A small band-pass filter based on half-mode resonator

Abstract

The application provides a small-sized band-pass filter based on a half-mode resonant cavity, which has excellent band-pass characteristics, and the structure thereof is as follows from top to bottom: an input port, an output port and a dielectric resonant cavity.The input port and the output port are formed by two 50-ohm coaxial lines which are completely same, the outer conductor of the coaxial line is connected with the upper surface of the resonant cavity, and the inner conductor is connected with the cavity body, a signal is coupled into the resonant cavity through the input port, and is transmitted to the outside through the output port after selective filtering.The dielectric resonant cavity is made of a high dielectric constant material, and the structure thereof is a rectangular cavity body which is provided with a cross-shaped gap in the middle and is cut at the corners.The upper surface, the lower surface and the cut surfaces are all covered with a metal layer to form a shielding cavity body so as to reduce external interference.The small-sized band-pass filter based on the half-mode resonant cavity has successfully realized the miniaturization of the equipment under the condition of keeping high band-pass performance, and becomes an excellent choice for base station filters in 5G applications.

Description

Technical Field

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

[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 crucial role in numerous fields, including wireless communication, radar, navigation, and measurement systems. The design and performance of a bandpass filter directly affect the overall system performance, such as frequency selectivity, signal transmission quality, and interference immunity.

[0003] As communication and sensor equipment evolves towards lighter, more portable, and multifunctional designs, the demand for miniaturized bandpass filters continues to grow. In satellite communications, systems require highly reliable and compact designs. Miniaturized bandpass filters can reduce the weight and size of satellite communication equipment, contributing to increased payload capacity and lower launch costs. In 5G and future wireless communication systems, the expansion of frequency ranges and improved spectral efficiency place even higher demands on filter performance. Miniaturized bandpass filters enable effective selection of high-frequency signals while maintaining a compact system design to meet the size and performance requirements of 5G base stations and terminal equipment. Summary of the Invention

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

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

[0006] The miniature bandpass filter based on a half-mode resonant cavity comprises, from top to bottom: an input port, an output port, and a dielectric resonant cavity. This half-mode resonant filter exhibits a high out-of-band rejection ratio, achieving miniaturization while maintaining high performance.

[0007] The input and output ports of the miniature bandpass filter based on a half-film resonator are composed of two identical 50-ohm coaxial cables. The lower surface of the outer conductor of the coaxial cable is connected to the upper surface of the dielectric resonator, which is coated with a metal layer, and the inner conductor is inserted into the cavity. The input and output ports are arranged in a mirror-symmetric manner with respect to the diagonal of the dielectric resonator. The dielectric resonator is a rectangular cube with a cross-shaped slit in the center and chamfered corners around the perimeter. The upper surface, lower surface, chamfered surfaces, and the surface of the cross-shaped slit of the resonator are all coated with a metal layer with excellent conductivity. The lower surface of the dielectric resonator has four cylindrical protrusions to optimize the frequency selectivity of the resonator, and the protrusions are centrally symmetrically distributed with respect to the center of the dielectric resonator.

[0008] As a preferred option, the inner conductor of the input port has a radius of r1 = 0.75 mm and a length of L1 = 5.78 mm. Silver is selected as the material for the inner conductor, and its conductivity at room temperature (20℃) is 6.301*10^7 S / m.

[0009] As a preferred embodiment, the outer conductor of the input port has a radius of r2 = 1.73 mm and a length of L2 = 2 mm. The outer conductor is filled with air and has a relative permittivity of 1.

[0010] As a preferred embodiment, the inner conductor of the output port has a radius of r1 = 0.75 mm and a length of L1 = 5.78 mm. Silver is chosen as the material for the inner conductor, and its conductivity at room temperature (20℃) is 6.301 × 10⁻⁶. 7 S / m.

[0011] As a preferred embodiment, the outer conductor of the output port has a radius of r2 = 1.73 mm and a length of L2 = 2 mm. The outer conductor is filled with air and has a relative permittivity of 1.

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

[0013] As a preferred option, the distance from the center of the input port and the center of the output port to the center of the dielectric resonant cavity is L4 = 20.2 mm.

