Integrated passive band-pass filter

Abstract

The invention provides an integrated passive band-pass filter. The integrated passive band-pass filter is provided with a symmetric structure region and an asymmetric structure region, the symmetric structure area is provided with a symmetric axis, structures in the symmetric structure area are symmetrically arranged, the symmetric axis penetrates through the asymmetric structure area, and the structures in the asymmetric structure area are asymmetrically arranged relative to the symmetric axis; comprising two first filtering units which are arranged in a symmetric structure area and are connected with input and output ports located at the same side of a symmetric axis; the two second filtering units are arranged in the symmetric structure area, and the second filtering units are connected with the first filtering units located on the same side of the symmetric axis; and the third filtering unit is at least partially arranged in the asymmetric structure area, and the third filtering unit is connected with the two second filtering units. According to the filter structure, the roll-off characteristic of the two sides of a passband is increased through the multi-order circuit design, the asymmetric structure is arranged in the middle of the structure, mutual interference of inductors and large occupied space are avoided, the symmetric structures on the two sides can be debugged and optimized at the same time, the debugging and optimization frequency can be reduced, and the design period is shortened.

Description

Technical Field

[0001] This application mainly relates to the field of passive electronic device technology, specifically to an integrated passive bandpass filter. Background Technology

[0002] Filters are core components in electronic systems used for signal processing. Their function is to selectively allow signals of specific frequencies to pass through while suppressing other frequency components. Traditional passive filters consist of discrete components (such as resistors, capacitors, and inductors). However, as electronic devices develop towards miniaturization, higher frequencies, and higher integration, discrete solutions face problems such as large size, significant parasitic effects, and limited high-frequency performance. Against this backdrop, integrated passive filters have emerged. Utilizing semiconductor technology, they integrate passive components onto a single substrate to achieve high-performance and high-reliability filtering functions.

[0003] Integrated passive filters were initially used in radio frequency (RF) front-end modules. With advancements in semiconductor processes, particularly the maturity of thin-film deposition and photolithography technologies, integrated passive technology has gradually become industrialized. Currently, integrated passive filters are widely used in smartphones, base stations, automotive electronics, and satellite communications. In these fields, the need for miniaturization and improved performance has become a new requirement for filters.

[0004] Traditional filters often employ symmetrical circuit architectures, which ensure good electrical characteristics, but the increased number of basic units results in a larger overall size, making it difficult to meet the miniaturization requirements of modern electronic systems. Summary of the Invention

[0005] To address or improve the problems existing in the aforementioned prior art, this application provides an integrated passive bandpass filter. This filter has a symmetrical structure region and an asymmetrical structure region. The symmetrical structure region has a symmetrical axis and the structure axis therein is symmetrically arranged. The symmetrical axis passes through the asymmetrical structure region, and the structure in the asymmetrical structure region is asymmetrically arranged relative to the symmetrical axis.

[0006] The integrated passive bandpass filter provided in this application includes:

[0007] Two first filter units are located in the symmetrical structure area, and the first filter units are connected to the input and output ports located on the same side of the axis of symmetry;

[0008] Two second filter units are located in the symmetrical structure region, and the second filter units are connected to the first filter unit located on the same side of the axis of symmetry.

[0009] The third filter unit is at least partially located in the asymmetric structure region, and the third filter unit is connected to the two second filter units.

[0010] In the aforementioned scheme, the filter has a semi-symmetrical structure. The first and second filter units are located in the symmetrical structure region. The capacitor and inductor structures (i.e., winding structures) in the two first filter units are arranged symmetrically with respect to the axis of symmetry. The capacitor and inductor structures in the two second filter units are also arranged symmetrically with respect to the axis of symmetry.

[0011] The filter structure in this design enhances the roll-off characteristics on both sides of the passband (the rate at which the filter's amplitude response transitions from the passband to the stopband near the cutoff frequency) through multi-stage circuit design. Furthermore, the symmetrical components allow for simultaneous debugging and optimization, reducing the number of optimization attempts and shortening the design cycle. The third filter unit, located at the center of the layout, employs an asymmetrical structure. Because this structure is in the middle of the circuit, a symmetrical design was not chosen to avoid mutual interference between the two inductors and to minimize space requirements. Instead, the parameters were optimized to create a single asymmetrical structure.

[0012] Optionally, the integrated passive bandpass filter includes: a substrate and a first metal layer on the substrate; a second metal layer located on the first metal layer and spaced apart from the first metal layer, the first metal layer being connected to the second metal layer through a connecting via, the second metal layer including multiple winding structures to serve as multiple inductor structures; a capacitor dielectric layer and a capacitor upper electrode layer being sequentially stacked on the first metal layer and forming multiple capacitor structures with the first metal layer; the capacitor upper electrode being connected to the second metal layer through a connecting via.

[0013] Optionally, the first filtering unit includes:

[0014] Both the first conductor and the first inductor structure are formed on the second metal layer, and the first conductor is connected to the input and output ports;

[0015] The first capacitor structure is connected to the first wire and the ground terminal;

[0016] The second capacitor structure is connected to the first wire and the fourth wire;

[0017] One end of the first inductor structure is connected to the first wire, and the other end is connected to the fourth wire;

[0018] The fourth conductor is formed in the first metal layer.

[0019] Optionally, the first inductor structure includes a polygonal spiral, and the second capacitor structure is disposed on one side of a short side of the first inductor structure;

[0020] The first capacitor structure and the second capacitor structure are disposed on different sides of the first inductor structure.

[0021] The ratio of the capacitance values ​​of the second capacitor structure to those of the first capacitor structure is greater than or equal to 1:1 and less than 2:1.

[0022] In the aforementioned scheme, the second capacitor structure is located on one side of a short side of the first inductor structure, which facilitates connection and layout and is beneficial for miniaturization design.

[0023] Optionally, the second filtering unit includes:

[0024] The second conductor and the second inductor structure are both formed on the second metal layer;

[0025] The third capacitor structure is connected to the fourth wire and the ground terminal;

[0026] The fourth capacitor structure is connected to the second and fourth wires;

[0027] The fifth capacitor structure is connected to the second wire and the ground terminal;

[0028] One end of the second inductor structure is connected to the second conductor, and the other end is connected to the ground terminal.

[0029] Optionally, the second conductor includes a rectangular extension, the length direction of which is perpendicular to the axis of symmetry, and the fourth capacitor structure is connected to the rectangular extension.

