JPH0473652B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for measuring envelope delay (shift in time position of modulation envelope) of a signal transmission path, which is a problem in waveform transmission such as television signals. It is something.

To measure this envelope delay, the relative delay time between measurement frequencies has traditionally been measured from the perspective that it is sufficient to measure the delay that causes waveform distortion (Radio Equipment Regulations: Characteristics of Video Transmitting Devices) . For example, when measuring the envelope delay at frequencies f ₁ and f ₂ , the delay time with respect to the reference signal is measured for each of those frequencies, and the difference is used as the relative delay time.

In this measurement method, the absolute delay time of the reference signal is not a problem, and the following explanation also applies to the case where the delay time for the reference signal at each measurement frequency is measured.

The present invention relates to a method for accurately measuring envelope delay by removing the effects of sag and amplitude distortion caused by the transmission path when measuring envelope delay using such a method. be.

[Prior art] In the conventionally known general measurement method for envelope delay, a reference signal is supplied via wire and measurement is performed. The envelope delay could only be measured for . As a result, when measuring a relay broadcaster for television broadcasting, for example, it has become necessary to disconnect the relay broadcaster from the line and input the measurement signal. As a result, measurements had to be taken during nighttime work after broadcasting, which resulted in the disadvantage that measurements could not be carried out efficiently.

Also, VITS (Vertical Intervel Test Signal)
An attempt has been made to measure the envelope delay characteristics during broadcast time, but with this method, it is not possible to measure the high-frequency characteristics of the envelope delay characteristics.
It was insufficient.

Therefore, as shown in the test signal shown in Figure 3, only one cycle of the waveform in which the carrier wave of the measurement frequency is amplitude-modulated with a sine wave of about 20 KHz is extracted, and this test signal is multiplexed into the VBL (vertical blanking period) and transmitted. There is a method for measuring the envelope delay amount by performing envelope detection on the test signal on the output side of the circuit, removing the carrier component, and finding the relative delay amount for each carrier frequency of the envelope waveform obtained. (Refer to Japanese Patent Application Laid-open No. 56-6588).

However, even with such a VBL multiplexed envelope delay measurement method, if there is a sag in the transmission path, simply clamping the pedestal level has the disadvantage that a measurement error will occur due to the influence of the sag. In other words, as shown in Figure 4, in addition to the true envelope delay amount E2, there is also an error due to sag.
E1 occurs.

Furthermore, when amplitude distortion occurs in the transmission path, the envelope waveform obtained by envelope detection of the test signal changes in amplitude. Therefore, when determining the amount of delay of the envelope waveform using a fixed reel, there is a drawback that an error E3 due to amplitude distortion occurs as shown in FIG.

In other words, the VBL in the television signal
During one horizontal scanning period, an envelope delay measurement signal (a signal obtained by extracting one or several cycles of an amplitude modulated wave obtained by amplitude modulating a carrier wave of the measurement frequency with a sine wave of approximately 20 KHz) is sent and received. At the end, the horizontal scanning period (horizontal synchronization signal)
The reference signal for measurement is regenerated based on the reference signal, thereby eliminating the need to send out the reference signal (see the above-mentioned patent publication), but in this case as well, the "measurement principle" of the envelope delay itself is a well-known technology. There was no significant difference between the two methods, but there was a drawback that the measurement accuracy decreased due to the influence of the measurement circuit on the receiving side and the influence of sag that occurred in the transmission line under test.

In this way, performing envelope delay measurements compatible with the transmission of television video signals using a specific horizontal scanning period within the vertical blanking period of the television signal is achieved by using the sag compensation circuit of the measurement circuit and the transfer detection circuit. The circuit became complicated and it was difficult to put it into practical use.

[Objective] The first object of the present invention is to eliminate the need for sag compensation using conventional methods for measurement signals generated in the transmission line under test;
An object of the present invention is to provide an envelope delay measurement method that prevents a decrease in measurement accuracy due to this.

