; an apparatus for improving circuit health configured to evaluate circuit health of the plurality of circuits and applying a replacement signal based on a result of the evaluation; a switch circuit configured to receive the replacement signal and select one of the plurality of circuits; and a power supply configured to supply power to one circuit selected by the switch circuit, wherein the apparatus for improving circuit health includes a memory; an S-parameter measurer configured to obtain an S-parameter plot of a circuit to be analyzed having an input port and an output port and store data regarding the S-parameter plot in the memory; and at least one processor configured to determine a resonance frequency of the circuit to be analyzed based on the data regarding the S-parameter plot stored in the memory and estimate health of the circuit to be analyzed based on the resonance frequency. 
     The apparatus for improving circuit health may estimate the remaining lifespan of the circuit to be analyzed based on a first resonance frequency when the circuit to be analyzed is in a fresh state, a second resonance frequency when the circuit to be analyzed is in an old state, and the resonance frequency, and, when the remaining lifespan of the circuit to be analyzed is less than or equal to a pre-set value, apply a replacement command to the switch circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a circuit diagram showing a serial LC circuit. 
         FIG. 2  is a circuit diagram showing components of a generalized two-terminal circuit. 
         FIG. 3  is a conceptual diagram for describing the S-parameters of the two-terminal circuit shown in  FIG. 2 . 
         FIG. 4  is a graph for describing the intrinsic impedance of the two-terminal circuit shown in  FIG. 2 . 
         FIG. 5  is a flowchart of a method of improving circuit health according to an embodiment. 
         FIG. 6  is a flowchart showing the operation of estimating circuit health shown in  FIG. 5  in detail. 
         FIG. 7  is a diagram showing an apparatus for improving circuit health according to an embodiment. 
         FIG. 8A ,  FIG. 8B  and  FIG. 8C  are diagrams showing various embodiments of connecting an apparatus for improving circuit health to a circuit to be analyzed. 
         FIG. 9  is a graph showing a change in the resistance and a change in the resonance frequency Fp of a circuit to be analyzed when a thermal stimulation is repeatedly applied thereto. 
         FIG. 10  is a graph showing a change in S-parameter plot data of a circuit to be analyzed when a thermal stimulation is repeatedly applied. 
         FIG. 11A ,  FIG. 11B ,  FIG. 11C  and  FIG. 11D  are scanning electron microscope photographs showing defects occurring in the wire bonding of a circuit to be analyzed when thermal stimulation is repeatedly applied. 
         FIG. 12  is a diagram showing an electronic device including an apparatus for improving circuit health according to an embodiment. 
         FIG. 13  is a block diagram showing an operation algorithm of the electronic device shown in  FIG. 12 . 
         FIG. 14A ,  FIG. 14B  and  FIG. 14C  are diagrams for describing an operation of the electronic device shown in  FIG. 12 . 
         FIG. 15A  and  FIG. 15B  are remaining lifetime-time graphs for describing application of a replacement command by an apparatus for improving circuit health based on the remaining lifespan, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     While one or more embodiments are susceptible to various modifications and variations, specific embodiments thereof are illustrated in the drawings and will be described in detail hereinafter. However, it is not intended to limit one or more embodiments to the particular forms disclosed herein. Rather, one or more embodiments include all modifications, equivalents, and substitutions consistent with the technical spirit of one or more embodiments as defined by the claims. 
     It will be understood that when an element, such as a layer, region, or substrate, is referred to as being “on” another component, it may be directly on the other element or an intervening elements may be therebetween. 
     Although the terms first, second, etc. may be used to describe various elements, components, regions, layers, and/or regions, It will be understood that such elements, components, regions, layers, and/or regions, should not be limited by these terms. 
     With reference to the accompanying drawings, one or more embodiments will be described in more detail. Hereinafter, the same reference numerals are used to denote the same components in the drawings, and repeated descriptions of the same components are omitted. 
       FIG. 1  is a circuit diagram showing a serial LC circuit. 
     Referring to  FIG. 1 , a serial LC circuit  10  includes an input port  11 , an input impedance  13 , an inductor-capacitor connection element  15 , an output impedance  17 , and an output port  19 . 
     Scattering parameters (S-parameters) are used as a value indicating a transfer characteristic from one stage to a next stage in a cascade system. In the serial LC circuit  10  shown in  FIG. 1 , an input voltage V in  is input to the input port  11 , and an output voltage Vow is output from an output port  19 . The inductance of the inductor-capacitor connection element  15  is Li, the capacitance is Ci, the input impedance  13  is R S , and the output impedance  17  is R L . 
     
