JP2000308031A - Upconverter for CATV system in building - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In an in-building CATV system for transmitting a signal in both directions between a two-way CATV system and a terminal device in a building, an upstream signal from the terminal device is converted into an in-building upstream signal. An up-converter used for frequency conversion has low signal loss and does not affect the operation of other transmission equipment. SOLUTION: A frequency conversion unit including a mixer 90 and the like converts an upstream signal input from a first terminal Tin into an in-building upstream signal having a higher frequency than a transmission signal on an external bidirectional CATV system. In the converter, the upstream signal input from the first terminal Tin is converted to an LPF
(Low-pass filter) 62 ′, input to the frequency conversion unit,
The ascending signal inside the building is passed through an HPF (high-pass filter) 40 ',
The signal is output to the second terminal Tout connected to the transmission line on the system side. Also, the downstream signal input to the second terminal Tout is:
The signal is guided to the downstream signal path L via the LPF 34 ', and is output from the downstream signal path L to the first terminal Tin via the HPF 32'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an external bidirectional CA.
In-building CATV that connects the transmission path of the TV system and the terminal terminal in the building to transmit each signal of up and down in both directions
The present invention relates to an up converter used in a system to frequency-convert an upstream signal output from a terminal device into a ridge upstream signal.

[0002]

2. Description of the Related Art Heretofore, a service line from an external two-way CATV system has been pulled into a building, and a down signal input from the service line via a transmission line in the building (specifically, a two-way CATV system). The downstream signal transmitted from the center device is transmitted to the terminal terminal in the building, and the upstream signal input from the terminal device on the subscriber side to the terminal terminal is transmitted to the service line, and the two-way CA is transmitted from the service line.
In-building CAT to output to TV system center equipment side
V systems are known.

In such an in-building CATV system, noise generated in each part of the building is superimposed on a transmission line via a terminal terminal or the like on a subscriber side, and this is combined with an upstream signal together with an upstream signal. May be output to an external bidirectional CATV system. Therefore, conventionally, in order to reduce ingress noise flowing out to an external two-way CATV system, an upstream signal generated by a subscriber-side terminal device such as a cable modem (a frequency band that can be transmitted by the two-way CATV system) is used. (For example, a signal of 10 to 55 MHz)
Using an up-converter, the transmission frequency of the downlink signal is higher than the original frequency (for example, 70 to 770 MHz).
z), and does not overlap with the UHF band (for example, 821M).
Hz to 866 MHz), the frequency is converted to an upstream signal (hereinafter referred to as an in-building up signal), 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 down-converted. Using a converter to convert the original frequency (in other words, the transmission frequency of the upstream signal in the bidirectional CATV system) has been considered.

[0004] An upconverter used in this kind of in-building CATV system is usually configured as shown in FIG. That is, first, the up-converter not only converts the frequency of the upstream signal output from the terminal device into a premises upstream signal, but also converts the downstream signal transmitted via the transmission line of the premises CATV system to the terminal device side. Need to output. For this reason, the conventional up-converter includes a first terminal Tin connected to a terminal device on the subscriber side, and a terminal terminal of the CATV system in the building, in order to make the internal signal path into two systems of up and down. Second connected to
Distribution circuits SP1 and SP2 are connected to the terminal Tout, respectively.

[0005] For the upstream signal input to the first terminal Tin from the terminal device, a low-pass filter (hereinafter, the low-pass filter is also simply referred to as LPF) 92 connected to one of the distribution terminals of the distribution circuit SP1. Is input to the frequency conversion unit 94 via the
The in-building up signal output from 4 is input to one distribution terminal of a distribution circuit SP2 connected to the second terminal Tout via a high-pass filter (hereinafter, the high-pass filter is also simply referred to as HPF) 96. As a result, the CATV in the building is connected from the second terminal Tout via the distribution circuit SP2.
Output to the transmission line of the system.

[0006] The down signal input to the second terminal Tout is sent from the other distribution terminal of the distribution circuit SP2.
By transmitting the signal to the other distribution terminal of the distribution circuit SP1 via the downstream signal path for transmitting the downstream signal provided with the LPF 98, the terminal device on the subscriber side is transmitted from the first terminal Tin via the distribution circuit SP1. To be output to

The LPF 92 provided before the frequency conversion section 94 is for selectively passing an upstream signal from the terminal device, and the HPF 96 provided after the frequency conversion section 94 is provided with a frequency conversion section. This is for selectively passing the in-building up signal output from the unit 94, and the LPF 98 provided in the down signal path is for selectively passing the down signal.

