JP2001189923A - In-private catv system, down-converter, up-converter, and amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a private CATY system, where a terminal uses an up- converter to convert an incoming signal into a private incoming signal with high frequency and a connection point to an external system uses a down- converter to convent the private incoming signal into the original incoming signal, that can accurately convert the frequency, without the need for using a pilot signal from the external system. SOLUTION: The down-converter 10 is provided with a reference oscillation circuit 36, that generates an outgoing signal and a reference signal with a frequency lower than that of the private incoming signal, uses the reference signal to convert the frequency of the private incoming signal and transmits the reference signal to a transmission line L at the terminal. A bidirectional amplifier 12 on the transmission line L can amplify the outgoing signal and the private incoming signal bidirectionally and also transmits the reference signal to the up-converter 20 at the terminal. The up-converter 20 extracts the transmitted reference signal and uses it to convert the frequency of the incoming signal into the frequency of the private incoming signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an external bidirectional CA.
A service line from the TV system is pulled into the building, and a down signal input from the bidirectional CATV system is transmitted to a plurality of terminal devices in the building via a transmission line in the building, and input from each terminal terminal. The present invention relates to an in-building CATV system that sends out an upstream signal to an external bidirectional CATV system via a drop-in line.

[0002]

2. Description of the Related Art In this type of in-building CATV system, noise generated in each part of a building is superimposed on a transmission line via a terminal terminal or the like on a subscriber side. Then, of these noises, those having the same frequency component as the upstream signal are output to the external bidirectional CATV system together with the upstream signal as ingress noise.

Therefore, conventionally, an external bidirectional CATV is used.
In order to reduce ingress noise flowing into the system, an upstream signal (a signal of a frequency (for example, 10 to 55 MHz) that can be transmitted in a bidirectional CATV system) generated by a subscriber terminal device such as a cable modem is increased. The converter uses a UHF band (for example, 821 MHz to 866 MHz) upstream signal (hereinafter referred to as an in-building upstream signal) that is higher than the original frequency and that does not overlap with the downstream signal transmission frequency (for example, 70 to 770 MHz). ), The signal is transmitted to the service line, and immediately before the upstream signal is output from the transmission line in the building to the service line, the upstream signal in the building is converted to the original frequency (in other words, bidirectional) using the down converter. CAT
It has been considered to convert it into a transmission frequency of an upstream signal in a V system.

[0004] By the way, as described above, the terminal of the CATV system in the building converts the frequency of the upstream signal into the upstream signal in the building, and at the connection point between the CATV system in the building and an external bidirectional CATV system, the terminal in the building CATV system. If the signal is frequency-converted to the original upstream signal, the ingress noise output from the in-building CATV system to the external bidirectional CATV system can be reduced, but the up-side signal used for frequency conversion on the terminal side can be reduced. When the converter and the down converter used for frequency conversion at the connection point between the in-building CATV system and the external bidirectional CATV system are configured to perform frequency conversion using the output from the dedicated oscillation circuit, respectively, The frequency of the reference signal for frequency conversion obtained by each oscillation circuit shifts, and the down converter converts the in-building up signal to the terminal. There is a possibility that it can not be converted into the original uplink signal location is generated.

Therefore, conventionally, a bidirectional CAT is used as a reference signal used by the up-converter and the down-converter for frequency conversion so that the down-converter can accurately restore the original up-signal from the in-building up-signal.
It is also considered to use a pilot signal used for level adjustment of a downstream signal in the V system. That is, by configuring the up converter and the down converter to perform frequency conversion on each uplink signal using the pilot signal of the bidirectional CATV system as a reference signal, the frequency of the reference signal in each converter is completely matched, and the down converter is down-converted. On the converter side, the in-building up signal can be accurately restored to the original up signal.

[0006]

However, as described above, when the up-converter and the down-converter are configured to use the pilot signal included in the down signal as the reference signal for frequency conversion, the bidirectional CATV system side When the transmission of pilot signals is temporarily stopped for maintenance and inspection, or when the CATV system inside the building is connected to a bidirectional CATV system that does not transmit pilot signals, the up converter and down converter operate normally. As a result, the upstream signal generated on the terminal device side of the in-building CATV system cannot be transmitted to the center device side of the bidirectional CATV system.

The present invention has been made in view of such a problem, and the terminal uses an up-converter to convert the frequency of an upstream signal into a high-frequency in-building upstream signal, which is connected to an external bidirectional CATV system. On the side, in a building CATV system in which a down converter is used to frequency-convert an in-building up signal into an original up signal, a pilot signal superimposed on a down signal from an external bidirectional CATV system is used for frequency conversion. An object of the present invention is to enable the down converter to accurately restore the original uplink signal without using it as a reference signal.

[0008]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the CA in a building according to claim 1 has been made.
In the TV system, the above-mentioned conventional building CATV
Similarly to the system, a down signal input from an external bidirectional CATV system via a service line is transmitted to a plurality of terminal terminals via a transmission line in a building, and input to the terminal terminals via an up converter. Signal to the outside of the building via a transmission line in the building
The terminal device transmits the signal from the system to the drop-in line, and furthermore, from the drop-in line to the external two-way CATV system, uses a down-converter provided between the drop-in line and the transmission line in the building to send the terminal signal to the terminal. An uplink signal that has been frequency-converted to the output uplink signal of the original frequency is transmitted.

In the CATV system according to the present invention, the reference signal generating means transmits the system signal by the reference signal generating means so that the down converter can accurately convert the frequency of the upstream signal into the original upstream signal. A reference signal having a fixed frequency is generated at a frequency different from the frequency of various transmission signals flowing in the line in the upward and downward directions (in other words, in both directions), and this reference signal is transmitted by the reference signal transmitting means to the inside of the building. On the transmission line.

Therefore, according to the in-building CATV system of the present invention, the down converter and the up converter are shared even when the pilot signal is not superimposed on the down signal input from the external bidirectional CATV system. Can convert the frequency of the upstream signal or the upstream signal by using the reference signal of, and the down converter can accurately restore the original upstream signal input from the terminal device to the up converter. Becomes

In the present invention, in particular, the frequency of the reference signal generated by the reference signal generating means is set to a frequency different from the frequencies of various transmission signals flowing bidirectionally through the transmission line of the system. The characteristics of the transmission signal transmitted bidirectionally in the system do not deteriorate due to the influence of the reference signal, and the transmission quality of each of the upstream and downstream signals can be ensured.

Further, when the down converter and the up converter take out the reference signal for frequency conversion, the reference signal can be easily and accurately taken out by using a band-pass filter corresponding to the frequency of the reference signal. Since it is not necessary to provide a complicated circuit for extracting the reference signal in the down converter and the up converter, the down converter and the up converter can be compared with the case where the pilot signal included in the downlink signal is used as the reference signal. There is no cost increase for the converter.

Here, the reference signal generating means and the reference signal sending means can be constituted as reference signal superimposing devices independent of various transmission devices constituting the in-building CATV system. As described in the above, it may be built in the down converter.

[0014] According to this configuration, the reference signal can be transmitted from the down converter to the up converter on each terminal side, and the reference signal generation means and the reference signal transmission means can be transmitted to the transmission line in the building. Since there is no need to separately connect a reference signal superimposing device having the above function, the construction cost when constructing the in-building CATV system of the present invention can be reduced.

On the other hand, the frequency of the reference signal transmitted by the reference signal transmitting means on the transmission line may be a frequency that does not overlap with the frequency of various transmission signals flowing bidirectionally through the transmission line of the system. Set to one frequency within the frequency band between the preset transmission frequency band of the downstream signal and the transmission frequency band of the upstream signal in the building, or in the frequency band higher than the transmission frequency band of the upstream signal in the building May be.

However, when the frequency of the reference signal is set in such a frequency band, the transmission loss of the reference signal on the transmission line increases, and the down converter and a large number of up converters provided on each terminal side are reduced. The reference signal may not be transmitted properly. For this reason, the frequency of the reference signal transmitted by the reference signal transmitting means on the transmission line is defined as a downlink signal within a frequency band set as a transmission frequency band of the downlink signal in the system. The frequency may be set to a frequency that does not overlap, or may be set to a frequency lower than the frequencies of various transmission signals flowing in the upstream and downstream directions on the transmission line.

That is, if the frequency of the reference signal flowing on the transmission line is set within the transmission frequency band of the downstream signal, the reference signal passes through an amplifier provided on the transmission line. Since the reference signal is amplified together with the downlink signal, the reference signal can be transmitted at an appropriate level without incorporating a dedicated amplifier circuit in an amplifier or the like to compensate for the transmission loss of the reference signal.

Further, if the frequency of the reference signal flowing on the transmission line is set to be lower than the frequency of other transmission signals (downstream signal and upstream signal) flowing on the transmission line, The transmission loss of the reference signal on the transmission line is reduced, and the reference signal can be transmitted well.

In this case, the frequency of the reference signal may be set within the transmission frequency band of the downlink signal, or may be set to a frequency lower than the transmission frequency band of the downlink signal. If the frequency of the reference signal is set within the transmission frequency band of the downlink signal by combining claim 4 and claim 3, the reference signal can be amplified together with the downlink signal using an amplifier provided on the transmission line. Therefore, the reference signal can be transmitted more favorably.

When the frequency of the reference signal is set lower than the transmission frequency band of the downstream signal, the frequency of the reference signal may be set as low as possible in order to reduce the transmission loss of the reference signal. Desirably, specifically, as set forth in claim 5, it is preferable to set within the range of 5 MHz to 26 MHz.

This is because a CATV system in a building includes a system for transmitting only a television broadcast signal as a downlink signal, a system for transmitting an FM radio broadcast signal in addition to a television broadcast signal, and a system for transmitting an FM radio broadcast signal and a television broadcast signal. There are various systems with different transmission frequency bands for downlink signals, such as systems for transmitting cable broadcasting signals such as music.
The lower limit frequency of the transmission frequency band of the downlink signal is the lowest because it is a system for transmitting cable broadcasting.
In other words, in this system, the lower limit frequency is 26 MHz, for example, the transmission frequency band of the downlink signal is 26 MHz to 770 MHz. Therefore, even in such a system, the frequency of the reference signal is changed to the transmission frequency band of the downlink signal. In order to reduce the transmission loss of the reference signal by setting it to a lower frequency, the frequency of the reference signal may be set within the range of 5 MHz to 26 MHz.

The reason why the lower limit of the frequency of the reference signal is set to 5 MHz is that the lower limit frequency of the signal which can be transmitted by the CATV system in the building is 5 MHz.
In a system in which the lower limit frequency of a signal that can be transmitted is 10 MHz, the frequency of the reference signal may be set to 10 MHz or more. In the future, the lower limit frequency of signals that can be transmitted is 5
If a system of less than 5 MHz is put into practical use, the frequency of the reference signal may be set to less than 5 MHz.

Further, the CATV system in a ridge according to the present invention comprises:
The up-converted signal output from the terminal device is once converted into a high-frequency in-building up-signal by an up-converter, and transmitted to the drop-in line via the transmission line in the system, so that it can be used in the building. Although the generated noise is prevented from being transmitted to an external bidirectional CATV system together with the upstream signal, if the signal that can flow through the transmission line in the upstream direction in the system is limited to only the upstream signal in the building, In order for the system subscriber on the terminal side to communicate with the center device of the external two-way CATV system using the terminal device, the system subscriber must have an upconverter, which leads to a decrease in service. There is a fear.

According to the sixth aspect of the present invention, there is provided an in-building CATV system which is output from a terminal device,
It is desirable that a low-frequency upstream signal that has not been frequency-converted by the up-converter be transmitted as it is to the drop-in line. And CATV in the ridge
If the system is configured in this manner, both the high-frequency in-building upstream signal and the low-frequency upstream signal can be transmitted in the upstream direction, so even a subscriber who does not own an up-converter can use the terminal device. Thus, communication can be performed with the center device of the external two-way CATV system, and communication services in the system can be improved.

