• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method of characterizing a section of a transmission line, a reference signal being injected into the line and a time measurement (301) of the reflection of said reference signal in the line being performed, said method comprising the following steps: • Apply a deconvolution step (302) to said time measurement so as to generate a deconvolved time sequence comprising a plurality of amplitude peaks each corresponding to an impedance discontinuity, • Eliminate (303), in the amplitude of at least one peak obtained, the contribution of at least one secondary rebound of the signal on an impedance discontinuity, • deducing, from the temporal position of each peak, a position of an associated impedance discontinuity in said line segment • deduce (304), from the amplitude of each peak, an estimate of the real part of the reflection coefficient of a reflected wave on each impedence discontinuity identified.
    公开号:FR3034203A1
    申请号:FR1552628
    申请日:2015-03-27
    公开日:2016-09-30
    发明作者:Josy Cohen；Nicolas Gregis
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    [0001] A method of characterizing a section of a transmission line, in particular a section corresponding to a connector or a series of connectors connecting a measurement equipment to a cable.
    [0002] The present invention relates to the field of systems and diagnostic methods for cable and in particular the field of methods for detecting and / or locating defects impacting a cable. The invention relates more specifically to a method for characterizing a section of a transmission line by modeling 10 in the form of a succession of characteristic impedance sections and clean lengths. In particular, the invention is advantageously applied to characterize a connector or a connector or a succession of connectors connecting a measuring equipment to a cable. The measurement equipment is configured to perform a reflectometry measurement by injecting a reference signal into the cable and by measuring the reflection of this signal on the impedance discontinuities encountered on its path. . The invention finds application in all fields where it is necessary to characterize the mechanical and / or electrical connections between a cable and a measuring apparatus. The invention applies to any type of electrical cable, in particular power transmission cables or communication cables, in fixed or mobile installations. The cables concerned may be coaxial, two-wire, parallel lines, twisted pairs, cable strand or the like. The invention can also be applied to mechanical cables, for example infrastructure support cables such as an elevator or a bridge.
    [0003] According to a known principle, so-called OTDR methods are used to detect and / or locate electrical or mechanical faults 3034203 2 that generate discontinuities or impedance breaks in a cable. These methods use a principle similar to that of the radar: an electrical signal, often of high frequency or wide band, is injected in one or more places of the cable to be tested. The signal propagates in the cable or network and returns some of its energy when it encounters an electrical discontinuity. An electrical discontinuity may result, for example, from a connection, the end of the cable or more generally a break in the conditions of propagation of the signal in the cable. It most often results from a fault which locally modifies the characteristic impedance of the cable by causing a discontinuity in its linear parameters. The analysis of the signals returned to the injection point makes it possible to deduce information on the presence and the location of these discontinuities, thus possible defects. An analysis in the time domain or frequency is usually performed. These methods are designated by the acronyms TDR from the English expression "Time Domain Reflectometry" and FDR from the English expression "Frequency Domain Reflectometry".
    [0004] The measuring apparatus used for injecting the signal into the cable and measuring the reflected signal can take various forms, it can be a network analyzer or an on-board device. The variety of possible measuring devices as well as the diversity of the types of cables to which the characterization of defects by reflectometry can be applied lead to the need to provide many types of connectors or connectors making it possible to connect the different measurement equipment to different types of cables. A connection is indeed necessary to achieve the mechanical and electrical connection between the cable under test and the measuring device.
    [0005] This fitting itself has a characteristic impedance of its own, but this information is not always accessible. For certain types of cables, for example twisted pairs, standard connectors do not exist, especially for network analyzers available at the current date. Sometimes it is necessary to associate several types of connectors in series to ensure a proper connection.
    [0006] The connection of the connector to the meter and to the cable creates an impedance breakage due to the different values of the characteristic impedances of the different elements. The signal injected by the measuring apparatus is thus reflected, even before it enters the cable, on the impedance discontinuity generated by the connector. This phenomenon generates the presence of blind zones in the temporal reflectogram obtained from the measurement of the reflected signal. A blind zone is located in particular at the connector. If a low amplitude defect is present in this zone, its signature on the reflectogram will be masked by the echo of the signal on the impedance discontinuity linked to the connector. Thus, there is a need to precisely characterize the connector (s) that can be used in the frame described above by estimating in particular their equivalent characteristic impedance. From this characterization, it is then possible to eliminate from a reflectogram the known contributions of the connectors to better identify the presence of defects, particularly unprepared faults located in the blind areas. The methods of the prior art which address the problem of blind zones in OTDR generally focus on the separation between the incident signal injected into the cable and the signals reflected on the defects of the cable. We are talking about blind zone reduction. The objective of these methods is not to characterize the nature of the reflections but simply, at constant frequency, to reduce the width of the trace of each contribution to the extent to limit the interactions. To this end, mention may be made of the European patent application EP0623827 or else the article 3034203 4 "Reduction of the blind spot in the time-frequency domain reflectometry", Kwak et al., IEICE Electronics Express 2008. The present invention aims to characterize the connector (s) connecting the measuring equipment to the cable by modeling the portion of the transmission line corresponding to the connector (s) in the form of a succession of constant characteristic impedance sections separated by interfaces corresponding to impedance discontinuities on which the signal is reflected.