A second object of the present invention is to provide an envelope delay measurement method that improves measurement accuracy by eliminating the influence of the amplitude characteristics of the transmission line under test and the receiving circuit.

[Structure of the Invention] In order to achieve the above object, the present invention separates a test signal generation section and an envelope delay measurement section, and uses an amplitude modulated test wave to be measured in which a carrier wave of a measurement frequency is amplitude modulated by a sine wave. Send it to the transmission line,
Envelope detection is performed on the amplitude modulated test wave received by the measurement unit to extract an envelope signal corresponding to the envelope of the amplitude modulated test wave, and a relative value of each carrier frequency of the extracted envelope signal is detected. In an envelope delay measurement method that measures an envelope delay from a typical delay time, the envelope signal is delayed by a time width corresponding to 1/2 period of the signal to generate a delayed envelope signal, and the A specific reference time of a reference signal that compares the levels of the envelope signal and the envelope signal to detect a level matching point, and reproduces the reference signal based on the reference signal information wrapped in the test wave;
The present invention is characterized in that a time difference between the level matching point and the time of occurrence is detected, and the time element is converted into an envelope delay amount.

According to a preferred embodiment of the present invention, when performing envelope delay measurement of a television transmission line, the vertical blanking period of the television signal to be sent to the transmission line to be measured is used to measure the envelope delay of the television signal. The color subcarrier frequency or synchronization signal frequency or both were reproduced, and the superimposition position of the amplitude modulated test wave was fixed based on the obtained synchronization related signal, and the carrier wave of the measurement frequency was amplitude modulated with a sine wave of approximately 20KHz. One to several cycles counted by the wave number of the envelope of the modulated wave are superimposed on the television signal and sent to the transmission line to be measured, and at the receiving end of the transmission line,
By extracting this signal and detecting the envelope with an envelope detector, the carrier component is removed and only the envelope signal is reproduced (this is referred to as W1). Furthermore, the color subcarrier frequency or The synchronization signal frequency or both of these are reproduced, and a reference signal is reproduced based on the obtained synchronization-related signal (this is referred to as W6). Next, the above-mentioned signal W1 is passed through a delay line having a delay amount of 1/2 period of the envelope signal W1, and this output is set as W3.These outputs W1 and W3 are compared with a power supply comparator, and the output is As W5, the envelope delay amount can be measured by phase-detecting this W5 with the above-mentioned W6. In addition, in the above, W1~
The symbols up to W6 are given in accordance with the explanation of FIG. 10, which will be described later.

Further, to describe the preferred embodiment of the present invention in detail, first, a horizontal sag compensation gray signal having an amplitude equal to the center potential of the signal is added to a part of the envelope delay measurement signal that is intermittently sent out. For horizontal sag compensation, the voltage around 1/2H of this signal is sampled and held for several μs on the receiving side, and the obtained voltage is used as the CD of the temporal center position of the envelope delay measurement signal. DC balance of the gate circuit is achieved as a potential, and envelope delay measurement errors due to horizontal sag are removed.

Furthermore, the envelope delay measurement signal that has passed through the gate circuit described above is detected by a commonly used synchronous detector, and the resulting envelope waveform is converted into a delay line with a delay approximately equal to 1/2 period of the envelope delay measurement signal. input. Then, by comparing the input signal with the output signal of the delay line using a voltage comparator. A square wave whose level changes in accordance with the half-width position of the envelope waveform is generated. Since horizontal sag compensation has been performed on the envelope waveform that is the output of the synchronous detector, even if the amplitude of the above-mentioned envelope delay measurement signal increases or decreases depending on the frequency characteristics of the transmission path under test, the half-width due to this No change in position occurs. That is, the temporal position at which the level of the square wave changes changes only when there is envelope delay distortion in the transmission path to be measured.

The amount of change in the temporal position of the level change in this square wave can be measured by comparing it with the temporal position where the level of the reference signal generated based on the received and reproduced color subcarrier frequency or synchronization signal frequency changes. , envelope delay measurements can be performed accurately. In addition, by adding an appropriate delay to the square wave mentioned above, creating a sample pulse, and sample-holding the peak value of the output signal sent from the delay line, accurate amplitude characteristics that are not affected by envelope delay distortion can be obtained. .

