Series noise absorption circuit

Abstract

The present invention relates to a series noise absorption circuit, comprising: a differential signal transmission line and an impedance matching circuit. The differential signal transmission line is electrically connected to two signal feed lines, and the differential signal transmission line has a first transmission line and a second transmission line, and the first transmission line and the second transmission line are used to receive differential input electrical signals from the two signal feed lines. The impedance matching circuit is connected in series with the second transmission line, and the impedance matching circuit is used to receive the reflected electrical signal from the noise reflection circuit, and match the input impedance of the corresponding series noise absorption circuit with the common mode characteristic impedance of the corresponding two signal feed lines, wherein there is a minimum electrical length between the impedance matching circuit and the noise reflection circuit, and the minimum electrical length is associated with the real part and the imaginary part of the matching impedance of the impedance matching circuit.

Description

Technical Field

[0001] The invention relates to a series noise absorption circuit, and in particular to a series noise absorption circuit capable of increasing design parameters of the noise absorption circuit. Background Art

[0002] Differential signals are composed of two signals of equal magnitude but opposite phases, and are widely used in high-speed digital circuits. However, common-mode noise is caused by the asymmetry of the output signal of the circuit and the asymmetric routing method on the circuit board, which leads to the problem of common-mode noise interfering with signal transmission. Common-mode noise filters are commonly used to suppress common-mode noise, and common-mode noise filters can be divided into reflective common-mode noise filters (R-CMF) and absorptive common-mode noise filters (A-CMF).

[0003] Absorption-type common-mode noise filters usually use a mushroom-type structure, which uses a three-layer circuit board structure at the noise absorption end, in which an impedance matching circuit is connected in parallel to the reflection-type common-mode noise filter, and the impedance matching circuit is used to absorb the common-mode noise of the dual frequency bands. The design parameters of the impedance matching circuit can be obtained based on a parameter of a differential signal transmission line such as a meandering transmission line, an inductive transmission line in the absorption-type common-mode noise filter, and a flat capacitor, to achieve impedance matching, thereby achieving the effect of absorbing the common-mode noise of the dual frequency bands. However, this design method not only increases the installation cost due to the use of more layers of circuit boards, but also increases the overall volume of the absorption-type common-mode noise filter. Summary of the invention

[0004] In view of the above, the present invention provides a series noise absorption circuit to meet the above requirements.

[0005] According to an embodiment of the present invention, a series noise absorbing circuit is electrically connected to two signal feeding lines. The series noise absorbing circuit includes: a differential signal transmission line electrically connected to the two signal feeding lines, the differential signal transmission line having a first transmission line and a second transmission line, the first transmission line and the second transmission line being used to receive a differential input electrical signal from the two signal feeding lines; and an impedance matching circuit connected in series to the second transmission line, the impedance matching circuit being used to receive a reflected electrical signal from a noise reflection circuit and to match an input impedance corresponding to the series noise absorbing circuit with a common mode characteristic impedance corresponding to the two signal feeding lines, wherein a minimum electrical length is provided between the impedance matching circuit and the noise reflection circuit, and the minimum electrical length is associated with a real part and an imaginary part of a matching impedance of the impedance matching circuit.

[0006] The above description of the contents of the present disclosure and the following description of the embodiments are used to demonstrate and explain the spirit and principle of the present invention, and to provide a further explanation of the scope of the patent application of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 FIG. 4 is a schematic diagram of an equivalent circuit of a series noise absorption circuit according to an embodiment of the present invention.

[0008] Figure 2 FIG. 4 is a structural diagram of a series noise absorption circuit according to an embodiment of the present invention.

[0009] Figure 3 is based on Figure 1 The equivalent circuit diagram of the series noise absorption circuit is shown.

[0010] Figure 4 FIG. 4 is a diagram showing the relationship between the length of an electrical device and the matching impedance according to an embodiment of the present invention.

