CN212874710U

CN212874710U - Thin film filter

Info

Publication number: CN212874710U
Application number: CN202022171710.4U
Authority: CN
Inventors: 潘绍榫; 曲克峰
Original assignee: Hangzhou Youwang Electronics Co ltd
Current assignee: Hangzhou Youwang Electronics Co ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-04-02
Anticipated expiration: 2030-09-28

Abstract

The utility model provides a film filter, including ceramic substrate, a plurality of syntonizers, input, output and shield cover, a plurality of syntonizers set up in ceramic substrate's top is last, the input with the output set up in on the ceramic substrate, just the input with the output all includes top and bottom, the top and the bottom electric connection of input, the top and the bottom electric connection of output, the top of input and the top of output respectively with corresponding syntonizer electric connection, the shield cover surrounds a plurality of syntonizers. The technical scheme of the utility model make thin film filter's size obtain reducing, and can avoid thin film filter's performance receives the influence of gold wire bonding technology to and make thin film filter's performance stability obtain improving.

Description

Thin film filter

Technical Field

The utility model relates to a wave filter technical field, in particular to film filter.

Background

The filter is mainly used for separating different microwave signals, and the high-efficiency frequency spectrum utilization rate of the prior art has urgent requirements on the filter which has high selectivity, small size and low cost and can be directly attached to a surface. The traditional filter mainly adopts FR-4 grade materials, but the FR-4 grade materials have small relative dielectric constant and cannot effectively reduce the size of the filter; in addition, the top surface circuit and the bottom surface circuit of the conventional filter are separated, and the top surface circuit and the bottom surface circuit are electrically connected in the actual use process by adopting a gold wire bonding mode, but the length, thickness and reliability of the gold wire bonding can influence the performance of the filter; in addition, no shielding cover is arranged on the traditional filter, so that the performance of the filter is easily influenced by other components in a high-frequency to millimeter-wave frequency range, and the instability of the performance of the filter is further increased.

Therefore, it is necessary to design a thin film filter to solve the problems of the conventional filter, such as large size, performance affected by the gold wire bonding process, and unstable performance.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a film filter can make film filter's size obtains reducing, and can avoid film filter's performance receives the influence of gold wire bonding technology, and makes film filter's stability of performance obtains improving.

In order to achieve the above object, the present invention provides a thin film filter, including:

a ceramic substrate;

a plurality of resonators disposed on a top surface of the ceramic substrate;

the input end and the output end are arranged on the ceramic substrate, the input end and the output end respectively comprise a top end and a bottom end, the top end and the bottom end of the input end are electrically connected, the top end and the bottom end of the output end are electrically connected, and the top end of the input end and the top end of the output end are respectively electrically connected with the corresponding resonators; and the number of the first and second groups,

a shield surrounding the plurality of resonators.

Optionally, the relative dielectric constant of the ceramic substrate is 12-38.

Optionally, the thickness of the ceramic substrate is 0.25mm to 0.7 mm.

Optionally, the ceramic substrate has two opposite first sides and two opposite second sides.

Optionally, the resonators are symmetrically disposed with respect to a center line of two opposite first sides of the ceramic substrate, and the input terminal and the output terminal are symmetrically disposed with respect to a center line of two opposite first sides of the ceramic substrate.

Optionally, all the resonators are perpendicular to the second side of the ceramic substrate, and all the resonators are parallel to each other.

Optionally, the gap between two adjacent resonators gradually increases from two ends of the second edge of the ceramic substrate to the middle of the second edge.

Optionally, the length of the resonator is one quarter of a wavelength corresponding to a center frequency of the thin film filter.

Optionally, the operating frequency of the thin film filter is 4.5GHz to 6.5 GHz.

Optionally, the order of the resonator is 7.

Optionally, the resonators form an interdigitated structure.

Optionally, the input end and the output end are respectively arranged on two opposite first edges of the ceramic substrate, the top end of the input end and the top end of the output end are arranged on the top surface of the ceramic substrate, the bottom end of the input end and the bottom end of the output end are arranged on the bottom surface of the ceramic substrate, and the top end and the bottom end of the input end and the top end and the bottom end of the output end are electrically connected through a first conductor layer.

Optionally, the first conductor layer is disposed in the first groove and the second groove on the side surfaces of the two opposite first sides of the ceramic substrate.

Optionally, the first groove and the second groove are rectangular or semicircular in shape.

Optionally, each resonator is rectangular, and the top end and the bottom end of the input end and the top end and the bottom end of the output end are crescent-shaped.

