Small band-pass filter based on half-mode resonant cavity

Abstract

The invention provides a small-sized band-pass filter based on a half-mode resonant cavity, which has excellent band-pass characteristics and structurally comprises an input port, an output port and a medium resonant cavity from top to bottom in sequence. Wherein the input port and the output port are composed of two identical 50-ohm coaxial lines, outer conductors of the input port and the output port are connected with the upper surface of the resonant cavity, inner conductors of the input port and the output port are connected into a cavity body of the resonant cavity, and signals enter the resonant cavity through coupling of the input port and are transmitted to the outside through the output port after selective filtering. The dielectric resonant cavity is made of a high-dielectric-constant material, and is a rectangular cavity with a cross-shaped gap in the middle and chamfered on the periphery. The upper surface, the lower surface and the peripheral tangent plane are covered with metal layers to form a shielding cavity so as to reduce external interference. According to the small band-pass filter based on the half-mode resonant cavity, equipment miniaturization is successfully achieved under the condition that high band-pass performance is kept, and the small band-pass filter becomes a superexcellent choice of a base station filter in 5G application.

Description

Technical Field

[0001] The invention relates to a small bandpass filter based on a half-mode resonant cavity, belonging to the technical field of communication. Background Art

[0002] A bandpass filter is a circuit element that allows signals within a specific frequency range to pass through while blocking signals of other frequencies. It plays a key role in many fields such as wireless communications, radar, navigation, and measurement systems. The design and performance of the bandpass filter directly affect the overall performance of the system, such as frequency selectivity, signal transmission quality, and anti-interference ability.

[0003] As communication equipment and sensor equipment develop towards lightweight, portable and multifunctional directions, the demand for miniaturized bandpass filters continues to grow. In the field of satellite communications, satellite communication systems require equipment to have high reliability and compact design. Miniaturized bandpass filters can reduce the weight and volume of satellite communication equipment, help increase the satellite's payload and reduce launch costs. In 5G and future wireless communication systems, the expansion of the frequency range and the improvement of spectrum utilization have put forward higher requirements on the performance of the filter. Miniaturized bandpass filters can achieve effective selection of high-frequency signals while maintaining the compact design of the system to adapt to the size and performance requirements of 5G base stations and terminal equipment. Summary of the invention

[0004] The object of the present invention is to provide a small bandpass filter based on a half-mode resonant cavity.

[0005] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0006] The small bandpass filter based on the half-mode resonant cavity comprises, from top to bottom, an input port, an output port, and a dielectric resonant cavity. The half-mode resonant filter has a high out-of-band suppression ratio, and realizes the miniaturization of the filter while ensuring high performance.

[0007] The input port and output port of the small bandpass filter based on the semi-membrane resonant cavity are composed of two 50-ohm coaxial lines of exactly the same size. The lower surface of the outer conductor of the coaxial line is connected to the upper surface of the dielectric resonant cavity coated with a metal layer, and the inner conductor is connected to the interior of the resonant cavity. The input port and the output port are arranged in mirror symmetry with respect to the diagonal of the dielectric resonant cavity. The dielectric resonant cavity is a rectangular cube with a cross slit in the center and cut corners on all sides. The upper surface, lower surface, surrounding cut surfaces and cross slit surface of the resonant cavity are all coated with a metal layer with excellent conductivity. Four cylindrical protrusions are provided on the lower surface of the dielectric resonant cavity to optimize the frequency selection characteristics of the resonant cavity, and the positions of the protrusions are centrally symmetrically distributed relative to the center of the dielectric resonant cavity.

[0008] As a preferred solution, the radius of the inner conductor of the input port is r1=0.75 mm, the length is L1=5.78 mm, and the inner conductor is made of silver, with a conductivity of 6.301*10^7 S / m at room temperature (20°C).

[0009] As a preferred solution, the radius of the outer conductor of the input port is r2=1.73 mm, the length is L2=2 mm, the interior of the outer conductor is filled with air, and the relative dielectric constant is 1.

[0010] As a preferred solution, the radius of the inner conductor of the output port is r1=0.75mm, the length is L1=5.78mm, and the inner conductor is made of silver, with a conductivity of 6.301*10 at room temperature (20°C). 7 S / m.

[0011] As a preferred solution, the radius of the outer conductor of the output port is r2=1.73 mm, the length is L2=2 mm, the interior of the outer conductor is filled with air, and the relative dielectric constant is 1.

[0012] As a preferred solution, the distance between the center of the input port and the center of the output port is L3 = 7 mm.