[0030] The second capacitor structure and the second inductor structure are located on the same side of the center line of the longitudinal direction of the rectangular extension.

[0031] The geometric centers of the first and second inductor structures are respectively located on both sides of the center line of the length direction of the rectangular extension.

[0032] The distance between the second inductor structure and the fourth capacitor structure is greater than 50 μm.

[0033] In the aforementioned scheme, the second capacitor structure and the second inductor structure are arranged on the same side, which can reduce the mutual interference between the first inductor structure and the second inductor structure.

[0034] Furthermore, due to the mutual interference between the second inductor structure and the fourth capacitor structure, spurious peaks may be generated outside the high-frequency band when they are placed close together. Therefore, the second inductor structure and the fourth capacitor structure are kept at a certain distance, greater than 50 μm.

[0035] Optionally, the area ratio of the first inductor structure to the second inductor structure is 1:0.6 to 1:1.8;

[0036] The ratio of the inductance values ​​of the first inductor structure and the second inductor structure is from 1:0.5 to 1:2.

[0037] The ratio of the capacitance values ​​of the fourth capacitor structure to those of the second capacitor structure is greater than 4:1.

[0038] In the aforementioned scheme, the inductance values ​​of the first and second inductor structures are used for frequency adjustment within the passband, so that the center frequency of the filter is located near 1.8 GHz.

[0039] Optionally, the third filter unit includes: a third conductor and a third inductor structure, both formed on the second metal layer; and two sixth capacitor structures, each connected to one of the two second conductors and both connected to the fifth conductor.

[0040] The seventh capacitor structure is connected to the fifth and third wires;

[0041] The eighth capacitor structure is connected to the third conductor and the ground terminal;

[0042] One end of the third inductor structure is connected to the third conductor, and the other end is connected to the ground terminal;

[0043] The fifth conductor is formed in the first metal layer.

[0044] Optionally, the third inductor structure includes a polygonal spiral, and the eighth capacitor structure is disposed on one side of a short side of the third inductor structure;

[0045] The ratio of the inductance values ​​of the third inductor structure to the second inductor structure is 1.5:1 to 4:1;

[0046] The area ratio of the third inductor structure to the second inductor structure is 1.2:1 to 3:1;

[0047] The ratio of the capacitance values ​​of the eighth capacitor structure to the first capacitor structure is 1:2 to 2:1.

[0048] In the aforementioned scheme, the third inductor structure is mainly used to adjust the out-of-band rejection at low frequencies. It mainly adjusts the out-of-band rejection at 1 GHz, so its inductance value is relatively large. Compared with the second inductor structure, its inductance value is set to a ratio of 1.5:1 to 4:1.

[0049] Optionally, the second conductor includes a rectangular extension, the length of which is perpendicular to the axis of symmetry. A fourth capacitor structure is connected to one end of the rectangular extension, and a sixth capacitor structure is connected to the other end. The second and third inductor structures are respectively positioned on either side of the centerline along the length of the rectangular extension. This arrangement primarily aims to increase the distance between the spiral inductors and reduce mutual interference between them.

[0050] Optionally, the symmetrical structure region is provided with multiple ground terminals and two input / output ports located at the edge of the integrated passive bandpass filter;

[0051] A grounding terminal is located on one side of the axis of symmetry within the asymmetric structure region.

[0052] In summary, the integrated passive bandpass filter provided in this application embodiment has the characteristics of small size and wide bandwidth. The filter achieves bandpass filtering function with center frequency at GHz through a semi-symmetrical structure, and has the characteristics of wide bandwidth, high out-of-band rejection and high roll-off.

[0053] In addition, using a capacitor structure as part of the trace connecting the two metal layers reduces the device size, optimizes the inductance distribution, and reduces mutual interference between inductors.

[0054] The filter structure provided in this application has good versatility and can be matched with flip-chip soldered package structures as well as package structures with gold back soldered wire bonding. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of this application or the background art, the accompanying drawings used in the embodiments of this application or the background art will be described below.

[0056] Figure 1 This is a circuit schematic diagram of the filter provided in an embodiment of this application;

[0057] Figure 2 This is a schematic diagram showing the layout of the symmetrical and asymmetrical structural regions of the filter provided in the embodiments of this application;

[0058] Figure 3 This is a schematic diagram of the overall structure of each filtering unit of the filter provided in the embodiments of this application;

[0059] Figure 4 This is a partial structural diagram of the filter provided in an embodiment of this application, showing the third filtering unit and its surrounding structure;

[0060] Figure 5 This is a schematic diagram of the layer structure of the filter provided in the embodiments of this application;

[0061] Figure 6 This is a characteristic curve diagram of the filter provided in the embodiments of this application;

[0062] Figure 7 This is a characteristic curve diagram of the first filtering unit in the filter provided in the embodiments of this application;

[0063] Figure 8 This is a comparison of the S21 (transmission coefficient between two ports) characteristics of the single-circuit structure and the symmetrical circuit structure of the first filter unit in the filter provided in the embodiments of this application.

[0064] Figure 9 This is a comparison of the S11 (reflection coefficient of one port) characteristics of the single-circuit structure and the symmetrical circuit structure of the first filter unit in the filter provided in the embodiments of this application.

[0065] Figure 10 This is a characteristic curve diagram of the second filtering unit in the filter provided in the embodiments of this application;

[0066] Figure 11 This is a characteristic curve diagram of the third filtering unit in the filter provided in the embodiments of this application;

[0067] Figure 12 This is a process flow diagram of the filter provided in the embodiments of this application;

[0068] Figure 13 These are top and cross-sectional views of the filter bonding and wire bonding application method provided in the embodiments of this application;

[0069] Figure 14 These are top and cross-sectional views of the filter flip-chip application method provided in the embodiments of this application;

[0070] Figure 15 This is a schematic diagram of a fully symmetrical filter circuit, presented as a comparison.

[0071] Figure 16 This is a diagram of a fully symmetrical filter structure, presented as a comparative example.

[0072] Figure 17 In the embodiments of this application, based on Figure 1 The circuit schematic shown is a structural diagram of another type of filter formed by this circuit.

[0073] The image is labeled as follows:

[0074] 00: Substrate, 01: First metal layer, 02: Second metal layer;

[0075] 11: Capacitor dielectric layer; 12: Capacitor top electrode; 13: Connection via.

