Filter circuit, filter, and electronic device

Abstract

Embodiments of the present application relate to the technical field of radio frequency devices, and in particular relate to a filter circuit, a filter, and an electronic device, which can weaken the coupling parasitic effect that may be generated with a shielding layer and improve the shielding robustness of external electromagnetic interference to the outside. The filter circuit can specifically comprise a first resonance unit to an Nth resonance unit, N≥3; the first resonance unit comprises a first inductor, and the second resonance unit comprises a second capacitor; the N-1th resonance unit comprises an N-1th capacitor, and the Nth resonance unit comprises an Nth inductor; the first inductor and an upper polar plate of the second capacitor are connected by means of a first cascade element; and / or the Nth inductor and an upper polar plate of the N-1th capacitor are connected by means of an N-1th cascade element.

Description

Filter circuit, filter and electronic device

[0001] The present application claims priority to the Chinese patent application No. 202410464825.2, filed on April 15, 2024, entitled "Filter circuit, filter and electronic device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of radio frequency devices, and in particular to a filter circuit, a filter and an electronic device. BACKGROUND

[0003] Low Temperature Co-fired Ceramic (LTCC) filters, which integrate various LC resonant elements inside, are easily affected by electromagnetic interference. For example, in the System in Package (Sip) of a radio frequency module, a shielding layer is sputtered on the surface of the module. The shielding layer is prone to produce coupling parasitic effects with the internal LC elements of the LTCC filter in the radio frequency module, affecting the performance of the LTCC filter.

[0004] At present, a solution is to spray a thin metal layer on the top layer of the LTCC filter, so that the filter has a shielding layer and has a certain ability to resist electromagnetic interference, reducing the possibility of coupling parasitic effects between the internal LC elements and the external metal (such as the shielding layer on the surface of the module). However, the internal elements of the LTCC filter may produce stronger coupling parasitic effects with the shielding layer. SUMMARY

[0005] The embodiments of the present application provide a filter circuit, a filter and an electronic device, which do not need to spray a shielding layer on the top layer, and only by optimizing the coupling mode between the resonant units and the component layout, the shielding robustness of the circuit to external electromagnetic interference is improved.

[0006] In a first aspect, the embodiments of the present application provide a filter circuit, comprising a first resonant unit to an Nth resonant unit, N≥3; wherein the first resonant unit comprises a first inductor, the second resonant unit comprises a second capacitor; the (N-1)th resonant unit comprises an (N-1)th capacitor, and the Nth resonant unit comprises an Nth inductor; wherein the upper plate of the first inductor and the second capacitor is connected through a first cascaded element; and / or the upper plate of the Nth inductor and the (N-1)th capacitor is connected through an (N-1)th cascaded element.

[0007] The filter circuit can include N resonant units (resonators), a first resonant unit to an Nth resonant unit (N is an integer), which can be a first resonant unit to an Nth resonant unit in the direction from the input end to the output end, or a first-level resonant unit to an Nth-level resonant unit. The first resonant unit and the second resonant unit are a group of adjacent resonant units close to the input end side, and the N-1th resonant unit and the Nth resonant unit are a group of adjacent resonant units close to the output end side. Among the two groups of resonant units on both sides (close to the input end side and close to the output end side), at least one group adopts a predetermined inductive coupling mode for cascading. The predetermined inductive coupling mode, that is, the upper plate of the multiplexed capacitor (for example, a MIM capacitor), connects the upper plate of the capacitor and the inductor in the adjacent resonant unit through the cascading element, discards the commonly used capacitive spatial coupling mode, and realizes inductive coupling between resonant units through the physical cascading element. Since the upper plate of the MIM capacitor can be arranged at a middle or lower position in the Z-axis direction of the filter, compared with the spatial coupling mode adopted by the capacitor formed by the space between the traces on the top layer of the filter, the relative height of the cascading element and other components in the Z-axis direction is reduced as a whole, the distance between the cascading element and other components and the shielding layer of the module surface is increased, the coupling parasitic effect between the top shielding layer and the internal devices of the filter is weakened, and the shielding robustness of the filter circuit is improved. In addition, the capacitor upper electrode of the multiplexed resonant unit (for example, the second resonant unit or the N-1th resonant unit) does not increase the area of the additional winding inductance, the XY direction layout area remains unchanged, and no additional space is occupied in the XY direction, which is beneficial to the miniaturization of the device.

[0008] In some embodiments, among the first resonant unit to the Nth resonant unit, the coupling mode between the two adjacent resonant units is inductive coupling.

[0009] When N≥4, in addition to the two groups of adjacent resonant units on both sides, the inductive coupling mode can also be adopted between other adjacent resonant units. For example, the second resonant unit and the third resonant unit adopt the inductive coupling mode, but it should be noted that the coupling mode or cascading mode between other adjacent resonant units can be the same as the above-mentioned predetermined inductive coupling mode, or can be different. For example, the cascading element between the second resonant unit and the third resonant unit can be an inductor or an entity component equivalent to an inductor, such as a trace, which connects the second resonant unit and the third resonant unit through the trace.

[0010] The cascading mode between the resonant units discards the traditional capacitive coupling mode (spatial coupling mode) and adopts the inductive coupling cascading mode. Compared with the spatial coupling mode, the inductive coupling mode has stronger anti-electromagnetic interference ability. Without significantly increasing the design complexity and process complexity, the shielding robustness of the circuit is only increased through the optimization of the architecture.

