JPH056937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a head end of a communal viewing and viewing device.

<Prior Art> Conventionally, the above-mentioned head end has been such as shown in FIG. 4, for example. This consists of n frequency converters 2 ₁ to 2 _o and n band pass filters 4.
It is equipped with a mixing section consisting of ₁ to 4 _o . Each of the frequency converters ₂₁ to _2o has the same configuration, and by adjusting the oscillation frequency of the built-in variable local oscillator, converts the input television signal into a television signal of another channel. It is configured to perform frequency conversion and then amplification.
For example, the frequency converter 2 ₁ converts the frequency of channel A1 to channel a1, the frequency converter 2 ₂ converts the frequency of channel A2 to channel a2, etc. The frequency converter 2 _o converts the frequency of channel A1 to channel a1, etc. The frequency of the variable local oscillator is adjusted to convert the frequency to each channel an. Moreover, each band pass filter 4 ₁ ~
4 _o has a relatively narrow passband that allows only the output signal of the connected frequency converter to pass. For example, the bandpass filter 4 ₁ has a passband that allows only channel a1 to pass, the bandpass filter 4 ₂ has a band that allows only channel a2 to pass, and...the bandpass filter 4 _o is
It has a band that allows only channel an to pass. The output side of each bandpass filter 4 ₁ to 4 _o is connected to an output terminal 6, and this output terminal 6 is connected to the main cable of the communal viewing device. In addition,
7 ₁ to 7 _o are input terminals of each frequency conversion section 2 ₁ to 2 _o .

<Problems to be Solved by the Invention> In the head end as described above, it may be necessary to change the frequency of the output signal of each frequency converter to another frequency different from the current frequency. For example, currently, the frequency converter 2 ₁ has channel A1
is frequency-converted to channel a1, but it may become necessary to frequency-convert this to channel am, which has not been used by any frequency converter so far. In such a case, the bandpass filter 4 ₁ cannot be used as is, so it is necessary to change the passband of the bandpass filter 4 ₁ so that channel am can pass through. However, changing the pass band like this cannot be done easily at the location where the head end is installed, so the head end must be taken back to the factory and readjusted, or a new band pass filter must be installed from the factory that allows channel AM to pass through. There was a problem in that the frequency of the output signal of each frequency conversion section could not be easily changed at the location where the head end was installed.

<Means for Solving the Problems> An object of the present invention is to provide a head end that solves the above problems. Therefore, the present invention provides a head end that solves the above problems. It consists of a processing device and an active combiner to which the output signals of these signal processing devices are supplied. Each signal processing device includes a signal processing unit configured to output an input signal as an output signal with a frequency selected from within a predetermined frequency range, and output signals with a plurality of different frequencies within the frequency range. A plurality of bandpass filters each having a pass band corresponding to each frequency band obtained by dividing the frequency band into a plurality of states are interposed between each of these bandpass filters and the signal processing unit, and the signal processing section of each of the bandpass filters is and a selection means for supplying the output signal of the signal processing section to a device having a band through which the output signal of the signal processing section passes. Further, the active combiner includes at least a plurality of splitters, each of which has broadband characteristics that allow output signals within the above frequency range to pass. Output signals from each signal processing device are supplied to branch terminals of these branchers. Each branch mixes the output signals of each signal processing device by connecting its input terminal to the output terminal of the preceding branch and connecting its output terminal to the input terminal of the subsequent branch. .
This mixed signal is amplified by a broadband amplifier.

<Operation> According to the present invention, the signal processing section of the signal processing device sends out an input signal as an output signal of a frequency selected from within a predetermined frequency range. The selection means then supplies the output signal of the signal processing section to a bandpass filter whose pass band includes the frequency of the output signal of the signal processing section. Therefore, the output signal of this bandpass filter is one in which signals other than the output signal of the signal processing section, such as noise and spurious, are considerably attenuated. The signals from the selected bandpass filters of each signal processing device are mixed in an active combiner and sent out. When changing the frequency of the output signal of the signal processing device, the selection means changes the bandpass filter to be used. In such cases, the active combiner
It consists of at least a splitter and a broadband amplifier, so
There is no need to make any adjustments.

<Effects> As described above, in the head end according to the present invention, when changing the frequency of the output signal of the signal processing device, since the active combiner is composed of a directional coupler and a wideband amplifier, no adjustment is required for the active combiner. The frequency of the output signal can be changed immediately, since it is only necessary to switch the bandpass filter to be used by the selection means of the signal processing device, and there is no need to replace the filter. Moreover, since each branching device receives the signal of the signal processing device from the branch terminal and sends it out to the input terminal side, the output signal of the signal processing device supplied to the branch terminal does not appear on the output terminal side. The output signals of each signal processing device do not interfere with each other, and each branching device has a wide band, so no matter which branching device is supplied with the output signal of any signal processing device, it will mix correctly. can. Additionally, since the active combiner includes a wideband amplifier, noise and spurious signals may also be amplified, but a bandpass filter installed after the signal processing section in the signal processing device attenuates the noise and spurious signals. Therefore, the amount of these sent out from the active combiner is very small and poses no problem at all.

