Waveguide polarizer with index curve diaphragm

Abstract

The waveguide polarizer comprises a square waveguide and the index curve diaphragm, the longitudinal section of the square waveguide is square, and the index curve diaphragm is arranged in the middle of the square waveguide. The index curve diaphragm is divided into a rectangular separation part and a curve part of which the height is gradually reduced in the form of an index curve along the length direction of the square waveguide; the height of the separation part is matched with that of an inner cavity of the square waveguide, and the inner cavity at the input side of the square waveguide is divided into two same rectangular waveguide cavities; according to the waveguide polarizer, an index curve diaphragm is arranged in a square waveguide, an electromagnetic signal input by a rectangular waveguide cavity end is differentiated into two paths of electromagnetic signals which are mutually orthogonal and have a phase difference of 90 degrees, and the two paths of electromagnetic signals are output from the square waveguide cavity end, so that a linear polarization signal or a circular polarization signal is formed.

Description

Technical Field

[0001] The invention relates to a waveguide polarizer provided with an exponential curve diaphragm, belonging to the technical field of microwave feeders. Background Art

[0002] To suppress cloud and rain clutter, civil aviation control radars require two time-sharing polarization modes: vertical linear polarization and circular polarization. Therefore, a polarizer is required to generate two orthogonal electromagnetic wave signals with a 90° phase difference to achieve different polarization operating states. Common polarizers include circular waveguide diaphragm, grid, and stepped baffle types. Circular waveguide diaphragm polarizers achieve polarization switching by rotating a metal diaphragm driven by a motor, resulting in relatively long switching times. Grid polarizers achieve polarization switching by raising a 45° grid at the feed aperture with a motor. Due to the thinness of the grid, machining deformation significantly affects polarization performance. Stepped baffle polarizers, combined with waveguide electronic switches, can achieve rapid polarization switching, but they involve numerous physical parameters and are complex to design, requiring six to seven steps to achieve optimal polarization performance. Summary of the Invention

[0003] In order to solve the problems in the prior art of difficult processing and many physical parameters of waveguide polarizers, the present invention provides a waveguide polarizer with a simple structure, easy processing and few physical parameters.

[0004] To achieve the above objectives, the present invention provides a technical solution: a waveguide polarizer provided with an exponential curve diaphragm, comprising a square waveguide and an exponential curve diaphragm, wherein the longitudinal cross-section of the square waveguide is square, and the exponential curve diaphragm is centrally arranged within the square waveguide. The exponential curve diaphragm is divided into a rectangular partition and a curved portion whose height varies exponentially along the signal transmission direction within the square waveguide. The height of the partition matches the height of the square waveguide cavity and divides the cavity on the input side of the square waveguide into two identical rectangular waveguide cavities.

[0005] Two electromagnetic signals of equal amplitude and phase are input from two rectangular waveguide cavities respectively, and through polarization synthesis, a horizontal linear polarization signal is formed at the output port of the square waveguide cavity;

[0006] Alternatively, two electromagnetic signals of equal amplitude and opposite phase are inputted from two rectangular waveguide cavities respectively, and a vertical linear polarization signal is formed at the output port of the square waveguide cavity through polarization synthesis;

[0007] Alternatively, an electromagnetic signal is input from any rectangular waveguide cavity of the waveguide polarizer, and a circularly polarized signal is formed at the output port of the square waveguide cavity through polarization decomposition.

[0008] A further design of the above technical solution is as follows: the exponential curve formula corresponding to the curve portion is:

[0009]

[0010] Where: a is the inner diameter of the square waveguide; c is the exponential coefficient; LF is the length of the square waveguide; L is the length of the exponential curve diaphragm separation part.

[0011] The inner diameter a of the square waveguide is 145.1 mm, the length LF of the square waveguide is 550 mm, the length L of the exponential curve diaphragm separation portion is 181.8 mm, and the exponential coefficient c is 0.009.

