JP2870874B2 - Method and apparatus for measuring relative delay - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to the measurement of the relative delay of two transmission channels, and in particular to the transmission of different component signals in a television (TV) analog component system. A method and apparatus for measuring the relative delay between two transmission channels.

Prior Art U.S. Pat. No. 4,829,366 (method and apparatus for measuring delay / gain differences using two different frequency sources) discloses a relative delay difference and gain between two transmission channels in a component video system. Techniques are disclosed that can be applied to measure differences. This technique uses two burst packets each consisting of a periodic signal as a test signal. The periodic signals in the packets have their frequencies different by some small frequency near the typical frequency in the frequency band of the transmission channel being tested (eg, 500 KHz and 502 KHz),
In addition, the phases match each other at a predetermined time position in the packet. These test signals are passed through the transmission channel to be tested and the resulting periodic signal is subtractively combined to generate a beat, which is displayed on an oscilloscope. In this technique, the delay difference between the two transmission channels is the amount of deviation in the time axis direction from the predetermined time position of the minimum amplitude point of the beat waveform, and the gain difference is the magnitude of the amplitude of the minimum amplitude point. It can be measured.

Another technique is described in the above-mentioned U.S.
International Broadcasting Conference (Inte
James and Marshall at the National Broadcasting Conference, "Measurements in a Television"
Component Environment by A. James and PJMarshal
l) is mentioned in the paper titled This technique simultaneously applies a 500 KHz sine wave signal to those transmission channels to measure the delay difference between the transmission channels, displays the resulting signal on a dual trace oscilloscope, and zero-crosses the sine wave output waveforms. To see if they are aligned with each other.

Challenges to be solved As is known, TV analog components
Each component signal (Y, B−Y, R−
Y, or R, G, B) usually has a bandwidth of 5-6 MHz. Only at a representative point frequency within this frequency band (ie, 500 KHz), the above two conventional techniques measure the transmission characteristics of the transmission channel of each component signal.

However, each component signal is subjected to various delays even at frequencies other than 500 KHz, and the amount of delay may vary greatly over the frequency band.

The main cause is various high-pass filters provided in component-type VTRs, switchers, encoders, and the like used in TV broadcast stations, TV productions, and the like forming transmission channels for digital processing of component signals. These filters are designed to cut off a certain frequency or more related to the sampling frequency due to the restriction by various sampling frequencies related to the digital processing.

However, in the above-described conventional technique, the delay difference cannot be measured over the entire frequency band in one test, and the change in the delay difference over the frequency band cannot be easily known.

Accordingly, an object of the present invention is to provide a measuring method and apparatus capable of easily knowing a relative delay of a signal between two transmission channels over a frequency band of interest.

Means and Action for Solving the Problems To achieve the above object, according to the present invention, in order to measure relative delays of signals in two transmission channels at a plurality of different frequencies, a first transmission and a second transmission are performed. First and second test signals are synchronously applied to one end of each of the channels, respectively. The first and second test signals are respectively
In order to measure the magnitude of the relative delay, a measurement signal including a portion of a frequency equal to the plurality of different frequencies and having a predetermined envelope waveform amplitude is included. Receiving the first and second test signals as a result of transmission from the other end of each of the transmission channels, combining the test signals with each other, and receiving the plurality of test signals during propagation on the transmission channel; A delay difference signal having an amplitude representative of information about the magnitude of the delay difference at each of the frequencies is formed. Thus, at a plurality of frequencies, the relative delay of the transmission channels is measured in one test.

According to the present invention, it is possible to further display the waveform of the delay difference signal.

Further, according to the present invention, the first and second test signals may include a marker for providing a reference regarding at least one of a polarity, a magnitude, and a frequency of a delay difference represented by an amplitude of the delay difference signal. Can be included.

