JP2001231033A - Joint receiving system and frequency conversion device for terminal thereof - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To convert a satellite digital broadcast signal into a frequency band receivable by a television receiver at a low cost. SOLUTION: Each of a plurality of satellite digital broadcast signals in a first frequency band is frequency-converted so as to be located at a constant frequency interval in a second frequency band lower than the first frequency band. Digital satellite broadcasting signal is converted into one mixer via the transmission path of the joint receiving system.
Supplied to 20. The local oscillator 22 supplies a local oscillation signal to the mixer 20, and the mixer 20 selects the frequency of the local oscillation signal so that the signal is converted into each signal in the frequency band for frequency-converting a plurality of converted satellite digital broadcast signals. And one local oscillator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a joint receiving system for transmitting a satellite digital broadcast signal, and a frequency converter for receiving a satellite digital broadcast signal provided at a terminal of the joint receiving system.

[0002]

2. Description of the Related Art Conventionally, satellite analog broadcast signals have been jointly used by utilizing a joint receiving system such as a CATV system and an SMTV system for transmitting terrestrial signals in the UHF band and VHF band, satellite analog broadcast signals, independent broadcast signals, and the like. When transmitting to each terminal of the receiving system, the frequency of the satellite analog broadcast signal is converted to a frequency that can be transmitted on the transmission path of the joint receiving system and transmitted. Near future,
It is planned to carry out a plurality of satellite digital broadcasting in satellite broadcasting. When these satellite digital broadcast signals are transmitted via the transmission path of the joint receiving system, it is considered that the frequency conversion is performed similarly.

[0003]

In this case, it is conceivable that each satellite digital signal is frequency-converted again so that it can be received by a satellite digital broadcast television receiver or a satellite digital broadcast tuner provided in the terminal. . In this re-frequency conversion, it is desirable to frequency-convert a plurality of frequency-converted satellite digital broadcast signals collectively in order to reduce costs.

The present invention relates to an inexpensive joint receiving system which converts a satellite digital broadcast signal into a frequency, transmits the signal on a transmission path, and receives the digital signal on a satellite digital broadcast television receiver or tuner in a terminal, and a terminal used in this system. It is an object of the present invention to provide a frequency conversion device that performs the following.

[0005]

The frequency converter according to the present invention has one mixer and one local oscillator. The block signal is supplied to the mixer via the transmission path of the joint receiving system. The block signal is a plurality of converted satellite digital broadcasts obtained by frequency-converting each of a plurality of satellite digital broadcast signals within a predetermined frequency band so as to be located at a constant frequency interval in a frequency band lower than the frequency band. Consists of signals. The frequency interval between some of the plurality of satellite digital broadcast signals is
It may be different from the others. The local oscillator supplies a local oscillation signal to the mixer. The frequency of the local oscillation signal is selected by the mixer such that the block signal is converted into each signal within the frequency band.

[0006] In the frequency converter configured as described above, a block signal composed of a plurality of satellite digital broadcast signals converted into frequencies into converted satellite digital broadcast signals at fixed frequency intervals is supplied to the mixer. This block signal is frequency-converted and output from the mixer. This frequency conversion is performed so that the frequency of each converted satellite digital broadcast signal constituting the block signal is collectively converted into a signal having a frequency within the original predetermined frequency band. Therefore, it is not necessary to individually convert the frequency of each converted satellite digital broadcast signal, and the cost can be reduced.

[0007] The frequency band of the block signal may be any one of a plurality of frequency bands. In this case, the local oscillator is configured to convert the block signal into a signal within the predetermined frequency band, regardless of a frequency band of the block signal, regardless of the plurality of frequency bands. The frequency of the oscillation signal can be varied. For example, the frequency band of the block signal may be different between one joint receiving system and another joint receiving system.
Even in this case, if the local oscillator is configured so that the frequency of the local oscillation signal can be varied, the same frequency converter can be shared by different common receiving systems, and the cost can be further reduced.

[0008] The joint receiving system according to the present invention has a transmission path. Frequency conversion means is provided in a head end connected to one end of the transmission path. The frequency conversion means converts a plurality of satellite digital broadcast signals transmitted from a broadcast satellite into a plurality of converted satellite digital broadcast signals and outputs the signals to a transmission path. The plurality of satellite digital broadcast signals are within a predetermined first frequency band. The plurality of converted satellite digital broadcast signals are lower than the first frequency band and are located at a constant frequency interval within a second frequency band that can be transmitted on the transmission path. A terminal of the transmission line is provided with a frequency conversion device including one mixer and one local oscillator. The plurality of converted satellite digital broadcast signals are supplied to one mixer from the transmission path. One local oscillator supplies a local oscillation signal to the mixer. The local oscillation frequency of the local oscillator is selected such that the plurality of converted satellite digital broadcast signals are converted to signals within the first frequency band.

