Impedance conversion device for adapting onboard gigabit ethernet chip to coaxial cable for transmission

Abstract

The present invention relates to the technical field of Ethernet communications, and provides an impedance conversion device for adapting an onboard gigabit Ethernet chip to a coaxial cable for transmission. The impedance conversion device comprises: a first impedance loop, wherein a cable wiring end of the first impedance loop is connected to a coaxial cable, a chip wiring end of the first impedance loop is connected to a first signal output end of an onboard Ethernet chip, a first chip resistor is connected between a first signal input end and the first signal output end of the onboard Ethernet chip, and the sum of the impedance value of the first impedance loop and the resistance value of the first chip resistor is equal to the equivalent resistance value of the coaxial cable; and a second impedance loop, wherein a cable wiring end of the second impedance loop is grounded, and a chip wiring end of the second impedance loop is connected to a second signal output end of the onboard Ethernet chip. The present invention has the beneficial effects that the impedance conversion device is arranged between the onboard Ethernet chip and the coaxial cable, so that the coaxial cable can also transmit gigabit Ethernet signals, thereby expanding application scenarios of the Ethernet chip.

Description

Impedance conversion device for adapting on-board Gigabit Ethernet chip to coaxial cable transmission Technical Field

[0001] The present invention relates to the technical field of Ethernet communications, and in particular to an impedance conversion device for adapting an on-board gigabit Ethernet chip to coaxial cable transmission. Background Art

[0002] Coaxial cables are primarily used to transmit video and data signals. Transmitting TV signals via 75ohm coaxial cables is a typical application. However, due to lagging infrastructure, many areas in China still rely on coaxial cables for TV signal transmission instead of gigabit fiber.

[0003] Current Gigabit Ethernet chips are not compatible with coaxial cables, so an impedance conversion device is needed to connect the coaxial cables so that Gigabit Ethernet signal transmission can be achieved through the coaxial cables.

[0004] Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides an impedance conversion device for adapting an on-board Gigabit Ethernet chip to coaxial cable transmission, comprising:

[0006] a first impedance loop, wherein a cable terminal of the first impedance loop is connected to the coaxial cable, and a chip terminal of the first impedance loop is connected to a first signal output terminal of the in-vehicle Ethernet chip;

[0007] A first chip resistor is connected between the first signal input terminal and the first signal output terminal of the in-vehicle Ethernet chip, and the sum of the impedance value of the first impedance loop and the resistance value of the first chip resistor is equal to the equivalent resistance value of the coaxial cable;

[0008] A second impedance loop, wherein a cable connection terminal of the second impedance loop is grounded, and a chip connection terminal of the second impedance loop is connected to a second signal output terminal of the in-vehicle Ethernet chip.

[0009] Preferably, the first impedance loop includes:

[0010] a first resistor, one end of the first resistor being connected to one end of a first DC blocking capacitor;

[0011] The other end of the first resistor serves as a chip connection terminal of the first impedance loop;

[0012] The other end of the first DC blocking capacitor serves as a cable connection terminal of the first impedance loop.

[0013] Preferably, the second impedance loop includes:

[0014] a second resistor, one end of the second resistor being connected to one end of the second DC blocking capacitor;

[0015] The other end of the second resistor serves as a chip connection terminal of the second impedance loop;

[0016] The other end of the second DC blocking capacitor serves as a cable connection terminal of the second impedance loop.

[0017] Preferably, the second impedance loop includes:

[0018] a third DC blocking capacitor, one end of the third DC blocking capacitor being connected to a third resistor as a cable terminal of the second impedance loop, and the other end of the third resistor being grounded;

[0019] The other end of the third DC blocking capacitor serves as a chip connection terminal of the second impedance loop.

[0020] Preferably, the in-vehicle Ethernet chip includes:

[0021] a first chip resistor connected between the first signal input terminal and the first signal output terminal;

[0022] a second chip resistor connected between the second signal input terminal and the second signal output terminal;

[0023] a first mixing circuit connected between the first signal input terminal and the second signal output terminal, and configured to cancel echoes between the first signal input terminal and the second signal output terminal;

[0024] The second mixing circuit is connected between the second signal input terminal and the first signal output terminal, and is used for echo cancellation between the second signal input terminal and the first signal output terminal.

[0025] Preferably, the first mixing circuit includes:

[0026] a first silencing resistor, one end of which is connected to one end of a second silencing resistor;

[0027] The other end of the first noise elimination resistor is connected to the first signal input end, and the other end of the second noise elimination resistor is connected to the first signal output end.