[0008]

However, in the conventional up-converter configured as described above,
Since the upstream signal path in which the frequency conversion unit 94 is provided and the downstream signal path are separated using the distribution circuits SP1 and SP2, the above-described signals are distributed to the distribution circuits SP1 and SP2.
There is a problem that the signal loss is increased by passing through SP2.

The upstream signal input from the terminal device to the first terminal Tin passes through the LPF 92 and is transmitted to the frequency converter 9.
4 as well as being output from the second terminal Tout through the LPF 98 to the transmission line of the in-building CATV system, as shown in FIG. 5B provided on the transmission line of the in-building CATV system. The operation of such a bidirectional amplifier may be adversely affected.

[0010] That is, in the building C equipped with a down converter
The signals to be transmitted in the ATV system are a down signal and an in-building up signal, and there is basically no problem even if an up signal having a different frequency from these signals is sent from the up converter to the transmission line of the in-building CATV system. . However, CAT in the ridge
On the transmission line of the V system, a bidirectional amplifier is provided, which is provided with HPF and LPF for signal selection at the front and rear stages, respectively, as shown in FIG. In the case where the amplification circuits AMP1 and AMP2 are configured to amplify, the amplification circuit AMP for amplifying the downstream signal is used.
2, the up signal output from the up converter is input. When the upstream signal is input as described above, the upstream signal is transmitted to the amplifier circuit AMP.
In this case, the signal goes around the input side of the amplifier circuit AMP2 via the feedback circuit 2 and the amplifier circuit AMP2 oscillates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an in-building CATV for transmitting signals bidirectionally between an external two-way CATV system and a terminal device in a building.
In the system, an up-converter used to frequency-convert an upstream signal from a terminal device into a premises upstream signal is provided with a small signal loss and does not affect other devices such as a bidirectional amplifier. The purpose is to.

[0012]

Means for Solving the Problems and Effects of the Invention A CAT in a building according to claim 1, which has been made to achieve the above object.
In the V system upconverter, the frequency conversion unit converts the frequency of the upstream signal input from the terminal device side to the first terminal into the upstream signal at the ridge, and then from the second terminal to the terminal terminal of the CATV system within the ridge. Side (in other words, CA in the building)
(On the transmission line of the TV system), and the downstream signal input from the second terminal is transmitted to the first terminal via the internal downstream signal path.
The signal is transmitted to the terminal and output from the first terminal to the terminal device side.
(1) Between the first terminal and the frequency conversion unit, a low-pass filter that cuts off the input of the downlink signal that has passed through the downlink signal path and selectively passes the uplink signal from the terminal device side is ( 2) Between the frequency conversion unit and the second terminal, a high-pass filter that blocks a downstream signal input from the second terminal and selectively passes an in-building upstream signal output from the frequency conversion unit, 3) A low-pass filter between the second terminal and the downstream signal path, which cuts off the input of the in-building upstream signal output from the frequency conversion unit and selectively passes the downstream signal input from the second terminal. (4) Downlink signal path and first
High-pass filters are provided between the terminals to block the upstream signal input from the first terminal and selectively pass the downstream signal.

As a result, only the down signal is output from the up converter of the present invention to the terminal device side, and the CAT
On the transmission line of the V system, only the in-building upstream signal frequency-converted by the frequency conversion unit is output, and the up signal output from the terminal device is output on the in-building CATV system transmission line. This can prevent adverse effects on the operation of other transmission equipment such as a bidirectional amplifier provided on the transmission line.

In the present invention, each of the signal paths (up and down signal paths) in the up-converter is separated by the above four types of filters, and the conventional apparatus shown in FIG. As described above, since the distribution circuit is not used for separating the signal path, the signal loss in the up-converter can be reduced.

Here, as is well known, the frequency conversion unit
By mixing a reference signal with a predetermined frequency and an uplink signal, the uplink signal is converted to a signal having a higher frequency (for more details,
This is for frequency conversion into an upstream signal (having a higher frequency than the downstream signal). As the reference signal used by the frequency converter for frequency conversion, a reference signal generated by an oscillation circuit built in the up-converter may be used.

