Transmission line diagnostics

Abstract

A method for characterizing a cable or transmission line is provided, comprising: obtaining a first echo response using time-domain reflectometry; coupling a first end of the cable or transmission line to a time-domain reflectometer; Obtaining a second echo response using time domain reflectometry; determining a characteristic of the cable or transmission line by comparing the first echo response and the second echo response.

Description

Technical field

[0001] The present disclosure relates to the characterization of cables or transmission lines and in particular to a method for characterizing the properties of a cable or transmission line. background

[0002] Cables or transmission lines, such as Ethernet cables, are used in a wide variety of applications and locations. A number of different technical standards define communication using these cables or transmission lines and set limits or ranges for the properties or characteristics of cables or transmission lines that can be used in accordance with those technical standards.

[0003] The increased communication speed and quality provided by some standards, such as IEEE 802.3cg, which includes the definition of 10BASE-T1L, creates a greater need to guarantee high-quality transmission lines. Cables or transmission lines can be characterized during manufacturing using a vector network analyzer. For example, the cable's impedance, insertion loss, and echo attenuation can be tested as part of a quality assurance process before it is shipped to a customer. However, once a cable has been deployed, it is uncommon for an installer or field service technician to characterize it due to the size and cost of vector network analyzers.

[0004] It is desirable to allow characterization of a cable using a compact, accurate system once it has been deployed. Brief description

[0005] A method for determining a characteristic of a cable or transmission line is provided. The method involves the following steps: obtaining one or more echo responses of the cable or transmission line using time-domain reflectometry; and comparing the frequency-domain characteristics of the one or more echo responses to determine the impedance, insertion loss, or echo attenuation of the cable or transmission line. By performing this, cable characteristics can be efficiently determined before and after commissioning.

[0006] According to a first aspect of the disclosure, a method for characterizing a cable or transmission line is provided, the method comprising: obtaining a first echo response using time-domain reflectometry; coupling a first end of the cable or transmission line to a time-domain reflectometer; obtaining a second echo response using time-domain reflectometry; determining a characteristic of the cable or transmission line by comparing the first echo response and the second echo response.

[0007] According to a second aspect of the disclosure, a method for characterizing a cable or transmission line is provided, the method comprising: obtaining a first echo response using time-domain reflectometry from a first end of a cable or transmission line using a first time-domain reflectometer, while a second end of the cable is coupled to a second time-domain reflectometer; obtaining a second echo response using time-domain reflectometry from the second end of the cable or transmission line, while the first end of the cable or transmission line is coupled to the first time-domain reflectometer; identifying a first complete reflection in the first echo response, wherein the first reflection corresponds to an impedance mismatch between the first time-domain reflectometer and the cable or transmission line;Identifying a second complete reflection in the second echo response, where the second complete reflection corresponds to an impedance mismatch between the cable or transmission line and the first time-domain reflectometer coupled to the first end of the cable; determining a ratio of a Fast Fourier transform of the first complete reflection within the first echo response to a Fast Fourier transform of the second complete reflection within the second echo response; performing a logarithmic transformation of the ratio to determine the insertion loss of the cable in decibels.

[0008] According to a third aspect of the disclosure, a method for characterizing a cable or transmission line is provided, the method comprising: obtaining a first echo response from a time-domain reflectometer using time-domain reflectometry; coupling a first end of the cable or transmission line to a time-domain reflectometer; obtaining a second echo response of the cable or transmission line using time-domain reflectometry; determining an echo attenuation of the cable or transmission line by comparing the first echo response and the second echo response. Brief description of the drawings

[0009] Aspects of the revelation will now be described only by way of examples and with reference to the accompanying drawings, whereby identical reference numbers refer to identical parts and whereby the following applies: Fig. Figure 1 is a schematic representation of a time-domain reflectometry system; Fig. Figure 2 is a schematic representation of a time domain reflectometry system coupled to a cable or transmission line; Fig. Figure 3 is a schematic representation of a time domain reflectometry system coupled to a cable or transmission line, with the second end of the cable coupled to a device; Fig. Figure 4 shows a flowchart of a procedure for determining a characteristic of a cable or transmission line; Fig. Figure 5a shows a flowchart of a procedure for determining the echo attenuation and impedance of a cable or transmission line; Fig. Figure 5b shows a flowchart of a procedure for determining echo attenuation while reducing the effects of a non-ideal time-domain reflectometer; Fig. Figure 6 is a graph showing a comparison of echo attenuation determined using a vector analyzer and a time-domain reflectometry method; Fig. Figure 7 is a graph showing a comparison of impedance determined using a vector analyzer and a time domain reflectometry method; Fig. Figure 8a shows a flowchart of a procedure for determining the insertion loss of a cable or transmission line; Fig. Figure 8b is a graph showing a comparison of insertion loss determined using a vector analyzer and a time-domain reflectometry method; Fig. Figure 8c shows a flowchart of a procedure for determining the echo attenuation of a cable or transmission line using alternative echo responses; Fig. Figure 9 is a graph showing an initial echo response obtained while the time domain reflectometer is disconnected from the cable or transmission line; Fig. Figure 10a is a graph showing a second echo response received while the second end of the cable or transmission line is open or disconnected; Fig. Figure 10b is a flowchart of a procedure for reducing spectral leakage by fitting a polynomial to the start and / or end of the sampling window; Fig. 10c is a graph of an echo response with selected samples and a polynomial fit; Fig. 10d is a subsection of the graph of Fig. 10c; Fig. Figure 11 is a flowchart of a procedure for determining the insertion loss of the cable or transmission line; Fig. Figure 12 is a flowchart of a procedure for tracking cable deterioration by monitoring the characteristics of the cable or transmission line 104 over time; Fig. Figure 13 is a schematic representation of a time-domain reflectometry system that has a trimmable output impedance; Fig. Figure 14 is a flowchart of a procedure for determining the echo attenuation of the time domain reflectometer or of a transceiver incorporating the time domain reflectometer. Detailed description

[0010] Cables or transmission lines can be used in communication systems to enable data to be transmitted between a sender or transceiver and a receiver or transceiver. Ethernet cables, for example, are commonly used in both residential and industrial environments.

[0011] Cables and transmission lines can be manufactured to varying quality standards and exhibit different characteristics depending on their intended use. For example, some cables or transmission lines can allow communication over distances exceeding 100 meters before the transmitted signal degrades to such an extent that it cannot be recovered. Other cables or transmission lines can allow communication over distances of 1000 meters or more before signal degradation occurs. Different cables can also have different characteristics that allow the use of different communication protocols with varying bandwidths. The bandwidth of a cable is a measure of how much data can be transmitted within a given period of time.

[0012] Each of the different cables or transmission lines can have a number of characteristics specified by the manufacturer, such as insertion loss, echo attenuation, and impedance. Manufacturers may test cables as part of quality assurance during production to ensure that these characteristics fall within acceptable limits. Equipment such as a vector network analyzer can be used as part of the testing process.

[0013] Vector network analyzers are large, expensive pieces of equipment and can be difficult to use without proper training. Both ends of the cable must be connected to the vector network analyzer in a laboratory setting to determine the cable characteristics. In many environments, these characteristics may never be tested again after a cable has been manufactured, due to the cost and impracticality of using a vector analyzer outside of a laboratory.

[0014] Many buildings have a number of historically installed cables that may be suitable for reuse with a more modern communication protocol. Furthermore, it is typical for only one end of the cable to be in an accessible position. The ability to easily determine the characteristics of these cables can allow for their reuse. This reduces the need to dispose of and replace the historical cables, further reducing the costs of upgrading building communication systems.

[0015] A time domain reflectometer (TDR) sends an initial signal along a cable or transmission line and receives an echo response that exhibits a series of reflections. These reflections can be caused by impedance mismatches along the cable or transmission line, for example, due to changes in impedance at the start and end of the cable or transmission line.

[0016] Time-domain reflectometers may be included in some communication systems, such as within an integrated circuit that is part of a transceiver (a system capable of sending and receiving communications). Using a time-domain reflectometer to determine cable or transmission line characteristics can allow for regular or periodic testing of cable characteristics and the reuse of historically installed cables.

