A T-shaped microstrip line capable of suppressing far-end crosstalk for specific frequencies and a design method thereof
By adding T-shaped protrusions to the inside of the microstrip line and optimizing the structural parameters, the problem of far-end crosstalk in high-density PCB layout was solved, achieving the effect of low crosstalk and high wiring density. Simulation results show that far-end crosstalk is significantly reduced and transmission performance is improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2023-06-27
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to effectively suppress far-end crosstalk in high-density PCB layouts, especially during high-frequency signal transmission, leading to signal quality degradation and system failure. Furthermore, existing solutions suffer from high costs or space requirements.
T-shaped protrusions were added to the inside of the parallel microstrip lines. By optimizing the structural parameters, far-end crosstalk at a specific frequency was suppressed. The simulation optimization was carried out using ANSYS HFSS and ADS simulation software, and the optimal structural parameters were selected to achieve low crosstalk and high wiring density.
At a specific frequency, the far-end crosstalk is minimized, resulting in excellent transmission performance, high wiring density, and relatively low cost. Simulation results show that the far-end crosstalk is below -35dB, and the transmission performance is superior to existing technologies.
Smart Images
Figure CN116960593B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a T-shaped microstrip line capable of suppressing far-end crosstalk at specific frequencies and its design method, belonging to the field of electrical equipment and electrical engineering technology. Background Technology
[0002] With the continuous development of modern digital circuits and communication technologies, electronic products are constantly evolving towards miniaturization and higher frequencies. Clock frequencies reaching GHz, picosecond rise times, and high-density PCB layouts present increasingly serious signal integrity challenges in circuit design. Crosstalk, as a key issue affecting signal quality, can cause data transmission disorder and even system failure. Therefore, how to suppress crosstalk while achieving high PCB density to ensure the complete transmission of high-speed, high-frequency signals is an urgent problem to be solved.
[0003] Patent CN116017843A proposes a PCB anti-crosstalk routing structure, which is a multi-layer structure. Multiple signal lines are arranged on the signal layer of this multi-layer structure, and multiple isolated first protective ground lines are provided between adjacent signal lines. However, when using ground lines, it is essential to ensure good via grounding and sufficient via density. When the via spacing is too large, resonance can easily occur between the traces, making the crosstalk situation between the lines very complex.
[0004] US Patent 11369020B2 discloses a stacked multilayer transmission line comprising at least one pair of conductive traces, each conductive trace having several conductive protrusions electrically coupled thereto, the protrusions being placed in one or more spatial layers separate from the conductive traces. However, the added conductive protrusions occupy the upper layer space of the conductive traces, increasing manufacturing costs.
[0005] In 2015, Intel proposed Tabbed routing, which has been used in ball grid array (BGA) package leads and high-density data signal traces. It can reduce trace impedance and increase mutual capacitance between traces to reduce far-end crosstalk. However, the specific design method has not been disclosed.
[0006] To address the problems existing in the prior art, this invention proposes a novel T-shaped microstrip line suitable for high-frequency, high-density PCBs, and proposes a design method for T-shaped microstrip line parameters that can suppress far-end crosstalk at specific frequencies. This method has the advantages of low crosstalk, clear method, and improved wiring density. Summary of the Invention
[0007] To address the far-end crosstalk problem of high-speed, high-density single-ended microstrip lines in fifth-generation double-rate synchronous dynamic random access memory (DDR5), this invention proposes a T-shaped microstrip line. A T-shaped protrusion is added to the inside of a parallel uniform microstrip line, and the structural parameters are optimized for a specific frequency to obtain the optimal T-shaped structure, thereby minimizing far-end crosstalk.
[0008] To achieve the above-mentioned objectives and solve the problems existing in the prior art, the technical solution adopted by the present invention is as follows:
[0009] A novel T-shaped microstrip line capable of suppressing far-end crosstalk is disclosed. The T-shaped microstrip line has a linewidth w as the minimum process linewidth and a line spacing of 3w. T-shaped protrusions are added to the inner side of the parallel and uniform microstrip line to maintain high density.
[0010] Furthermore, T-shaped protrusions are arranged at equal intervals on the two inner sides of the microstrip line, and the height of the T-shaped protrusions on both sides is the same.
[0011] A novel design method for T-type microstrip lines capable of suppressing far-end crosstalk at specific frequencies includes the following steps:
[0012] Step 1. Set the characteristic impedance and microstrip line width of the parallel microstrip line on the PCB.