[0076] 20: Insulation layer;

[0077] 100: First filter unit; 111: First wire; 112: First inductor structure;

[0078] 200: Second filter unit; 211: Second wire; 212: Second inductor structure;

[0079] 2111: Rectangular extension;

[0080] 300: Third filter unit; 311: Third wire; 312: Third inductor structure;

[0081] 410: Fourth conductor; 420: Fifth conductor;

[0082] C1 to C8: The structure of the first to eighth capacitors;

[0083] PORT: Input / output port;

[0084] GND: Ground terminal. Detailed Implementation

[0085] In this specification, it will also be understood that when a component is referred to as being "connected to" other components relative to them, such as "connected to" other components, the component may be directly connected to or directly coupled to the component, or there may be an intermediary third component; in addition, in the embodiments of this application, "connection" mainly refers to circuit connection.

[0086] In this specification, for a component with two electrodes, such as a capacitor or inductor, when describing the connection of the component to another first component and second component, it means that the two electrodes of the component are respectively connected to the first component and the second component.

[0087] This application will now be described more fully below with reference to the accompanying drawings. However, this application can be implemented in many different ways and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided herein to make this application more detailed and complete, and to fully convey the scope of this application to those skilled in the art. The same reference numerals denote the same objects throughout the drawings.

[0088] To further miniaturize the filter, the applicant attempted to optimize the product from a circuit design perspective, aiming to use fewer components. On the other hand, the core principle of the product layout design was to require a more compact layout and effectively suppress electromagnetic coupling between components.

[0089] In view of the above, the embodiments of this application aim to provide an integrated passive bandpass filter (hereinafter referred to as filter or bandpass filter) with small size, low insertion loss, and wide bandwidth. It achieves bandpass filtering function with a center frequency of 1.8 GHz and a passband width of 0.4 GHz through a semi-symmetrical structure design.

[0090] The bandpass filter provided in this application embodiment has the following circuit principle: Figure 1 As shown, it includes 14 capacitors and 5 inductors. Specifically, the bandpass filter includes five filtering units: two first filtering units 100, two second filtering units 200, and one third filtering unit 300. Each filtering unit includes a main path and a branch to ground.

[0091] The main circuit of the first filter unit 100 has a parallel structure of the second capacitor C2 and the first inductor L1, and the ground branch includes the first capacitor C1. The two first filter units 100 are arranged symmetrically.

[0092] The main circuit of the second filter unit 200 includes a fourth capacitor C4, which is connected between the main circuit of the first filter unit 100 and the main circuit of the third filter unit 300. A third capacitor C3 is connected in series in the ground branch on one side of the fourth capacitor C4, and a resonant unit consisting of a fifth capacitor C5 and a second inductor L2 connected in parallel is provided in the ground branch on the other side. The two second filter units 200 are arranged symmetrically.

[0093] The main circuit of the third filter unit 300 includes two sixth capacitors C6 connected in series, and the branch to ground includes a seventh capacitor C7 connected in series and a resonant unit. One end of the seventh capacitor C7 is connected between the two sixth capacitors C6, and the other end is connected to the resonant unit. The resonant unit includes an eighth capacitor C8 connected in parallel and a third inductor L3.

[0094] The aforementioned circuit structure design, on the one hand, facilitates better roll-off characteristics and reciprocity in electrical properties; on the other hand, it reduces the difficulty of layout design, and the more consistent component parameters also help to reduce the debugging cycle. The third filter unit 300 is mainly designed to further increase out-of-band rejection on both sides and optimize circuit characteristics.

[0095] The electrical characteristics of the aforementioned circuit structure are as follows: Figure 6 As shown in the figure, the dashed line S21 illustrates the circuit's low insertion loss in the passband, exhibiting a -30dB characteristic at frequencies below 1.05GHz, with better out-of-band rejection at lower frequencies. In the high-frequency range, it demonstrates high overall out-of-band rejection, consistently remaining below -40dB, effectively suppressing high-frequency harmonics. The solid line S11 in the figure illustrates the circuit's return loss characteristics. Within a specific frequency band, a higher return loss value indicates a lower ratio of reflected signal power to incident signal power, superior impedance matching performance, and significantly improved forward transmission power efficiency. The S11 curve shows that S11 can exceed -25dB in the passband, indicating good impedance matching.

[0096] Based on the aforementioned circuit structure and principle, the integrated passive bandpass filter provided in this application embodiment has the following characteristics: Figure 2 The illustrated "landmark" structure has symmetrical and asymmetrical structural regions. Figure 2 The asymmetric structure region is indicated by a dashed box, while the regions outside the asymmetric structure region are all symmetric structure regions. The symmetric structure region has an axis of symmetry and the structures within it are arranged axially symmetrically. The axis of symmetry passes through the asymmetric structure region, and the structures within the asymmetric structure region are arranged asymmetrically with respect to the axis of symmetry.

[0097] like Figures 2 to 4As shown, the integrated passive bandpass filter includes two first filter units 100 and two second filter units 200 disposed in the symmetrical structure region, and a third filter unit 300 at least partially located in the asymmetrical structure region. The two first filter units 100 are symmetrically arranged with respect to the axis of symmetry, and the two second filter units 200 are also symmetrically arranged with respect to the axis of symmetry. Each first filter unit 100 is connected to an input / output port PORT located on the same side of the axis of symmetry, and each second filter unit 200 is connected to a first filter unit 100 located on the same side of the axis of symmetry. The third filter unit 300 is connected to the two second filter units 200.

[0098] In a typical embodiment, all components located in the symmetrical structure region, as well as the traces used to connect the components, are symmetrical with respect to the axis of symmetry.

[0099] In a typical embodiment, the symmetrical structure region and the asymmetrical structure region are located on both sides of the axis of symmetry, and the axis of symmetry passes through both the symmetrical structure region and the asymmetrical structure region.

[0100] The integrated passive bandpass filter in the aforementioned embodiment has a semi-symmetrical structure, or a partially symmetrical structure, in which the two first filter units 100 and the two second filter units 200 are symmetrically arranged. This layout, on the one hand, increases the roll-off characteristics on both sides of the passband through multi-stage circuit design; on the other hand, the symmetrical components can be debugged and optimized simultaneously, which helps to reduce the number of debugging and optimization operations and shorten the design cycle.

