Method for optimizing simulation precision of 2.5 D high-speed transmission line

Abstract

The invention relates to a method for optimizing the simulation precision of a 2.5 D high-speed transmission line, and the method comprises the steps: building a variable inductance transmission line model based on the principle that a 2.5 D simulation model port has loop inductance, scanning different inductance values of the model to simulate TDR impedance, obtaining an inductance parameter capable of fitting a high point of a 2.5 D simulation TDR impedance curve through a comparison fitting mode, and obtaining the simulation precision of the 2.5 D high-speed transmission line. A 2.5 D transmission line model is improved by establishing a de-embedding module, and the influence of loop inductance in a 2.5 D simulation result on the signal transmission quality is effectively removed, so that the 2.5 D simulation precision is improved, and the simulation precision can be compared with that of 3D simulation. Therefore, the simulation method is based on the 2.5 D simulation technology, the simulation speed is high, the obtained simulation precision is comparable with the 3D simulation precision, the 2.5 D simulation efficiency and the 3D simulation precision can be considered at the same time, the practical value is very high, and the method is worthy of application and popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed transmission line simulation, and in particular to a method for optimizing the simulation accuracy of a 2.5D high-speed transmission line. Background Art

[0002] Printed Circuit Board (PCB) is an indispensable component of modern electronic devices. It not only provides physical support for electronic components, but also plays an important role in signal transmission. In PCB design, transmission lines, as the key path for signal transmission, are essential to ensure signal integrity and system performance. Especially in high-speed digital circuits and radio frequency (RF) applications, the design and simulation of transmission lines have become the foundation and core of the electronic design process.

[0003] In order to accurately simulate the frequency domain characteristics of transmission lines of different lengths, namely S parameters, the industry usually prefers three-dimensional (3D) electromagnetic simulation software to ensure the high accuracy of the results. However, the disadvantage of 3D simulation software is that it takes a long time to calculate, especially when analyzing longer traces, which significantly prolongs the overall design cycle. For this reason, people think of using 2.5D simulation software to save simulation time. Compared with 3D simulation software, 2.5D simulation software can shorten the time by several times or even ten times, greatly improving the speed of design iteration and work efficiency.

[0004] Although 2.5D simulation has significant advantages in speed, there is a clear accuracy gap between 2.5D simulation and 3D simulation in high-frequency applications. The key to the simulation accuracy gap lies in the different ways of port modeling. Specifically, the 2.5D simulation port is established in the form of a lumped port, and the transmission line is far away from the ground plane. Due to the nature of the lumped port, the physical length of the port is long, resulting in a larger inductive loop. As the inductive loop increases, the impedance at the port will increase abnormally, especially at high frequencies. Therefore, 2.5D simulation cannot accurately reflect the high-frequency behavior in the actual circuit.

[0005] The 3D simulation uses the wave port modeling method. The wave port can more accurately simulate the propagation characteristics of electromagnetic waves in the transmission line without being affected by the physical length of the port. It can more realistically reproduce the behavior of high-frequency signals and avoid impedance anomalies caused by port modeling.

[0006] In summary, when choosing a simulation strategy, it is necessary to balance the computing speed and simulation accuracy. For rapid prototyping or preliminary design, 2.5D simulation is used to improve the efficiency of the solution; while for those application scenarios with extremely high accuracy requirements, especially those involving high-frequency signal processing, 3D simulation technology is used. It can be seen that engineers can only make a trade-off between computing speed and simulation accuracy.

[0007] So, whether there is a high-speed transmission line simulation method that can take into account both the efficiency of 2.5D simulation and the accuracy of 3D simulation has become a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0008] In order to overcome the deficiencies of the prior art, the present invention provides a method for optimizing the simulation accuracy of a 2.5D high-speed transmission line.

[0009] The technical solution of the present invention is as follows:

[0010] A method for optimizing 2.5D high-speed transmission line simulation accuracy, comprising:

[0011] The 2.5D transmission line model is simulated to obtain the TDR impedance curve, and the impedance value of the highest point of the TDR impedance curve is screened out and defined as the first impedance;

[0012] A variable inductance transmission line model is constructed, and the inductance value is gradually adjusted in an iterative manner to update the TDR impedance simulation result of the variable inductance transmission line model, and the impedance value of the variable inductance transmission line model is defined as a second impedance;

[0013] When the difference between the second impedance and the first impedance is less than 1 ohm, the iterative simulation ends and the target inductance value is obtained;

[0014] Export a 4-port S-parameter structure with target inductance value as a de-embedded structure;

[0015] Add a de-embedding structure to the 2.5D transmission line model to obtain a 2.5D transmission line optimization model;

[0016] Simulate a 2.5D transmission line optimization model.