[0012] The height of the curved portion gradually decreases in an exponential curve along the signal transmission direction in the square waveguide.

[0013] The waveguide polarizer also includes an aperture conversion unit, which is connected to the square waveguide input port. The aperture conversion unit is symmetrically provided with two cavities, one end of which matches the aperture of the two rectangular waveguide cavities, and the other end converts the aperture of the two rectangular waveguide cavities to the required size and connects to the target rectangular waveguide.

[0014] The aperture conversion part is in an expanding shape with a gradually increasing aperture. The inner cavity of the aperture conversion part is divided into two symmetrical expanding cavities. The small-aperture end of the aperture conversion part is connected to the square waveguide input port, and the small apertures of the two expanding cavities match the aperture of the rectangular waveguide cavity.

[0015] The bottom surface of the aperture conversion portion is a plane parallel to the corresponding surface of the square waveguide, and the other three surfaces are expanded surfaces inclined outward.

[0016] The aperture size of the rectangular waveguide cavity is 145.1 mm×71.55 mm; the size of the large-aperture end of the expansion cavity of the aperture conversion part is 165.1 mm×82.55 mm.

[0017] The beneficial effects of the present invention are:

[0018] The present invention arranges an exponential curve diaphragm in a square waveguide to split the electromagnetic signal input from the rectangular waveguide cavity into two mutually orthogonal electromagnetic signals with a phase difference of 90°, which are output from the output end of the square waveguide cavity. This can form horizontal or vertical linear polarization signals or circular polarization signals, allowing the polarizer to have the above-mentioned multiple polarization functions.

[0019] The present invention adopts a monotonically decreasing exponential curve, so the difference in reactance values provided by each point on the curve is nonlinear, and a phase difference of 90° can be more easily formed within a limited length space, thereby producing good circular polarization performance; the combination of the four parameters of the exponential curve diaphragm of the present invention ultimately forms a total phase difference that is closer to 90°, which can produce optimal circular polarization performance.

[0020] The waveguide polarizer of the present invention has a simple structure, and the exponential curve diaphragm can achieve good circular polarization performance by only involving four physical parameters. Compared with the 13 physical parameters involved in the step baffles in the traditional stepped baffle polarizer, the present invention effectively improves design efficiency and reduces processing complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of waveguide polarizer;

[0022] Figure 2 Schematic diagram of a square waveguide;

[0023] Figure 3 Schematic diagram of the cavity separation of the square waveguide;

[0024] Figure 4 It is a schematic diagram of the exponential curve diaphragm;

[0025] Figure 5 This is a schematic diagram of the aperture conversion unit;

[0026] Figure 6 Schematic diagram for vertical linear polarization implementation;

[0027] Figure 7 Schematic diagram for horizontal linear polarization implementation;

[0028] Figure 8 Schematic diagram for circular polarization implementation;

[0029] Figure 9 is the voltage standing wave ratio of the waveguide polarizer of Example 3;

[0030] Figure 10 is the quadrature signal imbalance of the waveguide polarizer in Example 3;

[0031] Figure 11 is the phase difference of the orthogonal signals of the waveguide polarizer of Example 3;

[0032] Figure 12 Schematic diagram comparing the physical parameters of a conventional polarizer and the polarizer of the present invention;

[0033] Figure 13 is the voltage standing wave ratio of the waveguide polarizer of parameter combination 1 in the comparative example;

[0034] Figure 14 is the orthogonal signal imbalance of the waveguide polarizer of parameter combination 1 in the comparative example;

[0035] Figure 15 is the orthogonal signal phase difference of the waveguide polarizer of parameter combination 1 in the comparative example;

[0036] Figure 16 is the voltage standing wave ratio of the waveguide polarizer with parameter combination 2 in the comparative example;

[0037] Figure 17 is the orthogonal signal imbalance of the waveguide polarizer with parameter combination 2 in the comparative example;

[0038] Figure 18 is the phase difference of the orthogonal signals of the waveguide polarizer with the parameter combination 2 in the comparative example;