[0028] Preferably, the second mixing circuit includes:

[0029] a third silencing resistor, one end of the third silencing resistor being connected to one end of the fourth silencing resistor;

[0030] The other end of the third muffler resistor is connected to the first signal input end, and the other end of the fourth muffler resistor is connected to the second signal output end.

[0031] Preferably, the in-vehicle Ethernet chip, the first impedance loop and the second impedance loop are integrated on the same circuit board.

[0032] The above technical solution has the following advantages or beneficial effects: by providing an impedance conversion device between the in-vehicle Ethernet chip and the coaxial cable, the coaxial cable can also transmit Gigabit Ethernet signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic diagram showing the structure of an in-vehicle Ethernet chip connected to a twisted pair cable in the prior art;

[0034] FIG2 is a schematic structural diagram of an impedance conversion device for adapting an on-board Gigabit Ethernet chip to coaxial cable transmission in a preferred embodiment of the present invention;

[0035] FIG3 is a diagram showing another impedance conversion device for adapting an on-board Gigabit Ethernet chip to coaxial cable transmission in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0037] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, an impedance conversion device for adapting an on-board Gigabit Ethernet chip to coaxial cable transmission is provided, comprising:

[0038] a first impedance loop 1, wherein a cable terminal of the first impedance loop 1 is connected to a coaxial cable 3, and a chip terminal of the first impedance loop 1 is connected to a first signal output terminal of an in-vehicle Ethernet chip 4;

[0039] A first chip resistor R10 is connected between the first signal input terminal and the first signal output terminal of the in-vehicle Ethernet chip 4. The sum of the impedance value of the first impedance loop 1 and the resistance value of the first chip resistor R10 is equal to the equivalent resistance value of the coaxial cable 3.

[0040] The second impedance loop 2 has a cable connection terminal connected to the ground, and a chip connection terminal connected to the second signal output terminal of the in-vehicle Ethernet chip 4 .

[0041] In a preferred embodiment of the present invention, the first impedance loop 1 includes:

[0042] a first resistor R1, one end of the first resistor R1 being connected to one end of the first DC blocking capacitor C1;

[0043] The other end of the first resistor R1 serves as a chip connection terminal of the first impedance loop 1;

[0044] The other end of the first DC blocking capacitor C1 serves as a cable connection terminal of the first impedance loop 1 .

[0045] In a preferred embodiment of the present invention, the second impedance loop 2 includes:

[0046] a second resistor R2, one end of the second resistor R2 being connected to one end of the second DC blocking capacitor C2;

[0047] The other end of the second resistor R2 serves as the chip connection terminal of the second impedance loop 2;

[0048] The other end of the second DC blocking capacitor C2 serves as a cable connection terminal of the second impedance loop 2 .

[0049] In a preferred embodiment of the present invention, the resistance of the coaxial cable 4 is 75 ohms, the resistance of the first resistor R1 is 25 ohms, the first DC blocking capacitor C1 is 100 nf, the resistance of the second resistor R2 is 30 ohms, and the second DC blocking capacitor C2 is 100 nf.

[0050] In a preferred embodiment of the present invention, the vehicle Ethernet chip 4 includes:

[0051] A first chip resistor R10 is connected between the first signal input terminal drvp and the first signal output terminal outp;

[0052] A second chip resistor R11 is connected between the second signal input terminal drvn and the second signal output terminal outn;

[0053] A first hybrid circuit hybp is connected between the first signal input terminal drvp and the second signal output terminal outn, and is used for echo cancellation between the first signal input terminal drvn and the second signal output terminal outn;

[0054] The second hybrid circuit hybn is connected between the second signal input terminal drvn and the first signal output terminal outp, and is used for echo cancellation between the second signal input terminal drvn and the first signal output terminal outp.

[0055] In a preferred embodiment of the present invention, the first hybrid circuit hybp includes:

[0056] a first noise elimination resistor R21, one end of the first noise elimination resistor R21 being connected to one end of the second noise elimination resistor R22;

[0057] The other end of the first noise elimination resistor R21 is connected to the first signal input terminal drvp, and the other end of the second noise elimination resistor R22 is connected to the first signal output terminal outp.

[0058] In a preferred embodiment of the present invention, the second hybrid circuit hybn includes:

[0059] a third noise elimination resistor R23, one end of the third noise elimination resistor R23 being connected to one end of the fourth noise elimination resistor R24;

[0060] The other end of the third noise elimination resistor R23 is connected to the first signal input terminal drvp, and the other end of the fourth noise elimination resistor R24 ​​is connected to the second signal output terminal outn.

