Method for acquiring passive intermodulation interference caused by oxidation corrosion of base station antenna

Abstract

The invention discloses a method for acquiring passive intermodulation interference caused by oxidation corrosion of a base station antenna, and aims to further supplement and improve the existing research so as to quantitatively evaluate the passive intermodulation interference generated after the oxidation corrosion of the base station antenna. An analysis object is set as the side surface of a microstrip line conductor, firstly, the amplitude coefficient AD2 of voltage of each point in the lower edge area of the side surface of an unoxidized and corroded microstrip line under the action of a single carrier signal is determined, and then after it is determined that the microstrip line is oxidized and corroded, the amplitude coefficient AD2 of voltage of each point is determined. According to the method, the tunneling current density JMIM and the total tunneling current IMIM of the oxidation corrosion areas are obtained according to the average voltage value of the oxidation corrosion areas, and on the basis, the third-order passive intermodulation voltage V3rd-PIM (t) is calculated, so that the passive intermodulation interference generated after oxidation corrosion of the base station antenna is quantitatively evaluated.

Description

Technical Field

[0001] This invention belongs to the field of base station antenna maintenance technology, and more specifically, relates to a method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas. Background Technology

[0002] As a crucial component of wireless communication systems, base station antennas bear the core responsibility of transmitting and receiving electromagnetic waves into space. Unlike indoor electronic devices, base station antennas are exposed to complex and variable outdoor environments for extended periods, making them susceptible to oxidation and corrosion. For example, under high temperature and high humidity conditions, water films easily condense on the surface of the metal components of base station antennas. This phenomenon accelerates the electrochemical oxidation and corrosion process of the metal components, leading to a deterioration of their electrical properties, such as conductivity.

[0003] Furthermore, with the commercial deployment of 5G base stations and the in-depth research of 6G mobile communication technology, mobile communication frequencies are continuously increasing towards millimeter wave and even terahertz bands. The increase in communication frequency causes the transmitted signal current to be more concentrated on the surface of the metal carrier. Therefore, in-depth research on the impact of base station antenna oxidation and corrosion on the integrity of transmitted signals has become a critical issue that urgently needs to be addressed. Among these issues, passive intermodulation (PIM) interference, especially its third-order intermodulation, is difficult to filter out due to its proximity to the communication carrier frequency and its high amplitude energy, making it a challenging and hot research topic.

[0004] Chinese invention patent CN105071048B, authorized on December 22, 2017, discloses a method for determining passive intermodulation in a mesh reflector antenna. This method uses n carrier waves of different frequencies fed into an equivalent model of the mesh reflector antenna to calculate the nonlinear currents of each order of passive intermodulation. Chinese invention patent CN117993258A, published on May 7, 2024, discloses a method for simulating transmission line intermodulation by substituting the current density solution into a nonlinear function. This method substitutes the linear current density solution into a nonlinear transfer function for intermodulation calculation, achieving general nonlinear modeling and intermodulation prediction. In the Chinese invention patent application published on May 24, 2024, with publication number CN118074835A, a mathematical prediction method for passive intermodulation interference of high-speed signals was disclosed. This method combines the time-domain current expression of nonlinear interference of high-speed signals by electronic communication devices, and verifies the relevant characteristics of passive intermodulation interference of high-speed signals through a mathematical model of passive intermodulation and experimental tests.

[0005] Previous studies on passive intermodulation interference (PMI) have often used current density distribution as a starting point, but their methods are often limited to idealized deterministic models or assumptions about known nonlinear components. However, for base station antennas deployed in complex natural environments, the passive intermodulation sources exhibit significant dynamic evolution characteristics due to the time-varying nature of environmental factors during the oxidation and corrosion of the metal conductors. Theoretical research on this dynamic evolution mechanism is currently lacking. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas, so as to achieve quantitative evaluation of passive intermodulation interference generated after oxidation and corrosion of base station antennas.

[0007] To achieve the above-mentioned objective, the present invention provides a method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas, characterized by comprising the following steps:

[0008] (1) Establish the microstrip line coordinate system of the base station antenna and determine the coordinates of the four vertices of the microstrip line conductor side surface.

