JP2002199389A - Down converter, up converter and catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently convert the frequency of a BS receiving signal into that of a BS intermediate frequency signal in a CATV system for converting the frequency of the BS receiving signal into that of the BS intermediate frequency signal and transmitting the converted BS intermediate frequency signal through a transmission line common to a ground television broadcasting signal. SOLUTION: A 1st converting local oscillation signal (446 MHz) to be used for frequency conversion is generated by a 1st converting local oscillation signal generation part 31 constituted of a PLL circuit on the basis of a reference signal from a reference signal oscillator 29 and a 2nd converting local oscillation signal (892 MHz) to be used for frequency conversion also is generated by a 2nd converting local oscillation signal generation part 32 constituted of a PLL circuit on the basis of the reference signal from the oscillator 29. Since only one reference signal oscillator 29 is used for generating two converting local oscillation signals, the cost of a down converter 20 can be reduced and low power consumption can be attained as a compared with a case for requiring a reference signal oscillator in each converting local oscillation signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a broadcasting satellite (BS).
That transmits the BS reception signal from the BS antenna that receives the transmission radio wave from the terminal to the terminal side together with the terrestrial TV broadcast signal
The present invention relates to an ATV system, and a down converter and an up converter used in the CATV system and suitable for transmitting a BS reception signal to a terminal.

[0002]

2. Description of the Related Art Conventionally, a television receiving antenna for receiving a terrestrial television broadcasting signal and a BS antenna for receiving a transmission radio wave from a broadcasting satellite (BS) are provided at a head end, and receiving signals from these receiving antennas are provided. There is known a CATV system configured to transmit a signal to a terminal via a common transmission line (generally, a coaxial cable).

In the CATV system having the above configuration, B
The receiving section of the S antenna normally converts the transmission radio wave in the tens of GHz band transmitted from the BS to about 1 GHz to 2 GHz so that the received signal can be transmitted using a coaxial cable or the like (down-conversion). Converter is provided. However, a reception signal from such a BS antenna (BS reception signal) is transmitted as it is in an existing CATV system in which a transmission device such as an amplifier installed on a transmission line is designed to transmit a terrestrial television broadcast signal. If the transmission equipment installed on the transmission line uses a device that can transmit the BS reception signal, the BS reception signal has a higher frequency than the terrestrial TV broadcast signal. There is a problem that transmission loss caused by the flow increases and an expensive amplifier having high-level amplification characteristics is required to transmit the BS reception signal at an appropriate level.

[0004] Therefore, in order to be able to transmit a BS reception signal even with an existing CATV system designed to transmit a terrestrial television broadcast signal and to transmit the BS reception signal with low loss, A down-converter is provided at the head end for temporarily lowering the BS reception signal to the frequency band of the television broadcast signal, and the BS reception signal (hereinafter referred to as a BS intermediate frequency signal) frequency-converted by the down converter is transmitted to the terminal. Transmission is considered.

[0005] In the existing CATV system, the frequency band that can be transmitted generally ranges from 70 MHz to 77 MHz.
0 MHz, of which VHF band (90 to
222 MHz) is mainly assigned to terrestrial analog broadcast signals, and 451.25 MHz is assigned to pilot signals. Therefore, the frequency band that can be assigned for transmitting BS intermediate frequency signals is 70 to 90 MHz.
z, 222-451.25 MHz and 451.25-7
Limited to 70 MHz. Since the bandwidth of the BS reception signal is about 300 MHz, the BS intermediate frequency signal can be stored in the range of 451.25 to 770 MHz.
z only.

However, in the near future, the UHF band (470M
Hz or more) are allocated to digital terrestrial broadcast signals, and the UHF band (especially around 470 MHz) needs to be kept as far as possible. Therefore, BS intermediate frequency signals for all eight channels are contained in the UHF band. It is not possible.

That is, as described above, when the frequency of a BS reception signal is converted into a BS intermediate frequency signal for transmission using a down converter, the frequency conversion of the entire BS reception signal is performed with the channel arrangement as it is. Therefore, the BS intermediate frequency signal after the frequency conversion cannot be transmitted on the transmission line of the existing CATV system.

On the other hand, in order to solve such a problem, conventionally, for example, all eight channels (1, 3, 5, 7,
Of the BS reception signals (9, 11, 13, 15 channels), 4 channels (1, 3, 13, 15 channels) for BS digital broadcasting in a frequency band as shown in FIG.
For example, as shown in FIG.
A system has been considered in which a frequency is converted to a BS intermediate frequency signal of 253 to 407 MHz and transmitted, and as shown in FIG. 7C, the signals for these four channels are collectively frequency-converted in an up-converter on the terminal side. .

However, as is apparent from a comparison between FIG. 7A and FIG. 7C, when frequency conversion is performed by the terminal up-converter in this manner, the channel arrangement of the BS reception signal becomes the original. It differs from the channel arrangement of the BS reception signal. For this reason, a commercially available BS tuner that receives a signal from a BS antenna as it is cannot be used for a BS tuner that finally receives a BS reception signal (in this case, a BS digital tuner), and the subscriber has CA
It is necessary to prepare a BS tuner dedicated to the TV system.

Therefore, the applicant of the present application converts the BS reception signals for all channels into BS intermediate frequency signals by a down converter and transmits the signals to the terminal side. One or a plurality of continuous channels are taken as one group, and two or more groups are extracted, and the BS reception signals of each group are respectively assigned in the frequency domain from the VHF band to the UHF band assigned for the television broadcast signal, and , A frequency band (70 to 90 MHz, 222 to 45
A method was considered in which a frequency is converted to a BS intermediate frequency signal (to 1.25 MHz and 451.25 to 770 MHz) and transmitted on a transmission line.

As described above, by dividing the BS reception signals into a plurality of groups and frequency-converting them into BS intermediate frequency signals for each group, the BS intermediate frequency signals can be transmitted together with other television broadcast signals. Then, if the BS intermediate frequency signal of each group is converted again to the frequency of the original BS reception signal, the terminal side finally transmits the BS reception signal having the same channel arrangement as that of the original BS reception signal. In the subscriber terminal, the existing B
BS broadcasts can be received using the S tuner.

[0012]

However, as described above, the method of dividing a BS reception signal into groups (plurality) composed of one or a plurality of continuous channels and frequency-converting them into BS intermediate frequency signals, Although it is possible to effectively use the frequency range from the VHF band to the UHF band assigned for the television broadcast signal to reliably transmit the BS reception signals for all channels to the subscriber terminal,
In the down converter (and the up converter), a plurality of groups of BS reception signals (the up converter
A plurality of conversion reference signals used for frequency conversion of the intermediate frequency signal (hereinafter also referred to as “conversion local oscillation signal”)
Is usually generated using a plurality of oscillators, and each oscillator generates one of the plurality of reference signals for conversion.Therefore, as many oscillators as the number of reference signals for conversion are required, and the down converter and This not only increases the cost of the upconverter but also increases the size of the downconverter and the upconverter and increases the power consumption.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and converts a BS reception signal from a BS antenna into a BS intermediate frequency signal corresponding to a transmission frequency band of a terrestrial television broadcast signal, thereby obtaining a terrestrial television broadcast. It is an object of the present invention to efficiently perform frequency conversion from a BS reception signal to a BS intermediate frequency signal in a CATV system in which a signal is transmitted to a plurality of subscriber terminals via a common transmission line.

