Patent Publication Number: US-2023164008-A1

Title: Retiming circuit module, signal transmission system, and signal transmission method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 110143270, filed on Nov. 19, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a signal transmission circuit, and particularly relates to a retiming circuit module, a signal transmission system, and a signal transmission method. 
     Description of Related Art 
     As the signal transmission speed on the printed circuit board becomes faster and faster, the signal attenuation during the transmission process becomes more and more serious. Therefore, in practice, a retimer is often added between an upstream component and a downstream component to extend a signal transmission distance. However, although adding a retimer to a signal transmission path can extend the signal transmission distance, a delay time of data transmission is increased accordingly. In addition, during a period of adjusting a signal transmission frequency, an equalizer circuit at a signal receiving end also takes a while to calibrate. Therefore, how to improve the equalizer calibration efficiency at a signal receiving end during the period of adjusting the signal transmission frequency is indeed one of the topics that persons skilled in the art are devoted to research on. 
     SUMMARY 
     The disclosure provides a retiming circuit module, a signal transmission system, and a signal transmission method, which can improve the equalizer calibration efficiency at a signal receiving end during a period of adjusting a signal transmission frequency. 
     An exemplary embodiment of the disclosure provides a retiming circuit module, which is adapted to perform signal transmission between an upstream device and a downstream device. The retiming circuit module includes a path control circuit and a multipath signal transmission circuit. The multipath signal transmission circuit is coupled to the path control circuit. The multipath signal transmission circuit has built-in first signal transmission path and second signal transmission path. The multipath signal transmission circuit is configured to perform first signal transmission between the upstream device and the downstream device based on a first signal transmission frequency and the second signal transmission path. During a period of performing the first signal transmission, the path control circuit is configured to detect a first data sequence transmitted between the upstream device and the downstream device. The path control circuit is further configured to control the multipath signal transmission circuit to switch to perform second signal transmission between the upstream device and the downstream device based on the first signal transmission frequency and the first signal transmission path according to the first data sequence. 
     An exemplary embodiment of the disclosure further provides a signal transmission system, which includes an upstream device, a downstream device, and a retiming circuit module. The retiming circuit module is coupled between the upstream device and the downstream device to perform signal transmission between the upstream device and the downstream device. The retiming circuit module includes multiple signal transmission paths. The retiming circuit module is configured to perform first signal transmission between the upstream device and the downstream device based on a first signal transmission frequency and a second signal transmission path among the signal transmission paths. During a period of performing the first signal transmission, the retiming circuit module is further configured to detect a first data sequence transmitted between the upstream device and the downstream device. The retiming circuit module is further configured to switch to perform second signal transmission between the upstream device and the downstream device based on the first signal transmission frequency and a first signal transmission path among the signal transmission paths according to the first data sequence. 
     An exemplary embodiment of the disclosure further provides a signal transmission method for a retiming circuit module. The signal transmission method includes the following steps. First signal transmission between an upstream device and a downstream device is performed based on a first signal transmission frequency and a second signal transmission path among multiple signal transmission paths of the retiming circuit module. During a period of performing the first signal transmission, a first data sequence transmitted between the upstream device and the downstream device is detected. Second signal transmission between the upstream device and the downstream device is switched to be performed based on the first signal transmission frequency and a first signal transmission path among the signal transmission paths according to the first data sequence. 
     Based on the above, the retiming circuit module may perform the first signal transmission between the upstream device and the downstream device based on the first signal transmission frequency and the second signal transmission path among the signal transmission paths. During the period of performing the first signal transmission, the retiming circuit module may detect the first data sequence transmitted between the upstream device and the downstream device. According to the first data sequence, the retiming circuit module may switch to perform the second signal transmission between the upstream device and the downstream device based on the first signal transmission frequency and the first signal transmission path among the signal transmission paths. Through switching the signal transmission path early before changing the signal transmission frequency, the equalizer calibration efficiency at the signal receiving end can be effectively improved during the period of adjusting the signal transmission frequency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a signal transmission system according to an exemplary embodiment of the disclosure. 
         FIG.  2    is a schematic diagram of a retiming circuit module according to an exemplary embodiment of the disclosure. 
         FIG.  3    is a schematic diagram of a first signal transmission path and a second signal transmission path according to an exemplary embodiment of the disclosure. 
