Method for obtaining high-speed link loss through waveform conversion

Abstract

The invention relates to a method for obtaining high-speed link loss through waveform conversion. The method comprises the following steps: obtaining an actual time domain waveform of a to-be-detected transmission link receiving end and converting the actual time domain waveform into a first frequency domain frequency spectrum; constructing a lossless equivalent model based on geometric parameters and material parameters of a transmission link, wherein the transmission characteristic of the lossless equivalent model is consistent with that of an actual link, but the loss is zero; applying the same excitation signal to the model to obtain a second frequency domain spectrum; and extracting a frequency domain loss value through logarithm domain amplitude subtraction. According to the method, high-end frequency domain testing equipment is not needed, the oscilloscope is combined with simulation modeling, time domain signals are converted into quantifiable frequency domain loss data, pure loss effects such as conductor loss and dielectric loss are accurately separated, and the method is suitable for various high-speed transmission media such as printed circuit board transmission lines, coaxial cables, chip packaging leads and backboard interconnection; and a low-cost and high-precision loss measurement scheme is provided for high-frequency scenes such as 5G communication and a data center.

Description

Technical Field

[0001] The present invention relates to the field of high-speed circuit board design, and in particular to a loss measurement technology for a high-speed transmission link, and in particular to a method for obtaining high-speed link loss through waveform conversion. Background Art

[0002] Printed circuit boards (PCBs) play an indispensable role in modern electronics. They are key components for both physical support and signal transmission in electronic products. In high-speed signal transmission scenarios, such as 5G communications and high-speed data exchange in data centers, signal loss is inevitable as it travels along the PCB's high-speed transmission lines. This degrades signal quality and leads to problems such as signal attenuation and distortion. Therefore, accurately measuring the loss of high-speed links is crucial for improving the performance of electronic products and ensuring their stable operation.

[0003] Currently, there are two common methods for measuring high-speed link loss within the industry. One is to use an oscilloscope to indirectly assess link loss by acquiring time-domain waveforms at the receiving end, such as eye diagrams and step responses. However, existing analysis methods are mostly qualitative, providing only a rough estimate of signal quality but unable to accurately quantify link loss. The other method involves using a network analyzer to obtain loss data by testing frequency-domain S parameters. This method is widely used in PCB board loss certification, transmission line modeling, and other tasks. However, network analyzers are expensive, especially those capable of covering high-frequency measurement requirements. This makes them less widely available to small and medium-sized hardware development teams or PCB manufacturers.

[0004] Therefore, how to achieve high-precision measurement of high-frequency transmission line loss without relying on a network analyzer. Summary of the Invention

[0005] In order to overcome the problems in the prior art that oscilloscope measurements cannot accurately quantify link loss, and that network analyzers are expensive and have low penetration rates, making it difficult to meet the demand for high-precision measurement of high-frequency transmission line loss, the present invention provides a method for obtaining high-speed link loss through waveform conversion.

[0006] The technical solution of the present invention is as follows: A method for obtaining high-speed link loss through waveform conversion includes the following steps: Obtain the actual time domain waveform of the receiving end of the transmission link to be tested; Performing frequency domain conversion on the actual time domain waveform to obtain a first frequency domain spectrum containing loss information; Based on the transmission characteristic parameters of the transmission link to be measured, constructing a lossless equivalent model that is consistent with the transmission characteristic parameters of the transmission link to be measured, wherein the transmission loss of the lossless equivalent model is zero; Applying the same excitation signal as that of the transmission link to be tested to the lossless equivalent model to obtain a second frequency domain spectrum; Subtract the amplitude of the first frequency domain spectrum from the second frequency domain spectrum to obtain a frequency domain loss value of the transmission link to be measured.

[0007] As a preferred technical solution of the present invention, the transmission characteristic parameters include geometric parameters and material parameters. The geometric parameters at least include the routing length of the transmission link, and the material parameters at least include the dielectric constant of the plate material of the transmission link.

[0008] As a preferred technical solution of the present invention, the frequency domain conversion is achieved by Fourier transform or fast Fourier transform, which converts the amplitude and time relationship of the time domain signal into the amplitude and frequency relationship of the frequency domain signal.

[0009] As a preferred technical solution of the present invention, the lossless equivalent model is a transmission line model, and the influence of conductor loss and dielectric loss is eliminated by setting the conductor loss parameter and dielectric loss parameter of the transmission line model to zero.