[0013] As a preferred solution, the distances from the center of the input port and the center of the output port to the center of the dielectric resonant cavity are both L4=20.2 mm.

[0014] As a preferred solution, the upper and lower surfaces of the dielectric resonant cavity are squares with four corners cut off, and the side length is L5 = 16.7 mm.

[0015] As a preferred solution, the cut edges of the upper and lower surfaces of the dielectric resonant cavity are smoothed, and the cutting length is L6=1.2 mm.

[0016] As a preferred solution, the height of the dielectric resonant cavity is h1=6 mm, the thickness is d1=0.3 mm, and the material is a high dielectric constant medium with a relative dielectric constant of 20.3.

[0017] As a preferred solution, the center of the cross gap coincides with the center of the dielectric resonant cavity, the major axis length L7 of the cross is 25.3 mm, and the minor axis length L9 is 19.8 mm.

[0018] As a preferred solution, the radius of the cylindrical protrusion on the lower surface of the resonant cavity is r3 = 1.5 mm, and the height is h2 = 1.1 mm.

[0019] As a preferred solution, the four cylindrical protrusions are centrally symmetrically distributed relative to the center of the dielectric resonant cavity, and the distance between each protrusion is L10=6 mm.

[0020] As a preferred solution, the thickness of each metal coating layer is d2 = 0.01 mm.

[0021] The object of the present invention is to provide a miniaturized bandpass filter based on a half-mode resonant cavity.

[0022] Principle of the present invention:

[0023] According to the resonant cavity theory, the resonant frequency of the cubic resonant cavity satisfies the equation:

[0024]

[0025] Among them, f mnl is the resonant frequency, c is the speed of light, equal to 3*10 8 m / s,μ r , ε r are the relative magnetic permeability and relative dielectric constant of the filling medium material, a, b, l are the length, width and height of the rectangular resonant cavity, and m, n, p represent the number of resonant cavity modes. According to the above formula combined with Maxwell's equations and boundary conditions, it can be deduced that when the resonant cavity works at TE 101 When the mode is , the magnetic field distribution can be described by the following equation:

[0026]

[0027] Among them, H x , H z Represent the magnitude of the magnetic field in the x direction and the z direction respectively. x It is not difficult to see that the tangential magnetic field is always equal to 0 on the plane z = l / 2. Therefore, the plane z = l / 2 can be equivalent to an ideal magnetic wall.

[0028] According to the calculation formula of the reflection coefficient of electromagnetic waves on the interface of different media, when the electromagnetic wave is incident from the high dielectric constant medium to the air, its reflection coefficient satisfies the equation:

[0029]

[0030] Where Γ represents the reflection coefficient, ε r Represents the relative dielectric constant of the medium. It can be seen from the formula that when ε r When it approaches positive infinity, Γ approaches 1, at which point the medium interface can be equivalent to a virtual magnetic wall.

[0031] Therefore, by using ceramic materials with high dielectric constant to make the resonant cavity, cutting along the plane z=l / 2 and coating the remaining planes with silver, a virtual magnetic wall can be equivalently generated on the plane z=l / 2. In this way, the volume of the resonant cavity can be reduced to 1 / 2 of the original without destroying the resonant characteristics inside the cavity. z Calculation formula, the above principle also applies to the plane x=a / 2.

[0032] Compared with the prior art, the present invention has the following significant advantages: 1) Miniaturization: The volume is nearly 50% smaller than that of traditional filters, which greatly reduces the overall size of the device and is suitable for space-constrained applications such as mobile communication devices, Internet of Things terminals, and satellite communication systems. 2) High out-of-band suppression ratio: The filter has a high out-of-band suppression ratio, ensuring excellent frequency selectivity, effectively reducing interference from adjacent frequency bands, and improving the signal quality and performance stability of the system. 3) Easy to integrate: Due to its small size and excellent performance, the filter is easier to integrate into complex electronic systems, which helps to make the equipment lightweight and multifunctional, and improves the flexibility of system design.

[0033] The present invention is described in further detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of the half-mode dielectric filter of the present invention;

[0035] Figure 2 FIG1 is a component composition diagram of a half-mode dielectric filter of the present invention;

[0036] Figure 3 FIG2 is a component composition diagram of the half-mode dielectric filter of the present invention;

[0037] Figure 4 FIG3 is a component composition diagram of the half-mode dielectric filter of the present invention;

[0038] Figure 5 A top view of a half-mode dielectric filter of the present invention;

[0039] Figure 6 It is a front view of the half-mode dielectric filter of the present invention;

[0040] Figure 7 A bottom view of the half-mode dielectric filter of the present invention;

[0041] Figure 8 The reflection coefficient (S11) and the transmission coefficient (S21) of the half-mode dielectric filter of the present invention; DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] This example provides a small bandpass filter based on a half-mode resonant cavity, including an input port 1, an output port 2, and a dielectric resonant cavity 3. The filter has good frequency selectivity and successfully achieves miniaturization, which can perfectly meet the various requirements of 5G base stations for filters.

