JPS61145980A - Bidirectional catv - Google Patents

Abstract

PURPOSE:To make it possible easily to confirm a carrier wave outgo at an adjustment time by displaying for a designated carrier frequency that a carrier wave is outgone from a subscriber side to a feeder cable. CONSTITUTION:A CPU15 produces a pseudolike transmission request signal (RST signal) according as a command which was sent by utilizing an idle command of a remote controlled sender 20 and consequently produces a transmission frequency selective (SEL). These two signals; those of RST and SEL are supplied to a carrier wave frequency setting circuit 40 and then produce a signal which changes an oscillation frequency of an oscillator 50; for instance, its frequency to f1 or f2. The oscillation frequency of oscillator 50 which was designated by a control signal produced at this carrier wave setting circuit 40 performs a phase modulation of a pseudodata which was set, for example, to the CPU15 by means of a multiplier 70 and then sends out a carrier wave frequency signal to be adjusted through an amplifier 80 to the feeder cable side. A carrier wave which is outgone in that case is detected by a carrier wave outgoing display mode 110 and it is displayed accordingly.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a two-way CATV that enables two-way communication between a center side and subscriber terminals, and particularly relates to a two-way CATV that enables two-way communication between a center side and subscriber terminals. The bidirectional C is suitable for efficiently detecting the output level in order to set the output level to an appropriate value.
Regarding ATV. Also.

The data carrier is sent out via Artop Stream to the main cable and drives the display circuit during the period.

The present invention relates to a two-way CATV having means for notifying subscribers that a carrier wave is being transmitted.

[Summary of the invention]

In this invention, for example, as shown in FIG. 1, in a two-way CATVK that allows data communication between the center side and subscribers,
The carrier wave level in the transmission of pseudo data from the subscriber terminal 10 to the center side is detected and used for adjustment of the transmission level.

For example, CPU15. For example, a pseudo transmission request signal (RTS signal) is generated in response to a command sent by using a vacant command of the remote control transmitter 20, and a transmission frequency selection signal (SEL) is generated accordingly. Both the ST signal and the SEL signal are supplied to a carrier frequency setting circuit 40, which generates a signal for switching the oscillation frequency of the oscillator, for example f, f, Ic. The oscillation frequency of the oscillator group specified by the control signal generated by the carrier wave setting circuit is set to 1 in the multiplier 70.
For example, pseudo data set in the CPU 15 is phase-modulated and a carrier frequency signal to be adjusted is sent to the main cable side via an amplifier.

In this case, the carrier wave transmission display means detects and displays the fact that the carrier wave is being transmitted.

With this method, it is possible to send out a carrier wave for adjusting the data sending level of any subscriber simply by operating a remote controller, for example, without waiting for polling from the center, and this sending can be confirmed by the carrier wave sending confirmation means described above. You can know.

[Technical background of the invention and its problems]

In CATV, so-called two-way CATV, which enables two-way communication between the center and subscribers, as well as rebroadcasting of television broadcasts as a countermeasure for difficult viewing, has become popular as urban WCATV.

Since this bidirectional CATV allows communication between the center and subscribers, it is possible to make program reservations for subscribers, process billing information for paid broadcasting, and even perform services such as the security system using bidirectionality. .

In this case, since a plurality of subscribers transmit data upstream to the center, the data communication level needs to be set to an appropriate level corresponding to the cable length between the center or trunk amplifier and the subscribers. This is also necessary in order to suppress distortion of the main amplifier. Furthermore, since the level of the receiver on the center side varies depending on the distance between subscribers, a problem arises in that the dynamic range of the center must also be widened.

Furthermore, in order to adjust the data transmission level of each individual subscriber, data transmission is performed only for subscribers designated by polling from the center. The level of this sent data will be controlled. Therefore, in order to complete the adjustment of the data transmission level for all subscribers, the center must poll all subscribers.
A problem occurs that takes a long time.

Therefore, when adjusting the transmission level, it is desirable to transmit a data carrier wave from the subscriber side, detect the transmission level, and perform the adjustment without waiting for a designation such as polling from the center. Therefore, the problem is how to implement a means for giving priority to transmission from the subscriber side. In this case, when a carrier is being sent to the subscriber's trunk cable, whether for further adjustment of the sending level or to send data upstream, it may be necessary to indicate that the carrier is being sent. desired.

[Embodiments of the invention]

Figure 2 shows a general bidirectional CAT to which this invention is applied.
FIG. 2 is a circuit diagram showing the v system.

In the same figure, for air waves, parabolic antenna 1
The 8HF signal is converted to VHF by antenna 2.