[0010] As a preferred technical solution of the present invention, the excitation signal is a digital signal or an analog signal, and the transmission rate of the digital signal is not less than 100 Gbps.

[0011] As a preferred technical solution of the present invention, the amplitude subtraction is performed in the logarithmic domain, specifically, the amplitude value of the first frequency domain spectrum and the amplitude value of the second frequency domain spectrum are converted into decibels and then subtracted to obtain the loss value of each frequency point.

[0012] As a preferred technical solution of the present invention, the transmission link to be tested includes a high-speed transmission line on a printed circuit board, a coaxial cable, a chip package lead or a backplane interconnection link.

[0013] As a preferred technical solution of the present invention, the actual time domain waveform is obtained by: using an oscilloscope to measure the receiving end of the transmission link to be measured, or simulating an actual transmission link model including loss through time domain simulation software.

[0014] As a preferred technical solution of the present invention, the transmission characteristic parameters are obtained from a design file of the transmission link to be tested, and the design file at least includes a PCB layout file, a material parameter table or a three-dimensional structure model.

[0015] As a preferred technical solution of the present invention, the method of obtaining high-speed link loss through waveform conversion is used for high-speed signal transmission links in 5G communications, data centers or high-performance computing fields, and the frequency range of the high-speed signal covers 45GHz to 100GHz.

[0016] The present invention according to the above scheme has the following beneficial effects: By acquiring the actual time-domain waveform of the receiving end of the transmission link to be tested and performing frequency-domain conversion, the present invention combines a lossless equivalent model consistent with the transmission characteristic parameters of the transmission link to be tested and comparative analysis of its frequency-domain spectrum, eliminating the need for expensive network analyzers and effectively overcoming the bottleneck of high-speed link loss measurement in the existing technology. The present invention converts the actual time domain waveform into a first frequency domain spectrum containing loss information, and simultaneously applies the same excitation signal to the lossless equivalent model to obtain a second frequency domain spectrum. This is then processed by amplitude subtraction to effectively separate the signal attenuation caused by factors such as conductor loss and dielectric loss in the actual transmission link from the propagation characteristics affected by the transmission line geometric parameters. This ensures that the measurement results only reflect the pure loss effect, thereby achieving high-precision frequency domain loss measurement. It can be seen that the analysis method of the present invention, based on the lossless model with consistent time domain waveforms and parameters, not only reduces the dependence of high-speed link loss measurement on high-end frequency domain test equipment, but also elevates the time domain signal analysis, which originally remained at the qualitative level, to the level of precise quantification through standardized frequency domain conversion and comparison processes. This provides a low-cost, high-precision high-frequency transmission line loss measurement solution for small and medium-sized hardware development teams and PCB manufacturers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the method of the present invention; Figure 2 The time domain waveform of the transmission link to be tested is measured by an oscilloscope; Figure 3 A first frequency domain spectrum diagram of the actually measured transmission link to be tested; Figure 4 is the time domain waveform of the lossless model; Figure 5 This is the second frequency domain spectrum diagram of the lossless model; Figure 6 is the frequency domain loss value obtained by subtracting the amplitude of the first and second frequency domain spectra; Figure 7 This is a comparison chart of the frequency domain loss results of the method of the present invention and that of a network analyzer. DETAILED DESCRIPTION

[0018] To better understand the objectives, technical solutions, and technical effects of the present invention, the present invention is further explained below with reference to the accompanying drawings and embodiments. It should be noted that similar reference numerals 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 or explained in subsequent drawings. It should also be noted that the embodiments described below are intended only to illustrate the present invention and are not intended to limit the present invention.

[0019] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "first" and "second" are used solely for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of technical features.

[0020] like Figure 1 As shown, a method for obtaining high-speed link loss by waveform conversion includes the following steps: Step 1: Get the actual time domain waveform of the receiving end of the transmission link to be tested; connect the oscilloscope probe to the receiving end of the transmission line, start the oscilloscope to collect data, and refer to Figure 2 The time domain waveform uses time as the horizontal axis and voltage or current as the vertical axis, intuitively showing how the signal changes over time. In addition to using an oscilloscope to obtain actual time domain waveforms, in certain application scenarios, time domain simulation software can also be used to simulate actual transmission link models that include losses. This can occur in the early stages of high-speed circuit or high-speed backplane design, before hardware processing is complete, or when verifying the transmission link in extreme scenarios that exceed actual test conditions.