    [0007] The invention makes it possible to characterize any connector or more generally any portion of a transmission line. The characteristic impedance values obtained by the method as well as the positions of the impedance discontinuities are stored in a database which allows not only the characterization of a large number of connections but also a follow-up of the evolution of this characterization as a function of time or as a function of physical parameters such as temperature or humidity. The subject of the invention is a method of characterizing a section 20 of a transmission line, a reference signal being injected into the line and a temporal measurement of the reflection of said reference signal in the line being carried out, said method comprising the following steps: - Applying a deconvolution step to said time measurement so as to generate a deconvolved time sequence comprising a plurality of amplitude peaks each corresponding to an impedance discontinuity, - Eliminate, in the amplitude of at least one peak obtained, the contribution of at least one secondary rebound of the signal on an impedance discontinuity, Deduce, from the time position of each peak, a position of an associated impedance discontinuity in said section line, - Deduce, from the amplitude of each peak, an estimate of the real part 5 of the reflection coefficient of a reflected wave on each discontinuity identified impedance. According to a particular aspect of the invention, said section corresponds to a connector or series of connectors connecting a measurement equipment 10 to a cable, the reflection time measurement being taken in a time zone corresponding to the presence zone of the connector or of the series of connectors. According to a particular aspect of the invention, the deconvolution step further comprises linear interpolation and can be performed using a CLEAN algorithm. According to a particular aspect of the invention, the step of eliminating the contribution of at least one secondary rebound comprises the following sub-steps: Identify the peaks located at a time position potentially corresponding to a rebound. Calculate the contribution in amplitude of said rebound, - Subtract the calculated contribution from the amplitude of the peak identified, - If the amplitude obtained is substantially zero, eliminate the peak. According to a particular aspect of the invention, the step of eliminating the contribution of at least one secondary rebound comprises the following sub-steps: - Selecting a first peak and a second peak and measuring their time spacing d, - Search at least a third peak distant from the first peak of a temporal spacing nd multiple of the time spacing d between the first peak and the second peak, - determining an estimate of the real parts of the reflection coefficients associated with the discontinuities of impedance corresponding respectively to the first and second peak, from the amplitudes of the first and second peaks, 5 - determining an estimate of the amplitude of the nth bounce of the signal on the impedance discontinuity corresponding to the second peak, n varying on the values corresponding to the multiple nd of the temporal spacing d at which a third peak has been found, - subtracting the amplitude of the said at least one third peak , the estimate of the amplitude of the nth bounce of the determined signal, n corresponding to the multiple of the temporal spacing d between the first peak and the second peak at which the at least one third peak is located, - If the amplitude obtained is substantially zero, eliminating said at least one third peak. According to a particular aspect of the invention, the step of eliminating the contribution of at least one secondary rebound comprises the following sub-steps: - Selecting a first peak and a second peak and measuring their temporal spacing d, - Determining an estimate of the real parts of the reflection coefficients associated with the impedance discontinuities corresponding respectively to the first and second peaks, from the amplitudes of the first and second peaks, 25 - determining an estimate of the amplitude of the nth bounce of the signal on the impedance discontinuity corresponding to the second peak, n being a nonzero positive integer, - Subtracting the estimate of the amplitude of the nth bounce of the signal from the amplitude of a sample of the deconvolved sequence located at a distance nd multiple of the time spacing d between the first peak and the second peak, According to a particular aspect of the invention, said substeps are iterated and, - the first iteration, the first peak selected is the first peak 5 in the temporal order of appearance, the second peak selected is the second peak in the temporal order of appearance, - and at the following iterations, the second peak selected is the successive peak at the two peaks selected at the previous iteration and the first peak selected is one of the peaks selected at one of the previous 10 iterations. According to a particular aspect of the invention, the estimate of the real part of the reflection coefficient associated with each impedance discontinuity is determined by means of the following relationship: Pi = - 11) .11 (1- (PJ) 2) with A the amplitude of a peak indexed temporally by the integer i, pi the real part of the reflection coefficient of a wave reflected on the impedance discontinuity associated with said peak, pi the real parts of the reflection coefficients of a wave reflected on the impedance discontinuities associated with the preceding peaks said peak. In a particular variant, the method according to the invention further comprises a step of determining an estimate of the real part of the characteristic impedance associated with each transmission line section delimited by two successive impedance discontinuities from corresponding estimates of the real parts of the reflection coefficients associated with said two discontinuities of impedances. In a particular variant, the method according to the invention comprises, in a step of determining an estimate of the imaginary part of 15 A i for i varying from 2 to N, the characteristic impedance associated with each impedance discontinuity at from the real part of said characteristic impedance. In a particular variant, the method according to the invention further comprises the following steps: - Rebuilding an estimate of the signal reflected from the values of the real and imaginary parts of the determined characteristic impedances, - Determining a characteristic information of the degree of similarity 10 between the reconstructed estimate of the signal and the time measurement of the signal reflection. In a particular variant, the method according to the invention further comprises the following steps: - Convolving the time sequence consisting of compensated amplitude peaks of the contribution of at least one secondary rebound with the reference signal, - Determining a information characteristic of the degree of similarity between the convolved sequence and the temporal measurement of the signal reflection.
