JPS63204994A - Automatic meter inspection system utilizing catv circuit - Google Patents

Abstract

PURPOSE:To extremely narrow an exclussive band width on a circuit by providing low frequency data modulating demodulating parts and RF band converter parts for modulating a signal into an RF band, at a central device and a terminal transmitter. CONSTITUTION:The modulated signal of the RF band is inputted to the RF band converter part 31 of the terminal transmitter 30 through a two-way CATV circuit network 20, and is demodulated into the frequency modulated signal of low frequency by the RF converter part 31, and further, the frequency modulated signal of low frequency is demodulated into a digital signal by the low frequency data modulating demodulating part 32, and inputted to a meter inspection processing part 33. The meter inspection processing part 33 performs a call address check, and at the time of a coincidence with a self-address, reads the value of an automatic inspection meter 40, and assembles an answering telegram, and outputs it to the low frequency data modulating demodulating part 32. The low frequency data modulating demodulating part 32 converts the answering telegram into the frequency modulated signal of low frequency, and converts it into the RF band by the RF band converter part 31. By converting into the RF band after modulating at the low frequency, the deviation width of a frequency can be made extremely narrow, and the exclussive band can be narrowed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic meter reading system using a CATV line,
In particular, it relates to RF modulation and demodulation schemes for central equipment and terminal transmitters.

[Prior Art and Problems to Be Solved] Conventionally, this type of RF modulation/demodulation section for automatic meter reading systems has used a modulation method that directly shifts the RF band frequency.

In the conventional automatic meter reading system described above, the RF modulation/demodulation section is
Since it uses F-band frequency direct modulation and demodulation, the exclusive bandwidth of the transmission path is several 100 KH even if the data transmission speed is low.
It has the disadvantage that it requires a wide band of several 100 KHz and cannot be implemented unless a band of several 100 KHz is secured.

The direct frequency modulation method is a modulation method in which the frequency is shifted from logic "1" or "O" around an arbitrary carrier frequency within several tens to hundreds of MHz, but the modulated signal is demodulated. In the case of “It becomes difficult to judge. Therefore, in the direct frequency modulation method, the deviation width cannot be narrowed, resulting in a wide band.

[Means for solving problems] The present invention for solving the above-mentioned conventional problems is a two-way CATV
In an automatic meter reading system using a line, the central device and the terminal transmitter are equipped with a low frequency data modulation/demodulation section that modulates and demodulates a data signal into a low frequency FSX signal, and an RF band converter section that modulates the data signal to the RF band. Consists of composition.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram of an embodiment of the present invention. The automatic meter reading central device 10 is a meter reading control unit that processes and controls meter reading data! ! , a low frequency data modulation/demodulation unit 12 that modulates and demodulates the data signal into a low frequency FSK signal, CAT
It is comprised of an RF band converter section 13 for modulating to the RF band for interfacing with the V line. A terminal transmitter 30 is connected to the automatic meter reading central device 10 via a two-way CATV network 20, and includes an RF band converter section 31, a low frequency data modulation/demodulation section 32, and a meter reading processing section 33 that performs meter reading processing. The entire system is composed of the automatic meter reading meter 40.

When automatic meter reading is started in the meter reading control unit 11 of the automatic meter reading central device 10, a meter reading command is output to the low frequency data modulation/demodulation unit 12 in order to read the value of the automatic meter reading meter 40 connected to the terminal transmitter 30. .

The low frequency data modulation/demodulation section 12 converts the data code of the meter reading command into a low frequency frequency modulated signal and outputs it to the RF band converter section 13 . The RF band converter section 13 converts the low frequency modulation signal input from the low frequency data modulation/demodulation section 12 into an RF band modulation signal and converts it into a two-way CATV network 20.
Output to.

The RF band modulated signal is manually inputted to the RF band converter section 31 of the terminal transmitter 30 via the bidirectional CATV network 20, and is demodulated into a low frequency frequency modulated signal by the RF band converter section 31, and is converted into low frequency data. The modulation/demodulation section 32 further demodulates the low frequency frequency modulation signal into a digital signal and sends it to the meter reading processing section 3.
3. The meter reading processing unit 33 checks the calling address, and if it matches the own address, reads the value of the automatic meter reading meter 40, assembles a reply message, and outputs it to the low frequency data modulation/demodulation unit 32. The low frequency data modulation/demodulation section 32 converts the response message into a low frequency frequency modulation signal, and the RF band converter section 31 converts it into an RF band. The response signal converted to the RF band is manually input to the RF band converter section 13 via the bidirectional cATV line network 20, and the RF band converter section 13 demodulates the RF band to low frequency by the low frequency data modulation/demodulation section 12.
A series of meter reading processing is carried out in which the low frequency frequency modulated signal is demodulated into a digital signal, the reply message from the terminal transmitter 30 is input to the meter reading control section 11, and the meter reading control section 11 performs data processing.

Figures 2 (a) and (b) show the difference in exclusive bandwidth in the RF band between the direct modulation method based on the RF band frequency and the method that converts low frequency modulation to the RF band. . In the direct modulation method, considering the demodulation property of the signal, it is necessary to shift the frequency by several tens of KHz, and the exclusive band inevitably becomes wider and requires about several hundred KHz. On the other hand, the method of modulating at low frequency and then converting to the RF band makes it possible to make the frequency deviation width very narrow as shown in the figure, and the exclusive band is several tens of KHz, which is 1/10 of the former method.
The band can be narrowed as follows.

[Effects of the Invention] As explained above, the present invention provides a central device and a terminal transmitter with a low-frequency data modulation/demodulation section and an RF band converter section for modulating to the RF band, thereby enabling transmission on a line. If the dedicated bandwidth can be made very narrow and a bandwidth of several tens of KHz can be secured even when a large number of data services are being implemented, this automatic meter reading system can be implemented.

[Brief explanation of the drawing]

Figure 1 is a system configuration diagram of an embodiment of the present invention, and Figure 2 (
Figures a) and (b) are diagrams comparing the dedicated bandwidths on the line by the direct modulation method and the converter method, respectively. 10: Automatic meter reading central device! 1: Meter reading control section 12: Low frequency data modulation/demodulation section 13: RF band converter section 20: Bidirectional CATV line network 30: Terminal transmitter 31: RF band converter section 32: Low frequency data modulation/demodulation section 33: Meter reading processing section 40: Automatic meter reading meter

Claims (1)

[Claims] In an automatic meter reading system using a two-way CATV line, a central device and a terminal transmitter include a low frequency data modulation/demodulation section that modulates and demodulates a data signal into a low frequency FSK signal, and an RF
An automatic meter reading system using a CATV line, characterized in that it is equipped with an RF band converter unit for modulating into the RF band.