High out-of-band rejection interdigital filter based on TSV mixed wavelength SIR resonator and design method thereof

Abstract

The invention discloses a high out-of-band rejection interdigital filter based on a TSV mixed wavelength SIR resonator. The high out-of-band rejection interdigital filter comprises an RDL silicon dioxide layer, a third resonance RDL and a second resonance RDL which are nested together are arranged on the RDL silicon dioxide layer, a first resonance RDL is arranged on the outer side of the second resonance RDL, a fourth resonance RDL is arranged on the outer side of the third resonance RDL, and the first resonance RDL is connected with a grounding copper plate through a first TSV cylinder; the fourth resonance RDL is connected with the grounding copper plate through the second TSV cylinder, and the first TSV cylinder and the second TSV cylinder are both located in the silicon substrate. The invention further discloses a design method of the high out-of-band rejection interdigital filter based on the TSV mixed wavelength SIR resonator. The problems that an existing interdigital filter is high in insertion loss, insufficient in out-of-band rejection and large in occupied area are solved.

Description

Technical Field

[0001] This invention belongs to the field of filter technology and relates to a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator. This invention also relates to a design method for a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator. Background Technology

[0002] Filters play a crucial role in wireless communication systems and are widely used in radio frequency (RF) front-ends. Filters select useful frequency components of a signal to pass through while significantly attenuating other unwanted frequency components. Utilizing this frequency selection capability, interference noise can be filtered out or spectral analysis can be performed, ensuring the stability and reliability of the system.

[0003] With the continuous development of wireless communication technology, the mid- and low-frequency bands have long been occupied by traditional communication, broadcasting, television, and satellite navigation services, resulting in extremely limited mid- and low-frequency spectrum resources. However, the millimeter-wave band still has abundant untapped spectrum resources, and it possesses characteristics such as low latency, high resolution, and strong anti-interference capabilities. Furthermore, the short wavelength of millimeter waves facilitates device miniaturization, aligning with current trends in electronic technology development.

[0004] Traditional interdigital filters are typically only suitable for low to mid-frequency bands, and generally suffer from high insertion loss and insufficient out-of-band rejection in the millimeter-wave band. Furthermore, due to their large size, traditional filters struggle to meet the high integration requirements of current devices. Summary of the Invention

[0005] The purpose of this invention is to provide a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator, which solves the problems of high insertion loss, insufficient out-of-band rejection, and large area occupation of existing interdigital filters.

[0006] Another objective of this invention is to provide a design method for a high out-of-band suppression interdigital filter based on a TSV hybrid wavelength SIR resonator.

[0007] The technical solution adopted in this invention is a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator, including an RDL silicon dioxide layer, on which nested third and second resonant RDLs are provided. A first resonant RDL is provided outside the second resonant RDL, and a fourth resonant RDL is provided outside the third resonant RDL. The first resonant RDL is connected to a grounded copper plate through a first TSV cylinder; the fourth resonant RDL is connected to a grounded copper plate through a second TSV cylinder. Both the first and second TSV cylinders are located within a silicon substrate.

[0008] The first technical solution of this invention is further characterized by: The first resonant RDL is connected to the input terminal of the RDL tap; the fourth resonant RDL is connected to the output terminal of the RDL tap.

[0009] Both the RDL tap input and RDL tap output terminals are located on the RDL silicon dioxide layer.

[0010] The third resonant RDL has the same structure as the second resonant RDL, both being U-shaped structures. The third resonant RDL is positioned opposite to and nested with the second resonant RDL.

[0011] Both the third resonant RDL and the second resonant RDL include two sets of step-type metal RDLs. Each set of step-type metal RDLs includes a low-impedance segment RDL and a high-impedance segment RDL connected in sequence.

[0012] The first resonant RDL and the fourth resonant RDL have the same structure.

[0013] The first resonant RDL consists of a low-impedance segment RDL and a high-impedance segment RDL connected in sequence.

[0014] The second technical solution adopted in this invention is a design method for a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator. The specific process involves combining a quarter-wavelength step impedance resonator RDL with a half-wavelength step impedance resonator RDL, introducing transmission zeros on both sides of the passband. When the transmission line resonates, the impedance ratio of the SIR... R Z As shown in the following formula (1): (1).

