JP4472883B2 - Cable transmission characteristic measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cable transmission characteristic measuring apparatus for measuring transmission characteristics such as attenuation with respect to a wideband frequency for a measurement object such as a UTP (unshielded twisted pair) cable used in a LAN cable system.
[0002]
[Prior art]
In general, transmission characteristics such as an attenuation amount of a measurement object such as this type of UTP cable are measured by using a transmission characteristic measuring apparatus 31 having a configuration shown in FIG.
[0003]
The transmission characteristic measurement device 31 includes a signal generation unit 34 connected to one end side (far end side) of two pairs of twisted pair cables 33a and 33b in the UTP cable 32 via a first connector 3, and a twisted pair cable 33a. , 33b and a measuring unit 35 connected to the other end side (near end side) via the second connector 5.
[0004]
The signal generation unit 34 includes a receiving unit 36 connected to one of the twisted pair cables 33a and 33b, and a measurement signal generating unit 11 connected to the other twisted pair cable 33b as a measurement object. The high-frequency measurement signal Ss of a single pulse signal having a frequency band required for transmission characteristic measurement is output to the twisted pair cable 33b. In this case, the receiving unit 36 receives the guide signal Sg via the twisted pair cable 33a, and at this time, generates the trigger signal ST2 and outputs it to the measurement signal generating unit 11. The measurement signal generator 11 generates a high frequency measurement signal Ss when the trigger signal ST2 is input from the receiver 36, and outputs the high frequency measurement signal Ss to the twisted pair cable 33b.
[0005]
The measurement unit 35 includes a guide signal generation unit 37 connected to the twisted pair cable 33a, a measurement unit 38 connected to the twisted pair cable 33b, and a display unit 19. The high frequency measurement output to one end of the twisted pair cable 33b. By sampling a time response waveform of a voltage (hereinafter also referred to as “induced voltage”) Vs induced on the other end side based on the signal Ss, the transmission characteristic of the twisted pair cable 33b as a measurement object with respect to a wideband frequency is measured. In this case, the guide signal generation unit 37 generates a guide signal Sg when the activation signal SS1 is input from the measurement unit 38, and outputs it to the other end side of the twisted pair cable 33a. The measurement unit 38 generates the activation signal SS1 when receiving a measurement start instruction from the measurer. Further, the measurement unit 38 samples the time response waveform of the induced voltage Vs induced on the other end side of the twisted pair cable 33b within a predetermined time after generating the activation signal SS1, and performs FFT calculation on the measurement data obtained by the sampling. To convert the frequency. Further, the measurement unit 38 measures the transmission characteristic (for example, the attenuation characteristic with respect to the frequency) of the twisted pair cable 33b as the measurement object based on the frequency-converted data, and outputs the display data DD. The transmission characteristic of the twisted pair cable 33b is displayed on the display unit 19. The display unit 19 is composed of a monitor such as an LCD panel, and displays transmission characteristics based on the display data DD output from the measurement unit 38.
[0006]
In this transmission characteristic measuring apparatus 31, at the start of measurement, the measurement unit 38 generates the activation signal SS1 and outputs it to the guide signal generation unit 37. Next, the guide signal generation unit 37 generates a guide signal Sg and outputs it to the other end side of the twisted pair cable 33a. Thereby, the guide signal Sg is transmitted to the receiving unit 36 of the signal generation unit 34 via the twisted pair cable 33a. At this time, the receiving unit 36 generates the trigger signal ST2 and outputs it to the measurement signal generating unit 11. Next, the measurement signal generator 11 generates a high frequency measurement signal Ss and outputs it to the twisted pair cable 33b. In this case, the induced voltage Vs is generated on the other end side of the twisted pair cable 33b with a very short delay from the output of the start signal SS1 by the measurement unit 38 due to the output of the high frequency measurement signal Ss. The measurement unit 38 samples the time response waveform of the induced voltage Vs and calculates the transmission characteristic with respect to the wideband frequency of the twisted pair cable 33b as the measurement target by performing FFT calculation. Thereafter, the display unit 19 displays the transmission characteristic of the twisted pair cable 33b as the measurement object by outputting the display data DD for displaying the transmission characteristic by the measuring unit 38.