[0017] As another preferred solution of the present invention, the 2.5D transmission line model includes end load modules on both sides, a transmission line S parameter module in the middle, and a four-port converter module located between the end load module and the transmission line S parameter module.

[0018] As another preferred embodiment of the present invention, the steps of building a variable inductance transmission line model specifically include:

[0019] First, create a model identical to the 2.5D transmission line model;

[0020] Then replace the transmission line S parameter module in the model with an inductor module with a variable inductance value.

[0021] Furthermore, the inductor module includes a first inductor and a second inductor connected in parallel, and both ends of each inductor have open connection ends.

[0022] As another preferred solution of the present invention, the inductance values ​​of the first inductor and the second inductor are both variable values, and the first inductor is equal to the second inductor.

[0023] Optionally, the variable range of the inductance value is [0.05, 1nH], and the step size is 0.05nH.

[0024] Further, the first inductance and the second inductance of the 4-port S parameter structure are equal to the target inductance value, and the single-port impedance of the 4-port S parameter structure is equal to the line impedance of the 2.5D transmission line model.

[0025] Optionally, the line impedance of the 2.5D transmission line model is 50 ohms.

[0026] As another preferred embodiment of the present invention, the step of adding a de-embedding structure in the 2.5D transmission line model specifically includes:

[0027] Create a new de-embedding module;

[0028] Import the 4-port S-parameter file with the target inductance value;

[0029] Generate a de-embedding module, the de-embedding module has 4 connection pins and a ground pin;

[0030] Insert a de-embedding module on each side of the transmission line S parameter module of the 2.5D transmission line model.

[0031] As another preferred embodiment of the present invention, after the step of simulating the 2.5D transmission line optimization model, a verification step is further included: comparing the simulation results with the original 2.5D transmission line model and the 3D transmission line model to determine the simulation accuracy of the 2.5D transmission line optimization model.

[0032] Furthermore, the verification steps specifically include:

[0033] The 2.5D transmission line model is simulated to obtain a first TDR impedance curve and a first insertion loss curve;

[0034] Simulate the 2.5D transmission line optimization model to obtain the second TDR impedance curve and the second insertion loss curve;

[0035] Simulate the 3D transmission line model to obtain high-precision TDR impedance curve and high-precision insertion loss curve;

[0036] Compare the first TDR impedance curve, the second TDR impedance curve and the high-precision TDR impedance curve in the same impedance curve comparison diagram;

[0037] In the same insertion loss curve comparison diagram, the first insertion loss curve, the second insertion loss curve and the high-precision insertion loss curve are compared.

[0038] The present invention according to the above scheme has the following beneficial effects:

[0039] Based on the principle that there is loop inductance at the port of a 2.5D simulation model, the present invention first builds a model containing variable inductance, and scans different inductance values ​​for simulation, so as to obtain an inductance parameter model that can be fitted with the high point of the TDR impedance curve of the 2.5D simulation, and accordingly establishes a de-embedding module to improve the 2.5D transmission line model, effectively removing the influence of the loop inductance in the 2.5D simulation result on the signal transmission quality, thereby improving the 2.5D simulation accuracy, and the simulation accuracy can be compared with that of 3D simulation;

[0040] It can be seen that the simulation method of the present invention takes into account both the efficiency of 2.5D simulation and the accuracy of 3D simulation, has very high practical value, and is worthy of popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of the method of the present invention;

[0042] Figure 2 It is a structural schematic diagram of a 2.5D transmission line model;

[0043] Figure 3 It is a structural schematic diagram of a variable inductance transmission line model in the present invention;

[0044] Figure 4 is a fitting diagram of the second impedance and the first impedance when the inductance is equal to 0.15nH;

[0045] Figure 5 is a fitting diagram of the second impedance and the first impedance when the inductance is equal to 0.20nH;

[0046] Figure 6 It is a 4-port S parameter structure with an inductance equal to 0.2nH;

[0047] Figure 7 It is a structural schematic diagram of the 2.5D transmission line optimization model in the present invention;

[0048] Figure 8 This is a comparison chart of impedance curves;

[0049] Fig. 9 This is a comparison chart of the insertion loss curve.

[0050] In the figure,

[0051] 1. End load module; 2. Transmission line S parameter module; 3. Four-port converter module; 4. First inductor; 5. Second inductor; 6. De-embedding module. DETAILED DESCRIPTION

[0052] In order to better understand the purpose, technical scheme and technical effect of the present invention, the present invention is further explained in conjunction with the accompanying drawings and embodiments. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, it is stated that the embodiments described below are only used to explain the present invention and are not used to limit the present invention.

