Balun structure with compensation transmission line based on tsv and design method thereof

Abstract

This invention discloses a balun structure with compensated transmission lines based on TSV, including interleaved coupled transmission lines I and II; it also includes interleaved coupled transmission lines III and IV, with coupled transmission line II connected to coupled transmission line IV via a compensated transmission line RDL. This invention also discloses a design method for the balun structure with compensated transmission lines based on TSV. This invention effectively solves the technical problems of traditional Marchand balun structures, such as large processing errors, poor amplitude and phase balance performance, and inability to cover ultra-wideband scenarios of 15–40 GHz.

Description

Technical Field

[0001] This invention belongs to the field of three-dimensional integrated microwave passive device technology, and relates to a balun structure with a compensated transmission line based on TSV. This invention also relates to a design method for a balun structure with a compensated transmission line based on TSV. Background Technology

[0002] With the rapid development of portable electronic devices such as mobile phones, Bluetooth, and WiFi, as well as monolithic integrated circuits, device miniaturization and high-density integration have become core requirements. The Marchand balun combines the broadband characteristics of traditional baluns with the integration advantages of planar circuits, achieving efficient amplitude-phase balance conversion through coupled transmission line topology, making it a core device for high-performance and miniaturized design of RF systems.

[0003] Traditional Marchand balun structures require that the length, width, and spacing of the two coupled transmission lines be perfectly symmetrical. However, in actual manufacturing, such as printed circuit board (PCB) line width deviations and uneven chip wiring spacing, even slight structural asymmetry can directly disrupt the amplitude consistency (usually >0.5dB) and phase difference (usually >5°) of the differential signal, resulting in a significant drop in common-mode rejection ratio. Furthermore, traditional structures lack symmetrical compensation designs, amplifying the impact of manufacturing errors.

[0004] Traditional Marchand balun structures rely on two quarter-wavelength coupled transmission lines to achieve signal coupling and phase distribution. Furthermore, the electrical length of the transmission lines (λ / 4, where λ is the wavelength) is strongly tied to the operating frequency (λ = v / f, where v is the wave velocity in the transmission line and f is the operating frequency). When the frequency deviates from the center frequency, the electrical length of the transmission lines deviates from λ / 4, causing the coupling energy distribution ratio and phase difference to deviate from ideal values. This leads to a sharp deterioration in the amplitude / phase balance of the differential output, resulting in a bandwidth typically only 3 to 5 times the frequency, unable to cover ultra-wideband scenarios. This is an inherent defect of the structure's "wavelength dependence."

[0005] Three-dimensional integration technology, as a key support for microwave passive devices, breaks through the planar interconnection limitations of traditional 2.5D interposers through vertical interconnect through silicon via (TSV) technology, further shortening the interconnection distance between chips and significantly improving packaging bandwidth and system integration density. Summary of the Invention

[0006] The purpose of this invention is to provide a balun structure with a compensated transmission line based on TSV, which solves the problems of large error and inability to cover ultra-wideband scenarios (15~40 GHz) in the traditional Marchand balun structure.

[0007] Another object of the present invention is to provide a design method for a balun structure with a compensated transmission line based on TSV.

[0008] The first technical solution adopted in this invention is a balun structure based on TSV with a compensated transmission line, including interleaved coupled transmission lines I and II; it also includes interleaved coupled transmission lines III and IV, with coupled transmission line II connected to coupled transmission line IV through a compensated transmission line RDL.

[0009] The first technical solution of this invention is further characterized by:

[0010] One end of the coupled transmission line I is connected to the first ground RDL, and the other end of the coupled transmission line I is connected to the output RDL port I.

[0011] One end of the coupled transmission line III is connected to the first ground RDL, and the other end of the coupled transmission line III is connected to the output RDL port II.

[0012] One end of the coupled transmission line II is connected to the input RDL port, and the other end of the coupled transmission line II is connected to the coupled transmission line IV through the compensation transmission line RDL.

[0013] Coupled transmission lines I, II, III and IV have the same structure, all formed by spiral winding of upper RDL-TSV-lower RDL.

[0014] The input RDL port is an unbalanced input port, and the output RDL port I and output RDL port II are balanced output ports.

[0015] The output signals from output RDL port I and output RDL port II have equal amplitudes and a phase difference of exactly 180°.