However, in this case, the reference signal on the up-converter side does not correspond to the reference signal on the down-converter side, which converts the frequency of the in-building up signal into an up signal, so that the down converter side There is a possibility that the internal uplink signal cannot be converted to an uplink signal corresponding to an external bidirectional CATV system.

In order to prevent such a problem, the frequency converter may be installed in the building CA.
It is preferable that the reference signal of a predetermined frequency superimposed on the downstream signal transmitted from the TV system is used to convert the upstream signal into the ridge upstream signal. In other words, by doing so, the reference signal on the up-converter side and the reference signal on the down-converter side correspond to each other, and the down-converter converts the in-building up signal into an up signal corresponding to an external bidirectional CATV system. It can be converted accurately.

As the reference signal, a pilot signal used for adjusting the level of a downlink signal in an external bidirectional CATV system may be used, or a down converter may be used to generate a pilot signal. May be used.

On the other hand, as described above, the frequency conversion unit converts the upstream signal into the upstream signal by using the reference signal of a predetermined frequency superimposed on the downstream signal transmitted from the CATV system in the building. In this case, it is necessary to input this reference signal to the frequency converter in the up-converter.

For this purpose, a part of the downstream signal input from the terminal of the CATV system in the building to the second terminal may be branched to the frequency conversion unit. If the signal is provided on the signal path from the second terminal to each of the above filters, not only the down signal but also the in-building up signal will pass through the branch circuit, causing a signal loss of the in-building up signal in the branch circuit. become.

For this reason, the branch circuit is provided on a downstream signal path through which a downstream signal is input from the second terminal via a low-pass filter, and is input via the low-pass filter. It is preferable to input a part of the downstream signal to the frequency conversion unit. In other words, this way, without affecting the signal going up inside the building,
The reference signal superimposed on the downlink signal can be input to the frequency converter.

[0022]

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

As shown in FIG. 1, the CATV in the building according to the present embodiment.
The system draws a drop line 6 branched from a transmission line (CATV transmission line) 2 of an external bidirectional CATV system via a branching device 4 into a building 10 such as an apartment or an apartment via a protector 8. , A transmission line 12 in the building 10, and a branch 14 provided on the transmission line 12,
Downstream signals (frequency: 70 MHz to 770 MHz) of the bidirectional CATV system input from the service line 6 via the bidirectional amplifier 16, the distributor 18, and the like are transmitted to a number of subscriber terminal terminals 20 in the building 10. While transmitting, the upstream signal (upstream signal in the ridge) input from the terminal 20
Is transmitted to the service line 6.

In the in-building CATV system according to the present embodiment, the subscriber provided with the terminal 20 is provided with an external two-way CATV system center device for viewing reservation of pay programs and television shopping. When the data is generated by the information terminal device 22 such as a personal computer in order to transmit the data, the data is transmitted to the cable modem 24 in a predetermined frequency band that can be transmitted by an external bidirectional CATV system (this embodiment). Then, 10MHz to 55MHz)
, And further converts this upstream signal into a predetermined frequency band (in this embodiment,
821 MHz to 866 MHz), and the frequency is converted into an in-building upstream signal and input to the terminal 20.

For this reason, the transmission line 12 of the in-building CATV system and the drop-in line 6 from the external bidirectional CATV system are used.
Is connected to the external bidirectional CAT by transmitting the in-building upstream signal transmitted from the terminal 20 via the transmission line 12 to the terminal.
A down converter 28 is provided for returning (frequency conversion) to an upstream signal usable in the V system.

The down converter 28 includes:
A reception signal (frequency: 1035 MHz to 13) from the satellite broadcasting reception BS antenna 30 installed on the rooftop of the building
35 MHz band, hereinafter referred to as BS-IF signal). In FIG. 1, reference numeral 29 denotes a downlink signal or BS transmitted through the transmission line 12 connected to the terminal 20 to which the upconverter 26 is not connected.
-Represents a television receiver that receives and demodulates and reproduces IF signals.

Next, the down converter 28 is configured as shown in FIG. As shown in FIG. 2, the down converter 28 has an external connection terminal T1 for connecting a drop-in line from an external bidirectional CATV system, and a reception signal input for inputting a BS-IF signal from the BS antenna 30. A terminal T2 and an internal connection terminal T3 for connecting the transmission line 12 in the building 10 are provided. Then, the downstream signal input to the external connection terminal T1 is taken into the down converter 28 through the HPF 32 for blocking the upstream signal, and the LPF 34 for blocking the upstream signal in the building.
Output to the internal connection terminal T3 side.