[0017] Echo responses can be obtained while the time-domain reflectometer and cable are coupled in different configurations, for example, while the time-domain reflectometer system is decoupled from a cable or transmission line, and while the time-domain reflectometer is coupled to a cable or transmission line. Furthermore, the termination of the time-domain reflectometer ends can be modified. Obtaining and comparing a series of echo responses using the time-domain reflectometer allows the characteristics of the cable or transmission line to be determined.

[0018] Fig. Figure 1 is a schematic representation of a time-domain reflectometry system 100. The system 100 includes a time-domain reflectometer 102. The time-domain reflectometer 102 is configured to send or output a transmission signal to a pair of output terminals 110 of the system and to receive an echo response or a reflected signal. The time-domain reflectometer 102 can send any suitable transmission signal, such as a pseudorandom sequence of transmission symbols. The time-domain reflectometer 102 is coupled to a control system 106. The time-domain reflectometer provides the received echo response to the control system 106.

[0019] The time-domain reflectometer 102 and the control system 106 can be implemented separately or as part of a larger communication transceiver system. For example, the time-domain reflectometer 102 can be integrated into the transceiver.

[0020] The time domain reflectometer 102 from Fig. 1 Echo responses obtained or any obtained by a time domain reflectometer or a transceiver capable of time domain reflectometry can be obtained by sending a pseudorandom sequence of transmission symbols or some other type of signal, with a spectral power density that includes the frequency range of interest for a given communications standard or transceiver specification.

[0021] Where the time-domain reflectometer 102 forms part of the larger transceiver or communication system, it is desirable to understand the characteristics of the cable or transmission line 104 for the specific communication system. This can be achieved by sending a pseudorandom sequence of transmission symbols with a spectral power density that lies within the frequency range of interest to the communication system. The frequency range of interest to the communication system may be the frequency range or spectrum within which the communication system or transceiver transmits data during communication.

[0022] Fig. Figure 2 is a schematic representation of the time-domain reflectometry system 100, which is coupled to the output terminals 110 of the system 100 via the first end of a cable or transmission line 104. The second end of the cable or transmission line 104 is not coupled to any load or device, and therefore the second end is disconnected or open. The time-domain reflectometer 102 is configured to output a signal to the cable or transmission line 104 and to receive an echo response exhibiting a series of reflections caused by the changing impedance of the cable or transmission line 104. The coupling between the time-domain reflectometer 102 and the cable or transmission line 104 can be a differential connection or an unbalanced connection. The cable 104 can have a differential pair of data lines or an unbalanced data line.The TDR 102 can be connected to the two data lines of the cable or the transmission line 104.

[0023] The time-domain reflectometry system 100 is coupled to a first end of the cable or transmission line 104 and configured to obtain at least one echo response from the cable or transmission line 104 using time-domain reflectometry. The system 100 can additionally or alternatively be coupled to the second end of the cable or transmission line 104 and configured to obtain at least one echo response from the cable or transmission line 104 using time-domain reflectometry.

[0024] Fig. Figure 3 is a schematic representation of the time-domain reflectometry system 100, which is coupled to the output terminals 110 of the system 100 by a cable or transmission line 104. The second end of the cable or transmission line is coupled to a device 310. The device 310 can be a receiver or a transceiver that uses the cable or transmission line 310 for communication. Alternatively, the device 310 can be a load with an impedance matched to the impedance of the cable or transmission line. Although the exact impedance of the cable or transmission line may be unknown, typical matching impedances, such as 50 ohms, 75 ohms, or 100 ohms, can be used. For example, an impedance corresponding to the reference impedance specified by a given communication standard.The device 310 can be a second time domain reflectometer that is capable of receiving echo responses from the cable or transmission line 104.

[0025] Fig. Figure 4 is a flowchart outlining a procedure 400 for characterizing a cable or transmission line 104. The procedure can be performed by the control system 106 of the system 100. Alternatively, the procedure can be performed by a separate control system that is not coupled to the cable but receives the echo response from the time-domain reflectometer 102. The control system 106 can receive the echo responses from a memory or request / receive updated echo responses from the time-domain reflectometer 102.

[0026] In step S402, an initial echo response is obtained using time-domain reflectometry. The initial echo response may be obtained while the time-domain reflectometer 102 is not coupled to the cable or transmission line 104, as shown in Fig. Figure 1 shows that the first echo response represents an echo response from the open output of the time-domain reflectometer 102 or of the system 100, of which the time-domain reflectometer 102 is a part. This provides an echo response containing information about the system 100. The first echo response can be obtained from the expected behavior of the reflectometer or during the manufacture of the device and stored in a memory of the system 100. Alternatively, the first echo response can be obtained following the commissioning of the system 100 or the transceiver containing the time-domain reflectometer 102 and can be obtained regularly or periodically.

[0027] In step S404, a second echo response is obtained using time-domain reflectometry. The second echo response may include an echo response obtained while the time-domain reflectometer 102 is coupled to the cable or transmission line 104. Step S404 therefore instructs coupling a first end of the cable or transmission line to the time-domain reflectometer 104, as shown in Fig. 2 and Fig. Figure 3 shows that the second echo response exhibits reflections resulting from impedance variations in the input stage circuit arrangement of the time-domain reflectometer 102, reflections resulting from impedance mismatch between the output terminals 110 of the time-domain reflectometer 102 and the cable or transmission line, and reflections caused by impedance variations in the cable or transmission line 104 itself. Where the first echo response is obtained from a memory of the system 100, the cable or transmission line may already be coupled to the time-domain reflectometer.

[0028] In step S406, a characteristic of the cable or transmission line 104 is determined by comparing the first and second echo responses. The first and second echo responses will exhibit a series of reflections indicating changes in impedances in the time-domain reflectometer system 100 and the cable or transmission line 104. By comparing these, characteristics of the cable or transmission line 104, such as impedance, echo attenuation, or insertion loss, are determined. Echo attenuation and impedance determination

[0029] Fig. Figure 5a is a flowchart outlining a method 500 for characterizing a cable or transmission line 104, wherein the characteristic is the echo attenuation and impedance of the cable or transmission line 104. The method can be performed by the control system 106 of the system 100. Alternatively, the method can be performed by a separate control system that is not coupled to the cable but receives the echo response from the time-domain reflectometer 102.

[0030] In step S502, a first echo response is acquired using time-domain reflectometry. The first echo response is obtained while the time-domain reflectometer 102 is disconnected from the cable or transmission line 104. Therefore, the first echo response represents the echo response of the open output of the time-domain reflectometer 102 or of the system 100. This provides an indication of the frequency spectrum characteristics of the time-domain reflectometer 102 up to the output terminals 110, as shown in Fig. 1 is shown.

[0031] In step S504, the first end of a cable or transmission line 104 is connected to the time-domain reflectometer 102 at the output terminals 110 of the system 100. The second end of the cable or transmission line is connected to a device 310, as shown in Fig. Figure 3 shows that the second end of the cable or transmission line 104 is terminated using a matched impedance. This termination can be achieved using a receiver or transceiver used for communication, or an impedance matched to that of the cable or transmission line.

[0032] Although the procedure of Fig. 5a, which includes a step of coupling the time-domain reflectometer 102 to the cable or transmission line, implies that the time-domain reflectometer may already be coupled to the cable or transmission line 104. The first echo response may be an echo response received from a memory of the system 100, for example, an echo response received during the manufacture or commissioning of the system 100.

[0033] In step S506, a second echo response is received while the second end of the cable or transmission line 104 is terminated using the load, the matched load, or the communication system 310. Although the procedure of Fig. 5. Instead of using a second echo response obtained while the second end of the cable or transmission line is closed using the load, a second echo response obtained while the second end of the cable or transmission line is open-circuited may alternatively be used. Where an open-circuited echo response is used, the reflection caused by the open circuit at the end of the cable or transmission line 104 should be excluded from the following calculations, for example, by considering only the samples of the echo response that do not exhibit the reflection caused by the impedance change at the second end of the cable or transmission line 104.

[0034] In step S508, a first Fast Fourier Transform (FFT) of the first echo response and a second FFT of the second echo response are generated. This transforms the time-domain representation of the echo response into a frequency-domain representation. A ratio of the first FFT to the second FFT is then calculated. This yields a value representing the reflection coefficient of the cable or transmission line.