Optionally, a second conductor layer is disposed on the bottom surface of the ceramic substrate, and the second conductor layer is grounded.

Optionally, one end of each resonator is provided with at least one first through hole, the first through hole penetrates through the ceramic substrate, and the inner wall of the first through hole is provided with a third conductor layer, so that each resonator is electrically connected to the second conductor layer through the third conductor layer.

Optionally, the first through holes on two adjacent resonators are arranged at different ends of the resonators.

Optionally, the first through hole is circular, and the diameter of the first through hole is 0.1mm to 0.25 mm.

Optionally, the first through hole is rectangular, and the side length of the first through hole is 0.25mm to 0.5 mm.

Optionally, the shielding case includes a roof, set up respectively in two curb plates on the double-phase opposite side of roof and respectively with two the two mounting panels that the curb plate is connected, the roof is located ceramic substrate's top surface top and with ceramic substrate's top surface is parallel, two the curb plate with the roof is perpendicular, two the curb plate is located the periphery of a plurality of syntonizers, two the mounting panel with the curb plate is parallel, two the mounting panel is fixed in respectively on the side on two relative second limits of ceramic substrate.

Optionally, the side surfaces of the two opposite second sides of the ceramic substrate are respectively provided with a third groove, the inner wall of the third groove is provided with a fourth conductor layer, and the mounting plate is fixed on the fourth conductor layer in the third groove, so that the shielding cover passes through the fourth conductor layer and is electrically connected with the second conductor layer.

Optionally, the thin-film filter further includes a transmission line, and the top end of the input end and the top end of the output end are electrically connected to the closest resonator through the transmission line respectively.

Compared with the prior art, the thin film filter provided by the utility model comprises the ceramic substrate with high relative dielectric constant, so that the size of the thin film filter is reduced, and the performance of the thin film filter is greatly improved; furthermore, as the top end and the bottom end of the input end and the top end and the bottom end of the output end are electrically connected through the first conductor layers arranged in the first groove and the second groove on the side wall of the first edge of the ceramic substrate, the performance of the thin film filter can be prevented from being influenced by a gold wire bonding process; furthermore, as the ceramic substrate is provided with the shielding cover, the interference of external signals can be reduced, and the performance and the stability of the product are improved.

Drawings

Fig. 1 is a schematic diagram of a top surface of a thin film filter (without a shield) according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a bottom surface of a thin film filter (without a shield) according to an embodiment of the present invention;

fig. 3 is an exploded view of a thin film filter (including a shield) according to an embodiment of the present invention;

fig. 4 is a signal simulation diagram of a thin film filter according to an embodiment of the present invention;

fig. 5 is a schematic diagram of the top surface of a thin film filter (without a shield) according to another embodiment of the present invention;

fig. 6 is a schematic diagram of the bottom surface of a thin film filter (without a shield) according to another embodiment of the present invention;

fig. 7 is an exploded view of a thin film filter (including a shield) according to another embodiment of the present invention;

fig. 8 is a signal simulation diagram of a thin film filter according to another embodiment of the present invention.

Wherein the reference numerals of figures 1 to 8 are as follows:

11-a ceramic substrate; 111-first side; 112-a second edge; 113-a second conductor layer; 114-a solder layer; 115-a second via; 116-a third groove; 12-a resonator; 121 — a first via; 13-an input terminal; 131-a first top end; 132-a first bottom end; 133-a first groove; 14-an output terminal; 141-a second apex; 142-a second bottom end; 143-a second groove; 15. 16-a shield can; 151. 161-top plate; 152. 162-side plate; 153. 163-a mounting plate; 17-transmission line.

Detailed Description

To make the objects, advantages and features of the present invention clearer, the thin film filter of the present invention is further described in detail with reference to fig. 1 to 8. It should be noted that the drawings are in simplified form and are not to precise scale, and are provided for convenience and clarity in order to facilitate the description of the embodiments of the present invention.

An embodiment of the utility model provides a thin film filter, refer to fig. 1 to 8, thin film filter includes ceramic substrate 11, a plurality of syntonizers 12, input 13 and output 14, a plurality of syntonizers 12 set up in on ceramic substrate 11's the top surface, input 13 with output 14 set up in on ceramic substrate 11, just input 13 with output 14 all includes top and bottom, the top and the bottom electric connection of input 13, the top and the bottom electric connection of output 14, the top of input 13 with the top of output 14 respectively with corresponding syntonizer 12 electric connection, the shield surrounds a plurality of syntonizers 12.

