W-band airtight multistage transition structure based on HTCC

Abstract

The invention discloses a W-band airtight multistage transition structure based on an HTCC. The W-band airtight multistage transition structure comprises a WR-10 waveguide, an FR-4 substrate, a ball grid array, a multistage vertical SIW, a quarter-wave short road surface and a planar transmission structure. An FR-4 substrate is arranged above the WR-10 waveguide, an FR-4 substrate air cavity is formed after cavity digging and side wall metallization are carried out in the FR-4 substrate, and the size of the WR-10 waveguide is the same as that of the FR-4 substrate air cavity. A ball grid array is distributed above the FR-4 substrate, and the ball grid array is distributed around the air cavity of the FR-4 substrate. The multi-stage vertical SIW is arranged above the ball grid array, and the impedance matching effect is achieved through multi-stage gradual change. The quarter-wave short road surface and the planar transmission structure are placed on the multi-stage vertical SIW, and electromagnetic energy is coupled to the microstrip line.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a W-band airtight multi-stage transition structure based on HTCC. Background Art

[0002] With the rapid development of applications such as millimeter-wave communications, automotive radar, satellite communications, and high-resolution imaging, the W-band (75GHz to 110GHz) has become a key frequency band in current high-frequency communication systems due to its higher frequency and wider bandwidth. This band provides tens of GHz of available bandwidth, supporting higher data transmission rates and smaller antenna sizes. It is widely used in automotive millimeter-wave radar, 5G / 6G fronthaul, satellite communications, security imaging systems, and other fields. However, the high performance of W-band systems is highly dependent on low-loss, low-reflection, and highly consistent electromagnetic transition structures to ensure that the signal is smoothly introduced from the external antenna through the waveguide transition structure to the chip or probe.

[0003] In high-frequency millimeter-wave applications like the W-band, the reliability of an airtight transition structure is crucial. This is because W-band signals have extremely short wavelengths and are extremely sensitive to factors such as dielectric perturbations, humidity fluctuations, and metal oxidation within the packaging environment. Even tiny gas leaks, moisture infiltration, or oxidation reactions within the packaging cavity can lead to increased signal loss, degraded phase noise, and even system failure. This is particularly true in aerospace, military, and harsh-environment communication systems, where W-band modules often operate in environments subject to drastic temperature and humidity fluctuations or in vacuum environments. Therefore, the transition structure must possess long-term, stable airtightness, mechanical strength, and electromagnetic shielding capabilities.

[0004] To address these challenges, high-temperature co-fired ceramic (HTCC) technology is gaining increasing attention in high-frequency packaging. HTCC, a multilayer ceramic packaging process co-fired at high temperatures (approximately 1600°C), offers excellent electrical performance, thermal stability, and mechanical strength. It can vertically construct three-dimensional waveguide structures, such as dielectric integrated waveguides (SIWs), and features natural gas sealing capabilities, making it suitable for the manufacture of RF modules requiring airtightness.

[0005] However, in existing high-frequency module designs, the transition path from metal waveguides (such as WR-10) to chip-level interconnects still presents numerous challenges, including matching the waveguides to the ceramic substrate, controlling insertion loss of the vertical transition structure, modal consistency, maintaining hermetic packaging interfaces, and reliability issues. Therefore, a HTCC integration solution that combines high-performance electromagnetic transitions with structural hermetic packaging is urgently needed to meet the development needs of W-band communication systems. Summary of the Invention

[0006] The purpose of the present invention is to solve the above problems and provide a W-band airtight multi-stage transition structure based on HTCC with high airtightness, high reliability and broadband performance.

[0007] To solve the above technical problems, the present invention provides a W-band airtight multi-stage transition structure based on HTCC, comprising a WR-10 waveguide, an FR-4 substrate, a ball grid array (BGA), a multi-stage vertical SIW, a quarter-wavelength short-circuit board (SIW), and a planar transmission structure. The WR-10 waveguide is positioned above the FR-4 substrate, wherein an air cavity is formed in the FR-4 substrate after a cavity is excavated and sidewall metallization is performed. The WR-10 waveguide and the FR-4 substrate air cavity have the same size. A BGA is positioned above the FR-4 substrate, surrounding the FR-4 substrate air cavity. A multi-stage vertical SIW is positioned above the BGA, achieving impedance matching through multi-stage gradients. The quarter-wavelength short-circuit board and the planar transmission structure are positioned on the multi-stage vertical SIW to couple electromagnetic energy to the microstrip line.