[0011] Description of reference numerals:

[0012] FL signal feed line

[0013] DL Differential Signal Transmission Line

[0014] TL1 First transmission line

[0015] TL2 Second transmission line

[0016] MC Impedance Matching Circuit

[0017] P1 First port

[0018] P2 Second Port

[0019] R-CMF Noise Reflection Circuit

[0020] SUB substrate

[0021] GND Ground plane

[0022] d Minimum electrical length

[0023] Z in Input Impedance

[0024] Z 0e Common mode characteristic impedance

[0025] Z 11 , Z 12 , Z 22 Parameters of the open circuit impedance matrix

[0026] Y m Matching impedance DETAILED DESCRIPTION

[0027] The detailed features and advantages of the present invention are described in detail in the following embodiments, and the contents are sufficient to enable any person skilled in the art to understand the technical content of the present invention and implement it accordingly, and according to the contents, claims and drawings disclosed in this specification, any person skilled in the art can easily understand the relevant purposes and advantages of the present invention. The following examples further illustrate the viewpoints of the present invention in detail, but are not intended to limit the scope of the present invention in any way.

[0028] Please refer to Figure 1 , Figure 1 1 is a schematic diagram of an equivalent circuit of a series noise absorption circuit according to an embodiment of the present invention. The series noise absorption circuit of the present invention can be applied to the circuit layout of a server or a circuit layout of an in-vehicle electronic product, but is not limited thereto.

[0029] The serial noise absorption circuit of the present invention comprises two signal feeding lines FL, a differential signal transmission line DL and an impedance matching circuit MC, wherein the differential signal transmission line DTL comprises a first transmission line TL1 and a second transmission line TL2, and Figure 1 The structure of the differential signal transmission line DL and the impedance matching circuit MC is an absorptive common-mode filter (A-CMF).

[0030] The two signal feeding lines FL are electrically connected to the first transmission line TL1 and the second transmission line TL2 of the differential signal transmission line DL through the first port P1 to transmit a differential input electrical signal to the first transmission line TL1 and the second transmission line TL2, and the first transmission line TL1 is electrically connected to the noise reflection circuit R-CMF to receive the reflected electrical signal from the noise reflection circuit R-CMF.

[0031] In detail, the two signal feeding lines FL transmit the differential input electrical signal to the first transmission line TL1 of the differential signal transmission line DL through the first port P1, and the first transmission line TL1 transmits the differential input electrical signal to the noise reflection circuit R-CMF electrically connected thereto. The noise reflection circuit R-CMF transmits the differential input electrical signal to the circuit at its rear end through the second port P2, and receives the reflected electrical signal corresponding to the differential input electrical signal from the circuit at its rear end through another second port P2.

[0032] The noise reflection circuit R-CMF transmits the reflected electrical signal to the second transmission line TL2, and further transmits the reflected electrical signal to the impedance matching circuit MC connected in series to the second transmission line TL2, so as to absorb the noise in the reflected electrical signal by the structure of the impedance matching circuit MC connected in series to the second transmission line TL2.

[0033] Accordingly, compared to the existing mushroom-type structure, the series noise absorption circuit shown in the present invention can be implemented in a two-layer circuit board structure, which greatly reduces the installation cost and overall volume of the noise absorption circuit.

[0034] Please refer to Figure 2 , Figure 2 FIG. 4 is a structural diagram of a series noise absorption circuit according to an embodiment of the present invention.

[0035] The structure of the series noise absorption circuit of the present invention can be as follows: Figure 2 Specifically, the noise reflection circuit R-CMF can be disposed on the substrate SUB, the differential signal transmission line DL is electrically connected to the noise reflection circuit R-CMF, and the first port P1 of the differential signal transmission line DL and the second port P2 of the noise reflection circuit R-CMF are connected to the substrate SUB, wherein the differential signal transmission line DL is also spaced apart from the ground layer GND.

[0036] The impedance matching circuit MC is connected in series to the second transmission line TL2, and the electrical length between the impedance matching circuit MC and the noise reflection circuit R-CMF is the minimum electrical length d.

