Multilayer microwave comprehensive backboard structure

Abstract

The invention belongs to the technical field of microwave transmission, and particularly relates to a multilayer microwave comprehensive backboard structure, which comprises a PCB (Printed Circuit Board) and an adapter board, a plurality of combined connector modules are arranged on the PCB, and a plurality of radio frequency signal terminals and a plurality of high-speed signal terminals are arranged on the combined connector modules; the adapter plate is located on the side, away from the combined connector module, of the PCB, guide columns and a connector are arranged between the adapter plate and the PCB, and a three-dimensional space is established between the adapter plate and the PCB through the guide columns and the connector. According to the multi-layer microwave comprehensive backboard structure in the technical scheme, a three-dimensional space is established between the adapter plate and the PCB through the guide columns and the connectors, the problem of cable space occupancy is effectively solved, and equipment is miniaturized, light and integrated.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave transmission, and particularly relates to a multi-layer microwave integrated backplane structure. Background Art

[0002] A microwave integrated backplane is a structural component used in high-frequency electronic systems, especially in fields such as microwave communication, radar, and satellite communication. It integrates circuit design and backplane functions, provides various functions such as high-frequency signal transmission, signal distribution, and power distribution, and is suitable for application environments with high density, high frequency, and high reliability.

[0003] With the development of electronic systems towards miniaturization, high integration, high reliability, and multi-function, various interconnect components are increasingly applied in devices with limited space, requiring the interconnect components to have characteristics such as simple structure, transceiver integration, and high isolation. The existing backplane technology of separating modulus (the method of digital backplane + RF cable) can no longer fully meet the requirements of electronic systems, and new design ideas and integration methods must be adopted.

[0004] Therefore, how to optimize the cable space layout during microwave transmission, reduce the space occupancy rate of the device, effectively compatible with high-speed and RF signals, and transform the product into a miniaturized, lightweight, and integrated device is an urgent problem to be solved. Summary of the Invention

[0005] In view of the problems in the prior art, the present invention proposes the following technical solutions:

[0006] A multi-layer microwave integrated backplane structure includes a PCB board and an adapter board. A plurality of combined connector modules are arranged on the PCB board, and a plurality of RF signal terminals and a plurality of high-speed signal terminals are arranged on the combined connector modules;

[0007] The adapter board is located on the side of the PCB board away from the combined connector module. Guide posts and connectors are arranged between the adapter board and the PCB board, and a three-dimensional space is established between the adapter board and the PCB board through the guide posts and connectors.

[0008] Preferably, one end of the guide post is connected to the adapter board, and the other end of the guide post is connected to the PCB board by a second screw;

[0009] The connector is fixed on the PCB board and the adapter board by fixing screws.

[0010] Preferably, it further includes a positioning pin, and the positioning pin passes through the combined connector module and the PCB board and is threadedly engaged with a nut.

[0011] Preferably, as the above technical solution, a first blind hole is provided in the welding area of the PCB corresponding to the radio frequency signal terminal, and the radio frequency signal terminal extends into the first blind hole.

[0012] Preferably, as the above technical solution, the connector has a radio frequency connector and a high-speed connector. A counterbore is provided on the PCB at the position corresponding to the radio frequency head of the radio frequency connector, and the radio frequency head is introduced into the counterbore for pin soldering;

[0013] A metal shielding cap is soldered on the PCB through a solder ring, and the metal shielding cap covers the inner conductor of the radio frequency connector.

[0014] Preferably, as the above technical solution, a slot hole is provided in the crimping area of the PCB corresponding to the high-speed signal terminal, and the high-speed signal terminal extends into the slot hole;

[0015] Some of the slot holes are set as second blind holes, and the rest of the slot holes are set as through holes. The through holes use back drilling technology to remove the "Stub" branches.

[0016] Preferably, as the above technical solution, the PCB adopts a stacked design and is composed of multiple dielectric substrates, prepregs sandwiched between every two adjacent dielectric substrates, and copper layers etched on the front and back sides of the dielectric substrates. The dielectric substrate is set to 18 layers. The L1-L14 layers transmit digital signals, and the L15-L18 layers transmit radio frequency signals;

[0017] Among them, the copper layers of L1-L18 are Top Layer, GND02, ART03, GND04, ART05, GND06, ART07, GND08, PWR09, PWR10, GND11, ART12, GND13, ART14, GND15, ART16, GND17, Bottom Layer in sequence.

