JPH0738519A - RF modulator / demodulator - Google Patents

Abstract

(57) [Summary] [Object] To provide an RF modulator / demodulator for efficiently performing data communication by a personal computer using a CATV network. [Configuration] An RF modulation / demodulation device 10 including an RF transmitter 14 and an RF receiver 15 respectively corresponding to a plurality of channels in a predetermined frequency band and connected to a CATV network. A plurality of channels are respectively time-divided to form a plurality of packets Pa ... Pk. The RF transmitting unit and the RF receiving unit respectively select one of the plurality of packets and perform data communication, thereby improving the utilization efficiency of each channel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RF modulator / demodulator suitable for, for example, a CATV network.

[0002]

2. Description of the Related Art Conventionally, VHs have been provided through coaxial cables.
While retransmitting television broadcast and FM broadcast programs in the F broadcast frequency band, satellite broadcast and other television programs are transmitted in the middle and upper frequency bands of the television broadcast frequency band, and distributed to a large number of subscribers. A known CATV network is known. Receivers and transmitters for television broadcasting, satellite broadcasting, etc. are centrally arranged in the system center of the CATV network, and television signals of a large number of channels transmitted at appropriate levels are inserted into a coaxial cable. It is distributed to each subscriber through the distributor.

On the other hand, so-called personal computer communication is also known in which data is transferred between a plurality of personal computers or the like via a public telephone line. In personal computer communication, BB where many users use one host station
An S (Bulletin Board System) type network is generally used. Further, a modem (modulator / demodulator) for converting a digital signal to a voice signal is inserted between the personal computer and the telephone line.

[0004]

By the way, in the CATV network, for example, there are modems that utilize a specific RF band, such as below the FM broadcast frequency band. Such RF
It is possible to perform personal computer communication via the CATV network by using a modem. However, the conventional RF modem is configured to form a one-to-one dedicated line in any of a plurality of channels obtained by frequency-dividing a specific RF band as described above. However, when personal computer communication is performed via the CATV network, there is a problem that the number of lines cannot be increased because the bandwidth is limited to a specific RF band.

In view of the above point, the object of the present invention is to
An object of the present invention is to provide an RF modulator / demodulator capable of efficiently performing data communication by a personal computer using a TV network.

[0006]

In order to solve the above-mentioned problems, the RF modulator / demodulator according to the first aspect of the present invention has a plurality of parts formed by dividing a predetermined frequency band when the reference numerals of the embodiments described later are made to correspond. R corresponding to each channel
In the RF modulator / demodulator 10 including the F transmitter 14 and the RF receiver 15 and connected to the CATV network, a plurality of channels are time-divisionally divided into a plurality of packets Pa.
And the RF transmitter and the RF receiver respectively select any one of the plurality of packets.

Further, the RF modulator / demodulator according to the second aspect of the present invention is provided with an RF transmitter 14 and an RF receiver 15 respectively corresponding to a predetermined frequency band in correspondence with the reference numerals of the embodiments described later, In the RF modulator / demodulator 10 connected to the CATV network with the identification numbers Na ... Nn, the predetermined identification numbers for broadcast communication different from the series of identification numbers are individually assigned. .

[0008]

According to this structure, independent data communication is possible through a plurality of packets formed in each channel, and the number of substantial lines is significantly increased. Also, direct data communication between arbitrary subscribers and broadcast communication from the host station to each subscriber are possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of a CATV network to which the present invention is applied will be described with reference to FIG.
An embodiment of an RF modulator / demodulator according to the present invention will be described with reference to FIG.

In the CATV network, as shown in FIG. 4, the television signals in the RF band transmitted from the distributor 1 of the system center SC are distributed to the distributors 3a, 3b, ... 3n and service lines 4a, 4b, ... 4
.., Un, respectively, to the subscribers Ua, Ub ,.

Each of the subscribers Ua to Un has at least a television receiver 5. When the subscriber carries out personal computer communication, the distributors 3a to 3n of the CATV network are bidirectional, and the personal computer 6 and the duplexer 7 and the RF modem 10 according to the present invention are provided.

The television receiver 5 is connected to one output terminal 7a of the demultiplexer 7 connected to the distributors 3a to 3n, and the other output terminal 7b of the demultiplexer 7 and the personal computer 6 are connected. The RF modem 10 is inserted between them.
The RF modem 10 includes a personal computer 6
Data is transferred at a speed of, for example, 9600 bps from the RS232C interface incorporated in the.

Each RF modem 10 has an individual subscriber Ua.
~ A series of identification numbers (ID) Na to identify Un ~
Nn is given, and in addition to this ID, an ID for broadcast communication is given. Therefore, personal computer communication can be performed directly between arbitrary subscribers, and broadcast communication can be performed from the host station to each subscriber.

On the system center SC side, the RF modem 2 is provided between the distributor 1 and the host computer 8.
0 is inserted. A modem 9 for connecting to another personal computer communication network is inserted between the host computer 8 and the telephone line Lph.

As described above, in the CATV network, a specific R
Although the F band is frequency-divided to form a plurality of communication channels, in this example, for communication with a personal computer, one is provided under the FM broadcast band, for example, in the RF band of 44 to 46 MHz.
Channels of 10 waves are prepared at intervals of 00 kHz.