[0035] It is known that the reflection coefficient of a cable or transmission line is determined by the following equation: reflection coefficient=r=Zn−1Zn+1 Zn=Z / Z0

[0036] Where Z0 is the characteristic impedance of the reflectometer and Z is the impedance of the cable or transmission line.

[0037] The reflection coefficient can be found by taking the ratio of the transformations of the first echo response and the second echo response, where both Fast Fourier Transforms (FFTs) are given in RMS units: r=FFT(First Echo Response)FFT(Second Echo Response)

[0038] This can be used to determine the echo attenuation (return loss) of the cable or transmission line in decibels: Return Loss=RL=10 log10r2 RL=20∗log10FFT(First Echo Response)FFT(Second Echo Response)

[0039] The use of a logarithm can be considered an optional step in obtaining echo attenuation in decibels. It is understood that no logarithm can be performed, and the echo attenuation is given by the square of the reflection coefficient. Wherever a logarithm is described in the application, it cannot be used instead, and the resulting characteristic is given using units other than decibels.

[0040] Using the preceding equations, the impedance of the cable or transmission line can then be derived from the reflection coefficient: Z=ZN∗Z0

[0041] Therefore, in a system that uses 100 ohms as the reference impedance: Z=100(r+1(1−r))

[0042] Therefore, the reflection coefficient can be calculated by taking the ratio of the first and second Fast Fourier transforms.

[0043] Once the reflection coefficient of the cable or transmission line has been determined in step S508, the echo attenuation and impedance of the cable or transmission line can be calculated according to the equations above.

[0044] In step S510, the echo attenuation of the cable or transmission line is determined by a logarithm (20 ∗ log 10 r)) of the reflection coefficient is determined to determine the echo attenuation of the cable in decibels.

[0045] In step S512, the impedance of the cable or transmission line can be determined by calculating a ratio of the reflection coefficient of the cable or transmission line. As highlighted above, the impedance of cable or transmission line 104 can be determined using the following equation: Z=ZN∗Z0

[0046] In particular, the following applies in a 100 Ohm impedance system: Z=100(r+1(1−r))

[0047] Fig. 5b shows an adapted or alternative version of procedure 530 from Fig. 5a, which removes or reduces the effects of non-idealities of the time-domain reflectometer 102 in the echo attenuation determination. Steps S502-S506 are the same as those described with regard to Fig. 5a described, receiving a first echo response and a second echo response from the cable or transmission line 104.

[0048] In step S514, the cable or transmission line 104 is disconnected or uncoupled from the time-domain reflectometer 102. The output terminals 110 of the time-domain reflectometer 102 are terminated or coupled to an impedance matched to the nominal impedance of the time-domain reflectometer 102. Although the impedance of the time-domain reflectometer 102 may vary over time, it can be matched to the specified or datasheet impedance of the time-domain reflectometer 102.

[0049] In step S516 a third echo response is obtained while the output terminals 110 of the time domain reflectometer 102 are terminated using the matched impedance.

[0050] Steps S514 and S516 are in the procedure of Fig. Figure 5b shows steps S504 and S506, although it is understood that steps S514 and S516 could instead take place before step S504. Furthermore, the third echo response can be obtained during the fabrication of the time-domain reflectometer 102 or during its first use and stored in memory for later use. Alternatively, it can be performed each time to account for impedance changes of the reflectometer.

[0051] In step S518, the third echo response is subtracted from the first echo response to generate a relative frequency response of the cable. This subtraction can be a power subtraction, where the fast Fourier transform of the third echo response is subtracted from the fast Fourier transform of the second echo response. Thus, the terminated echo response of the time-domain reflectometer 102 is subtracted from the echo response of the cable or transmission line 104, while the second end of the cable or transmission line 104 is terminated using the load. This removes the non-idealities of the time-domain reflectometer 102 from the echo response before the echo attenuation is determined, resulting in the relative frequency response of the cable without the effects of the transmitter or the reflectometer 102. (Relative Frequency response of cable)2=FFT(second echo response)2−FFT(third echo response)2

[0052] In step S520, a ratio of a Fast Fourier Transform of the first echo response to the relative frequency response (which is already a Fast Fourier Transform / frequency response) is determined to calculate a reflection coefficient of the cable or transmission line: r=±FFT(First Echo Response)FFT(Relative Frequency response of cable)

[0053] In step S522, a logarithmic transformation of the ratio can be performed to determine the echo attenuation of the cable or transmission line in decibels. RL=20∗log10FFT(First Echo Response)FFT(Relative Frequency response of cable)

[0054] In this way, the echo attenuation of the cable or transmission line can be determined. Using the method of Fig. 5b The echo attenuation obtained can be more accurate than that of the method of Fig. 5a, since it removes the non-idealities of the time domain reflectometer, although it requires that further echo responses be obtained.

[0055] Fig. Figure 6 is a graph showing the determined echo attenuation of cable or transmission line 104. The echo attenuation of the cable or transmission line was analyzed using a vector analyzer and the previously described time-domain reflectometry method. The echo attenuation determined using the time-domain reflectometry method is shown as solid line 602. The echo attenuation determined using a vector analyzer is shown as line 604. As can be seen, there is good agreement between the echo attenuation determined using the two methods.

[0056] Fig. Figure 7 is a graph showing the determined impedance of cable or transmission line 104. The impedance of the cable or transmission line was analyzed using a vector analyzer and the time-domain reflectometry method outlined above. The impedance determined using the time-domain reflectometry method is shown as a solid line (702). The impedance determined using the vector analyzer is shown as a dashed line (704). As can be seen, there is good agreement between the impedances determined using the two methods. Insertion loss determination

[0057] The insertion loss of the cable or transmission line can also be determined using the method of Fig. 8a will be determined.

[0058] Fig. Figure 8a is a flowchart outlining a method 800 for characterizing a cable or transmission line 104, wherein the characteristic is an insertion loss of the cable or transmission line 104. The method can be performed by the control system 106 of the system 100. Alternatively, the method can be performed by a separate control system that is not coupled to the cable 104 but receives the echo response from the time-domain reflectometer 102.

[0059] In step S802, a first echo response is acquired using time-domain reflectometry. The first echo response is obtained while the time-domain reflectometer 102 is disconnected from the cable or transmission line 104. Therefore, the first echo response represents an echo response of the open output terminals 110 of the time-domain reflectometer 102 or of the system 100. This provides an indication of the characteristics of the system 102 up to the output terminals 110, as shown in Fig. 1 is shown.

[0060] Fig. Figure 9 is a graph showing an initial echo response obtained while the time domain reflectometer 102 is disconnected from the cable or transmission line 104.

[0061] In step S804, the first end of a cable or transmission line 104 is connected to the time-domain reflectometer 102 at the output terminals 110 of the system 100. The second end of the cable or transmission line is not connected to a device or load, as shown in Fig. Figure 2 shows that the second end of the cable or transmission line 104 is open-circuited. The open circuit can be achieved by disconnecting (or not connecting) a device 310 used for communication from the second end of the cable or transmission line. Alternatively, where the second end of the cable or transmission line is connected to a device that actively terminates the cable 104, the open circuit can be achieved by shutting down or turning off a device connected to the second end of the cable or transmission line 104. When the device is turned off, it behaves like an open circuit. This can be achieved, for example, by opening a switch between the second end of the cable or transmission line and the device 310.

[0062] In step S806, a second echo response is received while the second end of the cable or transmission line 104 is open or disconnected.

[0063] Fig. Figure 10a is a graph showing a second echo response received while the second end of cable or transmission line 104 is open or disconnected.

[0064] In step S808, a first Fast Fourier Transform of the first echo response and a second Fast Fourier Transform of the second echo response are generated. A ratio of the first Fast Fourier Transform to the second Fast Fourier Transform is then calculated. The insertion loss (IL) of the cable or transmission line 104 in decibels is determined by performing a logarithmic transformation (20 ∗ log ). 10 ratio)) of the ratio is taken as shown in the equation below: Insertion Loss=IL=12∗20∗log10(FFT(First Echo Response)FFT(Second Echo Response))

[0065] The factor of ½ included in the ratio is intended because the second echo response is affected twice by the insertion loss of the cable as the transmitted signal travels through the cable and back to the reflectometer. The open circuit results in a signal that travels from the time-domain reflectometer, is reflected from the second end of the cable or transmission line, and returns to the time-domain reflectometer. Therefore, the signal travels twice the length of the cable or transmission line. Multiplying the logarithmic result by ½ corrects this.

