JP4160936B2 - Line length measuring device and method for computer switch device - Google Patents

Description

The present invention relates to a line length measuring apparatus, and more particularly to an apparatus for measuring the line length of an analog signal transmission line.

With the rapid development of information technology, computers and peripheral devices have become very popular. Computer users typically operate the computer using input peripherals such as a mouse and keyboard. The computer user can always grasp the state of the computer through a display or voice instruction on the monitor through an output peripheral device such as a monitor or a speaker.

Display screens typically handle color changes by using three types of color signals, for example red, green and blue. All color changes can be generated by superimposing these three kinds of color signals. In addition, since a general display screen is an analog output, the color of the video screen can be adjusted by the voltage control method, and continuous gradations can be displayed on each pixel to reproduce truly vivid image quality. it can.

When a personal computer uses a video display card to output a video signal on a display screen via a network transmission line, a phenomenon occurs in the video signal that the signal attenuates in accordance with impedance matching of the network transmission line. If the video signal is not corrected, the screen on the display screen is blurred and unclear. On the other hand, when the video signal is excessively corrected, a severe phenomenon occurs on the display screen, and the usage period of the display screen is shortened.

When the transmission line exceeds 10 meters, the video signal is greatly attenuated, the image quality of the display screen deteriorates, and the operation screen on the display screen cannot be identified. Also, different types of transmission lines, such as Shielding Twisted Pair (STP) lines or Foil Twisted Pair (FTP) lines, have different frequency responses, and when video signals are transmitted, Cause different levels of signal attenuation or deformation due to transmission line differences. This is because, when actually applied, it is difficult to use a simple signal correction device that corrects the situation of signal attenuation or deformation occurring in transmission lines of different lengths and types depending on the fixing method.

In the prior art, there has been provided a method for calculating the line length of a transmission line from the time difference between transmission and return of a high-speed data stream. However, this method is very expensive and not easy to implement. Further, the prior art has provided another method for inputting an electronic signal for measurement superimposed on a UART subline in a transmission line every time. This UART subline was mainly used for transmission of electrical signals to a keyboard or a mouse. However, with this method, the line length of the transmission line cannot be measured without first stopping other signal communications in the UART subline. Also, if communication is very busy, such as when using a USB interface key board or mouse continuously, this method significantly reduces the signal communication bandwidth and delays the electrical signal. Occurred.

A first object of the present invention is to provide a line length measuring device that is low in cost, simple in circuit, and used in combination with other signal correcting devices to correct a signal attenuated by the line length. .
A second object of the present invention is provided in a computer switch device, used to measure the line length of a transmission line having various lengths and types of the computer switch device, and based on video signal correction performed thereafter. The object is to provide a line length measuring device.
The third object of the present invention is to occupy the communication bandwidth of other signals when measuring the line length of the transmission line, and is simple and easy to use in combination with other signal correction methods. It is to provide a line length measuring method.

In order to achieve the above object, the present invention provides a line length measuring apparatus for measuring a line length of a transmission line used for transmitting a video signal, and wherein the transmission line has at least three sublines. The line length measuring device includes at least a signal synthesis circuit, a signal conversion circuit, and a line length calculation circuit. When the vertical synchronizing signal of the video signal is valid, the electric signal is input to the signal synthesis circuit so as to overlap one of the sublines. The signal conversion circuit converts the electrical signal transmitted by the subline into a numerical value. The line length calculation circuit calculates the line length of the transmission line based on the numerical value.

The present invention also provides a line length measuring method for measuring a line length of a transmission line for transmitting a video signal. When the vertical synchronizing signal of the video signal is valid, the electric signal is input to be superimposed on one of the three color signals of the video signal. Subsequently, the electrical signal transmitted through the transmission line is converted into a numerical value. Thereafter, the line length of the transmission line is calculated based on this numerical value.

According to a preferred embodiment of the present invention, when the vertical synchronizing signal and the horizontal synchronizing signal of the video signal are respectively input to two of the color signals, this electrical signal is transferred to the other color signal. It is input repeatedly. This electrical signal is a standard square wave signal with a frequency in the range of about 4 million to 12 million hertz (Hz), preferably about 8 million hertz (Hz).

After the electrical signal is superimposed on the color signal and input, it is first converted into a differential signal and then transmitted through a transmission line. The transmitted differential signal is converted into a single line signal and then converted into a numerical value. Subsequently, when converting the numerical value, first, the electric signal after being transmitted by the transmission line is filtered to be a DC signal. Then, after adjusting the DC level of the DC signal, the DC signal of the already adjusted DC level is converted into a numerical value.