[0009] A three-dimensional coordinate system is established with the origin at the point below the center point of the microstrip line signal access terminal in the width direction, and at the lower surface of the dielectric substrate and the upper surface of the ground plane. The width direction is the x-axis, the height direction is the y-axis, and the length direction is the z-axis. This gives the coordinates of the four vertices of the microstrip line conductor's x-axis side surface located on the upper surface of the dielectric substrate, A(x0, h...). d ,0), B(x0,y0,0), C(x0,y0,z0), D(x0,h d ,z0), where points A and B are the lower and upper corners of the microstrip line conductor's x-axis side surface at the microstrip line signal input end, respectively, and points C and D are the upper and lower corners of the microstrip line conductor's x-axis side surface at the microstrip line signal distal end, respectively, h d The thickness of the dielectric substrate;

[0010] (2) Determine the lower edge of the microstrip conductor's x-axis side surface (x=x0, y=h) under the action of a single carrier signal. d Within the region (0≤z≤z0), the amplitude coefficient AD2 of the voltage at each point is:

[0011] 2.1) Take N measurement points between points A and D on the side surface of the microstrip conductor along the x-axis direction. The distance between each measurement point is z0 / N. Then the coordinates of the nth measurement point are (x0, h). d ,z n ), where z n = n × z0 / N, n = 1, 2, ..., N;

[0012] 2.2) After applying a single carrier signal to the microstrip line, the voltage amplitude V at n measurement points is measured using a voltage probe. Measure (x0,h d ,z n The average measured voltage amplitude is obtained by summing the voltage amplitudes at n measurement points and then averaging them.

[0013]

[0014] 2.3) Calculate the amplitude coefficient AD2:

[0015]

[0016] Where, k x Here are the tangential cutoff wavenumbers distributed along the x-axis:

[0017] k x =kn s cosa s

[0018] k and n s These represent the wave number and effective refractive index in free space, respectively. s This represents the angle between the wave vector and the x-axis;

[0019] For the dielectric substrate y = h d Regional normal cutoff wavenumber:

[0020]

[0021] ω is the angular frequency of the applied single carrier signal, μ and ε are the permeability and dielectric constant of the substrate material, respectively, and β is the propagation constant;

[0022] (3) Determine the oxidation and corrosion regions (x=x0, h) on the x-axis side surface of the microstrip line conductor after oxidation and corrosion. d Average voltage value (≤y≤y0, 0≤z≤z0)

[0023]

[0024] in:

[0025]

[0026] Where Δz is the width of the oxidation corrosion region, For the normal cutoff wavenumber of the microstrip conductor's x-axis side surface (h < y ≤ y0):

[0027]

[0028] Where μ0 and ε0 are the vacuum permeability and vacuum permittivity, respectively;

[0029] (4) Obtain the tunneling current density J in the oxidation and corrosion region of the microstrip conductor's side surface along the x-axis direction. MIM :

[0030]

[0031] in:

[0032]

[0033] Where: m is the effective mass of the electron, e is the electron charge, and h is Planck's constant. This is the Fermi level, where E is the electron energy and k is the energy level. B Where is Boltzmann's constant, and T is the absolute temperature. To reduce Planck's constant, The average barrier height;

[0034] (5) The total tunneling current I was calculated. MIM :

[0035] I MIM =J MIM ·A total

[0036] Among them, A total This represents the total area of ​​oxidation and corrosion.

[0037] (6) Calculate the third-order passive intermodulation voltage V caused by M different carrier signals in the corrosion region of the microstrip line after oxidation corrosion. 3rd-PIM (t):

[0038]

[0039] Where g3 are third-order coefficients, I MIM,i ,I MIM,j The total tunneling currents fi and fj of the i-th and j-th carrier signals obtained according to steps (2) to (5) are respectively. i ,f j and represent the frequencies of the i-th and j-th carrier signals, respectively.