[0066] Fig. Figure 8b is a graph showing the determined insertion loss of cable or transmission line 104. The insertion of the cable or transmission line was analyzed using a vector analyzer and the time-domain reflectometry method outlined below. The insertion determined using the time-domain reflectometry method is shown as a solid line (820). The insertion loss determined using the vector analyzer is shown as a dashed line (822). As can be seen, there is good agreement between the insertion loss determined using the two methods. Sampling selection

[0067] Echo responses acquired using time-domain reflectometry systems are typically sampled or discrete signals indicating the amplitude of the reflection at different sample numbers. The sample numbers refer to the distance along the cable (or from the time-domain reflectometer) at which the sample is acquired. Reflections in the echo responses are caused by impedance variations in the system 102, or the cable 104, and are represented by amplitude peaks in the echo response.

[0068] The in Fig. The first echo response shown in Figure 9 is obtained while the time-domain reflectometer 102 is disconnected from the cable or transmission line 104. The first echo response exhibits a first reflection 902 at a first sample number S1. The first reflection 902 is caused by the impedance change at the output terminals 110 of the system 100.

[0069] The in Fig. The second echo response shown in Figure 10a is obtained while a cable or transmission line 104 is coupled to the reflectometer 102 and the second end of the cable or transmission line 104 is open or disconnected. The second echo response has a first reflection 1002, which is obtained at the same sample number S1 as the first reflection 902 of the first echo response. Since the impedance of the cable is not ideal, there is an impedance mismatch between the time-domain reflectometer 102 and the cable 104. The first reflection 1002 in the second echo response is caused by the impedance mismatch between the impedance of the reflectometer 102 (which may be, for example, 50 ohms, 75 ohms, or 100 ohms) and the impedance of the cable or transmission line.

[0070] The first reflections 902 and 1002 correspond to the same point at the output terminals 110 of the system 100 (or between the output terminals and the cable or transmission line). In the first echo response, where there is no cable, the amplitude reflection is larger (due to the large impedance change at the open-circuited output of the time-domain reflectometer) compared to the reflection in the second echo response (which is caused by a relatively smaller impedance mismatch between the reflectometer 102 and the cable 104).

[0071] The second echo response, shown in Fig. 10a, furthermore exhibits a second reflection 1004 at a second sample number S2. The second reflection 1004 has a higher sample number than the first reflection 902, 1004 and is caused by the impedance change at the open circuit at the second end of the cable or transmission line 104.

[0072] The amplitude or strength of the second reflection 1004 depends on the length of the cable. The longer the cable, the lower the strength of the second reflection 1004, due to the insertion loss of the cable. Fig. Figure 10a shows the second reflection 1004, which has a slightly greater intensity compared to the first reflection 1002. This can cause the first reflection 1002, representing the output terminals 110 of the system 100, to significantly impair the determination of the insertion loss of a cable or transmission line 104 if the cable is long, and generally produces inaccuracies in the insertion loss calculation.

[0073] To avoid this, a series of echo response samples can be selected for use in determining insertion loss. Furthermore, the selected samples can be padded with zeros or other values ​​to complete the waveform. The same applies to echo responses used to determine the echo attenuation and impedance of a cable or transmission line.

[0074] If the respective Fast Fourier Transforms of the first echo response and the second echo response (for example, in steps S508 and S808) are determined, a predetermined set of samples of the first echo response and the second echo response can be used in the Fast Fourier Transforms instead of the entire echo response.

[0075] The predetermined set of samples can be determined with reference to the second echo response. For example, in Fig. As shown in Figure 10a, a predetermined set of samples 1006 or a sampling window 1006, including the samples between a third sample number S3 and a fourth sample number S4 in the second echo response, can be selected for the insertion loss determination.

[0076] For the insertion loss calculation, the predetermined set of samples 1006 can be selected depending on the determination of the presence of the first reflection 1002 and the second reflection 1004 in the second echo response. The predetermined set of samples is selected such that it includes the second reflection (especially the peak of the second reflection 1004) and excludes the first reflection. The sampling window, or the predetermined set of samples, can be a fixed number of samples before and after the second reflection 1004. Alternatively, the predetermined set of samples can include the first sample of the second reflection 1004 and a predetermined number of samples following the first sample. Several different methods for determining the sampling window are possible.

[0077] The selected samples from the first echo response for the insertion loss calculation can be such that the first reflection 902, corresponding to the open output terminals 110 of the reflectometer 102, is included in the samples and that the number of samples for both selections is the same. In cases where the number of samples does not match, data extrapolation and / or zeroing can be used.

[0078] In this way, the first reflection 1002, which does not represent the properties of the cable or transmission line 104 (but instead represents the properties of the system 100 or the output terminals 110), is excluded from the determination of the insertion loss of the cable or transmission line 104.

[0079] Where echo attenuation is determined on the basis of echo responses obtained while the second end of the cable is terminated with a load or device, such as a receiver or transceiver, the predetermined set of samples is all the samples in the response relating to the characteristics of the entire length of the cable, including reflection caused by the impedance mismatch between the second end of the cable or transmission line and the terminating device or load.

[0080] Where echo attenuation is determined on the basis of echo responses obtained while the second end of the cable or transmission line is disconnected, open-ended, or open-ended (i.e., where the same echo responses used to determine insertion loss are also used to calculate echo attenuation), the predetermined set of samples is all of the samples in the echo response except for samples 1006, which have the second reflection 1004.

[0081] Selecting a predetermined set of samples can result in the samples not starting and ending at the same amplitude. In the echo response of Fig. 10a The amplitude at the start and end of the second response is approximately centered at 0. If the predetermined set of samples is chosen such that there is a difference in amplitudes between the start and end of the predetermined set of samples, spectral leakage can occur, reducing the accuracy of the characteristic determination. To reduce spectral leakage, conventional windowing can be applied to the sample selection. However, polynomial functions can instead be used to extrapolate data points before and after the selected samples to ensure that the selected samples start and end at approximately the same amplitude.

[0082] For example, where the sampling window is defined as being between sampling S3 and S4 of Fig. The sampling window chosen for S3 is located at S10a, resulting in a difference in amplitude between the samples. Sampling S3 represents the first sample of the sampling window, and sampling S4 represents the final sample of the sampling window. In the fast Fourier process, the samples within the sampling window are always repeated; therefore, a difference in amplitude leads to an amplitude jump or a rapid change in amplitude.

[0083] Fig. Figure 10b is a flowchart of a procedure for reducing spectral leakage by fitting a polynomial to the start and / or end of the sampling window such that the start and end of the sampling window have essentially the same amplitude.

[0084] In step S1010, the amplitude of a first sample (S3) within the predetermined set of samples within the second echo response is determined.

[0085] In step S1012, the amplitude of a final sample (S4) within the predetermined set of samples within the second echo response is determined.

[0086] In step S1014, a difference between the amplitude of the first sample and the amplitude of the final sample is determined.

[0087] In step S1016, a polynomial function is determined and added to a start and / or end point of the predetermined set of samples within the second echo response, ensuring that the first and final samples have the same amplitude. This reduces or eliminates spectral leakage.

[0088] Fig. 10c and Fig. Figure 10d shows an echo response with selected samples 1006 and the polynomial fitting process of Fig. 10b. The in Fig. The echo response shown in Figure 10c has a predetermined set of samples between sample number S3 and sample number S4, i.e., 1006. The predetermined or selected set of samples is shown in Fig. Figure 10c is shown as the solid line of samples 1020. The amplitude of the echo response at sample S3 is not zero. The amplitude of the echo response at sample S4 is less than zero. Therefore, polynomial fitting can be applied to the side of the predetermined set of samples 1006 with a non-zero amplitude. Polynomial fitting is not required at sample S4 at the other end of the predetermined set of samples if the amplitude is zero. Where both samples S3 and S4 are non-zero, polynomial fitting can be applied to both the start and the end of the predetermined sampling window 1006.

[0089] The samples in the range 1022 of Fig. 10c shows how polynomial fitting can be applied. Fig. Figure 10d shows a subsection of the same echo response as in Fig. 10c provides a more detailed view of polynomial fitting. Polynomial fitting can be applied using the data points or the slope of the data points.