[0101] The third filter unit 300 is located at the center of the layout and adopts an asymmetrical structure. Since this structure is located in the middle of the circuit, in order to avoid mutual interference between the two inductors and large space occupation after a symmetrical design, a symmetrical structure design was not chosen, and it was adjusted to a single asymmetrical structure.

[0102] In a preferred embodiment, such as Figure 5 As shown (partial insulating layer 20 is omitted or made transparent in the figure), along the vertical direction of the figure, the integrated passive bandpass filter includes a substrate 00, a first metal layer 01 on the substrate 00, and a second metal layer 02 on the first metal layer 01, with the first metal layer 01 and the second metal layer 02 spaced apart; wherein a capacitor dielectric layer 11 and a capacitor upper electrode 12 are sequentially stacked on the first metal layer 01, so that the capacitor dielectric layer 11, the capacitor upper electrode 12, and the corresponding first metal layer 01 constitute a capacitor structure, that is, the capacitor upper electrode 12 and its corresponding portion of the first metal layer 01 serve as the upper and lower electrodes of the capacitor structure, respectively. Figure 5The dashed box in the middle represents a single MIM planar capacitor; however, in this embodiment, there are multiple capacitor structures, and only one is shown in the figure. The upper electrodes 12 of each capacitor are connected to the second metal layer 02 via vias 13 to facilitate electrical connection with other components or external circuits; in other words, a capacitor dielectric layer 11, capacitor upper electrodes 12, and vias 13 are provided between the first metal layer 01 and the second metal layer 02; depending on circuit connection requirements, in areas where the capacitor dielectric layer 11 and capacitor upper electrodes 12 are not provided, the first metal layer 01 can also be connected to the second metal layer 02 vias 13.

[0103] The second metal layer 02 includes multiple winding structures, each of which serves as an inductor structure. In actual manufacturing, the winding structures can be obtained by patterning the metal layer, or in other words, the inductor structure is formed in the second metal layer 02.

[0104] An insulating layer 20 is also covered on the second metal layer 02. The insulating layer 20 is patterned to expose a portion of the second metal layer 02 for easy electrical connection with external circuits.

[0105] In this embodiment, the circuit traces in the filter are formed by connecting patterns formed on the aforementioned first metal layer 01 and second metal layer 02 to achieve the required electrical connection. The first metal layer 01 and second metal layer 02 can be... Figure 5 The connection via 13 shown is directly connected.

[0106] In the embodiments, the winding structure constituting the above-described inductor structure is not limited to... Figure 2 and Figure 3 The octagon shown can also be a circle, rectangle (including square), hexagon, or other spiral shapes. By adjusting parameters such as the line size, spacing, number of turns, and area occupied by the winding structure formed on the second metal layer 02, the inductance and quality coefficient of the inductor structure can be adjusted.

[0107] The capacitor structure can be set as a rectangular structure, that is, the relative shape of the two electrode plates is rectangular, more specifically, the shape of the upper electrode plate is rectangular; or the orthographic projection of the capacitor electrode plate 12 on the surface of the first metal layer 01 is rectangular; by adjusting the relative area of ​​the two electrode plates, the thickness of the dielectric layer and the relative permittivity, etc., the electrical parameters of the capacitor structure can be adjusted.

[0108] In a preferred embodiment, such as Figure 1 and Figure 3 As shown, the first filtering unit 100 specifically includes:

[0109] The first wire 111 is formed on the second metal layer 02, that is, the first wire 111 is obtained by patterning the second metal layer 02; the first wire 111 is connected to the input / output port PORT.

[0110] The fourth conductor 410 is formed in the first metal layer 01;

[0111] The first capacitor structure C1 is connected to the first wire 111 and the ground terminal GND;

[0112] The second capacitor structure C2 is connected to the first wire 111 and the fourth wire 410;

[0113] First inductor structure 112 ( Figure 3 The first inductor structure 112 (marked as L1) is formed on the second metal layer 02. One end of the first inductor structure 112 is connected to the first wire 111, and the other end is connected to the fourth wire 410.

[0114] Furthermore, such as Figure 3 As shown, the first inductor structure 112 includes a polygonal spiral, and the second capacitor structure C2 is disposed on one side of a short side of the first inductor structure 112; the first capacitor structure C1 and the second capacitor structure C2 are disposed on different sides of the first inductor structure 112.

[0115] Based on the internal circuit structure of the first filter unit 100, the circuit characteristic curve of the first filter unit 100 is as follows: Figure 7 As shown, the second capacitor structure C2 and the first inductor structure 112 in the first filter unit 100 are connected in parallel to realize the high-frequency zero on the right side of the passband. Figure 7 The S21 curve has a dip on the right side of the passband; while the first capacitor structure C1, located in the grounding branch, can ground the high-frequency signal and enhance the suppression of the high-frequency signal.

[0116] In the foregoing embodiments, the S21 curve of a single first filter unit is as follows: Figure 8 As shown by the dashed line, the S21 curves of the two first filter units arranged symmetrically and in series are as follows: Figure 8 As shown by the solid line in the figure, it can be seen that the S21 curves of the two symmetrical first filter units have a higher slope and stronger out-of-band suppression.

[0117] like Figure 9The figure shows the S11 curves of a single first filter unit and two first filter units symmetrically connected in series. It can be seen that the S11 characteristic of the symmetrical structure, represented by the solid line, exhibits a significant dip within the passband range of 1.6 GHz to 2.0 GHz in this embodiment, indicating good input port matching and better transmission characteristics within the passband. However, outside the passband (high-frequency region, right side of the figure), compared to a single circuit first filter unit, the S11 of the two first filter units in the symmetrical structure is closer to 0 dB, resulting in stronger signal reflection in the out-of-passband frequency band. Furthermore, the symmetrical structure of the two first filter units also contributes to the consistency of the signal reflection curves at the two input and output ports.

[0118] In the first filter unit 100, the high-frequency side zero of the passband is achieved by connecting the second capacitor structure C2 and the first inductor structure 112 in parallel. The high-frequency signal is transmitted to the ground plane by the first capacitor structure C1 in the ground branch, which increases the suppression of the high-frequency signal. Therefore, the capacitance of the first capacitor structure C1 is the smallest, that is, it does not exceed the capacitance of the second capacitor structure C2. Specifically, the ratio of the second capacitor structure C2 to the first capacitor structure C1 is 1:1 ≤ C2:C1 < 2:1. That is to say, the capacitance of the second capacitor structure C2 is greater than or equal to the capacitance of the first capacitor structure C1, and less than twice the capacitance of the first capacitor structure C1.