[0011] In some embodiments, the first cascaded element includes a first via; one end of the first via is connected to the upper plate of the second capacitor; the other end of the first via is connected to the first inductor; and / or, the N-1th cascaded element includes an N-1th via; one end of the N-1th via is connected to the upper plate of the N-1th capacitor; the other end of the N-1th via is connected to the Nth inductor.

[0012] The specific implementation of the cascaded element can be a wire + via, or only a via. The via can be arranged at a spare space position in the z-axis direction. The height of the via can be controlled so that the overall position of the cascaded element in the z-axis direction is offset downward, away from the shielding layer, effectively reducing the coupling parasitic effect between the filter and the metal shielding layer.

[0013] In some embodiments, the first cascaded element includes a first via and a first wire; one end of the first via is connected to the upper plate of the second capacitor; the other end of the first via is connected to the first inductor through the first wire; and / or, the N-1th cascaded element includes an N-1th via and an N-1th wire; one end of the N-1th via is connected to the upper plate of the N-1th capacitor; the other end of the N-1th via is connected to the Nth inductor through the N-1th wire.

[0014] In some embodiments, the first via and / or the N-1th via is a vertical via.

[0015] The vertical via, that is, the central axis of the via is arranged along the z-axis direction, or in other words, is perpendicular to the XY direction of the filter circuit. In the overall architecture, the via and the MIM capacitor upper plate are fully utilized to realize the cascading of the resonant units. The design of the vertical via can reduce the opposite area with the top shielding layer, further weakening the coupling parasitic effect that may be generated.

[0016] In some embodiments, the filter circuit further includes a ground layer, an input pad, and an output pad; the ground layer and the input pad form a first capacitor; the first resonant unit includes the first capacitor and a first inductor.

[0017] In some embodiments, the filter circuit further includes a ground layer, an input pad, and an output pad; the ground layer and the output pad form an Nth capacitor; the Nth resonant unit includes the Nth capacitor and an Nth inductor.

[0018] The input pad and the output pad and the ground layer are used to form a capacitor, which can reduce two capacitor devices and realize device miniaturization.

[0019] In some embodiments, the filter circuit further comprises a ground layer; N=4; the second resonant unit comprises a second capacitor and a second inductor; an upper plate of the second capacitor forms the second capacitor with the ground layer; the second inductor comprises a third via hole, a fourth via hole, and a wire for connecting the third via hole and the fourth via hole; the third resonant unit comprises a third capacitor and a third inductor; an upper plate of the third capacitor forms the third capacitor with the ground layer; the third inductor comprises the fourth via hole, a fifth via hole, and a wire for connecting the fourth via hole and the fifth via hole; the second resonant unit and the third resonant unit are connected through a second cascaded element; and the second cascaded element comprises a wire for connecting the second resonant unit and the third resonant unit.

[0020] For example, the second capacitor can be capacitor C52, the second inductor can be inductor L52, the third capacitor can be C53, the third inductor can be L53, the third via hole can be via hole T05, the fourth via hole can be via hole T06, the fifth via hole can be via hole T07, the wire for connecting the third via hole and the fourth via hole can be wires W02, W23 and W07. The wire for connecting the fourth via hole and the fifth via hole can be wires W07, W23 and W03. The second cascaded element can be wire W23.

[0021] The second resonant unit and the third resonant unit adopt the above structural layout design and the above cascaded manner, can fully utilize the space in the z-axis direction under the premise of relatively improving the shielding robustness, reduce the volume occupied by the overall circuit, and realize the miniaturization design of the device.

[0022] In a second aspect, the embodiments of the present application further provide a filter, which can comprise the filter circuit according to any one of the above.

[0023] In a third aspect, the embodiments of the present application further provide an electronic device, which comprises the filter circuit or the filter according to any one of the above. BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is a three-dimensional structural schematic diagram of a design scheme of an LTCC filter in the related art;

[0025] FIG. 2 is a simulation data result diagram of the performance deterioration degree of a scheme in the related art under the influence of a Shielding layer on the surface of a module;

[0026] FIG. 3 is an application scenario example diagram of the filter circuit provided by the embodiments of the present application;

[0027] FIG. 4 is a system architecture example diagram of the filter circuit provided by the embodiments of the present application;

[0028] FIG. 5 is an equivalent circuit schematic diagram of the main structure of the filter circuit provided by the embodiments of the present application;

[0029] FIG. 6 is an equivalent circuit schematic diagram of an example of a 3-order cascade structure of a filter circuit provided in embodiments of the present application;

[0030] FIG. 7 is an equivalent circuit schematic diagram of an example of a 4-order cascade structure of a filter circuit in one embodiment provided in embodiments of the present application;

[0031] FIG. 8 is a three-dimensional structure schematic diagram corresponding to the equivalent circuit shown in FIG. 7;

[0032] FIG. 9a is performance test result data of a filter circuit provided in embodiments of the present application under the influence of a Shielding layer on the surface of a module;

[0033] FIG. 9b is a simulation data result graph of the degree of performance degradation of a filter circuit provided in embodiments of the present application under the influence of a Shielding layer on the surface of a module. DETAILED DESCRIPTION

[0034] In order to better understand the technical solutions of the present specification, the embodiments of the present application are described in detail below with reference to the drawings.