[0053] It should be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may also be a central element, and when an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time.

[0054] The indicated orientation or position relationship is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the application is usually placed when used, or the orientation or position relationship commonly understood by technical personnel in this field, or the orientation or position relationship in which the product of the application is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0055] The terms "first" and "second" are only used for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly specifying the number of technical features.

[0056] like Figure 1 As shown, a method for optimizing the simulation accuracy of a 2.5D high-speed transmission line includes:

[0057] Step 1, simulating the 2.5D transmission line model to obtain a TDR impedance curve, screening out the impedance value of the highest point of the TDR impedance curve, and defining it as the first impedance;

[0058] Specifically, Siwave software can be used to model a 2.5D transmission line model, and the 2.5D transmission line model can be simulated to obtain a TDR impedance curve (defined as a first TDR impedance curve). The first TDR impedance curve has two impedance sudden increases, and the impedance value of the highest point is defined as the first impedance.

[0059] Step 2: construct a variable inductance transmission line model, gradually adjust the inductance value in an iterative manner to update the TDR impedance simulation result of the variable inductance transmission line model, and define the impedance value of the variable inductance transmission line model as a second impedance;

[0060] Step 3: When the difference between the second impedance and the first impedance is less than 1 ohm, the iterative simulation is terminated to obtain the target inductance value;

[0061] The inductance value of the variable inductance transmission line model is a variable. Select an initial inductance value and simulate the TDR impedance result of the variable inductance transmission line model. Define it as the second impedance. Compare the second impedance with the first impedance. If the difference is greater than 1 ohm, increase the inductance value. At this time, the software runs the formula: L n =L n-1 +Δ, n is a natural number, Δ represents an incremental value or a step value, the inductance value is refreshed, and a new second impedance is simulated again; it is compared with the first impedance again until the difference between the second impedance and the first impedance is less than 1 ohm, then the above iterative simulation process is terminated, and the inductance Ln at this time is recorded as the target inductance value.

[0062] In other optional embodiments, the accuracy can be further improved by limiting the difference between the second impedance and the first impedance to be less than 0.05 ohms or 0.02 ohms, etc., and even further limiting the second impedance to be equal to the first impedance.

[0063] Step 4, deriving a 4-port S-parameter structure with a target inductance value as a de-embedded structure;

[0064] Step 5, adding a de-embedding structure to the 2.5D transmission line model to obtain a 2.5D transmission line optimization model;

[0065] Use the target inductance value obtained in step 3 to establish a 4-port S parameter structure as a de-embedded structure. The de-embedded structure contains the specific inductance value. When combined with the 2.5D transmission line model, it can remove the influence of the loop inductance in the original 2.5D simulation results.

[0066] Step 6: Simulate the 2.5D transmission line optimization model;

[0067] The optimized 2.5D transmission line optimization model is simulated, and the simulation result is the optimized result, which restores the performance that the original transmission line should have and improves the simulation accuracy.

[0068] like Figure 2 As shown, in this embodiment, the 2.5D transmission line model includes end load modules 1 on both sides, a transmission line S parameter module 2 in the middle, and a four-port converter module located between the end load module 1 and the transmission line S parameter module 2. Specifically, from left to right, it includes: the end load module 1 on the left, the four-port converter module on the left, the transmission line S parameter module 2, the four-port converter module on the right, and the end load module 1 on the right. Then the connection structure of the 2.5D transmission line model is:

[0069] The end load module 1 on the left is connected to pin d of the four-port converter module on the left, pin c of the four-port converter module on the left is grounded, pin “+” of the four-port converter module on the left is connected to pin 1 of the transmission line S parameter module 2, and pin “-” of the four-port converter module on the left is connected to pin 3 of the transmission line S parameter module 2; pin “-” of the four-port converter module on the right is connected to pin 4 of the transmission line S parameter module 2, pin “+” of the four-port converter module on the right is connected to pin 2 of the transmission line S parameter module 2, pin c of the four-port converter module on the right is grounded, and pin d of the four-port converter module on the right is connected to the end load module 1 on the right.

[0070] like Figure 3 As shown, the difference between the variable inductance transmission line model and the 2.5D transmission line model lies in the middle module. The middle module of the variable inductance transmission line model is an inductance module with an inductance value. The steps of building the variable inductance transmission line model specifically include:

[0071] Step 201, first establish a model identical to the 2.5D transmission line model;

[0072] Step 202: Replace the transmission line S parameter module 2 in the model with an inductance module whose inductance value is a variable.