Further, each of the test signals includes first, second, third and fourth signals.
The following signal components can be provided. The first
Is composed of one predetermined length section,
Since the section measures the magnitude of the delay difference, a sweep signal of the amplitude of the predetermined envelope waveform whose frequency changes in a predetermined frequency range is used as the measurement signal in a predetermined period portion within the section. Can be included. The second test signal portion includes at least one of the sections, and the one section includes a delay marker for giving a scale regarding the magnitude of the delay difference in a predetermined period part of the section. Can be included. The third test signal portion includes one of the sections, and the section includes a frequency marker for giving a scale regarding a frequency at which the delay difference occurs, in the predetermined period portion of the section, Can be included. The fourth test signal portion may include one section including a polarity marker for measuring the polarity of the delay difference.

According to the present invention, the display can be a display in which the waveform of the delay difference signal in each of the sections forming the first, second, third, and fourth test signal portions is superimposed.

Further, according to the present invention, in the first test signal portion, the first and second test signals can include the same sweep signal. The second test signal portion may include, in the predetermined period portion, the delay marker indicating the same one delay time reference value over the predetermined frequency range, and the delay marker includes i A) a first delay marker component comprising a predetermined first waveform included in the first test signal; and ii) a second delay marker component included in the second test signal. A second waveform having a predetermined level difference relationship over the predetermined period portion with respect to the first waveform, wherein the level difference has the same magnitude over the predetermined frequency range; And the second delay marker component described above, which represents the delay difference time of The third
May have the frequency marker indicating at least one frequency within the predetermined frequency range within the predetermined time period portion, the frequency marker comprising: i) the first test signal A first frequency marker component comprised of a predetermined constant level waveform included; ii) a second frequency impulse included in the second test signal.
The frequency marker component, wherein the position of the impulse within the predetermined period portion is coincident with the position of the corresponding frequency portion within the sweep waveform within the predetermined period portion, And a frequency marker component. In the fourth test signal portion, the first and second test signals may have the same waveform as the first and second components of the polarity marker, respectively.

Embodiment Next, an embodiment of a measuring apparatus in which the present invention is applied to a (Y-BY-RY) analog component system (ACS) will be described.

FIG. 1 shows three transmission channels 1 for each of the Y, BY and RY component signals for ACS,
2, 3, which are respectively input terminals 4,
5, 6 and output terminals 7, 8, 9 are provided.

The measuring device includes a signal generator 10, a difference detector 12, and a waveform display 14. The signal generator 10 has a PROM, and generates a pair of test signals T1 and T2 described below from this pre-programmed memory from the CH-1 and CH-2 outputs. In the illustrated example, the test signals T1, T2
Is the input terminal 4 of the Y channel 1, the BY channel 2
, Respectively. The test signal T1 of the transmission result obtained from the output terminals 7 and 8 of these transmission channels
a and T2a are respectively applied to two input terminals of a difference detector 12, and this detector 12 generates a difference between the signals, that is, (T1a-T
2a) is calculated to generate a difference signal DS at the output. The next waveform display 14 displays the waveform of the difference signal on a screen. As the difference detector 12 and the waveform display 14, a conventional oscilloscope or waveform monitor having a function of observing the difference between CH-1 and CH-2 can be used.

Next, referring to FIGS. 2A and 2B, test signals T1 and
Details of T2 and the difference signal DS will be described. The illustrated signal has a level value for the MII format. In these figures, the signals are shown on the same time axis.

The test signals T1, T2 are roughly divided into four test signal parts SP1, SP2, SP3, and SP4, each of which has one or more horizontal line (H) section lengths. . Each H section (length of 63.5 microseconds) includes a first half period I1 (16.8 microseconds in this embodiment) from the start time t0 to t1 including the horizontal synchronization pulse, and a remaining second half period I2 from t1. (46.7 microseconds in this embodiment).

SP1 is a delay measurement signal portion composed of one section. In this part, both the test signals T1 and T2 are used as delay measurement signals that receive a delay from the transmission channel during a period I3 from t1 to t2 (in this embodiment, at a time of 61.2 microseconds) of the period I2. It has sweep signals SS1 and SS2, respectively. However, since this test signal is for the Y-BY-RY analog component system, the signal T2 does not include a horizontal synchronization pulse. These sweep signals SS have a constant amplitude peak-to-peak value of 0.7 volts (ie, the envelopes EV1 and EV2 are flat) and have a center level of 0.35.
This is a packet (square part enclosed by a solid line) consisting of a sine wave of volts (note: simplified in the figure). The frequency of this swept sine wave is f1 (= 200 KHz) to f2 (= 5.5M
Hz), and the frequency sweep speed changes in a constant linear form. Those swept sine waves in signals T1 and T2
The amplitudes and phases of SS1 and SS2 are completely matched to each other so that the difference becomes zero when the difference is taken.

