TWI712212B - Second-order high penetration coefficient output power ratio branch coupler - Google Patents

Abstract

The present invention is a second-order high-penetration coefficient output power ratio branch-to-stem coupler, which is arranged on a substrate with a transmission line group, two first inductors and a second inductor. The transmission line group includes a first transmission line and a second transmission line. Two ends of the first transmission line are respectively provided with a first extension section and a second extension section that are symmetrical. Two ends of the second transmission line are respectively provided with a third extension section and a fourth extension section that are symmetrical. The bottom edges of the two ends of the first transmission line are respectively provided with a first trapezoidal section and a second trapezoidal section symmetrical. The top edges of the two ends of the second transmission line respectively protrude upwards with a third trapezoidal section and a fourth trapezoidal section. The bottom edge of the middle section of the first transmission line and the top edge of the middle section of the second transmission line are respectively provided with a fifth trapezoidal section and a sixth trapezoidal section which are symmetrical up and down. One of the first inductors is electrically connected between the first trapezoidal section and the third trapezoidal section; the second of the first inductors is electrically connected between the second trapezoidal section and the fourth trapezoidal section. The second inductor is electrically connected between the fifth ladder section and the sixth ladder section, so that the inductance can be used to replace the high-impedance branch trunk transmission line section to reduce the number of lumped components used in the circuit. In addition to making the overall circuit design very Besides being easy, the circuit size can be greatly reduced, so it has the characteristics of wide output bandwidth and flat frequency response.

Description

Second-order high penetration coefficient output power ratio branch coupler

The present invention relates to a second-order high penetration coefficient output power ratio branch coupler, especially a branch that allows users to complete different high penetration coefficient ratios by adjusting the angle of the main branch and the inductance value according to the use requirements Coupler technology.

According to, the traditional branch coupler structure has a four-port circuit with left-right and top-bottom symmetrical properties, and each port is divided into an input port, an output port, a coupling port, and an isolation port according to the usage mode. The basic structure of the traditional branch coupler is four transmission lines, the electrical length of which is a quarter wavelength ( θ =90°), where the output port | S ₂₁ | and the coupling port | S ₃₁ | output power are determined by the characteristic impedance of the transmission line , The phase difference between the two output signals is 90 degrees, and the input port | S ₁₁ | and the isolated port | S ₄₁ | reach below -15dB. In order to meet the requirements of different environments, the characteristic impedance of the transmission line is adjusted so that the output power ratio of the output port and the coupling port can have more changes.

Furthermore, with the advent of the era of mobile communications, the Internet of Things, cloud technology, big data, mobile devices and social media are indispensable elements for the construction of future conferences. Among them, the Internet of Things is the most critical force driving all needs, because it has the strongest relevance to people's lives and the highest demand, and it has become an indispensable and important area in people's daily life. The frequency bands of mobile communication systems are widely distributed, and various active and passive components that need to be used also need to be designed according to different frequency bands. Since the electrical length of the traditional branch coupler transmission line is a quarter wavelength, in the design circuit technology of the reference [3-7], the transmission line is generally used to convert the PI type or It is a T-type equivalent circuit such as reference [8], but at the same time it will produce a parallel capacitance value. Although the second-order branch coupler has the advantages of wideband output and flatness as in reference [2]; however, there are difficulties in manufacturing when designing a high transmission coefficient output power ratio. Therefore, how to develop a set of In view of this difficult point, the branch coupler technology for innovative circuit design has actually become a technical topic that the relevant industry and academia industries urgently want to solve and challenge.

According to what is currently known, there is no patent or paper on a branch coupler that can adjust the angle of the main branch and the inductance value according to the needs of use to achieve different high penetration coefficient ratios. Moreover, based on the urgent needs of the electronics industry, After continuous research and development efforts, the inventors have finally developed a set of the present invention which is different from the technical concept of the above-mentioned technical literature.