[0014]

Means for Solving the Problems and Effects of the Invention According to a first aspect of the present invention, there is provided a down converter which receives a transmission radio wave from a broadcasting satellite and converts the reception radio wave into an original frequency. A head antenna provided with a BS antenna that converts the frequency to a BS reception signal of a predetermined frequency band lower than a VHF band and a UHF band allocated to terrestrial television broadcasting and outputs the BS reception signal. This is provided on the head-end side in a CATV system for transmitting a BS reception signal from the Internet and another television broadcast signal to a plurality of subscriber terminals via a common transmission line.

The BS reception signal extraction means extracts two or more groups of BS reception signals for one or a plurality of continuous channels from the BS reception signals from the BS antenna, and the plurality of first frequency conversion means The BS reception signals of each group extracted by the BS reception signal extraction means are respectively
U to VHF band assigned for TV broadcast signal
In the frequency domain up to the HF band, the frequency is converted into a BS intermediate frequency signal in a predetermined frequency band that does not overlap with the television broadcast signal. A plurality of conversion reference signals required for the frequency conversion are generated by a first conversion reference signal generation unit. Then, the plurality of BS intermediate frequency signals are mixed by the BS intermediate frequency signal mixing means and transmitted on the transmission line.

As a method of generating a plurality of conversion reference signals by the first conversion reference signal generation means, for example, a method in which a plurality of oscillators are used and each of the oscillators generates one of the plurality of conversion reference signals. Although it is conceivable, in such a method, as described in the related art, as many oscillators as the number of reference signals for conversion are required, which not only increases the cost of the downconverter but also increases the size and consumption of the downconverter. It also causes an increase in power.

Therefore, the first conversion reference signal generation means of the present invention (claim 1) comprises: a reference input signal generation means for generating a reference input signal having a predetermined reference frequency; and an output signal having a frequency corresponding to the control signal. A plurality of variable frequency signal generating means for respectively generating a plurality of variable frequency signal generating means, a plurality of variable frequency signal generating means are provided corresponding to each of the variable frequency signal generating means, and an output signal generated by the corresponding variable frequency signal generating means is fed back and a reference input signal is input , Based on the output signal and the reference input signal,
Control signal generating means for generating a control signal for controlling the frequency of the output signal to a desired frequency, whereby the output signals generated by each variable frequency signal generating means are output as a plurality of conversion reference signals. It is configured so that

Therefore, according to the down converter of the first aspect, only one reference input signal is required irrespective of the type of the conversion reference signal, and only one oscillator for generating the reference input signal is provided. Therefore, compared with the case where a plurality of oscillators are provided according to the type of the reference signal for conversion, the cost of the downconverter can be reduced, the size and weight can be reduced, and the power consumption can be reduced. Can be efficiently converted.

Here, each control signal generation means in the first conversion reference signal generation means of the downconverter according to the first aspect is, specifically, for example, an output which is input as described in the second aspect. A PLL (Phase Lock) that captures a signal and a reference input signal as they are or by dividing or multiplying the frequency thereof, comparing the phases of the captured signals, and outputting a signal corresponding to the phase difference as a control signal.
ed Loop) circuit. With this configuration, a conversion reference signal having a desired frequency can be generated by appropriately setting the frequency division ratio or the multiplication rate of each input signal, and the conversion reference having high frequency accuracy can be achieved by using the PLL. A signal can be generated.

Next, the upconverter according to the third aspect of the present invention converts the BS reception signal from the BS antenna and another television broadcast signal through a common transmission line as in the first aspect.
While transmitting to a plurality of subscriber terminals, the head end side extracts two or more groups of BS reception signals for one or a plurality of continuous channels from the BS reception signals from the BS antenna, and receives the BS of each group. The signals are converted from the VHF band assigned to the television broadcast signal to the UH band, respectively.
In a CATV system provided with a down-converter for converting a frequency into a BS intermediate frequency signal in a predetermined frequency band not overlapping with a television broadcast signal in a frequency domain up to the F band and transmitting the signal on a transmission line, This is provided on the transmission line on the user side.

The BS intermediate frequency signal extracting means extracts the BS intermediate frequency signals of each group from the transmission signal from the head end, and the plurality of second frequency converting means
S of each group extracted by the S intermediate frequency signal extraction means
Each of the S intermediate frequency signals is frequency-converted into a BS reception signal in the original frequency band output from the BS antenna. The plurality of conversion reference signals necessary for this frequency conversion are set to have the same frequency as the plurality of conversion reference signals used by the down-converter to frequency-convert the BS reception signals of each group into BS intermediate frequency signals. , Generated by the second conversion reference signal generation means. Then, a plurality of frequency-converted Bs
The S reception signal is mixed by the BS reception signal mixing means and transmitted to the subscriber terminal.

The second conversion reference signal generation means of the present invention (claim 3) generates a plurality of conversion reference signals by the same method as the first conversion reference signal generation means of claim 1. Specifically, a reference input signal generating means for generating a reference input signal of a predetermined reference frequency, and a plurality of variable frequency signal generation means for respectively generating an output signal of a frequency corresponding to the control signal. Means, provided in plurality corresponding to each of the variable frequency signal generating means, feedback-input an output signal generated by the corresponding variable frequency signal generating means and input a reference input signal, and input the reference signal to the output signal and the reference input signal. Control signal generating means for generating a control signal for controlling the frequency of the output signal to a desired frequency based on the output signal generated by each variable frequency signal generating means. It is one that is configured to output as each of the plurality of conversion reference signal.

Therefore, according to the upconverter of the third aspect, only one reference input signal is required irrespective of the type of the conversion reference signal, and only one oscillator for generating the reference input signal is provided. For this reason, the cost of the upconverter can be reduced, the size and weight can be reduced, and the power consumption can be reduced as compared with the case where a plurality of oscillators are provided according to the type of the conversion reference signal.

Each of the control signal generation means in the second conversion reference signal generation means is, like the control signal generation means according to the second aspect, for example, an input output signal and a reference signal. The input signal may be fetched as it is or by dividing or multiplying the frequency thereof, and the phase of the two fetched signals may be compared, and a PLL circuit that outputs a signal corresponding to the phase difference as a control signal may be used. In this case, the same operation and effect as those of the second aspect can be obtained.

Next, a CATV system according to a fifth aspect receives a transmission radio wave from a broadcasting satellite and converts the reception radio wave into a VHF band lower than the original frequency and allocated to a terrestrial television broadcast. And a head end provided with a BS antenna for frequency-converting and outputting a BS reception signal in a predetermined frequency band higher than the broadcast frequency in the UHF band.
A CATV system for transmitting a BS reception signal from an antenna and another television broadcast signal to a plurality of subscriber terminals via a common transmission line, wherein a CATV system includes:
A down converter according to claim 1 or 2 is provided, and an up converter according to claim 3 or 4 is provided on a transmission line on each subscriber side.

As described above, in a CATV system for transmitting a BS reception signal and another television broadcast signal via a common transmission line, the down converter according to claim 1 or 2 and the up converter according to claim 3 or 4 are used. With the provision, the cost of the entire CATV system can be reduced, the power consumption can be reduced, and the frequency conversion from the BS reception signal to the BS intermediate frequency signal can be performed efficiently.