The next SP2 to SP4 are marker forming signal portions, and SP2
Is a delay marker forming signal portion, SP3 is a frequency marker forming signal portion, and SP4 is a polarity marker forming signal portion.

First, the delay marker forming signal portion SP2 is a portion that gives a scale of the magnitude of the relative delay amount, and in this embodiment,
To form four markers, a delay 0 ns marker DM1, a delay 20ns marker DM2, a delay 40ns marker DM3, and a delay 60ns marker DM4, it is composed of four sections. Each marker is a first marker component a in a period I3 of a corresponding section of the test signal T1.
And the second marker component b in the same period I3 of the corresponding section of the test signal T2.

The first components DM1a to DM4a of each marker have a constant level of 0.7 volts in the test signal T1. on the other hand,
In the test signal T2, the second component DM1b of the marker DM1 is D
The waveform is also a constant level of 0.7 volt so that it becomes zero when the difference from M1a is taken. Second component D of marker DM2
M2b is V1 volts (= 0.6912 volts to V2 volts (= 0.4
Up to 629 volts), the difference from DM2a changes in a curve C1, which is a part of a sine wave S1 described later. The second component DM3b of the next marker DM3 has a waveform from V3 volts (= 0.6824 volts) to V4 volts (= 0.2538 volts) whose difference from DM3a changes in a curve C2 which forms a part of a sine wave S2 described later. And the second component DM4 of the last marker DM4
b is from V5 volts (= 0.6736 volts) to V6 volts (= 0.0
Up to 975 volts), and the difference from DM4a is
3 is composed of a waveform that changes in a curve C3 which forms a part of FIG.

Here, the sine waves S1 to S3 will be described with reference to FIG. Each sine wave is approximately represented by 2Asin (θ / 2) (1), where A is the amplitude of the swept sine wave SS (= 0.35 volts). θ is represented by θ = 2π (td) f (2), and td is a delay time difference between the test signals T1 and T2. Equation (1) indicates that a signal at a certain frequency of the sweep signal of the test signal T1 is Asinωt, and a signal at the same frequency of the same sweep signal of the test signal delayed relatively by an angle θ is Asin ( ωt−θ), and the difference is calculated.

Therefore, the sine waves S1, S2, and S3 have td of 20 ns and 40n, respectively.
s and 60 ns are substituted and obtained from equations (1) and (2). In addition, the analog component
For the system, a curve from 0.2 to 5.5 MHz is used.
These curves C1, C2, C3 appear in the difference signal DS in the lower part of FIG. 2, and serve as a scale for the magnitude of the delay difference.

Next, the frequency marker forming signal portion SP3 will be described. The frequency marker FM gives a scale regarding the frequency of the delay difference, and is a period of one section constituting this signal portion.
In I2, the first marker component FMa included in the test signal T1
And the second marker component FMb included in the test signal T2. The first marker component FMa is composed of six impulses whose height gradually increases. In the present embodiment, since these impulses are markers of 0.5, 1, 2, 3, 4, and 5 MHz, their positions in the time axis direction within the period I3 correspond to the periods of the corresponding frequency portion of the swept sine wave SS. It matches the position in I3. The second marker component FMb has a constant level, that is, a waveform of 0 volt as shown in the figure.

Finally, the polarity marker forming signal component SP4 is composed of one section, and is a portion for forming a polarity marker PM for indicating the magnitude of the delay difference between the test signals T1 and T2. . This part is the first half period I1 of the test signals T1 and T2.
, Includes first and second marker components PMa and PMb composed of the same rectangular pulse from t3 (eg, 9.8 microseconds) to t4 (eg, 14.8 microseconds). This square pulse has a rising and falling frequency of
It is desirable that the frequency at one point in the sweep frequency range is close to the lower limit frequency f1.