[0037] In detail, the impedance matching circuit MC matches the input impedance of the series noise absorbing circuit with the common mode characteristic impedance of the two signal feeding lines FL, wherein the electrical length between the impedance matching circuit MC and the noise reflecting circuit R-CMF is associated with the real part and the imaginary part of the matching impedance of the impedance matching circuit MC, so that the electrical length is the minimum electrical length d, wherein the minimum electrical length d can be determined by the impedance matching formula that the common mode characteristic impedance of the two signal feeding lines FL is equal to the input impedance of the series noise absorbing circuit.

[0038] For a more detailed explanation of the above minimum electrical length d, please refer to Figure 3 ,in Figure 3 is based on Figure 1 The equivalent circuit diagram of the series noise absorption circuit shown in the figure, that is, the differential signal transmission line DL, the impedance matching circuit MC and the noise reflection circuit R-CMF are configured as follows Figure 3 The T-type equivalent circuit is shown.

[0039] Input impedance Z of series noise absorption circuit in Equal to the common mode characteristic impedance Z of the two signal feed lines FL 0e , and the input impedance Z in The impedance value of is related to the impedance value of the T-type equivalent circuit, so that the relationship between the minimum electrical length d and the impedance matching circuit MC is obtained based on the impedance value of the T-type equivalent circuit by using the impedance matching formula.

[0040] In detail, the impedance matching formula includes the following formula (1) to formula (5).

[0041] Input impedance Z of series noise absorption circuit in Equal to the common mode characteristic impedance Z of the two signal feed lines FL 0e Formula (1):

[0042] Z in =Z 0e - Formula (1)

[0043] The input impedance Z in The impedance value of is related to the impedance value of the T-type equivalent circuit as formula (2):

[0044] Z in =(Z 11 -Z 12 )+[(Z 22 -Z 12 +Z R ) / / Z 12 ]+1 / Y m - Formula (2),

[0045] Where Z 11 , Z 12 and Z 22 are the parameters of the open-circuit impedance matrix of the two-port network; Z R is the reflection circuit impedance (common mode input impedance) of the noise reflection circuit R-CMF; 1 / Y mm It is the reciprocal of the matching impedance of the impedance matching circuit MC, that is, the admittance of the matching impedance.

[0046] In other words, the input impedance Z in The impedance value of can be calculated based on the T-type equivalent circuit architecture. And, as shown in formula (1), Zin =Z 0e , so substituting formula (1) into formula (2) can obtain the following formula (3):

[0047] 1 / Y m =Z 0e -(Z 11 -Z 12 )+[(Z 22 -Z 12 +Z R ) / / Z 12 ]-Formula (3)

[0048] In addition, the parameter Z of the open circuit impedance matrix 11 , Z 12 and Z 22 It can be the following formula (4) and formula (5):

[0049] Where Z 11 =Z 22 =-jZ 0e cot(θ·f) - formula (4);

[0050] Z 12 =-jZ 0e csc(θ·f)- Formula (5),

[0051] Where θ is the electrical length between the impedance matching circuit MC and the noise reflection circuit R-CMF (in degrees); f is the propagation constant.

[0052] Substituting formula (4) and formula (5) into formula (3), we can obtain the electrical length θ between the impedance matching circuit MC and the noise reflection circuit R-CMF and the matching impedance Y of the impedance matching circuit MC: m The relationship between.

[0053] Please refer to Figure 4 , Figure 4 is a diagram showing the relationship between the length of an electrical device and the matching impedance according to an embodiment of the present invention, that is, Figure 4 It shows the electrical length θ between the impedance matching circuit MC and the noise reflection circuit R-CMF and the matching impedance Y of the impedance matching circuit MC. m The solid line represents the real part of the matching impedance, and the dotted line represents the imaginary part of the matching impedance.