[0119] The second capacitor structure C2 and the first inductor structure 112 are connected in parallel, therefore their two ends need to be interconnected. Considering that the second capacitor structure C2 is relatively small and the first inductor structure 112 is relatively large, if the first inductor structure 112 is rectangular or octagonal, the second capacitor structure C2 can be placed near the middle of the short side of the first inductor structure 112, which facilitates connection and layout and is beneficial for miniaturization design. The first capacitor structure C1 and the second capacitor structure C2 can be arranged on different sides of the winding structure. This distributed layout helps to improve space utilization and reduce mutual interference between components.

[0120] like Figure 3 As shown, the second filtering unit 200 includes:

[0121] The second inductor structure 212 (marked as L2 in the figure) and the second wire 211 are both formed on the second metal layer 02, and one end of the second inductor structure 212 is connected to the second wire 211, and the other end is grounded;

[0122] The third capacitor structure C3 is connected to the fourth conductor 410 and the ground terminal;

[0123] The fourth capacitor structure C4 is connected to the second wire 211 and the fourth wire 410;

[0124] The fifth capacitor structure C5 is connected to the second conductor 211 and the ground terminal.

[0125] The arrangement of the third capacitor structure C3, the fifth capacitor structure C5, and the second inductor structure 212 (L2) in the three ground-connected branches of the second filter unit 200 can significantly suppress out-of-band rejection on both sides of the passband, while simultaneously forming a transmission pole at the center of the passband at 1.8 GHz. Figure 10 At the peak of the dashed line in S21, the signal transmission loss is relatively small at the transmission pole, which helps to reduce insertion loss within the passband. Similarly, using a symmetrical structure helps to increase the overall slope of the curve and the out-of-band suppression effect.

[0126] In this embodiment, the main capacitor of the second filter unit 200, namely the fourth capacitor structure C4, is mainly used to connect the first filter unit 100 and the third filter unit 300 on both sides, adjust the impedance matching on both sides, and optimize the insertion loss of the circuit. Therefore, the capacitance value of the fourth capacitor structure C4 is relatively large, and the capacitance ratio with that of the second capacitor structure C2 is C4:C2>4:1, that is, the capacitance value of the fourth capacitor structure C4 is more than 4 times the capacitance value of the second capacitor structure C2.

[0127] In the embodiments, since the capacitance of the fourth capacitor structure C4 is relatively large, the relative shape of the two electrode plates or the shape of the upper electrode plate can be a rectangular strip structure with a large length-to-width ratio; in the preferred embodiments, the long side direction of the two fourth capacitor structures C4 is perpendicular to the axis of symmetry, and the fourth capacitor structure C4 is located near the center of the "layout".

[0128] The fifth capacitor structure C5 and the second inductor structure 212 in one branch of the second filter unit 200 are connected to the ground terminal GND. Since the four components (C3 to C5 and L2) are relatively large, to reduce interference between components, the second inductor structure 212 and the second capacitor structure C2 are placed on the same side, i.e., both are located on... Figure 3 More specifically, on the upper side of the circuit, the second inductor structure 212 and the second capacitor structure C2 are both located on one side of the long side connecting the two fourth capacitor structures C4, in order to reduce the mutual interference between the first inductor structure 112 (L1) and the second inductor structure 212 (L2). Since there is mutual interference between the second inductor structure 212 and the main circuit fourth capacitor structure C4, spurious peaks may be generated outside the high-frequency band when they are placed close together. Therefore, there is a certain distance between the second inductor structure 212 and the fourth capacitor structure C4, preferably greater than 50μm. The second inductor structure 212 and the fifth capacitor structure C5 are both connected to GND. The ports of these four devices (i.e., the two second inductor structures 212 and the two fifth capacitor structures C5) are interconnected and can share a single ground terminal GND. Of course, they can also be split into four or two ground terminals GND as needed.

[0129] The first inductor structure 112 and the second inductor structure 212 are mainly used for frequency adjustment within the passband, with their frequency point located around 1.8 GHz. Therefore, their inductance values ​​are close, with the ratio of inductance values ​​between the first inductor structure 112 and the second inductor structure 212 being close to 1:1, and their area ratios also being close to 1:1. Specifically, the area ratio of the first inductor structure 112 and the second inductor structure 212 is 1:0.6 to 1:1.8; the ratio of inductance values ​​between the first inductor structure 112 and the second inductor structure 212 is 1:0.5 to 1:2.

[0130] In a typical embodiment, such as Figure 3 and Figure 4 As shown, the third filtering unit 300 includes:

[0131] The third inductor structure 312 (L3) and the third conductor 311 are both formed on the second metal layer 02, and one end of the third inductor structure 312 is connected to the third conductor 311, and the other end is connected to the ground terminal GND.

[0132] The fifth conductor 420 is formed in the first metal layer 01;

[0133] Two sixth capacitor structures C6 are connected to two second wires 211 respectively, and both are connected to the fifth wire 420, thus realizing the series connection between the two sixth capacitor structures C6;

[0134] The seventh capacitor structure C7 is connected to the fifth wire 420 and the third wire 311;

[0135] The eighth capacitor structure C8 is connected to the third conductor 311 and the ground terminal GND;

[0136] Because the second filter unit 200 includes an inductor (i.e., the second inductor structure 212), the traces between the second filter unit 200 and the first filter unit 100 and the third filter unit 300 may have longer additional traces due to this. Figure 1 As shown in the circuit schematic, the fourth capacitor structure C4 of the second filter unit 200 is directly connected to the sixth capacitor structure C6 of the third filter unit 300. In the actual product, the upper plates (located in the second metal layer) of the fourth capacitor structure C4 and the sixth capacitor structure C6 are directly interconnected; the lower plates (located in the first metal layer) of the fourth capacitor structure C4 and the sixth capacitor structure C6 are not directly connected, but are respectively connected to other components.