       
         
           
             
               ω 
               = 
               
                 1 
                 
                   
                     
                       L 
                       1 
                     
                     ⁢ 
                     
                       C 
                       1 
                     
                   
                 
               
             
             , 
           
         
       
     
     When the frequency of the input voltage V in  input to the input port  11  is the inductor-capacitor connection element  15  is short-circuited, and thus the output voltage Vow output from the output port  19  has a maximum value. When the frequency of the input voltage V in  has a value different from the above-stated value, voltage attenuation occurs by the inductor-capacitor connection element  15 . In this case, the attenuating voltage may be understood as a reflected wave. In other words, the characteristics of a device may be expressed by using a ratio of an input signal to the input port  11  of the serial LC circuit  10  with respect to an output signal from the output port  19 . 
       FIG. 2  is a circuit diagram showing components of a generalized two-terminal circuit. 
     The serial LC circuit  10  having the inductor-capacitor connection element  15  shown in  FIG. 1  may be more generalized and shown as a two-terminal circuit  20  including various elements. 
     Referring to  FIG. 2 , the two-terminal circuit  20  may include an input port  21 , an input impedance  23 , an element network  25 , an output impedance  27 , and an output port  29 . 
     An incident wave and a reflected wave measured at the input port  21  may be expressed as V 1     +    and V 1     −   , respectively, and an incident wave and a reflected wave measured at the output port  29  may be expressed as V 2     +    and V 2     −   , respectively. At this time, the incident wave V 1     +    measured at the input port  21  is a signal generated by the input voltage V in  when the input impedance  23  is R S , and the reflected wave V 1     −    measured at the input port  21  is a signal generated by the input voltage Vu when the input impedance  23  is not R S . The incident wave V 2     +    measured at the output port  29  may be considered as a signal incident on the output impedance  27  or equivalently reflected by the output impedance  27 . 
     The incident wave and the reflected wave measured at the input port  21  and the incident wave and the reflected wave measured at the output port  29  may be expressed by below equations using an S-parameter. 
     
       
      
       V 
       1 
       − 
       =S 
       11 
       V 
       1 
       + 
       +S 
       12 
       V 
       2 
       + 
      
     
     
       
      
       V 
       2 
       − 
       =S 
       21 
       V 
       1 
       + 
       +S 
       22 
       V 
       2 
       + 
      
     
       FIG. 3  is a conceptual diagram for describing the S-parameters of the two-terminal circuit shown in  FIG. 2 . 
     Referring to  FIG. 3 , Su denotes a ratio between the incident wave and the reflected wave at the input port  21  of the two-terminal circuit  20 , S 12  denotes a ratio between the reflected wave at the input port  21  and the incident wave at the output port  29 , and S 22  denotes a ratio between the reflected wave at the output port  29  and the incident wave at the input port  21 . 
     S 11  is the ratio between the reflected wave and the incident wave measured at the input port  21  when a value reflected by the output impedance  27  R L  of the two-terminal circuit  20  is ‘0’. 
     
       
         
           
             
               S 
               11 
             
             = 
             
               
                 
                   
                     V 
                     1 
                     - 
                   
                   
                     V 
                     1 
                     + 
                   
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 when 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   V 
                   2 
                   + 
                 
               
               = 
               0 
             
           
         
       
     
     S 11  is a value indicating the matching accuracy of the input port  21  and refers to the reflection coefficient of the input port  21 . 
     S 12  is the ratio between the reflected wave measured at the input port  21  and the incident wave measured at the output port  29  when a value reflected by the input impedance  23  R S  of the two-terminal circuit  20  is ‘0’. 
     
       
         
           
             
               S 
               12 
             
             = 
             
               
                 
                   
                     V 
                     2 
                     - 
                   
                   
                     V 
                     1 
                     + 
                   
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 when 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   V 
                   1 
                   + 
                 
               
               = 
               0 
             
           
         
       
     
     S 12  refers to a reverse isolation coefficient of the two-terminal circuit  20  indicating the influence of an output signal on the input port  21 . 
     S 22  is the ratio between the reflected wave and the incident wave at the output port  29  when the value reflected by the input impedance  23  R S  is ‘0’. 
     
