Branch line coupler based on coaxial TSV and CPW

Abstract

The present invention discloses a branch-line coupler based on coaxial TSVs and CPWs. The coupler comprises two symmetrically arranged three-dimensional zigzag transmission lines, each vertically interconnected by the coaxial TSVs and CPWs, and two sets of planar zigzag CPW transmission lines. The two sets of three-dimensional zigzag transmission lines, each vertically interconnected by the coaxial TSVs and CPWs, are connected by the central conduction strips of the two planar zigzag CPWs. By combining coaxial TSVs and CPWs, the present invention significantly reduces the size of conventional branch-line couplers, achieving miniaturization of millimeter-wave branch-line couplers.

Description

Technical Field

[0001] The present invention belongs to the technical field of three-dimensional integrated circuits and relates to a branch line coupler based on coaxial TSV and CPW. Background Art

[0002] At present, a lot of research has been done at home and abroad on the design of branch-line couplers. Microstrip branch-line couplers are a common type due to their simple structure and easy implementation. However, with the popularization of high operating frequencies, the disadvantages of microstrip lines have gradually become apparent. Its loss at high frequencies seriously affects the performance of branch-line couplers. Compared with microstrip lines, coplanar waveguide (CPW) has lower loss at high frequencies. Therefore, CPW is often used to design branch-line couplers in the millimeter-wave band. However, this method still has the problems of large size and inability to integrate with other on-chip systems. Therefore, new methods are urgently needed to solve the problem of the current branch-line coupler that cannot take into account both size and performance at high frequencies.

[0003] The through-silicon via (TSV) technology developed in recent years is mainly used for vertical signal interconnection in three-dimensional integration (3DIC). It can greatly shorten the interconnection length and realize three-dimensional heterogeneous integration. Today, TSV technology has been applied to the design of RF passive devices, such as TSV spiral inductors, SIW filters, LC filters, etc., making miniaturized three-dimensional silicon-based on-chip passive devices a reality. It not only can achieve compact size, but also has potential advantages in improving electrical performance, packaging density and realizing heterogeneous integration. Coaxial TSV has more advantages than cylindrical TSV. It can suppress signal crosstalk, ensure signal integrity, and has low loss at high frequencies. The advantages of coaxial TSV and the good high-frequency response of CPW can be used to realize miniaturized on-chip millimeter-wave branch line couplers. Summary of the Invention

[0004] The purpose of the present invention is to provide a branch line coupler based on coaxial TSV and CPW. The coupler greatly reduces the volume of the traditional branch line coupler by combining coaxial TSV and CPW, and realizes the miniaturization of the millimeter wave band branch line coupler.

[0005] The technical solution adopted by the present invention is a branch line coupler based on coaxial TSV and CPW, including two groups of symmetrically arranged three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection, and the two groups of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection are connected by the central conduction bands of two groups of planar meandering CPW.

[0006] The present invention is also characterized in that:

[0007] Each group of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection includes TSV 1, TSV 2, TSV 3, and TSV 4, which are equidistantly arranged on the same straight line. The upper end of TSV 1 is connected to one end of the central conductive strip of CPW 1; the lower end of TSV 1 is connected to one end of the central conductive strip of CPW 2, the other end of the central conductive strip of CPW 2 is connected to the lower end of TSV 2, the upper end of TSV 2 is connected to one end of the central conductive strip of CPW 3, the other end of the central conductive strip of CPW 3 is connected to the upper end of TSV 3, the lower end of TSV 3 is connected to one end of the central conductive strip of CPW 4, the other end of the central conductive strip of CPW 4 is connected to the lower end of TSV 4, and the upper end of TSV 4 is connected to one end of the central conductive strip of CPW 5;

[0008] The other ends of two CPW center conduction strips in two sets of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection are respectively connected to the two ends of the center conduction strip of a set of planar meandering CPW. The two output ports of the center conduction strip of the planar meandering CPW are respectively provided with a CPW for leading out the coupling end and a CPW for leading out the isolation end.

[0009] The other ends of the two CPW five-center conduction strips in the two groups of three-dimensional zigzag transmission lines based on coaxial TSV and CPW vertical interconnection are respectively connected to the two ends of the center conduction strip of another group of planar zigzag CPW. The two output ports of the center conduction strip of this group of planar zigzag CPW are respectively provided with a CPW for leading out the input end and a CPW for leading out the through end.

[0010] In each set of three-dimensional zigzag transmission lines based on coaxial TSV and CPW vertical interconnects, CPW grounding strips on the silicon substrate are located on opposite sides of the line where the CPW single center conduction strip, CPW three center conduction strips, and CPW five center conduction strips are located. The CPW single center conduction strip, CPW three center conduction strips, CPW five center conduction strips, CPW grounding strips on the silicon substrate, and the center conduction strip of the planar zigzag CPW are all located in the upper silicon dioxide layer.

