JPS5938773Y2 - Characteristic measuring device - Google Patents

Description

[Detailed explanation of the invention] This invention converts the test signal that passed through the transmission line under test into digital data, converts it into digital data, and then digitally calculates the distortion characteristics of the transmission based on the digital data. This invention relates to a characteristic measuring device that automatically outputs.

Conventionally, as a device that automatically measures transmission characteristics using a test signal, the test signal after passing through the transmission system under test is
In some cases, the data is converted into a digital data value using an A/D converter, and then, based on the digital data value, distortion is calculated using a digital arithmetic unit to determine the initial transmission characteristics.

As a common method for these digital automatic measuring devices,
When sampling and quantizing a test signal to obtain digital data, the same measurement point of the periodic test signal is
Digital averaging is performed to remove the effects of random noise.

As is well known, as the number of averaging operations is increased, the influence of random noise is gradually reduced, and the reliability of measurement of the test signal level is improved.

In other words, it is known that the worse the S/N of the signal under test, the more it is necessary to increase the number of averaging operations in order to obtain a certain level of measurement reliability.

Conventionally, in such digital automatic measuring devices, the number of times of averaging has been fixed in advance, or it has been set artificially by a preset means on the operation panel of the measuring device.

However, since the S/N value of the transmission system under test cannot be predicted before measurement, conventional equipment sometimes uses the arithmetic average of the signal even though the S/N of the signal under test is good. If you measure too many times and it takes more time than necessary, or conversely, even though the S/N of the signal being measured is poor, the reliability of the measured value is low because the average number of times is too small. There was something irrational about it.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional method and provide a characteristic measuring device in which the number of times of addition and averaging is determined according to the S/N ratio of the signal under test, and which has approximately constant measurement reliability. .

According to the present invention, the S/N of the signal to be measured is first measured, the number of times the signal level is averaged is determined in accordance with the S/N ratio, and the signal level is averaged based on the number of times. A digital characteristic measuring device is obtained that uses digital values to perform strain calculations.

That is, the present invention includes an A/D conversion means for converting an input analog signal to be measured into digital data, a means for adding the digital data of the input signal, a means for square-adding the digital data of the noise measurement signal, and a means for adding the digital data of the noise measurement signal. a buffer memory for temporarily storing subsequent digital data; a digital calculation means for calculating the digital data stored in the buffer memory; and an output means for outputting the measured data after calculation;
It is comprised of a control means that controls the timing of each of the above parts, and checks the S/N ratio after a certain number of times of addition and averaging, and depending on the result, determines whether to continue adding and averaging further or to move to distortion calculation processing. It is characterized in that the distortion calculation of the transmission system under test is always executed based on the appropriate number of times of addition and averaging.

The present invention will now be described in detail with reference to drawings of embodiments of the present invention.

FIG. 1 shows an embodiment in which the present invention is applied to a VITS signal automatic measuring device used to measure distortion in a television video signal transmission system.

In Figure 1, VITS as a test signal is extracted from a television video signal that has passed through the transmission system under test, and
is added to the D converter 1.

A command from the start switch 8 is transmitted to the A/D converter 1 via the control circuit 7, and conversion of an analog input signal into digital data is started.

The digital data Si after A/D conversion is input to the adder 2 and the square adder 3, and the resultant 1 of ΣSi and ΣSi2 is
= 1 1= 1 results are obtained as respective outputs.

Here, N is the number of additions.

The data after addition is temporarily stored in the buffer memory 4 according to the address output from the control circuit 7.

Next, the arithmetic circuit 5 extracts data necessary for strain characteristic calculation from the buffer memory 4, performs a predetermined calculation, and outputs the result to the printer 6.

All calculation item commands and output commands in this case are issued from the control circuit 7.

Regarding the calculation of is/N, for the above number of additions N,
It is obtained using the well-known Tobutsu formula.

This is an example of the 1973 National Television Convention rV I T
Digital processing method of S” (Sawara Nikonida).