[0039] Figure 19 is the voltage standing wave ratio of the waveguide polarizer with parameter combination 3 in the comparative example;

[0040] Figure 20 is the orthogonal signal imbalance of the three-waveguide polarizer parameter combination in the comparative example;

[0041] Figure 21 is the phase difference of the orthogonal signals of the three waveguide polarizers with the parameter combination in the comparative example;

[0042] Figure 22 is the voltage standing wave ratio of the 4-waveguide polarizer with the parameter combination in the comparative example;

[0043] Figure 23 is the orthogonal signal imbalance of the parameter combination 4-waveguide polarizer in the comparative example;

[0044] Figure 24 is the phase difference of the orthogonal signals of the four-waveguide polarizer with the parameter combination in the comparative example;

[0045] In the figure: 1- square waveguide, 2- exponential curve diaphragm, 3- aperture conversion part, 4- step. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Example 1

[0048] The waveguide polarizer of this embodiment is as follows Figure 1 As shown, it includes a square waveguide 1 and an exponential curve diaphragm 2, combined with Figure 2 As shown, the square waveguide 1 is a metal waveguide tube with a square longitudinal section. Figure 3 and Figure 4 As shown, the exponential curve diaphragm 2 is centrally arranged in the square waveguide 1. The exponential curve diaphragm 2 is divided into a rectangular partition and a curved portion whose height changes in an exponential curve along the signal transmission direction in the square waveguide 1. The height of the partition matches the height of the square waveguide cavity and divides the cavity on the input side of the square waveguide into two identical rectangular waveguide cavities.

[0049] In this embodiment, the height of the curved portion gradually decreases in an exponential curve along the signal transmission direction in the square waveguide.

[0050] When the waveguide polarizer of this embodiment is used, two electromagnetic signals of equal amplitude and phase are input from two rectangular waveguide cavities respectively, and a horizontal linear polarization signal is formed at the output port of the square waveguide cavity through polarization synthesis;

[0051] Alternatively, two electromagnetic signals of equal amplitude and opposite phase are input from two rectangular waveguide cavities respectively, and through polarization synthesis, a vertical linear polarization signal is formed at the output port of the square waveguide cavity;

[0052] Alternatively, an electromagnetic signal is input from any rectangular waveguide cavity of the waveguide polarizer, and a circularly polarized signal is formed at the output port of the square waveguide cavity through polarization decomposition.

[0053] In this embodiment, the exponential curve diaphragm 2 decomposes the electric field input from the end of the rectangular waveguide cavity into two electric field components with orthogonal directions. Each point of the exponential curve provides reactance to one of the field components, ultimately making the two electric field components 90° out of phase. The height of each point on the curve provides a different phase change, thereby forming a linearly polarized signal or a circularly polarized signal.

[0054] Example 2

[0055] Combine Figure 5 As shown, the waveguide polarizer of this embodiment, based on the first embodiment, further includes an aperture conversion unit 3. This unit is connected to the square waveguide input port and comprises two symmetrically arranged cavities. The dimensions of the two cavities at one end of the aperture conversion unit 3 match the apertures of the two rectangular waveguide cavities, while the dimensions of the other end match the aperture of the waveguide to be connected. This converts the apertures of the two rectangular waveguide cavities to the required dimensions for connection to the target waveguide, such as the BJ14 standard rectangular waveguide used in civil aviation control radar. The aperture conversion unit has a three-dimensional, gradually increasing flared shape. The internal cavity of the aperture conversion unit is divided into two symmetrical flared cavities. The smaller end of the aperture conversion unit is connected to the square waveguide input port, and the smaller cavities of the two flared cavities match the aperture of the rectangular waveguide cavity. The bottom surface of the aperture conversion unit 3 is a plane parallel to the corresponding surfaces of the square waveguide, while the remaining three surfaces are outwardly inclined flared surfaces.

