An optimization method based on TRL calibration

Abstract

The present invention is an optimization method based on TRL calibration, which involves TRL calibration, active load traction technology and programming algorithm. In order to solve the problem of optimal impedance point position offset in TRL calibration of a fixture circuit and subsequent load traction test, an optimization algorithm based on Python programming is proposed. The algorithm is applied as a subsequent correction step of the classic TRL algorithm, and the continuity of the error coefficient phase curve obtained by calibration is judged, and the jump point therein is found and corrected to restore the continuity of the phase curve, so as to obtain the correct optimal impedance point in the actual active load traction test.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency circuits, and in particular to an optimization method based on TRL calibration. Background Art

[0002] TRL calibration is the most commonly used and important calibration method in microwave and millimeter wave device testing. It uses a vector network analyzer (VNA) to measure the S parameters of three standard calibration parts: Thru, Reflect, and Line. The error coefficient is obtained by algorithm processing, and then the measured data is converted into calibrated real data. On the other hand, in the test of large-signal nonlinear RF devices, in order to obtain the best performance of the output end of the device under test (DUT), it is necessary to continuously change the load conditions to find the load impedance point corresponding to the maximum output power or power added efficiency, which is the optimal impedance point. Active load pulling is a technology specifically used to find the optimal impedance point of the DUT. Its core is to use a signal source at the load end to input a signal corresponding to the fundamental or harmonic frequency to simulate different impedance values, and find the optimal impedance point through algorithm iteration.

[0003] After years of development, the TRL calibration method has become increasingly mature, with the advantages of low dependence on calibration standards and a certain calibration surface. However, it also inevitably has some defects, such as the length of the Line is too long under low-frequency test conditions; when the test frequency range is wide, multiple Lines are required for calibration; the impedance accuracy of the Line is high and must be consistent with the system impedance, etc. Due to the defects of the TRL algorithm, when performing active load-pull tests on high-power nonlinear devices, the problem of error coefficient phase jump is prone to occur, which in turn leads to a phase shift of the optimal impedance point. In summary, an improved TRL algorithm for identifying and correcting error coefficient phase jump points is of great significance. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and provide an optimization method based on TRL calibration.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions:

[0006] An optimization method based on TRL calibration includes the following steps:

[0007] Step 1: Divide all frequency points into several groups according to the total number of frequency points, and calculate the variance of the slope of each group of frequency points;

[0008] Step 2: Compare the obtained values ​​with the set thresholds in turn; if any frequency group has a value greater than the set threshold, it means that there are phase discontinuities in the frequency group, and the next step is entered; otherwise, all frequency groups are less than the threshold, and the frequency points in all groups are continuous, and the step ends;

[0009] Step 3: Obtain all frequency point groups whose variance is greater than the set threshold, and perform Fourier transform on the frequency points in these frequency point groups to obtain the corresponding spectrum diagram;

[0010] Step 4: Screen the phase jump point according to the component situation in the spectrum diagram to determine whether there is a phase jump point in the spectrum diagram; if there is a phase jump point, proceed to the next step; otherwise, end the step;

[0011] Step 5: There is a phase jump point in the spectrum diagram. The phases of other frequency points are corrected according to the phase change of the phase jump point.

[0012] Furthermore, in step 4, the step of screening the phase jump point includes:

[0013] Step 41: Obtain adjacent frequency points with a phase difference of 360° in the spectrum diagram and mark them as flip points;

[0014] Step 42: Obtain a simulated phase curve according to the electrical length of the fixture device;

[0015] Step 43: Adjust the simulation phase curve by using the minimum error approximation method;

[0016] Step 44: Compare the spectrum diagram with the adjusted simulation phase curve to obtain the phase jump point, and end the step.

[0017] Furthermore, in step 44, the frequency point in the spectrum diagram where the phase difference with the corresponding position of the simulation phase curve exceeds the set value is considered to be a phase jump point; wherein the phase jump point does not include the resonance point and the flip point, and the resonance point represents the frequency point part where multiple continuous high-frequency components appear in the spectrum diagram.

[0018] Furthermore, the phase jump point is a frequency point in the spectrum diagram where the phase difference with the corresponding position of the simulation phase curve exceeds 10°.

[0019] Furthermore, in step 5, when correcting the phase of other frequency points, the correction method adopted is: the phase of the phase jump point and the frequency points after the phase jump point are added with the jump amplitude of the phase jump point and the previous phase jump point.

[0020] Furthermore, after step 5, the corrected spectrum diagram is compared with the simulation result.

