Small hybrid mode filter with two resonant cavities

Abstract

The embodiment of the present invention discloses a small hybrid mode filter with two resonant cavities, belonging to the field of communication technology. The filter comprises: n resonant cavities connected in series, and a metal sheet is spaced between each two adjacent resonant cavities, n≥3; the first and last resonant cavities of the n resonant cavities are metal resonant cavities, and the remaining n‑2 resonant cavities are dielectric dual-mode resonant cavities; the n resonant cavities are coupled through the coupling window on the metal sheet. The filter provided by the embodiment of the present invention has the characteristics of compact size, low loss, large power capacity, high out-of-band suppression, and good harmonic performance, so as to effectively improve the anti-interference ability and spectrum utilization of the 5G communication system, reduce the power consumption of the 5G communication system, and improve the coverage of the 5G communication system.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of communication technology, and in particular to a small hybrid mode filter with two resonant cavities. Background Art

[0002] The Sub 6GHz in 5G (5th Generation) communications uses MIMO (Multi-Input Multi-Output) technology, which requires the integration of a large number of filters inside the antenna. Therefore, there are higher requirements for the filter's loss, out-of-band suppression, power capacity, volume, weight, etc.

[0003] If a traditional metal filter is used, it cannot be integrated into the antenna due to its large size and weight. If a small dielectric waveguide filter is used, although the size of the small dielectric waveguide filter is small, its insertion loss is large and its power capacity is low. Summary of the invention

[0004] The embodiment of the present invention provides a small hybrid mode filter with two resonant cavities, which is used to solve the problems in the prior art. The technical solution is as follows:

[0005] In one aspect, a small hybrid mode filter having two resonant cavities is provided, the filter comprising: n resonant cavities connected in series, with a metal sheet spaced between every two adjacent resonant cavities, n≥3;

[0006] The first and last resonant cavities among the n resonant cavities are metal resonant cavities, and the remaining n-2 resonant cavities are dielectric dual-mode resonant cavities;

[0007] The n resonant cavities are coupled through coupling windows on the metal sheet.

[0008] In a possible implementation, two symmetrical coupling holes are provided on the dielectric dual-mode resonant cavity, and the two coupling holes are used to generate coupling between two orthogonal resonant frequencies.

[0009] In a possible implementation manner, the diameter of the coupling hole is positively correlated with the coupling coefficient between the resonant frequencies.

[0010] In a possible implementation, the coupling holes on two adjacent dielectric dual-mode resonant cavities are staggered, and the four resonant frequencies contained in the two adjacent dielectric dual-mode resonant cavities generate negative cross-coupling and generate two symmetrical transmission zeros at both ends of the passband of the filter.

[0011] In a possible implementation, a cross-shaped coupling window is provided on the metal sheet located between the i-th and i+1-th dielectric dual-mode resonant cavities;

[0012] The long side of the cross-shaped coupling window is used to generate the coupling of the main path of the filter, and the short side is used to generate the cross coupling.

[0013] In a possible implementation manner, the size of the coupling window is positively correlated with the size of the coupling coefficient between the dielectric dual-mode resonant cavities.

[0014] In a possible implementation, the dielectric dual-mode resonant cavity includes a metal shell and a dielectric block located inside the metal shell, and the two coupling holes are located on the dielectric block.

[0015] In a possible implementation, through holes are provided on the metal shell and the metal resonant cavity, and the filter further includes a metal rod, which passes through the through hole to connect the resonant cavity and the metal sheet in series, and each metal rod is fixed to the two metal resonant cavities via a nut.

[0016] In a possible implementation manner, the dielectric block is a microwave ceramic dielectric block.

[0017] In a possible implementation, the filter is applied to a sub 6 GHz frequency band.

[0018] The beneficial effects of the technical solution provided by the embodiment of the present invention include at least:

[0019] Since the small hybrid mode filter with two resonant cavities includes n resonant cavities connected in series, the first and last resonant cavities of the n resonant cavities are metal resonant cavities, and the remaining n-2 resonant cavities are dielectric dual-mode resonant cavities, and a metal sheet is spaced between each two adjacent resonant cavities, the n resonant cavities can be coupled through the coupling window on the metal sheet. In this way, tap coupling can be achieved through two metal resonant cavities, and the far-end harmonics of the filter can be suppressed by utilizing the characteristic that the secondary resonant frequency of the metal resonant cavity is far from the working resonant frequency; the high dielectric constant and low loss characteristics of the medium in the dielectric dual-mode resonant cavity can also be utilized to reduce the volume and in-band insertion loss of the filter. In summary, the filter provided in this embodiment has the characteristics of compact size, low loss, large power capacity, high out-of-band suppression, and good harmonic performance, thereby effectively improving the anti-interference capability and spectrum utilization of the 5G system, reducing the power consumption of the 5G communication system, and improving the coverage of the 5G communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 is a schematic diagram of a small hybrid mode filter with two resonant cavities in one embodiment of the present invention;