The thin film filter will be described in detail with reference to fig. 1 to 8.

The ceramic substrate 11 may have a plate-like structure made of an insulating ceramic material, and the ceramic substrate 11 may be made of a ceramic material having a high relative dielectric constant. Preferably, the relative dielectric constant of the ceramic substrate 11 may be 12 to 38.

Because waves of the same frequency are transmitted in different media at different speeds, the ceramic substrate 11 has an inherent relative dielectric constant, according to the wave transmission concept, materials with high relative dielectric constants can be used for a low-frequency filter, materials with low relative dielectric constants can be used for a high-frequency filter, and by selecting ceramic materials with high relative dielectric constants to manufacture the ceramic substrate 11, the size of the thin-film filter (namely the length, the width and the thickness of the thin-film filter) can be effectively reduced, the order of the thin-film filter is increased, the attenuation amplitude of stop-band signals is improved, and the performance of the thin-film filter is greatly improved.

The surface of the ceramic substrate 11 may be subjected to a polishing process, and the thickness of the ceramic substrate 11 after the polishing process may be 0.25mm to 0.7 mm.

As shown in fig. 1 and 5, the plurality of resonators 12 are disposed on the top surface of the ceramic substrate 11, and may preferably be disposed near the middle of the top surface of the ceramic substrate 11. The number of the resonators 12 may be at least 4, and the number of the resonators 12 may be odd number or even number, for example, the number of the resonators 12 shown in fig. 1 and 5 is 7, which is equivalent to a 7-step LC resonator, and 7 resonators 12 are used as resonant rods, one end of which is short-circuited and the other end of which is open-circuited. The higher the order of the resonators 12, the better the filtering effect, but the corresponding cost is also higher, so that an appropriate number of the resonators 12 can be selected in combination with the required filtering effect and cost.

The ceramic substrate 11 has two opposite first sides 111 and two opposite second sides 112, for example, the ceramic substrate 11 may have a rectangular structure, the first sides 111 are short sides of the rectangular structure, and the second sides 112 are long sides of the rectangular structure, or the first sides 111 are long sides of the rectangular structure, and the second sides 112 are short sides of the rectangular structure. The plurality of resonators 12 may be symmetrically disposed with respect to a center line of two opposite first sides 111 of the ceramic substrate 11, and a gap between two adjacent resonators 12 may gradually increase from both ends of a second side 112 of the ceramic substrate 11 to a middle of the second side 112. The adjacent two resonators 12 are coupled by a gap, and the coupling between the adjacent two resonators 12 can be approximated to a capacitance, so that the coupling coefficient between the adjacent two resonators 12 can be adjusted by adjusting the width of the gap between the adjacent two resonators 12. The closer the distance between two adjacent resonators 12 is, that is, the smaller the gap between two adjacent resonators 12 is, the larger the coupling coefficient between two adjacent resonators 12 is, and the wider the bandwidth is; the farther the distance between two adjacent resonators 12 is, that is, the larger the gap between two adjacent resonators 12 is, the smaller the coupling coefficient between two adjacent resonators 12 is, and the narrower the bandwidth is, so that the operating bandwidth can be adjusted by changing the gap between two adjacent resonators 12.

The plurality of resonators 12 may be disposed symmetrically or asymmetrically with respect to the center line of two opposite second sides 112 of the ceramic substrate 11, that is, the same ends of two adjacent resonators 12 facing the second sides 112 of the ceramic substrate 11 may be flush or not flush with each other.

All of the resonators 12 may be perpendicular to the second side 112 of the ceramic substrate 11, all of the resonators 12 may be parallel to each other, and all of the resonators 12 may be parallel to the first side 111 of the ceramic substrate 11. All the resonators 12 form an interdigital structure, that is, two groups of parallel coupled line resonators are formed in an intersecting manner, and the interdigital structure is compact, so that the area is small.

The length of the resonator 12 is one quarter of the wavelength corresponding to the center frequency of the thin film filter, and the operating frequency can be adjusted by changing the length of the resonator 12. The center frequency of the thin film filter refers to the center frequency of the operating frequency of the thin film filter, for example, the operating frequency of the thin film filter of this embodiment is 4.5GHz to 6.5GHz, that is, the center frequency is 5.5 GHz.

As shown in fig. 2 and 6, a second conductor layer 113 is disposed on the bottom surface of the ceramic substrate 11, and the second conductor layer 113 is grounded. The area of the second conductor layer 113 is large, and the large area of the second conductor layer 113 can ensure effective grounding of the thin film filter, thereby ensuring good performance of the thin film filter.

