JP2908644B2 - Control method of automatic gain control circuit of CATV amplifier and CATV amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an automatic gain control circuit (hereinafter abbreviated as an AGC circuit) of an amplifier connected to a communication line of a CATV, and more particularly to a reference gain of an AGC circuit using a CATV status monitor. Regarding the adjustment method.

[0002]

2. Description of the Related Art In a CATV system, an amplifier is inserted and connected at various points in the system to compensate for the line loss. This amplifier has a predetermined gain determined in accordance with a portion where the amplifier is installed in order to transmit a signal of appropriate strength to each terminal. Here, if the gain of the amplifier in each part fluctuates, the effect will affect not only the next stage but also the terminal. Therefore, each amplifier is generally adjusted so that the gain is within a certain range, for example, ± 3 dB, based on a predetermined gain determined in the amplifier. And so-called AG as a circuit for that
A C circuit is built in.

On the other hand, the amplifier is provided with a status monitor for monitoring the state of the amplifier for a predetermined monitoring item such as an input / output level of a communication line, a voltage of an AC power supply, and a voltage of a DC power supply. In general, the status monitor returns a monitoring item data to the center device in response to a call by a polling signal from the center device and checks the data on the center device. Therefore, the operation status of the AGC circuit is also monitored via the status monitor by checking the input / output level of the amplifier.

[0004] Here, a reference gain, which is a reference for the operation of the AGC circuit, differs depending on a portion where each amplifier is installed, and has a unique value for each amplifier. Therefore, in the conventional amplifier of this type, the reference gain is set by adjusting the reference gain setting resistor provided in the AGC circuit at the time of shipment or installation at the site of each amplifier, and thereafter, the value is fixed as a reference. The gain is automatically controlled based on this.

[0005]

However, in such automatic gain control by the conventional AGC circuit,
Is it not possible to change the reference gain after setting the amplifier?
Or even if possible, it is necessary to go to each amplifier and adjust the reference gain setting resistor. When a CATV system fails, especially when an amplifier in the system has a failure and the current reference gain Thus, there has been a problem that when the terminal cannot obtain an appropriate signal strength, it is not easy to secure the signal strength by adjusting the reference gain of another amplifier. That is, for example, it has been impossible to take measures such as securing the gain of the downstream amplifier with the amplifier upstream of the failed amplifier and substituting the downstream amplifier with the upstream amplifier until the failure is recovered.

The present invention solves the above-mentioned problems, and makes it possible to adjust a reference gain of an AGC circuit using a status monitor.
Flexible response even in the event of a system failure,
The purpose is to improve the reliability of the system.

To achieve the above object, the CATV of the present invention
A control method of an automatic gain control circuit of an amplifier for use is a method in which a CA installed in an amplifier connected to a communication line of a CATV and checks the state of the amplifier based on a predetermined monitoring item.
In a method for controlling an automatic gain control circuit of a CATV amplifier, comprising: a status monitor for TV; and an automatic gain control circuit for automatically adjusting a gain of the amplifier within a predetermined range from a predetermined reference gain. ,
The automatic gain control circuit includes a reference gain adjustment unit variably set to an arbitrary resistance value for adjusting the reference gain of the amplifier. And a reference gain setting switch for selectively switching connection between the automatic gain control circuit amplifier circuit and the reference gain setting resistor or the reference gain adjustment unit.
The reference gain setting changeover switch is set to either the reference gain setting resistor side or the reference gain adjustment unit side according to a command from the TV status monitor, and the resistance value of the reference gain setting resistor set in advance or a predetermined value is set. The gain of the amplifier is automatically adjusted within a certain range from the reference gain of the amplifier determined based on the resistance value of the reference gain adjustment unit variably set to the above resistance value.

