A method for improving the detection accuracy of coaxial cable fault points and its implementation system

Abstract

The present invention relates to the field of fault detection technology, and in particular to a method for improving the detection accuracy of a coaxial cable fault point and its implementation system, the method comprising the following steps in sequence: arranging a port resistor on a coaxial cable, sending a characteristic code signal output from the port resistor and transmitting through the coaxial cable, a reference signal and a returned detection signal are both output from the port resistor; converting the reference signal and the detection signal into digital characteristic code representations; adjusting the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero; calculating the time difference T_N and the delay difference T_delay between the reference signal and the detection signal; calibrating the transmission speed parameters of the current model of the coaxial cable, and using the calibrated transmission speed parameters to calculate the location distance of the fault point. The present invention can eliminate the internal circuit delay difference, calculate the high-precision phase difference to improve the accuracy, calibrate the cable transmission speed parameters, and greatly improve the detection accuracy of the coaxial cable fault point.

Description

Technical Field

[0001] The present invention relates to the technical field of fault detection; in particular, the present invention relates to a method for improving the detection accuracy of a coaxial cable fault point and a system for realizing the method. Background Art

[0002] In the field of automotive communications, coaxial cables are often used for data transmission, such as the transmission of data collected by cameras to vehicle control systems. The absence of fault points in coaxial cables is a prerequisite for ensuring normal data transmission, so real-time detection of coaxial cable fault points is of great significance.

[0003] For example, the Chinese invention with application number 2024104717089 discloses a diagnostic system for an on-board video system, which can better detect the location of the fault point in the coaxial cable. However, the system also has certain defects. For example, due to the delay difference between the internal circuit of the sending signal and the return signal (referring to the part of the path from the sending signal circuit to the output and then from the output detection back), the fault point location is not accurate enough, that is, the fault point detection accuracy needs to be improved. Summary of the invention

[0004] In view of this, the present invention provides a method for improving the detection accuracy of a coaxial cable fault point and an implementation system thereof, which can improve the detection accuracy of a coaxial cable fault point.

[0005] In order to achieve the aforementioned object, the present invention provides the following technical solutions:

[0006] A method for improving the detection accuracy of coaxial cable fault points comprises the following steps in sequence:

[0007] A port resistor is arranged on the coaxial cable, a sending characteristic code signal is output from the port resistor and transmitted through the coaxial cable, and a reference signal and a returned detection signal are both output from the port resistor;

[0008] Converting the reference signal and the detection signal into digital feature code representation;

[0009] Adjust the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero;

[0010] Calculate the time difference T_N between the reference signal and the detection signal, and calculate the time delay difference T_delay between the detection signal and the reference signal according to the formula T_delay=T_N+phase_code*delta_t; delta_t is the adjustment accuracy parameter of the phase adjuster, and phase_code is the control code required to adjust the phase difference to zero;

[0011] The transmission speed parameters of the current coaxial cable model are calibrated, and the location distance of the fault point is calculated using the calibrated transmission speed parameters according to the formula L=(T_delay*v_cable) / 2, where v_cable is the transmission speed parameter of the coaxial cable and L is the distance of the fault point.

[0012] In the above scheme, the reference signal is directly returned after alignment at the transmitting end, and the reference signal is directly output from the port resistor, and the returned detection signal is also output from the port resistor, so all delay differences caused by the internal circuit can be eliminated, and then the detection accuracy can be improved. The phase adjuster adjusts the phase of the input reference signal through the control code phase_code, that is, the phase delay size of the actual circuit is controlled by digital coding. Different digital codes correspond to different phase delays. Adjust until alignment, so that it is known how much phase difference is actually adjusted, and high-precision measurement is achieved, from the traditional time accuracy T_N to delta_t. Delta_t is much smaller than T_N in application, so the distance accuracy obtained by this method is also much higher than the accuracy of the traditional method. Since there are many types of coaxial cables for vehicle-mounted video transmission, and the signal propagation speed corresponding to each type is slightly different, if the distance of the fault point is calculated according to a unified speed, it will also cause errors in the detection accuracy. In the above scheme, by recording and saving different transmission speed parameters corresponding to different models in advance, the corresponding transmission speed parameters are retrieved according to the currently used model during actual use, and then calculated, the detection error caused by the speed difference of different models can be eliminated, and then the detection accuracy can be further improved.

