WO2022103224A1

WO2022103224A1 - Multi-mode dielectric filter and multi-mode cascade filter

Info

Publication number: WO2022103224A1
Application number: PCT/KR2021/016639
Authority: WO
Inventors: Ming XIONG
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2020-11-16
Filing date: 2021-11-15
Publication date: 2022-05-19
Also published as: CN112542665B; CN112542665A

Abstract

The present invention provides a multi-mode dielectric filter which includes: one multi-mode dielectric resonant cavity, the multi-mode dielectric resonant cavity includes a solid dielectric body and a metal coating covering the outer surface of the dielectric body; a metal transmission line insulated from the dielectric resonant cavity by a dielectric material; and a plurality of coupling structures connecting the dielectric resonant cavity and the metal transmission line, the multi-mode dielectric resonant cavity is coupled with the metal transmission line through the coupling structures, to form a transmission zero point on an arbitrary side of a transmission channel and a plurality of (two or multiple) resonance frequencies in the channel.

Description

MULTI-MODE DIELECTRIC FILTER AND MULTI-MODE CASCADE FILTER

The present invention relates to filters, and particularly，to a multi-mode dielectric filter and a multi-mode cascade filter.

FIG. 1 is a schematic diagram illustrating the structure of a conventional multi-mode cascade filter. As shown in FIG. 1, the cascade filter includes two triple-

mode resonators

310 and 350, and one dual-mode resonator 330. The frequency tuning directions of the triple-mode resonator are three orthogonal directions, that is, extending directions of

resonance screws

311, 312, and 313 as shown in the figure. The frequency tuning directions of the dual-mode resonator 330 are two directions, that is, extending directions of

resonance screws

331 and 333 as shown in the figure.

In the cascade filter, the coupling between every two orthogonal modes in the same triple-mode or dual-mode resonator requires a special structure made at right-angle sides of the resonator (in a direction which crosses the two modes at a 45° angle with each of the two modes). The special structure is generally a concave structure, for example, the

grooves

315 and 335, for adjusting the amount of coupling between the two orthogonal modes in the same resonator. This special concave coupling structure requires a complicated manufacturing process, and also affects the insertion loss of the filter. In addition, the special concave structure is difficult to adjust, and needs to be adjusted from a 45° angle side, causing a complicated manufacturing process.

Further, the coupling (including adjacent coupling and non-adjacent cross-coupling) between different dual-mode or triple-mode resonators requires the insertion of a coupling diaphragm, for example,

diaphragms

320 and 340, with a cross-coupling slot in the middle. The cross-coupling slot is used for coupling modes of the two dual-mode dielectric resonators in two mutually perpendicular directions, including adjacent coupling and non-adjacent coupling (for generating transmission zeros). Such coupling diaphragm is generally welded between the two multi-mode resonant cavities, so the manufacturing process is very complicated. Once the welding is completed, the coupling amount cannot be adjusted, thus the multi-mode dielectric filter produced using this method has very low yield and poor adjustability, and often cannot achieve desired insertion loss (s21) and return loss (s11) indicators.

Therefore, the disadvantages of conventional multi-mode filters are: (1) the coupling structure between different modes of the same multi-mode resonator is complicated; and (2) the adjacent coupling and cross-coupling between different multi-mode resonators are difficult to achieve during manufacturing, which ultimately affects product performance and qualification rate.

The present invention provides a multi-mode dielectric filter and a multi-mode cascade filter which adopt direct coupling between the dielectric resonant cavity and the metal transmission line to produce transmission zero points without requiring inter-cavity cross-coupling and achieve adjacent coupling between different modes of the same multi-mode resonator through a direct connection with the metal transmission line, which can greatly simplify the structure of the multi-mode dielectric filter.

According to an embodiment, a multi-mode dielectric filter may include a dielectric resonant cavity comprising a dielectric body and a metal coating covering an outer surface of the dielectric body, the dielectric body is in a rectangular parallelepiped shape having a first surface, a second surface and a third surface which are orthogonal to each other; a metal transmission line comprising a first transmission line branch disposed to face the first surface and a second transmission line branch disposed to face the second surface; a first coupling structure electrically connected to the first transmission line branch, the first coupling structure extending in a first direction inward the dielectric body from the first transmission line branch so that the dielectric resonant cavity forms a first resonant frequency in the first direction; and a second coupling structure electrically connected to the second transmission line branch, the second coupling structure extending in a second direction inward the dielectric body from the second transmission line branch so that the dielectric resonant cavity forms a second resonant frequency in the second direction.

The first direction and the second direction may be perpendicular to the first surface and the second surface, respectively.

The multi-mode dielectric filter may form two transmission zero point by the first coupling structure and the second coupling structure.

The multi-mode dielectric filter may further comprise a first circuit board in which the first transmission line branch is embedded; and a second circuit board in which the second transmission line branch is embedded.

The first circuit board may be disposed to parallel to the first surface and the second circuit board may be disposed to parallel to the second surface.

The first coupling structure may not contact with a portion of the metal layer on the first surface, and the second coupling structure may not contact with a portion of the metal layer on the second surface.

The multi-mode dielectric filter may further comprise a first insulator disposed between the first circuit board and the dielectric body and surrounding the first coupling structure; and a second insulator disposed between the second circuit board and the dielectric body and surrounding the second coupling structure.

Each of the first coupling structure and the second structure may include a first portion embedded in the dielectric body and a second portion disposed outside the dielectric body.

An end portion of the first portion of one of the first coupling structure and the second coupling structure may be disposed inside the dielectric body and does not contact with the metal coating.

The first portion of the one of the first coupling structure and the second coupling structure has a shape extending in the first direction inside the dielectric body and then bent in another direction, and the bent end portion of the first portion may contact with the metal coating on the dielectric body.

The second portion of the first coupling structure may be electrically connected to the first transmission line branch through the first circuit board, and the second portion of the second coupling structure may be electrically connected to the second transmission line branch through the second circuit board.

