A terahertz chip three-dimensional packaging structure and implementation method

Abstract

The application discloses a terahertz chip three-dimensional packaging structure and an implementation method. The application provides a terahertz chip three-dimensional packaging structure based on a closed suspended line and a three-dimensional electromagnetic band gap, which to some extent, gets rid of the restriction of a processing mode, provides a feasible method for low-cost, low-loss and wide-band terahertz chip packaging, and has the advantages of simple processing and assembling mode, low processing precision requirement, low manufacturing cost and the like while ensuring the wide-band performance and low transmission loss of the packaging structure, and avoids complex process and high-frequency fine processing requirement; has the advantages of small transmission loss and large working bandwidth, and can realize high-performance interconnection between packaging and devices, and has wider applicability in the field of terahertz chip packaging; the whole packaging structure is made of metal processing, and the process and installation are relatively simple, the structure is stable, and the packaging structure can be applied on a large scale in the terahertz frequency band.

Description

Technical Field

[0001] This invention relates to terahertz technology, specifically to a three-dimensional packaging structure for a terahertz chip and its implementation method. Background Technology

[0002] Terahertz (THz) waves generally refer to electromagnetic waves with frequencies ranging from 0.1 to 10 THz (wavelengths from 3000 to 30 μm). Compared to microwave / millimeter-wave bands, they offer advantages such as higher transmission rates and larger operating bandwidths in wireless communication, and higher resolution and penetration in sensing and imaging. However, the higher frequencies also mean smaller sizes for terahertz chips and devices, posing significant challenges to their manufacturing and packaging. Furthermore, with the rapid development of fields like integrated sensing and the Internet of Things, chip integration is increasing, placing higher demands on the large-scale integration and interconnection of terahertz chips. Currently, due to the high manufacturing costs of standard metal waveguide structures in the terahertz band, the high losses and narrow bandwidth of planar transmission lines in the terahertz band, and the increased transmission losses introduced by the dielectric support required for suspension lines, the packaging performance of terahertz chips based on traditional metal waveguides, planar transmission lines, and suspension lines is severely limited, making it difficult to meet the current demands for low-loss packaging and broadband interconnection in terahertz chips. Therefore, researching and designing a low-cost, low-loss, wide-bandwidth terahertz chip packaging structure and implementation method is of great significance for improving the performance and compact integration of systems such as 6G terahertz high-speed communication, high-resolution imaging, and high-precision radar. Summary of the Invention

[0003] Based on the above-mentioned technologies and requirements, this invention proposes a three-dimensional packaging structure and implementation method for terahertz chips. By utilizing a closed suspension line structure and a three-dimensional electromagnetic bandgap structure formed by stacking multiple metal substrates, low-cost, low-loss, and wide-bandwidth terahertz chip packaging is achieved, which can be applied to the low-cost packaging and integration of terahertz chips.

[0004] One objective of this invention is to propose a three-dimensional packaging structure for terahertz chips.

[0005] The terahertz chip three-dimensional packaging structure of the present invention includes: an upper wall plate, an upper main body plate, a lower main body plate, a chip receiving plate, a lower wall plate, a reflector plate, and a fixing stage; wherein, on the fixing stage, from top to bottom, are the upper wall plate, the upper main body plate, the lower main body plate, the chip receiving plate, the lower wall plate, and the reflector plate;

[0006] The upper wall panel includes a first metal substrate and a first rectangular waveguide. The first metal substrate is a rectangular flat plate, and first rectangular waveguides that penetrate the upper and lower surfaces of the first metal substrate are respectively opened on the left and right sides of the first metal substrate.

[0007] The upper main body plate includes a second metal substrate, a second rectangular waveguide, an upper suspension conductor air cavity, an upper chip air cavity, and an upper support stub air cavity. The second metal substrate is a rectangular flat plate. The second rectangular waveguide, the upper suspension conductor air cavity, the upper chip air cavity, and the upper support stub air cavity are formed on the second metal substrate, penetrating both the upper and lower surfaces. The two second rectangular waveguides are located on the left and right sides of the second metal substrate, respectively. The upper suspension conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspension conductor air cavity is smaller than that of the second rectangular waveguide. The width of the upper chip air cavity is greater than the width of the upper suspension conductor air cavity, and the horizontal dimension of the upper chip air cavity is not less than that of the chip. The four upper support stub air cavities are respectively opened on the left and right sides of the upper suspension conductor air cavity near the rectangular waveguide and near the upper chip air cavity. The four upper support stub air cavities are respectively connected to the upper suspension conductor air cavity. The two upper support stub air cavities located on the same side of the upper chip air cavity are respectively located on both sides of the upper suspension conductor air cavity.