In the thus configured joint receiving system, each satellite digital broadcast signal is frequency-converted into each converted satellite digital broadcast signal by the frequency conversion means.
Since each converted satellite digital broadcast signal has been frequency-converted so that the frequency interval is constant, it is supplied via a transmission line to a mixer to which a local oscillation signal is supplied,
The signals are collectively reconverted into signals within the first frequency band. The re-converted signal can be received by a satellite digital broadcast receiving television receiver or tuner provided in the terminal. In addition, since the frequency conversion of a plurality of converted satellite digital broadcast signals in the terminal is performed collectively by one mixer and one local oscillator, the cost can be reduced.

[0010] The local oscillator converts each of the converted satellite digital broadcast signals into each signal within the first frequency band, even if the second frequency band is selected in advance from a plurality of frequency bands. Thus, the frequency of the local oscillation signal can be made variable. Therefore, even when the second frequency band is set differently for each installed joint receiving system, it can be dealt with by changing the local oscillation frequency, and it is not necessary to change the local oscillator one by one, and the cost is reduced. Can be reduced.

[0011] The terminal frequency conversion device according to the present invention comprises:
It has one mixer and one local oscillator. The mixer receives a plurality of channels of satellite digital broadcast signals, converts the frequency of the plurality of channels of digital satellite broadcast first intermediate frequency signals, and transmits the first intermediate frequency signal through a transmission path of a joint receiving system. A second intermediate frequency signal of a plurality of channels of satellite digital broadcasting adjacent to each other in a lower frequency band than the frequency signal is supplied. The satellite digital broadcast second intermediate frequency signal of these multiple channels is converted into a single local oscillation signal.
The frequency is converted to the third intermediate frequency signal of the satellite digital broadcast of a plurality of channels by the mixer. A local oscillator supplies the mixer with the one local oscillation signal, and the frequency of the local oscillation signal is such that the third intermediate frequency signal is located in an upper frequency band in a frequency band including the first intermediate frequency signal. Is selected.

According to this frequency converter, the second intermediate frequency signal of the digital satellite broadcasting of a plurality of channels is collectively frequency-converted into the third intermediate frequency signal of the digital satellite broadcasting of a plurality of channels. In addition, since each channel of the satellite digital broadcast third intermediate frequency signal is frequency-converted to the frequency band of the satellite digital broadcast first intermediate frequency signal, the channel is directly supplied to a digital television receiver or tuner for viewing. be able to. Further, each channel of the satellite digital broadcast third intermediate frequency signal is located in an upper frequency band in the frequency band including the first intermediate frequency signal. Accordingly, the lower frequency band in the frequency band including the first intermediate frequency signal is vacant, and the third intermediate frequency signal obtained by frequency-converting the satellite digital broadcast signal which will be increased in the future is arranged in this vacant frequency band. can do. In addition, the second intermediate frequency signal obtained by frequency-converting the first intermediate frequency signal of the satellite digital broadcast signal, which is increased in the future, is arranged at the upper frequency of the second intermediate frequency signal currently used. If the provided mixer converts the frequency of the local oscillation signal supplied thereto to be higher than the frequency of the signal to be frequency-converted, and converts the frequency of the signal to be frequency-converted from the frequency of the local oscillation signal to a value obtained by subtracting the frequency, In addition to the current second intermediate frequency signal, the added second intermediate frequency signal can be collectively frequency-converted into a third intermediate frequency signal.

The first intermediate frequency signal of the multi-channel satellite digital broadcast is a part m (n ≧ n) of the total number n of the multi-channel satellite analog and digital broadcast first intermediate frequency signals.
m). The second intermediate frequency signal of the multi-channel satellite digital broadcasting has the same frequency interval as the first intermediate frequency signal of the multi-channel satellite analog and digital broadcasting between adjacent channels. The plurality of channels of the third intermediate frequency satellite digital broadcast signal have the same frequency band as m channels from the highest frequency band to the lower frequency band of the satellite analog and digital broadcast first intermediate frequency signals. I have.

In this case, the third intermediate frequency signal of the satellite broadcast is
Since m channels are arranged below the highest frequency channel of the satellite analog and digital broadcast first intermediate frequency signals, the maximum number of empty channels of the satellite analog and digital broadcast first intermediate frequency signals can be maximized. Therefore, it is possible to cope with the case where the number of added satellite digital broadcast signals is large.

A joint receiving system according to the present invention includes a head end and a transmission line, and is provided with the above-described frequency conversion device. The head end receives the satellite digital broadcast signals of a plurality of channels, and converts the frequency-converted first intermediate frequency signals of the satellite digital broadcasts of the plurality of channels into a plurality of frequency bands lower than these and in which each frequency band is adjacent to each other. Channel Digital Satellite Broadcasting 2
There is provided frequency conversion means for converting the frequency to an intermediate frequency signal. The transmission path transmits the second intermediate frequency signal of the digital satellite broadcasting of the plurality of channels supplied from the head end.

