Methods for measuring the propagation constant of electromagnetic waves in electromagnetic structures

Abstract

This invention discloses a method for measuring the electromagnetic wave propagation constant of an electromagnetic structure. Based on the field values ​​at three equally spaced points, this invention uses analytical expressions incorporating these three field values ​​to represent the phase constant and attenuation constant of a one-dimensional homogeneous or periodic structure. This method is simple, fast, and accurate. It can be applied to both homogeneous and periodic structures; both closed transmission line structures such as waveguides and open transmission lines such as microstrip lines; both waveguide structures of transmission lines and radiating structures of antennas; and both lossless and lossy structures.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic field microwave technology, specifically relating to a method for measuring the propagation constant of electromagnetic waves in electromagnetic structures. Background Technology

[0002] In the field of microwaves and antennas, it is often necessary to measure certain propagation characteristic parameters of electromagnetic waves in electromagnetic structures, such as the propagation constant of electromagnetic waves in a one-dimensional periodic transmission line or a one-dimensional periodic leaky antenna. In the design of microwave components and antennas such as power dividers, phase shifters, filters, and amplifiers, it is often necessary to know the propagation constant of electromagnetic waves within the structure. In electromagnetic structures such as uniform transmission lines, the propagation direction in the transmission line is called the longitudinal direction. In electromagnetic structures such as one-dimensional periodic structures, the periodic direction within the structure is also the longitudinal direction, i.e., the propagation direction of the electromagnetic wave. The propagation constant of electromagnetic waves in an electromagnetic structure is the most important parameter characterizing the propagation characteristics of electromagnetic waves; the propagation constant includes the phase constant and the attenuation constant.

[0003] Currently, most methods for measuring the propagation constant of electromagnetic waves in electromagnetic structures are based on scattering parameter measurement. This involves first measuring the scattering parameters of one or more microwave network elements within an electromagnetic structure, then transforming these parameters into network transfer parameters. This leads to eigenvalue equations with the propagation constant as the unknown quantity. Solving these eigenvalue equations yields the propagation constant of the electromagnetic wave within the electromagnetic structure. This method relies on the assumption that the electromagnetic characteristics of the electromagnetic structure elements can be represented by a microwave network. However, some electromagnetic structure elements cannot be represented using microwave networks. For example, if an element is a perfectly serrated periodic waveguide, the lack of uniform waveguide segments makes it impossible to define equivalent voltages and currents, thus preventing its representation by a microwave network. Besides measuring the scattering parameters of electromagnetic structure elements, the driving mode solver in electromagnetic field simulation software can also be used to obtain these parameters. Additionally, eigenmode solvers can be used to obtain the phase constant of the electromagnetic structure. However, eigenmode solvers cannot obtain the attenuation constant of the stopband; therefore, they cannot provide the complete propagation constant of the electromagnetic wave within the electromagnetic structure. Furthermore, some commercial software's eigenmode solvers do not reflect the effect of losses in their calculated phase constants. Uniform or periodic transmission lines are typically lossy, and the radiation loss in leaky antennas is even greater. On the other hand, many transmission lines are open structures, such as microstrip lines, coplanar waveguides, or slot lines; antennas, however, are always open structures. Additionally, the phase difference set between periodic boundaries by the eigenmode solver cannot exceed 180 degrees, and it can only solve for the phase constant of the first passband of a mode, unable to solve for the phase constants of higher frequency multiple passbands. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for measuring the electromagnetic wave propagation constant of an electromagnetic structure, which is insufficient in existing technologies where scattering parameters must be based on microwave networks. This method does not require microwave networks to represent the characteristics of the electromagnetic structure. Such a measurement method is more applicable to various types of electromagnetic structures, including uniform or periodic structures, and lossy or open radiating structures, for calculating the electromagnetic wave propagation constant.

[0005] To solve the above technical problems, the present invention provides the following technical solution: a method for measuring the propagation constant of electromagnetic waves in an electromagnetic structure, comprising the following steps:

[0006] S1. In the electromagnetic structure, take a point; the point is defined as the middle point, and take a point on the left and right sides of the middle point along the longitudinal direction at a preset interval p, and define them as the left point and the right point respectively;

[0007] S2. Measure the electric or magnetic field values ​​in any one direction at the three points: the left point, the middle point, and the right point. These values ​​are F. -1 F0 and F1;

[0008] S3. Calculate the complex value a of the middle point based on the field values ​​of the left point, the middle point, and the right point;

[0009] S4. Calculate the intermediate complex number b based on the complex number a;

[0010] S5. Perform deconvolution operation on the phase angle of the intermediate complex number b to obtain the phase change of the calculation interval p;

[0011] S6. Calculate the phase constant β based on the phase change and interval p;

[0012] S7. Calculate the attenuation constant α based on the complex number b and the interval p;

[0013] Furthermore, in the aforementioned step S1, the electromagnetic structure includes: a uniform structure and a periodic structure; the preset interval p is set as follows:

[0014] When the electromagnetic structure is a uniform structure, p is any length not greater than half the length of the entire structure, but it must be ensured that the left point, the middle point, and the right point are all inside the structure.

