Background technology
At present, PC becomes indispensable modernized information equipment in daily life and the work gradually.Usually PC comprises a main frame and a display unit, and this main frame is connected with this display unit by a data line, the data-signal that this main frame produces transfers to this display unit via this data line, and the display interface in display unit carries out the corresponding contents demonstration after treatment.
Seeing also Fig. 1, is a kind of structure chart of prior art PC.This PC 1 comprises a main frame 11, a data line 13, a liquid crystal indicator 15 and a resistor 17.This main frame 11 comprises a processor 111, a video card unit 113 and a shows signal output interface 115.This liquid crystal indicator 15 comprises that shows signal input connects 151, one processing unit 153 and a demonstration connects 155.This data line 13 connect this shows signal output connect 115 and this shows signal input connect 151.The outside of this data line 13 generally has the mark that can discern, can discern the sign impedance of this data line 13 by this mark.
These processor 111 handled data are to this video card unit 113, this video card unit 113 is corresponding shows signal with this data shift signal, and the shows signal input that transfers to this liquid crystal indicator 15 by this shows signal output interface 115 and this data line 13 successively connects 151, this shows signal input interface 151 transfers to this processing unit 153 with this shows signal and handles, and the shows signal after the processing is carried out content corresponding by this display interface 155 and shown.
This shows signal is through these data line 13 transmission the time, owing to the impedance of this data line 13 in its end reason such as discontinuous that becomes, cause this shows signal to reflect easily, transmission is caused interference and produces the shows signal transmission distortion, and then influence the display effect of this liquid crystal indicator 15.Therefore, for making this liquid crystal indicator 15 reach optimal display result, usually insert this resistor 17 in parallel at the end of data line 13 with this liquid crystal indicator 15, and the resistance that makes this resistor 17 equals the sign impedance of this data line 13, to eliminate the negative effect that the shows signal reflection is produced.
Yet, the shows signal that this data line 13 is transmitted is generally the high-frequency signal of frequency change, and when the shows signal of transmission different frequency, equivalent capacity in this data line 13 is corresponding with equivalent inductance to present different impedances, the actual characteristic impedance of this data line 13 is also not exclusively equated with the sign impedance, and then make and the actual characteristic impedance of the resistance of this resistor 17 and this data line 13 and unequal cause impedance matching not good.Therefore need the resistance of this resistor 17 of corresponding adjustment, so that the resistance of this resistor 17 equates with the actual characteristic impedance of this data line 13, thereby the realization optimum impedance is mated.For solving foregoing problems, industry is adjusted the resistance of this resistor 17 usually by manual operation, and detect the shows signal that this data line 13 transmitted by a detecting instrument (figure do not show) simultaneously and whether reach the best transmission effect, when detecting the best transmission effect, promptly finish resistance adjustment, thereby finish optimum impedance coupling this data line 13 to this resistor 17.What these PC 1 need were comparatively frequent carries out manual operation to adjust the resistance of resistor 17, so that this data line 13 is issued to the optimum impedance coupling in different transmission frequencies, its realization is more loaded down with trivial details.
Summary of the invention
In order to solve the comparatively loaded down with trivial details problem of prior art impedance matching adjustment, be necessary to provide a kind of impedance matching circuit of automatic realization impedance matching.
Also be necessary to provide a kind of impedance matching methods of automatic realization impedance matching.
In addition, also be necessary to provide a kind of PC of automatic realization impedance matching.
A kind of impedance matching circuit, it comprises a signal processing unit and a resistance access unit.This signal processing unit receives a data line data signals transmitted, discerns the transmission frequency of this data-signal and produces an identification signal, exports a control signal according to this identification signal.This resistance access unit receives this control signal, and selects resistance with this data line impedance matching according to this control signal, and this resistance is inserted this data line.
A kind of impedance matching methods, it may further comprise the steps: set up a corresponding relation between the identification signal of designate data signal transmission frequency and the control signal of representing matched impedance; By the transmission frequency of signal processing unit identification data signals, and transmission frequency is converted to an identification signal; By signal processing unit and according to corresponding relation is that identification signal is distributed a control signal; Receive control signal by the resistance access unit, according to the resistance of control signal selection with this data line impedance matching, and with this resistance access data line.