[0013] In a further optimized solution, the signal sending circuit outputs the characteristic code signal with the amplitude of the power supply voltage when sending the characteristic code signal.

[0014] In the above scheme, by increasing the amplitude of the characteristic code signal, the amplitude of the returned detection signal is increased, that is, the signal-to-noise ratio of the overall circuit is improved, thereby reducing the detection error of the hardware circuit and further improving the detection accuracy.

[0015] The implementation system of the above method for improving the detection accuracy of coaxial cable fault points includes:

[0016] A signal generating circuit, the signal generating circuit comprising a port resistor arranged on the coaxial cable, the signal generating circuit is used to send a characteristic code signal and make it output from the port resistor and then transmitted through the coaxial cable, and is used to receive a reference signal output from the port resistor and a returned detection signal, and convert the reference signal and the detection signal into a digital characteristic code representation;

[0017] A phase difference processing circuit, used for adjusting the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero, and calculating the time difference T_N between the reference signal and the detection signal;

[0018] The algorithm module is used to calculate the time delay difference T_delay between the detection signal and the reference signal according to the formula T_delay=T_N+phase_code*delta_t, and calibrate the transmission speed parameters of the current model of coaxial cable, and use the calibrated transmission speed parameters to calculate the location distance of the fault point according to the formula L=(T_delay*v_cable) / 2; delta_t is the adjustment accuracy parameter of the phase adjuster, phase_code is the control code required to adjust the phase difference to zero, v_cable is the transmission speed parameter of the coaxial cable, and L is the distance of the fault point.

[0019] The signal generating circuit further comprises a signal sending circuit, a reference signal processing circuit, and a detection signal receiving circuit, wherein the signal sending circuit, the reference signal processing circuit, and the detection signal receiving circuit are all electrically connected to the port resistor;

[0020] The characteristic code signal sent by the signal sending circuit is output to the port resistor and then transmitted through the coaxial cable; the detection signal receiving circuit receives the returned detection signal and extracts the characteristic code representation from the detection signal; the reference signal processing circuit extracts the characteristic code representation from the reference signal.

[0021] The signal generating circuit also includes a first signal amplifying circuit, a second signal amplifying circuit and a third signal amplifying circuit. The signal sending circuit is electrically connected to the first signal amplifying circuit, the second signal amplifying circuit is electrically connected to the reference signal processing circuit, and the third signal amplifying circuit is electrically connected to the detection signal receiving circuit. The first signal amplifying circuit, the second signal amplifying circuit and the third signal amplifying circuit are all electrically connected to the port resistor. The characteristic code signal sent by the signal sending circuit is amplified by the first signal amplifying circuit and then output to the port resistor. The returned detection signal is amplified by the third signal amplifying circuit and then received by the detection signal receiving circuit. The reference signal is amplified by the second signal amplifying circuit and then received by the reference signal processing circuit.

[0022] In the above scheme, by setting a signal amplification circuit to amplify the signal before outputting it, it is beneficial to more accurately extract the characteristic code in the signal and provide technical support for accurate detection of the fault point.

[0023] The phase difference processing circuit includes a phase adjuster, a phase detector, a signature comparator and a filter, the reference signal processing circuit is connected to the input end of the phase adjuster, the detection signal receiving circuit is respectively connected to the input end of the phase detector and the input end of the signature comparator, the output end of the phase adjuster is connected to the input end of the phase detector, the output end of the phase detector is connected to the input end of the filter, and the output end of the filter is connected to the input end of the phase adjuster;

[0024] The phase adjuster is used to adjust the phase of the reference signal according to the control code output by the filter, the phase detector is used to compare the phase difference between the reference signal and the detection signal after phase adjustment, the filter outputs the control code according to the phase difference, and the signature comparator is used to calculate the time difference T_N between the signature code representation of the reference signal and the detection signal after phase alignment.