[0008] Preferably, the planar transmission structure includes a reduced-height waveguide and a quartz substrate, the reduced-height waveguide is located on the quartz substrate, and a rectangular probe, a high-impedance line, and a low-impedance line are provided on the quartz substrate, the high-impedance line includes a first-level high-impedance line and a second-level high-impedance line, and the low-impedance line includes a first-level low-impedance line and a second-level low-impedance line; a rectangular probe is provided above the quartz substrate, one end of the rectangular probe is not connected, and the other end is connected to the end of the first-level high-impedance line, the other end of the first-level high-impedance line is connected to the end of the first-level low-impedance line, the other end of the first-level low-impedance line is connected to the end of the second-level high-impedance line, the end of the second-level high-impedance line is connected to the end of the second-level low-impedance line, and the other end of the second-level low-impedance line is connected to a 50-ohm microstrip line. The rectangular probe is connected to the high-impedance line and the low-impedance line for broadband matching; the rectangular probe, high-impedance line, low-impedance line, and 50-ohm microstrip line constitute a transmission line, the end of the reduced-height waveguide is connected to a quarter-wavelength short-circuit board, and the reduced-height waveguide surrounds the quartz substrate and the transmission line thereon.

[0009] Preferably, the quarter-wavelength stub surface is arranged above the multi-level vertical SIW, with an open structure below. The wide side of the quarter-wavelength stub surface is connected to the height-reducing waveguide, and the quartz substrate, the rectangular probe, and a portion of the high-impedance line are inserted into the quarter-wavelength stub surface from the wide side. The quarter-wavelength stub surface and the multi-level vertical SIW below it form a closed space.

[0010] Preferably, the multi-level vertical SIW includes metal through holes and a multi-layer HTCC substrate, the multi-layer HTCC substrate includes an HTCC substrate dielectric layer and an HTCC substrate metal layer, the HTCC substrate has 10 dielectric layers, namely, the first HTCC substrate dielectric layer to the tenth HTCC substrate dielectric layer from top to bottom, and the HTCC substrate has 11 metal layers, namely, the first HTCC substrate metal layer to the eleventh HTCC substrate metal layer from top to bottom, and the HTCC substrate dielectric layers and the HTCC substrate metal layers are arranged alternately; the first HTCC substrate dielectric layer, the second HTCC substrate dielectric layer, and the first to third HTCC substrate metal layers are hollowed out in the center of the multi-layer HTCC substrate to form a substrate cavity, and metallization is performed on the side of the substrate cavity to form an HTCC vacuum cavity, and metal is hollowed out in the remaining HTCC substrate metal layers to form metal grooves; the metal through holes are formed by penetrating different HTCC substrate dielectric layers. The metal through-holes are classified according to the number of material layers, and are divided into the first type of metal through-holes, the second type of metal through-holes, the third type of metal through-holes, the fourth type of metal through-holes, the fifth type of metal through-holes and the sixth type of metal through-holes. The first type of metal through-holes penetrate from the first HTCC substrate dielectric layer to the fourth HTCC substrate dielectric layer from top to bottom, the second type of metal through-holes penetrate from the fourth HTCC substrate dielectric layer from top to bottom, the third type of metal through-holes penetrate from the fourth HTCC substrate dielectric layer and the fifth HTCC substrate dielectric layer from top to bottom, the fourth type of metal through-holes penetrate from the fifth HTCC substrate dielectric layer to the eighth HTCC substrate dielectric layer from top to bottom, the fifth type of metal through-holes penetrate from the sixth HTCC substrate dielectric layer and the seventh HTCC substrate dielectric layer from top to bottom, and the sixth type of metal through-holes penetrate from the eighth HTCC substrate dielectric layer to the tenth HTCC substrate dielectric layer from top to bottom. The combination of metal slots of different sizes and metal through-holes penetrating different layers is equivalent to waveguide cascades of different sizes.

