JP2003087755A - Equalizer for catv - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equalizer for CATV capable of simply being inserted as required to an optional position of a CATV cable network, a lead-in wire, or the like properly applying tilt adjustment or CR adjustment to a signal depending on the degree. SOLUTION: The equalizer for CATV is configured to comprise a case 2, at least two input output terminals 3 provided to the case 2, two high pass filters 5 passing through only a signal of down band and/or two low pass filters 4 passing through only a signal of up band connected between the input output terminals 3, and a tilt circuit 8 (or a cable replacer circuit 9) placed between the two high pass filters 5 (or between the two low pass filters 4), and to provide an output of a signal received by one of the input output terminals 3, the down band (or up band) of which is subjected to tilt adjustment (or CR adjustment), from the other input output terminal 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for performing signal level tilt adjustment or cable replayer adjustment (CR adjustment) according to loss frequency characteristics of a coaxial cable used for transmission of CATV broadcast signals, In particular, CA
CATV can be easily inserted at any position such as a TV cable network or a lead-in wire whenever necessary.
Related to equalizer.

[0002]

2. Description of the Related Art In a current general CATV broadcasting system, broadcasting signals are often transmitted via a coaxial cable. In a signal transmitted over a predetermined distance by a coaxial cable, "loss" occurs in proportion to the distance, but the magnitude (attenuation) is
There is a characteristic that it depends on the frequency of the transmitted signal (loss frequency characteristic of the coaxial cable). More specifically, the loss of low frequency signals is not so great, and the loss is higher for higher frequency signals.

Therefore, when the length of the coaxial cable arranged between the relay amplifiers exceeds a predetermined value, or when the number of cascade stages of the relay amplifiers to be connected becomes large, it is low. The level of the high frequency signal (up to 770 MHz) may be too low with respect to the level of the high frequency signal (from 70 MHz), which may fall outside the allowable level range, making it impossible to adjust the level.

Therefore, in the relay amplifier, a "tilt circuit" is attached to the output side so that the output level on the high frequency side becomes higher than the output level on the low frequency side, and the frequency is increased. The idea is to compensate the output level according to the characteristics of.

Further, as a result of the level adjustment of the signal output from the relay amplifier on the head end side by the tilt circuit (or due to other reasons), the low frequency band of the signal input to the relay amplifier in the subsequent stage is adjusted. The input level of the high frequency signal may become too high with respect to the input level of the signal, and it may fall outside the allowable level range.To avoid such a situation, a "cable replay" is added to the input side of the relay amplifier. It has also been devised to attach a "circuit" and attenuate the level of the signal input to the relay amplifier on the high frequency side to compensate for the slope of the input signal.

[0006]

Since the conventional tilt circuit and cable replacer circuit are used only in the form of being built in the relay amplifier, at the design stage of the CATV cable network, the "tilt circuit" is used within the expected range. Adjustment ”and“ C
Although "R adjustment" can be performed, it cannot be inserted into a CATV cable network or an arbitrary position of the lead-in line by so-called "retrofitting", and it is difficult to flexibly cope with it.

Further, the degree of tilt adjustment and CR adjustment required is various, and in addition to the case where a slight inclination is sufficient, a large inclination may be required.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to easily insert it at any position such as a CATV cable network or a lead-in wire whenever necessary. The CAT can perform the tilt adjustment or the CR adjustment appropriately according to the degree.
An object is to provide an equalizer for V.

[0009]

A CATV equalizer according to claim 1 of the present invention includes a case, at least two input / output terminals provided in the case, and a connection between the input / output terminals. Two high-pass filters that pass only the down band signal and / or two low pass filters that pass only the up band signal, and a tilt circuit arranged between the two high pass filters or between the two low pass filters Alternatively, the signal is input from one of the input / output terminals, and the signal of the downlink band or the signal of the uplink band is tilt-adjusted or CR-adjusted, and then output from the other input / output terminal. It is characterized in that it is configured to be.