The operation of the measurement apparatus using the test signals T1 and T2 described above will be described next.

As a result of applying these test signals to the transmission channels 1 and 2 by the measuring apparatus, a difference signal as shown in the lower part of FIG.
DS is generated at the output of difference detector 12. It is assumed that the transmission channels 1 and 2 have already been adjusted so that their gain difference becomes zero. In the difference signal shown in the figure, the delay amount of the channel 1 is larger than that of the channel 2
Is assumed to be smaller than

First, in the first section of the difference signal DS, a waveform SD that is the difference (SS1-SS2) between the sweep signals appears in the period I2. This waveform
SD is a flat line of 0 volts if the difference is zero. On the other hand, when there is a relative delay as in the example shown in the figure, the waveform SD has an envelope in which the frequency continuously increases.
It becomes a sine wave with EV3. The duration of this envelope EV3
The magnitude X at any point in I3 is related to the magnitude of the delay difference at its corresponding sweep frequency fx.

Scaling the size X of the envelope EV3 to the delay difference time is the delay markers DM1 to DM4 in the second to fifth sections that follow, and these are the corresponding first marker components.
As described above, it is obtained from the difference between DM1a to DM4a and the second marker components DM1b to DM4b. Note that the relative delay between the first component and the second component of the delay markers can be substantially ignored. Therefore, the above envelope EV3
Is, for example, a delay difference of 20 over the entire swept frequency range.
If the value is a constant value of ns, it matches the curve C1 of the 20ns marker DM2.

As described above, the first component of the frequency marker FM in the next sixth section and the polarity marker PM of the seventh section are also described above.
It is obtained from the difference between FMa, PMa and the second components FMb, PMb. For the polarity marker PM, it is assumed that the delay of the test signal T2 is longer, so that a positive impulse precedes and a negative impulse follows. The opposite is true if the delay of T2 is smaller.

FIG. 4 shows a display example when the difference signal DS is displayed on the waveform display 14. As you can see, 7 of the difference signal DS
The waveforms of the two sections are displayed on top of each other (Note:
Some of the displayed waveforms have been omitted for clarity).
Based on this display, the polarity and magnitude of the relative delay in the frequency range f1 to f2 can be known. Based on the display result, an equalizer (not shown) provided in the transmission channel can be adjusted to make the relative delay between the transmission channels within an allowable range.

The following changes can be made to the embodiment of the present invention described above.

First, the number of sections of the signal component SP2 of the test signal can be changed according to the number of delay markers to be displayed. Also, to reduce the number of sections required for each test signal,
For example, a polarity marker that does not interfere with each other, a 0 ns delay marker,
The frequency marker can be formed in one section.

Second, the envelopes EV1, EV2 of the sweep signals SS1, SS2
Can be changed so that the amplitude at the frequency f1 becomes maximum and the amplitude decreases toward the frequency f2 in order to facilitate reading on the low frequency side in FIG. In this case, a change corresponding to the delay marker may be made to make the inclination of the delay marker gentler.

Third, the frequency sweep speed of the swept sine wave can be changed to be a logarithmic sweep. Also in this case, the corresponding change of the delay marker and the frequency marker may be performed.

Fourth, first components for forming a delay marker (DM1a to DM4a)
And the waveforms of the second components (DM1b to DM4b) are such that their differences form zero and curves C1, C2 and C3, respectively.
It can be changed arbitrarily.

Fifth, the sweep mode of the sweep signal can be changed from continuous sweep to step sweep, so that a sine wave of one frequency can be continued for a certain period of time until the sine wave of the next frequency is changed. Corresponding changes in delay markers and frequency markers will also be apparent to those skilled in the art.

Sixth, the test signal can be repeated by returning to the first section after the seventh section ends. As another repetition method, there is a method of repeating each section many times before moving to the next section. In this case, for example, in each field of the video signal, the first section is repeated for 100H (horizontal line), each of the second to fifth sections is 15H, the sixth section is 41H, and the seventh section is Can be repeated for 41H.