The first coupling structure and the second coupling structure may be in a form of metal cylinder or a metalized blind hole.

The multi-mode dielectric filter may further comprise a third transmission line branch disposed to face the third surface; and a third coupling structure electrically connected to the third transmission line branch, the third coupling structure extending in a third direction inward the dielectric body so that the dielectric resonant cavity forms a third resonant frequency in the third direction.

According to an embodiment, a multi-mode cascade filter may include a first multi-mode dielectric filter of any one of above described multi-mode dielectric filter and a second multi-mode dielectric filter of any one of above described multi-mode dielectric filter.

A signal input end of the metal transmission line of the first multi-mode dielectric filter and a signal output end of the metal transmission line of the second multi-mode dielectric filter may be electrically connected with each other.

It can be seen from the above technical schemes that, in this embodiment, the directional resonance frequency is achieved by the dielectric resonant cavity 10 and a metal transmission line branch through a coupling structure connecting the dielectric resonant cavity and the metal transmission line branch, and metal transmission line branches and coupling structures are in a one-to-one correspondence relationship. The adjacent coupling of two orthogonal resonance frequencies is converted into the connection of two metal transmission line branches, thereby the three-dimensional structure is replaced by a planar structure which greatly reduces the complexity. Therefore, the adjacent coupling structure of multi-mode dielectric filters in this embodiment is simple, and can avoid the complexity of configuring coupling structures in a direction which crosses two modes at a 45° angle as in the prior art.

Further, the multi-mode dielectric filter of this embodiment only includes one dielectric resonant cavity 10, and the coupling method is not the cross-coupling established between different resonant cavities, but the coupling between a dielectric resonant cavity and a metal transmission line (micro-strip line, etc.) which is the coupling between a resonant cavity and an object other than resonant cavity, and both ends of the metal transmission line 30 are open to form a non-enclosed resonance node which forms a resonance peak in the transmission channel and a transmission zero point on an arbitrary side of the transmission channel. The mutual coupling between a resonant cavity and an object other than resonant cavity enables the dielectric filter to generate transmission zero points by itself without cross-coupling with other dielectric filters, thereby avoids the conventional cross-coupling structure and further reduces the complexity of the coupling structure.

In the multi-mode cascade filter of this embodiment, since each multi-mode dielectric filter itself is coupled with a metal transmission line (micro-strip line, etc.) through a dielectric resonant cavity, which is the coupling between a resonant cavity and an object other than resonant cavity, to form a transmission zero point, in order to achieve coupling between any two or multiple multi-mode dielectric filters, it is only necessary to enable adjacent coupling of the resonant frequencies in any direction of multi-mode dielectric filters, and the adjacent coupling can be realized only by direct connecting the input end and the output end of the metal transmission line.

The following drawings are only examples for illustrating and explaining the present invention, and do not for limiting the scope of the present invention.

FIG. 1 is a schematic diagram illustrating the structure of a conventionaThe following drawings are only examples for illustrating and explaining the present invention, and do not for limiting the scope of the present invention.

FIG. 1 is a schematic diagram illustrating the structure of a conventional multi-mode cascade filter.

FIG. 2 is a schematic diagram illustrating the structure of a multi-mode dielectric filter according to an embodiment of the present invention.

FIG. 3a to FIG.3c are cross-sectional views of the multi-mode dielectric filter of FIG. 2.

FIG. 4 is a diagram illustrating a waveform of the multi-mode dielectric filter of FIG. 1.

FIG. 5 is a schematic diagram illustrating the structure of a multi-mode dielectric filter according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view of the multi-mode dielectric filter of FIG.5.

FIG. 7 is a schematic diagram illustrating the structure of a coupling structure in a multi-mode dielectric filter according to another embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating the structure of a multi-mode cascade filter according to an embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating the structure of a multi-mode cascade filter according to another embodiment of the present invention.

For facilitating understanding of the technical features, objectives and merits of the present invention, specific embodiments of the present invention are hereinafter described with reference to the accompanying drawings. In the drawings, the same reference signs denote the same parts.

The term "schematic" herein means "serving as an example, instance, or illustration", and any drawing or embodiment described as "schematic" herein should not be interpreted as a more preferred or more advantageous technical solution.

For conciseness of the drawings, each figure only schematically shows the parts involved in the present invention, and is not the actual structure of a product. Moreover, in order to make the drawings concise and readily understood, in some drawings, only one of components having the same structure or function is schematically shown, or only one of them is labeled.

In the present invention, "upper", "lower", "front", "rear", "left", "right", etc. are only used to indicate relative position relationships between relevant parts, not for limiting the absolute positions of the relevant parts.

In the present invention, "first", "second", etc. are only used to distinguish one another, not indicating the degree of importance or order, or the premise of mutual existence.

In the present invention, "equal", "same", etc. are not strict mathematical and/or geometrical limitations, may also include errors that can be understood by those skilled in the art and allowed for manufacturing or use. Unless otherwise stated, a numerical range herein includes not only the entire range within the two endpoints, but also several sub-ranges contained therein.

Exemplary embodiments are now described in more detail with reference to the drawings.

In order to solve the problems in the prior art, the present invention provides a multi-mode dielectric filter and a multi-mode cascade filter, which can generate a transmission zero using direct coupling between a dielectric resonant cavity and a metal transmission line without requiring cross-coupling between multiple cavities, and can achieve adjacent coupling between different modes of the same multi-mode resonator using a direct connection with a metal transmission line, therefore, the structure of the multi-mode dielectric filter can be greatly simplified.

FIG. 2 is a schematic diagram illustrating the structure of a multi-mode dielectric filter according to a first embodiment of the present invention, and FIGs. 3a to 3c are cross-sectional views of the multi-mode dielectric filter of FIG. 2.

