A lambda / 4 stepped impedance transformation method and system

Abstract

The application discloses a kind of λ / 4 stepped impedance transformation method and system.Therein, the method includes: in the impedance mismatching of partial discharge ultrahigh frequency load impedance and the characteristic impedance of partial discharge ultrahigh frequency measurement system, access λ / 4 stepped impedance transformation two-port network, the load impedance is wave impedance;According to characteristic impedance Z 0, wave impedance Z L And the characteristic impedance of two-section λ / 4 transmission line Z 1, Z 2, determine partial voltage reflection coefficient;According to the partial voltage reflection coefficient, determine total voltage reflection coefficient;According to the total voltage reflection coefficient, broaden the working frequency band of λ / 4 stepped impedance transformer.Therefore, break through the limitation of direct matching, by the progressive stepped impedance matching mode of sensor element, realize partial discharge ultrahigh frequency signal sensor element and subsequent radio frequency processing circuit good matching, thereby reduce the partial discharge ultrahigh frequency signal attenuation caused by impedance mismatching.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment testing technology, and more specifically, to a λ / 4 stepped impedance transformation method and system. Background Technology

[0002] Partial discharge measurement of the insulation of high-voltage electrical equipment is a common method for assessing the insulation condition of such equipment. Partial discharge measurement techniques include traditional pulse current methods, as well as a series of newer live-line detection techniques such as ultra-high frequency (UHF), high frequency, and ultrasonic methods. Among these, the UHF partial discharge detection technique, based on the measurement of pulsed electromagnetic fields, achieves quantitative and localized partial discharge detection and is increasingly widely used. However, its sensing element, namely the UHF partial discharge sensor, is one of the main bottlenecks limiting the performance of its measurement system.

[0003] To accurately measure UHF partial discharge signals, high-performance sensing elements are required, which should have good impedance matching with the subsequent signal processing circuitry. Currently, UHF partial discharge sensors are mainly based on antenna principles. Since antennas possess "reciprocity"—meaning their transmitting and receiving properties are identical—this is one of the theoretical foundations for studying antenna (UHF sensor) impedance transformation. Currently, UHF sensors vary in design principles and performance; however, in the UHF sensor bandwidth of up to 300MHz… Z ~3GH Z Achieving impedance transformation over a wide frequency band is one of the current technical challenges. How to transition the wave impedance from 120πΩ to the characteristic impedance of an RF measurement system of 50Ω over a relatively wide frequency band determines the electrical performance of ultra-high frequency sensors.

[0004] For impedance matching at a single frequency or in a narrow bandwidth, the bandwidth provided by a single-stage converter is generally sufficient, but impedance matching cannot be achieved in a wide bandwidth. Summary of the Invention

[0005] According to the present invention, a λ / 4 stepped impedance transformation method and system are provided to solve the technical problem that the bandwidth provided by a general single-section converter in the prior art cannot achieve impedance matching in a wide frequency band.

[0006] According to a first aspect of the present invention, a λ / 4 stepped impedance transformation method is provided, comprising:

[0007] A two-port network with λ / 4 stepped impedance transformation is connected at the impedance mismatch point between the load impedance of the UHF partial discharge and the characteristic impedance of the UHF partial discharge measurement system. The load impedance is the wave impedance.

[0008] Based on characteristic impedance Z 0. Wave impedance ZL and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient;

[0009] The total voltage reflection coefficient is determined based on the local voltage reflection coefficient.

[0010] Based on the total voltage reflection coefficient, the operating bandwidth of the λ / 4 stepped impedance transformer is widened.

[0011] Optionally, based on characteristic impedance Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient, including:

[0012] The local voltage reflection coefficient is determined using the following formula:

[0013]

[0014]

[0015]

[0016] Wherein, the wavelength of the electromagnetic wave is λ, and the length of each step in the transmission line is λ / 4. G 0、 G 1. G 2 represents the first step reference plane. T Local voltage reflection coefficient at 0, second step reference plane T Local voltage reflection coefficient on 1 and third step reference plane T The local voltage reflection coefficient on line 2, and the characteristic impedances of the two λ / 4 transmission lines are respectively... Z 1. Z 2, and Z L > Z 2> Z 1> Z 0.