In order to transmit the in-building up signal and the up signal together, for example, CA
As in the Internet using a TV system, high-speed data transmission is performed bidirectionally, and for communication in which transmission quality is required, an up-converter and a down-converter are used to frequency-convert an uplink signal. For example, Even if data transmission is erroneous, such as data transmission for automatic meter reading that transmits the amount of electricity or gas used to the center device, if the data is retransmitted at the request of the center device, For communication that does not cause inconvenience, the uplink signal from the terminal device may be transmitted as it is without frequency conversion.

However, when performing such a two-way communication,
The upstream signal transmitted using the up converter and the down converter, and the upstream signal transmitted as it is without using the up converter and the down converter,
It is necessary to set different frequencies.

That is, in the CATV system in the building,
When the upstream signal is transmitted as it is, the noise component of the frequency of the upstream signal is directly transmitted to the external bidirectional CA.
If the frequency of this upstream signal and the frequency of the upstream signal transmitted using the up-converter and the down-converter are set to the same frequency, the effect of the up-converter and the down-converter cannot be exhibited. Become.

For this reason, as described above, in a building CATV system, when both a building upstream signal and an upstream signal can be transmitted, an upstream signal that is frequency-converted into a building upstream signal and a frequency Uplink signals transmitted directly through the transmission line without conversion must be set to different frequencies.

When each of the upstream signals is set to a different frequency as described above, the frequency of the upstream signal transmitted as it is through the transmission line without frequency conversion is changed to the upstream signal which is frequency-converted into the ridge upstream signal. It is better to be higher. In other words, since the noise generated in the building has a relatively low frequency, as described above, if the frequency of the uplink signal transmitted directly through the transmission line without frequency conversion is increased, the Noise of the same frequency is external bidirectional C
Transmission to the ATV system can be suppressed.

On the other hand, the in-building CATV system of the present invention
It is connected to an external bidirectional CATV system and bidirectionally transmits and receives uplink and downlink signals to and from a center device of the system.
If the TV system does not distribute broadcast signals from a broadcast satellite (BS) or a communication satellite (CS), a subscriber who wants to receive these broadcast signals must use a receiving antenna (parabolic antenna, flat antenna, etc.) on the veranda. Etc. must be installed separately.

Therefore, in a building CATV system connected to such a bidirectional CATV system, a receiving antenna for receiving a desired broadcast signal is installed in a building, and the receiving antenna from the receiving antenna is provided. The received signal
It is preferable that the terminal can be transmitted to each terminal terminal together with a downlink signal from an external bidirectional CATV system via a transmission line. That is, according to the in-building CATV system according to the seventh aspect, the external bidirectional CATV system is BS, C
Even when broadcasting signals such as S are not distributed, CAT
The subscribers of the V system can view these broadcasts without installing a receiving antenna individually, and the service to the subscribers can be improved.

Next, the downconverter according to claim 8 is the downconverter CATV system according to claim 1,
Using the reference signal of a constant frequency transmitted from the reference signal transmitting means on the transmission line, the frequency of the in-building upstream signal is converted into the original upstream signal. In this down converter, an external bidirectional CA is connected via a drop-in line.
The downstream signal input from the TV system is transmitted to a transmission line in the building via the first downstream signal passage.

In this down converter,
The first reference signal extracting means extracts a constant frequency reference signal transmitted by the reference signal transmitting means from the upstream transmission signals input via the transmission line, and the first frequency converting means extracts the transmission line. Out of the upstream transmission signal input through the terminal, extracts the in-building upstream signal output from the terminal-side down-converter, and extracts it using the reference signal extracted by the first reference signal extraction means. , And frequency-converted to the original upstream signal, and the frequency-converted upstream signal is transmitted to the service line side.

Therefore, according to the down converter of the present invention, the down signal input from the external bidirectional CATV system can be transmitted to the terminal side via the drop-in line, and the terminal side can transmit the down signal via the up converter. The transmitted in-building upstream signal can be frequency-converted into an upstream signal of the original frequency and transmitted to an external bidirectional CATV system.

In the down converter according to the present invention, the reference signal transmitted from the reference signal transmitting means onto the transmission line is extracted by the first reference signal extracting means, and the extracted signal is used to extract the in-building up signal. Frequency conversion to the upstream signal of
For example, when the reference signal transmitting means for transmitting the reference signal on the transmission line or the reference signal generating means for generating the reference signal breaks down, or when the operation is temporarily stopped for maintenance or the like, the transmission line The reference signal does not flow, and it becomes impossible to perform frequency conversion on the in-building up signal.

Therefore, in the downconverter according to the eighth aspect, the first determination means for determining whether the reference signal has been extracted by the first reference signal extraction means as described in the ninth aspect. When the first determination unit determines that the reference signal cannot be extracted, the first specific transmission signal extraction unit fixes the frequency from among the downstream signals flowing through the first downstream signal passage path. The extracted specific transmission signal (for example, the pilot signal described above) may be extracted, and the specific transmission signal may be output to the first frequency conversion means as a reference signal.

That is, if the down converter is configured in this manner, when the reference signal transmitting means and the reference signal generating means provided on the transmission line are not operating normally, a specific transmission signal such as a pilot signal included in the downlink signal is transmitted. It can be used to convert the frequency of an in-building upstream signal.

Therefore, this downconverter can be used as a CAT in a building connected to a bidirectional CATV system in which a specific transmission signal such as a pilot signal is transmitted as one of the downlink signals.
When applied to the V system, the probability that the down converter cannot convert the frequency of the in-building up signal to the original up signal is reduced (in other words, the probability that the up signal cannot be transmitted as the in-building up signal in the in-building CATV system) is reduced. be able to.

When the down converter is configured in this manner, the up converter provided on the terminal side also converts the up signal into the in-building up signal using a specific transmission signal such as a pilot signal included in the down signal. It is necessary to be able to perform frequency conversion. For this purpose, the up-converter may be configured as described in claim 20 described later.

On the other hand, a down converter according to a tenth aspect is for constructing a CATV system in a building according to the second aspect, and incorporates the aforementioned reference signal generating means and reference signal transmitting means. . In this down converter, an external bidirectional CAT is connected via a drop line.
The down signal input from the V system is sent out onto the transmission line in the building via the first down signal passing path, and the first frequency conversion means includes a reference signal generation means built in the down converter. Using the generated reference signal, the in-building upstream signal is frequency-converted into the original upstream signal, and the frequency-converted upstream signal is sent out on the service line.
The reference signal transmitting means transmits the reference signal generated by the reference signal generating means to the transmission line.

As described above, according to the down converter of the tenth aspect, the in-building up signal is frequency-converted into the original up signal using the reference signal from the built-in reference signal generating means. For this reason, as long as the down converter itself does not break down, the in-building up signal can be frequency-converted to the original up signal, and is separate from the down converter as in the down converter according to claim 9. In order to enable the frequency conversion of the in-building upstream signal to the original upstream signal when the reference signal generating means and the reference signal transmitting means constituted by the above are not operating, the first determining means and the first specific transmission are separately provided. There is no need to provide signal extraction means.

According to the down converter of the tenth aspect, the CATV system in the building according to the second aspect is constructed, and the reference signal is transmitted from the down converter to the up converter of each terminal. Therefore, it is not necessary to separately connect a reference signal superimposing device having a function as a reference signal generating means and a reference signal transmitting means to the transmission line in the building.
The construction cost when constructing the ATV system can be reduced.

Even when the reference signal generating means and the reference signal transmitting means are provided in the down converter as described above, the frequency of the reference signal transmitted by the reference signal transmitting means onto the transmission line is defined by the following claims. 12. A method as set forth in claim 11, wherein the frequency is set to a frequency that does not overlap with the downlink signal within a frequency band set as the transmission frequency band of the downlink signal.
As set forth in claim 2, the transmission line is set to a frequency lower than the frequency of various transmission signals flowing in the up and down directions, or as set forth in claim 13, set as the transmission frequency band of the down signal. 5M lower than the specified frequency band
It is desirable to set the frequency in the range of Hz to 26 MHz.

In other words, in this way, the CATV system according to any one of claims 3 to 5 can be constructed, and the reference signal can be transmitted well to the terminal up-converter. It becomes possible. When the downconverter is used as a reference signal source for the upconverter, the reference signal generated by the reference signal generating means in the downconverter may be directly transmitted to the transmission line. Preferably, for example, as described in claim 14, the reference signal transmitting means generates a reference signal for transmission by dividing or multiplying the reference signal generated by the reference signal generating means, and generating the reference signal. You may comprise so that it may transmit on a transmission line.

That is, even in this case, the down converter can send out a reference signal of a specific frequency corresponding to the reference signal used by the first frequency conversion means for frequency conversion of the in-building up signal. If the up-converter restores the original reference signal by multiplying or dividing this reference signal, the down-converter and the up-converter perform frequency conversion. The reference signals used can be matched.

In the down converter, the first frequency conversion means converts the frequency of the in-building up signal into an up signal using the reference signal generated by the reference signal generation means. If the frequency is set to a low frequency, the in-building up signal cannot be converted to the original up signal, so a high-frequency signal for frequency conversion is generated from the reference signal and mixed with the in-building up signal. By doing so, the in-building up signal is frequency-converted to the original up signal. In this case, the up-converter also generates a high-frequency signal for frequency conversion from the reference signal.

In the case where the first frequency converting means generates the high frequency signal for frequency conversion using the reference signal generated by the reference signal generating means,
As described in, the reference signal transmitting means generates a reference signal for transmission by dividing or multiplying the high-frequency signal for frequency conversion generated by the first frequency conversion means, and places the reference signal on a transmission line. You may comprise so that it may transmit. That is, in this case as well, the reference signal used for frequency conversion can be matched between the down converter and the up converter, as in the fourteenth aspect.

[0048] Next, the downconverter according to the sixteenth aspect provides the downconverter according to any one of the eighth to fifteenth aspects, further comprising an upstream transmission signal input via a transmission line. Among them, a first upstream signal passing path for transmitting a low frequency upstream signal, which has not been frequency-converted by the up-converter, onto the service line is provided.

According to the down-converter of the sixteenth aspect, the low-frequency upstream signal transmitted from the terminal side without using the up-converter can be directly transmitted to the service line. The in-building CATV system described can be constructed.

Next, the downconverter according to claim 17 is the downconverter according to any one of claims 8 to 16, wherein the downconverter transmits the down signal passing through this first down signal path to the first down signal path. A downstream signal amplifying means for amplifying is provided, and an in-building ascending signal or an ascending signal passing through the path is provided on the input path of the in-building up signal to the first frequency conversion means or the output path of the ascending signal from the first frequency conversion means. An upstream signal amplifying means for amplifying a signal is provided.

According to the down-converter according to the seventeenth aspect, the down signal and the up signal passing through the down converter can be amplified respectively, and have a function as an amplifying device. An amplifying device for amplifying a transmission signal that is usually used in a CATV system can be eliminated.

Therefore, if this downconverter is used, transmission equipment (specifically, an amplifying device) when constructing the CATV system in the building can be reduced, and the construction cost of the CATV system in the building can be reduced. Next, claim 1
The downconverter according to claim 8 is the ridge C according to claim 7.
The purpose of the present invention is to make it easier to construct an ATV system. A reception signal input terminal for inputting a reception signal from a reception antenna installed in a building, and a reception signal input to the reception signal input terminal. A reception signal passing path for transmitting a signal together with a downstream signal onto a transmission line.

In other words, when constructing a building CATV system that transmits not only a downlink signal from an external bidirectional CATV system but also a reception signal from a receiving antenna installed in a building to a terminal, an external bidirectional CATV system is required. It is necessary to mix the downlink signal from the CATV system and the signal received from the receiving antenna with a mixer or the like and transmit the mixed signal on the transmission line on the terminal side. Such a mixer is provided in the CATV system in the building. , Which increases costs.

However, according to the downconverter of the present invention, not only the down signal from the external bidirectional CATV system but also the reception signal from the reception antenna input to the reception signal input terminal is transmitted to the terminal side. Can be output to Therefore, when the down-converter according to claim 18 is used in constructing the in-building CATV system according to claim 7, mixing for mixing the reception signal from the reception antenna and the downstream signal is performed. It is not necessary to separately provide a device on the transmission line, and the cost required for constructing the CATV system in the building can be reduced.