[0090] The dashed line 1024 shows the samples of the echo response. As can be seen, these deviate from zero. Therefore, a set of extrapolated samples 1026 is determined from the first sample S3 of the set of preselected samples 1006. The extrapolated samples 1026 buffer the predetermined set of samples 1006, thus ensuring that the predetermined set of samples ends at zero. Echo attenuation determination with alternative echo responses

[0091] The first and second echo responses, received in steps S802 and S806 from Fig. 8. The methods used to determine insertion loss can also be used, alternatively or additionally, to determine the echo attenuation of the cable or transmission line using a method that is suitable for Fig. to determine the similar scanning method described in 10b.

[0092] Reusing the first echo response obtained while the time-domain reflectometer 102 is disconnected from the cable or transmission line 104, and the second echo response obtained while the second end of the cable or transmission line 104 is open or disconnected, reduces the number of echo responses that need to be obtained. It also allows the echo attenuation to be determined while the second end of the cable or transmission line 104 is open or disconnected, rather than closed (as with regard to Fig. 5 is described). Where a cable is pre-installed or historical, the second end of the cable or transmission line may be inaccessible. Being able to determine the echo attenuation, regardless of the type of coupling at the second end of the cable or transmission line 104, allows a technician or installer to easily characterize the cable.

[0093] Fig. Figure 8c shows how to determine the echo attenuation of the cable or transmission line. Steps S802-S806 are the same as described with regard to Fig. 8a. After the second echo response has been received, the procedure continues to step S810.

[0094] In step S810, the procedure involves determining the presence of reflection in the second echo response, caused by the second end of the cable or transmission line being open. This is described in Fig. 10a as the second reflection 1004 shown.

[0095] In step S812, the procedure involves selecting a predetermined set of samples within the second echo response that do not exhibit the reflection caused by the open circuit at the end of the cable or transmission line 104. For example, a predetermined set of samples or a sampling window 1008, as in Fig. As shown in Figure 10a, a corresponding predetermined set of samples within the first echo response is selected (i.e., samples with the same sample number).

[0096] In step S814, the procedure involves determining a ratio of a Fast Fourier Transform of the predetermined set of samples within the first echo response to a Fast Fourier Transform of the predetermined set of samples within the second echo response.

[0097] Several of the described methods involve performing a Fast Fourier Transform on the echo responses. To reduce the computational processing required for this transform, the number of samples can be a power of two. Alternatively, the echo responses or selected samples can be padded with zeros to ensure the sample count is a power of two.

[0098] In step S816, the procedure involves determining a ratio of a Fast Fourier Transform of the predetermined set of samples within the first echo response to a Fast Fourier Transform of the predetermined set of samples within the second echo response in order to determine the echo attenuation of the cable or transmission line. RL=20∗log10FFT(Selected Samples of First Echo response)FFT(Selected Samples of Second Echo Response) Bidirectional TDR for insertion loss determination:

[0099] As in Fig. As shown in Figure 3, a second time-domain reflectometer 310 can be coupled to the second end of the cable or transmission line. The second time-domain reflectometer 310 can be part of a communication system or transceiver and can be permanently coupled to the cable or transmission line. Alternatively, the time-domain reflectometer can be disconnected from the first end of the cable or transmission line and coupled to the second end.

[0100] Instead of determining the insertion loss of the cable or transmission line using echo response of the time domain reflectometer coupled to the first end of the cable or transmission line 104, the insertion loss can instead be determined using echo responses obtained from opposite ends or both ends of the cable or transmission line 104.

[0101] Fig. Figure 11 is a flowchart of a procedure for determining the insertion loss of the cable or transmission line 104.

[0102] In step S1102, an initial echo response is acquired using time-domain reflectometry. The initial echo response is obtained from the first end of the cable or transmission line 104, while the time-domain reflectometer 102 is connected to the first end of the cable or transmission line 104 and the second end of the cable or transmission line 104 is connected to the reflectometer 310. Therefore, the end of the cable can be terminated by the terminating impedance of the reflectometer 310. The initial echo response can be acquired without interrupting normal data traffic or communication by utilizing the echo cancellation coefficients of the transceiver, of which the reflectometer 100 is a part.

[0103] In step S1104, a second echo response is acquired using time-domain reflectometry. The second echo response is received from the second end of the cable or transmission line 104, while the time-domain reflectometer 310 is connected to the second end of the cable or transmission line 104 and the first end of the cable or transmission line 104 is connected to the reflectometer 102. Therefore, the first end of the cable 104 can be terminated by the termination impedance of the reflectometer 100. The second echo response can be acquired without interrupting normal data traffic by using the echo cancellation coefficients of the transceiver, of which the reflectometer 310 is a part.

[0104] In step S1106, a first reflection is identified in the first echo response. The first reflection corresponds to the impedance mismatch between the output impedance of the reflectometer 102 and the cable or transmission line 104.

[0105] In step S1108, a second reflection is identified in the second echo response. This second reflection is the last valid reflection in the second echo response and occurs at a time point corresponding to the length of the cable. Therefore, the second reflection corresponds to the impedance mismatch between the cable or transmission line 104 and the impedance of the first time-domain reflectometer 102.

[0106] Therefore, the first reflection in the first echo response and the second reflection in the second echo response affect the same impedance mismatch, although the second reflection is also affected by the insertion loss of the cable, since it comes from the end of the cable with respect to the measurement point.

[0107] In step S1110, a ratio of a Fast Fourier transform of the first complete reflection in the first echo response to a Fast Fourier transform of the second complete reflection in the second echo response is determined. IL=20∗12∗log10FFT(First Complete Reflection in first Echo Response)FFT(Second Complete Reflection in second Echo Response)

[0108] In step S1112, a logarithm of the ratio can be obtained to determine the insertion loss of the cable in decibels.

[0109] In addition to or as an alternative to using the first and second echo responses to determine insertion loss, a third complete reflection can be identified within the first echo response. This third complete reflection corresponds to an impedance mismatch between the cable or transmission line and the second time-domain reflectometer, coupled to the second end of the cable or transmission line. A ratio of a Fast Fourier transform of the first complete reflection within the first echo response to a Fast Fourier transform of the third complete reflection within the first echo response yields a value that indicates the insertion loss. A logarithm can be used to determine this value in decibels. In this way, the insertion loss can be determined based solely on a single echo response. IL=20∗12∗log10FFT(First Complete Reflection in First Echo Response)FFT(Third Complete Reflection in First Echo Response) Transceivereigenschaften

[0110] The time-domain reflectometer 102 can be a dedicated time-domain reflectometer. Alternatively, it can be part of a transceiver, transmitter, receiver, or communication system. Therefore, the echo responses described above can be obtained using a transceiver, and in particular, can be obtained using the transceiver's echo cancellation coefficients. Echo cancellation coefficients are coefficients applied to a filter, typically used in a transceiver, transmitter, or receiver, to cancel reflections present along the transmission line. This enables improved communication with reduced noise. The filter and the echo cancellation coefficients applied to it can be used to function as a time-domain reflectometer within the system without interfering with the data communication carried out by the system.This allows the determination of characteristics of cables or transmission lines in the background while communication is taking place.

[0111] Using echo cancellation coefficients allows the transceiver to obtain the echo response of the cable or transmission line while operating, in order to provide data communication with a transceiver or receiver connected to the other end of the cable or transmission line. This allows for periodic or regular updates of cable or transmission line characteristic determinations in the background while the system is operating.

[0112] Where the procedure exhibits echo responses that were further obtained from the first end and the second end of the cable or transmission line (as with regard to Fig. As described in section 11, echo responses can be obtained by the respective transceivers. For example, a second echo response can be obtained using the echo cancellation coefficients of a first transceiver connected to the first end of the cable or transmission line while the first transceiver is operating to provide data communication. A further, third echo response can be obtained using the echo cancellation coefficients of a second transceiver connected to the second end of the cable or transmission line while the second transceiver is operating to provide data communication to the first transceiver. Influence of characteristic determination on a communication system

[0113] Once the respective characteristic (echo attenuation, impedance or insertion loss) of a cable or transmission line 104 has been determined, it can be used to trace characteristics of the cable.