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 shows a schematic circuit configuration for implementing the present invention. In this figure, 4A is a synchronous circuit,
Based on the input television video signal 11, a stable jitter-free synchronization system is reproduced using the color subcarrier as a reference. Further, 5 is a digital test signal generation circuit, which generates a test signal whose phase is fixed by stable synchronization from the synchronization circuit 4A. Then, in the multiplexing circuit 6, the signals are multiplexed onto one line in the characteristic VBL period of the television video signal. The test signal sending unit 20 is configured as described above.

FIGS. 2A to 2C are schematic waveform diagrams of signals sent from the test signal sending unit 20 to the television video signal transmission path 12 (see FIG. 1). As shown in the figure, there are three types of signals to be sent. That is, the first signal shown in FIG. 2A indicates the start of envelope delay measurement, and is an identification signal necessary for synchronizing the sending section and the measuring section.

The second signal shown in FIG. 2B is a test signal for performing sag compensation, and is used to set the DC level, which will be described in detail later.

The third signal shown in FIG. 2C is a test signal for measuring envelope delay characteristics and amplitude characteristics. The envelope shown in the center of this signal is a sine wave, and as detailed later, as the measurement progresses, the measurement frequency (carrier frequency), which is a modulated wave, is used as a parameter and changes sequentially for each measurement. I'll let you do it.

Returning to FIG. 1 again, this will be explained. The signal subjected to envelope delay and amplitude distortion by the television video signal transmission line 12 is transmitted to the measuring section 30.
reach.

The measurement section 30 includes a synchronization circuit 4B, an identification signal reception circuit 7, an envelope delay/amplitude characteristic measurement circuit 9, and a data processing circuit 10.

Similar to the synchronization circuit 4A of the transmission section 20, the synchronization circuit 4B of the measurement section 30 identifies the stabilized synchronization system and the signal indicating the multiplex position of the test signal (multiple position information) based on the television video signal. It is output to the signal receiving circuit 7 and the envelope delay/amplitude characteristic measuring circuit 9.

The identification signal receiving circuit 7 extracts the identification signal from the television video signal based on the multiplexed position information obtained from the synchronization circuit 4B. Thus, the second
The identification signal shown in Figure A is first detected.

The envelope delay/amplitude characteristic measuring circuit 9 receives the next arriving test signal for sag compensation (the signal shown in FIG. 2B) in response to the identification signal sent from the identification signal receiving circuit 7. This performs sag compensation for the test signal (signal shown in Figure 2 C) for measuring envelope delay characteristics and amplitude characteristics (if a sag compensation test signal is not sent, or if sag compensation is necessary). If not, sag compensation may be omitted). By comparing the test signal with a test signal delayed by π radians (1/2 cycle) after sag compensation, the envelope delay amount can be measured at the highest sensitivity part without being affected by amplitude distortion ( (The detailed specific contents will be explained later).

Finally, the measured values are given to the data processing circuit 10 for addition and averaging, and the processing results are displayed using a CRT or printer. In this case, a graphical display or the like is suitable.

In order to explain one embodiment of the present invention more specifically, a detailed explanation will be given below with reference to various waveform diagrams and detailed block diagrams.

FIGS. 6A to 6D show more detailed envelope delay measurement signal waveforms.

Here, FIG. 6A is the identification signal shown in FIG. 2A, but it shows an FSK signal having frequencies Fh and Fl, and it shows the FSK signal on the transmitting side (sending unit 20) and receiving side for performing envelope delay measurement. (measuring section 30).

FIG. 6B shows a gray signal waveform for performing sag compensation on the receiving side (measuring section 30).

FIG. 6C shows a signal waveform for envelope delay measurement with 100% amplitude modulation.