[0021] Step 2: performing frequency domain conversion on the actual time domain waveform to obtain a first frequency domain spectrum containing loss information; Signal loss in actual transmission links can cause amplitude attenuation and waveform distortion in the time domain signal. The loss manifests itself as amplitude attenuation of specific frequency components in the frequency domain. By performing frequency domain transformation on the receiving end's time domain waveform, such as Fourier transform, the "frequency-related loss information" implicit in the time domain can be converted into an "amplitude-frequency" relationship curve of the frequency domain spectrum, i.e., the first frequency domain spectrum. Figure 3 This process uses the linear characteristics of Fourier transform to decompose the time domain signal into a superposition of different frequency components. The amplitude attenuation of each frequency point directly reflects the loss effect of the actual link on the frequency signal, thereby converting the loss that is difficult to quantify in the time domain into an amplitude value that can be accurately measured in the frequency domain.

[0022] Step 3: Based on the transmission characteristic parameters of the transmission link to be measured, construct a lossless equivalent model that is consistent with the transmission characteristic parameters of the transmission link to be measured, wherein the transmission loss of the lossless equivalent model is zero; In this step, a lossless equivalent model is constructed based on the transmission characteristic parameters of the transmission link under test. The key is to ensure that the model is completely consistent with the "lossless transmission characteristics" of the actual link. The lossless equivalent model sets conductor loss and dielectric loss to zero, retaining only these non-loss characteristics. For example, the trace length and dielectric constant of the transmission line determine the propagation delay of the signal. While the delay of the lossless model is exactly the same as that of the actual link, there is no amplitude attenuation. Parameter consistency ensures equivalence between the model and the actual link in terms of signal propagation patterns, providing a reliable benchmark for subsequent loss separation.

[0023] Step 4: Apply the same excitation signal as the transmission link to be tested to the lossless equivalent model to obtain a second frequency domain spectrum; specifically, after inputting the excitation signal to the lossless model, the time domain waveform of the receiving end is calculated by time domain simulation, referring to Figure 4 , perform Fourier transform on the time domain waveform to obtain the second frequency domain spectrum, refer to Figure 5 .

[0024] The frequency content of the stimulus signal directly determines the scope of frequency domain analysis. For example, a 112Gbps digital signal contains abundant high-frequency components. If the stimulus signal applied by the model differs from the actual link, the frequency content and amplitude distribution of the frequency domain spectrum will be inconsistent, rendering subsequent comparison meaningless. Therefore, applying the same stimulus signal is essential to ensure consistent input conditions, so that the frequency domain differences between the actual link and the model are solely due to the presence of loss. The stimulus signal can be a digital signal (such as a PRBS code) or an analog signal (such as a sine wave or step signal) and must be consistent with the operating signal of the actual link.

[0025] Step 5. Subtract the amplitude of the first frequency domain spectrum from the second frequency domain spectrum to obtain the frequency domain loss value of the transmission link to be tested. As can be seen from the previous steps, the first frequency domain spectrum is a spectrum containing the actual link loss information, while the second frequency domain spectrum is the spectrum of the lossless equivalent model, which represents the transmission characteristics of the signal in the absence of loss; the loss is manifested as the attenuation of the signal amplitude in the frequency domain. The first frequency domain spectrum and the second frequency domain spectrum are both functions of frequency, respectively representing the signal amplitude at different frequencies, and the amplitude value is in logarithmic units, i.e. decibels (dB). By subtracting the amplitude of the first frequency domain spectrum from the second frequency domain spectrum, when performing amplitude subtraction, it is necessary to subtract the amplitude value at each frequency point. After subtracting each frequency point, a series of frequency domain loss values ​​at different frequencies are obtained. The loss characteristics of the actual link can be separated from the comprehensive frequency domain response, and the amplitude change caused only by the loss is obtained, i.e. the frequency domain loss value. The curve drawn with frequency as the horizontal axis and the frequency domain loss value (dB) as the vertical axis intuitively shows the loss of the transmission link to be tested at different frequencies. For reference, Figure 6 .