As shown in FIG. 2, and FIGs. 3a-3c, a multi-mode dielectric filter 100 includes a dielectric resonant cavity 10, metal transmission line 30, first coupling structure 41 and second coupling structure 42. The dielectric resonant cavity 10 includes a dielectric body 11 and a metal coating 12 covering an outer surface of the dielectric body 11 and the dielectric body 11 is in a rectangular parallelepiped shape having a first surface 11a, a second surface 11b and a third surface 11c which are orthogonal to each other. The metal transmission line 30 includes a first transmission line branch 31 disposed to face the first surface 11a and a second transmission line branch 32 disposed to face the second surface 11b. The first coupling structure 41 is electrically connected to the first transmission line branch 31 and extends in a first direction inward the dielectric body 11 so that the dielectric resonant cavity 10 forms a first resonant frequency in the first direction. The second coupling structure 42 is electrically connected to the second transmission line branch 32 and extends in a second direction inward the dielectric body 11 so that the dielectric resonant cavity 10 forms a second resonant frequency in the second direction.

The first direction and the second direction may be perpendicular to the first surface 11a and the second surface 11b, respectively.

The detailed structure of the multi-mode dielectric filter 100 are as follows.

The dielectric resonant cavity 10includes a dielectric body 11, and a metal coating 12 covering the outer surface of the dielectric body 11. The dielectric body 11 is in the shape of a rectangular parallelepiped, preferably a cube, and the outer surface of the dielectric body 11 includes a pair of parallel first surfaces 11a, a pair of parallel second surfaces 11b, and a pair of parallel third surfaces 11c. The first surface 11a, the second surface 11b, and the third surface 11c are orthogonal to each other. The dielectric body 11 of the dielectric resonant cavity 10 is solid with the surface covered with a metal coating 12. The dielectric body 11 is made of a solid dielectric material.

The coupling structure, includes a first coupling structure 41 and a second coupling structure 42. The first coupling structure 41 and the second coupling structure 42 extend inward the dielectric body 11 respectively from one of the first surfaces 11a and one of the second surfaces 11b.

The first and

second coupling structure

41, 42 may be a columnar solid metal structure, or may be in the form of a metalized blind hole formed in the dielectric body 11.

The metal transmission line 30, formed by a plurality of inter-connected metal transmission line branches and two ends of the metal transmission line 30 serve as a signal input end 30a and a signal output end 30b respectively/ The metal transmission line branches include a first metal transmission line branch 31 and a second metal transmission line branch 32 which are connected to each other. The first metal transmission line branch 31 is disposed outside of a first surface 11a corresponding to the first coupling structure 41, and the second metal transmission line branch 32 is arranged outside a second surface 11b corresponding to the second coupling structure 42.

The first coupling structure 41 is connected to the first metal transmission line branch 31, and the dielectric resonant cavity 10 is coupled to the first metal transmission line branch 31 through the first coupling structure 41 to form a first resonance frequency in the extending direction of the first coupling structure 41. By the first coupling structure 41,a first transmission zero point is formed on an arbitrary side(left side or right side) of a transmission channel(filter passband).

The second coupling structure 4242 is connected to the second metal transmission line branch 32, and the dielectric resonant cavity 10 is coupled to the second metal transmission line branch 32 through the second coupling structure 42to form a second resonance frequency in the extending direction of the second coupling structure 42. By the second coupling structure 42, a second transmission zero point on an arbitrary side(left side or right side) of the filter passband.

In this embodiment, the multi-mode dielectric filter 100 forms two transmission zero points by the first coupling structure 41 and the second coupling structure 42.

In this embodiment, a directional resonance frequency is generated by the dielectric resonant cavity 10 and a metal transmission line branch through a coupling structure connecting the dielectric resonant cavity 10 and a metal transmission line branch, and the metal transmission line branch and coupling structures are in a one-to-one correspondence relationship. The dielectric filter of this embodiment includes only one dielectric resonant cavity 10, and the coupling method is not the cross-coupling between different resonant cavities, but the coupling between the dielectric resonant cavity and the metal transmission line (a microstrip line, etc.) which is the coupling between a resonant cavity and an object other than resonant cavity, both ends of the metal transmission line 30 are open to form a non-enclosed resonance node which forms a resonance peak in the transmission channel and a transmission zero point on an arbitrary side of the transmission channel. In the extending direction of the coupling structure 40, the coupling structure 40 makes a signal of the metal transmission line resonates in the dielectric resonant cavity through exciting a mode in a specific direction, thereby generating a corresponding resonance frequency in the extending direction.

Further, the dielectric body 11 of the dielectric resonant cavity 10 is in the form of a rectangular parallelepiped or a cube, which has three groups of mutually orthogonal surfaces: a pair of first surfaces 11a, a pair of second surfaces 11b, and a pair of third surfaces 11c, and the coupling structure extends vertically inwards from two of the three groups of surfaces, thereby generating two mutually orthogonal resonance frequencies.

Specifically, in this embodiment, the first coupling structure 41 extends vertically inward the dielectric body 11 from one of the first surfaces 11a, and the first coupling structure 41 is connected to the first metal transmission line branch 31 to make the dielectric resonant cavity 10 coupled with the first metal transmission line branch 31 through the first coupling structure 41, to form a first resonance frequency in the extending direction of the first coupling structure 41 and a first transmission zero point on an arbitrary side of the transmission channel. The second coupling structure 42 extends vertically inward the dielectric body 11 from one of the second surfaces 11b, and the second coupling structure 42 is connected to the second metal transmission line branch 32 to make the dielectric resonant cavity 10 coupled with the second metal transmission line branch 32 through the second coupling structure 42, to form a second resonance frequency in the extending direction of the second coupling structure 42, and to form one second transmission zero point on an arbitrary side of the transmission channel. The resonance directions of the first resonance frequency and the second resonance frequency are orthogonal to each other.

The adjacent coupling of the first resonance frequency and the second resonance frequency is achieved through the connection of the first metal transmission line branch 31 and the second metal transmission line branch 32. As such, the adjacent coupling of two mutually orthogonal resonance frequencies is converted into the connection of the two metal transmission line branches, thereby the three-dimensional structure is replaced by a planar structure which greatly reduces the complexity. Therefore, the adjacent coupling structure of the multi-mode dielectric filter in this embodiment is simple, and can avoid the complexity of configuring coupling structures in a direction which crosses two modes at a 45° angle as in the prior art.