According to a second aspect of the present invention, there is provided a CA installed in an amplifier connected to a communication line of a CATV to check the state of the amplifier based on a predetermined monitoring item.
A CATV amplifier comprising: a status monitor for TV; and an automatic gain control circuit for automatically adjusting the gain of the amplifier within a predetermined range from a predetermined reference gain.
The TV status monitor includes a reference gain adjustment unit variably set to an arbitrary resistance value for adjusting the reference gain of the amplifier. The automatic gain control circuit includes an automatic gain control circuit amplification circuit and the amplifier. A reference gain setting resistor for setting the reference gain in advance, and connecting the automatic gain control circuit amplifier circuit and the reference gain setting resistor or the reference gain adjustment unit variably set to a predetermined resistance value. Said C
And a reference gain setting changeover switch for selectively changing over according to a command from the ATV status monitor.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a CA according to a first embodiment to which the present invention is applied.
It is a block diagram which shows the structure of the amplifier for TV. In the present embodiment, the gain of the trunk RF amplifier is controlled by the CATV status monitor. The main part of this amplifier 1 is composed of a down amplifier 2, an up amplifier 3, a pseudo line (BON) 4, filters 5, 6 and a status monitor 7, as in a normal CATV amplifier. The output unit 9 is connected to a CATV line (not shown). Note that, in FIG.
Is shown as a block diagram, the upstream amplifier 3
Has a similar configuration.

The downstream amplifier 2 includes an AGC circuit 10, a tilt circuit 21 for compensating the frequency characteristic of the signal attenuation in the communication line, a slope circuit 22 for adjusting the gain difference between the highest and lowest frequencies, and a trunk line 23. RF amplifier 24,
25, a detection circuit 26 for branching from the AGC circuit and sending the data to the status monitor, and a DC amplifier 27.

On the other hand, the AGC circuit 10 includes a surface acoustic wave filter (SAW filter) 11, an RF amplifier 12, a detection circuit 13, a DC amplifier 14 for the AGC circuit, a reference gain setting resistor 15, and a reference gain setting changeover switch 16. It is configured. In this case, the reference gain setting switch 16
The contact 16a on the common side is connected to the DC amplifier 14, the contact 16b on one side of the switching contact is connected to the reference gain setting resistor 15, and the contact 16c on the other side is connected to the status monitor 7. This switching is performed by the status monitor 7
It is performed by the command of.

Next, the status monitor 7 comprises a CPU 71, an A / D converter (not shown) and the like, like a normal status monitor.
3 is connected. In this embodiment, AGC
A reference gain adjuster 73 capable of setting the reference gain of the circuit to an arbitrary value is provided connected to the CPU 71. The reference gain adjuster 73 is connected to a contact 16c of the reference gain setting switch 16 of the AGC circuit 10.
The CPU 7 receives a command from a center device (not shown).
When 1 sets a predetermined value, the reference gain of the AGC circuit 10 is set.

Next, the operation of this embodiment will be described.
When the amplifier 1 is installed, a predetermined reference gain is set. Here, the reference gain setting switch 16 is normally
It is connected to the contact 16b side, and this setting is performed by adjusting the reference gain setting resistor 15. Normally, the set reference gain is not changed thereafter. Then, based on the reference gain, the AGC circuit 10
The RF amplifier 24 is adjusted so that the gain of the amplifier 1 is in the range of, for example, the reference gain ± 3 dB.

Now, assume that, for example, an amplifier downstream of the amplifier 1 fails and a predetermined gain cannot be obtained in the amplifier. In this case, on the terminal side, the signal strength is reduced by the gain of the failed amplifier, and a predetermined signal strength cannot be obtained, resulting in image distortion or the like.

In such a case, the center device first determines the amount of decrease in signal strength and determines whether another amplifier upstream of the failed amplifier can substitute for the failed amplifier. Then, for example, if the gain of the amplifier 1 of the present embodiment is increased,
When a predetermined signal strength can be obtained on the terminal side, this is dealt with by adjusting the reference gain of the amplifier 1.