         FIG.  4    is a schematic diagram of adjusting a signal transmission frequency according to an exemplary embodiment of the disclosure. 
         FIG.  5    is a schematic diagram of switching a signal transmission path during a period of changing a signal transmission frequency according to an exemplary embodiment of the disclosure. 
         FIG.  6    is a flowchart of a signal transmission method according to an exemplary embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
     A number of exemplary embodiments are presented below to illustrate the disclosure, but the disclosure is not limited to the exemplary embodiments illustrated. Also, appropriate combinations are allowed between the exemplary embodiments. The term “coupling” used in the entire specification (including the claims) of the present application may refer to any direct or indirect connection means. For example, if it is according to the text that a first device is coupled to a second device, it should be interpreted as that the first device may be directly connected to the second device, or the first device may be indirectly connected to the second device through other devices or certain connection means. In addition, the term “signal” may refer to one or more signals of at least one current, voltage, charge, temperature, data, or others. 
       FIG.  1    is a schematic diagram of a signal transmission system according to an exemplary embodiment of the disclosure. Please refer to  FIG.  1   . A signal transmission system  100  includes a retiming circuit module  10 , an upstream device  11 , and a downstream device  12 . The retiming circuit module  10  is adapted to be coupled between the upstream device  11  and the downstream device  12  to perform signal transmission between the upstream device  11  and the downstream device  12  (that is, to send a signal received from the upstream device  11  to the downstream device  12  or to send a signal received from the downstream device  12  to the upstream device  11 ). For example, the retiming circuit module  10  may include a retimer or a circuit module with similar functions. For example, the upstream device  11  and the downstream device  12  may include any electronic components that support the signal transmission function. 
     In an exemplary embodiment, the retiming circuit module  10  may be configured to perform signal processing such as signal buffering, signal resampling, signal serial to parallel (S2P), signal content analysis, signal content modification, and signal retransmission to extend a signal transmission distance between the upstream device  11  and the downstream device  12  and/or improve the signal transmission quality between the upstream device  11  and the downstream device  12 . In addition, the retiming circuit module  10 , the upstream device  11 , and the downstream device  12  may be disposed on one or more circuit boards. 
     The retiming circuit module  10  may include a path control circuit  110  and a multipath signal transmission circuit  120 . The path control circuit  110  is coupled to the multipath signal transmission circuit  120 . The multipath signal transmission circuit  120  may include a signal transmission path (also referred to as a first signal transmission path)  101  and a signal transmission path (also referred to as a second signal transmission path)  102 . The path control circuit  110  may indicate the multipath signal transmission circuit  120  to perform the signal transmission between the upstream device  11  and the downstream device  12  based on one of the signal transmission paths  101  and  102  at different time points. 
     In an exemplary embodiment, the signal delay of the signal transmission path  101  may be higher than the signal delay of the signal transmission path  102 . Therefore, the signal transmission path  101  is also referred to as a long latency path or a data analysis path, and the signal transmission path  102  is also referred to as a short latency path relative to the signal transmission path  101 . In an exemplary embodiment, the signal delay of the signal transmission path  101  is higher than the signal delay of the signal transmission path  102 , which represents that the signal transmission speed of the signal transmission path  101  is lower than the signal transmission speed of the signal transmission path  102 . 
     In an exemplary embodiment, the signal transmission path  101  is a parallel signal transmission path, and the signal transmission path  102  is a serial signal transmission path. For example, the signal transmission path  101  may include multiple parallel signal transmission channels to perform parallel signal transmission. The signal transmission path  102  contains only a single signal transmission channel, and cannot perform the parallel signal transmission. 
     In an exemplary embodiment, the signal transmission paths  101  and  102  are both parallel signal transmission paths. For example, the signal transmission path  101  may include multiple first parallel signal transmission channels, the signal transmission path  102  may include multiple second parallel signal transmission channels, and the signal transmission paths  101  and  102  may both perform the parallel signal transmission. The total number of first parallel signal transmission channels may be the same as or different from the total number of second parallel signal transmission channels. 
