Rectangular cavity dual-mode filter

Abstract

The invention discloses a dual-mode filter with a rectangular cavity. Relates to the technical field of microwave filters. The metal perturbation element comprises a first metal probe, a second metal probe, a transverse metal ridge and a vertical metal ridge. And a metal cross-shaped ridge formed by the transverse metal ridge and the vertical metal ridge is arranged at the central position of the bottom in the rectangular metal cavity. Coaxial feed at the top of the cavity is adopted for excitation, and an input port and an output port are arranged on the left side and the right side of the cross-shaped ridge respectively. A feed structure is arranged at the position with the maximum electric field intensity, and a TE102 mode and a TE201 mode in a rectangular resonant cavity are excited through perturbation of a metal probe and a cross ridge. Besides, the position of a transmission zero point can be regulated and controlled by replacing a metal cross ridge arranged at the bottom of the rectangular resonant cavity, and the metal cross ridge can be randomly arranged on the left side or the right side of a passband, so that miniaturization and passband selectivity of the filter are further realized.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave filters, and in particular relates to a rectangular cavity dual-mode filter. Background Art

[0002] Cavity filters have been widely used in wireless communications and terahertz imaging due to their low production cost, high quality factor, good thermal stability and strong power handling capability. In wireless communications, they can be used as base station filters to assist base stations in sending and receiving electromagnetic waves of specific frequencies, thereby achieving high-quality signal transmission. In the field of terahertz imaging, metal cavity filters are also widely used due to their high precision and stability.

[0003] In traditional cavity filter design, in order to achieve multi-mode filter design, multiple resonators are cascaded to increase the filter order and passband selectivity. However, this method will increase the filter size and make the structure more complicated. Using multi-mode resonators instead of the original single-mode resonator can reduce the size to a certain extent when used alone or in cascade. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a rectangular cavity dual-mode filter, which excites two modes in a rectangular metal resonant cavity by loading a cross-ridge metal perturbation to generate a transmission zero point on the right side of the passband.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A rectangular cavity dual-mode filter comprises a rectangular metal cavity formed by a cavity top shell and a base; a first SMA connector and a second SMA connector are respectively arranged above the cavity top shell; a metal perturbation element is arranged inside the rectangular metal cavity, and the metal perturbation element comprises a first metal probe, a second metal probe and a metal cross ridge located at the center of the base; the metal cross ridge is composed of a horizontal metal ridge and a vertical metal ridge; the horizontal metal ridge and the vertical metal ridge are perpendicular to each other; the first metal probe is installed on the right side of the horizontal metal ridge and on the upper side of the vertical metal ridge; the second metal probe is installed on the left side of the horizontal metal ridge and on the upper side of the vertical metal ridge.

[0007] In some embodiments, the first metal probe is connected to a first SMA connector extending into the top shell of the cavity to form a coaxial feeding structure, and the second metal probe is connected to a second SMA connector extending into the top shell of the cavity to form a coaxial feeding structure.

[0008] In some embodiments, the length and width of the horizontal metal ridges and the vertical metal ridges are the same.

[0009] In some embodiments, the lengths of the horizontal metal ridges and the vertical metal ridges of the metal cross ridges can be replaced by changing the base to change the cross ridges of different lengths to adjust the position of the transmission zero point.

[0010] In some embodiments, the height of the first SMA connector and the second SMA connector is 0.6 mm, the length thereof extending into the cavity is 0.3 mm, and the first SMA connector and the second SMA connector are parallel to the vertical metal ridge.

[0011] In some embodiments, the top shell of the cavity is made of an aluminum metal shell, which is assembled with the base through screws to form a rectangular metal cavity, and a resonance cavity filled with air is formed inside the rectangular metal cavity.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] One-cavity multi-mode technology: A metal cross-ridge perturbation is set in the rectangular resonant cavity, and mutually orthogonal modes TE102 and TE201 are excited by parallel coaxial feeding. Compared with the traditional cascade method, this technology significantly reduces the size and processing cost of the filter.

[0014] Coaxial feeding excitation: Excitation is carried out through the coaxial feeding structure at the top of the cavity, and the input and output ports are placed on the left and right sides of the cross ridge respectively. The feeding structure is set at the point where the electric field strength is maximum to effectively excite the TE102 and TE201 modes.

[0015] Transmission zero point control: When the two metal ridges are the same length, the transmission zero point is located on the right side of the passband. The present invention can also flexibly move the transmission zero point position to the left or right side of the passband by replacing the bottom cover and adjusting the length of the metal cross ridge. This feature greatly improves the selectivity of the passband.

[0016] Miniaturization and passband selectivity: By changing the length of the metal ridge to adjust the position of the transmission zero point, compared with other traditional filters, the present invention further realizes the miniaturization of the filter and enhances the passband selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a three-dimensional model of a rectangular cavity dual-mode filter of the present invention.