[0044] The central operating frequency of the semi-mode dielectric filter satisfies:

[0045]

[0046] Among them, f mnl is the resonant frequency, c is the speed of light, equal to 3*10 8 m / s,μ r , ε r are the relative magnetic permeability and relative dielectric constant of the filling dielectric material, a, b, l are the length, width and height of the equivalent rectangular resonant cavity, m, n, p represent the number of resonant cavity modes.

[0047] The small bandpass filter based on the half-mode resonant cavity comprises, from top to bottom, an input port 1, an output port 2, and a dielectric resonant cavity 3. The bandpass filter has excellent frequency selectivity, a high out-of-band suppression ratio, and a volume that is reduced by nearly 50% compared to filters with the same performance.

[0048] The input port 1 and output port 2 of the small bandpass filter based on the semi-membrane resonant cavity are composed of two 50-ohm coaxial lines 101 and 102 of exactly the same size. The lower surfaces of the outer conductors of the two coaxial lines are connected to the upper surface of the dielectric resonant cavity coated with a metal layer, and the inner conductor is connected to the inside of the resonant cavity. The input port and the output port are arranged in mirror symmetry relative to the diagonal 1 of the dielectric resonant cavity. The dielectric resonant cavity 3 is a rectangular cube with a cross slit 301 in the center and cut corners around. The upper surface, lower surface, surrounding cut surfaces and cross slit surfaces 302, 303, 304, 305, 306, 307, 308 of the resonant cavity are all coated with a metal layer with excellent conductivity. Four cylindrical protrusions 309, 310, 311, 312 are provided on the lower surface of the dielectric resonant cavity to optimize the frequency selection characteristics of the resonant cavity. The protrusion positions are centrally symmetrically distributed relative to the center of the dielectric resonant cavity.

[0049] In a further embodiment, the radius of the inner conductor of the input port is r1=0.75 mm, the length is L1=5.78 mm, the inner conductor is made of silver, and the conductivity is 6.301*10^7 S / m at room temperature (20°C).

[0050] In a further embodiment, the radius of the outer conductor of the input port is r2=1.73 mm, the length is L2=2 mm, the interior of the outer conductor is filled with air, and the relative dielectric constant is 1.

[0051] In a further embodiment, the radius of the inner conductor of the output port is r1=0.75 mm, the length is L1=5.78 mm, the inner conductor is made of silver, and the conductivity is 6.301*10 7 S / m.

[0052] In a further embodiment, the radius of the outer conductor of the output port is r2=1.73 mm, the length is L2=2 mm, the interior of the outer conductor is filled with air, and the relative dielectric constant is 1.

[0053] In a further embodiment, the distance between the center of the input port and the center of the output port is L3 = 7 mm.

[0054] In a further embodiment, the distances from the centers of the input port and the output port to the center of the dielectric resonant cavity are both L4=20.2 mm.

[0055] In a further embodiment, the upper and lower surfaces of the dielectric resonant cavity are squares with four corners cut off, and the side length is L5 = 16.7 mm.

[0056] In a further embodiment, the cut edges of the upper and lower surfaces of the dielectric resonant cavity are smoothed, and the cutting length is L6=1.2 mm.

[0057] In a further embodiment, the height of the dielectric resonant cavity is h1=6 mm, the thickness is d1=0.3 mm, and the material is a high dielectric constant dielectric with a relative dielectric constant of 20.3.

[0058] In a further embodiment, the center of the cross gap coincides with the center of the dielectric resonant cavity, the major axis length L7 of the cross is 25.3 mm, and the minor axis length L9 is 19.8 mm.

[0059] In a further embodiment, the radius r3 of the cylindrical protrusion on the lower surface of the resonant cavity is 1.5 mm, and the height h2 is 1.1 mm.

[0060] In a further embodiment, the four cylindrical protrusions are centrally symmetrically distributed relative to the center of the dielectric resonant cavity, and the distance between each protrusion is L10=6 mm.

[0061] In a further embodiment, the thickness of each metal coating layer is d2 = 0.01 mm.