Also, the DC level is adjusted by comparing the standard voltage with the DC level of the DC signal by the above-described steps. The larger the difference between the DC level of the DC signal and the standard voltage, the higher the output voltage of the DC signal. The smaller the difference between the DC level of the DC signal and the standard voltage, the lower the output voltage of the DC signal.

In the preferred embodiment, a vertical synchronization signal is extracted from the color signals of the vertical synchronization signals that have already been input, and when the extracted vertical synchronization signal is valid, the line length of the transmission line is calculated. The three color signals include a red color signal, a green color signal, and a blue color signal. According to another preferred embodiment of the present invention, the three color signals include a luminance color signal, a chromaticity signal, and a color difference color signal.

In this preferred embodiment, when the vertical sync signal is valid, the standard square wave signal is input into another non-overlapping horizontal or vertical sync signal color signal, and this standard square wave signal is transmitted by the transmission line. The line length of the transmission line is calculated based on the attenuation level after transmission. When the vertical synchronization signal is valid, no other electrical signal input on the display appears on the display unit, so that no inconvenience is given to the user.

Also, in this preferred embodiment, the bandwidth that is not used in the transmission line is fully utilized to occupy the UART subline and improve the problem that the signal is delayed by reducing the communication bandwidth. can do. Also, the electronic device structure used in this preferred embodiment is simpler and less expensive, so it is easier to implement and use, and is combined with another signal correction device, attenuated by the line length of the transmission line. Analog signals can be corrected effectively and accurately.

FIG. 1 shows a preferred embodiment of the present invention. The line length of the transmission line 104 that transmits the video signal is measured using the line length measuring apparatus 100. The transmission line 104 includes, for example, red (R), green (G), and blue (B) color signals, or luminance (Y), chromaticity (U), and color difference (V). And at least three sub-lines for transmitting three color signals such as the color signal of the first color signal. The video signal generally further includes a horizontal synchronizing signal (H) and a vertical synchronizing signal (V) in addition to the three color signals.

The above three color signals are analog signals, and the horizontal synchronizing signal and the vertical synchronizing signal are digital signals. When an analog signal is transmitted over a long distance, the signal is attenuated, so that the signal itself is deformed and distorted. However, such a problem does not occur in a digital signal.

The line length measuring apparatus 100 includes at least a signal synthesis circuit 102, a signal conversion circuit 106, and a line length calculation circuit 108. The video signal is first input into the signal synthesis circuit 102. When the vertical synchronizing signal of the video signal is valid, an electric signal such as a standard square wave signal is superimposed on one color signal and input to the signal synthesis circuit 102. When the vertical sync signal is valid, the display does not output any video signal. That is, when the vertical synchronization signal is valid, the electric signal input in a superimposed manner is not displayed at all on the screen of the display device, so that no inconvenience is given to the user.

After being transmitted by the transmission line 104, the signal conversion circuit 106 converts the transmitted electrical signal into a numerical value, and converts between an analog signal and data by, for example, an analog-digital conversion circuit. Thereafter, the line length calculation circuit 108 calculates the line length of the transmission line 104 based on this numerical value, and other subsequent signal correction devices correct the signal attenuation of the transmission line 104 having a different length or type.

FIG. 2 shows a preferred embodiment of FIG. 1, and this preferred embodiment will be described in conjunction with FIG. An image output device 212 such as a video display card provided in the computer outputs a video signal to the display 242 through the transmission line 204. This video signal has a red color signal (R), a green color signal (G), a blue color signal (B), a horizontal synchronizing signal (H), and a vertical synchronizing signal (V). Each transmission line 204 includes three sublines for transmitting a red color signal (R), a green color signal (G), and a blue color signal (B). The horizontal synchronizing signal (H) and the vertical synchronizing signal (V) are input to overlap any two of the three color signals described above.

The frequency of the video signal should theoretically reach about 66 million hertz, but most video signals have signal attenuation levels in the range of about 4 to 12 million hertz (Hz) and the transmission line 204 Is related to the frequency response of the signal and the frequency of the signal itself. Therefore, in this preferred embodiment, an 8 MHz signal generator 214 is used to generate a standard square wave signal with a frequency of about 8 million hertz (Hz) and measure the line length of the transmission line 204.

When the vertical synchronization signal is valid, the signal synthesis circuit 210 compresses the 8 MHz standard square wave signal into a color signal without being compressed by the horizontal or vertical synchronization signal. In other words, when three color signals are transmitted through the transmission line, the three color signals are compressed separately from the horizontal synchronization signal, the vertical synchronization signal, and the 8 MHz standard square wave signal.
This preferred embodiment does not limit the combination system when different color signals and horizontal, vertical sync signals and standard square wave signals are input in a superimposed manner, and any combination can be applied in this preferred embodiment. can do.