[0022] Figure 2 is an internal structure diagram of a filter in one embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of electric field distribution of a dielectric dual-mode resonant cavity in one embodiment of the present invention;

[0024] Figure 4 is a structural diagram of a dielectric dual-mode resonant cavity in one embodiment of the present invention;

[0025] Figure 5 is a structural diagram of a filter with a hidden metal housing and a metal sheet in one embodiment of the present invention;

[0026] Figure 6 is a schematic diagram of a near-end frequency response curve of a filter in one embodiment of the present invention;

[0027] Figure 7 is a schematic diagram of a metal sheet in one embodiment of the present invention;

[0028] Figure 8 It is a schematic diagram of a far-end harmonic characteristic curve of a filter in one embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Please refer to Figure 1 , which shows a small hybrid mode filter with two resonant cavities provided by an embodiment of the present invention, the filter comprises: n resonant cavities 110 connected in series, and a metal sheet 120 is spaced between every two adjacent resonant cavities 110, n≥3.

[0031] If the number of the resonant cavities 110 is n, the number of the metal sheets 120 is n-1, and the number n can be determined according to actual filter indicators, which is not limited in this embodiment.

[0032] Figure 1In this example, n is 6. Figure 1 The figure shows a tenth-order four-zero-point mixed mode filter, which includes a first resonant cavity 110, a first metal sheet 120, a second resonant cavity 110, a second metal sheet 120, a third resonant cavity 110, a third metal sheet 120, a fourth resonant cavity 110, a fourth metal sheet 120, a fifth resonant cavity 110, a fifth metal sheet 120, and a sixth resonant cavity 110.

[0033] In this embodiment, a mixed mode of a metal resonant cavity and a dielectric dual-mode resonant cavity is used to realize the filter. In one implementation, the first and last resonant cavities 110 of the n resonant cavities 110 are metal resonant cavities, and the remaining n-2 resonant cavities 110 are dielectric dual-mode resonant cavities. Figure 1 Taking the filter in the example as an example, the first resonant cavity 110 ( Figure 1 The leftmost resonant cavity 110) and the sixth resonant cavity 110 ( Figure 1 The rightmost resonant cavity 110 is a metal resonant cavity, and the second to fourth resonant cavities 110 in the middle are dielectric dual-mode resonant cavities. Figure 1 110-1 represents a metal resonant cavity, and 110-2 represents a dielectric dual-mode resonant cavity. The metal resonant cavity needs to be grounded to solve the problem of lightning strike.

[0034] Since the first resonant cavity 110 is the input end of the filter and the last resonant cavity 110 is the output end of the filter, and a metal resonant column is used for loading, the far-end harmonics of the filter can be suppressed by utilizing the characteristic that the secondary resonant frequency of the metal resonant cavity is far away from the working resonant frequency, that is, the far-end parasitic passband of the filter can be suppressed.

[0035] A high dielectric constant dual-mode resonant cavity is used as the intermediate resonant cavity, so that the high dielectric constant characteristics and dual-mode characteristics can be used to reduce the size of the resonant cavity 110 in the filter. In one implementation, the dielectric dual-mode resonant cavity can be a microwave ceramic medium, and the low loss characteristics of the microwave ceramic medium can be used to improve the loss characteristics of the filter.

[0036] In this embodiment, a coupling window 121 is provided on the metal sheet 120 , so that the n resonant cavities 110 can be coupled through the coupling window 121 on the metal sheet 120 .

[0037] Among them, the resonant cavity 110 can be manufactured separately as an independent component, and the metal sheet 120 can also be manufactured separately as an independent component. Then, the resonant cavity 110 and the metal sheet 120 are assembled to obtain a filter, thereby reducing the difficulty of filter production and facilitating filter production.

[0038] In summary, the small hybrid mode filter with two resonant cavities provided in this embodiment includes n resonant cavities connected in series, the first and last resonant cavities of the n resonant cavities are metal resonant cavities, and the remaining n-2 resonant cavities are dielectric dual-mode resonant cavities, and a metal sheet is spaced between each two adjacent resonant cavities, and the n resonant cavities can be coupled through the coupling window on the metal sheet. In this way, tap coupling can be achieved through two metal resonant cavities, and the far-end harmonics of the filter can be suppressed by utilizing the characteristic that the secondary resonant frequency of the metal resonant cavity is far from the working resonant frequency; the high dielectric constant characteristics and low loss characteristics of the medium in the dielectric dual-mode resonant cavity can also be utilized to reduce the volume and in-band insertion loss of the filter. In summary, the filter provided in this embodiment has the characteristics of compact size, low loss, large power capacity, high out-of-band suppression, and good harmonic performance, thereby effectively improving the anti-interference capability and spectrum utilization of the 5G system, reducing the power consumption of the 5G communication system, and improving the coverage of the 5G communication system.

