JP2857171B2 - Method for extracting monitor signal from bidirectional amplifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a monitor signal extracting method for measuring the level of an input signal and an output signal at an input / output terminal of a bidirectional amplifier of a CATV system.

(Prior Art) A conventional method for extracting a monitor signal of a bidirectional amplifier is described in the third section.
This was performed as shown in FIG. 4 and FIG. The monitor signal extracting method shown in FIG.
DF ₁ directional coupler 41 _{1-41 6} inside the ～DF ₃ is provided, the input and output terminals 42 ₁ to downlink mains input signal a directional coupler 41 ₁ input from the input and output terminals 42 ₂ the downlink trunk output signal b is directional coupler 41 ₂ output, uplink uplink trunk output signal c inputted from the input and output terminals 42 ₂ by the directional coupler 41 _3, which is output to the input and output terminals 42 ₁ mains output signal d is branched by the directional coupler 41 _4, in addition, the downstream branch output signal e which is branched from the main line directional coupler 41 _6, upstream branch output signal f from the terminal side directional coupler 41 ₅ is branched by, it is obtained so as to be taken out as a monitor signal to the monitor terminal 43 ₁ to 43 ₆ each.

The fourth monitoring signal is taken out the method of figure outside the demultiplexing filter DF ₁ ~DF ₃ of bi-directional amplifier 40, down mains input signals a and upstream mains output signal d of the input and output terminals 44 ₁ resistance
Divided by R _1, R _2, downlink trunk output signal b and upstream mains input signal c to the output terminal 44 ₂ is divided by the resistors R _3, R _4, further downstream branch output signal e and the upstream branch from the terminal is divided input signal f is the resistance R _5, R _6, is obtained so as to be taken out as a monitor signal to each of the monitor terminals 45 ₁ to 45 _3.

(Problems to be Solved by the Invention) The monitor signal extracting method shown in FIG. 3 has the following problems.

. Configuration because the directional coupler is six (41 ₁ to 41 ₆₎ required it becomes complicated and increases the cost.

. Since there are demultiplexed filter DF ₁ ~DF ₃ between the directional coupler 41 _{1-41 6} each input and output terminals 42 ₁ to 42 _3, demultiplexed filter DF ₁ if there is an abnormality in the monitor signal whether there is an abnormality in ~DF _3, distinguished whether there is an abnormality in the external line of the bi-directional amplifier 40 does not attach.

The monitor signal extracting method shown in FIG. 4 has the following problem.

. There is an advantage that a monitor signal can be extracted without using a directional coupler, but the monitor terminals 45 _{1 to} 45 ₃
There because on the outside of the bidirectional amplifier 40, the monitoring cable connected to the terminals 45 ₁ to 45 ₃ is longer affect its impedance, no particular is consistent with the impedance of the impedance and the bidirectional amplifier 40 And accurate measurement is not possible.

. The level of the monitor signal is set to be about −20 dB from the main line level. However, if the impedance of the monitor cable and the impedance of the bidirectional amplifier 40 cannot be matched, the amount of attenuation of the monitor signal changes.

(Object of the Invention) It is an object of the present invention to realize a monitor signal extracting method capable of extracting a monitor signal with a small number of directional couplers and capable of monitoring with high accuracy and high reliability.

(Means for Solving the Problems) A method for extracting a monitor signal of a bidirectional amplifier according to the present invention is as follows.
Bidirectional coupler 3 ₁ to 3 ₃ provided immediately after or immediately before the input and output terminals 2 ₁ to 2 ₃ of a bidirectional amplifier 1 as in the first view, the monitor signal is branched both uplink and downlink signals Is taken out. Immediately after for the same signal when the here downlink signal or the uplink signal from the input and output terminals 2 ₁ to 2 ₃ immediately after or immediately before is input, input and output terminals 2 ₁ to 2 ₃
When a down signal or an up signal is output from, this means that the signal is immediately before.