    [0008] According to a particular aspect of the invention, the characteristic information of the similarity is taken equal to the coefficient of determination R2 or the likelihood coefficient V2. According to a particular aspect of the invention, said method is iterated by modifying at each iteration the number of peaks of amplitude extracted during the deconvolution step, the solution chosen being that which has the highest degree of similarity. In an alternative embodiment, the method according to the invention further comprises a step of supplying a database with the positions and reflection coefficients and / or impedances characteristic of the calculated impedance discontinuities, each input of the The database 3034203 9 is associated with a connector or a set of connectors connected in series for interconnecting a measuring device with a cable. The subject of the invention is also a database comprising a plurality of pairs of values of positions and reflection coefficients and / or impedances characteristic of impedance discontinuities determined by performing the method of characterizing a section of a line. According to the invention, each value pair in the database is indexed by an input associated with a connector or set of connectors connected in series for interconnecting a measuring device with a cable. The invention also relates to a computer program comprising instructions for executing the method of characterizing a section of a transmission line according to the invention, when the program is executed by a processor as well as a recording medium readable by a processor on which is recorded a program comprising instructions for executing the method of characterizing a section of a transmission line according to the invention, when the program is executed by a processor.
    [0009] Other features and advantages of the present invention will become more apparent upon reading the following description in conjunction with the accompanying drawings which show: FIGS. 1a and 1b, a block diagram of a transmission line and FIG. 2, a reflectogram representing the temporal signatures of two types of connectors, FIG. 3, a flowchart detailing the stages of implementation of the method according to the invention, FIG. 4, FIG. a diagram and a diagram illustrating an example of results obtained by application of the invention.
    [0010] FIG. 1 a represents, in a simplified diagram, a cable 101 to be analyzed connected to a measuring device 103 able to generate a signal for injecting it into the cable 101 and to measure the reflection of the signal on the discontinuities of FIG. impedance of the cable. Alternatively the measuring apparatus 103 may be split into two separate apparatuses, a first apparatus for generating and injecting the test signal and a second apparatus for measuring the reflected signal. The meter 103 is connected to the cable 101 through a connector or connector 102. The connector 102 may be comprised of a plurality of connectors connected in series. The connector 102 can be composed of solder connections, dominoes, coaxial connection cables or any other connection means for connecting a measuring equipment to a cable. FIG. 1b shows a temporal reflectogram obtained by a reflectometry measurement made by the measurement apparatus 103. On this reflectogram, there is a first peak 110 which corresponds to the reflection of the signal on the impedance break associated with the connection. 102 and a second peak 111 which corresponds to the reflection of the signal on the impedance break due to the termination of the cable. These two reflection peaks are related to impedance discontinuities corresponding to controlled physical characteristics of the system under test. Depending on the width of the pulse of the transmitted signal, the return pulses located in the zones 110 and 111 may be more or less wide. The primary purpose of a reflectometry test is to detect and locate the presence of defects on the cable 25 to be analyzed. If a fault exists on the cable near the zones 110 and 111, the echo associated with this fault may be masked by the echoes associated with the connector and the termination of the cable. This is why we speak of blind zones to designate the zones 110 and 111. An object of the invention is notably to characterize the portion of line 30 corresponding to the connector 102 and the beginning of the cable 101 in order to be able to correctly model the contribution of a reflection of the signal on this area. This characterization can make it possible to compensate for the echo associated with the connector 102 during a reflectometry test intended to detect unprepared faults in the zone situated just at the beginning of the cable, after the connector 102. In this view, the invention makes it possible to to improve the characterization of 5 defects located in or near the blind zones. The invention also makes it possible to monitor the evolution over time of the characteristics of a connector 102 to identify the influence of aging or of certain physical parameters such as temperature, pressure or humidity.
