CN117638436A - Band-pass filter and filtering method based on LTCC technology - Google Patents

Abstract

The invention relates to the technical field of filters, in particular to a bandpass filter based on an LTCC technology and a filtering method, wherein the bandpass filter comprises a metal shielding shell, a filter main body, a plurality of dielectric layers and a plurality of metal layers; the metal shielding shell is used for sealing and wrapping the filter main body, the filter main body comprises a feed structure, a resonator structure and a grounding structure, the feed structure is connected with an external circuit of the metal shielding shell through a metal feed pad, the resonator structure is coupled with the feed structure, and the grounding structure is directly connected with the resonator structure; the dielectric layers are arranged in parallel inside the metal shielding shell, and a metal layer is arranged between two adjacent dielectric layers. The invention solves the problems of poor anti-interference capability, complex design, difficult simulation and debugging, difficult cascade connection, unsatisfied miniaturization development trend and the like of the band-pass filter in the prior art.

Description

Band-pass filter and filtering method based on LTCC technology

Technical Field

The invention relates to the technical field of filters, in particular to a bandpass filter based on an LTCC technology and a filtering method.

Background

With the rapid development of the information communication technology industry, especially the continuous deep placement of 5G millimeter wave frequency bands in recent years, the rf front-end module will meet a wide incremental market opportunity. Filters are one of the key components of the rf front-end and are also one of the hot content of current research.

The Low-temperature co-fired ceramic (Low-temperature Cofired Ceramics, LTCC) technology has the characteristics of excellent high-frequency characteristics, high integration level and the like, and the filter designed and produced based on the technology has higher quality factor and better reliability, and can well meet the requirements of a 5G millimeter wave frequency band on the high performance and high standard of the filter.

In the prior art, most filters realized based on the LTCC technology adopt a design scheme of lumped parameters, the filters are complex in design, difficult to simulate and debug, difficult to cascade, meanwhile, due to overlong circuit wiring, larger loss is caused, the filters are limited by capacitance values and inductance values of lumped elements, and millimeter wave frequency bands are generally difficult to achieve by adopting the design scheme of lumped parameters.

Although there are designs using distributed parameters in the prior art, the coupling mode of the same plane/vertical direction is basically adopted, which makes the size of the filter in the horizontal/vertical direction realized based on the LTCC technology larger, and the development trend of miniaturization is not satisfied.

With the increase of the application frequency of the filter and the increase of the integration number of related components of the radio frequency front end, the problem of electromagnetic interference is also increasingly prominent. Conventional filters implemented based on LTCC technology lack designs that block electromagnetic interference transmission paths. In addition, considering the sensitivity of the millimeter wave frequency band electromagnetic field, in the practical application process, the electromagnetic field of the millimeter wave frequency band is easy to generate mutual interference with the surrounding environment or other devices from the non-isolated part, thereby reducing the quality of information transmission.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a band-pass filter and a filtering method based on the LTCC technology, and solves the problems that the band-pass filter in the prior art is poor in anti-interference capability, complex in design, difficult in simulation and debugging, difficult in cascading and unsatisfactory in miniaturization development trend.

The first aspect of the present invention provides a bandpass filter based on LTCC technology, comprising: the filter comprises a metal shielding shell, a filter main body, a plurality of dielectric layers and a plurality of metal layers;

the metal shielding shell is used for sealing and wrapping the filter main body; the filter main body comprises a feed structure, a resonator structure and a grounding structure, wherein the feed structure is connected with a circuit outside the metal shielding shell through a metal feed pad, the resonator structure is coupled and connected with the feed structure, and the grounding structure is directly connected with the resonator structure; the dielectric layers are arranged in parallel inside the metal shielding shell, and the metal layer is arranged between two adjacent dielectric layers.

As an achievable mode, the feeding structures are symmetrically arranged based on the feeding defect grooves, and each feeding structure comprises a metal feeding bonding pad, a metalized feeding blind hole and a feeding metal strip which are sequentially connected;

the metal feed pads are positioned in symmetrically arranged feed defect grooves;

the feed metal strip is located in the metal layer;

the metal feed pad is electrically connected with the feed metal strip through the metallized feed blind hole.

As one realizable form, the ground structure comprises a metallized ground via and a ground metal strap, the ground metal strap being located in the metal layer;

the grounding metal strip is electrically connected with the metal shielding shell through the metallized grounding through hole.

As one realizable form, the resonator structure comprises a plurality of resonators disposed in the metal layer.

As an achievable way, the resonator is a short-circuit metal strip connected to a ground metal strip distributed on the same metal layer.