In addition, when a situation occurs in which the vertical synchronization signal and the horizontal synchronization signal are combined in the input video signal, for example, the video signal of the SUN system, the vertical synchronization signal and the horizontal synchronization signal are first decomposed, and then the color signal Are input in layers.

The color signal that has already been input to the other digital signal is transmitted through the transmission line 204 and then received by the signal receiving circuit 216. Thereafter, the color signal input to be superimposed on the other digital signals is recovered to three color signals not including the other digital signals by the color signal recovery circuit 222. However, after being transmitted through the transmission line 204, the analog color signals were more or less attenuated or deformed, and the display 242 was distorted.

The horizontal and vertical synchronization signal extraction circuits 232 are input to the color signals of other digital signals, and extract the horizontal synchronization signal and the vertical synchronization signal. The 8 MHz signal extraction circuit 234 extracts a standard square wave signal having a color signal of 8 MHz, which is superimposed on another digital signal and input. In the preferred embodiment, horizontal and vertical sync signal extraction circuit 232 and 8 MHz signal decoder circuit 234 are each connected to three signal extraction circuits, which are actually three sublines, each corresponding to a horizontal sync signal, Extract a vertical sync signal and a standard square wave signal.

The standard square wave signal of 8 MHz transmitted through the transmission line 204 is converted into data such as a voltage value by the signal conversion circuit 206. Thereafter, the central processing unit 208 calculates the length of the transmission line 204 based on the size of the data, and corrects the color signal in which the above-described signal attenuation or deformation occurs using the color signal correction circuit 224. The horizontal synchronization signal, the vertical synchronization signal, and the corrected color signal are output to the display unit 242 through the image signal output port 240, and an accurate and undistorted video screen is displayed.

FIG. 3 shows a detailed circuit diagram of the 8 MHz signal generator 214 and signal synthesis circuit 210 in the preferred embodiment of FIG. The frequency dividing element 302 divides the standard square wave signal of 16 MHz by 2 and outputs the standard square wave signal of 8 MHz only when the vertical synchronization signal is valid. After that, an 8 MHz standard square wave signal and a vertical synchronization signal are input using the differential circuit 304, and the signal after the input is converted into a differential signal and transmitted through the transmission line .

In the preferred embodiment, the horizontal synchronizing signal and the vertical synchronizing signal are input to the other two color signals by using another differential circuit 304, respectively. Since the transmission speed of the differential signal is relatively fast, this is a signal transmission system with relatively little distortion for an analog color signal .

FIG. 4 is a detailed diagram of the horizontal and vertical sync signal extraction circuit 232 in the preferred embodiment of FIG. The differential signal is transmitted through a long-distance transmission line 204 and then converted into an ordinary single-line signal. In this single-line signal, the color signal is a positive signal, and the horizontal or vertical synchronization signal input in a superimposed manner is a negative signal.

Therefore, in the horizontal and vertical synchronization signal extraction circuit 232, when the input single-line signal is positive, the transistor 402 is not energized, but the transistor 404 is energized and the output signal is close to zero. That is, the signal is a positive color signal and is not output to the outside. When the input single line signal is negative, the transistor 402 is energized but the transistor 404 is not energized, and the output signal is positive. That is, the horizontal and vertical synchronization signal extraction circuit 232 uses the two transistors 402 and 404 to extract a negative signal in the single-line signal and reduce it to a horizontal or vertical synchronization signal.

It should be noted here that in one preferred embodiment, one horizontal and vertical sync signal extraction circuit 232 is used to extract the horizontal sync signal and the vertical sync signal. Further, the horizontal or vertical synchronization signal extracted and output is a positive signal. And since this is a situation opposite to the original negative signal, no adverse effect occurs during the subsequent signal processing steps.

Figure 5 is a detailed circuit diagram of 8MHz signal decoder circuit 234 and the signal conversion circuit 206 in the preferred embodiment of FIG. Similarly, the differential signal is transmitted through a long-distance transmission line 204 and then converted into an ordinary single-line signal. When the single wire signal is filtered by the filtering circuit 502, it is converted to a DC signal and output to the DC level conversion circuit 504. The longer the transmission line 204 is, the greater the attenuation of the DC signal, so the DC current becomes smaller. Conversely, the shorter the transmission line 204, the lower the attenuation and the higher the direct current.

The DC level conversion circuit 504 includes an amplifying device 512, an amplifying device 514, and an amplifying device 516, and the amplifying device 516 is an emitter follower. PWR1 is a standard voltage, and the amplifying device 512 provides a function of adjusting to 0 by dividing the voltage. The output voltage of the amplifying device 514 becomes a voltage obtained by amplifying the voltage difference between the DC level of the DC signal and the standard voltage, and the DC level is converted. When the transmission line 204 is the longest, the voltage value amplifier 514 outputs is maximum.

