阅读说明：本技术 一种介质谐振器和滤波器 (Dielectric resonator and filter ) 是由 乔冬春 蒲国胜 于 2020-06-09 设计创作，主要内容包括：本申请实施例公开了一种介质谐振器和滤波器,介质谐振器包括：介质主体,覆盖介质主体的导电层,介质谐振器至少具有第一谐振模式和第二谐振模式,第一谐振模式与第二谐振模式的电场方向正交；在介质主体的第一表面上设有盲孔,第一表面与第一谐振模式的电场方向垂直,盲孔的深度用于调节第一谐振模式对应的谐振频率；在介质主体的第二表面上设有第一通槽,第二表面与第一谐振模式的电场方向平行、并且与第二谐振模式的电场方向垂直,第一通槽的槽长方向与第一谐振模式的电场方向平行,第一通槽的大小用于改变第二谐振模式对应的谐振频率。本申请有利于实现介质谐振器的小型化、可以进行谐振频率的独立调试,还有利于实现介质谐振器尺寸归一。(The embodiment of the application discloses dielectric resonator and filter, dielectric resonator includes: a dielectric body, a conductive layer covering the dielectric body, the dielectric resonator having at least a first resonance mode and a second resonance mode, the first resonance mode being orthogonal to the electric field direction of the second resonance mode; a blind hole is formed in the first surface of the medium main body, the first surface is perpendicular to the direction of an electric field of the first resonance mode, and the depth of the blind hole is used for adjusting the resonance frequency corresponding to the first resonance mode; the second surface of the medium main body is provided with a first through groove, the second surface is parallel to the direction of an electric field of the first resonance mode and is vertical to the direction of the electric field of the second resonance mode, the length direction of the first through groove is parallel to the direction of the electric field of the first resonance mode, and the size of the first through groove is used for changing the resonance frequency corresponding to the second resonance mode. The method and the device are beneficial to realizing the miniaturization of the dielectric resonator, can independently debug the resonant frequency and are also beneficial to realizing the size normalization of the dielectric resonator.)

1. A dielectric resonator, comprising: a dielectric body, a conductive layer overlying the dielectric body,

the dielectric resonator at least has a first resonance mode and a second resonance mode, and the direction of an electric field of the first resonance mode is orthogonal to the direction of an electric field of the second resonance mode;

a blind hole is formed in the first surface of the medium main body, the first surface is perpendicular to the direction of an electric field of the first resonance mode, and the depth of the blind hole is used for adjusting the resonance frequency corresponding to the first resonance mode;

a first through groove is arranged on a second surface of the medium main body, the second surface is parallel to the direction of the electric field of the first resonance mode and perpendicular to the direction of the electric field of the second resonance mode, the length direction of the first through groove is parallel to the direction of the electric field of the first resonance mode, and the size of the first through groove is used for changing the resonance frequency corresponding to the second resonance mode.

2. The dielectric resonator according to claim 1, wherein the dielectric resonator has a third resonance mode, and an electric field direction of the third resonance mode is orthogonal to an electric field direction of the first resonance mode and an electric field direction of the second resonance mode;

a second through groove is provided on a third surface of the dielectric body, the third surface being perpendicular to the electric field direction of the third resonance mode and parallel to the electric field direction of the first resonance mode and the electric field direction of the second resonance mode.

3. A dielectric resonator according to claim 1 or 2, further comprising: a first blind groove is arranged on the first side of the groove,

the first blind slot is disposed between the blind hole and the first through slot for adjusting coupling between the first resonant mode and the second resonant mode.

4. A dielectric resonator as claimed in claim 3,

one end of the first blind groove is communicated with the first through groove, and the other end of the first blind groove is communicated with the blind hole;

or one end of the first blind groove is communicated with the first through groove, and the other end of the first blind groove faces the blind hole and is not communicated with the blind hole;

or one end of the first blind groove faces the first through groove and is not communicated with the first through groove, and the other end of the first blind groove is communicated with the blind hole;

or one end of the first blind groove faces the first through groove, the other end of the first blind groove faces the blind hole, and the two ends of the first blind groove are not communicated with the first through groove and the blind hole.

5. A dielectric resonator according to claim 2 or 3, further comprising: a second blind groove is formed on the outer wall of the first blind groove,

the second blind slot is disposed between the blind hole and the second through slot for adjusting coupling between the first resonant mode and the third resonant mode.