As one implementation, the bandpass filter further includes a capacitive coupling structure for providing cross-coupling paths.

As one possible way, the capacitive coupling structure is shaped like a dumbbell-like metal sheet.

As an achievable mode, the metal shielding shell is used for sealing and wrapping the top and the periphery of the filter main body, and the feed defect grooves are symmetrically arranged at two ends of the bottom of the filter main body along the length direction respectively so as to avoid the feed short circuit of the band-pass filter.

As one possible way, all dielectric layers are the same thickness and all metal layers are the same thickness.

A second aspect of the present invention provides a filtering method, the filtering method comprising: the input signal is introduced into a bandpass filter according to the first aspect of the invention.

The invention at least comprises the following beneficial effects:

1. the feed defect groove carved on the bottom of the metal shielding shell structure is stuck to the PCB or other circuit boards to form a completely closed environment, which can cut off electromagnetic interference transmission paths in all directions, completely restrict electromagnetic field energy in the internal space of the filter, avoid interaction with the outside, greatly improve the anti-interference capability of the filter and ensure the quality of information transmission.

2. The invention reduces the design complexity by adopting the quarter-wavelength short-circuit strip line structure, and the center frequency of the filter is determined by the length of the quarter-wavelength short-circuit strip line; the bandwidth of the filter is mainly determined by the size of the main coupling, and comprises the following two parts: 1) The distance between the feeding metal strip and the adjacent quarter-wavelength short-circuited strip line, 2) the distance between the adjacent two quarter-wavelength short-circuited strip lines. The clear parameter control makes the simulation debugging process simpler and clearer.

3. The method is simple and easy to cascade, and can adapt to different requirements on the filter order under different application scenes.

4. The coupling mode provided by the invention is not limited to a certain plane or a certain vertical direction, so that the plane size and the height size of the filter are effectively balanced, and the development trend of miniaturization of the filter is met.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic three-dimensional structure of a band-pass filter based on LTCC technology according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a metal shielding case of a bandpass filter based on LTCC technology according to an embodiment of the invention.

Fig. 3 is a schematic diagram of a xoz side stacked structure of a band-pass filter based on LTCC technology according to an embodiment of the present invention.

Fig. 4 is an exploded view of an internal structure of a band-pass filter based on LTCC technology according to an embodiment of the present invention.

Fig. 5 is a coupling topology diagram of a bandpass filter based on LTCC technology in an embodiment of the invention.

Fig. 6 is a diagram showing simulation results of a band-pass filter based on LTCC technology according to an embodiment of the present invention.

Reference numerals

1-a metal shielding shell; 2-a feeding defect groove; a 3-feed structure; a 4-resonator structure; 5-a ground structure; tz-capacitive coupling structure; 21-a first feed defect slot; 22-a second feed defect slot; p 1-metal feed pads; p 2-metal feed pad.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, based on the embodiments herein, which are within the scope of the protection of the present application, will be within the skill of the art without inventive effort. Furthermore, it should be understood that the detailed description is presented herein for purposes of illustration and explanation only and is not intended to limit the present application. In this application, unless otherwise indicated, terms of orientation such as "upper", "lower", "left", "right", "front", "rear" are generally used to refer to the upper, lower, left and right directions of the device in actual use or operation, and specifically to the directions of the drawings in the drawings.

It should be noted that the following description order of the embodiments is not intended to limit the preferred order of the embodiments of the present application. In the following embodiments, the descriptions of the embodiments are focused on, and for the part that is not described in detail in a certain embodiment, reference may be made to the related descriptions of other embodiments.

As shown in fig. 1 to fig. 4, a bandpass filter based on LTCC technology is provided in a first aspect of the present invention, which includes a metal shielding shell 1, a filter body, a plurality of dielectric layers and a plurality of metal layers, where each of the dielectric layers is disposed in parallel, and the metal layers are disposed between two connected dielectric layers.

The filter body is enclosed and wrapped by the metal shielding shell 1, and a first feed defect groove 21 and a first feed defect groove 22 are symmetrically arranged at the bottom of the metal shielding shell 1.

As shown in fig. 2, the structure of the metal shielding shell 1 is basically in a fully-closed form, the metal shielding shell 1 is used for enclosing the top and the periphery of the filter main body, and a feeding defect groove 2 for preventing the short circuit of the band-pass filter is engraved only at the bottom of the metal shielding shell 1, specifically, the feeding defect groove 2 is symmetrically arranged at two ends of the bottom of the filter main body along the length direction so as to avoid the short circuit of the band-pass filter, wherein the feeding defect groove 2 comprises a first feeding defect groove 21 and a second feeding defect groove 22.