It receives the UHF signal, converts it into a retransmission signal at the head end, and sends it out to the main line. Further, signals such as independent broadcast signals and pay broadcast signals are mixed by the transmitter 4 with the retransmission signal in a mixer and then sent to the main line.

Regarding two-way communication, downstream signals to subscribers are sent to the center CPU 5.
The data is subjected to FSK modulation, for example, by a modulator 6, and then sent to the main line. In this case, which subscriber the message is sent to is specified by the address specified by the center PU. Note that by using a group address, data can be sent to a specific group, and depending on the settings of the specific address, data can also be sent to all subscribers. On the other hand, regarding upstream, a PSK modulated signal is demodulated by a demodulator 7 at the subscriber, the demodulated data is processed by the center CPU 5, and the processing result is output to an output device such as a CRT display or a line printer. 8 is output as necessary.

In this way, data from the center side to each terminal subscriber is polled sequentially according to the address of the subscriber terminal, and responses from the subscribers are sent to the center via the upstream, thereby performing two-way communication.

The main cable has a unique frequency characteristic and needs to be tilted for high-range attenuation, which is done by the bidirectional amplifier 9.

Each subscriber terminal 10 sends and receives signals via the trunk amplifier 10.

Signals are sent and received to and from each subscriber terminal 10 via a two-way coupler, and the two-way coupler 11 is added to a converter team 12 that performs frequency conversion, converting it into a predetermined fixed channel signal and transmitting it to a television channel. It is added to the receiver 13. Further, among the data signals, a downstream signal is applied to the demodulator 14, where the data is demodulated to F8.
Data processing is performed in rtr15. Regarding the upstream, when the address is specified by polling from the center, it is compared with the address set in the address section 16, and if they match, the data to be sent set by the CPU 15 is converted into PSK by the modulator 17 that constitutes the PSK modulator.
The data is modulated and sent to the main line via the bidirectional coupler 11.

What is the data transmission level from this subscriber terminal side?

As mentioned above, the distance to the center and the dynamic range of the demodulator 7, which is the receiver on the center side.

It is necessary to set it at an appropriate level from the viewpoint of saturation of the main amplifier 9, etc. Furthermore, in order to perform adjustment for all subscribers, polling is performed for each subscriber, and each transmission level is checked and the transmission level is adjusted, which poses a problem in terms of adjustment time. Further, when a spare carrier frequency is set for upstream data communication, it is necessary to perform level detection on this frequency as well to bring it to an appropriate level, but in this case as well, adjustment time becomes a problem.

In the embodiment of the two-way CATV according to the present invention, a remote control of a subscriber terminal is used to send a command to send data, and the level of data sent at this time is detected and level adjustment is performed.

This makes it possible to adjust the transmission level for any subscriber terminal at any time without waiting for polling from the center. Furthermore, the transmission level can be adjusted for a plurality of carrier frequencies without restricting the center.

In the embodiment shown in FIG. 3, only the subscriber terminal side of the bidirectional CATV is shown. In this figure, parts having functions corresponding to those in FIG. 2 are designated by the same reference numerals, and their explanations will be omitted.

In FIG. 3, among the downstream signals from the center, signals such as television broadcast signals are applied to a converter tuner 12 via a bidirectional coupler 11, where the frequency is converted to a predetermined television channel frequency. After being televised! ' is applied to the antenna input terminal of the receiver 13.

On the other hand, the FSX-modulated data signal is applied to an FSK demodulator 14 that performs FSK demodulation, and the data demodulated here is processed by the CPU 15.

For upstream data transmission, when the addresses in the address section 16 match based on polling from the center, the data set by the CPU is passed through the low-pass filter 70, and the oscillator is excited for one data transmission request period. This is done by, for example, performing two-phase phase modulation using the output of the oscillator using a multiplier ω. The phase-modulated sending data is sent to the main line via the bidirectional coupler 11 and sent to the center side. The transmission level at this time needs to be a constant level regardless of the difference in the length of the cable connecting the subscriber terminal. This level adjustment is performed by adjusting the signal gain of an amplifier that amplifies the phase-modulated data to be sent out from the multiplier 70. For this purpose, the amplification gain of the amplifier (equipment) is controlled or the amount of attenuation of an attenuator (not shown) is controlled to adjust and prescribe the output level sent to the trunk cable to an appropriate level. This prevents input distortion of the trunk-width bidirectional amplifier 9, and furthermore suppresses data distortion during demodulation due to excessive input or low level in the center receiving section.