[0016] The second technical solution adopted in this invention is a design method for a balun structure with a compensated transmission line based on TSV, the specific process of which is as follows: Set the initial electrical length θ of the compensated transmission line RDL x Set the initial electrical lengths of coupled transmission lines I, II, III, and IV. θ L Meanwhile, define auxiliary parameters x , y, z The details are as follows: (1) (2) (3) In the formula, k Let be the coupling coefficients of coupled transmission lines I, II, III, and IV. θ L This is the initial electrical length of the coupling line; Input the RDL port return loss corresponding to S 11: (4) Isolation parameters between output RDL port I and output RDL port II S 12. S twenty one: (5) Transmission coefficients from input RDL port to output RDL port I and output RDL port II S 13. S 31: (6) in, θ x It is the initial electrical length of the compensation transmission line RDL. θ L It is the initial electrical length of the coupling line. x , y, z The auxiliary parameter is the coupling coefficient. k and electrical length θ L The function.

[0017] The beneficial effects of this invention are that it obtains the S-parameters of the Marchand balun by designing a compensated transmission line and adjusting the coupling line parameters, thereby summarizing the design method. A symmetrical structure is designed using TSV technology for simulation verification, achieving low amplitude and phase imbalance and good impedance matching. This solves the problems of traditional Marchand balun structures lacking symmetrical compensation, where the effects of manufacturing errors are amplified by the structure, and the inability to cover ultra-wideband scenarios. Furthermore, this invention has low design difficulty, significantly shortens the design cycle, and improves design efficiency; the introduction of the transmission line increases the electrical length. θ The independently adjustable parameter x can be related to the coupling coefficient of the coupling line. k and electrical length θ L This collaborative optimization improves design flexibility. Furthermore, the matching compensation structure proposed in this invention is fully compatible with standard 3D integrated circuit processes, requiring no additional process steps, and has minimal impact from parasitic parameters. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural schematic diagram of the balun structure with compensated transmission line based on TSV according to the present invention. Figure 2 This is a top view of the balun structure with compensated transmission line based on TSV according to the present invention. Figure 3 This is a schematic diagram of the circuit structure of the balun structure with compensated transmission line based on TSV of the present invention. Figure 4 This is a schematic diagram illustrating the integrated design process of the balun structure with compensated transmission line based on TSV according to the present invention. Figure 5 The simulation curves of return loss and insertion loss of the balun structure with compensated transmission line based on TSV in Ansys HFSS are shown. Figure 6 This is a graph showing the amplitude and phase balance performance of the balun structure with compensated transmission line based on TSV in Ansys HFSS.

[0019] In the diagram, 1. Input RDL port, 2. Output RDL port I, 3. Output RDL port II, 4. First ground RDL, 5. Second ground RDL, 6. TSV, 8. Compensating transmission line RDL, 9. Coupled transmission line I, 10. Coupled transmission line II, 11. Coupled transmission line III, 12. Coupled transmission line IV. Detailed Implementation

[0020] The following detailed description is provided in conjunction with specific implementation methods.

[0021] Example 1 This invention relates to a balun structure with a compensated transmission line based on TSV. Traditional Marchand balun structures lack symmetrical compensation design, amplifying the impact of manufacturing errors. Furthermore, the inherent "wavelength-dependent" nature of the structure easily leads to amplitude-phase imbalance, resulting in an inability to cover ultra-wideband scenarios. This invention improves the traditional topology by introducing a compensated transmission line and optimizes the design process through S-parameter analysis, thus addressing these problems to some extent.

[0022] Example 2 This invention is based on a balun structure with a compensated transmission line using TSV, such as... Figure 1 As shown, there are four identical coupled transmission lines, namely coupled transmission line I9, coupled transmission line II10, coupled transmission line III11 and coupled transmission line IV12. Each coupled transmission line is formed by spirally winding RDL (Redistribution Layer) - TSV (Through Silicon Via) - RDL (Metal Wiring Layer). Each TSV, together with the upper RDL, silicon substrate and lower RDL, constitutes two identical coupled transmission lines placed in parallel. The electrical length of each transmission line is one-quarter wavelength.

[0023] Coupled transmission lines II10 and IV12 are connected by a compensating transmission line RDL8. The upper and lower RDLs of the coupled transmission lines are encapsulated in polyimide material. A silicon substrate is placed between the upper and lower RDLs. Several TSV6s are arranged within the silicon substrate. Each TSV6 includes an inner metal cylinder, which is encapsulated by a silicon dioxide insulating layer. The upper and lower RDLs of coupled transmission lines I9, II10, III11, and IV12, as well as the compensating transmission line 8, are embedded in the polyimide. The TSV6s are located within the silicon substrate. The upper and lower RDLs have the same dimensions.