As shown in FIG. 1, the RF modem 10 on the subscriber (user) side includes a CPU 11, a system ROM 12 and a CMOS memory 13, and all of them are PL.
L (phase locked loop) type FSK modulation circuit 14
And an FSK demodulation circuit 15.

Personal computer 6 (see FIG. 4)
The transmission data from is supplied from the CPU 11 to the modulation circuit 14, and the FSK signal output from the modulation circuit 14 is supplied to the t-side contact of the transmission / reception changeover switch 17 through the output amplifier 16 and sent from the movable contact.

In the RF band for personal computer communication as described above, the main coaxial cable 2 of the CATV network exhibits a low loss characteristic, so that the output of the amplifier 16 is sufficient, for example, about 1 mW at maximum. Then, at the RF level of this level, the radio interference to the television receivers 5 of the subscribers Ua to Un is unlikely to occur.

The received FSK signal is supplied to the demodulation circuit 15 through the r-side contact of the switch 17 and the amplifier 18, and the received data output from the demodulation circuit 15 is sent to the personal computer 6 (see FIG. 4) through the CPU 11. C that is supplied and has a mailbox function
It is stored in the MOS memory 13. As a result, even when the power of the personal computer is off, it is possible to receive an electronic mail by personal computer communication.

Reference numeral 19 denotes an I / O port, to which a channel selection key Kch is connected, and the I / O port 19, the FSK modulation circuit and the FSK corresponding to the operation of the key Kch.
Data for controlling the transmission frequency and the reception frequency is exchanged with each PLL (not shown) of the demodulation circuits 14 and 15.

Further, the I / O port 19 outputs a control signal for switching between the operation / non-operation of the output amplifier 16 and the transmission / reception of the switch 17. Although not shown, a plurality of light emitting diodes are connected to the I / O port 19 to display various operating states of the RF modem 10.

As shown in FIG. 2, the RF modem 20 on the host side includes a CPU 21, a system ROM 22 and a CMO.
The S memory 23, the FSK modulation circuit 24, and the FSK demodulation circuit 25 are provided. The RF modem 2 on the host side corresponding to a plurality of channels for personal computer communication as described above.
In 0, m sets of CPU to demodulation circuits 21a to 25m are prepared.

In this embodiment, the plurality of channels as described above are time-divided into a plurality of packets Pa, Pb ... Pk, respectively, as shown in FIG. In this communication, only one arbitrary packet Pi is selected for personal computer communication. This packet is formed in accordance with, for example, the "X25" standard.

By forming this packet, a single wave channel can be used by a plurality of users independently of each other, and the use efficiency of the line in a limited frequency band is significantly improved. .

Further, in the embodiment shown in FIG. 1, in the same manner as the manual channel selection by operating the key Kch,
A so-called watchdog timer (not shown) automatically retrieves the usage statuses of a plurality of packets and a plurality of channels as described above during non-communication. The search result is stored in the CMOS memory 13 for each time zone.

When personal computer communication is carried out in an arbitrary time zone, the user can use the channel with the fewest number by referring to the retrieval result of the utilization status of the packet and the channel in the time zone. , Interference can be avoided, or waiting time can be shortened, and communication efficiency can be improved.

During communication, due to interference, congestion, etc.,
When the waiting time becomes long, a comfortable communication environment can be maintained by automatically setting the next channel and avoiding interference.

[0028]

As described above, according to the present invention, there is provided an RF modulator / demodulator which is equipped with an RF transmitter and an RF receiver respectively corresponding to a plurality of channels in a predetermined frequency band and which is connected to a CATV network. , The RF transmitting unit and the RF receiving unit respectively select one of a plurality of packets formed by time-sharing a plurality of channels to perform data communication, thereby improving the utilization efficiency of each channel. Thus, an RF modulator / demodulator that can be used is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an RF modulator / demodulator according to the present invention.

FIG. 2 is a block diagram for explaining the operation of the embodiment of the present invention.

FIG. 3 is a conceptual diagram for explaining the operation of one embodiment of the present invention.

FIG. 4 is a block diagram for explaining the present invention.

[Explanation of symbols]

 10 RF modem (subscriber side) 11 CPU 13 CMOS memory 14 FSK modulation circuit 15 FSK demodulation circuit 20 RF modem (host side) 21 CPU 23 CMOS memory 24 FSK modulation circuit 25 FSK demodulation circuit Kch channel selection key

Claims (4)

[Claims] 1. An RF modulator / demodulator connected to a CATV network, comprising: an RF transmitter and an RF receiver, each of which corresponds to a plurality of channels formed by dividing a predetermined frequency band. Time division is performed to form a plurality of packets, and one of the plurality of packets is transmitted to the RF transmitter and the RF.
An RF modulation / demodulation device characterized in that the receiving section and the receiving section respectively select. 2. R corresponding to each predetermined frequency band
In an RF modulator / demodulator that includes an F transmitter and an RF receiver and is connected to a CATV network by being given a series of identification numbers, a predetermined identification number for broadcast communication, which is different from the series of identification numbers, is individually provided. RF characterized by being applied
Modulator / demodulator. 3. The RF modulator / demodulator according to claim 1, further comprising means for retrieving utilization statuses of the plurality of channels and the plurality of packets. 4. The RF modulation / demodulation device according to claim 1, further comprising a memory unit that stores the reception data from the RF reception unit.