[0018] Preferably, as the above technical solution, the L15-L18 layers are completely isolated by a grounding layer, laminated with microwave material TSM-DS3, use strip lines as conductors for transmitting signals, the radio frequency signal layers are entirely grounded, and contact buried vias are provided along the outside of the strip lines. The overall height of the grounding buried vias penetrates from the metal ground plane of the 15th layer to the metal ground plane of the 17th layer; both the upper and lower ends of the strip line have outer conductors as shielding layers, and the outer conductors are connected to the ground plane through the grounding buried vias.

[0019] The beneficial effects of the present invention are:

[0020] 1. A multi-layer microwave integrated backplane structure in this technical solution creates a three-dimensional space between the adapter board and the PCB board through guide posts and connectors, effectively solving the problem of cable space occupancy, making the equipment smaller, lighter, and more integrated, and can be applied to small electronic system fields such as missile-borne, airborne, and UAVs.

[0021] 2. A multi-layer microwave integrated backplane structure in this technical solution combines a digital backplane and a radio frequency backplane. By setting the structure of "via one", the transmission performance of radio frequency signals is ensured; by setting the structure of "via two" + "using back drilling technology to remove the through holes of the 'Stub' branches", the transmission performance of high-speed signals is ensured. The stacked design and quasi-coaxial structure are adopted to ensure high electromagnetic compatibility performance and the integrity of signals after the combination of the digital backplane and the radio frequency backplane.

[0022] 3. A multi-layer microwave integrated backplane structure in this technical solution solves the cable space layout during microwave transmission, reduces the space occupancy of the equipment, effectively accommodates 12.5 Gbps+ high-speed signals and DC~22 GHz radio frequency signals, and transforms the product into a smaller, lighter, and more integrated device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 1 shows a schematic structural diagram of a multi-layer microwave integrated backplane structure in Embodiment 1;

[0024] Figure 2 FIG. 2 shows a side view schematic diagram of a multi-layer microwave integrated backplane structure in Embodiment 1;

[0025] Figure 3 FIG. 3 shows a schematic diagram of the installation of solder rings and shielding caps of a multi-layer microwave integrated backplane structure in Embodiment 1;

[0026] Figure 4 FIG. 4 shows a schematic diagram of the layer stack structure of the PCB board in Embodiment 1;

[0027] Figure 5 FIG. 5 shows a wiring diagram of the radio frequency connector in Embodiment 1;

[0028] Figure 6 FIG. 6 is a simulation result diagram of the isolation degree in this embodiment;

[0029] Figure 7 FIG. 7 is a simulation result diagram of the insertion loss in this embodiment.

[0030] Reference numerals: PCB board 1; adapter board 2; positioning pin 3; fixing screw 4; radio frequency signal terminal 5; high-speed signal terminal 6; combined connector module 7; screw two 8; nut 9; guide post 10; connector 11. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0032] Embodiment 1

[0033] As Figure 1 、 Figure 2 shown, a multi-layer microwave integrated backplane structure includes a PCB board 1 and an adapter board 2. Among them, the PCB board 1 is a rigid printed board with dimensions of 88.6 mm * 65 mm * 4 mm. The positions of the high-speed connector crimping holes are arranged on the front side, and the positions of the high-speed connector crimping holes and the RF connector soldering holes are arranged on the back side. A plurality of combined connector modules 7 are provided on the PCB board 1. A plurality of RF signal terminals 5 and a plurality of high-speed signal terminals 6 are provided on the combined connector module 7. The plurality of RF signal terminals 5 and the plurality of high-speed signal terminals 6 form a signal integration end;

[0034] The combined connector module 7 includes an RF connector module corresponding to the RF signal terminal 5 and a high-speed connector module corresponding to the high-speed signal terminal 6. Among them, as Figure 5 shown, in the structure part of the RF connector module, the distance between each RF contact is greater than 200 mil, the width of the RF trace is about 10 mil, the diameter of the RF center hole is 0.5 mm, the diameter of the surrounding ground buried hole is 0.71 mm, and the wavelength corresponding to the 22 GHz RF signal is about 8.75 mm. At this time, the RF signal is basically completely "constrained" in the quasi-rectangular cavity.