[0035] It should be clear that the described embodiments are only some of the embodiments of the present specification, not all. Based on the embodiments in the present specification, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present specification.

[0036] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present specification. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0037] Low Temperature Co-fired Ceramic (LTCC) technology, as one of the mainstream technologies of passive integration, is often used in the design and processing of passive devices (such as inductors, capacitors, filters, etc.). Among them, the LTCC filter is widely used and has many advantages such as large bandwidth, low cost, small package, high power tolerance, etc. In the communication scenario of more than 3GHz, compared with the surface acoustic filter, the performance advantage of the LTCC filter is more obvious, and it becomes the first choice of the filter in the Sub6G radio frequency circuit.

[0038] However, the radio frequency front-end link is developing towards high integration and miniaturization, and the electromagnetic interference on the radio frequency device may become more serious. Compared with power amplifiers (PA), low noise amplifiers (LNA), switches and other active devices, the LTCC filter internally integrates various LC resonant elements, which is more susceptible to electromagnetic interference.

[0039] For example, in the radio frequency module Sip, the module surface is sputtered with a metal shielding layer (hereinafter referred to as Shielding layer), and the Shielding layer is easy to produce a coupling parasitic effect (or parasitic coupling effect) with the internal LC elements of the LTCC filter in the radio frequency module, affecting the filter performance. Generally speaking, the elements closer to the top layer of the LTCC filter are more affected.

[0040] At present, the mainstream cascading method of the LTCC filter is generally to form a coupling capacitor by spatial coupling between the parallel wires of two resonant units to connect the two-stage resonant units, which can save space and realize miniaturized design. However, this inter-stage spatial coupling scheme is easy to be affected by the Shielding layer sprayed on the module surface. After introducing the coupling parasitic effect with the Shielding layer, the radio frequency performance of the LTCC filter is changed, which affects the overall index of the radio frequency link, thereby causing the deterioration of the overall index of the radio frequency link. It can be seen that the application scenarios of the LTCC filter are restricted to a certain extent in the complex electromagnetic environment.

[0041] For this problem, there are two solutions as follows: One solution is to add the actual use environment of the module during the design process of the filter model, and to place the filter model under the Shielding layer for simulation. The disadvantage of this solution is that the LTCC filter is simulated in a specific module environment, and the universality is poor, which cannot be applied to different modules.

[0042] Another solution is to spray a thin metal layer on the top layer of the LTCC filter, so that the filter has a Shielding layer and has a certain anti-electromagnetic interference capability, which avoids the parasitic coupling between the internal LC elements and the external metal to affect the performance. However, the internal elements of the filter and the Shielding layer of the filter may produce a stronger coupling parasitic effect, which needs to be optimized to improve the internal LC elements, resulting in more complex filter design, which is not conducive to the development of high performance and miniaturization of the filter.

[0043] For example, as shown in FIG. 1, in a related art, a top of an LTCC filter is added with a layer of shielding layer by printing, sputtering or the like, so as to reduce the influence of external electromagnetic interference on internal capacitance and inductance. The LTCC filter scheme adopts a four-order capacitance coupling form, and the filter architecture borne by the LTCC ceramic body includes four resonant units, and each resonant unit includes an inductance and a capacitance. Among them, the first resonant unit and the second resonant unit, and the third resonant unit and the fourth resonant unit are all coupled in cascade by capacitance, as shown in FIG. 1, and the coupling cascade capacitances are formed by space coupling between the top parallel wires of the inductance L3 and the inductance L1, and the inductance L5 and the inductance L2, so as to simplify two capacitance elements. However, on the one hand, the LTCC filter surface is covered with the shielding layer, which increases the design difficulty, process complexity and filter height, and is not conducive to the miniaturization and low-cost design of the filter; on the other hand, the closer shielding layer is designed to increase the coupling parasitic effect, resulting in a sacrifice of part of the inductance Q value (Quality Factor, quality factor), which is difficult to avoid performance loss and is not conducive to the development of high-performance filters.

[0044] In addition, in another related art scheme, a four-order capacitance coupling form is also adopted, and the first resonant unit and the second resonant unit, and the third resonant unit and the fourth resonant unit are all coupled by capacitance, so as to reduce the insertion loss and increase the low-frequency suppression degree. Among them, the cascade capacitance is formed by space coupling between the top parallel wires of the inductance in the adjacent resonant units, and the inductance in the resonant unit adopts a space vertical winding design, and the top inductance adopts a thinner wire to reduce the opposite area with the shielding layer and thus reduce the coupling parasitic effect. In this scheme design, the inter-stage interconnection also adopts space coupling, and the cascade capacitance is composed of top parallel wires and is located at the top layer position of the filter. Due to the vertical winding design of the inductance, the overall height of the filter is higher, and the top layer of the filter is closer to the shielding layer of the module surface, which is more susceptible to the influence of the coupling parasitic effect and sacrifices part of the inductance Q value. For example, based on another related art scheme, when the top of the LTCC filter is 100 um away from the shielding layer of the module, the in-band standing wave is deteriorated by about 10 dB, the bandwidth is expanded by about 300 MHz towards high frequency, and the radio frequency performance of the filter changes greatly.

[0045] In view of this, the embodiments of the present application propose a filter circuit or an LTCC filter, which can solve the performance deterioration problem of the LTCC filter under the shielding layer of the module, reduce the parasitic coupling effect between the LTCC filter and the shielding layer, enhance the shielding robustness of the LTCC filter, and be applicable to different radio frequency front-end modules or other complex electromagnetic scenarios.

