JPH08116228A - Digital signal distributer - Google Patents

Abstract

PURPOSE: To use an inexpensive amplifier not requiring gain control for a distributer by providing an impedance adjustment circuit to supply a digital signal with a prescribed voltage level to a 2nd connector. CONSTITUTION: When an equipment B is not connected, a contact 13 is in contact with a signal contact of a connector 12 to form a circuit pulling-down a bit stream signal through a resistor 14. Thus, the resistor 14 acts like a termination resistor, the bit stream signal is divided by an output impedance of a BS tuner 2 and the resistance of the resistor 14 to keep a level of the bit stream signal to be 0.5VP- P. When a plug is plugged into the connector 12, a center pin of the plug comes into contact with the signal contact of the connector 12 and depresses the signal contact simultaneously. In this case, the function of the termination resistor is lost from the resistor 14 and the input impedance of the equipment B offers the similar effect to that of the termination resistor, then the level of the bit stream signal is also kept to be 0.5VP- P in this case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal distributor for distributing digital signals such as bit stream signals based on BS satellite broadcasting to non-stationary household electric appliances such as TV game machines.

[0002]

2. Description of the Related Art An example of a device for distributing an analog signal to a plurality of devices is a TV RF signal distributor. RF
The signal distributor distributes the RF signal from the antenna to TV1 and TV2 as shown in the block diagram of FIG. As a result, TV broadcasts can be viewed simultaneously on TV1 and TV2. An example of a device that distributes a digital signal to a plurality of devices is a SCSI interface defined by the ANSI standard. An example of a SCSI interface is shown in FIG. For example, when a command signal is generated from the computer as an initiator, the device A interprets whether the command is issued to itself, and at the same time, distributes the command signal to the device B. The device B receives the command signal and interprets whether the command is issued to itself, like the device A. Therefore, in this case, device A
Can be interpreted as having a built-in device for distributing digital signals. Noise is reduced by adding an impedance adjusting circuit called a terminator to the final stage of the SCSI signal wiring.

[0003]

In the RF signal distributor, when two TVs are connected, the RF signal is attenuated. 1
When a book TV signal is distributed to two TVs, the amplitude of the distributed RF signal becomes half or less due to the input impedance of both TVs. (It goes down by more than 3 dB.) However, TV
Each has a built-in amplifier capable of gain control, by which the RF signal is amplified and finally automatically demodulated into a video signal of 1 V _PP , for example. Since high-frequency analog signals are easily attenuated even with slight impedance mismatch in the signal path, each TV must be equipped with an amplifier that can control Geni, and an inexpensive amplifier circuit without gain control function is used. I couldn't. Furthermore, in order to reduce noise, it was necessary to connect a terminating resistor of 75Ω to the empty terminal.

Further, in the case of a digital signal, a gain control that is more delicate than that of an analog signal is not required, and therefore, a gain controllable amplifier is not usually installed in a device. A device with a low input impedance is equipped with an amplifier that takes into account the voltage drop that accompanies the connection. However, the signal level changes depending on whether this device is connected, so distribute the signal to another device. In this case, the fluctuation of the signal level becomes a serious problem. Furthermore, in order to reduce noise when the frequency of the signal is high,
After all, it is necessary to adjust the impedance with a resistor separate from the distributor. For example, in the case of a daisy chain connection digital signal line such as SCSI, a terminator must be connected to the final connector. SC
Since SI is usually used for the interface of a personal computer, it is often used for business purposes, but in the case of household equipment, there is a high risk of losing these separate resistors. Further, in the case of the daisy chain connection as described above, there is a problem that wiring is an obstacle in non-stationary household appliances. For example, when wiring a digital cable to a home-use TV game machine, if a thick cable is connected in a daisy chain, troubles such as catching a leg on the cable are likely to occur.