[0039] Please refer to Figure 2 As shown in the internal structure diagram of the filter, two symmetrical coupling holes 111 are provided on the dielectric dual-mode resonant cavity in this embodiment, and the two coupling holes 111 are used to generate coupling between two orthogonal resonant frequencies. Figure 2 If n is 6, the filter includes 4 dielectric dual-mode resonant cavities. Since each dielectric dual-mode resonant cavity produces two orthogonal resonant frequencies, these 4 dielectric dual-mode resonant cavities constitute 8 resonant frequencies.

[0040] The diameter of the coupling hole 111 is positively correlated with the coupling coefficient between the resonant frequencies. That is, the larger the diameter of the coupling hole 111, the larger the coupling coefficient between the resonant frequencies; the smaller the diameter of the coupling hole 111, the smaller the coupling coefficient between the resonant frequencies. In this way, the coupling coefficient between the resonant frequencies can be adjusted by adjusting the diameter of the coupling hole 111.

[0041] Figure 3 Two symmetrical coupling holes 111 are shown in FIG. 1 , and the dotted line between the dielectric blocks 113 represents the electric field distribution 115 of two orthogonal resonant frequencies on the dielectric dual-mode resonant cavity.

[0042] Please refer to Figure 4 As shown in the structural diagram of the dielectric dual-mode resonant cavity, the dielectric dual-mode resonant cavity in this embodiment includes a metal shell 112 and a dielectric block 113 located inside the metal shell 112 , and two coupling holes 111 are located on the dielectric block 113 .

[0043] The metal shell 112 is a hollow shell. The outer surface of the metal shell 112 may be rectangular or in other shapes. The inner surface of the metal shell 112 has the same shape as the dielectric block 113, so that the dielectric block 113 can be glued into the metal shell 112. The dielectric block 113 may be circular or polygonal, and the polygon may be hexagonal, octagonal, etc., which is not limited in this embodiment.

[0044] Figure 4 In the example, the dielectric block 113 is circular, and the circular dielectric block 113 can be glued into a circular metal cylinder (ie, the metal shell 112), and the metal is used as a boundary condition to form a fully functional resonant cavity 110. The dielectric block 113 can be a microwave ceramic dielectric block.

[0045] Please refer to Figure 5 In the filter with hidden metal shell 112 and metal sheet 120 shown in the figure, coupling holes 111 on two adjacent dielectric dual-mode resonant cavities are staggered, and the four resonant frequencies contained in the two adjacent dielectric dual-mode resonant cavities produce negative cross-coupling and generate two symmetrical transmission zeros at both ends of the passband of the filter.

[0046] Among them, two adjacent dielectric dual-mode resonant cavities are cross-installed at a certain angle, and the four resonant frequencies contained therein are used as a subset to generate negative cross-coupling, thereby generating two symmetrical transmission zeros at both ends of the passband of the filter. Similarly, if there are multiple such subsets, multiple symmetrical transmission zeros can be generated, so that the symmetrical transmission zeros can be used to obtain steep out-of-band suppression.

[0047] Please refer to Figure 6 The near-end frequency response curve of the filter shown in FIG. 1 is a graph showing a near-end frequency response curve of the filter. From the response curve, it can be seen that the tenth-order four-zero mixed mode filter shown in this embodiment has four transmission zeros on the left and right sides of the passband. Figure 6 They are marked with 1 and 2.

[0048] Please refer to Figure 7 The schematic diagram of the metal sheet 120 is shown in FIG. Figure 7 Five metal sheets 120 are used as an example, and the number of the metal sheets 120 is not limited in this embodiment.

[0049] In this embodiment, each metal sheet 120 is provided with a coupling window 121, and the size of the coupling window 112 is positively correlated with the size of the coupling coefficient between the dielectric dual-mode resonant cavities. That is, the larger the coupling window 112, the larger the coupling coefficient; the smaller the coupling window 112, the smaller the coupling coefficient. Therefore, the size of the coupling window 121 can be adjusted according to the coupling coefficient requirements between the resonant cavities 110.

[0050] For example, the coupling coefficient between the metal resonant cavity and the dielectric dual-mode resonant cavity is required to be relatively large, so the coupling window of the metal sheet 120 between the metal resonant cavity and the dielectric dual-mode resonant cavity is relatively large. Figure 6 The coupling windows of the first and last metal sheets 120 are larger.