[0017] Optionally, determining the total voltage reflection coefficient based on the local voltage reflection coefficient includes:

[0018] For a two-stage stepped impedance transformer, the total voltage reflection coefficient of the two-stage stepped impedance transformer is determined as follows:

[0019]

[0020] Among them, U rU is the voltage across λ / 4 of the two-section stepped impedance transformer. i For the total voltage, e -j2θ The second step reference plane T The phase lag introduced by the reflected voltage wave after traveling different distances, e -j4θ The third step reference plane T 2. Phase lag introduced by the voltage reflected wave traveling different distances.

[0021] Optionally, determining the total voltage reflection coefficient based on the local voltage reflection coefficient further includes:

[0022] for N For an N-section stepped impedance transformer, the total voltage reflection coefficient of the N-section stepped impedance transformer is determined as follows:

[0023]

[0024] in, T 0、 T 1. T 2…, is the step reference plane, totaling ( N +1) items, G 0= G N , G 1= G N-1 ...to select the local reflection coefficient for symmetry.

[0025] Optionally, determining the total voltage reflection coefficient based on the local voltage reflection coefficient further includes:

[0026] for N For N-section stepped impedance transformers, determine the magnitude of the total voltage reflection coefficient of the N-section stepped impedance transformers as follows:

[0027]

[0028] If let | G If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, when more than one frequency satisfies the condition. G |=0, enabling multi-section λ / 4 stepped impedance transformers to widen the operating bandwidth.

[0029] According to another aspect of the present invention, a λ / 4 stepped impedance transformation system is also provided, comprising:

[0030] A two-port network module is used to connect a λ / 4 stepped impedance transformation two-port network at the impedance mismatch point between the load impedance of the partial discharge ultra-high frequency and the characteristic impedance of the partial discharge ultra-high frequency measurement system, wherein the load impedance is the wave impedance.

[0031] The module for determining the local voltage reflection coefficient is used based on the characteristic impedance. Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient;

[0032] The module for determining the total voltage reflection coefficient is used to determine the total voltage reflection coefficient based on the local voltage reflection coefficient.

[0033] The widening operating bandwidth module is used to widen the operating bandwidth of the λ / 4 stepped impedance transformer according to the total voltage reflection coefficient.

[0034] Optionally, the module for determining the local voltage reflection coefficient includes:

[0035] The local voltage reflection coefficient determination submodule is used to determine the local voltage reflection coefficient according to the following formula:

[0036]

[0037]

[0038]

[0039] Wherein, the wavelength of the electromagnetic wave is λ, and the length of each step in the transmission line is λ / 4. G 0、 G 1. G 2 represents the first step reference plane. T Local voltage reflection coefficient at 0, second step reference plane T Local voltage reflection coefficient on 1 and third step reference plane T The local voltage reflection coefficient on line 2, and the characteristic impedances of the two λ / 4 transmission lines are respectively... Z 1. Z 2, and Z L > Z 2> Z 1> Z 0.

[0040] Optionally, the module for determining the total voltage reflection coefficient includes:

[0041] The submodule for determining the total voltage reflection coefficient of two stepped impedance transformers is used to determine the total voltage reflection coefficient of the two stepped impedance transformers as follows:

[0042]

[0043] Among them, U rU is the voltage across λ / 4 of the two-section stepped impedance transformer. i For the total voltage, e -j2θ The second step reference plane T The phase lag introduced by the reflected voltage wave after traveling different distances, e -j4θ The third step reference plane T 2. Phase lag introduced by the voltage reflected wave traveling different distances.

[0044] Optionally, the module for determining the total voltage reflection coefficient further includes:

[0045] Determine the N total voltage reflection coefficient submodules for use in... N For an N-section stepped impedance transformer, the total voltage reflection coefficient of the N-section stepped impedance transformer is determined as follows:

[0046]

[0047] in, T 0、 T 1. T 2…, is the step reference plane, totaling ( N +1) items, G 0= G N , G 1= G N-1 ...to select the local reflection coefficient for symmetry.

[0048] Optionally, the module for determining the total voltage reflection coefficient further includes:

[0049] Determine the magnitude submodule of the total voltage reflection coefficient for N sections. N For N-section stepped impedance transformers, determine the magnitude of the total voltage reflection coefficient of the N-section stepped impedance transformers as follows:

[0050]

[0051] If let | G If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, when more than one frequency satisfies the condition. G |=0, enabling multi-section λ / 4 stepped impedance transformers to widen the operating bandwidth.