[0015] The beneficial effects of this invention are as follows: This invention is a compact, high out-of-band rejection interdigital filter based on TSV and employing a hybrid wavelength SIR resonator. This invention uses a hybrid RDL (Resonant Line Array) with a quarter-wavelength step impedance and a half-wavelength step impedance as the resonator of the filter. The impedance step design effectively reduces the resonator size, and the use of a hybrid wavelength resonator effectively reduces the overall size of the filter. Utilizing the centrally symmetrical arrangement of the half-wavelength step impedance metal line RDL, cross-coupling is achieved, successfully introducing transmission zeros on both sides of the passband and improving the out-of-band rejection characteristics of the filter. Insertion loss attenuation to -48dB in the left passband at 33.8GHz and to -56dB in the right passband at 79.7GHz are achieved. Extending the high-impedance sections of the resonators at the input and output ends improves return loss while increasing the effective coupling area and improving bandwidth. The filter achieves excellent performance with insertion loss less than 1.5dB and return loss better than 25dB. Utilizing the low-loss electrical characteristics of TSV, the signal transmission path is significantly shortened, effectively improving the transmission speed of millimeter-wave signals. Compared to ordinary microstrip filters, this filter boasts advantages such as operating in the millimeter-wave band, broad application prospects, relatively larger bandwidth, compact structure, and high out-of-band rejection. Based on TSV implementation, this invention can be used not only as a standalone component but also interconnected with chips via RDL on the substrate, enabling three-dimensional integrated packaging and widespread application in various wireless communication systems. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a quarter-wavelength step impedance resonator; Figure 2 This is a schematic diagram of a half-wavelength step impedance resonator. Figure 3 This is a curve showing the variation of the coupling coefficient between adjacent resonators with the spacing in the high out-of-band suppression interdigital filter design method based on TSV hybrid wavelength SIR resonators of this invention; Figure 4 This is the S-parameter curve of the interdigital bandpass filter in the high out-of-band suppression interdigital filter design method based on TSV hybrid wavelength SIR resonator of this invention; Figure 5 This is an isometric view of the high out-of-band suppression interdigital filter based on a TSV hybrid wavelength SIR resonator according to the present invention; Figure 6 This is a cross-sectional view of the first and fourth resonant RDLs of the high out-of-band suppression interdigital filter based on the TSV hybrid wavelength SIR resonator of this invention.

[0017] In the figure, 1. RDL tap input terminal, 2. First resonant RDL, 3. First TSV cylinder, 4. Second resonant RDL, 5. Third resonant RDL, 6. Fourth resonant RDL, 7. RDL tap output terminal, 8. Second TSV cylinder, 9. RDL silicon dioxide layer, 10. TSV copper layer, 11. Ground copper plate, 12. Silicon substrate, 13. TSV silicon dioxide layer. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 This invention relates to a compact, high out-of-band rejection interdigital filter based on a TSV (Transient Voltage Filter) employing a hybrid wavelength SIR (Stepped Impedance Resonator). It includes a metal line RDL (Rapid Line Filter), with the input and output RDLs connected to the TSV cylinder. A silicon substrate is used, and tapped input structures are employed at the input and output ends of the RDL. This invention achieves basic filtering functionality through the design of a fourth-order bandpass filter. The TSV serves as the path connecting the upper RDL to the lower grounded copper plate. Miniaturization is achieved by combining a quarter-wavelength step impedance with a half-wavelength step impedance RDL resonator. Furthermore, the centrally symmetrical coupling design of the half-wavelength resonator introduces cross-coupling and a transmission zero, thereby achieving the target performance of high out-of-band rejection.

[0020] Example 2 This invention relates to a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator. The design principle employed is as follows: This invention uses a Chebyshev response low-pass filter as a prototype, combining a quarter-wavelength step impedance resonator with a half-wavelength step impedance resonator. Transmission zeros are introduced on both sides of the passband to improve out-of-band rejection, achieving both filter compactness and high signal filtering performance. The structural principles of the quarter-wavelength and half-wavelength step impedance resonators are as follows: Figure 1 , 2 As shown; when the transmission line resonates, the impedance ratio of SIR is... R Z As shown in the formula: (1) The structure of a step impedance resonator is divided into a high-impedance section and a low-impedance section, where Z1 is the impedance of the high-impedance section and Z2 is the impedance of the low-impedance section; θ1 and θ2 are the electrical lengths of the high-impedance section. By adjusting the impedance ratio of the high-impedance and low-impedance sections, the spurious frequency of the filter is moved away from the passband, and the filter design area is reduced. To achieve the design frequency, the total length of the resonator is determined based on the center operating frequency of the filter.