Further, the multi-mode dielectric filter 100 of this embodiment includes only one dielectric resonant cavity 10, and the coupling mode is not the cross-coupling between different resonant cavities, but the coupling between a dielectric resonant cavity and the metal transmission line (a microstrip line, etc.) which is the coupling between a resonant cavity and an object other than resonant cavity, and both ends of the metal transmission line 30 are open to form a non-enclosed resonance node which forms a resonance peak in the transmission channel and a transmission zero point on an arbitrary side of the transmission channel. The mutual coupling between a resonant cavity and an object other than resonant cavity enables the dielectric filter to generate transmission zero points by itself without cross-coupling with other dielectric filters, thereby avoids the conventional cross-coupling structure and further reduces the complexity of the coupling structure.

In conventional dielectric filters, generating a transmission zero point requires a coupling structure between non-adjacent resonant cavities, that is, generating a transmission zero point requires a dielectric filter composed of at least three resonant cavities and requires cross-coupling (mostly negative coupling) structures provided between the resonant cavities. Since the generation of a transmission zero point requires the coupling between two non-adjacent resonant cavities, the resonant cavities of the conventional dielectric filters are mostly arranged in a Z shape, an S shape, or a U shape. Taking a dielectric filter composed of three resonant cavities as an example, three resonant peaks can be formed in the transmission channel with only one transmission zero point.

The multi-mode dielectric filter 100 may include a first circuit board 61 and a second circuit board 62. The metal transmission line 30 is usually a metallized line arranged on a surface of the circuit board. The transmission line branch 31 may be embedded in the first circuit board 61 and the transmission line branch 32 may be embedded in the second circuit board 62. The first circuit board 61 and the second circuit board may respectively include plurality of layers formed of dielectric material and the first transmission line branch 31 and the second transmission line branch 32 may be disposed on a surface of the layers. The filter circuit or the like of the dielectric filter can be formed together with the metal transmission line 30 on the first circuit board 61 or the second circuit board 62. That is, the dielectric filter of this embodiment can form a plurality of independent transmission zero points using only one dielectric resonant cavity 10 with corresponding accessory circuits, which can optimize the filtering performances of the filter.

As shown in FIG. 2, two ends of each metal transmission line branch respectively correspond to two sides of an outer surface corresponding to the metal transmission line branch. The first circuit board 61 may be disposed to face the first surface 11a and may be parallel to the first surface 11a. The second circuit board 62 may be disposed to face the second surface 11b and may be parallel to the second surface 11b. The first circuit board 61 and the second circuit board 62 can be arranged on the outer surface of the dielectric body 11 corresponding to the first coupling structure 41 and the second coupling structure 42, and can be attached to the outer surface or insulated from the outer surface by an air layer. Preferably, the first and second

transmission line branches

31 and 32 can be arranged on the surface of the

circuit board

61 and 62 facing away from the dielectric resonant cavity 10, so as to be insulated from the dielectric resonant cavity 10 by a dielectric material.

As shown in FIGS 3a to 3c, the first coupling structure 41 includes a first portion 41a embedded in the dielectric body 11 and a second portion 41b disposed outside the dielectric body 11, and the second coupling structure 42 includes a first portion 42a embedded in the dielectric body 11 and a second portion 42b disposed outside the dielectric body 11. An end portion E1 of the first portion 41a of one of the first coupling structure 41 and an end portion E2 of the first portion 42a of the second coupling structure 42 may be disposed inside the dielectric body 11 and does not contact with the metal coating 12. Such coupling structure may form a capacitive transmission zero point on the left side of the transmission channel(filter passband).

The first portion 41a of the first coupling structure 40 is embedded in the dielectric body 11, and is not electrically connected to the metal coating 12 on the surface of the dielectric resonant cavity 10, and thus is not connected to the ground. A second portion 41b of the first coupling structure 41 is connected (electrically or by signals) to the first transmission line branch 31, and negative coupling (electrical coupling) of the dielectric resonant cavity 10 and the metal transmission line 30 is achieved through the first coupling structure 41, thereby a capacitive transmission zero point is formed on the left side of the transmission channel.

Similarly, the second coupling structure 42 may form a capacitive transmission zero point is formed on the left side of the transmission channel.

The

second portion

41b, 42b of the

first coupling structure

41, 42 may penetrates the first and

second circuit board

61, 62 respectively, to form an electrical connection with the first and

second transmission line

31 and 32.

The multi-mode dielectric filter may further include a first insulator 21 and a second insulator 22. The first insulator 21 may be disposed between the first circuit board 61 and the dielectric body 11 and surrounds the first coupling structure 41. The second insulator 22 may be disposed between the second circuit board 62 and the dielectric body 11 and surrounds the second coupling structure 42.

The size of the first circuit board 61 may correspond to the first surface 11a, and two ends of the first transmission line branch 31 respectively correspond to two edges of the first surface 11a. The two edges may be two adjacent or non-adjacent edges. In other words, the extending direction and the shape of the first transmission line branch 31 may be in various forms such as a straight line, a broken line, or a curve. Similarly, the size of the second circuit board 62 may correspond to the second surface 11b, and two ends of the second transmission line branch 32 respectively correspond to two edges of the second surface 11b.

The dielectric resonant cavity 10 may further include a first adjustment hole 51 and a second adjustment hole 52. The first and

second adjustment hole

51, 52 are formed on a surfaces opposite to the surfaces where the first coupling structure 41 and the second coupling structure are located, and the metal coating 12 also covers the surface of the first and

second adjustment hole

51, 52. The first and

second adjustment hole

51, 52 are blind hole for adjusting the resonance frequency.