[0052] This overcomes the limitations of direct matching by using a progressive, stepped impedance matching method for the sensing element to achieve a good match between the partial discharge UHF signal sensing element and the subsequent RF processing circuit, thereby reducing the attenuation of the partial discharge UHF signal caused by impedance mismatch. The bandwidth of the partial discharge high-frequency signal reaches 300MHz. Z ~3GH ZHowever, conventional impedance transformation techniques are suitable for impedance matching at a single frequency point and are difficult to adapt to impedance matching problems over a wider frequency band. This paper aims to solve the challenge of impedance transformation over a wide frequency band. Attached Figure Description

[0053] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0054] Figure 1 This is a flowchart illustrating a λ / 4 stepped impedance transformation method according to this embodiment.

[0055] Figure 2 This is a schematic diagram of a stepped impedance transformer composed of two λ / 4 impedance transformers according to this embodiment;

[0056] Figure 3 According to the embodiments described herein, the method is as follows: N A schematic diagram of a stepped impedance transformer composed of λ / 4 impedance transformers;

[0057] Figure 4 This is a schematic diagram of a λ / 4 stepped impedance transformation system according to this embodiment. Detailed Implementation

[0058] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0059] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0060] According to a first aspect of the present invention, a λ / 4 stepped impedance transformation method 100 is provided, with reference to... Figure 1 As shown, the method 100 includes:

[0061] S101: A two-port network of λ / 4 stepped impedance transformation is connected at the impedance mismatch point between the load impedance of the partial discharge ultra-high frequency and the characteristic impedance of the partial discharge ultra-high frequency measurement system, wherein the load impedance is the wave impedance.

[0062] S102: Based on characteristic impedanceZ 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient;

[0063] S103: Determine the total voltage reflection coefficient based on the local voltage reflection coefficient;

[0064] S104: Based on the total voltage reflection coefficient, widen the operating bandwidth of the λ / 4 stepped impedance converter.

[0065] Specifically, in the partial discharge ultra-high frequency signal sensing technology, when the local discharge ultra-high frequency load impedance (i.e., the gas medium 120πΩ wave impedance) is not equal to the characteristic impedance of the measurement system (usually 50Ω), reflection will occur due to the impedance mismatch at both ends of the sensing element (or sensor), which will lead to a decrease in the measurement capability of the partial discharge ultra-high frequency signal and make it difficult to extract the useful partial discharge ultra-high frequency signal from a large amount of electromagnetic noise.

[0066] To eliminate this undesirable reflection phenomenon, this invention proposes a λ / 4 stepped impedance transformation method for sensing ultra-high frequency signals of partial discharge. This method involves connecting a two-port network at the impedance mismatch point to eliminate reflected waves on the transmission line of the measurement system, thereby achieving good matching.

[0067] like Figure 2 As shown, the characteristic impedance of the UHF partial discharge measurement system is Z 0 = 50Ω, the terminal load is the surge impedance. Z L =120Ω, the wavelength of the electromagnetic wave is λ, then the length of each step of the transmission line is λ / 4, when operating at the center frequency. f At 0, the phase angle θ = π / 2. Let... T 0、 T 1. T 2 represents the reference plane at each step. G 0、 G 1. G 2 represents the local voltage reflection coefficient on the corresponding reference plane, and the characteristic impedances of the two λ / 4 transmission lines are respectively... Z 1. Z 2, and Z L > Z 2> Z 1> Z If 0, then the local voltage reflection coefficients are respectively:

[0068] (Equation 1)

[0069] (Equation 2)

[0070] (Equation 3)

[0071] Assuming that the moduli of these local reflection coefficients are very small, it can be assumed that the amplitudes of the incident wave voltages on each reference surface are equal. As a first-order approximation, T The total voltage reflected wave on the 0 reference plane is only the sum of the primary voltage reflected waves from each reference plane, that is:

[0072] (Equation 4)

[0073] T The total voltage reflection coefficient on the 0 surface is

[0074] (Equation 5)

[0075] In the formula, e -j2θ e -j4θ for T 1. T 2. Phase lag introduced by voltage reflection waves on the reference surface after traveling different distances.

[0076] A single-stage converter has only two abrupt change surfaces, where the reflection coefficient is... G If only the first two items are taken, G 0= G 1. Phase at the center frequency θ = π / 2, the sum of these two terms is zero, meaning the reflected waves from the two abrupt change surfaces cancel each other out at the input, thus achieving matching. However, when deviating from the center frequency, because θ ≠ π / 2, these two reflected waves cannot completely cancel each other out. In the case of a multi-stage stepped converter, due to the increased number of abrupt change surfaces, such as... Figure 1 The two-stage stepped converter has three reflected waves participating in the cancellation, thus reducing the total reflection coefficient at multiple frequency points. G =0. Therefore | G │ m Under the same conditions, two λ / 4 stepped impedance transformers widen the operating bandwidth.