[0025] Compared with the prior art, the present invention proposes a complete system and method for improving the detection accuracy of coaxial cable fault points, including a hardware circuit delay elimination solution, a hardware algorithm for precise delay detection (phase alignment), and a software calibration algorithm for different types of cables. Therefore, the detection accuracy of the fault point location can be greatly improved.

[0026] Moreover, in the solution of the present invention, only the host side needs to participate in the detection, and no operation is required from the machine side; the host side embedded in the video transmission system does not require additional expensive equipment.

[0027] In addition, the solution of the present invention can detect the aging of the coaxial cable (excessive impedance change in a certain section or the whole) and accurately locate the position. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The disclosure of the present invention will become more apparent with reference to the accompanying drawings. It should be understood that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings:

[0029] Figure 1 is a structural diagram of a signal generating circuit in an embodiment.

[0030] Figure 2 This is the logic diagram for impedance change detection.

[0031] Figure 3 FIG. 4 is a block diagram of a phase difference processing circuit in an embodiment.

[0032] Figure 4 Schematic diagram of the bit stream of the reference signal and the detection signal input before phase adjustment.

[0033] Figure 5 Schematic diagram of the bit stream of the reference signal and the detection signal after phase adjustment. DETAILED DESCRIPTION

[0034] With reference to the accompanying drawings and specific embodiments, the structure, composition, characteristics and advantages of the vehicle-mounted high-speed transmitting circuit of the present invention, including the serializer / deserializer thereof and the use method thereof, will be explained below in an exemplary manner. However, all descriptions should not be used to form any limitations on the present invention.

[0035] In addition, for any single technical feature described or implied in the embodiments mentioned in this document, or any single technical feature displayed or implied in the accompanying drawings, the present invention still allows for continued arbitrary combination or deletion between these technical features (or their equivalents) without any technical obstacles, and thus it should be considered that these more embodiments according to the present invention are also within the scope of the description of this document.

[0036] In addition, the terms "first", "second", and "third" are used only for descriptive purposes and to facilitate distinction, and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include at least one of the features.

[0037] This embodiment provides a method for improving the accuracy of coaxial cable fault point detection, which includes the following steps in sequence:

[0038] A port resistor is arranged on the coaxial cable, a sending characteristic code signal is output from the port resistor and transmitted through the coaxial cable, and a reference signal and a returned detection signal are both output from the port resistor;

[0039] Converting the reference signal and the detection signal into digital feature code representation;

[0040] Adjust the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero;

[0041] Calculate the time difference T_N between the reference signal and the detection signal, and calculate the time delay difference T_delay between the detection signal and the reference signal according to the formula T_delay=T_N+phase_code*delta_t; delta_t is the adjustment accuracy parameter of the phase adjuster, and phase_code is the control code required to adjust the phase difference to zero;

[0042] The transmission speed parameters of the current coaxial cable model are calibrated, and the location distance of the fault point is calculated using the calibrated transmission speed parameters according to the formula L=(T_delay*v_cable) / 2, where v_cable is the transmission speed parameter of the coaxial cable and L is the distance of the fault point.

[0043] That is to say, the present invention proposes a complete set of methods for improving detection accuracy, including improvements in both hardware circuits and software methods. The hardware circuit improves accuracy by eliminating the internal circuit delay difference between the sent signal and the returned detection signal, and calculating the high-precision phase difference between the reference signal and the detection signal to improve accuracy. The software method improves accuracy through parameter calibration. The analog circuit architecture reduces the internal circuit delay error, and the analog and digital algorithms cooperate to accurately calculate the phase difference between the reference signal and the return signal. At the same time, the cable transmission speed parameters are calibrated in conjunction with the software method, thereby greatly improving the fault point detection accuracy.