As shown in fig. 3, the metal layers and the dielectric layers are arranged in parallel and cross inside the metal shielding shell 1, and in an application scenario, the metal layers include a metal layer metal_1, a metal layer metal_2, a metal layer metal_3, a metal layer metal_4 and a metal layer metal_5; the dielectric layers comprise dielectric layer substratum_1, dielectric layer substratum_2, dielectric layer substratum_3, dielectric layer substratum_4, substratum_5 and dielectric layer substratum_6.

In order to reduce the complexity of the process, the thickness of the dielectric layers is consistent, and the thickness of all metal layers is consistent.

Specifically, in the invention, the number of metal layers is 5, the number of dielectric layers is 6, the substrate_1 is used as a first dielectric layer to be arranged at the bottom of the metal shielding shell 1, the metal_1 is used as a first metal layer to be arranged above the first dielectric layer, the substrate_2 is used as a second dielectric layer to be arranged above the first metal layer, and similarly, the substrate_6 is arranged at the uppermost part inside the metal shielding shell 1.

As shown in fig. 4, the filter body comprises a feed structure 3, a resonator structure 4 and a ground structure 5.

Specifically, the feeding structure 3 is symmetrically arranged based on the feeding defect groove 2, the feeding structure 3 is composed of a metal feeding pad, a metalized feeding blind hole and a feeding metal strip which are sequentially connected, the metal feeding pad is located in the feeding defect groove 2 which is symmetrically arranged, the metalized feeding blind hole is used for electrically connecting the feeding metal strip and the metal feeding pad together, the metal feeding pad is arranged at the bottom of the band-pass filter, and the metal feeding pad is specifically located in the middle of the defect groove carved out of the bottom of the metal shielding shell 1 and used for feeding.

Specifically, the feeding metal strips in the feeding structure 3 comprise a feeding metal strip ms1 and a feeding metal strip ms2, the metallized feeding blind holes comprise metallized feeding blind holes v1 and metallized feeding blind holes v2, and the metal feeding bonding pads comprise metal feeding bonding pads p1 and metal feeding bonding pads p2; the metal feed pad p1 and the metal feed pad p2 are respectively and electrically connected with the feed metal strip ms1 and the feed metal strip ms2 on the metal layer metal_3 through the metal feed blind hole v1 and the metal feed blind hole v2, namely the metal feed pad p1, the metal feed blind hole v1 is connected with the feed metal strip ms1 on the metal layer metal_3, and the metal feed pad p2 is connected with the feed metal strip ms2 on the metal layer metal_3.

Specifically, the feeding metal strip is not necessarily disposed on the metal layer metal_3, but may be disposed on the metal layer metal_4 or the metal layer metal_5, and different metal layers may need to have corresponding feeding structure dimensions, for example, the width and the length of the feeding metal strip may need to be adjusted, the diameter of the metalized feeding blind hole may need to be adjusted, and the overlapping dimensions of the feeding metal strip and the resonator R1 and the resonator R4 in the vertical direction may need to be adjusted.

The resonator structure 4 comprises a plurality of resonators arranged in the metal layer, at least one group of resonators being located in different metal layers, and illustratively the resonator structure 4 comprises a resonator R1, a resonator R2, a resonator R3 and a resonator R4, the resonator R1 and the resonator R4 being distributed over the metal layer metal_2, and the resonator R2 and the resonator R3 being distributed over the metal layer metal_4.

The resonator structure 4 is a short-circuit metal strip, the short-circuit metal strip is connected with a grounding metal strip distributed on the same metal layer, specifically, the resonator structure 4 is composed of a quarter-wavelength short-circuit metal strip, that is, the quarter-wavelength short-circuit strip line resonator R1 and the resonator R4 are distributed on the metal layer metal_2, and the quarter-wavelength short-circuit strip line resonator R2 and the resonator R3 are distributed on the metal layer metal_4.

In addition, the design complexity can be reduced by adopting the structure of the quarter-wavelength short-circuit strip line, the number of the resonators of the quarter-wavelength short-circuit strip line can be increased or reduced, the order of the filter can be increased, and the requirements of different application scenes on the order of the filter can be met.

In the present invention, the band-pass filter further includes a capacitive coupling structure tz for providing a cross coupling path, and the capacitive coupling structure tz is located on the metal layer metal_1 and is a metal sheet similar to a dumbbell shape. The sheet metal pattern, number, etc. may vary with increasing filter order or with different placement of resonator locations within the filter. The location of the metal layer where the capacitive coupling structure tz is located is not unique, and the main factor is to see the amount of cross coupling energy provided.

