JPH0818944A - Monitor signal measurement method for catv amplifier and catv amplifier capable of measuring the signal - Google Patents

Abstract

PURPOSE:To grasp dispersion in level deviations or levels while directly observing it on a spectrum analyzer by measuring a monitor signal for a CATV amplifier through a pseudo-transmission network built in the amplifier or mounted externally. CONSTITUTION:A broadcast signal sent from a center is received by an amplifier 1, which amplifies the input signal and the amplified signal is uniformly attenuated by an ATT independently of frequencies and the resulting signal is outputted to an output side monitor terminal 5. In the case of the measurement, a pseudo-transmission network 2 having an entirely reverse frequency characteristic to that of a desired monitor signal is connected to the monitor terminal 5 of the amplifier 1 and a spectrum analyzer 3 is connected to the transmission network 2. Although more or less high low differences are in existence on peak lines of a frequency spectrum displayed on a CRT of the spectrum analyzer 3, the difference represents a level deviation in the signal. Moreover, the amplifier 1 is adjusted in a way that the difference on the peak lines of the frequency spectrum is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor signal measuring method which can be used for maintenance, inspection and adjustment of a CATV amplifier connected to a transmission line of a CATV system, and a CATV amplifier which enables the measurement. is there.

[0002]

2. Description of the Related Art In maintenance, inspection, and adjustment work of a CATV amplifier connected to a transmission line of a CATV system, a monitor signal of the amplifier is often measured by a spectrum analyzer (spana). This monitor signal is measured by connecting a spectrum analyzer C to the monitor terminal B of the CATV amplifier A as shown in FIG.
On the CRT, the monitor signal of the amplifier A output from the monitor terminal B is displayed as a frequency spectrum having many peak lines. The position of the peak line in this frequency spectrum represents the broadcast channel, ie its frequency,
The level of the peak line represents the signal level of the channel. Therefore, in this measurement, the channel frequency of the signal transmitted to the amplifier A and the signal level of each channel can be known from the monitor signal of the amplifier A.

On the other hand, the CA used for measuring the monitor signal
The monitor terminal B of the TV amplifier A is an ATT having a uniform attenuation amount in a wide frequency band for the signal branched in the amplifier A.
It is designed to be output after being attenuated by several to several tens of dB. Therefore, the level of the peak line of the frequency spectrum normally displayed on the CRT of spectrum analyzer C is located at the upper right as the frequency becomes higher, and the frequency characteristic of the monitor signal is displayed as it is. In addition, the level of the peak line is in the upper right, because the amplifier A compensates for the transmission loss proportional to f ^1/2 (f: frequency) of the coaxial cable, so the gain on the low frequency side is low, This is because the gain on the high frequency side is high.

[0004]

In the above-described monitor signal measuring method, the monitor signal is measured as it is, so it is good to see the level and frequency characteristics of the signal, but the level deviation of the signal is measured. However, it was not good to check the signal level variation for the following reasons. That is, in order to measure the level deviation and confirm the signal level variation, the channel-signal level correspondence table as shown in Table 1 below is used, and the signal level read from the frequency spectrum on the CRT and the table 1 are written. It is necessary to compare the signal levels with the measured signal levels for each channel, which is a troublesome and time-consuming task.

[0005]

[Table 1]

An object of the present invention is to make it possible to easily and directly check channel level deviations and signal level variations, and also useful for adjusting amplifiers.
It is to provide a method of measuring a monitor signal of an amplifier for CATV and an amplifier for CATV capable of easily realizing the method.

[0007]

According to a first aspect of the present invention, there is provided a method for measuring a monitor signal of an amplifier for CATV as shown in FIG.
It is characterized in that the measurement is carried out through the pseudo transmission network 2 built in or externally attached.

In the monitor signal measuring method for a CATV amplifier according to a second aspect of the present invention, the pseudo transmission network 2 has a frequency characteristic opposite to a desired monitor signal frequency characteristic.

In the amplifier according to claim 3 of the present invention, as shown in FIG. 2, the monitor terminal 5 of the CATV amplifier 1 is provided with the pseudo transmission network 2 having a frequency characteristic opposite to that of the desired monitor signal. It is characterized by that.

[0010]

In the monitor signal measuring method for the CATV amplifier according to the present invention, the monitor signal is measured through the pseudo transmission network 2 having a frequency characteristic opposite to that of the desired monitor signal. The frequency characteristics of the monitor signal are flat. Therefore, in the stage before the desired frequency characteristic of the monitor signal is obtained, the frequency characteristic of the monitor signal displayed on the CRT of the spectrum analyzer 3 may have irregularities. There will be variations in level.
Therefore, the adjustment of the amplifier 1 can be made easy because it can be made flat while watching the frequency spectrum displayed on the CRT of the spectrum analyzer 3.

In the CATV amplifier of the present invention, since the monitor terminal 5 is provided with the pseudo transmission network 2 having the frequency characteristic opposite to the desired monitor signal frequency characteristic, a measuring device such as a spectrum analyzer is provided at the terminal 5. The measurement of claim 1 can be easily performed only by connecting.