[0062] Figure 1 The overall structure diagram of the half-mode dielectric filter of the present invention;

[0063] Figure 2 , 3 4. is a component composition diagram of the half-mode dielectric filter of the present invention.

[0064] Figure 5 , 67 are the top view, bottom view and front view of the half-mode dielectric filter of the present invention, which includes an input port, an output port and a dielectric resonant cavity.

[0065] Figure 8 The reflection coefficient (S11) and transmission coefficient (S21) of the half-mode dielectric filter of the present invention show that the half-mode dielectric filter has excellent frequency selection characteristics, and the higher out-of-band suppression ratio can effectively improve the signal quality and performance stability.

Claims

1. A small bandpass filter based on a half-mode resonant cavity with excellent frequency selection characteristics and a small size; The bandpass filter comprises, from top to bottom: An input port, an output port, and a dielectric resonant cavity, wherein the input port (1) and the output port (2) are at the same height and are both located on the upper surface of the dielectric resonant cavity (3); The input port (1) and the output port (2) are composed of two coaxial lines (101) and (201) with completely identical dimensions and structures. The two coaxial lines are distributed in a mirror-symmetrical manner with respect to the diagonal of the resonant cavity. The lower surface of the outer conductor of the coaxial line is connected to the upper surface of the resonant cavity, and the inner conductor is connected to the interior of the resonant cavity. A cross gap (301) is provided at the center of the dielectric resonant cavity (3), the center of the gap coincides with the center of the resonant cavity, and the two sides coincide with the diagonals of the resonant cavity respectively. The resonant cavity (3) is cut at four corners, and its upper surface, lower surface, four cut surfaces and cross gap surface are coated with metallic silver (302), (303), (304), (305), (306), (307) and (308) having excellent electrical conductivity. Four cylindrical protrusions (309), (310), (311) and (312) are provided on the lower surface of the dielectric resonant cavity, and the protrusions are symmetrically distributed relative to the center of the dielectric resonant cavity.

2. According to claim 1, a small bandpass filter based on a semi-membrane resonant cavity, the resonant frequency of which satisfies the equation: in, f mnl is the resonant frequency, c is the speed of light, equal to 3*10 8 m / s,μ r , ε r are the relative magnetic permeability and relative dielectric constant of the filling dielectric material, a, b, l are the length, width and height of the equivalent rectangular resonant cavity, m, n, p represent the number of resonant cavity modes.

3. A small bandpass filter based on a half-mode resonant cavity according to claim 1, characterized in that: A high dielectric constant medium is used as the material for making the resonant cavity, and silver is coated on the planes except the cross-section, so as to establish an equivalent magnetic wall on the cross-section, thereby reducing the volume to half of the original without destroying the resonant characteristics of the cavity.

4. A small bandpass filter based on a half-mode resonant cavity according to claim 3, characterized in that: The inner conductor radius of the coaxial line (101) and the coaxial line (201) is r1 and the length is L1, and the outer conductor radius is r2 and the length is L2.

5. A small bandpass filter based on a half-mode resonant cavity according to claim 3, characterized in that: The center distance between the coaxial lines (101) and (201) is L3, and the distance between the centers of the two and the center of the dielectric resonant cavity is L4.

6. A small bandpass filter based on a half-mode resonant cavity according to claim 4, characterized in that: The upper and lower surfaces of the dielectric resonant cavity (3) are squares with four corners cut off, with a side length of L5. The cut edges of the upper and lower surfaces are smoothed, with a cutting length of L6. The dielectric resonant cavity (3) has a height of h1 and a thickness of d1. The material selected is a high dielectric constant medium with a relative dielectric constant of 20.

3.

7. A small bandpass filter based on a half-mode resonant cavity according to claim 3, characterized in that: The center of the cross gap (301) coincides with the center of the dielectric resonant cavity (3), and the major axis length of the cross is L7, and the minor axis length is L9.

8. A small bandpass filter based on a half-mode resonant cavity according to claim 3, characterized in that: The cylindrical protrusions (309), (310), (311), (312) on the lower surface of the resonant cavity (3) have a radius r3 and a height h2. The four cylindrical protrusions (309), (310), (311), (312) are centrally symmetrically distributed relative to the center of the dielectric resonant cavity (3), and the distance between each protrusion is L1.

9. A small bandpass filter based on a half-mode resonant cavity according to claim 3, characterized in that: The thickness of each metal coating layer (302), (303), (304), (305), (306), (307), and (308) is d2.

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