<Embodiment> As shown in FIG. 2, this embodiment consists of channel processors 8 ₁ to 8 ₁₆ and an active combiner ₉ .
The ₁₆ output signals are fed to an active combiner 9 and mixed. Each channel processor 8
₁ to 8 ₁₆ have the same configuration, and each
As shown in the figure, it has a signal processing section 10, a plurality of band pass filters 12 ₁ to 12 ₅ , and a selection means 14 .

This signal processing section 10 converts the frequency of the channel signal supplied to the input terminal 7 into a desired channel signal. mixed with a first local oscillator signal from
The signal is frequency-converted to an intermediate frequency signal and amplified. This intermediate frequency signal is supplied to the processor section 20, where it is separated into a video signal and an audio signal, and after adjusting the signal levels of both, they are combined again and output. The purpose of performing such processing is to suppress noise. Processor section 2
The output signal of 0 is supplied to the output amplifier section 22,
Here, it is mixed with a second local oscillation signal from the second local oscillator 24, frequency-converted into an output signal, and amplified. Note that an automatic gain control circuit (AGC) 26 is provided between the input amplifier section 16 and the output amplifier section 22.
The gain of the input amplifier section 16 is controlled according to the signal No.2.

First local oscillator 18 and second local oscillator 24
The first local oscillator 18 is configured by a voltage controlled oscillator, and the first local oscillator 18 is connected to a PLL control circuit 28.
and the first frequency setting digital switch 30 constitute a PLL, and the second local oscillator 2
4 constitutes a PLL together with a PLL control circuit 28 and a second frequency setting digital switch 32. Therefore, by operating the first frequency setting digital switch 30, the frequency of the first local oscillation signal can be changed, and similarly the frequency of the second local oscillation signal can be changed.
By operating the frequency setting digital switch 32, the frequency of the second local oscillation signal can be changed. Therefore, the frequency of the first local oscillation signal is selected to convert the input channel signal into an intermediate frequency signal, and the intermediate frequency signal is converted within a predetermined frequency range (for example, from the A channel to the T channel). By selecting the oscillation frequency of the second local oscillator 24 such that the frequency can be converted into an arbitrary channel signal, the signal processing section 10 converts the input channel signal into an arbitrary channel signal within a predetermined frequency range. It can be frequency-converted to a channel signal and output.

Each of the bandpass filters 12 ₁ to 12 ₅ has a different passband width, and for example, the signal processing unit 1
0 outputs one of a total of 20 channels of output signals from the A channel to the T channel, the first band pass filter ₁₂₁ has a wide pass band width that allows the signals from the A channel to the D channel to pass. and the second bandpass filter 12 ₂
has a relatively wide passband width that allows the passage from the E channel to the H channel, and the third
The fourth band pass filter 12 ₃ has a wide pass band width from the I channel to the L channel, and the fourth band pass filter 12 ₄ has a wide pass band width for passing from the I channel to the L channel.
The fifth bandpass filter 12 ₅ has a relatively wide passband width for passing from the channel to the P channel, and a relatively wide passband width for passing from the Q channel to the T channel, respectively. It is configured.

The selection means 14 includes input side PIN diodes 34 ₁ to 34 ₅ provided between the output amplifier section 22 and the input side of each of the bandpass filters 12 ₁ to 12 ₅ .
and output-side PIN diodes 36 ₁ to 36 ₅ provided between each of the band pass filters 12 ₁ to 12 ₅ and the output terminal, respectively. The anodes of the input side PIN diode 34 ₁ and the output side PIN diode 36 ₁ are high frequency blocking chains 38 ₁ and 4, respectively.
0 ₁ of the bandpass filter selection unit 42
connected to the output side of the input side PIN diode 34
The anodes of the output side PIN diode 36 ₂ and the output side PIN diode 36 ₂ are connected to the second output side of the band pass filter 12 ₁ to 12 ₅ selection section via high frequency blocking chains 38 ₂ and 40 ₂ , respectively. 34
The anodes of the output side PIN diode 36 ₅ and the output side PIN diode 36 ₅ are respectively connected to the fifth output side of the bandpass filter selection section 42 via high frequency blocking chains 38 ₅ and 40 ₅ . The bandpass filter selection section 42 has five selection switches (not shown), and when the first selection switch is operated, a signal is generated on the first output side, the input side PIN diodes 34 ₁ and 36 ₁ are made conductive, and the signal is The output signal of the processing unit 10 is supplied to the output terminal 33 via the bandpass filter 12 ₁ .
Similarly, when the fourth selection switch is operated, the fourth
A signal is generated on the output side of the input side PIN diode 3.
4 ₄ and 36 ₄ are conductive, and the output signal of the signal processing section 10 is passed through the band pass filter 12 ₄ to the output terminal 3.
3. The same applies when operating other selection switches. Note that 44, 44, . . . are bypass capacitors.

