TSV-based fourth-order SIW compact interdigital band-pass filter and design method thereof

Abstract

The invention discloses a TSV-based four-order SIW compact interdigital band-pass filter, which comprises an upper RDL and a lower RDL which are arranged in parallel up and down, a silicon substrate is arranged between the upper RDL and the lower RDL, a plurality of TSVs are arranged on the silicon substrate, each TSV, the upper RDL, the silicon substrate and the lower RDL form a cavity structure in an SIW, a uniform impedance resonator is arranged at the center of the cavity structure, and a plurality of TSVs are arranged in the cavity structure. Two opposite sides of the upper layer RDL are respectively provided with an input RDL port and an output RDL port; the invention further discloses a design method of the TSV-based fourth-order SIW compact interdigital band-pass filter. The problems that a traditional band-pass filter is large in occupied area and high in high-frequency loss are solved.

Description

Technical Field

[0001] This invention belongs to the field of three-dimensional integrated microwave passive device technology, and relates to a fourth-order SIW compact interdigital bandpass filter based on TSV. This invention also relates to a design method for a fourth-order SIW compact interdigital bandpass filter based on TSV. Background Technology

[0002] With the rapid development of 5G, IoT, and millimeter-wave communication, the performance requirements of radio frequency systems for filters are increasing. Substrate integrated waveguide (SIW) technology combines the advantages of traditional waveguides and microstrip lines, realizing waveguide functions on a dielectric substrate through periodic metallized vias, and has become an important direction for the high-frequency and miniaturized design of filters.

[0003] TSV-based SIW technology has broken through the size and performance bottlenecks of traditional planar filters, providing key component support for next-generation high-frequency, highly integrated wireless systems. Its core advantages lie in miniaturization, low loss, design flexibility, and process compatibility, and it is gradually becoming a new technology applied to microwave and millimeter-wave filters.

[0004] Traditional SIW filters typically have a complex structure, containing multiple independent resonant cavities connected by coupling slots or holes. This layout is not compact, leading to structural redundancy and wasted area. Furthermore, they are prone to mode interference and energy leakage at high frequencies and are not conducive to integration with other active devices. Traditional interdigital filters, based on the interdigital structure of microstrip lines, suffer from high high-frequency losses, are difficult to integrate in three dimensions, and occupy a large area. Summary of the Invention

[0005] The purpose of this invention is to provide a compact interdigital bandpass filter based on TSV (Third-Order SIW), which solves the problems of large area occupation and high high-frequency loss in traditional bandpass filters.

[0006] Another objective of this invention is to provide a design method for a fourth-order SIW compact interdigital bandpass filter based on TSV.

[0007] The first technical solution adopted in this invention is a fourth-order SIW compact interdigital bandpass filter based on TSV, which includes an upper RDL and a lower RDL arranged in parallel. A silicon substrate is provided between the upper RDL and the lower RDL. Several TSVs are arranged on the silicon substrate. Each TSV, together with the upper RDL, the silicon substrate and the lower RDL, constitutes the cavity structure in the SIW. A uniform impedance resonator is provided at the center of the cavity structure. Input RDL port and output RDL port are respectively provided on opposite sides of the upper RDL.

[0008] The first technical solution of this invention is further characterized by: Two resonant cavities composed of several TSVs are distributed within the silicon substrate. The uniform impedance resonator is located between the two resonant cavities and on the upper RDL.

[0009] The two resonant cavities are centrally symmetrical, with the input RDL port and output RDL port of the first resonant cavity and the second resonant cavity respectively located on one side wall of the first resonant cavity and the second resonant cavity.

[0010] A window A is provided between the first resonant cavity and the uniform impedance resonator, and a window B is provided between the uniform impedance resonator and the second resonant cavity.

[0011] The uniform impedance resonator consists of two parallel microstrip lines of equal width, namely the first half-wavelength short line and the second half-wavelength short line.

[0012] Magnetic coupling is used between the first resonant cavity and the first 1 / 2 wavelength short circuit, between the first 1 / 2 wavelength short circuit and the second 1 / 2 wavelength short circuit, and between the second 1 / 2 wavelength short circuit and the second resonant cavity.

[0013] The coupling structure between the input RDL port and the first resonant cavity is the same as that between the second resonant cavity and the output RDL port, both adopting a coplanar waveguide-microstrip line method with a concave transition structure.