[0021] Example 3 The spacing between resonators is determined by the coupling coefficient between them. The coupling coefficient in the filter circuit model is derived from the normalized conductance of the interdigital capacitor structure and characterizes the coupling strength between the resonators. This method of determining the spacing between resonators using the coupling coefficient is widely applicable to any form of coupled resonant filter, offering considerable versatility and flexibility. The coupling coefficient of the filter circuit model is used... M N，N+1 express: (2) in, FBW (Fractional Bandwidth) is the fractional bandwidth of the filter. g N and g N+1 In the low-pass prototype filter, the first... N , N +1 normalized value of the component.

[0022] Coupling coefficient between adjacent resonator units K i，i+1 Directly expressed as the coupling strength between adjacent resonators: (3) in, f 1 and f 2 represents the two resonant frequencies generated by the splitting of the resonant frequency after coupling between two adjacent resonators. When the coupling coefficient K between adjacent resonators is equal to the coupling coefficient M in the filter circuit model, the spacing between adjacent resonators in the filter can be determined. During design, models of adjacent resonators are built using HFSS software, and the relationship curve between the coupling coefficient and the spacing is simulated to determine the spacing between the corresponding resonators. Taking the spacing between the first and second resonators as an example, the specific relationship is as follows... Figure 3 As shown; from Figure 3 It can be seen that as the spacing between resonators increases, the coupling strength between resonators decreases, and therefore the coupling coefficient decreases. In the design, the simulation results are matched with the theoretical calculation results. When the two match, the final distance between adjacent resonators can be determined.

[0023] Example 4 This invention employs a centrally symmetrical arrangement of half-wavelength step impedance resonators, enabling cross-coupling between them and introducing transmission zeros on both sides of the passband, thereby improving the out-of-band rejection performance of the filter. The final design is a centrally symmetrical structure with one end of the terminating resonator short-circuited and the other open-circuited. The terminating resonator functions as an impedance converter and external circuit connection within the filter, without affecting the circuit conversion itself. To facilitate on-chip integration, the resonators utilize an RDL (Redistribution Layer), and the short-circuiting of the terminating resonator employs TSV (Through Silicon Via) technology, reducing transmission loss in the U-band and further minimizing the size of the bandpass filter.

[0024] To verify and analyze the final performance of the filter, this invention employs HFSS software for full-wave simulation. HFSS, developed by Ansys, is a three-dimensional high-frequency electromagnetic field simulation software widely used in the design and analysis of microwave, radio frequency, and high-speed electronic devices. Based on the finite element method (FEM), this software accurately solves for the electromagnetic characteristics of complex structures, such as S-parameters, field distribution, and antenna gain, through adaptive mesh generation technology. Its applications cover antenna design, filter optimization, and electromagnetic compatibility analysis. With its high-precision calculations, parametric modeling, and powerful post-processing capabilities, HFSS has become an industry standard tool in the field of high-frequency electromagnetic simulation. Since the error between the HFSS simulation results and the fabrication measurement results is small, the specific performance of this invention can be verified and compared with the expected results using HFSS software; the simulation results have reference value. The S-parameter simulation results of this invention are as follows: Figure 4 As shown; Example 5 The simulation results were analyzed. The red curve in the figure represents the S21 insertion loss, which characterizes the energy loss of electromagnetic waves in the filter after entering the circuit. A lower insertion loss indicates higher signal transmission efficiency. The green curve represents the S11 return loss, which characterizes the filter's ability to reflect input power, reflecting the degree of signal attenuation. A higher value indicates less reflection and better impedance matching. The figure clearly shows that this invention successfully introduces transmission zeros on both sides of the passband, improving out-of-band rejection, and the performance meets design expectations. Analyzing specific performance, m1 indicates an insertion loss of approximately 0.83dB at the center frequency; m2 indicates an insertion loss attenuating to -56dB at 79.7GHz; m3 indicates the worst return loss in the passband exceeding 25.7dB; and m4 indicates an insertion loss attenuating to -48dB at 33.8GHz. The overall filter area is 0.55 × 0.52 mm². 2Compared with existing millimeter-wave bandpass filters, the filter designed in this invention exhibits excellent out-of-band suppression, return loss, and insertion loss performance.