In this joint receiving system, the above-mentioned frequency converter is provided, and the second digital intermediate frequency signal of satellite digital broadcasting is frequency-converted into a third digital intermediate frequency signal of satellite digital broadcasting at once. The cost of the converter can be reduced, which in turn reduces the cost of the joint receiving system. Moreover, since each channel of the satellite digital broadcast third intermediate frequency signal is frequency-converted to the frequency band of the satellite digital broadcast first intermediate frequency signal,
It can be viewed by directly supplying it to a digital television receiver. Furthermore, since each channel of the satellite digital broadcast third intermediate frequency signal is located in the upper frequency band in the frequency band in which the first intermediate frequency signal is included, the channel in the frequency band in which the first intermediate frequency signal is included. The lower frequency band is vacant, and in this vacant frequency band, a third intermediate frequency signal obtained by frequency-converting a satellite digital broadcast signal which will be increased in the future can be arranged. (1) A second intermediate frequency signal obtained by frequency-converting the intermediate frequency signal is arranged at a frequency higher than the currently used second intermediate frequency signal. If the frequency is higher than the signal to be frequency-converted and the frequency is converted to a value obtained by subtracting the frequency of the signal to be frequency-converted from the frequency of the local oscillation signal, the current second
Not only the intermediate frequency signal but also the added second intermediate frequency signal can be collectively converted into a third intermediate frequency signal, and the existing mixer can be used as it is, so that the satellite digital broadcast signal is added. Can be dealt with with little cost.

The first intermediate frequency signal of the multi-channel satellite digital broadcast is a part m (n ≧ n) of the total number n of the multi-channel satellite analog and digital broadcast first intermediate frequency signals.
m), wherein the second intermediate frequency signal of the multi-channel satellite digital broadcast has the same frequency interval as the first intermediate frequency signal of the multi-channel satellite analog and digital broadcast between adjacent ones, and Is the same frequency band as the m channels from the highest frequency band to the lower frequency band in the satellite analog and digital broadcast first intermediate frequency signals. In this case, it is possible to cope with the case where the number of added satellite digital broadcasts is large.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A joint receiving system according to a first embodiment of the present invention has a head end 2 as shown in FIG. The head end 2 transmits the UHF band and VHF band terrestrial television broadcast signals received by the UHF band and VHF band receiving antennas 3U and 3V, and an independent broadcast signal from an independent broadcast device (not shown) to a transmission path. For example, it is supplied to the coaxial cable 6. In order to transmit the above-mentioned signals, the joint receiving system is designed to transmit a downstream signal at a frequency of 70 to 450 MHz. In the middle of the coaxial cable 6, amplifiers such as branch amplifiers 7 are provided at predetermined intervals, and the above-described signals are transmitted from the branch amplifiers 7 to the terminal devices 8 via the branch units 10. Although one terminal device 8 and one branch amplifier 7 are shown in the figure, a large number of terminal devices 8 and branch amplifiers 7 are actually used. The branch amplifier 7
In some cases, a branch amplifier or a distribution amplifier may be further provided between the power supply and the branch unit 10.

The head end 2 receives approximately 10 signals received by a satellite broadcast receiving antenna 4 and converted into an intermediate frequency signal by a converter 4a attached thereto.
4 in the first frequency band from 35 MHz to 1332 MHz
Two satellite analog satellite broadcast signals are provided. These are four channels of BS5, BS7, BS9, and BS11, and the first intermediate frequency signals BS5-IF1, BS7-IF1, and BS9- in the frequency band that can be transmitted by the coaxial cable 6 by the frequency converter provided in the head end 2. I
The frequency is converted to F1-IF1 and BS11-IF1, and transmitted to each terminal device 8.

In a state where an existing joint receiving system corresponding to such a satellite analog broadcast signal exists, a plurality of, for example, four satellite digital broadcast signals in the first frequency band are newly transmitted from a broadcast satellite. Will be sent. These satellite digital broadcast signals have a modulation scheme of P
SK, which is frequency-converted and transmitted to the terminal device as described later.
K is maintained. The broadcast satellite includes eight transponders, and the transponders transmit the eight satellite broadcast signals (the satellite analog broadcast signal and the satellite digital broadcast signal) of the above-described BS1 to BS15 channels.
One transponder corresponds to one satellite digital broadcast signal. The four satellite digital broadcast signals are also received by the satellite broadcast receiving antenna 4, and the converter 4a
Is converted into an intermediate frequency signal. They are,
BS1-IF1, BS3-IF1, BS13-IF1,
These are four channels of BS15-IF1. BS1-IF
One channel has a center frequency of 1049.48 MHz
The BS3-IF1 channel has a center frequency of 108
7.84 MHz, the center frequency of the BS13-IF1 channel is 1279.64 MHz, and the center frequency of the BS15-IF1 channel is 1318.00 MHz.
The frequency interval between the BS1-IF1 and BS3-IF1 channels and the frequency interval between the BS13-IF1 and BS15-IF1 channels are the same, but the BS3-IF1 and the BS3-IF1 have the same frequency interval.
Between the S11-IF1 channel, BS5-IF
1, BS7-IF1, BS9-IF1-IF1, and BS
There is a satellite analog broadcast first intermediate frequency signal of 11-IF1.