On the other hand, the upconverter according to claim 19 is the CATV according to any one of claims 1 to 7.
In the system, an upstream signal output from a terminal device is frequency-converted into an in-building up signal, and the frequency-converted in-building up signal is transmitted to a transmission line via a terminal terminal. Then, in this upconverter, the down signal transmitted to the terminal via the transmission line is transmitted to the terminal device side via the second down signal passage.

In this upconverter,
A second reference signal extracting means for extracting a constant frequency reference signal transmitted by the reference signal transmitting means from the downlink transmission signals transmitted to the terminal via the transmission line; Uses the reference signal extracted by the second reference signal extraction means to frequency-convert the upstream signal output from the terminal device into a ridge upstream signal, and converts the frequency-converted ridge upstream signal into a terminal signal. The signal is transmitted to the CATV system transmission line in the building via the terminal.

Therefore, according to the upconverter of the nineteenth aspect, the down signal transmitted to the terminal via the transmission line can be input to the terminal, and the up signal output from the terminal is The frequency can be converted to an in-building up signal and transmitted from the terminal to the transmission line.

In the upconverter according to the nineteenth aspect, the reference signal of a constant frequency transmitted by the reference signal transmitting means is selected from among the downlink transmission signals transmitted to the terminal via the transmission line. Is extracted, and the frequency of the upstream signal is converted into the upstream signal in the building by using this. Therefore, in constructing the CATV system in the building according to the present invention (claims 1 to 7), the above-mentioned claims 8 to claim Item 1
When used in combination with any of the downconverters described in any one of the above, the downconverter can restore the in-building up signal to the original up signal with high accuracy.

Next, the up-converter according to the twentieth aspect is similar to the down-converter according to the ninth aspect, when the reference signal transmitting means and the reference signal generating means provided on the transmission line are not operating normally. In order to be able to frequency-convert an upstream signal into a ridge upstream signal using a specific transmission signal such as a pilot signal included in a downstream signal, the up converter according to claim 19 described above,
Further, there is provided a second determining means for determining whether or not the reference signal has been successfully extracted by the second reference signal extracting means. If the second determining means determines that the reference signal cannot be extracted, the second specific transmission is performed. The signal extracting means extracts a specific transmission signal having a fixed frequency from the downstream signals flowing through the second downstream signal passing path, and outputs the specific transmission signal to the second frequency converting means as a reference signal. Have been.

Therefore, according to the upconverter of the twentieth aspect, when building a CATV system in a building in which a reference signal superimposing device having a function as a reference signal transmitting means and a reference signal generating means is connected to a transmission line. In addition, by using the down converter according to the ninth aspect, it is possible to reduce the probability that the upstream signal output from the terminal device cannot be transmitted to an external bidirectional CATV system.

Next, the up-converter according to claim 21 is used when a building CATV system is constructed using the down-converter according to claim 14 or 15. In the up converter, the reference signal restoring means divides or multiplies the reference signal extracted by the second reference signal extracting means, so that the down converter frequency-converts the in-building up signal into an up signal. The second frequency conversion means converts the frequency of the upstream signal into a building upstream signal using the recovered reference signal.

Therefore, if a CATV system in a building is constructed by using the up converter according to claim 21 and the down converter according to claim 14 or 15,
The reference signal used for frequency conversion can be reliably matched between the down converter and the up converter.

On the other hand, the amplifier according to claim 22 is provided on the transmission line of the CATV system in a building according to the present invention (claims 1 to 7), and amplifies the transmission signal flowing through this transmission line. belongs to. The amplifying device has a third downstream signal passing path for transmitting the downstream signal transmitted from the down converter side via the transmission line to the terminal side, and the downstream side signal transmitted from the terminal side via the transmission line. And an in-building up signal passage for transmitting the in-building up signal to the down-converter side. The down-signal amplifying means and the in-building up-signal amplifying means provided on each of these paths form a down-going signal. The signal and the in-building up signal are each amplified.

Further, in addition to the above two types of paths, a first reference signal passing path for connecting a transmission line on the down converter side and a transmission line on the terminal side so that a reference signal can pass therethrough is formed in this amplifier. Have been. This is the present invention (claims 1 to 5).
In the in-building CATV system according to claim 7, when the frequency of the reference signal flowing on the transmission line is set to a frequency different from the transmission frequency band of another transmission signal, the reference signal constitutes the in-building CATV system. Passive devices (such as splitters and distributors) other than the amplifying device that can amplify the signal can pass through the device as it is. However, the amplifying device forms a path through which each of the upstream and downstream signals to be amplified is selectively passed. This is because a signal amplifying circuit (amplifying means) is provided on the upper side, and such a general amplifying device cannot transmit a reference signal.

That is, in the amplifier according to the twenty-second aspect, the general amplifying apparatus including the third downstream signal passage, the downstream signal amplifying means, the in-building up-signal passing path, and the in-building up signal amplifying means can be used. On the other hand, by further forming a passage for exclusive use of the reference signal (first reference signal passage), the reference signal can be transmitted in both directions.

Therefore, in constructing the CATV system in a building according to the present invention (claims 1 to 7), claim 2
If the amplifying device described in 2 is provided on the transmission line of the system, not only can the downstream signal and the upstream signal inside the building be amplified, but also the reference signal for frequency conversion in each converter can be passed with low loss. And the reference signal can be transmitted to each converter satisfactorily.

The reference signal passage may be provided with an amplifier circuit for amplifying the reference signal. And
In this way, the transmission loss of the reference signal generated on the transmission line can be compensated, and the reference signal can be transmitted well. In the CATV system according to the seventh aspect, in addition to the downlink signal from the external bidirectional CATV system, the received signal from the receiving antenna is also transmitted in the downlink direction on the transmission line. In such a case, since the received signal is also a kind of the downlink signal, the signal may be passed through the third downlink signal passage path, or the third downlink signal passage path may be transmitted from an external bidirectional CATV system. It may be configured with two paths, a path through which a signal passes and a path through which a signal from a receiving antenna passes.

Next, the amplifying device according to the twenty-third aspect further comprises an up-converter for connecting the transmission line on the down-converter side and the transmission line on the terminal side to the amplifying device according to the twenty-second aspect. A second upstream signal passage path is formed so that a low frequency upstream signal that has not been frequency-converted is connected to pass therethrough.

According to the amplifier of the twenty-third aspect, the low-frequency upstream signal transmitted from the terminal side without using the up-converter can be passed as it is. Building C described
An ATV system can be constructed.

Next, the amplifying device according to claim 24 is provided with one or more branch terminals in addition to the amplifying device according to claim 22 or 23.
This constitutes a so-called branching amplifier. In such a branching amplifying device, it is necessary not only to transmit the downlink signal on the transmission line on the terminal side but also on the transmission line connected to the branch terminal. Downstream signal branching means is provided for branching a part of the downstream signal and outputting it from the branch terminal.

Also, the in-building up signal input to the branch terminal from the terminal side needs to be transmitted on the transmission line on the down-converter side. An in-building up signal input means is provided for transmitting a signal to an in-building up signal passage on the input side of the up signal amplifying means.

In order to construct the CATV system in a building according to the present invention (claims 1 to 7), not only the down converter and the up converter connected to the input / output terminal of the amplifying apparatus via the transmission line but also the up converter. Since it is necessary to transmit the reference signal also to the up-converter connected to the branch terminal via the transmission line, the amplification device according to claim 24 further includes a branch terminal and a reference signal passage path. A second reference signal passage path is formed to connect the reference signal so that it can pass.

As a result, according to the amplifying device of the twenty-fourth aspect, not only does it have a function as a branching amplifying device capable of bidirectionally amplifying each of the up-going and down-going signals, but also has a CAT
The reference signal can be transmitted to all the converters connected to the transmission line of the V system, and the branch amplification device is optimal for constructing the in-building CATV system according to the present invention (claims 1 to 7). .

According to this amplifying device, the input terminal connected to the transmission line on the down converter side, the output terminal connected to the transmission line on the terminal side, and the branch terminal are connected to the first and second reference lines, respectively. The terminals are connected to each other via a signal passing path, and the reference signal can be freely passed between these terminals.

For this reason, when the reference signal superimposing device having the functions of the reference signal generating means and the reference signal transmitting means is constituted as a single unit, the installation position can be freely selected. In other words, as long as the transmission line forms a CATV system in a building, a transmission line (branch line) connected to an input terminal or an output terminal of the amplification device is connected to a branch terminal of the amplification device (branch line). Line), a reference signal superimposing device can be connected.

It is to be noted that the amplifying device according to claims 22 to 24 is a CAT in a building according to the present invention (claims 1 to 7).
It is not always necessary to use it when constructing the V system, but may be used as appropriate. For example, the down converter includes amplifying means for amplifying each signal of up and down.
When the downconverter described in 7 is used, the downconverter alone can compensate for the transmission loss of each transmission signal in the up and down directions, so the CATV system in the building can be constructed without providing an amplification device. can do.

In the case where the frequency of the reference signal is set in the transmission frequency band of the downlink signal, the present invention (claim 2)
It is also possible to construct a CATV system in a building according to the present invention by using a general amplifying device that does not have a reference signal passing path (second reference signal passing path) like the amplifying apparatus of the second to 24th aspects. it can.

[0078]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a configuration diagram showing a configuration of an entire CATV system in a building according to a first embodiment of the present invention.

As shown in FIG. 1, the CATV in the ridge of this embodiment
The system draws a drop line 6 branched from a transmission line (CATV transmission line) 2 of an external two-way CATV system via a branching device 4 into a building such as an apartment or an apartment via a protector 8, A transmission line L composed of a coaxial cable wired in the building, and a bidirectional amplifier 12, a branch unit 14, and a distributor 16 provided on the transmission line L.
And the like, the downstream signal of the bidirectional CATV system (transmission frequency band: 70 MHz to 770)
MHz) to a plurality of terminal terminals 18 such as a series unit installed at each subscriber's house in the building, and from various terminal devices on the subscriber side via an up-converter 20 described later. Is transmitted to the drop-in line 6. Incidentally, the bidirectional amplifier 12 corresponds to the amplifying device of the present invention.

In the in-building CATV system according to the present embodiment, the subscriber can enjoy the Internet via an external two-way CATV system center device, or can reserve a pay program for the center device or watch television. When transmitting data for shopping or the like, an information terminal device (such as a personal computer) 24 for data communication is connected to the terminal 18 on the subscriber side via an up-converter 20 and a cable modem 22. .

As a result, the transmission data for data communication output from the information terminal device 24 is transmitted by the cable modem 22 to a predetermined frequency band (10 MHz to 55 MHz in this embodiment) which can be transmitted by an external bidirectional CATV system. ), And is converted by the up-converter 20 into a predetermined frequency band (821 in this embodiment).
(MHz to 866 MHz), which is frequency-converted into an in-building upstream signal and input to the terminal 18.

For this reason, the connection between the transmission line L of the in-building CATV system and the drop-in line 6 from the external bidirectional CATV system is connected to the in-building which is transmitted from each terminal 18 via the transmission line L. The upstream signal is sent to an external bidirectional CATV
A down converter 10 is provided for frequency conversion into an original upstream signal that can be transmitted by the system.

In FIG. 1, reference numeral 26 denotes a terminal terminal 18 to which the up-converter 20 is not connected (or a downstream signal output terminal provided on the up-converter 20).
, And receives a downstream signal transmitted from the external bidirectional CATV system via the transmission line L, and demodulates and reproduces a television broadcast of a desired channel.

Next, the down converter 10, the bidirectional amplifier 12, and the down converter 10 used in the CATV system in the building according to the present embodiment.
Each configuration of the up-converter 20 and the up-converter 20 will be described with reference to FIG. "Downconverter" As shown in FIG. 2, the downconverter 10 has an external connection terminal T1 for connecting a service line 6 from an external bidirectional CATV system, and a building 1
And an internal connection terminal T2 for connecting the transmission line L within 0.

The down signal input to the external connection terminal T1 is once taken into the down converter 10 via a high-pass filter (hereinafter, referred to as HPF) 31, and is then low-pass filtered (hereinafter, referred to as LPF). ), The HPF 33, and the internal connection terminal T2, and transmitted onto the transmission line L on the terminal side.