The transmission data level on the trunk line must be adjusted to an appropriate level as described above, but even if the amplification gain of the trunk cable system is appropriate, there may be problems such as excessive signal levels when transmitting data from the subscriber terminal side. If a signal of an inappropriate level is applied, data demodulation error may occur on the center side.

Therefore, adjustment of the transmission level on the subscriber side is required, especially regarding data transmission.

In this case, the problem is how to send data for level adjustment from the subscriber terminal.

In Jin's embodiment, a carrier wave for adjusting the sending level is sent out by using the data sending means in normal data communication without providing a special table circuit means for sending out the data sending level.

That is, in this embodiment, during normal operation, the remote control transmitter 20 adds a carrier wave transmission command to the transmitted command, operates the remote control receiver according to this command, controls the crty 15, and issues a carrier wave transmission request. When the oscillator father is excited during the period R8F which excites the oscillator group by generating a signal (R8T signal), its oscillation output is sent to the data output terminal DAT of the CPU by the multiplier 70.
A, The state signal from OUT is multiplied by the signal obtained through the low-pass filter ω. The output of the multiplier 70 is further sent as a carrier wave to the trunk cable via an amplifier.

The CPU 15 generates a RAT signal under the control of a remote control receiver (equipment).

With the remote control transmitter 4, the CPU 15 is transmitted as shown in Fig. 4.
' 7th day - char)K Process the contents shown. In the figure, when an interrupt request is received from the remote controller transmitter in step S, numerical values such as channel selection values are set F1 in step SY in accordance with a predetermined command. Volume control F
3. Channel up/down control.

Controls functions such as the famous contract system XIF4 for paid programs.

Here, among the remote control command commands, if an idle command is made to correspond as a carrier wave transmission command for adjusting the data transmission level, a level test command F can be set. FIG. 5 shows a code example as a command data configuration example corresponding to the type of control command at this time. In the same figure, the control code for generating an RTS signal to the CPU 15 to adjust the data sending level is [111
It is 10000J.

Therefore, when adjusting the level of the carrier wave sent to the trunk cable, use the remote control transmitter
ooooJ code to remote control receiver (9)!・When K is sent, the level test command F1 in the flowchart shown in FIG. 4 is sent to C via the remote control receiver.
Sent to PU15. The data structure at the time of transmitting the remote control signal is, for example, as shown in FIG. As shown in the figure, the remote control data from the remote controller/2 transmitter 20 includes a reader section indicating the start of transmission, a data section DATA, and a data section DATA.
It consists of DATA.

For command data, original data and inverted data are transmitted serially to prevent malfunctions.

Next, when the remote control transmitter 20 sends a command corresponding to the level test command F to the CPU 15, the carrier wave is sent to the main cable side under the control of the CPU 15 of the subscriber terminal to adjust the transmission level. The sending operation will be explained using the circuit diagram shown in FIG. 3 above.

In order to adjust the data transmission level from the remote control transmitter 20 of the subscriber side terminal 10, the level test command F,
When this is sent to the remote control receiver (equipment), this is received by the remote control receiver (9) and an interrupt request is made to the CPU 15 to execute the level test command F.

CPU152>E level test; When receiving the command data (Fig. 7(a)) corresponding to the cloak Fll, the CPU
sets the frequency selection signal (SEL) that defines the carrier frequency to a low level (FIG. 7 Φ)) and generates a data transmission request signal (ST signal) (FIG. 7(C)). Also, at this time, cpty 15 has its data output terminal D
ATA.

Set suspicious data to OUT. Among the output signals of the CPU 15, one frequency selection signal (SEL) indicates that in bidirectional communication, when the frequency of the carrier wave sent to the upstream is the first frequency f1, the subscriber side terminal goes out of control and there is no transmission data. If the carrier wave continues to be transmitted in spite of this, the center side gives a control signal to the downstream side to change the data transmission carrier wave frequency to be transmitted upstream to a different frequency f for each subscriber side terminal. This is a signal that responds to a command given. That is, in a situation where a subscriber terminal exhibits abnormal oscillation or the like and interferes with upstream communications of other subscribers, each subscriber terminal is commanded to change the frequency of the transmitted carrier wave. Each terminal subscriber who received this instruction.

The frequency of the carrier wave to be currently transmitted by each CPU 15 is defined by generating the frequency selection signal (SEL).

The frequency selection signal (SEL) is at a low voltage level when the subscriber sends normal data to the upstream at the carrier frequency f1, and when the carrier oscillator on the subscriber side oscillates abnormally, the carrier wave oscillator from the center side A control signal is sent to change the frequency, and when the frequency selection signal goes low, the carrier frequency changes.