The DC signal is converted by the DC level conversion circuit 504 and then input to an analog-digital conversion circuit such as an 8-bit analog-digital conversion circuit 522. The analog-digital conversion circuit 522 converts the voltage of the DC signal into a numerical value. This numerical value is input to a line length calculation circuit which is the only central processing unit 208 in this embodiment.

As shown in FIG. 2, since the standard square wave signal works only when the vertical synchronizing signal is valid, the vertical synchronizing signal is also input into the central processing unit 208 together. The central processing unit 208 calculates this numerical value only when the vertical synchronizing signal is valid. The central processing unit 208 calculates the line length of the transmission line 204 based on data based on, for example, a lookup table. Thereafter, the color signal correction circuit performs subsequent signal correction processing such as amplifying and adjusting the color signal according to the line length of the transmission line 204 and adjusting the frequency correction.

In the present invention, preferred embodiments have been disclosed as described above. However, these embodiments are not intended to limit the present invention, and any person who is familiar with the technology can use various embodiments within the scope and spirit of the present invention. Fluctuations and hydration can be added. Therefore, the scope of protection of the present invention is based on the contents specified in the claims.

1 is a block diagram illustrating a preferred embodiment of the present invention. FIG. 2 is a block diagram illustrating the preferred embodiment of FIG. FIG. 3 is an 8 MHz signal generator and signal synthesis circuit diagram of the preferred embodiment of FIG. 2. FIG. 3 is a horizontal and vertical synchronization signal extraction circuit diagram in the preferred embodiment of FIG. 2. FIG. 3 is an 8 MHz signal extraction circuit diagram and a signal conversion circuit diagram in the preferred embodiment of FIG. 2.

Explanation of symbols

100 line length measuring apparatus 102 signal synthesis circuit 104 transmission line 106 signal conversion circuit 108 line length calculation circuit 204 transmission line 206 signal conversion circuit 208 central processing unit 210 signal synthesis circuit 212 image output unit 214 8 MHz signal generator 216 signal reception Circuit 222 Color signal recovery circuit 224 Color signal correction circuit 232 Horizontal and vertical synchronization signal extraction circuit 234 8 MHz signal decoder circuit 240 Image signal output port 242 Display 302 Dividing element 304 Differential circuit 402, 404 Transistor 502 Filter circuit 504 DC level Conversion circuit 512, 514, 516 Amplifier 522 Analog-digital conversion circuit

Claims (3)

A line length measuring device for measuring a line length of a transmission line used for transmitting a video signal,
The video signal includes a three color signal, a horizontal synchronization signal, and a vertical synchronization signal, and the transmission line includes three sublines each transmitting the three color signal, and the horizontal synchronization signal and the vertical synchronization signal Are superimposed on the two color signals transmitted by the three sub-lines, respectively,
When the vertical synchronizing signal is valid, the standard square wave signal is superimposed on the remaining color signal not superimposed by the horizontal synchronizing signal or the vertical synchronizing signal, and the color signal superimposed by the square signal is converted into a differential signal. A synthesis circuit; a differential reduction circuit that reduces the differential signal after being transmitted by the sub-line to a single-line signal; and a signal conversion circuit that converts the single-line signal into a numerical value corresponding to the voltage level of the single-line signal; A line length measurement device comprising: a line length calculation circuit for calculating a line length of the transmission line based on the numerical value. And further comprising a signal extraction circuit arranged to decode a vertical synchronization signal from a color signal superimposed by the vertical synchronization signal, and the line length calculation circuit is configured such that when the extracted vertical synchronization signal is valid, A line length measuring device for calculating a line length of a transmission line,
The signal conversion circuit filters the single line signal into a DC signal, a DC level conversion circuit that adjusts the DC level of the DC signal, and converts the DC signal of the already adjusted DC level into the numerical value. The line length measuring device according to claim 1, further comprising an analog-digital conversion circuit. A line length measurement method for measuring a line length of a transmission line for transmitting a video signal,
When the vertical sync signal of the video signal is valid, the standard square wave signal is input to the remaining color signal that is not overlapped by the horizontal sync signal or the vertical sync signal, and after being superimposed by the standard square wave signal, Converting the signal to a differential signal and reducing the differential signal to a single wire signal;
Converting the single line signal after being transmitted by the transmission line into a numerical value corresponding to the voltage level of the single line signal; calculating a line length of the transmission line based on the numerical value;
A line length measuring method including at least.

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