The HPF 31 allows the downstream signal to pass through,
The cutoff frequency is set to, for example, 70 MHz to prevent the passage of the upstream signal after the frequency conversion. The LPF 32 is for passing a downstream signal and preventing a passage of an upstream signal in a building before frequency conversion, and the cutoff frequency is set to 770 MHz, for example. The HPF 33 is for preventing a later-described reference signal having a lower frequency than the downstream signal from passing therethrough, and has a cutoff frequency set to, for example, 70 MHz. Therefore, the down converter 1 of the present embodiment
0, HPF31, LPF32, HPF3
3 forms the first downstream signal passage of the present invention.

Next, the in-building up signal from the terminal side input to the internal connection terminal T 2 is taken into the up-converter 20 via the HPF 33 and the HPF 34. HP
F34 is for preventing the sneak of the down signal output from the LPF 32 and selectively taking in only the in-building up signal, and the cutoff frequency is, for example, 821 MHz.
Is set to Then, the in-building up signal taken into the down-converter 10 via the HPF 34 is input to a frequency conversion mixer 35.

The mixer 35 receives a signal (a high-frequency signal for frequency conversion) from a frequency-variable type local oscillation circuit 36 whose oscillation frequency is controlled to be constant (for example, 876 MHz) by a PLL circuit 38, and receives an in-building up signal. , Two-way CA
The frequency is converted into an upstream signal for a TV system. The upstream signal frequency-converted by the mixer 35 is amplified to a predetermined level by an amplifier circuit 39 serving as upstream signal amplifying means, and then transmitted to the service line 6 via the LPF 40 and the external connection terminal T1. You. In addition, LPF
Reference numeral 40 denotes a block for blocking the passage of the downstream signal input to the external connection terminal T1 and passing only the upstream signal after the frequency conversion.
MHz.

On the other hand, the PLL circuit 38
6 controls the oscillation frequency of the local oscillation circuit 36 so that the phase of the high-frequency signal for frequency conversion output from the reference signal coincides with the phase of the reference signal. In the present embodiment, the PLL circuit 38 is A reference signal used to control the oscillation frequency of the oscillation circuit 36 is generated by a reference oscillation circuit 37 in the down converter 10. still,
This reference oscillation circuit 37 functions as reference signal generation means of the present invention.

The reference oscillation circuit 37 operates at a constant frequency (70 MHz) lower than the transmission frequency band of the downlink signal.
(less than z), the PLL circuit 38 divides this reference signal, divides the output from the local oscillation circuit 36, and matches the phases of these divided signals. By generating a control signal and outputting it to the local oscillation circuit 36, the output from the local oscillation circuit 36 is controlled to a constant frequency (876 MHz) corresponding to the reference signal.

In order to transmit the reference signal generated by the reference oscillation circuit 37 from the internal connection terminal T2 onto the transmission line L, the output terminal of the reference oscillation circuit 37 is connected to the PLL circuit 38.
In addition, a narrow band-pass filter (hereinafter, referred to as BPF) 42 for passing only the reference signal is connected. The reference signal that has passed through the BPF 42 is sent out onto the transmission line L via the LPF 41 and the internal connection terminal T2.

The cut-off frequency of the LPF 41 is set to, for example, 70 MHz, and an in-building upstream signal input to the internal connection terminal T 2 via the transmission line L or the HPF 33.
From the transmission line L via the internal connection terminal T2 can be prevented from flowing to the BPF 42 side. In this embodiment, the LPF 4
1 and the BPF 42 function as reference signal transmitting means of the present invention. Further, in the down converter 10 of the present embodiment, the local oscillation circuit 36 provided to convert the frequency of the in-building up signal to the up signal using the reference signal,
The circuit 38 and the mixer 35 function as first frequency conversion means of the present invention. "Bidirectional amplifier" As shown in FIG.
Has an input terminal T3 connected to the internal connection terminal T2 of the downconverter 10 via the transmission line L, and an output terminal T4 for connection to the transmission line L closer to the terminal than the bidirectional amplifier 12. ing.

The down signal and the reference signal input from the internal connection terminal T 2 of the down converter 10 to the input terminal T 3 via the transmission line L are taken into the bidirectional amplifier 12 via the LPF 51. Among these signals, the downstream signal is input to an amplifier circuit 53 as downstream signal amplifying means via the HPF 52, and the amplifier circuit 53
After being amplified to a predetermined level by the HPF 54, LPF
55 and the output terminal T4, the reference signal is sent out onto the transmission line L on the terminal side, and the reference signals are LPF59, LPF60, LPF
The signal is transmitted onto the transmission line L on the terminal side via F55 and the output terminal T4.

Here, the LPF connected to the input terminal T3
Reference numeral 51 denotes a down signal and a reference signal which prevent the in-building up signal passing through the bidirectional amplifier 12 from flowing to the output terminal T4 together with the down signal and the reference signal, and which are input to the input terminal T3 from the down converter 10 side. And a cutoff frequency of 770 MHz, for example.
Is set to

The HPF 52 and the HPF 54 provided before and after the amplifying circuit 53, respectively, prevent the passage of the reference signal and form the third downstream signal passing path of the present invention which allows only the downstream signal to pass. And the cutoff frequency is set to, for example, 70 MHz.

The LPF 59 and the LPF 60 are for forming the first reference signal passing path of the present invention which blocks the passage of the downstream signal and allows only the reference signal to pass therethrough. For example, it is set to 70 MHz. Also, an LPF connected to the output terminal T4
55 prevents the in-building down signal input from the transmission line L on the terminal side to the output terminal T4 from flowing around the amplification circuit 53 through the HPF 54, and the down signal and the reference signal passing through the HPF 54 and the LPF 60 This is for allowing the signal to pass through the output terminal T4, and has a cutoff frequency of, for example, 77.
It is set to 0 MHz.

Next, from the transmission line L on the terminal side to the output terminal T4
Is input to an amplification circuit 57 as an in-building up signal amplifying means via the HPF 56,
After being amplified to a predetermined level by this amplifier circuit 57, H
Downconverter 1 via PF58 and input terminal T3
It is transmitted on the transmission line on the 0 side.

The HPFs 56 and 58 provided before and after the amplifying circuit 57, respectively, prevent the down signal and the reference signal from entering the amplifying circuit 57 and allow only the in-building up signal to pass therethrough. The cut-off frequency is set to, for example, 821 MHz for forming the in-building upstream signal passage of the invention. "Up-converter" As shown in FIG. 2, the up-converter 20 includes a first connection terminal T5 for connecting to the terminal 18 via a coaxial cable or the like, and a cable modem 22 for outputting an up signal. A second connection terminal T6 for connecting to a communication terminal device and a third connection terminal T7 for connecting to a reproduction terminal device such as the television receiver 26 are provided.

Then, from the terminal terminal 18 to the first connection terminal T
5 is taken into the up-converter 20 via the HPF 71, and the LPF 72 and the third
The signal is output to a reproduction terminal device such as the television receiver 26 via the connection terminal T7. A branch circuit 73 composed of a directional coupler for branching a part of the downstream signal is provided on the path of the downstream signal from the LPF 72 to the third connection terminal T7. The downlink signal is guided to the second connection terminal T6 via the mixing circuit 74 including a directional coupler, and is output from the second connection terminal T6 to a communication terminal device such as the cable modem 22.

The HPF 71 is connected to the first terminal from the terminal 18.
This is for blocking the passage of the reference signal input to the connection terminal T5 and passing the down signal and the up signal in the building after the frequency conversion, and the cutoff frequency is, for example, 70 MHz.
Is set to The LPF 72 is for blocking the passage of the in-building up signal after the frequency conversion and passing only the down signal input to the first connection terminal T5.
The cutoff frequency is set to, for example, 770 MHz. Therefore, the upconverter 20 of the present embodiment has H
PF71, LPF72, branch circuit 73, and mixing circuit 7
4 means that two systems of the second downstream signal passage of the present invention are formed.

Next, the upstream signal input from the communication terminal device such as the cable modem 22 to the second connection terminal T6 is input to the mixer 75 for frequency conversion through the mixing circuit 74. The mixer 75 receives the signal from the frequency-variable type local oscillation circuit 76 whose oscillation frequency is controlled to be constant (for example, 876 MHz) by the PLL circuit 79, and frequency-converts the upstream signal into a premises upstream signal.

The in-building upstream signal frequency-converted by the mixer 75 is amplified to a predetermined level by an amplifier circuit 77 as a building upstream signal amplifying means.
8, is transmitted to the terminal 18 via the HPF 71 and the first connection terminal T5. The HPF 78 is for blocking the passage of the downstream signal input to the first connection terminal T5 and passing only the upstream signal after the frequency conversion, and the cutoff frequency thereof is set to, for example, 821 MHz. Have been.

On the other hand, the PLL circuit 79 includes the local oscillation circuit 7
This is for controlling the oscillation frequency of the local oscillation circuit 76 so that the phase of the signal for frequency conversion output from 6 and the reference signal match. The reference signal is generated by a reference oscillation circuit 37 in the downconverter 10 and transmitted from the downconverter 10 to the terminal 18 of each subscriber via various transmission devices such as the transmission line L and the bidirectional amplifier 12. To be transmitted.

Therefore, the up-converter 20 selectively receives the reference signal input to the first connection terminal T 5 via the terminal 18, and inputs the reference signal to the PLL circuit 79. LPF80 and B as
PF81 is provided, and each of these filters (LPF80, LPF80,
The reference signal extracted by the BPF 81) is input to the PLL circuit 79 as a reference signal for frequency conversion.

The LPF 80 prevents a downstream signal input to the first connection terminal T5 or an in-building upstream signal after frequency conversion from passing therethrough, and takes in only the reference signal input to the first connection terminal T5. The cutoff frequency is set to, for example, 70 MHz. Also, BP
F81 is for allowing only the reference signal of the signal passed through the LPF 80 to be input to the PLL circuit 79, and is configured as a narrow band BPF corresponding to the frequency of the reference signal.

The PLL circuit 79 has a BPF 81 like the PLL circuit 38 provided in the down converter 10.
Divides the reference signal input from the oscillating circuit, divides the output from the local oscillation circuit 76, and generates a control signal for matching the phases of these divided signals to the local oscillation circuit 76. By outputting, the output from the local oscillation circuit 76 is controlled to a constant frequency (876 MHz) corresponding to the reference signal. In the up-converter 20 of the present embodiment, the local oscillation circuit 76, P, which is provided for frequency-converting the upstream signal into the ridge upstream signal using the reference signal.
The LL circuit 79 and the mixer 75 function as the second frequency conversion means of the present invention.

As described above, the CA in the building according to the present embodiment is
In the TV system, the in-building up signal frequency-converted by the up converter 20 is converted into the down converter 10
In order to accurately convert the frequency to the original uplink signal, a reference oscillation circuit 37 is provided as reference signal generation means, and the reference signal generated by the reference oscillation circuit 37 is added via the transmission line L. The data is transmitted to each terminal 18 on the user side.

Therefore, according to the in-building CATV system of the present embodiment, the up-converter 20 connected to each terminal terminal 18 converts the up signal output from the communication terminal device such as the cable modem 22 into the in-building up signal. The reference signal used for frequency conversion to the reference signal used by the down-converter 10 to convert the frequency of the in-building up signal to the original up signal can be used as the reference signal for the down signal. Even if no specific transmission signal (such as a pilot signal) is included, the down converter 10
Side accurately restores the original upstream signal from the building's upstream signal,
It can be transmitted to the transmission line 2 of an external bidirectional CATV system.

Since the frequency of the reference signal is different from the transmission frequency bands of the downstream signal and the in-building upstream signal flowing bidirectionally through the transmission line L of the system, the characteristics of each of these transmission signals influence the influence of the reference signal. The transmission quality of each transmission signal can be ensured without being deteriorated by the reception. Further, since the frequency of the reference signal is set to a frequency lower than the transmission frequency band of these transmission signals, the transmission loss on the transmission line L is smaller than that of other transmission signals.
For this reason, for example, it is possible to prevent a situation in which the signal level of the reference signal is reduced on the terminal side and an additional amplifier circuit for amplifying the reference signal is required.