In the channel processor configured in this way, for example, when a certain channel signal is supplied to the input terminal 7 and the frequency of this signal is converted into an F channel, the frequencies of the first local oscillation signal and the second local oscillation signal are changed to Select the frequency of the output signal to be the F channel. At the same time, the second selection switch of the bandpass filter selection section 42 is operated to pass the output signal of the signal processing section 10 to the second bandpass filter 1.
2 to the output terminal 35 through ₂ . As a result, only the output signal of the F channel is supplied to the active combiner 9, and unnecessary noise in other frequency bands is removed by the bandpass filter ₁₂₂ .
At the same time, spurious signals from the output signal of the F channel are also removed by the bandpass filter 12 ₂ .

In this state, when it becomes necessary to change the output signal of the signal processing section 10 from the F channel to the A channel, the oscillation frequency of the second local oscillation signal is changed so that the output signal becomes the A channel, and at the same time, the bandpass The first selection switch of the filter selection section 42 is operated. As a result, the signal processing section 1
The output signal of the A channel 0 is supplied to the output terminal 33 via the bandpass filter 12 ₁ . Even in this state, the noise is filtered out by the bandpass filter 12 ₁
At the same time, the spurious of the output signal of the F channel is also removed by the bandpass filter 12 ₁ .

The channel signals supplied to each channel processor 8 ₁ to 8 ₁₆ have different frequencies, and each channel processor 8 ₁ to 8 16 has a different frequency.
_{The 16} output signals are different output channel signals from the A channel to the T channel.

Each of these output channel signals is supplied to an active combiner 9. This active combiner 9 consists of 16 single-branchers 4 as shown in Figure 3.
6 ₁ to 46 ₁₆ and three 2-way distributors 48, 50, 5
2 and one broadband amplifier 54. 1 each
Branch terminals of the branchers 46 ₁ to 46 ₁₆ are connected to terminals 56 ₁ to 5 on the output side of each channel processor 8 ₁ to 8 ₁₆ .
Connected via 6 ₁₆ . 1 branch each 46 ₁
The input terminals and output terminals of ~ ₄₆₄ are connected in cascade, the output terminal of the 1 _- brancher 461 is connected to a dummy resistor 58, and the input terminal of the 1-brancher ₄₆₄ is connected to one side of the 2-divider 48. is connected to the distribution terminal of the 1 branchers 46 ₅ to 46 ₈ are similarly connected in cascade,
The output terminal of the 1-brancher 46 ₈ is also connected to the dummy resistor 58 , and the input terminal of the 1-brancher 46 ₅ is also connected to the other distribution terminal of the 2-brancher 48 . The 1 branchers 46a to ₄₆₁₆ are similarly connected to the dummy resistor 58 and the 2-way divider 50. The input terminals of these two-way dividers 48 and 50 are connected to both distribution terminals of a two-way divider 52, respectively. The input terminal of this two-way divider 52 is connected to a broadband amplifier 54. This active combiner 9 includes 1-branchers 46 ₁ to _{46 16} , 2-branchers 48, 50, 52,
Because they are reversely coupled, when a signal is input from a branch terminal or distribution terminal, it is difficult for the signal to flow back to the other distribution terminals of the distributor or to the output terminal of the branch, and instead flows to the input terminal of the distributor or branch. , the signal supplied to the output terminal of the splitter flows to the input terminal side, and the 1-brancher 46 ₁ to 46 ₁₆ and the 2-brancher 4
8, 50, and 52 are used as a type of directional coupler, and the output signals of the channel processors 8 ₁ to 8 ₁₆ inputted from each branch terminal 56 ₁ to 56 ₁₆ are sent to each branch terminal 46 _{1 to} 56 16 . The output signal is generated at the input side of 46 ₁₆ by a loss corresponding to the branching loss, and is added to the output side of the adjacent one-branchers 46 ₁ to 46 ₁₆ . In this way, the output signal of each channel processor 8 ₁ to 8 ₁₆ is supplied to the 2-way divider 48, 50, and from there, it is supplied via the 2-way divider 52 to the broadband amplifier 54, where it is amplified and sent to the output terminal 60. to the main cable of the communal viewing equipment.
In this case, each of the 1-branchers 46 ₁ to 46 ₈ and the 2-dividers 48 , 50 , 52 is configured to have a wide band so as to pass signals from the A channel to the T channel, and the wide band amplifier 54 is similarly configured. Configured for wideband. Therefore, even if the frequency of the output signal of each channel processor is changed, the output signals from each channel processor 8 ₁ to 8 ₁₆ can be mixed by the active combiner 9 without making any adjustment to the active combiner 9. and then sent out to the trunk cable.

