JPH0265464A - Modulator-demodulator for picture data communication - Google Patents

Abstract

PURPOSE:To use only one set of a MODEM for the data transmission of a facsimile equipment and a TV telephone set by providing a changeover means of the operating mode applying data transmission reception of the facsimile equipment and the operating mode of the transmission reception of the data of the TV telephone set to a modulation section and a demodulation section. CONSTITUTION:A TV telephone set MODEM in common use for the G2 mode consists of a modulation section 1, a demodulation section 2 and a changeover device 3 similarly to those of a conventional MODEM. A logical signal inputted from a host device (G2 facsimile equipment or a TV telephone set) is subject to modulation in the modulation section 1 and sent to a telephone line via the changeover device 3. A control signal is inputted to the modulation section 1 from a host device, while an analog signal inputted to the switch 3 from the telephone line is sent to the demodulation section 2, where the signal is subject to demodulation and the result is sent to the host device. Thus, the data transmission of the facsimile equipment and the TV telephone set is applied by one set of MODEM.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a modulation/demodulation device for image data communication.

(Prior Art) Facsimile machines have been widely used as means for image data communication. Facsimile machines connected to the public telephone network are categorized by the Consultative Committee for International Telegraph and Telephone (CCITT) as Group 1, Group 2, and Group 3 (hereinafter referred to as ``G1'' and ``G
2" and "G3") standards have been recommended, and facsimile machines compliant with G2 and G3 are now common.

Recently, as a new means of image data communication, so-called video telephones (TV telephones), which transmit still images obtained by an imaging device via the public telephone network and reproduce the images on a display device on the receiving side, have been introduced.
(hereinafter referred to as "rTVt story") has been put into practical use.

Although the technical idea behind the TV story itself has existed for some time, recent advances in electronics technology have made it possible to reduce costs and improve performance, and it has now been put into practical use.

Both facsimile machines and video telephones are equipped with a modem (hereinafter referred to as a "modem") for transmitting data over the public telephone network. The transmission method in the modem of a facsimile machine is vestigial sideband amplitude phase modulation (AM-PM-VSB) for G2 facsimile machines.
G3 facsimile machines use polyphase phase keying (polyphase PSK)
and orthogonal S-width variable N (QAM). On the other hand,
Standards are about to be established for transmission methods for video telephones. According to this standard, for example, when expressing 16 gray levels with 4 bits, the modem converts 3 of the 4 bits to obtain 8 levels of amplitude and the value of the remaining 1 bit. It is supposed to use a phase change m with amplitude (AM-PM) that modulates a carrier wave by a combination of two phases according to the following.

(Problems to be Solved by the Invention) Various attempts have been made to combine different types of electronic devices. For image data communication devices as well, there is a desire for a combination of facsimile devices and video telephones.

However, as mentioned above, the transmission methods are different between facsimile machines and video telephones. Therefore, even if an attempt is made to combine a facsimile device and a TV phone, a plurality of modems must be installed, and the advantages of the combination, such as cost reduction and miniaturization of the device, cannot be fully obtained.

In addition, the image quality of conventional videophones cannot necessarily be said to be high, and TVs that can transmit images of higher quality
It is hoped that telephones will become a reality.

The present invention was made in view of the current situation, and
Its purpose is to provide facsimile and 771
To provide a modem which can transmit voice data with a single modem and can contribute to cost reduction and miniaturization of the device when a facsimile device and 771 voice communication are combined.

Another object of the present invention is to provide a modem that can perform data transmission for a facsimile device and a video phone in one device, and can improve the quality of images in the video phone.

(Means for Solving the Problems) A modulation and demodulation device for image data communication according to the present invention is a modulation and demodulation device for image data communication that includes a modulation section and a demodulation section, and the modulation section receives input from the outside. The demodulator has a means for switching the operation mode between an operation mode for transmitting data for a facsimile machine and an operation mode for transmitting data for a videophone based on a control signal, and the demodulator receives a signal input from a telephone line. The apparatus has means for switching the operation mode between an operation mode for receiving data for the facsimile machine and an operation mode for receiving data for the television based on the above, thereby achieving the above object. Ru.

Further, in the modulation/demodulation device for image data communication according to the present invention, the facsimile device is a group 2 facsimile device, thereby achieving the above object.

Furthermore, in the modem apparatus for image data communication according to the present invention, the facsimile apparatus is a group 3 facsimile apparatus, thereby achieving the above object.