       FIG.  2    is a schematic diagram of a retiming circuit module according to an exemplary embodiment of the disclosure. Please refer to  FIG.  1    and  FIG.  2   . The retiming circuit module  10  may include the path control circuit  110 , the multipath signal transmission circuit  120 , a signal receiving circuit  210 , and a signal outputting circuit  220 . The signal receiving circuit  210  is coupled to an input end of the multipath signal transmission circuit  120 . The signal outputting circuit  220  is coupled to an output end of the multipath signal transmission circuit  120 . 
     The signal receiving circuit  210  may receive a signal (also referred to as a first signal) S 1  and output a signal (also referred to as a second signal) S 2 . The signal S 1  may include a signal issued by the upstream device  11  and intended to be sent to the downstream device  12  or a signal issued by the downstream device  12  and intended to be sent to the upstream device  11 . 
     The multipath signal transmission circuit  120  may include a multiplexer circuit  103 . The multiplexer circuit  103  is coupled to the path control circuit  110 , the signal transmission path  101 , the signal transmission path  102 , and the signal outputting circuit  220 . The path control circuit  110  may control the multiplexer circuit  103  to turn on one of the signal transmission paths  101  and  102 . For example, the multiplexer circuit  103  may send a signal (also referred to as a selection signal) SEL to the multiplexer circuit  103 . The multiplexer circuit  103  may turn on the signal transmission path  101  or  102  in response to the signal SEL. The signal transmission path that is turned on may be regarded as a target signal transmission path. For example, assuming that the target signal transmission path is the signal transmission path  101 , at least one signal channel in the signal transmission path  101  may be configured to receive the signal S 2  and output a signal S 3 . Alternatively, assuming that the target signal transmission path is the signal transmission path  102 , at least one signal channel in the signal transmission path  102  may be configured to receive the signal S 2  and output the signal S 3 . 
     The multipath signal transmission circuit  120  may receive the signal S 2  from the signal receiving circuit  210  based on the target signal transmission path and output the signal (also referred to as a third signal) S 3 . For example, the multiplexer circuit  103  may receive the signal S 3  from one of the signal transmission paths  101  and  102  and transmit the signal S 3  to the signal outputting circuit  220 . 
     The signal outputting circuit  220  may receive the signal S 3  from the multipath signal transmission circuit  120  and output a signal (also referred to as a fourth signal) S 4 . For example, assuming that the signal S 1  is issued by the upstream device  11 , the signal S 4  output according to the signal S 1  will be transmitted to the downstream device  12 . Alternatively, assuming that the signal S 1  is issued by the downstream device  12 , the signal S 4  output according to the signal S 1  will be transmitted to the upstream device  11 . 
     In an exemplary embodiment, the total number of circuits (and/or circuit complexity) on the signal transmission path  101  may be higher than the total number of circuits (and/or circuit complexity) on the signal transmission path  102 . Therefore, the signal delay of the signal transmission path  101  may be higher than the signal delay of the signal transmission path  102 . 
     In an exemplary embodiment, a circuit on the signal transmission path  101  may be configured to analyze and adjust the signal transmitted via the signal transmission path  101 . In an exemplary embodiment, a circuit on the signal transmission path  102  may be configured to buffer the signal transmitted via the signal transmission path  102 , but cannot perform the analysis and adjustment of the signal. 
       FIG.  3    is a schematic diagram of a first signal transmission path and a second signal transmission path according to an exemplary embodiment of the disclosure. Please refer to  FIG.  3   . Circuits (also referred to as processing circuits) on the signal transmission path  101  may include an alignment circuit  31 , an elastic buffer  32 , a de-scramble circuit  33 , a de-skew circuit  34 , a data processing circuit  35 , and a scramble circuit  36 . The alignment circuit  31 , the elastic buffer  32 , the de-scramble circuit  33 , the de-skew circuit  34 , the data processing circuit  35 , and the scramble circuit  36  may be coupled to the signal transmission path  101  and configured to analyze and process a signal transmitted via the signal transmission path  101 . That is, the signal S 2  may be analyzed and/or processed, such as performing signal alignment, buffering, de-scrambling, de-skewing, signal content analysis, signal content modification and/or scrambling, by at least one of the circuits  31  to  36  when passing through the signal transmission path  101 . The signal S 3  may be output at an output end of the signal transmission path  101 . In addition, the total number and types of circuits  31  to  36  may be adjusted according to practical requirements, which is not limited in the disclosure. 