6. A dielectric resonator as recited in claim 5,

one end of the second blind groove is communicated with the second through groove, and the other end of the second blind groove is communicated with the blind hole;

or one end of the second blind groove is communicated with the second through groove, and the other end of the second blind groove faces the blind hole and is not communicated with the blind hole;

or one end of the second blind groove faces the second through groove and is not communicated with the second through groove, and the other end of the second blind groove is communicated with the blind hole;

or one end of the second blind groove faces the second through groove, the other end of the second blind groove faces the blind hole, and the two ends of the second blind groove are not communicated with the second through groove and the blind hole.

7. A dielectric resonator as claimed in any one of claims 2 to 6, wherein the dielectric body is a cube, the dielectric resonator further comprising a coupling window of a de-conducting layer provided on a fourth surface, the fourth surface being parallel to the third surface, the coupling window being adapted to couple with another dielectric resonator;

the dielectric resonator further includes: and the through hole is arranged near the coupling window and is parallel to the electric field of the first resonance mode, the through hole is used for reducing crosstalk in coupling with other dielectric resonators, and the distance between the through hole and the coupling window is less than twice of the width of the coupling window.

8. A dielectric resonator as claimed in any one of claims 2 to 6, wherein the dielectric body is a cube, the dielectric resonator further comprising a coupling window of a de-conducting layer provided on a fourth surface, the fourth surface being parallel to the third surface, the coupling window being adapted to couple with another resonator;

the dielectric resonator further includes: and the third through groove is arranged near the coupling window and is parallel to the electric field of the first resonance mode, the third through groove is used for reducing crosstalk when the third through groove is coupled with other dielectric resonators, and the distance between the third through groove and the coupling window is less than twice of the width of the coupling window.

9. A dielectric resonator according to any of claims 2 to 8, characterized in that at least one area of the depletive layer is provided in at least one of the first, second and third surfaces.

10. A filter comprising a dielectric resonator as claimed in any one of claims 1 to 9.

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a dielectric resonator and a filter including the dielectric resonator.

Background

With the popularization of the fifth Generation mobile communication technology (5th-Generation, abbreviated as 5G), more and more channels of the base station are provided, from 16 channels to 32 channels or even more channels, which puts higher and higher requirements on the miniaturization of the base station, and the dielectric filter can meet the requirements due to its excellent performance and size advantages.

The dielectric filter includes: single mode dielectric filters, dual mode dielectric filters, triple mode dielectric filters, and the like. The single-mode dielectric filter usually adopts a plurality of cascade connections, and occupies a large volume.

The multimode dielectric filter is composed of dielectric resonators, and one dielectric resonator can generate two or more resonant modes by utilizing the multimode characteristics of the dielectric resonators, so that one multimode resonant cavity can replace two or more traditional single-mode resonant cavities, the size of the filter can be reduced compared with the traditional single-mode dielectric filter, and the cost of the filter is reduced.

Taking a three-mode dielectric resonator as an example, as shown in fig. 1, which is a schematic structural diagram of the three-mode dielectric resonator, according to the electric field theory, a calculation formula of the resonant frequency of the rectangular waveguide is as follows:

where μ is the permeability and ε is the dielectric constant. a. b and l are the lengths of the rectangular dielectric waveguide resonator along the X-axis direction, the Y-axis direction and the Z-axis direction respectively. The resonant frequencies of the mode 1, the mode 2 and the mode 3 of the three-mode dielectric resonator are respectively as follows: f. of₀₁₁、f₁₀₁And f₁₁₀When the resonant frequency corresponding to each mode needs to be changed, the length of a, b or l needs to be changed. This causes the size of the plurality of resonators in the filter to be different, and there is a problem that the sizes are not unified.

Disclosure of Invention

The application provides a dielectric resonator and a filter, which are used for solving the problems that the dielectric resonator in the prior art is large in size, inconvenient in resonant frequency debugging and non-uniform in size.