(Example) The invention will now be described with reference to examples.

FIG. 3 shows a schematic configuration of an embodiment of the present invention.

This embodiment is a modem for transmitting data between a G2 facsimile machine and a TV phone (hereinafter referred to as a "G2 and TV phone modem").This G2 and TV phone modem is a normal modem. Similarly, a logical signal input from a host device (G2 facsimile unit or TVili talk unit) not shown in Figure 9, which is composed of a modulator 1, a demodulator 2, and a switch 3, undergoes a modulation effect in the modulator 1. After receiving it, it is sent out to the telephone line via the switching device 3. A control signal is also input to the modulation unit 1 from the host device. On the other hand, the analog signal input from the telephone line to the switch 3 is sent to the demodulator 2, and after being demodulated by the demodulator 2, is sent to the host device.

A block diagram of the modulation unit 1 is shown in FIG. 1. In the modulation unit 1, a logical input signal is subjected to sampling and code conversion for phase modulation in a sampling/code conversion unit 10. A low-pass r-wave filter (hereinafter referred to as LPF) 11 is connected to the downstream of the sampling/code conversion unit 10, and noise components outside the frequency band of the telephone line are removed here. Modulator 1 connected after LPFII
2, the carrier wave generated by the carrier wave generating section 13 is modulated by the signal output from the L P F 11. The output signal of the modulator 12 is input to the filter section 15 via the adder 14, and one or more signal processings therein are performed in digital form. The output of the filter section 15 is D/A converted by the D/A converter 16 and then converted to L.
Components outside the band of the telephone line are removed by the PF 17, and the signal is sent to the telephone line via the switch 3.

The control signal from the host device is sent to the mode switching signal generator 18.
and is input to the video telephone dual tone signal generator 19. The mode switching signal generating section 18 outputs a mode switching signal for switching between the 02 facsimile mode and the TV telephone mode in accordance with the control signal.

Among the elements constituting the conversion section 1, the sampling/code conversion section 10, the carrier wave generation section 13, the filter section 15, and the D/A
The conversion unit 16 operates differently in the G2 facsimile mode and the TVi talk mode according to the mode switching signal.

The sampling/code conversion unit 10 includes a sampler 101 and a code converter 102 for G2 facsimile, a sampler 103 and code converter 104 for TVt talk, and a switch 105. Logical input signal is G2
The signal is input to a video telephone sampling device 101 and a video telephone sampling device 103. The output of the sampler 101 is G
2 code converter 102, and the sampler 10
The output of No. 3 is input to the video telephone code converter 104.

The outputs of code converters 102 and 104 are both input to a switch 105. The sampler 101 and the sampler 103 sample the input signal at sampling frequencies for G2 and TV telephone, respectively. Code converter 1
At step 02, binary/ternary conversion is performed on the input signal.

That is, the pulses appearing in the input signal are made negative every other pulse. FIG. 4 schematically shows how binary/ternary conversion occurs in the code converter 102. In the code converter 104,
For example, when the input signal expresses 16 gradations, code conversion is performed as shown in the correspondence table in Table 1 below. According to the mode switching signal, the switch 105 converts the signal from the code converter 102 into the TV in the G2 facsimile mode.
In the telephone mode, each signal from the code converter 104 is output.

Table 1 (blank below) The carrier wave generator 13 selectively selects the carrier waves output by the G2 facsimile carrier generator 131, the TV telephone carrier generator 132, and the two carrier wave generators 131 and 132 according to the mode switching signal. Switch 1 to send to modulator 12
It is equipped with 33. The carrier wave generator 131 outputs a 2100 Hz carrier wave for G2 facsimile, and the carrier wave generator 132 outputs a 1747.82 Hz carrier wave for TVi talk.

The filter section 15 includes a sideband filter 151 for implementing the residual sideband method in G2 facsimile, an LPF 152 for TV telephone, and a switch 153. The signal output from the adder 14 is sent to the sideband filter 1
51 and LPF 152. Switch 15
3 is a sideband filter 15 in G2 facsimile mode.
Outputs the signal from 1, and in TV talk mode LPF15
Outputs the signal from 2.

The D/A converter 16 includes a D/A converter 161, a G2 facsimile timing generator 162, a TV telephone timing generator 163, and a switch 164. The timing generator 162 is 103681 for G2 facsimile.
(The timing generator 163 generates a 6991.28Hz clock for the TV phone.The switch 164 uses the clock generated from the timing generator 162 in the G2 facsimile mode, and the timing generator 164 in the TV phone mode. A clock generated by a generator 163 is supplied to the D/A converter 161.

The videophone dual tone signal generator 19 generates G, m1633Hz and 2006Hz at the start of the videophone mode.
Outputs dual tones with two frequencies. Dual tone is output for 400 m5 followed by 4
A pause of 00m5 will be provided. The dual tone output from the TV phone dual tone signal generator 19 is input to the adder 14, filter section 15, and D/A converter 1.
6 and LPF], 7 to the telephone line. This dual-tone transmission is specified in the standard room for video telephones mentioned in the ``Prior Art'' section.

FIG. 2 shows a block diagram of the demodulator 2. Analog signals from the speech line are input to the AGC 20 and the TV detector 28. The analog signal is compensated for amplitude fluctuations in the telephone line by the AGC 20 and is
The signal is converted into f-wave at F21 and converted into a digital signal by A/D converter 22. The output of the A/D converter 22 is 2
0-th power 1 detector 2 input to 25 product detectors 23 and 25
3 is supplied with a reference carrier wave from the VCO in the PLL circuit 24 via a line 241, and a zero-power product detector 25 in which demodulation is performed here is provided to realize phase synchronization in the PLL circuit 24. The zero product detector 25 has a PLL
The first power product detector 23 to which a wave having a phase different from the reference carrier wave by π/2 is provided via a line 242 from the circuit 24 receives the modulated signal input from the A/D converter 22 and the reference carrier wave. A signal proportional to the cosine of the phase error between them is output, and the product detector 25 outputs a signal proportional to the sine of the phase error. These signals are input to the PLL circuit 24, and the VCO is controlled in the PLL circuit 24 so that the signal proportional to the sine becomes 0.The signal demodulated by the zero-product detector 23 passes through the telephone line band. let L
The signal is sent to the threshold detection section 27 via the PF 26, where it is waveform-shaped and then sent to the host device.

In a video telephone, a frame synchronization signal consisting of sections a to e is transmitted following the dual tone and pause described above. When the TV detection unit 28 detects the dual tone and pause as well as the carrier wave of L747.82Hz and 16 cycles included in the a section of the frame synchronization signal, the TV detection unit 28 outputs the TVtV signal to the mode switching signal generation unit 29.
A mode switching signal indicating t-mode is output. This mode switching signal is given to the A/D converter 22, the PLL circuit 24, and the threshold detector 27. That is, the demodulator 2 normally operates in G2 facsimile mode,
It operates in the TV telephone mode only when the TV detection unit 28 performs the above-mentioned detection.

The A/D converter 22 includes a timing generator 222 for the A/D converter 221.02 and a timing generator 22 for the TV telephone.
3 and a switch 224. According to the mode switching signal, the switch 224 selects G2 facsimile mode in G2 facsimile mode.
10368H output from the timing generator 222
z clock, and in the TV phone mode, the 6991°288 clock output from the TV phone timing generator 223.
The Z clock is supplied to the A//D converter 221.

The VCO in the PLL circuit 24 follows the mode switching signal.
In the G2 facsimile mode, a reference carrier wave of 2100 Hz is generated, and in the TV telephone mode, a reference carrier wave of 1747.82 Hz is generated.

The threshold detection section 27 includes G
2 threshold detector 271, a TV phone threshold detector 272, and a switch 273. In the G2 facsimile mode, the switch 273 switches the output of the G2 threshold detector 271 to
In the TV phone mode, the output of the TV phone threshold detector 272 is sent to the host device.

The modem for G2 and TV phone described above is
2 facsimile mode and TVtVt-mode use the same transmission method as before, so this modem can communicate with conventional 02 facsimile equipment or T.
You can use the V phone as is. Furthermore, since this modem has many common parts with the conventional modem for G2 facsimile machines, it can be realized at a low cost based on the conventional modem for G2 facsimile machines.

FIG. 5 shows a schematic configuration of a second embodiment of the present invention. This embodiment uses a G3 facsimile machine and a modem for transmitting data for TV calls (hereinafter referred to as an rGB/TV telephone modem). ).

Similar to the modem of the first embodiment, this modem for G3 and TV telephone is composed of a modulation section 4, a demodulation section 5, and a switch 6. It is similar to that of modem.

A logical input signal from a host device is input to a synchronization input section 70, which is shown in a block diagram of the modulation section 4 in FIG. The synchronization input section 70 samples the logical input signal while synchronizing with the host device.
The output signal of 0 is input to the scrambler 71. The scrambler 71 scrambles a bit string, which is an input signal, according to a predetermined generator polynomial. scrambler 71
The output of is input to the QAM modulator 72. In the QAM modulator 72, the carrier wave input from the carrier wave generating section 73 is modulated by the signal input from the scrambler 71 using the QAM method. The modulated signal output from the QAM modulator 72 is passed through an adder 74 and a digital filter 75 to the D
/ is input to the A converter 76. The modulated signal D/A converted by the D/A converter 76 is output to the telephone line via the LPF 77.

The modem of this embodiment has two operating modes: G3 facsimile mode and TV telephone mode. Selection of the operating mode is performed by the mode switching signal generating section 78. The mode switching signal generating section 78 generates a mode switching signal according to a control signal input from the host device.

Among the elements constituting the modulation section 4, a mode switching signal is input to the synchronization input section 70, carrier wave generation section 73, and D/A converter 76, and these elements operate differently depending on the operation mode.

The synchronization input section 70 is a synchronization input device 70 that performs sampling.
4. A switch 703, and two timing generators 70 connected to the synchronous input device 704 via the switch 703.
1,702. The timing generator 701 is G
96 used as a synchronization signal in 3 facsimile mode
Generates a 00Hz clock. timing generator 70
2 is 6991.28H used in TV'iJ talk mode
Generates a clock for z. The switch 703 supplies the tarock generated by the G3 timing generator 701 in the G3 facsimile mode and the clock generated by the TVt conversation timing generator 702 in the TVi conversation mode to the synchronization input device 704 in accordance with the mode switching signal.

The clock output from the switch 703 is sent to the D/A converter 7.
6, and is used to determine the sampling rate in the D/A converter 76.

The carrier wave generator 73 has two carrier wave generators 731 and 732 connected to the QAM modulator 72 via a switch 733 and a switch 733, similar to the carrier wave generator 13 in the first embodiment. are doing. The carrier wave generator 731 is G
Outputs a 1700Hz carrier wave for carrier wave generator 7.
32 outputs a carrier wave of 1747.82 Hz for TVi talk. The switch 733 selects one of the carrier waves output from the two carrier wave generators 731 and 732 according to the mode switching signal, and supplies the selected carrier wave to the QAM modulator 72.

The control signal from the host device is also input to the dual tone signal generator 79 for TV telephone. Similar to the dual tone signal generating section 19 for a TV telephone in the first embodiment, the TV telephone dual tone signal generating section 79 generates a dual tone having two frequencies of 1633f (z and 2006 Hz) at the start of the TVi talk mode. The dual tone digital wave output from the TV telephone dual tone signal generator 79 is input to the adder 74, and then the digital filter 75, the D/A converter 76 and the LPF 77
is sent out to the telephone line via.

FIG. 7 shows a block diagram of the demodulator 5. The analog signal from the speech line is processed by the analog filter 80 and the AGC 81.
The signal is input to the A/D converter 82 via the A/D converter 82, where it is A/D converted. The output signal of the A/D converter 82 is demodulated by a QAM demodulator 83. The QAM demodulator 83 is provided with a reference carrier generated by a reference carrier generator 84 . Distortion caused by the telephone line is removed from the demodulated signal by an automatic line equalizer 85 that generates an inverse characteristic of the transfer function of the telephone line. Finally, the descrambler 86 restores the original sequence to the digital signal.

The demodulator 5 normally operates in G3 facsimile mode. Similar to the demodulator 2 of the first embodiment, the TV detector 8
7 detects a dual tone and a carrier wave of 1747.82 Hz, the mode switching signal generator 88 outputs a T
A mode switching signal is output to switch to V-telephone mode. The mode switching signal is input to the A/D converter 82 and the reference carrier generator 84.

The A/D converter 82 has 9 for A/D converter 821.03.
Timing generator 82 that outputs a 600Hz clock
2. A timing generator 823 that outputs a 6991.28 Hz clock for TV'9 episode and an A/D converter 821 that outputs one of two types of tarok according to the mode switching signal.
A switching device 824 is provided to supply the The clock output from switch 824 is also input to descrambler 86 .

The reference carrier generator 84 includes a switch 841, a reference carrier generator 842 for G3, and a reference carrier generator 843 for TV telephone. According to the mode switching signal, the switch 841 switches the 1700H2 reference carrier generated from the reference carrier generator 842 to the TV in the G3 facsimile mode.
In the ii talk mode, the reference carrier wave of 1747.82H2 generated by the reference carrier generator 843 is input to the QAM demodulator 83.

The modem of this embodiment is thus configured based on the modem for the 03 facsimile machine.1 The transmission method of the modem of this embodiment in the TV phone mode is different from that in the conventional TV phone. Therefore, the other party's video phone must also use the same transmission method as this modem.

However, the transmission method of G3 facsimile machines is much superior to that of G2 facsimile machines, and CCITT Recommendation V, 29, 96 for G3 facsimile machines.
By taking advantage of the commonality that both 00 bps modems and video phones perform 4-value conversion, by using a G3 facsimile modem for video phone image transmission,
It is possible to transmit high-quality images with less distortion than conventional videophones.

FIG. 8 shows a schematic configuration of an example of a device that combines facsimile and TVi communication by applying the G2 and TV phone modems described above and the G3 and TV phone modem. It consists of a device 91, a composite modem 92, and a hybrid transformer 93. The host device 91 includes a control unit 911, a G2/G3 facsimile unit 912, and a video telephone transmitting/receiving unit 913. The composite modem 92 includes a G3/TV telephone modem 921, a G22/TVt modem 922, and a switch 923. Modem 92 for G33 and TVt
The modems 922 for TV 1 and 02 and for TVt talk can share a considerable part of the circuit for digital signal processing. The control unit 911 controls the G2/G3 facsimile unit 912 and the TVi communication unit 913, and also controls the mode switching between the 03 and TV telephone modem 921 and the G22 and TV telephone modem 922 in the composite modem 92. Send control signal to switch 923 G33
A control signal for switching between the modem 921 for both personal use and TV phone use and the modem 922 for use as both personal use and TV phone use is sent out. TV
The telephone transmitting/receiving unit 913 is a modem 9 for G33 and TV power.
Image transmission can be performed using both the G.21 and G22/TV power modems 922. When using the G33/TV modem 921, it is possible to use the data scrambling method adopted in the modem of the G3 facsimile machine, so it is resistant to transmission line noise.
High-quality image transmission with fewer signal errors becomes possible.

(Effects of the Invention) According to the present invention, a modem is provided that can perform data transmission with 21 facsimile machines and TV telephones6.
By using the modem of the present invention, it is possible to provide a device combining a facsimile device and a TV telephone at a low cost, and the device can be made smaller by using VLSI or the like. Further, according to the modem of the present invention in which the facsimile device is a G3 facsimile device, in addition to the above-mentioned effects, it is possible to perform image communication for a video telephone with higher quality than before.

Figure 1 is a block diagram of the modulation section of a modem for G22 and TV power, which is an embodiment of the present invention, Figure 2 is a block diagram of the demodulation part of that embodiment, and Figure 3 is its block diagram. FIG. 4 is a block diagram showing a schematic configuration of the embodiment; FIG. 4 is a diagram showing an example of binary/ternary conversion performed in the G2 facsimile code converter provided in the modulation section of the embodiment; FIG. is the second aspect of the present invention.
FIG. 6 is a block diagram of the modulation section of the second embodiment, and FIG. 7 is a block diagram of the demodulation section of the second embodiment. figure,
FIG. 8 is a block diagram of an example of a device that combines a facsimile device and a TV telephone.

1.4...Modulation section, 2.5...Demodulation section, 18.78
...Mode switching signal generation section, 19.79...Dual tone signal generation section for TV telephone, 28.87...TV
Detection unit, 29.88...Mode switching signal generation unit, 10
5.133.153.164.224.273.703
．． 733.824...Switcher.

that's all

Claims (1)

[Scope of Claims] 1. A modulation/demodulation device for image data communication comprising a modulation section and a demodulation section, wherein the modulation section changes the operation mode for a facsimile machine based on a control signal input from the outside. having means for switching between an operation mode for transmitting data and an operation mode for transmitting data for videophone;
Image data in which the demodulation unit has means for switching an operation mode between an operation mode for receiving data for a facsimile machine and an operation mode for receiving data for a videophone based on a signal input from a telephone line. Modem and modem for communication. 2. The modulation/demodulation device for image data communication according to claim 1, wherein the facsimile device is a group 2 facsimile device. 3. The modulation/demodulation device for image data communication according to claim 1, wherein the facsimile device is a group 3 facsimile device.