Specifically, the capacitive coupling structure tz provides a cross coupling path for the resonator R1 and the resonator R4 for generating a pair of transmission zeroes, thereby improving the frequency selectivity of the filter.

The invention makes the simulation debugging process more convenient through definite parameter control, and the center frequency of the filter is determined by the length of a quarter-wavelength short-circuit strip line, namely the length of a resonator, and the coupling part is shown in figure 5, wherein a solid line represents a main coupling path, a dotted line represents a cross coupling path, the main coupling comprises feed coupling and inter-resonator coupling, the bandwidth of the filter is mainly influenced, the size of the feed coupling is mainly controlled by the distance between a feed metal strip ms1 and a resonator R1 and the distance between a feed metal strip ms2 and a resonator R4, and the size of the inter-resonator coupling is mainly controlled by the distance between two adjacent resonators of the resonators R1, R2, R3 and R4; the cross coupling mainly affects the transmission zero and out-of-band rejection capability of the filter, and is controlled by the distances between the resonator R1, the resonator R4 and the capacitive coupling structure tz and the dimensions of the capacitive coupling structure tz.

The grounding structure 5 is composed of a metallized grounding through hole and a grounding metal strip connected with the metallized grounding through hole, the grounding metal strip is located in the metal layer, the grounding metal strip is electrically connected with the metal shielding shell 1 through the metallized grounding through hole, specifically, two ends of the metallized grounding through hole are respectively contacted with the top and the bottom of the metal shielding shell 1, namely, the metallized grounding through hole penetrates through the grounding metal strip, and the metallized grounding through hole penetrates through the top of the metal shielding shell 1 from the bottom of the metal shielding shell 1.

Directly connected to the resonators R1, R2, R3 and R4 in the resonator structure 4 is a grounding structure 5, and the resonator structure 4 is a short-circuit metal strip, and the short-circuit metal strip is connected to the grounding metal strips distributed on the same metal layer.

It should be noted that, names of the metal strips, such as the short-circuit metal strip, the feed metal strip, and the ground metal strip, etc., are consistent, for example, silver, gold, etc., and prefix words short-circuit, feed, ground, etc. are merely distinguished based on the expressed functions, and the dielectric layer, the metal layer, the resonator, etc. in the present invention are not particularly limited to only exemplary analysis, and may be changed by those skilled in the art by referring to the design concept of the present invention, and still fall within the scope of the present invention.

Specifically, referring to fig. 3, the grounding metal strips are distributed on each metal layer;

the metallized ground vias extend through the ground strap and extend from the bottom of the metallic shield shell 1 to the top of the metallic shield shell 1.

In one example scenario, the ground metal strips include ground metal strip gs1, ground metal strip gs2, ground metal strip gs3, ground metal strip gs4, ground metal strip gs5, ground metal strip gs6, ground metal strip gs7, ground metal strip gs8, ground metal strip gs9, and ground metal strip gs10; the ground metal vias include ground metal via gv1, ground metal via gv2, ground metal via gv3, ground metal via gv4, ground metal via gv5, ground metal via gv6, ground metal via gv7, ground metal via gv8, ground metal via gv9, and ground metal via gv10.

Ground metal vias gv1, gv2, gv3, gv4, gv5 longitudinally pass through ground metal strips gs1, gs2, gs3, gs4, gs5; ground metal vias gv6, gv7, gv8, gv9, and gv10 extend longitudinally through ground metal strips gs6, gs7, gs8, gs9, and gs10.

The ground metal through holes gv1, gv2, gv3, gv4 and gv5 are longitudinally parallel and penetrate from the bottom of the filter to the top of the filter; the ground metal strips gs1, gs2, gs3, gs4 and gs5 are parallel in the transverse direction.

As shown in FIG. 6, the simulation experiment is carried out and the dielectric constant of the dielectric ceramic material used in the simulation is 6.3, the loss tangent value is 0.0015, metal is gold, the final size of the designed filter is 2.5mm multiplied by 2mm multiplied by 0.584mm, the center frequency of the filter is 28GHz, the 3dB bandwidth is 25.4 GH-30.6 GHz, the minimum insertion loss in the passband is-0.93 dB, the insertion loss in the frequency band of 26 GHz-30 GHz is better than 1.4dB, the in-band out-of-band suppression in the frequency band of 10 GHz-24 GHz is better than 30dB, and the in-band out-of-band suppression in the frequency band of 33 GHz-50 GHz is better than 28dB.