[0073] Therefore, the variable inductor transmission line model includes the end load module 1 on the left, the four-port converter module on the left, the inductor module, the four-port converter module on the right and the end load module 1 on the right in sequence; wherein the inductor module includes the first inductor 4 and the second inductor 5 connected in parallel, and both ends of each inductor have open connection ends. Then the connection structure of the variable inductor transmission line model is:

[0074] The end load module 1 on the left is connected to pin d of the four-port converter module on the left, pin c of the four-port converter module on the left is grounded, pin "+" of the four-port converter module on the left is connected to the left end of the first inductor 4, and pin "-" of the four-port converter module on the left is connected to the left end of the second inductor 5; pin "-" of the four-port converter module on the right is connected to the right end of the second inductor 5, pin "+" of the four-port converter module on the right is connected to the right end of the first inductor 4, pin c of the four-port converter module on the right is grounded, and pin d of the four-port converter module on the right is connected to the end load module 1 on the right.

[0075] like Figure 4 and Figure 5As shown, in this embodiment, the inductance values ​​of the first inductor and the second inductor are both variable values, the variable range of the inductance value is [0.05, 1nH], the step size is 0.05nH, and the first inductor is equal to the second inductor, that is, the first inductor and the second inductor are equal. First, take the initial inductance value L0 = 0.05nH, simulate and obtain the TDR impedance result (second impedance) when L0 = 0.05nH, and compare it with the first impedance; the iterative formula is L n =L n-1 +0.05nH, n is a natural number, up to L n =0.2nH, the difference between the TDR impedance result and the first impedance is very small, and the second impedance can fit the first impedance, that is, the highest points of the two TDR impedance curves almost coincide, and the target inductance value is 0.2nH. At this time, the variable inductance transmission line model becomes an inductance parameter model with an exact inductance value of 0.2nH, and the impedance result of the inductance parameter model fits the high impedance point in the original 2.5D simulation result.

[0076] like Figure 6 As shown, step 4 is performed to derive a 4-port S parameter structure of 0.2nH as a de-embedded structure. The first inductor 4 and the second inductor 5 of the 4-port S parameter structure are equal to the target inductance value, i.e., 0.2nH; the single-port impedance of the 4-port S parameter structure is equal to the line impedance of the 2.5D transmission line model. In a specific embodiment, the line impedance of the 2.5D transmission line model is 50 ohms, so the single-port impedance of the 4-port S parameter structure is equal to 50 ohms.

[0077] Execute step 5 to obtain the 2.5D transmission line optimization model, which specifically includes:

[0078] Step 501: Establish a new de-embedding module;

[0079] Open the execution command of adding the de-embedding module in the design software, enter the command name, and select the de-embedding command function;

[0080] Step 502, importing a 4-port S parameter file having a target inductance value;

[0081] Import the 0.2nH 4-port S parameter file in the file import column;

[0082] Step 503: Generate a de-embedding module, the de-embedding module having four connection pins and one ground pin;

[0083] The system automatically generates a de-embedding module to remove the 0.2nH loop inductance;

[0084] Step 504, inserting a de-embedding module 6 on both sides of the transmission line S parameter module 2 of the 2.5D transmission line model;

[0085] like Figure 7 As shown, it can be seen from the foregoing that the 2.5D transmission line model includes in sequence: an end load module 1 on the left, a four-port converter module on the left, a transmission line S parameter module 2, a four-port converter module on the right and an end load module 1 on the right; when a de-embedding module 6 is inserted on both sides of the transmission line S parameter module 2, the formed 2.5D transmission line optimization model includes in sequence: an end load module 1 on the left, a four-port converter module on the left, a de-embedding module 6 on the left, a transmission line S parameter module 2, a de-embedding module 6 on the right, a four-port converter module on the right and an end load module 1 on the right.

[0086] Execute step 6 to simulate the link of the above optimization model to obtain a transmission line simulation result in which the influence of the head and tail inductances is removed.