[0014] The second technical solution adopted in this invention is as follows: the coupling matrix of the filter is designed according to the coupling theory, and the coupling matrix of the structure is shown in the following formula (1): (1) Since there is no asynchronous tuning path in the filter structure, the structural parameters of the uniform impedance resonator are determined according to the coupling coefficient calculation method in equation (2). As shown in formula (2) below: (2) In the formula, The frequency of the lower absorption peak among the two absorption peaks of the coupled structure is the frequency point at which the coupled system exhibits the strongest absorption resonance for low-frequency signals. The frequency of the higher absorption peak among the two absorption peaks after coupling represents the frequency at which the coupled system exhibits the strongest absorption resonance for high-frequency signals. FBW is the relative bandwidth of the filter, i.e., the ratio of bandwidth to center frequency.

[0015] The beneficial effects of this invention are that it establishes an electromagnetic coupling mechanism between two SIW resonant cavities composed of TSVs and an intermediate interdigital uniform impedance resonator, allowing for continuous inter-resonator coupling design and reducing design complexity. The number of cavities required for a traditional fourth-order filter is reduced from the theoretical four to two, achieving a significant reduction in device area while maintaining the filter order. Furthermore, the transmission zero-point position can be flexibly controlled by adjusting the interdigital parameter to adapt to different frequency band requirements. Simultaneously, the input and output terminals employ a coplanar waveguide-microstrip line transition structure, achieving low-reflection integration with millimeter-wave microchips (MMICs). Attached Figure Description

[0016] Figure 1 This invention relates to the topology of a fourth-order SIW compact interdigitated bandpass filter based on TSV. Figure 2 This invention relates to a fourth-order SIW compact interdigital bandpass filter uniform impedance resonator structure based on TSV. Figure 3 This is a schematic diagram of the magnetic field distribution of the fourth-order SIW compact interdigital bandpass filter based on TSV of the present invention; Figure 4 This invention relates to the coupling coefficient of a fourth-order SIW compact interdigital bandpass filter with uniform impedance resonator based on TSV. Spacing between microstrip lines Relationship; Figure 5 This invention relates to the coupling coefficient of a fourth-order SIW compact interdigital bandpass filter with uniform impedance resonator based on TSV. and staggered distance Relationship; Figure 6 This is a simulation model of the fourth-order SIW compact interdigital bandpass filter based on TSV, as described in this invention. With TSV window distance Changes; Figure 7 This is a three-dimensional view of the fourth-order SIW compact interdigitated bandpass filter based on TSV of the present invention; Figure 8 This is a top view of a fourth-order SIW compact interdigital bandpass filter based on TSV; Figure 9 This invention relates to the return loss of a fourth-order SIW compact interdigital bandpass filter based on TSV in Ansys HFSS. and insertion loss Simulation curve.

[0017] Figure 1In the diagram, 1. Upper RDL, 2. Lower RDL, 3. Silicon substrate, 4. Uniform impedance resonator, 5. Input RDL port, 6. Output RDL port, 7. First resonant cavity, 8. Second resonant cavity, 9. First 1 / 2 wavelength short path, 10. Second 1 / 2 wavelength short path, 11. Window A, 12. Window B, 13. TSV. 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 presents a design method for a fourth-order SIW compact interdigital bandpass filter based on TSV, as follows: To further reduce the area, passive filter designs often incorporate windowed structures. However, the introduced full-wavelength microstrip resonator is not sufficiently miniaturized and cannot achieve continuous design of the two microstrip structures, increasing the design difficulty of the filter. This invention employs a similar uniform impedance resonator structure for SIW-microstrip filter design, which to some extent alleviates these problems.

[0020] Since the resonant cavity is coupled to the uniform impedance resonator through its edge, the coupling method is magnetic coupling, and there is magnetic coupling between the two microstrip structures. Based on coupling theory, the coupling matrix of the filter is designed, and the coupling path of this invention is... Figure 1 ,in Represents the Nth resonant cavity, where , ,and , and The coupling between them is magnetic coupling. The cavity edge also magnetically couples with the microstrip structure. By adding TSVs in the silicon dielectric between the cavity edge and the microstrip structure taps, the coupling strength between the uniform impedance resonator and the cavity is suppressed, forming a magnetic window similar to that between SIW cavities. The coupling parameters between the SIW cavity and the microstrip resonator can be adjusted by controlling the width of the window.

