A microwave interconnection structure between boards adapted to DC to 40 GHz

Abstract

The present invention provides a microwave interconnection structure between boards adaptable to DC to 40 GHz, adopting a cross-shaped rounded corner mirror symmetry structure, which includes left and right high-impedance parts, a middle rounded corner low-impedance part and an arc structure. The left and right high-impedance parts are arranged on both sides of the middle rounded corner low-impedance part, and the arc structure is used for the connection transition between the left and right high-impedance parts and the middle rounded corner low-impedance part; the center line of the interconnection structure of the middle rounded corner low-impedance part is sunken downward to the bottom of the gap between the microwave boards. The present invention realizes the uniform transmission of broadband microwave signal energy between microwave substrates, the insertion loss of microwave signals at each frequency within the working bandwidth is the same, and at the same time, the reflection signals at any frequency within the bandwidth can be reduced to an extremely low level, achieving good matching.

Description

Technical Field

[0001] The invention relates to an interconnection structure adapted to DC to 40 GHz microwave boards, belonging to the field of microwave technology. Background Art

[0002] Interconnection between microwave boards is a very flexible and effective means to achieve electrical connection between microwave modules and the whole machine substrate, and is widely used in current microwave whole machine design.

[0003] Traditional interconnection between microwave boards is gold wire or standard-width strip line. In order to eliminate impedance mismatch caused by discontinuity between different microwave dielectrics, it is necessary to make high-low impedance anisotropic extended sections on the transmission conduction band of the microwave dielectric substrate for impedance matching. However, this type of matching method belongs to narrow-band matching, which restricts the available working frequency band of the module or the whole machine. Taking the interconnection with standard-width strip line as an example: the frequency range is narrow, the absolute bandwidth is 10 GHz (DC to 10 GHz), and the in-band return loss is not greater than -15 dB, which affects the use of high-frequency broadband microwave single machines. It cannot meet the urgent needs of existing ultra-wideband whole machines and has poor flexibility. Summary of the Invention

[0004] The technical problem solved by the invention is: overcoming the deficiencies of the prior art, the invention provides an interconnection structure adapted to DC to 40 GHz microwave boards, reducing the narrow-band matching size in the substrate transmission direction, further reducing the module size, and realizing ultra-wideband characteristics. This structure can be realized by high-efficiency stamping processing; the interconnection structure between the boards is recessed in a circular arc shape towards the ground plane, reducing the width size of the interconnection structure, eliminating stress, and expanding the working frequency band.

[0005] The technical solution of the invention is: an interconnection structure adapted to DC to 40 GHz microwave boards, adopting a cross-shaped cross-rounding mirror symmetry structure, including left and right high-impedance parts, a middle rounded-corner low-impedance part, and an arc structure. The left and right high-impedance parts are arranged on both sides of the middle rounded-corner low-impedance part, and the arc structure is used for the connection and transition between the left and right high-impedance parts and the middle rounded-corner low-impedance part; the center line of the interconnection structure of the middle rounded-corner low-impedance part is recessed downward towards the bottom of the gap between the microwave boards.

[0006] Further, the material of the interconnection structure between the microwave boards is a single-material metal sheet.

[0007] Further, the sizes of the left and right high-impedance parts are symmetrical and equal, the width is equal to that of the 50-ohm microstrip transmission line of the microwave substrate, and the length meets the process requirements for the combination of the interconnection structure and the substrate microstrip line.

[0008] Further, all four right angles of the middle rounded-corner low-impedance part are rounded.

[0009] Further, the middle rounded-corner low-impedance part starts from the edge of the interconnected microwave substrate.

[0010] Furthermore, the width of the middle rounded-corner low-impedance part is w, and the method for analyzing and calculating the height h of the center line from the bottom of the gap is as follows:

[0011] Analyze and calculate ε r = ε r ' = 1 for the characteristic impedance Z'0 of a zero-thickness, single-medium microstrip line, where ε r and ε r ' both represent the relative dielectric constant of the air medium;

[0012] Given the width between two microstrip substrates and the gap depth, calculate the initial values of the width w and the height h;

[0013] Use a three-dimensional simulation software to establish a three-dimensional simulation model of the interconnection structure between the microwave boards, and fine-tune the width w and the height h for model optimization. The optimization goal is that the return loss from DC to 40 GHz ≤ -25 dB.