[0007]
As described above, in the transmission characteristic measuring apparatus 31, the measurement unit 35 outputs the guide signal Sg to the signal generation unit 34 via the twisted pair cable 33a, whereby the signal generation unit 34 transmits the high frequency measurement signal to the twisted pair cable 33b. The output timing of Ss is controlled. For this reason, the output timing of the high-frequency measurement signal Ss to the twisted pair cable 33b by the signal generating unit 34 and the sampling start (measurement start) timing by the measuring unit 35 can be synchronized, so that one end side of the twisted pair cable 33b can be provided. Based on the output high-frequency measurement signal Ss, the induced voltage Vs induced on the other end side can be sampled.
[0008]
[Problems to be solved by the invention]
However, this conventional transmission characteristic measuring device 31 has the following problems. That is, in this transmission characteristic measuring apparatus 31, in order to synchronize the output timing of the high frequency measurement signal Ss to the twisted pair cable 33b by the signal generating unit 34 and the sampling start timing by the measuring unit 35, the twisted pair cable from the measuring unit 35 is synchronized. It is necessary to output the guide signal Sg to the signal generation unit 34 via 33a. For this reason, in order to transmit the guide signal Sg, a dedicated twisted pair cable other than the twisted pair cable 33b as a measurement object is required. Therefore, the conventional transmission characteristic measuring device 31 cannot transmit the guide signal Sg to the signal generation unit 34 side when a connection failure or disconnection occurs in the twisted pair cable 33a that transmits the guide signal Sg. There is a problem that the transmission characteristic of the twisted pair cable 33b becomes impossible to measure. In addition, when measurement is impossible, it is difficult to immediately identify which of the twisted pair cables 33a and 33b is defective, so that it takes a long time to identify the cause of the measurement failure.
[0009]
The present invention has been made in view of such problems, and reliably synchronizes the output timing of the high-frequency measurement signal by the signal generation unit and the measurement start timing in the measurement unit without using a dedicated cable other than the measurement object. It is a main object of the present invention to provide a cable transmission characteristic measuring apparatus capable of accurately measuring the cable transmission characteristic.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a cable transmission characteristic measuring apparatus according to claim 1 is connected to one end of a cable as a measurement object and outputs a high-frequency measurement signal over a wide band to the cable, and the cable A measurement unit connected to the other end of the cable and sampling a time response waveform of a voltage induced on the other end of the cable based on the output high-frequency measurement signal, and measuring a transmission characteristic with respect to the broadband frequency of the cable. wherein the signal generating unit, a guide signal prior to the high frequency measurement signal output to the cable, the measuring unit, the transmission of the start to Luque Buru measurement of the transmission characteristics of the reception of the guide signal condition a characteristic measurement apparatus, the signal generation unit, repeated and the guide signal and the high-frequency measuring signal in a constant cycle And generating a time interval between the guide signal and the high-frequency measurement signal for each period while increasing or decreasing the unit time by a predetermined unit time, and the measurement unit The measurement of the transmission characteristic is started when a predetermined time has elapsed from the reception time point, and the transmission characteristic is measured by synthesizing the sampled and digitized digital data in the measurement on the time axis .
[0011]
The cable transmission characteristic measuring apparatus according to claim 2, wherein the signal generation unit is configured to measure the high frequency when a predetermined time elapses from a transmission end time of the guide signal. A signal is output to the cable, and the measurement unit starts measuring the transmission characteristics before the predetermined time has elapsed from the end of reception of the guide signal.
[0013]
The cable transmission characteristic measurement device according to claim 3 is the cable transmission characteristic measurement device according to claim 1 or 2 , wherein the measurement unit outputs a measurement start request signal to the cable, and the signal generation unit includes: After the measurement start request signal is received, output of the guide signal and the high frequency measurement signal to the cable is started.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a cable transmission characteristic measuring apparatus according to the invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the structure same as the conventional transmission characteristic measuring apparatus 31, and the UTP cable 32, and the overlapping description is abbreviate | omitted.
[0015]
First, the configuration of the transmission characteristic measuring apparatus 1 will be described with reference to FIG. Hereinafter, the measurement of the attenuation characteristic of the twisted pair cable 33b in the UTP cable 32 will be described as an example. However, the transmission characteristic measurement device is not limited to the attenuation characteristic but is also used for measuring transmission characteristics such as impedance characteristics and crosstalk characteristics. 1 can be applied.