[0021] Uniform impedance resonators, due to their transmission line structure's impedance continuity, can effectively reduce various losses caused by impedance abrupt changes. When microstrip resonator units are introduced into SIW cavity structures, the originally intact electromagnetic enclosure is affected to varying degrees. This structural disruption can lead to increased electromagnetic field leakage and a decrease in Q value. Based on the above technical considerations, especially in application scenarios where low-loss characteristics and structural stability are paramount, this invention ultimately adopts... Figure 2A uniform impedance resonator is used as the core resonant unit to construct a high-performance SIW-microstrip hybrid filter design. The uniform impedance resonator and the SIW cavity are connected via a tapped transition. A window is created on the upper surface between the two cavities, and a microstrip structure is etched into it. The two uniform impedance resonators are coupled in a manner similar to a terminated short-circuited interdigital filter. Figure 2 middle, For TSV windows, The length of the microstrip line. For staggered distances, For microstrip line spacing, For window width, The length of the window; Figure 3 In the diagram, the strongest magnetic field within the cavity is located at the edge of the window on the upper surface of the SIW, and the magnetic field is radially distributed along the cavity edge. As shown in the figure, the strongest magnetic field is found at the transition point between the SIW cavity and the microstrip structure. The magnetic field strength decreases as the distance to the TSVs (Transient Voltage Suppliers) surrounding the window on the upper surface redistribution layer decreases. Therefore, the metallized vias (TSVs) around the window structure suppress the coupling between the SIW and the microstrip structure. The coupling matrix of this structure is shown below: (1) The M matrix refers to the coupling matrix, which is an N+2 order matrix, where N is the order of the filter (4th order), and the matrix is ​​a 6th order (4+2) matrix. Equation (1) is the coupling parameter M matrix of this fourth-order filter. Matrix elements (No. i Line 1 j The values ​​in the column represent the resonant cavity. i and j The coupling strength between the resonant cavities. Since the coupling between the resonant cavities in this tandem structure is all direct coupling, and there is no asynchronous tuning or cross coupling, the elements on the diagonal of the coupling matrix are all 0, meaning that the resonant frequency of each resonant cavity is the same as the center frequency of the filter. Therefore, when designing, the coupling strength between individual resonant cavities of the filter is... The resonant frequency in this mode is designed based on the filter's center frequency of 100 GHz.

[0022] Because of the topology of this filter and Both are microstrip resonators, with the uniform impedance resonator situated between two SIW cavities. Therefore, when establishing the coupling coefficient simulation model, the influence of the surrounding TSVs on the simulation results and the additional reactance generated by the micro-UIR structure need to be considered. Thus, the microstrip port and microstrip structure, as well as the open window of the upper metal layer and the TSVs surrounding the window, are retained in the model, while the cavity portion is removed. Regarding the coupling method between the two uniform impedance resonators, the coupling method of an interdigital filter can be referenced. The coupling coefficient between the two microstrip lines in the figure is determined by the spacing between the resonators. In addition, the microstrip resonators are arranged in an interleaved manner, and the degree of interleaving between the resonators also affects the coupling coefficient. Figure 4 and Figure 5 These are the coupling coefficients of the dual uniform impedance structure. The changing trend as the spacing and degree of overlap change.

[0023] Since there is no asynchronous tuning path in this structure, the coupling coefficient calculation method according to equation (2) is combined with... The structural parameters of the uniform impedance resonator can be determined by observing the trend of the curve.

[0024] (2) After coupling two resonant cavities with the same center resonant frequency, the S-parameters of this dual-cavity coupled structure will exhibit two absorption peaks. In the equation... The frequency of the lower absorption peak among the two absorption peaks in the coupled structure is the frequency point at which the coupled system exhibits the strongest absorption (resonance) for low-frequency signals; The frequency of the higher absorption peak among the two absorption peaks after coupling represents the frequency at which the coupled system exhibits the strongest absorption (resonance) for high-frequency signals. FBW is the relative bandwidth of the filter, i.e., the ratio of bandwidth to center frequency. For magnetic window sizes of 200... up to 400 Frequency sweep simulation was performed between them to obtain Figure 6 The S-parameter simulation results are obtained. The final structural parameters of the uniform impedance resonator are obtained through fitting optimization.