These BS1-IF1, BS3-IF1,
The satellite digital broadcast signals of the BS13-IF1 and BS15-IF1 channels are converted into frequency bands lower than the first frequency band, for example, about 222 to 388 MHz by frequency conversion means provided in the head end 2, for example, a down converter. The frequency is converted (down-converted) into a converted satellite digital broadcast signal in the frequency band No. 2. The downconverter is a single channel provided for each channel. The downconverter converts the BS15-IF1 channel into an A channel having a center frequency of 246.00 MHz and the BS13-IF1 channel.
-IF1 channel has a center frequency of 284.36 MHz
The BS3-IF1 channel is set to the C channel with a center frequency of 322.72 MHz, and the BS1-IF1 channel is set to the
The IF 1 channel is frequency-converted to a D channel having a center frequency of 361.08 MHz. These A channel to D channel have a frequency interval of 38.
Constant at 36MHz (transponder frequency interval)
The band is a block signal of about 166 MHz. The frequency band from channel A to channel D is selected as a frequency band that can be transmitted on the transmission line 6 of the joint reception system.

The converted satellite digital broadcast signal from channel A to channel D is transmitted to the terminal device 8 via the coaxial cable 6. The terminal device 8 has a frequency conversion device as shown in FIG. This frequency conversion device has A
To D-channel converted satellite digital broadcast signals, and each of the converted satellite digital broadcast signals from the input terminal 12 is extracted by an extracting means for removing unnecessary noise components, for example, a band-pass filter. The signal is supplied to a level adjusting means, for example, an amplifier 16 and a variable resistor 18 connected in series.

The converted satellite digital broadcast signals of the A to D channels whose levels have been adjusted are supplied to the mixer 20. The mixer 20 is supplied with a local oscillation signal from a local oscillator 22. The frequency of this local oscillation signal is
For example, 1484.28 MHz is selected. The mixer 20 mixes the local oscillation signal and the converted satellite digital broadcast signals of the A to D channels and performs frequency conversion. This frequency conversion is performed in the upper local. Therefore, the A channel signal is frequency-converted into a BS11-IF3 channel signal having a center frequency of 1318.00 MHz as shown in FIG. The B channel signal is
The frequency is converted to a BS9-IF3 channel signal having a center frequency of 1202.92 MHz. The C-channel signal is BS7-I having a center frequency of 1164.56 MHz.
The frequency is converted to an F3 channel signal. The D channel has a BS5- center frequency of 1122.60 MHz.
The frequency is converted to a signal of three channels of IF. BS1
The 1-IF3 channels are BS11-IF1 and BS9
-IF3 channels are BS9-IF1 and BS7-I
The F3 channel includes BS7-IF1 and BS9-IF3
The channel is in the same frequency band as the BS11-IF1 channel.

Since the converted satellite digital broadcast signals have a fixed frequency interval, these converted satellite digital broadcast signals can be collectively frequency-converted into a signal in the first frequency band. BS5 obtained by frequency-converting A to D channel signals
The signals of the -IF1 to BS11-IF1 channels are amplified by the amplifier 24, and unnecessary signal components are removed by the low-pass filter 26.
3 is supplied to a commercially available digital television receiver 30 as shown in FIG. 3 and is viewed by a viewer.

The amplifier 16 and the variable resistor 18 are
It is provided to frequency-convert the converted satellite digital broadcast signal to a signal level suitable for collectively converting the frequency of the four converted satellite digital broadcast signals.

A to D channel signals are collectively transmitted to BS
Since the frequency can be converted into 5-IF1 to BS11-IF1 channel signals, the cost of the frequency converter can be reduced, and the cost of the existing joint receiving system can be reduced. In the above embodiment, the A to D channel signals are converted to BS5-IF1 to BS5.
11-IF1, but BS1-IF1 through BS9-IF1 or BS9-IF1 through BS15-I
The frequency can be converted to F1.

In the second embodiment, as shown in FIG. 4, the bandpass filter 14 in the first embodiment is used.
Is a variable input filter 14a including a band-pass filter whose pass band is variable. Local oscillator 22
a is variable in frequency. Control means, for example PL
L32 allows the pass band of the variable input filter 14a and the local oscillation signal frequency of the local oscillator 22a to be variable. In addition, the joint receiving system is capable of transmitting the frequency of the downstream signal from 70 MHz to 550 MHz. Otherwise, the configuration is the same as that of the frequency conversion device of FIG. 1, and a detailed description thereof will be omitted.

In the joint receiving system, the frequency band of the converted satellite digital broadcast signal may differ depending on the service provider. For example, as shown in FIG. 5, a certain carrier converts a converted satellite digital broadcast signal to a center frequency of 246.00 or 28.
A, B which are 4.36, 322.72, 361.08,
Channels C and D, and another carrier has a center frequency of 3
99.44, 437.80, 476.16, 514.5
There may be A1, B1, C1, and D1 channels of 2 MHz.

In this case, in the first embodiment, the local oscillator 22 and the band-pass filter 14 are separately prepared in advance for the A to D channels and for the A1 to D1 channels. , According to the request of the operator,
One of the local oscillators 22 and the band pass filter 14 is used. However, the number of terminal devices used in one joint receiving system is enormous. Preparing and stocking two types of local oscillators 22 and local oscillators 22 used in the terminal device is a problem in terms of management and cost.