[0011] Preferably, the FR-4 substrate includes a cross-arranged FR-4 substrate metal layer and a FR-4 substrate dielectric layer, the FR-4 substrate metal layer has 6 layers, the FR-4 substrate dielectric layer has 5 layers, and an FR-4 substrate air cavity is formed through the FR-4 substrate and has the same size as the WR-10 waveguide. The sidewalls of the FR-4 substrate air cavity are metallized to prevent electromagnetic energy from leaking into the medium, and the opening position of the FR-4 substrate air cavity is the same as the opening position of the WR-10 waveguide.

[0012] Preferably, the medium constituting the FR-4 substrate dielectric layer is FR-4, the metal constituting the FR-4 substrate metal layer is copper, the lower side of the FR-4 substrate layer is connected to the WR-10 waveguide, and the upper side of the FR-4 substrate layer is provided with a ball grid array.

[0013] Preferably, the ball grid array is periodically distributed between the multi-level vertical SIW and the FR-4 substrate, and contacts the 11th HTCC substrate metal layer of the multi-layer HTCC substrate and the first FR-4 substrate metal layer of the FR-4 substrate.

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

[0015] 1. The present invention provides a W-band airtight multi-stage transition structure based on HTCC, which realizes a multi-stage transition from rectangular waveguide to microstrip probe. During signal transmission, the RF signal passes through the FR-4 substrate with metallized sidewalls, which not only prevents the leakage of electromagnetic energy but also ensures that the signal routing in the FR-4 substrate is not disturbed.

[0016] 2. In this invention, signals are transmitted via a ball grid array (BGA) to the vertical SIW in the HTCC. The BGA confines the electromagnetic field. Considering the BGA's reliability, even if the solder joint becomes desolderable, the EBG structure formed by the BGA will still confine the field. The signal flows into multiple vertical SIWs, which are cascaded with multiple dielectric waveguides to ensure broadband matching. Furthermore, the top cavity of the HTCC is excavated and the sidewalls are metallized to prevent electromagnetic energy leakage. The planar transmission structure acts as an H-plane probe, enabling the transition of electromagnetic energy from the waveguide to the microstrip transmission line.

[0017] 3. The present invention uses quartz substrate and gold as the medium and metal of the probe, which further reduces transmission loss and return loss.

[0018] 4. The present invention realizes a multi-stage transition from waveguide to microstrip probe, and has the characteristics of low loss, wide bandwidth, high airtightness, and high reliability. It also takes the reliability of the ball grid array into consideration and innovatively constructs an EBG bandgap structure, which can meet the stringent technical requirements for transmitting W-band RF signals from waveguide to chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a back-to-back structure of a W-band airtight multi-stage transition structure based on HTCC of the present invention;

[0020] Figure 2 is a side view of a back-to-back structure of the transition structure of the present invention;

[0021] Figure 3 It is a structural schematic diagram of the planar transmission structure in the transition structure of the present invention;

[0022] Figure 4 It is a schematic diagram of the dimensions of the planar transmission structure in the transition structure of the present invention;

[0023] Figure 5 It is a schematic structural diagram of a multi-stage vertical SIW in the transition structure of the present invention;

[0024] Figure 6 is a top view of a multi-stage vertical SIW in the transition structure of the present invention;

[0025] Figure 7 is a side view of a multi-stage vertical SIW in the transition structure of the present invention;

[0026] Figure 8 is a side view of the FR-4 substrate in the transition structure of the present invention;

[0027] Figure 9 2 is a simulation result diagram of the transition structure of the present invention.