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

[0015] As a preferred option, the chamfered edges of the upper and lower surfaces of the dielectric resonator are smoothed, with a cutting length of L6 = 1.2 mm.

[0016] As a preferred option, the height of the dielectric resonator 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.

[0017] As a preferred embodiment, the center of the cross-shaped slit coincides with the center of the dielectric resonant cavity, the major axis of the cross is L7 = 25.3 mm, and the minor axis is L9 = 19.8 mm.

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

[0019] As a preferred 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 = 6mm.

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

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

[0022] The principle of this invention:

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

[0024]

[0025] Among them, f mnl Where c is the resonant frequency, and c is the speed of light, which is 3 * 10⁻⁶ 8 m / s, μ r ε r Let be the relative permeability and relative permittivity of the filling dielectric material, respectively; a, b, and l be the length, width, and height of the rectangular resonant cavity, respectively; and m, n, and p represent the number of modes in the resonant cavity. Based on the above formulas and Maxwell's equations and boundary conditions, it can be derived that when the resonant cavity operates at TE... 101 When the modulus is constant, its magnetic field distribution can be described by the following equation:

[0026]

[0027] Among them, H x H z These represent the magnitudes of the magnetic field in the x and z directions, respectively. (Through H...) x It is easy to see that the tangential magnetic field is always equal to 0 in the plane z = l / 2. Therefore, the plane z = l / 2 can be considered as an ideal magnetic wall.

[0028] According to the formula for calculating the reflection coefficient of electromagnetic waves at the interface between different media, when an electromagnetic wave is incident from a medium with a high dielectric constant into air, its reflection coefficient satisfies the following equation:

[0029]

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

[0031] Therefore, by using a ceramic material with a high dielectric constant to fabricate the resonant cavity, cutting along the plane z = l / 2, and coating the remaining planes with silver, an equivalent virtual magnetic wall can be generated at the plane z = l / 2. In this way, the volume of the resonant cavity can be reduced to half of its original size without compromising the internal resonant characteristics. According to H... z The calculation formula and the principles described above also apply to the plane x = a / 2.

[0032] Compared with existing technologies, the significant advantages of this invention are: 1) Miniaturization: The size is reduced by nearly 50% compared to traditional filters, significantly reducing the overall size of the device and making it suitable for space-constrained applications such as mobile communication devices, IoT terminals, and satellite communication systems. 2) High out-of-band rejection ratio: The filter has a high out-of-band rejection 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 integration: Due to its small size and excellent performance, this filter is easier to integrate into complex electronic systems, contributing to lightweight and multifunctional device design and improving the flexibility of system design.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

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

[0035] Figure 2 Figure 1 shows the component composition of the half-mode dielectric filter of the present invention;

[0036] Figure 3 Figure 2 shows the component composition of the half-mode dielectric filter of the present invention;

[0037] Figure 4 Figure 3 shows the component composition of the half-mode dielectric filter of the present invention;

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

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

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

[0041] Figure 8 The reflection coefficient (S11) and transmission coefficient (S21) of the half-mode dielectric filter of the present invention are shown. Detailed Implementation

[0042] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed 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 exhibits good frequency selectivity and successfully achieves miniaturization, perfectly meeting the various requirements of 5G base stations for filters.

[0044] The center operating frequency of the half-mode dielectric filter satisfies:

[0045]

[0046] Among them, f mnl Where c is the resonant frequency, and c is the speed of light, which is 3 * 10⁻⁶ 8 m / s, μ r ε r denoted as the relative permeability and relative permittivity of the filling dielectric material, respectively; a, b, and l represent the length, width, and height of the equivalent rectangular resonant cavity, respectively; and m, n, and p represent the number of resonant cavity modes.

[0047] The miniature bandpass filter based on a half-mode resonator comprises, from top to bottom: input port 1, output port 2, and dielectric resonator 3. This bandpass filter exhibits excellent frequency selectivity, high out-of-band rejection ratio, and a volume reduction of nearly 50% compared to filters with similar performance.