At this time, the center device first calculates a required reference gain value, and the CPU 71 of the status monitor 7
Command. Based on this command, the CPU 71 operates the reference gain adjuster 73 to set a resistance value required for the set reference gain. Next, the CPU 71 switches the reference gain setting changeover switch 16 to the contact 16c side based on a command from the center device side. As a result, the reference gain adjuster 73 of the status monitor 7 is connected to the DC amplifier 14, and the AGC circuit 10 operates by the reference gain set in the reference gain adjuster 73, thereby controlling the gain of the amplifier 1. You. Therefore, thereafter, the reference gain of the AGC circuit becomes the value set in the reference gain adjustment unit 73 according to a command from the center device side, and the automatic gain control is performed based on this value. As a result, in the system, a decrease in signal strength due to a failure of the lower amplifier is compensated. Note that the normal AGC circuit is ± 3 dB
When the gain control of the amplifier is performed by the reference gain adjustment unit 73, the control is further performed within a range of ± 3 dB from the changed reference gain, for example.

On the other hand, when the failure of the lower amplifier has been corrected, the CPU 71 switches the reference gain setting changeover switch 16 to the contact 16b in response to a command from the center device, contrary to the above. As a result, the AGC circuit 10 returns to the automatic gain control state based on the previous predetermined reference gain.

Next, a second embodiment according to the present invention will be described. FIG. 2 is a block diagram showing the configuration of the second embodiment. This embodiment has substantially the same configuration as that of the first embodiment. However, in this embodiment, the first embodiment controls the main-line RF amplifier 24, whereas the RF amplifier 24
Is fixed, and the reference gain of the amplifier 1 is adjusted by controlling the amount of attenuation of the tilt circuit 21.

The configuration of this embodiment is almost the same as that of the first embodiment as shown in FIG.
The difference is that the gain control at 0 is performed by controlling the amount of attenuation of the tilt circuit 21 by the DC amplifier 14. The other configuration is the same as that of the first embodiment, and the description is omitted.

Here, in this embodiment, the amplification factor of the RF amplifier 24 is fixed to the maximum value of the amplifier. On the other hand, in the amplifier 1, the fixed gain obtained by the RF amplifier 24 is adjusted using the tilt circuit 21 having an attenuation having frequency characteristics so that the gain is set to a predetermined value determined for the amplifier. doing.
In this embodiment, the amount of attenuation of the tilt circuit 21 is variable. Therefore, in this embodiment, the AGC circuit 10 controls the gain of the amplifier 1 by adjusting the amount of attenuation in the tilt circuit 21.

That is, for example, the reference gain of the amplifier 1 is 450
Assuming that the frequency is 22 dB in MHz, the RF amplifier 24 first uses the one corresponding thereto and further fixes this to its maximum gain. In this case, for example, when an RF amplifier having a maximum gain of 25 dB is used, 25 dB is used.
Fixed to. On the other hand, the amount of attenuation of the tilt circuit 21 has a frequency characteristic. However, considering at 450 MHz for simplicity, the reference attenuation is set to -3 dB in order to obtain the reference gain 22 dB of the amplifier 1. This usually results in 22 dB
Will be obtained. And the AGC circuit 10
By adjusting the amount of attenuation of the tilt circuit 21 so as to be 0 to -6 dB, the gain of the amplifier 1 is ± 3.
Control is performed so that a reference gain of 22 dB is obtained within the range of dB.

Here, considering the case where some kind of failure occurs in the system as described above, the tilt circuit 21 is switched by switching the reference gain setting changeover switch 16 as in the first embodiment.
Is changed. That is, in the above example, the case where the reference attenuation is −3 dB is, for example, 0%.
Change to dB. As a result, the reference gain of the amplifier 1 becomes 25
The gain is changed to dB, and the AGC circuit 10 operates based on this, and gain control is performed. Therefore, the gain of the amplifier 1 is increased by +3 dB with respect to the lower system, and the lowering of the signal strength in the lower stage is compensated.