[0025] This invention employs a hybrid RDL (Relative Dynamic Range) with both quarter-wavelength and half-wavelength step impedance forms as the resonator of the filter. The impedance step design effectively reduces the resonator size. The use of hybrid wavelength resonators further reduces the overall size of the filter. Extending the high-impedance sections of the resonators at the input and output ends improves return loss while increasing the effective coupling area and bandwidth. Utilizing a centrally symmetrical arrangement of the half-step impedance metal wire RDL, cross-coupling is achieved, successfully introducing transmission zeros on both sides of the passband and improving the filter's out-of-band rejection characteristics. The filter of this invention achieves an insertion loss attenuation of -56dB on the right passband at 79.7GHz and an insertion loss attenuation of -48dB on the left passband at 33.8GHz, with an insertion loss of less than 1.5dB and a return loss better than 25dB. The metal line RDL includes an RDL wiring layer, on which a silicon dioxide layer is disposed. The short-circuit terminals of the first resonant RDL 2 and the fourth resonant RDL 6 wiring layers are connected to the TSV copper pillars. The two edge-coupled RDL lines of the filter serve as the input and output of the filter, respectively.

[0026] Example 6 like Figure 5 As shown, this filter is a fourth-order filter with four resonant RDLs. The step-type metal RDLs are divided into low-impedance RDLs and high-impedance RDLs. These include the first resonant RDL2, the second resonant RDL4, the third resonant RDL5, and the fourth resonant RDL6. The first resonant RDL2 and the second resonant RDL4, the second resonant RDL4 and the third resonant RDL5, and the third resonant RDL5 and the fourth resonant RDL6 interact through positive coupling.

[0027] The total length of the wiring layers in the first resonant RDL 2 and the fourth resonant RDL 6 is 449 μm. The low-impedance segment is 184 μm long, and the high-impedance segment is 265 μm long. The wiring layer width of the low-impedance segment is 50 μm, the wiring layer width of the high-impedance segment is 10 μm, and the thickness of the RDL wiring layer is 3 μm. The second resonant RDL 4 and the third resonant RDL 5 have a U-shaped structure, specifically with low-impedance RDL segments at both ends and a high-impedance RDL segment in the middle. The low-impedance RDL segment is 184 μm long and 50 μm wide. The high-impedance RDL segment is divided into three parts: two parallel to the directions of the first resonant RDL 2 and the fourth resonant RDL 6, and one perpendicular to the directions of the first resonant RDL 2 and the fourth resonant RDL 6. The RDL segment parallel to the directions of the first resonant RDL 2 and the fourth resonant RDL 6 is 245 μm long. The 6-direction perpendicular RDL segment is 152μm long. A 10μm 45° chamfer is used at the junction of the RDL segments parallel to and perpendicular to the first resonant RDL 2 and the fourth resonant RDL 6. The high-impedance RDL wiring layer is 10μm wide and 3μm thick. The RDL tap input terminal 1 and RDL tap output terminal 7 are located 211μm from the ground terminals of the first resonant RDL 2 and the fourth resonant RDL 6. Both RDL tap input 1 and RDL tap output 7 are 10μm wide and 116μm long. There are two TSV cylinders, which are copper TSV cylinders formed by subtracting two concentric cylinders. The inner cylinder is electroplated copper for signal transmission, and the outer layer uses silicon dioxide as an insulating layer to isolate the silicon substrate from the conductive material. In the first TSV cylinder 3 and the second TSV cylinder 8 (see structure...), Figure 6The radius of the TSV copper layer 10 is 4.7 μm, the thickness of the TSV silicon dioxide layer 13 outside the TSV copper layer 10 is 0.3 μm, and the height of the first TSV cylinder 3 and the second TSV cylinder 8 is 100 μm; the horizontal distance between the first resonant RDL 2 and the second resonant RDL 4 is 15 μm, and the vertical distance between the low impedance segment of the first resonant RDL 2 and the low impedance segment of the second resonant RDL 4 is 8 μm; the horizontal distance between the second resonant RDL 4 and the third resonant RDL 5 is 24 μm on the near side and 78 μm on the far side, the vertical distance between the low impedance segment of the second resonant RDL 4 and the low impedance segment of the third resonant RDL 5 is 8 μm, and the vertical distance between the low impedance segment of the second resonant RDL 4 and the high impedance segment of the third resonant RDL 5 is 23 μm; the horizontal distance between the third resonant RDL 5 and the fourth resonant RDL 6 is 15 μm, and the vertical distance between the low impedance segment of the third resonant RDL 5 and the high impedance segment of the fourth resonant RDL 6 is 15 μm. The vertical distance of the low-impedance section is 8μm; each resonant RDL is covered with a 5μm thick RDL silicon dioxide layer 9. The first TSV cylinder 3 and the second TSV cylinder 8 are grounded TSVs to reduce filter transmission loss and transmission delay. The first TSV cylinder 3 and the second TSV cylinder 8 are centrally symmetrical; the distance between the center of the first TSV cylinder 3 and the short-circuit terminal of the first resonant RDL 2 is 5μm; the distance between the center of the second TSV cylinder 8 and the short-circuit terminal of the fourth resonant RDL 6 is 5μm.