Further, the CATV according to claim 2 of the present invention.
The equalizer for use in a CATV equalizer according to claim 1, wherein a switch is arranged between the two high-pass filters or between the two low-pass filters, and the switch is
It is characterized in that a path circuit is connected to a plurality of types of tilt circuits and / or cable replacer circuits with different attenuations, and any one of them can be selected by switching this switch. There is.

Further, the CATV according to claim 3 of the present invention.
The equalizer for CATV according to claim 1, wherein at least two switches are arranged in series between the two high-pass filters or between the two low-pass filters, and the first switch includes: The pass circuit, the tilt circuit, and the cable replacer circuit are connected so as to be selectable, and the pass circuit, the tilt circuit, and the cable replacer circuit are also selectable for other switches. It is characterized by being connected to.

Further, the CATV according to claim 4 of the present invention.
The equalizer for CATV according to claim 1, characterized in that the tilt circuit or the cable replacer circuit is a continuously variable circuit.

It should be noted that, here, the tilt circuit is used to incline the output level on the high frequency side to be higher than the output level on the low frequency side, and to compensate the output level according to the frequency characteristic. The tilt adjustment is called "tilt adjustment", and the cable replay circuit adds a slope so that the output level on the low frequency side becomes higher than the output level on the high frequency side and compensates the output level according to the frequency characteristics. ".

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an equalizer 1 for CATV according to a first embodiment of the present invention.
In this figure, 2 is a box-shaped (or tubular) metal case, 3a is a first input / output terminal provided on one end side of the case 2, and 3b is the other end side. Is a second input / output terminal provided in the.

Reference numeral 4 is a low-pass filter (LPF) that passes only an upstream band (10-55 MHz) signal (upstream signal) sent from the viewer terminal to the headend, and 5 is a viewer from the headend. It is a high-pass filter (HPF) that passes only the signal (downstream signal) in the downstream band (70 to 770 MHz) sent toward.

As shown in FIG. 1, two switches 6 (a first switch 6a and a second switch 6b) are connected in series between the two high pass filters 5 and 5. Further, a path circuit 7 and a tilt circuit 8 (first to third tilt circuits 8a, 8b, 8c) are switchably connected to the switches 6a and 6b, respectively.

More specifically, the first switch 6a includes
The pass circuit 7 and the first tilt circuit 8a are connected so that only one of them can be selected by switching. Further, the second tilt circuit 8b and the third tilt circuit 8c are connected to the second switch 6b so that only one of them can be selected by switching.

Each of these three tilt circuits 8 uses the high frequency side (up to 770 MHz) as a reference, and the low frequency side (70 M).
The first tilt circuit 8a and the second tilt circuit 8b are included in the first tilt circuit 8a and the second tilt circuit 8b.
Is designed so that the 70 MHz signal is attenuated by 3 dB as shown by the solid line in FIG. 2, and the third tilt circuit 8c is as shown by the chain line in FIG. The 70 MHz signal is designed to be attenuated by 9 dB. In addition, the pass circuit 7 is from the low range to the high range,
This is for simply passing the signal in any frequency band without attenuating it.

As described above, the equalizer 1 in this embodiment
Connects two switches 6a and 6b in series between the two high-pass filters 5 and 5, and further connects these switches 6a and 6b with a tilt circuit 8 having different attenuation amounts.
(8a to 8c) and the pass circuit 7 are connected so as to be selectable. With such a configuration, the input from the first input / output terminal 3a (or the second input / output terminal 3b) is performed. The second input / output terminal attenuates the signal in the downlink band of the output signals in an inclined manner according to the frequency characteristic so that the output level on the high frequency side becomes higher than the output level on the low frequency side. 3b (or the first input / output terminal 3a) can be used for output.