       
         
           
             
               S 
               22 
             
             = 
             
               
                 
                   
                     V 
                     2 
                     - 
                   
                   
                     V 
                     2 
                     + 
                   
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 when 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   V 
                   1 
                   + 
                 
               
               = 
               0 
             
           
         
       
     
     S 22  is a value indicating the matching accuracy of the output port  29  and refers to the reflection coefficient of the output port  29 . 
     S 21  is the ratio between the incident wave at the input port  21  and the reflected wave at the output port  29  when a value reflected by the output impedance  27  is ‘0’. 
     
       
         
           
             
               S 
               21 
             
             = 
             
               
                 
                   
                     V 
                     2 
                     - 
                   
                   
                     V 
                     1 
                     + 
                   
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 when 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   V 
                   2 
                   + 
                 
               
               = 
               0 
             
           
         
       
     
     S 21  refers to a transfer coefficient expressing the gain of the two-terminal circuit  20 . 
     As described above, in the case of the two-terminal circuit  20 , unique characteristics of the two-terminal circuit  20  may be expressed by using S-parameters S 11 , S 12 , S 22 , and S 21 . 
       FIG. 4  is a graph for describing the intrinsic impedance of the two-terminal circuit shown in  FIG. 2 . 
     Referring to  FIG. 4 , it may be seen that the intrinsic impedance of the two-terminal circuit  20  changes according to frequency values. In the case of a capacitor, the impedance thereof decreases as the frequency of an applied signal increases. On the contrary, in the case of an inductor, the impedance thereof increases as the frequency of an applied signal increases. Since the two-terminal circuit  20  includes an element network  25  consisting of a combination of capacitors, inductors, or resistors, the impedance of the two-terminal circuit  20  also changes according to the frequency value of an applied signal. 
     Since the ratio between an incident wave and a reflected wave changes according to a change of impedance, S-parameters are also affected by the frequency value. For example, when an input impedance according to the frequency value of a particular circuit or connection is as shown in  FIG. 4 , the input impedance has a minimum value at a matching frequency value Fm. At this time, from among the S-parameters of the simple two-terminal circuit  20 , the reflection coefficient S 11  of the input port  21  has the minimum value and the transmission coefficient S 21  has the maximum value at the matching frequency value Fm. At frequencies other than the matching frequency value Fm, the reflection coefficient S 11  of the input port  21  increases, and the transmission coefficient S 21  decreases. In the case of a two-terminal circuit or connection having a complicated configuration, frequency characteristics of the S-parameters become more complicated due to parasitic components, signal line effects, etc. As the frequency characteristics become more complicated, a significant difference may be confirmed even with a small change. 
       FIG. 5  is a flowchart of a method of improving circuit health according to an embodiment. 
     Referring to  FIG. 5 , the method of improving circuit health according to an embodiment includes operation S 10  of obtaining an S-parameter plot of a circuit to be analyzed, operation S 20  of determining a resonance frequency Fp based on the S-parameter plot, and operation S 30  of estimating circuit health based on the resonance frequency Fp. 
     In operation S 10  of obtaining the S-parameter plot of the circuit to be analyzed, S-parameters are obtained by measuring incident waves and reflected waves at an input port, an output port, or the input port and the output port of circuit to be analyzed. By storing S-parameter values obtained by varying the frequency, an S-parameter plot is obtained with frequency values and the intensity of the S-parameters as respective axes. 
     In an embodiment, the S-parameter plot may be a plot of the reflection coefficient S 11  of the circuit to be analyzed obtained by measuring a ratio between a reflected wave and an incident wave of an input port. 
     In an embodiment, the S-parameter plot may be a plot of the reverse transfer coefficient S 12  of the circuit to be analyzed obtained by measuring a ratio between a reflected wave of the input port and an incident wave of an output port. 