[0077] like Figure 3 As shown, for N The stepped impedance transformer has a sudden change surface. T 0、 T 1. T 2…, total ( N +1). If symmetrical selection of local reflection coefficients... G 0= G N , G 1= G N-1 ...The total reflection coefficient of the multi-section λ / 4 stepped impedance transformer is:

[0078] (Equation 6)

[0079] Its modulus is

[0080] (Equation 7)

[0081] If let | G If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, meaning there is more than one frequency that satisfies the condition. G |=0, thereby enabling a multi-section λ / 4 stepped impedance transformer to widen the operating bandwidth.

[0082] The reason why multi-stage impedance transformers can broaden the matching bandwidth can be understood as follows: N Impedance converters have N Characteristic impedance value, N +1 connecting surface, correspondingly there are N +1 reflected wave. These reflected waves return to... T At the zero-plane, the waves are superimposed with a certain phase. Since there are many reflected waves and the amplitude of each reflected wave is very small, the result of superposition is that some waves will always cancel each other out or partially cancel each other out. Therefore, the total reflected wave can maintain a small value over a wider frequency band. This λ / 4 step impedance transformation method achieves better impedance matching over a wider frequency band.

[0083] Optionally, based on characteristic impedance Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient, including:

[0084] The local voltage reflection coefficient is determined using the following formula:

[0085]

[0086]

[0087]

[0088] Wherein, the wavelength of the electromagnetic wave is λ, and the length of each step in the transmission line is λ / 4. G 0、 G 1. G 2 represents the first step reference plane. T Local voltage reflection coefficient at 0, second step reference planeT Local voltage reflection coefficient on 1 and third step reference plane T The local voltage reflection coefficient on line 2, and the characteristic impedances of the two λ / 4 transmission lines are respectively... Z 1. Z 2, and Z L > Z 2> Z 1> Z 0.

[0089] Optionally, determining the total voltage reflection coefficient based on the local voltage reflection coefficient includes:

[0090] For a two-stage stepped impedance transformer, the total voltage reflection coefficient of the two-stage stepped impedance transformer is determined as follows:

[0091]

[0092] Among them, U r U is the voltage across λ / 4 of the two stepped impedance transformers. i For the total voltage, e -j2θ The second step reference plane T The phase lag introduced by the reflected voltage wave after traveling different distances, e -j4θ The third step reference plane T 2. Phase lag introduced by the voltage reflected wave traveling different distances.

[0093] Optionally, determining the total voltage reflection coefficient based on the local voltage reflection coefficient further includes:

[0094] for N For an N-section stepped impedance transformer, the total voltage reflection coefficient of the N-section stepped impedance transformer is determined as follows:

[0095]

[0096] in, T 0、 T 1. T 2…, is the step reference plane, totaling ( N +1) items, G 0= G N , G 1= G N-1 ...to select the local reflection coefficient for symmetry.

[0097] Optionally, determining the total voltage reflection coefficient based on the local voltage reflection coefficient further includes:

[0098] for NFor N-section stepped impedance transformers, determine the magnitude of the total voltage reflection coefficient of the N-section stepped impedance transformers as follows:

[0099]

[0100] If let | G If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, when more than one frequency satisfies the condition. G |=0, enabling multi-section λ / 4 stepped impedance transformers to widen the operating bandwidth.

[0101] This overcomes the limitations of direct matching by using a progressive, stepped impedance matching method for the sensing element to achieve a good match between the partial discharge UHF signal sensing element and the subsequent RF processing circuit, thereby reducing the attenuation of the partial discharge UHF signal caused by impedance mismatch. The bandwidth of the partial discharge high-frequency signal reaches 300MHz. Z ~3GH Z However, conventional impedance transformation techniques are suitable for impedance matching at a single frequency point and are difficult to adapt to impedance matching problems over a wider frequency band. This paper aims to solve the challenge of impedance transformation over a wide frequency band.

[0102] According to another aspect of the present invention, a λ / 4 stepped impedance transformation system is also provided, comprising:

[0103] The two-port network module 410 is used to connect a λ / 4 stepped impedance transformation two-port network at the impedance mismatch point between the load impedance of the partial discharge ultra-high frequency and the characteristic impedance of the partial discharge ultra-high frequency measurement system, wherein the load impedance is the wave impedance.