The main purpose of the present invention is to provide a second-order high-penetration coefficient output power ratio branch coupler, which mainly uses inductance to replace high-impedance branch trunk transmission line segments to reduce the number of lumped components used in the circuit, in addition to making the overall The circuit design is very easy, and the overall area size of the circuit can be greatly reduced, so it has the characteristics of wider output bandwidth and flat frequency response. The technical means used to achieve the above objectives is to cover the transmission line group, two first inductors and a second inductor on the substrate. The transmission line group includes a first transmission line and a second transmission line. Two ends of the first transmission line are respectively provided with a first extension section and a second extension section that are symmetrical. Two ends of the second transmission line are respectively provided with a third extension section and a fourth extension section that are symmetrical. The bottom edges of the two ends of the first transmission line are respectively provided with a first trapezoidal section and a second trapezoidal section symmetrical. The top edges of the two ends of the second transmission line respectively protrude upwards with a third trapezoidal section and a fourth trapezoidal section. The bottom edge of the middle section of the first transmission line and the top edge of the middle section of the second transmission line are respectively provided with a fifth trapezoidal section and a sixth trapezoidal section which are symmetrical up and down. One of the first inductors is electrically connected between the first trapezoidal section and the third trapezoidal section; the second of the first inductors is electrically connected between the second trapezoidal section and the fourth trapezoidal section. Between trapezoidal segments. The second inductor is electrically connected between the fifth trapezoidal section and the sixth trapezoidal section.

10‧‧‧Substrate

20‧‧‧Transmission line group

21‧‧‧The first transmission line

210‧‧‧First extension

210a,211a,220a,221a1‧‧‧Parallelogram segment

210b,211b,220b,221b‧‧‧rectangular segment

211‧‧‧Second extension

212‧‧‧First ladder section

213‧‧‧Second ladder section

214‧‧‧Fifth trapezoid section

22‧‧‧Second transmission line

220‧‧‧third extension

221‧‧‧ Fourth extension

222‧‧‧Third trapezoidal section

223‧‧‧Fourth trapezoidal section

224‧‧‧The sixth trapezoidal section

30‧‧‧Input port

31‧‧‧Output port

32‧‧‧Coupling port

33‧‧‧Isolated Port

L1‧‧‧First inductor

L2‧‧‧Second inductor

Fig. 1 is a schematic diagram of the circuit structure of the second-stage branch coupler of the present invention.

Fig. 2 is a schematic diagram of the circuit structure of a traditional second-order branch coupler.

Figure 3 is a schematic diagram of the PI type equivalent circuit of the second-order branch coupler of the present invention.

Fig. 4 is a circuit diagram of circuit one of the present invention.

Fig. 5 is a schematic diagram of the physical circuit of circuit 1 of the present invention.

Figure 6 is a schematic diagram of the circuit frequency response of circuit one of the present invention.

Fig. 7 is a circuit diagram of circuit 2 of the present invention.

FIG. 8 is a schematic diagram of the physical circuit of the second circuit of the present invention.

Fig. 9 is a schematic diagram of the circuit frequency response of circuit 2 of the present invention.

In order to allow your reviewer to further understand the overall technical features of the present invention and the technical means to achieve the purpose of the invention, a detailed description is given with specific examples and accompanying drawings:

The circuit design of the present invention is mainly analyzed by a four-port network, as in reference [1]. Since the electrical length of the traditional branch coupler transmission line is a quarter wavelength, in the design circuit technology of the reference [3-7], the transmission line is generally used to convert the PI type or the T type equivalent circuit. For example, reference [8], but at the same time, the problem of parallel capacitance value will also occur. Therefore, the present invention proposes a method of changing the electrical length of the main branch transmission line to generate a negative parallel capacitance value and the aforementioned parallel capacitance value to cancel each other to form a simple and effective Innovative circuit. The circuit structure of the second-order high penetration coefficient output power ratio branch coupler proposed by the present invention is shown in FIG. 1. Design high penetration coefficient in the second-order branch coupler, such as reference [9-10] output power ratio, the branch resistance value mainly To affect the amount of the coupled signal to the coupling port, the higher the penetration coefficient ratio, the higher the impedance value of the branch trunk. The width of the microstrip transmission line may be less than 0.1mm, and there will be difficulties in production. Therefore, the present invention uses a transmission line PI-type equivalent conversion circuit, which uses inductance to replace the high-impedance branch trunk transmission line segment. In addition, it is equivalent to the equivalent negative capacitance value generated by the positive capacitance value of the capacitor by the main branch lengthening. The two capacitors offset each other in addition to achieving the goal of circuit design, while reducing the number of lumped components used in the circuit. Moreover, the designer only needs to adjust the angle of the main branch and the inductance value to complete the design of different high penetration coefficient ratios. Therefore, the overall circuit design of the present invention is very easy and greatly reduces the overall area of the circuit to 20% of the traditional size. The width is also very wide, and the frequency response is also quite flat, which greatly assists the wiring and construction of radio frequency circuits.