     In an embodiment, the S-parameter plot may be a plot of the transfer coefficient S 21  of the circuit to be analyzed obtained by measuring a ratio between a reflected wave of the output port and an incident wave of the input port. 
     In another embodiment, the S-parameter plot may be a plot of the reflection coefficient S 22  of the circuit to be analyzed obtained by measuring a ratio between a reflected wave and an incident wave of the output port. 
     A plurality of S-parameter plots may be obtained by measuring any one or more of the plot of the reflection coefficient S 11  of the input port, the plot of the reverse transfer coefficient S 12 , the plot of the transfer coefficient S 21 , and the plot of the reflection coefficient S 22  of the output port and may be used to estimate the health of a circuit. 
     In operation S 20  of determining the value of the resonance frequency Fp based on the S-parameter plots, the value of the resonance frequency Fp having a local minimum value or a local maximum value in a certain range from the S-parameter plots of the circuit to be analyzed. 
     As described above, S-parameters may exhibit a complex variation pattern depending on the frequency due to a connection, a capacitor, an inductor, a parasitic component, and a signal line effect of the circuit to be analyzed. 
     A particular range exhibiting the most sensitive change to mechanical, chemical, and thermal damage of the circuit to be analyzed is selected, and the resonance frequency Fp, which is a local minimum value or a local maximum value of the particular range, is determined. 
     In operation S 30  of estimating circuit health based on the resonance frequency Fp, a current circuit health of the circuit to be analyzed is determined by comparing a current resonance frequency Fp of the circuit to be analyzed with a change pattern of the resonance frequency Fp of S-parameters of the circuit to be analyzed measured in advance. 
     As the frequency characteristics of S-parameters become more complicated, a significant difference occurs even with a small change in the circuit to be analyzed. The trend of such frequency changes of S-parameter may be organized into data and, based on the data, the health of a circuit to be analyzed may be quantitatively estimated. 
       FIG. 6  is a flowchart showing the operation of estimating circuit health shown in  FIG. 5  in detail. 
     Referring to  FIG. 6 , operation S 30  of estimating circuit health includes operation S 31  of obtaining a first resonance frequency Fp 1  in a fresh state, operation S 32  of obtaining a second resonance frequency Fp 2  in an old state, and operation S 33  of estimating the remaining lifespan the first resonance frequency Fp 1 , the second resonance frequency Fp 2 , and a current resonance frequency Fp 3 . 
     In operation S 31  of obtaining the first resonance frequency Fp 1  in the fresh state, an S-parameter plot of a circuit, which is identical to the circuit to be analyzed and is without mechanical, chemical, or thermal damage after being manufactured, and the first resonance frequency Fp 1 , which is a local minimum value or a local maximum value of a certain range. 
     The first resonance frequency Fp 1  may be calculated by measuring a circuit identical to a circuit to be analyzed for a plurality of number of times or by averaging resonance frequencies Fp 1  obtained by measuring a plurality of circuits. 
     In operations S 32  of obtaining second resonance frequency Fp 2  in the old state, after chemical, physical, or thermal stimulation is repeatedly applied to the circuit, from which the first resonance frequency Fp 1  is measured in the fresh state, for a pre-set number of times, an S-parameter plot of the circuit is obtained, and the second resonance frequency Fp 2 , which is a local minimum value or a local maximum value of a certain range, is obtained. 
     In an embodiment, after a chemical, mechanical, or thermal stimulation that may occur as the circuit is used is repeatedly applied to the circuit from which the first resonance frequency Fp 1  is measured in the fresh state, an S-parameter plot of the circuit is obtained, and the second resonance frequency Fp 2  is obtained based on the S-parameter plot. 
     Alternatively, in another embodiment, after driving a circuit for a pre-set time interval in an environment similar to a system to which the circuit is actually applied, an S-parameter plot is obtained, and, based on the S-parameter plot, the second resonance frequency Fp 2  is obtained. As described above, the second resonance frequency Fp 2  may be an average value obtained by measuring a plurality of number of times. 
     The first resonance frequency Fp 1  and the second resonance frequency Fp 2  may be obtained in advance and stored in a memory and may be values partially corrected from experimental values by analyzing design characteristics, operating conditions, and maintenance history of a system. 