[0011] CPW grounding conduction strips are provided on opposite sides of the straight line where the CPW two-center conduction strip and the CPW four-center conduction strip are located. The CPW two-center conduction strip, the CPW four-center conduction strip and the CPW grounding conduction strips are all located in the lower silicon dioxide layer.

[0012] TSV 1, TSV 2, TSV 3, and TSV 4 are all arranged in a silicon substrate, and the silicon substrate is arranged between an upper silicon dioxide layer and a lower silicon dioxide layer.

[0013] The design method of the branch line coupler based on coaxial TSV and CPW adopts a three-dimensional meandering transmission line based on coaxial TSV and CPW vertical interconnection as the 50Ω transmission line of the 3dB branch line coupler, and a planar meandering CPW is used as the 35.35Ω transmission line. The four ports are respectively led out by CPW with a characteristic impedance of 50Ω.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. The branch line coupler uses a silicon-based substrate, which is compatible with existing silicon process products and can be integrated with other RF active devices to improve the integration of the RF system.

[0016] 2. The vertical interconnection of coaxial TSV and CPW can effectively shorten the length of the transmission line, thereby realizing a miniaturized branch line coupler.

[0017] 3. The outer copper ring of the coaxial TSV can act as a shield, suppressing signal crosstalk and electromagnetic interference, reducing signal transmission loss and delay, and ensuring the integrity of high-frequency signals; CPW has the characteristic of low loss in the millimeter wave band. Combining the above advantages, the present invention can be applied to the millimeter wave band and has the characteristics of low loss and high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the branch line coupler based on coaxial TSV and CPW of the present invention;

[0019] Figure 2 It is a schematic structural diagram of a three-dimensional meandering transmission line based on vertical interconnection of coaxial TSV and CPW in a branch line coupler based on coaxial TSV and CPW of the present invention;

[0020] Figure 3 1 is a schematic structural diagram of TSV 1 in a branch line coupler based on coaxial TSV and CPW according to the present invention;

[0021] Figure 4 1 is a schematic diagram of simulation results of S parameters of a branch line coupler based on coaxial TSV and CPW according to the present invention;

[0022] Figure 5 This is a simulation result diagram of the phase difference and amplitude imbalance of the branch line coupler based on coaxial TSV and CPW of the present invention.

[0023] In the figure, 1. TSV copper pillar, 2. shielding layer, 3. outer copper ring pillar, 4. oxide isolation layer, 5. silicon substrate, 6. upper silicon dioxide layer, 7. lower silicon dioxide layer, 8. CPW one center conduction strip, 9. CPW two center conduction strip, 10. CPW three center conduction strip, 11. CPW four center conduction strip, 12. CPW five center conduction strip, 13. CPW ground conduction strip on the upper layer of silicon substrate, 14. CPW ground conduction strip on the lower layer of silicon substrate, 15. TSV one, 16. TSV two, 17. TSV three, 18. TSV four, 19. CPW for leading out the input end, 20. CPW for leading out the through end, 21. CPW for leading out the coupled end, 22. CPW for leading out the isolated end, 23. The center conduction strip of the planar zigzag CPW. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] A branch-line directional coupler is a typical four-port microwave passive device. A traditional branch-line coupler consists of four quarter-wavelength (90° electrical length) transmission lines. Within the frequency range near the center frequency, there is a 90° phase shift between the through-port and the coupled port. The characteristic impedances of the branch and main lines of a 3dB branch-line coupler are 50Ω and 35.35Ω, respectively.

[0026] This branch-line coupler, based on coaxial TSVs and CPWs, uses a three-dimensional, meandering transmission line based on vertical interconnections of coaxial TSVs and CPWs as the 50Ω transmission line for the 3dB branch-line coupler, while a planar, meandering CPW acts as the 35.35Ω transmission line. The four ports (CPW19 for the input, CPW20 for the through-port, CPW21 for the coupled port, and CPW22 for the isolated port) are each connected by a CPW with a characteristic impedance of 50Ω.

[0027] Example 1

[0028] The present invention is based on a branch line coupler of coaxial TSV and CPW, such as Figure 1 As shown, the 35.35Ω transmission line of the branch line coupler is realized by the central conduction strip 23 of the planar meander CPW, which is located in the upper silicon dioxide layer 6. The two sets of three-dimensional meander transmission lines based on coaxial TSV and the two sets of central conduction strips 23 of the planar meander CPW are arranged symmetrically.