Please refer to Figs. 3~4. In order to achieve the main purpose of the present invention, the embodiment includes a substrate 10, a transmission line group 20 covering the substrate 10, two first inductors L1 and a second inductor L2, etc. Technical characteristics. The transmission line group 20 includes a first transmission line 21 and a second transmission line 22 that are juxtaposed laterally. Each of the two ends of the first transmission line 21 is provided with a first extension section 210 and a second extension section 211 that are symmetrical and extend diagonally downward. Each of the two ends of the second transmission line 22 is provided with a third extension section 220 and a fourth extension section 221 that are symmetrical and extend diagonally downward. A first trapezoidal section 212 and a second trapezoidal section 213 symmetrically protrude downward from the bottom edges of the two ends of the first transmission line 21 respectively. A third trapezoidal section 222 and a fourth trapezoidal section 223 that are symmetrical to each other protrude upward from the top edges of the two ends of the second transmission line 22. The third trapezoidal section 222 and the fourth trapezoidal section 223 are symmetrical with the first trapezoidal section 212 and the second trapezoidal section 213 respectively. A fifth trapezoidal section 214 and a sixth trapezoidal section 224 are respectively provided near the bottom edge of the middle section of the first transmission line 21 and near the top edge of the middle section of the second transmission line 22. One of the first inductors L1 is electrically connected between the first trapezoidal section 212 and the third trapezoidal section 222. Second, the first inductor L1 is electrically connected to the Between the two trapezoidal sections 213 and the fourth trapezoidal section 223, the second inductor L2 is electrically connected between the fifth trapezoidal section 214 and the sixth trapezoidal section 224.

Please refer to an embodiment shown in FIG. 4, the length of the first transmission line 21 and the second transmission line 22 are both L3=99mm, and the width is W2=3mm. The distances from the end of the first extension section 210 to the end of the second extension section 211 and the end of the third extension section 220 to the end of the fourth extension section 221 are all L6=123 mm. The distances from the top edge of the first extension section 210 to the bottom edge of the third extension section 220 and the top edge of the second extension section 211 to the bottom edge of the fourth extension section 221 are all W1=18.5mm.

Please refer to another embodiment shown in FIG. 7, the length of the first transmission line 21 and the second transmission line 22 are both L3=96.5 mm, and the widths are both W2=3 mm. The distances from the end of the first extension section 210 to the end of the second extension section 211 and the end of the third extension section 220 to the end of the fourth extension section 221 are all L6=120.5 mm. The distances from the top edge of the first extension section 210 to the bottom edge of the third extension section 220 and the top edge of the second extension section 211 to the bottom edge of the fourth extension section 221 are all W1=18.5mm.

Specifically, as shown in FIGS. 4 and 7, the distance between the first transmission line 21 and the second transmission line 22 is W3=2.5 mm. The first extension section 210, the second extension section 211, the third extension section 220 and the fourth extension section 221 each include a parallelogram section 210a, 211a, 220a, 221a and a rectangular section 210b extending from the end of the parallelogram section, 211b, 220b, 221b. The length of each rectangular section is L1=5mm. The length of the two long sides of each parallelogram segment is L2=8.6mm.

Specifically, as shown in FIGS. 4 and 7, the length of the lower bottom of the first trapezoidal section 212, the second trapezoidal section 213, the third trapezoidal section 222, and the fourth trapezoidal section 223 are all L4=2mm. The width of the opposite upper bottom of the fifth trapezoidal section 214 and the sixth trapezoidal section 224 is L5=0.5mm. The The distances between the first trapezoidal section 212 and the third trapezoidal section 222, and the second trapezoidal section 213 and the fourth trapezoidal section 223 are all W4=0.5 mm.

Please refer to FIGS. 5 and 8, the end of the first extension 210 is electrically connected to an input port 30, the end of the second extension 211 is electrically connected to an output port 31, and the end of the third extension 220 is electrically connected to an Isolated port 33. The end of the fourth extension 221 is electrically connected to a coupling port 32. When the output power ratio of the output port 31 to the coupling port 32 is 10:1, the inductance value of the two first inductors L1 is between 50~ Between 60nH, the inductance value of the second inductor L2 is between 25~35nH. When the output power ratio of the output port 31 to the coupling port 32 is 20:1, the inductance value of the two first inductors L1 is between 70~85nH, and the inductance value of the second inductor L2 is between 30~45nH .