     In operation S 33  of estimating the remaining lifespan based on the first resonance frequency Fp 1 , the second resonance frequency Fp 2 , and the current resonance frequency Fp 3 , the remaining lifespan of the circuit to be analyzed is estimated by comparing the first resonance frequency Fp 1  and the second resonance frequency Fp 2  obtained and stored in advance with the current resonance frequency Fp 3  of the circuit to be analyzed. 
     The remaining lifespan of the circuit to be analyzed may be a quantitative value indicating the current health of the circuit to be analyzed based on data regarding the circuit to be analyzed in the fresh state and the circuit to be analyzed in the old state. 
     For example, the remaining lifespan of the circuit to be analyzed may be estimated based on a ratio between a difference Fp-Fp 2  between the resonance frequency Fp and the second resonance frequency Fp 2  and a difference Fp 1 -Fp 2  between the first resonance frequency Fp 1  and the second resonance frequency Fp 2 . 
     Therefore, the health of the circuit to be analyzed may be measured as a quantitative value, and the malfunction probability of the circuit to be analyzed may be measured according to the remaining lifespan of the circuit to be analyzed and matched to the quantitative value. By using this, a circuit to be analyzed may be replaced or a repair schedule may be set before the circuit to be analyzed fails, thereby improving the reliability and the operation rate of a system including the circuit to be analyzed. 
       FIG. 7  is a diagram showing an apparatus for improving circuit health according to an embodiment. 
     Referring to  FIG. 7 , an apparatus  30  for improving circuit health according to an embodiment includes an S-parameter measurer  31 , a memory  33 , and a processor  35 . 
     The S-parameter measurer  31  obtains an S-parameter plot of a circuit to be analyzed having an input port and an output port and stores the S-parameter plot in the memory  33 . 
     The S-parameter measuring device  31  may be connected to an input port, an output port, or both the input port and the output port of the circuit to be analyzed and measure an incident wave and a reflected wave of each port and store a ratio between the incident wave and the reflected wave. 
     According to an embodiment, the S-parameter measurer  31  may be connected to an input port of a circuit to be analyzed, measure a reflection coefficient of the input port, and obtain an S-parameter plot. 
     According to an embodiment, the S-parameter measurer  31  may be connected to an input port and an output port of a circuit to be analyzed, measure a reverse transfer coefficient or a transfer coefficient, and obtain an S-parameter plot. 
     Alternatively, the S-parameter measurer  31  may be connected to an output port of a circuit to be analyzed, measure a reflection coefficient of the output port, and obtain an S-parameter plot. 
     The memory  33  stores an S-parameter plot data obtained by the S-parameter measurer  31 . The memory  33  may store various data for estimating circuit health. For example, the memory  33  may store S-parameter plots or resonance frequencies Fp 1  and Fp 2  of a circuit to be analyzed in a fresh state and an old state and may store input data or output data regarding software and related commands. 
     The memory  33  may be a computer-readable recording medium and may include a storage medium like a magnetic storage medium (e.g., a ROM, a floppy disk, a hard disk, etc.) and an optically readable medium (e.g., a CD-ROM, a DVD, etc.). 
     The processor  35  may be configured to determine the resonance frequency Fp of the circuit to be analyzed based on data regarding S-parameter plots in the memory  33  and estimate the health of the circuit to be analyzed based on the resonance frequency Fp. 
     The processor  35  estimates the remaining lifespan of the circuit to be analyzed based on the first resonance frequency Fp 1  when the circuit to be analyzed is in the fresh state, the second resonance frequency Fp 2  when the circuit to be analyzed is in the old state, and the resonance frequency Fp, wherein the first resonance frequency Fp 1 , the second resonance frequency Fp 2 , and the resonance frequency Fp are stored in the memory  33 . 
     The remaining lifespan of the circuit to be analyzed may be quantitatively estimated based on a ratio between a difference Fp-Fp 2  between the resonance frequency Fp and the second resonance frequency Fp 2  and a difference Fp 1 -Fp 2  between the first resonance frequency Fp 1  and the second resonance frequency Fp 2 . 
     The second resonance frequency Fp 2  may be a resonance frequency of the circuit to be analyzed obtained by repeatedly applying a chemical, physical, or thermal stimulation to the circuit for a pre-set number of times. 
     The processor  35  may be configured to be included in other hardware devices, such as a microprocessor or general purpose computer system. 
     According to an embodiment, the S-parameter measurer  31 , the memory  33 , and the processor  35  may be embedded in a circuit to be analyzed or an electronic device to be analyzed to configure an embedded system. 
       FIG. 8A ,  FIG. 8B  and  FIG. 8C  are diagrams showing various embodiments of connecting an apparatus for improving circuit health to a circuit to be analyzed. 