[0114] Communication systems typically operate according to a technical or communication standard. The IEEE 802.3cg 10BASE-T1L specifications outline a set of requirements for communication systems for Ethernet data over a single wire pair. These requirements pertain to the communication system transceiver and the cable or transmission line 104 used with the transceiver. The requirements may include boundaries or ranges within which certain characteristics of the cable or transmission line 104 must be compliant with the technical standard. Once the characteristic of the cable or transmission line 104 has been determined using time-domain reflectometry, it can be compared to a predefined range for that characteristic within the technical standard.

[0115] If it is determined that the cable or transmission line 104 has suitable characteristics that meet the technical standard, communication in accordance with this standard may be carried out using this cable or transmission line. If it is determined that the cable or transmission line 104 has unsuitable characteristics that do not meet the technical standard, a replacement cable may be installed. This allows for the reuse of existing historical cables already installed in a building if they are suitable for use with the technical standard.

[0116] The characteristics of the cable or transmission line can be monitored over time to determine possible deterioration of the cable characteristics.

[0117] Fig. Figure 12 is a flowchart outlining a procedure 1200 for tracking cable deterioration by monitoring the characteristics of the cable or transmission line 104 over time. The procedure can be performed by the control system 106 of the system 100. Alternatively, the procedure can be performed by a separate control system that is not coupled to the cable but receives the echo response from the time-domain reflectometer 102. A second characteristic of the cable or transmission line of the same type as the first characteristic (e.g., impedance, insertion loss, echo attenuation) can be determined at a second time point, which is later than the determination of the first characteristic. Deterioration of the cable or transmission line can then be determined by comparing the second characteristic of the cable or transmission line with the first characteristic of the cable or transmission line.

[0118] Procedure 1200 can be carried out by following any of the procedures 400, 500 or 800.

[0119] In step S1202, a third echo response can be obtained using time-domain reflectometry. The third echo response is obtained while the time-domain reflectometer 102 is coupled to the cable or transmission line 104. The second end of the cable or transmission line can be terminated using the load or communication system 310 if the characteristic is an impedance or echo attenuation of the cable or transmission line 104 (if procedure 1100 follows procedure 500), or open if the characteristic is an insertion loss (if procedure 1100 follows procedure 800).

[0120] In step S1204, a second characteristic of the cable or transmission line is determined by comparing the third echo response obtained in step S1102 with the first echo response obtained in step S502 or step S802. The second characteristic is the same type of characteristic as the earlier characteristic determined in procedure 500 or 800, but relates to the characteristic in comparison with the earlier characteristic at a different time. Although only a third echo response is obtained in procedure 1200, a third echo response corresponding to the first echo response and a fourth echo response corresponding to (i.e., acquired in the same way with) the second echo response can instead be obtained. Therefore, the second characteristic of the cable or transmission line 104 can be determined by comparing the fourth echo response and the third echo response.In this way, the echo response relating to the time domain reflectometer is updated instead of being reused.

[0121] In step S1206, procedure 1200 involves determining deterioration of the characteristics of the cable or transmission line 104 by comparing the second characteristic of the cable or transmission line with the characteristic of the cable or transmission line. Determining cable deterioration may involve determining whether the characteristic of the cable or transmission line 104 falls within an acceptable value provided by an engineering standard, or determining whether the characteristic has changed by a certain percentage compared to the previously determined characteristic.

[0122] The system 100, which includes the time-domain reflectometer 102, can form part of a communication system. Therefore, the procedure 1200 can be repeated regularly or periodically across the cable or transmission line 104. This allows the communication system to determine whether the cable has deteriorated to such an extent that communication is no longer possible or a certain level of service can no longer be provided.

[0123] Following the determination of a cable characteristic, the method can further include determining a maximum possible length of the cable or transmission line that can be supported by a communication system 100, depending on the determined characteristic of the cable or transmission line 104. For example, a section of cable or transmission line 104 with a first length X can be connected to the time-domain reflectometer, and a characteristic of the cable or transmission line 104 can be determined. Based on this, the maximum possible length of cable or transmission line 104 with this characteristic can be determined by extrapolating the characteristic to other cable lengths and comparing it with a technical standard.

[0124] Where the specific characteristic of the cable or transmission line 104 is an impedance of the cable or transmission line 104, the output impedance of the transceiver or system 100 can be modified to match the specific impedance of the cable or transmission line.

[0125] Fig. Figure 13 shows the system 100, which can be a time-domain reflectometer 102 or a communication system 100 incorporating the time-domain reflectometer 102. The system 100 has a trimmable or controllable output impedance 1202. The controllable output impedance of the transceiver, coupled to the first end of the cable or transmission line 104, can be modified to match the specific impedance of the cable or transmission line. This provides a better match between the communication system 100 and the cable or transmission line.

[0126] Where the impedance is determined periodically or regularly using method 1100, the output impedance of the system 100 can be updated to adapt to any changes in the impedance of the cable or transmission line 104.

[0127] This reduces the degradation of a communication link's quality, enabling the communication system to deliver high service quality even if the cable or transmission line deteriorates or ages. This extends the cable's or transmission line's lifespan without the need for manual testing of cable characteristics using vector analyzers.

[0128] The time-domain reflectometer 102, or the transceiver incorporating the time-domain reflectometer 102, provides a communication signal or a sequence of transmission symbols with a certain output power. The output power of the transceiver can change over time. This can be tracked or characterized by determining a Fast Fourier transform of the first echo response received while the output terminals 110 of the time-domain reflectometer are open or closed. The output power can be determined at multiple time points by receiving new echo responses while the time-domain reflectometer or the transceiver is open.Where the time domain reflectometer is part of a transceiver, the power of the communication output signal can be adjusted to ensure that it is of a suitable level, for example according to a technical or communication standard, depending on the specified output power.

[0129] Although the determination of the echo attenuation of the cable or transmission line has been outlined above, the echo attenuation of the time-domain reflectometer 102 or of the transceiver itself can also be determined using a suitable procedure with echo responses recorded when no cable or transmission line is coupled to the reflectometer. This allows the effects of the transceiver to be taken into account when establishing a communications link. The output power, echo attenuation, insertion loss, and impedance of the reflectometer or transceiver can be obtained repeatedly or periodically and compared to monitor changes in the reflectometer's or transceiver's characteristics over time.

[0130] Fig. Figure 14 is a flowchart of a procedure for determining the echo attenuation of the time domain reflectometer 102 or of a transceiver incorporating the time domain reflectometer.

[0131] In step S1402, the first echo response is obtained using time-domain reflectometry while the time-domain reflectometer 102 is not coupled to the cable or transmission line 104, as shown in Fig. Figure 1 shows that the first echo response represents an echo response from open output terminals of the time-domain reflectometer 102 or of the system 100, of which the time-domain reflectometer 102 is a part. This provides an echo response containing information about the system 100.

[0132] In step S1404, the procedure involves terminating the output terminals 110 of the time domain reflectometer using an impedance matched to the nominal impedance of the time domain reflectometer.

[0133] In step S1406, the procedure involves obtaining a second echo response while the output terminals of the time domain reflectometer are coupled to a matched impedance.

[0134] In step S1408, a ratio of a Fast Fourier transform of the first echo response to a Fast Fourier transform of the second echo response is obtained to determine a reflection coefficient of the time domain reflectometer 102.

[0135] In step S1410, a logarithm of the ratio is obtained to determine the echo attenuation of the cable or transmission line in decibels.

[0136] The systems described above feature one or two time-domain reflectometers coupled by a single cable or transmission line. Larger networks can include a multitude of transceivers (for example, 2, 4, 6, 8, 10, or more) coupled at various points along a large number of cables or transmission lines distributed throughout the network. The network may also include transceivers acting as repeaters at certain points within the network. As part of a communication system or network, the transceivers can communicate with each other. Therefore, upon a command from a primary or main controller, the distributed transceivers can perform echo responses on the respective cables or transmission lines to which they are connected or coupled.Echo responses can be used locally at each transceiver to determine cable characteristics according to the previously described procedures and then sent to the primary transceiver. Alternatively, the echo responses can be sent to the primary transceiver, which then determines the characteristics centrally. A map of the network, including all transceivers and cables or transmission lines, can be generated and periodically updated to track degradation and aging in different parts of the network.