The attenuation amount of the output signal can be adjusted in four stages according to the purpose by appropriately switching the switches 6a and 6b. For example, the connection of the first switch 6a is set to the pass circuit 7 side, and the connection of the second switch 6b is set to the second tilt circuit 8b.
When it is set to the side, the tilt adjustment can be performed so that the 70 MHz signal is attenuated by 3 dB, and from this state, the connection of the first switch 6a is switched to the side of the first tilt circuit 8a. In this case, tilt adjustment can be performed so that the 70 MHz signal is attenuated by 6 dB in total.

Further, from this state, the second switch 6b
When the connection of is switched to the side of the third tilt circuit 8c, a total of 12 dB is attenuated, and when the connection of the first switch 6a is switched to the side of the pass circuit 7 from that state, it is attenuated by 9 dB. Such tilt adjustment can be performed.

In this embodiment, the switch 6 and the tilt circuit 8 are arranged between the two high-pass filters 5 and 5 so that the tilt adjustment of the down band signal can be performed. However, the switch 6, the tilt circuit 8 and the like may be arranged between the low pass filters 4 and 4, and in this case, tilt adjustment of the signal in the upstream band can be performed.

Next, a second embodiment of the present invention will be described. FIG. 3 is a configuration diagram of the CATV equalizer 1 according to the second embodiment. As shown in this figure,
The equalizer 1 according to the present embodiment has a tilt circuit 8 (first to third tilt circuits 8a, 8a) of the equalizer 1 according to the first embodiment.
b, 3c) (see FIG. 1) to the cable replacer circuit 9
(First to third cable replayer circuits 9a, 9b, 9
It is obtained by substituting it into c).

These three cable replacer circuits 9
In each case, the high frequency side (up to 770 MHz) is attenuated in an inclined manner on the basis of the low frequency side (70 MHz to). Among these, the first cable represor circuit 9 is used.
a and the second cable replayer circuit 9b are designed so that the signal at 770 MHz is attenuated by 3 dB as shown by the solid line in FIG. 4, and the third cable replayer circuit 9c is The signal at 770 MHz is designed to be attenuated by 9 dB, as indicated by the dashed-dotted line of 4.

As described above, the equalizer 1 in this embodiment
Connects two switches 6a and 6b in series between the two high-pass filters 5 and 5, and further connects these switches 6a and 6b to the cable represor circuits 9 (9a to 9c) and the attenuation amounts different from each other. The pass circuit 7 is connected in a selectable manner. With such a configuration, among the signals input from the first input / output terminal 3a (or the second input / output terminal 3b), The signal in the downlink band is attenuated in an inclined manner in accordance with the frequency characteristics so that the output level on the low frequency side becomes higher than the output level on the high frequency side, and the second input / output terminal 3b (or the first input / output terminal 3b). Input / output terminal 3
It is possible to output from a).

The first point is that the attenuation amount of the output signal can be adjusted in four steps according to the application by appropriately switching the switches 6a and 6b.
The same as the equalizer 1 according to the embodiment. For example, the first
Of the switch 6a is set to the side of the path circuit 7, and the connection of the second switch 6b is set to the second cable replay circuit 9
When set to the b side, the 770MHz signal is 3dB
It is possible to perform CR adjustment so as to be attenuated, and from this state, when the connection of the first switch 6a is switched to the first cable replayer circuit 9a side, 770
CR adjustment can be performed such that the MHz signal is attenuated by 6 dB in total.

Further, from this state, the second switch 6b
When the connection of the switch is switched to the side of the third cable replayer circuit 9c, a total of 12 dB is attenuated, and from that state, when the connection of the first switch 6a is switched to the side of the pass circuit 7, it is attenuated by 9 dB. CR adjustment as described above can be performed.

In this embodiment, the switch 6 and the CR tilt circuit 9 are arranged between the two high pass filters 5 and 5 so that the CR adjustment of the downlink band signal can be performed. But switch 6 and C
The R circuit 9 and the like may be arranged between the low pass filters 4 and 4, and in this case, CR adjustment of the signal in the upstream band can be performed.