[0056] Example 3

[0057] The waveguide polarizer of this embodiment comprises a square waveguide 1, an exponential curve diaphragm 2 and an aperture conversion unit 3. Figure 1As shown, the square waveguide is a metal waveguide tube with a square cross-section. The size of its cross-sectional aperture determines the operating frequency range of the waveguide polarizer. Since the waveguide is a high-pass device, if the size is too small, its corresponding operating frequency range will be higher than the operating frequency of the civil aviation control radar. If the size is too large, high-order modes will appear within the operating frequency range of the civil aviation control radar, forming a resonance point, thereby hindering the transmission of electromagnetic signals. Therefore, this embodiment designs a suitable square waveguide aperture to meet the use requirements of the civil aviation control radar. At the same time, the length of the square waveguide also ensures that the exponential curve diaphragm can be installed. Specifically, in this embodiment, the inner diameter of the square waveguide is 145.1mm×145.1mm and the length is 550mm. The schematic diagram of the square waveguide is shown in the attached figure. Figure 2 shown.

[0058] The exponential curve diaphragm 2 is a metal diaphragm with a thickness of 2 mm, which is centrally installed in the square waveguide 1 to separate the inner cavity of one side of the square waveguide 1 into two identical rectangular waveguide cavities. The size of the rectangular waveguide cavity is 145.1 mm × 71.55 mm. Figure 3 shown.

[0059] The exponential curve diaphragm splits the electromagnetic signal input from the rectangular waveguide cavity into two mutually orthogonal electromagnetic signals with a phase difference of 90°, which are output from the square waveguide cavity end, thereby forming a linear polarization signal or a circular polarization signal. Figure 4 As shown, the curve formula of the exponential curve segment is shown in formula (1).

[0060]

[0061] Where: a is the inner diameter of the square waveguide; c is the exponential coefficient; LF is the length of the square waveguide; L is the length of the exponential curve diaphragm separation part.

[0062] In this embodiment, the values of the above parameters are: the inner diameter a of the square waveguide is 145.1 mm, the length LF of the square waveguide is 550 mm, the length L of the exponential curve diaphragm separation portion is 181.8 mm, and the exponential coefficient c is 0.009. Civil aviation control radar uses the BJ14 standard rectangular waveguide for the transmission of high-power electromagnetic signals. The cavity size of the BJ14 standard rectangular waveguide is 165.1mm×82.55mm. The cavity size of the non-standard rectangular waveguide composed of the exponential curve diaphragm 2 and the square waveguide 1 is 145.1mm×71.55mm. Therefore, it is necessary to design a non-standard aperture conversion unit 3 for aperture conversion. The aperture conversion unit 3 is in the shape of an expanded mouth with gradually increasing diameter. The inner cavity of the aperture conversion unit 3 is divided into two symmetrical expanded cavities. The small-diameter end of the aperture conversion unit is connected to the input port of the square waveguide, and the small diameters of the two expanded cavities match the ports of the rectangular waveguide cavity. The bottom surface of the aperture conversion unit is a plane parallel to the corresponding surface of the square waveguide, and the other three surfaces are expanded surfaces inclined outward. The large diameter end size of the expansion cavity of the caliber conversion part is 165.1mm×82.55mm, which changes the cavity size from 145.1mm×71.55mm to 165.1mm×82.55mm. Figure 5 shown.

[0063] When the waveguide polarizer of this embodiment performs vertical linear polarization, two electromagnetic signals of equal amplitude and opposite phase enter the two rectangular waveguide cavities of the waveguide polarizer respectively. Through polarization synthesis, a vertical linear polarization signal is formed at the port of the square waveguide cavity, as shown in the schematic diagram. Figure 6 shown.

[0064] When the waveguide polarizer of this embodiment performs horizontal linear polarization, two electromagnetic signals of equal amplitude and phase enter the two rectangular waveguide cavities of the waveguide polarizer respectively. Through polarization synthesis, a horizontal linear polarization signal is formed at the port of the square waveguide cavity, as shown in the schematic diagram. Figure 7 shown.

