JPH0286383A - Data communication method for catv system - Google Patents

Abstract

PURPOSE:To compensate the loss including a cable loss or the like due to a temperature change and to improve the stability by measuring a level of a data carrier frequency from a center, comparing the measured level with a prescribed level and varying an incoming carrier level of a response data to the center based on the result of comparison. CONSTITUTION:An outgoing signal sent from the center is given to an amplifier 3 via a branch 2 from a CATV line 1, amplified up to a required level by the amplifier 3 and only the data carrier frequency passes though a band pass filter 4. The level of the data carrier frequency is measured by a level detection section 10 and compared with a preset level by a microprocessor 6. Then a variable attenuator 8 is controlled based on the result of comparison and the incoming carrier level to the amplifier 9 is adjusted. Since the center and a terminal equipment are connected by one coaxial CATV line 1, the loss from the terminal equipment to the center is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data communication method for a CATV system that performs bidirectional data communication.

[Conventional technology]

Conventionally, two-way data communication in this type of CATV system has adopted a method in which data signals of a specific frequency sent from the center are received and analyzed at the terminal, and response data is sent from the terminal to the center as necessary. are doing.

FIG. 2 is a block circuit configuration diagram showing an example of this data communication system.

The downlink signal sent from the center is CATV line 1.
is applied to the amplifier 3 via the demultiplexer 2, and this amplifier 3
After being amplified to a required level at , only the data carrier frequency passes through the bandpass filter 4 and is input to the data demodulator 5, where it is detected as data. The detected data is received and analyzed by the microprocessor 6, and when a response is deemed necessary, the microprocessor 6 sends response data to the data signal modulator 7. The response data given to the data signal modulator 7 is here converted into uplink modulation data (uplink carrier), passed through a variable attenuator 8, and amplified by an amplifier 9. sent to l.

In such a communication system, the upstream carrier level is adjusted by controlling the variable attenuator 8 with the microprocessor 6 based on command data from the center.

[Problem to be solved by the invention]

However, according to such conventional data communication systems, the uplink carrier level is adjusted based on command data from the center, so the center takes into account loss conditions such as the distance to the terminal and sets the uplink carrier level. It was necessary to do this.

Furthermore, this level setting did not include the temperature characteristics of the cable, and there were fluctuations in loss after the level was set.

Furthermore, there may be changes such as movement and distribution at the input after the level is set, so it is necessary to increase the dynamic range of the input to the data demodulator for receiving uplink carriers on the center side. Even with this, there are cases where sufficient data cannot be secured and a data error occurs, resulting in the problem that data communication is not performed correctly.

[Means to solve the problem]

The present invention was made to solve such problems, and it measures the level of the data carrier frequency from the center, compares this measured level value with a predetermined level value, and based on the comparison result, transmits data to the center. The uplink carrier level of response data is made variable.

[Effect]

Therefore, according to the present invention, the upstream carrier level of response data to the center is varied based on the level value of the data carrier frequency from the center.

〔Example〕

The data communication method of the CATV system according to the present invention will be explained in detail below.

FIG. 1 is a block circuit configuration diagram showing an embodiment of the data communication method of this CATV system, and the same reference numerals as in FIG. 2 indicate the same or equivalent components, and the explanation thereof will be omitted.

In the figure, 10 is a level detection unit that detects (measures) the level of the data carrier frequency that has passed through the bandpass filter 4, and the detected (measured) level value of the data carrier frequency in this level detection unit 10 is determined by the microprocessor 6. It is to be given to The microprocessor 6 compares the supplied measured level value with a predetermined level value set therein, and adjusts the upstream carrier level by controlling the variable attenuator 8 based on the comparison result. It has the function to do.

In the data communication system configured in this way, the downlink signal sent from the center is sent from the CATV line 1 through the duplexer 2 to the amplifier 3, where it is amplified to the required level. Only the data carrier frequency passes through the bandpass filter 4.The data carrier frequency that has passed through the bandpass filter 4 is transferred to the data demodulator 5.
The detected data is received and analyzed by the microprocessor 6. When a response is deemed necessary, the microprocessor 6 sends response data to the data signal modulator 7. The response data given to the data signal modulator 7 is converted into an uplink carrier here, and is amplified by an amplifier 9 via a variable attenuator 8.
Sent to TV line 1.

On the other hand, the level value of the data carrier frequency that has passed through the bandpass filter 4 is measured in the level detecting section 10, and the measured level value is compared in the microprocessor 6 with a predetermined level value set therein in advance. Based on the comparison result, the microprocessor 6 controls the variable attenuator 8 to adjust the upstream carrier level to the amplifier 9. In other words, since the center and terminals are connected by a single coaxial cable via CATV line 1, by measuring the level value of the data carrier frequency sent from the center, variable attenuation is applied according to the measured level value. By controlling the device 8 by the microprocessor 6 and making the upstream carrier level variable, it is possible to compensate for loss from the terminal to the center, and also compensate for fluctuations in cable loss due to temperature changes. , the effect of realizing a highly stable system can be obtained.

Furthermore, if the measured level value of the data carrier frequency is sent as data to the center, it is possible to know the loss from the center to the terminal, and it is also possible to manage it as a system.

〔Effect of the invention〕

As explained above, according to the data communication method of the CATV system according to the present invention, the level of the data carrier frequency from the center is measured, this measured level value is compared with a predetermined level value, and based on the result of this comparison, the level of the data carrier frequency from the center is measured. Since the upstream carrier level of response data is made variable,
It is no longer necessary to give command data at the center taking into consideration conditions such as the distance to the terminal, and it is now possible to compensate for fluctuations such as cable loss due to temperature changes, resulting in a highly stable system. play.

[Brief explanation of drawings]

FIG. 1 is a block circuit configuration diagram showing an example of a data communication method of a CATV system according to the present invention, and FIG. 2 is a block circuit diagram showing an example of a data communication method of a conventional CATV system. DESCRIPTION OF SYMBOLS 1... CATV line, 2... Branch filter, 4... Bandpass filter, 5... Data demodulation part, 6... Microprocessor, 7... Data signal modulator, 8... Variable attenuator, 10...level detection section.

Claims (1)

[Claims] In the data communication method of a CATV system that performs two-way data communication, the level of the data carrier frequency from the center is measured, this measured level value is compared with a predetermined level value, and based on the comparison result, response data to the center is determined. CATV characterized by variable upstream carrier level
System data communication method.