The first adjustment hole 51 and the first circuit board 61 may be respectively located on opposite surfaces of the dielectric resonant cavity 10. For example, as shown in the FIG.2, FIGS.3a to 3c, the first adjustment hole 31 are formed on the third surface 11c and the first circuit board 61 are adjacent and faces the other third surface 11c. The second adjustment hole 32 is formed on the first surface 11a and the second circuit board 62 are adjacent and faces the other first surface 11a.

As shown in FIG. 2, the metal transmission line 30 is disposed on the surface of the first and

second circuit board

61, 62 facing away from the dielectric resonant cavity 10, the dielectric resonant cavity 10 can be fixed to the first and

second circuit board

61, 62 through the surfaces of the dielectric resonant cavity 10, and the dielectric material of the first and

second circuit board

61 and 62 can form insulation between the dielectric resonant cavity 10 and the metal transmission line 30. The surfaces of the dielectric resonant cavity 10 is covered by the metal coating 12, and the gap between the dielectric resonant cavity 10 and the circuit board or the metal transmission line can be filled with soldering tin.

According to the characteristics of the cube shape, the first surface 11a and the second surface 11b are certainly adjacent to each other. By configuring the extending directions of the first transmission line branch 31 and the second transmission line branch 32, the connection and coupling of the first transmission line branch 31 and the second transmission line branch 32 can be easily achieved, thereby facilitating adjacent coupling of the two mutually orthogonal resonance frequencies.

Referring to FIG. 4, the multi-mode dielectric filter 100 as shown in FIG. 2 may have two resonance frequencies, and two transmission zeros are respectively generated corresponding to the two resonance frequencies.

FIG. 5 is a schematic diagram illustrating the structure of a multi-mode dielectric filter according to another embodiment of the present invention. FIG. 6 is a cross-sectional view of the multi-mode dielectric filter of FIG.5.

The multi-mode dielectric filter 101 of this embodiment is different from the above described multi-mode dielectric filter 100 in a structure of the second coupling structure 48 and the second transmission line branch 38.

In the multi-mode dielectric filter 101, similar to the multi-mode dielectric filter 100, the first coupling structure 41 includes a first portion 41a embedded in the dielectric body 11 and a second portion 41b disposed outside the dielectric body 11.

In the multi-mode dielectric filter 101, different to the multi-mode dielectric filter 100, the second portion 48a of the second coupling structure 48 has a shape extending in one direction(for example, Z direction) inside the dielectric body 11 and then bent in another direction(for example, Y direction), and the bent end portion E3 of the first portion 48a is in contact with the metal coating 12 on the dielectric body 11. Such coupling structure may form a inductive transmission zero point on the right side of the filter passband.

Except the main difference in a structure of the second coupling structure 48, other components are similar to the multi-mode dielectric filter 100 of FIG.2. The second transmission line branch 38 electrically connected to the second coupling structure 48 may be embedded in the second circuit board 68. The second portion 48b of the second coupling structure has a form of metal through-hole connecting the first portion 48a and the second transmission line branch 38, through the second circuit board 68. The shape of the second transmission line branch is an example, and is modified to another shape, for example, to straight line. The second insulator 28 may be disposed between the second circuit board 68 and the dielectric body 11 and surrounds the second coupling structure 48.

FIG. 7 shows another embodiment of the present invention. In this embodiment, the multi-mode dielectric filter 102 is a triple-mode dielectric filter. The multi-mode dielectric filter 102 includes a first coupling structure 41, a second coupling structure 42 and a third coupling structure 43. Addition to the first and

second coupling structure

41 and 42 on the basis of the dual-mode dielectric filter in FIG. 2, a third coupling structure 43 is further provided and thereby a new resonance frequency is introduced.

Specifically, the third coupling structure 43 extends inward the dielectric body 11 from one of the third surfaces 11c, in a third direction. By the third coupling structure the dielectric resonant cavity may form a third resonant frequency in the third direction

In the multi-mode dielectric filter 102, metal transmission line 30 includes first transmission line branch 31, a second transmission line branch 32 and a third transmission line branch 33. The first metal transmission line branch 31, the second metal transmission line branch 32 and the third metal transmission line branch 33 are connected to form the metal transmission line 30. The third transmission line branch 33 is arranged outside a third surface 11c corresponding to the third coupling structure 43.

The third coupling structure 43 is connected to the third transmission line branch 33 to make the dielectric resonant cavity 10 coupled with the third transmission line branch 33 through the third coupling structure 43, to form a third resonance frequency in an extending direction of the third coupling structure 43 and a third transmission zero point on an arbitrary side of the transmission channel(filter passband).

Similarly, the three mutually orthogonal resonance frequencies are coupled together through the connection of the metal transmission line branches. Specifically, the metal transmission line 30 is formed by the first metal transmission line branch 31, the second transmission line branch 32 and the third transmission line branch 33 connected with each other. The three metal transmission line branches are sequentially connected to form a complete transmission line whose both ends form a signal input end 30a and a signal output end 30b of the metal transmission line 30.

For example, in this embodiment, a first end of the first metal transmission line branch 31 is open to serve as the signal input end 30a, a second end of the first metal transmission line branch 31 is connected to a first end of the second transmission line branch 32, a second end of the second transmission line branch 32 is connected to a first end of the third transmission line branch 33, and a second end of the third transmission line branch 33 is open to serve as the signal output end 30b. This example only illustrates a connection manner of the metal transmission line branches, not for limiting the connection sequence of the metal transmission line branches.

The dielectric body 11 of the dielectric resonant cavity 10 is solid with the surface covered with a metal coating. The dielectric body 11 is made of a solid dielectric material.

In this embodiment, the position of a cross zero point in the transmission channel is determined by the connection manner of the coupling structures. Two types of example coupling structures have been described with reference to FIGS 2, 3a to 3c, 5 and 6. In FIG.7, shape of the first, second, third coupling structures have same shape, however, this is just an example. One or more coupling structures provided in the multi-mode dielectric filter 102 may be modified to have another shape, like as coupling structure 48 in FIG. 5, 6.