In a first aspect, an embodiment of the present application provides a dielectric resonator, including: a dielectric body, a conductive layer overlying the dielectric body,

the dielectric resonator at least has a first resonance mode and a second resonance mode, and the direction of an electric field of the first resonance mode is orthogonal to the direction of an electric field of the second resonance mode;

a blind hole is formed in the first surface of the medium main body, the first surface is perpendicular to the direction of an electric field of the first resonance mode, and the depth of the blind hole is used for adjusting the resonance frequency corresponding to the first resonance mode;

a first through groove is arranged on a second surface of the medium main body, the second surface is parallel to the direction of the electric field of the first resonance mode and perpendicular to the direction of the electric field of the second resonance mode, the length direction of the first through groove is parallel to the direction of the electric field of the first resonance mode, and the size of the first through groove is used for changing the resonance frequency corresponding to the second resonance mode.

By adopting the technical scheme provided by the embodiment of the application, when the resonant frequency is adjusted, the external size of the dielectric resonator can be not changed, the resonant frequency of the first resonant mode can be changed by changing the depth of the first through hole, or the resonant frequency corresponding to the second resonant mode can be changed by changing the size of the first through groove, so that the dielectric resonator is favorably miniaturized, the independent adjustment of the resonant frequency can be carried out, and the size normalization of the dielectric resonator is favorably realized.

With reference to the first aspect, in some possible implementations, the dielectric resonator has a third resonance mode, and an electric field direction of the third resonance mode is orthogonal to an electric field direction of the first resonance mode and an electric field direction of the second resonance mode;

a second through groove is provided on a third surface of the dielectric body, the third surface being perpendicular to the electric field direction of the third resonance mode and parallel to the electric field direction of the first resonance mode and the electric field direction of the second resonance mode.

By adopting the technical scheme provided by the embodiment of the application, the resonance frequency corresponding to the third resonance mode can be changed by changing the size of the second through slot, so that the dielectric resonator is favorably miniaturized, the independent debugging of the resonance frequency can be realized, and the size normalization of the dielectric resonator is favorably realized.

With reference to the first aspect, in some possible embodiments, the dielectric resonator further includes: a first blind slot disposed between the blind hole and the first through slot for adjusting coupling between the first resonant mode and the second resonant mode.

In some possible embodiments, one end of the first blind groove is communicated with the first through groove, and the other end of the first blind groove is communicated with the blind hole; or one end of the first blind groove is communicated with the first through groove, and the other end of the first blind groove faces the blind hole and is not communicated with the blind hole; or one end of the first blind groove faces the first through groove and is not communicated with the first through groove, and the other end of the first blind groove is communicated with the blind hole; or one end of the first blind groove faces the first through groove, the other end of the first blind groove faces the blind hole, and the two ends of the first blind groove are not communicated with the first through groove and the blind hole.

With reference to the first aspect, in some possible embodiments, the dielectric resonator further includes: a second blind groove is formed on the outer wall of the first blind groove,

the second blind slot is disposed between the blind hole and the second through slot for adjusting coupling between the first resonant mode and the third resonant mode.

With reference to the first aspect, in some possible embodiments, one end of the second blind groove is communicated with the second through groove, and the other end of the second blind groove is communicated with the blind hole; or one end of the second blind groove is communicated with the second through groove, and the other end of the second blind groove faces the blind hole and is not communicated with the blind hole; or one end of the second blind groove faces the second through groove and is not communicated with the second through groove, and the other end of the second blind groove is communicated with the blind hole; or one end of the second blind groove faces the second through groove, the other end of the second blind groove faces the blind hole, and the two ends of the second blind groove are not communicated with the second through groove and the blind hole.

With reference to the first aspect, in some possible embodiments, the dielectric body is a cube, the dielectric resonator further includes a coupling window of a de-conductive layer disposed on a fourth surface, the fourth surface is parallel to the third surface, and the coupling window is configured to couple with another dielectric resonator; the dielectric resonator further includes: and the through hole is arranged near the coupling window and is parallel to the electric field of the first resonance mode, the through hole is used for reducing crosstalk in coupling with other dielectric resonators, and the distance between the through hole and the coupling window is less than twice of the width of the coupling window.

With reference to the first aspect, in some possible embodiments, the dielectric body is a cube, the dielectric resonator further includes a coupling window disposed on a third surface of the de-conductive layer, the third surface is orthogonal to the first surface and the second surface, and the coupling window is configured to couple with another resonator;

the dielectric resonator further includes: and the third through groove is arranged near the coupling window and is parallel to the electric field of the first resonance mode, the third through groove is used for reducing crosstalk when the third through groove is coupled with other dielectric resonators, and the distance between the third through groove and the coupling window is less than twice of the width of the coupling window.