[0046] The filter circuit proposed in the embodiments of the present application can be a LTCC filter architecture with shielding robustness. In the architecture design, the conventional spatial coupling mode is abandoned, that is, no inter-stage capacitance coupling is adopted, but inductive coupling is adopted. For example, in some embodiments, the upper electrode plate of a via+MIM capacitor or a wire+via+MIM capacitor can be used to form a cascaded inductor, that is, the upper electrode plate of the MIM capacitor is connected to another resonant unit through a via, so as to realize the inter-stage inductive coupling between resonant units (or resonators).

[0047] In the above structure, the upper electrode plate of the MIM capacitor is generally located at a middle or lower position in the Z-axis direction of the filter, and one end of the via is connected to the upper electrode plate of the MIM capacitor. The position of the cascaded inductor in the Z-axis direction can be lowered, which is equivalent to that the wire and the MIM capacitor are placed in the lower layer (close to the pad) of the LTCC filter in the architecture, and the parasitic coupling effect with the top Shielding layer is small. Compared with the conventional inter-stage spatial coupling, the coupling mode is more stable, the design and processing are simpler, and the interference of the module Shielding layer on the cascaded inductive coupling inside the LTCC can be effectively reduced, so as to achieve the purpose of shielding robustness design of the LTCC filter.

[0048] In the above structure, the via can be a vertical via with a central axis along the Z-axis direction, which further reduces the opposite area with the Shielding layer, thereby reducing the coupling parasitic effect.

[0049] As shown in FIG. 3, the filter circuit proposed in the embodiments of the present application can be applied to application scenarios such as the transceiving process of a communication system, for example, to realize the gating and filtering of radio frequency signals in the transceiving channel. In the above structure, RFIC refers to a radio frequency integrated circuit (Radio Frequency Integrated Circuit), PA refers to a power amplifier (Power Amplifier), and LNA refers to a low noise amplifier (Low Noise Amplifier).

[0050] Specifically, the filter circuit provided by the embodiment of the present application can be applied to radio frequency filters such as filters, duplexers, and multiplexers, and can also be applied to other radio frequency devices containing resonant units. The inductive coupling method adopted by the embodiment of the present application can be applied not only to LTCC filters but also to other types of filters, for example, 2D IPD filters, and has a wider range of application. The space coupling method in the related art is only applicable to LTCC filters and is difficult to use in other types of filters such as 2D IPD filters, thereby limiting its range of application. The 2D IPD filter is a 2-order integrated passive device (IPD) filter.

[0051] The main architecture of the filter circuit provided by the embodiment of the present application can be a radio frequency filter architecture, and specifically can be a resonator coupling cascade form of 2-order, 3-order, and 3-order or more, that is, at least 2 resonant units are included, and generally 3 or more resonant units are included, and adjacent resonators are coupled through a coupling cascade element to realize inductive coupling.

[0052] Exemplarily, as shown in FIG. 4, taking a four-order band-pass LTCC filter architecture as an example, the filter circuit can include resonant unit 1, resonant unit 2, resonant unit 3, resonant unit 4, input pad (i.e., IN pad), ground pad, and output pad (i.e., OUT pad), and an LTCC ceramic body carrying these components, and the LTCC ceramic body serves as a filter substrate. Among them, adjacent resonant units are coupled through a coupling cascade element (hereinafter referred to as a cascade element), for example, resonant unit 1 and resonant unit 2 are coupled through coupling cascade element 12; resonant unit 2 and resonant unit 3 are coupled through coupling cascade element 23; and resonant unit 3 and resonant unit 4 are coupled through coupling cascade element 34. Exemplarily, the coupling cascade element can be an inductor. Each resonant unit can include a metal-insulator-metal (MIM) capacitor and an inductor.

[0053] The radio frequency signal flows in from the IN pad, passes through resonant unit 1, coupling cascade element 12, resonant unit 2, coupling cascade element 23, resonant unit 3, coupling cascade element 34, resonant unit 4, and finally flows out from the OUT pad, thereby completing the gating of the radio frequency signal.

[0054] Exemplarily, in the filter circuit of the embodiment of the present application, the cascade element can adopt a solid such as a via, for example, can be a vertical via.

[0055] The upper plate of the MIM capacitor in the cascaded element multiplexing two-side resonant unit is connected through a mode of wire + via hole + upper plate of MIM capacitor, or a mode of via hole + upper plate of MIM capacitor, the cascading between resonant units is realized, and it can be understood that, in the overall architecture design, the vertical via hole and the upper plate of the MIM capacitor are fully utilized to realize the cascading of the resonant units, the coupling parasitic between the filter and the metal shielding layer can be effectively reduced, the shielding robustness of the LTCC filter is increased, and the performance influence caused by the shielding layer is reduced. Moreover, since the upper electrode of the capacitor in the intermediate-stage resonant unit is multiplexed, no additional winding inductance area is increased, and the XY direction layout area is unchanged.

[0056] Specifically, as shown in FIG. 5, the filter circuit can include a first resonant unit to an Nth resonant unit, N≥3, N being an integer. For example, in the direction from an input terminal P31 to an output terminal P32, the resonant units are sequentially arranged as a resonant unit 31 (a first resonant unit), a resonant unit 32 (a second resonant unit),..., a resonant unit 33 (an (N-1)th resonant unit), and a resonant unit 34 (an Nth resonant unit).