    [0011] An electric cable serves to convey an electromagnetic wave which can generally be broken down into two main components: a voltage wave (V) and a current wave (I). If we consider a homogeneous cable over its entire length, there is a simple relation between these two components V (w) = Zc (w) * 1 (w), w is the frequency, a frequency-uniform magnitude. Zc is the characteristic impedance of the cable. This quantity, expressed in ohms, is complex and depends on the frequency. However, this magnitude is decisive in the energy exchanges between the cable and the systems connected to its ends. Indeed, to ensure the transfer of the maximum energy from one system to another, it is necessary to minimize the differences between the input or output impedances of the cable and its characteristic impedance Zc. When this is not the case, we observe what is called an impedance mismatch as well as a reflected wave at the interface between the two systems. This principle is valid irrespective of the position of the impedance break in the cable, may be due to cable faults and is the founding principle of OTDR. In general, an impedance mismatch between a cable and a measuring apparatus results from the difference between the connected geometrical shapes and the nature of the materials used. The associated impedance variation is progressive and not localized and therefore complex to describe. For example, it is understood that the connection between a network analyzer with an SMA output and a twisted pair whose spacing between the strands is not constant can not be described by the play of a single intermediate impedance. However, it is possible, given the size of the connection elements and the working frequency, to provide a discrete model with more or fewer interfaces. At each of these interfaces, we associate a reflection coefficient pi in voltage (or in current if we work in current) that we define in the following way: pi (w) = zi + 1 (6)) zi (6) ) (0) zi + 1 (60) + zi (60) with Z1 and Z2 the characteristic impedances of the line sections 10 located respectively on either side of the interface. There is a perfect duality between the characteristic impedances and the reflection coefficients. The characteristic impedances describe the waveguide sections, while the reflection coefficients describe the links or interfaces between these sections.
    [0012] Under certain conditions it is possible to describe the behavior of a complex mismatch such as the succession of several waveguide sections of varying sizes and characteristic impedances, as well as for the speed of propagation and attenuation in these areas. sections. Thus, for a given maximum working frequency, each piece of the mismatch can be mathematically described by the doublet (y (f), Zc (p) where y (f) contains the attenuation and the velocity of the wave in the The combination of these sections forms what will be called an equivalent mismatch, which is supposed to describe as closely as possible the behavior of the actual mismatch at the study frequencies.From a point of view of the reflectogram, the mismatch results in the reflection at several points of the incident wave, which from the temporal point of view is transcribed by a more or less rapid succession of peaks, while in frequency, we will see oscillations of greater or lesser amplitude and period It is, moreover, the study of these traces that makes it possible to go back to the equivalent mismatch Finally, the mismatch is a function of the physical nature of the connection between the cable and the systems. It can therefore, for the same system and the same cable, be different depending on the connection mode.
    [0013] FIG. 2 illustrates this phenomenon on a reflectogram which comprises two curves 201, 202. The first curve 201 corresponds to a mismatch between a coaxial cable and a twisted pair interconnected by a domino. The second curve 202 always corresponds to a connection between a coaxial cable and a twisted pair but this time connected by a solder. Note that the nature of the connector influences very clearly the pace of the mismatch as represented by the echoes 201,202. Actual mismatch has a frequency-independent configuration (although its response varies with frequency), but some details of its composition have a more or less noticeable influence depending on whether one works at high or low frequency. It is well understood, for example, that certain imperfections in a weld which are of the order of a tenth of a millimeter have a visible influence only at very high frequency. This is why the configuration of the equivalent mismatch will change according to the study bandwidth. It will only consider major contributions and will therefore become increasingly complex as the maximum study frequency increases. The invention is based on modeling each equivalent mismatch in a succession of characteristic impedance and clean length sections. The attenuation of the signal is neglected because we consider weak lengths, which are of the order of the average length of a connector. From this model, it is possible to represent the transfer function H (f) of a transmission line as a function of frequency by the following formula: ## EQU1 ## .e -2 * j * Tuf * ti Xrebonds (1) i = 2 I1J = 1 According to relation (1), the number of distinct characteristic impedance sections is equal to N + 1. N is the number of interfaces 5 between two sections on which the signal can be reflected. ti is the length of the ith section. pi is the real part of the reflection coefficient of the signal on the interface between the i th section and the (i + 1) è "section Xrebonds is a term that depends on the multiple bounces of the signal on the different interfaces. t) reflected by reflectometry is modeled by the relation s (t) = Si (t) * Rimp (t) where Si is the injection signal and Rimp is the impulse response of the cable which is equal to the inverse frequency transform of the transfer function H (f) To characterize a mismatch modeled using relation (1), this amounts to finding the values of the real parts of the reflection coefficients pi and the lengths of sections ti. The method according to the invention for characterizing an equivalent mismatch from the modeling given by relation (1) is now described in detail in Figure 3. Figure 3 details the various steps of this process. a reflectometry measurement 301, preferably a time measurement, performed by a measuring apparatus 103 on a cable 101. When the invention applies for the characterization of a blind zone corresponding to the connection zone between the measurement 103 and the cable 101, in a preliminary step of the method, the measurement portion 301 corresponding to the blind zone or to a mismatch that one wishes to characterize