[0065] When the waveguide polarizer of this embodiment performs circular polarization, the electromagnetic signal enters any rectangular waveguide cavity of the waveguide polarizer, and forms a circularly polarized signal at the port of the square waveguide cavity through polarization decomposition, as shown in the schematic diagram. Figure 8 shown.

[0066] The waveguide polarizer of this embodiment has good circular polarization characteristics, and the circular polarization axis ratio is about 0.3dB. The voltage standing wave ratio of the waveguide polarizer is shown in FIG. Figure 9 , the maximum value is 1.17; the orthogonal signal imbalance is shown in Figure 10 , the maximum difference is 0.11dB; the phase difference of the orthogonal signal is shown in Figure 11 , which is 89.6°~91.6°.

[0067] like Figure 12As shown in FIG, the physical parameters of the stepped partition in the traditional stepped partition type polarizer include 10 other parameters besides the square waveguide inner diameter a, the square waveguide length LF, and the partition length L, such as Figure 12 As shown in the left figure, each step 4 of the step partition has two parameters that need to be designed and determined. Figure 12 The physical parameters involved in the exponential curve diaphragm in the waveguide polarizer of this embodiment shown in the figure on the right include four parameters: the square waveguide inner diameter a, the square waveguide length LF, the exponential curve diaphragm separator length L, and the exponential coefficient c. Compared with the traditional stepped baffle polarizer, in addition to the three parameters of the square waveguide inner diameter a, the square waveguide length LF, and the exponential curve diaphragm separator length L, the waveguide polarizer of this embodiment only requires one physical parameter, c, to be further designed and determined. Therefore, this waveguide polarizer can effectively improve design efficiency and reduce processing complexity.

[0068] The process of parameter selection in this embodiment is as follows:

[0069] a) The initial value of the square waveguide aperture size a is selected as the long side size of the BJ14 waveguide, that is, 165.1 mm. The initial value of the square waveguide length LF is selected as 2.5 times the wavelength corresponding to the lower limit operating frequency, that is, 600 mm.

[0070] b) Selecting the initial value of the exponential curve diaphragm separator length L as the wavelength corresponding to the lower limit operating frequency, i.e., 240 mm, and the initial value of the exponential coefficient c as 0.01;

[0071] c) Use electromagnetic simulation software for modeling, simulation, and optimization;

[0072] d) Initial simulation results show that when the square waveguide aperture size a is selected to be the long side dimension of the BJ14 waveguide, that is, 165.1 mm, resonance will occur within the frequency band. Therefore, the value of a needs to be reduced to eliminate the resonance within the frequency band.

[0073] e) After selecting an appropriate square waveguide aperture a value of 145.1 mm to eliminate in-band resonance, simulation optimization was continued for different parameters. The final value of LF was determined to be 550 mm, L was 181.8 mm, and c was 0.009.

[0074] Comparative Example

[0075] The polarizer of the above embodiment is used in the L-band. The above parameter combination is compared with the simulation results of the following three groups of different parameter combinations also working in the L-band. The results are as follows:

[0076] 1) Parameter combination a=165.1mm,LF=600mm,L=240m,c=0.01;Simulation results are as follows Figure 13-15As shown in FIG, when the square waveguide aperture a is equal to the long side dimension of the BJ14 standard waveguide 165.1 mm, high-order mode resonance is generated within the operating frequency band, which is an undesirable result.

[0077] 2) Parameter combination a=145.1mm,LF=600mm,L=240m,c=0.01;Simulation results are as follows Figure 16-18 As shown in Figure 1, when the square waveguide aperture is reduced to 145.1 mm, the high-order mode resonance within the operating frequency band disappears.

[0078] 3) Parameter combination a=145.1mm,LF=600mm,L=181.8m,c=0.01;Simulation results are as follows Figure 19-21 As shown, compared with the optimal result of the above embodiment, the orthogonal signal imbalance and the orthogonal signal phase difference of this set of results are relatively poor.