[0061] Specifically, in this embodiment, as shown in FIG1 , a schematic diagram of the structure of an on-board Ethernet chip connected to a twisted pair for signal transmission in the prior art is shown. The figure includes three parts: the on-board Ethernet chip on the left, the twisted pair connected on the far right, and two DC blocking capacitors connecting them. The on-board Ethernet chip is provided with a hybrid circuit for echo cancellation to achieve Gigabit Ethernet full-duplex communication, enabling simultaneous signal transmission and reception on the twisted pair.

[0062] In Figure 1, each signal line in the twisted pair is 50 ohms, and a 50 ohm resistor is connected between the signal output end and the signal input end of the on-board Ethernet chip (including the p-end and n-end, the first signal output end and the second signal output end are represented by outp and outn respectively, and the first signal input end and the second signal input and output end are represented by drvp and drvn respectively). At this time, the impedance of the on-board Ethernet chip and the opposite end are matched. A hybrid circuit is provided in the on-board Ethernet chip (the first hybrid circuit and the second hybrid circuit are represented by hybp and hybn corresponding to the n-end and p-end respectively) for implementing echo cancellation, allowing the on-board Ethernet chip to simultaneously transmit and receive signals on the same twisted pair, realizing Gigabit Ethernet full-duplex communication. The hybrid circuit here is a conventional technical means in the field of Ethernet communication, and the specific implementation principle is not repeated here.

[0063] The impedance conversion device provided by the present invention is connected between the coaxial cable 4 and the in-vehicle Ethernet chip, so that the coaxial cable 4 can also realize Gigabit Ethernet signal transmission. As shown in Figure 2, the impedance conversion device is connected after the outp and outn of the chip, including a first impedance loop 1 (a first resistor R1 and a first DC blocking capacitor C1) and a second impedance loop 2 (a second resistor R2 and a second DC blocking capacitor C2). The two impedance loops are respectively connected to outp and outn. The first impedance loop 1 is connected to the coaxial cable 4, and the second impedance loop 2 is connected to the virtual ground. In this embodiment, the coaxial cable is a 75ohm coaxial cable 4 (a closed line used for traditional home TV transmission signals);

[0064] Specifically, the first resistor R1 is 25 ohm, and a 50 ohm first chip resistor R11 is connected between drvp and outp. At this time, for the first impedance loop 1, the resistance of the first chip resistor R11 (50 ohm) + the resistance of the first resistor R1 (25 ohm) = the resistance of the coaxial cable 4 (75 ohm). At this time, the impedance matching between the on-board Ethernet chip and the opposite end (here is a 75 ohm coaxial cable) is achieved, but the echo cancellation effect of the HYBP circuit corresponding to the first impedance loop 1 is destroyed;

[0065] To this end, in this embodiment, the resistance of the second resistor R2 is set to 30 ohms. The drvp and drvn in the chip are respectively connected to the op amp. The op amp transmits a signal to the outside through drvp and drvn. Assuming that the amplitude of the signal transmitted by the op amp is 1, then the amplitude of drvp is 1 at this time. The amplitude at outp here is due to the voltage division of the first resistor R1, the first chip resistor R11 and the coaxial cable 4. (Right now, ), dvrn and drvp are in opposite directions, so the amplitude is -1. The amplitude of outn can be calculated similarly as (Right now, ), in the hybp circuit, a first mute resistor R21 and a second mute resistor R22 are connected between drvp and outn. The resistance ratio of the two mute resistors is R21=2*R22 (and much larger than 50ohm), and the voltage divider ratio is 2:1. In this embodiment, the resistance values ​​of the first mute resistor R21 and the second mute resistor R22 are 4Kohm and 2Kohm respectively, so the signal amplitude in hybp is In the hybn circuit, a third muffler resistor R23 and a fourth muffler resistor R24 ​​are also connected between drvn and outp. The resistance ratio of the two muffler resistors is R23 = 2*R24 (and much larger than 50 ohms), and the voltage divider ratio is 2:1. In this embodiment, the resistance values ​​of the third muffler resistor R23 and the fourth muffler resistor R24 ​​are 4 Kohm and 2 Kohm respectively, so the signal amplitude in the hybn circuit is At this time, the signal amplitude difference between hybn and hybp (i.e., the amplitude of the uneliminated signal) is It can be seen There is a gap of nearly 50 times between the signal amplitude 1 emitted by the op amp and the signal amplitude 1, which can be ignored. Therefore, by connecting the impedance conversion device provided by the present invention between the vehicle Ethernet chip and the 75ohm coaxial cable, the vehicle Ethernet chip can also adapt to the coaxial cable signal transmission, achieving the same Gigabit Ethernet signal transmission effect as the twisted pair cable, thereby enabling Gigabit Ethernet signal transmission technology to cover more areas.