[0008] The lower main body plate includes a third metal substrate, a third rectangular waveguide, a suspension conductor mounting cavity, a lower chip air cavity, and a support stub mounting cavity, and is equipped with suspension conductors and support stubs. The third metal substrate is a rectangular plate, and the third rectangular waveguide, suspension conductor mounting cavity, lower chip air cavity, and support stub mounting cavity are formed on the third metal substrate, penetrating the upper and lower surfaces of the third metal substrate. Two third rectangular waveguides are located on the left and right sides of the third metal substrate, respectively. The suspension conductor mounting cavity connects the two third rectangular waveguides, and the shape and size of the suspension conductor mounting cavity are the same as those of the upper suspension conductor air cavity and are aligned vertically. The lower chip air cavity is located in the middle of the suspension conductor mounting cavity, and the shape and size of the lower chip air cavity are the same as those of the upper chip air cavity and are aligned vertically. The lower chip air cavity divides the suspension conductor mounting cavity into a left suspension conductor mounting cavity. The cavity and the right suspension conductor mounting cavity; four supporting stub mounting cavities are respectively opened in the left suspension conductor mounting cavity and the right suspension conductor mounting cavity near the rectangular waveguide and near the lower chip air cavity. The two supporting stub mounting cavities on the left are connected to the left suspension conductor mounting cavity, and the two supporting stub mounting cavities on the right are connected to the right suspension conductor mounting cavity. The shape and size of each supporting stub mounting cavity are the same as the upper supporting stub air cavity and are aligned vertically. Suspension conductors are placed in the left suspension conductor mounting cavity and the right suspension conductor mounting cavity, and supporting stubs are set in the supporting stub mounting cavities. The two supporting stubs on the left connect the left suspension conductor to the lower main body plate, and the two supporting stubs on the right connect the right suspension conductor to the lower main body plate. The supporting stubs and suspension conductors constitute suspension lines.

[0009] The chip mounting board includes a fourth metal substrate, a fourth rectangular waveguide, a lower left suspended conductor air cavity, a lower right suspended conductor air cavity, and a lower support stub air cavity. The fourth metal substrate is a rectangular flat plate. The fourth rectangular waveguide, the lower left suspended conductor air cavity, the lower right suspended conductor air cavity, and the lower support stub air cavity are formed on the fourth metal substrate, penetrating both the upper and lower surfaces. The two fourth rectangular waveguides are located on the left and right sides of the fourth metal substrate, respectively. The terahertz chip to be packaged is positioned at the center of the upper surface of the fourth metal substrate, directly opposite the lower and upper chip air cavities. The lower left and lower right suspended conductor air cavities are located at... On the left and right sides of the terahertz chip, the lower left and lower right suspended conductor air cavities are vertically aligned with the left and right suspended conductor mounting cavities of the lower main body plate, respectively. Four lower support stub air cavities are respectively located near the fourth rectangular waveguide and near the terahertz chip in the lower left and lower right suspended conductor air cavities. These four lower support stub air cavities are connected to the upper suspended conductor air cavities and are vertically aligned with them. The pins of the terahertz chip are connected to the suspended conductors on the left and right sides of the lower main body plate via gold bonding wires.

[0010] The lower wall panel includes a fifth metal substrate and a fifth rectangular waveguide. The fifth metal substrate is a rectangular flat plate, and a fifth rectangular waveguide is provided on the left and right sides of the fifth metal substrate, respectively, penetrating the upper and lower surfaces of the fifth metal substrate.

[0011] The first to fifth rectangular waveguides have the same shape and size, and are aligned in the vertical direction;

[0012] The upper wall panel, upper main body panel, lower main body panel, chip receiving plate, and lower wall panel constitute a closed suspension line structure;

[0013] The reflector includes a sixth metal substrate, which is a rectangular flat plate.

[0014] The lengths and widths of the first to sixth metal substrates are all the same;

[0015] One or more rings of sliding symmetrical holes are formed on the first to sixth metal substrates and around the rectangular waveguide, penetrating their respective upper and lower surfaces. Each ring of sliding symmetrical holes includes multiple sliding symmetrical holes. The sliding symmetrical holes in each metal substrate layer constitute a three-dimensional electromagnetic bandgap structure. The diameter of each sliding symmetrical hole is half the wavelength of the center operating frequency of the terahertz chip three-dimensional packaging structure. The distance between adjacent sliding symmetrical holes is one wavelength. The sliding symmetrical holes of corresponding rings between adjacent metal substrate layers are staggered, and the positions of the sliding symmetrical holes are vertically offset by one-quarter wavelength. The sliding symmetrical holes of different rings in the same metal substrate layer are staggered, and the positions of the sliding symmetrical holes are horizontally offset by one-quarter wavelength.