A kind of PC, it comprises a main frame, a data line, a display unit and an impedance matching circuit.This main frame produces data-signal.This data line transmits this data-signal.This display unit receives this data-signal and carries out corresponding contents and shows.This impedance matching circuit inserts the end of this data line, and it comprises a signal processing unit and a resistance access unit.This signal processing unit is discerned the transmission frequency of this data-signal, and produces an identification signal, exports a control signal according to this identification signal.This resistance access unit receives this control signal, selects the resistance that carries out impedance matching with this data line according to this control signal, and this resistance is inserted this data line.
Compared with the prior art, impedance matching circuit of the present invention and impedance matching methods be the transmission frequency of recognition data transmission line institute transmission of data signals automatically, and according to transmission frequency output control signal corresponding, automatically adjust the resistance that inserts data line according to this control signal, thereby for data line carries out impedance matching, its realization is comparatively convenient, thereby adopts the PC of this impedance matching circuit also can realize the automatic impedance coupling easily.
Embodiment
Seeing also Fig. 2, is the structure chart of PC one better embodiment of the present invention.This PC 2 comprises a main frame 27, a data line 23, a display unit 29 and an impedance matching circuit 20.The data that this data line 23 produces this main frame 27 is to this display unit 29, this display unit 29 receives this data-signal and it is carried out corresponding contents and shows, this impedance matching circuit 20 is connected to the end of this data line 23, and in parallel with this display unit 29 or this main frame 27, this impedance matching circuit 20 can provide matched impedance for this data line 23.This display unit 29 can for a LCD (Liquid Crystal Display, LCD) or cathode ray tube (Cathode Ray Tube, CRT) display.
This impedance matching circuit 20 comprises a signal processing unit 22 and a resistance access unit 24.This signal processing unit 22 receives these data line 23 data signals transmitted, produces an identification signal according to the transmission frequency of this data-signal, produces a control signal according to this identification signal again.This resistance access unit 24 receives these control signals, selects resistance with these data line 23 impedance matchings according to this control signal, and it is inserted this data line 23.
This signal processing unit 22 comprises a micro-control unit (Micro ControllerUnit, MCU) 220, one firmware (Firmware) unit 222 and a data storage cell 224.This micro-control unit 220 receives these data line 23 data signals transmitted, and this data-signal carried out sample count, thereby discern the transmission frequency of this data-signal, finish a recognition cycle, and this transmission frequency is converted to corresponding identification signal is sent to this data storage cell 224 and stores.This data storage cell 224 be an electricity cause the erasable programmable read-only memory unit (Electrically ErasableProgrammable Read-Only Memory, EEPROM).This micro-control unit 220 regularly sends an enabling signal, controls the startup of this firmware unit 222, and timing cycle can be self-defined.This firmware unit 222 comprises a nonvolatile memory (figure does not show), and this nonvolatile memory stores has application program.This nonvolatile memory can for electricity cause Erasable Programmable Read Only Memory EPROM, Erasable Programmable Read Only Memory EPROM (Erasable Programmable Read-Only Memory, EPROM) or flash memory (Flash Memory) etc.Corresponding relation between this identification signal of this application setting and the control signal.This micro-control unit 220 reads the identification signal that is stored in data storage cell 224, and distributes the control signal of a correspondence according to this corresponding relation for this identification signal, and exports this control signal, and this control signal is a digital voltage signal.
This resistance access unit 24 comprises a variable connector integrated circuit 240 and a plurality of resistor 242.These a plurality of resistors 242 are connected serially to the variable connector of this variable connector integrated circuit 240 respectively, it can carry out impedance matching with this data line 23 respectively under different frequency, promptly the resistance of these a plurality of resistors 242 equals the actual characteristic impedance of data line 23 under the different transmission frequencies respectively.Other each way switch disconnects this variable connector integrated circuit 240 according to the corresponding way switch of this control signal control is closed, thereby selected resistor 242 is connected with this data line 23, and then is embodied as this data line 23 automatically and carries out impedance matching.