     Referring to  FIG. 8A , the apparatus  30  for improving circuit health may be connected to both the input port  21  and the output port  29  of a circuit  20  to be analyzed. The apparatus  30  for improving circuit health may obtain an S-parameter plot by measuring any one or more of the reflection coefficient S 11  of the input port  21 , the reverse transfer coefficient S 12 , the transfer coefficient S 21 , and the reflection coefficient S 22  of the output port  29  and estimate the health of the circuit  20  to be analyzed based thereon. 
     Referring to  FIG. 8B , the apparatus  30  for improving circuit health may be connected to the input port  21  of the circuit  20  to be analyzed. The apparatus  30  for improving circuit health may obtain a plot of the reflection coefficient SH of the input port  21 , which is a ratio between a reflected wave and an incident wave of the input port  21 , and estimate the health of the circuit  20  to be analyzed based thereon. 
     Referring to  FIG. 8C , the apparatus  30  for improving circuit health may be connected to the output port  29  of the circuit  20  to be analyzed. The apparatus  30  for improving circuit health may obtain a plot of the reflection coefficient S 22  of the output port  29 , which is a ratio between a reflected wave and an incident wave of the output port  29 , and estimate the health of the circuit  20  to be analyzed based thereon. 
       FIG. 9  is a graph showing a change in the resistance and a change in the resonance frequency Fp of a circuit to be analyzed when a thermal stimulation is repeatedly applied thereto. 
     Referring to  FIG. 9 , it may be seen that, when a thermal stimulation is repeatedly applied to the circuit to be analyzed, the resistance of the circuit to be analyzed does not change significantly until a wire bonding is completely destroyed and the circuit to be analyzed malfunctions. On the other hand, it may be seen that the resonance frequency Fp of the circuit to be analyzed decreases from a time point at which the 2500 th  thermal stimulation is applied to the circuit to be analyzed and exhibits a significant change until a time point at which the wire bonding is destroyed. 
     Therefore, by obtaining an S-parameter plot of the circuit to be analyzed and measuring a change in the resonance frequency thereof, the damage to the circuit to be analyzed may be traced from the beginning, and, by quantifying the same, the circuit to be analyzed may be repaired or repaired before the circuit to be analyzed fails, thereby improving the reliability of an electronic device including the circuit to be analyzed. 
       FIG. 10  is a graph showing a change in S-parameter plot data of a circuit to be analyzed when a thermal stimulation is repeatedly applied. 
       FIG. 10  shows a plot of the reflection coefficient S 11  obtained by measuring a ratio between a reflected wave and an incident wave at an input port of a circuit to be analyzed according to an embodiment. The S-parameter plot has a resonance frequency Fp that is a local minimum in the frequency range from 5 GHz to 14.0 GHz. 
     When the thermal stimulation is applied to the circuit to be analyzed 0 times, the circuit to be analyzed is in the fresh state, and the first resonance frequency Fp 1  is 12.7 GHz. 
     When the circuit to be analyzed is damaged by the thermal stimulation, the circuit to be analyzed is in the old state, and the second resonance frequency Fp 2  is 5.5 GHz. 
     As the thermal stimulation is repeatedly applied to the circuit to be analyzed, the resonance frequency Fp changes in a direction from the first resonance frequency Fp 1  toward the second resonance frequency Fp 2 . Therefore, based on a ratio of a difference between the first resonance frequency Fp 1  and the second resonance frequency Fp 2  and a difference between the resonance frequency Fp and the second resonance frequency Fp 2 , the remaining life of the circuit to be analyzed may be quantitatively measured. 
       FIG. 11A ,  FIG. 11B ,  FIG. 11C  and  FIG. 11D  are scanning electron microscope photographs showing defects occurring in the wire bonding of a circuit to be analyzed when thermal stimulation is repeatedly applied. 
       FIG. 11A  is a scanning electron microscope photograph of the wire bonding of the circuit to be analyzed before thermal stimulation is applied,  FIG. 11B  is a scanning electron microscope photograph of the wire bonding when thermal stimulation is applied 5400 times,  FIG. 11C  is a scanning electron microscope photograph of the wire bonding when thermal stimulation is applied 7200 times, and  FIG. 11D  is a scanning electron microscope photograph of the wire bonding when thermal stimulation is applied 10020 times. 
     It may be seen that cracks are formed at junctions of wires due to the repeatedly applied thermal stimulation. When further thermal stimulation is repeatedly applied, disconnection may occur due to deterioration of wires and may cause the complete failure of the circuit to be analyzed. 