[0015] When the electromagnetic structure is a periodic structure, p is an integer multiple of the length of the structure's period and is no greater than half the length of the entire structure, but it must be ensured that the left point, the middle point, and the right point are all within the structure.

[0016] Furthermore, in step S3 above, the complex number a is calculated according to the following formula:

[0017]

[0018] Furthermore, in step S4 above, the complex number b is calculated according to the following formula:

[0019]

[0020] Furthermore, step S5 described above specifically involves: performing a deconvolution operation on the phase angle of the complex number b to obtain the phase change at the calculation interval p.

[0021] φ = Phase decoupling (∠b)

[0022] In the formula, ∠b is the phase angle of the complex number b.

[0023] Furthermore, in step S6 above, the phase constant β is calculated according to the following formula:

[0024]

[0025] Furthermore, in step S7 above, the attenuation constant α is calculated according to the following formula:

[0026]

[0027] Furthermore, in step S2 mentioned above, F -1 F0 and F1 are complex field values ​​that include phase.

[0028] Furthermore, in the aforementioned step S2, the field value of any component of the electric or magnetic field in the same direction at the three points—the left point, the middle point, and the right point—is measured using a direct measurement method, an indirect measurement method, or a method calculated by electromagnetic field simulation software.

[0029] Furthermore, the aforementioned method for measuring the propagation constant of electromagnetic waves in a magnetic structure involves two electromagnetic waves propagating in opposite directions simultaneously along the longitudinal direction of the electromagnetic structure. The propagation constants of these two opposite directions are the same, and when represented in a coordinate system, they differ by one sign.

[0030] Compared with the prior art, the beneficial technical effects of the present invention using the above technical solution are as follows:

[0031] This method for measuring the propagation constant of electromagnetic waves in an electromagnetic structure uses complex field values ​​of the electric or magnetic fields measured at three points within the structure. A simple analytical expression yields the propagation constant, including the phase constant and attenuation constant. The method is simple and fast. Its sole premise is the periodicity of the electromagnetic structure, thus theoretically making it an accurate method. This method can obtain the propagation constants for all passbands and stopbands of the structure. It can be applied to both homogeneous and periodic structures; both closed transmission line structures such as waveguides and open transmission lines such as microstrip lines; both waveguide structures of transmission lines and radiating structures of antennas; and both lossless and lossy structures. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method of the present invention.

[0033] Figure 2 This is a schematic diagram of the electromagnetic structure sampling points of the present invention. Detailed Implementation

[0034] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0035] In this invention, various aspects of the invention are described with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. Embodiments of the invention are not limited to those depicted in the drawings. It should be understood that the invention is implemented through any of the various concepts and embodiments described above, as well as the concepts and embodiments described in detail below, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0036] like Figure 1 As shown, the method for measuring the electromagnetic wave propagation constant of an electromagnetic structure includes the following steps:

[0037] S1, Reference Figure 2 In the electromagnetic structure, a point is selected; the point is defined as the middle point, and a point is selected on the left and right sides along the longitudinal direction of the middle point at a preset interval p, and defined as the left point and the right point respectively.

[0038] When the structure is a uniform structure, p is any length not greater than half the length of the entire structure, but it must be ensured that the left point, the middle point, and the right point are all inside the structure.

[0039] When the structure is a periodic structure, p is an integer multiple of the period length of the structure and no more than half of the total length of the structure, but it must be ensured that the left point, the middle point, and the right point are all within the structure.

[0040] S2. Measure the electric or magnetic field values ​​in any one direction at the three points: the left point, the middle point, and the right point. These values ​​are F. -1 F0 and F1. Field value F -1 F0 and F1 must be components of the electric field in the same direction, or components of the magnetic field in the same direction. Field value F -1 F0 and F1 can be measured directly, such as using a near-field probe, or indirectly, or calculated using electromagnetic field simulation software. This invention is not limited to the field value F. -1 The specific measurement methods or calculation tools for F0 and F1.