[0013] First, select a PCB board made of copper-clad material (high-frequency board material such as PTFE material). Then, set the microstrip line thickness and determine the distance between the microstrip line and the ground plane according to the calculation formula (1) of the characteristic impedance Z0 of the parallel microstrip line.
[0014]
[0015] In the formula, ε r The relative permittivity of the PCB material is represented by h, the distance between the microstrip line and the ground plane is represented by w, the microstrip line width is represented by t, and the microstrip line thickness is represented by t. Generally, the characteristic impedance of a parallel microstrip line is selected as 50Ω.
[0016] Step 2. Determine the length *l* of two parallel uniform microstrip lines as needed. Add uniformly staggered T-shaped protrusions to the inner sides of the two microstrip lines. The structural parameters of the T-shape are short side *a*, long side *b*, T-pair length *D*, and number *n*, forming a novel T-shaped microstrip line. Other unspecified lengths (such as long side thickness and short side thickness) are all 1 *w*, controlling the microstrip line capacitance while maintaining a high-density PCB layout. The T-pair length *D* refers to the distance on the same side of the long side of two adjacent T-shaped protrusions on the same microstrip line, including the two relatively distributed T-shaped protrusions on the inner sides of the two microstrip lines.
[0017] Step 3. The values of n and D are mutually constrained, and the sparse T-shaped bumps have a weak effect on suppressing crosstalk. The value of D that has a significant effect on suppressing crosstalk is generally between 8w and 13w, where w is the linewidth of a single microstrip line. D is selected within this range, and then n is determined by l and D.
[0018] Step 4. Using ANSYS HFSS simulation software, simulate and obtain the far-end crosstalk coefficient S within a frequency band covering a specific frequency range. 41 , as an indicator for measuring signal transmission performance and crosstalk suppression effectiveness. 41 There are crosstalk trough frequencies, which are related to the parameters of the T-shaped protrusion structure. Specifically:
[0019] (a) Take the D and n selected in step 3, scan a from 1 to 3w, and scan b from a to (D / 2-w). Record the far-end crosstalk coefficient S when a and b change. 41 The curve shows how the frequency changes, and the far-end crosstalk coefficient S at a specific frequency on the curve is recorded simultaneously. 41 The structural parameters of the T-shaped protrusions that exhibit crosstalk troughs at multiple specific frequencies were recorded.
[0020] (b) Change the values of D and n in step 3. The value of n will also change after the selected value of D is changed. Therefore, there are multiple combinations of n and D. Repeat step (a).
[0021] Step 5. For the multiple combinations of n, D, a, and b obtained in Step 4, consider the following indicators to select the optimal combination. The selection indicators include, in order, S at a specific frequency. 41 With a relatively small value of <-35dB and (b×n) / l, the structural parameters were initially screened under the optimal selection criteria. Time-domain simulation was then performed, and the eye diagram was obtained using ADS simulation software. The combination of structural parameters with the best eye diagram index was selected as the optimal T-type microstrip line structure for this specific frequency.
[0022] The advantages of this invention are: low far-end crosstalk at a specific frequency, clear design method, and high wiring density. Attached Figure Description
[0023] Figure 1 For PCB parallel microstrip lines.
[0024] Figure 2 This is a novel T-shaped microstrip line model.
[0025] Figure 3 This is a schematic diagram of the parameters of a T-shaped microstrip line structure.
[0026] Figure 4 The far-end crosstalk coefficient S varies with n and D. 41 Changes; Figure 4 (a) The sparse T-shaped protrusions have a weak effect on suppressing crosstalk; Figure 4 (b) shows the variation of far-end crosstalk under different combinations of n and D.
[0027] Figure 5 Flowchart for optimizing T-type microstrip line structure parameters.
[0028] Figure 6 The far-end crosstalk coefficient S varies with a and b. 41 Changes; Figure 6 (a) represents the far-end crosstalk coefficient S when a varies. 41 Curve showing how the frequency changes; Figure 6 (b) represents the far-end crosstalk coefficient S when b varies. 41 Curve showing how frequency changes. Detailed Implementation
[0029] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.
[0030] This embodiment optimizes the transmission line with a main frequency of 3.2 GHz.
[0031] In the first aspect, a novel T-shaped microstrip line that can suppress far-end crosstalk can suppress far-end crosstalk at a specific frequency. The described T-shaped microstrip line has a line width w of 0.1 mm and a line spacing of 3 w. T-shaped protrusions are added inside the parallel uniform microstrip line to maintain high density.