is selected. In order for the negligible attenuation hypothesis to be valid, the selected measurement portion 30 must have a maximum duration. A measurement portion of duration corresponding to four times the width halfway up the pulse of the signal injected into the cable makes it possible, for example, to ensure a good compromise between a sufficient measurement time and a low attenuation of the signal. signal on this duration. According to a first step of the method according to the invention, a deconvolution 302 is applied to the measurement or measurement portion 301. The purpose of the deconvolution step 302 is to remove, from the measurement 301, the contribution of the signal injected in order to obtain a sequence comprising a set of amplitude peaks which correspond to the response of the propagation channel in which the signal propagates. Each peak is identified by its temporal position and amplitude. The deconvolution step may, for example, be performed by a deconvolution algorithm known as the CLEAN algorithm or any other equivalent algorithm. According to an alternative embodiment of the invention, the deconvolution algorithm can be coupled to an additional linear interpolation step in order to improve the accuracy of the temporal positioning of the peaks which is limited by the sampling resolution of the measuring device. The peak sequence obtained at the end of the deconvolution step 302 is intended to provide a representation of the impedance mismatch in the measurement zone. More precisely, and as explained upstream of the present text, the equivalent impedance mismatch can be modeled by a succession of sections each having a constant characteristic impedance along the length of the section, two consecutive segments being separated by an interface corresponding to a rupture. or an impedance discontinuity on which a portion of the injected signal can be reflected. The amplitude Ai of each peak is connected to the value of the real part of the reflection coefficient pi of the signal on the time index interface i which corresponds to the ith peak of the sequence and to the values of the real parts of the coefficients of reflection pi interfaces corresponding to the peaks prior to the ith peak, by the following relation: 3034203 16 P1 = Ai (2) Ai Vi E [2, N], pi = nT = 11 (1- (PJ) 2) The sequence of peaks obtained at the output of step 302 thus gives a first approximation of the equivalent mismatch according to the above-mentioned modeling. However, as indicated by the relation (1), the amplitude Ai of each peak also consists, in whole or in part, of the contributions of secondary reflections or rebounds of the signal on the interfaces. Secondary rebound of the signal is referred to as multiple reflections of the signal on an interface, i.e., reflections occurring after the first reflection. A second step 303 of the method is therefore applied to the sequence of peaks resulting from the deconvolution step 302 to eliminate, on each amplitude Ah, the contribution of the secondary rebounds of the signal.
    [0014] According to a particular embodiment of the invention, step 303 may consist of the following substeps. First, it is to identify the peaks located at a time position that potentially corresponds to an echo resulting from a multiple reflection of the signal on an interface. Then, for these identified peaks, the contribution in amplitude of a multiple reflection is calculated, and then this contribution is subtracted from the amplitude of said identified peak. If the resulting amplitude after the subtraction is substantially zero, this peak is eliminated which corresponds entirely to a secondary reflection of the signal. More specifically, step 303 of the method according to the invention can be carried out using the following algorithm. In a first iteration of the method, the first two peaks of the deconvolved sequence are selected. It is known that these first two peaks correspond to interfaces on which no multiple bounce of the signal has occurred. The temporal spacing between these two peaks is measured, and then, in the sequence, the peaks located at positions are searched. temporal multiples of the temporal distance between the first two peaks. In other words, if we note the time distance between the first two selected peaks, we look for the peaks located at distances nd from the first peak, where n is a positive integer. Indeed, it is known that secondary reflections only appear at these positions. From the relation (2) and the amplitudes of the first two selected peaks, it is possible to calculate the real parts of the reflection coefficients pi and pi associated with the interfaces corresponding to these two first peaks. Then, the following relation (3) makes it possible to determine the amplitude of the nth signal bounce on the interface i: Vi E [1: 1 1], Vj E [1: I 1], Vn E 11: = (-1) npr * prl * FIL Tk (3) piest the real part of the reflection coefficient on the interface i pi is the real part of the reflection coefficient on the interface j is the amplitude of the nth rebound between the Interface i and j Test the real part of the transmission coefficient on the interface k The value of the amplitude of the nth rebound is then subtracted from the amplitudes of the peaks detected at the time positions nd. In other words, for a given value of n for which a peak has been detected at the position nd, the value Rrui is subtracted from its amplitude.
    [0015] If the result of the subtraction is substantially zero, the associated peak is eliminated from the sequence because it corresponds entirely to a multiple reflection of the signal. This test can be performed by comparing the compensated amplitude to a threshold below which the amplitude is considered zero. In an alternative embodiment, the Riui value of the amplitude of the nth rebound is subtracted from the samples of the sequence located at all the time positions nd, even those at which no peak is detected. The parameter n equal to the number of reflections of the signal on an interface is an adjustable parameter of the process.
    [0016] The process described above can be reiterated for all the peaks of the sequence by modifying each time the first two selected peaks for which the Riui value of the amplitude of the nth rebound is calculated. More precisely, at each iteration, the following pairs of peaks, identified by their order number, are selected: {1; 2}, {1; 3}, {2; 3}, {1; 4}, {2; 4}, {3; 4} and so on. In other words, at each new iteration, the peak at the two peaks selected at the previous iteration is selected as the second peak and, as the first peak, one of the peaks selected at one of the preceding iterations by varying the first peak on all peaks selected at previous iterations.