[0016]
As shown in the figure, the transmission characteristic measuring apparatus 1 includes a signal generating unit 4 and a measuring unit 6. The signal generation unit 4 is connected to one end side (far end side) of a twisted pair cable 33b (hereinafter, also referred to as “cable 33b”) as a measurement object in the UTP cable 32 via the first connector 3, The measurement signal Ss is output to the cable 33b. The measurement unit 6 is connected to the other end side (near end side) of the cable 33b via the second connector 5 and induced voltage Vs induced on the other end side of the cable 33b due to the output of the high frequency measurement signal Ss. The amount of attenuation of the cable 33b with respect to the wideband frequency is measured by sampling the time response waveform.
[0017]
Specifically, the signal generation unit 4 includes a first bidirectional transmission unit 7, a command reception unit 8, a first timing control unit 9, a guide signal generation unit 10, a measurement signal generation unit 11, and a signal synthesis unit 12. It has. In this case, the first bidirectional transmitter 7 is connected to the first connector 3, receives a signal transmitted from the measurement unit 6 via the cable 33 b, outputs the signal to the command receiver 8, and performs signal synthesis. The signal output from the unit 12 is output to the cable 33b. The command receiving unit 8 detects and decodes the measurement start request command (measurement start request signal) DCM included in the signal received by the first bidirectional transmission unit 7, and the signal generation start signal SST2 is the first. Are output to the timing controller 9. When the signal generation start signal SST2 is input, the first timing control unit 9 outputs the trigger signal ST1 to the guide signal generation unit 10, and at the time when a predetermined time T1 has elapsed from the start of the output of the trigger signal ST1. The trigger signal ST2 is output to the measurement signal generator 11. The guide signal generator 10 generates a guide signal Sg having a predetermined pulse width TPW when the trigger signal ST1 is input, and outputs it to the signal synthesizer 12. When the trigger signal ST2 is input, the measurement signal generator 11 generates the high frequency measurement signal Ss and outputs it to the signal synthesizer 12. The guide signal Sg has a pulse width TPW that is set sufficiently larger than the pulse width of the high-frequency measurement signal Ss. For this reason, both signals Sg and Ss on the measurement unit 6 side can be distinguished from each other by the pulse width. Further, the signal synthesis unit 12 synthesizes the guide signal Sg and the high-frequency measurement signal Ss output by the guide signal generation unit 10 and the measurement signal generation unit 11, respectively, and outputs them to the first bidirectional transmission unit 7. With this configuration, the signal generation unit 4 sequentially outputs the guide signal Sg and the high frequency measurement signal Ss to the cable 33b when the measurement start request command DCM is output from the measurement unit 6.
[0018]
The measurement unit 6 includes a second bidirectional transmission unit 13, a command generation unit 14, a guide signal detection unit 15, a second timing control unit 16, a digitizing unit 17, an FFT analysis unit 18, a display unit 19, a control unit 20, and An operation unit 21 is provided. In this case, the second bidirectional transmission unit 13 is connected to the second connector 5 and outputs the signal output by the command generation unit 14 to the cable 33b and is transmitted by the signal generation unit 4 via the cable 33b. The received signal is received and output to the guide signal detector 15 and the digitizer 17. The command generation unit 14 generates a measurement start request command DCM and outputs it to the second bidirectional transmission unit 13 when the measurement start signal SST1 is input. The guide signal detection unit 15 extracts a signal exceeding a predetermined pulse length from the signals output from the second bidirectional transmission unit 13 as a guide signal Sg, and at the same time, the trailing edge of the guide signal Sg (the tail end of the signal). The trigger signal ST3 is generated in synchronization with the part) and output to the second timing control unit 16. The second timing control unit 16 detects the rising edge (leading portion of the signal) of the trigger signal ST3 output from the guide signal detection unit 15, and sets a time Td (usually a predetermined time) from the rising edge. When a time equal to T or a time slightly shorter than the predetermined time T has elapsed, the drive signal Sd is output to the digitizing unit 17.