FIG. 6D shows a state in which only the carrier frequency is changed with respect to the signal shown in FIG. 6C. That is, by sequentially changing the carrier frequency as a parameter according to each envelope delay measurement frequency, it is possible to set a desired measurement frequency range.

FIGS. 7A to 7E depict in detail the sending order of envelope delay measurement signals over time.

FIGS. 8A to 8E show waveforms at the receiving end when a horizontal sag occurs in the transmission line to be measured when the measurement signal shown in FIG. 7 is supplied to the transmission line.

Figures 9A to 9E show sag compensation for envelope delay measurement signals with horizontal sag,
Shows how to reproduce the original envelope waveform. That is, FIG. 9A shows a sag compensation signal, which is sent out prior to the envelope delay measurement signal (see FIGS. 7A to 7E). This performs pedestal clamping and samples and holds the level E ₀ of the compensation reference point P.

FIG. 9B shows that by pedestally clamping the envelope delay measurement signal in which horizontal sag has occurred, the potential E ₀ at point P becomes intermediate in amplitude _2ES .

FIG. 9C shows the measurement signal off-gateout waveform. That is, DC balance is achieved by voltage _E0 , and the clamped signal (see FIG. 9B) is gated to remove the horizontal synchronizing signal.

FIG. 9D shows a waveform in which the negative side signal is folded around the level of the reference point P. That is,
When a signal centered around voltage E ₀ (see FIG. 9C) is subjected to double-wave rectification, the signal below E ₀ is inverted upward as shown by the dashed line.

FIG. 9E shows a state in which the carrier wave component of the signal shown in FIG. 9D is removed by a low-pass filter or an envelope detector to reproduce the envelope. As a result, the half-width position T required for phase detection of the present invention
It is clear that the points are sag compensated.

FIG. 10 shows a method of detecting the half-width position from the reproduced envelope waveform, comparing the phase with a reference signal obtained from the above-mentioned related signals described later, and measuring the amount of envelope delay and the method of measuring the amplitude characteristic. There is. Here, the waveform W1 is the ninth
The method described in the figure may be used to express an envelope waveform reproduced using an envelope detector as described in relation to the waveform W1 in FIG. (In this example, water-based sag does not occur in the transmission line under test, so there is no convex portion on both sides as shown in Figure 9E, resulting in a single-peaked convex waveform, but horizontal sag does not occur.) (Even if there were, they were removed by the method described in Figures 9A-E).

Then, the signal shown by waveform W1 is converted to T/2(π
When the signal is input to a delay line having a delay amount (equivalent to radians), its output waveform becomes a waveform as shown in W3. Furthermore, by comparing waveform W1 and waveform W3 with a voltage comparator, it is found that the magnitude of the signal level is reversed at the point where the amplitudes of both waveforms W1 and W3 match, that is, point A and point B. , a stepwise wave that inverts from "H _i " to "L _p " at point D in waveform W5 indicating the temporal position (phase) of inversion is output. In this case, the waveform W1
When the amplitude changes, the amplitude of waveform W3 also changes by the same amount, so the phase at the above points A and B (temporal position of the cross point of waveform W1 and waveform W3)
No fluctuation occurs. That is, even if the amplitude of the envelope delay measurement signal changes in accordance with the frequency characteristics of the transmission path under test, the phase at point D of the waveform W5 does not change.

The condition for the phase of point D in waveform W5 to change in this way is limited to the case where the phase (shift in the temporal position of the envelope) of the envelope delay measurement signal changes due to the envelope delay of the transmission line under test. Therefore, by measuring the phase difference (corresponding to the time difference t) between point E and point D obtained from the reference signal (waveform W6) obtained in relation to the phase of the synchronization-related signal, the signal for envelope delay measurement can be obtained. Even if the amplitude change occurs in relation to the frequency characteristics of the transmission line under test, the envelope delay amount can be measured regardless of this.