[0048] The input port 1 and output port 2 of the miniature bandpass filter based on a half-film resonator are composed of two identical 50-ohm coaxial cables 101 and 102. The lower surfaces of the outer conductors of the two coaxial cables are connected to the upper surface of the dielectric resonator coated with a metal layer, and the inner conductors are connected to the interior of the resonator. The input and output ports are arranged in a mirror-symmetric manner with respect to the diagonal 1 of the dielectric resonator. The dielectric resonator 3 is a rectangular cube with a cross-shaped slit 301 in the center and chamfered corners around the perimeter. The upper surface, lower surface, chamfered surfaces, and cross-shaped slit surfaces 302, 303, 304, 305, 306, 307, and 308 of the resonator are all coated with a metal layer with excellent conductivity. The lower surface of the dielectric resonator has four cylindrical protrusions 309, 310, 311, and 312, which are used to optimize the frequency selectivity of the resonator. The protrusions are centrally symmetrically distributed with respect to the center of the dielectric resonator.

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

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

[0051] In a further embodiment, the inner conductor of the output port has a radius of r1 = 0.75 mm and a length of L1 = 5.78 mm. Silver is chosen as the material for the inner conductor, and its conductivity at room temperature (20°C) is 6.301 × 10⁻⁶. 7 S / m.

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

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

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

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

[0056] In a further embodiment, the chamfered edges of the upper and lower surfaces of the dielectric resonator are smoothed, with a cutting length of 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 slit coincides with the center of the dielectric resonant cavity, the major axis of the cross is L7 = 25.3 mm, and the minor axis is L9 = 19.8 mm.

[0059] In a further embodiment, the cylindrical protrusion on the lower surface of the resonant cavity has a radius r3 = 1.5 mm and a height h2 = 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 Overall structural diagram of the half-mode dielectric filter of the present invention;

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

[0064] Figure 5 , 6Figures 7 and 8 are top view, bottom view, and front view of the half-mode dielectric filter of the present invention, including 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 selectivity characteristics and the high out-of-band rejection ratio can effectively improve signal quality and performance stability.

Claims

1. A small bandpass filter based on a half-mode resonant cavity; The bandpass filter, from top to bottom, includes: The input port, output port, and dielectric resonant cavity are located at the same height, and both are situated 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 identical dimensions and structures. The two coaxial lines are distributed in a mirror symmetry relative 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 inside of the resonant cavity. The dielectric resonant cavity (3) has a cross-shaped slit (301) at its center, the center of the slit coincides with the center of the resonant cavity, and the two sides coincide with the diagonal of the resonant cavity respectively. The resonant cavity (3) has chamfered corners around its perimeter, and its upper surface, lower surface, surrounding chamfered surfaces and cross-shaped slit surface are all coated with metallic silver (302), (303), (304), (305), (306), (307), (308) with excellent conductivity. The lower surface of the dielectric resonant cavity is provided with four cylindrical protrusions (309), (310), (311), (312), and the positions of the protrusions are centrally symmetrically distributed relative to the center of the dielectric resonant cavity.

2. The miniature bandpass filter based on a half-mode resonant cavity according to claim 1, wherein its resonant frequency satisfies the equation: ； in, The resonant frequency, The speed of light is 3 * 10 8 m / s, , These represent the relative permeability and relative permittivity of the filling dielectric material, respectively. , , These represent the length, width, and height of the equivalent rectangular resonant cavity, respectively. , , This represents 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 medium with a high dielectric constant is used as the material for the resonant cavity. Silver is coated on the planes other than the cross-section to create 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 of coaxial line (101) and coaxial line (201) has a radius of r1 and a length of L1, and the outer conductor has a radius of r2 and a length of 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 from the center of both lines to 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 resonator (3) are squares with four corners cut off, with a side length of L5. The edges of the cut corners on the upper and lower surfaces are smoothed, with a cutting length of L6. The height of the dielectric resonator (3) is h1, and the thickness is d1. The material 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-shaped slit (301) coincides with the center of the dielectric resonant cavity (3), with the long axis of the cross being L7 and the short axis being 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), and (312) on the lower surface of the resonant cavity (3) have a radius of r3 and a height of h2. The four cylindrical protrusions (309), (310), (311), and (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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