In this embodiment, the function as the reference signal generating means and the reference signal transmitting means is performed by the down converter 10.
Therefore, there is no need to install a reference signal superimposing device on the transmission line L for generating a reference signal and transmitting it on the transmission line L. For this reason, the construction cost when actually constructing the in-building CATV system can be reduced.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various embodiments can be adopted. For example, in the above embodiment, when transmitting the reference signal generated by the reference oscillation circuit 37 onto the transmission line L, the reference signal transmission means including the BPF 42 and the LPF 41 is used, and the reference signal is directly transmitted to the transmission line L.
As described above, the carrier wave generation circuit 43 is provided in the downconverter 10 as shown in FIG.
And a modulator 44, and a carrier (for example, 10 MHz) having a lower frequency than the reference signal generated by the carrier generation circuit 43 using an output (reference signal) from the reference oscillation circuit 37.
(For example, amplitude modulation), and the modulated signal (modulated signal) may be sent out onto the transmission line L.

However, in this case, as shown in FIG.
The up-converter 20 is provided with a demodulator 82 for demodulating a reference signal from a modulated signal of the reference signal passed through the LPF 80, and the reference signal demodulated by the demodulator 82 is input to the PLL circuit 79 via the BPF 81. To

In this way, even if the signal level of the modulation signal input to the up-converter 20 decreases due to the transmission loss generated when the modulation signal flows through the transmission line L, the demodulator 82 outputs A high-quality reference signal having a high / N (signal-to-noise ratio) can be restored.

FIG. 3 is a diagram showing a modified example of the down converter 10 and the up converter 20. All the components other than the above description are the same as those shown in FIG. The reference numerals are given, and the description is omitted. Further, in the above embodiment, the down converter 10 is provided with the reference oscillation circuit 37 as reference signal generation means and the LPF 41 and the BPF 42 as reference signal transmission means. The function as the means is realized by, for example, a reference signal superimposing device including a reference oscillation circuit 37 and a signal inserter 28 which are formed separately from the down converter 10 as shown in FIG. Is also good.

The signal inserter 28 is for realizing the function as the reference signal transmitting means, and is shown in FIG.
As shown in (1), the reference signal input to the reference signal input terminal Tin from the reference oscillation circuit 37 is connected to the LPFs 92 and 93 having a cutoff frequency of 70 MHz and the signal inserter 28 in series with the transmission line L. Terminals T8 and T
9 and transmitted on the transmission line L on the terminal side and the down-converter side, respectively, for the down signal and the in-building up signal flowing through the transmission line L, the H provided between the terminals T8 and T9.
What is necessary is just to comprise so that it may pass through PF91 (cutoff frequency: 70 MHz, for example).

When the reference signal superimposing device is formed separately from the downconverter 10 as described above, FIG.
As shown in (c), the downconverter 1 shown in FIG.
0, the reference oscillation circuit 37 is deleted, and the reference signal input from the transmission line L to the internal connection terminal T2 is changed to the LPF 41, B
What is necessary is just to input to the PLL circuit 38 via PF42. In this case, the LPF 41 and the BPF 42 function as the first reference signal extracting means of the present invention.

On the other hand, in the above embodiment, the in-building CATV system in which the bidirectional amplifier 12 is provided on the transmission line L has been described. However, instead of the bidirectional amplifier 12, a branch amplifier 13 having a branch terminal is provided. When constructing a CATV system in a building, the branch amplifier 13 may be configured as shown in FIG.

That is, the branch amplifier 13 shown in FIG.
Is provided with four branch terminals Tb1, Tb2, Tb3, and Tb4 for the bidirectional amplifier 12 shown in FIG. 2, and a part of the downstream signal amplified by the amplifier 53 is supplied to the branch circuit 61. And the branched down signal is sent to the HPF
The signal is guided to the distribution circuit 64 via the LPF 63 and the distribution circuit 64, is divided into four by the distribution circuit 64, and the downstream signal after the distribution is transmitted from each of the branch terminals Tb1 to Tb4 to the transmission line (branch line) L on the terminal side.
It is sent out above.

In the branch amplifier 13, since the in-building up signal is also input from the transmission line (branch line) L on the terminal side connected to each of the branch terminals Tb1 to Tb4, each of the branch terminals Tb1 to Tb4. The inbound ridge signal input to
The signal is taken into the branch amplifier 13 via the distribution circuit 64 and the HPF 66, and the taken in-building upstream signal is sent to the mixing circuit 6
5, the signal is guided to the amplifier circuit 57, amplified by the amplifier circuit 57, and then transmitted to the transmission line L on the down converter 10 side via the HPF 58 and the input terminal T3.

To convert the in-building up signal input to each of the branch terminals Tb1 to Tb4 into the original up signal by the down-converter 10, the up-converter 20 on the terminal side must be connected to the branch terminals Tb1 to Tb4. Since the reference signal needs to be transmitted, a mixing circuit 67 is provided on the first reference signal passage between the LPFs 59 and 60, and the first reference signal passage is connected to the HPF 62 through the mixing circuit 67 and the LPF 68. To the connection point between the first reference signal passing path and each of the branch terminals Tb1 to Tb4.
And the reference signal can pass in both directions.

The HPF 62 is for blocking the passage of the reference signal and for passing the downstream signal, and has a cutoff frequency set to, for example, 70 MHz. Also,
The LPF 68 is for blocking the passage of the downstream signal and passing the reference signal, and has a cutoff frequency set to, for example, 70 MHz. The LPF 63 is for blocking the passage of the in-building up signal and passing the reference signal and the down signal, and has a cutoff frequency set to, for example, 770 MHz. Also, HPF66 is
The cutoff frequency is set to, for example, 821 MHz to block the passage of the reference signal and the down signal and allow the up signal in the building to pass.

In the branch amplifier 13 configured as described above, the downstream signal input to the input terminal T3 from the transmission line L on the downconverter 10 side is amplified by the amplifier circuit 53, and then the output terminal T4 and the branch The signals are transmitted from the terminals Tb1 to Tb4 onto the transmission line L on the terminal side, respectively, and are transmitted from the transmission line L on the terminal side to the output terminal T4 or the branch terminals Tb1 to Tb1.
The in-building up signal input to b4 is amplified by the amplifier circuit 57, and then transmitted from the input terminal T3 onto the transmission line L on the down converter 10 side.

The reference signal can pass not only between the input terminal T3 and the output terminal T4, but also between the input terminal T3 and the branch terminals Tb1 to Tb4 or between the output terminal T4 and the branch terminals Tb1 to Tb4. , Can also pass between the branch terminals Tb1 to Tb4 via the distribution circuit 64.

Therefore, if the branching amplifier 13 is configured in this manner, as in the CATV system in a building shown in FIG.
An amplifier (FIG. 4) using a signal inserter 28 or the like as in the case where the reference signal is output from the down converter 10 or as in a CATV system in a building as shown in FIG.
In the case where the reference signal is transmitted on the transmission line (main line) L connected to the input terminal T3 or the output terminal T4 of the bidirectional amplifier 12) having no branch terminal, as a matter of course, FIG. As shown in a), a transmission line (branch line) connected to the branch terminals Tb1 to Tb4 of the branch amplifier 13
L, the signal inserter 28 is connected to the transmission line (branch line) L, and when the reference signal is transmitted to this transmission line (branch line) L, all the up converters connected to the transmission line L of the CATV system in the building 20 and the downconverter 10 can convert the frequency of the upstream signal with the reference signal of the same frequency.

In the branch amplifier 13, the branch circuit 61, the HPF 62, the LPF 63, and the distribution circuit 64 function as downstream signal branching means of the present invention.
The HPF 66 and the mixing circuit 65 function as the in-building upstream signal input means of the present invention. By the way, as in the in-building CATV system shown in FIG. 4A, the reference signal generated by the reference oscillation circuit 37 is transmitted to the signal inserter 28 provided on the transmission line L.
If the reference oscillation circuit 37 and the signal inserter 28 are out of order or temporarily stopped for maintenance and inspection, the down converter In spite of the normal functioning of the upconverter 10 and the upconverter 20, it becomes impossible to transmit the uplink signal.

In such a case, if the down converter 10 and the up converter 20 detect that fact and cannot receive the reference signal from the reference oscillation circuit 37, the external bidirectional CATV system cannot receive the reference signal. A specific transmission signal (a signal having a fixed frequency) such as a pilot signal included in the downlink signal may be extracted and supplied to the PLL circuits 38 and 79 as a reference signal for frequency conversion.

Hereinafter, the down converter 10 and the up converter 20 configured as described above will be described with reference to FIG.
This will be described with reference to FIG. Note that the down converter 10 and the up converter 20 shown in FIG. 6 are basically the same as the down converter 10 and the up converter 20 shown in FIG. Only the differences will be described.

First, in the down converter 10 shown in FIG. 6A, a branch circuit 45 is provided in the path of the downstream signal between the HPF 31 and the LPF 32, and a part of the downstream signal is branched and included in the downstream signal. A predetermined frequency (for example, 45
1.25 MHz) pilot signal of narrow band BPF4
6, and the extracted pilot signal can be input to the PLL circuit 38 via the switch 47.

The switch 47 is for selectively inputting the pilot signal extracted from the downstream signal by the BPF 46 and the reference signal extracted by the BPF 42 as the first reference signal extracting means to the PLL circuit 38. In general, a reference signal is input to the PLL circuit 38.

The down converter 10 shown in FIG. 6A is provided with a reference signal detecting circuit 48 as first determining means for determining whether or not a reference signal is output from the BPF 42. Reference signal detection circuit 48
Only when the reference signal is not output from the BPF 42, the switch 47 is set to a direction different from the normal direction (specifically, the pilot signal extracted by the BPF 46 is
(The input side to the circuit 38), and the pilot signal is input to the PLL circuit 38.

The reference signal detecting circuit 48 not only switches the switch 47 but also controls the PLL circuit 38.
Is controlled such that the oscillation frequency of the local oscillation circuit 36 controlled by the
The PLL circuit 38 outputs to the PLL circuit 38 a frequency division number switching signal for switching the frequency division number when the LL circuit 38 takes in the output from the local oscillation circuit 36 and the multiplication number when taking in the pilot signal to a predetermined value. I do.

Therefore, according to the down converter 10 shown in FIG. 6A, when the reference signal is not transmitted from the signal inserter 28 onto the transmission line L, the pilot signal included in the downlink signal is used. As a result, the in-building up signal can be frequency-converted into the original down signal. In the down converter 10 shown in FIG.
The BPF 46 and the switch 47 function as a first specific transmission signal extracting unit of the present invention.

On the other hand, in the up-converter 20 shown in FIG. 6B, a branch circuit 83 is provided in a path for passing a downstream signal between the LPF 72 and the third connection terminal T7, and a part of the downstream signal is branched. A pilot signal included in the signal is extracted through a narrow-band BPF 84, and the extracted pilot signal can be input to a PLL circuit 79 via a switch 85.

The switch 85 is for selectively inputting the pilot signal extracted from the downstream signal by the BPF 84 and the reference signal extracted by the BPF 81 as the second reference signal extracting means to the PLL circuit 79. Yes, like the switch 47 on the down converter 10 side,
The reference signal is input to the PLL circuit 79.

The upconverter 20 shown in FIG. 6 (b) is provided with a reference signal detection circuit 86 as second determination means for determining whether or not a reference signal is output from the BPF 81. Reference signal detection circuit 86
Only when the reference signal is not output from the BPF 81, the switch 85 is turned in a direction different from the normal direction (specifically, the pilot signal extracted by the
(The input side to the circuit 79), and the pilot signal is input to the PLL circuit 79.

The reference signal detecting circuit 86 not only switches the switch 85 but also switches the PLL circuit 79.
, So that the oscillation frequency of the local oscillation circuit 76 controlled by the
A frequency division number switching signal for switching the frequency division number when the LL circuit 79 captures the output from the local oscillation circuit 76 and the multiplication number when capturing the pilot signal to a predetermined value is output to the PLL circuit 79. I do.