Furthermore, if a sample pulse F is generated that is delayed by T/4 (equivalent to π/2 radians) from point D of waveform W5, and point C of waveform W3 is sampled and held at this timing, the result will be expressed as waveform W8. A step pulse of amplitude E _S is obtained. Thereby, by extracting the amplitude of the envelope delay measurement signal, it is possible to simultaneously measure the amplitude characteristics of the transmission line to be measured.

FIG. 11 is a detailed block diagram of a measuring section (receiving side device) used to implement the present invention.

In this figure, a signal for performing envelope delay measurement is input to a signal input connector 31 via a transmission path to be measured (not shown). next,
The FM demodulator 32 demodulates the identification signal (signal shown in FIG. 6A) formed by the FSK (frequency shift keying) signal, and synchronizes the transmitting side (sending section) and receiving side (measuring section). be exposed.

The pedestal clamp circuit 33 clamps the pedestal level of the input television signal based on the signal from the sync separation circuit 57, and uses the sag compensation circuit 34 to compensate for horizontal sag. This timing is set by the FM demodulator 32, decoder 35 and decoder 61.

The gate circuit 36 is controlled by the decoder 61, and only the envelope delay measurement signal is taken out (see FIG. 9C). Next, the synchronous detection circuit (double-wave rectifier circuit) 37 performs envelope detection of the signal (see FIG. 9D), and a signal representing the envelope is obtained from the phase-compensated low-pass filter 38 (see FIG. 9D). (see E).

The output signal of the low-pass filter 38 is input to one input terminal of the voltage comparator 40, and the filter output signal passed through the delay line 39 is input to the other input terminal of the voltage comparator 40. As a result, a square wave (see waveform W5 in FIG. 10) corresponding to the half-width position of the envelope signal is obtained at the output end of the voltage comparator 40. This pulse is input to the phase detection circuit 41, and the phase is compared with the reference signal (see waveform W6 in FIG. 9) generated by the decoder 56 of the horizontal counter 55.
A DC voltage (proportional to the phase difference) is input to the analog switch (selector) 44.

A signal passing through the delay line 39 is input to the sample/hold circuit 43, and the output parallel from the voltage comparator 40 is input to the delay circuit 42.
The signal is delayed by a predetermined time (see waveform W7 in FIG. 10) and applied to the sample/hold circuit 43. As a result, the peak value of the signal sent from the delay line 39 is sampled and held and input to the analog switch (selector) 44.

The analog switch (selector) 44 inputs the DC signals sent from the phase detection circuit 41 and the sample/hold circuit 43, and selectively sends these signals to the A/D converter 45 according to the timing controlled by the decoder 56. do. The A/D converter 45 digitizes the signal, and the controller 46 inputting the digital signal outputs the display 4.
Display the envelope delay characteristics on 7.

Further, numerals 48 to 56 indicate general genlock circuits. That is, the color burst gate circuit 4
8 to separate the color burst signal A. 4
9 is a selector, and 50 is a phase comparator.

51 is 4fsc (fsc = color subcarrier frequency 3.579545MHz)
A voltage-controlled crystal oscillator (hereinafter referred to as
VCO), whose output is a 1/4 frequency divider 53
The frequency is divided by , and applied to the phase comparator 50 via the selector 52, so that the VCO 51 is color-locked to the frequency x 4 of the color burst gate circuit 48. The output signal of the VCO 51 is supplied to a horizontal counter 55, and the reference signal sent from the decoder 56 is applied to the previously described phase detection circuit 41 and analog switch (selector) 44.

The horizontal counter 55 is reset by the synchronization separation circuit 57 and the horizontal synchronization signal separation circuit 58, so that the start of the counter 55 coincides with the horizontal synchronization signal.

Further, the vertical synchronization signal separation circuit 59 resets the vertical counter 60, thereby making the start of the counter 60 coincide with the vertical synchronization signal. and,
The decoder 61 determines the vertical blanking period (VBL).
A pulse (i.e., VBL) for gating the envelope delay measurement signal sent within
A signal for selecting one particular line of the line is formed.