     As it may be seen in  FIG. 9 , despite the damage to the wires, which can be confirmed by the scanning electron microscope photographs, the resistance of the circuit to be analyzed increased only slightly after the thermal stimulation was applied 8500 times. On the other hand, it was confirmed that the resonance frequency Fp of the S-parameter plot sensitively reflected the damage of the wires and showed a significant change from the beginning. 
       FIG. 12  is a diagram showing an electronic device including an apparatus for improving circuit health according to an embodiment. 
     Referring to  FIG. 12 , an electronic device includes a plurality of circuits  20   a ,  20   b , and  20   c , the apparatus  30  for improving circuit health, a switch circuit  41 , and a power supply  43 . 
     The plurality of circuits  20   a ,  20   b , and  20   c  may include a plurality of identical circuits for driving the electronic device connected in parallel to one another. The plurality of circuits  20   a ,  20   b , and  20   c  may each include an input port and an output port, and the apparatus  30  for improving circuit health may be connected to the input port, the output port, or both the input port and the output port. 
     The apparatus  30  for improving circuit health evaluates the circuit health of the plurality of circuits  20   a ,  20   b , and  20   c  and applies a replacement signal to the switch circuit  41  based thereon. 
     The apparatus  30  for improving circuit health may select and determine one circuit connected to the system and driven from among the plurality of circuits  20   a ,  20   b , and  20   c  as a circuit to be analyzed and determine the circuit health of the circuit to be analyzed. 
     The apparatus  30  for improving circuit health may include a memory, an S-parameter measurer that obtains an S-parameter plot of a circuit to be analyzed having an input port and an output port, and a processor configured to determine the resonance frequency Fp of the circuit to be analyzed based on data regarding the S-parameter plot and estimate the circuit health of the circuit to be analyzed based on the resonance frequency Fp. 
     The apparatus  30  for improving circuit health may quantitatively estimate the remaining lifespan of the circuit to be analyzed based on the first resonance frequency Fp 1  when the circuit to be analyzed is in the fresh state, the second resonance frequency Fp 2  when the circuit to be analyzed is in the old state, and the resonance frequency Fp. 
     The apparatus  30  for improving circuit health applies a replacement command to the switch circuit  41  when the estimated remaining lifespan is equal to or less than a pre-set value. Here, the pre-set value may be a value determined in consideration of the electrical characteristics of a circuit to be analyzed and economic feasibility and efficiency regarding replacement. 
     The switch circuit  41  may receive a replacement signal applied by the apparatus  30  for improving circuit health and select one of the plurality of circuits  20   a ,  20   b , and  20   c . The switch circuit  41  may control a switch for connecting the plurality of circuits  20   a ,  20   b , and  20   c  to an electronic device or a switch for connecting the plurality of circuits  20   a ,  20   b , and  20   c  to a power supply for supplying power to the plurality of circuits  20   a ,  20   b , and  20   c.    
     The switch circuit  41  removes an existing connection of a circuit to be analyzed to an electronic device or the power supply  43  according to a replacement command of the apparatus  30  for improving circuit health, selects a new circuit from among the plurality of circuits  20   a ,  20   b , and  20   c , and connect the new circuit to the electronic device or the power supply  43 . 
       FIG. 13  is a block diagram showing an operation algorithm of the electronic device shown in  FIG. 12 . 
     Referring to  FIG. 13 , the operation algorithm of the electronic device includes operation S 10  of obtaining S-parameter plot data, operation S 20  of setting a resonance frequency of an existing circuit, operation S 30  of estimating circuit health, and operation S 40  of determining whether to replace a circuit. 
     In operation S 40  of determining whether to replace a circuit, when the remaining lifespan of an existing circuit is less than a pre-set value, the apparatus  30  for improving circuit health applies a replacement signal to the switch circuit  41 , such that any one of circuits  20   a ,  20   b , and  20   c  operates as a replacement circuit (operation S 41 ). On the other hand, when the remaining lifespan of the existing circuit is greater than the pre-set value, the operation of the existing circuit is continued (operation S 42 ). 
     A circuit health estimation and replacement algorithm may be repeatedly performed at regular time intervals or cycles. 
       FIG. 14A ,  FIG. 14B  and  FIG. 14C  are diagrams for describing an operation of the electronic device shown in  FIG. 12 . 
     Referring to  FIG. 14A , when the electronic device is initially operated, the switch circuit  41  may connect the power supply  43  and a first circuit  20   a  to drive the electronic device. When the first circuit  20   a  is degraded due to the driving of the electronic device, the apparatus  30  for improving circuit health determines the circuit health of the first circuit  20   a  and determines whether to replace the first circuit  20   a  based on the remaining lifespan. 