Therefore, according to the upconverter 20 shown in FIG. 6B, when the reference signal is not transmitted from the signal inserter 28 onto the transmission line L, the downconverter 10 The frequency of an up signal can be converted into a down signal in a ridge by using the pilot signal included in the signal. The up-converter 20 shown in FIG.
, The branch circuit 83, the BPF 84, the switch 85
Function as the second specific transmission signal extracting means of the present invention.

If the CATV system is constructed using the down converter 10 and the up converter 20 shown in FIGS. 6A and 6B, the reference oscillation circuit 37
The downconverter 10 and the upconverter 20 can convert the frequency of the uplink signal using the common pilot signal included in the downlink signal at the time of failure of the signal inserter 28 or a temporary stop of the operation. In the internal CATV system, it is possible to further reduce the probability that the uplink signal cannot be transmitted.

Next, in the above-described embodiment, the down converter 10 is described as passing the down signal as it is. For example, as shown in FIG.
An amplifying circuit 49 as a down signal amplifying means is provided on a down signal passing path between the LPFs 32, and the down converter 1
The downstream signal may be amplified to a predetermined level within 0.

By doing so, the down signal and the up signal can be amplified to predetermined levels by the down signal amplification circuit 49 and the up signal amplification circuit 39 provided in the down converter 10, respectively. Therefore, it is possible to construct an in-building CATV system without providing the bidirectional amplifier 12 and the branch amplifier 13 on the transmission line L.

Further, the in-building CATV system of the above embodiment transmits three types of signals on the transmission line L: a down signal, an in-building up signal, and a reference signal in different transmission frequency bands. However, for example, among the upstream signals output from various terminal devices, the upstream signal whose transmission quality is significantly reduced due to ambient noise or the like is subjected to frequency conversion into a premises upstream signal using the up-converter 20. ,
For an upstream signal which flows on the transmission line L and whose transmission quality does not deteriorate even when noise or the like invades, the signal may be directly passed over the transmission line L without frequency conversion using the up-converter 20. Good.

Next, the configuration of the downconverter 10 used when the in-building CATV system is configured as described above will be described with reference to FIG. The downconverter 10 shown in FIG. 8 is basically the same as the downconverter 10 shown in FIG. 7 provided with an amplifying circuit 49 for amplifying a down signal. In the following description, only different points will be described. I do.

When two types of upstream signals, that is, an in-building upstream signal whose frequency has been converted by the up-converter 20 and an upstream signal whose frequency has not been converted, flow through the transmission line L, the external connection of the down-converter 10 At the terminal T1, the upstream signal that has passed through the down converter 10 as it is goes around to the amplifier circuit 39 that amplifies the frequency-converted upstream signal, or conversely, the frequency-converted upstream signal is converted to the upstream signal that is not frequency-converted. To the internal connection terminal T
It is necessary to set different frequencies for the upstream signal that is frequency-converted into an in-building upstream signal by the up-converter 20 and the upstream signal that is not frequency-converted so that the upstream signal does not flow from the terminal 2 to the terminal side.

Therefore, in the following description, the frequency of the upstream signal that is frequency-converted into an in-building upstream signal by the up-converter 20 is set to 10 MHz to 30 MHz, and the frequency of the upstream signal that is not frequency-converted is 30 MHz to 55 MHz.
The description will be made assuming that the frequency is set to Hz.

Further, since it is necessary that the frequency of the reference signal does not overlap with the frequency of the upstream signal that is not frequency-converted, the following description assumes that the frequency of the reference signal is set to less than 10 MHz. I do. As shown in FIG. 8, in the downconverter 10, the down signal input to the external connection terminal T1 is the same as that of the above-described embodiment.
The signal is once taken into the down converter 10 via F31, amplified by the amplifier circuit 49, and input to the BPF 50a. The BPF 50a has a higher frequency than the upstream signal input from the internal connection terminal T2, and a lower frequency than the upstream signal inside the ridge. The signal pass band is, for example, 70 MHz to
It is set to 770 MHz. And this BPF5
The downstream signal passing through Oa is sent out onto the transmission line L on the terminal side via the HPF 33 'and the internal connection terminal T2.

The HPF 33 'is for preventing a reference signal having a frequency lower than that of the upstream signal from passing therethrough, and has a cutoff frequency of, for example, 10 MHz. Therefore, in the down converter 10 of the present embodiment, the HPF 31, the BPF 50a, and the HPF 33 '
Thus, the first downstream signal passage of the present invention is formed.

Next, the in-building up signal from the terminal input to the internal connection terminal T2 is sent to the HPF 33 'and HPF 34
And is taken into the up-converter 20 via the Then, the in-building up signal taken into the down-converter 10 via the HPF 34 is converted into a low-frequency (1
0 MHz to 30 MHz) is converted to an upstream signal,
After being amplified by the amplifying circuit 39, it is transmitted to the service line 6 via the LPF 40 'and the external connection terminal T1. still,
The LPF 40 'is for blocking the passage of the downstream signal and the high-frequency upstream signal (30 MHz to 55 MHz) which is not frequency-converted, and allows only the frequency-converted upstream signal to pass therethrough.
Is set to

Next, the upstream signal input to the internal connection terminal T2 from the terminal side is supplied to the HPF 33 'and the LPF 50.
The signal is taken into the up-converter 20 via b.
Then, the up signal taken into the down converter 10 via the LPF 50b is amplified by the amplifier circuit 39 ', and then is passed through the BPF 50c and the external connection terminal T1.
It is sent out to the service line 6.

The LPF 50b blocks the passing of the down signal and the up signal in the building, and prevents the high frequency (30
MHz-55 MHz), and the cut-off frequency is determined by the above-described LPF.
Similarly to 32, for example, it is set to 55 MHz. The BPF 50c also blocks the passage of the downstream signal and the low-frequency (10 MHz to 30 MHz) upstream signal after the frequency conversion, and prevents the high frequency (30 MHz to 55
MHz), and the signal pass band is set to, for example, 30 MHz to 55 MHz. Therefore, in the down converter 10, the HPF 33 ', the LPF 50b, and the BPF 50
With c, the first upstream signal passage of the present invention is formed.

The down-converter 10 shown in FIG. 8 has a built-in reference oscillation circuit 37 as a reference signal generating means. The generated reference signal is transmitted through a BPF 42 and an LPF 41 as reference signal transmitting means. Out of the internal connection terminal T2 onto the transmission line L. Of these filters, the LPF 41 has a cut-off frequency of, for example, 10% for passing a reference signal having a frequency of less than 10 MHz and blocking other signals. The frequency is set to 10 MHz, and the signal pass band of the BPF 42 is set to a narrow band corresponding to the frequency of the reference signal.

As described above, in the down converter 10 shown in FIG. 8, the down signal can be passed, the in-building up signal can be frequency-converted into the original up signal and transmitted to the drop-in line 6 side. The transmitted upstream signal that has not been frequency-converted can be sent to the service line 6 as it is. Therefore, if this downconverter 10 is used, in addition to the three types of signals, that is, the down signal, the in-building up signal, and the reference signal, the up signal that has not been frequency-converted by the up converter 20 can be transmitted through the transmission line L. Can flow over.

According to the in-building CATV system capable of transmitting four types of transmission signals as described above, even a subscriber who does not own the up-converter 20 can use an external bi-directional system by using a predetermined terminal device. Communication with the center apparatus of the CATV system can be performed, and communication services in the system can be improved.

When a CATV system in a building is constructed using the down converter 10 shown in FIG.
When the bidirectional amplifier 12 or the branch amplifier 13 is provided on the upper side, the passing path of the reference signal can function as the second upstream signal passing path of the present invention. Can be used as is. Also, regarding the up converter 20, the LPF 8
0 and the cut-off frequency and the signal pass band of the BPF 81 are changed to the LPF 41 and the BPF 42
It may be set to the same characteristics as. [Second Embodiment] Next, in the above description, the external bidirectional C
The in-building CATV system that transmits and receives each signal of up and down to and from the ATV system and the transmission equipment such as a down converter used to construct this system have been described. A receiving antenna shared by each subscriber is installed in the building where the system is to be installed, and the received signal from this receiving antenna is also distributed to each subscriber via the transmission line of the CATV system in the building. You can also.

Thus, a CATV system in a building as described above will be described as a second embodiment of the present invention. In the following description, the same components as those of the in-building CATV system of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 9 is a configuration diagram showing the configuration of the entire in-building CATV system of the second embodiment.

As shown in FIG. 9, the CATV in the ridge of this embodiment
The system is basically configured in the same manner as the in-building CATV system of the first embodiment shown in FIG. 1 except that a BS antenna 100 installed on the rooftop of a building or the like is used as a receiving antenna. In that the received signal from the BS antenna 100 can be transmitted to the terminal via the down converter 10.

The BS antenna 100 is connected to a satellite broadcast (B
S) receives the transmission radio wave from S), converts the reception radio wave into a reception signal (hereinafter, referred to as a BS-IF signal) in a predetermined frequency band (1035 MHz to 1335 MHz), and outputs the converted signal. ing. "Down Converter" FIG. 10 shows the CAT in the ridge of this embodiment.
1 shows a configuration of a down converter 10 used in a V system.

As shown in FIG.
0 has a reception signal input terminal T10 for inputting a BS-IF signal from the BS antenna 100, in addition to an external connection terminal T1 for connecting a service line from an external bidirectional CATV system. Each connection terminal T1,
The downlink signal and the BS-IF signal input to T2 can be transmitted from the internal connection terminal T2 onto the transmission line L in the building 10.

That is, first, the downstream signal input to the external connection terminal T1 is taken into the down-converter 10 via the HPF 31, is transmitted to the LPF 32 through the internal downstream signal passage, and is transmitted through the LPF 32. Is output to the internal connection terminal T2. A mixing circuit 104 is provided between the LPF 32 and the internal connection terminal T2.
The BS-IF signal input to 10 and the downstream signal passing through the LPF 32 are mixed and output from the internal connection terminal T2 to the transmission line L. In addition, on a passage path (reception signal passage path) of the BS-IF signal from the reception signal input terminal T10 to the mixing circuit 104, an HP for blocking the in-building up signal and passing only the BS-IF signal is provided.
F102 (cut-off frequency: for example, 1035 MH
z) is provided.

Next, the in-building up signal from the terminal input to the internal connection terminal T2 is sent to the mixing circuit 104 and the HP
It is taken into the down converter 10 via F34. Then, the in-building up signal taken in through the HPF 34 passes through an attenuator 106 for attenuating the in-building up signal and a BPF 108 for passing the in-building up signal, and is input to an amplification circuit 110 for amplifying the in-building up signal. , This amplification circuit 1
At 10, the attenuation of the attenuator 106 and the amplification circuit 11
After being amplified to a predetermined level determined by the amplification factor of 0, it is input to the mixer 35.

The mixer 35 includes a PLL as in the above embodiment.
The oscillation frequency is fixed by the circuit 38 (876 in this embodiment as well).
MHz), and receives the high-frequency signal from the local oscillation circuit 36 and converts the frequency of the in-building up signal to the original up signal. The frequency-converted up signal is a BPF 122 for passing the up signal, Amplifier circuit 3 for amplifying upstream signal
9, transmitted to the LPF 40 via the LPF 124 for passing the upstream signal and the attenuator 126 for attenuating the upstream signal, and from the LPF 40 to the drop-in line 6 via the external connection terminal T1.
Output to the side. The attenuator 126 is for adjusting the level of the upstream signal output from the external connection terminal T1 to the service line 6. The LPF 124 is
The cutoff frequency is set to, for example, 55 MHz to block the downstream signal input to the external connection terminal T1 and pass the frequency-converted upstream signal.

The downconverter 10 of this embodiment has a reference oscillation circuit 37 having an oscillation frequency of 10 MHz, and a signal having a constant frequency (this In the example, 1.25 MH
and a frequency dividing circuit 112 for generating the reference signal of z). The output from the frequency divider 112 is P
The PLL circuit 38 receives the input signal from the frequency dividing circuit 112 and the output signal from the local oscillation circuit 36 via an internal frequency dividing circuit, and outputs the divided signal. By controlling the local oscillation circuit 36 on the basis of the phase difference, the oscillation frequency of the local oscillation circuit 36 is controlled to a constant frequency (876 MHz). The down converter 10 of the present embodiment has an oscillation frequency (specifically, a PLL) of the local oscillation circuit 36 controlled by the PLL circuit 38.
A microcomputer (CPU) 114 is provided so that the frequency division ratio of the frequency dividing circuit in the circuit 38 can be set and changed by an external command.