Seeing also Fig. 3, is the flow chart that PC 2 shown in Figure 2 is carried out the method for impedance matching.This impedance matching methods may further comprise the steps:
Step S1: between the identification signal of designate data signal transmission frequency and the control signal of representing matched impedance, set up a corresponding relation;
Detect the transmission frequency of 23 transmission of data signals of data line, under this transmission frequency, this data line 23 is carried out impedance matching, promptly at signal receiving device one an end resistor in parallel, make the resistance of this resistor equal the sign impedance of data line 23, then this resistor is finely tuned.When the laser propagation effect of data signal under test reaches optimum efficiency, promptly stop to finely tune and determine that current resistance is the optimum Match impedance of data line 23.Repeat abovementioned steps, add up a plurality of different transmission frequencies and, thereby set up the corresponding relation between transmission frequency and the optimum Match impedance respectively to optimum Match impedance that should transmission frequency.This transmission frequency is represented with identification signal respectively, and this optimum Match impedance is represented with control signal respectively, thereby set up a corresponding relation between this identification signal and this control signal.Corresponding relation between identification signal and the control signal is write application program and is stored in a nonvolatile memory, thereby constitute this firmware unit 222.
Step S2:, and transmission frequency is converted to an identification signal by the transmission frequency of signal processing unit 22 identification data signals;
The micro-control unit 220 of this signal processing unit 22 receives 23 data signals transmitted of data line, this data-signal is carried out sample count, and then discern the transmission frequency of this data-signal, and this transmission frequency is converted to an identification signal, finish a recognition cycle.This micro-control unit 220 transfers to this data storage cell 224 storages with this identification signal.
Step S3: by signal processing unit 22 and according to corresponding relation is that identification signal is distributed a control signal;
The micro-control unit 220 of this signal processing unit 22 regularly sends an enabling signal, call the application program in this firmware unit 222, and read this identification signal, carrying out this application program handles this identification signal, thereby distribute a control signal for this identification signal, and with this control signal output according to the corresponding relation between identification signal and control signal.
Step S4: receive control signals by resistance access unit 24,, and resistance inserted data line according to the resistance of control signal selection and access and data line 23 impedance matchings.
This resistance access unit 24 receives the input signal of this control signal as its control end, make corresponding way switch closure and other switch disconnection according to this control signal, and then select resistor 242 these data lines 23 of access connect with this road Closing Switch, move thereby finish impedance matching.
Aforesaid PC is at display unit 29 1 an ends impedance matching circuit 20 in parallel, the data of being added up when this impedance matching circuit 20 and impedance matching methods can utilize previous manual operation to carry out impedance matching are set up a corresponding relation, transmission frequency by the data-signal on the micro-control unit 220 recognition data transmission lines 23, regularly or according to the variation of transmission frequency call this corresponding relation output to control signal that should transmission frequency, according to the resistance of this control signal selection with these data line 23 impedance matchings, and this resistance inserted this data line 23, thereby automatically for the data line 23 of this PC 2 carries out impedance matching, its realization is comparatively convenient.
It is described that the present invention is not limited to above-mentioned execution mode, also can replace as these a plurality of resistors 242 by a variable resistance, as a digital variable resistor, it can directly receive the control signal of these micro-control unit 220 outputs, according to the resistance of this this data line 23 of control signal control access, realize impedance matching to this data line 23.This micro-control unit 220 before can being sent to this data storage cell 240 in the identification signal that this recognition cycle produced does not compare the identification signal that this identification signal and last recognition cycle produced yet, if comparative result shows when the transmission frequency difference of being discerned in the two adjacent recognition cycles surpasses a preset range, promptly export an enabling signal and start this firmware unit 222, this preset range also can be self-defined.It is closed and other way switch disconnects that this control signal also can be controlled at least two-way switch, and the combined resistance of at least two resistors 242 that are connected with Closing Switch can carry out impedance matching with this data line 23.