A composite transmission line design method

Abstract

The present invention relates to the field of microwave technology, and specifically to a composite transmission line design method, wherein the composite transmission line refers to a waveguide plus microstrip transmission line. For this transmission line, the present invention suspends the microstrip line in the air instead of placing it at the bottom of the waveguide, and by optimizing the size of the waveguide cavity, changing the bending angle of the microstrip line, etc., the same transmission efficiency as that of a conventional waveguide can be obtained when the waveguide size is very small. Through this design, the thickness and weight of the antenna are greatly reduced without affecting the radiation efficiency of the antenna, and the cost of the antenna is also greatly reduced.

Description

Technical Field

[0001] The invention relates to the field of microwave technology, and in particular to a composite transmission line design method. Background Art

[0002] With the development of satellite communications, backpack satellite communication terminals are becoming increasingly smaller and lighter to meet the needs of emergency communications and reduce the pressure on the backpackers. However, at the same time, the communication quality cannot deteriorate because the terminals are becoming increasingly smaller and lighter. At present, there are three types of antennas in backpack satellite communication terminals: parabolic dish, waveguide horn, and microstrip antenna. Parabolic dish and waveguide horn are very thick and heavy, which puts great pressure on the backpackers. Microstrip antenna is very light, but the efficiency is very low, and the communication quality is very poor. A composite transmission line design method is needed to solve this problem. Summary of the invention

[0003] The object of the present invention is to provide a composite transmission line design method to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a composite transmission line design method, comprising the following steps: S1. First, it is necessary to construct an equivalent circuit model of the composite transmission line, and then fit multiple sets of lumped circuit parameter values; S2, verify the lumped circuit parameter values ​​and then determine the physical structure parameters; S3. Select the appropriate position of the microstrip in the waveguide, select the thickness of the medium as 0.508mm, there is a microstrip transmission line on the medium, the microstrip transmission line is 400mm, place the microstrip board at the bottom of the waveguide, and use HFSS software simulation calculation to analyze the impact of insertion loss as the microstrip board moves from the bottom to the middle; S4. Selection of dielectric thickness: Place the microstrip plate in the middle of the waveguide and change the dielectric thickness in sequence. The thicknesses are 0.762mm, 0.508mm, 0.254mm, and 0.127mm respectively. Analyze the change trend of insertion loss as the thickness decreases. S5. For the selection of waveguide cavity size, let the waveguide cavity width be a, the depth be h, and the wavelength corresponding to the highest working frequency be λ. Place the microstrip plate in the middle of the waveguide, change the waveguide cavity size in turn, and analyze its influence on insertion loss. S6. Finally, design the corners of the transmission line.

[0005] As a preferred technical solution of the present invention, the model in step S1 will help understand and analyze the electrical characteristics of the transmission line, and then obtain multiple groups of lumped circuit parameter values ​​through fitting, which will be used for subsequent physical structure design.

[0006] As a preferred technical solution of the present invention, in step S2, the fitted lumped circuit parameter values ​​are verified to ensure their effectiveness in practical applications, and the specific parameters of the physical structure, including the dielectric constant and thickness of the dielectric substrate, are determined based on the equivalent circuit model and the lumped circuit parameter values.

[0007] As a preferred technical solution of the present invention, in step S3, the position of the microstrip plate in the waveguide is moved, and the depth of the waveguide is set to h, and the distances of the microstrip plate from the bottom of the waveguide are selected to be 0.125h, 0.25h, 0.375h, and 0.5h.

[0008] As a preferred technical solution of the present invention, in step S5, when the frequency is 19-20G, the width is set to a=3mm, and the depth is gradually increased from h=3mm. It can be found that the standing wave does not change at the beginning, but when h≥0.5λ, the standing wave begins to have high-order harmonics; the depth is gradually reduced from h=3mm, but when h≤0.1λ, the standing wave begins to have high-order harmonics. Assuming the depth is h=3mm, the width is gradually increased from a=3mm, and it can be found that when h≥0.5λ, the standing wave begins to have high-order harmonics, and the width is gradually reduced from a=3mm, and it can be found that when h≤0.1λ, the standing wave begins to have high-order harmonics.

[0009] As the preferred technical solution of the present invention, it is inevitable to encounter corners in step S6. For microstrip antennas, the conventional method is to use chamfering. The following is a comparison between chamfering and arc. Through HFSS software calculation, it is found that when the chamfering method is used, the standing wave is 1.4 at the frequency of 19-20G, while the standing wave is 1.15 when the arc is used. Therefore, at the corner, the waveguide microstrip composite transmission line should abandon the traditional chamfering and use the arc.