     On the other hand, a circuit on the signal transmission path  102  may include a circuit (also referred to as a buffer circuit)  37 . The buffer circuit  37  is coupled to the signal transmission path  102  and is configured to buffer a signal transmitted via the signal transmission path  102 . For example, the signal S 2  may be buffered in the buffer circuit  37  when passing through the signal transmission path  102 , and the signal S 3  may then be output at an output end of the signal transmission path  102 . In addition, the total number and types of circuits  37  may be adjusted according to practical requirements, which is not limited in the disclosure. 
     In an exemplary embodiment, the path control circuit  110  may be coupled to the signal transmission path  101  and send the signal SEL according to the signal transmitted on the signal transmission path  101  to switch the target signal transmission path. For example, the path control circuit  110  may be coupled to an output end of the de-scramble circuit  33  and generate the signal SEL according to an output of the de-scramble circuit  33 . 
     In an exemplary embodiment, the upstream device  11  and the downstream device  12  may transmit a signal to each other based on different signal transmission frequencies (for example, 2.5 GT/s, 8 GT/s, 16 GT/s, and/or 32 GT/s). During a period of changing the signal transmission frequency, the path control circuit  110  may switch the target signal transmission path. 
       FIG.  4    is a schematic diagram of adjusting a signal transmission frequency according to an exemplary embodiment of the disclosure. Please refer to  FIG.  4   . It is assumed that the signal transmission frequency between the upstream device  11  and the downstream device  12  is gradually increased from 2.5 GT/s to 32 GT/s. During periods of changing the signal transmission frequency from 2.5 GT/s to 8 GT/s, from 8 GT/s to 16 GT/s, and from 16 GT/s to 32 GT/s, a signal transmission link between the upstream device  11  and the downstream device  12  may be sequentially in an LO state (that is, a normal data transmission state), a de-scramble state for changing a transmission rate, a de-scramble state for equalizer calibration, an overall de-scramble state, and the LO state after completing link handshake. The LO state and the de-scramble state for changing the transmission rate are operated at a previous signal transmission frequency (for example, 2.5 GT/s), and the de-scramble state for the equalizer calibration, the overall de-scramble state, and the LO state after completing the link handshake are operated at a new signal transmission frequency (for example, 8 GT/s). 
       FIG.  5    is a schematic diagram of switching a signal transmission path during a period of changing a signal transmission frequency according to an exemplary embodiment of the disclosure. Please refer to  FIG.  1   ,  FIG.  2   , and  FIG.  5   . A signal  501  is configured to represent a signal transmitted between the upstream device  11  and the downstream device  12 . During a signal transmission period  510 , the path control circuit  110  may set the target signal transmission path to the low latency signal transmission path  102 . During the signal transmission period  510 , the multipath signal transmission circuit  120  may perform signal transmission (also referred to as first signal transmission) between the upstream device  11  and the downstream device  12  based on a specific signal transmission frequency (also referred to as a first signal transmission frequency) and the signal transmission path  102 . 
     During the period of performing the first signal transmission (that is, the signal transmission period  510 ), the path control circuit  110  may detect a specific data sequence (also referred to as a first data sequence or a first training sequence) TS( 1 ) transmitted between the upstream device  11  and the downstream device  12 . For example, the data sequence TS( 1 ) may carry information indicating the adjustment of the signal transmission frequency. For example, the data sequence TS( 1 ) may contain at least one indicator bit whose bit value is “1” to indicate that the signal transmission frequency between the upstream device  11  and the downstream device  12  will be adjusted. 
     According to the data sequence TS( 1 ), at a time point T( 1 ), the path control circuit  110  may switch the target signal transmission path from the signal transmission path  102  to the signal transmission path  101 . During a signal transmission period  520  after the time point T( 1 ), the multipath signal transmission circuit  120  may perform signal transmission (also referred to as second signal transmission) between the upstream device  11  and the downstream device  12  based on the first signal transmission frequency and the signal transmission path  101 . 