At least one first through hole 121 is disposed at one end of each resonator 12, the first through hole 121 penetrates through the ceramic substrate 11, and a third conductor layer (not shown) is disposed on an inner wall of the first through hole 121, so that each resonator 12 is electrically connected to the second conductor layer 113 through the third conductor layer, and all the resonators 12 can be grounded.

All the first through holes 121 are symmetrically disposed with respect to a center line of the two opposite first sides 111 of the ceramic substrate 11. The first through holes 121 on two adjacent resonators 12 are disposed at different ends of the resonators 12, so that all resonators 12 form an inductance-like structure through the first through holes 121.

The first through hole 121 may be formed by laser drilling, and the third conductor layer is grown on the inner wall of the first through hole 121 by a metal via process, so that the third conductor layer is uniformly covered on the inner wall of the first through hole 121.

Each of the resonators 12 may be rectangular in shape. As shown in fig. 1 to 3, the first through hole 121 may have a rectangular shape (i.e., a cross-sectional shape), and the first through hole 121 may have a side length of 0.25mm to 0.5mm, in which case, the number of the first through holes 121 may be one; as shown in fig. 5 to 7, the first through-hole 121 may have a circular shape (i.e., a cross-sectional shape), and the diameter of the first through-hole 121 may be 0.1mm to 0.25mm, in which case the number of the first through-holes 121 is at least one. It should be noted that the shape of the first through hole 121 is not limited to the two shapes. By increasing the number of the first through holes 121, the hole inner areas of all the first through holes 121 can be increased, so that the area of the third conductor layer in the first through holes 121 is increased, and the larger the area of the third conductor layer is, the better the performance of the first through holes 121 is, and further the service power of the product is improved.

The input terminal 13 and the output terminal 14 are respectively disposed on two opposite first sides 111 of the ceramic substrate 11, and the input terminal 13 and the output terminal 14 are symmetrically disposed with respect to a center line of the two opposite first sides 111 of the ceramic substrate 11.

The input end 13 and the output end 14 each include a top end, a bottom end, and a first conductor layer (not shown) electrically connecting the top end and the bottom end, the first conductor layer is disposed in the first groove 133 and the second groove 143 on the side surfaces of the two opposite first edges 111 of the ceramic substrate 11, the first groove 133 is located on the input end 13 side, and the second groove 143 is located on the output end 14 side. For the convenience of description, the top end of the input end 13 is defined as a first top end 131, the bottom end of the input end 13 is defined as a first bottom end 132, the top end of the output end 14 is defined as a second top end 141, and the bottom end of the output end 14 is defined as a second bottom end 142.

The first top end 131 and the second top end 141 are both disposed on the top surface of the ceramic substrate 11, and the first top end 131 and the second top end 141 are symmetrically disposed with respect to a center line of two opposite first sides 111 of the ceramic substrate 11; the first bottom end 132 and the second bottom end 142 are both disposed on the bottom surface of the ceramic substrate 11, and the first bottom end 132 and the second bottom end 142 are symmetrically disposed with respect to a center line of two opposite first sides 111 of the ceramic substrate 11; the first top end 131 is electrically connected to the first bottom end 132 through the first conductive layer located in the first groove 133, the second top end 141 is electrically connected to the second bottom end 142 through the first conductive layer located in the second groove 143, and the first groove 133 and the second groove 143 are symmetrically disposed with respect to a center line of two opposite first sides 111 of the ceramic substrate 11; the first top end 131 of the input end 13 and the second top end 141 of the output end 14 are electrically connected to the corresponding resonators 12 respectively; the first bottom end 132 of the input terminal 13 and the second bottom end 142 of the output terminal 14 are insulated from the second conductor layer 113 on the bottom surface of the ceramic substrate 11.

The first top end 131, the first bottom end 132, the second top end 141 and the second bottom end 142 have the same shape, may be crescent-shaped, and have the same size. As shown in fig. 1 and 2, the crescent outer ring may be a broken line formed by connecting a plurality of line segments; as shown in fig. 5 and 6, the crescent-shaped outer ring may be semicircular, and the diameter of the semicircle may be 0.15mm to 0.35mm, for example, for the thin film filter having the center frequency of 5.5GHz, the diameter of the semicircle of the crescent-shaped outer ring is 0.25 mm.