In addition, the present invention is mainly a second-order branch coupler design that can be applied to the IoT frequency band (915MHz) with high penetration coefficient and output power ratio. The traditional second-order branch coupler (as shown in Figure 2) is used as the design basis. Given the output power ratio P2: P3, the characteristic impedance value of each transmission line, Z ₁ , Z ₂ , and Z ₃ , can be obtained by formula (1-3). The electrical lengths θ ₁ , θ ₂ , and θ ₃ of each transmission line are all 90 ^° . The new second-order high-penetration coefficient output power ratio branch coupler is converted by using two PI-type equivalent circuits for each transmission line segment of the traditional second-order branch coupler. These two PI-type equivalent circuits are (1) C-TL-C; (2) CLC. C-TL-C equivalent circuit is applied to a main transmission line branches Z _1, 90 ^0; its conversion formula such as formula (4-5) as shown, and applied to CLC is an equivalent circuit of the transmission line branches off Z _2, 90 ⁰ With Z ₃ , 90 ⁰ ; its conversion formulas correspond to formula (6-7) and formula (8-9) respectively. In order to make each branch of the trunk transmission line through the PI type equivalent conversion capacitors can cancel each other, the parallel capacitance must meet the formula (10-12). The characteristic impedance of branch trunk Z ₂ formula (1), Z ₃ formula (2) and the main branch characteristic impedance Z ₁ formula (3), the branch trunk transmission line is equivalent to the inductance L ₁ Formula (6) and L ₂ formula (8), capacitor C ₁ formula (7) and C ₂ formula (9), and the main branch transmission line through PI type equivalent conversion to obtain the corresponding transmission line impedance Z _o1 And capacitor C _o1 , as shown in Figure 3, then add the four diagonal C _o1 and C ₁ capacitors to offset the formula as (9), and add the two C _o1 capacitors in the middle and one C ₂ capacitor to offset The pin formula is as formula (10), the capacitor C _o1 can offset the capacitance of C ₁ and C ₂ as formula (11), and then the electrical length θ _{o1 of the} main branch is calculated as formula (13), the characteristic impedance of the main branch The _Zo1 formula is as (14). According to the above design process, the design of the second-order branch coupler applied to the 915MHz high penetration coefficient output power ratio of the Internet of Things frequency band can be completed, and the circuit architecture is shown in Figure 1. The present invention provides two output power ratio conditions for theory and practice to verify the correctness of the design process, as shown in Table 1.

θ _o1 =cos ^-1 (C _o1 ×ω×Z ₁ ×sin θ ₁ +cos θ ₁ ) (4)

C _o1 +C ₁ =0 (10)

C _o1 +C _o1 +C ₂ =0 (11)

θ _o1 =cos ^-1 (C _o1 ×ω×Z ₁ ×sin θ ₁ +cos θ ₁ ) (13)

The second-order high-penetration coefficient output power ratio of the present invention is designed with a branch-to-stem coupler. After analysis and adjustment, given conditions, theoretical values of different output power ratios are obtained, as shown in Table 1. The circuit characteristics are verified by electromagnetic simulation software. The thickness of FR-4 is 1.6mm and the relative dielectric constant is 4.3. After the structure is optimized and adjusted, the circuit size is calculated by the LineGauge of the simulation software IE3D. The circuit is shown in Figure 4. As shown, circuit two is shown in Figure 7. After being processed by the engraving machine, the finished circuit of circuit one is shown in Figure 5, and the finished circuit of circuit two is shown in Figure 8. The Anritsu-MS46122B-010 vector network analyzer measures the frequency from 1MHz to 8GHz and obtains the circuit The measured value is compared with the analog value, and the frequency response of circuit one output power ratio of 10:1 is shown in Figure 6, and the frequency response of circuit two output power ratio of 20:1 is shown in Figure 9. The second-order branch coupler with high penetration coefficient and output power ratio at the working frequency of 915MHz, the rebound of the signal at the input and isolation ends |S ₁₁ | and |S ₄₁ | are both below -15dB, and the output power at both ends of the output and coupling signal The ratios |S ₂₁ | and |S ₃₁ | are maintained at the design ratios as shown in Table 2. The above simulation and measurement results are quite consistent.