The CATV of the present invention (claim 5)
In the system, each down-converter and up-converter has only one reference input signal generation means required to generate a plurality of conversion reference signals. However, if the downconverter and the upconverter each have the reference input signal generating means as described above, the downconverter and the upconverter may be down-converted due to aging of the reference input signal generating means and differences in the installation environment. And the BS reception signal before the conversion by the first frequency conversion means in B and the B signal after the conversion by the second frequency conversion means in the up-converter.
There is a risk that so-called frequency drift will occur even though the S-received signal should have exactly the same frequency as before, that is, a CATV system. It is common for the upconverter on the user side to be installed at a location away from the other, and there is a large difference between the environment where the downconverter is installed (such as weather conditions and electromagnetic environment) and the environment where the upconverter is installed. Is likely to occur, and the greater the difference in the environment, the larger the frequency drift may be.

Therefore, for example, the reference input signal used in the downconverter and the reference input signal used in the upconverter are shared to form the same single reference input signal, and the downconverter and the upconverter share the same reference input signal. It is preferable to construct a CATV system using one reference input signal.

In order to realize the above CATV system,
Specifically, the down converter according to claim 1 or 2 may be configured, for example, as described in claim 6. That is, the down converter according to the sixth aspect is provided with a local signal transmitting means for transmitting a reference input signal generated by the reference input signal generating means as a local signal on a transmission line. That is, the reference input signal generated by the reference input signal generating means is not only used in the down converter, but is also sent out of the down converter via the transmission line. By doing so, it becomes possible for the subscriber to use the reference input signal used for frequency conversion in the down converter.

Here, if the frequency of the reference input signal is a frequency that can be transmitted on the transmission line, the reference input signal can be transmitted as it is as a local signal. If a frequency that cannot be used is adopted, it cannot be transmitted as it is as a local signal.

Therefore, the local signal transmitting means provided in the down converter according to claim 6 further transmits, for example, the reference input signal generated by the reference input signal generating means via a transmission line as described in claim 7. It is preferable that the apparatus further includes reference input signal frequency conversion means for converting a signal into a local signal in a frequency band that can be transmitted to the subscriber terminal and is not used for signal transmission to the subscriber terminal. . In this way, even if the reference input signal has a frequency that cannot be transmitted on the transmission line, it is frequency-converted and transmitted onto the transmission line, so that a local signal is reliably generated regardless of the frequency of the reference input signal. be able to.

On the other hand, in order to realize the above CATV system (a system in which a reference input signal is shared by a down converter and an up converter), an up converter according to claim 3 or 4 is provided, for example, as described in claim 8. It is good to constitute. That is, in the upconverter according to the eighth aspect, the second conversion reference signal generating means extracts a local signal of a predetermined frequency from a transmission signal from the head end instead of the reference input signal generating means, and Local signal extracting means for inputting the obtained local signal to the control signal generating means instead of the reference input signal.

That is, the second conversion reference signal generating means includes:
It does not have its own reference signal generating means but generates a reference signal for conversion using a local signal transmitted via a transmission line. Thus, for example, when the reference input signal used for frequency conversion from the BS reception signal to the BS intermediate frequency signal by the down converter is transmitted as it is or is frequency converted and transmitted as a local signal on the transmission line, the up converter is used. The side can use the local signal to perform frequency conversion (conversion from the BS intermediate frequency signal to the BS reception signal).

Therefore, it is possible to prevent a frequency drift from occurring between the BS reception signal before frequency conversion in the down converter and the BS reception signal after frequency conversion in the up converter. Moreover, since the reference input signal generating means is not required, the cost of the upconverter can be reduced.

Here, if the frequency of the local signal extracted from the transmission signal is such that the control signal generating means can operate normally and generate the control signal, the local signal is directly used as the control signal generating means. However, there is a possibility that a local signal having a frequency at which the control signal generating means does not operate normally will be transmitted if it is directly input to the control signal generating means.

Therefore, the local signal extracting means provided in the upconverter according to claim 8 further converts the extracted local signal into a frequency at which the control signal generating means can operate, for example, as described in claim 9. It is preferable that a local signal frequency conversion means is provided. With this configuration, the control signal generation unit can be reliably operated regardless of the frequency of the extracted local signal.

Then, as described in claim 10, C
If the ATV system is configured to include the down converter according to claim 6 or 7 on the head end side and the up converter according to claim 8 or 9 on the transmission line of each subscriber, the down converter and the up converter are provided. A system in which the converters perform frequency conversion using the same reference input signal can be configured, and the long-term stability of the CATV system is improved.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, the CAT of the present embodiment
The overall configuration of the V system will be described. FIG.
FIG. 2 is a block diagram for explaining the overall configuration of the TV system.

As shown in FIG. 1, the CATV system according to the present embodiment is configured to be able to transmit a signal of 70 to 770 MHz, transmits a broadcast signal from the head end 1, and transmits a transmission line (specifically, a main line, a branch line). , A distribution line, a drop-in line) 6 and a branch amplifier 2, an extension amplifier 3, a tap-off 4, and a protector 5 provided on the transmission line 6 to supply a broadcast signal to a subscriber's home of the CATV system. is there.

Next, the headend 1 constituting the CATV system will be described. FIG. 2 is a block diagram for explaining the configuration of the head end 1. As shown in FIG. 2, the head end 1 includes a terrestrial broadcast signal transmitted from a ground station, more specifically, a VHF band analog broadcast signal (90 to 108, 170 to 222 MHz in this embodiment) and a UHF band broadcast. A terrestrial broadcast receiving antenna 11 for receiving signals (analog and digital; 470 to 770 MHz in this embodiment), and a reception for amplifying a terrestrial broadcast signal received by the terrestrial broadcast receiving antenna 11 to a predetermined level. An amplifier 12 for receiving a satellite broadcast signal transmitted from a broadcast satellite;
A BS antenna 14 for frequency-converting and outputting a 37 MHz BS reception signal (BS-IF signal), a reception amplifier 15 for amplifying the BS reception signal to a predetermined level, and a BS reception signal that can be transmitted in the CATV system. A down-converter unit for converting the frequency into a BS intermediate frequency signal in a frequency band (70 to 770 MHz); and a mixer for mixing the terrestrial broadcast signal and the BS intermediate frequency signal frequency-converted in the down-converter unit. The signal is output from the output terminal Tout. Although not shown, the head end 1 has 451.25 used for adjusting the level of a transmission signal in the branch amplifier 2 or the like.
A pilot signal generator for generating a pilot signal of MHz is also provided, and the generated pilot signal is mixed with a terrestrial broadcast signal and a BS intermediate frequency signal frequency-converted in the down-converter unit 20,
Output from the output terminal Tout.

In the down-converter section 20, the BS reception signal is first split into two by the splitter 21, and the split signal is input to band-pass filters (hereinafter referred to as "BPF") 22, 26, respectively. The passable frequency band of the BPF 22 is 1030
1145 MHz, and the passable frequency band of the BPF 26 is 1145 to 1337 MHz. For this reason, BP
From F22, one of satellite broadcasts of all eight channels
1030-1145MHz corresponding to 3,5 channels
, And similarly, the BPF 26 outputs BS reception signals of 1145 to 1337 MHz corresponding to the 7, 9, 11, 13, and 15 channels. The signal output from the BPF 22 is input to the mixer 23, and the signal output from the BPF 26 is input to the mixer 27.

The mixer 23 outputs a signal from the first conversion local oscillation signal generator 31 (specifically, the voltage-controlled oscillator 31).
a) of the first conversion local oscillation signal of 446 MHz which is output from the second conversion local oscillation signal generation unit 32 (specifically, the voltage controlled oscillator 32).
892 MHz of the second local oscillation signal for conversion, which is output from (a). In addition, both the first local oscillation signal for conversion and the second local oscillation signal for conversion correspond to the conversion reference signal of the present invention.

