JPH10145438A - Modem, and data transmitting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate data transmission speed without lowering signal quality by preparing transmission data while combining specified kinds of special waveforms. SOLUTION: A signal generating circuit is provided for preparing specially formed signals of four kinds while combining longitudinal and lateral waves and for transmitting the signal of 2 bits with the signal waves of 2.4kHz in that combination. Namely, four kinds of special waveforms #1-#4 are prepared by combining a 1/4 cycle T1 and a 1/4 cycle T2 for longitudinal waves with a 1/4 cycle Y1 and a 1/4 cycle Y2 for lateral waves for every 1/4 cycle corresponding to transmission data. In this case, the waveform #1 is a wave combining T1 and Y2, the special waveform #2 is the wave of quick rise within the half cycle combining T1 and T2, the special waveform #3 is the wave of slow rise within the half cycle combining Y1 and Y2, and the special waveform #4 is a wave combining Y1 and T2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem and a data transmission method, and more particularly, to a modem and a data transmission method characterized by a portion enabling high-speed data transmission.

[0002]

2. Description of the Related Art In recent years, various data communication technologies in the computer field including the Internet technology have been remarkably developed, and there has been a problem how to improve the data transmission speed. However, the maximum frequency of a signal in a telephone network guaranteed by the telephone company (NTT) is 3.4 kHz, and a signal having a frequency of 3.4 kHz or more is not passed.
First, there is a restriction from this point.

According to international standards for data transmission, a multiple of 300 bits / sec, ie, 600,
Standards such as 1200 and 2400 bit / sec are provided. Therefore, due to such circumstances and the above-mentioned restrictions on the line, 2400 Hz (2.4 kHz) is currently used as the highest frequency in data transmission. Therefore, as a modem for realizing data transmission between computers via a telephone line, a transmission frequency of 2.4 kHz is mainly used today, in which high-speed data transmission is often required.

[0004] However, 2400 bits / sec is not sufficient as a data transmission speed, and the data transmission speed has been conventionally improved under the restriction of a transmission frequency of 2.4 kHz.

FIG. 8 is a diagram illustrating a conventional technique for improving the data transmission speed. In the same figure (a), 2.4 kHz
This is a basic example in which data of 2400 bits / sec is transmitted at the frequency of z.

FIG. 1B shows a first example of the prior art, in which signals of two kinds of wave heights are superimposed at 2.4 kHz.
At a frequency of 4800 bits / sec.

FIG. 1C shows a second example of the prior art, in which a plurality of signals (four in this example) can be transmitted within one cycle by shifting the phase from the reference waveform. age,
The figure shows a case where data of 9600 bits / sec is transmitted at a frequency of 2.4 kHz.

In the method shown in FIG. 8 (c), about 12 signals can be transmitted in one cycle by the phase shift at present, and as a result, the maximum of 28.times. An 8 kbps (kbit / sec) high-speed modem has been realized.

[0009]

However, in the technique of improving the data transmission speed by the phase shift, there is a limit to the minimum phase angle that can be shifted. That is, the data transmission signal is transmitted from the modem to the telephone company exchange via the telephone and exchange, and then reaches the other party's modem via a similar line. There is a delay. Therefore, if the phase shift angle is smaller than the delay, normal data transmission becomes impossible. Therefore, there is a predetermined limit to the number of signals that can be transmitted in one cycle due to signal delay.

Under these circumstances, when the phase shift technique is used, the data transmission speed of the modem is 2
It is believed that 8.8 kbps will be the limit. However, in the future, with regard to data transmission by modem, further improvement in data transmission speed is required, and it is required to realize data transmission by an inexpensive method without lowering the signal quality. .

The present invention has been made in view of such circumstances, and has as its object to provide a modem and a data transmission method capable of improving a data transmission speed without deteriorating signal quality. I do.

[0012]

According to a first aspect of the present invention, in a modem, a first special waveform having a fast peak rise within a half cycle is provided as a waveform of a data transmission signal. A second special waveform having a late peak rise, a third special waveform having a peak height at two peak positions of an early rise peak and a late rise peak in the half cycle higher than at least a predetermined level, One of the fourth special waveforms whose wave heights at the two peak positions are lower than a predetermined level is output,
A modem provided with a signal generating means for transmitting 2-bit information in a half cycle of the waveform by combining the fourth to fourth special waveforms.