Through the above specific examples, the present invention is indeed a second-order high-penetration system Digital output power ratio. Branch-to-stem coupler design, high penetration coefficient output power ratio, made with microstrip transmission line on common board (FR-4), high coupling coefficient output power ratio design can basically achieve high penetration smoothly The coefficient output power ratio design will encounter many manufacturing difficulties due to the high impedance value generated by the transmission line. Therefore, the present invention replaces the high impedance transmission line with an inductance, and only needs to adjust the electrical length and inductance value of the main branch to adjust different outputs. The power ratio and the main branch impedance can be maintained at 50Ω to reduce the discontinuous contact with the port. The circuit production area is 20% of the traditional circuit size, and the area is greatly reduced. The above circuits are all simulated by circuit simulation software to simulate their design feasibility. Using sheet material FR-4, the thickness is 1.6mm, the relative permittivity is 4.3, and the circuit structure has been optimized and adjusted. The simulation results are quite close to the actual measurement results. It is feasible and can be widely used in other power distribution systems with different center frequency applications.

The above are only feasible embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent implementation of other changes based on the content, characteristics and spirit of the following claims shall be It is included in the scope of the patent of the present invention. The structural features of the invention specifically defined in the claim are not found in similar articles, and are practical and progressive, and have already met the requirements of an invention patent. The application is filed in accordance with the law. I would like to request the Bureau of Jun to approve the patent in order to protect this The legitimate rights and interests of the applicant.

references

[1] J. Reed, and GJ Wheeler, "A Method of Analysis of Symmetrical Four-Port Networks," IRE Transactions on Microwave Theory and Techniques , vol. 4, no. 4, pp. 246-252, Oct. 1956.

[2] Chen Xuanyu, Research on Broadband Trunk Coupler with Highly Flat Power and Phase Bandwidth, Master ± Thesis, Institute of Communication Engineering, Fengjia University, Republic of China 1999.

[3] Satoshi Kondo, Hajime Kondo, and Hitoshi Ishida, "A Reduced-Size and Tunable Branch-Line 3dB Hybrid," Microwave Conference Proceedings (APMC) , pp. 37-40, Dec. 2011.

[4] Tsu-Wei Lin, Yi-Chyun Chiou, and Jen-Tsai Kuo, "Distributed and Lumped-Element Realizations of Wideband Branch-Line Hybrids with Arbitrary Power Division," Microwave Conference Proceedings (APMC) , pp. 2112-2115 , Dec. 2009.

[5] Yi-Chyun Chiang, and Chong-Yi Chen, "Design of a Wide-Band Lumped-Element 3-dB Quadrature Coupler," IEEE Transactions on Microwave Theory and Techniques , vol. 49, no. 3, pp. 476 -479, Mar. 2001.

[6] SND Azizi, SKA Rahim, and MI Sabran, "Realization of a compact branch line couple using semi-lumped element," Wireless Technology and Applications (ISWTA), pp. 21-23, Sept. 2011.

[7] Chia-Hung Mou, and Chao-Hsiung Tseng, "A Bandwidth-Enhanced 3-dB Lumped-Element Branch-Line Coupler Based on Asymmetrical E-Equivalent Sections," Microwave Conference Proceedings (APMC) , pp. 29-32 , Dec. 2011.

[8] WI Bowman, and JM McNamee, "Development of Equivalent Pi and T Matrix Circuits for Long Untransposed Transmission Lines," IEEE Transactions on Power Apparatus and Systems , vol. 83, no. 6, pp. 625-632, Jun. 1964.

[9] Henning Mextorf, and Reinhard Knöchel, "Ultra-wideband loose coupling directional couplers with high directivity," Microwave Conference (EuMC) , pp. 294-297, Oct. 2013.

[10] A. Abramowicz, A. Golaszewski, and L. Kowalczyk, "High Directivity Couplers Realized in Microstrip Line Technology," Electromagnetics in Advanced Applications (ICEAA) , pp. 730-733, Sept. 2015.