[0057] Among the two groups of adjacent resonant units on both sides, at least one group is coupled through a cascaded inductor, and specifically, the upper plate of the capacitor and the inductor of the adjacent resonant unit are connected through a cascaded element.

[0058] Specifically, in some embodiments, the resonant unit 31 includes an inductor L31 and a capacitor C31, the resonant unit 32 includes a capacitor C32 and an inductor L32, the upper plate of the inductor L31 and the capacitor C32 is connected through a cascaded element L312 (a first cascaded element), and the resonant unit 33 includes a capacitor C N-1 and an inductor L N-1 , the resonant unit 34 includes an inductor L N and a capacitor C N ; the upper plate of the inductor L N and the capacitor C N-1 is connected through a cascaded element L N-1N (an (N-1)th cascaded element). In other embodiments, only one group of adjacent resonant units can be connected in the above-mentioned manner.

[0059] Among the N resonant units, in some embodiments, the coupling mode between adjacent resonant units is inductive coupling.

[0060] It should be noted that in the embodiments of the present application, the cascaded element can be an inductor, or can be other physical components equivalent to an inductor. For example, in some embodiments, the cascaded element can be a via or a via plus a wire. In the equivalent circuit shown in FIG. 5 and FIG. 6, the cascaded element is represented by an inductor symbol, and it should be understood that the cascaded element can be a via or a physical entity composed of a via and a wire in actual application, which can be equivalent to an inductor in the circuit.

[0061] A specific embodiment is listed below.

[0062] For example, when N = 3, the equivalent circuit diagram of the filter circuit is shown in FIG. 6. Specifically, the filter circuit includes three resonant units, and in the direction from the input terminal P41 to the output terminal P42, the first resonant unit includes an inductor L41 and a capacitor C41, the second resonant unit includes an inductor L42 and a capacitor C42 (generally a MIM capacitor), and the third resonant unit includes an inductor L43 and a capacitor C43. The first resonant unit and the second resonant unit are inductively coupled through the cascaded element L412, and the second resonant unit and the third resonant unit are inductively coupled through the cascaded element L423.

[0063] Specifically, in the equivalent circuit example of the filter circuit shown in FIG. 6, the capacitor C41 in the first resonant unit can be composed of an input pad and a ground layer, and one end of the inductor L41 is grounded, and the other end is connected to the upper plate of the MIM capacitor C42 in the adjacent resonant unit (the second resonant unit) through the cascaded element L412. For example, in some embodiments, the cascaded element L412 is a physical component composed of a wire and a via, or is only a via without a wire. One end of the via is connected to the upper plate of the MIM capacitor C42, and the other end is directly or through a wire connected to one end (non-ground end) of the inductor L41.

[0064] The via can be a vertical via. The vertical via means that the central axis of the via is parallel to the z-axis direction or along the z-axis direction. The surface of the green sheet (or ceramic substrate) of the LTCC ceramic body is a two-dimensional plane determined in the XY direction, and the Z-axis direction is perpendicular to the two-dimensional plane in the XY direction.

[0065] Similarly, the capacitor C43 in the second resonant unit can be composed of an output pad and a ground layer, and one end of the inductor L43 is grounded, and the other end is connected to the upper plate of the MIM capacitor C42 in the adjacent resonant unit (the second resonant unit) through the cascaded element L423. Similarly, the cascaded element L423 can be a physical component composed of a wire and a via, or be only a via without a wire. One end of the via is connected to the upper plate of the MIM capacitor C42, and the other end is directly or through a wire connected to one end (non-ground end) of the inductor L43.

[0066] Another specific embodiment is listed below.

[0067] Taking N79 LTCC band-pass filter as an example, when N=4, the equivalent circuit diagram is shown in FIG. 7. The inductor L51 and the capacitor C51, the inductor L52 and the capacitor C52, the inductor L53 and the capacitor C53, and the inductor L54 and the capacitor C54 are connected in parallel to the ground, forming four resonant units. The resonant units are cascaded in the form of inductive coupling, and a four-order band-pass filter is composed.

[0068] Specifically, in the direction from the input terminal P51 to the output terminal P52, the first resonant unit includes the inductor L51 and the capacitor C51, the second resonant unit includes the inductor L52 and the capacitor C52 (for example, a MIM capacitor), the third resonant unit includes the inductor L53 and the capacitor C53 (for example, a MIM capacitor), and the fourth resonant unit includes the inductor L54 and the capacitor C54. The adjacent resonant units are inductively coupled through the cascaded elements L512, L523, and L534, respectively.

[0069] Similarly, in the equivalent circuit shown in FIG. 7, for example, the capacitor C51 can be composed of an input pad and a ground layer. One end of the inductor L51 is connected to the ground, and the other end is connected to the upper plate of the MIM capacitor C52 in the adjacent resonant unit through the cascaded element L512. For example, the cascaded element L512 is an entity component composed of a trace and a via, or only a via without a trace. One end of the via is connected to the upper plate of the MIM capacitor C52, and the other end is directly or through a trace connected to one end (non-ground end) of the inductor L51. In some embodiments, the via can be a vertical via. The capacitor C54 can be composed of an output pad and a ground layer. One end of the inductor L54 is connected to the ground, and the other end is connected to the upper plate of the MIM capacitor C53 in the adjacent resonant unit through the cascaded element L534. Similarly, the cascaded element L534 can be an entity component composed of a trace and a via, or only a via without a trace. One end of the via is connected to the upper plate of the MIM capacitor C53, and the other end is directly or through a trace connected to one end (non-ground end) of the inductor L54.