When the above-mentioned television video signal is a white signal, the selectors 49 and 52 are switched from the A side to the B side, the output of the VCO 51 is divided by the 1/910 frequency divider 54, and the signal is output from the horizontal synchronizing signal separation circuit 58. The resulting horizontal synchronization signal is used for genlock.

FIG. 12 is a detailed block diagram of a transmission section (transmission side device) used to implement the present invention. This figure shows an example of a device configured to generate an envelope delay measurement signal using a specific horizontal scanning period within VBL.

A color television video signal is input to the illustrated input connector 100. Also, 148-1
Each block indicated by 62 performs the same operation as each block 48 to 61 shown in FIG. 11. That is, 148 is a color burst gate circuit, 149 is a selector, 150 is a phase comparator,
151 is a VCO, 152 is a selector, 153 and 154 are frequency dividers, 155 is a horizontal counter, 15
Reference numeral 7 indicates a sync separation circuit, 158 a horizontal sync signal separation circuit, 159 a vertical sync signal separation circuit, 160 a vertical counter, and 161 a decoder.

Further, 180 is a ROM that stores various measurement signal waveforms, and 182 is a D/A converter, which together constitute a digital signal generation circuit. The output signal sent from this digital signal generation circuit is introduced into a low-pass filter 184, and the signals shown in FIGS. 6A to 6D are sequentially
It is sent to the VITS inserter 186. Then, the envelope delay measurement signal is sent to the transmission line to be measured via the output connector 190.

The explanation so far has been about normal television broadcasting, but it also applies when measuring the envelope delay characteristics of general signal transmission paths such as teletext broadcasting or other general digital communications. Of course, the present invention can be applied.

[Effects] As explained above, according to the present invention, it is possible not only to accurately measure the envelope delay without inserting special means for sag or amplitude compensation in the measuring section (receiving side device). Since it is possible to measure the envelope delay of the entire transmission system including the transmitting/receiving device and the signal transmission line, it is possible to obtain a special effect of being able to perform accurate measurement at low cost.

Further, according to the present invention, the amplitude characteristics of the transmission line to be measured can be measured by simply adding a simple circuit, so it is possible to realize a versatile measurement method.

Furthermore, by repeating measurements and averaging them according to the present invention, it is possible to measure envelope delay characteristics with reduced measurement errors due to the influence of noise.

In one embodiment of the present invention, a test signal is multiplexed onto a television video signal and the envelope delay is measured using a special method, so that the envelope delay characteristics of the television video signal transmission system can be
Measurements can be made without being affected by transmission line sag or amplitude distortion.

Furthermore, according to an embodiment of the present invention, in addition to the above effects, the following advantages can be obtained.

Since double-wave rectification is performed by synchronous detection,
Measurement errors in low frequencies are reduced.

By comparing the envelope waveform obtained by detection with a waveform whose phase is shifted by π radians, it is possible to eliminate measurement errors in envelope delay due to amplitude distortion of the transmission line under test and to increase measurement sensitivity.