[0024] Figure 2 middle, l s is the length of the connecting line. l wire The length of the RDL metal wire directly connected to the TSV structure. W wire The width of the coupled transmission line, L 1 represents the length of the Marchand balun structure based on TSV. W 1 represents the width of the TSV-based Marchand balun structure.

[0025] Example 3 The unbalanced input port is input RDL port 1, and the balanced output ports are output RDL port I2 and output RDL port II3. During operation, this invention converts the signal input from input RDL port 1 and outputs it from output RDL port I2 and output RDL port II3. The output signals from output RDL port I2 and output RDL port II3 have equal amplitudes and a phase difference of exactly 180°. Furthermore, the first ground RDL4 and the second ground RDL5 are externally connected to GND (ground). A top view of the HFSS model constructed by this invention is shown below. Figure 2 The geometric parameters are as follows: l s=50 μm, l wire =159 μm, w wire =14 μm. The final device structure size is W 1 = 165 μm L 1 = 370 μm, which fully meets the miniaturization requirements based on TSV technology.

[0026] Example 4 This invention employs, as follows Figure 3The Marchand balun topology and its equivalent circuit consist of two coupled lines and a bridging line. The midpoints of the two upper coupled lines are connected by a bridging line, and the two lower coupled lines are grounded. This structure degenerates a four-port network into a three-port balun network by applying boundary conditions at specific ports. It has one unbalanced input port and two balanced output ports on each side. P 1: Single-ended input (0°) P 2: Balance end -(-90°), P 3: Balanced Port Two (+90°). During operation, it can convert the signal input from the unbalanced port and output it from the two balanced ports. The two output signals have equal amplitudes and a phase difference of exactly 180°. This amplitude and phase balance characteristic can be derived through parity-even mode theory. When the even mode transmission coefficient is 0, the above amplitude and phase balance conditions can be met.

[0027] Example 5 This invention employs, as follows Figure 4 A schematic diagram of the integrated design process of Marchand Baron.

[0028] The first step is to define the design objectives: performance indicators: amplitude imbalance (e.g., ≤0.5dB), phase imbalance (e.g., ≤±5°), input port return loss (e.g., ≥15dB), insertion loss (e.g., ≤1dB); size constraints: miniaturization requirements based on TSV technology. The core design constraints and performance requirements of the balun are clearly defined, and classic parameters of the traditional Marchand balun are selected. k =0.577 and θ(f0) =90 This set of parameters ensures the basic broadband characteristics of the device and facilitates subsequent parameter iteration and optimization.

[0029] The second step ignores the connecting lines for calculation. θ L， k Based on the design objectives and the physical parameters of the TSV process, determine the coupling coefficients of coupled transmission lines I9, II10, III11, and IV12. k =0.577, coupling coefficient k The size of the coupling line determines the electromagnetic coupling strength of the coupling line.

[0030] The third step is to introduce the connecting wires. θ x Referring to the structure of the balun, the initial electrical length of the compensation transmission line RDL8 is set. θ x The initial value is usually referenced to the operating frequency. λ / 4, or 90°, sets the initial electrical length of coupled transmission lines I9, II10, III11, and IV12. θ L The initial value can also be referenced to 90° corresponding to λ / 4. Simultaneously, auxiliary parameters are defined. x , y, z Subsequently used in Barron's S Derivation and calculation of parameters: (1) (2) (3) In the above formula k Let I be the coupling coefficient of coupled transmission lines I9, II10, III11, and IV12. θ L This represents the initial electrical length of the coupled line. The already determined coupling coefficient... k (Corresponding auxiliary parameters x, y), compensated transmission line electrical length θ X (Corresponding auxiliary parameter z), coupling line electrical length θ L Substitute Baron S The calculation formulas yield the following core parameters: Input the return loss corresponding to port 1 of the RDL S 11: (4) Isolation parameters between output RDL port I2 and output RDL port II3 S 12. S twenty one: (5) Transmission coefficients from input RDL port 1 to output RDL port I2 and output RDL port II3 S 13. S 31: (6) In the above formula θ x It is the initial electrical length of the connecting wire. θ L It is the initial electrical length of the coupling line. x , y, z The auxiliary parameter is the coupling coefficient. k and electrical length θ L The function.

[0031] Step 4: Adjust parameters θ L The initial electrical lengths of coupled transmission lines I9, II10, III11, and IV12 are readjusted. This step enables precise impedance matching between the balun and the preceding and following stage circuits, and ensures an ideal -3 dB power distribution between the two balanced output ports, effectively avoiding increased insertion loss due to impedance mismatch.