[0070] In the circuit shown in FIG. 7, the first resonant unit and the second resonant unit are a group of adjacent resonant units close to the input end side, the third resonant unit and the fourth resonant unit are a group of adjacent resonant units close to the output end side, and the inductive coupling between the second resonant unit and the third resonant unit can be implemented differently from the inductive coupling between the two groups of adjacent resonant units on the two sides. For example, the inductive coupling between the second resonant unit and the third resonant unit is implemented through cascaded element L523, which can be an entity equivalent to an inductor, such as a wire. That is, in some embodiments, one end (non-ground end) of inductor L52 and one end (non-ground end) of inductor L53 are connected through a wire.

[0071] In the equivalent circuit shown in FIG. 7, capacitor C0 is connected between input end P51 and output end P52, and two transmission zeros are introduced at low frequencies through cross coupling, and one transmission zero is introduced at high frequency position, for suppressing low frequency signals and high frequency signals.

[0072] FIG. 7 shows an equivalent circuit schematic diagram of a four-order N79 LTCC bandpass filter using inductive coupling, and FIG. 8 is a three-dimensional structure schematic diagram corresponding to the equivalent circuit shown in FIG. 7. The three-dimensional structure can include a ceramic main body 600, a capacitor-inductor assembly, and a pad.

[0073] The raw materials of the ceramic main body 600 include alumina powder, inorganic substances such as glass materials, and organic binders, etc. After stirring, a ceramic slurry is formed, and a ceramic substrate (or green sheet) with excellent electrical insulation and high thermal conductivity is formed after flow casting. Then, the ceramic main body is made by stacking and sintering different substrates.

[0074] The capacitor-inductor assembly and the pad, etc. can be made of conductive materials such as silver, copper, palladium, platinum, or silver-palladium alloy. For example, in the LTCC process, the three-dimensional model of the designed capacitor-inductor assembly and pad is split into various plane patterns according to different layers, and then the conductive material is drawn as a conductive pattern on the ceramic substrate using printing, thin film process or photolithography process. Then, different ceramic substrates are stacked according to the splitting rule and sintered. The conductive patterns between the ceramic substrates can be interconnected through vertical vias, and finally the complete capacitor-inductor assembly is obtained. The capacitor-inductor assembly includes wires, vias, internal electrical level plates, ground layers, etc. The pad can include an input pad 601, an output pad 603, and a ground pad 602.

[0075] Specifically, in combination with FIGS. 7 and 8, the specific implementation of each component in the capacitor-inductor assembly can adopt the following design:

[0076] One end of the vertical via T01 and one end of the vertical via T02 are connected by the wire W01 to form an inductor L51; the input pad 601 and the ground layer 604 form a capacitor C51; the other end of the vertical via T02 is connected to the ground layer, the other end of the vertical via T01 is connected to the vertical via T09, and the vertical via T09 is connected to the input pad 601, or in other words, the other end of the vertical via T01 is connected to the input pad 601 through the vertical via T09, so the inductor L51 and the capacitor C51 form the first-stage resonant unit.

[0077] One end of the vertical via T05 and one end of the vertical via T06 are connected by the wire W02, the wire W23, and the wire W07 to form an inductor L52; the MIM capacitor upper plate 521 and the ground layer 604 form a capacitor C52; the other end of the vertical via T05 is connected to the upper plate 521 of the capacitor C52, and the other end of the vertical via T06 is connected to the ground layer 604, so the inductor L52 and the capacitor C52 form the second-stage resonant unit.

[0078] One end of the vertical via T07 and one end of the vertical via T06 are connected by the wire W03, the wire W23, and the wire W07 to form an inductor L53; the MIM capacitor upper plate 531 and the ground layer 604 form a capacitor C53; the other end of the vertical via T07 is connected to the upper plate 531 of the capacitor C53, and the other end of the vertical via T06 is connected to the ground layer, so the inductor L53 and the capacitor C53 form the third-stage resonant unit.

[0079] One end of the vertical via T03 and one end of the vertical via T04 are connected by the wire W04 to form an inductor L54; the output pad 603 and the ground layer 604 form a capacitor C54; the other end of the vertical via T03 is connected to the ground layer 604, and the other end of the vertical via T04 is connected to the output pad 603 through the vertical via T10, so the inductor L54 and the capacitor C54 form the fourth-stage resonant unit.

[0080] The wire W02, the wire W03, the wire W23, and the wire W07 form a cascaded element L523, so the cascaded element L523 connects the second-stage and third-stage resonant units. It should be noted that the cascaded element L523 can be equivalent to an inductor component, so it can also be called a coupled cascaded inductor or a cascaded inductor, and other cascaded elements are similar and will not be described again.

[0081] In this embodiment, the inductive coupling between the first-stage resonant unit and the second-stage resonant unit, and between the third-stage resonant unit and the fourth-stage resonant unit, is achieved by wire and via.

[0082] Specifically, the wire W12 and the vertical via T12 form a cascade element L512 (or a cascade inductor), the bottom end of the vertical via T12 is connected to the upper plate 521 of the capacitor C52, the wire W12 is connected to the vertical via T02, the upper plate 521 of the capacitor C52 is connected to the vertical via T05, and thus the cascade element L512 is connected to the first and second resonant units.

