A rectangular waveguide filter

Abstract

The application discloses a rectangular waveguide filter, and the filter comprises a double-layer hollow waveguide, and four rectangular resonant cavities are formed by two hollow waveguides in each of upper and lower layers; adjacent hollow waveguides in the same layer are communicated through a first coupling hollow waveguide serving as a coupling window, so that the filter structure is more compact, the loss is lower, and the filter is more suitable for application in a modern microwave and millimeter wave circuit system; adjacent hollow waveguides in the upper and lower layers are communicated through a hollow rectangular waveguide, a hollow cylindrical waveguide, a third coupling hollow waveguide and a second coupling hollow waveguide serving as coupling windows; the coupling windows arranged in this way not only do not affect the coupling of the main mode TM 110 , but also can inhibit the coupling of high-order modes TM 210 , so that the effect of keeping high selectivity and extending the filter stopband is achieved.

Description

Technical Field

[0001] This invention relates to a rectangular waveguide filter, belonging to the field of microwave technology. Background Technology

[0002] As an important component in radio frequency and microwave circuit systems, filters have been used in the vast majority of communication equipment. Waveguide filters have obvious advantages, with higher Q values, greater power capacity, and more stable structures.

[0003] As modern communication circuit systems become increasingly integrated, circuits integrating multiple components often exhibit interleaved or even overlapping signal frequencies. This undoubtedly severely impacts signal reception, degrades communication signal quality, and can even render the communication system malfunctioning. Furthermore, many nonlinear active components within the radio frequency front-end, such as mixers and frequency multipliers, also experience interleaved signals, significantly affecting transceiver performance.

[0004] To solve the above problems, the filter needs not only to have good passband transmission characteristics, but also to have higher selectivity and a sufficiently wide stopband to suppress unwanted harmonic signals. Therefore, there is an urgent need to study filters with high selectivity and wide stopband. Summary of the Invention

[0005] This invention provides a rectangular waveguide filter that solves the problems disclosed in the background art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A rectangular waveguide filter includes an input hollow waveguide, an output hollow waveguide, an upper unit, and a lower unit; Both the upper and lower units include a first hollow waveguide and a second hollow waveguide connected by a first coupled hollow waveguide. The input hollow waveguide is connected to the first hollow waveguide of the upper unit through a second coupled hollow waveguide, and the output hollow waveguide is connected to the second hollow waveguide of the upper unit through a third coupled hollow waveguide. The first hollow waveguide of the upper unit and the first hollow waveguide of the lower unit are connected by a hollow cylindrical waveguide, and the second hollow waveguide of the upper unit and the second hollow waveguide of the lower unit are connected by a pair of hollow rectangular waveguides. The first and second hollow waveguides of the upper unit and the first and second hollow waveguides of the lower unit all constitute a rectangular resonant cavity. All coupled hollow waveguides, hollow rectangular waveguides, and hollow cylindrical waveguides constitute a coupling window of the connected rectangular resonant cavity. The hollow cylindrical waveguide is located in the dominant mode TM. 110 The strongest electric field is located at the hollow rectangular waveguide in the dominant mode TM. 110 The strongest magnetic field is located at the point of higher-order mode TM. 210The weakest electric and magnetic fields are located at the center of the first coupled hollow waveguide, which is situated at the center of the higher-order mode TM. 210 The weakest points of electric and magnetic fields.

[0007] Hollow cylindrical waveguide provides dominant mode™ 110 Electrical coupling, adjusting the radius of the hollow cylindrical waveguide, and controlling the dominant mode TM 110 Electrical coupling quantity.

[0008] Hollow rectangular waveguide provides dominant mode TM 110 Magnetic coupling, adjusting the length of the hollow rectangular waveguide, and controlling the dominant mode TM 110 Magnetic coupling quantity.

[0009] The input hollow waveguide, output hollow waveguide, first hollow waveguide, second hollow waveguide, and all coupled hollow waveguides are rectangular structures.

[0010] The central axis of the hollow cylindrical waveguide passes through the center of the first hollow waveguide of the upper unit and the center of the first hollow waveguide of the lower unit.

[0011] A pair of hollow rectangular waveguides are parallel to the first coupled hollow waveguide, and the pair of hollow rectangular waveguides are located on both sides of the second hollow waveguide of the lower unit.

[0012] The second and third coupled hollow waveguides are both perpendicular to the first coupled hollow waveguide, and the second coupled hollow waveguide is located on side A of the first hollow waveguide of the upper unit, while the third coupled hollow waveguide is located on side B of the second hollow waveguide of the upper unit; wherein, side A and side B are opposite sides.