[0044] The present invention also provides a system for implementing the above method, including:

[0045] A signal generating circuit, the signal generating circuit comprising a port resistor arranged on the coaxial cable, the signal generating circuit is used to send a characteristic code signal and make it output from the port resistor and then transmitted through the coaxial cable, and is used to receive a reference signal output from the port resistor and a returned detection signal, and convert the reference signal and the detection signal into a digital characteristic code representation;

[0046] A phase difference processing circuit, used for adjusting the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero, and calculating the time difference T_N between the reference signal and the detection signal;

[0047] The algorithm module is used to calculate the time delay difference T_delay between the detection signal and the reference signal according to the formula T_delay=T_N+phase_code*delta_t, and calibrate the transmission speed parameters of the current model of coaxial cable, and use the calibrated transmission speed parameters to calculate the location distance of the fault point according to the formula L=(T_delay*v_cable) / 2; delta_t is the adjustment accuracy parameter of the phase adjuster, phase_code is the control code required to adjust the phase difference to zero, v_cable is the transmission speed parameter of the coaxial cable, and L is the distance of the fault point.

[0048] Figure 1 The structure of the signal generating circuit provided in this embodiment is shown. Specifically, the signal generating circuit includes a signal transmitting circuit, a first signal amplifying circuit, a port resistor, a second signal amplifying circuit, a reference signal processing circuit, a third signal amplifying circuit, a detection signal receiving circuit and a coaxial cable, the signal transmitting circuit is electrically connected to the first signal amplifying circuit, the second signal amplifying circuit is electrically connected to the reference signal processing circuit, the third signal amplifying circuit is electrically connected to the detection signal receiving circuit, the first signal amplifying circuit, the second signal amplifying circuit and the third signal amplifying circuit are all electrically connected to the port resistor, and the port resistor is connected to the coaxial cable.

[0049] Figure 1The arrow in the figure indicates the direction of signal transmission. Figure 1 As shown, the characteristic code signal sent by the signal sending circuit is amplified by the first signal amplifying circuit and then output to the port resistor, and then transmitted through the coaxial cable. The other end of the coaxial cable is connected to the slave end such as the vehicle-mounted video. If there is no fault point in the coaxial cable, the characteristic code signal will be transmitted to the slave end after passing through the coaxial cable and received by the slave end; if there is a fault point in the coaxial cable, the characteristic code signal will stop transmitting at the fault point after passing through the coaxial cable, and return a detection signal, which will be received by the detection signal receiving circuit.

[0050] like Figure 2 As shown in the figure, when there is a fault point, the impedance of the coaxial cable will change suddenly. After sending the characteristic code signal, if the area where the cable impedance changes too much is encountered, the following will be returned Figure 2 The spike waveform shown in the figure can be used to determine whether there is a fault point and the specific location of the fault point through the returned detection signal. Figure 2 The analog circuit shown (which is built into the detection signal receiving circuit) is used to process and extract relevant useful logic signals, which are then further processed to obtain a characteristic code representation of the detection signal.

[0051] Similarly, the reference signal processing circuit performs analog-to-digital conversion on the reference signal, extracts relevant useful logic signals, and further processes to obtain the characteristic code representation of the reference signal. After the reference signal and the detection signal extract the characteristic code, the time difference can be calculated, and the time difference multiplied by the transmission speed can obtain the location distance of the fault point.

[0052] because Figure 1 In the structure shown, the alignment at the transmitting end is directly returned as a reference signal, the reference signal is directly output from the port resistor, and the returned detection signal is also output from the port resistor, so all delay differences caused by the internal circuit can be eliminated.

[0053] In addition, the signal sending circuit preferably outputs the characteristic code signal with a full swing amplitude (amplitude of the power supply voltage), thereby increasing the amplitude of the returned detection signal, that is, improving the signal-to-noise ratio of the overall circuit, thereby reducing the detection error of the hardware circuit and further improving the detection accuracy.

[0054] The detection signal is the reflected signal, and the reference signal is the source. The time when the detection signal returns is related to the location of the fault point of the coaxial cable. Therefore, there is a phase difference between the reference signal and the detection signal, and the phase difference will also affect the detection accuracy. Therefore, in order to improve the accuracy loss caused by the phase difference between the reference signal and the detection signal, this embodiment provides Figure 3 The phase difference processing circuit shown.