According to a second aspect of the present invention, in the modem, the waveform of the data transmission signal includes a first special waveform having a fast rising peak and a second special waveform having a slow rising peak within a half cycle. A third special waveform in which the peak heights of the two peak positions of the early rising peak and the late rising peak in the half cycle are at least higher than a predetermined level, and a third special waveform in which the wave heights of the two peak positions in the half cycle are lower than the predetermined level. 4), the waveform signal value is detected at a timing near the early rising peak and the late rising peak to determine whether or not the waveform signal value is equal to or higher than a predetermined level. This is a modem provided with signal demodulation means for detecting 2-bit information.

Further, a third aspect of the present invention provides a modem according to the first aspect of the present invention,
According to a second aspect of the present invention, there is provided a modem including a signal demodulating means in the modem.

Further, the invention corresponding to claim 4 is:
A modem for transmitting data via a telephone line according to any one of the first to third aspects of the present invention, wherein a plurality of special waveforms can be included in one transmission cycle by phase shift.

On the other hand, the invention according to claim 5 is the invention according to claims 1 to 4, wherein the first to fourth special waveforms include a first composite waveform having a fast rising peak in a half cycle, The second synthesized waveform having a slow rise is reduced to 1/4
This is a modem created by combining in units of cycles.

According to a sixth aspect of the present invention, in the first aspect, the first and second combined waveforms include a signal having a frequency higher than a half-period frequency and a half-period signal. This is a modem created by synthesizing triangular waveforms of frequency.

Next, a seventh aspect of the present invention is the invention according to the first to fifth aspects, wherein the first and second combined waveforms include a signal having a frequency higher than a half-period frequency and a half-period signal. This is a modem created by synthesizing a signal with a frequency lower than the frequency of the modem.

According to an eighth aspect of the present invention, in the data transmission method, the waveform of the data transmission signal includes a first special waveform having a fast rising peak and a second special waveform having a slow rising peak within a half cycle. A third special waveform in which the peak heights of the two peak positions of the early rising peak and the late rising peak in the half cycle are at least higher than a predetermined level, and the wave heights of the two peak positions in the half cycle are higher than the predetermined level This is a data transmission method that uses a low fourth special waveform and includes 2-bit information in a half cycle of the waveform by a combination of the first to fourth special waveforms.

Further, the invention according to claim 9 is as follows.
In the invention according to claim 8, when a waveform of a data transmission signal is received, it is detected whether or not the waveform signal value is equal to or higher than a predetermined level at a timing near a rising peak and a rising peak. , A data transmission method for detecting 2-bit information in a half cycle of a waveform.

On the other hand, a tenth aspect of the present invention is the invention according to the eighth or ninth aspect, wherein the first to fourth special waveforms include a first synthesized waveform having a fast rising peak in a half cycle, The second synthesized waveform with a slow rise is 1
This is a data transmission method created by combining in 組 み 合 わ せ cycle units.

An invention corresponding to claim 11 is a data transmission method in a modem using a telephone line to which the data transmission method according to any one of claims 8 to 10 is applied. (Operation) Therefore, first, in the modem and the data transmission method according to the first or eighth aspect of the present invention, the waveform of the data transmission signal includes a first special waveform having a fast rising peak within a half cycle, A second special waveform that is late, a third special waveform in which the peak heights of two peak positions of an early rising peak and a late rising peak in the half cycle are at least higher than a predetermined level, and two peak positions in a half cycle Of the fourth special waveform whose wave height is lower than a predetermined level is output.

That is, the height of the wave height at the portion where the peak rises early in the half cycle is 1 bit, and the height of the wave height at the portion where the peak rises late in the half cycle is 1 bit, and the first to fourth special waveforms are set. The combination is transmitted in a half cycle of the waveform including 2-bit information.