[0025] Example 2 The final optimized fit yields the present invention, namely, a fourth-order SIW compact interdigital bandpass filter based on TSV. The invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Figure 7 , 8As shown, an upper RDL (Redistribution Layer) 1 and a lower RDL 2, both copper layers, are used as the upper and lower metal plates of the SIW filter, respectively. A silicon substrate 3 is placed between the upper RDL 1 and the lower RDL 2. Several TSV13s are arranged on the silicon substrate 3. Each TSV13, together with the upper RDL 1 and the lower RDL structure 2, constitutes the cavity structure in the SIW. Structure 4 is a uniform impedance resonator with double-ended short circuit formed by microstrip lines to realize the coupling of the filter. The upper RDL 1 has an input RDL port 5 and an output RDL port 6 introduced on opposite sides.

[0026] Example 3 Two resonant cavities composed of TSV arrays are distributed within the silicon substrate 3. Between the two resonant cavities of the upper RDL1 is a uniform impedance resonator composed of an interdigital structure. Input RDL port 5 and output RDL port 6 are provided on opposite sides of the upper RDL1. The two resonant cavities are centrally symmetrical and are designated as the first resonant cavity 7 and the second resonant cavity 8, respectively. Input RDL port 5 and output RDL port 6 are respectively located on one sidewall of the first resonant cavity 7 and the second resonant cavity 8.

[0027] Example 4 A window A11 is provided between the first resonant cavity 7 and the uniform impedance resonator 4, and a window B12 is provided between the uniform impedance resonator and the second resonant cavity.

[0028] The uniform impedance resonator 4 includes two parallel microstrip lines of equal width, namely the first 1 / 2 wavelength short line 9 and the second 1 / 2 wavelength short line 10.

[0029] Example 5 The coupling structure between the input RDL port 5 and the first resonant cavity 7 is the same as the coupling structure between the second resonant cavity 8 and the output RDL port 6, both adopting a coplanar waveguide-microstrip line method with a concave transition structure.

[0030] Example 6 This invention relates to a fourth-order SIW compact interdigital bandpass filter based on TSVs. The sidewalls of the waveguide cavity are formed by the periodic arrangement of each TSV13, and two resonant cavities are constructed by a number of TSVs13. Magnetic coupling is used between the first resonant cavity 7 and the first 1 / 2 wavelength shorting line 9, the first 1 / 2 wavelength shorting line 9 and the second 1 / 2 wavelength shorting line 10, and the second 1 / 2 wavelength shorting line 10 and the second resonant cavity 8.

[0031] The first resonant cavity 7 is formed by being surrounded by TSV sidewall I, TSV sidewall II, TSV sidewall III, TSV sidewall VII, TSV sidewall VIII, TSV sidewall IX, TSV sidewall XI, TSV sidewall XIII, TSV sidewall XIV and TSV sidewall XVI; Window A11 is located between TSV sidewall IX and TSV sidewall XI. Input RDL port 5 is located between TSV sidewall I and TSV sidewall XVI. TSV sidewall II and TSV sidewall XIV are located on opposite sides of input RDL port 5, respectively.

[0032] The first 1 / 2 wavelength short line 9 is connected to the first resonant cavity 7 via a microstrip line, and the second 1 / 2 wavelength short line 10 is connected to the second resonant cavity 8 via a microstrip line. The two lines are connected by line coupling and are surrounded by TSV sidewalls VIII, IX, X, XI, XII and XIII.

[0033] The second resonant cavity 8 is formed by being surrounded by TSV sidewalls IV, VII, X, XII, XIII, XIV, XV, VI, and V.

[0034] Window B12 is located between TSV sidewall X and TSV sidewall XII, and output RDL port 6 is located between TSV sidewall IV and TSV sidewall V. TSV sidewall VII and TSV sidewall VI are respectively located on opposite sides of output RDL port 6.

[0035] The upper RDL1 and the lower RDL2 have the same dimensions. Metal slots are added to the locations of the input RDL port 5 and the output RDL port 6 of the upper RDL1. Compared with the directly coupled fourth-order filter, the present invention has the feature of compact structure.