Therefore, in the second embodiment, the local oscillator 22a is configured to change the local oscillation frequency based on a control signal from the PLL 32. For example, when the above A to D channels are used, the frequency of the local oscillator 22a is set to 1564 MHz.
In this case, as shown in FIG.
Since the mixer 20 performs frequency conversion in the upper local, the frequency conversion is performed to the BS9-IF3 through BS15-IF3 channels. When the A1 to D1 channels are used, the frequency of the local oscillator 22a is 1717.44M.
Hz. Also in this case, the A1 to D1 channels are frequency-converted into BS9-IF3 to BS15-IF3 channels because the mixer 20 performs frequency conversion locally in the upper region.

By simply changing the setting of the PLL 32 in this way, no matter which frequency band is used for the converted satellite digital broadcast signal, it is not necessary to replace the local oscillator 22a, and many local oscillators are kept in stock. There is no need to hold.

It should be noted that the control signal from the PLL 32 is also supplied to the variable input filter 14a, and the pass band is about 222 MHz which can pass the A to D channels.
z to 388 MHz, and about 375 MHz to 54 which can pass the A1 to D1 channels.
It is configured so that the pass band can be changed to a state of 1 MHz. Therefore, it is not necessary to replace the bandpass filter, and it is not necessary to store a large number of bandpass filters as inventory.

In this embodiment, channel A is
S15-IF1, B channel is BS13-IF1
, C channel is BS3-IF1, D channel is B
S1-IF1 is frequency-converted. A1 channel is BS15-IF1, B1 channel is BS1.
3-IF1, C1 channel is BS3-IF1, D1
The channel is obtained by frequency-converting BS1-IF1. Therefore, the arrangement order and the frequency interval of the A to D channels and the A1 to D1 channels are the same. Therefore, for some reason, the local oscillation frequency is changed as described above even if the transmission has been performed on the A to D channels until now, even if the transmission is changed to the A1 to D1 channels, that is, the transmission block frequency is changed. Then, the receiver does not need to change the setting of the digital television receiver 30 at all.

The frequencies of the channels A to D and the channels A1 to D1 shown in the first and second embodiments are merely examples, and the usage conditions and the transmittable frequency on the transmission line 6 are changed. In such a case, it is changed according to this change. Similarly, the local oscillator 22,
The local oscillation frequency 22a is also merely an example, and can be changed within a frequency band that can be received by the television receiver 30 depending on the situation. In the first and second embodiments, the mixer 20 performs the frequency conversion in the upper local, but may perform the frequency conversion in the lower local in some cases.

The joint receiving system according to the third embodiment of the present invention has a head end 102 as shown in FIG. The head end 102 is supplied with a UHF band and a VHF band terrestrial television broadcast signal received by the UHF band receiving antenna 103U and the VHF band receiving antenna 103V, and an independent broadcast signal from an independent broadcast device.
These are supplied to a transmission line, for example, a coaxial cable 106. The coaxial cable 106 is provided with an amplifier, for example, a branch amplifier 107 at predetermined intervals, and a signal branched from the branch amplifier 107 is transmitted through the branch unit 108 to the terminal device 11.
0 is supplied. Although only one branch amplifier 107 and one terminal device 110 are shown in the figure, many branch amplifiers 107, branch devices 108, and terminal devices 110 are actually provided.

A first satellite broadcast intermediate frequency signal obtained by frequency-converting a satellite broadcast signal received by a satellite broadcast receiving antenna 104 by a converter 104a attached to the antenna 104 is supplied. Satellite signals are
Multiple channels, eg BS1, BS3, BS5, BS
7, 8 channels of BS9, BS11, BS13 and BS15. Of these, BS5, BS7, BS9,
Four channels of BS11 are analog satellite broadcast signals, which are currently being broadcast. Remaining BS1, BS3, BS1
3. Four channels of BS15 are satellite digital broadcasting signals, and broadcasting will be started in the near future. These satellite digital broadcast signals are PSK-modulated and frequency-converted and transmitted to the terminal device as described later.
K is maintained.

In the converter 104a, when satellite digital broadcasting is not started, the BS5 is connected to the BS5-IF having a center frequency of 1126.20 MHz as shown in FIG.
1, BS7 with center frequency of 1164.56 MHz
The center frequency of BS9 is set to 1202.92 in S7-IF1.
The center frequency of BS11 is 1 in BS9-IF1 of MHz.
The frequency is converted to BS11-IF1 of 241.2 MHz. These are frequency-converted to a frequency band that the head end 102 can transmit by the coaxial cable 106,
The signal is transmitted to each terminal device 110 via the branch amplifier 107 and the branch unit 108. When the satellite digital broadcasting starts, the converter 104a adds, in addition to the above conversion,
BS1 has a center frequency of 1049.48 as shown in FIG.
The center frequency of BS3 is 10
The BS13-IF1 with the center frequency of 1279.64 MHz,
BS15 whose center frequency is 1318.00 MHz
The frequency is converted to S15-IF1.