[0137] Because the fourth capacitor structure C4 is relatively large, one side length of the second metal layer corresponding to C4 is changed to be the same as that of the second metal layer corresponding to the sixth capacitor structure C6. In the top view, the second metal layers corresponding to the fourth capacitor structure C4 and the sixth capacitor structure C6 together form a rectangle with a large length-to-width ratio, i.e., a long strip shape. By setting the second metal layer corresponding to the upper plate of the fourth capacitor structure C4 and the sixth capacitor structure C6 as a long strip rectangle, the shape of the second metal layer is smoother, without protruding parts, reducing signal scattering at right angles, which is beneficial to signal transmission and provides better impedance matching.

[0138] Therefore, in a typical embodiment, such as Figure 3 and Figure 4 As shown, the second conductor 211 includes a long rectangular extension 2111, the length direction of which is perpendicular to the axis of symmetry. The fourth capacitor structure C4 is connected to the rectangular extension 2111. The second capacitor structure C2 and the second inductor structure 212 are located on the same side of the center line of the length direction of the rectangular extension 2111. The geometric centers of the first inductor structure 112 (L1) and the second inductor structure 212 (L2) are respectively located on both sides of the center line of the length direction of the rectangular extension 2111. The distance between the second inductor structure 212 and the fourth capacitor structure C4 along the axis of symmetry is greater than 50 μm.

[0139] The filter provided in this embodiment has a total of five inductor structures. Two first inductor structures 112 are identical and symmetrically arranged, two second inductor structures 212 are identical and symmetrically arranged, and the third inductor structure 312 is a separate structure. For example... Figure 3 As shown, the first inductor structure 112 is located in the middle of the horizontal direction of the filter layout structure (the axis of symmetry extends along the vertical direction), and the second inductor structure 212 and the third inductor structure 312 are located on both sides along the vertical direction in the figure. This layout is mainly to increase the distance between each spiral inductor and reduce the mutual interference between inductors.

[0140] The inductance value formed by the third inductor structure 312 is mainly used to adjust the out-of-band rejection at low frequencies, and it mainly adjusts the out-of-band rejection at 1 GHz. Therefore, its inductance value is relatively large. The ratio of the inductance values ​​of the third inductor structure 312 to the second inductor structure 212 is 1.5:1 to 4:1. The ratio of the area occupied by the third inductor structure 312 and the second inductor structure 212 is 1.2:1 to 3:1.

[0141] In the foregoing embodiments, such as Figure 11 As shown, the circuit structure of the third filter unit 300 adds a new transmission pole in the passband, which is beneficial to increase the passband width and reduce transmission loss.

[0142] In the third filter unit, the two sixth capacitor structures C6 form a branch through the fifth wire 420. This branch is a series connection between the seventh capacitor structure C7 and the resonant unit (the parallel connection of the eighth capacitor structure C8 and the third inductor structure 312 constitutes one resonant unit). This structure adds a new transmission pole in the passband, which helps to increase the passband width and reduce transmission loss. The eighth capacitor structure C8 mainly adjusts the high-frequency out-of-band rejection, so its capacitance value is relatively small, usually in the pF range, generally close to that of the first capacitor structure C1. The ratio of the capacitance values ​​of the eighth capacitor structure C8 and the first capacitor structure C1 is 1:2 to 2:1, close to 1:1. The eighth capacitor structure C8 is connected in parallel with the third inductor structure 312 and then connected to the ground terminal GND. If the third inductor structure 312 is rectangular or octagonal, the eighth capacitor structure C8 can be placed on one side of the short side of the third inductor structure 312, close to the middle of the short side, which facilitates connection and layout and is beneficial for miniaturization design. Other shapes are connected according to the circuit principle.

[0143] To reduce mutual interference between inductors formed by different winding structures, in a typical embodiment, such as Figure 3 and Figure 4 As shown, the second conductor 211 includes the aforementioned rectangular extension 2111, the fourth capacitor structure is connected to one end of the rectangular extension 2111, and the sixth capacitor structure C6 is connected to the other end of the rectangular extension 2111; the second inductor structure 212 and the third inductor structure 312 are respectively disposed on both sides of the center line of the length direction of the rectangular extension 2111.

[0144] The following is combined Figure 12 The manufacturing process route of the filter provided in the embodiments of this application is explained, and the process route is only an example.

[0145] S1. Forming an insulating layer on the substrate surface

[0146] The substrates mentioned above can include common substrates such as silicon, glass, ceramics, and gallium arsenide. Before forming the insulating layer, the substrate can be cleaned using various solvents such as acids and organic solvents to remove surface contaminants. Subsequently, the insulating layer is fabricated on the clean substrate surface. The insulating layer can be an inorganic insulating layer, such as silicon oxide or silicon nitride, or an organic material, such as resin or polyimide. The specific method of forming the insulating layer can be determined based on the specific insulating material, such as by spin coating or deposition. The thickness of the insulating layer is generally 0.1-10 μm.

[0147] S2. Forming a first metal layer on the substrate surface

[0148] The first metal layer serves as both the lower electrode of the capacitor structure and the connection structure between the capacitor and the inductor. Its formation steps include: first, patterning the insulating layer to expose the substrate surface; then, depositing a metal layer on the patterned insulating layer. The metal material can include conductive materials or alloys such as gold, silver, aluminum, and copper, or it can be a composite structure of multiple metal layers; finally, planarizing the metal layer using processes such as chemical mechanical polishing (CMP) to obtain a smooth metal layer surface. In the figure, the metal layer and the patterned insulating layer are coplanar, and the patterned insulating layer provides support and isolation for the metal layer.

[0149] S3. A capacitor dielectric layer and an upper electrode are sequentially formed on the first metal layer.

[0150] A dielectric material layer and a metal material layer are sequentially formed on the first metal layer and the insulating layer. Then, the metal material layer and the dielectric material layer are patterned to obtain the metal layer and the capacitor dielectric layer that serve as the upper electrode.

[0151] The dielectric layer of the capacitor can be made of highly insulating materials such as ceramics, silicon nitride, and alumina, while the metal material can be the metal material commonly used to manufacture the electrode plates of the capacitor.

[0152] The first metal layer, the capacitor dielectric layer, and the upper electrode plate together constitute several capacitor structures, one of the functions of the first metal layer is to serve as the lower electrode plate of the corresponding capacitor structure.

[0153] S4. Form an electrical connection structure that leads out the first metal layer and the upper electrode plate.