[0032] A single-segment TSV coupling line can be abstracted as a 4-port symmetrical coupling line, and its scattering matrix is ​​as follows: (7) in x , y, z The auxiliary parameter is the coupling coefficient. k and electrical length θ L The function is determined by the TSV spacing, diameter, RDL width, etc.

[0033] The compensated transmission line RDL8 is considered as a two-port transmission line. S The matrix is: (8) The fifth step is to determine whether the phase balance performance is met: If the phase balance performance does not meet the design requirements, continue to adjust the initial electrical lengths of coupled transmission lines I9, II10, III11, and IV12; if the phase balance performance meets the design requirements, proceed to the next design step.

[0034] Step 6: Adjust parameters k Match the input and output impedances of the balun (e.g., 50Ω for single-ended input and 100Ω for differential output) to reduce signal reflection.

[0035] Step 7: Determine if the ports match. If the ports do not match, adjust the coupling coefficient. k (e.g., changing the transmission line spacing or coupling method); if the ports match, proceed to the final verification stage.

[0036] Step 8: Determine if the port meets the design goals: Comprehensively check whether all indicators (frequency, insertion loss, return loss, balance, size, etc.) meet the initial design requirements. If not, return to "Adjust parameters". θ L "Step, iterate again; if satisfied, the design is complete."

[0037] Example 6 Based on the device model built using the aforementioned geometric parameters, full-wave electromagnetic simulations were performed in Ansys HFSS covering the 10–48 GHz frequency band to ensure complete coverage of the electromagnetic characteristic variation patterns within the target frequency band. Figure 5 This is a loss simulation curve of the improved Marchand balun of this invention in Ansys HFSS, with the horizontal axis covering the frequency range of 10~48 GHz and the vertical axis representing... S The parameters, and the three curves in the figure, correspond to the core RF performance of the balun: the red curve represents the input port. P 1 return loss S 11 (dB (S(P1, P1)), the purple curve represents the signal from the input port) P 1 to output port P Insertion loss of 2 S 21 (dB (S ( P2 , P 1)), The blue curve represents the signal from the input port. P 1 to output port P Insertion loss of 3 S 31 (dB(S( P3 , P 1)), of which P 1 represents input RDL port 1. P 2 is the output RDL port I2, P 3 is the output RDL port II3.

[0038] As shown by the curves, this invention achieves an input port return loss S11 ≤ -54.16 dB (with a maximum absolute return loss of 54.16 dB, realizing excellent input matching) within the ultra-wide frequency band of 15–40 GHz, significantly outperforming traditional baluns, with a device center frequency of 27 GHz. This figure reflects that the invention achieves excellent input matching and amplitude-phase balance near 27 GHz, while maintaining good transmission loss and amplitude consistency across the wide frequency band of 15–40 GHz.

[0039] The wideband characteristic curves representing the balanced performance of the balun device of this invention are shown in the figure below. Figure 6 Covering an operating frequency range of 20~40 GHz, it employs a clear dual-axis design to simultaneously display the core's balanced performance indicators. The left axis corresponds to "amplitude imbalance," a parameter used to measure the signal amplitude difference between the two balanced output ports of the balun. Ideally, its value should be 0 dB; the smaller the absolute value, the better the signal amplitude consistency between the two ports. The right axis corresponds to "phase imbalance," a parameter reflecting the degree of deviation of the signal phase of the two balanced output ports from the ideal 180° phase difference. The closer the value is to 180°, the better the phase balance performance.

[0040] The horizontal axis represents the operating frequency across the entire analysis range. The red curve in the figure represents the trend of amplitude imbalance: near 20 GHz, the amplitude imbalance is approximately -0.2 dB; as the frequency increases, the curve gradually approaches the ideal value of 0 dB, and almost approaches 0 dB in the 25~30 GHz range, meaning that the difference in signal amplitude between the two balanced output ports is extremely small. However, near 40 GHz, the absolute value of amplitude imbalance remains within a small range, showing a stable and excellent amplitude consistency overall.

[0041] The corresponding blue curve represents the characteristics of phase imbalance: around 20 GHz, the phase imbalance value is slightly lower than 180°, about 179.6°; as the frequency increases, the curve gradually approaches the ideal phase difference of 180°, and in the frequency band around 30 GHz, it almost matches the ideal phase difference value of 180°. Even at the end of the frequency band of 40 GHz, the phase imbalance value remains above 179°, and the phase deviation is always within a very small range.

[0042] Meanwhile, the combination of red circles and arrows in the figure specifically points to the amplitude imbalance curve region around 25 GHz, which is the range where the amplitude imbalance performance is optimal. The blue circles and arrows correspond to the phase imbalance curve around 30 GHz, which is also the region where the phase balance performance is closest to the ideal state.