    [0017] At the end of step 303 of the method according to the invention, a corrected sequence is obtained which contains only peaks whose amplitude is characteristic of a single reflection of the signal on the corresponding interface. The actual portions of the reflection coefficients can then be calculated from the amplitudes of each peak according to equation (2). The temporal positions of the peaks give the real positions of the interfaces according to the modeling considered and according to a principle well known in the field of OTDR which makes it possible to convert time measurements on a reflectogram into distances.
    [0018] From the real parts of the reflection coefficients, it is possible to deduce therefrom the real parts of the characteristic impedances of each section delimited by two successive interfaces by means of the relation (0).
    [0019] In an alternative embodiment of the invention, an additional step 306 is performed consisting of determining information indicative of the degree of similarity between an estimate of the reconstructed reflected signal from the amplitude peak sequence obtained at the same time. from step 303 and measurement 301. To reconstruct an estimate of the reflected signal, one possibility is to convolve the sequence composed of the amplitude peaks retained in step 303 with the reference signal initially injected into the cable. The reconstructed estimate is then compared with the measure 301, for example a point-to-point difference between the two signals is performed or any other calculation to represent the difference between the two signals.
    [0020] In another alternative embodiment of the invention, it is possible to calculate the imaginary part of the characteristic impedances in addition to the real parts determined in step 305. One possible method for this is to apply the teaching of the request for French patent filed in the name of the Applicant under filing number FR1457980.
    [0021] By having both real and imaginary parts of the characteristic impedances, the signal reflected in the cable can be reconstructed for example using a known method of the ABCD method type as described, for example, in the article "Whatever the method chosen to reconstruct an estimate of the signal reflected in the cable at the end of the spectrum." From the modeling parameters obtained using the method according to the invention, it is envisaged, in another variant embodiment, to iterate all the steps of the method several times by modifying at each iteration one or more parameters of the invention. deconvolution algorithm used in step 302. For example, it is possible to modify the number of peaks generated by the deconvolution algorithm at each iteration. At the end of all the iterations, the solution chosen is that which makes it possible to obtain the highest degree of similarity between the reconstructed measurement and the initial measurement 301.
    [0022] By way of example, the characteristic information of the degree of similarity can be taken equal to the coefficient of determination R2 or the likelihood coefficient V2.
    [0023] FIG. 4 illustrates an example of results obtained by applying the method according to the invention. At the top of FIG. 4 is shown a temporal reflectogram 401 obtained for the study of a two-wire cable connected to a network analyzer having a 50 ohm output by a coaxial cable of 50 ohms of 10 25 cm and a "domino" . The injected signal is a pulse width equal to 0.22 ns. In the upper diagram of FIG. 4 is also represented the reconstruction 402 of the measurement 401 obtained by the method according to the invention. At the bottom of FIG. 4 is a diagram illustrating the splitting into sections of characteristic lengths and impedances identified in the figure. We find well the detail of the connection with the first 28 centimeters corresponding to the coaxial cable 50 ohms then the details of the domino and the configuration change of the two-wire cable.
    [0024] According to one possible application of the method according to the invention, the latter furthermore comprises a step of supplying a database with the positions and reflection coefficients and / or impedances characteristic of the calculated impedance discontinuities, each input the database being associated with a connector or set of connectors mounted in series for interconnecting a meter with a cable. Such a database makes it possible to gather information on a large number of different connectors and to allow a follow-up of the evolution of the characteristics of these connectors in time but also a follow-up of their evolution as a function of certain physical parameters such as temperature, humidity or any other parameter that could impact the characteristic impedance of the equivalent mismatch. The method according to the invention can be implemented from hardware and / or software elements. The method according to the invention can be implemented directly by a processor embedded in the measurement equipment 103 or in a specific device. The processor may be a generic processor, a specific processor, an application-specific integrated circuit (also known as ASIC for Application-Specific Integrated Circuit) or a network of programmable gates in situ (also known as under the English name of FPGA for "Field-Programmable Gate Array"). The device according to the invention can use one or more dedicated electronic circuits or a general purpose circuit. The technique of the invention can be carried out on a reprogrammable calculation machine (a processor or a microcontroller for example) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of doors as an FPGA or an ASIC, or any other hardware module).
    [0025] The invention can also be implemented exclusively as a computer program, the method then being applied to a previously acquired reflectometry measurement using a conventional reflectometry device. In such a case, the invention can be implemented as a computer program including instructions for executing it. The computer program can be recorded on a processor-readable recording medium. The support can be electronic, magnetic, optical or electromagnetic. The reference to a computer program which, when executed, performs any of the functions described above, is not limited to an application program running on a single host computer.