[0079] 4) Using the same design method and structure as the above embodiment, a polarizer working in the S band is designed, with a value of 66.6 mm, LF value of 231 mm, L value of 90.9 mm, and c value of 0.0093. The simulation results are shown in Figure 22-Figure 24 As can be seen from the figure, the comparative example obtains an ideal circular polarization effect, with a maximum voltage standing wave ratio of 1.26, a maximum difference in quadrature signal imbalance of 0.12dB, and a quadrature signal phase difference of 88.7° to 92.4°, indicating that the polarizer can also be used as an S-band polarizer.

[0080] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and any technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A waveguide polarizer with an exponential curve diaphragm, characterized in that: The exponential curve diaphragm comprises a square waveguide, wherein the longitudinal cross-section of the square waveguide is square, and the exponential curve diaphragm is centrally arranged in the square waveguide. The exponential curve diaphragm is divided into a rectangular partition and a curved portion whose height changes in an exponential curve along the signal transmission direction in the square waveguide. The height of the partition matches the height of the square waveguide cavity and divides the cavity on the input side of the square waveguide into two identical rectangular waveguide cavities. Two electromagnetic signals of equal amplitude and phase are input from two rectangular waveguide cavities respectively, and through polarization synthesis, a horizontal linear polarization signal is formed at the output port of the square waveguide cavity; Alternatively, two electromagnetic signals of equal amplitude and opposite phase are inputted from two rectangular waveguide cavities respectively, and a vertical linear polarization signal is formed at the output port of the square waveguide cavity through polarization synthesis; Alternatively, an electromagnetic signal is input from any rectangular waveguide cavity of the waveguide polarizer, and a circularly polarized signal is formed at the output port of the square waveguide cavity through polarization decomposition.

2. The waveguide polarizer with an exponential curve diaphragm according to claim 1, characterized in that: The exponential curve formula corresponding to the curve portion is: Where: a is the inner diameter of the square waveguide; c is the exponential coefficient; LF is the length of the square waveguide; L is the length of the exponential curve diaphragm separation part.

3. The waveguide polarizer with an exponential curve diaphragm according to claim 1, characterized in that: The inner diameter a of the square waveguide is 145.1 mm, the length LF of the square waveguide is 550 mm, the length L of the exponential curve diaphragm separation portion is 181.8 mm, and the exponential coefficient c is 0.

009.

4. The waveguide polarizer with an exponential curve diaphragm according to claim 3, characterized in that: The height of the curved portion gradually decreases in an exponential curve along the signal transmission direction in the square waveguide.

5. The waveguide polarizer with an exponential curve diaphragm according to any one of claims 1 to 4, characterized in that: It also includes an aperture conversion unit, which is connected to the square waveguide input port. The aperture conversion unit is symmetrically provided with two cavities, one end of which matches the aperture of the two rectangular waveguide cavities, and the other end converts the aperture of the two rectangular waveguide cavities into the required size for connection with the target rectangular waveguide.

6. The waveguide polarizer with an exponential curve diaphragm according to claim 5, characterized in that: The aperture conversion part is in an expanding shape with a gradually increasing aperture. The inner cavity of the aperture conversion part is divided into two symmetrical expanding cavities. The small-aperture end of the aperture conversion part is connected to the square waveguide input port, and the small apertures of the two expanding cavities match the aperture of the rectangular waveguide cavity.

7. The waveguide polarizer with an exponential curve diaphragm according to claim 6, characterized in that: The bottom surface of the aperture conversion portion is a plane parallel to the corresponding surface of the square waveguide, and the other three surfaces are expanded surfaces inclined outward.

8. The waveguide polarizer with an exponential curve diaphragm according to claim 7, characterized in that: The aperture size of the rectangular waveguide cavity is 145.1 mm×71.55 mm; the size of the large-aperture end of the expansion cavity of the aperture conversion part is 165.1 mm×82.55 mm.

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