Therefore, the data transmission speed can be improved without lowering the signal quality. Further, in the modem and the data transmission method according to the second or ninth aspect of the present invention, when any of the first to fourth special waveforms is received, at the timings near the fast rising peak and the slow rising peak, By detecting whether the waveform signal value is above or below a predetermined level, 2-bit information is detected in a half cycle of the waveform.

Further, the modem according to the third aspect of the invention operates in the same manner as the first and second aspects of the invention. Further, the modem according to the fourth aspect of the present invention operates in the same manner as the first to third aspects of the present invention. In addition, the modem transmits data via a telephone line, and each special waveform is A plurality of waveforms are included in one transmission cycle by the phase shift. Therefore, this modem can perform data transmission at a data transmission speed that is twice the product of the transmission frequency and the number of phase shifts.

Furthermore, in the modem according to the fifth or tenth aspect of the present invention, in addition to the same operation as the invention according to the first to fourth or eighth or ninth aspects, the first to fourth special waveforms are: It is created by combining a first combined waveform with a fast peak rise in a half cycle and a second combined waveform with a slow peak rise in quarter cycle units.

On the other hand, in the modem according to the sixth aspect of the present invention, in addition to the same operation as the first to fifth aspects of the present invention, the first and second combined waveforms have a higher frequency than a half cycle frequency. And a triangular waveform having a half-period frequency is synthesized.

On the other hand, in the modem according to the seventh aspect of the present invention, in addition to the same operation as the first to fifth aspects of the present invention, the first and second combined waveforms have a higher frequency than a half cycle frequency. And a signal having a frequency lower than the half-period frequency is synthesized.

In the modem according to the eleventh aspect, the data transmission method according to any one of the eighth to tenth aspects is applied to a modem using a telephone line.

[0030]

Embodiments of the present invention will be described below. (First Embodiment of the Invention) FIG. 1 is an overall configuration diagram showing an example of a network system to which a modem according to a first embodiment of the present invention is applied.

In this network system, a modem 2 is connected to a computer 1 such as a personal computer or a workstation, which is a data transmission / reception source, and these modems 2 are connected via a telephone line 3. Note that, in the network system of FIG.
Although shown as an example of sets, in practice many sets are interconnected.

The computer 1 outputs transmission data to be transmitted to the modem and receives received data from the modem 2 when receiving data. Each modem has
A signal generating circuit 6 for converting the transmission data 4 into a signal that can be transmitted to the telephone line 3;
Is provided. The modem 2 is characterized by the configuration of the signal generation circuit 6 and the signal demodulation circuit 7. Although not shown, the modem 2 has all the components necessary for data transmission as a modem. Note that the modem 2 may be in a form incorporated in the main body of the computer 1.

FIG. 2 is a block diagram showing a detailed configuration of the signal generation circuit and the signal demodulation circuit in the modem of the present embodiment. As shown in the figure, the signal generation circuit 6 includes a reference signal generation circuit 10, a synchronization signal generation circuit 11, and a 3.4 kHz frequency.
a z signal generation circuit 12, a triangular waveform signal generation circuit 13,
It comprises a logic value generation circuit 14, a modulation circuit 15, and other peripheral elements not shown. The signal generating circuit 6 uses a 2.4 kHz signal as a transmission frequency.

Although not shown, the signal generating circuit 6 employs the transmission speed improving method based on the phase shift described with reference to FIG. 8C in the related art. The signal of the book is transmitted.

The signal generating circuit 6 is capable of generating four types of specially shaped signals by combining longitudinal waves and transverse waves, which will be described later.
It is possible to transmit a 2-bit signal using the above signal wave. That is, in the modem of the present embodiment, 2.4k
A data transmission rate of 57.6 kbps is realized by combining the technique of putting 2-bit logic on the special waveform of Hz and the technique of the above phase shift.

Hereinafter, the signal generating circuit 6 operates at 2.4 kHz.
Each configuration for putting 2-bit logic on a signal will be described.
The reference signal generation circuit 10 generates a 2.4 kHz reference signal as a carrier that carries binary information to be transmitted,
The signals are input to the synchronization signal generation circuit 11 and the modulation circuit 15.