     When the apparatus  30  for improving circuit health determines that the remaining lifespan of the first circuit  20   a  is less than a pre-set value, the apparatus  30  for improving circuit health may apply a replacement signal to the switch circuit  41 . 
     Referring to  FIG. 14B , the switch circuit  41  may receive the replacement signal, remove the connection between the first circuit  20   a  and the power supply  43 , and connects a second circuit  20   b  to the power supply  43 . The electronic device may be driven by using the second circuit  20   b.    
     The apparatus  30  for improving circuit health may periodically determine the circuit health of the second circuit  20   b  and determine whether to replace the second circuit  20   b  based on the remaining lifespan. 
     Referring to  FIG. 14C , the switch circuit  41  may receive a replacement signal of the apparatus  30  for improving circuit health, remove the connection between the second circuit  20   b  and the power supply  43 , and connect a third circuit  20   c  to the power supply  43 . 
     The plurality of circuits  20   a ,  20   b , and  20   c , the apparatus  30  for improving circuit health, and the switch circuit  41  may be formed on one substrate or form an embedded system constituting one packaging. In this case, the apparatus  30  for improving circuit health and the plurality of circuits  20   a ,  20   b , and  20   c  may operate as one circuit, thereby improving the reliability of the electronic device without human judgment or manipulation. 
       FIG. 15A  and  FIG. 15B  are remaining lifetime-time graphs for describing application of a replacement command by an apparatus for improving circuit health based on the remaining lifespan, according to an embodiment. 
     Referring to  FIG. 15A , it may be confirmed that the remaining lifespan of a circuit decreases with a steep slope near a point F 1  and a failure occurs. Therefore, the reliability of an electronic device may be improved by replacing the circuit before the remaining life of the circuit reaches the point F 1  at which the probability of a failure or a malfunction is very high. 
       FIG. 15B  shows a graph of the remaining lifespan in the case of applying a replacement signal by selecting a remaining lifespan value D 1  before the remaining lifespan of a circuit decreases with a steep slope. The remaining lifespan value D 1  may be selected in consideration of electrical characteristics, use environment, and purpose of a circuit and economic feasibility and efficiency regarding replacement of the circuit. 
     When the remaining lifespan of a circuit reaches D 1 , the switch circuit  41  applies a replacement signal to remove an existing connection of the circuit and connect a new circuit, thereby minimizing malfunction and failure of an electronic device. 
     According to a method and an apparatus for improving circuit health according to an embodiment, circuit health is estimated by using a change pattern of an S-parameter plot, thereby discovering and estimating a defect at an earlier stage as compared to a method of measuring resistance generally used for estimating circuit health. Also, since an S-parameter is measured in a high-frequency region, a defect or damage in a small circuit may be more accurately detected as compared to a method of measuring impedance. 
     Also, by using a first resonance frequency when a circuit to be analyzed is in a fresh state, a second resonance frequency when the circuit to be analyzed is in an old state, and a current resonance frequency of the circuit to be analyzed, the remaining lifespan of the circuit to be analyzed may be quantitatively estimated. 
     When the remaining lifespan of a circuit to be analyzed is less than or equal to a pre-set value, an electronic device according to an embodiment selects any one of a plurality of circuits connected in parallel and replaces the circuit to be analyzed with a selected circuit, thereby preventing a failure of the electronic device due to a failure of the circuit to be analyzed. Therefore, the reliability of the entire electronic device may be improved. 
     A method, an apparatus, and an electronic device according to one or more embodiments may be applied to parts, devices, or systems that are packaged and difficult or time-consuming to be partially repaired or replaced. Therefore, not only improvement of reliability of components, devices, or systems, but also synergistic effects like improvement of operation rate, improvement of quality, improvement of productivity, and improvement of energy efficiency may be expected. 
     The technical effects of one or more embodiments are not limited to those mentioned above, and other technical effects not mentioned will be clearly understood by one of ordinary skill in the art from the following description. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the following claims.