That is, 1. During normal data transmission, the frequency selection signal is C.
set to low level by PU15 (in Figure 7))
S The above carrier wave frequency is designated as fl.

The above test command F causes the test command data (FIG. 7(a)) to generate the above carrier wave request signal (ST).
signal) arrives and the frequency selection signal (SDI) is at a low level (Fig. 7-)), the diode 41 is cut off and the transistor is also cut off, and the output of the inverter is in a low level state. . Therefore, the diode D1 becomes conductive, and the crystal resonator X is excited.

This excitation frequency ft is the base III of the transistor 52.
IK added. At this time, the R8T signal causes the transistor 52 to conduct, and the frequency f determined by the crystal oscillator X1 is fed back by the feedback capacitor C0.
1 to continue oscillation.

In this case, the R8T signal at the high voltage level is converted to a low voltage level by the inverter 45, so that the R8T signal is
While the signal is at a high voltage level, the transistor is in a cut-off state. Therefore, the capacitor 49 is charged via the resistors 47 and 48, and the terminal voltage of the capacitor 49 (
Point A) gradually rises (point A).

Figure 7(d)). When the terminal voltage of the capacitor 49 increases to the point where it exceeds the diode voltage of the Zener diode DZ, the transistor 49 becomes conductive regardless of the SEL signal. When the transistor 42 becomes conductive, the collector potential of the transistor 42 is lowered, and the output of the inverter becomes a high voltage level.The diode D1 changes to a cutoff state, and the diode D1 cuts off, stopping the excitation of the crystal resonator. Ru. At the same time, as the collector voltage of the transistor 42 drops, the diode D, which has been in a cut-off state, changes to a conductive state, and the crystal resonator X starts to excite. At this time, the oscillation frequency of the transistor 52 □ is the oscillation frequency f! determined by the crystal oscillator X. becomes.

That is, the potential at the output terminal (point B) of the inverter 4 is at a low level from the time the R8T signal arrives and the transistor 46 is cut off until the terminal voltage of the capacitor 49 rises and exceeds the Zener diode ZD. The frequency of the carrier wave is set to fl for a period of , and when the terminal voltage of the capacitor 49 rises to the Zener voltage and the SEL signal reaches a high voltage level, the transistor 42 becomes conductive, and the frequency of the carrier wave changes to the frequency of the crystal resonator. X! The frequency changes to f, which is determined by .

From this carrier wave frequency f1 to f! Switching to R8 above
After the arrival of the T signal, the resistances 47, 48 . This is done automatically after a period of time determined by the capacitor.

Therefore, when sending data normally upstream, if a situation occurs in which a carrier wave is sent beyond the R8T signal period, the carrier wave of the same wave number ft is automatically stopped and the carrier wave frequency is switched to f. (Figure 7 &i)
).

In this way, when transmitting a carrier wave beyond the period during which data transmission is allowed, the carrier wave is switched, so it is necessary to adjust the transmission level for data transmission with respect to a plurality of frequencies.

The level adjustment of the transmitted carrier wave for the plurality of carrier frequencies is performed by using the resistors 47, 48. After a time constant period determined by capacitor 49,
The oscillation frequency between the oscillators is set to a different oscillation frequency than K.

The carrier wave obtained in this way is added to the 1 multiplier 70, where the pseudo data set in the CPU 15 (FIG. 7(f)) is modulated into, for example, P8, and is sent to the amplifier 80 via the attenuator 100. After being added to the main cable, it is sent out.

When the oscillator is supplying a carrier wave to the multiplier 70, a predetermined DC voltage is obtained by the detection means 111K of the carrier wave sending and display means 110 to turn on the display transistor 112 and drive the LED 113.

As a result, when transmitting a carrier wave, the frequency is f1+'! LF)D of the carrier wave transmission display means 110
113 is lit to indicate that carrier waves are being transmitted. In other words, 1. Even in the case of normal communication.

Even when adjusting the transmission level, it is detected that the carrier wave is transmitted. If the level is adjusted after confirming that the LED 113 is lit, the adjustment is made while the carrier wave is being transmitted, thereby preventing erroneous adjustment.

Further, the transistor 1 of the carrier wave transmission display means 110
If the configuration is such that the pace of 12 is connected to the RTS terminal of the CPU 15, as can be seen from FIG.
That is, carrier wave transmission can be confirmed only for the transmission frequency f in normal communication. In this way, the carrier wave transmission level can be adjusted after confirming the transmission of the carrier wave to be adjusted.