[0026] This method breaks through the reliance of traditional high-speed link loss measurements on expensive network analyzers by integrating oscilloscope time-domain waveform acquisition, frequency-domain conversion algorithms, parameter-consistent lossless model construction, and spectrum comparison technology, achieving a quantitative conversion from time-domain signals to frequency-domain losses. This method upgrades the oscilloscope from a qualitative observation tool to a precise quantification device through standardized processes. It can accurately isolate the pure loss effects in actual links, providing a low-cost, high-precision loss measurement solution for the design and optimization of high-speed transmission links. This effectively addresses the core issues of low device penetration and inaccurate loss analysis in existing technologies.

[0027] In the present invention, transmission characteristic parameters include geometric parameters and material parameters. The geometric parameters include at least the transmission link's trace length, and the material parameters include at least the transmission link's plate dielectric constant. Thread length and plate dielectric constant are key factors in determining the signal propagation characteristics within a transmission link. Thread length directly affects the signal's propagation delay, while plate dielectric constant affects the signal's propagation speed and phase shift. By ensuring that the lossless equivalent model and the actual link are consistent in these two key parameters, it is possible to ensure that the model and actual link are highly equivalent in terms of signal propagation patterns. That is, when the signal propagates through the model and actual link, other propagation characteristics are essentially the same, except for the loss factor. Furthermore, specifying trace length and plate dielectric constant as key parameters makes this method applicable to high-speed transmission links of different types and specifications. Whether it's a transmission line on a PCB, a coaxial cable, or chip package leads, as long as these key parameters can be obtained, this method can be used to measure loss, enhancing the versatility and applicability of the solution.

[0028] Frequency-domain conversion is achieved through Fourier transforms or fast Fourier transforms. By converting the amplitude-time relationship of the time-domain signal into the amplitude-frequency relationship of the frequency-domain signal, the amplitude attenuation of signals with different frequency components during transmission can be intuitively observed. Many professional signal processing software and hardware devices support both transforms, making the method compatible with existing signal processing tools and platforms. This allows implementers to utilize existing resources for high-speed link loss measurement, lowering the barrier to entry for technical application.

[0029] In the present invention, the lossless equivalent model is a transmission line model. The loss of high-speed transmission lines is mainly caused by conductor loss and dielectric loss. These two types of loss parameters are explicitly eliminated, and the conductor loss parameters and dielectric loss parameters of the transmission line model are set to zero. The second frequency domain spectrum output by the model only contains the phase delay of the signal, which is determined by the trace length and dielectric constant, without any amplitude attenuation. At this time, the amplitude difference between the first frequency domain spectrum of the actual link and the model spectrum only reflects the superposition effect of conductor loss and dielectric loss, avoiding the interference of other non-loss factors such as radiation loss and impedance mismatch. In high-frequency scenarios such as 5G and data centers, such as above 50GHz, conductor loss and dielectric loss show a significant upward trend with increasing frequency, which is the main factor affecting signal integrity. By eliminating these two types of losses and constructing a model, this solution can accurately capture the loss characteristics of the high-frequency band, providing key data for plate selection and trace optimization, while traditional time domain methods are difficult to achieve such quantitative analysis in the high-frequency band. It can be seen that the method of the present invention is suitable for high-speed signal transmission links in 5G communications, data centers or high-performance computing fields, and the frequency range of high-speed signals covers 45GHz to 100GHz.

[0030] The excitation signal for the transmission line model is a digital or analog signal with a transmission rate of no less than 100Gbps, including but not limited to a 112Gbps PRBS code. This digital signal contains abundant high-frequency harmonics, such as those at 50GHz. By frequency-domain conversion and model comparison of such signals, the loss characteristics of the high-frequency band can be accurately extracted. This invention directly matches high-speed communication scenarios such as 5G and data centers, enhancing its relevance for practical engineering applications.

[0031] In step 5, the amplitude subtraction is performed in the logarithmic domain, specifically, the amplitude value of the first frequency domain spectrum and the amplitude value of the second frequency domain spectrum are converted into decibels and then subtracted to obtain the loss value of each frequency point. This step converts nonlinear attenuation into a linear operation: loss value (dB) = 20log 10 (A 实际 )-20log 10 (A 理想 )=20log 10 (A 实际 / A 理想 );Simplifying complex exponential operations into direct subtraction significantly reduces algorithm complexity and facilitates real-time calculation and hardware implementation.