Here, the first conversion local oscillation signal generator 3
The first and second conversion local oscillation signal generators 32 will be described. First, in the first conversion local oscillation signal generator 31,
In order to output a first conversion local oscillation signal of 446 MHz from the voltage controlled oscillator (VCO) 31a, a reference signal of an oscillation frequency of 10 MHz output from a reference signal oscillator 29 such as a crystal oscillator (for example, a reference input signal of the present invention) Equivalent)
The frequency divider 31b divides the frequency into 1/10 the frequency (that is, 1 MHz) and inputs the frequency to the phase comparator 31c.
Further, the first local oscillation signal for conversion output from the VCO 31a is also input to the phase comparator 31c by the frequency divider 31e.
The signal is frequency-divided to 446 and fed back.

In the phase comparator 31c, the input 1 MH
The phase of the z reference signal and the phase of the first local oscillation signal for frequency division are compared, and an error signal proportional to the phase difference is output. This error signal is input to a loop filter (low-pass filter) 31d to remove unnecessary harmonic components, extract a signal component necessary for controlling the VCO 31a, and output it as a control signal to the VCO 31a. In the VCO 31a, the frequency of the first conversion local oscillation signal as an output signal thereof is controlled by the input control signal (controlled so that the phase difference between the signals input to the phase comparator 31c is eliminated). 446M in form
Hz.

That is, the first conversion local oscillation signal generator 3
1 is a PLL circuit (more specifically, the VCO 3 of the first conversion local oscillation signal generator 31).
1a corresponds to the PLL circuit), and the VCO 3
The first conversion local oscillation signal output from 1a is 1/44
6 is compared with the phase of the 10 MHz reference signal output from the reference signal oscillator 29 so that the frequency of the divided signal becomes 1/10.
1a is feedback-controlled, and as a result, the VCO 31a
446 MHz of the first local oscillation signal for conversion.

The second conversion local oscillation signal generator 32 has exactly the same configuration as the first conversion local oscillation signal generator 31 except that the frequency division ratio of the frequency divider is different. That is, 10 MH from the reference signal oscillator 29 is supplied to the phase comparator 32c.
The z reference signal is frequency-divided (that is, 1 MHz) by the frequency divider 32b to 1/10 frequency, and is input.
An output signal output as a second local oscillation signal for conversion from O32a is frequency-divided by a frequency divider 32e to a frequency of 1/892, and is fed back and input.

The phase comparator 32c, like the phase comparator 31c, compares the phases of the input signals and outputs an error signal, and the error signal passes through a loop filter 32d (the same as the loop filter 31d). V as a control signal
It is input to the CO 32a. This controls the second conversion local oscillation signal output from the VCO 32a to be 892 MHz. In other words, the second conversion local oscillation signal generator 32 is also configured by a PLL circuit.

The mixer 23 has 1030 to 114
The 5 MHz BS reception signal is frequency-converted using the first conversion local oscillation signal of 446 MHz, and is input to the BPF 24 (passable frequency band: 584 to 699 MHz).
Then, from the BPF 24, the frequency of the BS reception signal corresponding to the 1, 3, and 5 channels is reduced by 446 MHz.
BS intermediate frequency signal of 4 to 699 MHz (hereinafter referred to as "first BS
(Referred to as “intermediate frequency signal”). Similarly, the mixer 27 converts the frequency of the BS received signal of 1145 to 1337 MHz using the 892 MHz second local oscillation signal for conversion, and outputs the BPF 28 (passable frequency band:
253-445 MHz). Then, BPF2
8, the frequency of BS reception signals corresponding to channels 7, 9, 11, 13, and 15 is reduced by 892 MHz to 253.
A BS intermediate frequency signal of ４445 MHz (hereinafter, referred to as “second BS intermediate frequency signal”) is output. Then, the first BS intermediate frequency signal and the second BS intermediate frequency signal are input to the mixer 13 after being mixed by the mixer 25, and mixed with the terrestrial broadcast signal by the mixer 13 as described above, and the output terminal Tout Output from B
The frequency distributions of the S intermediate frequency signal, the first BS intermediate frequency signal, and the second BS intermediate frequency signal are as shown in FIG.

When the transmission signal in which the terrestrial broadcast signal, the first BS intermediate frequency signal, and the second BS intermediate frequency signal are mixed is transmitted to the subscriber's home, the up converter 40 in the subscriber's home uses the first BS intermediate frequency. Signal and second BS
The intermediate frequency signal is returned to the original BS reception signal, and terrestrial broadcasting and satellite broadcasting are viewed.

Next, the up converter 40 will be described. FIG. 4 is a block diagram for explaining the configuration of the upconverter. As shown in FIG. 4, in the up-converter 40, the transmission signal input from the input terminal Tin includes a splitter 41 that splits a part of the signal, and a low-pass filter (hereinafter referred to as “LPF”) having a cutoff frequency of 770 MHz. ) Is output from the output terminal Tout1 via the output terminal Tout1.

The transmission signal split by the splitter 41 is input to the splitter 44 via the amplifier 43, split into two by the splitter 44, and input to the BPFs 45 and 50, respectively. The passable frequency band of BPF45 is 584-6
It is 99 MHz, and the passable frequency band of the BPF 50 is 253 to 445 MHz.
The first BS intermediate frequency signal is output, and from the BPF 50,
A second BS intermediate frequency signal is output. And BPF4
The first BS intermediate frequency signal output from 5 is input to mixer 46, and the second BS intermediate frequency signal output from BPF 50 is input to mixer 51. Similarly to the down-converter unit 20 of the head end 1, the mixer 46 supplies 446 output from the third conversion local oscillation signal generator 56 to the mixer 46.
The third conversion local oscillation signal of MHz is input to the mixer 5.
1 is supplied with the 892 MHz fourth conversion local oscillation signal output from the fourth conversion local oscillation signal generation unit 57.

The third conversion local oscillation signal generator 56 and the fourth conversion local oscillation signal generator 57 are respectively the first conversion local oscillation signal generator in the down converter 20 of FIG. 31 and the second local oscillation signal generator 32 for conversion.
The third conversion local oscillation signal (same as the first conversion local oscillation signal in FIG. 2) of the above-described desired frequency is obtained by taking in the reference signal having the oscillation frequency of 10 MHz output from 9.
And a fourth conversion local oscillation signal (same as the second conversion local oscillation signal in FIG. 2). Therefore, the third
Each of the components of the conversion local oscillation signal generator 56 and the fourth conversion local oscillation signal generator 57 includes the first conversion local oscillation signal generator 31 and the second conversion local oscillation signal generator 32 shown in FIG. The same reference numerals are given and the description is omitted.

The mixer 46 has a capacity of 584 to 699M.
Hz first BS intermediate frequency signal is subjected to frequency conversion using a 446 MHz third conversion local oscillation signal, and the BPF 47
(Passable frequency band: 1030 to 1145 MHz). Therefore, the BPF 47 outputs BS reception signals of 1030 to 1145 MHz corresponding to the 1, 3, and 5 channels. Similarly, the mixer 51
Is the second BS intermediate frequency signal of 253 to 445 MHz,
The frequency is converted by using the 892 MHz fourth local oscillation signal for conversion, and the BPF 52 (passable frequency band: 1145 to
1337MHz), and from BPF52, 7,
1145 corresponding to 9, 11, 13, and 15 channels
A 1337 MHz BS reception signal is output. And 1030 corresponding to channels 1, 3, and 5
BS received signal of １１４1145 MHz and 7, 9, 11, 1
1145 to 1337MH corresponding to 3,15 channels
The BS received signal of signal z is mixed by a mixer 48 and output via a high-pass filter (hereinafter referred to as “HPF”) 49 (cutoff frequency: 1030 MHz or more) to an output terminal T.
Output from out2.