In this case, the CPU 15 uses the remote control transmitter 20 to send a test command to the remote control receiver I in response to, for example, an unused key, decodes it in the CPU 15, and sends the test command to the RAT regardless of the command from the center side.
Generate a signal. That is, by operating a remote control transmitter on the subscriber side, for example, without receiving a designation from the center through polling or the like, the R8T signal can be generated in a pseudo manner and a carrier wave can be obtained for gain adjustment.

In this way, under direction from the subscriber side.

By transmitting a carrier wave and detecting the gain for this carrier wave, for example, at a test point (TP) on the output side of an amplifier (equipment), it is possible to know the transmission level of the carrier wave transmitted from the subscriber side to the center side.

Here, by adjusting the nine levels suitable for sending out to the main line level in accordance with the carrier wave level observed at the above test point TP, the data is sent from the subscriber side to the main line cable. The level can be adjusted appropriately.

In this case, the level adjustment for the above amplifier (equipment) is as follows.

Gain adjustment may be performed on the amplifier itself.

Alternatively, the attenuation amount of the attenuator 100 may be controlled without controlling the gain of the amplifier.

Further, in order to adjust the transmission level, the carrier wave generated by the remote control transmitter 20 is input to the amplifier (supply), and at this time, the amplifier 80 is caused to perform automatic gain control, and the automatic gain control voltage at this time is maintained. , data may be sent to the main line using the gain at this time.

That is, in the flowchart shown in FIG. 4 above, the control command of Lepertes) Fs is inserted into the step S1 of remote control data processing, and various commands are transmitted after the sending level is always properly automatically controlled. Then, control may be performed so that the gain of the amplifier (equipment) becomes appropriate automatically at the time of remote control operation.

〔Effect of the invention〕

As described above, according to the present invention, two-way CATV
In this method, level adjustment when sending data from a subscriber to the center side via an upstream is performed by generating a pseudo data transmission request signal, and a separate signal generation means for adjustment is provided. It can be done without. For this reason, if you use, for example, an empty command from a remote control transmitter as a means of pseudo-generating a data transmission request signal, there is no need to provide a separate circuit for adjustment, and furthermore, you can wait for polling from the sester side. It is possible to easily know the transmission level on the subscriber side and adjust the data transmission level independently of polling from the center.

Furthermore, since a plurality of carrier frequencies can be automatically generated for adjusting the transmission level, efficient adjustment of subscriber equipment can be achieved. Note that the means for causing the CPU 15 to generate a pseudo R8T signal from the subscriber side to adjust the level of the transmitted carrier wave is not limited to the use of the idle command of the remote controller 20, but is essentially a means for exciting the oscillators. Other means may be used if necessary.

In this way, without being tied down to the center side.

At the time of adjustment, carrier waves can be sent out to the trunk cable side as needed from the subscriber side. Also, when adjusting,
Since the apparatus is provided with means for displaying whether or not the carrier wave to be adjusted is being transmitted, it is possible to easily confirm whether or not the carrier wave is being transmitted at the time of adjustment.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an overview of an embodiment of a two-way CATV according to the present invention, FIG. 2 is a circuit diagram showing an example of a general two-way CATV, and FIG. 3 is a circuit diagram showing an example of a two-way CATV according to the present invention.
FIG. 4 is a flowchart for explaining the operation of the circuit shown in FIG. 3. FIG. 5 is a data correspondence diagram showing an example of data corresponding to the control contents shown in FIG. 4, and FIGS. 6 and 7 are waveform diagrams for explaining the operation of the circuit shown in FIG. 3. 15...Data transmission control means. 20.30... Carrier wave transmission control means. 40...Carrier frequency setting circuit. Father... Oscillator. 70...Modulator. 110...Carrier wave transmission display means. Agent Patent attorney Noriyuki Chikasai (and 1 other person) Aku 4- Utsuka s6 tth Hibi 7 (9) τF
=====1117F.

Claims (1)

[Claims] In CATV that enables two-way communication between a center side and non-subscribers at each end via a main cable, data to be sent from the subscriber side terminal to the center side. a data transmission control means having a function of generating a data transmission request signal which sets the data and defines a period for transmitting a carrier wave for modulating this data; an oscillator that generates data transmission, a carrier wave transmission control means that generates the data transmission request signal by a control means provided on the subscriber side, and a carrier wave that indicates the transmission of the carrier wave that is generated in response to a control signal of the carrier wave transmission control means. A two-way CATV comprising at least a transmission display means, the two-way CATV displaying at a predetermined carrier frequency that a carrier wave is being transmitted from the subscriber side to the trunk cable.