The cross-sections (i.e., sections parallel to the top surface of the ceramic substrate 11) of the first groove 133 and the second groove 143 may each be rectangular in shape, and as shown in fig. 1 and 2, the sides of the rectangle may be 0.1mm to 0.5 mm; alternatively, as shown in fig. 5 and 6, the cross-sections (i.e., the sections parallel to the top surface of the ceramic substrate 11) of the first groove 133 and the second groove 143 may each have a semicircular shape, and the diameter of the semicircular shape may be 0.1mm to 0.25mm, for example, 0.13mm for the thin film filter having a center frequency of 5.5 GHz. Also, the cross-sectional shapes of the first groove 133 and the second groove 143 are the crescent shapes of the first top end 131, the first bottom end 132, the second top end 141, and the second bottom end 142.

Moreover, since the first bottom end 132 and the second bottom end 142 are insulated from the second conductor layer 113, the second conductor layer 113 located at the periphery of the first bottom end 132 and the second bottom end 142 may be disposed in a zigzag shape corresponding to the outer circle shape of the crescent shape, as shown in fig. 2; alternatively, as shown in fig. 6, the second conductor layer 113 located at the periphery of the first bottom end 132 and the second bottom end 142 may be provided in a semicircular shape corresponding to the outer circle shape of the crescent, and the diameter of the semicircular shape on the second conductor layer 113 may be 0.5mm to 0.7mm, for example, for the thin film filter having the center frequency of 5.5GHz, the diameter of the semicircle on the second conductor layer 113 is 0.5 mm.

The first groove 133 and the second groove 143 may be formed by laser drilling, and a first conductive layer may be grown on inner walls of the first groove 133 and the second groove 143 by a metal via process, so that the first conductive layer is uniformly covered on the inner walls of the first groove 133 and the second groove 143.

Because the first top end 131 is electrically connected with the first bottom end 132 through the first conductor layer located in the first groove 133, and the second top end 141 is electrically connected with the second bottom end 142 through the first conductor layer located in the second groove 143, the structure is stable, the effect of the electrical connection is little influenced by the process, adverse effects on the performance of the thin film filter caused by the electrical connection between the first top end 131 and the first bottom end 132 and between the second top end 141 and the second bottom end 142 in a gold wire bonding mode are avoided, and the performance of the thin film filter is prevented from being fluctuated. In the practical application process, the film filter can be fixed on other components by adopting a reflow soldering surface-mounting technology, so that the application consistency of products is improved.

The thin film filter further includes a transmission line 17, the transmission line 17 is disposed on the top surface of the ceramic substrate 11, and the top end (i.e., the first top end 131) of the input terminal 13 and the top end (i.e., the second top end 141) of the output terminal 14 are electrically connected to the respective closest resonators 12 through the transmission line 17, respectively, and the transmission line 17 connected to the first top end 131 and the transmission line 17 connected to the second top end 141 are disposed symmetrically with respect to the center line of the two opposite first sides 111 of the ceramic substrate 11. If 7 resonators 12 in fig. 1 and 5 are sequentially defined as a first-stage resonator to a seventh-stage resonator from a direction close to the input end 13 to a direction close to the output end 14, the first top end 131 is electrically connected to the first-stage resonator through the transmission line 17, and the second top end 141 is electrically connected to the seventh-stage resonator through the transmission line 17.

As can be seen from the above, all the resonators 12, all the first through holes 121, all the input ends 13 and the output ends 14, and all the transmission lines 17 connecting the first top ends 131 and the transmission lines 17 connecting the second top ends 141 are symmetrically disposed with respect to the center line of the two opposite first sides 111 of the ceramic substrate 11, and have the same shape and size.

In operation, based on the above-mentioned structure of the thin film filter, the first bottom end 132 of the input end 13 is connected to the input port, and a signal enters from the first bottom end 132, then sequentially passes through the first conductor layer in the first groove 133, the first top end 131, the transmission line 17, all the resonators 12, the transmission line 17, the second top end 141, and the first conductor layer in the second groove 143, and finally is output from the second bottom end 142 of the output end 14, so that the pass band width, the center frequency, and the in-band characteristic of the thin film filter can be independently adjusted, and thus the size of the thin film filter can be effectively adjusted as required in initial design.

The shield surrounds all of the resonators 12. Fig. 3 and 7 show two different configurations of the shielding and the corresponding connection to the ceramic substrate 11. For ease of distinction, the shield, top plate, side plates and mounting plate in fig. 3 and 7 have been given different reference numerals.