With reference to the first aspect, in some possible embodiments, at least one region of the first surface, the second surface and the third surface, in which at least one depletive layer is provided, may be obtained by polishing, and the resonant frequency and the coupling may be tuned by changing the size and/or depth of the polishing region, which may be very convenient to tune.

In a second aspect, an embodiment of the present application provides a filter, which includes the dielectric resonator described in the first aspect or any one of the possible implementation manners of the first aspect.

By adopting the technical scheme provided by the embodiment of the application, when the resonant frequency of the dielectric resonator in the filter is adjusted, the external size of the dielectric resonator can be not changed, the resonant frequency of the first resonant mode can be changed by changing the depth of the first through hole, or the resonant frequency corresponding to the second resonant mode can be changed by changing the size of the first through groove, so that the miniaturization of the dielectric resonator can be realized, the independent adjustment of the resonant frequency can be performed, and the size normalization of the dielectric resonator can be realized.

Drawings

Fig. 1 is a schematic diagram of a prior art three-mode dielectric resonator.

Fig. 2A is a schematic structural diagram of a dielectric resonator in an embodiment of the present application.

Fig. 2B is a schematic structural diagram of a dielectric resonator according to an embodiment of the present application.

Fig. 2C is a schematic structural diagram of a dielectric resonator according to an embodiment of the present application.

Fig. 2D is a schematic diagram of a coupling structure of two dielectric resonators according to an embodiment of the present application.

Fig. 2E is a schematic top view of a dielectric resonator in an embodiment of the present application.

Fig. 2F is a schematic top view of a dielectric resonator in an embodiment of the present application.

Detailed Description

The embodiments of the present application will be described below with reference to the drawings.

According to the dielectric resonator provided by the embodiment of the application, when the resonant frequency is adjusted, the external size of the dielectric resonator can be not changed, and the resonant frequency is changed by changing the structure of the dielectric main body, so that the consistency of the appearance of the dielectric main body is facilitated, and the size normalization of the dielectric resonator is facilitated.

The dielectric resonator provided by the embodiment of the application comprises: a dielectric body, a conductive layer covering the dielectric body. The dielectric resonator at least has a first resonance mode and a second resonance mode, and the direction of an electric field of the first resonance mode is orthogonal to the direction of an electric field of the second resonance mode; a blind hole is formed in the first surface of the medium main body, the first surface is perpendicular to the direction of an electric field of the first resonance mode, and the depth of the blind hole is used for adjusting the resonance frequency corresponding to the first resonance mode; and a first through groove is arranged on a second surface of the medium main body, the second surface is parallel to the direction of an electric field of the first resonance mode and is vertical to the direction of an electric field of the second resonance mode, the length direction of the first through groove is parallel to the direction of the electric field of the first resonance mode, and the size of the first through groove is used for changing the resonance frequency corresponding to the second resonance mode. Wherein the conductive layer may be formed of a highly conductive material, and the highly conductive material may be a metal.

By adopting the technical scheme provided by the embodiment of the application, when the resonant frequency of the dielectric resonator in the filter is adjusted, the external size of the dielectric resonator can be not changed, the resonant frequency of the first resonant mode can be changed by changing the depth of the first through hole, or the resonant frequency corresponding to the second resonant mode can be changed by changing the size of the first through groove, so that the miniaturization of the dielectric resonator can be realized, the independent adjustment of the resonant frequency can be performed, and the size normalization of the dielectric resonator can be realized.

The interface of the first through groove in the vertical groove length direction may be circular, polygonal, or the like.

In some possible embodiments, the dielectric resonator has a third resonance mode, an electric field direction of the third resonance mode being orthogonal to an electric field direction of the first resonance mode and an electric field direction of the second resonance mode; a second through groove is provided on a third surface of the dielectric body, the third surface being perpendicular to the electric field direction of the third resonance mode and parallel to the electric field direction of the first resonance mode and the electric field direction of the second resonance mode.

In some possible embodiments, the dielectric resonator further comprises: and the first blind groove is arranged between the blind hole and the first through groove and used for adjusting the coupling between the first resonance mode and the second resonance mode.