[0035] In the structure part of the high-speed connector module, the diameter of the crimping hole is 0.31 mm. The routing part is simulated by SI9000 software. The single-ended signal impedance is 50 Ω, and the routing width is about 0.20 mm; the differential signal impedance is 100 Ω, the impedance error is ±10%, and the routing width is about 0.13 mm.

[0036] The adapter board 2 is located on the side of the PCB board 1 away from the combined connector module 7. Guide posts 10 and connectors 11 are provided between the adapter board 2 and the PCB board 1. The setting of the connectors 11 realizes the output of external signals. A three-dimensional space is established between the adapter board 2 and the PCB board 1 through the guide posts 10 and the connectors 11.

[0037] In a multi-layer microwave integrated backplane structure in this technical solution, an integrated combined connector module 7 is provided on the PCB board 1. A plurality of RF signal terminals 5 and a plurality of high-speed signal terminals 6 are provided on the combined connector module 7. A connector 11 is provided between the adapter board 2 and the PCB board 1. A signal path is formed among the terminals (RF signal terminal 5, high-speed signal terminal 6), the PCB board 1, and the connector 11 to ensure signal transmission.

[0038] Since RF signals are mainly interconnected and converted by RF cables, the spatial layout of RF cables needs to be considered during microwave transmission to reduce the space occupancy of cable equipment. Moreover, the use of RF cables is more inconvenient during the conversion process of single-sided RF signals. In this application, a three-dimensional space is established between the adapter board 2 and the PCB board 1 through the guide posts 10 and the connectors 11, effectively solving the problem of cable space occupancy and making the equipment smaller, lighter, and more integrated. It can be applied to small electronic system fields such as missile-borne, airborne, and UAV

[0039] Merging the RF signal terminals 5 and the high-speed signal terminals 6 at the same level on the combined connector module 7 can reduce the space occupancy rate of the RF cable structure layout, providing technical support for the development of future smaller, more integrated, and lighter equipment. At the same time, this technology development also pushes the interconnected signal transmission to a higher-level application structure.

[0040] To solve the assembly problems among the PCB board 1, the adapter board 2, the guide posts 10, and the connectors 11, as Figure 1 、 Figure 2 shown, one end of the guide post 10 is connected to the adapter board 2, and the other end of the guide post 10 is connected to the PCB board 1 through the screw two 8, realizing the fixation of the relative positions among the PCB board 1, the adapter board 2, and the guide post 10; the connector 11 is fixed on the PCB board 1 and the adapter board 2 through the fixing screw 4, realizing the fixation of the relative positions among the PCB board 1, the adapter board 2, and the connector 11; solving the assembly problems among the PCB board 1, the adapter board 2, the guide post 10, and the connectors 11.

[0041] To solve the assembly problem between the combined connector module 7 and the PCB board 1, a multi-layer microwave integrated backplane structure further includes a positioning pin 3. The positioning pin 3 passes through the combined connector module 7 and the PCB board 1 and is threadedly fitted with a nut 9; the positioning pin 3 and the nut 9 are threadedly fitted to realize the fixation of the relative positions of the combined connector module 7 and the PCB board 1.

[0042] In a multi-layer microwave integrated backplane structure of this technical solution, the PCB board 1, the adapter board 2, and the guide posts 10, the PCB board 1, the adapter board 2, and the connectors 11, and the combined connector module 7 and the PCB board 1 are all assembled by means of threaded fitting, which is simple in operation and convenient for assembly.