     Thereafter, at a time point T( 2 ), a signal transmission frequency (that is, a signal transmission rate) between the upstream device  11  and the downstream device  12  changes. For example, during the signal transmission period  520 , the upstream device  11  and the downstream device  12  transmit a signal based on a new signal transmission frequency (also referred to as a second signal transmission frequency). The second signal transmission frequency is different from the first signal transmission frequency. For example, assuming that the first signal transmission frequency is 2.5 GT/s, the second signal transmission frequency may be 8 GT/s. During a signal transmission period  530  after the time point T( 2 ), the multipath signal transmission circuit  120  may perform signal transmission (also referred to as third signal transmission) between the upstream device  11  and the downstream device  12  based on the second signal transmission frequency and the signal transmission path  101 . 
     During the third signal transmission period (the signal transmission period  530 ), the path control circuit  110  may detect a specific data sequence (also referred to as a second data sequence or a second training sequence) TS( 2 ) transmitted between the upstream device  11  and the downstream device  12 . For example, the data sequence TS( 2 ) may carry information indicating the completion of the equalizer calibration. For example, the data sequence TS( 2 ) may contain at least one indicator bit whose bit value is “0” to indicate that an equalizer calibration phase between the upstream device  11  and the downstream device  12  has been completed. 
     According to the data sequence TS( 2 ), at a time point T( 3 ), the path control circuit  110  may switch the target signal transmission path from the signal transmission path  101  back to the low latency signal transmission path  102 . During a signal transmission period  540  after the time point T( 3 ), the multipath signal transmission circuit  120  may perform signal transmission (also referred to as fourth signal transmission) between the upstream device  11  and the downstream device  12  based on the second signal transmission frequency and the signal transmission path  102 . So far, a single change operation of the signal transmission frequency (for example, changing the signal transmission frequency from 2.5 GT/s to 8 GT/s, from 8 GT/s to 16 GT/s, or from 16 GT/s to 32 GT/s) between the upstream device  11  and the downstream device  12  has been completed. 
     In an exemplary embodiment, regardless of whether the signal transmission path  101  or  102  is turned on, the circuits (for example, the circuits  31  to  36  in  FIG.  3   ) on the signal transmission path  101  may all continue to be configured to analyze the signal S 2  transmitted via the signal transmission path  101 . In an exemplary embodiment, during the period of performing the first signal transmission (that is, the signal transmission period  510 ), the path control circuit  110  may detect the data sequence TS( 1 ) via the signal transmission path  101 . Similarly, during the period of performing the third signal transmission (that is, the signal transmission period  530 ), the path control circuit  110  may detect the data sequence TS( 2 ) via the signal transmission path  101 . 
     Taking  FIG.  3    as an example, in an exemplary embodiment, the path control circuit  110  may detect the data sequence TS( 1 ) and/or TS( 2 ) according to the signal transmitted on the signal transmission path  101 . For example, the path control circuit  110  may detect the data sequence TS( 1 ) and/or TS( 2 ) according to the output of the de-scramble circuit  33  (for example, analyze the output of the de-scramble circuit  33 ). 
     In an exemplary embodiment, during the period of performing the second signal transmission (that is, the signal transmission period  520 ), the multipath signal transmission circuit  120  may modify a specific data sequence (also referred to as a third data sequence) EQP transmitted via the signal transmission path  101 . Then, the multipath signal transmission circuit  120  may output the modified data sequence EQP via the signal transmission path  101 . For example, the data sequence EQP may carry setting information of an equalizer circuit (for example, setting parameters of the equalizer circuit) at a signal receiving end. For example, assuming that a signal currently in transmission is transmitted from the upstream device  11  to the downstream device  12 , the signal receiving end is the downstream device  12 . Alternatively, assuming that a signal currently in transmission is transmitted from the downstream device  12  to the upstream device  11 , the signal receiving end is the upstream device  11 . For example, the signal receiving end may calibrate the equalizer circuit according to the setting information. For example, in an exemplary embodiment, at least one of the upstream device  11  and the downstream device  12  may set the parameters of the equalizer circuit according to the modified data sequence EQP (or the setting information). 
     Taking  FIG.  3    as an example, in an exemplary embodiment, the data processing circuit  35  may be configured to detect and modify the data sequence EQP transmitted via the signal transmission path  101 . For example, the data processing circuit  35  may capture the data sequence EQP from a signal transmitted by the signal transmission path  101 . According to device information (for example, a device type and/or a device model) of the signal receiving end, the data processing circuit  35  may modify (for example, optimize) the setting information of the equalizer circuit in the captured data sequence EQP. Then, the data processing circuit  35  may send the modified data sequence EQP to the signal receiving end via the signal transmission path  101 . 
