JPS6012385Y2 - CATV equipment - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to CATV equipment, and provides an equipment in which bidirectional lines and unidirectional lines are mixed, in which a door transducer is connected to completely impedance matching the uplink line. With the goal.

Bidirectional CATV systems include space division method, time division method,
There are three frequency division methods.

Of these, the most commonly used frequency division method will be explained.

As shown in Figure 1, on the frequency axis, A to B is assigned to the upstream band, and C to D is assigned to the downstream band, and a filter is used to separate the upstream and downstream signals and transmit them. It is a split method.

FIG. 2 shows an example of a system diagram of a CATV system that uses a frequency division method and includes both bidirectional lines and unidirectional lines.

The downlink signal passes through the main line 1 from the head end 8, and is connected to the main line 1a and branch lines 2at 2bt 2 by the bidirectional trunk branch amplifier 9.
ct 2d and transmitted.

The downlink signal of the trunk line 1a is transmitted to the next bidirectional trunk branch amplifier 9a,
It is further transmitted to the unidirectional main branch amplifier 10.

Branch lines 2e and 2f from the amplifier 9a. 2gv2h is connected, and branch lines 3a, 3 be 3 C? are connected from the amplifier 10.
3d is connected.

The downstream signal of the branch line 2ce2h is transmitted to the bidirectional distribution amplifier 11 or the unidirectional distribution amplifier 12, and is transmitted from the distribution terminal to the distribution lines 4 af 4 be 4 C, 4d or 5at 5b, 5c, 5d.

When the distribution capacity is insufficient, the extension amplifiers 13a and 13b are used to increase the distribution capacity, and the extension line 6a is used to transmit the downstream signal.

On the other hand, the downlink signal of the distribution line 4c is transmitted to the subscriber terminal 15 via the drop-in line 7 using the tap-off 14.

Uplink at the two-way subscriber terminal 15. Downlink signal split filter 1
6, a downstream signal can be received from the terminal 17.

On the other hand, the upstream signal is transmitted from the upstream terminal 18 to the dividing filter 16
The downstream signal is sent back to the head end 8 via the reverse route along which the downstream signal was transmitted.

In FIG. 2, signals can be transmitted in the direction of the arrow.

Therefore, → is a unidirectional transmission path, and 0 is a bidirectional transmission path.

In the CATV system shown in FIG. 2, trunk line 1c.

In the branch line 2h and the distribution line 4d, impedance matching is incomplete in the upstream band.

The upstream band of many two-way CATV systems is l QMH
z to 50MHz is used.

If the impedance of the line is mismatched and a connector failure occurs due to poor construction, etc., short waves in the air will enter through the connector failure point, pass through the upstream transmission path, and gather at the center head end 8, making upstream transmission impossible. In some cases,

Another drawback is that if the impedances are mismatched, the upstream signal will be distorted in that band.

As described above, impedance mismatch in the upstream signal band poses a problem in conventional CATV systems in which bidirectional lines and unidirectional lines coexist.

The present invention provides a high-pass filter that solves this upstream band noise problem, and one embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, the upstream signal band is impedance matched, and the downstream signal band is below the high-pass filter through which it passes.

19 is a high-pass filter, and capacitors 22, 23 .
24, 25, 29, coil 26, 27, 28, 30, 3
From 1, 32 and 33, the downlink signal will pass.

On the other hand, 20 is a matching circuit for impedance matching in the upstream signal band, and is separated from the capacitor 35 for cutting line superimposed current, the low-pass filter 21 for passing the downstream signal band, and the terminating resistor 47.

The low-pass filter 21 has coils 36°37, 38, 39,
Capacitor 40. 41.42.43.4・4.45.
From 46 onwards.

The high-pass filtering and matching means 48 consisting of the high-pass filter 19 and the matching circuit 20 are connected as shown in FIG.

In FIG. 4, the same parts as in FIG. 2 are given the same numbers and will be explained.

The high-pass filtering and matching means 48 is provided between the bidirectional trunk branch amplifier 9a and the unidirectional trunk branch amplifier 10, between the bidirectional trunk branch amplifier 9a and the unidirectional distribution amplifier 12, and between the bidirectional distribution amplifier 11 and the bidirectional trunk branch amplifier 9a and the unidirectional distribution amplifier 12. and the extension amplifier 13a.

Note that, in place of the high-pass filter 19, a band-pass filter that passes only the downstream signal band may be used to achieve the same effect.

By providing the high-pass filtering and matching means 48 in this way, the main line 1c, the branch line 2h, and the distribution line 4d, which had upstream signal band mismatch, have perfect impedance matching, which eliminates disturbances in upstream signals and shortwave, etc. This can prevent the intrusion of band interference waves.

As described above, according to the present invention, in a CATV device in which bidirectional lines and unidirectional lines coexist, a filter and an impedance matching circuit are connected at the point where bidirectional lines are converted to unidirectional lines, so that desired The signal flows only in the direction of
It can provide an ATV system.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of frequency division bidirectional CATV, Figure 2
The diagram shows a CATV with a mix of conventional bidirectional lines and unidirectional lines.
Figure 3 is a block diagram of the device, and Figure 3 is a circuit diagram of the main parts of CATV in an embodiment of the present invention. Figure 4 is a diagram of a CATV system that uses the filter of the present invention and has both bidirectional and unidirectional lines. It is a block diagram. 1.1a... Trunk line, 9... Bidirectional trunk branch amplifier, 10... Unidirectional trunk branch amplifier,
11...Bidirectional distribution amplifier, 12...
One-way distribution amplifier, 13...extension amplifier.

Claims (1)

[Scope of utility model registration request] A means is provided for transmitting downlink signals transmitted from the center to a plurality of terminals and uplink signals transmitted from any one of the plurality of terminals to the center in different frequency bands, and Bidirectional branching means is provided for branching the downlink signal from the branch line to the branch line and for passing the upstream signal from the branch line to the center side, and branching the downlink signal outputted from the bidirectional branching means to the branch line. One-way branching means is provided for supplying downlink signals to terminals that do not generate uplink signals and receive only downlink signals among the plurality of terminals, and the downlink branching means is provided between the two-way branching means and the one-way branching means. A CATV equipped with a matching means including a filter and a terminating resistor that passes only the signal and blocks the upstream signal and noise while performing impedance matching for the frequency of the upstream signal.
Device.