[0028] This invention combines a quarter-wavelength step impedance resonator with a half-wavelength step impedance resonator, significantly reducing the filter area while introducing new transmission zeros through cross-coupling, improving out-of-band rejection and overall filter performance, thus achieving excellent filtering performance in the U-band. The technical problem solved is enabling traditional microstrip filters to be used in the millimeter-wave band while achieving a more compact and miniaturized structure through the mixed use of different wavelength SIR resonators. Furthermore, the design of the resonator arrangement creates cross-coupling, introducing transmission zeros on both sides of the passband, achieving superior high out-of-band rejection performance. The use of three-dimensional integration technology further enhances its integration density. TSV technology, as a core technology of advanced semiconductor packaging, is widely used in 2.5D-IC and 3D-IC. TSV can be combined with traditional filters, utilizing its low transmission loss and low transmission delay electrical characteristics to obtain microwave filters with low transmission loss, wide bandwidth, small size, and high integration density. In addition, the compact high out-of-band rejection interdigitated filter based on TSV using mixed-wavelength SIR resonators offers excellent performance and better integration with other RF modules.

Claims

1. A high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator, characterized in that: The RDL includes a silicon dioxide layer (9), on which nested third resonant RDL (5) and second resonant RDL (4) are provided. A first resonant RDL (2) is provided outside the second resonant RDL (4), and a fourth resonant RDL (6) is provided outside the third resonant RDL (5). The first resonant RDL (2) is connected to a grounded copper plate (11) through a first TSV cylinder (3); the fourth resonant RDL (6) is connected to a grounded copper plate (11) through a second TSV cylinder (8). Both the first TSV cylinder (3) and the second TSV cylinder (8) are located within a silicon substrate (12).

2. The high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator according to claim 1, characterized in that: The first resonant RDL (2) is connected to the input terminal (1) of the RDL tap, and the fourth resonant RDL (6) is connected to the output terminal (7) of the RDL tap.

3. The high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator according to claim 2, characterized in that: The RDL tap input terminal (1) and the RDL tap output terminal (7) are both located in the RDL silicon dioxide layer (9).

4. The high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator according to claim 3, characterized in that: The third resonant RDL (5) has the same structure as the second resonant RDL (4), both being U-shaped structures. The third resonant RDL (5) and the second resonant RDL (4) are arranged opposite to each other and nested together.

5. The high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator according to claim 4, characterized in that: The third resonant RDL (5) and the second resonant RDL (4) both include two sets of step-type metal RDLs. Each set of step-type metal RDLs includes a low-impedance segment RDL and a high-impedance segment RDL connected in sequence.

6. The high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator according to claim 5, characterized in that: The first resonant RDL (2) has the same structure as the fourth resonant RDL (6).

7. The high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator according to claim 6, characterized in that: The first resonant RDL (2) includes a low-impedance segment RDL and a high-impedance segment RDL connected in sequence.

8. A design method for a high out-of-band rejection interdigital filter based on a TSV hybrid wavelength SIR resonator, characterized by: The specific process is as follows: A quarter-wavelength step impedance resonant RDL is combined with a half-wavelength step impedance resonant RDL, introducing transmission zeros on both sides of the passband. When the transmission line resonates, the impedance ratio of the SIR... R Z As shown in the following formula (1): （1）。

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