[0040] The objective of this invention is achieved as follows:

[0041] This invention provides a method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas. The aim is to further supplement and improve existing research, enabling a quantitative assessment of passive intermodulation interference generated after oxidation and corrosion of base station antennas. The analysis object of this invention is set as the side surface of a microstrip line conductor. First, the amplitude coefficient AD2 of the voltage at each point in the lower edge region of the side surface of the unoxidized microstrip line under the action of a single carrier signal is determined. Then, the average voltage value of each oxidation and corrosion region is determined after the microstrip line undergoes oxidation and corrosion. This allows us to obtain the tunneling current density J in the oxidized and corroded region. MIM Total tunneling current I MIM Based on this, the third-order passive intermodulation voltage V was calculated. 3rd-PIM (t), thus enabling a quantitative assessment of the passive intermodulation interference generated by the oxidation and corrosion of base station antennas. Attached Figure Description

[0042] Figure 1 This is a flowchart of a specific implementation of the method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas according to the present invention;

[0043] Figure 2 It is a two-dimensional coordinate graph of a microstrip line;

[0044] Figure 3 It is a three-dimensional coordinate graph of a microstrip line;

[0045] Figure 4 yes Figure 1 The flowchart for step S2, which determines the amplitude coefficient AD2 of the voltage at each point, is shown below. Detailed Implementation

[0046] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0047] This invention aims to further supplement and improve existing research, and proposes a method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas, so as to realize the quantitative assessment of passive intermodulation interference generated by oxidation and corrosion of base station antennas.

[0048] In the microstrip line structure involved in this invention, the current distribution in the microstrip line conductor exhibits non-uniform characteristics. Due to the skin effect, the current is mainly concentrated on the surface of the microstrip line conductor, particularly on the lower and side surfaces. Since oxidation corrosion typically occurs on the side surface, this invention focuses on the side surface of the microstrip line conductor. Due to oxidation corrosion, the chemical composition of the material on the side surface of the microstrip line conductor changes, leading to alterations in the microscopic barrier characteristics, inducing tunneling current, and ultimately manifesting as a passive intermodulation effect at the macroscopic level.

[0049] To facilitate the description of the analysis method, the structural dimensions of the microstrip line and the establishment of the relevant coordinate system will be explained below.

[0050] Figure 1 This is a flowchart of a specific implementation of the method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas according to the present invention.

[0051] In this embodiment, as Figure 1 As shown, the method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas according to the present invention includes the following steps:

[0052] Step S1: Establish the microstrip line coordinate system for the base station antenna and determine the coordinates of the four vertices of the microstrip line conductor side surface.

[0053] A three-dimensional coordinate system is established with the origin at the point below the center point of the microstrip line signal access terminal in the width direction, and at the lower surface of the dielectric substrate and the upper surface of the ground plane. The width direction is the x-axis, the height direction is the y-axis, and the length direction is the z-axis. This gives the coordinates of the four vertices of the microstrip line conductor's x-axis side surface located on the upper surface of the dielectric substrate, A(x0, h...). d ,0), B(x0,y0,0), C(x0,y0,z0), D(x0,h d ,z0), where points A and B are the lower and upper corners of the microstrip line conductor's x-axis side surface at the microstrip line signal input end, respectively, and points C and D are the upper and lower corners of the microstrip line conductor's x-axis side surface at the microstrip line signal distal end, respectively, h d The thickness of the dielectric substrate.

[0054] In this embodiment, as Figure 2 , 3 As shown, the overall structure of the microstrip line consists of three parts: a conductor, a dielectric substrate (thickness h), and a dielectric substrate. d ), and grounding plate. In this embodiment, as Figure 3As shown, the research object is the right surface of the microstrip conductor (red area). The analysis principle is the same for both the left and right surfaces. The coordinates of the four vertices of the right surface are set as: A(x0,h,0), B(x0,y0,0), C(x0,y0,z0), D(x0,h,z0). The difference between the left and right surfaces lies in the different coordinates of the left and right edges of the x-axis. In this implementation, positive coordinates are taken for the right surface, and negative coordinates are taken for the left surface.

[0055] Step S2: Determine the lower edge of the microstrip line conductor's x-axis side surface (x=x0, y=h) under the action of a single carrier signal. d Within the region (0≤z≤z0), the amplitude coefficient AD2 of the voltage at each point is:

[0056] Step S2.1: Take N measurement points between the straight line containing point A and point D on the side surface of the microstrip conductor along the x-axis direction. The distance between each measurement point is z0 / N. Then the coordinates of the nth measurement point are (x0, h). d ,z n ), where z n = n × z0 / N, n = 1, 2, ..., N;

[0057] Step S2.2: After applying a single carrier signal to the microstrip line, measure the voltage amplitude V at n measurement points using a voltage probe. Measure (x0,h d ,z n To improve measurement accuracy, the voltage amplitudes at n measurement points are summed and averaged to obtain the average measured voltage amplitude.