[0018] Figure 2 It is a top view schematic diagram of a rectangular cavity dual-mode filter of the present invention.

[0019] Figure 3 It is a left schematic view of a rectangular cavity dual-mode filter of the present invention.

[0020] Figure 4 It is a front view schematic diagram of a rectangular cavity dual-mode filter of the present invention.

[0021] Figure 5 It is a simulation curve diagram of a rectangular cavity dual-mode filter of the present invention with the transmission zero point on the right.

[0022] Figure 6 It is a structural schematic diagram of a base of the present invention provided with a horizontal metal ridge and a vertical metal ridge.

[0023] Figure 7 It is a simulation curve diagram of a rectangular cavity dual-mode filter of the present invention with the transmission zero point on the left.

[0024] In the attached drawings, 1 is the top shell of the cavity, 2 is the first metal probe, 3 is the first SMA connector, 4 is the second metal probe, 5 is the second SMA connector, 6 is the horizontal metal ridge, 7 is the vertical metal ridge, and 8 is the base. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] See also Figure 1 The embodiment of the present invention provides a rectangular cavity dual-mode filter, including a cavity top shell 1, and a first SMA connector 3 and a second SMA connector 5 are respectively arranged above the cavity top shell 1, and the joints of the first SMA connector 3 and the second SMA connector 5 are respectively placed at the input and output ports of the filter, which are responsible for connecting with the external circuit through the ports to apply the excitation source. Several metal perturbation elements are arranged inside the cavity top shell 1, and their function is to excite two modes in the rectangular resonant cavity to realize a dual-mode filter; the metal perturbation elements include a first metal probe 2, a second metal probe 4, and a metal cross ridge composed of a horizontal metal ridge 6 and a vertical metal ridge 7 arranged at the center of the base 8.

[0027] See also Figure 2In some embodiments, the upper surface of the cavity top shell 1 is a square with a side length of 15.799mm, and the side surface is a rectangle with a size of 15.799mm*7.899mm. The horizontal metal ridge 6 and the vertical metal ridge 7 are arranged perpendicularly to each other at the center of the base 8, the first metal probe 2 is installed on the right side of the horizontal metal ridge 6 and the upper side of the vertical metal ridge 7, and the second metal probe 4 is installed on the left side of the horizontal metal ridge 6 and the upper side of the vertical metal ridge 7; the first metal probe 2 and the first SMA connector 3 together form a coaxial feeding structure, and the second metal probe 4 and the second SMA connector 5 together form a coaxial feeding structure for exciting the TE102 mode and the TE201 mode; the feeding structure composed of the first metal probe 2 and the first SMA interface 3 is 4.4mm away from the right side wall of the rectangular metal cavity and 5.4mm away from the upper side wall of the rectangular metal cavity; the feeding structure composed of the second metal probe 4 and the second SMA interface 5 is 4.9mm away from the left side wall of the rectangular metal cavity and 5.2mm away from the upper side wall of the rectangular metal cavity.

[0028] In some embodiments, a plane rectangular coordinate system is established with the center of the cross-ridge metal perturbation as the origin. The x-axis is parallel to the horizontal metal ridge, and the y-axis is parallel to the vertical metal ridge. The first metal probe 2 and the first SMA connector 3 are arranged on the upper left side of the cross-ridge metal perturbation, and their specific positions are 2.5 mm from the x-axis and 3 mm from the y-axis. The radius of the first metal probe 2 is 0.65 mm, and the radius of the first SMA connector 3 is 2.17 mm; the second metal probe 4 and the second SMA connector 5 are arranged on the upper right side of the cross-ridge metal perturbation, and their specific positions are 3.5 mm from the x-axis and 3 mm from the y-axis. The radius of the second metal probe 4 is 0.65 mm, and the radius of the second SMA connector 5 is 2.17 mm. The first SMA connector 3 and the second SMA connector 5 are both made of Teflon material.

[0029] In some embodiments, see Figure 3 and Figure 4 The length of the first metal probe 2 is 2.3mm, and the length of the first SMA connector 3 is 0.6mm, and the length of the second metal probe 4 is 2.3mm, and the length of the second SMA connector 5 is 0.6mm, and the length of the second SMA connector 5 is 0.3mm. The height of the top shell 1 of the cavity is 7.899mm, and the heights of the horizontal metal ridges 6 and the vertical metal ridges 7 of the two cross ridges are the same, both 7mm.

[0030] In some implementations, the bottom of the cavity top housing 1 of the present invention can be connected by snapping, threading or integrally connected with the base 8. A metal cross ridge is provided at the center of the base 8. By replacing the base 8 in a detachable connection manner such as snapping or threading, the metal cross ridges with different sizes can be easily replaced, thereby adjusting the position of the transmission zero point.