These satellite digital broadcast first intermediate frequency signals BS1-IF1 to BS15-IF1 are transmitted to the head end 1
02. Among these, satellite digital broadcast first intermediate frequency signals BS1-IF1, BS3-IF1, BS
13-IF1, BS15-IF1 is the headend 10
The frequency is converted into the second intermediate frequency signal of the satellite digital broadcast of the adjacent A to D channels by a frequency conversion means provided in 2, for example, a single channel converter (not shown) provided for each channel. Channel A is obtained by frequency-converting BS15-IF1, and its center frequency is 246.00 MHz. The B channel is obtained by frequency-converting BS13-IF1, and has a center frequency of 284.36 MHz. The C channel is obtained by frequency-converting BS3-IF1, and has a center frequency of 322.72 MHz. D channel is BS
1-IF1 is frequency-converted, and its center frequency is 361.08 MHz. The frequency bands of the A to D channels are frequency bands that can be transmitted by the coaxial cable 106. Each single-channel converter of the head end 102 performs down-conversion for frequency-converting a high frequency band channel to a low frequency band. A
To the D channel are constant, for example, 38.3.
6 MHz. This frequency interval of 38.36 MHz is the same as the frequency interval of each transponder of the broadcasting satellite.

The second intermediate frequency signals of the satellite digital broadcasts of the A to D channels are supplied to a transmission line shown in FIG. 7, for example, a coaxial cable 106, and transmitted through a branch amplifier 107 and a branch unit 108 to the frequency of each terminal device 110. Conversion device 1
12 is supplied.

As shown in FIG. 6, the frequency conversion device 112 has an input terminal 114 to which a first intermediate frequency signal of satellite digital broadcasting of channels A to D is supplied. The first intermediate frequency signals of the satellite digital broadcasts of the A to D channels supplied to the input terminal 114 are transmitted through a band-pass filter 11 having a pass band capable of passing them.
After unnecessary noise components are removed by the amplifier 6, the amplifier 11
8 and supplied to the mixer 120. The mixer 120 is supplied with a local oscillation signal from a local oscillator 122. The frequency of this local oscillation signal is
The satellite digital broadcast second intermediate frequency signal of the A to D channels is selected so as to be capable of frequency conversion to a frequency band in the frequency band of the satellite digital broadcast first intermediate frequency signal. In this embodiment, 1564 MHz is selected. Further, the mixer 120 performs upper local frequency conversion for converting the frequency of the input signal to a frequency obtained by subtracting the frequency of the input signal from the frequency of the local oscillation signal.

Therefore, channel A has a center frequency of 1
The frequency is converted to BS15-IF3 having a frequency equal to BS15-IF1, which is 318 MHz.
BS13-IF1 whose center frequency is 1279.64 MHz
Is converted to BS13-IF3 having a frequency equal to
Channel C has a center frequency of 1241.2 MHz B
The frequency is converted to BS11-IF3 equal to S11-IF1, and channel D has a center frequency of 1202.92M.
The frequency is converted to BS9-IF3 equal to BS9-IF1 in Hz. As described above, the satellite digital broadcast second intermediate frequency signals of the A to D channels are frequency-converted into four lower channels in order from the upper channel in the frequency bands of the satellite analog and digital broadcast first intermediate frequency signals. I have.

These satellite digital broadcast third intermediate frequency signals BS9-IF3 to BS15-IF3 are supplied to an amplifier 124.
After that, the noise component is removed by a low-pass filter 126 whose cutoff frequency is selected so as to remove a frequency component higher than that of BS15-IF3, and is output to an output terminal 128. Satellite digital broadcast third intermediate frequency signal BS9-IF3 to BS from output terminal 128
As shown in FIG. 7, the 15-IF3 is supplied to the digital television receiver 130 and viewed.

As described above, the first intermediate frequency signals BS1-IF1, BS3-IF1, and BS13-IF of the digital satellite broadcasting are provided.
1 and BS15-IF1, finally the satellite digital broadcast third intermediate frequency signals BS9-IF3, BS11-IF3,
Since the frequency has been converted to BS13-IF3 and BS15-IF3, the digital television receiver 130
, The content can be viewed as it is. Moreover, the satellite digital broadcast second intermediate frequency signals BS9-IF3, BS11-IF3, and BS13-IF3 are converted from the satellite digital broadcast second intermediate frequency signals of the A to D channels.
And the frequency conversion to the BS 15-IF3 is performed collectively for all of the A to D channels. Therefore, the frequency conversion device 112 has a simple configuration including one mixer 120 and one local oscillator 122. Things can be adopted.

Further, the third intermediate frequency signals BS9-IF3, BS11-IF3, BS13-IF3 of the satellite digital broadcast.
And BS15-IF3 are BS1-1 to BS15-1.
Channel satellite analog and digital broadcasting High frequency channels BS9-IF1, BS of the first intermediate frequency signal
11-IF1, BS13-IF1 and BS15-IF1
Has the same frequency as. Therefore, BS1-1 to BS15
-1 channel satellite analog and digital broadcast first intermediate frequency signal, low frequency band channel BS1-
IF1, BS3-IF1, BS5-IF1, BS7-I
BS1-IF3, BS3-I in the same frequency band as F1
F3, BS5-IF3 and BS7-IF3 are empty channels.