[0013] The second coupled hollow waveguide is located at the side of the first hollow waveguide A of the upper unit. l / 4, the distance between the third coupled hollow waveguide and the side of the upper unit's second hollow waveguide B. l / 4; where, l Let be the length of the horizontal side of the first hollow waveguide and the second hollow waveguide.

[0014] The beneficial effects achieved by this invention are as follows: This invention features a double-layer hollow waveguide, with two hollow waveguides on each of the upper and lower layers forming four rectangular resonant cavities. Adjacent hollow waveguides on the same layer are connected through a first coupling hollow waveguide serving as a coupling window, resulting in a more compact filter structure, lower loss, and greater suitability for modern microwave and millimeter-wave circuit systems. The upper and lower adjacent hollow waveguides are connected through a hollow rectangular waveguide, a hollow cylindrical waveguide, a third coupling hollow waveguide, and a second coupling hollow waveguide serving as coupling windows. This coupling window design ensures that it does not affect the master mode (TM). 110 It can also suppress the coupling of higher-order TM modes. 210 The coupling achieves the effect of maintaining high selectivity while extending the filter stopband. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of a rectangular waveguide filter; Figure 2 This is a top view of a rectangular waveguide filter; Figure 3 This is a circuit topology diagram of a rectangular waveguide filter; Figure 4(a) shows the first coupled hollow waveguide of the upper unit and the main mode TM. 110 and higher order mode TM 210 A graph showing the relationship between coupling coefficients; Figure 4(b) shows the hollow rectangular waveguide and the dominant mode TM. 110 and higher order mode TM 210 A graph showing the relationship between coupling coefficients; Figure 5 The S-parameter plot of the filter's passband; Figure 6 This is a plot of the out-of-band S-parameters of the filter. Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0017] like Figure 1 and 2 As shown, a rectangular waveguide filter includes an input hollow waveguide 1, an output hollow waveguide 2, an upper unit, and a lower unit. Both the upper and lower units include a first hollow waveguide 3 and a second hollow waveguide 4 connected by a first coupling hollow waveguide 5. The input hollow waveguide 1 is connected to the first hollow waveguide 3 of the upper unit via a second coupling hollow waveguide 7. The output hollow waveguide 2 is connected to the second hollow waveguide 4 of the upper unit via a third coupling hollow waveguide 6. The first hollow waveguide 3 of the upper unit and the first hollow waveguide 3 of the lower unit are connected by a hollow cylindrical waveguide 8. The second hollow waveguide 4 of the upper unit and the second hollow waveguide 4 of the lower unit are connected by a pair of hollow rectangular waveguides 9. The input hollow waveguide 1, output hollow waveguide 2, first hollow waveguide 3, second hollow waveguide 4, and all coupling hollow waveguides are rectangular structures, and when connected, they are all perpendicular to the plane of the connected hollow wave.

[0018] The first hollow waveguide 3 and the second hollow waveguide 4 of the upper unit, and the first hollow waveguide 3 and the second hollow waveguide 4 of the lower unit all constitute a rectangular resonant cavity. All coupled hollow waveguides, hollow rectangular waveguides 9 and hollow cylindrical waveguides 8 constitute a coupling window of the connected rectangular resonant cavity.

[0019] Hollow cylindrical waveguide 8 is located in the dominant mode TM 110 The hollow cylindrical waveguide 8 provides the dominant mode TM at the point where the electric field is strongest.110 Electrical coupling, adjusting the radius of the hollow cylindrical waveguide 8, and controlling the main mode TM 110 Electrical coupling. Specifically, the central axis of the hollow cylindrical waveguide 8 passes through the center of the upper unit first hollow waveguide 3 and the center of the lower unit first hollow waveguide 3.

[0020] Hollow rectangular waveguide 9 is located in the dominant mode TM 110 The strongest magnetic field is located at the point of higher-order mode TM. 210 The hollow rectangular waveguide 9 provides the dominant mode TM at the weakest point of the electric and magnetic fields. 110 Magnetic coupling, adjusting the length of the hollow rectangular waveguide 9, controls the main mode TM 110 The magnetic coupling quantity. Specifically, a pair of hollow rectangular waveguides 9 are parallel to the first coupled hollow waveguide 5, and the pair of hollow rectangular waveguides 9 are located on both sides of the second hollow waveguide 4 of the lower unit, with their center lines located on the bisectors of the corresponding rectangular resonant cavities.