[0055] like Figure 3As shown, the phase difference processing circuit includes a phase adjuster, a phase detector, a signature comparator and a filter, a reference signal is input into the phase adjuster (i.e., the reference signal processing circuit is connected to the phase adjuster), a detection signal is input into the phase detector and the signature comparator (i.e., the detection signal receiving circuit is respectively connected to the phase detector and the signature comparator), the reference signal after the phase is adjusted by the phase adjuster is input into the phase detector, the output end of the phase detector is connected to the input end of the filter, the output end of the filter is connected to the input end of the phase adjuster, a reference is provided for the control strategy of the phase adjuster through the feedback control code phase_code, and the reference signal after the phase is adjusted by the phase adjuster is simultaneously used as the input of the signature comparator.

[0056] The phase adjuster can adjust the phase of the input reference signal through the control code phase_code; the phase detector compares the phase difference between the detection signal and the adjusted reference signal, and outputs the phase difference information; the filter filters the phase difference information and outputs the control code phase_code. After filtering, the fluctuation of phase_code is small; the control code phase_code output by the filter is fed back to the phase adjuster to prompt the phase adjuster to adjust the phase of the input reference signal through the control code phase_code so that the phase difference between the reference signal and the detection signal is 0, that is, phase alignment is achieved; after the phase alignment, the signature comparator calculates the time difference between the signature representation of the reference signal and the detection signal, and outputs the time difference T_N.

[0057] The phase adjuster can adjust the phase of the input reference signal through the control code phase_code, that is, control the phase delay of the actual circuit through digital coding. Different digital codes correspond to different phase delays. The phase is adjusted until it is aligned, that is, until the phase difference is zero. In this way, we know how much the phase difference is actually adjusted.

[0058] Figure 4 It represents the bit stream of the input reference signal and the detection signal. There is a phase difference between the detection signal and the reference signal, and the time difference between their feature codes is T_N+phase difference, which represents the bit cycle interval of T_N integer. The phase difference represents the phase difference between the edges of the two signals. Figure 5 For passing Figure 3 The bit streams of the reference signal and the detection signal adjusted by the phase adjuster in the embodiment have a phase difference of 0 and a characteristic code time difference of T_N.

[0059] Therefore, the delay difference between the detection signal and the reference signal is:

[0060] T_delay=T_N+phase_code*delta_t;

[0061] delta_t is Figure 3 The phase_code in this formula refers to the control code required to adjust the phase difference to zero. This solution changes the traditional time accuracy T_N to delta_t. In the application, delta_t is much smaller than T_N. Therefore, the distance accuracy obtained by this method is much higher than the detection accuracy of the traditional method.

[0062] Since there are many types of coaxial cables for vehicle video transmission, and the signal propagation speed corresponding to each type is slightly different, if the distance to the fault point is calculated according to a unified speed, it will also lead to errors in detection accuracy. Therefore, software calibration is performed for any type of coaxial cable used and the model parameters are saved. The coaxial cable parameters are calibrated according to the following formula:

[0063] L = (T_delay*v_cable) / 2;

[0064] v_cable is the transmission speed parameter of the coaxial cable, and L is the distance of the fault point, that is, the distance from the fault point to the signal sending end. This parameter is different for each cable, so the cable parameters are saved first, and the corresponding parameters are found according to the cable model during calculation. In other words, different transmission speed parameters are used for different types of coaxial cables, thereby reducing the error caused by different cable models and further improving the detection accuracy.

[0065] The above-described embodiments are only specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications, replacements and improvements within the technical scope disclosed by the present invention, and these modifications, replacements and improvements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for improving the accuracy of coaxial cable fault point detection, characterized in that: The following steps are included in sequence: A port resistor is arranged on the coaxial cable, a sending characteristic code signal is output from the port resistor and transmitted through the coaxial cable, the characteristic code signal is aligned at the sending end and directly returned as a reference signal, and both the reference signal and the returned detection signal are output from the port resistor; Converting the reference signal and the detection signal into digital feature code representation; Adjust the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero; Calculate the time difference T_N between the reference signal and the detection signal, and calculate the time delay difference T_delay between the detection signal and the reference signal according to the formula T_delay=T_N+phase_code*delta_t; delta_t is the adjustment accuracy parameter of the phase adjuster, and phase_code is the control code required to adjust the phase difference to zero; The transmission speed parameters of the current coaxial cable model are calibrated, and the location distance of the fault point is calculated using the calibrated transmission speed parameters according to the formula L=(T_delay*v_cable) / 2, where v_cable is the transmission speed parameter of the coaxial cable and L is the distance of the fault point.