If a satellite digital broadcast signal is added in the future, for example, if four channels are added, the added four digital satellite digital broadcast signals are converted by the converter 10.
The first intermediate frequency signals of the four-channel additional satellite digital broadcasting frequency-converted by 4a are sequentially converted to those having a higher center frequency, with a center frequency of 399.44 MHz.
It is assumed that the frequency has been converted into an E channel of z, an F channel having a center frequency of 437.80 MHz, a G channel having a center frequency of 476.16 MHz, and an H channel having a center frequency of 514.52 MHz. Of course, these frequency bands are also frequency bands that can be transmitted by the coaxial cable 106. In this case, if the bandpass filter 116 of FIG. 6 having a pass band through which the second intermediate frequency signal of the satellite digital broadcast of eight channels in total can be used is used, the frequency converter 112 is not modified at all. As shown in FIG. 8, the second intermediate frequency signals of the satellite digital broadcasting of the A to H channels are converted into BS1-IF3 to BS15 having the same frequency band as BS1-1 to BS15-1, respectively.
-The frequency can be collectively converted to IF3. Therefore, even if the number of satellite digital broadcasting channels is newly increased, it is possible to easily cope with the cost without increasing the cost.

In order to remove unnecessary signal components after frequency conversion, a low-pass filter 126 is used, and the channel BS15-IF3 of the highest frequency band of the current satellite digital broadcast third intermediate frequency signal is connected to the satellite analog and analog signals. It is set equal to the highest frequency channel BS15-IF1 of the digital broadcast first intermediate frequency signal. Therefore, the third intermediate frequency signal of the newly added satellite digital broadcast obtained by frequency-converting the newly added satellite digital broadcast signal is BS15-IF3.
Therefore, the cutoff frequency of the low-pass filter 126 does not need to be changed even if the satellite digital broadcasting is added.

If the satellite digital broadcast second intermediate frequency signals of the A to D channels are transmitted as shown in FIG.
IF1, BS3-IF1, BS5-IF1, and BS7-
If the frequency is converted to IF1, the second intermediate frequency signal of the additional satellite digital broadcast of E to H channels based on the newly added satellite digital broadcast signal is transmitted to BS9-IF.
1, BS11-IF1, BS13-IF1, and BS15
In order to convert the frequency to -IF1, the local oscillation frequency must be 1679.08 MHz, and in addition to the frequency converter 12, the local oscillation frequency is 1679.08 MHz.
Must be newly provided, which increases the cost. However, as in this embodiment, each of the channels of the satellite digital broadcast third intermediate frequency signal is placed in a frequency band equal to the lower one in order from the higher frequency band of the satellite analog and digital broadcast first intermediate frequency signals. Is assigned, as described above, the satellite digital broadcast second intermediate frequency signals of the E to H channels corresponding to the satellite digital broadcast signals added by one frequency converter 112 can be frequency-converted at once. .

In the third embodiment, the third intermediate frequency signal of the satellite digital broadcasting is transmitted from BS15-IF3 to BS15-IF3.
Although the frequency has been converted to each channel of 9-IF3, if the number of satellite digital broadcast signals to be added is small, the channel of the highest frequency band is not necessarily changed to BS15-I.
It is not necessary to assign to F3. For example, the channel of the highest frequency band may be assigned to BS13-IF3 or BS11-IF3.

[0049]

As described above, according to the present invention, one mixer and one local oscillator convert a plurality of converted satellite digital broadcast signals into signals of a predetermined frequency band at once. Therefore, it is not necessary to provide a frequency conversion device for each converted satellite digital broadcast signal, and a frequency conversion device and a joint reception system that can view satellite digital broadcasts at low cost can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a frequency conversion device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a state of frequency conversion in the frequency conversion device of FIG. 1;

FIG. 3 is a block diagram of a joint receiving system in which the frequency conversion device of FIG. 1 is used.

FIG. 4 is a block diagram of a frequency conversion device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a state of frequency conversion in the frequency conversion device of FIG. 4;

FIG. 6 is a block diagram of a terminal frequency converter used for a joint receiving system according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a joint receiving system according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a frequency relationship of signals of respective units in the joint receiving system of FIG. 7;

9 is a diagram illustrating a frequency relationship of signals of respective units when the frequency band of the satellite digital broadcast third intermediate frequency signal is changed in the joint receiving system of FIG. 7;

[Explanation of symbols]

 2 102 Headend 6 106 Coaxial cable (transmission line) 12 112 Frequency converter 20 120 Mixer 22 22a 122 Local oscillator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/00 101 H04N 5/00 101 (72) Inventor Hiroo Arada 2-2-2 Jinnan, Shibuya-ku, Tokyo 1 Japan Broadcasting Corporation Broadcasting Center (72) Inventor Yasumi Shibata 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center

Claims (8)