[0054] When the impedance matching circuit MC includes a resistor, a capacitor and an inductor, and the resistance value of the resistor is, for example, associated with the real part (Re) of the matching impedance corresponding to the minimum electrical length d; the capacitance value of the capacitor and the inductor are, for example, associated with the imaginary part (Im) of the matching impedance corresponding to the minimum electrical length d, and the resistor, capacitor and inductor are RLC circuits (the RLC circuit may be, for example, an RLC series circuit formed by connecting a resistor R in series to an LC series circuit), then the electrical length between the impedance matching circuit MC and the noise reflection circuit R-CMF is associated with the real part (Re) and the imaginary part (Im) of the matching impedance of the impedance matching circuit MC, for example, as shown in the following formulas (6) and (7):

[0055] r = 1 / (2*Re{Ym}) - formula (6); and

[0056] Im{Ym}=jω(0.5*c)+(1 / jω2*1) - formula (7),

[0057] Wherein r is the resistance value of the resistor element; c is the capacitance value of the capacitor element; l is the inductance value of the inductor element.

[0058] For example, when the resistance value r of the resistor element is known, the real part (Re) of the matching impedance Ym can be obtained by formula (6), and Figure 4 The electrical length θ corresponding to the real part (Re) of Ym is taken as the minimum electrical length d between the impedance matching circuit MC and the noise reflection circuit R-CMF.

[0059] In other words, when the resistance element of the impedance matching circuit MC is preset, Figure 4 The electrical length θ corresponding to the real part (Re) of Ym is used to determine the minimum electrical length d that can be achieved between the impedance matching circuit MC and the noise reflection circuit R-CMF when the resistance value r of the resistor element is known.

[0060] Similarly, when the capacitor and the inductor are pre-set, the Figure 4 The electrical length θ corresponding to the imaginary part (Im) of Ym can be used to determine the minimum electrical length d that can be achieved between the impedance matching circuit MC and the noise reflection circuit R-CMF when the capacitance value c of the capacitor element and the inductance value l of the inductor element are known.

[0061] For example, when the resistance value r of the resistor element is known, the real part (Re) of the matching impedance Ym can be determined based on formula (6), and the real part (Re) of the matching impedance Ym is, for example, 0.7. Figure 4 It can be seen that in this case the electrical length θ is at least 25 degrees.

[0062] Similarly, when the capacitance c of the capacitor and the inductance l of the inductor are known, the imaginary part (Im) of the matching impedance Ym can be determined based on formula (7). The imaginary part (Im) of the matching impedance Ym is, for example, 2.54. Figure 4 It can be seen that in this case the electrical length θ is at least 25 degrees.

[0063] Please continue to refer to Figure 4 In addition, when the electrical length θ is desired, it can also be based on Figure 4 The real part (Re) and imaginary part (Im) of the matching impedance Ym corresponding to the electrical length θ can be used to determine what the resistance value r of the resistor element, the capacitance value c of the capacitor element, and the inductance value l of the inductor element need to be set when the electrical length θ is the desired length.

[0064] For example, when the desired electrical length θ is 100 degrees, Figure 4 The real part (Re) of the matching impedance Ym in this case is 0.4 and the imaginary part (Im) is 2.07, and it is further deduced that when the desired electrical length θ is 100 degrees, the resistance value r of the resistor element, the capacitance value c of the capacitor element, and the inductance value l of the inductor element need to be set.

[0065] Accordingly, when the resistance value r is the same, the effect of noise absorption can be achieved in different frequency bands of noise.

[0066] In addition, the relationship between the electrical length θ between the impedance matching circuit MC and the noise reflection circuit R-CMF and the matching impedance Ym of the impedance matching circuit MC can also be presented in a pre-established table. Figure 4 After the relationship diagram shown, the real part (Re) and the imaginary part (Im) of the matching impedance Ym corresponding to each electrical length θ can be presented in a table. Accordingly, when designing the impedance matching circuit MC, the design parameters such as the electrical length θ or the resistance value r of the resistor element, the capacitance value c of the capacitor element, and the inductance value l of the inductor element can be determined by looking up the table.

[0067] The impedance matching circuit MC may be implemented by a transmission line layout in addition to being implemented by an RLC circuit.