[0028] Explanation of the accompanying symbols: 1. WR-10 waveguide; 2. FR-4 substrate; 3. Ball grid array; 4. Multi-level vertical SIW; 5. Quarter-wavelength short-circuit board; 6. Planar transmission structure; 7. Rectangular probe; 8. High-impedance line; 9. Low-impedance line; 10. 50-ohm microstrip line; 11. Quartz substrate; 12. Metal through hole; 13. Multi-layer HTCC substrate; 14. HTCC vacuum cavity; 15. Metal slot; 16. FR-4 substrate air cavity; 17. Reduced-height waveguide. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0030] like Figures 1 to 9 As shown, the present invention provides a W-band airtight multi-level transition structure based on HTCC, comprising a WR-10 waveguide 1, an FR-4 substrate 2, a ball grid array 3, a multi-level vertical SIW 4, a quarter-wavelength short-circuit board 5, and a planar transmission structure 6. The WR-10 waveguide 1 is located above the FR-4 substrate 2. The FR-4 substrate 2 is hollowed and sidewall metallized to form an FR-4 substrate air cavity 16. The WR-10 waveguide 1 and the FR-4 substrate air cavity 16 have the same size. A ball grid array 3 is located above the FR-4 substrate 2, surrounding the FR-4 substrate air cavity 16. Above the ball grid array 3 are multi-level vertical SIW 4, which achieve impedance matching through multi-level gradients. The quarter-wavelength short-circuit board 5 and the planar transmission structure 6 are placed on the multi-level vertical SIW 4 to couple electromagnetic energy to the microstrip line.

[0031] In this embodiment, the present invention provides a W-band airtight multi-stage transition structure based on HTCC, which is a back-to-back structure with symmetrical left and right sides. The two symmetrically arranged transition structures are connected by a planar transmission structure 6 in the middle. The dimensions of the WR-10 waveguide 1 and the FR-4 substrate air cavity 16 are both 2.54mm × 1.27mm. The ball grid array 3 is distributed around the FR-4 substrate air cavity 16, serving two purposes: first, it can confine the electromagnetic field and prevent electromagnetic energy leakage; second, to ensure reliability, even if the ball grid array 3 becomes desolderable to the multi-stage vertical SIW4 above or the FR-4 substrate 2 below, the ball grid array 3 can still form a bandgap structure to prevent electromagnetic energy leakage.

[0032] like Figures 1 to 4 As shown, the planar transmission structure 6 includes a reduced-height waveguide 17 and a quartz substrate 11. The reduced-height waveguide 17 is located on the quartz substrate 11. A rectangular probe 7, a high-impedance line 8, and a low-impedance line 9 are provided on the quartz substrate 11. The high-impedance line 8 includes a first-stage high-impedance line and a second-stage high-impedance line, and the low-impedance line 9 includes a first-stage low-impedance line and a second-stage low-impedance line. The rectangular probe 7, located above the quartz substrate 11, is unconnected at one end and connected at the other end to the end of the first-stage high-impedance line. The other end of the first-stage high-impedance line is connected to the end of the first-stage low-impedance line. The other end of the first-stage low-impedance line is connected to the end of the second-stage high-impedance line. The other end of the second-stage high-impedance line is connected to the end of the second-stage low-impedance line. The other end of the second-stage low-impedance line is connected to a 50-ohm microstrip line 10. The high-impedance line 8 and the low-impedance line 9 are connected to the rectangular probe 7 to achieve broadband matching. The rectangular probe 7, high-impedance line 8, low-impedance line 9, and 50-ohm microstrip line 10 form a transmission line. The end of the reduced-height waveguide 17 is connected to the quarter-wavelength short-circuit board 5. The reduced-height waveguide 17 surrounds the quartz substrate 11 and the transmission line thereon, ensuring airtightness while also extending bandwidth. In actual use, because the HTCC-based W-band airtight multi-stage transition structure of the present invention is symmetrical, the other end of the 50-ohm microstrip line 10 is connected to a symmetrically arranged 50-ohm microstrip line.

[0033] In this embodiment, the quartz substrate 11 has a length Ls of 2 mm, a width Ws of 0.7 mm, and a thickness of 0.05 mm. The rectangular probe 7 has a width W1 of 0.4 mm and a narrow side L1 of 0.12 mm. The first-stage high-impedance line connected to the rectangular probe 7 has a width W2 of 0.14 mm and a length L2 of 0.49 mm. The first-stage low-impedance line has a long side W3 of 0.29 mm and a wide side L3 of 0.26 mm. The second-stage high-impedance line has a width W4 of 0.20 mm and a length L4 of 0.29 mm. The second-stage low-impedance line has a long side W5 of 0.35 mm and a wide side L5 of 0.28 mm. The 50-ohm microstrip line 10 has a width W6 of 0.15 mm and a length L6 of 0.46 mm.