[0005]

The digital signal distributor according to the first aspect of the present invention comprises a first connector for connecting to a first electric device and a second connector for connecting to a second electric device. A connector, a third connector for connecting to a signal source, and circuit wiring for distributing a digital signal from the third connector to the first and second connectors, An impedance adjustment circuit for applying the digital signal having a constant voltage amplitude to the second connector is provided regardless of whether or not an electric device is connected to the first connector. The digital signal distributor according to the second aspect of the present invention includes a relatively thick and short first cable for connecting to a signal source, a first connector for connecting to a first electric device, and a relatively thin connector. An impedance adjusting circuit for applying the digital signal having a constant voltage amplitude to the second cable regardless of whether or not the second long cable is connected to the first electric device and the first connector. And a digital signal supplied from the first cable is supplied via the second cable to a second non-stationary household electric device, and at the same time, the digital signal is supplied to the impedance adjustment unit. It is supplied to the first connector through a circuit.

[0006]

The impedance adjustment circuit is a simple circuit that keeps the signal level constant regardless of whether the equipment is connected or not. Therefore, the voltage amplitude of the digital signal supplied to the second electric device is kept constant, and an inexpensive amplifier that does not require a gain control function can be used for the first and second devices. Further, since impedance adjustment is automatically performed, it is not necessary to add a terminating resistor separately. Furthermore, this case is relatively thin and long from distributors to non-stationary home electric appliances such as home game machines.
Since the cables are connected with each other, the cables do not get in the way, and troubles can be relatively reduced.

[0007]

[Embodiment] Data broadcasting by satellite broadcasting has been conventionally used only for transmitting scrambled data of pay broadcasting, but in recent years, preparations have been made to start a data broadcasting service that uses data itself. . Therefore, in this field, a method for distributing broadcast data to each receiving device is being sought. The invention of the present application is suitably applied to such fields. FIG. 1 shows a block diagram when the digital signal distributor is applied to a bit stream signal based on satellite broadcasting. Satellite broadcasting is received by the BS antenna 1, and the BS tuner 2 selects an arbitrary broadcasting channel. The sub-carrier signal of the selected broadcast channel is demodulated by the BS tuner and output as a bit stream signal which is a serial digital signal. The distributor 3 distributes the bit stream signal to the devices A4 and B5. Here, the device A4 is
For example, a non-stationary home electric device such as a TV game machine is shown, and a device B5 is a decoder for descrambling in pay satellite broadcasting, for example.

Among the users who have purchased the device A4 and the distributor 3, the user who already has the BS antenna 1, the BS tuner 2, and the scramble decoder (device B5) set is the BS tuner 2 and the scramble decoder (device B5). ), A bit stream signal is distributed to the device A4 and the device B5, and both broadcasts can be enjoyed alternately or simultaneously. On the other hand, a user who does not have a scramble decoder (device B5) may directly connect the BS tuner 2 and the device A4, but for that purpose, it is necessary to bundle a direct connection cable in addition to the distributor 3. It is uneconomical. The distributor 3 may be used as a substitute for the direct connection cable, but in this case the connector to be connected to the device B5 is an open end.

The bit stream signal is output from the BS tuner with 1 V _PP and an output impedance of 75Ω, but since the device B5 receives the signal with an input impedance of 75Ω, it is eventually divided into ½ and the voltage is reduced to 0. 5V
It becomes the amplitude of _PP . However, if there is no device B5,
The bitstream signal is not divided and remains at 1V _PP . That is, the voltage amplitude of the bit stream signal supplied to the device A4 varies depending on whether the device B5 is connected or not, and it becomes necessary to mount an expensive gain controllable amplifier in the device A. As one means for solving this problem, when the device B5 is not connected, there is a method of connecting a separate 75Ω terminating resistor to the open end based on the prior art. However, the separate resistor is easily lost, and if the user forgets to connect the terminating resistor, the data broadcast cannot be received normally. On the other hand, since the distributor 3 of the present invention has a built-in circuit for automatically adjusting the impedance, it is not necessary to provide a resistor separately.