Further, a mixing circuit 36 is provided between the LPF 34 and the internal connection terminal T3, and a reception signal input terminal T
2 and the downstream signal passing through the LPF 34 are mixed and output from the internal connection terminal T3 to the transmission line 12. An HPF 38 for passing only the BS-IF signal is provided on the transmission path of the BS-IF signal from the reception signal input terminal T2 to the mixing circuit 36.

Next, the in-building up signal from the terminal, which is input to the internal connection terminal T3, is passed through the mixing circuit 36 and the down-converter HPF 40 to the down-converter 28.
Is taken in. Then, the captured in-building up signal is passed through an attenuator 42 for attenuating the in-building up signal and a band-pass filter 44 for passing the in-building up signal (hereinafter, the band-pass filter is simply referred to as BPF) 44. ,
The signal is input to an amplification circuit 46 for amplifying the in-building up signal, and is amplified by the amplification circuit 46 to a predetermined level determined by the attenuation of the attenuator 42 and the amplification factor of the amplification circuit 46. Input to the mixer 48.

The mixer 48 receives a signal from the local oscillation circuit 52 whose oscillation frequency is controlled to be constant (876 MHz in this embodiment) by a PLL circuit 50 described later, and converts the in-building up signal into a bidirectional CATV system. The frequency is converted to an upstream signal for use, and the upstream signal after the frequency conversion is
A BPF 54 for passing an upstream signal, an amplifier circuit 56 for amplifying an upstream signal, an LPF 58 for passing an upstream signal, and an LPF for blocking a downstream signal via an attenuator 60 for attenuating the upstream signal.
62, and is output from the LPF 62 to the service line 6 via the external connection terminal T1. The attenuator 60
Is for adjusting the level of the upstream signal output from the external connection terminal T1 to the service line 6.

Next, on the path of the downstream signal from the HPF 32 to the LPF 34, a branch circuit 64 for branching a part of the downstream signal passing through the HPF 32 is provided. The signal is input to the BPF 66 that passes a pilot signal (451.25 MHz) used for level adjustment of a downstream signal in the bidirectional CATV system. The downstream signal (specifically, a pilot signal) that has passed through the BPF 66 is input to a carrier reproducing circuit 68 that reproduces a carrier of the pilot signal.
The carrier of the pilot signal reproduced by the carrier reproducing circuit 68 is divided into 1/361 cycles to generate a reference signal of a predetermined frequency (in this embodiment, 1.25 MHz). 70 is input.

In the down converter 28, a reference oscillation circuit 72 having an oscillation frequency of 10 MHz, and an output signal from the reference oscillation circuit 72 are divided by ８ to generate a frequency dividing circuit 70. A frequency dividing circuit 74 for generating a reference signal having the same frequency as the reference signal (1.25 MHz in the present embodiment). The output (reference signal) from each of the frequency dividing circuits 70 and 74 is selectively input to the PLL circuit 50 via a reference signal switching switch SW1.

The PLL circuit 50 takes in the reference signal input via the switch SW1 and the output from the local oscillation circuit 52 via an internal frequency dividing circuit, respectively, and obtains the phase difference of the frequency-divided signal. Based on the above, by controlling the local oscillation circuit 52, the oscillation frequency of the local oscillation circuit 52 is controlled to a constant frequency (876 MHz). The down converter 28 has an oscillation frequency of the local oscillation circuit 52 controlled by the PLL circuit 50 (specifically,
A microcomputer (hereinafter simply referred to as a CPU) for setting the frequency dividing ratio of the frequency dividing circuit in the PLL circuit 50
76 are provided.

Further, a carrier detecting circuit 69 for detecting a carrier of a pilot signal is provided in parallel with the carrier reproducing circuit 68, and the presence or absence of the carrier output from the carrier detecting circuit 69 (in other words, the presence or absence of the pilot signal) ) Is input to the CPU 76. Then, the CPU 76 switches the switch SW based on the detection signal.
Switch 1.