Referring to fig. 3, the shielding case 16 is fixed to the top surfaces of two opposite second sides 112 of the ceramic substrate 11. The shielding case 16 includes a top plate 161, two side plates 162 respectively disposed on two opposite sides of the top plate 161, and two mounting plates 163 respectively connected to the two side plates 162, where the top plate 161 is located above the top surface of the ceramic substrate 11, the top plate 161 is parallel to the top surface of the ceramic substrate 11, the two side plates 162 are perpendicular to the top plate 161, the two side plates 162 are located at the periphery of the plurality of resonators 12, the two mounting plates 163 are parallel to the side plates 162, and the two mounting plates 163 are respectively fixed to the sides of two opposite second sides 112 of the ceramic substrate 11.

A third groove 116 is formed on each of the two opposite side surfaces of the second side 112 of the ceramic substrate 11, a fourth conductor layer (not shown) is formed on the inner wall of the third groove 116, and the mounting plate 163 is fixed to the fourth conductor layer in the third groove 116, so that the shield can 16 is electrically connected to the second conductor layer 113 through the fourth conductor layer, and the shield can 16 can be grounded. The fourth conductor layer is formed by adopting a sputtering method; the bottom surfaces of the two side plates 162 of the shield case 16 are in contact with the top surfaces of the two opposite second sides 112 of the ceramic substrate 11, and the shield case 16 is fixed to the ceramic substrate 11 by soldering the mounting plate 163 to the fourth conductor layer in the third recess 116.

Referring to fig. 7, the shielding case 15 is fixed to the top surfaces of two opposite second sides 112 of the ceramic substrate 11. The shielding case 15 includes a top plate 151, two side plates 152 respectively disposed at two opposite sides of the top plate 151, and two mounting plates 153 respectively connected to the two side plates 152. The top plate 151 is located above the top surface of the ceramic substrate 11, the top plate 151 is parallel to the top surface of the ceramic substrate 11, the two side plates 152 are perpendicular to the top plate 151, the two side plates 152 are respectively located on the top surfaces of the two opposite second sides 112 of the ceramic substrate 11, and the two side plates 152 are disposed at the periphery of the resonator 12. The two mounting plates 153 are perpendicular to the side plate 152, the two mounting plates 153 are parallel to the top plate 151, the mounting plates 153 are disposed at the bottom ends of the side plates 152, and the mounting plates 153 extend toward the lateral direction of the two opposite second sides 112 of the ceramic substrate 11 (i.e., the direction away from the resonator 12), or the mounting plates 153 extend toward the lateral direction of the two opposite second sides 112 of the ceramic substrate 11 (i.e., the direction toward the resonator 12), so that the shield case 15 is fixed to the top surface of the ceramic substrate 11 by the mounting plates 153.

And, a soldering layer 114 is disposed on the top surface of each of the two opposite second sides 112 of the ceramic substrate 11, the soldering layer 114 is located near the edge on the top surface of the ceramic substrate 11, the soldering layer 114 is not in contact with the resonator 12, and the bottom surface of the mounting board 153 is fixed on the soldering layer 114. The shield case 15 may be fixed to the top surface of the ceramic substrate 11 by soldering the mounting plate 153 to the solder layer 114. By solder-fixing the shield can 15 to the top surface of the ceramic substrate 11, handling is easier and fixing of the shield can 15 is made more stable.

The structure of the

shield cases

15 and 16 and the manner of fixing the

shield cases

15 and 16 to the ceramic substrate 11 are not limited to the examples shown in fig. 3 and 7, and other suitable structures and fixing manners of the

shield cases

15 and 16 may be selected to satisfy the performance of the thin film filter.

The soldering layer 114 is provided with a plurality of second through holes 115, the second through holes 115 penetrate through the ceramic substrate 11, a fourth conductor layer (not shown) is provided on an inner wall of the second through holes 115, and the shielding can 15 is electrically connected to the second conductor layer 113 through the fourth conductor layer, so that the shielding can 15 can be grounded. The second through hole 115 may be formed by laser drilling, and a fourth conductor layer is grown on the inner wall of the second through hole 115 by a metal via process, so that the fourth conductor layer is uniformly covered on the inner wall of the second through hole 115.

The second through hole 115 is circular (i.e., cross-sectional shape), and the diameter of the second through hole 115 is 0.1mm to 0.25 mm; or, the second through hole 115 (i.e., the cross section) is rectangular, and the side length of the second through hole 115 is 0.1mm to 0.25 mm. The shape of the second through hole 115 is not limited to the two shapes. The number of the second through holes 115 is at least 9 to avoid affecting the performance of the thin film filter. By increasing the number of the second through holes 115, the area of the fourth conductor layer can be increased, and thus the grounding effect is satisfied. For example, for the thin film filter with the center frequency of 5.5GHz, the number of the second through holes 115 is at least 15.