In some possible embodiments, one end of the first blind groove is communicated with the first through groove, and the other end is communicated with the blind hole; or one end of the first blind groove is communicated with the first through groove, and the other end of the first blind groove faces the blind hole and is not communicated with the blind hole; or one end of the first blind groove faces the first through groove and is not communicated with the first through groove, and the other end of the first blind groove is communicated with the blind hole; or one end of the first blind groove faces the first through groove, the other end of the first blind groove faces the blind hole, and the two ends of the first blind groove are not communicated with the first through groove and the blind hole.

In some possible embodiments, the dielectric resonator further comprises: a second blind slot disposed between the blind hole and the second through slot for adjusting coupling between the first resonant mode and the third resonant mode.

In some possible embodiments, one end of the second blind groove is communicated with the second through groove, and the other end is communicated with the blind hole; or one end of the second blind groove is communicated with the second through groove, and the other end of the second blind groove faces the blind hole and is not communicated with the blind hole; or one end of the second blind groove faces the second through groove and is not communicated with the second through groove, and the other end of the second blind groove is communicated with the blind hole; or one end of the second blind groove faces the second through groove, the other end of the second blind groove faces the blind hole, and the two ends of the second blind groove are not communicated with the second through groove and the blind hole.

In some possible embodiments, the dielectric body is a cube, the dielectric resonator further includes a coupling window disposed on the de-conductive layer of the fourth surface, the fourth surface is parallel to the third surface, and the coupling window is used for coupling with other dielectric resonators; the dielectric resonator further includes: and the through hole is arranged near the coupling window and is parallel to the electric field of the first resonance mode, the through hole is used for reducing crosstalk in coupling with other dielectric resonators, and the distance between the through hole and the coupling window is less than twice of the width of the coupling window.

In some possible embodiments, the dielectric body is a cube, the dielectric resonator further includes a coupling window of a de-conductive layer disposed on a fourth surface, the fourth surface is parallel to the third surface, and the coupling window is used for coupling with other resonators;

the dielectric resonator further includes: and the third through groove is arranged near the coupling window and is parallel to the electric field of the first resonance mode, the third through groove is used for reducing crosstalk when the third through groove is coupled with other dielectric resonators, and the distance between the third through groove and the coupling window is less than twice of the width of the coupling window.

In some possible embodiments, at least one region of the first surface, the second surface and the third surface, in which at least one depletive layer is provided, is obtained by polishing, and the resonant frequency and the coupling can be tuned by changing the size and/or depth of the polished region, which is very convenient and tunable.

The following describes the technical solution of the present application by taking a dielectric resonator having three resonance modes (mode 1, mode 2, and mode 3) and a cubic dielectric body as an example. Referring to fig. 2A, fig. 2A is a schematic structural diagram of a dielectric resonator according to an embodiment of the present application. The dielectric resonator has three resonance modes of mode 1, mode 2, and mode 3, the battery directions of the three resonance modes being orthogonal.

An upper surface perpendicular to the Z axis and parallel to the X axis and the Y axis is a first surface on which a blind hole 201 is provided, and a depth of the blind hole 201 is used to adjust a resonance frequency corresponding to the mode 1.

In fig. 2A, an outer surface perpendicular to the X axis and parallel to the Y axis and the Z axis is a second surface on which a first through groove 202 is disposed, a groove length direction of the first through groove 202 is parallel to an electric field direction of the mode 1, and a size of the first through groove 202 is used to change a resonance frequency corresponding to the mode 2. In fig. 2A, the first through slot 202 is rectangular. It should be noted that the cross-sectional view of the first through groove and the cross-sectional view perpendicular to the groove length may be a regular pattern or an irregular pattern. As shown in fig. 2E and 2F, a sectional view of the first through groove perpendicular to the groove length may be a semicircle or a polygon.

In fig. 2A, an outer surface perpendicular to the Y axis and parallel to the X axis and the Z axis is a third surface on which a second through groove 205 is provided, a groove length direction of the second through groove 205 is parallel to the electric field direction of mode 1, and a size of the second through groove 205 is used to change the resonance frequency corresponding to mode 3. In fig. 2A, the second through-slot 205 is rectangular. It should be noted that the cross-sectional view of the second through groove and the cross-sectional view perpendicular to the groove length may be a regular pattern or an irregular pattern. As shown in fig. 2E and 2F, the cross-sectional view of the second through-groove perpendicular to the groove length may be a semicircle or a polygon.