[0016] Terahertz waves enter the three-dimensional packaging structure of the terahertz chip from the first rectangular waveguide on one side. They are transmitted through rectangular waveguides located on each layer of the metal substrate until they are reflected by a reflector, which serves as a transition between the closed suspension line structure and the rectangular waveguide. The terahertz waves, after reflection, are transmitted upwards into the suspension line conductor on one side. The terahertz waves are then transmitted to the terahertz chip via gold wire bonding. After signal processing by the terahertz chip, the terahertz waves are transmitted through the gold wire bonding to the suspension line conductor on the other side. During transmission through the suspension line conductor, the terahertz waves are transmitted both upwards and downwards. The downward-transmitting terahertz waves are reflected by the reflector layer and transmitted upwards. Finally, all the terahertz waves are transmitted upwards and output from the first rectangular waveguide on the other side. The three-dimensional electromagnetic bandgap structure suppresses terahertz wave leakage from the gap and increases the operating bandwidth.

[0017] The upper support stub air cavities located on both sides near the rectangular waveguide are less than 0.2 mm away from the rectangular waveguide; the upper support stub air cavity located in the middle near the upper chip air cavity is also less than 0.2 mm away from the upper chip air cavity.

[0018] The number of turns for the sliding symmetrical hole is 1 to 4.

[0019] The upper wall plate, upper main plate, lower main plate, chip receiving plate, lower wall plate, and reflector are all made of highly conductive metals, such as copper or copper plated with gold. The mounting platform is made of solid material, such as copper or plastic. The upper wall plate, upper main plate, lower main plate, chip receiving plate, lower wall plate, and reflector are sequentially fixed to the mounting platform using pins. The thickness of each metal substrate layer is one-tenth of the wavelength of the center operating frequency of the terahertz chip three-dimensional packaging structure. The thickness b of the upper main plate, lower main plate, chip receiving plate, and lower wall plate, as well as the thickness w of the suspension conductor, determine the characteristic impedance Z0 of the closed suspension line, which satisfies the following formula:

[0020]

[0021] Where, ε rLet be the relative permittivity of the cavity, here for air, therefore ε r =1, b / w is generally in the range of 0.5 to 1.5 to ensure a good matching effect between the closed suspension line and the rectangular waveguide.

[0022] The terahertz chip is fixed to the chip substrate using conductive adhesive. The suspension conductor located on the lower main board is as close as possible to the chip to be packaged, and direct contact between the suspension conductor and the chip pins is avoided. Direct connection is not very effective, so gold wire bonding must be used for jumper connection. The distance between the suspension conductor and the chip is 0.1 to 0.2 mm.

[0023] The four support stubs are divided into two pairs. One pair consists of two stubs closer to the rectangular waveguide, and the other pair consists of two stubs closer to the terahertz chip. These two pairs serve as circuit breakers and support suspension lines. The two pairs are not identical in length. The pair closer to the terahertz chip has a length corresponding to a quarter wavelength of the lower sideband frequency of the terahertz chip's operating bandwidth, while the pair closer to the rectangular waveguide has a length corresponding to a quarter wavelength of the upper sideband frequency of the terahertz chip's operating bandwidth. This allows the two pairs of support stubs to operate at different optimal frequencies, further improving the operating bandwidth of the package structure. The support stubs introduce a filtering effect into the suspension lines; the more stubs there are, the greater the transmission loss of the suspension lines. Therefore, four are optimal, providing both support and minimizing transmission loss.

[0024] The sliding symmetrical holes on each metal substrate are identical in size and shape, and adjacent sliding symmetrical holes on each metal substrate are staggered to suppress terahertz wave leakage caused by gaps between metal substrates; the staggered arrangement of adjacent sliding symmetrical holes increases the operating bandwidth of the packaging structure.

[0025] The center frequencies of the terahertz chip, the terahertz chip, and the terahertz wave are the same. In this invention, the size of the terahertz chip three-dimensional packaging structure is designed based on the operating frequency of the terahertz chip. That is, it is necessary to ensure that the operating frequency range of the terahertz chip three-dimensional packaging structure is greater than the operating frequency range of the terahertz chip, which is equal to the operating frequency range of the terahertz wave.

[0026] Both the three-dimensional electromagnetic bandgap structure and the closed suspension wire structure are manufactured by metal wire cutting, without the need for additional processes or media.