[0087] Finally, the simulation results of the optimized model can be compared with the original 2.5D simulation results to observe whether the simulation accuracy is improved after optimization; the simulation results of the optimized model can also be compared with the simulation results of the 3D simulation software, and the optimized 2.5D simulation results can be compared with the 3D simulation results. Therefore, after the step of simulating the 2.5D transmission line optimization model, a verification step is also included: the simulation results of the 2.5D transmission line optimization model are compared with the simulation results of the original 2.5D transmission line model and the 3D transmission line model, specifically including:

[0088] Step 701, simulating a 2.5D transmission line model to obtain a first TDR impedance curve and a first insertion loss curve;

[0089] Step 702, simulating the 2.5D transmission line optimization model to obtain a second TDR impedance curve and a second insertion loss curve;

[0090] Step 703, simulating the 3D transmission line model to obtain a high-precision TDR impedance curve and a high-precision insertion loss curve;

[0091] Step 704: compare the first TDR impedance curve, the second TDR impedance curve, and the high-precision TDR impedance curve in the same impedance curve comparison diagram;

[0092] Step 705: compare the first insertion loss curve, the second insertion loss curve, and the high-precision insertion loss curve in the same insertion loss curve comparison diagram.

[0093] Execute step 704 to obtain Figure 8 The impedance curve comparison diagram shown in FIG. 1 is shown in FIG. 1 , and step 705 is performed to obtain Fig. 9 It can be seen that the simulation accuracy of the 2.5D transmission line model optimized by the method of the present invention is improved compared with the simulation result of the original 2.5D transmission line model, and the simulation accuracy can be compared with the 3D simulation result. Figure 8 and Fig. 9In FIG. 5 , curves a1 and a2 represent the simulation results of the 2.5D transmission line model; curves b1 and b2 represent the simulation results of the 2.5D transmission line optimization model; and curves c1 and c2 represent the simulation results of the 3D transmission line model.

[0094] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for optimizing the simulation accuracy of 2.5D high-speed transmission lines, characterized in that: The 2.5D transmission line model is simulated to obtain the TDR impedance curve, and the impedance value of the highest point of the TDR impedance curve is screened out and defined as the first impedance; A variable inductance transmission line model is constructed, and the inductance value is gradually adjusted in an iterative manner to update the TDR impedance simulation result of the variable inductance transmission line model, and the impedance value of the variable inductance transmission line model is defined as a second impedance; When the difference between the second impedance and the first impedance is less than 1 ohm, the iterative simulation ends and the target inductance value is obtained; Export a 4-port S-parameter structure with target inductance value as a de-embedded structure; Add a de-embedding structure to the 2.5D transmission line model to obtain a 2.5D transmission line optimization model; Simulate a 2.5D transmission line optimization model.

2. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 1, characterized in that: The 2.5D transmission line model includes end load modules at both sides, a transmission line S parameter module in the middle, and a four-port converter module located between the end load module and the transmission line S parameter module.

3. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 1, characterized in that: The steps to build a variable inductance transmission line model include: First, create a model identical to the 2.5D transmission line model; Then replace the transmission line S parameter module in the model with an inductor module with a variable inductance value.

4. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 3, characterized in that: The inductor module includes a first inductor and a second inductor connected in parallel, and both ends of each inductor have open connection ends.

5. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 4, characterized in that: The inductance values ​​of the first inductor and the second inductor are both variable values, and the first inductor is equal to the second inductor.

6. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to any one of claims 3 to 5, characterized in that: The variable range of the inductance value is [0.05, 1nH], and the step size is 0.05nH.

7. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 1, characterized in that: The first inductance and the second inductance of the 4-port S parameter structure are equal to the target inductance value, and the single-port impedance of the 4-port S parameter structure is equal to the line impedance of the 2.5D transmission line model.

8. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 1, characterized in that: The step of adding a de-embedding structure in the 2.5D transmission line model specifically includes: Create a new de-embedding module; Import the 4-port S-parameter file with the target inductance value; Generate a de-embedding module, the de-embedding module has 4 connection pins and a ground pin; Insert a de-embedding module on each side of the transmission line S parameter module of the 2.5D transmission line model.

9. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 1, characterized in that: After the step of simulating the 2.5D transmission line optimization model, a verification step is also included: comparing the simulation results with the original 2.5D transmission line model and the 3D transmission line model to determine the simulation accuracy of the 2.5D transmission line optimization model.

10. The method for optimizing the simulation accuracy of 2.5D high-speed transmission lines according to claim 9, characterized in that: The verification steps include: The 2.5D transmission line model is simulated to obtain a first TDR impedance curve and a first insertion loss curve; Simulate the 2.5D transmission line optimization model to obtain the second TDR impedance curve and the second insertion loss curve; Simulate the 3D transmission line model to obtain high-precision TDR impedance curve and high-precision insertion loss curve; Compare the first TDR impedance curve, the second TDR impedance curve and the high-precision TDR impedance curve in the same impedance curve comparison diagram; In the same insertion loss curve comparison diagram, the first insertion loss curve, the second insertion loss curve and the high-precision insertion loss curve are compared.

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