    [0026] On the contrary, the terms computer program and software are used herein in a general sense to refer to any type of computer code (eg, application software, firmware, microcode, or any other form computer instruction) which can be used to program one or more processors to implement aspects of the techniques described herein. The means or computer resources can be distributed ("cloud computing"), possibly using peer-to-peer technologies. The software code can be executed on any suitable processor (for example, a microprocessor) or processor core or set of processors, whether provided in a single computing device or distributed among a plurality of computing devices ( for example as possibly accessible in the environment of the device). The executable code of each program enabling the programmable device to implement the processes according to the invention can be stored, for example, in the hard disk or in read-only memory. In general, the program or programs may be loaded into one of the storage means of the device before being executed. The central unit can control and direct the execution of instructions or portions of software code of the program or programs according to the invention, instructions which are stored in the hard disk or in the ROM or in the other storage elements mentioned above. . The invention may also comprise a database fed by the data obtained by the execution of the method described in FIG.
    权利要求:
    Claims (18)
    [0001]
    REVENDICATIONS1. A method of characterizing a section of a transmission line, a reference signal being injected into the line and a time measurement (301) of the reflection of said reference signal in the line being performed, said method comprising the following steps: - Apply a deconvolution step (302) to said time measurement so as to generate a deconvolved time sequence comprising a plurality of amplitude peaks each corresponding to an impedance discontinuity, - Eliminate (303), in the amplitude of at least one peak obtained, the contribution of at least one secondary rebound of the signal on an impedance discontinuity, - deducing, from the temporal position of each peak, a position of an associated impedance discontinuity in said line segment - Deduce (304), from the amplitude of each peak, an estimate of the real part of the reflection coefficient of a reflected wave on each impedance discontinuity ntifiée.
    [0002]
    2. A method of characterizing a portion of a transmission line according to claim 1 wherein said section corresponds to a connector (102) or a series of connectors connecting a measuring equipment (103) to a cable (101), the reflection time measurement being taken in a time zone corresponding to the presence zone of the connector or the series of connectors.
    [0003]
    3. A method of characterizing a section of a transmission line according to one of the preceding claims wherein the deconvolution step (302) further comprises a linear interpolation. 3034203 2
    [0004]
    4. A method of characterizing a section of a transmission line according to one of the preceding claims wherein the deconvolution step (302) is performed using a CLEAN type algorithm. 5
    [0005]
    5. A method of characterizing a portion of a transmission line according to one of the preceding claims wherein the step (303) of eliminating the contribution of at least one secondary rebound comprises the following substeps: - Identify the peaks located at a time position corresponding potentially to a rebound, - Calculate the amplitude contribution of said rebound, - Subtract the calculated peak amplitude from the peak amplitude, - If the amplitude obtained is substantially zero, eliminate the peak . 15
    [0006]
    A method of characterizing a portion of a transmission line according to claim 5 wherein the step (303) of removing the contribution of at least one secondary rebound comprises the following substeps: 20 - Selecting a first peak and a second peak and measure their temporal spacing d, - search for at least a third peak distant from the first peak of a temporal spacing nd multiple of the temporal spacing d between the first peak and the second peak, 25 - determine a estimating real parts of the reflection coefficients associated with the impedance discontinuities corresponding respectively to the first and second peak, from the amplitudes of the first and second peaks, - determining an estimate of the amplitude of the nth bounce of the signal 30 on the impedance discontinuity corresponding to the second peak, n varying over the values corresponding to the multiple nd of the time spacing d at which a third peak, 3034203 3 - Subtract from the amplitude of said at least one third peak, the estimate of the amplitude of the nth rebound of the determined signal, n corresponding to the multiple of the time spacing d between the first peak and the second peak at which said at least one third peak is located; if the amplitude obtained is substantially zero, eliminating said at least one third peak.
    [0007]
    7. A method of characterizing a section of a transmission line according to claim 5 wherein the step (303) of eliminating the contribution of at least one secondary rebound comprises the following substeps: - Select a first peak and a second peak and measure their time spacing d, 15 - Determine an estimate of the real parts of the reflection coefficients associated with the impedance discontinuities corresponding respectively to the first and second peak, from the amplitudes of the first and second peaks - Determining an estimate of the amplitude of the nth bounce of the signal 20 on the impedance discontinuity corresponding to the second peak, n being a nonzero positive integer, - Subtracting the estimate of the amplitude of the nth bounce of the signal from the amplitude of a sample of the deconvolved sequence located at a distance nd multiple of the time spacing d between the first peak and the second peak,
    [0008]
    8. A method of characterizing a section of a transmission line according to one of claims 6 or 7 wherein said substeps are iterated and, 3034203 4 - at the first iteration, the first peak selected is the first peak in the temporal order of appearance, the second peak selected is the second peak in the temporal order of appearance, - and at the following iterations, the second peak selected is the peak 5 in succession to the two peaks selected at the previous iteration and the first peak selected is one of the peaks selected at one of the previous iterations.