[0029] The four ports CPW19 for leading the input end, CPW20 for leading the through end, CPW21 for leading the coupled end, and CPW22 for leading the isolated end are led out by 50Ω CPW.

[0030] like Figure 2As shown, the 50Ω transmission line of each branch line coupler is composed of five CPW segments and four coaxial TSVs, including CPW 1 center guide strip 8, CPW 2 center guide strip 9, CPW 3 center guide strip 10, CPW 4 center guide strip 11, CPW 5 center guide strip 12, TSV 1 15, TSV 2 16, TSV 3 17, and TSV 4 18.

[0031] Among them, the CPW-1 center conduction strip 8 and the CPW-2 center conduction strip 9 are vertically interconnected through TSV-1 15, the CPW-2 center conduction strip 9 and the CPW-3 center conduction strip 10 are vertically interconnected through TSV-2 16, the CPW-3 center conduction strip 10 and the CPW-4 center conduction strip 11 are vertically interconnected through TSV-3 17, and the CPW-4 center conduction strip 11 and the CPW-5 center conduction strip 12 are vertically interconnected through TSV-4.

[0032] The two ends of the central conducting strip 23 of one group of planar zigzag CPWs are respectively connected to the two CPW-1 central conducting strips 8 , and the two ends of the central conducting strip 23 of the other group of zigzag CPWs are respectively connected to the CPW-5 central conducting strip 12 .

[0033] The first CPW center strip 8, the third CPW center strip 10, and the fifth CPW center strip 12 are located on the same straight line, with CPW grounding strips 13 located on the upper silicon substrate on opposite sides of the line. The second CPW center strip 9 and the fourth CPW center strip 11 are located on the same straight line, with CPW grounding strips 14 located on the lower silicon substrate on opposite sides of the line. The first CPW center strip 8, the third CPW center strip 10, the fifth CPW center strip 12, and the upper CPW grounding strip 13 are all located in the upper silicon dioxide layer 6. The second CPW center strip 9, the fourth CPW center strip 11, and the lower CPW grounding strip 14 are all located in the lower silicon dioxide layer 7. This creates a three-dimensional zigzag transmission line structure composed of CPW and coaxial TSVs connected end-to-end.

[0034] The structures of TSV 1 15, TSV 2 16, TSV 3 17, and TSV 4 18 are identical. The structure of TSV 15 is taken as an example for explanation. Figure 3 As shown, it includes a TSV copper pillar 1, the outside of the TSV copper pillar 1 is coaxially wrapped with a shielding layer 2 (the material of the shielding layer 2 is benzocyclobutene (BCB)), an outer copper ring pillar 3, and a (silicon dioxide) oxide isolation layer 4. The overall structure of TSV one 15, TSV two 16, TSV three 17, and TSV four 18 are all arranged in a silicon substrate 5.

[0035] Example 2

[0036] The branch line coupler based on coaxial TSV and CPW of the present invention is simulated. The upper silicon dioxide layer 6 and the lower silicon dioxide layer 7 have the same size specifications, both of which are 420 μm in length, 400 μm in width, and 20 μm in thickness. The silicon substrate 5 has a length of 420 μm, a width of 400 μm, and a thickness of 100 μm. TSV 1 15, TSV 2 16, TSV 3 17, and TSV 4 18 have the same dimensions and height of 100 μm. The radius of the TSV copper pillar 1 is 2 μm, the outer radius of the shielding layer 2 is 7.7 μm, the outer radius of the outer copper ring pillar 3 is 9.7 μm, the thickness of the oxide isolation layer 4 is 0.3 μm, and the CPW 1 center conduction strip 8, CPW 2 center conduction strip 9, CPW 3 center conduction strip 10, CPW 4 center conduction strip 11, and CPW 5 center conduction strip 12 are all made of copper and have a width of 20 μm. The thickness of the CPW 4 center conduction strip 11, CPW 5 center conduction strip 12, the silicon substrate upper layer CPW grounding conduction strip 13, and the silicon substrate lower layer CPW grounding conduction strip 14 are all 3 μm. The overall structure of the branch line coupler based on coaxial TSV and CPW of the present invention is only 768.7×695 μm. 2 (0.265×0.240λg 2 ).

[0037] The S parameters of the branch line coupler based on coaxial TSV and CPW of the present invention are simulated, and the simulation results are as follows: Figure 4 As shown, at the operating frequency of 30 GHz, the return loss S11 and insertion loss S12 of the branch line coupler are -45.24 dB and -3.56 dB respectively, the coupling degree S31 and isolation degree S41 are -3.83 dB and -23.95 dB respectively. In the range of 28 to 32 GHz, the return loss is less than -17.3 dB and the isolation degree is less than -15.8 dB.