[0058]

[0059] Step S2.3: Calculate the amplitude coefficient AD2:

[0060]

[0061] Where, k x Here are the tangential cutoff wavenumbers distributed along the x-axis:

[0062] k x =kn s cosa s (3)

[0063] k and n s These represent the wave number and effective refractive index in free space, respectively. s This represents the angle between the wave vector and the x-axis;

[0064] For the dielectric substrate y = h d Region normal cutoff wavenumber:

[0065]

[0066] β is the propagation constant, and ω is the angular frequency of the applied single - carrier signal.

[0067] Apply a single - carrier signal to the microstrip line that has not undergone oxidation corrosion, and the specific form is as follows:

[0068] I single (t) = Icos(2πft)(5)

[0069] Among them, I is the amplitude coefficient of the single - carrier signal, f is the frequency of the single - carrier signal, and the conversion relationship between the frequency f and the angular velocity ω is f = ω / 2π.

[0070] By analyzing the boundary conditions involved in the conductor - side surface of the microstrip line, further calculate the specific form of the longitudinal electric - field component E z :

[0071]

[0072] Under the action of the carrier signal, a specific electric - field and magnetic - field distribution is formed around the microstrip - line structure. The theoretical expression of the electric field E z on the conductor - side surface is:

[0073]

[0074] Among them, AD2 represents the amplitude coefficient, j is the imaginary unit, which is used to process the phase information of the electromagnetic - field components in phasor analysis, and β is the propagation constant.

[0075] k x represents the tangential cut - off wave number distributed along the x - axis, represents the normal cut - off wave number of the right - hand side surface (h d <y ≤ y0) of the microstrip - line conductor, ω represents the angular frequency of the carrier signal, k and n s respectively represent the wave number in free space and the effective refractive index, a s is the angle between the wave vector and the x - axis, and μ0 and ε0 respectively represent the vacuum permeability and the vacuum permittivity.

[0076] represents the normal cut - off wave number of the dielectric - substrate region (y = h d )), and μ and ε respectively represent the permeability and the permittivity of the dielectric - substrate material.

[0077] Based on the longitudinal electric - field component E z , derive the non - oxidized - corrosion microstrip line at (x = x0, y = h dThe theoretical expression for the voltage value at each point in the region (0≤z≤z0):

[0078]

[0079] To quantify the amplitude coefficient AD2 required by the theoretical model in the above formula (10), the unoxidized and corroded microstrip line is calculated in (x=x0, y=h d The voltage values ​​at each point within the region (0≤z≤z0) will be applied by the present invention to the voltage values ​​at each point. single (t) Experimental measurements were performed on an unoxidized and corroded microstrip line under excitation. The specific voltage amplitude obtained from the experiment was fitted to the theoretical expression, and the equation was used... The amplitude coefficient AD2 is calculated, as detailed in steps S2.1 to S2.3 above.

[0080] Step S3: Each oxidation corrosion region (x=x0,h) d The voltage values ​​for (≤y≤y0, 0≤z≤z0) are expressed as:

[0081]

[0082] Thus, after the microstrip line undergoes oxidation and corrosion, the oxidation and corrosion regions (x=x0,h) on the x-axis side surface of the microstrip line conductor are as follows: d Average voltage value (≤y≤y0, 0≤z≤z0) for:

[0083]

[0084] in:

[0085]

[0086] Where Δz is the width of the oxidation corrosion region, For the normal cutoff wavenumber of the microstrip conductor's x-axis side surface (h < y ≤ y0):

[0087]

[0088] When oxidation and corrosion occur on the conductor side surface, the resulting MIM (Metal-Insulator-Metal) structure induces a tunneling effect, which in turn generates a nonlinear tunneling current. This is the main source of PIM after oxidation and corrosion of the microstrip line, as derived from equation (12). The value can be used to calculate the tunneling current in each oxidation and corrosion zone.

[0089] Step S4: Obtain the tunneling current density J in the oxidation and corrosion region of the microstrip conductor's x-axis side surface. MIM :

[0090]

[0091] in:

[0092]

[0093] Where: m is the effective mass of the electron, e is the electron charge, and h is Planck's constant. The Fermi level describes the highest energy level of an electron at a specific temperature, where E is the electron energy and k is the energy level. B Where is Boltzmann's constant, T is absolute temperature in Kelvin (K), and h is the reduced Planck constant. The conversion relationship between h and Planck's constant is as follows: The average barrier height represents the degree to which the insulating layer impedes electron tunneling.