     In an exemplary embodiment, compared to the original data sequence EQP, the modified data sequence EQP may contain the setting information of the equalizer circuit that is more compliant with the requirements of the current signal receiving end, thereby effectively improving the efficiency of performing the equalizer calibration at the signal receiving end. For example, assuming that the original data sequence EQP indicates the signal receiving end to perform testing and calibration from a first set of setting parameters of the equalizer circuit, but in fact the optimal setting parameters of the equalizer circuit for the adjusted signal transmission frequency (that is, the second signal transmission frequency) at the signal receiving end are obviously not the first set of setting parameters. Therefore, the modified data sequence EQP may indicate the signal receiving end to start calibrating the equalizer circuit or perform other optimized calibration procedures from an n-th set of setting parameters (where n is greater than 1) (that is, skipping the first set of setting parameters). 
     In addition, in the exemplary embodiment of  FIG.  5   , the target signal transmission path is switched to the signal transmission path  101  early before changing the signal transmission frequency, and calibration parameters of the optimized equalizer circuit may also be provided to the signal receiving end early. In this way, the equalizer calibration efficiency at the signal receiving end can be effectively improved during the period of adjusting the signal transmission frequency. 
     It should be noted that the settings and coupling manner of all circuits in the retiming circuit module  10  mentioned in the above exemplary embodiment are only examples and are not intended to limit the disclosure. In some exemplary embodiments, the settings and coupling manners of all circuits in the retiming circuit module  10  may be adjusted according to practical requirements. In addition, in some exemplary embodiments, more useful circuits and/or electronic components may be added to the retiming circuit module  10  or configured to replace specific circuits and/or electronic components in the retiming circuit module  10 , depending on practical requirements. 
     It should be noted that the retiming circuit module  10  may contain a combination of multiple sets of the path control circuits  110  and the multipath signal transmission circuit  120  to be responsible for processing and transmitting signals in different transmission directions. For example, a combination of one set of the path control circuits  110  and the multipath signal transmission circuit  120  in the retiming circuit module  10  may be responsible for processing and transmitting a signal transmitted from the upstream device  11  to the downstream device  12 , and a combination of another set of the path control circuits  110  and the multipath signal transmission circuit  120  in the retiming circuit module  10  may be responsible for processing and transmitting a signal transmitted from the downstream device  12  to the upstream device  11 . 
       FIG.  6    is a flowchart of a signal transmission method according to an exemplary embodiment of the disclosure. Please refer to  FIG.  6   . In Step S 601 , first signal transmission between an upstream device and a downstream device is performed based on a first signal transmission frequency and a second signal transmission path among multiple signal transmission paths of a retiming circuit module. In Step S 602 , during a period of performing the first signal transmission, a first data sequence transmitted between the upstream device and the downstream device is detected. In Step S 603 , according to the first data sequence, second signal transmission between the upstream device and the downstream device is switched to be performed based on the first signal transmission frequency and a first signal transmission path among the signal transmission paths. 
     It should be noted that each step in  FIG.  6    may be implemented as multiple program codes or circuits, which is not limited in the disclosure. In addition, the method in  FIG.  6    may be used in conjunction with the above exemplary embodiments or may be used alone, which is not limited in the disclosure. 
     In summary, in the exemplary embodiments of the disclosure, the signal transmission path between the upstream device and the downstream device may be switched to the long latency path before actually changing the signal transmission frequency to improve the equalizer calibration efficiency at the signal receiving end. In addition, after completing the equalizer calibration at the signal receiving end, the signal transmission path is quickly switched back to the short latency path. In this way, under the premise of reducing the signal transmission delay as much as possible, the exemplary embodiments of the disclosure can effectively improve the equalizer calibration efficiency at the signal receiving end during the period of adjusting the signal transmission frequency. 
     Although the disclosure has been disclosed in the above embodiments, the embodiments are not intended to limit the disclosure. Persons skilled in the art may make some changes and modifications without departing from the spirit and scope of the disclosure. The protection scope of the disclosure shall be defined by the appended claims.