[0012]

Embodiment 1 FIG. 1 is a first embodiment of a monitor signal measuring method for a CATV amplifier according to the present invention. In the figure, 1 is C
An amplifier, 2 is a pseudo transmission network, and 3 is a spectrum analyzer connected to the transmission line of the ATV system. A broadcast signal sent from the center is input to the amplifier 1. The input signal is amplified by the amplifier of the amplifier 1 and further attenuated uniformly by an ATT (not shown) regardless of the frequency, and the output signal is output. It is output to the monitor terminal 5. For the measurement, a pseudo transmission network 2 having a frequency characteristic completely opposite to the frequency characteristic of a desired monitor signal is applied to a monitor terminal 5 of this amplifier 1.
And the spectrum analyzer 3 is connected to the pseudo transmission network 2.

At this time, the peak line of the frequency spectrum displayed on the CRT of the spectrum analyzer 3 may have some level difference as shown in FIG. 1, but this level difference represents the level deviation of the signal. The amplifier may be adjusted so that the peak line of this frequency spectrum has no difference in height.

[0014]

[Embodiment 2] FIG. 2 shows a second embodiment of the method of measuring the monitor signal of the CATV amplifier according to the present invention. In the figure, 1 is C
An amplifier 2 connected to the transmission line of the ATV system is a pseudo transmission network built in the amplifier 1, and 3 is a spectrum analyzer. A broadcast signal sent from the center is input to the amplifier 1, the input signal is amplified by the amplifier of the amplifier 1 and is uniformly attenuated by an ATT (not shown) regardless of frequency, and a desired monitor Pseudo transmission network 2 having frequency characteristics that are completely opposite to the frequency characteristics of signals
It is attenuated by and is output to the monitor terminal 5 on the output side. The measurement is performed by directly connecting the spectrum analyzer 3 to the monitor terminal 5 of the amplifier 1.

Then, as in the first embodiment, the CR of the spectrum analyzer 3 is
The peak line of the frequency spectrum displayed at T has some height difference as shown in FIG. This height difference represents the level deviation of the signal. The amplifier may be adjusted so that the peak line of this frequency spectrum has no difference in height.

[0016]

[Third Embodiment] FIG. 3 shows an embodiment of a CATV amplifier according to the present invention. The amplifier 1 is provided with a monitor terminal 5 for branching the signal amplified by the amplifier 12 by a branching device 13 and outputting the branched signal to the outside. Then, between the monitor terminal 5 and the branching device 13, the pseudo transmission network 2 having a frequency characteristic completely opposite to the frequency characteristic of the desired monitor signal and the simple conduction circuit 10 can be switched by the changeover switch 11. It is provided as follows.
When the changeover switch 11 is switched to the side of the pseudo transmission network 2, the signal output from the amplifier 12 of the amplifier 1 becomes a pseudo transmission network 2.
The signal output from the amplifier 12 of the amplifier 1 is directly output to the monitor terminal 5 when the changeover switch 11 is switched to the side of the conduction circuit 10 after being attenuated by the monitor terminal 5. The monitor signal measuring method of the present invention can be performed by switching the selector switch 11 to the pseudo transmission network 2 side and connecting the spectrum analyzer 3 to the monitor terminal 5.

Although the embodiment described above is for the output side monitor signal for monitoring the signal after being amplified by the amplifier, the input side monitor signal before being amplified by the amplifier may be measured. . In this case, the pseudo-transmission network 2 as described above is externally attached to the monitor terminal on the input side, or the pseudo-transmission network 2 is built in the monitor terminal on the input side to measure the monitor signal on the input side. As the configuration of the amplifier 1, the pseudo transmission network 2 is attached to the monitor terminal on the input side.

[0018]

The CATV amplifier monitor signal measuring method of the present invention has the following effects. ． It is possible to grasp the level deviation and level variation of the monitor signal while directly looking at the CRT of the spectrum analyzer 3. ． Since the adjustment of the amplifier may be performed so that the frequency spectrum of the monitor signal displayed on the CRT of the spectrum analyzer 3 becomes flat, the adjustment is intuitive and easy to understand.

If the CATV amplifier of the present invention is used, the above-mentioned measurement can be performed easily and easily.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a monitor signal measuring method for a CATV amplifier according to the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the monitor signal measuring method for the CATV amplifier of the present invention.

FIG. 3 is a block diagram showing an embodiment of a CATV amplifier of the present invention.

FIG. 4 is a schematic diagram showing an example of a method of measuring a monitor signal of a conventional CATV amplifier.

[Explanation of symbols]

 1 Amplifier 2 Pseudo transmission network 5 Monitor terminal

Claims (3)

[Claims] 1. A monitor signal measurement of a CATV amplifier, characterized in that a monitor signal of the CATV amplifier (1) is measured through a pseudo transmission network (2) which is built in or externally attached to the amplifier (1). Method. 2. The monitor signal measuring method for a CATV amplifier according to claim 1, wherein the pseudo transmission network (2) has a frequency characteristic opposite to a desired monitor signal frequency characteristic. 3. A CATV amplifier characterized in that a pseudo transmission network (2) having a frequency characteristic opposite to a desired monitor signal frequency characteristic is provided at a monitor terminal (5) of the CATV amplifier (1). .