Moreover, since the ceramic substrate 11 is hard and brittle, if a large-area punching operation is performed on the ceramic substrate 11, the processing difficulty is high, the time consumption is long, and the ceramic substrate 11 is easily broken, so that when the first through hole 121, the second through hole 115, the first groove 133, and the second groove 143 are formed in a laser punching manner, the punching diameters are small, and for the embodiment shown in fig. 7, it is ensured that the performance of the thin film filter is not affected by increasing the number of the first through holes 121 and the second through holes 115, so that the processing difficulty is reduced on the basis of not reducing the performance of the thin film filter, the processing efficiency is improved, the processing cost is finally reduced, and the market competitiveness is improved.

In addition, since the input terminal 13 and the output terminal 14 are respectively disposed on the two opposite first sides 111 of the ceramic substrate 11, the mounting plate 153 and the mounting plate 163 can be fixed only on the two opposite second sides 112 of the ceramic substrate 11, so that the shielding cover 15 and the shielding cover 16 can shield signals and also avoid short circuit of the input terminal 13 and the output terminal 14 when the shielding cover 15 and the shielding cover 16 are mounted by welding.

The shielding cover is made of metal such as stainless steel, and the thickness of the shielding cover can be 0.2 mm-0.5 mm.

In the working process, the filter is interfered by other signals in the space, especially in the high-frequency to millimeter-wave frequency band, the performance of the filter is more easily affected by other components, and the instability of the performance of the filter is increased, so that the shielding cover is arranged on the ceramic substrate 11, the thin film filter can be prevented from being interfered by external signals in the working process, the leakage of internal signals of the thin film filter can be reduced, the stability of the performance of the thin film filter is further improved, the performance parameters of the thin film filter are effectively improved, for example, the energy loss is smaller, and the insertion loss of the thin film filter is also smaller.

The resonator 12, the first top end 131, the first bottom end 132, the second top end 141, the second bottom end 142, the transmission line 17, the first conductor layer, the second conductor layer 113, the third conductor layer, the fourth conductor layer, and the solder layer 114 are made of, for example, gold.

In addition, the resonator 12, the second conductor layer 113, the first top end 131, the first bottom end 132, the second top end 141, the second bottom end 142, the transmission line 17, and the solder layer 114 are all formed by magnetron sputtering, photolithography, and etching processes in a semiconductor process, and the structure on the top surface of the ceramic substrate 11 may be formed at the same time, and the structure on the bottom surface of the ceramic substrate 11 may be formed at the same time, which has certain advantages in terms of cost.

Referring to fig. 4, fig. 4 is a signal simulation diagram based on the thin film filter shown in fig. 1 to 3, which shows a variation trend L1 of the pass band of the operating frequency and a variation trend L2 of the insertion loss, the abscissa is frequency, and the ordinate is the number of suppression stages, and it can be seen from fig. 4 that the center frequency of the operation of the thin film filter is 5.5GHz, the bandwidth is 1GHz, and a transmission zero is generated at a right position P1 on the variation trend L1 of the pass band, which greatly improves the out-of-band suppression characteristic, especially the near-end suppression characteristic of the thin film filter. Therefore, based on the structure of the thin film filter, the performance of the thin film filter is improved.

Referring to fig. 8, fig. 8 is a signal simulation diagram based on the thin film filter shown in fig. 5 to 7, which shows a variation trend L3 of the pass band of the operating frequency and a variation trend L4 of the insertion loss, the abscissa is frequency and the ordinate is the number of suppression stages, and it can be seen from fig. 8 that the center frequency of the operation of the thin film filter is 5.5GHz and the bandwidth is 1GHz, and a transmission zero is generated at a right position P2 on the variation trend L3 of the pass band, which greatly improves the out-of-band suppression characteristic, especially the near-end suppression characteristic of the thin film filter. Therefore, based on the structure of the thin film filter, the performance of the thin film filter is improved.

In summary, the thin film filter provided by the present invention includes the ceramic substrate with a high relative dielectric constant, so that the size of the thin film filter is reduced, and the performance of the thin film filter is greatly improved; furthermore, as the top end and the bottom end of the input end and the top end and the bottom end of the output end are electrically connected through the first conductor layers arranged in the first groove and the second groove on the side surface of the first edge of the ceramic substrate, the performance of the thin film filter can be prevented from being influenced by a gold wire bonding process; furthermore, the ceramic substrate is provided with the shielding case, so that the performance stability of the thin film filter is improved.