(Operation) In the monitor signal extracting method of the present invention, the upstream signal (upstream trunk input signal c, the upstream trunk output signal b, the upstream branch input signal f) and the downstream signal (downstream trunk input signal a, downstream trunk output signal d, a downlink branch output signal e), but bi-directional amplifier 1 of the input and output terminals 2 ₁ to 2 ₃ immediately after or is branched by the bidirectional coupler 3 ₁ to 3 ₃ provided immediately before the monitor terminal ₄₁ to _It is taken out as monitor signal at ₆ .

Among these, for example, a bidirectional coupler 3 to monitor a monitor signal of the downlink trunk input signal a extracted by _1, fitted with a dummy resistor DR to monitor terminal 4 _1, the dummy resistor DR to remove the monitor terminal 4 ₂ Connect a monitor device to the monitor and measure the monitor signal.

Also when measuring the monitor signal extracted in other monitoring terminals 4 _{3-4 6} can be carried out in the same manner as the to.

(Embodiment) FIG. 1 is an explanatory diagram showing an example of a bidirectional amplifier of the present invention.

1 bi-directional amplifier in this figure, 2 ₁ to 2 ₃ is input and output terminals of the amplifier 1, DF ₁ ～DF ₃ branching filter, 10 downstream trunk amplifier, 11 upstream trunk amplifier, 12 upstream branch amplifier ,13
Downlink branch amplifier is a ₄₁ to ₆ monitor terminal.

These are all the same as the conventional ones shown in FIG. 3 and FIG.

In FIG. 1, a is a downstream main line input signal, b is a downstream main line output signal, c is an upstream main line input signal, d is an upstream main line output signal, and e is
Is a downstream branch output signal, and f is an upstream branch input signal.

Then 3 ₁ to 3 ₃ of FIG. 1 is a two-way coupler and features of the present invention, a bidirectional coupler to allow branching both upstream and downstream signals, they are each input and output terminals 2 ₁
Provided immediately after or immediately before to 2 _3.

The bi-directional coupler 3 ₁ to 3 ₃ Yes to allow branching both upstream and downstream signals, each of the bidirectional coupler 3 ₁ -
3 ₃ monitor terminal 4 ₂ for uplink signals, 4 _3, 4 monitor terminal for ₆ and downlink signals 4 _1, 4 _4, 4 ₅ are connected to.

Also the monitor terminal ₄₁ to ₆ each dummy resistor DR is connected. This dummy resistor DR is set to 75Ω in accordance with the characteristic impedance of CATV.

Incidentally, the bidirectional coupler 3 ₁ to 3 ₃ in FIG. 1 is configured as in the second view as in the conventional directional coupler.

(Effect of the Invention) Monitor signal extraction of the bidirectional amplifier of the present invention has the following effects.

. It is possible to branch both uplink and downlink signals as a monitor signal in the bidirectional coupler 3 ₁ to 3 _3, requires less number of bidirectional coupler 3 ₁ to 3 ₃ (conventional half), The structure is simple and economical.

. Since the monitor signal extraction position is in the immediate vicinity of the input and output terminals 2 ₁ to 2 _3, without being outside the influence of impacts and the amplifier 1 demultiplexing filter DF ₁ ～DF ₃ in bidirectional amplifiers 1, reliability Monitor with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a monitor signal extracting method according to the present invention, FIG. 2 is an explanatory view of a bidirectional coupler in the monitor signal extracting method, and FIGS. 3 and 4 are different descriptions of a conventional amplifier. FIG. 1 is a bidirectional amplifier 2 _{1 to} 2 ₃ are input / output terminals 3 _{1 to} 3 ₃ are bidirectional couplers DF _{1 to} DF ₃ are demultiplexing filters

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 7 / 10,7 / 14-7 / 173,7 / 20-7/22 H04N 17/00-17 / 06

Claims (1)

(57) [Claims] By 1. A bidirectional coupler 3 ₁ to 3 ₃ provided immediately after or immediately before the input and output terminals 2 ₁ to 2 ₃ of the bidirectional amplifier 1, a monitor signal branches both uplink and downlink signals A method for extracting a monitor signal of a bidirectional amplifier, wherein the monitor signal is extracted.