[0038] Example 3

[0039] Based on the parameters set in Example 2, the phase difference and amplitude imbalance of the branch line coupler based on coaxial TSV and CPW of the present invention are simulated. The simulation results are as follows: Figure 5 As shown, at the operating frequency, the phase difference between the output signals at the through-end and the coupled end is 90.32°, the output port phase difference imbalance is ±2.84°, and the amplitude imbalance is within 0.9dB.

[0040] The characteristics of the branch line coupler based on coaxial TSV and CPW of the present invention are as follows: the branch line coupler is implemented based on coaxial TSV technology and has a compact three-dimensional on-chip structure. It uses three-dimensional zigzag transmission lines based on coaxial TSV and CPW and planar zigzag CPW as branch lines and main lines respectively. Compared with traditional branch line couplers, it is smaller in size and can meet the current development needs of high integration of radio frequency systems. In addition, it has the characteristics of low loss and high reliability in the millimeter wave band. In general, the present invention solves the problems of traditional branch line couplers that are large in size and difficult to integrate, as well as high loss and difficulty in improving performance in the millimeter wave band.

Claims

1. A branch line coupler based on coaxial TSV and CPW, characterized by: The invention comprises two groups of symmetrically arranged three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection, wherein the two groups of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection are connected by two groups of central conduction strips (23) of planar meandering CPW respectively; Each group of three-dimensional zigzag transmission lines based on coaxial TSV and CPW vertical interconnection includes TSV one (15), TSV two (16), TSV three (17), and TSV four (18) which are equidistantly arranged on the same straight line in sequence, the upper end of TSV one (15) is connected to one end of the CPW one center conduction strip (8); the lower end of TSV one (15) is connected to one end of the CPW two center conduction strip (9), the other end of the CPW two center conduction strip (9) is connected to the lower end of TSV two (16), the upper end of TSV two (16) is connected to one end of the CPW three center conduction strip (10), the other end of the CPW three center conduction strip (10) is connected to the upper end of TSV three (17), the lower end of TSV three (17) is connected to one end of the CPW four center conduction strip (11), the other end of the CPW four center conduction strip (11) is connected to the lower end of TSV four (18), and the upper end of TSV four (18) is connected to one end of the CPW five center conduction strip (12); The other ends of two CPW-centered conductive strips (8) in two groups of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection are respectively connected to the two ends of a group of planar meandering CPW-centered conductive strips (23), and the two output ports of the group of planar meandering CPW-centered conductive strips (23) are respectively provided with a CPW (21) for leading out a coupling end and a CPW (22) for leading out an isolation end; The other ends of two CPW five-center conduction strips (12) in two groups of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection are respectively connected to the two ends of the center conduction strip (23) of another group of planar meandering CPW, and the two output ports of the center conduction strip (23) of the group of planar meandering CPW are respectively provided with a CPW (19) for leading out the input end and a CPW (20) for leading out the through end.

2. The branch line coupler based on coaxial TSV and CPW according to claim 1, characterized in that: In each group of three-dimensional meandering transmission lines based on coaxial TSV and CPW vertical interconnection, CPW one-center conduction band (8), CPW three-center conduction band (10), and CPW five-center conduction band (12) are respectively provided with CPW grounding conduction bands (13) on the upper layer of the silicon substrate on opposite sides of the straight line; the CPW one-center conduction band (8), CPW three-center conduction band (10), CPW five-center conduction band (12), CPW grounding conduction band (13) on the upper layer of the silicon substrate, and the center conduction band (23) of the planar meandering CPW are all located in the upper silicon dioxide layer (6); CPW grounding conduction bands (14) in the lower layer of the silicon substrate are respectively provided on opposite sides of the straight line where the CPW second center conduction band (9) and the CPW fourth center conduction band (11) are located. The CPW second center conduction band (9), the CPW fourth center conduction band (11) and the CPW grounding conduction band (14) in the lower layer of the silicon substrate are all located in the lower silicon dioxide layer (7).

3. The branch line coupler based on coaxial TSV and CPW according to claim 2, characterized in that: The TSV 1 (15), TSV 2 (16), TSV 3 (17), and TSV 4 (18) are all arranged in a silicon substrate (5), and the silicon substrate (5) is arranged between an upper silicon dioxide layer (6) and a lower silicon dioxide layer (7).

4. The design method of a branch line coupler based on coaxial TSV and CPW according to claim 3, characterized in that: A three-dimensional meandering transmission line based on coaxial TSV and CPW vertical interconnection is used as the 50Ω transmission line of the 3dB branch line coupler, and a planar meandering CPW is used as the 35.35Ω transmission line. The four ports are respectively led out by CPW with a characteristic impedance of 50Ω.

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