Seventh, the measurement method and apparatus may be used for other RGB analog component systems,
The same applies to the Betacam video format with minor changes.

Advantages According to the measurement method and apparatus of the present invention described in detail above, the relative delay in a number of different frequencies or frequency ranges of interest can be known in one measurement.
Further, the characteristics of the transmission channel can be finely adjusted using the measurement results.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a transmission channel of an analog component system and a measuring device according to the present invention. FIGS. 2A and 2B are combined waveform diagrams showing a waveform of a set of test signals used by the measuring apparatus of the present invention and a difference signal generated from the pair on the same time axis. FIG. 3 is a diagram showing a sine wave from which a different curve for a delay marker is obtained. FIG. 4 is an enlarged waveform diagram showing a display example in which the difference signal shown in FIGS. 2A and 2B is shown on a waveform display. (Explanation of symbols) 1, 2, 3: Transmission channel, 4, 5, 6: Input terminal, 7, 8, 9: Output terminal, 10: Signal generator, 12: Difference detector, 14: Waveform display, T1 , T2: test signal, T1a, T2a: test signal of transmission result, DS: difference signal, SP1 to SP4: first to fourth test signal parts, I1: first half period, I2: second half period, I3: predetermined period , SS1, SS2: Sweep signal, SD: Waveform of difference between sweep signals, EV1, EV2, EV3: Envelope, f1: Lower sweep frequency, f2: Upper sweep frequency, DM1 to DM4: Delay marker, DM1a to DM4a: Each delay First component of marker, DM1b to DM4b: Second component of each delay marker, S1 to S3: Sine wave, C1 to C3: Curve of delay marker, FM: Frequency marker, FMa, FMb: First and second of frequency marker 2 components, PM: polar marker, PMa, PMb: first and second components of polar marker

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01R 27/28 G01R 25/00 H04B 3/46

Claims (10)