[0021] The center of the first coupled hollow waveguide 5 is set at the higher-order mode TM. 210 The weakest electric and magnetic fields can effectively suppress higher-order modes TM. 210 .

[0022] Both the second coupled hollow waveguide 7 and the third coupled hollow waveguide 6 are perpendicular to the first coupled hollow waveguide 5. The second coupled hollow waveguide 7 is located on side A of the upper unit first hollow waveguide 3, and the third coupled hollow waveguide 6 is located on side B of the upper unit second hollow waveguide 4. The second coupled hollow waveguide 7 is located at the side A of the upper unit first hollow waveguide 3. l / 4, the third coupled hollow waveguide 6 is 4B away from the side of the upper unit's second hollow waveguide. l / 4; where side A and side B are opposite sides. l The lengths of the horizontal sides of the first hollow waveguide 3 and the second hollow waveguide 4 are given.

[0023] like Figure 3 R1, R2, R3, and R4 are four rectangular resonant cavities, corresponding to the first hollow waveguide 3 of the upper unit, the first hollow waveguide 3 of the lower unit, the second hollow waveguide 4 of the lower unit, and the second hollow waveguide 4 of the upper unit, respectively. S and L correspond to the input hollow waveguide 1 and the output hollow waveguide 2, respectively. Solid lines indicate magnetic coupling between the resonant cavities, and dashed lines indicate electrical coupling between them. This circuit topology can be used to design a fourth-order bandpass filter with a transmission zero on each side of the passband. The hollow cylindrical waveguide 8 provides the dominant mode TM between R1 and R2. 110 The electrical coupling can be adjusted by changing the radius of the hollow cylindrical waveguide 8, thereby controlling the dominant mode TM between R1 and R2. 110The electrical coupling. A pair of hollow rectangular waveguides 9 provide the dominant mode TM between R3 and R4. 110 The magnetic coupling, by adjusting the length of the hollow rectangular waveguide 9, allows control of the dominant mode TM between R3 and R4. 110 Magnetic coupling quantity.

[0024] from Figure 2 It can be seen that both the input and output coupling windows are offset towards the center of the resonant cavity, to a distance of approximately 1 / 4 of the cavity's side length from the cavity edge. This offset structure causes the second coupled hollow waveguide 7 and the third coupled hollow waveguide 6 to be located in the TM... 210 At the point where the electric field is strongest and the magnetic field is weakest, the input hollow waveguide 1 and the output hollow waveguide 2 are coupled to the first hollow waveguide 3 and the second hollow waveguide 4 of the upper unit respectively through magnetic coupling, and at this location TM 210 The magnetic field is the weakest, making it difficult to excite higher-order TM modes. 210 It can be used to generate high-order mode TM from the source 210 Suppressed; at the same time, the higher-order mode TM generated in the resonant cavity at this location 120 The magnetic field is perpendicular to the second and third coupling windows, making it difficult to excite higher-order TM modes. 120 (TM 120 With TM 210 It is a pair of degenerate modes.

[0025] Additionally, higher-order mode TM 210 Alternatively, both the first coupled hollow waveguide 5 and the hollow rectangular waveguide 9, which provide magnetic coupling, can be placed in the higher-order mode TM. 210 Suppression is achieved at the standing wave nodes, and combined with the port, higher-order mode TM 120 It can also be suppressed, ultimately resulting in higher-order TM modes. 210 and TM 120 Both can be suppressed.

[0026] Figure 4(a) shows the extracted master module TM. 110 and higher order mode TM 210 The relationship between the coupling coefficient of the mode and the first coupled hollow waveguide 5 of the upper unit is shown in Figure 4(b), which is the extracted main mode TM. 110 and higher order mode TM 210 The relationship between the coupling coefficient of the mode and the hollow rectangular waveguide 9. The results show that the higher-order mode TM 210 The coupling coefficients of the modules are much smaller than those of the master module (TM). 110 The coupling coefficient can suppress higher-order modes.

[0027] Figure 5The S-parameter curves of the passband filter are shown. The filter center frequency is 12.8 GHz, the 3-dB relative bandwidth is 1.9%, and the in-band return loss S11 is below -18 dB. A transmission zero is generated on both sides of the passband. Figure 6 The image shows the out-of-band S-parameter curve of the filter; the stopband rejection of -38 dB extends to 30.5 GHz. It can be seen that the stopband of the filter designed using the above structure can be extended to 2.4 GHz. f 0( f (0 is the center frequency of the filter), which widens the stopband width of the rectangular waveguide filter while maintaining high selectivity.