[0094] To ensure the accuracy of the tunneling current density calculation, in this embodiment, formula (15) is solved by numerical integration using Simpson's formula, specifically in the form of:

[0095]

[0096] Among them, E l To reduce 0 to The value of the l-th point, which is divided into L points according to the interval ΔE.

[0097] Step S5: Calculate the total tunneling current I MIM :

[0098] I MIM =J MIM ·A total (twenty one)

[0099] Among them, A total This represents the total area of ​​oxidation and corrosion.

[0100] The expression for the change of oxidation corrosion point density N(t) per unit area with time is as follows:

[0101] N(t)=N s [1-exp(-(kt) n )](twenty two)

[0102] Where, N s The saturated corrosion point density is defined as the maximum number of corrosion points that can be achieved per unit area, where k represents the rate constant and n represents the Avrami exponent.

[0103] When the area of ​​each corrosion point is 'a', the total area of ​​corrosion points per unit area can be expressed as:

[0104] A = aN(t) (23)

[0105] In the event of oxidation corrosion, the total tunneling current on the right side surface of the conductor is:

[0106] A total =A·S (24)

[0107] I MIM =J MIM ·A total (25)

[0108] Where S represents the surface area of ​​the right side of the conductor.

[0109] Step S6: Calculate the third-order passive intermodulation voltage V caused by M different carrier signals in the etched region of the microstrip line after oxidation and etching. 3rd-PIM (t):

[0110]

[0111] Where g3 are third-order coefficients, I MIM,i ,I MIM,j f represents the total tunneling current obtained by the i-th and j-th carrier signals according to steps S2 to S5, respectively. i ,f j and represent the frequencies of the i-th and j-th carrier signals, respectively.

[0112] When multiple carrier signals exist in a microstrip line, these signals can be represented as:

[0113]

[0114] Among them, I i and f i This represents the amplitude and frequency of the i-th carrier signal.

[0115] After oxidation and corrosion, the tunneling current formed by different carrier signals in the corroded region of the microstrip line can be expressed as:

[0116]

[0117] Wherein, I of the i-th carrier signal MIM,i It can be calculated using formula (19), that is, obtained by following steps S2 to S5.

[0118] Nonlinear tunneling voltage V MIM (t) can be expressed as tunneling current I using Taylor series expansion. S-MIM Polynomial function of (t):

[0119] V MIM (t)=g0+g1I S-MIM (t)+g2I S-MIM (t) 2 +g3IS-MIM (t) 3 +…(29)

[0120] Where g0, g1, g2, g3... represent the coefficients of the corresponding order.

[0121] Substituting equation (28) into equation (29) and simplifying, we can obtain the third-order passive intermodulation voltage, which is as follows:

[0122]

[0123] Example

[0124] To better understand the feasibility of the above scheme and method, the present invention will be further explained below using a two-tone signal as the excitation source.

[0125] When a two-tone signal is used as the input signal source, its input current can be expressed as:

[0126] I in (t)=I in1 cos(2πf1t)+I in2 cos(2πf²t)(31)

[0127] Among them, I in1 I in2 f1 and f2 represent the current amplitude of the two-tone signal, and f1 and f2 represent the frequencies of the two-tone signal.

[0128] Nonlinear tunneling voltage V generated in the oxidation and corrosion region of the microstrip line MIM (t), which can be expressed as tunneling current I using Taylor series expansion. S-MIM Polynomial function of (t):

[0129] V MIM (t)=g0+g1I S-MIM (t)+g2I S-MIM (t) 2 +g3I S-MIM (t) 3 +…(32)

[0130] Among them, I S-MIM (t)=I MIM,1 cos(2πf1t)+I MIM,2 cos(2πf2t), I MIM,1 and I MIM,2 Calculated from equation (21), g0, g1, g2, g3… represent the coefficients of the corresponding order.

[0131] Will I S-MIM Substituting the specific form of (t) into equation (29) and simplifying, we can obtain the third-order passive intermodulation voltage, which has the following specific form:

[0132]

[0133] This embodiment establishes an accurate tunneling current model and combines it with numerical calculation methods to quantitatively predict the third-order PIM voltage value. This will help to deepen the understanding of the contribution mechanism of oxidation corrosion to PIM performance and provide theoretical guidance and design basis for engineering practice.