Next, the down converter 1 of this embodiment will be described.
By dividing the output from the local oscillation circuit 36 (in other words, the high-frequency signal for frequency conversion) into a period of 1/12, a constant frequency (in the present embodiment, the transmission frequency band of the down signal 70 MHz) is set to 0. A frequency divider circuit 118 that generates a reference signal for transmission (up to 770 MHz and does not overlap with a downlink signal) (73 MHz), a BPF 42 that passes a reference signal for transmission output from the frequency divider 118, a reference signal that has passed through the BPF 42 An amplification circuit 120 that amplifies the signal to a predetermined level,
And a transmission reference signal amplified by the amplifier circuit 120,
A superimposition circuit 116 is provided which superimposes the signal on the downstream signal passage route from the HPF 31 to the LPF 32 and outputs the signal from the LPF 32 to the terminal side.

As described above, in the downconverter 10 of the present embodiment, the output from the built-in reference oscillation circuit 37 is divided by the divider circuit 112 to generate an internal reference signal. PLL circuit 38 using
Generates a high-frequency signal for frequency conversion by controlling the local oscillation circuit 36, and mixes the high-frequency signal with the in-building up signal in the mixer 35 to convert the in-building up signal into the original up signal. Perform frequency conversion. In order for the down converter 10 and the up converter 20 on the terminal side to match the reference signal used for frequency conversion, the frequency dividing circuit 118 divides the output from the local oscillation circuit 36 to obtain a reference signal for transmission. A signal is generated and this is
2 and transmitted via the amplification circuit 120 onto the transmission line L.

Note that the down converter 10 of this embodiment is
The reference oscillation circuit 37 and the frequency division circuit 112 function as reference signal generation means, the local oscillation circuit 36 and the PLL circuit 38 function as first frequency conversion means, and The circuit 118, the BPF 42, and the amplifier circuit 120 function as a reference signal transmitting unit. "Upconverter" On the other hand, the upconverter 20 of the present embodiment is configured as shown in FIG.

[0165] As shown in FIG.
In the above, the BS-IF signal input to the first connection terminal T5 via the transmission line L is connected to an arrester (arrestor; hereinafter, A
RR) 130 and an HPF 132 that allows only the BS-IF signal to pass through, and are taken into the up-converter 20, after which the HPF 134 and the AR
The signal is output from the second connection terminal T6 to the terminal via R136.

Also, the first connection terminal T5 is connected via the transmission line L.
Is input to the up-converter 20 via the ARR 130, the LPF 138 for blocking the BS-IF signal and passing other transmission signals, and the LPF 72 for blocking the up signal and passing the down signal in the building. , Are input to an internal downstream signal passage path. Then, the downstream signal passing through the downstream signal passage path passes through an HPF 140 for blocking an upstream signal and passing a downstream signal, an LPF 142 for blocking a BS-IF signal and passing another transmission signal, and an ARR 136.
The signal is output from the second connection terminal T6 to the terminal.

On the other hand, the upstream signal input to the second connection terminal T6 from the terminal side is taken into the up-converter 20 via the ARR 136, the LPF 142, and the LPF 144 for blocking the downstream signal and passing the upstream signal. Then, the captured upstream signal is input to the mixer 75 via the upstream signal attenuation attenuator 146, and the mixer 75 uses the high frequency signal for frequency conversion output from the local oscillation circuit 76 to output the signal. The frequency is converted to an inbound signal.

The mixer 75 is similar to the above-described embodiment.
By mixing a high-frequency signal from the local oscillation circuit 76 whose oscillation frequency is controlled to be constant by the PLL circuit 79 and an upstream signal input from the terminal side, the upstream signal is frequency-converted into a ridge upstream signal. The frequency of the high-frequency signal used by the mixer 75 for frequency conversion (in other words, the oscillation frequency of the local oscillation circuit 76) can be adjusted by the down converter 10 to convert the in-building up signal into an up signal by the configuration described below. The same frequency (8
76 MHz).

The in-building upstream signal frequency-converted by the mixer 75 is the BPF 1 that allows only the in-building upstream signal to pass through.
56, an amplifying circuit 158 for amplifying the in-building up signal, an LPF 160 for passing an in-building up signal, an amplifying circuit 77 for amplifying the in-building up signal, and an attenuator 1 for attenuating the in-building up signal.
H for blocking the down signal and passing the up signal in the building via 62
The signal is transmitted to the PF 78, and the LPF 13 is transmitted from the HPF 78.
8, is output to the transmission line L via the ARR 130 and the first connection terminal T5.

Further, a branch circuit 148 for branching a part of the downstream signal passing through the LPF 72 is provided in the downstream signal passing path from the LPF 72 to the HPF 140. The downstream signal branched by the branch circuit 148 is provided. Is input to the BPF 81 which allows the transmission reference signal (73 MHz in this embodiment) transmitted from the down converter 10 to pass. Then, the reference signal that has passed through the BPF 91 is input to the waveform shaping circuit 150, and after being shaped by the waveform shaping circuit 150, is input to the frequency dividing circuit 152. The frequency dividing circuit 152 divides the reference signal transmitted from the down converter 10 into, for example, a period of 1/292, thereby reducing the reference signal generated by the frequency dividing circuit 112 of the down converter 10 to one fifth. The reference signal having the frequency (0.25 MHz) is generated, and the generated reference signal is input to the PLL circuit 79.

The PLL circuit 79 includes the frequency dividing circuit 15
2 and an output signal from the local oscillation circuit 76 are respectively fetched via an internal frequency dividing circuit, and based on the phase difference of the frequency-divided signal, the local oscillation circuit 76
, The oscillation frequency of the local oscillation circuit 76 is controlled to the same constant frequency (876 MHz) as that of the local oscillation circuit 36 of the downconverter 10. Note that, like the down converter 10, the up converter 20 of the present embodiment has the oscillation frequency of the local oscillation circuit 76 controlled by the PLL circuit 79 (specifically, the frequency division ratio of the frequency divider in the PLL circuit 79). (CPU) 154 in order to enable setting and changing according to an external command.
Is provided.

As described above, in the up-converter 20 of the present embodiment, the reference signal transmitted from the down-converter 10 is frequency-divided by the frequency dividing circuit 152, whereby the reference signal generated in the down-converter 10 is generated. Is restored, and the PLL circuit 79 controls the local oscillation circuit 76 using this reference signal,
The local oscillation circuit 76 generates a high-frequency signal having the same frequency as the high-frequency signal generated by the local oscillation circuit 36 on the down converter 10 side.

Therefore, also in this embodiment, the down converter 10 and the up converter 20 can match the frequency of the in-building up signal or the high frequency signal mixed with the up signal for frequency conversion.
On the 0 side, the original upstream signal before the frequency conversion by the up-converter 20 can be accurately restored.

The up converter 20 of this embodiment is
The invention according to claim 21 is applied, wherein the branch circuit 14
8 and the BPF 81 function as second reference signal extracting means, and the waveform shaping circuit 150 and the frequency dividing circuit 152 function as reference signal restoring means. And CA in the ridge of this embodiment
In the TV system, not only can the down converter 10 and the up converter 20 match the oscillation frequencies of the local oscillation circuits 36 and 76 to accurately restore the up signal generated by the cable modem 22 or the like on the down converter 10 side. In addition to the downlink signal transmitted from the external bidirectional CATV system, the terminal signal 18 on each subscriber side can also transmit the received signal from the BS antenna 100. Therefore, according to the in-building CATV system of the present embodiment, even when the external two-way CATV system does not distribute the BS broadcast, the subscriber of the in-building CATV system does not need to separately install the BS antenna, and the BS broadcast is not required. Can be viewed and the service to the subscriber can be improved.

In the above description, the bidirectional amplifier 12 provided on the transmission line L is not specifically described. However, in the present embodiment, the transmission from the down converter 10 to the transmission line L Since the frequency of the reference signal is set to 73 MHz which does not overlap with the downlink signal in the transmission frequency band 70 MHz to 770 MHz of the downlink signal, like the bidirectional amplifier 12 of the first embodiment shown in FIG. There is no need to provide a dedicated path for passing the reference signal therein, and a general bidirectional amplifier without such a path can be used.

[0176] In this case, the reference signal is sent out on the transmission line L on the terminal side through the path of the downstream signal in the bidirectional amplifier 12 together with other downstream signals, and passes through this path. At this time, the reference signal is transmitted to the up-converter 20 at an appropriate signal level even if the transmission line L becomes long, because the signal is amplified together with the downstream signal by the downstream signal amplifier circuit. .

Next, in the present embodiment, in order to transmit a BS broadcast received signal (BS-IF signal) to the terminal side, the down converter 10 is provided with a function of mixing the BS-IF signal and the downlink signal. Since each of these signals is transmitted to the terminal via the transmission line L connected to the down converter 10, a transmission line dedicated to the BS-IF signal is installed, or the BS-IF signal and the There is no need to separately install a mixer for mixing the downstream signal, and such an in-building CATV system can be constructed at low cost.

Although the second embodiment has been described with respect to a system having the BS antenna 100 as a receiving antenna, for example, when there are many subscribers who want to receive a broadcast signal from a communication satellite (CS), the What is necessary is just to install an antenna and transmit. Also in this case, if the down converter 10 of the present embodiment is used, CS
An in-building CATV system can be constructed without providing a mixer or the like for mixing a broadcast reception signal and a downstream signal.

In the in-building CATV system of the present embodiment, the reference signal for transmission transmitted by the down converter 10 to the terminal side is not the signal generated by the reference oscillation circuit 37 in the down converter 10 but this signal. Which is obtained by further dividing the frequency of the high-frequency signal for frequency conversion generated from. For this reason, the frequency of the reference signal for transmission can be arbitrarily set, and the system design is facilitated.

The down converter 10 of this embodiment is
The reference signal for transmission is generated by dividing the high-frequency signal output from the local oscillation circuit 36. For example, as shown in FIG. Reference signal (1.25 MHz)
May be divided (１ ／) and multiplied (× 292) using a frequency dividing circuit 170 and a multiplying circuit 172 to generate a transmission reference signal (73 MHz).

On the other hand, in the first and second embodiments, the transmission frequency band of the downstream signal is set to 70 MHz to 770 MHz so that the FM radio broadcast signal and the television broadcast signal can be transmitted as the downstream signal. Although the internal CATV system has been described, the present invention provides, for example, an FM radio broadcast signal (transmission frequency band: 76M
Hz to 90 MHz) and a television broadcast signal (transmission frequency band 90 MHz to 770 MHz), and a cable broadcast signal (transmission frequency band: 26 MHz to 76 MH) for distributing music and the like.
Needless to say, the present invention can be applied to an in-building CATV system in which the transmission frequency band of the downstream signal is set to 26 MHz to 770 MHz so that z) can also be transmitted.

In the case of the in-building CATV system, the frequency of the reference signal flowing on the transmission line L is set to, for example,
If the frequency is set in the range of 5 MHz to 26 MHz, the frequency of the reference signal is set lower than the transmission frequency band of the downlink signal as in the first embodiment, and the transmission loss generated when the reference signal passes through the transmission line L is set. Can be reduced. In the case of this in-building CATV system, the pass band of a downstream signal by a bidirectional amplifier or the like provided on the transmission line L is 26 MHz to 7 MHz.
70 MHz.

For example, as a downlink signal, an FM radio broadcast signal (transmission frequency band: 76 MHz to 90 MHz)
z), TV broadcast signal (transmission frequency band 90 MHz to 77
0 MHz) and a cable broadcast signal (transmission frequency band: 26M)
Hz to 76 MHz), in order to enable the reference signal to be transmitted as one of the downlink signals as in the second embodiment, as in the second embodiment, the CA
The transmission frequency band of the downstream signal in the TV system is set to, for example, 10 MHz to 770 MHz, and the frequency of the transmission reference signal is set to 10 MH, which is lower than the above transmission signals.
The frequency may be set in the range of z to 26 MHz (for example, 10.7 MHz).