[0043] In summary, this result clearly demonstrates that within the wide operating frequency band of 20~40 GHz, the present invention consistently maintains a near-ideal range for both amplitude and phase imbalances, exhibiting stable and excellent balance performance, perfectly meeting the core design requirements of broadband baluns for signal balance conversion.

[0044] This invention achieves low amplitude and phase imbalance and good impedance matching by designing a compensating transmission line and adjusting the coupling line parameters. The introduction of the transmission line increases the electrical length. θ The independently adjustable parameter 'x' enhances design flexibility. This design improvement addresses the limitations of traditional Marchand baluns in certain applications, particularly in scenarios requiring strict balancing and power distribution.

[0045] The improved Marchand balun structure with a compensated transmission line is a highly efficient optimization solution addressing the core defects of the traditional structure. By adding a compensated transmission line with adjustable parameters to the coupled transmission line branch, it precisely solves the problems of the traditional structure's lack of asymmetric compensation design, amplified manufacturing errors, and inability to cover ultra-wideband scenarios. Specifically, addressing the shortcomings of the traditional structure's lack of asymmetric compensation design, the improved structure's added compensated transmission line can flexibly adjust its electrical length, characteristic impedance, or linewidth parameters to form a reverse error cancellation mechanism. That is, when structural asymmetry defects such as coupling line length deviations or uneven line spacing occur during manufacturing, the compensated transmission line can achieve precise compensation through its controllable phase delay and amplitude attenuation, effectively offsetting the amplitude and phase deviations caused by structural asymmetry in the two branches, thereby weakening the amplification effect of manufacturing errors on the balun's balance performance.

Claims

1. A balun structure with a compensated transmission line based on TSV, characterized in that: It includes interleaved coupled transmission lines I (9) and II (10); it also includes interleaved coupled transmission lines III (11) and IV (12), with coupled transmission line II (10) connected to coupled transmission line IV (12) via compensating transmission line RDL (8).

2. The balun structure with compensated transmission line based on TSV according to claim 1, characterized in that: One end of the coupling transmission line I (9) is connected to the first ground RDL (4), and the other end of the coupling transmission line I (9) is connected to the output RDL port I (2).

3. The balun structure with compensated transmission line based on TSV according to claim 2, characterized in that: One end of the coupling transmission line III (11) is connected to the first ground RDL (5), and the other end of the coupling transmission line III (11) is connected to the output RDL port II (3).

4. The balun structure with compensated transmission line based on TSV according to claim 3, characterized in that: One end of the coupling transmission line II (10) is connected to the input RDL port (1), and the other end of the coupling transmission line II (10) is connected to the coupling transmission line IV (12) through the compensation transmission line RDL (8).

5. The balun structure with compensated transmission line based on TSV according to claim 4, characterized in that: The coupled transmission lines I (9), II (10), III (11) and IV (12) have the same structure, and are all formed by spiral winding of the upper RDL-TSV-lower RDL.

6. The balun structure with compensated transmission line based on TSV according to claim 5, characterized in that: The input RDL port (1) is an unbalanced input port, and the output RDL port I (2) and output RDL port II (3) are balanced output ports.

7. The balun structure with compensated transmission line based on TSV according to claim 6, characterized in that: The output signals of the output RDL port I (2) and the output RDL port II (3) have equal amplitudes and a phase difference of exactly 180°.

8. A design method for a balun structure with a compensated transmission line based on TSV, characterized in that: The specific process is as follows: Set the initial electrical length θ of the compensation transmission line RDL (8). x Set the initial electrical lengths of coupled transmission lines I (9), II (10), III (11), and IV (12). θ L Meanwhile, define auxiliary parameters x , y, z The details are as follows: (1) (2) (3) In the formula, k Let be the coupling coefficients of coupled transmission lines I (9), II (10), III (11), and IV (12). θ L This is the initial electrical length of the coupling line; Input RDL port (1) return loss corresponding to S 11: (4) Isolation parameters between output RDL port I (2) and output RDL port II (3) S 12. S twenty one: (5) Transmission coefficients from input RDL port (1) to output RDL port I (2) and output RDL port II (3) S 13. S 31: (6) in, θ x It is the initial electrical length of the compensation transmission line RDL(8). θ L The initial electrical lengths of coupled transmission lines I (9), II (10), III (11), and IV (12) are given. x , y, z The auxiliary parameter is the coupling coefficient. k and electrical length θ L The function.

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