FIG. 4 shows the simplest embodiment of the present invention. The connector 10 is connected to the BS tuner 2 and inputs a bitstream signal. The connector 10 includes a relatively thick and short cable with an RCA pin plug that is directly attached to a board, for example. The connector 11 is a device A4.
(For example, a home TV game machine), and a connector 1
The bit stream signal from 0 is output. Connector 1
1 comprises a relatively thin and long cable with RCA pin plugs, for example directly attached to the substrate. Since the device A4 has a high input impedance, this connection has no effect on the voltage amplitude of the bitstream signal. The connector 12 is a device B5 (for example, a scramble decoder).
And outputs the bit stream signal from the connector 10. The connector 12 is, for example, an RCA with contacts 13.
Including pin jack. A resistor 14 is connected to the contact 13, and the resistance value of the resistor 14 is set to a value equivalent to the input impedance of the device B.

If device B5 is not connected, contact 1
Reference numeral 3 is in contact with the signal contact piece of the connector 12 and constitutes a circuit for pulling down the bit stream signal with the resistor 14. As a result, the resistor 14 functions as a terminating resistor, the bit stream signal is divided by the output impedance of the BS tuner 2 and the resistor 14, and the amplitude of the bit stream signal is maintained at 0.5V _PP . When the plug is inserted into the connector 12, the center pin of the plug comes into contact with the signal contact piece of the connector 12 and simultaneously pushes down the signal contact piece. As a result, the contact between the signal contact piece and the contact 13 is released, and the resistor 14 loses its function as a terminating resistor. However, in this case, since the input impedance of the device B has the same effect as that of the terminating resistor, the amplitude of the bit stream signal also holds 0.5 V _PP .
Therefore, it can be said that the connector 12 with contacts and the resistor 14 constitute an impedance adjustment circuit.

FIG. 5 shows another more complex embodiment of the present invention. In this figure, parts common to those in FIG. 4 are given the same reference numerals. The amplifier circuit 20 is a very general amplifier circuit having an input impedance of 75Ω. The amplifier circuit is usually composed of operational amplifiers,
Since the bit stream signal is a digital signal, a digital buffer such as a transistor or CMOS logic may be used. The output impedance of the amplifier circuit 20 is also set to 75Ω so as to match the input impedance of the device B5. The bit stream signal from the amplifier circuit is supplied to the device B5 by the connector 21. Also, the bitstream signal is the capacitor 2
2 and is supplied to the device A4 via the connector 11. The bit stream signal from the connector 10 is passed through another amplifier circuit to the capacitor 2
May be given to 2. A DC voltage of, for example, 5V is superimposed on the coupled bitstream signal by a circuit in the device A4 described later. The superimposed DC voltage is
It is separated from the bit stream signal by the inductor 23 and is given to the amplifier circuit 20 as a power supply voltage.

The amplifier circuit 20 keeps the input impedance constant at 75Ω regardless of whether or not the device B5 is connected. Therefore, the amplifier circuit 20 functions as an impedance adjusting circuit. The bitstream signal supplied to the amplifier circuit is amplified to 1V _PP in the amplifier circuit 20. The amplified bit stream signal is divided into 0.5 V _PP again by the output impedance of the amplifier circuit itself and the input impedance of the device B5, and is supplied to the device B5. When the device B5 is not connected, a 1V _PP bit stream signal is output to the open end of the connector 21, but the bit stream signal supplied to the device A4 via the capacitor 22 is output from the BS tuner 2. The voltage is constantly divided by the impedance and the input impedance of the amplifier circuit 20, and the voltage amplitude of 0.5 V _PP is maintained.

FIG. 6 shows a power supply circuit included in device A4 for superimposing a DC voltage on the bitstream signal. The DC voltage is superimposed on the bitstream signal via the inductor 30 and the current limiting resistor 31. This DC power source needs to be constantly supplied regardless of the power switch of the device A4 in order to always operate the amplifier circuit 20 in the distributor 3. The bit stream signal input from the connector 33 is coupled again by the capacitor 32 and supplied to the data broadcast receiving circuit in the device A4.