[Claims] 1. A plurality of converted satellite digital signals obtained by frequency-converting a plurality of satellite digital broadcast signals within a predetermined frequency band so as to be positioned at a fixed frequency interval in a frequency band lower than the frequency band. A mixer in which a block signal composed of a broadcast signal is supplied via a transmission path of a joint reception system; and a local oscillation signal is supplied to the mixer. The mixer outputs the block signal in each of the frequency bands. A frequency conversion device for a joint receiving system terminal, comprising: one local oscillator in which the frequency of the local oscillation signal is selected so as to be converted into a signal. 2. The frequency conversion device for a joint reception system terminal according to claim 1, wherein the local oscillator transmits the block signal in advance to the block signal regardless of a frequency band of the block signal. A frequency conversion device for a joint reception system terminal capable of changing the frequency of a local oscillation signal so as to be converted into each signal within a predetermined frequency band. 3. A transmission line, and a plurality of satellite digital broadcast signals provided in a head end connected to one end of the transmission line, transmitted from a broadcasting satellite, and in a predetermined first frequency band. Converting a plurality of converted satellite digital broadcast signals frequency-converted so as to be lower than the first frequency band and located at a constant frequency interval within a second frequency band that can be transmitted in the transmission line; And a frequency converter for supplying the plurality of converted satellite digital broadcast signals from the transmission path, wherein the frequency converter converts the plurality of converted satellite digital broadcast signals into frequencies. One mixer for conversion, and a local oscillation signal supplied to the mixer so that the plurality of converted satellite digital broadcast signals are converted into signals within the first frequency band. And a single local oscillator for which the frequency of the local oscillation signal is selected. 4. The co-reception system according to claim 3, wherein the local oscillator is configured such that each of the converted satellite digital broadcast signals is transmitted even if the second frequency band is selected from a plurality of frequency bands in advance. A joint receiving system that can vary the frequency of a local oscillation signal so that is converted into each signal within a first frequency band. 5. The multi-channel satellite digital broadcast signal, which has received a plurality of channels of digital satellite broadcast signals and has been frequency-converted, has been frequency-converted, and can be transmitted through a transmission path of a joint receiving system. A plurality of satellite digital broadcast second intermediate frequency signals of a plurality of channels adjacent to each other in a frequency band lower than the intermediate frequency signal are supplied, and the plurality of satellite digital broadcast second intermediate frequency signals of the plurality of channels are converted into one local oscillation signal. A single mixer that converts the frequency of the local oscillation signal into a third intermediate frequency signal of a multi-channel satellite digital broadcast, and a local oscillator that supplies the local oscillation signal to the mixer. Is such that the third intermediate frequency signal is located in an upper frequency band in a frequency band including the first intermediate frequency signal, -Option has been that the frequency converter terminals. 6. The frequency converter for a terminal according to claim 5, wherein the first intermediate frequency signal of the satellite digital broadcast of the plurality of channels is a part of the total number n of the first intermediate frequency signals of the satellite analog and digital broadcasts of the plurality of channels. m (n ≧ m)
Wherein the second intermediate frequency signal of the multi-channel satellite digital broadcasting has the same frequency interval as that of the first analog frequency signal of the multi-channel satellite analog and digital broadcasting, and the second multi-channel satellite digital broadcasting. The third intermediate frequency broadcast signal is a frequency conversion device for a terminal, which has the same frequency band as m channels from the highest frequency band to the lower frequency band in the satellite analog and digital broadcast first intermediate frequency signals. . 7. A multi-channel satellite digital broadcast first intermediate frequency signal obtained by receiving a multi-channel satellite digital broadcast signal and converting the frequency into a lower frequency band and adjacent to each other in each frequency band. A head end including frequency conversion means for converting the frequency into a second digital signal of the second digital satellite broadcasting of a plurality of channels, and a transmission line for transmitting the second intermediate frequency signal of the digital satellite broadcasting of the plurality of channels supplied from the head end And a second intermediate frequency signal of the digital satellite broadcasting of the plurality of channels is supplied from the transmission line, and the second intermediate frequency signal of the digital satellite broadcasting of the plurality of channels is converted into a third intermediate frequency signal of the multi-channel satellite digital broadcasting by a local oscillation signal. And one mixer that converts the frequency to the above, and supplies the local oscillation signal to this mixer One local oscillator, and the frequency of the local oscillation signal is such that the third intermediate frequency signal is located in an upper frequency band in a frequency band including the first intermediate frequency signal, The selected joint receiving system. 8. The joint receiving system according to claim 7, wherein the first intermediate frequency signal of the multi-channel satellite digital broadcast is a part m (m) of the total number n of the multi-channel satellite analog and digital broadcast first intermediate frequency signals. n ≧ m), and the second intermediate frequency signal of the multi-channel satellite digital broadcast has the same frequency interval as the first intermediate frequency signal of the multi-channel analog and satellite digital broadcast between adjacent ones, and The satellite digital broadcast third intermediate frequency signal of the plurality of channels has the same frequency band as m channels from the highest frequency band to the lower frequency band of the satellite analog and digital broadcast first intermediate frequency signals. Joint receiving system.