The synchronizing signal generation circuit 11 outputs a timing for synthesizing a longitudinal wave and a transverse wave for generating the above-mentioned special waveform for mounting a 2-bit logic based on a reference signal of 2.4 kHz. That is, a 3.4 kHz signal and 2.4
The timing for generating a triangular waveform of kHz is 3.4 kHz.
The signals are input to the z signal generation circuit 12 and the triangular waveform signal generation circuit 13.

Here, the longitudinal wave and the transverse wave are 3.4
This is a synthesized signal that is the basis of a special waveform created by synthesizing a kHz signal and a 2.4 kHz triangular waveform. FIG. 3 is a diagram showing a composite signal used in the present embodiment.

FIG. 3A shows a reference signal of 2.4 kHz. On the other hand, in the present embodiment, FIG.
A composite waveform (referred to as a vertical wave and a horizontal wave, respectively) shown in (c) is used, and a signal for data transmission is created by combining these composite waveforms. This composite waveform is created by connecting a 3.4 kHz sine waveform and a 2.4 kHz triangular waveform, and a method for creating the waveform will be described later.

The 3.4 kHz signal generating circuit 12 outputs a 3.4 kHz sine waveform in accordance with the timing given by the synchronizing signal generating circuit 11 in order to create each of the above-mentioned synthesized signals.

The triangular waveform signal generating circuit 13 outputs a 2.4 kHz triangular waveform in accordance with the timing given by the synchronizing signal generating circuit 11 in order to generate each of the composite signals.

The logical value generation circuit 14 combines the longitudinal wave and the transverse wave generated by the signal input from the 3.4 kHz signal generation circuit 12 and the triangular waveform signal generation circuit 13, thereby obtaining the transmission data 4 input from the computer 1. Is generated and input to the modulation circuit 15. At this time, since the signal pattern of the special waveform to be generated includes 2-bit information, the transmission data 4 is confirmed two bits at a time.
In response to this, a special waveform as shown in FIG. 4 is created.

FIG. 4 is a diagram showing how a special waveform according to the present embodiment is created by a composite waveform. As shown in the figure, in the longitudinal wave, the rising peak of the 3.4 kHz sine waveform is in the first quarter period T1, and the next quarter period T2 is the 2.4 kHz triangular waveform. This is a configuration that becomes a falling portion. That is, the longitudinal wave is a wave that rises quickly within the first half cycle.

Similarly, in the transverse wave, the rising edge of the 2.4 kHz triangular waveform is in the first quarter period Y1, and the next quarter period Y2 is the rising peak of the 3.4 kHz sine waveform. That is, the transverse wave is a wave that rises slowly within the first half cycle.

Corresponding to the transmission data 4, the 1/4 cycle T1 and 1/4 cycle T2 of the longitudinal wave and the 1/4 cycle Y1 and 1/4 of the
Four types of special waveforms # 1, # 2, # 3, and # 4 are created by combining the four periods Y2 every quarter period.

As shown in the figure, the special waveform # 1 is T1
The special waveform # 2 is a wave that rises fast within a half cycle in which T1 and T2 are combined, and the special waveform # 3 is a wave that rises in a half cycle in which Y1 and Y2 are combined. It is a slow rising wave, and the special waveform # 4 is Y1 and T2
And are combined.

By combining the special waveforms, 2-bit information can be transmitted in a half cycle of one waveform. FIG. 5 is a diagram illustrating the determination of the logical value of the special waveform in the present embodiment.

As shown in the figure, at a predetermined judgment timing TI1, TI2 near the peak of the longitudinal wave and the transverse wave, a signal when a signal of a predetermined judgment level or more is detected is defined as "
If the signal level is equal to or lower than the judgment level, and if the signal level is equal to or less than "0", the special waveform # 1 is "11", the special waveform # 2 is "10", the special waveform # 3 is "01", the special waveform. #
From "4", "00" is obtained. In this manner, transmission of 2-bit information can be performed in a half cycle. The determination of the logical value is performed in the signal demodulation circuit 7 on the receiving side.

The modulation circuit 15 modulates the logical value signal created in this way with a reference signal, and sends the modulated signal to the telephone line 3 toward the destination. Now, a method of creating a composite waveform such as a longitudinal wave and a transverse wave will be described.