[0019]
The digitizing unit 17 includes an analog-to-digital converter and an internal memory for data recording. The digitizing unit 17 is synchronized with the sampling synchronization signal only during a period in which the drive signal Sd is output, and is connected to the other end of the cable 33b. The time response waveform of the induced voltage Vs induced by is sampled and digitized. In this case, the sampling synchronization signal is set to a time sufficiently short with respect to the pulse width of the high-frequency measurement signal Ss so that the sampling of the high-frequency measurement signal Ss can be executed several times. Also, the digitizing unit 17 digitizes the induced voltage Vs and outputs it as digital data DVS to the FFT analyzing unit 18. The FFT analysis unit 18 is configured by a DSP, for example, and performs an FFT calculation process on the digital data DVS according to a pre-programmed procedure, and calculates a transmission characteristic such as an attenuation amount of the cable 33b with respect to the wideband frequency based on the calculation result. The display data DD for displaying the calculation result is output. The display unit 19 is composed of a monitor such as an LCD panel, and displays the transmission characteristics according to the operation of the measurer or automatically based on the display data DD output from the FFT analysis unit 18. The control unit 20 comprehensively controls each component of the measurement unit 6. Specifically, the control unit 20 outputs the measurement start signal SST1 to the command generation unit 14 at the start of measurement, and the second time Td and pulse width of the drive signal Sd input by the operation of the operation unit 21. A setting process for the timing control unit 16 is executed. The operation unit 21 includes a numeric keypad and operation switches, and is configured to be able to input the time Td and the drive signal Sd described above.
[0020]
Next, the overall operation of the transmission characteristic measuring apparatus 1 will be described.
[0021]
The control unit 20 outputs a measurement start signal SST1 to the command generation unit 14 at the start of measurement upon accepting a measurement request from the measurer. Next, the command generation unit 14 generates a measurement start request command DCM and outputs the measurement start request command DCM to the other end side of the cable 33 b via the second bidirectional transmission unit 13. Thereafter, the control unit 20 causes the guide signal detection unit 15 to start extracting the guide signal Sg.
[0022]
On the other hand, on the signal generation unit 4 side, the first bidirectional transmitter 7 outputs the measurement start request command DCM input via the cable 33b to the command receiver 8. At this time, the command receiving unit 8 decodes the measurement start request command DCM and outputs the signal generation start signal SST2 to the first timing control unit 9. Next, as shown in FIG. 2, the first timing control unit 9 outputs a trigger signal ST1 to the guide signal generation unit 10, and generates a measurement signal when a predetermined time T1 has elapsed from the rising edge of the trigger signal ST1. The trigger signal ST2 is output to the unit 11. In this case, the guide signal generator 10 generates a guide signal Sg having a predetermined pulse width TPW in synchronization with the rising edge of the trigger signal ST1, and outputs it to the signal synthesizer 12, as shown in FIG. On the other hand, the measurement signal generator 11 generates a high-frequency measurement signal Ss in synchronization with the rising edge of the trigger signal ST2 and outputs it to the signal synthesizer 12. At this time, the signal synthesis unit 12 synthesizes the input guide signal Sg and the high-frequency measurement signal Ss and outputs the synthesized signal to the first bidirectional transmission unit 7. Next, as shown in the figure, the first bidirectional transmitter 7 outputs a pulse train composed of the guide signal Sg and the high-frequency measurement signal Ss having a predetermined time T (= T1-TPW) to the cable 33b. To do.
[0023]
In the measurement unit 6, the second bidirectional transmission unit 13 outputs the guide signal Sg input via the cable 33 b to the guide signal detection unit 15. Next, the guide signal detection unit 15 generates a trigger signal ST3 in synchronization with the falling edge of the guide signal Sg and outputs it to the second timing control unit 16, as shown in FIG. Next, the second timing control unit 16 outputs a drive signal Sd having a preset pulse width to the digitizing unit 17 when the time Td has elapsed from the rising edge of the trigger signal ST3. In this case, the digitizing unit 17 samples the voltage at the other end of the cable 33b only during the period during which the drive signal Sd is input. In this case, an induced voltage Vs based on the high-frequency measurement signal Ss is induced on the other end side of the cable 33b with a delay of a predetermined time T1 (a predetermined time T from the falling edge of the guide signal Sg) from the rising edge of the guide signal Sg. The Therefore, the digitizing unit 17 reliably samples the induced voltage Vs. Next, the digitizing unit 17 outputs the sampled data to the FFT analyzing unit 18 as digital data DVS. Thereafter, the FFT analysis unit 18 calculates the attenuation amount of the cable 33b for each frequency over a wide band by performing an FFT operation on the digital data DVS, and outputs the calculation result to the display unit 19 as display data DD. As a result, the display unit 19 displays the transmission characteristics calculated by the FFT analysis unit 18.
