JPH0398357A - Digital fsk modem equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is capable of transmitting data at any desired modulation frequency,
This invention relates to a digital FSK modem device that generates a modulated wave output with a modulation index.

[Latest technology and its problems]

Currently, Jitsukawa is 4'l. The carrier frequency and modulation index of the FSK modulation modem in the power communication line system remote monitoring and control equipment vary depending on the transmission specifications of each company, so the digital 2FS-K modem equipment used for it must match those specifications. To ensure this, a dedicated circuit is designed for each specification to match the desired carrier frequency and modulation index.

For example, a standardized modulation circuit 5 as shown in FIG. 1 is used, which is an integrated circuit of a dedicated modem circuit adapted to regulations.

This circuit consists of a program counter la that operates at a preset frequency division ratio according to transmitted data, a program counter 1 that operates from a frequency correction counter 1b with a constant frequency division ratio, and a sine wave output from this counter. Convert to D/A
A sine converter 2, a switched capacitor filter 3 that removes unnecessary band signals from the output signal of the D/A sine converter 2, and a control timing circuit 4 that drives these.
When transmission data T In order to maintain accuracy, the frequency is set to a sufficiently higher frequency than the carrier frequency by the counter 1b, and then converted into an analog signal by the D/A sine converter 3.

Since this analog signal contains an unnecessary band signal as shown in FIG. 2, it is then passed through a switched capacitor filter 3 to remove it and obtain an output signal AO.

In this conventional circuit, since the clock frequency of the clock oscillator OSC to be applied is fixed, it is impossible to generate a non-standard carrier frequency.

Therefore, it was necessary to use one that met the transmission specifications.

So. SUMMARY OF THE INVENTION The present invention aims to provide a digital FSK modem device that can obtain a modulated output of the target carrier l4 wave number by combining a simple device with the above-mentioned standardized modulation circuit.

[Means to solve the problem]

In order to solve the above problems, the present invention includes a program counter that operates at a preset frequency division ratio according to transmitted data, a D/A sine converter that converts the output of this counter into a sine wave, and a D/A sine converter that converts the output of this counter into a sine wave. A Swiss capacitor filter that removes unnecessary band signals from the output signal of the A-sine converter, a normalized modulation circuit that is made up of a control timing circuit that drives these, and an appropriate number of clock oscillators with different frequencies on the human power side. , the output terminal is connected to the clock signal manual terminal of the normalized modulation circuit, and a clock switcher is used to switch the connection of the clock oscillator depending on the transmitted data.

[Effect]

According to the present invention, the clock frequency applied to the programmable counter and the switched capacitor filter is switched by a 1.0 signal transmitted overnight, and the frequency division ratio of the program counter and the switched capacitor filter, which are already fixed, are changed. Regardless of the center frequency of the tough-f filter, by changing the external cross-clock, the same effect as changing the frequency division ratio of the program count can be obtained, and the D/A
The frequency applied to the sine converter changes, and a modulated output with an arbitrary non-standard carrier frequency can be obtained.

Further, due to its principle characteristics, the center frequency of the switched capacitor filter also changes in proportion to the switched clock frequency, so that the carrier frequency and the filter center frequency always match.

In this way, it is already specially designed and operates with a single clock,
Using a standardized modulation circuit with a fixed frequency, a desired non-standard modulated output can be obtained by shifting the input clock by the transmitted data.

〔Example〕

FIG. 3 shows an embodiment of the present invention 1, where 5 is the same standardized modulation circuit as shown in FIG. 1, and the same parts are given the same reference numerals.

The present invention differs from conventional circuits in that an appropriate number of clock oscillators OSCI, OSC2, etc. with different frequencies are connected to the input side, and clock oscillators OSCI, OSC2, . A clock switch 6 is provided which is connected to the signal input terminal 5a and switches the connection of the clock oscillator according to the transmitted data.

With this configuration, the clock oscillator electrically connected to the clock signal input terminal 5a is switched by the transmission data TXD, so that the carrier frequency given to the programmable counter 1 and the center of the switched capacitor filter are switched. The frequency can be switched to obtain the desired modulated output outside the standard.

〔Effect of the invention〕

According to the present invention, there is no need to design a digital 2FSK modem device according to the specifications as in the past, but by simply adding a cutout Ivy oscillator and a clock switch 6 to a commercially available standardized modulation circuit 5, it is possible to create a desired A digital FSK modem device can be proposed with a carrier frequency and modulation index of .

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional device, FIG. 2 is a time chart of signal waveforms, and FIG. 3 is a block diagram of an embodiment of the present invention.・Program counter ・Counter ・D/A sine converter ・Switched capacitor filter ・Control timing circuit ・Standardized modulation circuit ・Clock switch

Claims (1)

[Claims] A program counter 1 that operates at a preset frequency division ratio according to the transmitted data, a D/A sine converter 2 that converts the counter output into a sine wave, and an output signal from the D/A sine converter 2. A normalized modulation circuit 5 comprising a switched capacitor filter 3 for removing unnecessary band signals and a control timing circuit 4 for driving these, and an appropriate number of clock oscillators OSC1 having different frequencies on the input side.
The clock switching device 6 connects the OSC 2 . Digital FSK
modem equipment.