[0010] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention is a composite transmission line design method. For this transmission line, the present invention suspends the microstrip line in the air instead of placing it at the bottom of the waveguide. By optimizing the size of the waveguide cavity and changing the bending angle of the microstrip line, the same transmission efficiency as that of a conventional waveguide can be obtained when the waveguide size is very small. Through this design, the thickness and weight of the antenna are greatly reduced without affecting the radiation efficiency of the antenna, and the cost of the antenna is also greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 It is a schematic diagram of an insertion loss curve of a composite transmission line design method according to an embodiment of the present invention, in which the maximum insertion loss of the entire frequency band is less than 0.025dB; Figure 2 It is a schematic diagram of a composite transmission line design method according to an embodiment of the present invention, in which the standing wave curve has a full-frequency standing wave less than 1.01; Figure 3 is a composite transmission line corner design diagram of a composite transmission line design method according to an embodiment of the present invention; Figure 4 is a standing wave diagram corresponding to a composite transmission line corner design according to a composite transmission line design method of an embodiment of the present invention; Figure 5 is a schematic diagram of placing a microstrip plate at the bottom of a waveguide according to a composite transmission line design method according to an embodiment of the present invention; Figure 6 This is a comparison diagram of materials from Rogers Company and domestic Taizhou Wangling Company according to a composite transmission line design method according to an embodiment of the present invention; Figure 7 is a schematic diagram of the position of a moving microstrip plate in a waveguide according to a composite transmission line design method according to an embodiment of the present invention; Figure 8 It is a standing wave diagram of a material of a domestic manufacturer of a mobile microstrip plate in a waveguide according to a composite transmission line design method according to an embodiment of the present invention; Fig. 9 It is a standing wave diagram of the material of the imported manufacturer of the position of the mobile microstrip plate in the waveguide according to a composite transmission line design method according to an embodiment of the present invention; Fig.10 A standing wave diagram of a microstrip plate placed in the middle of a waveguide as the thickness decreases according to a composite transmission line design method according to an embodiment of the present invention; Fig.11 is a schematic diagram of waveguide cavity dimensions according to a composite transmission line design method according to an embodiment of the present invention; Fig.12 is a standing wave diagram when a microstrip plate designed for a composite transmission line according to an embodiment of the present invention is placed in the middle of a waveguide at a position h≥0.5λ; Fig.13 is a standing wave diagram when a microstrip plate is placed in the middle of a waveguide at a position h≤0.08λ according to a composite transmission line design method of an embodiment of the present invention; Fig.14 is a standing wave diagram when a microstrip plate according to a composite transmission line design method of an embodiment of the present invention is placed in the middle of a waveguide at a position greater than or equal to 0.5λ; Fig.15The present invention is a standing wave diagram when a≤0.08λ and a microstrip plate is placed in the middle of a waveguide according to a composite transmission line design method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0013] Below, the invention is further described in conjunction with the accompanying drawings and specific embodiments: Example 1

[0014] refer to Figures 1 to 15 Example 1 is described, comprising the following steps: S1. First, it is necessary to construct an equivalent circuit model of the composite transmission line, and then fit multiple sets of lumped circuit parameter values; S2, verify the lumped circuit parameter values ​​and then determine the physical structure parameters; S3. Select the appropriate position of the microstrip in the waveguide, and select the thickness of the medium as 0.508mm. The materials are domestic Taizhou Wangling and imported Rogers. There is a microstrip transmission line on the medium, and the length of the microstrip transmission line is 400mm.

[0015] Through HFSS software simulation calculation, it can be found that at the frequency of 19-20G, for Rogers' materials, the insertion loss is 0.25dB, and for the domestic Taizhou Wangling Company's materials, the insertion loss is 0.82dB; Among them, the position of the microstrip plate in the waveguide is moved, the depth of the waveguide is set to h, and the distance between the microstrip plate and the bottom of the waveguide is selected to be 0.125h, 0.25h, 0.375h, and 0.5h. It can be seen that with the increase of the distance from the bottom of the waveguide, the insertion loss of the materials of the two manufacturers is significantly reduced. In the middle of the waveguide, the insertion loss of the materials of the two manufacturers is almost the same at 0.2 dB; S4. For the selection of dielectric thickness, the microstrip plate is placed in the middle of the waveguide, and the dielectric thickness is changed in sequence. The thicknesses are 0.762mm, 0.508mm, 0.254mm, and 0.127mm respectively. It can be found that as the thickness decreases, the insertion loss also decreases significantly.

[0016] refer to Figure 4 Example 2 is described. This embodiment further describes Example 1, including the selection of the waveguide cavity size. Assume that the wide side size of the waveguide cavity is a and the depth is h, as shown in the following figure: Assume that the wavelength corresponding to the highest working frequency is λ. Place the microstrip plate in the middle of the waveguide and change the waveguide cavity dimensions a and h in turn.