FIG. 6 is a diagram for explaining the creation of a composite waveform in this embodiment. As shown in FIG.
The half cycle of the kHz signal is 208.3 μsec, and 1 /
Four cycles are 104.15 μsec.

Therefore, the 3.4 kHz sine waveform is changed to 104.
After outputting about 15 μsec, the triangular waveform is started at the fall from the maximum peak to 208.3 μsec.
And a 3.4 kHz sinusoidal waveform of 104.1 is connected so that a quarter period from 7 / 4π to 2π is connected.
If the signal is output for about 5 μsec, as shown in FIG.
A longitudinal wave of 4 kHz is obtained.

It should be noted that the synthesis is performed in the same manner in the case of a transverse wave. Next, the configuration of the signal demodulation circuit 7 that receives a signal and determines a logical value will be described.

As shown in FIG. 2, the signal demodulation circuit 7 includes a reference signal generation circuit 20, a synchronization signal generation circuit 21, a logical value judgment timing signal generation circuit 22, and a demodulation circuit 23.
, A logical value determination circuit 24, and other peripheral elements (not shown). Although not shown, the signal demodulation circuit 7 is also provided with a means for reproducing the phase shift signal described in FIG. 8C in the related art, and corresponds to the signal generation circuit 6.

The reference signal generating circuit 20 generates a 2.4 kHz reference signal synchronized with the received signal by a PLL circuit (phase locked loop circuit) (not shown) based on the received signal, It is input to the synchronization signal generation circuit 21.

The synchronization signal generation circuit 21 receives the input 2.
In synchronization with the 4 kHz reference signal, a signal of a timing TI0 for generating the timings TI1 and TI2 of the logical value determination shown in FIG. 5 is generated and input to the logical value determination timing signal generation circuit 22.

Logic value judgment timing signal generation circuit 22
Is a timing adapted to the local maximum value in the special waveform, creates determination timings TI1 and TI2 for detecting the local maximum peak of the special waveform, and inputs the timing signal to the logical value determination circuit 24.

The demodulation circuit 23 extracts a logical value signal from the carrier based on the 2.4 kHz reference signal from the reference signal generating circuit 20, and inputs the signal to the logical value judging circuit 24. The logical value judging circuit 24 applies a logical value judging timing signal generating circuit 22 to the logical value signal extracted by the demodulating circuit 23.
The signal is detected at the decision timings TI1 and TI2 input from the controller, and if the signal value at that timing is above a predetermined threshold value (the decision level shown in FIG. 5), it is set to "1"; The logical value of “0” is extracted and output to the computer 1 as received data 5. That is, this logical value determination method is performed by the method shown in FIG. 5, as described above.

Next, the operation of the thus configured modem according to the embodiment of the present invention will be described. First,
Transmission data 4 is input to the signal generation circuit 6 of the modem 2 from the computer 1 on the data transmission side.

On the other hand, in the reference signal generation circuit 10, 2.4
Although a reference signal of kHz is generated, this reference signal is input to the synchronization signal
Timing for generating a composite waveform is given to the signal generation circuit 12 and the triangular waveform signal generation circuit 13.

The 3.4 kHz signal generating circuit 12 and the triangular waveform signal generating circuit 13 output a sine waveform and a triangular waveform, respectively, to the logical value generating circuit 14, thereby generating a composite waveform of a longitudinal wave and a transverse wave.

In the logical value generation circuit 14, the computer 1 applies the transmission data 4 to a logical value in units of 2 bits, and combines the longitudinal wave and the transverse wave so as to conform to the logical value, thereby generating a special waveform.

The transmission signal having this special waveform is
Approximately 12 lines are generated per transmission cycle by a phase shift means (not shown), and transmitted from the modulation circuit 15. The transmitted signal is input via the telephone line 3 to the signal demodulation circuit 7 of the receiving modem.

In the signal demodulation circuit 7, the received data is taken into the demodulation circuit 23 in synchronization with the timing from the reference signal generation circuit 20, while the synchronization signal generation circuit 21
The timings TI1 and TI2 for determining the logical value are generated by the logical value determination timing signal generation circuit 22.