[0014] The advantages of the present invention compared with the prior art are as follows:

[0015] (1) Compared with traditional standard strip lines and gold wire interconnections, the present invention does not have matching segments for different frequency bands, is small in size, and the bandwidth can cover microwave products from DC to the EHF band. It can be directly applied as a standard circuit, once and for all;

[0016] (2) Compared with traditional standard strip lines and gold wire interconnections, the present invention does not need to fill the gap between the substrates with conductive glue to improve the matching, nor does it need to perform high-low impedance narrow-band matching through the conductive strip on the substrate. It simplifies the production process, reduces production links, thereby reducing costs and improving reliability. At the same time, it will not introduce some unnecessary parasitic effects, thus improving the in-band amplitude-frequency characteristics;

[0017] (3) Compared with traditional standard strip lines and gold wire interconnections, the present invention can achieve the optimal matching standard setting of various gap widths and depths, achieving perfect matching. At the same time, the present invention uses mature materials in implementation, has a simple form, and can be realized by a direct stamping process, with good product realizability. The ultra-wideband compact characteristics have universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a three-dimensional simulation model diagram of the interconnection structure between DC~40 GHz microwave boards of the present invention;

[0019] Figure 2 is a three-dimensional simulation result diagram of the interconnection structure between DC~40 GHz microwave boards of the present invention;

[0020] Figure 3It is a measured result diagram of the transmission characteristics and return loss of a physical microwave substrate of the microwave board - to - board interconnection structure applying the design concept of the present invention. Detailed implementation manners

[0021] The present invention will be described in conjunction with the accompanying drawings and embodiments.

[0022] A microwave board - to - board interconnection structure adapted to DC to 40 GHz adopts a brand - new cross - shaped cross - rounded - corner mirror - symmetric topology form. The interconnection structure material is a single - material metal sheet with a certain thickness. As Figure 1 shown in the top view, the microwave board - to - board interconnection structure includes left - and - right high - impedance parts 1, a middle rounded - corner low - impedance part 2, and an arc structure 3 at the interconnection of the left - and - right high - impedance parts 1 and the middle rounded - corner low - impedance part 2. Among them, the width of the left - and - right high - impedance parts 1 is equal to the width of the 50 - ohm microstrip transmission line of the microwave substrate, and the length is 0.3 mm, and this length meets the process requirements of the combination of the interconnection structure and the substrate microstrip line. The width of the middle rounded - corner low - impedance part 2 is w, the height of the center line from the bottom of the gap is h, and the thickness is t.

[0023] According to Figure 1 shown, the method for analyzing and calculating the width w and height h of the middle rounded - corner low - impedance part 2 is as follows:

[0024] First, analyze and calculate the characteristic impedance Z'0 of the zero - thickness, "single - dielectric microstrip line" with ε r =ε r ' = 1. The characteristic impedance calculation formula is as shown in formula (1). ε r 、ε r ' both represent the relative dielectric constant of the air medium. Assuming that the width between two microstrip substrates is 0.3 mm and the gap depth is 1.3 mm, using formula (1) for calculation, the initial values of the width w and height h can be obtained. The width w is 2.95 mm and the height h is 0.6 mm, and these initial values are used as the basis for 3D field simulation.

[0025]

[0026] Use 3D simulation software to establish a model. The thickness of the microwave substrate is 0.381 mm, the dielectric constant ε r of the microwave substrate is taken as 9.9, the thickness of the conductive strip is 0.005 mm, the distance between the ground plane of the microwave substrate and the bottom of the gap is 0.919 mm, the distance between two completely symmetric microwave substrates is 0.3 mm, the interconnection structure is set as an ideal conductor with zero thickness, the air height is 2.5 mm, and the outside of the air box is an ideal conductor. The specific configuration is as Figure 1 shown. Through the initial values of this topological structure, fine - tuning the key dimensions w and h of the 3D simulation software model can achieve high - efficiency transmission characteristics from DC to 40 GHz and low return loss. The optimization goal is that the return loss dB(S(1,1)) from DC to 40 GHz is less than or equal to - 25 dB.

[0027] The simulation optimization results are as follows Figure 2 shown Figure 2 In the simulation result graph, the abscissa is the frequency with the unit of GHz; the ordinate is the logarithmic result of the amplitudes of S21 and S11 with the unit of dB. The return loss dB(S(1,1)) from DC to 40 GHz is less than or equal to -26 dB, meeting the design requirements.

[0028] Based on the interconnection structure, reasonably adjusting the size of the depression of the structure between the slots towards the bottom of the slots can achieve the optimal matching between microwave boards from DC to 40 GHz. When the center line of the low-impedance part 2 with intermediate rounded corners of the interconnection structure is at the same distance from the substrate transmission conduction band and the bottom of the slot, the width w of the low-impedance interconnection structure in the middle is relatively wide, which is not conducive to processing and manufacturing. Depressing the center line of the low-impedance part 2 with intermediate rounded corners of the interconnection structure towards the bottom of the slot, that is, reducing the dimension h from the bottom of the slot, can thus reduce the width dimension of the low-impedance part 2 with intermediate rounded corners of the interconnection structure.