[0031] Specifically, the size of the first metal cross ridge is that the length and width of the horizontal metal ridge and the vertical metal ridge are the same. Specifically, the length of the horizontal metal ridge 6 of the first metal cross ridge is 11 mm, the width is 1.4 mm, and the length of the vertical metal ridge 7 is also 11 mm. The distance between the two metal ridges and the side wall of the cavity is 2.4 mm. At this time, the transmission zero point of the dual-mode filter is located on the right side of the passband.

[0032] See also Figure 5 The S11 and S21 curves of a rectangular cavity dual-mode filter are obtained by simulating the electromagnetic simulation software HFSS. According to the simulation results, when the lengths of the horizontal metal ridge 6 and the vertical metal ridge 7 of the filter are the same, the return loss of the filter is better than 20dB, and a transmission zero point is generated on the right side of the passband.

[0033] The size of the second type of metal cross ridge is: the lengths of the horizontal metal ridge and the vertical metal ridge of the metal cross ridge are different.

[0034] See also Figure 6 The length of the horizontal metal ridge 6 of the second cross-ridge perturbation dual-mode filter is 9.1 mm, the width is 1.4 mm, and the length of the vertical cross ridge 7 is 9.94 mm, the width is 1.4 mm. The cross ridge metal is still set at the center of the rectangular resonant cavity base 8.

[0035] See also Figure 7 , the S11 and S21 curves of a rectangular cavity dual-mode filter simulated by electromagnetic simulation software HFSS. The simulation results show that when the base 8 is replaced, the length of the horizontal metal ridge 6 and the vertical metal ridge 7 are changed, which destroys the length symmetry of the two metal ridges. Since the lengths of the horizontal metal ridge 6 and the vertical metal ridge 7 respectively regulate the resonant frequencies of the two modes, the transmission zero point will be moved to the left side of the passband.

[0036] Therefore, by replacing different bases 8, the transmission zero point can be arbitrarily set on the right side or the left side of the passband without affecting the passband while only modifying the length of the metal ridge without changing the size and structure of the rectangular metal cavity, which greatly improves the transmission performance and selectivity of the filter. This structure has shown great application value and potential in subsequent production applications.

[0037] By changing the length of the horizontal and vertical metal ridges, the size of the perturbation structure in the resonant cavity (rectangular metal cavity) can be simply adjusted to adjust the resonant frequency without changing the coupling coefficient or having a significant impact on the in-band return loss. In this way, the transmission zero point can be moved to the upper stopband or lower stopband at will.

[0038] Compared with the first metal cross ridge structure, the second metal cross ridge of the present invention has the same height of two metal ridges, but the length is changed and no longer the same, and the overall length is reduced, but the length of the vertical metal ridge is slightly longer than the horizontal metal column. By changing the symmetry of the length, the resonant frequency of the two modes can be controlled, thereby affecting the positive and negative signs of their self-coupling coefficients, thereby controlling the movement of the transmission zero position.

[0039] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A rectangular cavity dual-mode filter, characterized in that: The invention comprises a rectangular metal cavity formed by a cavity top shell (1) and a base (8); a first SMA connector (3) and a second SMA connector (5) are respectively arranged above the cavity top shell (1); a metal perturbation element is arranged inside the rectangular metal cavity (1), and the metal perturbation element comprises a first metal probe (2), a second metal probe (4) and a metal cross ridge located at the center of the base (8); the metal cross ridge is composed of a horizontal metal ridge (6) and a vertical metal ridge (7); the horizontal metal ridge (6) and the vertical metal ridge (7) are perpendicular to each other; the first metal probe (2) is installed on the right side of the horizontal metal ridge (6) and on the upper side of the vertical metal ridge (7); and the second metal probe (4) is installed on the left side of the horizontal metal ridge (6) and on the upper side of the vertical metal ridge (7).

2. A rectangular cavity dual-mode filter according to claim 1, characterized in that: The first metal probe (2) and a first SMA connector (3) extending into the top shell (1) of the cavity are connected to form a coaxial feeding structure, and the second metal probe (4) and a second SMA connector (5) extending into the top shell (1) of the cavity are connected to form a coaxial feeding structure.

3. A rectangular cavity dual-mode filter according to claim 1, characterized in that: The length and width of the horizontal metal ridge (6) and the vertical metal ridge (7) are the same.

4. A rectangular cavity dual-mode filter according to claim 1, characterized in that: The lengths of the transverse metal ridge (6) and the vertical metal ridge (7) of the metal cross ridge can be changed to metal cross ridges of different lengths by replacing the base (8) to adjust the position of the transmission zero point.

5. The rectangular cavity dual-mode filter according to claim 2, characterized in that: The height of the first SMA connector (3) and the second SMA connector (5) is 0.6 mm, the length thereof penetrating into the cavity is 0.3 mm, and the first SMA connector (3) and the second SMA connector (5) are parallel to the vertical metal ridge (7).

6. The rectangular cavity dual-mode filter according to claim 1, characterized in that: The cavity top shell (1) is composed of an aluminum metal shell, which is assembled with the base (8) by means of screws to form a rectangular metal cavity.

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