[0154] An insulating layer is formed on the first metal layer and the upper electrode plate, and the insulating layer is patterned to form a connection via. The connection via exposes part of the surface of the upper electrode plate and part of the surface of the first metal layer. Then, a metal material layer is deposited and patterned or planarized. The metal material layer in other areas is removed, and the metal material layer in the connection via is retained to obtain a metal plug. Then, a patterned insulating layer is formed on the insulating layer and the metal plug, and the patterned insulating layer exposes the metal plug. Finally, a patterned metal material layer is filled in the patterned insulating layer. The patterned metal material layer serves as the second metal layer, which together with the metal plug forms an electrical connection structure to realize the lead-out of the first metal layer and the upper electrode plate.

[0155] S5, Forming an insulating layer

[0156] A patterned insulating layer is fabricated, which is mainly used to protect the surface of the device from oxidation, wear, etc. In addition, the patterned insulating layer exposes part of the surface of the second metal layer to facilitate electrical connection with external circuitry.

[0157] The above process omits some well-known steps, such as back-side thinning of the substrate.

[0158] In a typical embodiment, such as Figure 3 As shown, the symmetrical structure region has multiple ground terminals GND and two input / output ports PORT located at the edge of the integrated passive bandpass filter; the asymmetrical structure region has one ground terminal GND located on one side of the axis of symmetry.

[0159] In the aforementioned embodiments, the input / output ports (PORT) and ground (GND) are located around the perimeter of the device, which can effectively match the soldering and wire bonding packaging structure of the back metal layer, and also match the flip-chip soldering package. The packaging method is as follows... Figure 13 , 14 As shown. Among them. Figure 13 This is a schematic diagram of a package structure with gold bonding and wire bonding. The substrate is etched to create openings, exposing a portion of the first metal layer. Metal is then filled into the through-holes. The through-hole structure connects the ground terminal (GND) to the back side. This patent does not specify the method of metal filling; in-hole gold plating or other methods can be used. Furthermore, a full-surface metal layer (back metal layer) can be formed on the back side of the substrate, serving as a ground plane and facilitating subsequent soldering. The signals at the input / output ports (PORTs) formed on the second metal layer on the front side can be connected to the outside via wire bonding, enabling filter applications.

[0160] Figure 14 This paper illustrates another method of filter usage, where a flip-chip metal structure is fabricated at the output port (PORT) and the ground terminal (GND) opening. This structure can be made of various conductive materials such as solder balls, copper pillars, and gold balls. This allows the filter components to be electrically connected to the substrate and chip via flip-chip bonding, enabling miniaturization. Since the area of ​​flip-chip bonding is reduced compared to full-surface bonding, additional soldering positions are added around the chip to increase structural stability. These soldering positions are not directly connected to the filter and do not affect the device characteristics. The added soldering positions in the surrounding blank areas effectively increase the number and area of ​​connections between the filter and the substrate. The symmetrical addition around the perimeter also contributes to the overall structural stability and improves reliability.

[0161] The dimensions of these two packaging structures are basically the same, and the height of the flip-chip structure and the substrate via is basically in the range of 50-500μm.

[0162] In summary, the integrated passive bandpass filter provided in this application embodiment has the characteristics of small size and wide bandwidth. The filter achieves bandpass filtering function with center frequency at GHz through a semi-symmetrical structure, and has the characteristics of wide bandwidth, high out-of-band rejection and high roll-off.

[0163] In addition, using a capacitor structure as part of the trace connecting the two metal layers reduces the device size and optimizes the inductor distribution to reduce mutual interference between inductors.

[0164] The filter structure provided in this application has good versatility and can be matched with flip-chip soldered package structures as well as package structures with gold back soldered wire bonding.

[0165] This application provides the following two comparative examples to further illustrate the embodiments of this application.

[0166] Comparative Example 1

[0167] Comparative Example 1 uses a fully symmetrical structure, and its circuit principle is as follows: Figure 15 As shown, it also contains three filtering units. The difference from the previous embodiment is that there are two third filtering units in Comparative Example 1, and they are also symmetrically arranged. For easy distinction, the main circuit of the third filtering unit includes two capacitors connected in series, denoted as C6 and C9, respectively. The capacitance values ​​of C6 and C9 are the same. In the previous embodiment, the third filtering unit in the filter is one, and at least part of its structure is asymmetrical.

[0168] The layout structure corresponding to Comparative Example 1 is as follows: Figure 16 As shown, the two third filter units 300 are arranged symmetrically in a mirror image. To avoid interference and also to achieve miniaturization, the first filter units 100 on both sides are relatively small. Figure 3 It is further away from the third filter unit.

[0169] like Figure 16 As shown, due to the large size of the two inductors L3, the spacing between inductors L1 and L2 is compressed, and the distance between the two inductors L3 is also small. Simulation results show that crosstalk spikes appear at high frequencies, affecting the out-of-band rejection characteristics of the device. Conversely, to avoid crosstalk, the spacing between all components is increased, which obviously does not meet the requirements of miniaturization design.

[0170] Compared with the scheme in Comparative Example 1 that uses two third filter units with a symmetrical structure, the single asymmetrical third filter unit in the aforementioned embodiment can directly reduce the area occupied by the third filter unit, adapting to the miniaturization trend. Meanwhile, in the symmetrical structure of Comparative Example 1, since the third filter unit is located at the center of the layout, the two inductor winding structures are directly adjacent, which will lead to increased mutual interference between inductors, affecting the performance of the filter. Increasing the distance will further increase the layout area, which is not conducive to miniaturization.

[0171] Comparative Example 2

[0172] The circuit principle of Comparative Example 2 is the same as that of the aforementioned embodiments of this application. Figure 1As shown, however, the layout of Comparative Example 2 differs from the aforementioned embodiments.

[0173] like Figure 17 As shown, in Comparative Example 2, L1 and L2 are located on the same side (upper side), while in the aforementioned embodiment, the geometric centers of the first inductor structure and the second inductor structure are respectively located on both sides of the center line of the length direction of the rectangular extension. That is, in the aforementioned embodiment, the first inductor structure and the second inductor structure are staggered in the longitudinal direction.

[0174] In Comparative Example 2, to avoid / reduce mutual interference, the spacing between L1 and L2 (horizontally in the figure) is relatively large. Since L3 is larger, it is also located on the opposite side of the center (vertically). With this layout, four inductors (two L1s and two L2s) are distributed on one side of the layout, and one inductor L3 is distributed on the other side. There are some blank areas on both sides of L3. Therefore, the space utilization of this layout is not high, and the overall size of the filter (the area it occupies) is larger than that in the previous embodiments. Figure 3 The layout shown has increased by about 1.2 times.