[0137] Where the description outlines a procedure in which an echo response is obtained using an open-circuit connection (either an open connection at the terminals of the time-domain reflectometer if no cable or transmission line is coupled to the reflectometer, or an open connection at the second end of the cable or transmission line if a cable or transmission line is coupled to the reflectometer), an echo response acquired with a short circuit at the terminals or at the second end of the cable or transmission line may be used instead. The equations described previously do not change in this situation. Furthermore, a mix or selection of open and short-circuited connections may be used.

[0138] Various modifications, whether by adding, removing or replacing features, can be made to the examples described above to provide further examples, any and all of which are intended to be included in the attached claims. Aspects of Revelation:

[0139] The following is a set of numbered aspects according to the revelation: 1. A method for characterizing a cable or transmission line, wherein the method comprises: Obtaining an initial echo response using time-domain reflectometry; Connecting one end of the cable or transmission line to a time domain reflectometer; Obtaining a second echo response using time-domain reflectometry; Determining a characteristic of the cable or transmission line by comparing the first echo response and the second echo response. 2. The procedure according to aspect 1, wherein obtaining the first echo response involves obtaining an echo response from a time domain reflectometer. 3. The method according to aspect 2, wherein receiving the first echo response while the output terminals of the time domain reflectometer are open or short-circuited. 4. The procedure according to a preceding aspect, wherein obtaining the first echo response involves obtaining an echo response from the time domain reflectometer and the cable or transmission line. 5. The method according to a preceding aspect, wherein the method further comprises terminating the second end of the cable or transmission line using a load. 6. The procedure according to aspect 5, wherein terminating the second end of the cable or transmission line using a load of one of: Terminating the second end of the cable or transmission line using a receiver or transceiver used for communication; Terminating the second end of the cable or transmission line using an impedance matched to the impedance of the cable or transmission line. 7. The method according to a preceding aspect, wherein the method further comprises receiving the second echo response while the second end of the cable or transmission line is terminated using a load. 8. The method according to one of aspects 4 - 7, wherein the characteristic of the cable or transmission line has an echo attenuation of the cable or transmission line, and wherein determining the echo attenuation has the following: Determining the ratio of a Fast Fourier Transform of the first echo response to a Fast Fourier Transform of the second echo response to determine a reflection coefficient of the cable or transmission line. 9. The procedure according to aspect 8, wherein determining the echo attenuation further comprises the following: Performing a logarithmic transformation of the ratio to determine the echo attenuation of the cable in decibels. 10. The method according to one of aspects 8 or 9, wherein the characteristic of the cable or transmission line has an impedance of the cable or transmission line, and wherein determining the impedance of the cable or transmission line has the following: Determining the ratio of the reflection coefficient of the cable or transmission line. 11. The procedure according to aspect 10, which further includes the following: Modifying the output impedance of the time domain reflectometer, coupled to the first end of the cable or transmission line, so that it is adapted to the specific impedance of the cable or transmission line. 12. The procedure according to a preceding aspect 5 - 7, which further includes the following: Terminating the first output terminal and the second output terminal of the time domain reflectometer using an impedance matched to the impedance of the time domain reflectometer; Receiving a third echo response; Subtracting a Fast Fourier Transform of the third echo response from a Fast Fourier Transform of the second echo response to obtain the relative frequency response of the cable or transmission line; Determining the ratio of a fast Fourier transform of the first echo response to the relative frequency response of the cable or transmission line to determine a reflection coefficient of the cable or transmission line; Performing a logarithmic transformation of the ratio to determine the echo attenuation of the cable in decibels. 13. The method according to aspect 1, wherein the method further comprises decoupling a load from a second end of the cable or transmission line. 14. The method according to aspect 1 or aspect 13, wherein the method further comprises receiving the second echo response while the second end of the cable or transmission line is open. 15. The method according to aspect 13 or aspect 14, wherein the characteristic of the cable or transmission line has an insertion loss of the cable or transmission line, and wherein determining the insertion loss has the following: Determining the ratio of a Fast Fourier Transform of the first echo response to a Fast Fourier Transform of the second echo response to determine the insertion loss of the cable or transmission line. 16. The procedure according to aspect 15, wherein determining the insertion loss in decibels involves performing a logarithm and multiplying the logarithm by 1 / 2. 17. The procedure according to a preceding aspect, which further includes the following: Selecting a predetermined set of samples within the second echo response and a corresponding predetermined set of samples within the first echo response for comparison. 18. The procedure according to aspect 17, which further includes the following: Determining the presence of a first reflection and a second reflection in the second echo response; Selecting the predetermined set of samples such that they include the second reflection and do not include the first reflection. 19. The procedure according to aspect 18, which further includes the following: Determining the amplitude of a first sample within the predetermined set of samples within the second echo response; Determining the amplitude of a final sample within the predetermined set of samples within the second echo response; Determining the difference between the amplitude of the first sample and the amplitude of the final sample; Fitting a polynomial function to a start and / or end of the predetermined set of samples within the second echo response, such that the first sample and the final sample have the same amplitude. 20. The procedure according to a preceding aspect 14 - 16, which further includes the following: Determining the presence of a first reflection in the second echo response, caused by the second end of the cable or transmission line being open; Selecting a predetermined set of samples within the second echo response that do not include the first reflection, and a corresponding predetermined set of samples within the first echo response for comparison; Determining the ratio of a Fast Fourier transform of the predetermined set of samples within the first echo response to a Fast Fourier transform of the predetermined set of samples within the second echo response; Performing a logarithmic transformation of the ratio to determine the echo attenuation of the cable in decibels. 21. The method according to a preceding aspect, wherein the time domain reflectometer is a transceiver and wherein the first and second echo responses are obtained using the echo cancellation coefficients of the transceiver. 22. The procedure according to aspect 21, wherein the second echo response is obtained using the echo cancellation coefficients of the transceiver while the transceiver is operating to deliver data communication. 23. The method according to claim 21, wherein the second echo response is obtained using the echo cancellation coefficients of a first transceiver coupled to the first end of the cable or transmission line while the first transceiver is operating to provide data communication, and wherein the third echo response is obtained using the echo cancellation coefficients of a second transceiver coupled to the second end of the cable or transmission line while the second transceiver is operating to provide data communication with the first transceiver. 24. The procedure according to a preceding aspect, which further includes the following: Comparing the specific characteristics of the cable or transmission line with a cable standard or a communication standard that includes cable definitions; Determine whether the cable or transmission line conforms to the cable standard or the communication standard. 25. The procedure according to a preceding aspect, which further includes the following: Determining a second characteristic of the cable or transmission line; Determining deterioration of cable characteristics by comparing the second characteristic of the cable or transmission line with the characteristic of the cable or transmission line. 26. The procedure according to a preceding aspect, which further includes the following: Determining a maximum possible length of cable or transmission line that can be supported by a communication system, depending on the specific characteristic of the cable or transmission line, by extrapolating the specific characteristic of the cable or transmission line and comparing the extrapolation with a limit curve. 27. The procedure according to a preceding aspect, which further includes the following: Determining the output power of a transceiver or reflectometer by determining a fast Fourier transform of the first echo response. 28. The procedure according to a preceding aspect 1-4, which further includes the following: Terminating the time domain reflectometer using an impedance matched to the impedance of the time domain reflectometer; Receiving a third echo response; Determining the ratio of a Fast Fourier transform of the first echo response to a Fast Fourier transform of the third echo response to determine a reflection coefficient of the time domain reflectometer; Taking a logarithmic calculation of the ratio to determine the echo attenuation in decibels. 29. The procedure according to a preceding aspect, wherein receiving the first echo response and receiving the second echo response involves transmitting a pseudorandom sequence of transmission symbols or other signal with a spectral power density that includes the frequency range of interest for a given communications standard or transceiver specification. 30. A method for characterizing a cable or transmission line, wherein the method comprises: Obtaining a first echo response using time domain reflectometry from a first end of a cable or transmission line using a first time domain reflectometer, while a second end of the cable is coupled to a second time domain reflectometer; Obtaining a second echo response using time domain reflectometry from the second end of the cable or transmission line while the first end of the cable or transmission line is coupled to the first time domain reflectometer; Identifying a first complete reflection in the first echo response, where the first reflection corresponds to an impedance mismatch between the first time domain reflectometer and the cable or transmission line; Identifying a second complete reflection in the second echo response, wherein the second complete reflection corresponds to an impedance mismatch between the cable or transmission line and the first time domain reflectometer coupled to the first end of the cable; Determining the ratio of a Fast Fourier transform of the first complete reflection within the first echo response to a Fast Fourier transform of the second complete reflection within the second echo response; Taking a logarithmic calculation of the ratio and multiplying by ½ to determine the insertion loss of the cable or transmission line in decibels. 31. The procedure according to aspect 30, which further includes the following: Identifying a third complete reflection in the first echo response, wherein the third complete reflection corresponds to an impedance mismatch between the cable or transmission line and the second reflectometer coupled to the second end of the cable or transmission line; Determining the ratio of a Fast Fourier transform of the first complete reflection within the first echo response to a Fast Fourier transform of the third complete reflection within the first echo response; Taking a logarithmic calculation of the ratio and multiplying by ½ to determine the insertion loss of the cable or transmission line in decibels. 32. A method for characterizing a cable or transmission line, wherein the method comprises: Obtaining an initial echo response from a time-domain reflectometer using time-domain reflectometry; Connecting one end of the cable or transmission line to a time domain reflectometer; Obtaining a second echo response from the cable or transmission line using time-domain reflectometry; Determining the echo attenuation of the cable or transmission line by comparing the first echo response and the second echo response. 33. Method for characterizing a time domain reflectometer, wherein the method comprises: Obtaining an initial echo response from the time domain reflectometer; Terminating one output terminal of the time domain reflectometer; Obtain a second echo response from the time domain reflectometer; Determining a characteristic of the time domain reflectometer by determining a ratio of a fast Fourier transform of the first echo response to a fast Fourier transform of the second echo response. 34. Method for characterizing the time domain reflectometer according to aspect 33, wherein the method further comprises: Determining a change in a property of the time domain reflectometer by monitoring a change in the characteristic over time.