As shown in fig. 2A, the dielectric resonator may further include a first blind slot 204 and a second blind slot 203. A first blind groove 204 is provided between the blind hole 201 and the first through groove 202 for adjusting coupling between the modes 1 and 2. A second blind slot 203 is provided between the blind hole 201 and the second through slot 205 for adjusting the coupling between mode 1 and mode 3.

As shown in fig. 2A, one end of the first blind groove 204 is communicated with the first through groove 202, and the other end is communicated with the blind hole 201. In some possible embodiments, one end of the first blind groove 204 may communicate with the first through groove 202, and the other end faces the blind hole 201 and does not communicate with the blind hole 201. Alternatively, in some other possible embodiments, one end of the first blind groove 204 may face the first through groove 202 and not communicate with the first through groove 202, and the other end communicates with the blind hole 201. Alternatively, in some other possible embodiments, one end of the first blind groove 204 may face the first through groove 202, the other end faces the blind hole 201, and both ends of the first blind groove 204 are not communicated with the first through groove 202 and the blind hole 201.

As shown in fig. 2A, one end of the second blind groove 203 communicates with the second through groove 205, and the other end communicates with the blind hole 201. In some possible embodiments, one end of the second blind groove 203 may communicate with the second through groove 205, and the other end faces the blind hole 201 and does not communicate with the blind hole 201. Alternatively, in some other possible embodiments, one end of the second blind groove 203 may face the second through groove 205 and not communicate with the second through groove 205, and the other end communicates with the blind hole 201. Alternatively, in some other possible embodiments, one end of the second blind groove 203 may face the second through groove 205, the other end faces the blind hole 201, and both ends of the second blind groove 203 are not communicated with the second through groove 205 and the blind hole 201.

In fig. 2A, the dielectric body is a cube, the other surface parallel to the third surface is a fourth surface, and a coupling window of the de-conducting layer may be disposed on the fourth surface, the coupling window being used for coupling with other dielectric resonators, as shown in fig. 2D, and the two dielectric resonators are coupled through the coupling window 206. As shown in fig. 2B, through holes 2071 and 2072 are further provided in the dielectric filter in a region close to the coupling window 206, the through holes are used to reduce crosstalk in coupling with other dielectric resonators, the distance between the through holes and the coupling window is less than twice the width of the coupling window, and the width direction of the coupling window may be the direction of the X axis in fig. 2A.

In some possible embodiments, as shown in fig. 2C, the slots 2073 and 2074 may be disposed near the coupling window 206, the slots 2073 and 2074 may be used to reduce crosstalk when coupling with other dielectric resonators, and the slots 2073 and 2074 may be spaced from the coupling window 206 by twice the width of the coupling window.

In some possible embodiments, a region of at least one depletive layer may be provided in at least one of the first surface, the second surface, and the third surface. The region can be obtained by polishing, the resonant frequency and the coupling can be debugged by changing the size and/or the depth of the polishing region, and the method has very convenient debugging performance.

By adopting the technical scheme provided by the embodiment of the application, when the resonant frequency of the dielectric resonator in the filter is adjusted, the external size of the dielectric resonator can be not changed, the resonant frequency of the first resonant mode can be changed by changing the depth of the first through hole, or the resonant frequency corresponding to the second resonant mode can be changed by changing the size of the first through groove, so that the miniaturization of the dielectric resonator can be realized, the independent adjustment of the resonant frequency can be performed, and the size normalization of the dielectric resonator can be realized.

The embodiment of the application also provides a filter, which comprises the protective structure of the dielectric resonator in any embodiment. The protective structure of the dielectric resonator is described in the foregoing, and is not described in detail herein.

It should be understood that the terms "first," "second," and the like in the description and claims of this application and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Moreover, the terms "comprises," "comprising," and any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or modules is not necessarily limited to those steps or modules explicitly listed, but may include other steps or modules not expressly listed or inherent to such process, method, article, or apparatus. The number of the structures such as the blind grooves, the blind holes, the through grooves and the through holes is not limited to that shown in fig. 2A, and can be increased or decreased as required.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.