The novel coupling mechanism provided by the invention for the filter is characterized in that the energy of the filter is fed into the energy coupling and fed out of the filter, a space coupling mode is adopted, the novel coupling mechanism is not limited to a certain plane or a certain vertical direction, the space structure in the filter is fully utilized, the plane size and the height size of the filter are effectively balanced, the novel coupling mechanism is more close to practical application, and the development requirement of miniaturization of the filter is met.

In the practical application process of the invention, the filter provided by the invention can be surface-mounted on a PCB or other types of circuit boards to form a completely closed environment, so that electromagnetic interference transmission paths in all directions are well blocked, electromagnetic field energy is completely restrained in the internal space of the filter, no interaction occurs with the outside, the anti-interference capability of the filter is greatly improved, and the quality of information transmission is ensured.

A second aspect of the invention provides a filtering method comprising introducing an input signal into a bandpass filter as described in any one of the embodiments above.

The foregoing has outlined rather broadly the more detailed description of the present application, and the detailed description of the principles and embodiments herein has been given using specific examples, which are included to provide an additional understanding of the method and concepts of the present application; meanwhile, as those skilled in the art will have modifications in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.

Reference throughout this specification to "one embodiment," "an embodiment," or "a particular embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment, and not necessarily all embodiments, of the present application. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present application may be combined in any suitable manner with one or more other embodiments. It will be appreciated that other variations and modifications of the embodiments of the application described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the application.

It will also be appreciated that one or more of the elements shown in the figures may also be implemented in a more separated or integrated manner, or even removed because of inoperability in certain circumstances or provided because it may be useful depending on the particular application.

In addition, any labeled arrows in the drawings/figures should be considered only as exemplary, and not limiting, unless otherwise specifically indicated. Furthermore, the term "or" as used herein is generally intended to mean "and/or" unless specified otherwise. Combinations of parts or steps will also be considered as being noted where terminology is foreseen as rendering the ability to separate or combine is unclear.

Claims (10)

1. A bandpass filter based on LTCC technology, comprising: the filter comprises a metal shielding shell, a filter main body, a plurality of dielectric layers and a plurality of metal layers;

the metal shielding shell is used for sealing and wrapping the filter main body, the filter main body comprises a feed structure, a resonator structure and a grounding structure, the feed structure is connected with the outside of the metal shielding shell through a metal feed pad, the resonator structure is coupled with the feed structure, and the grounding structure is directly connected with the resonator structure; the dielectric layers are arranged in parallel inside the metal shielding shell, and a metal layer is arranged between two adjacent dielectric layers.

2. The LTCC technology based bandpass filter of claim 1 wherein the feed structures are symmetrically arranged based on feed defect slots, each feed structure comprising a metal feed pad, a metallized feed blind via, and a feed metal strip connected in sequence, respectively;

the metal feed pads are positioned in symmetrically arranged feed defect grooves;

the feed metal strip is located in the metal layer;

the metal feed pad is electrically connected with the feed metal strip through the metallized feed blind hole.

3. The LTCC technology based bandpass filter of claim 1 wherein the ground structure comprises a metallized ground via and a ground metal strap, the ground metal strap being located in the metal layer;

the grounding metal strip is electrically connected with the metal shielding shell through the metallized grounding through hole.

4. The LTCC technology based bandpass filter of claim 1 wherein the resonator structure comprises a plurality of resonators disposed in the metal layer.

5. The LTCC technology based bandpass filter of claim 4 wherein the resonator is a shorting metal strip connected to a ground metal strip distributed over the same metal layer.

6. The LTCC technology based bandpass filter of claim 1 further comprising a capacitive coupling structure for providing cross-coupling paths.

7. The LTCC technology based bandpass filter of claim 6 wherein the capacitive coupling structure is in the shape of a dumbbell-shaped metal sheet.

8. The LTCC technology based bandpass filter according to any one of claims 1-7, wherein the metal shielding case encloses the top and the periphery of the filter body, and the feeding defect grooves are symmetrically provided only at both ends of the bottom of the filter body in the length direction, respectively, so as to avoid a short circuit of the feeding of the bandpass filter.

9. The LTCC technology based bandpass filter according to any one of claims 1-8 wherein all dielectric layers are of the same thickness and all metal layers are of the same thickness.

10. A method of filtering, the method comprising: introducing an input signal into a bandpass filter as claimed in any one of the preceding claims 1-9.