JPS62190989A - Superhigh-band signal transmission system - Google Patents

Abstract

PURPOSE:To reduce the cost of an amplifier and to improve picture quality by sending a superhigh-band signal and other signals for CATV out of a head end, amplifying the signals to a wide band and sending them to a trunk line rear stage, and separating and sending the signals at nearly equal levels at a branching amplification part. CONSTITUTION:The superhigh-band signal passes through a high-pass filter 27 and is amplified by an amplifier 29 and sent out from a branch output terminal 6 at a level almost as high as an FM signal and a television VHF signal. The FM signal, VHF signal, and superhigh-band signal which are sent to a distribution line 9 are branched by a branching device 11 respectively and transmitted to a CAT converter 14 through a lead-in line 10. The superhigh-band signal is attenuated through the branch line 9 and lead-in line 10 more than any other signal. A frequency converting circuit 42, however, has a conversion gain, so respective signal levels are nearly equal in output of the converter 14 and a uniform picture can be viewed on a television receiver 15.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a super high band signal transmission system used in a CATV system.

(Prior Art) In a multi-channel transmission CATV system, mid-band signals and super high-band signals are transmitted in addition to television VHF signals and FM signals. In such a CATV system, the main line system and the branch line system taken out from the main line and branched are each equipped with a main line amplification section and a branch amplification section that amplify in a wide band from 70 MHz to 450 MHz, and super high band signals are transmitted to other channels. It is amplified and transmitted together with CATV signals (FM signals, TV VHF signals, Yamid band signals).

(Problems to be Solved by the Invention) The above-mentioned super high band signal transmission system in CATV has the following problems. In other words, 70M for the main line amplification part of the main line system and the branch amplification part of the branch line system! A wide amplification bandwidth from -1z to 450 MH2 is required, and the amplification characteristics are such that the higher the frequency of the signal, the higher the gain is required to be amplified. The branch amplifying section is particularly difficult to realize because the signal output level is higher than that of the main amplifying section, and it is difficult to manufacture it even using an expensive high-output amplifying element.

The present invention was made to solve the above-mentioned problems, and allows super high band signals to be viewed on a general all-channel type TV receiver, and TV VHF channels (ch1 to 12) can be viewed as specified. This is a super high band signal transmission system in which the main branch output level of the main branch is reduced by 1q, and the main branch amplifier or branch amplifier with a built-in branch amplifier is a super high band signal transmission system that can be constructed at low cost using inexpensive amplification elements. The purpose is to provide a signal transmission method.

(Means for solving the problem) In order to solve this object, the measures described in the claims have been taken, and their effects are as follows.

(Operation) The super high band signal sent out from the head end is amplified by each main line amplifier along with other CATV signals and transmitted to the terminal side. On the other hand, in the branch amplification section that amplifies the signal branched from the main line and taken out, the super high band signal is separated from other CATV signals and amplified, and the super high band signal is separated and amplified from other CATV signals that have been amplified separately. It is mixed again to an even level and sent to the distribution line. The terminal uses TV U so that super high band signals can be received by all-channel TV receivers.
The signal is converted into an HF channel signal, amplified to a predetermined level, and sent to a television receiver. The other CATV signals mentioned above are also added to the television receiver. The above TV UHF channel signal and the other CATV signals are applied to the TV receiver at approximately the same level,
On a television receiver, you can see the signals of any channel on a high-quality screen.

(Example) The drawings showing the embodiments of the present application will be described below.

FIG. 1 shows a system diagram of the CATV system, where 1 indicates the head end. This headend 1 simultaneously retransmits normal TV VHF waves (ch'l to 12) and FM waves, and also transmits heavy information such as independent VHF as a mid-band or super high-band TV signal. .

The super high band TV signal channel is S.
A channel with a higher frequency than 5 is selected. 2 indicates the main line.

3 is a trunk branch amplifier, and in this example, a bidirectional type is used. Reference numeral 4 indicates an input terminal of the main branch amplifier, 5 indicates an output terminal, and 6 indicates a branch output terminal.

Reference numeral 7 indicates a main line amplifying section, and 8 indicates a branch amplifying section, the configurations of which will be described in detail later. 9 is a distribution line, 10 is a lead-in line,
Reference numeral 11 indicates a turnout. 12 indicates a protector. 13 is a lead-in line. 14 is a CATV converter, which converts TV Vl-IF signals from channels 1 to 12 as they are.
Moreover, the mid-band and super-high band signals are converted into television signals of the television tJHF band and sent out. Reference numeral 15 indicates an all-channel type television receiver.

Next, the configuration of the trunk branch amplifier 3 will be described in detail.

The trunk amplification section 7 receives FM signals and mid-band signals.

Bypass filters 16 and 17 that pass downlink signals (70 to 450M1-12> such as TV VHF signals and super high band signals), a downlink signal amplification circuit 18 that tilts and amplifies the downlink signals, and a branch for taking out the main downlink output. It is composed of a circuit 19, low-pass filters 20 and 21 that pass uplink signals, an uplink signal amplification circuit 22, and a branch circuit 23 for extracting main uplink input.

The branch amplification section 8 includes low-pass filters 24 and 25 that pass the frequency band from the FM band to the TV VHF signal (including mid-band signals), and the filter 24.
and a first branch amplifier circuit 26 that amplifies the signal passing through channel 85, bypass filters 27 and 28 that amplifies the super high band signal of channels 85 and above, and a first branch amplifier circuit 26 that amplifies the signal that passes through the filters 27 and 28. 2, a branch amplifier circuit 29; 30 is a bypass filter having the same function as the bypass filters 16 and 17; 31 is a low-pass filter having the same function as the low-pass filters 20 and 21; and 32 is a signal A distribution circuit that divides into two parts is shown.