The control sequence of the control circuit 1 is designed so that the S/H calculation described above is performed before other distortion characteristic calculations, such as white level, synchronization level, 2T pulse distortion, etc., and after the S/N calculation. , further performs an addition operation, or determines whether to proceed to another distortion characteristic operation.

That is, the arithmetic circuit 5 has the S/N value and
The relationship with the number of additions is stored, and the number of additions is determined so that a predetermined measurement reliability can be obtained.

In the example, the reliability coefficient is assumed to be 0.95, and S/N-30d
For B or below, 512 (=29) times, S/N 30-4
256 (=2”) times for 0dB, S/N=40~
128 (-27 times) for 50 dB, S/N = 50
For dB or more, it is stored as 64 (-26) times.

FIG. 2 is a system diagram showing a second embodiment of the present invention.

In the second embodiment, the adder 2, square adder 3, arithmetic circuit 5, and control circuit 7 in the first embodiment are replaced with a microprocessor 12, and the addition, square addition, characteristic calculation, and sequence control are all performed by software. It has become

The operation will be described below according to the system diagram in FIG. 2 and the software processing flow in FIG. 3.

In FIG. 2, when the start switch 14 is turned on, the microprocessor 12 starts executing the program shown in FIG. After converting into digital data, it is taken into the microprocessor 12.

Next, in the input data by addition and square addition processing 23,
Addition and square addition calculations are performed for signal locations for S/N measurement, and only addition calculations are performed for other signal locations.

Next, in step 24, it is determined whether the number of additions N has reached 2n.

(In this case, n is initially set to 6.

) If N has not reached 2n, return to process 22 and set N=
If it is 2, the process proceeds to S/N calculation processing 25.

In process 25, S/H is calculated according to equation (1) described above.

Next, in process 26, it is checked whether the current number of additions N satisfies the required reliability with respect to the S/N value obtained in process 25, using the method described in Example 1, and if it is not satisfied, process 27 After that, the process returns to process 22.

In addition, in process 27, n is replaced with n+m, but m is 1.2
．． It is determined by the S/N value of one of the three values.

On the other hand, if N satisfies the required reliability in process 26, the process proceeds to the next characteristic calculation process 28, where various characteristic calculations are performed, such as white level, synchronization level, 2T pulse distortion, etc. Execute.

After that, in process 29, the calculation result is sent to the printer 13.
Output to.

When the printing to the printer 13 is completed, in process 30,
The series of automatic characteristic measurement processing ends.

As explained above, the present invention improves the reliability of characteristic measurement results by appropriately determining the number of times of addition and averaging for signal level measurement during digital signal measurement in accordance with the S/H value. The function as an automatic measuring device is improved because there is no variation in the degree of measurement, and the measuring time is not taken unnecessarily long.

In the above embodiment, the VITS automatic m1J9 device was explained, but the present invention is not limited to VITS measurements, but is applicable to all measuring instruments that measure transmission distortion using repetitive test signals. There is nothing that applies to this.

Further, in the above embodiments, a printer is used as the output unit, but this can be replaced with another device, such as a digital display.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a first embodiment of the present invention. Fig. 2 is a system diagram showing a second embodiment of the present invention. Fig. 3 is a system diagram showing a system according to a second embodiment of the present invention. It is a flowchart of the processing program of the micro 7'' O setter. In the figure, 1 and 11... A/D converter, 2...
Adder, 3... Square adder, 4... Buffer memory, 5-... Arithmetic circuit, 6, 13... Printer, 7...
- Control circuit, 8, 14...start switch.

Claims (1)

[Scope of utility model registration request] an A/D converter that converts an analog input signal into a digital signal; an S/N measuring means that receives the output of the A/D converter and measures the S/N of the analog input signal; and the S/N
It is characterized by comprising: averaging means for controlling the number of times of averaging according to the output of the measuring means; and characteristic measuring means for receiving the output of the averaging means and measuring the characteristics of the input analog input signal. Characteristic measuring device.