The output signal from the output terminal Tout1 is directly input to a television receiver (not shown).
An output signal from the output terminal Tout2, that is, a BS reception signal is input to a television receiver via a BS tuner (not shown). In the present embodiment, the BPFs 22 and B
Each of the PFs 26 corresponds to the BS reception signal extracting means of the present invention, and includes the mixer 23 and the BPF 24 and the mixer 27 and the BP
F28 corresponds to the first frequency conversion means of the present invention, and the mixer 25 corresponds to the BS intermediate frequency signal mixing means of the present invention. The reference signal oscillator 29, the first conversion local oscillation signal generation section 31, The two-conversion local oscillation signal generator 32 constitutes the first conversion reference signal generator of the present invention, and the reference signal oscillator 29 among them corresponds to the reference input signal generator of the present invention (claims 1 and 2). And each VCO 31a, 32a
All correspond to the variable frequency signal generating means of the present invention (claims 1 and 2), the configuration of the first conversion local oscillation signal generator 31 excluding the VCO 31a, and the second conversion local oscillation signal generator Any of the components 32 except for the VCO 32a corresponds to the control signal generating means of the present invention (claims 1 and 2).

Each of the BPFs 45 and 50 corresponds to the BS intermediate frequency signal extracting means of the present invention.
6 and BPF 47, and the mixers 51 and BPF 52 all correspond to the second frequency conversion means of the present invention, the mixer 48 corresponds to the BS reception signal mixing means of the present invention, the reference signal oscillator 29, and the third conversion local part. The oscillation signal generator 56 and the fourth conversion local oscillation signal generator 57 constitute a second conversion reference signal generator of the present invention.
9 corresponds to the reference input signal generating means of the present invention (claims 3 and 4), and each of the VCOs 31a and 32a corresponds to the variable frequency signal generating means of the present invention (claims 3 and 4).
The configuration of the conversion local oscillation signal generator 56 excluding the VCO 31a and the configuration of the fourth conversion local oscillation signal generator 57 excluding the VCO 32a are both control signal generation according to the present invention (claims 3 and 4). It corresponds to a means.

Next, the effects of the CATV system of the present embodiment will be described. According to the CATV system of the present embodiment, the downconverter unit 20 on the head end 1 side
In the above, one reference signal is sufficient regardless of the type of the local oscillation signal for conversion (two types in the above embodiment), and only one reference signal oscillator 29 for generating the reference signal is required. Compared with the case where a plurality of reference signal oscillators are provided according to the type of the local oscillation signal, the down converter unit 20 can be reduced in cost, reduced in size and weight, and further reduced in power consumption. Similarly, for the upconverter 40, only one reference signal oscillator 29 needs to be provided irrespective of the type of the local oscillation signal for conversion, so that the upconverter 40 can be reduced in cost, reduced in size and weight, and further reduced in power consumption. Becomes possible. As a result, the cost and the power consumption of the entire CATV system can be reduced, and the frequency conversion from the BS reception signal to the BS intermediate frequency signal can be performed efficiently.

The embodiments of the present invention are not limited to the above-mentioned embodiments at all, and it goes without saying that various forms can be adopted as long as they fall within the technical scope of the present invention. For example, the frequency division ratio of each frequency divider in each of the conversion local oscillation signal generators 31, 32, 56, and 57 of the above embodiment is not limited to the above example, and the output signal of a desired frequency from each VCO may be used. (Each conversion local oscillation signal) may be appropriately set. The oscillation frequency of the reference signal oscillator 29 can also be arbitrarily selected.

The frequency division of the reference signal and the conversion local oscillation signal is not limited to the frequency division by the frequency divider. Or both of them may be frequency-multiplied and input to the phase comparator. That is, it is only necessary that the desired local oscillation signal for conversion can be obtained as a result by dividing or multiplying the reference signal and the local oscillation signal for conversion, respectively.

In particular, for example, the oscillation frequency of the reference signal oscillator 29 in the down-converter section 20 is 446 MHz.
z, the reference signal and the first local oscillation signal for conversion may be input to the phase comparator 31c as they are, so that the frequency divider 31b and the frequency divider 3
1e becomes unnecessary, and the downconverter section 20 can be configured more economically and efficiently. The same applies to the up converter 40.

Further, in the above embodiment, the upconverter 40 is provided at each subscriber's house.
For example, as shown in FIG. 5A, an up-converter 59 may be provided between the extension amplifier 3 and the tap-off 4. In the above embodiment, the terrestrial broadcast signal is output from the output terminal Tout1, and the BS reception signal is output from the output terminal Tout2.
When the up-converter 59 is installed on the transmission line 6 as shown in (a), a mixer is installed before the LPF 42 and the HPF 49, and the terrestrial broadcast signal, the BS reception signal, and one output terminal are provided. (Not shown).

When the up-converter 59 is installed between the extension amplifier 3 and the tap-off 4, the number of up-converters is smaller than when the up-converter is provided for each subscriber's house. Is significantly less and very economical. However, the up converter 59
To each subscriber's house, it is necessary to transmit the signal through a transmission line capable of transmitting a BS reception signal, that is, a transmission line capable of transmitting up to about 1340 MHz.

Also, as shown in FIG. 5 (a), a branch unit, a branch amplifier, a distributor, a distribution amplifier, an extension amplifier, a tap-off unit, which is not installed alone on the transmission line 6, but is installed on the transmission line 6 And so on. FIG. 5B shows a CAT when an upconverter is built in an extension amplifier.
FIG. 6 is a block diagram for explaining a configuration of the extension amplifier 60 with a built-in up-converter shown in FIG. 5B. The extension amplifier with built-in up-converter 60 is a modified example of the up-converter 40 of the above embodiment.

As shown in FIG. 6, in the extension amplifier 60 with a built-in up-converter, the transmission signal input from the input terminal Tin is divided into an equivalent amplifier 61, an attenuator 62, an amplifier 63, an automatic gain controller 64, an amplifier 65, and a branch. Vessel 66, LPF6
7 (cutoff frequency: 770 MHz), which is output from the output terminal Tout via the mixer 68. Note that the equivalent amplifier 61, the attenuator 62, and the automatic gain controller 64 are well-known and will not be described.

The transmission signal split by the splitter 66 is split into two by the splitter 69, and the BPF 70,
74 is input. The passable frequency band of the BPF 70 is 584 to 699 MHz, and the passable frequency band of the BPF 74 is 253 to 445 MHz.
0, the first BS intermediate frequency signal is output and the BPF7
4 outputs the second BS intermediate frequency signal and the first BS
The intermediate frequency signal is input to mixer 71, and the second BS intermediate frequency signal is input to mixer 75.

The mixer 71 receives the 446 MHz third conversion local oscillation signal output from the third conversion local oscillation signal generating section 56, and the mixer 75 inputs the fourth conversion local oscillation signal generation section. 892 MHz output from the unit 57
Of the fourth conversion local oscillation signal. The third conversion local oscillation signal generator 56 is exactly the same as the third conversion local oscillation signal generator 56 in the up-converter 40 (FIG. 4) of the above-described embodiment (therefore, the sign is also the same).
The fourth conversion local oscillation signal generation section 57 is also the same as the fourth conversion local oscillation signal generation section 57 in the up-converter 40 of the above embodiment (therefore, the sign is also the same).