[0175] It should also be noted that the above dimensions are calculated omitting the port (PORT) and ground (GND). In reality, it's easy to understand that adding the port and ground would further increase the dimensions, potentially making them larger than [the specified value]. Figure 3 The layout shown is 1.3 times larger than the one in Comparative Example 2. While the layout shown in Comparative Example 2 also achieves correct functionality and performance... Figure 3 The structure shown is similar, but its size is large, making it difficult to meet the needs of miniaturized applications.

[0176] A comparison reveals that, compared to Comparative Example 2, the solution described in the aforementioned embodiments, especially... Figure 3 The layout shown makes full use of the space structure, reduces mutual interference between inductors, and is conducive to product miniaturization.

[0177] The above are merely some specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An integrated passive bandpass filter, characterized in that, It has a symmetrical structure region and an asymmetrical structure region; the symmetrical structure region has an axis of symmetry and the structures therein are arranged axially symmetrically, the axis of symmetry passes through the asymmetrical structure region, and the structures in the asymmetrical structure region are arranged asymmetrically with respect to the axis of symmetry; The integrated passive bandpass filter includes: Two first filter units (100) are disposed in the symmetrical structure area, and the first filter units (100) are connected to the input and output ports located on the same side of the symmetrical axis; Two second filter units (200) are disposed in the symmetrical structure region, and the second filter units (200) are connected to the first filter unit (100) located on the same side of the symmetrical axis; The third filter unit (300) is at least partially disposed in the asymmetric structure region, and the third filter unit (300) is connected to the two second filter units (200).

2. The integrated passive bandpass filter according to claim 1, characterized in that, The integrated passive bandpass filter includes: Substrate (00) and a first metal layer (01) located on the substrate (00); The second metal layer (02) is located on the first metal layer (01) and spaced apart from the first metal layer (01). The first metal layer (01) is connected to the second metal layer (02) through a connecting via (13). The second metal layer (02) includes multiple winding structures to serve as multiple inductor structures. The capacitor dielectric layer (11) and the capacitor upper electrode (12) are stacked sequentially on the first metal layer (01) and together with the first metal layer (01) form multiple capacitor structures; the capacitor upper electrode (12) is connected to the second metal layer (02) through a connecting via (13).

3. The integrated passive bandpass filter according to claim 2, characterized in that, The first filtering unit (100) includes: The first conductor (111) and the first inductor structure (112) are both formed on the second metal layer (02), and the first conductor (111) is connected to the input and output ports; The first capacitor structure is connected to the first wire (111) and the ground terminal; The second capacitor structure is connected to the first wire (111) and the fourth wire (410); One end of the first inductor structure (112) is connected to the first wire (111), and the other end is connected to the fourth wire (410). The fourth conductor (410) is formed on the first metal layer (01).

4. The integrated passive bandpass filter according to claim 3, characterized in that, The first inductor structure (112) includes a polygonal spiral, and the second capacitor structure is disposed on one side of a short side of the first inductor structure (112); The first capacitor structure and the second capacitor structure are disposed on different sides of the first inductor structure (112); The ratio of the capacitance values ​​of the second capacitor structure to those of the first capacitor structure is greater than or equal to 1:1 and less than 2:

1.

5. The integrated passive bandpass filter according to claim 3, characterized in that, The second filtering unit (200) includes: The second conductor (211) and the second inductor structure (212) are both formed on the second metal layer (02); The third capacitor structure is connected to the fourth conductor (410) and the ground terminal; A fourth capacitor structure is connected to the second wire (211) and the fourth wire (410); The fifth capacitor structure is connected to the second conductor (211) and the ground terminal; One end of the second inductor structure (212) is connected to the second conductor (211), and the other end is connected to the ground terminal.

6. The integrated passive bandpass filter according to claim 5, characterized in that, The second conductor (211) includes a rectangular extension (2111), the length direction of which is perpendicular to the axis of symmetry, and the fourth capacitor structure is connected to the rectangular extension (2111). The second capacitor structure and the second inductor structure (212) are disposed on the same side of the center line of the length direction of the rectangular extension (2111); The geometric centers of the first inductor structure (112) and the second inductor structure (212) are respectively located on both sides of the center line of the length direction of the rectangular extension (2111).

7. The integrated passive bandpass filter according to claim 5, characterized in that, The area ratio of the first inductor structure (112) and the second inductor structure (212) is 1:0.6 to 1:1.8; The ratio of the inductance values ​​of the first inductor structure (112) and the second inductor structure (212) is from 1:0.5 to 1:2; The ratio of the capacitance values ​​of the fourth capacitor structure to those of the second capacitor structure is greater than 4:

1.

8. The integrated passive bandpass filter according to claim 5, characterized in that, The third filtering unit (300) includes: The third conductor (311) and the third inductor structure (312) are both formed on the second metal layer (02). Two sixth capacitor structures are respectively connected to two second wires (211), and both are connected to the fifth wire (420); The seventh capacitor structure is connected to the fifth wire (420) and the third wire (311); The eighth capacitor structure is connected to the third conductor (311) and the ground terminal; One end of the third inductor structure (312) is connected to the third conductor (311), and the other end is connected to the ground terminal; The fifth conductor (420) is formed on the first metal layer (01).

9. The integrated passive bandpass filter according to claim 8, characterized in that, The third inductor structure (312) includes a polygonal spiral, and the eighth capacitor structure is disposed on one side of a short side of the third inductor structure (312). The ratio of the inductance values ​​of the third inductor structure (312) to the second inductor structure (212) is 1.5:1 to 4:1; The area ratio of the third inductor structure (312) to the second inductor structure (212) is 1.2:1 to 3:1; The ratio of the capacitance value of the eighth capacitor structure to that of the first capacitor structure is 1:2 to 2:

1.

10. The integrated passive bandpass filter according to claim 8, characterized in that, The second conductor (211) includes a rectangular extension (2111), the length direction of which is perpendicular to the axis of symmetry. The fourth capacitor structure is connected to one end of the rectangular extension (2111), and the sixth capacitor structure is connected to the other end of the rectangular extension (2111). The second inductor structure (212) and the third inductor structure (312) are respectively disposed on both sides of the center line of the length direction of the rectangular extension (2111).

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