By supplying the pulse obtained by the above comparison to an appropriate delay line, thereby generating a sample pulse, and sampling and holding the peak value of the internal force signal of the delay line,
Accurate amplitude characteristics that are not affected by envelope delay distortion can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic circuit configuration for carrying out the present invention, and FIGS. 2A to 2C are schematic waveform diagrams showing various signals sent from a test signal sending section to a television video signal transmission path. Figure 3 is a waveform diagram showing the test signal used for VBL multiplexed envelope delay measurement, Figure 4 is a waveform diagram illustrating how the delay amount of the envelope waveform is affected by sag.
Figure 5 is a waveform diagram explaining how the amount of delay of the envelope waveform changes due to amplitude distortion, Figures 6A to D are waveform diagrams showing more detailed envelope delay measurement signals, and Figure 7A. ~E are waveform diagrams showing the sending order of envelope delay measurement signals, Figures 8A~E
is a waveform diagram showing the output state at the receiving end when horizontal sag occurs in the transmission line when the measurement signal shown in Figure 7 is supplied to the transmission line under test. A waveform diagram showing a method of performing sag compensation on the accompanying envelope delay measurement signal and reproducing the original envelope waveform. Figure 10 shows a method of measuring the envelope delay amount and amplitude characteristics based on the reproduced envelope waveform. A waveform diagram, FIG. 11 is a detailed block diagram showing the configuration of the measuring section (receiving side device) used to implement the present invention, and FIG. 12 is a detailed block diagram showing the configuration of the transmitting section (transmitting side device) used to implement the present invention. FIG. 3 is a detailed block diagram. 4A, 4B... Synchronization circuit, 5... Test signal generation circuit, 6... Multiplexing circuit, 7... Identification signal receiving circuit, 9... Envelope delay/amplitude characteristic measurement circuit, 10... Data processing circuit, DESCRIPTION OF SYMBOLS 11...Television video signal, 12...Television video signal transmission line, 20...Test signal sending section, 30...Measurement section, 31...Signal input connector, 32...FM demodulator, 33...Pedestal Clamp circuit, 34...
... Sag compensation circuit, 35 ... Decoder, 36 ... Gate circuit, 37 ... Double wave rectifier circuit, 38 ... Low pass filter, 39 ... Delay line, 40 ...
... Voltage comparator, 41 ... Phase detection circuit, 4
2... Delay circuit, 43... Sample/hold circuit, 44... Selector, 45... A/D converter, 46... Controller, 47... Display, 48... Color burst gate circuit, 49
... Selector, 50 ... Phase comparator, 51 ...
VCO, 52...Selector, 53...1/4 frequency divider,
54...1/910 frequency divider, 55...horizontal counter,
56...Decoder, 57...Synchronization separation circuit, 58
...Horizontal synchronization signal separation circuit, 59 ... Vertical synchronization signal separation circuit, 60 ... Vertical counter, 61 ... Decoder, 100 ... Input connector, 148 ... Color burst gate circuit, 149 ... Selector, 150 ... ...Phase comparator, 151...VCO,
152...Selector, 153...1/4 frequency divider, 1
54...1/910 frequency divider, 155...Horizontal counter,
157... Synchronization separation circuit, 158... Horizontal synchronization signal separation circuit, 159... Vertical synchronization signal separation circuit,
160... Vertical counter, 161... Decoder,
180...ROM, 182...D/A converter, 184...Low pass filter, 186...
VITS inserter, 190...output connector.

Claims (1)

[Claims] 1. A test signal generation section and an envelope delay measurement section are separated, and an amplitude modulated test wave obtained by amplitude modulating a carrier wave of a measurement frequency with a sine wave is sent to the transmission line under test, and the test signal is sent to the measurement section. Thus, the received amplitude modulated test wave is envelope-detected to extract an envelope signal corresponding to the envelope of the amplitude modulated test wave, and the relative delay time of each carrier frequency of the extracted envelope signal is detected. In an envelope delay measurement method for measuring an envelope delay from a signal, the envelope signal is delayed by a time width corresponding to 1/2 period of the signal to generate a delayed envelope signal, and the delayed envelope signal and A level matching point is detected by performing a level comparison with the envelope signal, and a time difference between a specific reference time of a reference signal reproduced based on reference signal information wrapped in the test wave and the time of occurrence of the level matching point. An envelope delay measurement method characterized by detecting the time difference and converting the time difference into an envelope delay amount. 2. The reference signal is generated by the same method as that in which the test signal generator generates a reference signal necessary for generating the amplitude modulated measurement signal constituting the amplitude modulated test wave from the reference signal information. The envelope delay measurement method according to claim 1, wherein the envelope delay measurement method is reproduced. 3. The amplitude-modulated measurement signal is a signal having a center potential at a voltage level equal to the temporal center position of the sag compensation gray signal sent out prior to sending out the amplitude-modulated measurement signal, and 3. The envelope delay measurement method according to claim 2, wherein the amplitude-modulated measurement signal is extracted using a voltage level equal to the target center position as a reference to obtain a signal capable of compensating for sag.