[0034] The quarter-wavelength stub 5 is positioned above the multi-stage vertical SIW 4, with an opening below it measuring 2.06 mm x 1.43 mm. The wide side of the quarter-wavelength stub 5 is connected to the reduced-height waveguide 17. The quartz substrate 11, rectangular probe 7, and a portion of the high-impedance line 8 are inserted into the quarter-wavelength stub 5 from the wide side. The quarter-wavelength stub 5, the area below it, and the multi-stage vertical SIW 4 form a closed space.

[0035] like Figure 1 、 Figure 2 、 Figure 5 、 Figure 6 、 Figure 7As shown, the multi-level vertical SIW 4 includes metal vias 12 and a multi-layer HTCC substrate 13. The multi-layer HTCC substrate 13 includes a 65 μm thick dielectric layer and a 10 μm thick metal layer. The HTCC substrate has 10 dielectric layers, from top to bottom, from the first to the tenth HTCC dielectric layer. The HTCC substrate has 11 metal layers, from top to bottom, from the first to the eleventh HTCC metal layer. The dielectric and metal layers are arranged alternately. A substrate cavity is formed by hollowing out the first and second HTCC dielectric layers and the first to third HTCC metal layers in the center of the multi-layer HTCC substrate 13. Metallization is then applied to the sides of the substrate cavity to create an HTCC vacuum chamber 14, measuring 1.66 mm x 1.03 mm. Metal grooves 15 are formed by hollowing out metal in the remaining HTCC substrate metal layers. The dimensions of the metal grooves located in the 4th and 5th HTCC substrate metal layers are 0.96 mm×0.87 mm, the dimensions of the metal grooves located in the 6th to 8th HTCC substrate metal layers are 0.48 mm×0.52 mm, the dimensions of the metal grooves located in the 9th HTCC substrate metal layer are 1.45 mm×0.81 mm, the dimensions of the metal grooves located in the 10th HTCC substrate metal layer are 1 mm×1.79 mm, and the dimensions of the metal grooves located in the 11th HTCC substrate metal layer are 1.96 mm×1.17 mm.

[0036] The metal through-holes 12 are classified according to the number of HTCC substrate dielectric layers they penetrate, into first, second, third, fourth, fifth and sixth types of metal through-holes. The first type of metal through-holes penetrate from the first HTCC substrate dielectric layer to the fourth HTCC substrate dielectric layer from top to bottom. The second type of metal through-holes penetrate from the fourth HTCC substrate dielectric layer from top to bottom. The third type of metal through-holes penetrate from the fourth and fifth HTCC substrate dielectric layers from top to bottom. The fourth type of metal through-holes penetrate from the fifth to the eighth HTCC substrate dielectric layer from top to bottom. The fifth type of metal through-holes penetrate from the sixth and seventh HTCC substrate dielectric layers from top to bottom. The sixth type of metal through-holes penetrate from the eighth to the tenth HTCC substrate dielectric layer from top to bottom. The combination of metal slots 15 of different sizes and metal vias 12 running through different layers is equivalent to a cascade of waveguides of different sizes, which reduces electromagnetic energy leakage and forms a multi-level transition, thereby expanding bandwidth. In this embodiment, the diameter of the metal vias 12 is 75 μm.

[0037] like Figure 8 As shown, the FR-4 substrate 2 includes a cross-arranged FR-4 substrate metal layer and a FR-4 substrate dielectric layer. The FR-4 substrate metal layer has 6 layers and the FR-4 substrate dielectric layer has 5 layers. An FR-4 substrate air cavity 16 is formed through the FR-4 substrate 2 and has the same size as the WR-10 waveguide 1. The sidewalls of the FR-4 substrate air cavity 16 are metallized to prevent electromagnetic energy from leaking into the dielectric. The opening position of the FR-4 substrate air cavity 16 is the same as the opening position of the WR-10 waveguide 1.

[0038] The FR-4 substrate dielectric layer is made of FR-4, the FR-4 substrate metal layer is made of copper, the WR-10 waveguide 1 is connected to the bottom of the FR-4 substrate layer 2, and a ball grid array 3 is provided on the top of the FR-4 substrate layer 2.