[0032] The present invention covers all scenarios of high-speed signal transmission media. The transmission links to be tested include high-speed transmission lines on printed circuit boards, coaxial cables, chip package leads or backplane interconnect links. Although the physical structures and loss mechanisms of different transmission media are different, this solution achieves high-precision measurement of the loss of various media through a unified process of time domain waveform acquisition - frequency domain conversion - lossless model comparison. For example: for PCB transmission lines, the lossless model is based on the trace length and dielectric constant; for coaxial cables, it is based on the inner and outer conductor diameters and the dielectric constant of the insulation layer; for package leads, it is based on the lead length and the dielectric constant of the substrate.

[0033] In one optional embodiment, the transmission characteristic parameters are obtained from the design file of the transmission link to be tested, which may include at least a PCB layout file, a material parameter table, or a three-dimensional structural model. Extracting parameters directly from the design file avoids the subjective bias caused by manual parameter selection and makes the lossless model construction process objective and standardized.

[0034] In summary, the present invention obtains the receiving end time domain waveform obtained by testing, obtains the frequency domain spectrum by performing Fourier frequency domain changes, and then obtains the length and dielectric constant information of the object to be tested based on the description of the length of the object to be tested and the dielectric constant of the board material in the PCB file. Then, an ideal transmission line model with the same length and dielectric constant but without loss is built in the simulation software, and its waveform is obtained by time domain simulation. Finally, the spectrum of the lossless transmission line model is subtracted from the spectrum of the actual transmission link to be tested to obtain the frequency domain loss result of the transmission link to be tested.

[0035] In order to verify the feasibility of the method of the present invention, a method for obtaining high-speed link loss by waveform conversion also includes a verification step: the frequency domain loss result of the transmission link to be tested obtained in step 5 is compared with the frequency domain result value directly measured by the network analyzer on the same curve, and it is found that the two curves are completely corresponding. Figure 7 , indicating that the method of the present invention has very high accuracy.

[0036] The technical features of the above embodiments can 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.

[0037] The above embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for obtaining high-speed link loss by waveform conversion, characterized in that: The following steps are involved: Obtain the actual time domain waveform of the receiving end of the transmission link to be tested; Performing frequency domain conversion on the actual time domain waveform to obtain a first frequency domain spectrum containing loss information; Based on the transmission characteristic parameters of the transmission link to be measured, constructing a lossless equivalent model that is consistent with the transmission characteristic parameters of the transmission link to be measured, wherein the transmission loss of the lossless equivalent model is zero; Applying the same excitation signal as that of the transmission link to be tested to the lossless equivalent model to obtain a second frequency domain spectrum; Subtract the amplitude of the first frequency domain spectrum from the second frequency domain spectrum to obtain a frequency domain loss value of the transmission link to be measured.

2. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The transmission characteristic parameters include geometric parameters and material parameters. The geometric parameters at least include the routing length of the transmission link, and the material parameters at least include the dielectric constant of the plate material of the transmission link.

3. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The frequency domain conversion is achieved by Fourier transform or fast Fourier transform, which converts the amplitude and time relationship of the time domain signal into the amplitude and frequency relationship of the frequency domain signal.

4. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The lossless equivalent model is a transmission line model, and the influence of conductor loss and dielectric loss is eliminated by setting the conductor loss parameter and dielectric loss parameter of the transmission line model to zero.

5. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The excitation signal is a digital signal or an analog signal, and the transmission rate of the digital signal is not less than 100 Gbps.

6. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The amplitude subtraction is performed in the logarithmic domain, specifically, the amplitude value of the first frequency domain spectrum and the amplitude value of the second frequency domain spectrum are converted into decibels and then subtracted to obtain the loss value of each frequency point.

7. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The transmission link to be tested includes a high-speed transmission line on a printed circuit board, a coaxial cable, a chip packaging lead or a backplane interconnection link.

8. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The actual time domain waveform is obtained by: performing actual measurement on the receiving end of the transmission link to be measured using an oscilloscope, or simulating an actual transmission link model including loss using time domain simulation software.

9. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The transmission characteristic parameters are obtained from a design file of the transmission link to be tested, and the design file at least includes a PCB layout file, a material parameter table or a three-dimensional structure model.

10. The method for obtaining high-speed link loss through waveform conversion according to claim 1, characterized in that: The method for obtaining high-speed link loss through waveform conversion is used for high-speed signal transmission links in 5G communications, data centers or high-performance computing fields, and the frequency range of high-speed signals covers 45GHz to 100GHz.

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