[0104] The local voltage reflection coefficient determination module 420 is used to determine the local voltage reflection coefficient based on the characteristic impedance. Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient;

[0105] The total voltage reflection coefficient determination module 430 is used to determine the total voltage reflection coefficient based on the local voltage reflection coefficient;

[0106] The widening operating bandwidth module 440 is used to widen the operating bandwidth of the λ / 4 stepped impedance transformer according to the total voltage reflection coefficient.

[0107] Optionally, the module 420 for determining the local voltage reflection coefficient includes:

[0108] The local voltage reflection coefficient determination submodule is used to determine the local voltage reflection coefficient according to the following formula:

[0109]

[0110]

[0111]

[0112] Wherein, the wavelength of the electromagnetic wave is λ, and the length of each step in the transmission line is λ / 4. G 0、 G 1. G 2 represents the first step reference plane. T Local voltage reflection coefficient at 0, second step reference plane T Local voltage reflection coefficient on 1 and third step reference plane T The local voltage reflection coefficient on line 2, and the characteristic impedances of the two λ / 4 transmission lines are respectively... Z 1. Z 2, and Z L > Z 2> Z 1> Z 0.

[0113] Optionally, the total voltage reflection coefficient determination module 430 includes:

[0114] The submodule for determining the total voltage reflection coefficient of two stepped impedance transformers is used to determine the total voltage reflection coefficient of the two stepped impedance transformers as follows:

[0115]

[0116] Among them, U r U is the voltage across λ / 4 of the two-section stepped impedance transformer. i For the total voltage, e -j2θ The second step reference plane T The phase lag introduced by the reflected voltage wave after traveling different distances, e -j4θ The third step reference plane T 2. Phase lag introduced by the voltage reflected wave traveling different distances.

[0117] Optionally, the module 430 for determining the total voltage reflection coefficient also includes:

[0118] Determine the N total voltage reflection coefficient submodules for use in... N For an N-section stepped impedance transformer, the total voltage reflection coefficient of the N-section stepped impedance transformer is determined as follows:

[0119]

[0120] in, T 0、 T 1.T 2…, is the step reference plane, totaling ( N +1) items, G 0= G N , G 1= G N-1 ...to select the local reflection coefficient for symmetry.

[0121] Optionally, the module 430 for determining the total voltage reflection coefficient also includes:

[0122] Determine the magnitude submodule of the total voltage reflection coefficient for N sections. N For N-section stepped impedance transformers, determine the magnitude of the total voltage reflection coefficient of the N-section stepped impedance transformers as follows:

[0123]

[0124] If let | G If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, when more than one frequency satisfies the condition. G |=0, enabling multi-section λ / 4 stepped impedance transformers to widen the operating bandwidth.

[0125] The λ / 4 stepped impedance transformation system 400 of one embodiment of the present invention corresponds to the λ / 4 stepped impedance transformation method 100 of another embodiment of the present invention, and will not be described again here.

[0126] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0127] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Picture one One or more processes and / or boxes Picture one A device that provides the functions specified in one or more boxes.

[0128] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Picture one One or more processes and / or boxes Picture one The function specified in one or more boxes.

[0129] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Picture one One or more processes and / or boxes Picture one The steps of the function specified in one or more boxes.

[0130] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0131] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A λ / 4 stepped impedance transformation method, characterized in that, include: A two-port network with λ / 4 stepped impedance transformation is connected at the impedance mismatch point between the load impedance of the UHF partial discharge and the characteristic impedance of the UHF partial discharge measurement system. The load impedance is the wave impedance. Based on characteristic impedance Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient; The total voltage reflection coefficient is determined based on the local voltage reflection coefficient. Based on the total voltage reflection coefficient, the operating bandwidth of the λ / 4 stepped impedance converter is widened; Based on characteristic impedance Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient, including: The local voltage reflection coefficient is determined using the following formula: , , Wherein, the wavelength of the electromagnetic wave is λ, and the length of each step in the transmission line is λ / 4. Г 0、 Г 1. Г 2 represents the first step reference plane. T Local voltage reflection coefficient at 0, second step reference plane T Local voltage reflection coefficient on 1 and third step reference plane T The local voltage reflection coefficient on 2, and the characteristic impedances of the two λ / 4 transmission lines are respectively Z 1. Z 2, and Z L > Z 2> Z 1> Z 0; The total voltage reflection coefficient is determined based on the local voltage reflection coefficient, including: For a two-stage stepped impedance transformer, the total voltage reflection coefficient of the two-stage stepped impedance transformer is determined as follows: , among which, U r U is the voltage across λ / 4 of the two-section stepped impedance transformer. i For the total voltage, e -j2θ The second step reference plane T The phase lag introduced by the reflected voltage wave after traveling different distances, e -j4θ The third step reference plane T 2. Phase lag introduced by the voltage reflected wave traveling different distances.