20‧‧‧Transmission line group

21‧‧‧The first transmission line

210‧‧‧First extension

210a,211a,220a,221a‧‧‧parallelogram segment

210b,211b,220b,221b‧‧‧rectangular segment

211‧‧‧Second extension

212‧‧‧First ladder section

213‧‧‧Second ladder section

214‧‧‧Fifth trapezoid section

22‧‧‧Second transmission line

220‧‧‧third extension

221‧‧‧ Fourth extension

222‧‧‧Third trapezoidal section

223‧‧‧Fourth trapezoidal section

224‧‧‧The sixth trapezoidal section

Claims (7)

A second-order high-penetration coefficient output power ratio branch-to-stem coupler, which comprises a substrate, a transmission line group covering the substrate, two first inductors and a second inductor; the transmission line group includes two lateral linear extensions A first transmission line and a second transmission line are juxtaposed. The two ends of the first transmission line are each provided with a first extension section and a second extension section that are symmetrical and extend downward obliquely; each of the two ends of the second transmission line A third extension section and a fourth extension section that are symmetrical and extend downward obliquely are provided; the bottom edges of the two ends of the first transmission line respectively protrude downwardly with a first trapezoidal section and a second section symmetrically. Two trapezoidal sections; the top edges of the two ends of the second transmission line each project upwardly with a third trapezoidal section and a fourth trapezoidal section symmetrically, the third trapezoidal section and the fourth trapezoidal section are respectively the same as the first trapezoid Section and the second trapezoidal section are symmetrical up and down; the bottom edge of the middle section of the first transmission line and the top edge of the middle section of the second transmission line are respectively provided with a fifth trapezoidal section and a sixth trapezoidal section that are symmetrical up and down; The inductor is electrically connected between the first trapezoidal section and the third trapezoidal section; the second inductance is electrically connected between the second trapezoidal section and the fourth trapezoidal section; the second inductor is electrically connected to the first trapezoidal section Between the five trapezoidal segments and the sixth trapezoidal segment; wherein the end of the first extension is electrically connected to an input port; the end of the second extension is electrically connected to an output port; the end of the third extension is electrically connected to an Coupling port; the end of the fourth extension section is electrically connected to an isolation port; when the output power ratio of the output port to the coupling port is 10:1, the inductance value of the two first inductors is between 50-60 nH; The inductance value of the second inductor is between 25 and 35 nH; when the output power ratio of the output port to the coupling port is 20:1, the inductance value of the two first inductors is between 70 and 85 nH; the The inductance value of the second inductor is between 30~45nH. The second-order high-penetration coefficient output power ratio branch coupler described in claim 1, wherein the lengths of the first transmission line and the second transmission line are both L3=99mm, and the widths are both W2=3mm; the first The distances from the end of the extension section to the end of the second extension section and the end of the third extension section to the end of the fourth extension section are all L6=123mm; the top edge of the first extension section to the first extension section The distance between the bottom edge of the three extension sections and the top edge of the second extension section to the bottom edge of the fourth extension section is W1=18.5mm. The second-order high-penetration coefficient output power ratio branch coupler described in claim 1, wherein the lengths of the first transmission line and the second transmission line are both L3=96.5mm, and the widths are both W2=3mm; The distances from the end of an extension section to the end of the second extension section and the end of the third extension section to the end of the fourth extension section are all L6=120.5mm; the top edge of the first extension section to the bottom edge of the third extension section and The distance from the top edge of the second extension section to the bottom edge of the fourth extension section is W1=18.5mm. The second-order high-penetration coefficient output power ratio branch-to-branch coupler according to claim 1, wherein the distance between the first transmission line and the second transmission line is W3=2.5mm. The second-order high-penetration coefficient output power ratio branch coupler according to claim 1, wherein the first extension section, the second extension section, the third extension section and the fourth extension section each comprise a parallelogram Segment and a rectangular segment extending from the end of the parallelogram segment. The second-order high penetration coefficient output power ratio branch coupler as described in claim 5, wherein the length of each rectangular section is L1=5mm; the length of the two long sides of each parallelogram section is L2=8.6 mm. The second-stage high-penetration coefficient output power ratio branch-to-stem coupler according to claim 1, wherein the lower bottom lengths of the first ladder section, the second ladder section, the third ladder section, and the fourth ladder section are relative to each other All are L4=2mm; the width of the opposite upper bottom of the fifth trapezoidal section and the sixth trapezoidal section are both L5=0.5mm; the first trapezoidal section and the third trapezoidal section, and the second trapezoidal section and the first The spacing between the four trapezoidal segments is W4=0.5mm.

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