[0043] To ensure the signal transmission performance of a multi-layer microwave integrated backplane structure in this technical solution, more specifically, for the transmission of RF signals, at the RF signal terminal 5, the "blind hole" process is adopted to achieve the "crimping method". A blind hole one is provided in the welding area of the PCB board 1 corresponding to the RF signal terminal 5. The RF signal terminal 5 extends into the interior of the blind hole one, increasing the length of the RF connector and extending its contact surface with the PCB printed board into the "blind hole" to improve the RF signal transmission performance;

[0044] The "blind hole" process is adopted at the radio frequency welding hole part of the multi-layer microwave integrated backplane structure to reduce the "short post effect", thereby effectively ensuring the transmission performance of the radio frequency connector signal in the DC~22GHz bandwidth and solving the technical problem of poor radio frequency signal transmission performance in the thick backplane.

[0045] For the radio frequency head of the radio frequency connector, the connector 11 has a radio frequency connector and a high-speed connector. A counterbore is provided at the position of the PCB board 1 corresponding to the radio frequency head on the radio frequency connector, and the radio frequency head is introduced into the counterbore for pin welding; more specifically, in this example, the counterbore penetrates through layers L1-L14, and the radio frequency head is sunk into the PCB board 1 for pin welding, avoiding the direct exposure of the pins of the radio frequency connector to the air, ensuring the consistency of the radio frequency coaxial structure, and at the same time ensuring the welding reliability of the radio frequency connector.

[0046] Furthermore, as Figure 3 shown, since the combined connector module 7 includes signals such as radio frequency signals and high-speed signals, in order to avoid signal crosstalk, a metal shielding cap is welded on the PCB board 1 through a solder ring (maintaining at least a 1mm distance from the radio frequency head), and the metal shielding cap covers the inner conductor of the radio frequency connector, effectively suppressing the interference between the radio frequency signals on the back of the PCB board 1; the metal shielding cap is set to absorb the crosstalk signals, thereby effectively ensuring the transmission performance of the radio frequency connector signal in the DC~22GHz bandwidth and solving the problem that the "antenna" effect will be generated due to the leakage of the tail end of the radio frequency head pin after the radio frequency connector is welded, affecting the radio frequency performance.

[0047] For the transmission of high-speed signals, due to the limitation of the "thickness-diameter ratio" in the PCB processing technology for the "fish-eye" crimp through holes of the high-speed connectors in the thick backplane, a slot hole is provided on the PCB board 1 at the crimping area corresponding to the high-speed signal terminal 6, and the high-speed signal terminal 6 extends into the interior of the slot hole;

[0048] Among them, a part of the slot holes are set as blind holes two, and the high-speed signal terminal 6 extends into the interior of the blind holes two to connect the outer layer and the inner layer of the PCB board 1, physically reducing the cross-sectional area of the metal surface in the hole and reducing the "short post effect"; the remaining part of the slot holes are set as through holes, and the "Stub" branches are removed from the through holes by back drilling technology, and part of the deposited copper in the through holes is cleaned, reducing the cross-sectional area of the metal surface in the hole and reducing the "short post effect".

[0049] By adopting the structure of "blind holes two" + "through holes with the 'Stub' branches removed by back drilling technology" for the "fish-eye" crimp part of the high-speed connector module and reasonably arranging it on the printed circuit board, the influence of the "short post effect" is reduced, thereby effectively improving the integrity transmission performance of high-speed signals and solving the problem that the "short post effect" of the vias in the thick printed circuit board has a greater impact on the system transmission performance at the Gbit transmission rate.

[0050] Since there are many and dense signal types in the multi-layer microwave integrated backplane structure, to improve the compatibility of various signals, such as Figure 4 As shown, the PCB board 1 adopts a stacked design and is composed of multiple dielectric substrates, prepregs sandwiched between every two adjacent dielectric substrates, and copper layers etched on the front and back sides of the dielectric substrates. The dielectric substrates are set to 18 layers. From top to bottom, layers L1-L14 transmit digital signals with a copper thickness of 1 oz per layer, and layers L15-L18 transmit RF signals with a copper thickness of 1 oz per layer.

[0051] Among them, four connector heads are arranged on the surface of the first layer, namely a power module, a transceiver module, a frequency synthesizer module, and a signal processing module, to transmit power signals, high-speed differential signals, and RF signals; a connector socket and multiple RF heads are arranged on the surface of the 18th layer.