When the active combiner 9 is used as a mixing section in this way, even if the frequency of the output signals of the channel processors is changed, the output signals of each channel processor can be mixed without adjustment and sent to the main cable. Therefore, in the conventional filter shown in FIG. 4, it is conceivable to use an active combiner in place of each of the bandpass filters 4 ₁ to 4 _o . However, the active combiner has a wide band so that it can cover all the frequency bands of the output signals of the frequency converters 2 ₁ to 2 _o in order to amplify and output signals of various input frequencies. Moreover, since each frequency converter 2 ₁ to 2 _o is also capable of varying the frequency of the output signal,
The built-in amplifier is also configured to have a wide band. Therefore, as shown in Fig. 5a and b, when the output signals of two frequency converters whose noise level N and signal level S are equal and whose output signals differ only in frequency are mixed by an active combiner, the output signal shown in Fig. 5c is obtained. As shown, the noise level increases and the C/N ratio deteriorates as a result. Moreover, since it has a wide band, spurious signals output from each frequency conversion section are also amplified.

However, in this embodiment, the output signals supplied to the active combiner 9 from each channel processor 8 ₁ to _{8 16} are
Since noise is removed and spurious is also removed by the bandpass filter in ~ ₈₁₆ , it is possible to achieve a C// A good N ratio can be obtained, and spurious signals can be suppressed to the same level.

FIG. 5d shows the output when the outputs of the two channel processors configured as shown in FIG. 1 are supplied to the active combiner 9, and a comparison between this and FIG. It is clear that this can be improved.

In the above embodiment, the number of channel processors is 16, but this number can be changed arbitrarily. Furthermore, although the number of channels that can convert the frequency of an input signal with one channel processor is 20, this number can be changed as desired. Furthermore, in the above embodiment, the channel processor converts the frequency of the input signal and outputs it, but after converting the input signal to a signal of another frequency,
It is also possible to use a configuration in which the processor section 20 processes the signal and converts it back to the same frequency as the input signal. Furthermore, although the output side PIN diodes 36 ₁ to 36 ₅ are provided in the selection means, these may be removed and the output side of each bandpass filter may be directly connected to the output terminal.

[Brief explanation of the drawing]

FIG. 1 shows one of the head end devices according to the present invention.
Block diagram of the signal processing device used in the example, Part 2
The figure is a block diagram of the same embodiment, Figure 3 is a block diagram of the active combiner used in the same embodiment, and Figure 4 is a block diagram of the active combiner used in the same embodiment.
The figure shows a block diagram of a conventional head end, Figures 5a and b are frequency characteristic diagrams of the channel processor used in the head end of Figure 4, and Figure 5c shows the output of the frequency converter shown in Figure 4 used in an active combiner. FIG. 5d is a frequency characteristic diagram of the output of the active combiner in FIG. 2. 8 ₁ to 8 ₁₆ ... Channel processor (signal processing device), 9 ... Active combiner, 10 ...
... Signal processing unit, 12 ₁ - 12 ₅ ... Band pass filter, 14 ... Selection means, 46 ₁ - 46 ₁₆ ... Branch, 48, 50, 52 ... Divider, 54 ... Broadband amplifier.

Claims (1)

[Claims] 1. A signal processing unit configured to send out the input signals received from a plurality of input terminals, each of which is supplied with input signals of different frequencies, as an output signal of a frequency selected from within a predetermined frequency range. , a plurality of bandpass filters each having a pass band corresponding to each frequency band obtained by dividing the frequency range into a plurality of sections each including a plurality of output signals of different frequencies; each of these bandpass filters and the signal processing section; and selecting means for supplying the output signal of the signal processing section to one of the bandpass filters having a band for passing the output signal of the signal processing section. , a plurality of branchers are provided, and the output signals from these signal processing devices are supplied to an active combiner, and the active combiner is provided with a plurality of branchers, each having a wide band characteristic that allows output signals within the above frequency range to pass. The output signal of each signal processing device is supplied to the branch terminals of these branching devices, and each branching device has an input terminal connected to an output terminal of a preceding branching device, and an output terminal connected to a subsequent branching device. A head end configured to mix the output signals of the respective signal processing devices by connecting to the input terminals of the signal processing devices, and to amplify the mixed output by a wideband amplifier.