The mixer 71 frequency-converts the first BS intermediate frequency signal using the third conversion local oscillation signal,
BPF72 (passable frequency band: 1030 to 1145)
MHz). Then, from the BPF 72, 1,
1030-1145MHz corresponding to 3,5 channels
Is output. Similarly, mixer 75
The second BS intermediate frequency signal is frequency-converted using the fourth conversion local oscillation signal, and the BPF 76 (passable frequency: 114
5 to 1337 MHz), and from the BPF 76,
114 corresponding to channels 7, 9, 11, 13, and 15
A BS reception signal of 5 to 1337 MHz is output. Then, 1030 to 114 corresponding to channels 1, 3, and 5
5 MHz BS reception signal and 7, 9, 11, 13, 15
1145 to 1337 MHz BS corresponding to the channel
The received signal is mixed by the mixer 73 and the amplifier 8
2, output from an output terminal Tout via an automatic gain controller 83, an amplifier 84, an HPF 85 (cutoff frequency: 1030 MHz), and a mixer 68.

When the up-converter is incorporated in the extension amplifier as described above, the number of the up-converters is greatly reduced as compared with the case where the up-converter is provided for each subscriber's house, which is very economical. It is a target. However,
A transmission line capable of transmitting a BS reception signal, that is, about 134
Signals need to be transmitted over transmission lines that can transmit up to 0 MHz.

In the above embodiment, the head end 1
Down converter section 20 and up converter 40 inside
However, reference signals necessary for performing frequency conversion are individually generated. That is, in the down converter section 20, the reference signal oscillator 29 generates a 10 MHz reference signal, and in the up converter 40, the reference signal oscillator 29 also generates a 10 MHz reference signal.

As described above, when the down-converter section 20 and the up-converter 40 are each provided with the reference signal oscillator 29, the down-converter section 20 and the up-converter 40 generate the reference signal oscillator 29, for example, due to aging, temperature difference, or ambient environment. There is a possibility that the frequency of the reference signal may be different even if it is a slight difference. Then, for example, the BS intermediate frequency signal (channels 1, 3, and 5) before frequency conversion by the mixer 23 in the down converter unit 20 and the BS intermediate frequency signal after frequency conversion by the mixer 46 in the up converter 40 (Same as 1,3,5
Frequency drift with respect to the channel).

Therefore, the CATV system of the above embodiment converts the reference signal generated by, for example, the reference signal oscillator 29 of the down-converter section 20 into a frequency that can be transmitted on the transmission line 6 to another signal ( The signal is transmitted onto the transmission line 6 together with each BS intermediate frequency signal and the terrestrial broadcasting signal. The up-converter 40 extracts the above-mentioned reference signal from various signals transmitted on the transmission line 6 and converts it into the up-converter 40. It may be configured to be used for frequency conversion within. FIGS. 8 and 9 show one configuration example of a headend and an upconverter for realizing the CATV system having the above configuration.

First, in the head end 80 shown in FIG. 8, the reference signal generated by the reference signal oscillator 29 is also input to the local signal generator 86, and the local signal generator 8
The configuration is exactly the same as that of the head end 1 of FIG. 2 except that the local signal from the head end 6 is transmitted onto the transmission line 6 via the LPF 87 and the mixer 88. Therefore, the same components as those in FIG. 2 are denoted by the same reference numerals as those in FIG.

Downconverter section 8 of head end 80
1, the frequency of 10 MHz generated by the reference signal oscillator 29
Is also input to the local signal generator 86. The local signal generator 86 is configured as a PLL circuit, similarly to the conversion local oscillation signal generators 31 and 32, and the reference signal from the reference signal oscillator 29 is divided by a frequency divider 86b into a 1/20 frequency. The output signal output from the VCO 86a as a local signal is also frequency-divided by the frequency divider 86e into a frequency of 1/139 and fed back to the phase comparator 86c. Is done. A local signal of 69.5 MHz is output from the local signal generator 86 configured as described above, and the LPF 87 (cutoff frequency: 70M) is output.
Hz) and the mixer 88 to be transmitted onto the transmission line 6.

Here, in the description of the above embodiment, the present C
The frequency band of signals that can be transmitted by the ATV system is 70-
Although described as being 770 MHz, this band has no attenuation by a filter when a signal passes through a filter (not shown) provided in various transmission devices such as the branch amplifier 2 and the extension amplifier 3 installed on the transmission line 6. (Approximately 0 dB) band, which does not mean that a signal of a frequency slightly deviating from the above band cannot be transmitted at all.

More specifically, the passing attenuation amount of the filters provided in the various transmission devices on the transmission line 6 is, for example, always about 0 dB in the signal frequency band (70 to 770 MHz). , Or as the frequency becomes higher than 770 MHz. This is a characteristic that a general filter usually has. Therefore, the frequency band of the signal that can be transmitted in the above embodiment is strictly 70 to 770 MHz.
In addition to the band, the signal level is slightly lower than 70 MHz or higher than 770 MHz, and the signal level when the signal from the head end is transmitted to the terminal (up-converter) is higher than the signal level at the terminal. A band that holds the minimum level or more that can use the signal is included.

Then, 69.5 which is the frequency of the local signal generated from local signal generating section 86 shown in FIG.
In the case of MHz, although the signal is slightly attenuated by the filter as compared with a signal in the band of 70 to 770 MHz, when the signal is transmitted to the subscriber premises (up-converter), the signal is frequency-converted in the up-converter (details will be described later).
Holds levels available for use. Of course, it is of course possible to use the band of 70 to 770 MHz as a local signal.
70MHz band is for CATV for TV signal transmission etc.
Bandwidth used for various services in the system,
Which channel is actually used in which band depends on CA
Each TV service provider differs.

Therefore, in the above example (FIGS. 8 and 9), the frequency of the local signal is a frequency other than the band 70 to 770 MHz actually used for the CATV service, and is slightly lower than the lower limit (70 MHz) of the band. Low 6
9.5 MHz is adopted.

It is needless to say that 69.5 MHz used as the frequency of the local signal is merely an example. For example, an unused band within the band of 70 to 770 MHz may be used, or 70 to 770 MHz may be used. The frequency band outside the band and can be transmitted to the subscriber's home (downlink transmission) may be determined as appropriate, and can be reliably transmitted to the subscriber's home side. Any frequency band can be used as long as it can be used as a reference signal). Further, in order to compensate for the attenuation caused by the local signal passing through the filters of various transmission devices, the local signal may be appropriately amplified by an amplifier or the like and transmitted to the transmission line 6. If you do this,
A frequency band usable as a local signal other than the 770 MHz band can be wider.

Next, the up-converter 90 shown in FIG.
The signal from the amplifier 43 is further divided into two by the divider 91, and the signal passing through the BPF 92 is divided by the divider 93.
4 to the third local oscillation signal generator 94 and the fourth local oscillator signal generator 95 for conversion, and the configuration of each local oscillator signal generator 94 and 95 for conversion is shown in FIG. The configuration is exactly the same as that of the up-converter 40 shown in FIG. 4, except that it is slightly different from the conversion local oscillation signal generators 56 and 57. Therefore, the same components as those in FIG. 4 are denoted by the same reference numerals as those in FIG. 4, and the description thereof will be omitted.