[0041] S3. Calculate the complex number a based on the field values ​​at the left, middle, and right points:

[0042] S4. Calculate complex number b based on complex number a:

[0043] S5. Perform decoupling on the phase angle of the complex number b to obtain the phase change of the calculation interval p, specifically: φ = phase decoupling (∠b), where ∠b is the phase angle of the complex number b.

[0044] S6. Calculate the phase constant β based on the phase change and interval:

[0045] S7. Calculate the attenuation constant α based on the complex number b and the interval p:

[0046] In step S2 mentioned above, F -1 F0 and F1 are complex field values ​​that include phase.

[0047] An electromagnetic structure can simultaneously contain two electromagnetic waves propagating in opposite directions. The propagation constants of these two directions are actually the same, but if represented in a coordinate system, they differ by one sign.

[0048] Measuring the electric or magnetic field values ​​in any one component of the same direction at three points—left, middle, and right—can be achieved using direct measurement methods, such as near-field probes, indirect measurement methods, or calculations using electromagnetic field simulation software. In this invention, the uniform structure can be considered a periodic structure with an arbitrary period. Because phase decoupling is performed during the calculation process, this invention can calculate not only the propagation constants of the first passband and stopband of the involved mode, but also the propagation constants of multiple passbands and stopbands at higher frequencies.

[0049] An electromagnetic structure can simultaneously contain two electromagnetic waves propagating in opposite directions. The propagation constants of these two directions are actually the same, but if represented in a coordinate system, they differ by one sign.

[0050] When used for a uniform structure, the three points on the left, middle and right sides are spaced at the same interval. This interval can be any size, but it cannot be too small to avoid the field values ​​of the three points being too close, which would result in a large calculation error.

[0051] When used in periodic structures, the three points on the left, middle, and right sides of the longitudinal axis are spaced equidistant. This interval should not be too small to avoid the field values ​​at the three points being too close, resulting in a large calculation error. Therefore, if the period length is relatively small, the interval can be the length of several periods.

[0052] The existence of this invention depends on the periodicity of the structure. Therefore, this invention can also be applied to periodic structures in other technical fields. The embodiments of this invention in the electromagnetic field are not intended to limit its application in other fields, all of which should be included within the scope of protection of this invention. For example, this invention can also be used to measure or calculate the acoustic wave propagation characteristic parameters of a one-dimensional acoustic structure, and it can also be used to measure or calculate the characteristic parameters of electronic waves in a one-dimensional crystal structure.

[0053] While the present invention has been described above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for measuring the propagation constant of electromagnetic waves in an electromagnetic structure, characterized in that, Includes the following steps: S1. In the electromagnetic structure, take a point; the point is defined as the middle point, and take a point on the left and right sides of the middle point along the longitudinal direction at a preset interval p, and define them as the left point and the right point respectively; The electromagnetic structure includes: a uniform structure and a periodic structure; the preset interval p is set as follows: When the electromagnetic structure is a uniform structure, p is any length not greater than half the length of the entire structure, but it must be ensured that the left, middle, and right points are all inside the structure; when the electromagnetic structure is a periodic structure, p is an integer multiple of the period length of the structure, and not greater than half the length of the entire structure, but it must be ensured that the left, middle, and right points are all inside the structure. S2. Measure the electric or magnetic field values ​​in any one direction at the three points: the left point, the middle point, and the right point. These values ​​are F. -1 F0 and F1; the F -1 F0 and F1 are complex field values ​​that include phase; S3. Based on the field values ​​at the left, middle, and right points, calculate the intermediate complex value 'a' using the following formula: ； S4. Calculate the intermediate complex value b based on the complex number a, using the following formula: ; S5. Perform deconvolution on the phase angle of the complex number b to obtain the phase change of the calculation interval p, as shown in the following formula: ， In the formula, Let b be the phase angle of the complex number b; S6. Calculate the phase constant based on the phase change and interval p. The formula is as follows: ; S7. Calculate the attenuation constant based on the complex number b and the interval p. The formula is as follows: .

2. The method for measuring the electromagnetic wave propagation constant of an electromagnetic structure according to claim 1, characterized in that, In step S2, the field value of any component of the electric or magnetic field in the same direction at the three points—left, middle, and right—is measured using a direct measurement method, an indirect measurement method, or a method calculated by electromagnetic field simulation software.

3. The method for measuring the electromagnetic wave propagation constant of a magnetic structure according to claim 1, characterized in that, An electromagnetic structure contains two electromagnetic waves propagating in opposite directions simultaneously. The propagation constants of these two opposite directions are the same, and they differ by one sign in the coordinate system.

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