[0052] The digital substrates of layers L1-L14 use TU872 material (dielectric constant 3.5, loss tangent 0.006), and the RF backplane of layers L15-L18 uses TSM-DS3 (dielectric constant 2.94, loss tangent 0.0012). During the production process, due to the different thermal expansion coefficients of different materials, in order to ensure the bonding of the board, the "pre-pressing" step is adopted in the process, that is, according to the material expansion and contraction values, pre-treatment stretching is carried out, and the size becomes the size required by the design after pressing.

[0053] Among them, the copper layers of L1-L18 are successively Top Layer, GND02, ART03, GND04, ART05, GND06, ART07, GND08, PWR09, PWR10, GND11, ART12, GND13, ART14, GND15, ART16, GND17, Bottom Layer.

[0054] The specific data values corresponding to layers L1-L18 in PCB board 1 are as follows in the table:

[0055]

[0056]

[0057] The PCB board 1 in this application adopts a stacked design with low dielectric constant and low dissipation factor plates, which can reduce signal delay and signal attenuation and effectively improve signal integrity. Physical isolation is carried out for signals such as "high-speed signals", "RF signals", "high-speed ground", and "RF ground", and electromagnetic compatibility is also ensured.

[0058] The multi-layer microwave integrated backplane structure includes digital signals, power signals, low-frequency control signals, and radio frequency signals. The addition of radio frequency signals (maximum bandwidth 22GHz) is one of the key technologies of the invention. The main transmission route of radio frequency signals enters the PCB board 1 layer from an radio frequency connector (16# radio frequency head) on the backplane, and then outputs from the layer to the outside through the contact pin of another 16# radio frequency head for transfer. In order to avoid interference between radio frequency signals and other signals, such as Figure 5 As shown, the L15-L18 layers are completely isolated by a ground layer, and the microwave material TSM-DS3 is used for lamination. The stripline is used as the conductor for transmitting signals, the RF signal layer is grounded as a whole, and contact buried vias are set along the outer side of the stripline. Under high-speed signals, in order to reduce resonance, the center spacing of the ground buried vias is determined according to the wavelength of the highest transmission frequency, so that the RF signal is completely "bound" in the transmission path. The overall height of the ground buried vias runs from the metal ground plane of the 15th layer to the metal ground plane of the 17th layer.

[0059] The upper and lower ends of the strip line both have an outer conductor as a shielding layer, and the outer conductor is connected to the ground plane through a grounding buried via. A rectangular cavity is formed between the outer conductors distributed in the upper and lower directions and the grounding buried vias distributed along the strip line, and the RF signal is confined in the rectangular cavity.

[0060] Between the L15-L18 layers, the stripline is used as a conductor for transmitting signals. Two outer conductors distributed in the upper and lower directions of the stripline are used, and ground buried vias distributed along the stripline are used to form a quasi-coaxial structure. A quasi-rectangular cavity is formed between the outer conductors distributed in the upper and lower directions and the ground buried vias distributed along the stripline. The RF signal is confined in the quasi-rectangular cavity to avoid interference between the RF signal and other signals.

[0061] For the RF signal hole, the coaxial cut-off frequency calculation formula is as follows:

[0062]

[0063] Where c is the speed of light in vacuum, ε r is the relative dielectric constant of the dielectric body, a is the radius of the inner conductor, and b is the inner diameter of the outer conductor.

[0064] According to the above formula, the diameter of the RF signal hole is designed to be approximately 0.5 times the width of the RF routing line. After verification by simulation analysis, the optimal width of the aperture can be obtained.

[0065] like Figure 6 , Figure 7 As shown in the figure, it is the simulation result of the multi-layer microwave integrated backplane. It can be seen from the figure that in the frequency range of DC to 22GHz, the isolation is ≥77dB, the insertion loss is ≤0.3dB, and the backplane has good transmission performance.

[0066] The present invention has completed the development of the multi-layer microwave integrated backplane structure, integrating 10Gbps+ high-speed signals and radio frequency signals up to 22GHz in one board, achieving high electromagnetic compatibility performance.