Next, a third embodiment of the present invention will be described. FIG. 5 is a configuration diagram of the CATV equalizer 1 according to the third embodiment. As shown in this figure,
In the equalizer 1 of the present embodiment, the path circuit 7a, the tilt circuit 8d, and the cable replayer circuit 9d are switched and connected to the first switch 6a, and similarly, to the second switch 6b, The pass circuit 7b, the tilt circuit 8e, and the cable replayer circuit 9e are switch-connected.

More specifically, the first switch 6a includes
The path circuit 7a, the tilt circuit 8d, and the cable replayer circuit 9d are connected so that only one of them can be selected by switching. Further, a path circuit 7b, a tilt circuit 8e, and a cable replayer circuit 9e are connected to the second switch 6b so that only one of them can be selected by switching.

Of these, the tilt circuits 8d and 8e are
In both cases, the low frequency side (70 MHz to) is attenuated in an inclined manner with reference to the high frequency side (to 770 MHz).
However, the amount of attenuation is different, and the tilt circuit 8d is
As shown by the solid line in,
The tilt circuit 8e is designed to be attenuated by B.
Is 70 MHz, as indicated by the chain double-dashed line in FIG.
Is designed to be attenuated by 6 dB.

All of the cable replacer circuits 9 use the low frequency side (70 MHz to) as a reference, and the high frequency side (to 770 MHz).
(MHz) is attenuated in an inclined manner. However, the amount of attenuation is different, and the cable represor circuit 9d is designed so that the signal at 770 MHz is attenuated by 3 dB as shown by the solid line in FIG. As shown by the chain double-dashed line in FIG. 4, the 770 MHz signal is designed to be attenuated by 6 dB.

As described above, the equalizer 1 according to the present embodiment.
Connects two switches 6a and 6b in series between the two high-pass filters 5 and 5, and these switches 6a and 6b are connected in series.
6b includes a tilt circuit 8 (8d, 8e), a cable replacer circuit 9 (9d, 9e), and a pass circuit 7 (7a,
7b) are connected in a selectable manner. With such a configuration, among the signals input from the first input / output terminal 3a (or the second input / output terminal 3b), For the signal in the downlink band, the output level on the high frequency side should be higher than the output level on the low frequency side, and conversely, the output level on the low frequency side be higher than the output level on the high frequency side. , The second input / output terminal 3b (or the first input / output terminal 3) is attenuated in an inclined manner according to the frequency characteristic.
It is possible to output from a).

The attenuation amount and the inclination direction of the output signal can be adjusted in several steps according to the purpose by appropriately switching the switches 6a and 6b. For example, connect the first switch 6a to the pass circuit 7
Set to the side, and connect the second switch 6b to the tilt circuit 8
When set to the e side, tilt adjustment can be performed so that the 70 MHz signal is attenuated by 6 dB, and from this state, the connection of the first switch 6a is changed to the tilt circuit 8
When switching to the d side, tilt adjustment can be performed such that the 70 MHz signal is attenuated by 9 dB in total. Furthermore, from this state, when the connection of the second switch 6b is switched to the side of the path circuit 7b, tilt adjustment can be performed such that the 70 MHz signal is attenuated by 3 dB.

On the other hand, when the connection of the first switch 6a is set to the path circuit 7 side and the connection of the second switch 6b is set to the cable replayer circuit 9e side, 770 MH
CR adjustment can be performed such that the z signal is attenuated by 6 dB, and when the connection of the first switch 6a is switched to the cable replayer circuit 9d side from this state, the 770 MHz signal is summed up. It is possible to perform CR adjustment so as to be attenuated by 9 dB. Furthermore, from this state,
When the connection of the second switch 6b is switched to the path circuit 7b side, CR adjustment can be performed so that the signal of 770 MHz is attenuated by 3 dB.

In this embodiment, the switch 6 and the like are arranged between the two high-pass filters 5 and 5, so that the tilt adjustment or CR adjustment of the signal in the downstream band can be performed. , Switch 6 or the like may be arranged between the low-pass filters 4 and 4. In this case,
It is possible to perform tilt adjustment or CR adjustment of the signal in the upstream band.