As shown in FIG. 7, when an end portion of the first, second,

third coupling structure

41, 42, or 42is embedded in the dielectric body 11, and the end portion is not electrically connected to the metal coating 12 on the surface of the dielectric resonant cavity 10, a capacitive transmission zero point is formed on the left side of the transmission channel.

As described in reference to FIGS.3b, the first portion 41a of the coupling structure 41 is embedded in the dielectric body 11, and is not electrically connected to the metal coating 12 on the surface of the dielectric resonant cavity 10, and thus is not connected to the ground. A second portion 41b of the first coupling structure 41is connected (electrically or by signals) to the metal transmission line 30, and negative coupling (electrical coupling) of the dielectric resonant cavity 10 and the metal transmission line 30 is achieved through the coupling structure 41, thereby a capacitive transmission zero point is formed on the left side of the transmission channel. Similarly, the second coupling structure 42 and the third coupling structure 43 may form another capacitive transmission zero points.

The first, second,

third coupling structures

41, 42, 43 may be a columnar solid metal structure, or may be in the form of a metalized blind hole formed in the dielectric body 11.

As shown in FIG. 7, the dielectric resonant cavity 10 further includes a first, second and

third adjustment hole

51, 52 and 53. The first adjustment hole 51 may be formed on a surface opposite to the surface where the coupling structure 41 is located, and the metal coating 12 also covers the surface of the first adjustment hole 51. The adjustment hole 51 may be a blind hole for adjusting the first resonance frequency. Similarly, the second adjustment hole 52 may be formed on a surface opposite to the surface where the second coupling structure 42 is located, and the metal coating 12 also covers the surface of the first adjustment hole 52. The second adjustment hole 52 may be a blind hole for adjusting the second resonance frequency. The third adjustment hole 53 may be formed on a surface opposite to the surface where the third coupling structure 43 is located, and the metal coating 12 also covers the surface of the third adjustment hole 53. The adjustment hole 53 may be a blind hole for adjusting the third resonance frequency.

The adjustment holes 51, 52, 53 and the

circuit board

61,62,63 are respectively located on opposite surfaces of the dielectric resonant cavity 10. For example, as shown in FIG. 7, the first adjustment hole 51 may be formed to face the first coupling structure 41, the second adjustment hole 52 may be formed to face the second coupling structure, and the third adjustment hole may be formed to face the third coupling structure.

As shown in FIG. 7, the metal transmission line 30 is disposed on the surfaces of the

circuit board

61, 62, 63 facing away from the dielectric resonant cavity 10, the dielectric resonant cavity 10 can be fixed to the

circuit boards

61, 62, 63 through the surfaces of the dielectric resonant cavity 10, and the dielectric material of the

circuit boards

61, 62, 63 can form insulation between the dielectric resonant cavity 10 and the metal transmission line 30. The surfaces of the dielectric resonant cavity 10 is covered by the metal coating 12, and the gap between the dielectric resonant cavity 10 and the

circuit boards

61, 62, 63 or the metal

transmission line branches

31, 32, 33 may be filled with soldering tin.

Like as the multi-mode dielectric filter 100 of FIG.2a, the second portions of the first, second,

third coupling structure

41, 42, 43 penetrates the

circuit board

61, 62, 63 to form an electrical connection with the

transmission line branch

31, 32, 33, respectively.

The insulators may be disposed between the first, second,

third circuit board

61, 62, 63 and the dielectric body 11 and surrounds the first, second,

third coupling structure

41, 42, 43, respectively. In the modified embodiment, one of the first, second,

third coupling structure

41, 42, 43 is modified to have a shape as coupling structure 48 as in FIG.6. That is, one of the first, second,

third coupling structure

41, 42, 43 may have a shape bent inside dielectric resonant cavity 10 and the bent end is in contact with and electrically connected to the metal coating 12 covering a surface of the dielectric body 11. When an end portion of the first portion of the coupling structure embedded in the dielectric resonant cavity 10 is electrically connected to the metal coating 12 on the surface of the dielectric resonant cavity 10, the coupling structure may form an inductive transmission zero point on the right side of the transmission channel.

In the modified embodiment, a first portion of one of the first, second,

third coupling structure

41, 42, 43 is embedded in the dielectric body 11, and is connected to the grounded through the electrical connection with the metal coating 12 on the surface of the dielectric resonant cavity 10. The second portion of the coupling structure is connected (electrically or by signals) to the metal transmission line 30, and positive coupling (magnetic coupling) between the dielectric resonant cavity 10 and the metal transmission line 30 is achieved through the coupling structure, thereby the inductive transmission zero point is formed on the right side of the transmission channel.

Also in the modified embodiment, the dielectric resonant cavity 10 further includes first, second

third adjustment hole

51, 52, 53, as shown in FIG.7. The first, second and

third adjustment hole

51, 52, 53 are formed on a surfaces opposite to the surfaces where the first, second,

third coupling structure

41, 42, 43 are respectively located, and the metal coating 12 also covers the surface of the first, second,

third adjustment hole

51, 52, 53. The adjustment holes are a blind hole for adjusting the resonance frequency.

The adjustment holes 51, 52, 53 and the

circuit board

61, 62, 63 are respectively disposed on opposite surfaces of the dielectric resonant cavity 10. As shown in FIG. 7, the first adjustment hole 51 faces first coupling structure 41, the second adjustment hole 52 faces the second coupling structure 42 and the third adjustment hole faces the third coupling structure 43.

Also in the modified embodiment, the metal transmission line 30 is arranged on the surface of the

circuit board

61, 62, 63 facing away from the dielectric resonant cavity 10. The dielectric resonant cavity 10 can be fixed to the

circuit board

61, 62, 63 through the surface of the dielectric resonant cavity 10, and the dielectric material of the

circuit board

61, 62, 63 can form insulation between the dielectric resonant cavity 10 and the metal transmission line 30. The gap between the dielectric resonant cavity 10 and the circuit board or the metal transmission line can be filled with soldering tin.