[0066] For different in-vehicle Ethernet chips and different coaxial cables, the resistance values ​​of the first resistor and the second resistor in the impedance conversion device in this embodiment need to be adjusted after calculation so that the signal amplitude difference between hybp and hybn is as small as possible to achieve the best Ethernet communication effect.

[0067] Specifically, as shown in FIG3 , in this embodiment, the resistor R2 in the second impedance loop 2 may be connected to the side of the DC blocking capacitor C2 close to the coaxial cable A4 , and may be arranged inside or outside the impedance transformation device.

[0068] In a preferred embodiment of the present invention, the in-vehicle Ethernet chip, the first impedance loop 1 and the second impedance loop 2 are integrated on the same circuit board.

[0069] Specifically, the on-board Ethernet chip, the first impedance loop 1, and the second impedance loop 2 are integrated on the same circuit board. The impedance conversion device of the present invention can be added to the circuit board that implements Ethernet communication via traditional twisted pair cables to connect the two signal output terminals of the on-board Ethernet chip and the coaxial cable, and twisted pair communication or coaxial cable communication can be selected according to user needs.

[0070] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. An impedance conversion device for adapting a vehicle-mounted Gigabit Ethernet chip to coaxial cable transmission, characterized in that: include: a first impedance loop, wherein a cable terminal of the first impedance loop is connected to the coaxial cable, and a chip terminal of the first impedance loop is connected to a first signal output terminal of the vehicle Ethernet chip; A first chip resistor is connected between the first signal input terminal and the first signal output terminal of the vehicle Ethernet chip, and the sum of the impedance value of the first impedance loop and the resistance value of the first chip resistor is equal to the equivalent resistance value of the coaxial cable; A second impedance loop, wherein a cable terminal of the second impedance loop is grounded, and a chip terminal of the second impedance loop is connected to a second signal output terminal of the vehicle Ethernet chip.

2. The impedance conversion device according to claim 1, characterized in that: The first impedance loop comprises: A first resistor, one end of which is connected to one end of a first DC blocking capacitor; The other end of the first resistor serves as a chip connection terminal of the first impedance loop; The other end of the first DC blocking capacitor serves as a cable connection terminal of the first impedance loop.

3. The impedance conversion device according to claim 1, characterized in that: The second impedance loop comprises: a second resistor, one end of which is connected to one end of a second DC blocking capacitor; The other end of the second resistor serves as a chip connection terminal of the second impedance loop; The other end of the second DC blocking capacitor serves as a cable connection terminal of the second impedance loop.

4. The impedance conversion device according to claim 1, characterized in that: The second impedance loop comprises: a third DC blocking capacitor, one end of the third DC blocking capacitor being connected to a third resistor as a cable terminal of the second impedance loop, and the other end of the third resistor being grounded; The other end of the third DC blocking capacitor serves as a chip connection terminal of the second impedance loop.

5. The impedance conversion device according to claim 1, characterized in that: The vehicle-mounted Ethernet chip comprises: A first chip resistor, connected between the first signal input terminal and the first signal output terminal; A second chip resistor is connected between the second signal input terminal and the second signal output terminal; A first mixing circuit, connected between a first signal input terminal and a second signal output terminal, and used for echo cancellation between the first signal input terminal and the second signal output terminal; The second mixing circuit is connected between the second signal input terminal and the first signal output terminal, and is used for echo elimination between the second signal input terminal and the first signal output terminal.

6. The impedance conversion device according to claim 5, characterized in that: The first mixing circuit comprises: A first silencing resistor, one end of which is connected to one end of a second silencing resistor; The other end of the first noise elimination resistor is connected to the first signal input end, and the other end of the second noise elimination resistor is connected to the first signal output end.

7. The impedance conversion device according to claim 5, characterized in that: The second mixing circuit comprises: a third silencing resistor, one end of which is connected to one end of a fourth silencing resistor; The other end of the third noise elimination resistor is connected to the first signal input end, and the other end of the fourth noise elimination resistor is connected to the second signal output end.

8. The impedance conversion device according to claim 1, characterized in that: The in-vehicle Ethernet chip, the first impedance loop and the second impedance loop are integrated on the same circuit board.

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