2. The method according to claim 1, characterized in that, Determining the total voltage reflection coefficient based on the local voltage reflection coefficient also includes: for N For an N-section stepped impedance transformer, the total voltage reflection coefficient of the N-section stepped impedance transformer is determined as follows: ,in, Г 0= Г N , Г 1= Г N-1 ...to select the local reflection coefficient for symmetry, The phase angle, For the ladder reference plane T N+1 Phase lag introduced by the reflected wave of the voltage traveling at different distances.

3. The method according to claim 2, characterized in that, Determining the total voltage reflection coefficient based on the local voltage reflection coefficient also includes: for N For N-section stepped impedance transformers, determine the magnitude of the total voltage reflection coefficient of the N-section stepped impedance transformers as follows: If let | Г If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, when more than one frequency satisfies the condition. Г |=0, enabling multi-section λ / 4 stepped impedance transformers to widen the operating bandwidth.

4. A λ / 4 stepped impedance transformation system, characterized in that, include: A two-port network module is used to connect a λ / 4 stepped impedance transformation two-port network at the impedance mismatch point between the load impedance of the partial discharge ultra-high frequency and the characteristic impedance of the partial discharge ultra-high frequency measurement system, wherein the load impedance is the wave impedance. The module for determining the local voltage reflection coefficient is used based on the characteristic impedance. Z 0. Wave impedance Z L and the characteristic impedance of the two λ / 4 transmission lines Z 1. Z 2. Determine the local voltage reflection coefficient; The module for determining the total voltage reflection coefficient is used to determine the total voltage reflection coefficient based on the local voltage reflection coefficient. The operating bandwidth widening module is used to widen the operating bandwidth of the λ / 4 stepped impedance transformer according to the total voltage reflection coefficient. The module for determining the local voltage reflection coefficient includes: The local voltage reflection coefficient determination submodule is used to determine the local voltage reflection coefficient according to the following formula: , , Wherein, the wavelength of the electromagnetic wave is λ, and the length of each step in the transmission line is λ / 4. Г 0、 Г 1. Г 2 represents the first step reference plane. T Local voltage reflection coefficient at 0, second step reference plane T Local voltage reflection coefficient on 1 and third step reference plane T The local voltage reflection coefficient on line 2, and the characteristic impedances of the two λ / 4 transmission lines are respectively... Z 1. Z 2, and Z L > Z 2> Z 1> Z 0; The module for determining the total voltage reflection coefficient includes: The submodule for determining the total voltage reflection coefficient of two stepped impedance transformers is used to determine the total voltage reflection coefficient of the two stepped impedance transformers as follows: , among which, U r U is the voltage across λ / 4 of the two-section stepped impedance transformer. i For the total voltage, e -j2θ The second step reference plane T The phase lag introduced by the reflected voltage wave after traveling different distances, e -j4θ The third step reference plane T 2. Phase lag introduced by the voltage reflected wave traveling different distances.

5. The system according to claim 4, the module for determining the total voltage reflection coefficient, further includes: Determine the N total voltage reflection coefficient submodules for use in... N For an N-section stepped impedance transformer, the total voltage reflection coefficient of the N-section stepped impedance transformer is determined as follows: ,in, Г 0= Г N , Г 1= Г N-1 ...to select the local reflection coefficient for symmetry, The phase angle, For the ladder reference plane T N+1 Phase lag introduced by the reflected wave of the voltage traveling at different distances.

6. The system according to claim 5, characterized in that, The module for determining the total voltage reflection coefficient also includes: Determine the magnitude submodule of the total voltage reflection coefficient for N sections. N For N-section stepped impedance transformers, determine the magnitude of the total voltage reflection coefficient of the N-section stepped impedance transformers as follows: If let | Г If |=0, then the above expression cos θ There are multiple solutions that satisfy the condition, when more than one frequency satisfies the condition. Г |=0, enabling multi-section λ / 4 stepped impedance transformers to widen the operating bandwidth.

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