[0068] In one embodiment of the present invention, a server using the serial noise absorption circuit of the present invention can be used for artificial intelligence (AI) computing, edge computing, and can also be used as a 5G server, a cloud server, or an Internet of Vehicles server.

[0069] In one embodiment of the present invention, the vehicle-mounted electronic product using the serial noise absorption circuit of the present invention can be applied to vehicle-mounted devices, such as self-driving cars, electric cars, or semi-self-driving cars.

[0070] In summary, according to the series noise absorption circuit shown in one or more embodiments of the present invention, compared with the existing three-layer circuit board structure, the present invention can be implemented only with a double-layer circuit board structure, which can not only reduce the manufacturing cost, but also reduce the overall volume of the noise absorption circuit. In addition, according to the series noise absorption circuit shown in one or more embodiments of the present invention, the design parameters of the noise absorption circuit can be increased to reduce the dependence of the impedance matching circuit on the length of the differential signal transmission line, thereby reducing the overall volume of the noise absorption circuit.

Claims

1. A series noise absorption circuit electrically connected to two signal feed lines, the series noise absorption circuit comprising: A differential signal transmission line is electrically connected to the two signal feeding lines, and the differential signal transmission line has a first transmission line and a second transmission line, and the first transmission line and the second transmission line are used to receive differential input electrical signals from the two signal feeding lines; as well as An impedance matching circuit is connected in series to the second transmission line, and is used to receive the reflected electrical signal from the noise reflection circuit and match the input impedance of the series noise absorption circuit with the common mode characteristic impedance of the two signal feed lines. There is a minimum electrical length between the impedance matching circuit and the noise reflection circuit, and the minimum electrical length is associated with the real part and the imaginary part of the matching impedance of the impedance matching circuit; the minimum electrical length is obtained by an impedance matching formula, and the impedance matching formula is that the common mode characteristic impedance is equal to the matching impedance of the impedance matching circuit; The differential signal transmission line, the impedance matching circuit and the noise reflection circuit are configured as a T-type equivalent circuit, and the impedance matching formula includes: WITH in =Z 0e ; WITH in =(From 11 -WITH 12 )+[(From 22 -WITH 12 +Z R ) / / WITH 12 ]+1 / Y m ; as well as 1 / Y m =Z 0e -(WITH 11 -WITH 12 )+[(From 22 -WITH 12 +Z R ) / / WITH 12 ], Where Z 11 =Z 22 =-jZ 0e cot(θ·f); Z 12 =-jZ 0e csc(θ·f), Where Z in is the input impedance; Z 0e is the common mode characteristic impedance; Z 11 , Z 12 and Z 22 are the parameters of the open-circuit impedance matrix of the two-port network; Z R is the reflection circuit impedance of the noise reflection circuit; 1 / Y m is the reciprocal of the matching impedance; θ is the minimum electrical length; f is the propagation constant. 2 . The series noise absorbing circuit according to claim 1 , wherein the impedance matching circuit comprises a resistance element, and a resistance value of the resistance element is associated with the real part of the matching impedance corresponding to the minimum electrical length.

3. The series noise absorption circuit according to claim 1, wherein the impedance matching circuit comprises a capacitor and an inductor, and the capacitance value of the capacitor and the inductance value of the inductor are associated with the imaginary part of the matching impedance corresponding to the minimum electrical length.

4. The series noise absorption circuit according to claim 2, wherein the resistance value of the resistor element is associated with the real part of the matching impedance corresponding to the minimum electrical length: R = 1 / (2*Re{Ym}), where R is the resistance value of the resistor element.

5. The series noise absorption circuit according to claim 3, wherein the capacitance value of the capacitor element and the inductance value of the inductor element are associated with the imaginary part of the matching impedance corresponding to the minimum electrical length: Im{Y m }=jω(0.5*C)+(1 / jω2*L), where C is the capacitance value of the capacitor element; L is the inductance value of the inductor element. 6 . The series noise absorbing circuit according to claim 1 , further comprising a ground layer, wherein the ground layer is spaced apart from the differential signal transmission line.

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