As described above, in this embodiment, the case where the downstream amplifier has a failure has been described as an example. However, it is needless to say that the failure of the upstream amplifier can be compensated. Further, the failure of another amplifier is compensated not only for one amplifier but also for a plurality of normal amplifiers. Furthermore, in the present embodiment, a configuration is adopted in which a command is issued from the center device to the status monitor 7.
Of course, this can be performed by directly operating the status monitor 7 of the amplifier. In addition, RF amplifier 2
Even if the amplification characteristic of No. 4 has a certain frequency characteristic and the characteristic is flat regardless of the frequency, the present method can of course be applied.

[0024]

As described above, the CA according to the present invention is used.
Control method of automatic gain control circuit of TV amplifier and CAT
According to the amplifier for V, the status monitor for CATV includes a reference gain adjuster variably set to an arbitrary resistance value,
The automatic gain control circuit includes a reference gain setting changeover switch, etc., and selects a reference gain setting resistor side or a reference gain adjustment unit side according to a command from a CATV status monitor,
The AGC of the amplifier is automatically adjusted within a certain range from the reference gain of the amplifier determined based on the resistance value of the reference gain setting resistor or the resistance value of the reference gain adjustment unit. There is an effect that the reference gain of the circuit can be arbitrarily changed even after the amplifier is installed.
Therefore, even in the event of a system failure such as an amplifier failure, the gain of another normal amplifier can be changed in order to secure a predetermined signal strength, thereby compensating for a decrease in signal strength due to the failed amplifier or the like. Reliability can be improved. In particular, since the resistance value of the reference gain setting resistor of the CATV status monitor is changed without changing the resistance value of the reference gain setting resistor of the AGC circuit, the reference gain of the AGC circuit is changed to the reference gain setting value. It is possible to return to the initial automatic gain adjustment state simply by returning to the resistor side, and it is very easy to restore the system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a CATV amplifier using a method according to the present invention.

FIG. 2 is a block diagram showing a configuration of a second embodiment of the CATV amplifier using the method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 amplifier 7 status monitor 10 AGC circuit 15 reference gain setting resistor 16 reference gain setting switch 16a common side contact 16b reference gain setting resistor side contact 16c status monitor side contact 71 CPU 73 reference gain adjustment unit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 7/10 H04N 7/16

Claims (2)

(57) [Claims] 1. A CATV status monitor which is installed in an amplifier connected to a communication line of a CATV and checks a state of the amplifier based on a predetermined monitoring item, and a gain of the amplifier is set to a predetermined reference gain. An automatic gain control circuit for a CATV amplifier, comprising: an automatic gain control circuit that automatically adjusts a reference value of the amplifier to a predetermined range. The automatic gain control circuit, an automatic gain control circuit amplifying circuit, a reference gain setting resistor for presetting the reference gain of the amplifier, and the automatic gain control. and a reference gain setting changeover switch for switching the connection between the circuit amplifier circuit the reference gain setting resistors or the reference gain controller selectively, prior to The reference gain setting resistor side the reference gain setting changeover switch in response to a command from the CATV status monitor
Alternatively, select one of the reference gain adjustment units and
Resistance value of the reference gain setting resistor
The resistance value of the reference gain adjustment unit variably set to the resistance value of
A certain range from the reference gain of the amplifier determined based on
A method for controlling an automatic gain control circuit of a CATV amplifier, wherein the gain of the amplifier is automatically adjusted. 2. A CATV status monitor which is installed in an amplifier connected to a communication line of a CATV and checks the state of the amplifier based on a predetermined monitoring item, and a gain of the amplifier is set to a predetermined reference gain. And an automatic gain control circuit that automatically adjusts the gain to within a certain range, wherein the CATV status monitor includes a base that can be variably set to an arbitrary resistance value for adjusting a reference gain of the amplifier. an automatic gain control circuit, an automatic gain control circuit amplifying circuit, a reference gain setting resistor for presetting a reference gain of the amplifier, and an automatic gain control circuit. Amplifying circuit and the reference gain setting resistor or variably set to a predetermined resistance value;
A reference gain setting changeover switch for selectively switching the connection with the reference gain adjustment section in accordance with a command from the CATV status monitor.
V amplifier.