[0039] The ball grid array 3 is periodically distributed between the multi-level vertical SIW4 and the FR-4 substrate 2, with two cycles in this embodiment. The ball grid array 3 contacts the 11th HTCC metal layer of the multi-level HTCC substrate 13 and the first FR-4 metal layer of the FR-4 substrate 2. The presence of the ball grid array 3 confines the electromagnetic field, reducing transmission losses from the FR-4 substrate 2 to the multi-level vertical SIW4 and limiting energy leakage. Specifically, the ball grid array 3 forms a bandgap structure, or EBG. During use, if the connection between the solder balls and the multi-level vertical SIW4 or FR-4 substrate 2 fails and desoldering occurs, the EBG structure formed by the ball grid array 3 will also limit lateral leakage of electromagnetic energy.

[0040] Figure 9 The S-parameter curve of the back-to-back transition structure is shown as it changes with frequency. Within the frequency range of 90.257 GHz to 95.924 GHz, the return loss of the vertical device is greater than 18 dB, and the insertion loss is better than 3.5 dB. This simulation model is a back-to-back transition structure. Theoretically, the insertion loss of a single-arm structure should be half that of a back-to-back structure, and the return loss should also be lower. These results demonstrate that the present invention has the advantages of high reliability, high airtightness, and a wide operating frequency band, meeting the stringent requirements for transmitting W-band RF signals from waveguide to chip.

[0041] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. A W-band airtight multi-stage transition structure based on HTCC, characterized by: The invention comprises a WR-10 waveguide (1), an FR-4 substrate (2), a ball grid array (3), a multi-level vertical SIW (4), a quarter-wavelength short-circuit (5) and a planar transmission structure (6); the WR-10 waveguide (1) is located above the FR-4 substrate (2); a FR-4 substrate air cavity (16) is formed in the FR-4 substrate (2) after a cavity is dug and the sidewalls are metallized; the WR-10 waveguide (1) and the FR-4 substrate air cavity (16) have the same size; a ball grid array (3) is distributed above the FR-4 substrate (2), and the ball grid array (3) is distributed around the FR-4 substrate air cavity (16); the ball grid array (3) is located above the multi-level vertical SIW (4), and the impedance matching effect is achieved through multi-level gradient; the quarter-wavelength short-circuit (5) and the planar transmission structure (6) are placed on the multi-level vertical SIW (4) to couple electromagnetic energy to the microstrip line.

2. The W-band airtight multi-stage transition structure based on HTCC according to claim 1, characterized in that: The planar transmission structure (6) comprises a height-reducing waveguide (17) and a quartz substrate (11), wherein the height-reducing waveguide (17) is located on the quartz substrate (11), and a rectangular probe (7), a high-impedance line (8), and a low-impedance line (9) are provided on the quartz substrate (11), wherein the high-impedance line (8) comprises a first-level high-impedance line and a second-level high-impedance line, and the low-impedance line (9) comprises a first-level low-impedance line and a second-level low-impedance line; and a rectangular probe (7) is provided above the quartz substrate (11), wherein one end of the rectangular probe (7) is not connected and the other end is connected to the end of the first-level high-impedance line, and the other end of the first-level high-impedance line is connected to the end of the first-level low-impedance line. The other end of the first-stage low-impedance line is connected to the end of the second-stage high-impedance line, the end of the second-stage high-impedance line is connected to the end of the second-stage low-impedance line, the other end of the second-stage low-impedance line is connected to a 50-ohm microstrip line (10), and the rectangular probe (7) is connected to the high-impedance line (8) and the low-impedance line (9) for the purpose of achieving broadband matching; the rectangular probe (7), the high-impedance line (8), the low-impedance line (9) and the 50-ohm microstrip line (10) constitute a transmission line, the end of the height-reducing waveguide (17) is connected to the quarter-wavelength short-circuit surface (5), and the height-reducing waveguide (17) surrounds the quartz substrate (11) and the transmission line thereon.