Next, the down converter 28 divides the output from the local oscillation circuit 52 into a 1/12 cycle to generate a pseudo pilot signal of a predetermined frequency (73 MHz in this embodiment). Frequency dividing circuit 78, frequency dividing circuit 7
8 that passes the pseudo pilot signal output from
F80, an amplification circuit 82 for amplifying the pseudo pilot signal passing through the BPF 80 to a predetermined level, and an amplification circuit 8
2 is superimposed on the path of the downstream signal from the HPF 32 to the LPF 34,
A superimposing circuit 84 for outputting the signal from the terminal 34 to the terminal side is provided. On the path of the pseudo pilot signal from the amplifier circuit 82 to the superimposing circuit 84, a switch SW2 for conducting / cutting off the path is provided. The switch SW2 is turned on when the carrier detection circuit 69 determines that there is no pilot signal based on the drive signal from the CPU 76.

FIG. 3 is a flowchart showing a signal switching process executed by the CPU 76 to switch the switches SW1 and SW2 based on the detection signal from the carrier detection circuit 69. This processing is repeatedly executed at predetermined time intervals by the CPU 76. When the processing is started, first, in S110 (S represents a step), a carrier is detected based on a detection signal from the carrier detection circuit 69. The detection circuit 69 determines whether the carrier of the pilot signal has been detected.

If the carrier of the pilot signal has been detected (in other words, if the pilot signal has been inputted from the external bidirectional CATV system via the service line 6), the switch SW1 is switched to the carrier in S120. Switching to the reproducing circuit 68 side, the reference signal generated based on the pilot signal in the frequency dividing circuit 70 is input to the PLL circuit 50, and in S130, the switch SW2 is turned off to send the pseudo pilot signal to the terminal side. Is prohibited, and the process ends.

On the other hand, if the carrier of the pilot signal has not been detected (in other words, if the pilot signal has not been input from the external bidirectional CATV system via the service line 6), the switch SW1 is referenced in S140. The reference signal generated based on the output from the reference oscillation circuit 72 by the frequency dividing circuit 74 is switched to the oscillation circuit 72 side.
At S150, switch SW2 is turned on to output a pseudo pilot signal to the terminal side, and the process is terminated.

As described above, the down converter 28 of the present embodiment converts the pilot signal if the downlink signal input from the external bidirectional CATV system via the service line 6 includes the pilot signal. Using the generated reference signal, the in-building up signal is frequency-converted into an up signal for an external bidirectional CATV system. Conversely, if the down signal does not include a pilot signal, the built-in reference oscillation circuit is used. Using the reference signal generated based on the output from 72, the in-building up signal is frequency-converted into an up signal for an external bidirectional CATV system. When the pilot signal is not included in the downlink signal, the down converter 28 generates a pseudo pilot signal instead of the pilot signal and transmits the pseudo pilot signal to the terminal.

On the other hand, the up-converter 26, which is a main part of the present invention, is configured as shown in FIG.
In FIG. 4, components having the same functions as those of the components of the downconverter 28 are denoted by the same reference numerals with dashes.

As shown in FIG. 4, the up-converter 26 outputs a first terminal Tin, which is an input terminal for inputting an up signal from the cable modem 24, and an in-building up signal after frequency conversion to the terminal 20 side. And a second terminal Tout which is an output terminal. Then, the BS-IF signal input to the second terminal Tout via the transmission line 12 is transmitted to the BS-I
Via an HPF 38 ′ (cutoff frequency: 1.035 MHz, for example) that allows only the F signal to pass through, the signal is once taken into the up-converter 26, and then the HPF 38
The signal is output from the first terminal Tin to the terminal via the 38 ".

Further, the second terminal Tout is transmitted via the transmission line 12.
Is input to the LPF 86 (cutoff frequency: for example, 86) for blocking the BS-IF signal and passing the downlink signal.
6 MHz) and an LPF 34 ′ (cutoff frequency: 770 MH, for example) for blocking an ascending signal and passing a descending signal in the building
z), is once taken into the up-converter 26, and is input to the internal downstream signal path L. The downstream signal that has passed through the downstream signal path L is
A terminal from the first terminal Tin via an HPF 32 ′ (cutoff frequency: 70 MHz, for example) for passing down signals and an LPF 88 (cutoff frequency: 770 MHz, for example) for blocking BS-IF signals and passing other transmission signals. Output to the side.