Next, a fourth embodiment of the present invention will be described. FIG. 6 is a block diagram of the equalizer 1 for CATV according to the fourth embodiment. As shown in this figure,
In the equalizer 1 of the present embodiment, the tilt continuously variable circuit 10 is arranged between the two high pass filters 5 and 5.

The continuously variable tilt circuit 10 is a tilt circuit having a variable resistor. By rotating and adjusting a volume knob (not shown), the signal level on the low frequency side of the downlink band is tilted at an arbitrary attenuation amount. It can be attenuated (tilt adjustment).

In the CATV equalizer 1 shown in FIG. 6, when the CR continuous variable circuit, not the tilt continuous variable circuit 10, is arranged between the two high pass filters 5 and 5, the downlink band The signal level on the high frequency side can be attenuated (CR adjusted) in an inclined manner with an arbitrary amount of attenuation.

Further, the tilt continuously variable circuit 10 or C
When the R continuous variable circuit is arranged not between the two high pass filters 5 and 5 but between the two low pass filters 4 and 4, the signal level on the low band side of the up band is tilt-adjusted or the up band is increased. The signal level on the high frequency side of can be adjusted by CR.

[0041]

As described above, the C according to the present invention
Since the equalizer for ATV is not used by being built in the relay amplifier or the like, but is configured as an independent device, it can be retrofitted at an arbitrary position on the CATV cable network or its lead-in wire. It can be easily inserted and is always flexible when adjustments are found to be necessary.

Further, the tilt direction and the attenuation amount can be adjusted in several steps or continuously according to the required degree of tilt adjustment or CR adjustment, so that versatility is high and appropriate measures can be taken. ing.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a CATV equalizer 1 according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an attenuation amount of a tilt circuit 8 used in the equalizer 1 of FIG.

FIG. 3 is a configuration diagram of a CATV equalizer 1 according to a second embodiment of the present invention.

FIG. 4 is a diagram showing the amount of attenuation of a cable replacer circuit 9 used in the equalizer 1 of FIG.

FIG. 5 is a configuration diagram of a CATV equalizer 1 according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a CATV equalizer 1 according to a fourth embodiment of the present invention.

[Explanation of symbols]

1: Equalizer 1, 2: Case, 3, 3a, 3b: input / output terminals, 4: Low pass filter, 5: high-pass filter, 6, 6a, 6b: switch, 7, 7a, 7b: pass circuit, 8, 8a to 8e: tilt circuit, 9, 9a-9e: Cable replacer circuit, 10: Continuous tilt variable circuit,

Claims (4)

[Claims] 1. A case, at least two input / output terminals provided in the case, and two high-pass filters and / or upstream bands, which are arranged between these input / output terminals and pass only signals in the downlink band. Signal that is input from one of the input / output terminals, which is composed of two low-pass filters that pass only the signal and a tilt circuit or cable replacer circuit that is arranged between the two high-pass filters or between the two low-pass filters. Among them, the down band signal or the up band signal is configured to be output from the other input / output terminal after being tilt-adjusted or cable-replacer-adjusted.
Equalizer. 2. A switch is arranged between the two high-pass filters or between the two low-pass filters, and the switch includes a pass circuit and a plurality of types of tilt circuits and / or cable replacer circuits having different attenuation amounts. It is connected, and is configured to be able to select one by switching this switch,
The equalizer for CATV according to claim 1. 3. At least two switches are arranged in series between the two high-pass filters or between the two low-pass filters, and a first switch includes a pass circuit, a tilt circuit, and a cable replacer circuit. 3. Each of them is selectably connected, and a path circuit, a tilt circuit, and a cable replacer circuit are also connected to other switches in a selectable manner. The equalizer for CATV as described in 1. 4. The tilt circuit or the cable replacer circuit is a continuously variable circuit.
The equalizer for CATV as described in 1.