[0051] In this embodiment, a cross-shaped coupling window is provided on the metal sheet 120 located between the i-th and i+1-th dielectric dual-mode resonant cavities; the long side of the cross-shaped coupling window is used to generate coupling of the main path of the filter, and the short side is used to generate cross coupling.

[0052] For example, the metal sheet 120 (i.e. Figure 7 The second metal sheet 120 in the middle), the metal sheet 120 between the third dielectric dual-mode resonant cavity and the fourth dielectric dual-mode resonant cavity (ie Figure 7 In the fourth metal sheet 120 in the filter, the coupling window 121 is a cross-shaped coupling window. The cross-shaped coupling window structure and its two adjacent dielectric dual-mode resonant cavities couple a subset of four resonant frequencies, and by cross-placing the dielectric dual-mode resonant cavities and the cross-shaped coupling window structure, a transmission zero point can be formed on both sides of the filter passband.

[0053] The following describes the serial connection of the resonant cavity 110 and the metal sheet 120. In this embodiment, a relatively long metal rod 130 can be used to serially connect the resonant cavity 110 and the metal sheet 120, thereby obtaining an assembled filter.

[0054] Please refer to Figure 4 In this embodiment, a through hole 114 is provided on the metal shell 112 and the metal resonant cavity, and the filter further includes a metal rod 130, which penetrates the through hole 114 to connect the resonant cavity 110 and the metal sheet 120 in series, and each metal rod 130 is fixed to the two metal resonant cavities by a nut 140 respectively.

[0055] In this embodiment, the resonant cavity 110 and the metal sheet 120 may be connected in series on the metal rod 130 in sequence, and then a nut 140 may be used to lock the metal rod 130 at its head and tail.

[0056] The filter provided in this embodiment can be applied to the sub 6GHz frequency band, and of course, can also be applied to other frequency bands, which is not limited in this embodiment. It should be noted that the size of the filter in this embodiment can be optimized and determined by electromagnetic simulation software such as HFSS (High Frequency Structure Simulator) according to actual filter indicators.

[0057] Please refer to Figure 8The far-end harmonic characteristic curve of the filter shown is given by Figure 8 It can be seen that the far end of the filter has excellent harmonic suppression characteristics. The harmonics of ordinary dielectric filters will have parasitic passbands at 1.2-1.3 times the passband, while this filter has no obvious parasitic passbands.

[0058] The above description is not intended to limit the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A small hybrid mode filter having two resonant cavities, characterized in that: The filter comprises: n resonant cavities connected in series, with a metal sheet between every two adjacent resonant cavities, n≥3; The first and last resonant cavities among the n resonant cavities are metal resonant cavities, and the remaining n-2 resonant cavities are dielectric dual-mode resonant cavities; The n resonant cavities are coupled through a coupling window on the metal sheet; The dielectric dual-mode resonant cavity is provided with two symmetrical coupling holes, and the two coupling holes are used to generate coupling between two orthogonal resonant frequencies; the diameter of the coupling hole is positively correlated with the coupling coefficient between the resonant frequencies; The coupling holes on two adjacent dielectric dual-mode resonant cavities are staggered at a certain angle, and the four resonant frequencies contained in the two adjacent dielectric dual-mode resonant cavities are used as a subset to generate negative cross-coupling and generate two symmetrical transmission zeros at both ends of the passband of the filter.

2. The small hybrid mode filter with two resonant cavities according to claim 1, characterized in that: A cross-shaped coupling window is provided on the metal sheet located between the i-th and i+1-th dielectric dual-mode resonant cavities; The long side of the cross-shaped coupling window is used to generate the coupling of the main path of the filter, and the short side is used to generate the cross coupling.

3. The small hybrid mode filter with two resonant cavities according to claim 2, characterized in that: The size of the coupling window is positively correlated with the size of the coupling coefficient between the dielectric dual-mode resonant cavities.

4. The small hybrid mode filter with two resonant cavities according to claim 1, characterized in that: The dielectric dual-mode resonant cavity comprises a metal shell and a dielectric block located inside the metal shell, and the two coupling holes are located on the dielectric block.

5. The small hybrid mode filter with two resonant cavities according to claim 4, characterized in that: The metal shell and the metal resonant cavity are provided with through holes, and the filter further comprises metal rods, which penetrate through the through holes to connect the resonant cavity and the metal sheet in series, and each metal rod is fixed to the two metal resonant cavities via nuts.

6. The small hybrid mode filter with two resonant cavities according to claim 4, characterized in that: The dielectric block is a microwave ceramic dielectric block.

7. The small hybrid mode filter with two resonant cavities according to any one of claims 1 to 6, characterized in that: The filter is applied to the sub 6 GHz frequency band.

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