The received reception signal is subjected to logical value judgment by the logical value judgment circuit 24 at timings TI1 and TI2.
The result is sent to the receiving computer 1 as received data 5.

As described above, the modem according to the embodiment of the present invention has a special waveform # 1 having two peaks within a half cycle.
A special waveform # 2 having a fast rise, a special waveform # 3 having a slow rise, and a special waveform # 4 having a low peak are used to generate a logical value, which is mounted on a 2.4 kHz carrier for data transmission. Therefore, the data transmission speed can be improved without lowering the signal quality in the data transmission. Specifically, it is possible to realize a transmission rate twice as long as the conventional one per transmission cycle.

In the modem of the present embodiment, the logical value is determined from the special waveform at a predetermined determination timing. Therefore, the logical value is reliably detected from the transmission signal on the receiving side. Then, the transmission data can be reproduced.

Since data transmission by phase shift is also combined in data transmission, the data transmission speed multiplied by the number of phase shifts is further doubled to 57.6k.
A modem with a transmission rate of bps can be realized.

Note that this data transmission rate is a value very close to the transmission rate of 64 kbps by ISDN, and according to the present embodiment, a data transmission rate comparable to that of ISDN can be easily secured by using a telephone line. (Second Embodiment of the Invention) The modem of the present embodiment
The method is the same as that of the first embodiment, except that the method of creating the composite waveform (longitudinal wave, transverse wave) is different.

That is, in the first embodiment, the composite waveform is created using the 3.4 kHz sine wave and the triangular waveform, but in the present embodiment, the 3.4 kHz sine wave and the 1.4 kHz are used.
Created using a kHz sine wave. Therefore, the difference in the configuration of the signal generation circuit 6 is that the triangular waveform signal generation circuit 13 of the first embodiment shown in FIG.
An Hz signal generation circuit is provided.

FIG. 7 is a diagram for explaining a method of creating a composite waveform in the modem according to the second embodiment of the present invention.
That is, the rising peak portion of the 3.4 kHz sine waveform signal shown in FIG.
A falling portion of the sine wave signal of Hz is synthesized to create a synthesized waveform (longitudinal wave) having a frequency of 2.4 kHz as shown in FIG. Note that the transverse wave shown in FIG.

These synthesized waveforms are changed to characteristic features in the shape of longitudinal waves and transverse waves only by using a slowly changing signal of a 1.4 kHz sine waveform instead of a linearly changing signal of a triangular waveform. There is no. Therefore, 3.4 kHz
At the rising peak of the sine waveform signal
Is detected, and a logical value "0" is detected in the portion of the 1.4 kHz sine waveform signal.

Therefore, the operation of the thus configured modem according to the embodiment of the present invention is the same as that of the first embodiment. As described above, the modem according to the embodiment of the present invention uses a 1.4 kHz sine waveform instead of a triangular waveform to create a composite waveform of a longitudinal wave and a transverse wave. Since the configuration similar to that of the first embodiment is provided, the same effect as that of the first embodiment can be obtained.

The present invention is not limited to the above embodiments, but can be variously modified without departing from the scope of the invention. That is, in the above embodiment, the case of data transmission between computers by the modem has been described. However, the application target of the data transmission method of the present invention is not limited to the data transmission by the modem, but is the data transmission by a signal of a predetermined transmission frequency. If there is, it can be applied to various data transmissions.

Further, the method described in the embodiment can be executed by a computer as a program that can be executed by a computer in a storage medium such as a magnetic disk (floppy disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.), and a semiconductor memory. It can also be stored and distributed.

[0075]

As described above in detail, according to the present invention, 4
Since transmission data is created by combining different kinds of special waveforms, it is possible to provide a modem and a data transmission method capable of improving the data transmission speed without deteriorating the signal quality.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an example of a network system to which a modem according to a first embodiment of the present invention is applied.

FIG. 2 is an exemplary block diagram showing a detailed configuration of a signal generation circuit and a signal demodulation circuit in the modem of the embodiment.

FIG. 3 is an exemplary view showing a combined signal used in the embodiment;

FIG. 4 is an exemplary view showing a state in which a special waveform in the embodiment is created using a composite waveform.