Claims

[1] Method for characterizing a cable or transmission line, wherein the method comprises: Obtaining an initial echo response using time-domain reflectometry; Connecting one end of the cable or transmission line to a time domain reflectometer; Obtaining a second echo response using time-domain reflectometry; and Determining a characteristic of the cable or transmission line by comparing the first echo response and the second echo response. [2] Method according to claim 1, wherein receiving the first echo response includes receiving the first echo response while a first output terminal and a second output terminal of the time domain reflectometer are open or short-circuited. [3] Method according to claim 1, wherein the method further comprises terminating the second end of the cable or transmission line using a load. [4] Method according to claim 3, wherein terminating the second end of the cable or transmission line using a load comprises: Terminating the second end of the cable or transmission line using a receiver or transceiver used for communication; and Terminating the second end of the cable or transmission line using an impedance matched to the impedance of the cable or transmission line. [5] Method according to claim 1, wherein the method further comprises receiving the second echo response while the second end of the cable or transmission line is terminated using a load. [6] Method according to claim 3, wherein the characteristic of the cable or transmission line has an echo attenuation of the cable or transmission line, and wherein determining the echo attenuation has the following: Determining the ratio of a Fast Fourier Transform of the first echo response to a Fast Fourier Transform of the second echo response to determine a reflection coefficient of the cable or transmission line. [7] Method according to claim 6, wherein the characteristic of the cable or transmission line comprises an impedance of the cable or transmission line, and wherein determining the impedance of the cable or transmission line comprises: Determining the ratio of the reflection coefficient of the cable or transmission line. [8] The method of claim 7, further comprising: Modifying the output impedance of the time domain reflectometer, coupled to the first end of the cable or transmission line, so that it is adapted to the specific impedance of the cable or transmission line. [9] The method of claim 3, further comprising: Terminating a first output terminal and a second output terminal of the time domain reflectometer using an impedance matched to the impedance of the time domain reflectometer; Receiving a third echo response; Subtracting a Fast Fourier Transform of the third echo response from a Fast Fourier Transform of the second echo response to obtain a relative frequency response of the cable or transmission line; Determining the ratio of a fast Fourier transform of the first echo response to the relative frequency response of the cable or transmission line to determine a reflection coefficient of the cable or transmission line; and Performing a logarithmic transformation of the ratio to determine the echo attenuation of the cable or transmission line in decibels. [10] Method according to claim 1, wherein the method further comprises receiving the second echo response while the second end of the cable or transmission line is open. [11] Method according to claim 10, wherein the characteristic of the cable or transmission line has an insertion loss of the cable or transmission line, and wherein determining the insertion loss has the following: Determining the ratio of a Fast Fourier Transform of the first echo response to a Fast Fourier Transform of the second echo response to determine the insertion loss of the cable or transmission line. [12] The method of claim 1, further comprising: Selecting a predetermined set of samples within the second echo response and a corresponding predetermined set of samples within the first echo response for comparison. [13] The method of claim 12, further comprising: Determining the presence of a first reflection and a second reflection in the second echo response; and Selecting the predetermined set of samples such that they include the second reflection and do not include the first reflection. [14] The method of claim 13, further comprising: Determining the amplitude of a first sample within the predetermined set of samples within the second echo response; Determining the amplitude of a final sample within the predetermined set of samples within the second echo response; Determining the difference between the amplitude of the first sample and the amplitude of the final sample; and Fitting a polynomial function to a start and / or end of the predetermined set of samples within the second echo response, such that the first sample and the final sample have the same amplitude. [15] The method of claim 10, further comprising: Determining the presence of a first reflection in the second echo response, caused by the second end of the cable or transmission line being open; Selecting a predetermined set of samples within the second echo response that do not include the first reflection, and a corresponding predetermined set of samples within the first echo response for comparison; Determining the ratio of a Fast Fourier transform of the predetermined set of samples within the first echo response to a Fast Fourier transform of the predetermined set of samples within the second echo response; and Performing a logarithmic transformation of the ratio to determine the echo attenuation of the cable in decibels. [16] The method of claim 1, further comprising: Comparing the specific characteristics of the cable or transmission line with a cable standard or a communications standard that includes cable definitions; and Determine whether the cable or transmission line conforms to the cable standard or the communication standard. [17] The method of claim 1, further comprising: Determining a second characteristic of the cable or transmission line; and Determining deterioration of cable characteristics by comparing the second characteristic of the cable or transmission line with the characteristic of the cable or transmission line. [18] Method for characterizing a cable or transmission line, wherein the method comprises: Obtaining a first echo response using time domain reflectometry from a first end of a cable or transmission line using a first time domain reflectometer, while a second end of the cable is coupled to a second time domain reflectometer; Obtaining a second echo response using time domain reflectometry from the second end of the cable or transmission line while the first end of the cable or transmission line is coupled to the first time domain reflectometer; Identifying a first complete reflection in the first echo response, where the first reflection corresponds to an impedance mismatch between the first time domain reflectometer and the cable or transmission line; Identifying a second complete reflection in the second echo response, where the second complete reflection corresponds to an impedance mismatch between the cable or transmission line and the first time domain reflectometer coupled to the first end of the cable; Determining the ratio of a Fast Fourier transform of the first complete reflection within the first echo response to a Fast Fourier transform of the second complete reflection within the second echo response; and Taking a logarithmic calculation of the ratio and multiplying by ½ to determine the insertion loss of the cable in decibels. [19] The method of claim 18, further comprising: Identifying a third complete reflection in the first echo response, wherein the third complete reflection corresponds to an impedance mismatch between the cable or transmission line and the second reflectometer coupled to the second end of the cable or transmission line; Determining the ratio of a Fast Fourier transform of the first complete reflection within the first echo response to a Fast Fourier transform of the third complete reflection within the first echo response; and Taking a logarithm of the ratio and multiplying by ½ to determine the insertion loss of the cable in decibels. [20] Method for characterizing a cable or transmission line, wherein the method comprises: Obtaining an initial echo response from a time-domain reflectometer using time-domain reflectometry; Connecting one end of the cable or transmission line to a time domain reflectometer; Obtaining a second echo response from the cable or transmission line using time-domain reflectometry; and Determining the echo attenuation of the cable or transmission line by comparing the first echo response and the second echo response.

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