[0083] It should be noted that in other embodiments, the size of the wire W12 can be further shortened or the wire W12 is not provided, and the vertical via T12 is directly connected to the vertical via T02, for example, the vertical via T12 is arranged below the wire W01, and the vertical via T02 and the vertical via T12 are connected through the wire W01.

[0084] The wire W34 and the vertical via T34 form a cascade element L534, the bottom end of the vertical via T34 is connected to the upper plate 531 of the capacitor C53, the wire W34 is connected to the vertical via T03, and the upper plate 531 of the capacitor C53 is connected to the vertical via T07, and thus the cascade element L534 is connected to the third and fourth resonant units.

[0085] The wire W05, the wire W00 and the wire W06 form a capacitor C0, the capacitor C0 is connected to the input pad 601 through the vertical via T09 and connected to the output pad 603 through the vertical via T10.

[0086] It should be noted that the via hole connected between the resonant units can provide the Q value and the inductance value of the cascade inductor, and according to the different diameters, in some embodiments, it can be provided as solid or hollow. It can be realized by one or more of various punching technologies such as laser punching, mechanical punching, through silicon via (TSV), through glass via (TGV) and the like.

[0087] Based on the above-mentioned embodiments, simulation tests are carried out, and the simulation results are shown in FIGS. 9a and 9b. In FIG. 9a, m1 represents that the sampling frequency of the sampling point 1 is 4.4 GHz, m2 represents that the sampling frequency of the sampling point is 5 GHz. 2, S(2, 2) represents the in-band standing wave of the output port, S(1, 1) represents the in-band standing wave of the input port, and S(2, 1) represents the in-band insertion loss. From the data in the figure, it can be seen that the in-band insertion loss is ≥-1.4 dB, the in-band standing wave is ≤-18 dB, the low-frequency out-of-band suppression is ≤-40 dB or more, the high-frequency suppression is ≤-15 dB, and the overall performance is good.

[0088] As shown in FIG. 9b, the inductive coupling mode of the wiring + vertical via connecting the upper electrode plate of the MIM capacitor is adopted, the LTCC filter is designed, the in-band standing wave is deteriorated within 3dB when the top distance from the shielding layer is 100um, the bandwidth is only expanded by about 100MHz towards high frequency, and the degree of change of the radio frequency performance of the filter is obviously reduced.

[0089] In the above structure design, in order to reduce the parasitic influence of the lower ground layer and the top shielding layer on the LTCC filter, the cascade mode between the resonators (i.e. the resonant units) fully utilizes the upper electrode of the MIM capacitor located in the bottom layer, which can be a short wiring + via + MIM capacitor upper electrode or a via + MIM capacitor upper electrode.

[0090] The specific overall architecture layout is as follows: the capacitor component (such as the MIM capacitor) is placed in the middle and lower layer position in the z-axis direction of the LTCC filter, the pads are placed in the bottom layer of the LTCC filter, and the 1st, 2nd, 3rd and 4th parallel resonant units are arranged from left to right, that is, from the input end to the output end. Among them, the two side cascade elements, such as the coupled cascade inductors (such as L512 and L534), are placed in the middle and lower layer of the filter. In the direction from the input end to the output end, the middle cascade element, such as the coupled cascade inductor L523, is placed in the upper layer of the filter. The inductor component, such as L51 and L54, is limited by the via height, and the top end of the inductor component is in the upper layer of the LTCC filter. Among them, the middle cascade element is arranged in the upper layer, in order to fully utilize the space in the z-axis direction, reduce the volume occupied by the overall structure of the filter, and realize the miniaturization of the filter.

[0091] In the related art, the space coupling mode is often used between adjacent resonant units. According to the above exemplary description in the present application, it can be seen that in the scheme proposed in the present application, the entity inductive coupling mode is adopted, the cascade element reuses the MIM capacitor upper plate, the MIM capacitor upper plate is arranged in the middle and lower layer position in the z-axis direction in the filter, the MIM capacitor upper plate and the inductor in the adjacent resonant unit are connected through the via and other entities to realize the cascade, and the relative position of the cascade element is in the middle and lower layer of the filter. Compared with the space coupling mode in the top layer position in the related art, the space position of the coupled cascade element is moved downward along the z-axis direction, which on the one hand, pulls apart the distance between the cascade inductor and the top shielding layer, and weakens the influence of the top shielding layer; on the other hand, the inductive coupling is connected between different resonant units through the entity component, and the stability of the anti-electromagnetic interference is relatively stronger than that of the space coupling.

[0092] It should be noted that the above embodiments are only exemplary, and the filter circuit proposed in the embodiments of the present application can be designed based on the LTCC process or the IPD process, and the substrate can be ceramic material, silicon or glass, etc. The IPD process, i.e. integrated passive device (Integrated Passive Devices), the IPD technology uses advanced semiconductor process (including thin film process and photolithography process) to realize the manufacturing of passive devices, which can be used to manufacture LC filter, duplexer, balun, etc.

[0093] It should be noted that the above embodiments of the present application only list the specific implementation of the three-order and four-order circuit, and in actual application, the filter circuit form can be a two-order, three-order or three-order or more resonator coupling cascade form.

[0094] The embodiments of the present application also provide a filter, which comprises the filter circuit according to any one of the above embodiments.