[0021] The beneficial effects of the present invention are:

[0022] The phase jump of the error coefficients e23 and e32 obtained by TRL calibration is identified and corrected, and the interference of the resonance point is eliminated in the process of identifying the phase jump point, so that the curve optimized according to the phase jump is restored to continuity and close to the simulation curve. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of an optimization algorithm according to Embodiment 1 of the present invention;

[0024] Figure 2 The phase-frequency curves of the measured and simulated error coefficients of the first embodiment of the present invention;

[0025] Figure 3 Schematic diagram of a test fixture according to Embodiment 1 of the present invention;

[0026] Figure 4 For the first embodiment of the present invention Figure 3 Error coefficient phase-frequency curve before and after the measured curve correction;

[0027] Figure 5 The error coefficient phase-frequency curve of the measured curve containing noise points before and after correction in the first embodiment of the present invention;

[0028] Figure 6 The active load-pull test system of the first embodiment of the present invention;

[0029] Figure 7 is an error network signal flow diagram of embodiment 1 of the present invention;

[0030] Figure 8 The optimal impedance point positions before and after the algorithm optimization of the first embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0033] Embodiment 1:

[0034] like Figure 1 As shown, an optimization method based on TRL calibration includes the following steps:

[0035] Step 1: Divide all frequency points into several groups and find the variance of the slope of each group of frequency points;

[0036] Step 2: Compare the obtained variance with the set threshold in turn; if the variance of any frequency group is greater than the set threshold, it means that there is a phase discontinuous point in the frequency group, and proceed to the next step; otherwise, the variance of all frequency groups is less than the threshold, the frequency points in all groups are continuous, and the step ends;

[0037] Step 3: Obtain all frequency point groups whose variance is greater than the set threshold, and perform Fourier transform on the frequency points in these frequency point groups to obtain the corresponding spectrum diagram;

[0038] Step 4: Screen the phase jump point according to the component situation in the spectrum diagram to determine whether there is a phase jump point in the spectrum diagram; if there is a phase jump point, proceed to the next step; otherwise, end the step;

[0039] Step 5: There is a phase jump point in the spectrum diagram. The phases of other frequency points are corrected according to the phase change of the phase jump point.

[0040] When the frequency point groups are equally divided in step 1, it is required that the number of equally divided frequency point groups should be greater than twice the number of harmonics, and the corresponding total number of frequency points should be greater than six times the number of harmonics.

[0041] In step 3, in this example, the spectrum diagram is a phase-frequency curve diagram.

[0042] like Figure 2 As shown, in step 4, the step of screening the phase jump point includes:

[0043] Step 41: Obtain adjacent frequency points with a phase difference of 360° in the spectrum diagram and mark them as flip points;

[0044] Step 42: Obtain a simulated phase curve according to the electrical length of the fixture device;

[0045] Step 43: Adjust the simulation phase curve by using the minimum error approximation method;

[0046] Step 44: Compare the spectrum diagram with the adjusted simulation phase curve to obtain the phase jump point, and end the step.

[0047] In step 42, the electrical length of the fixture device represents the physical length of the fixture divided by the waveguide wavelength. Because the fixture device is generally composed of a passive transmission line; in the microwave band, as the frequency increases, the wavelength becomes shorter and shorter, and the geometric dimensions of the transmission line are often longer than the working wavelength of the electromagnetic wave, or the dimensions of the transmission line are comparable to the working wavelength. It should be noted that the electrical length of the fixture is an approximate calculated value, because in the process of measuring the physical length and the waveguide wavelength, it is difficult to achieve accurate measurement, and only an approximate value can be obtained.

[0048] In step 43, when adjusting the simulation phase curve, the simulation phase curve is compared with the measured curve to reduce the difference between the two, so as to adjust the simulation phase curve and obtain an accurate limit curve of the fixture device.

[0049] like Figure 4 As shown, in step 44, the frequency point in the spectrum graph where the phase difference with the corresponding position of the simulation phase curve exceeds 10° is considered as a phase jump point; wherein the phase jump point does not include the resonance point and the flip point. The resonance point refers to the frequency point part where multiple continuous high-frequency components appear in the spectrum graph. The purpose of removing the resonance point is to avoid misjudgment caused by the resonance of the test fixture.

[0050] In step 5, when correcting the phase of other frequency points, the correction method used is: the phase of the phase jump point and the frequency points after the phase jump point are added with the jump amplitude of the phase jump point and the previous phase jump point, wherein the jump amplitude represents the phase difference between the corrected spectrum diagram and the simulated phase curve. For example, if there are two phase jump points in the spectrum diagram, for the frequency points between the first phase jump and the second phase jump point, including the first phase jump point, the jump amplitude of the first phase jump point needs to be added; for the frequency points after the second phase jump point, the jump amplitude of the first phase jump point and the jump amplitude of the second phase jump point need to be added.