2. The method for improving the detection accuracy of coaxial cable fault points according to claim 1, characterized in that: When the characteristic code signal is transmitted, the characteristic code signal is outputted with the amplitude of the power supply voltage.

3. The system for implementing the method for improving the detection accuracy of coaxial cable fault points as claimed in claim 1, characterized in that: include: A signal generating circuit, the signal generating circuit comprising a port resistor arranged on the coaxial cable, the signal generating circuit is used to send a characteristic code signal and make it output from the port resistor and then transmitted through the coaxial cable, and is used to receive a reference signal output from the port resistor and a returned detection signal, and convert the reference signal and the detection signal into a digital characteristic code representation; A phase difference processing circuit, used for adjusting the phase of the reference signal so that the phase difference between the reference signal and the detection signal is zero, and calculating the time difference T_N between the reference signal and the detection signal; The algorithm module is used to calculate the time delay difference T_delay between the detection signal and the reference signal according to the formula T_delay=T_N+phase_code*delta_t, and calibrate the transmission speed parameters of the current model of coaxial cable, and use the calibrated transmission speed parameters to calculate the location distance of the fault point according to the formula L=(T_delay*v_cable) / 2; delta_t is the adjustment accuracy parameter of the phase adjuster, phase_code is the control code required to adjust the phase difference to zero, v_cable is the transmission speed parameter of the coaxial cable, and L is the distance of the fault point.

4. The implementation system according to claim 3, characterized in that: The signal generating circuit further comprises a signal sending circuit, a reference signal processing circuit, and a detection signal receiving circuit, wherein the signal sending circuit, the reference signal processing circuit, and the detection signal receiving circuit are all electrically connected to the port resistor; The characteristic code signal sent by the signal sending circuit is output to the port resistor and then transmitted through the coaxial cable; the detection signal receiving circuit receives the returned detection signal and extracts the characteristic code representation from the detection signal; The reference signal processing circuit extracts the signature representation from the reference signal.

5. The implementation system according to claim 4, characterized in that: The signal generating circuit also includes a first signal amplifying circuit, a second signal amplifying circuit and a third signal amplifying circuit. The signal sending circuit is electrically connected to the first signal amplifying circuit, the second signal amplifying circuit is electrically connected to the reference signal processing circuit, and the third signal amplifying circuit is electrically connected to the detection signal receiving circuit. The first signal amplifying circuit, the second signal amplifying circuit and the third signal amplifying circuit are all electrically connected to the port resistor. The characteristic code signal sent by the signal sending circuit is amplified by the first signal amplifying circuit and then output to the port resistor. The returned detection signal is amplified by the third signal amplifying circuit and then received by the detection signal receiving circuit. The reference signal is amplified by the second signal amplifying circuit and then received by the reference signal processing circuit.

6. The implementation system according to claim 4, characterized in that: The phase difference processing circuit includes a phase adjuster, a phase detector, a signature comparator and a filter, the reference signal processing circuit is connected to the input end of the phase adjuster, the detection signal receiving circuit is respectively connected to the input end of the phase detector and the input end of the signature comparator, the output end of the phase adjuster is connected to the input end of the phase detector, the output end of the phase detector is connected to the input end of the filter, and the output end of the filter is connected to the input end of the phase adjuster; The phase adjuster is used to adjust the phase of the reference signal according to the control code output by the filter, the phase detector is used to compare the phase difference between the reference signal and the detection signal after phase adjustment, the filter outputs the control code according to the phase difference, and the signature comparator is used to calculate the time difference T_N between the signature code representation of the reference signal and the detection signal after phase alignment.

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