3. The W-band airtight multi-stage transition structure based on HTCC according to claim 1, characterized in that: The quarter-wavelength short-circuit surface (5) is arranged on the multi-level vertical SIW (4), and has an open structure below. The wide side of the quarter-wavelength short-circuit surface (5) is connected to the height-reducing waveguide (17). The quartz substrate (11), the rectangular probe (7) and a part of the high-impedance line (8) are inserted into the quarter-wavelength short-circuit surface (5) from the wide side. The quarter-wavelength short-circuit surface (5) and the bottom thereof and the multi-level vertical SIW (4) form a closed space.

4. The W-band airtight multi-stage transition structure based on HTCC according to claim 1, characterized in that: The multi-level vertical SIW (4) includes a metal through hole (12) and a multi-layer HTCC substrate (13). The multi-layer HTCC substrate (13) includes an HTCC substrate dielectric layer and an HTCC substrate metal layer. The HTCC substrate dielectric layer has 10 layers, which are respectively from the first HTCC substrate dielectric layer to the tenth HTCC substrate dielectric layer from top to bottom. The HTCC substrate metal layer has 11 layers, which are respectively from the first HTCC substrate metal layer to the eleventh HTCC substrate metal layer from top to bottom. The HTCC substrate dielectric layer and the HTCC substrate metal layer are arranged alternately. The first HTCC substrate dielectric layer, the second HTCC substrate dielectric layer and the first HTCC substrate metal layer to the third HTCC substrate metal layer are hollowed out in the center of the multi-layer HTCC substrate (13) to form a substrate cavity. Metallization is performed on the side of the substrate cavity to form an HTCC vacuum cavity (14). Metal is hollowed out in the remaining HTCC substrate metal layers to form metal slots (15). The metal through hole (12) is formed by penetrating Different HTCC substrate dielectric layers are classified into the first type of metal through-holes, the second type of metal through-holes, the third type of metal through-holes, the fourth type of metal through-holes, the fifth type of metal through-holes and the sixth type of metal through-holes. The first type of metal through-holes penetrate from the top to the bottom of the 1st HTCC substrate dielectric layer to the 4th HTCC substrate dielectric layer, the second type of metal through-holes penetrate from the top to the bottom of the 4th HTCC substrate dielectric layer, and the third type of metal through-holes penetrate from the top to the bottom of the 4th HTCC substrate dielectric layer and the 5th HTCC substrate dielectric layer. The fourth type of metal through-holes penetrate the fifth HTCC substrate dielectric layer to the eighth HTCC substrate dielectric layer from top to bottom, the fifth type of metal through-holes penetrate the sixth HTCC substrate dielectric layer and the seventh HTCC substrate dielectric layer from top to bottom, and the sixth type of metal through-holes penetrate the eighth HTCC substrate dielectric layer to the tenth HTCC substrate dielectric layer from top to bottom; the combination of metal slots (15) of different sizes and metal through-holes (12) penetrating different layers is equivalent to a waveguide cascade of different sizes.

5. The W-band airtight multi-stage transition structure based on HTCC according to claim 1, characterized in that: The FR-4 substrate (2) comprises a cross-arranged FR-4 substrate metal layer and a FR-4 substrate dielectric layer, wherein the FR-4 substrate metal layer has six layers and the FR-4 substrate dielectric layer has five layers, and an FR-4 substrate air cavity (16) is formed through the FR-4 substrate (2) and has the same size as the WR-10 waveguide (1). The sidewall of the FR-4 substrate air cavity (16) is metallized, and the opening position of the FR-4 substrate air cavity (16) is the same as the opening position of the WR-10 waveguide (1).

6. The W-band airtight multi-stage transition structure based on HTCC according to claim 1, characterized in that: The FR-4 substrate dielectric layer is formed of FR-4, the FR-4 substrate metal layer is formed of copper, the FR-4 substrate layer (2) is connected to the WR-10 waveguide (1) below, and a ball grid array (3) is provided on the FR-4 substrate layer (2).

7. The W-band airtight multi-stage transition structure based on HTCC according to claim 1, characterized in that: The ball grid array (3) is periodically distributed between the multi-level vertical SIW (4) and the FR-4 substrate (2), and contacts the 11th HTCC substrate metal layer of the multi-layer HTCC substrate (13) and the first FR-4 substrate metal layer of the FR-4 substrate (2).

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