(57) [Claims] 1. A method for measuring the relative delay of signals in two transmission channels at different frequencies, the method comprising: a) a first and a second transmission channel at one end of each of the first and second transmission channels, respectively. Applying the two test signals in synchronism, wherein the first and second test signals each include a portion of a frequency equal to the different plurality of frequencies to measure the magnitude of the relative delay. And b) receiving the first and second test signals as a result of transmission from the other end of each of the transmission channels, including the measurement signal having a predetermined envelope waveform amplitude. Combining test signals with each other to form a delay difference signal having an amplitude that is received during propagation on the transmission channel and that represents information about the magnitude of the delay difference at each of the plurality of frequencies; A relative delay measuring method for measuring relative delays of the first and second channels at the plurality of frequencies using the delay difference signal, wherein each of the test signals is a first, a second and a third. I) said first test signal portion comprises a section of a predetermined length, said section being within said section for measuring the magnitude of said delay difference. A predetermined period portion includes a sweep signal having an amplitude of the predetermined envelope waveform whose frequency changes in a predetermined frequency range as the measurement signal; and ii) the second test signal portion includes at least one signal. The one section comprises a delay marker for providing a scale for the magnitude of the delay difference,
Iii) the third test signal component is comprised of one of the intervals, wherein the interval is a scale relating to the frequency at which the delay difference occurs. Frequency marker to give
A relative delay measurement method, wherein the time interval is included in the predetermined period portion of the section. 2. The method according to claim 1, further comprising the step of displaying a waveform of said delay difference signal. 3. The method of claim 2, wherein each of the test signals has a fourth signal portion, the fourth test signal portion for measuring the polarity of the delay difference. A relative delay measurement method characterized by comprising one section including the polarity marker of (1). 4. The method according to claim 3, wherein said displaying step includes the step of forming a waveform of said delay difference signal in each of said sections forming said first, second, third, and fourth test signal components. The relative delay measurement method, which is displayed in a superimposed manner. 5. The method according to claim 4, wherein a) in the first test signal portion, the first and second test signals include the same sweep signal; The second test signal component includes the delay marker indicating the same one delay time reference value over the predetermined frequency range in the predetermined period portion, wherein the delay marker is: A first delay marker component comprising a predetermined first waveform included in a first test signal; and ii) a second delay marker component included in the second test signal, wherein Has a predetermined second waveform having a predetermined level difference relationship over the predetermined period portion, and the level difference is the same magnitude of delay over the predetermined frequency range. Said second delay marker adapted to represent a time difference. And c) the third test signal component has the frequency marker indicating at least one frequency within the predetermined frequency range within the predetermined period portion, and The frequency marker includes: i) a first frequency marker component including a predetermined constant level waveform included in the first test signal; and ii) a first frequency marker component including an impulse included in the second test signal. The second frequency marker component, wherein a position of the impulse within the predetermined period portion coincides with a position of a corresponding frequency portion within the sweep waveform within the predetermined period portion. D) In the fourth test signal portion, the first and second test signals are the same as the first and second components of the polarity marker, respectively. Waveform Having a relative delay measurement method. 6. A relative delay measuring device for measuring a relative delay of a signal in two transmission channels at a plurality of different frequencies, a) applying the signal to one end of each of a first and a second transmission channel. Test signal generating means for generating first and second test signals, wherein the first and second test signals are respectively
Said test signal generating means for measuring the magnitude of the relative delay, said test signal generating means including a measuring signal having a portion equal to said plurality of different frequencies and having a predetermined envelope amplitude; Receiving the first and second test signals as a result of transmission from the other end of each of the channels, combining the test signals with each other, and receiving a delay at each of the plurality of frequencies during propagation on the transmission channel; Signal processing means for forming a delay difference signal having an amplitude representing information on a difference between the first and second channels, the relative difference being measured at the plurality of frequencies using the delay difference signal. In the delay measuring apparatus, each of the test signals has a first, a second, and a third signal portion; i) the first test signal portion has a length of one predetermined length; The section comprises the predetermined envelope waveform whose frequency changes in a predetermined frequency range as the measurement signal in a predetermined period portion within the section in order to measure the magnitude of the delay difference. Ii) said second test signal portion comprises at least one said interval, said one interval for providing a scale for the magnitude of said delay difference. The delay marker,
Iii) the third test signal component comprises one of the intervals, wherein the interval is a scale relating to the frequency at which the delay difference occurs. Frequency marker to give
A relative delay measuring device, wherein: 7. The relative delay measuring device according to claim 6, further comprising display means for displaying a waveform of said delay difference signal. 8. The apparatus of claim 7, wherein each said test signal has a fourth signal portion, said fourth test signal portion for measuring the polarity of said delay difference. A relative delay measuring device, comprising one section including a polarity marker of (1). 9. The apparatus according to claim 8, wherein said display means superimposes the waveform of said delay difference signal in each of said sections forming said first, second, third and fourth signal portions. And displaying the relative delay. 10. The apparatus according to claim 9, wherein: a) in said first test signal portion, said first and second test signals include the same sweep signal; The second test signal component includes, in the predetermined period portion, the delay marker indicating the same one delayed signal reference value over the predetermined frequency range,
The delay marker includes: i) a first delay marker component including a predetermined first waveform included in the first test signal; and ii) a second delay marker included in the second test signal. A predetermined second waveform having a predetermined level difference relationship over the predetermined period portion with respect to the first waveform, and the level difference falls within the predetermined frequency range. And a second delay marker component adapted to represent a delay difference time of the same magnitude across the third test signal component within the predetermined period portion. , Said frequency marker indicating at least one frequency within said predetermined frequency range, said frequency marker comprising: i) a first constant-level waveform included in said first test signal. 1) a frequency marker component, and ii) the second A second frequency marker component comprised of an impulse included in the test signal, wherein a position of the impulse within the predetermined period portion is within a corresponding frequency portion of the sweep waveform within the predetermined period portion. And d) the second frequency marker component is coincident with the position. D) In the fourth test signal portion, the first and second test signals are the second of the polarity markers. The relative delay measuring device, wherein each of the first and second components has the same waveform.