[0029] Embodiment:

[0030] The microwave substrate is A-493 (dielectric constant 9.9), the substrate thickness is 0.381 mm, the conductor thickness is 0.003 mm, and the air height of the box is 2.5 mm. The slot width between two completely identical substrates is 0.3 mm, and the slot depth is 1.3 mm. In the frequency range from DC to 40 GHz, by reasonably selecting the key dimensions of the interconnection structure: the width, length, and depression height of the transition section structure, it is possible to ensure a small insertion loss and an optimal voltage standing wave ratio within the entire broadband frequency band.

[0031] In practical applications, the thickness of the microwave substrate is different and the slot depth between the boards is different. At the same time, the actual assembly slot width process of the microwave substrate can be realized within a specific range. Therefore, the types of slots between microwave substrates are predictable two-dimensional matrix units. According to the predictable two-dimensional matrix units, in order to meet the slot widths and depths between different microwave substrates, the corresponding slot broadband interconnection structures can be pre-designed, and they can be classified by size to form shelf products. During the production process, during operation, directly select the corresponding broadband interconnection structure between microwave boards according to the drawing for connecting the microwave boards. This greatly improves production efficiency, and the microwave ultra-wideband performance is excellent.

[0032] Figure 3The test results of directly using the microwave board - to - board interconnection structure of the present invention for two microwave substrates with a slot width of 0.3 mm and a depth of 1.3 mm are given. The test results show that the return loss is better than - 19 dB in the frequency range of 0.1 - 20 GHz and better than - 9 dB in the frequency range of 0.1 - 32 GHz. From the test results, it can be seen that the amplitude flatness and return loss in the frequency band above 25 GHz deteriorate significantly. The main reason is that the actual size and shape of the downward - sunken gold strip are not completely consistent with the simulation, and it is also affected by the limited high - frequency performance of the CPWG port. Therefore, the actual transmission and return loss performance are better than the test results.

[0033] In summary, the present invention adopts a microwave board - to - board interconnection structure suitable for DC - 40 GHz to directly perform ultra - wideband interconnection matching between substrates. Thus, it saves the work of designing narrow - band multi - stage high - and - low - impedance transmission - line matching segments for the impedance discontinuity caused by the propagation of signals with different frequencies in dielectrics with different dielectric constants for the substrates. At the same time, it saves the heavy work of using conductive glue filling to optimize the matching for ultra - wide and ultra - deep slots between multiple LTCC substrates at present to slightly improve the in - band amplitude flatness index. This board - to - board matching interconnection can meet the interconnection requirements between microwave modules or whole - machine substrates in the DC to EHF frequency bands, and can be directly applied without re - design, which speeds up the development speed.

[0034] The parts not detailed in the present invention belong to the well - known technologies in the art.

Claims

1. A microwave interconnection structure adapted to DC to 40 GHz, characterized in that: Adopt a cross - cross rounded - corner mirror - symmetric structure, which includes left - and - right high - impedance parts (1), a middle rounded - corner low - impedance part (2) and an arc structure (3). The left - and - right high - impedance parts (1) are arranged on both sides of the middle rounded - corner low - impedance part (2). The arc structure (3) is used for the connection and transition between the left - and - right high - impedance parts (1) and the middle rounded - corner low - impedance part (2); the center line of the interconnection structure of the middle rounded - corner low - impedance part (2) is sunken downward to the bottom of the gap between the microwave boards. The width of the middle rounded - corner low - impedance part (2) is w, and the method for analyzing and calculating the height h of the center line from the bottom of the gap is as follows: Analysis and calculation of ε r = ε r ' is the characteristic impedance Z'0 of a zero-thickness, single-medium microstrip line with ε r , ε r ' both representing the relative permittivity of air medium; Given the width between two microstrip substrates and the gap depth, the initial values of the width w and the height h are calculated using the following formula: Use a three - dimensional simulation software to establish a three - dimensional simulation model of the microwave board and the interconnection structure between the microwave boards, and fine - tune the width w and the height h to optimize the model. The optimization goal is that the return loss from DC to 40 GHz is ≤ - 25 dB.

2. The microwave board - to - board interconnection structure adapted to DC to 40 GHz according to claim 1, wherein: The material of the interconnection structure between the microwave boards is a single - material metal sheet.

3. The microwave board - to - board interconnection structure adapted to DC to 40 GHz according to claim 1, characterized in that: The sizes of the left - and - right high - impedance parts (1) are symmetric and equal. The width is the same as that of the 50 - ohm microstrip transmission line of the microwave substrate, and the length meets the requirements of the bonding process between the interconnection structure and the substrate microstrip line.

4. A microwave interconnection structure between boards adapted to DC to 40 GHz, characterized in that: All four right - angles of the middle rounded - corner low - impedance part (2) are rounded.

5. A microwave interconnection structure between boards adapted to DC to 40 GHz, characterized in that: The middle rounded - corner low - impedance part (2) starts from the edge of the interconnected microwave substrate.

Images