FIG. 7 is a diagram showing a usage state of the distributor 3. The BS tuner 2 demodulates the bit stream signal from the satellite broadcast from the BS antenna, and outputs the bit stream signal to the distributor 3 via the relatively thick and short cable 41. The BS tuner is a stationary type device, and the distributor 3 is installed on the back surface of the BS tuner. The bit stream signal distributed by the distributor 3 is supplied to a home TV game machine 4 having a data broadcast receiving function by a relatively thin and long cable 40. Normally, the TV game machine is taken out of the storage area only when it is used.
0 must be relatively long to reach the TV game console taken from the back of the BS tuner. Further, the stationary scramble decoder 5 and the distributor 3 are connected by a cable attached to the scramble decoder 5,
Since the distributor 3 is installed on the back surface of the BS tuner, the condition of the cable length is the same as that without the distributor 3. As described above, in this case, since the bit stream signal is supplied to the home-use TV game console with a relatively thin cable, it is easier to handle than the daisy chain connection as shown in FIG. Inadvertent trouble such as catching can be relatively reduced.

[0016]

According to the digital distributor of the present invention, the voltage amplitude of the signal is always constant irrespective of the presence or absence of the connection of the distribution destination device, so that an inexpensive amplifier which does not require gain control can be used. Further, since it is not necessary to have a terminating resistor as a separate body, it is possible to provide a distributor that is easy to connect / separate and does not worry about losing parts. Furthermore, according to the present invention,
It is possible to provide a distributor that is easy to handle and can relatively prevent troubles when distributing digital signals to non-stationary household electric appliances.

[Brief description of drawings]

FIG. 1 is a block diagram when satellite data broadcasting is received by a plurality of devices.

FIG. 2 is a block diagram when an RF signal from a TV antenna is received by a plurality of TVs.

FIG. 3 is a block diagram when a command from a computer is received by a plurality of devices in a SCSI interface.

FIG. 4 is a circuit diagram showing the simplest embodiment of the present invention.

FIG. 5 is a circuit diagram showing another embodiment of the present invention.

6 is a circuit diagram corresponding to the embodiment of FIG. 5 for superimposing a DC voltage on a signal line.

FIG. 7 is an external view showing a usage state of the digital distributor of the present invention.

Claims (5)

[Claims] 1. A digital signal distributor for distributing a digital signal from a single signal source to a plurality of electric devices, a first connector for connecting to a first electric device, and a second connector. A second connector for connecting to an electric device, a third connector for connecting to a signal source, and a device for distributing a digital signal from the third connector to the first and second connectors An impedance adjusting circuit having circuit wiring, for applying the digital signal having a constant voltage amplitude to the second connector regardless of whether or not the first electric device is connected to the first connector. A digital signal distributor having. 2. The first connector has a contact whose contact with the digital signal terminal is released by inserting a connection plug, and the impedance adjustment circuit has the contact and a termination connected thereto. The digital signal distributor according to claim 1, comprising a resistor. 3. A digital signal distributor for distributing a digital signal from a single signal source to a plurality of electric devices, a relatively thick and short first cable for connecting to the signal source, and a first cable. A second connector for connecting to the electric device, a second cable that is relatively thin and long, and the second cable regardless of whether the first electric device is connected to the first connector An impedance adjusting circuit for giving the digital signal having a constant voltage amplitude to the digital signal supplied from the first cable via the second cable, which is not a stationary type for home use. 2. The digital signal distributor, wherein the digital signal is supplied to the second electric device, and at the same time, the digital signal is supplied to the first connector via the impedance adjustment circuit. 4. The first connector has a contact whose contact with the digital signal terminal is released by inserting a connection plug, and the impedance adjustment circuit has the contact and a terminal connected thereto. The digital signal distributor according to claim 3, which is composed of a resistor. 5. The impedance adjusting circuit includes an amplifier circuit, and the power source of the amplifier circuit is supplied from the second device by being superimposed on a digital signal passing through the second cable. A digital signal distributor according to claim 3.