[0024]
Thus, according to this transmission characteristic measuring apparatus 1, in order to transmit the guide signal Sg and the high frequency measurement signal Ss via the cable 33b as the measurement object, the measurement dedicated cable for transmitting the guide signal Sg is provided. Without being used, the output timing of the high-frequency measurement signal Ss from the signal generation unit 4 and the measurement start timing in the measurement unit 6 can be reliably synchronized with each other, so that an unmeasurable state due to unconnected or disconnected measurement cables is avoided. However, the transmission characteristics of the cable 33b can be accurately measured. The measurement unit 6 outputs a measurement start request command DCM to the cable 33b, and the signal generation unit 4 starts outputting the guide signal Sg and the high frequency measurement signal Ss to the cable 33b after receiving the measurement start request command DCM. Thus, the output timing of the high-frequency measurement signal Ss can be remotely controlled on the measurement unit 6 side.
[0025]
The present invention is not limited to the above-described embodiments. For example, the ratio of the period of the sampling synchronization signal in the digitizing unit 17 to the pulse width of the high-frequency measurement signal Ss can be increased. That is, the frequency of the sampling synchronization signal can be specified to be low. Specifically, the first timing control unit 9 increases (or decreases) the trigger signal ST2 from the predetermined time T by the unit time ΔT with respect to the falling edge of the trigger signal ST1, and sends the trigger signal ST2 to the measurement signal generation unit 11 at a predetermined cycle. Output at TCY. Thereby, as shown in FIG. 3, the signal synthesizer 12 repeatedly outputs a pulse train in which the time interval between the guide signal Sg and the high-frequency measurement signal Ss is increased (or decreased) by a unit time ΔT at a predetermined cycle TCY. In this case, the time length of the unit time ΔT is set to, for example, a time obtained by dividing the period of the sampling synchronization signal in the digitizing unit 17 by the number of pulse train outputs by the signal generation unit 4.
[0026]
On the other hand, in the measurement unit 6, every time the guide signal detection unit 15 detects the guide signal Sg and outputs the trigger signal ST3, the second timing control unit 16 digitizes after the elapse of time Td from the rising edge of the trigger signal ST3. The drive signal Sd is output to the unit 17. Further, each time the drive signal Sd is output, the digitizing unit 17 synchronizes with the rising edge of the drive signal Sd, and the induced voltage Vs (Vs1, Vs2,. Vs3,...) Are sampled and digitized, and stored in the internal memory as digital data DVS (DVS1, DVS2, DVS3,...). Further, the digitizing unit 17 synthesizes the stored digital data DVS (DVS1, DVS2, DVS3,...) On the time axis and outputs the synthesized data to the FFT analyzing unit 18. As a result, the measurement unit 6 can sample the induced voltage Vs with the same high accuracy as the configuration in which sampling is performed using a high-frequency sampling synchronization signal.
[0027]
The signal generating unit 4 is not limited to the configuration in which the pulse interval obtained by increasing or decreasing the time interval between the guide signal Sg and the high-frequency measurement signal Ss by the unit time ΔT is repeatedly output with the predetermined period TCY, but the digitizing unit 17 in the measuring unit 6 is also used. It is also possible to adopt a configuration in which the sampling start timing (time Td) is increased or decreased by unit time ΔT. Even with this configuration, the induced voltage Vs can be sampled with high accuracy. Furthermore, the present invention is not limited to the output timing of various signals in the transmission characteristic measuring apparatus 1, and can be changed as appropriate. For example, in the transmission characteristic measuring apparatus 1, various signals are generated in synchronization with rising edges of various signals, but various signals may be generated in synchronization with falling edges of various signals.