[0067] The multi-layer microwave integrated backplane structure in this technical solution fills the gap in integrating DC~22GHz radio frequency signals and 12.5Gbps+ high-speed signals in one board. This integrated backplane achieves high electromagnetic compatibility performance in the transmission of radio frequency signals and high-speed signals on multi-layer boards, and successfully brings a more complete technical solution for the miniaturization, lightweight, and integration development of the entire electronic and communication equipment. The radio frequency signals, like high-speed, power supply, control and other signals, can achieve cable-free and integrated design. This technology can be applied to multiple high-speed and microwave integrated transmission fields, including small devices with higher requirements for space and weight such as unmanned aerial vehicles, unmanned vehicles, and wireless devices.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it.

Claims

1. A multi-layer microwave integrated backplane structure, comprising a PCB board (1) and an adapter board (2), characterized in that: A plurality of combined connector modules (7) are arranged on the PCB board (1), and a plurality of radio frequency signal terminals (5) and a plurality of high-speed signal terminals (6) are arranged on the combined connector module (7); The adapter plate (2) is located on a side of the PCB board (1) away from the combined connector module (7); a guide column (10) and a connector (11) are provided between the adapter plate (2) and the PCB board (1); a three-dimensional space is established between the adapter plate (2) and the PCB board (1) via the guide column (10) and the connector (11).

2. A multi-layer microwave integrated backplane structure according to claim 1, characterized in that: One end of the guide column (10) is connected to the adapter plate (2), and the other end of the guide column (10) is connected to the PCB board (1) via a second screw (8); The connector (11) is fixed on the PCB board (1) and the adapter board (2) by means of fixing screws (4).

3. The multi-layer microwave integrated backplane structure according to claim 1, characterized in that: It also includes a positioning pin (3), which passes through the combined connector module (7) and the PCB board (1) and is threadedly matched with a nut (9).

4. The multi-layer microwave integrated backplane structure according to claim 1, characterized in that: A blind hole 1 is provided in a welding area on the PCB board (1) corresponding to the radio frequency signal terminal (5), and the radio frequency signal terminal (5) extends into the interior of the blind hole 1.

5. The multi-layer microwave integrated backplane structure according to claim 4, characterized in that: The connector (11) comprises a radio frequency connector and a high-speed connector, and a recessed groove is provided at a position of a radio frequency head on the radio frequency connector corresponding to the PCB board (1), and the radio frequency head is introduced into the recessed groove for pin welding; A metal shielding cap is welded on the PCB board (1) via a welding ring, and the metal shielding cap covers the inner conductor of the radio frequency connector.

6. The multi-layer microwave integrated backplane structure according to claim 1, characterized in that: A slot hole is provided in a crimping area corresponding to the high-speed signal terminal (6) on the PCB board (1), and the high-speed signal terminal (6) extends into the interior of the slot hole; A portion of the slots are set as blind holes 2, and the remaining portions of the slots are set as through holes, and the through holes are back-drilled to remove "Stub" branches.

7. The multi-layer microwave integrated backplane structure according to claim 1, characterized in that: The PCB board (1) adopts a laminated design and is composed of a multi-layer dielectric substrate, a prepreg sandwiched between two adjacent dielectric substrates, and copper layers etched on the front and back sides of the dielectric substrate. The dielectric substrate is arranged to have 18 layers, the L1-L14 layers transmit digital signals, and the L15-L18 layers transmit radio frequency signals. Among them, the copper layers of L1-L18 are Top Layer, GND02, ART03, GND04, ART05, GND06, ART07, GND08, PWR09, PWR10, GND11, ART12, GND13, ART14, GND15, ART16, GND17, and Bottom Layer.

8. The multi-layer microwave integrated backplane structure according to claim 7, characterized in that: The L15-L18 layers are completely isolated by a ground layer, and are laminated using microwave material TSM-DS3. Strip lines are used as conductors for transmitting signals, and the RF signal layer is grounded as a whole. Contact buried holes are set along the outside of the strip lines. The overall height of the ground buried holes extends from the metal ground plane of the 15th layer to the metal ground plane of the 17th layer. The upper and lower ends of the strip lines have outer conductors as shielding layers, and the outer conductors are connected to the ground plane through ground buried holes.

Images