In the up-converter 90, the head-end 8 branched by the branching device 41 and amplified by the amplifier 43.
The transmission signal from 0 is split into two by the splitter 91, and one of the split outputs is input to the splitter 44 and the other is input to the BPF 92. The BPF 92 is for passing a local signal of 69.5 MHz and blocking a signal of 70 MHz or more. In order to pass only a narrow band signal having a bandwidth of 20 KHz centered on 69.5 MHz, the narrow band pass filter is used. It is composed of a crystal filter with excellent characteristics.

69.5M extracted by this BPF92
The local signal of Hz is frequency-divided by a frequency divider 93 to a half frequency (34.75 MHz), and is input to each of the local oscillation signal generators 94 and 95 for conversion. That is, in the upconverter 40 of the above embodiment, the reference signal oscillator 2
9, the up-converter 90 of FIG. 9 does not include a reference signal oscillator. Instead, the up-converter 90 is generated by the down-converter section 81 of the head end 80 and transmitted through the transmission line 6. The local signal is used as a reference signal to be input to each of the conversion local oscillation signal generators 94 and 95.

Local oscillation signal generators 94 and 95 for conversion
4 is configured as a PLL circuit in substantially the same manner as each of the conversion local oscillation signal generators 56 and 57 in FIG.
In comparison with, the operation itself is exactly the same except for the frequency division ratio in each of the frequency dividers 94b, 94e, 95b, 95e. Therefore, a detailed description of the conversion local oscillation signal generators 94 and 95 is omitted here.

In the case where the up-converter is built in the extension amplifier as described with reference to FIG. 6, for example, the up-converter built-in extension amplifier 10 shown in FIG.
It may be configured as 0. That is, the up-converter built-in extension amplifier 100 of FIG. 10 has the BPF 102 (the BPF 92 of FIG. 9) just like the up-converter 90 of FIG.
), A local signal is extracted from the signal transmitted on the transmission line 6 and divided by the frequency divider 103 (the frequency divider 93 in FIG. 9).
) Is input to the local oscillation signal generators 94 and 95 for conversion. As a result, each local oscillation signal for conversion input to each of the mixers 71 and 75 is generated. The other configuration is the same as that of the up-converter built-in extension amplifier 60 of FIG.

In the down converter 81 of FIG. 8, the local signal generator 86, the LPF 87 and the mixer 8
Reference numeral 8 denotes the local signal transmitting means of the present invention, and the local signal generating section 86 corresponds to the reference input signal frequency converting means of the present invention. Further, in the up-converter 90 of FIG. 9, the BPF 92 and the frequency divider 93 constitute the local signal extracting means of the present invention, and the frequency divider 93 corresponds to the local signal frequency converting means of the present invention.

As described above, in the CATV system including the head end 80 of FIG. 8 and the up converter of FIG.
The reference signal from the reference signal oscillator 29 included in
The signal is converted into a local signal of 5 MHz and transmitted onto the transmission line 6. Then, the local signal is extracted by the up-converter 90, and the extracted local signal is used as a reference signal when frequency conversion is performed by the up-converter 90.

Therefore, in the upconverter 90, an expensive reference signal oscillator is generally unnecessary, and the cost of the upconverter 90 can be reduced, and the cost of the CATV system can be reduced. Moreover, the down converter unit 8
Since the same reference signal (local signal) as that used for frequency conversion in 1 is used for frequency conversion in the up-converter 90, no frequency drift occurs and the long-term stability of the entire system is improved.

In the head end 80 shown in FIG.
Although the local signal is transmitted via the mixer 88, for example, as shown in FIG. 11, the local signal passing through the LPF 87 is transmitted from the output terminal Tout as it is, and the ground signal mixed by the mixer 13 is output. The wave broadcast signal and the BS intermediate frequency signal are also HPF (cutoff frequency: 9).
(0 MHz) 111 and transmitted from the output terminal Tout together with the local signal.

The up-converter 90 shown in FIG.
In the above, the signal from the amplifier 43 is divided into two by the distributor 91. For example, as shown in FIG.
3 from the HPF 121 (cutoff frequency: 5).
84 MHz), LPF122 (cutoff frequency: 70)
MHz) and the BPF 50 may be used to extract signals in required frequency bands through three filters.

Further, in the up-converter 90 shown in FIG.
The local signal of 69.5 MHz is halved by the frequency divider 93.
, And is input to the conversion local oscillation signal generators 94 and 95. The conversion local oscillation signal generators 94 and 95 convert the input local signal into the frequency dividers 94b and 95b. Although the frequency is divided into 1/3475, the local signal after frequency-dividing by 1/2 in frequency divider 93 is further divided into 1 by frequency divider 123 as in an up-converter 120 shown in FIG. / 3475, and the divided local signal is distributed by the distributor 124 and input to the third conversion local oscillation signal generator 125 and the fourth conversion local oscillation signal generator 126, respectively. You can do it. Each of the conversion local oscillation signal generators 125 and 12 shown in FIG.
Reference numeral 6 denotes each of the conversion local oscillation signal generators 94 and 9 shown in FIG. 9 except that the input stage has no frequency divider (divided by 1/3475).
Exactly the same as 5.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a CATV system according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of a head end according to the present embodiment.

FIG. 3 is a frequency distribution diagram of a BS reception signal, a first BS intermediate frequency signal, and a second BS intermediate frequency signal of the present embodiment.

FIG. 4 is a block diagram illustrating a configuration of an upconverter according to the embodiment.

FIG. 5 is a block diagram for explaining another example of the CATV system of the present embodiment.

FIG. 6 is a block diagram for explaining a configuration of an extension amplifier with a built-in up-converter.

FIG. 7 is a frequency distribution diagram of a conventional BS reception signal and a BS intermediate frequency signal.

FIG. 8 is a block diagram showing another example of the head end of the embodiment.

FIG. 9 is a block diagram showing another example of the upconverter of the present embodiment.

FIG. 10 is a block diagram showing another embodiment of the extension amplifier with a built-in up-converter.

FIG. 11 is a block diagram showing another example of the head end of the embodiment.

FIG. 12 is a block diagram showing another example of the upconverter of the present embodiment.

[Explanation of symbols]

1, 80 head end, 2 branch amplifier, 3 extension amplifier, 4 tap-off, 5 protector, 6 transmission line, 11
... terrestrial broadcast receiving antenna, 12, 15 ... receiving amplifier,
13, 25, 48, 68, 73, 88 ... mixer, 14 ...
BS antenna, 20, 81, 110 ... down converter section, 21, 44, 69, 91, 101 ... distributor, 22,
24, 26, 28, 45, 47, 50, 52, 70, 7
2, 74, 76, 92, 102... BPF (bandpass filter), 23, 27, 46, 51, 71, 75... Mixer, 29... Reference signal oscillator, 31. , 32a, 86a, 94a, 95a
... voltage controlled oscillators, 31b, 32b, 31e, 32e,
86b, 86e, 93, 94b, 94e, 95b, 95
e, 103, 123 ... frequency divider, 31c, 32c, 86
c, 94c, 95c... phase comparators, 31d, 32d, 8
6d, 94d, 95d: loop filter, 32: second conversion local oscillation signal generator, 40, 59, 90, 120 ...
Up-converter, 41, 66 ... branch device, 42, 67,
87, 122... LPF (low-pass filter), 43, 6
3, 65, 82, 84 ... amplifier, 49, 85, 111,
121 ... HPF (High Pass Filter), 56, 94, 1
25: third conversion local oscillation signal generator, 57, 95, 1
26: fourth conversion local oscillation signal generator, 60, 100 ...
Extension amplifier with built-in up-converter, 61 ... Equivalent amplifier,
62: attenuator, 64, 83: automatic gain controller, 86: local signal generator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C064 BA01 BA07 BB05 BC16 BC21 BD08 DA05 5K020 AA03 AA05 BB09 DD11 DD13 FF04 FF05 5K062 AA07 AA08 AA09 AA10 AA11 AB14 AE01