[0028] In summary, this invention features a double-layer hollow waveguide, with two hollow waveguides on each of the upper and lower layers forming four rectangular resonant cavities. Adjacent hollow waveguides on the same layer are connected by a first coupling hollow waveguide 5, which serves as a coupling window. This makes the filter structure more compact, reduces loss, and is more suitable for application in modern microwave and millimeter-wave circuit systems. The upper and lower adjacent hollow waveguides are connected by a hollow rectangular waveguide 9, a hollow cylindrical waveguide 8, a third coupling hollow waveguide 6, and a second coupling hollow waveguide 7, which also serve as coupling windows. This coupling window design does not affect the main mode TM. 110 It can also suppress the coupling of higher-order TM modes. 210 The coupling achieves the effect of maintaining high selectivity while extending the filter stopband; and the structure proposed in this invention is not limited to rectangular metal waveguides, but can also be applied to substrate integrated waveguides to achieve high selectivity and wide stopband.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rectangular waveguide filter, characterized in that, It includes an input hollow waveguide, an output hollow waveguide, an upper unit, and a lower unit; Both the upper and lower units include a first hollow waveguide and a second hollow waveguide connected by a first coupled hollow waveguide. The input hollow waveguide is connected to the first hollow waveguide of the upper unit through a second coupled hollow waveguide, and the output hollow waveguide is connected to the second hollow waveguide of the upper unit through a third coupled hollow waveguide. The first hollow waveguide of the upper unit and the first hollow waveguide of the lower unit are connected by a hollow cylindrical waveguide, and the second hollow waveguide of the upper unit and the second hollow waveguide of the lower unit are connected by a pair of hollow rectangular waveguides. The first and second hollow waveguides of the upper unit and the first and second hollow waveguides of the lower unit all constitute a rectangular resonant cavity. All coupled hollow waveguides, hollow rectangular waveguides, and hollow cylindrical waveguides constitute a coupling window of the connected rectangular resonant cavity. The hollow cylindrical waveguide is located in the dominant mode TM. 110 The strongest electric field is located at the hollow rectangular waveguide in the dominant mode TM. 110 The strongest magnetic field is located at the point of higher-order mode TM. 210 The weakest electric and magnetic fields are located at the center of the first coupled hollow waveguide, which is situated at the center of the higher-order mode TM. 210 The weakest electric and magnetic fields are located at the points where the second and third coupled hollow waveguides are located in higher-order TM modes. 210 The point where the electric field is strongest and the magnetic field is weakest.

2. The rectangular waveguide filter according to claim 1, characterized in that, Hollow cylindrical waveguide provides dominant mode™ 110 Electrical coupling, adjusting the radius of the hollow cylindrical waveguide, and controlling the dominant mode TM 110 Electrical coupling quantity.

3. The rectangular waveguide filter according to claim 1, characterized in that, Hollow rectangular waveguide provides dominant mode TM 110 Magnetic coupling, adjusting the length of the hollow rectangular waveguide, and controlling the dominant mode TM 110 Magnetic coupling quantity.

4. The rectangular waveguide filter according to any one of claims 1 to 3, characterized in that, The input hollow waveguide, output hollow waveguide, first hollow waveguide, second hollow waveguide, and all coupled hollow waveguides are rectangular structures.

5. The rectangular waveguide filter according to claim 4, characterized in that, The central axis of the hollow cylindrical waveguide passes through the center of the first hollow waveguide of the upper unit and the center of the first hollow waveguide of the lower unit.

6. The rectangular waveguide filter according to claim 4, characterized in that, A pair of hollow rectangular waveguides are parallel to the first coupled hollow waveguide, and the pair of hollow rectangular waveguides are located on both sides of the second hollow waveguide of the lower unit.

7. The rectangular waveguide filter according to claim 4, characterized in that, The second and third coupled hollow waveguides are both perpendicular to the first coupled hollow waveguide, and the second coupled hollow waveguide is located on side A of the first hollow waveguide of the upper unit, while the third coupled hollow waveguide is located on side B of the second hollow waveguide of the upper unit; wherein, side A and side B are opposite sides.

8. The rectangular waveguide filter according to claim 7, characterized in that, The second coupled hollow waveguide is located at the side of the first hollow waveguide A of the upper unit. l / 4, the distance between the third coupled hollow waveguide and the side of the upper unit's second hollow waveguide B. l / 4; where, l Let be the length of the horizontal side of the first hollow waveguide and the second hollow waveguide.

Images