JPS6148262A - Data transmission circuit - Google Patents

Abstract

PURPOSE:To standardize a transmission circuit by bringing the oscillating frequency of a voltage controlled oscillator into the attenuation region of a filter in a system transmitting a data on a common transmission line and in the same frequency. CONSTITUTION:A digital transmission data is converted into a serial digital signal and inputted to the voltage controlled oscillator 15 and the signal of a transmission end DC voltage generating section 14 is inputted also to the voltage controlled oscillator. When the transmission data is finished, a signal having a large DC level is inputted to the voltage-controlled oscillator 15, which outputs a signal brought into the attenuation region of a band pass filter 16, then no signal comes from a transmission station when the station has no transmission data.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an FM or FSX data transmission circuit using a filter. FM or FSK data from this
The present invention relates to a data transmitting circuit 1 in a data transmitting system that communicates with a receiving station based on a method. □ [Prior Art] An example of a conventional transmission system is shown in FIG. 4 (al).

Figure 4 (at a1%, transmitting station 1 and receiving station 3 (11 to 1)
Transmitting station 1 uses transmission line 2 to receive 3%
On the other hand, the data is modulated by 1 kFsK and transmitted.

[Problem that the invention seeks to solve]

In this data transmission system, the transmitting station 1 transmits either the frequency signal corresponding to w1'' or WO'' even when there is no data to send.

Then, when there is transmission data, the transmission frequency is switched. When multiple transmitting stations are connected to a common transmission line 4 as shown in Figure 4, one transmitting station sends a 1'' or 0'' corresponding signal to transmit data. Even if the data is sent out, a signal corresponding to 11" or O" is always sent to the common transmission line 4, so the receiving station cannot receive the data well.

As countermeasure 4, it is possible to change the frequency of the signal transmitted by each transmitting station, but it has the following drawbacks.

′ (b) Requires a wide frequency band.

(b) As many bandpass filters as there are transmitting stations are required in the receiving section.

(c) The system cannot be standardized because each transmitting station has different specifications.

[Means and effects for solving the problems] The present invention provides a data transmitting circuit that solves the above problems, and the means is to provide a data transmitting circuit in which a plurality of transmitting stations use a common transmission path and transmit the same frequency. A data transmission system that modulates soy sauce data and transmits the data to a receiving station includes a voltage controlled oscillator for each transmitting station, a voltage generator that applies a specific voltage to the voltage controlled oscillator at the end of transmission, and the voltage controlled oscillator. The output stage has a companion filter, and the transmission data 1
Therefore, the oscillation frequency of the voltage controlled oscillator is controlled, and the voltage from the transmission end DC voltage generator is applied to the voltage controlled oscillator so that the oscillation frequency of the voltage controlled oscillator falls within the attenuation range of the filter. This is done by directing the transmitting circuit.

゛[Examples of the invention] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the method according to the present invention, which includes:
11 is a control unit %13 is a parallel/serial converter, 14
1 is a transmission end series voltage generator, 15 is a voltage controlled oscillator, 1
6 indicates a bandpass filter.

In Figure 1, digital transmission data (parallel)
, are converted into serial digital signals by the parallel-to-serial converter 13 and input to the voltage controlled oscillator 15.

The output of the transmission end DC voltage generator 14 is also input to the voltage controlled oscillator 15.Next, the operation of the voltage controlled oscillator 15 in FIG. 1 will be explained with reference to FIG. 2. In FIG. 2, the frequency f0. fl is the frequency at which the digital signal is 10'' or 1'', fo,
.

is the frequency of the output 1 from the transmission end DC voltage generator when the transmission ends. The output of the voltage controlled oscillator 15 as shown in FIG. 2 is input to a 16% band pass filter. The operation of the bandpass filter 16 will be explained with reference to FIG. In FIG. 3, the horizontal axis shows the digital transmission data (serial) frequency ζ, and the vertical axis shows the analog signal level output to the transmission path. As shown in FIG. 3, when the transmission of the transmission data is completed, a signal with a high DC level (transmission completion data) is input to the voltage controlled oscillator 15, and it is even more alarming that the signal may be in the attenuation range of the bandpass filter 16. Since it outputs a signal that

If there is no data to transmit, the flea will not emit a signal from its transmitting station.

The system of the present invention as shown in Figure 1 is applied to the transmission of CATV repeater monitoring data. In this case, the transmitting station is used as a repeater, and the receiving station is used as a receiving section in the head end. The t-FSK method of the present invention has been described above, but it can also be applied to the FM method.

〔Effect of the invention〕

As explained in detail above, according to the present invention, it is possible to configure a same-frequency FSK system transmitting circuit that can be standardized in an extremely simple circuit. The effect of using it is enormous.

[Brief explanation of the drawing]

Figure 1 is a block diagram of one embodiment of the FSK data transmission circuit (which is important to the present invention), Figure 2 is an explanatory diagram of the operation of the voltage controlled oscillator in Figure 1, and Figure 3 is the band diagram in Figure 1. FIG. 4, which is an explanatory diagram of the operation of the pass filter, shows a block diagram of an FSK data transmission system to which the present invention is applied. In the figure, 11 is a control section, 13 is a parallel-to-serial converter, 14 is a transmission end series voltage generator, 15 is a voltage controlled oscillator, and 16 is a bandpass filter.

Claims (1)

[Claims] In a data transmission system in which multiple transmitting stations use a common transmission path and transmit data to a receiving station by modulating data at the same frequency, each transmitting station has a voltage controlled oscillator and a voltage control device that controls a specific voltage at the end of transmission. It has a voltage generator that supplies the voltage to the oscillator, and a filter provided at the output stage of the voltage-controlled oscillator, and controls the oscillation frequency of the voltage-controlled oscillator based on the transmitted data, and also controls the voltage from the voltage generator at the end of transmission. A data transmitting circuit characterized in that the voltage is applied to the voltage controlled oscillator so that the oscillation frequency of the voltage controlled oscillator falls within the attenuation range of the filter.