When such an in-building CATV system is constructed, the pass band of a downstream signal by a bidirectional amplifier or the like provided on the transmission line L is set to 10 MHz to 770 MHz.
However, since the reference signal can be amplified together with the downstream signal in the bidirectional amplifier,
The same effect as that of the embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of an in-building CATV system according to a first embodiment.

FIG. 2 is a block diagram showing a configuration of a down converter, a bidirectional amplifier, and an up converter used in the system of FIG. 1;

FIG. 3 is a block diagram showing a modified example of a down converter and an up converter used in the system of FIG.

FIG. 4 is an explanatory diagram of an in-building CATV system in a case where a reference signal is transmitted onto a transmission line using a signal inserter.

FIG. 5 is a block diagram showing a configuration of a branch amplifier used in place of the bidirectional amplifier shown in FIG.

FIG. 6 is a block diagram illustrating a configuration of a down converter and an up converter that can use a pilot signal as a reference signal.

FIG. 7 is a block diagram illustrating a configuration of a down converter provided with a down signal amplification circuit.

FIG. 8 is a block diagram illustrating a configuration of a downconverter configured to allow an upstream signal that has not been frequency-converted to pass through.

FIG. 9 is a configuration diagram illustrating a configuration of an in-building CATV system according to a second embodiment.

FIG. 10 is a block diagram illustrating a configuration of a down converter used in the system of FIG.

FIG. 11 is a block diagram illustrating a configuration of an upconverter used in the system of FIG.

FIG. 12 is a block diagram illustrating a modification of the down converter illustrated in FIG.

[Explanation of symbols]

L: Transmission line, 6: Drop-in line, 8: Security device, 10: Down converter, 12: Bidirectional amplifier, 14: Branch device, 16:
Distributor, 18 ... Terminal terminal, 20 ... Up converter, 2
2 cable modem, 24 information terminal device, 26 television receiver, 28 signal inserter, 35, 75 mixer, 3
6, 76 local oscillation circuit, 37 reference oscillation circuit, 38,
79: PLL circuit, 39, 53, 57, 77, 110,
120, 158 ... amplifying circuit, 31, 34, 33, 52,
54, 56, 58, 71, 78, 102, 132, 13
4,140 ... HPF (high-pass filter), 32,4
0, 41, 51, 55, 59, 60, 80, 124, 1
38, 142, 144, 160... LPF (low-pass filter), 42, 81, 108, 122, 156.
(Band pass filter), 112, 118, 170, 1
52: frequency dividing circuit, 150: waveform shaping circuit, 172: multiplying circuit.

Continued on the front page (72) Inventor Yasuo Nakayama 80 Nogami, Asada-cho, Nisshin-shi, Aichi Prefecture F-term (reference) 5C056 FA03 FA05 FA08 GA14 HA01 HA04 HA13 HA14 HA15 5C064 BA01 BB05 BC11 BC20 BC21 BD07

Claims (24)

[Claims] 1. A drop line from an external two-way CATV system is drawn into a building, and a down signal input from the drop line is transmitted to a plurality of terminal terminals in the building via a transmission line in the building. A ridge input to the terminal via an up-converter that transmits and frequency-converts an upstream signal having a lower frequency than the downstream signal output from the terminal device into a ridge upstream signal having a higher frequency than the downstream signal. An inbound signal is transmitted to the service line via the transmission line, and the terminal device outputs the inbound signal through a down converter provided between the transmission line and the service line. In a CATV system in a building, which converts the frequency of the transmission signal into the upstream signal of the original frequency and sends it out onto the drop-in line, the frequency of various transmission signals flowing up and down the transmission line is reduced. A reference signal generating means for generating a reference signal having a constant frequency at a frequency different from the wave number; anda reference signal transmitting means for transmitting the reference signal generated by the reference signal generating means onto the transmission line. An up-converter and a down-converter on the drop-in side can use the reference signal of the constant frequency to convert the frequency of the up signal and the up signal in the ridge, respectively.
system. 2. The CATV system according to claim 1, wherein said reference signal generating means and said reference signal sending means are built in said down converter. 3. The frequency of the reference signal transmitted by the reference signal transmitting means on the transmission line is set to a frequency that does not overlap with the downlink signal within a frequency band set as a transmission frequency band of the downlink signal in the system. The building C according to claim 1 or 2, wherein the building is set.
ATV system. 4. The frequency of a reference signal transmitted by the reference signal transmitting means on the transmission line is set to be lower than the frequencies of various transmission signals flowing in the upstream and downstream directions on the transmission line. The CATV system according to any one of claims 1 to 3, wherein the CATV system is a building. 5. A frequency of a reference signal transmitted by the reference signal transmitting means on the transmission line is set in a range of 5 MHz to 26 MHz which is lower than a frequency band set as a transmission frequency band of the downlink signal in the system. The in-building CATV system according to claim 4, wherein: 6. The in-building CATV system is characterized in that a low-frequency upstream signal output from the terminal device and not frequency-converted by the up-converter can be directly transmitted to the service line. The in-building CATV system according to any one of claims 1 to 5. 7. A reception antenna installed in the building, wherein a reception signal from the reception antenna can be transmitted to the plurality of terminal terminals together with the downlink signal via the transmission line. The CATV system according to any one of claims 1 to 6, wherein: 8. The in-building CATV system according to claim 1, further comprising a down converter provided between the service line and the transmission line, wherein the down converter is inputted from an external bidirectional CATV system via the service line. A first downlink signal passing path for transmitting a signal on the transmission line, and a first reference signal extraction for extracting the reference signal of the constant frequency from an uplink transmission signal input via the transmission line. Means, extracting the in-building up signal from the up-stream transmission signal input through the transmission line,
First frequency conversion means for frequency-converting the original uplink signal output by the terminal device using the reference signal extracted by the reference signal extraction means, and transmitting the frequency-converted uplink signal onto the service line; A downconverter characterized by comprising: 9. A first judging means for judging whether or not a reference signal has been successfully extracted by said first reference signal extracting means, and when the first judging means judges that the reference signal cannot be extracted, A first specific transmission signal extracting unit that extracts a specific transmission signal having a fixed frequency from the downstream signals flowing through one downstream signal passage path, and outputs the specific transmission signal as the reference signal to the first frequency conversion unit; The down converter according to claim 8, comprising: 10. The in-building CATV system according to claim 2, wherein the down converter is provided between the service line and the transmission line, and the down converter is inputted from an external bidirectional CATV system via the service line. A first downstream signal passing path for transmitting a signal onto the transmission line, reference signal generating means for generating a reference signal having a constant frequency at a frequency different from the frequency of each of the upstream and downstream signals flowing through the transmission line, Extracting the in-building up signal from the up-stream transmission signals input through the transmission line,
First frequency conversion means for frequency-converting the original uplink signal output by the terminal device using the reference signal generated by the reference signal generation means, and sending the frequency-converted uplink signal onto the service line; A down-converter comprising: a reference signal transmitting unit that transmits a reference signal generated by the reference signal generating unit onto the transmission line. 11. The frequency of a reference signal transmitted by the reference signal transmitting means on the transmission line is within a frequency band set as a transmission frequency band of the downlink signal in a CATV system in a building where the downconverter is installed. The down converter according to claim 10, wherein the frequency is set to a frequency that does not overlap with the downlink signal. 12. The frequency of a reference signal transmitted by the reference signal transmitting means on the transmission line is set to a lower frequency than the frequencies of various transmission signals flowing in the transmission line in the upward direction and the downward direction. The down converter according to claim 10 or 11, wherein 13. The frequency of a reference signal transmitted by the reference signal transmitting means on the transmission line is higher than a frequency band set as a transmission frequency band of the downlink signal in a premises CATV system in which the downconverter is installed. 13. The down converter according to claim 12, wherein the frequency is set in a low range of 5 MHz to 26 MHz. 14. The reference signal sending means generates a reference signal for transmission by dividing or multiplying the reference signal generated by the reference signal generating means, and sending the reference signal onto the transmission line. The down converter according to any one of claims 10 to 13, characterized in that: 15. The reference signal transmitting means, wherein the first frequency converting means divides or multiplies a high frequency signal for frequency conversion generated based on the reference signal generated by the reference signal generating means, thereby transmitting the signal for transmission. The downconverter according to any one of claims 10 to 13, wherein a reference signal is generated, and the reference signal is transmitted on the transmission line. 16. A first upstream signal for transmitting a low-frequency upstream signal, which has not been frequency-converted by the up-converter, out of the upstream transmission signal input via the transmission line onto the drop-in line. The down converter according to any one of claims 8 to 15, further comprising a passage path. 17. A method according to claim 17, further comprising: a downstream signal amplifying means for amplifying said downstream signal passing through said first downstream signal passing path, and an input path of an in-building upstream signal to said first frequency converting means, 17. An output path for an upstream signal from the first frequency conversion means, wherein an upstream signal amplifying means for amplifying the in-building upstream signal or the upstream signal passing through the path is provided. Downconverter according to any of the above. 18. A reception signal input terminal for inputting a reception signal from a reception antenna installed on a building provided with the down converter, and transmitting the reception signal input to the reception signal input terminal together with the downlink signal to the transmission. The down converter according to any one of claims 8 to 17, further comprising: a reception signal passage for transmitting the signal on a line. 19. The in-building CATV system according to any one of claims 1 to 7, wherein the up-converter is provided between the terminal terminal and the terminal device, wherein the terminal terminal is connected via the transmission line. A second downlink signal passing path for transmitting the downlink signal transmitted to the terminal device side, and the downlink transmission signal transmitted to the terminal terminal via the transmission line, and A second reference signal extracting means for extracting a reference signal of a frequency, and an upstream signal output from the terminal device is frequency-converted into the in-building upstream signal using the reference signal extracted by the reference signal extracting means, And a second frequency conversion means for transmitting a frequency-converted in-building upstream signal onto the transmission line via the terminal terminal. 20. A second judging means for judging whether or not the reference signal has been successfully extracted by the second reference signal extracting means, and when the second judging means judges that the reference signal cannot be extracted, (2) A second specific transmission signal extracting means for extracting a specific transmission signal having a fixed frequency from the downstream signals flowing through the downstream signal passing path, and outputting the specific transmission signal as the reference signal to the second frequency conversion means. 20. The up-converter according to claim 19, comprising: 21. The reference signal extracted by the second reference signal extracting means is divided or multiplied, so that the down converter corresponds to a reference signal used to frequency-convert an in-building up signal into an up signal. Reference signal restoring means for restoring the extracted reference signal, wherein the second frequency conversion means frequency-converts the upstream signal into the ridge upstream signal using the reference signal restored by the reference signal restoring means. The upconverter according to claim 19 or 20, wherein: 22. The CATV system according to any one of claims 1 to 7, wherein the CATV system is provided on a transmission line extending from the down converter to each of the terminal terminals, and amplifies a transmission signal flowing through the transmission line. An amplifying device, comprising: a third downstream signal passing path for transmitting a downstream signal transmitted from the down converter side via the transmission line to a terminal; and a third downstream signal passing path provided on the third downstream signal passing path. A downstream signal amplifying means for amplifying the downstream signal; a ridge upstream signal passing path for transmitting the ridge upstream signal transmitted from the terminal side via the transmission line to the down converter side; An in-building up-signal amplifying means provided on the in-building up signal passage path and amplifying the in-building up signal; and Amplifier apparatus characterized by comprising: a first reference signal passing through path through connected, the. 23. A second upstream signal passing path connecting the transmission line on the down converter side and the transmission line on the terminal side so as to allow a low frequency upstream signal not frequency-converted by the up converter to pass through. 23. The amplifying device according to claim 22, further comprising: 24. One or a plurality of branch terminals, down signal branching means for branching a part of the down signal amplified by the down signal amplifying means and outputting the branched signal from the branch terminal, An in-building ascending signal input means for transmitting the in-building ascending signal to the in-building ascending signal passage on the input side of the in-building ascending signal amplifying means; 24. The amplifying device according to claim 22, further comprising: a second reference signal passage path through which a signal is connected.