[0017] At the frequency of 19-20G, assuming that the width dimension is a=3mm, and the depth gradually increases from h=3mm, it can be found that the standing wave does not change at the beginning, but when h≥0.5λ, the standing wave begins to have high-order harmonics; the depth gradually decreases from h=3mm, but when h≤0.08λ, the standing wave begins to have high-order harmonics; Assuming the depth h=3mm, and the width gradually increases from a=3mm, it can be found that when a≥0.5λ, the standing wave begins to have high-order harmonics. The width gradually decreases from a=3mm, and it can be found that when a≤0.08λ, the standing wave begins to have high-order harmonics: In order to avoid high-order harmonics, the wide side size and depth of the waveguide only need to be greater than 0.08λ (but not less than 0.5λ), which is much smaller than the conventional waveguide size requirement of a minimum of more than 0.5λ.

[0018] S6. Finally, the corner design of the transmission line is inevitable. For microstrip antennas, the conventional method is to use chamfering. Through HFSS software calculation, it is found that when the chamfering method is used, the standing wave is 1.25 at the frequency of 19-20G, while the standing wave is 1.02 when the arc is used. Therefore, at the corner, the waveguide microstrip composite transmission line should abandon the traditional chamfering and use the arc.

[0019] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "top", "bottom", "one side", "the other side", "front", "back", "middle part", "inside", "top end", "bottom end", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Example 2

[0020] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite transmission line design method, characterized in that: The following steps are involved: S1. First, it is necessary to construct an equivalent circuit model of the composite transmission line, and then fit multiple sets of lumped circuit parameter values; S2, verify the lumped circuit parameter values ​​and then determine the physical structure parameters; S3. Select the appropriate position of the microstrip in the waveguide, select the thickness of the medium as 0.508mm, there is a microstrip transmission line on the medium, the microstrip transmission line is 400mm, place the microstrip board at the bottom of the waveguide, and use HFSS software simulation calculation to analyze the impact of insertion loss as the microstrip board moves from the bottom to the middle; S4. Selection of dielectric thickness: Place the microstrip plate in the middle of the waveguide and change the dielectric thickness in sequence. The thicknesses are 0.762mm, 0.508mm, 0.254mm, and 0.127mm respectively. Analyze the change trend of insertion loss as the thickness decreases. S5. For the selection of waveguide cavity size, let the waveguide cavity width be a, the depth be h, and the wavelength corresponding to the highest working frequency be λ. Place the microstrip plate in the middle of the waveguide, change the waveguide cavity size in turn, and analyze its influence on insertion loss. S6. Finally, design the corners of the transmission line.

2. A composite transmission line design method according to claim 1, characterized in that: The model in step S1 will help understand and analyze the electrical characteristics of the transmission line, and then obtain multiple sets of lumped circuit parameter values ​​through fitting, which will be used for subsequent physical structure design.

3. A composite transmission line design method according to claim 1, characterized in that: In the step S2, the fitted lumped circuit parameter values ​​are verified to ensure their effectiveness in practical applications, and specific parameters of the physical structure, including the dielectric constant and thickness of the dielectric substrate, are determined based on the equivalent circuit model and the lumped circuit parameter values.

4. A composite transmission line design method according to claim 1, characterized in that: In step S3, the position of the microstrip plate in the waveguide is moved, and the depth of the waveguide is set to h. The distances of the microstrip plate from the bottom of the waveguide are selected to be 0.125h, 0.25h, 0.375h, and 0.5h. As the microstrip plate is gradually moved toward the middle, the insertion loss is gradually reduced.

5. A composite transmission line design method according to claim 1, characterized in that: In step S4, as the thickness of the microstrip board decreases, the insertion loss also decreases significantly.

6. A composite transmission line design method according to claim 1, characterized in that: In step S5, when the frequency is 19-20G, the width is set to a=3mm, and the depth is gradually increased from h=3mm. It can be found that the standing wave does not change at the beginning, but when h≥0.5λ, the standing wave begins to have high-order harmonics; the depth is gradually reduced from h=3mm, but when h≤0.1λ, the standing wave begins to have high-order harmonics. Assuming the depth is h=3mm, the width is gradually increased from a=3mm, and it can be found that when h≥0.5λ, the standing wave begins to have high-order harmonics, and the width is gradually reduced from a=3mm, and it can be found that when h≤0.1λ, the standing wave begins to have high-order harmonics.

7. A composite transmission line design method according to claim 1, characterized in that: In the step S6, it is inevitable to encounter corners. For microstrip antennas, the conventional method is to use chamfering. Through HFSS software calculation, it is found that when the chamfering method is used, the standing wave is 1.4 at the frequency of 19-20G, while the standing wave is 1.15 when the circular arc is used. Therefore, at the corners, the waveguide microstrip composite transmission line should abandon the traditional chamfering and use the circular arc.

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