[0134] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas, characterized in that, Includes the following steps: (1) Establish the microstrip line coordinate system of the base station antenna and determine the coordinates of the four vertices of the microstrip line conductor side surface. A three-dimensional coordinate system is established with the origin at the point below the center point of the microstrip line signal access terminal in the width direction, and at the lower surface of the dielectric substrate and the upper surface of the ground plane. The width direction is the x-axis, the height direction is the y-axis, and the length direction is the z-axis. This gives the coordinates of the four vertices of the microstrip line conductor's x-axis side surface located on the upper surface of the dielectric substrate, A(x0, h...). d ,0), B(x0,y0,0), C(x0,y0,z0), D(x0,h d ,z0), where points A and B are the lower and upper corners of the microstrip line conductor's x-axis side surface at the microstrip line signal input end, respectively, and points C and D are the upper and lower corners of the microstrip line conductor's x-axis side surface at the microstrip line signal distal end, respectively, h d The thickness of the dielectric substrate; (2) Determine the lower edge of the microstrip conductor's x-axis side surface (x=x0, y=h) under the action of a single carrier signal. d Within the region (0≤z≤z0), the amplitude coefficient AD2 of the voltage at each point is: 2.1) Take N measurement points between points A and D on the side surface of the microstrip conductor along the x-axis direction. The distance between each measurement point is z0 / N. Then the coordinates of the nth measurement point are (x0, h). d ,z n ), where z n = n × z0 / N, n = 1, 2, ..., N; 2.2) After applying a single carrier signal to the microstrip line, the voltage amplitude V at n measurement points is measured using a voltage probe. Measure (x0,h d ,z n The average measured voltage amplitude is obtained by summing the voltage amplitudes at n measurement points and then averaging them. 2.3) Calculate the amplitude coefficient AD2: Where, k x Here are the tangential cutoff wavenumbers distributed along the x-axis: k x =kn s What s k and n s These represent the wave number and effective refractive index in free space, respectively. s This represents the angle between the wave vector and the x-axis; For the dielectric substrate y = h d Regional normal cutoff wavenumber: ω is the angular frequency of the applied single carrier signal, μ and ε are the permeability and dielectric constant of the substrate material, respectively, and β is the propagation constant; (3) Determine the oxidation and corrosion regions (x=x0, h) on the x-axis side surface of the microstrip line conductor after oxidation and corrosion. d Average voltage value (≤y≤y0, 0≤z≤z0) in: Where Δz is the width of the oxidation corrosion region, For the normal cutoff wavenumber of the microstrip conductor's x-axis side surface (h < y ≤ y0): Where μ0 and ε0 are the vacuum permeability and vacuum permittivity, respectively; (4) Obtain the tunneling current density J in the oxidation and corrosion region of the microstrip conductor's side surface along the x-axis direction. MIM : in: Where: m is the effective mass of the electron, e is the electron charge, and h is Planck's constant. This is the Fermi level, where E is the electron energy and k is the energy level. B Here, T is the Boltzmann constant, and T is the absolute temperature. To reduce Planck's constant, The average barrier height; (5) The total tunneling current I was calculated. MIM : I MIM ×J MIM ·A total Among them, A total This represents the total area of ​​oxidation and corrosion. (6) Calculate the third-order passive intermodulation voltage V caused by M different carrier signals in the corrosion region of the microstrip line after oxidation corrosion. 3rd-PIM (t): Where g3 are third-order coefficients, I MIM,i ,I MIM,j The total tunneling currents fi and fj of the i-th and j-th carrier signals obtained according to steps (2) to (5) are respectively. i ,f j and represent the frequencies of the i-th and j-th carrier signals, respectively.

2. The method for obtaining passive intermodulation interference caused by oxidation and corrosion of base station antennas according to claim 1, characterized in that, Step (4) is used to obtain the tunneling current density J in the oxidation and corrosion region of the side surface of the microstrip conductor in the x-axis direction. MIM The numerical integration method using Simpson's formula is employed, and the specific form is as follows: Among them, E l To reduce 0 to The value of the l-th point, which is divided into L points according to the interval ΔE.

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