Claims (10)

[Claims] A radio wave transmitted from a broadcast satellite is received, and the received radio wave is transmitted at a predetermined frequency lower than an original frequency and higher than a broadcast frequency of a VHF band and a UHF band allocated to a terrestrial television broadcast. A BS antenna for frequency-converting and outputting a BS reception signal in a frequency band is provided at a head end, and a BS reception signal from the BS antenna and another television broadcast signal are transmitted to a plurality of subscribers via a common transmission line. In a CATV system for transmitting to a user terminal, a BS reception signal provided on the head end side and extracting two or more groups of BS reception signals for one or a plurality of continuous channels from BS reception signals from the BS antenna Extracting means; and B of each group extracted by the BS received signal extracting means.
S received signals are respectively assigned in the frequency domain from the VHF band to the UHF band assigned for the television broadcast signal,
And a plurality of first frequency-converted BS intermediate frequency signals in a predetermined frequency band that do not overlap with the television broadcast signal.
Frequency conversion means; BS intermediate frequency signal mixing means for mixing the plurality of BS intermediate frequency signals frequency-converted by the plurality of first frequency conversion means and transmitting the mixed signal on the transmission line; and the plurality of first frequency conversion means The means is the BS of each group.
A first conversion reference signal generating means for generating a plurality of conversion reference signals necessary for frequency-converting a received signal into the BS intermediate frequency signal in a predetermined frequency band, respectively, The first conversion reference signal generation means includes: a reference input signal generation means for generating a reference input signal having a predetermined reference frequency; a plurality of variable frequency signal generation means each for generating an output signal having a frequency corresponding to the control signal; A plurality of output signals are provided corresponding to the respective variable frequency signal generating means, and the output signals generated by the corresponding variable frequency signal generating means are fed back and the reference input signal is input. Based on the control signal generating means for generating the control signal for controlling the frequency of the output signal to a desired frequency, Down converter, wherein the variable frequency signal generating means for outputting an output signal generated as each of the plurality of conversion reference signal. 2. The control signal generating means receives the output signal and the reference input signal as they are or by dividing or multiplying the frequency of the output signal and the reference input signal, and compares the phases of the two signals. 2. The down converter according to claim 1, further comprising a PLL circuit that outputs a signal corresponding to the phase difference as the control signal. 3. Receiving a transmission radio wave from a broadcasting satellite, and setting the reception radio wave to a predetermined frequency lower than the original frequency and higher than the VHF band and UHF band broadcasting frequencies allocated to terrestrial television broadcasting. A BS antenna for frequency-converting and outputting a BS reception signal in a frequency band is provided at a head end, and a BS reception signal from the BS antenna and another television broadcast signal are transmitted to a plurality of subscribers via a common transmission line. At the head end side, from one of the BS reception signals from the BS antenna,
S Received signals are extracted from two or more groups, and BS of each group is extracted.
Each of the received signals is frequency-converted into a BS intermediate frequency signal of a predetermined frequency band in a frequency range from a VHF band to a UHF band allocated for the television broadcast signal and not overlapping with the television broadcast signal. In a CATV system provided with a downconverter for transmitting the signal on the transmission line, the CATV system is provided on the transmission line of each of the subscribers, and converts a BS intermediate frequency signal of each group from among transmission signals from the head end. The BS intermediate frequency signal extracting means to be extracted, and the BS intermediate frequency signals of each group extracted by the BS intermediate frequency signal extracting means are respectively frequency-converted into BS reception signals in the original frequency band output from the BS antenna. A plurality of second frequency conversion means for converting; and a plurality of BS reception signals frequency-converted by the plurality of second frequency conversion means. BS reception signal mixing means for transmitting to the subscriber side terminal, and the plurality of second frequency conversion means includes a BS for each group.
The down-converter was used to frequency-convert the BS reception signals of each group into the BS intermediate frequency signals, respectively, as reference signals for conversion used to frequency-convert the intermediate frequency signals into the original BS reception signals. A second conversion reference signal generating means for generating a conversion reference signal having the same frequency as the plurality of conversion reference signals, wherein the second conversion reference signal generation means comprises a predetermined reference. A reference input signal generating means for generating a reference input signal of a frequency; a plurality of variable frequency signal generating means for respectively generating an output signal of a frequency corresponding to the control signal; and a plurality of variable frequency signal generating means provided corresponding to each of the variable frequency signal generating means. The feedback signal is input to the output signal generated by the corresponding variable frequency signal generating means, and the reference input signal is input. Control signal generating means for generating the control signal for controlling the frequency of the output signal to a desired frequency based on a reference input signal, whereby the output signal generated by each of the variable frequency signal generating means is provided. Are output as the conversion reference signals. 4. The control signal generating means receives the output signal and the reference input signal as they are, or divides or multiplies the frequency of the output signal and the reference input signal, and compares the phases of the fetched signals. The up-converter according to claim 3, further comprising a PLL circuit that outputs a signal corresponding to the phase difference as the control signal. 5. Receiving a transmission radio wave from a broadcasting satellite, and making the reception radio wave a predetermined frequency lower than the original frequency and higher than the VHF band and UHF band broadcasting frequencies allocated to terrestrial television broadcasting. A BS antenna for frequency-converting and outputting a BS reception signal in a frequency band is provided at a head end, and a BS reception signal from the BS antenna and another television broadcast signal are transmitted to a plurality of subscribers via a common transmission line. A CATV system for transmitting data to a subscriber terminal, comprising: a down converter according to claim 1 or 2 on the head end side; and an up converter according to claim 3 or 4 on a transmission line on each subscriber side. A CATV system comprising: 6. The downconverter according to claim 1, further comprising a local signal transmitting means for transmitting a reference input signal generated by said reference input signal generating means as a local signal onto said transmission line. 7. The local signal transmitting means has a frequency band in which the reference input signal can be transmitted to the subscriber terminal via the transmission line, and for transmitting a signal to the subscriber terminal. 7. The down-converter according to claim 6, further comprising a reference input signal frequency conversion means for converting the input signal into a local signal in an unused frequency band. 8. The second conversion reference signal generation means extracts a local signal of a predetermined frequency from a transmission signal from the head end instead of the reference input signal generation means, and extracts the extracted local signal. 5. The up-converter according to claim 3, further comprising: a local signal extracting unit that inputs a reference signal to the control signal generating unit instead of the reference input signal. 6. 9. The local signal extracting means according to claim 8, wherein said local signal extracting means includes a local signal frequency converting means for converting said extracted local signal into a frequency operable by said control signal generating means. Upconverter. 10. A radio wave transmitted from a broadcasting satellite is received, and the received radio wave is transmitted at a predetermined frequency lower than the original frequency and higher than the VHF band and UHF band broadcast frequencies allocated to terrestrial television broadcasting. A BS antenna for frequency-converting and outputting a BS reception signal in a frequency band is provided at a head end, and a BS reception signal from the BS antenna and another television broadcast signal are transmitted to a plurality of subscribers via a common transmission line. A CATV system for transmitting data to a subscriber terminal, comprising: a down converter according to claim 6 or 7 on the head end side; and an up converter according to claim 8 or 9 on a transmission line on each subscriber side. A CATV system comprising: