CN102695029A - Video signal remote transmission system - Google Patents
Video signal remote transmission system Download PDFInfo
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- CN102695029A CN102695029A CN2012101446608A CN201210144660A CN102695029A CN 102695029 A CN102695029 A CN 102695029A CN 2012101446608 A CN2012101446608 A CN 2012101446608A CN 201210144660 A CN201210144660 A CN 201210144660A CN 102695029 A CN102695029 A CN 102695029A
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Abstract
The invention discloses a video signal remote transmission system. After being connected in parallel with a first ESD (Electronic Static Discharge) protection circuit, a filter circuit and a differential conversion circuit, a signal input interface is connected in series with a RED demodulation circuit, a GREEN demodulation circuit, a BLUE demodulation circuit, a Vsync demodulation circuit and a Hsync demodulation circuit which are connected in parallel, then is connected in series with a second ESD protection circuit and is connected in parallel with two signal output interfaces. The video signal remote transmission system disclosed by the invention overcomes the bad phenomena that a VGA (Video Graphics Array) signal has short transmission distance and is easy to interfere by the environment, the trailing, ghosting and the like can be generated on a display screen and the like, and can normally operate in the complex operating environment.
Description
Technical field
The present invention relates to information transmission technology field, be specifically related to a kind of analog video signal long-distance transmissions scheme of DB9 serial line interface.
Background technology
In the systems such as common railway, subway; Often need be transferred to each display screen to vision signal through a segment distance; Common VGA signal transmission distance is shorter, receives environmental interference easily, on display screen, bad phenomenon such as hangover, ghost image can occur; And in complicated running environment, be more prone to occur various bad phenomenon, so the transmission of VGA signal long-distance needs to adopt the mode of twisted-pair feeder differential transfer.
The interface of output analog signal generally adopts the VGA connector, and the applicant considers the environment more complicated of operation, and considers from each side such as costs, so adopt the DB9 interface to realize the connection of signal.
The remote biography scheme of R, G, B tricolor signal and row, field sync signal is a lot of on the market now; Comprise that all there is own exclusive chip solution in companies such as intersil, AD, MAXIM; Based on the consideration of the interference free performance of purchase cost and design, finally adopted the scheme of CADEKA.
The scheme that CADEKA provides is to use CLC2000 amplifier chip to handle the VGA differential signal, and the main body thinking is following:
RED?CM?=?K?*?(Vsync?-?Hsync)?+?mid-supply
GREEN?CM?=?K?*?(-2Vsync)?+?mid-supply
BLUE?CM?=?K?*?(Vsync?+?Hsync)?+?mid-supply
Building analog circuit through three top formula can come out RED, GREEN, BLUE, Vsync, Hsync demodulation.
In low supply voltage is used, no matter be to use single supply, or the low-voltage bipolar power supply, the input range of amplifier and output voltage swing all have certain restriction, and limited input range and limited output voltage swing all can reduce the dynamic range of amplifier.Rail-to-rail amplifier not only helps to expand this dynamic range, and can also improve performance.
Amplifier adopts emitter follower (source follower) or common emitter (common source) output-stage circuit usually.Emitter follower can provide lower distortion, but output voltage swing is also less, and this is because output stage transistor need can make output voltage swing reduce about 1V in linear domain work like this.Rail-to-rail output amplifier generally adopts common emitter or common source output circuit, though this output circuit can't provide the picture emitter follower so good performance, it can provide the wideer amplitude of oscillation.The amplitude of oscillation of rail-to-rail output can be very near power rail, but owing on the transistor certain pressure drop is arranged, so can not reach rail voltage fully, but both differences are within several millivolts.Comprehensive each side is considered, adopts rail-to-rail amplifier chip SGM8052 to realize the demodulation of VGA signal.
When using at the scene according to the VGA signal decoding plate of the conceptual design of CADEKA; The demonstration problem appears on the display screen that has; Like phenomena of the failure such as display screen blank screen (the display screen blank screen signal occurs and adjusts the back recovery automatically normally), display screen quickflashings, its circuit is made amendment through analysis and research; Use through reality after the modification, this phenomenon of the failure does not occur again.
Summary of the invention
The objective of the invention is to overcome the above problem that prior art exists, a kind of vision signal distance transmission system is provided.
For realizing above-mentioned technical purpose, reach above-mentioned technique effect, the present invention realizes through following technical scheme:
A kind of vision signal distance transmission system; Comprise a signal input interface; Said signal input interface is connected in parallel with first esd protection circuit, filter circuit and differential conversion circuit and then is connected in series with the RED demodulator circuit that is connected parallel with one another, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and Hsync demodulator circuit, and two signal output interfaces are connected in parallel behind one second esd protection circuit that is connected in series again afterwards;
Said vision signal distance transmission system is produced+DC-voltage supply of 5V by a power circuit;
Said RED demodulator circuit, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and Hsync demodulator circuit are produced+DC-voltage supply of 2.5V by a reference voltage circuit.
Preferably, said filter circuit is formed by connecting with second resistance after first resistance and electric capacity parallel connection.
Preferably, said differential conversion circuit is formed by connecting the 3rd resistance and the series connection of the 4th resistance.
Preferably, use rail-to-rail operational amplifier in said RED demodulator circuit, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and the Hsync demodulator circuit.
Preferably, the input and the outgoing position of said Vsync demodulator circuit and Hsync demodulator circuit are provided with filter capacitor.
What preferably, use in said Vsync demodulator circuit and the Hsync demodulator circuit is Schmidt trigger.
Preferably, said signal input interface and signal output interface are all the DB9 interface.
The invention has the beneficial effects as follows:
Overcome the VGA signal transmission distance and lacked, receive environmental interference easily, on display screen, bad phenomenon such as hangover, ghost image can occur, and can normally run in the complicated running environment.
Above-mentioned explanation only is the general introduction of technical scheme of the present invention, understands technological means of the present invention in order can more to know, and can implement according to the content of specification, below with preferred embodiment of the present invention and conjunction with figs. specify as after.Embodiment of the present invention is provided by following examples and accompanying drawing thereof in detail.
Description of drawings
Accompanying drawing described herein is used to provide further understanding of the present invention, constitutes the application's a part, and illustrative examples of the present invention and explanation thereof are used to explain the present invention, do not constitute improper qualification of the present invention.In the accompanying drawings:
Fig. 1 system architecture diagram;
Fig. 2 VGA differential signal input interface;
Fig. 3 VGA signal output interface;
Fig. 4 esd protection circuit;
Fig. 5 video match circuit;
Fig. 6 reference voltage circuit;
Fig. 7 R, G, B decoding circuit;
Fig. 8 field signal decoding circuit;
The capable signal decoding circuit of Fig. 9.
Embodiment
Below with reference to accompanying drawing and combine embodiment, specify the present invention.
A kind of vision signal distance transmission system; Comprise a signal input interface; Signal input interface is connected in parallel with first esd protection circuit, filter circuit and differential conversion circuit and then is connected in series with the RED demodulator circuit that is connected parallel with one another, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and Hsync demodulator circuit; Two signal output interfaces that are connected in parallel behind one second esd protection circuit afterwards again are connected in series; The vision signal distance transmission system is produced+DC-voltage supply of 5V by a power circuit; RED demodulator circuit, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and Hsync demodulator circuit are produced+DC-voltage supply of 2.5V by a reference voltage circuit, with reference to shown in Figure 1.
1, VGA differential signal input interface and VGA signal output interface
What the input interface of VGA differential signal adopted is the DB9 interface; Pinout such as Fig. 2, wherein: 1 pin and 2 pin are a pair of differential signals of RED, 3 pin and 6 pin are a pair of differential signals of GREEN; 4 pin and 5 pin are a pair of differential signals of BLUE; The 7th pin and the 8th pin connect signal ground through resistance, and the 9th pin connects signal ground through magnetic bead, and M1 and M2 connect shell and receive signal ground through resistance capacitance.
What the output interface of two VGA signals adopted equally is the DB9 interface; Pinout such as Fig. 3, wherein: 1,3,5 pin are received signal ground, and 2 pin are received the RED signal; 4 pin are received the BLUE signal; 6 pin are received the GREEN signal, and the 9th pin connects signal ground through magnetic bead, and M1 and M2 connect shell and receive signal ground through resistance, electric capacity.
In the scheme of CADEKA ground connection is not related to, from aspect consideration altogether, in using at the scene; We are to use 8 core netting twines transmission VGA differential signal; We are welded to the shielding conductor in the netting twine on the shell of DB9 socket, make shielding conductor ground connection, thereby improve signal transfer quality.
2, esd protection circuit
In the scheme of CADEKA esd protection is not related to; During product design, be on the one hand, in addition on the one hand owing to the VGA differential signal is received on the signal decoding deck through the DB9 interface because rail-to-rail operational amplifier SGM8052 requires esd protection; In the process of contacts such as plug, possibly have static; So we have used esd protection chip PESD12VS5UD when design, the back has added BAV99 again and has been used for drawing with drop-down, makes the signal of telecommunication that is transferred to the back circuit remain on 0-5V; Thereby guaranteed the reliability of circuit, concrete visible Fig. 4.
3, video match circuit
The video match circuit is formed through the filter circuit, the differential conversion circuit that connect successively; Filter circuit is formed by connecting with second resistance R 10 first resistance R 11 and capacitor C 9 parallel connection backs; The differential conversion circuit is connected in series by the 3rd resistance R 9 and the 4th resistance R 12 and forms, like Fig. 5.Vref+ among Fig. 5 is a reference voltage, is connected to operational amplifier by+5V through behind the electric resistance partial pressure, bypass 0.1uf capacitor filtering behind the voltage follow, and output Vref+ reference voltage is like Fig. 6.
4, RED, GREEN, BLUE signal demodulating circuit
The differential signal of R, G, B is through after the differential conversion, and through comparing input operational amplifier, the output signal is divided into two-way output, like Fig. 7 through amplifying R, G, the B tristimulus signal that obtains primary colors again.