On the other hand, the upstream signal input from the terminal side to the first terminal Tin includes the above-described LPF 88 and the LPF 62 ′ (cutoff frequency:
(For example, 55 MHz). The captured upstream signal is input to a mixer 90 via an upstream signal attenuation attenuator 60 ', and the mixer 90 causes the local oscillation circuit 5
Using the signal (876 MHz) from 2 ', the frequency is converted to an in-building up signal.

The mixer 90 receives the signal from the local oscillation circuit 52 'whose oscillation frequency is controlled to be constant (876 MHz) by the PLL circuit 50', and converts the frequency of the upstream signal into the upstream signal in the building. It is. The in-building upstream signal after the frequency conversion is a BPF 44 ′ (pass band: 821 MHz to 86
6 MHz), amplifying circuit 46 'for amplifying the in-building up signal, LPF 89 for passing the in-building up signal (cutoff frequency: 866 MHz, for example), and amplifying circuit 4 for amplifying the in-building up signal
6 "and an attenuator 42 'for attenuating the upstream signal in the building.
HPF for blocking down signal and passing up signal in building
40 '(cut-off frequency: 821 MHz, for example), and the LPF 86 and the second terminal T
The signal is output to the transmission line 12 via out.

In the downstream signal path L from the LPF 34 'to the HPF 32', a branch circuit 64 'for branching a part of the downstream signal passing through the LPF 34' is provided. The signal is input to a pilot signal passing BPF 66 '.

The downstream signal (pilot signal) that has passed through the BPF 66 'is input to a carrier reproducing circuit 68', and the carrier of the pilot signal reproduced by the carrier reproducing circuit 68 'has a period of 1/1805. Is input to a frequency dividing circuit 70 'that generates a reference signal having a predetermined frequency (0.25 MHz). Then, the reference signal generated by the frequency dividing circuit 70 'is input to the PLL circuit 50.

On the other hand, in this embodiment, the down converter 2
8 generates a pseudo pilot signal having a frequency different from that of the pilot signal when there is no pilot signal, and transmits the pseudo pilot signal to the terminal side. A circuit for generating an input reference signal is provided.

That is, the BPF 6 for passing the pseudo pilot signal out of the downstream signals branched by the branch circuit 64 '.
6 ", a carrier reproducing circuit 68" for reproducing a carrier from the pseudo pilot signal passed through the BPF 66 ", and a carrier of the reproduced pseudo pilot signal is 1/292.
Of the predetermined frequency (0.25 MHz)
This is the frequency dividing circuit 70 "that generates the reference signal z). The reference signal generated by the frequency dividing circuit 70" is also input to the PLL circuit 50 '. Note that, like the down converter 28, the up converter 26 has a PLL.
A CPU 76 'is provided for setting the oscillation frequency of the local oscillation circuit 52' controlled by the circuit 50 '.

Accordingly, the up-converter 26 of the present embodiment
In, a pilot signal input as one of the downlink signals from an external bidirectional CATV system, or
Based on the pseudo pilot signal generated by the downconverter 28, the frequency of the upstream signal can be accurately converted to the indoor upstream signal.

The up-converter 26 of this embodiment is connected to the HPF 38 ″ and the input terminal Tin from the input terminal Tin in order to protect the internal circuit from abnormal high voltage input from the terminal side or the CATV system inside the building due to a lightning strike or the like. The signal path leading to the LPF 88 and the output terminal Tout to the HPF 38 '
A lightning arrester (so-called arrester) ARR is provided on the signal path leading to the LPF 86 and the LPF 86, respectively.

As described above, in the up-converter 26 of this embodiment, the up-converted signal input to the first terminal Tin is input to the up-converted signal path provided with the mixer 90 and the like as the frequency conversion unit. An LPF 62 'for blocking the downstream signal and passing the upstream signal is provided on the path, and the upstream signal, which has been frequency-converted by the mixer 90 as a frequency converter, is output to the second terminal Tout. HPF4 for blocking / passing up signal inside building
0 'is on the signal path for inputting the downstream signal input to the second terminal Tout to the downstream signal path L, and the LPF 34' for blocking the upstream signal in the building and passing the downstream signal is downstream of the downstream signal path L passing through the downstream signal path L. The signal to the first terminal Tin
HPFs 32 ′ for blocking the upstream signal and passing the downstream signal are provided on the signal path to be output to the side.