[0036] This invention allows for flexible adjustment of the transmission zero position during design by adjusting the parameters of the uniform impedance resonator 4. The input RDL port 5 and the output RDL port 6 are implemented using a coplanar waveguide structure with TSVs arranged on both sides, which can effectively reduce the coupling between ports and other device ports when integrated with other devices.

[0037] Figure 9 This is a simulation curve of the fourth-order SIW compact interdigital bandpass filter based on TSV according to the present invention. Figure 9 As can be seen, this filter achieves the lowest insertion loss within the passband of 96.1 GHz to 105.3 GHz. Maximum return loss above -2.9dB With an insertion loss below -12.65dB, superior to traditional SIW filters, and a center frequency of 100.7GHz, this structure is suitable for the millimeter-wave band. It exhibits excellent lower stopband performance, with insertion loss below -40dB in the stopband below 85.5GHz. Furthermore, by introducing transmission zeros in the stopband to suppress higher-order modes close to the passband, this structure achieves insertion loss below -45dB in the stopband from 116GHz to 136GHz.

Claims

1. A fourth-order SIW compact interdigital bandpass filter based on TSV, characterized in that: It includes an upper RDL (1) and a lower RDL (2) arranged in parallel. A silicon substrate (3) is provided between the upper RDL (1) and the lower RDL (2). Several TSVs (13) are arranged on the silicon substrate (3). Each TSV (13), together with the upper RDL (1), the silicon substrate (3) and the lower RDL (2), constitutes the cavity structure in SIW. A uniform impedance resonator (4) is provided at the center of the cavity structure. An input RDL port (5) and an output RDL port (6) are provided on opposite sides of the upper RDL (1).

2. The fourth-order SIW compact interdigital bandpass filter based on TSV according to claim 1, characterized in that: The silicon substrate (3) contains two resonant cavities composed of several TSVs (13), and the uniform impedance resonator (4) is located between the two resonant cavities and on the upper RDL (1).

3. The fourth-order SIW compact interdigital bandpass filter based on TSV according to claim 2, characterized in that: The two resonant cavities are centrally symmetrical, and the input RDL port (5) and output RDL port (6) of the first resonant cavity (7) and the second resonant cavity (8) are respectively opened on one of the side walls of the first resonant cavity (7) and the second resonant cavity (8).

4. The fourth-order SIW compact interdigitated bandpass filter based on TSV according to claim 3, characterized in that: A window A (11) is provided between the first resonant cavity (7) and the uniform impedance resonator (4), and a window B (12) is provided between the uniform impedance resonator (4) and the second resonant cavity (8).

5. The fourth-order SIW compact interdigital bandpass filter based on TSV according to claim 4, characterized in that: The uniform impedance resonator (4) includes two parallel microstrip lines of equal width, namely a first 1 / 2 wavelength short line (9) and a second 1 / 2 wavelength short line (10).

6. The fourth-order SIW compact interdigital bandpass filter based on TSV according to claim 5, characterized in that: The first resonant cavity (7) is magnetically coupled to the first 1 / 2 wavelength short circuit (9), the first 1 / 2 wavelength short circuit (9) is magnetically coupled to the second 1 / 2 wavelength short circuit (10), and the second 1 / 2 wavelength short circuit (10) is magnetically coupled to the second resonant cavity (8).

7. The fourth-order SIW compact interdigital bandpass filter based on TSV according to claim 6, characterized in that: The coupling structure between the input RDL port (5) and the first resonant cavity (7) is the same as the coupling structure between the second resonant cavity (8) and the output RDL port (6), both adopting a coplanar waveguide-microstrip line method with a concave transition structure.

8. A design method for a fourth-order SIW compact interdigital bandpass filter based on TSV, characterized in that: The specific process is as follows: The coupling matrix of the filter is designed according to the coupling theory. The coupling matrix of this structure is shown in the following formula (1): （1） Since there is no asynchronous tuning path in the filter structure, the structural parameters of the uniform impedance resonator are determined according to the coupling coefficient calculation method in equation (2). As shown in formula (2) below: （2） In the formula, The frequency of the lower absorption peak among the two absorption peaks in the coupled structure. The frequency of the higher absorption peak among the two absorption peaks after coupling.

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