5, Vsync (field signal), Hsync (row signal) demodulator circuit
Demodulation to Vsync and Hsync in the scheme of CADEKA has detail circuits; But in actual use; The VGA differential signal has more crosstalk signal, and we are according to time constant T=RC, is expert at, the input position of field signal demodulator circuit increases electric capacity can the certain clutter of filtering; Like the filtering among Fig. 8, Fig. 91, filtering 2, two filter capacitors in like manner when output, have been increased.
Longer when transmission line, and the impedance of the impedance of receiving terminal and transmission line is not when matching, and will produce oscillatory occurences at the rising edge and the trailing edge of waveform; When other pulse signals are added to rectangular pulse signal through distributed capacitance between lead or public power wire, additional noise will appear on the signal.Above-mentioned any situation no matter occurs, all can obtain more satisfactory rectangular pulse waveform through the shaping of Schmidt's inverter trigger.In actual the use; The rising of the waveform that operational amplifier comes out, the time of decline are longer, and on the rising edge of waveform and trailing edge, have certain reflected signal, so used Schmidt trigger here; Oppositely make it obtain better signal, like the inverter among Fig. 8, Fig. 9.
The above is merely the preferred embodiments of the present invention, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.All within spirit of the present invention and principle, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (7)
1. vision signal distance transmission system is characterized in that:
Comprise a signal input interface; Said signal input interface is connected in parallel with first esd protection circuit, filter circuit and differential conversion circuit and then is connected in series with the RED demodulator circuit that is connected parallel with one another, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and Hsync demodulator circuit, and two signal output interfaces are connected in parallel behind one second esd protection circuit that is connected in series again afterwards;
Said vision signal distance transmission system is produced+DC-voltage supply of 5V by a power circuit;
Said RED demodulator circuit, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and Hsync demodulator circuit are produced+DC-voltage supply of 2.5V by a reference voltage circuit.
2. vision signal distance transmission system according to claim 1 is characterized in that: said filter circuit is formed by connecting with second resistance (R10) first resistance (R11) and electric capacity (C9) parallel connection back.
3. vision signal distance transmission system according to claim 1 is characterized in that: said differential conversion circuit is connected in series by the 3rd resistance (R9) and the 4th resistance (R12) and forms.
4. vision signal distance transmission system according to claim 1 is characterized in that: the input and the outgoing position of said Vsync demodulator circuit and Hsync demodulator circuit are provided with filter capacitor.
5. vision signal distance transmission system according to claim 1 is characterized in that: use rail-to-rail operational amplifier in said RED demodulator circuit, GREEN demodulator circuit, BLUE demodulator circuit, Vsync demodulator circuit and the Hsync demodulator circuit.
6. vision signal distance transmission system according to claim 1 is characterized in that: what use in said Vsync demodulator circuit and the Hsync demodulator circuit is Schmidt trigger.
7. vision signal distance transmission system according to claim 1 is characterized in that: said signal input interface and signal output interface are all the DB9 interface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012101446608A CN102695029A (en) | 2012-05-11 | 2012-05-11 | Video signal remote transmission system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012101446608A CN102695029A (en) | 2012-05-11 | 2012-05-11 | Video signal remote transmission system |
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| CN102695029A true CN102695029A (en) | 2012-09-26 |
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| CN2012101446608A Pending CN102695029A (en) | 2012-05-11 | 2012-05-11 | Video signal remote transmission system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104424911A (en) * | 2013-08-26 | 2015-03-18 | 英业达科技有限公司 | VGA interface protection circuit |
| CN104460446A (en) * | 2014-11-19 | 2015-03-25 | 柳州航盛科技有限公司 | Intelligent pet feeding system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001030009A2 (en) * | 1999-10-15 | 2001-04-26 | Thomson Licensing S.A. | Secure internet compatible bi-directional communication system and user interface |
| CN201491136U (en) * | 2009-09-16 | 2010-05-26 | 青岛海信电器股份有限公司 | Video signal distributor |
| CN202652410U (en) * | 2012-05-11 | 2013-01-02 | 易程（苏州）智能系统有限公司 | Video signal long-distance transmission apparatus |
-
2012
- 2012-05-11 CN CN2012101446608A patent/CN102695029A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001030009A2 (en) * | 1999-10-15 | 2001-04-26 | Thomson Licensing S.A. | Secure internet compatible bi-directional communication system and user interface |
| CN201491136U (en) * | 2009-09-16 | 2010-05-26 | 青岛海信电器股份有限公司 | Video signal distributor |
| CN202652410U (en) * | 2012-05-11 | 2013-01-02 | 易程（苏州）智能系统有限公司 | Video signal long-distance transmission apparatus |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104424911A (en) * | 2013-08-26 | 2015-03-18 | 英业达科技有限公司 | VGA interface protection circuit |
| CN104424911B (en) * | 2013-08-26 | 2016-08-31 | 英业达科技有限公司 | Video graphics array (VGA) interface protective circuit |
| CN104460446A (en) * | 2014-11-19 | 2015-03-25 | 柳州航盛科技有限公司 | Intelligent pet feeding system |
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Application publication date: 20120926 |