The up-converter 26 of the present embodiment
Transmits a BS-IF signal having a frequency higher than that of a transmission signal in an external bidirectional CATV system, but a BS-IF signal and a first terminal Tin or a second terminal Tout are provided between each of the filters. HPFs 38 ', 38 "and LPFs 86, 88 are provided for separating the signals from other transmission signals.

For this reason, the up-converter 2 of the present embodiment
From 6, only the in-building up signal frequency-converted by the frequency conversion unit including the local oscillation circuit 52 ′ and the mixer 90 is output on the transmission line 12 of the in-building CATV system. It is possible to prevent the upstream signal before the frequency conversion from being output onto the transmission line 12 of the system and adversely affecting the operation of another transmission device such as the bidirectional amplifier 16 provided on the transmission line 12.

In the up-converter 26 of this embodiment, the LPF or HPF is used to separate the above-described signals including the BS-IF signal, and the distribution circuit is not used. Loss can be reduced.
As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, You can employ | adopt various aspects.

For example, in the above-described embodiment, the upconverter 26 is described as selectively using the pilot signal and the pseudo pilot signal superimposed on the downlink signal in order to frequency-convert the uplink signal. In a CATV system equipped with a down converter capable of generating no down-conversion, the up-converting signal may be frequency-converted using a pilot signal, or the frequency conversion may be performed only by the local oscillation circuit 52 '. May be generated.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration of a down converter.

FIG. 3 is a flowchart illustrating a signal switching process executed by a CPU of the down converter.

FIG. 4 is a block diagram illustrating a configuration of an upconverter.

FIG. 5 is a block diagram illustrating a configuration example of a conventional upconverter.

[Explanation of symbols]

6 ... drop-in line, 12 ... transmission line, 14 ... branching device, 16 ... bidirectional amplifier, 20 ... terminal terminal, 22 ... information terminal device, 24
... cable modem, 26 ... up converter, 28 ... down converter, Tin ... first terminal, Tout ... second terminal,
52 ': local oscillation circuit; 90: mixer; 38', 3
8 ", 40 ', 32' ... HPF (high-pass filter),
34 ', 62', 86, 88,... LPF (low-pass filter).

Claims (2)

[Claims] 1. A service line from an external two-way CATV system is drawn into a building, and a down signal of the two-way CATV system input via the service line is transmitted to a terminal via a transmission line in the building. A terminal, and further transmits an in-building up signal higher than the transmission frequency in the bidirectional CATV system input from the terminal terminal to the drop-in line via the transmission line, and transmits the in-building up signal. Is converted into a transmission frequency in the bidirectional CATV system by a down converter provided between the drop-in line and the transmission line, and is output to the bidirectional CATV system side. An up-converter provided between a terminal and a terminal device on the subscriber side for frequency-converting an upstream signal output from the terminal device to the indoor upstream signal; A first terminal connected to the terminal device side, a second terminal connected to the terminal terminal side, and an up signal from the terminal device side input from the first terminal, The frequency is converted to an inbound signal, and the second
A frequency converter that outputs to the terminal side, a downlink signal path that transmits a downlink signal input from the second terminal to the first terminal, and is provided between the first terminal and the frequency converter,
Blocking the input of the downstream signal passing through the downstream signal path,
A low-pass filter for selectively passing an uplink signal from the terminal device side, provided between the frequency conversion unit and the second terminal,
A high-pass filter that blocks a downstream signal input from the second terminal and selectively passes an in-building upstream signal output from the frequency conversion unit; and a high-pass filter provided between the second terminal and the downstream signal path. Being
A low-pass filter that cuts off the input of the in-building up signal output from the frequency conversion unit and selectively passes the down signal input from the second terminal; and between the down signal path and the first terminal. Provided in
An upconverter for a CATV system in a building, comprising: a high-pass filter that blocks an upstream signal input from the first terminal and selectively passes the downstream signal. 2. The frequency conversion unit is configured to frequency-convert the upstream signal into a ridge upstream signal using a reference signal of a predetermined frequency superimposed on the downstream signal, and the downstream signal path includes: 2. The building according to claim 1, wherein a branch circuit that branches a part of the downstream signal input from the second terminal via the low-pass filter and inputs the branched signal to the frequency conversion unit is provided. 3. Upconverter for CATV system.