Next, the CATV converter 1 at the receiving subscriber's home 33
The configuration of No. 4 will be explained. 34.35 is a low pass filter that passes FM band and TV VHF low band signals, 36.37 is a band pass filter that passes TV VHF high band signals, 38 is a band pass filter that passes mid band signals, and 39 is a band pass filter that passes TV VHF high band signals. A frequency conversion circuit converts a mid-band signal into a TV tJI-IF signal, 40 is a bandpass filter that passes the converted TV tJHF signal, 41 is a bypass filter that passes a super high band signal, 42 is a super high band 43 represents a bypass filter that passes the television UHF signal output from the frequency conversion circuit 42. Note that the frequency conversion circuit 42 has a conversion gain of about 15 dB.

Next, the operation of the CATV system as described above will be explained. From head end 1 there are FM signals, TV VHF low band signals, and mid band signals.

Television VHF high band signals and super high band signals are transmitted. These signals are tilt-amplified in the main line amplification section 7 of each main line branch amplifier 3, and are transmitted one after another while being attenuated in a reverse tilt manner on each main line 2 and reach the terminal.

On the other hand, in the branch amplifier section 8 of the trunk branch amplifier 3, the FM
Signal, VHF low band signal, mid band signal, VH
The F high band signal @ (also referred to as other CATV signal in this specification) passes through a low pass filter 24, is amplified by an amplifier circuit 26, passes through a low pass filter 25, and is sent out from the branch output terminal 6. Further, the super high band signal passes through a bypass filter 27, is amplified by an amplifier circuit 29, passes through a bypass filter 28, and is sent out from the branch output terminal 6. The output characteristics with respect to frequency at the branch output terminal 6 are as shown in FIG. 2, for example. As is clear from FIG. 2, the super high band signal is transmitted at a level approximately equal to that of the FM signal and the TV VHF signal (in this specification, the term "approximately equal" means up to about 10 dB lower). The above-mentioned FM signal, VHF low band signal, mid band signal, VHF high band signal, and super high band signal sent to the distribution line 9 are branched by a brancher 11, transmitted through a lead-in line 10, and then sent to a CATV converter 14.
leading to.

In the converter 14, the TV V)-IF multiplied signal is output at its original frequency, while the mid-band signal and super high band signal are output to the TV U of a predetermined channel.
It is converted into an HF signal and reaches the television receiver 15. Super high band signals are attenuated more than other low frequency signals in the distribution line 9 and drop-in line 10, but since the frequency conversion circuit 42 has a conversion gain, each of the above signals is attenuated at the output of the CATV converter 14. The levels are all the same, and a uniform, high-quality television screen can be viewed on the television receiver 15. There is no such thing as the image quality worsening only on a specific channel.

Although not shown, upstream signals from each subscriber's home etc. are mixed into the drop-in line 10. This signal reaches the branch output terminal 6 of the main branch amplifier 3 from the distribution line 9, and the distribution circuit 32
．． The signal passes through a low-pass filter 31, is amplified by an upstream amplifier circuit 22, and heads toward the head end 1. In the head end 1, VTR control, computer processing, etc. are performed using upstream signals.

(Effects of the Invention) As described above, in the present application, super high band signals and other CATV signals are sent from the head end, and the main line amplification section installed in each main line transmits the above signals in a wide band. Since the signals are amplified and sent one after another to the later stages of the main line, it has the effect of delivering high-quality signals over a wide area.

Moreover, in the branch amplifier section that branches off from the main line and takes out the signal, the super high band signal is separated from other CATV signals and sent out at approximately the same level, so the TV VHF signal is output at the specified output level. In addition, there is no need to use an expensive high output type amplification element for the branch amplifier circuit, and it becomes possible to use an inexpensive main line branch amplifier or branch amplifier.

Also, the super high band signal is approximately equal to other signals.
Even if the signal is sent from the output of the branch amplifier at a level of
It converts it into a JHF signal and adds it to the television receiver, and the conversion involves a conversion gain.
Super high band signal information can be viewed on an all-channel TV receiver.In addition, the converted signal has almost the same level as the original CATV signal, so you can receive high-quality images. Another feature is that it is possible.

[Brief explanation of drawings]

The drawings relate to embodiments of the present invention, and FIG.
FIG. 2 is a graph showing the output level of each frequency signal at the branch output of the main branch amplifier. 1... Head end, 2... Main line, 3... Main line branch amplifier, 6... Branch output terminal, 7... Main line amplifying section, 8... Branch amplifying section, 9... Min. Wiring, 14...C
ATV converter, 15...TV receiver. Patent applicant Representative of Maspro Electric Works Co., Ltd.
Takashi Hatade

Claims (1)

[Claims] At the head end, the super high band signal is sent out together with other CATV signals including TV VHF signals, etc., and each main line amplification unit installed in cascade on the main line transmits the super high band signal and the other CATV signals. The super high band signal and the other CATV signals are separately amplified and amplified in the branch amplification section that amplifies the signal branched from the main line and sent to the subsequent main line. After that, the signals are mixed again to have a substantially uniform level relationship and sent to the distribution line, and the terminal side converts the frequency of the super high band signal to make it a TV UHF channel signal that can be viewed on a TV receiver. A super high band signal transmission method that is characterized by amplifying to approximately the same level as other CATV signals and sending it to a television receiver.