FIG. 5 is an exemplary view showing determination of a logical value of a special waveform in the embodiment.

FIG. 6 is an exemplary view for explaining creation of a composite waveform in the embodiment.

FIG. 7 is an exemplary view for explaining a method of creating a synthetic waveform in a modem according to a second embodiment of the present invention.

FIG. 8 is a diagram exemplifying a conventional technique for improving a data transmission speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Computer 2 ... Modem 3 ... Telephone line 4 ... Transmission data 5 ... Reception data 6 ... Signal generation circuit 7 ... Signal demodulation circuit 10 ... Reference signal generation circuit 11 ... Synchronization signal generation circuit 12 ... 3.4kHz signal generation circuit 13 ... Triangle waveform signal generation circuit 14 Logic value generation circuit 15 Modulation circuit 20 Reference signal generation circuit 21 Synchronization signal generation circuit 22 Logic value judgment timing signal generation circuit 23 Demodulation circuit 24 Logic value judgment circuit

Claims (11)

[Claims] In a modem, as a waveform of a data transmission signal, a first special waveform having a fast peak rise in a half cycle, a second special waveform having a slow peak rise, and a fast rise in the half cycle are provided. A third and third peaks whose peak heights are at least higher than a predetermined level;
And a fourth special waveform whose peak height at the two peak positions within the half cycle is lower than the predetermined level is output, and the waveform is obtained by a combination of the first to fourth special waveforms. A signal generating means for sending out including 2-bit information in a half cycle of the modem. 2. A modem according to claim 1, wherein a waveform of the data transmission signal includes a first special waveform having a fast peak rise in a half cycle, a second special waveform having a slow peak rise, and a fast rise in the half cycle. A third and third peaks whose peak heights are at least higher than a predetermined level;
When receiving any of a special waveform and a fourth special waveform in which the peak heights of the two peak positions within the half cycle are lower than the predetermined level, the peak of the rising edge and the peak of the rising edge are received. A modem comprising signal demodulating means for detecting whether a waveform signal value is equal to or higher than the predetermined level or not at a timing close to the signal, thereby detecting 2-bit information in a half cycle of the waveform. 3. A modem comprising: a signal generator in the modem according to claim 1; and a signal demodulator in the modem according to claim 2. 4. The modem according to claim 1, wherein data transmission is performed via a telephone line. Each of the special waveforms can include a plurality of waveforms in one transmission cycle by phase shift. A modem, characterized in that: 5. The first to fourth special waveforms are created by combining a first composite waveform having a fast peak rise in a half cycle and a second composite waveform having a slow peak rise in quarter cycle units. The modem according to any one of claims 1 to 4, wherein: 6. The method according to claim 1, wherein the first and second combined waveforms are created by combining a signal having a frequency higher than the half-period frequency and a triangular waveform having the half-period frequency. Item 6. A modem according to any one of Items 1 to 5. 7. The first and second combined waveforms are created by combining a signal having a frequency higher than the half-period frequency and a signal having a lower frequency than the half-period frequency. The modem according to any one of claims 1 to 5, wherein 8. A data transmission method, wherein a waveform of a data transmission signal includes a first special waveform having a fast rising peak within a half cycle, a second special waveform having a slow rising peak, and the rising waveform within the half cycle. The wave height at the two peak positions of the early peak and the late peak is at least higher than a predetermined level.
And a fourth special waveform whose wave height at the two peak positions in the half cycle is lower than a predetermined level is used, and a combination of the first to fourth special waveforms is used for two half cycles of the waveform. A data transmission method characterized by including bit information. 9. When receiving the waveform of the data transmission signal, detecting whether the waveform signal value is equal to or higher than the predetermined level is detected at a timing near the early rising peak and the late rising peak. 9. The data transmission method according to claim 8, wherein two bits of information are detected in a half cycle of the waveform. 10. The first to fourth special waveforms are created by combining a first composite waveform having a fast peak rise in a half cycle and a second composite waveform having a slow peak rise in quarter cycle units. 9. The method according to claim 8, wherein
Or the data transmission method according to 9. 11. The method according to claim 8, wherein
A data transmission method in a modem using a telephone line to which the data transmission method described in the item is applied.