[0032] Secondly, a novel T-shaped microstrip line design method for suppressing far-end crosstalk includes the following steps:
[0033] Step 1. Set the characteristic impedance and microstrip line width of the parallel microstrip line on the PCB, such as... Figure 1 As shown (from top to bottom including signal layer, dielectric, and ground layer), first select a PCB board made of copper-clad material (PTFE material), then set the microstrip line thickness to t, and calculate the distance between the microstrip line and the ground layer according to the formula for calculating the characteristic impedance Z0 of the parallel microstrip line. Here, the characteristic impedance of the parallel microstrip line is selected as 50Ω, the microstrip line width w is set to 0.1mm, the dielectric constant of the PCB board (dielectric) is 4.6, the microstrip line thickness t is 0.04mm, and the distance h between the microstrip line and the ground layer is calculated according to formula (1) as 0.07mm.
[0034] Step 2. Determine the length l of the two parallel uniform microstrip lines as needed. In this embodiment, the microstrip line length l = 30 mm, the minimum linewidth w = 0.1 mm, and the spacing s between the two microstrip lines = 0.3 mm. Add uniformly staggered T-shaped protrusions to the inner side of the two microstrip lines, such as... Figure 2 As shown, the structural parameters of the T-shape are the short side a, the long side b, the length D of the T-shape pair, and the number n, as follows: Figure 3As shown, a novel T-shaped microstrip line is formed. All other unspecified lengths are 1w (e.g., long side thickness, short side thickness), which controls the microstrip line capacitance while maintaining a high-density PCB layout. The T-pair length D refers to the distance between the long sides of two adjacent T-shaped protrusions on the same microstrip line, including two relatively distributed T-shaped protrusions on the inner sides of the two microstrip lines.
[0035] Step 3. The values of n and D are mutually constrained, and the sparse T-shaped bulges have a weak effect on suppressing crosstalk. Values of D with significant crosstalk suppression effects are between 8w and 13w, such as... Figure 4 As shown, select D within this range, and then determine n based on l and D. Take n = 28 and D = 1.016 mm.
[0036] Step 4. Using ANSYS HFSS simulation software, the far-end crosstalk coefficient S is obtained by simulation within a specific frequency band covering 3.2 GHz. 41 , as an indicator for measuring signal transmission performance and crosstalk suppression effectiveness. 41 There is a crosstalk trough frequency, which is related to the T-shaped protrusion structure parameters. The structural parameter optimization flowchart is as follows: Figure 5 As shown, the details are as follows:
[0037] (a) Take the D and n selected in step 3, scan a from 1 to 3w, and scan b from a to (D / 2-w). Record the far-end crosstalk coefficient S when a and b change. 41 The curve shows how the frequency changes, and the far-end crosstalk coefficient S at a specific frequency on the curve is recorded simultaneously. 41 The structural parameters of the T-shaped protrusions that exhibit crosstalk troughs at multiple specific frequencies were recorded. Figure 6 The far-end crosstalk coefficient S varies with a and b. 41 The changes in structural parameters show that changes in these parameters will cause changes in far-end crosstalk at a certain frequency.
[0038] (b) Changing the selected value of D will also change the value of n, so there are multiple combinations of n and D. In this example, there are four combinations: n = 25, D = 1.1176 mm, n = 28, D = 1.016 mm, n = 32, D = 0.9144 mm, and n = 36, D = 0.8128 mm. Change the values of D and n in step 3 and repeat step (a).
[0039] Step 5. For the multiple combinations of n, D, a, and b obtained in Step 4, consider the following indicators to select the optimal combination. The selection indicators include, in order, S at a specific frequency. 41 With a relatively small value of <-35dB and (b×n) / l, the structural parameters were initially screened under the optimal selection criteria. Time-domain simulation was then performed, and the eye diagram was obtained using ADS simulation software. The combination of structural parameters with the best eye diagram index was selected as the optimal T-type microstrip line structure for this specific frequency.
[0040] In one specific embodiment, the structural parameters of a DDR5 main frequency of 3.2GHz were optimized according to this design method, resulting in an optimal T-shaped structure with a = 0.1mm, b = 0.3mm, n = 28, and D = 1.016mm. This was compared with parallel microstrip lines and tabbed lines of the same density. The linewidth w of the parallel uniform microstrip line is 0.1mm, and the line spacing is 3w, which is 0.3mm. The minimum linewidth of the tabbed line is still 0.1mm, the long side of the tab is 0.12mm, the short side is 0.11mm, the height is 0.19mm, the spacing is 0.6mm, and the number of tabs is 50.