    [0009]
    9. A method of characterizing a portion of a transmission line according to one of the preceding claims wherein the estimate of the real part of the reflection coefficient associated with each impedance discontinuity is determined using the following relation: P1 = A1 Ai Pi = - for i varying from 2 to N, with A the amplitude of a peak indexed temporally by the integer i, pi the real part of the reflection coefficient of a wave reflected on the impedance discontinuity associated with said peak, pi the real parts of the reflection coefficients of a wave reflected on the impedance discontinuities associated with the preceding peaks said peak. 20
    [0010]
    10. A method of characterizing a section of a transmission line according to one of the preceding claims further comprising a step (305) for determining an estimate of the real part of the characteristic impedance associated with each section of the transmission. transmission line delimited by two successive impedance discontinuities from the corresponding estimates of the real parts of the reflection coefficients associated with said two impedance discontinuities.
    [0011]
    11. A method of characterizing a portion of a transmission line according to claim 10, further comprising a step of determining an estimate of the imaginary portion of the characteristic impedance 3034203 associated with each impedance discontinuity at from the real part of said characteristic impedance.
    [0012]
    12. A method of characterizing a section of a transmission line according to claim 11, further comprising the following steps: reconstructing an estimate of the signal reflected from the values of the real and imaginary parts of the determined characteristic impedances, (306) information indicative of the degree of similarity between the reconstructed estimate of the signal and the time measurement of signal reflection.
    [0013]
    13. A method of characterizing a section of a transmission line according to one of claims 1 to 10 further comprising the following steps: - Convolute the time sequence consists compensated amplitude peaks of the contribution of minus a secondary rebound with the reference signal, - Determine (306) information characteristic of the degree of similarity between the convolved sequence and the time measurement of signal reflection.
    [0014]
    14. A method of characterizing a section of a transmission line according to one of claims 12 or 13 wherein the characteristic information of the similarity is taken equal to the coefficient of determination R2 or the likelihood coefficient V2.
    [0015]
    15. A method of characterizing a section of a transmission line according to one of claims 12 to 14 wherein said method is iterated by modifying at each iteration the number of peaks of amplitude extracted during 3034203 6 step of deconvolution, the solution chosen being the one with the highest degree of similarity.
    [0016]
    16. A method of characterizing a section of a transmission line according to one of the preceding claims further comprising a step of supplying a database with the positions and reflection coefficients and / or impedances characteristics of Calculated impedance discontinuities, each database entry being associated with a series-mounted connector or set of connectors for interconnecting a meter with a cable.
    [0017]
    17. A computer program comprising instructions for performing the method of characterizing a section of a transmission line according to one of claims 1 to 16, when the program is executed by a processor.
    [0018]
    18. A processor-readable recording medium on which is recorded a program comprising instructions for performing the method of characterizing a section of a transmission line according to one of claims 1 to 16, when the program is executed by a processor.
    类似技术:
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    FR3034203A1|2016-09-30|METHOD FOR CHARACTERIZING A TRUNK OF A TRANSMISSION LINE, ESPECIALLY A TRUNK CORRESPONDING TO A CONNECTOR OR A SERIES OF CONNECTORS CONNECTING A MEASURING EQUIPMENT TO A CABLE
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    同族专利:
    公开号 | 公开日
    EP3274731A1|2018-01-31|
    US20180059164A1|2018-03-01|
    FR3034203B1|2018-07-13|
    US10598719B2|2020-03-24|
    WO2016156259A1|2016-10-06|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1552628|2015-03-27|
    FR1552628A|FR3034203B1|2015-03-27|2015-03-27|METHOD FOR CHARACTERIZING A TRUNK OF A TRANSMISSION LINE, ESPECIALLY A TRUNK CORRESPONDING TO A CONNECTOR OR A SERIES OF CONNECTORS CONNECTING A MEASURING EQUIPMENT TO A CABLE|FR1552628A| FR3034203B1|2015-03-27|2015-03-27|METHOD FOR CHARACTERIZING A TRUNK OF A TRANSMISSION LINE, ESPECIALLY A TRUNK CORRESPONDING TO A CONNECTOR OR A SERIES OF CONNECTORS CONNECTING A MEASURING EQUIPMENT TO A CABLE|
    US15/560,477| US10598719B2|2015-03-27|2016-03-25|Method of characterizing a section of a transmission line, in particular section corresponding to a connector or series of connectors linking a measurement apparatus to a cable|
    EP16714816.2A| EP3274731A1|2015-03-27|2016-03-25|Method of characterizing a section of a transmission line, in particular section corresponding to a connector or series of connectors linking a measurement apparatus to a cable|
    PCT/EP2016/056692| WO2016156259A1|2015-03-27|2016-03-25|Method of characterizing a section of a transmission line, in particular section corresponding to a connector or series of connectors linking a measurement apparatus to a cable|
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