Also in the modified embodiment, the second portions of the first, second,

third coupling structure

41, 42, 43 penetrates the

circuit board

61, 62, 63 to form an electrical connection with the

transmission line branch

31, 32, 33, respectively..

Also in the modified embodiment,, the insulators may be disposed between the first, second,

third circuit board

61, 62, 63 and the dielectric body 11 and surrounds the first, second,

third coupling structure

41, 42, 43, respectively.

In the above described embodiments of multi-mode

dielectric filter

100, 101, 102, the second portions of any one the

coupling structure

41, 42, 43 may be connected (electrically or by signals) to a specific position (for example, a midpoint) on the metal transmission line 30. The shape, width, and extending direction of the metal transmission line 30 can affect the amplitude and frequency of the resulted transmission zero point. Therefore, the shape of the metal transmission line 30 is not limited to the shapes as shown in the drawings.

In the embodiment of the present invention, a single resonant cavity is used to generate a plurality of resonance frequencies and a plurality of transmission zero points. Therefore, the frequencies and positions of the transmission zero points are not affected by the characteristics of resonant cavities of other filters, and each resonant cavity can be manufactured individually, thus the performances of each dielectric filter can be improved and the machining precision requirements of each dielectric filter can be reduced, thereby product performances can be improved with reduced costs. However, the dielectric filter of the present invention is not limited to the single resonant cavity. As shown in FIG. 8 and FIG. 9, another embodiment of the present invention further provides a multi-mode cascade filter which is composed of the multi-mode dielectric filters provided by the present invention.

Specifically, the multi-mode cascade filter includes plurality of multi-mode dielectric filter, for example, a first multi-mode dielectric filter and a second multi-mode dielectric filter.

The first multi-mode dielectric filter and the second multi-mode dielectric filter independently includes any one or modified one of above described multi-mode

dielectric filters

100, 101, 102.

In the multi-mode cascade filter, the signal input end of the metal transmission line of the first multi-mode dielectric filter and a signal output end of the metal transmission line of the second multi-mode dielectric filter are electrically connected with each other. The first multi-mode dielectric filter and the second multi-mode dielectric filter may be arranged symmetrically with each other.

The dielectric resonant cavities 10 of the plurality of multi-mode dielectric filters are arranged side by side, and the signal output end 30b of one of two adjacent multi-mode dielectric filters is directly connected to the signal input end 30a of the other of the two adjacent multi-mode dielectric filters, to achieve adjacent coupling of the resonance frequencies in an arbitrary direction of each of the two multi-mode dielectric filters.

In conventional cascade filters, in order to generate a transmission zero point, different dielectric filters have to be cross-coupled. Since resonance frequencies of different dielectric filters have different directions, the cross-coupling structure is very complicated. In this embodiment, however, each multi-mode dielectric filter alone can generate a transmission zero point through the coupling between the dielectric resonant cavity and the metal transmission line (microstrip line, etc.), which is mutual coupling of a resonant cavity and an object other than resonant cavity. Therefore, when coupling of any two or multiple multi-mode dielectric filters is required, it is only necessary to adjacently couple the resonance frequencies in an arbitrary direction of each multi-mode dielectric filter which can be achieved simply by directly connecting the input end and output end of the metal transmission line.

Specifically, the multi-mode cascade filter 300 as shown in FIG. 8 includes two dual-mode dielectric filters 1 and 2. The two dual-mode dielectric filters 1 and 2 each may be substantially same as the multi-mode dielectric filter 100 of FIG.2. The signal output end 30b of the first dual-mode dielectric filter 1 is one end of the second metal transmission line branch 32 of the first dual-mode dielectric filter 1, and the signal input end 30a of the second dual-mode dielectric filter 2 is one end of the first metal transmission line branch 31 of the second dual-mode dielectric filter 2. Thus, by connecting the metal transmission line branches of the two dual-mode dielectric filters, adjacent coupling of the resonance frequencies in the extending direction of the second coupling structure of the first dual-mode dielectric filter 1 and the resonance frequencies in the extending direction of the first coupling structure of the second dual-mode dielectric filter 2 can be achieved, and the multi-mode cascade filter as shown in FIG. 8 is enabled to have four resonance frequencies.

Similarly, the multi-mode cascade filter 301 shown in FIG. 9 includes two triple-

mode dielectric filters

3 and 4. The two triple-

mode dielectric filters

3 and 4 each may be substantially same as the multi-mode dielectric filter 102 of FIG.7. The signal output end 30b of the first triple-mode dielectric filter 3 is one end of the third metal transmission line branch 33 of the first triple-mode dielectric filter 3, and the signal input end 30a of the second triple-mode dielectric filter 4 is one end of the first metal transmission line branch 31 of the second triple-mode dielectric filter 4. Thus, by connecting the metal transmission line branches of the two triple-mode dielectric filters, adjacent coupling of the resonance frequencies in the extending direction of the third coupling structure of the first triple-mode dielectric filter 3 and the resonance frequencies in the extending direction of the first coupling structure of the second triple-mode dielectric filter 4 can be achieved, and the multi-mode cascade filter shown in FIG. 9 is enabled to have six resonance frequencies.

In order to adjust the position of the signal input end of the metal transmission line relative to the position of the output end of the metal transmission line, two adjacent multi-mode dielectric filters can be arranged at different positions, for example, the circuit board where the signal output end 30b of one of the multi-mode dielectric filters is located and the circuit board where the signal input end 30a of the other of the multi-mode dielectric filters is located can be arranged side by side in the same plane as shown in FIG. 8 to have the two dielectric resonant cavities are located on the same side of the circuit boards, or can be attached to each other as shown in FIG. 9 to have the two dielectric cavities are located on different sides of the circuit boards.

Apparently, the multi-mode cascade filter of the present invention is not limited to the modes as shown in FIG. 8 and FIG. 9. For example, the cascade filter may include a cascade connection of more than two dielectric filters; or, the dielectric filters in the multi-mode cascade filter are not limited to the multi-mode dielectric filters as shown in FIG. 2 and FIG. 7, but may also include, for example, single-mode dielectric filters; or, the dielectric filters in the multi-mode cascade filter are not limited to the same type of multi-mode dielectric filters, but may be, for example, combinations of single-mode, dual-mode and triple-mode dielectric filters, or the like.