[0028]
【The invention's effect】
Thus transmission, according to the transmission characteristic measuring apparatus according to claim 1 Symbol placement of the cable, a guide signal and outputs to the cable signal generation unit prior to the high-frequency measuring signal, the reception of the measurement unit guide signal condition By starting the measurement of the characteristics, it is possible to transmit the guide signal and the high frequency measurement signal via the cable as the measurement object, so that the signal generation unit does not use a dedicated cable for transmitting the guide signal. The output timing of the high-frequency measurement signal and the measurement start timing in the measurement unit can be reliably synchronized. As a result, it is possible to accurately measure the transmission characteristics of the cable serving as the measurement object while avoiding a state where measurement cannot be performed due to unconnected or disconnected dedicated cables. In addition, since the transmission characteristics of this cable can be measured using only the cable itself as a measurement object, even if a measurement impossible state occurs, a faulty cable as a measurement object is immediately detected. Can be determined.
[0029]
According to the transmission characteristic measuring apparatus for a cable according to claim 2 , the signal generation unit repeatedly generates the guide signal and the high frequency measurement signal at a constant period, and the guide signal and the high frequency measurement signal are generated for each period. The measurement unit of the cable is output to the cable while changing the time interval of each predetermined unit time, and the measurement unit starts measuring the transmission characteristics at a certain time after the reception of each guide signal. The transmission characteristics of the cable can be measured with high accuracy based on the high frequency measurement signal induced on the side.
[0030]
According to the cable transmission characteristic measuring apparatus of claim 3 , the guide unit and the high-frequency measurement signal cable after the measurement unit outputs the measurement start request signal to the cable and the signal generation unit receives the measurement start request signal. The output timing of the high frequency measurement signal can be remotely controlled on the measurement unit side.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a transmission characteristic measuring apparatus 1 according to an embodiment of the present invention.
2 is a timing chart for explaining generation (output) timings of the trigger signal ST1, the guide signal Sg, the trigger signal ST2, the high-frequency measurement signal Ss, the pulse train, the trigger signal ST3, and the drive signal Sd in FIG. 1;
FIG. 3 is a timing chart for explaining the generation (output) timing of the pulse train in a configuration in which the pulse train is repeatedly output to measure the transmission characteristics of the cable 33b.
4 is a block diagram showing a configuration of a conventional transmission characteristic measuring apparatus 31. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transmission characteristic measuring apparatus 4 Signal generation unit 6 Measurement unit 8 Command receiving part 9 1st timing control part 10 Guide signal generation part 11 Measurement signal generation part 12 Signal synthesis part 14 Command generation part 15 Guide signal detection part 16 2nd Timing control unit 17 Digitization unit 18 FFT analysis unit 20 Control unit 32 UTP cable 33b Twisted pair cable Sg Guide signal Ss High frequency measurement signal Vs Induced voltage ΔT Unit time

Claims (3)

A signal generating unit connected to one end of a cable as a measurement object and outputting a high-frequency measurement signal over a wide band to the cable, and the cable based on the output high-frequency measurement signal connected to the other end of the cable A measurement unit that samples the time response waveform of the voltage induced on the other end of the cable and measures the transmission characteristics with respect to the broadband frequency of the cable ,
The signal generating unit, said prior to the high-frequency measuring signal and outputs the guide signal on said cable, said measuring unit, the transmission characteristic measurement start to Luque Buru measurement of the transmission characteristics of the reception of the guide signal condition A device ,
The signal generation unit repeatedly generates the guide signal and the high-frequency measurement signal at a constant period, and increases a time interval between the guide signal and the high-frequency measurement signal by a predetermined unit time for each period. Alternatively, the data is output to the cable while being reduced, and the measurement unit starts measuring the transmission characteristics at a point in time after the reception of each guide signal, and the sampled and digitized digital data in the measurement A transmission characteristic measuring device for a cable, characterized in that the transmission characteristic is measured by synthesizing them on a time axis .   The signal generation unit outputs the high-frequency measurement signal to the cable when a predetermined time has elapsed from the end of transmission of the guide signal, and the measurement unit passes the predetermined time from the end of reception of the guide signal. 2. The cable transmission characteristic measuring apparatus according to claim 1, wherein measurement of the transmission characteristic is started before. The measurement unit outputs a measurement start request signal to the cable, and the signal generation unit starts outputting the guide signal and the high frequency measurement signal to the cable after receiving the measurement start request signal. The cable transmission characteristic measuring device according to claim 1 or 2 .

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