[0041] Far-end crosstalk S of the optimal T-type microstrip line at 3.2 GHz 41 The voltage rating is -53.69 dB, the peak far-end crosstalk voltage is 3.4 mV, the eye height is 0.453 V, and the eye width is 152.3 ps; the S-axis of the parallel microstrip line is... 41 The voltage is -23.6dB, the peak far-end crosstalk voltage is 17mV, the eye height is 0.451V, and the eye width is 153.1ps; the S of the tabbed line 41 The voltage rating is -31.8576dB, the peak voltage of far-end crosstalk is 7.5mV, the eye height is 0.456V, and the eye width is 152.3ps, indicating that the T-type microstrip line has good transmission performance and can effectively suppress crosstalk in high-speed, high-density PCB layout.
[0042] Other signal transmission frequencies can also be optimized using the above method to design T-shaped microstrip lines and suppress far-end crosstalk.
[0043] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.
Claims
1. A design method for a T-shaped microstrip line, characterized in that, The following steps are included: Step 1. Set the characteristic impedance and microstrip line width of the parallel microstrip line on the PCB; First, select a PCB board made of copper-clad material. Then, set the microstrip line thickness based on the characteristic impedance of the parallel microstrip line. Determine the distance between the microstrip line and the formation; Step 2. Determine the lengths of the two parallel uniform microstrip lines as needed. l Evenly staggered T-shaped protrusions are added to the inner sides of the two microstrip lines. The structural parameters of the T-shaped protrusions are the width of the vertical structure. a Length of the horizontal structure b T-type length D Sum of logarithms n This forms a novel T-shaped microstrip line, controlling the microstrip line capacitance while maintaining a high-density PCB layout; the T-shape has a length... D Refers to the distance between two adjacent T-shaped protrusions on the same side of the long side on the same microstrip line, including two T-shaped protrusions that are relatively distributed on the inner side of the two microstrip lines; Step 3. n and D The values of these variables are mutually constrained, resulting in a significant effect in suppressing crosstalk. D Values in the range of 8 w ~13 w Between, among w For the linewidth of a single microstrip line, select within this range. D Then by l and D Sure n ; Step 4. Use ANSYS HFSS simulation software to simulate and obtain the far-end crosstalk coefficient within a frequency band covering a specific frequency range. S 41 As an indicator for measuring signal transmission performance and crosstalk suppression effectiveness; S 41 There are crosstalk trough frequencies, which are related to the parameters of the T-shaped protrusion structure; the details are as follows: (a) Take the one selected in step 3 D and n , a From 1 to 3 w Perform a scan. b from a up to (0.5) D - w Scan and record. a , b When it changes, the far-end crosstalk coefficient S 41 The curve shows how the frequency changes, and the far-end crosstalk coefficient at a specific frequency in the curve is recorded. S 41 Record the structural parameters of T-shaped protrusions that exhibit crosstalk troughs at multiple specific frequencies; (b) Change step 3 D and n The size of the selected [item] can be changed. D After the value n The value will also change accordingly, therefore there are multiple n , D Repeat step (a) for the combination of ; Step 5. For the multiple results obtained in Step 4 n , D , a , b The combination of factors is considered comprehensively to select the best combination.
2. The design method for a T-shaped microstrip line according to claim 1, characterized in that, In step 5, the selection criteria include, in order, specific frequencies. S 41 <-35dB, ( b × n ) / l After preliminary screening of structural parameters under the selection criteria, time-domain simulation was performed. Eye diagrams were obtained using ADS simulation software, and the combination of structural parameters with the best eye diagram index was selected as the optimal T-type microstrip line structure for that specific frequency.
3. The design method for a T-shaped microstrip line according to claim 1, characterized in that, The characteristic impedance of the parallel microstrip line in step 1 The calculation formula is as follows: (1) In the formula, This represents the relative permittivity of the PCB material. Indicates the distance between the microstrip line and the stratum. Indicates the microstrip linewidth. This indicates the microstrip line thickness; the characteristic impedance of a parallel microstrip line is selected as 50Ω.
4. A T-shaped microstrip line, characterized in that, The T-shaped microstrip line, obtained by using the design method described in any one of claims 1-3, has a linewidth of... w Minimum process linewidth and line spacing is 3. w T-shaped protrusions are added inside the parallel and uniform microstrip lines to maintain high density.
5. A T-shaped microstrip line according to claim 4, characterized in that, The T-shaped microstrip line has T-shaped protrusions arranged at equal intervals on its two inner sides, and the height of the T-shaped protrusions on both sides is the same.