The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and any modification and modification made by those skilled in the art according to the above disclosure are all within the scope of the claims.

Claims

1. A thin film filter, comprising:

a ceramic substrate;

a plurality of resonators disposed on a top surface of the ceramic substrate;

a shield surrounding the plurality of resonators.

2. The thin film filter according to claim 1, wherein the ceramic substrate has a relative dielectric constant of 12 to 38.

3. The thin film filter according to claim 1, wherein the ceramic substrate has a thickness of 0.25mm to 0.7 mm.

4. The thin film filter of claim 1, wherein the ceramic substrate has two opposing first sides and two opposing second sides.

5. The thin film filter according to claim 4, wherein the plurality of resonators are symmetrically disposed with respect to a center line of two opposite first sides of the ceramic substrate, and the input terminal and the output terminal are symmetrically disposed with respect to a center line of two opposite first sides of the ceramic substrate.

6. A thin film filter as claimed in claim 4, wherein all of the resonators are perpendicular to the second side of the ceramic substrate and all of the resonators are parallel to each other.

7. The thin film filter according to claim 4, wherein a gap between adjacent two of the resonators is gradually increased from both ends of the second side of the ceramic substrate to a middle of the second side.

8. The thin film filter of claim 1, wherein the resonator has a length of one quarter of a wavelength corresponding to a center frequency of the thin film filter.

9. The thin film filter of claim 1, wherein the thin film filter has an operating frequency of 4.5GHz to 6.5 GHz.

10. The thin film filter of claim 1, wherein the resonator has an order of 7.

11. A thin film filter as claimed in claim 1, characterized in that the resonators form an interdigital structure.

12. The thin film filter according to claim 4, wherein the input terminal and the output terminal are respectively disposed on two opposite first sides of the ceramic substrate, a top end of the input terminal and a top end of the output terminal are disposed on a top surface of the ceramic substrate, a bottom end of the input terminal and a bottom end of the output terminal are disposed on a bottom surface of the ceramic substrate, and the top end and the bottom end of the input terminal and the top end and the bottom end of the output terminal are electrically connected through a first conductor layer.

13. The thin film filter according to claim 12, wherein the first conductor layer is provided in a first groove and a second groove on sides of two opposite first sides of the ceramic substrate.

14. The thin film filter of claim 13, wherein the first and second grooves are rectangular or semicircular in shape.

15. The thin film filter of claim 1, wherein each of the resonators has a rectangular shape, and the top and bottom ends of the input terminal and the top and bottom ends of the output terminal have a crescent shape.

16. The thin film filter according to claim 4, wherein a second conductor layer is provided on a bottom surface of the ceramic substrate, the second conductor layer being grounded.

17. The thin film filter according to claim 16, wherein each of the resonators has at least one first via hole provided at one end thereof, the first via hole penetrating the ceramic substrate, and a third conductor layer provided on an inner wall of the first via hole, so that each of the resonators is electrically connected to the second conductor layer through the third conductor layer.

18. The thin film filter of claim 17, wherein the first vias on two adjacent resonators are disposed at different ends of the resonators.

19. The thin film filter of claim 17, wherein the first through hole has a circular shape, and a diameter of the first through hole is 0.1mm to 0.25 mm.

20. The thin film filter of claim 17, wherein the first through hole has a rectangular shape, and a side length of the first through hole is 0.25mm to 0.5 mm.

21. The thin-film filter of claim 16, wherein the shield case includes a top plate, two side plates respectively disposed at two opposite sides of the top plate, and two mounting plates respectively connected to the two side plates, the top plate being located above and parallel to a top surface of the ceramic substrate, the two side plates being perpendicular to the top plate, the two side plates being located at peripheries of the plurality of resonators, the two mounting plates being parallel to the side plates, the two mounting plates being respectively fixed to sides of two opposite second sides of the ceramic substrate.

22. The thin film filter according to claim 21, wherein a third groove is formed on each of two opposite second sides of the ceramic substrate, a fourth conductor layer is formed on an inner wall of the third groove, and the mounting plate is fixed to the fourth conductor layer in the third groove, so that the shield can is electrically connected to the second conductor layer through the fourth conductor layer.

23. The thin film filter according to claim 1, further comprising a transmission line, wherein a top end of the input terminal and a top end of the output terminal are electrically connected to the respective closest resonators through the transmission line, respectively.