[0095] The embodiments of the present application also provide an electronic device, which comprises the filter circuit or the filter according to any one of the above embodiments.

[0096] In summary, in the related art, a metal shielding layer is added on the top layer of the LTCC filter by sputtering, spraying and other processes, which increases the coupling parasitic effect and may sacrifice part of the inductance Q value. The embodiments of the present application optimize and innovate the internal architecture of the filter, without adding additional electromagnetic shielding design or new process procedures, and without increasing the design complexity and process complexity under the premise of ensuring the performance of the filter.

[0097] In addition, in the related art, the space coupling mode is used to realize the capacitor cascade between the resonant units in the filter, and only the own trace design is used to increase the robustness, and the performance under the shielding layer is still very poor, which cannot meet the needs of complex electromagnetic environment.

[0098] The resonant units in the filter circuit proposed in the embodiments of the present application are coupled in an inductive coupling cascade, and the radio frequency performance stability is better under the premise of not sacrificing the performance of the filter itself.

[0099] It should be further noted that in the related art, the space coupling mode is generally only applicable to the LTCC filter, and it is difficult to use in other types of filters, such as 2D IPD filter. The filter circuit with inductive coupling mode proposed in the embodiments of the present application can be applied to various types of filters such as 2D IPD filter, and has a wider application range.

[0100] In the description of the application, reference can be made to terms such as "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" etc. It is intended that there are at least one embodiment or example where the particular feature, structure, material or characteristic described is included in at least one embodiment or example. These developments of the described embodiments or examples are not necessarily alternatives to each other, but can be combined in any way, unless otherwise stated. Also, descriptions of a particular feature, structure, material or characteristic are not necessarily being confined to a single or particular embodiment or example, but can be combined in any way with one or more other embodiments or examples, or used as a module, part or segment of either, as appropriate.

[0101] Furthermore, the terms "first", "second", etc. are used herein only to describe the different features, and do not imply or suggest relative importance or a number of the indicated technical features. Thus, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise explicitly specified.

[0102] Any process or method descriptions or descriptions of the flow diagrams in the present application can be understood as representing code modules, segments, or portions of code which include one or more executable instructions for performing specific logic functions (or steps) or portions of the application, and that the various components described herein can be implemented or performed by a computer or hardware- based processing (e.g., analog or digital) system, which can interact with a receiver or transmitter or both. Alternatively, the steps of the processes or methods described herein can be performed by a processor of a device or hardware-based system.

Claims

1. A filter circuit, characterized by, The filter circuit comprises a first resonant unit to an Nth resonant unit, N≥3; The first resonant unit comprises a first inductor, the second resonant unit comprises a second capacitor; the N-1th resonant unit comprises an N-1th capacitor, and the Nth resonant unit comprises an Nth inductor; The upper plate of the first inductor and the second capacitor is connected through a first cascaded element; and / or, the upper plate of the Nth inductor and the N-1th capacitor is connected through an N-1th cascaded element.

2. The method of claim 1, wherein, The coupling mode between two adjacent resonant units in the first resonant unit to the Nth resonant unit is inductive coupling.

3. The method of claim 1 or 2, wherein, The first cascaded element comprises a first via; one end of the first via is connected to the upper plate of the second capacitor; the other end of the first via is connected to the first inductor; And / or, The N-1th cascaded element comprises an N-1th via; one end of the N-1th via is connected to the upper plate of the N-1th capacitor; the other end of the N-1th via is connected to the Nth inductor.

4. The method of claim 1 or 2, wherein, The first cascaded element comprises a first via and a first trace; one end of the first via is connected to the upper plate of the second capacitor; the other end of the first via is connected to the first inductor through the first trace; And / or, the N-1th cascaded element comprises an N-1th via and an N-1th trace; one end of the N-1th via is connected to the upper plate of the N-1th capacitor; the other end of the N-1th via is connected to the Nth inductor through the N-1th trace.

5. The method of claim 3 or 4, wherein, The first via and / or the N-1th via is a vertical via.

6. The method of any one of claims 1-5, wherein, The filter circuit further comprises a ground layer, an input pad and an output pad; The ground layer and the input pad form a first capacitor; The first resonant unit comprises the first capacitor and the first inductor.

7. The method of any one of claims 1-6, wherein, The filter circuit further comprises a ground layer, an input pad and an output pad; The ground layer and the output pad form an Nth capacitor; The Nth resonant unit comprises the Nth capacitor and the Nth inductor.

8. The method of any one of claims 1-7, wherein, The filter circuit further comprises a ground layer; and N=4; The second resonant unit comprises a second capacitor and a second inductor; the upper plate of the second capacitor and the ground layer form the second capacitor; The second inductor comprises a third via, a fourth via, and a trace for connecting the third via and the fourth via; The third resonant unit comprises a third capacitor and a third inductor; the upper plate of the third capacitor and the ground layer form the third capacitor; The third inductor comprises a fifth via, a sixth via, and a trace for connecting the fifth via and the sixth via; The second resonant unit and the third resonant unit are connected through a second cascaded element; wherein the second cascaded element comprises a wire for connecting the second resonant unit and the third resonant unit.

9. A filter, characterized by The filter comprises the filter circuit according to any one of claims 1-8.

10. An electronic device, comprising: The electronic device comprises the filter circuit according to any one of claims 1-8 or the filter according to claim 9.

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