It can be seen from the above technical solutions that, in this embodiment, a directional resonance frequency is achieved by the dielectric resonant cavity 10 and a metal transmission line branch through a coupling structure connecting the dielectric resonant cavity 10 and a metal transmission line branch, and the metal transmission line branch and the coupling structure are in a one-to-one correspondence relationship. The adjacent coupling of two mutually orthogonal resonance frequencies is converted into the connection of the two metal transmission line branches, so the three-dimensional structure is replaced by a planar structure which greatly reduces the complexity. Therefore, the adjacent coupling structure of the multi-mode dielectric filter in this embodiment is simple, which avoids the complexity of configuring coupling structures in a direction which crosses two modes at a 45° angle as in the prior art.

Further, the multi-mode dielectric filter of this embodiment includes only one dielectric resonant cavity 10, and the coupling manner is not cross-coupling between different resonant cavities, but the coupling between a dielectric resonant cavity and a metal transmission line (a microstrip line, etc.) which is the coupling between a resonant cavity and an object other than resonant cavity, and both ends of the metal transmission line 30 are open to form a non-enclosed resonance node which forms a resonance peak in the transmission channel and a transmission zero point on an arbitrary side of the transmission channel. The mutual coupling of the resonant cavity and the object other than resonant cavity enables the dielectric filter to generate a transmission zero point by itself without cross-coupling with other dielectric filters, which omits the cross-coupling structure in the prior art and further reduces the complexity of the coupling structure.

In the multi-mode cascade filter of this embodiment, each multi-mode dielectric filter forms a transmission zero point by itself through the coupling between a dielectric resonant cavity and a metal transmission line (microstrip line, etc.) which is the mutual coupling between a resonant cavity and an object other than resonant cavity. Therefore, when coupling of any two or multiple multi-mode dielectric filters is required, it is only necessary to adjacently couple the resonance frequencies in an arbitrary direction of each multi-mode dielectric filter, and the adjacent coupling can be achieved only by the directly connecting the input end and the output end of the metal transmission line.

The above detailed description merely serves as illustrations directed to some feasible embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any equivalent implementation scheme or alteration, such as combination, division or repetition of features, made without departing from the technical spirit of the present invention, shall fall within the protection scope of the present invention.

Claims

A multi-mode dielectric filter, comprising:

a dielectric resonant cavity comprising a dielectric body and a metal coating covering an outer surface of the dielectric body, the dielectric body is in a rectangular parallelepiped shape having a first surface, a second surface and a third surface which are orthogonal to each other;

a metal transmission line comprising a first transmission line branch disposed to face the first surface and a second transmission line branch disposed to face the second surface;

a first coupling structure electrically connected to the first transmission line branch, the first coupling structure extending in a first direction inward the dielectric body from the first transmission line branch so that the dielectric resonant cavity forms a first resonant frequency in the first direction;

a second coupling structure electrically connected to the second transmission line branch, the second coupling structure extending in a second direction inward the dielectric body from the second transmission line branch so that the dielectric resonant cavity forms a second resonant frequency in the second direction.
The multi-mode dielectric filter of claim 1, wherein the first direction and the second direction are perpendicular to the first surface and the second surface, respectively.
The multi-mode dielectric filter of claim 1, wherein the multi-mode dielectric filter forms two transmission zero point by the first coupling structure and the second coupling structure.
The multi-mode dielectric filter of claim 1, further comprising:

a first circuit board in which the first transmission line branch is embedded; and

a second circuit board in which the second transmission line branch is embedded.
The multi-mode dielectric filter of claim 4, wherein the first circuit board is disposed to parallel to the first surface and the second circuit board is disposed to parallel to the second surface.
The multi-mode dielectric filter of claim 4, wherein the first coupling structure does not contact with a portion of the metal layer on the first surface, and the second coupling structure does not contact with a portion of the metal layer on the second surface.
The multi-mode dielectric filter of claim 4, further comprising:

a first insulator disposed between the first circuit board and the dielectric body and surrounding the first coupling structure;

a second insulator disposed between the second circuit board and the dielectric body and surrounding the second coupling structure.
The multi-mode dielectric filter of claim 4, wherein each of the first coupling structure and the second structure includes a first portion embedded in the dielectric body and a second portion disposed outside the dielectric body.
The multi-mode dielectric filter of claim 8, an end portion of the first portion of one of the first coupling structure and the second coupling structure is disposed inside the dielectric body and does not contact with the metal coating.
The multi-mode dielectric filter of claim 8, the first portion of the one of the first coupling structure and the second coupling structure has a shape extending in the first direction inside the dielectric body and then bent in another direction, and the bent end portion of the first portion is in contact with the metal coating on the dielectric body.
The multi-mode dielectric filter of claim 8, wherein the second portion of the first coupling structure is electrically connected to the first transmission line branch through the first circuit board, and the second portion of the second coupling structure is electrically connected to the second transmission line branch through the second circuit board.
The multi-mode dielectric filter of claim 1, wherein the first coupling structure and the second coupling structure are in a form of metal cylinder or a metalized blind hole.
The multi-mode dielectric filter of claim 1, further comprising:

a third transmission line branch disposed to face the third surface; and

a third coupling structure electrically connected to the third transmission line branch, the third coupling structure extending in a third direction inward the dielectric body so that the dielectric resonant cavity forms a third resonant frequency in the third direction.
The multi-mode cascade filter comprising:

a first multi-mode dielectric filter of any one of claims 1 to 13; and

a second multi-mode dielectric filter of any one of claims 1 to 13.
The multi-mode cascade filter of claim 14,

a signal input end of the metal transmission line of the first multi-mode dielectric filter and a signal output end of the metal transmission line of the second multi-mode dielectric filter are electrically connected with each other.