[0051] like Figure 5-6 As shown in Figure 5, after the correction is completed in step 5, in order to verify the optimization effect of the above optimization method, the corrected phase-frequency curve, that is, the spectrum diagram, is compared with the simulation results to confirm the rationality of the jump point correction and the continuity of the phase curve. Figure 2 The phase-frequency curve of the measured error coefficient in the , and the phase-frequency curve filled with noise points with a phase deviation less than 10°, complete the optimization and obtain the following Figure 4 , 5 The correction curve is shown in Figure 2. Figure 6 The detection equipment shown performs active load-pull test on the device, and compares the measured results with the measured results before algorithm optimization and the simulation results to verify the effect of the algorithm optimization results. The specific steps of the active load-pull test are as follows:

[0052] Step 61: Correct the error coefficient according to the phase jump amplitude of the jump point, and import the corrected error coefficient into the test software as a calibration file to eliminate the system error; the test software is active load pull test software;

[0053] Step 62: Fix the load impedance of the device to 50Ω and perform a power scan;

[0054] Step 63: Gain-P in ) to find the 1dB gain compression point (P in,1dB ) position, and perform fundamental wave load pulling near it to find the optimal impedance point position of the device's PAE (Power Added Efficiency).

[0055] When correcting the error coefficient in step 61, the same phase jump amplitude is directly applied to the error coefficient. In this example, because the phase jump is mainly caused by the phase change after the square root of the error coefficients e23 and e01, it is necessary to directly correct the phase jump of the error coefficients e23 and e01 to achieve the correction of the error coefficient. The correction process is to directly apply the same phase change to the error coefficients e23 and e01. The phase change is obtained through steps 4 and 5. The error coefficient in this example represents the error in the vector network analyzer. Figure 7 As shown, among the 8 parameters, a 0 , b 0 , a 3 , b 3 represents the traveling wave measured by the vector network analyzer, a 1 , b 1 , a 2 , b 2 represents the actual traveling wave of the device under test (DUT) incident and reflected at the dual ports. In this embodiment, the error network A causes the error term e 00 , e 11 , e 01 , e 10 ; The error network B leads to e 22 , e 23 , e 33 , e 32 .

[0056] like Figure 8 As shown in the figure, after algorithm optimization, the measured PAE optimal impedance point increases by 0.04 and the phase shift is 96.21° compared with the test results before algorithm correction, which is basically consistent with the simulation results in ADS, reflecting the optimization effect.

[0057] During the implementation process, the phase jump of the error coefficient e23 obtained by TRL calibration is identified and corrected, and the interference of the resonance point is eliminated in the process of identifying the phase jump point, ensuring that the curve optimized according to the phase jump is close to the simulation curve; the error coefficients e23 and e01 are related, so only one of them needs to be corrected, and the sign of the other error coefficient is determined.

[0058] It should be noted that the solution of this embodiment is also applicable to other calibration methods based on straight transmission lines, including LRL, LRM, LRRM and other calibration methods.

[0059] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principle of the present invention, various modifications and changes in form and details may be made without departing from the principle and structure of the present invention, but these modifications and changes based on the idea of ​​the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. An optimization method based on TRL calibration, It is characterized in that The method comprises the following steps: Step 1: dividing all frequency points into several groups according to the total number of frequency points, and obtaining the variance of the slope of each group of frequency points; Step 2: Compare the obtained variance with the set threshold in turn; if the variance of any group of frequency points is greater than the set threshold, it means that there is a phase discontinuity point in the group of frequency points, and proceed to the next step; Otherwise, the variance of all frequency groups is less than the threshold, the frequency points in all groups are continuous, and the step ends; Step 3: Obtain all frequency point groups whose variance is greater than the set threshold, and perform Fourier transform on the frequency points in these frequency point groups to obtain the corresponding spectrum diagram; Step 4: Screen the phase jump point according to the component situation in the spectrum diagram to determine whether there is a phase jump point in the spectrum diagram; if there is a phase jump point, proceed to the next step; Otherwise, end the step; Step 5: If there is a phase jump point in the spectrum diagram, the phase of the phase jump point and the frequency points after the phase jump point are corrected by adding the jump amplitude of the phase jump point and the previous phase jump point according to the phase change of the phase jump point.

2. The optimization method based on TRL calibration according to claim 1, It is characterized in that In the step 4, the step of screening the phase jump point includes: step 41: obtaining adjacent frequency points with a phase difference of 360° in the spectrum diagram, and marking them as flip points; Step 42: Obtain a simulated phase curve according to the electrical length of the fixture device; Step 43: Adjust the simulation phase curve by using the minimum error approximation method; Step 44: Compare the spectrum diagram with the adjusted simulation phase curve to obtain the phase jump point, and end the step.

3. The optimization method based on TRL calibration according to claim 2, It is characterized in that In step 44, the frequency point in the spectrum diagram where the phase difference with the corresponding position of the simulation phase curve exceeds the set value is considered to be a phase jump point; wherein the phase jump point does not include the resonance point and the flip point, and the resonance point represents the frequency point part where multiple continuous high-frequency components appear in the spectrum diagram.

4. The optimization method based on TRL calibration according to claim 3, It is characterized in that The phase jump point is a frequency point in the spectrum diagram where the phase difference with the corresponding position of the simulation phase curve exceeds 10°.

5. The optimization method based on TRL calibration according to claim 1, It is characterized in that After step 5, the corrected spectrum diagram is compared with the simulation result.

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