[0027] The corresponding rectangular waveguide size is selected according to the terahertz frequency; there is no limit to the length of the upper and lower suspension conductor air cavity, but for the convenience of test interface connection, it is generally more than three times the wavelength corresponding to the center working frequency of the terahertz chip three-dimensional packaging structure; the width of the upper and lower suspension conductor air cavity and the upper and lower support stub air cavity are the same, which is three times the width of the suspension conductor, and the width of the suspension conductor is not less than the height of the suspension conductor.

[0028] Another objective of this invention is to propose a method for implementing a three-dimensional packaging structure for terahertz chips.

[0029] The method for implementing the terahertz chip three-dimensional packaging structure of the present invention includes the following steps:

[0030] 1) Fabrication of a three-dimensional packaging structure for terahertz chips:

[0031] The first to sixth metal substrates are provided, all of which are rectangular flat plates with the same length, width and thickness;

[0032] First to fifth rectangular waveguides of the same shape and size are respectively formed at the same positions on the left and right sides of the first to fifth metal substrates;

[0033] A first metal substrate with a first rectangular waveguide forms the upper wall panel; a fifth metal substrate with a fifth rectangular waveguide forms the lower wall panel.

[0034] A second rectangular waveguide penetrating the upper and lower surfaces of the second metal substrate, an upper suspended conductor air cavity, an upper chip air cavity, and an upper support stub air cavity are formed on the second metal substrate. Two second rectangular waveguides are located on the left and right sides of the second metal substrate, respectively. The upper suspended conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspended conductor air cavity is smaller than the width of the second rectangular waveguides. The upper chip air cavity is located in the middle of the upper suspended conductor air cavity, and its width is greater than the width of the upper suspended conductor air cavity. The horizontal dimension of the upper chip air cavity is not smaller than that of the chip. Four upper support stub air cavities are respectively formed on the left and right sides of the upper suspended conductor air cavity, near the rectangular waveguides and near the upper chip air cavity. The four upper support stub air cavities are connected to the upper suspended conductor air cavity. Two upper support stub air cavities located on the same side as the upper chip air cavity are located on either side of the upper suspended conductor air cavity on the second metal substrate. The substrate has a second rectangular waveguide penetrating the upper and lower surfaces of the second metal substrate, an upper suspended conductor air cavity, an upper chip air cavity, and an upper support stub air cavity. The two second rectangular waveguides are located on the left and right sides of the second metal substrate, respectively. The upper suspended conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspended conductor air cavity is smaller than the width of the second rectangular waveguide. The upper chip air cavity is located in the middle of the upper suspended conductor air cavity, and the width of the upper chip air cavity is greater than the width of the upper suspended conductor air cavity. The horizontal dimension of the upper chip air cavity is not smaller than that of the chip. The four upper support stub air cavities are located on the left and right sides of the upper suspended conductor air cavity, near the rectangular waveguides and near the upper chip air cavity, respectively. The four upper support stub air cavities are connected to the upper suspended conductor air cavity. The two upper support stub air cavities located on the same side as the upper chip air cavity are located on both sides of the upper suspended conductor air cavity, forming the upper main body plate.

[0035] A third rectangular waveguide penetrating the upper and lower surfaces of the third metal substrate, a suspended conductor mounting cavity, a lower chip air cavity, and a support stub mounting cavity are formed on the third metal substrate. Two third rectangular waveguides are located on the left and right sides of the third metal substrate, respectively. The suspended conductor mounting cavity connects the two third rectangular waveguides, and its shape and size are the same as the upper suspended conductor air cavity, and its position is aligned vertically. The lower chip air cavity is located in the middle of the suspended conductor mounting cavity, and its shape and size are the same as the upper chip air cavity, and its position is aligned vertically. The lower chip air cavity divides the suspended conductor mounting cavity into a left suspended conductor mounting cavity and a right suspended conductor mounting cavity. Four support stub mounting cavities are respectively formed in the left and right suspended conductor mounting cavities. The mounting cavities are located near the rectangular waveguide and near the lower chip air cavity. The two supporting stub mounting cavities on the left are connected to the left suspended conductor mounting cavity, and the two supporting stub mounting cavities on the right are connected to the right suspended conductor mounting cavity. The shape and size of each supporting stub mounting cavity are the same as the upper supporting stub air cavity, and their positions are aligned vertically. Suspended conductors are placed in the left and right suspended conductor mounting cavities, and supporting stubs are set in the supporting stub mounting cavities. The two supporting stubs on the left connect the left suspended conductor to the lower main body plate, and the two supporting stubs on the right connect the right suspended conductor to the lower main body plate. The supporting stubs and suspended conductors constitute the suspended line, which in turn constitutes the lower main body plate.

[0036] A fourth rectangular waveguide penetrating the upper and lower surfaces of the fourth metal substrate, a lower left suspended conductor air cavity, a lower right suspended conductor air cavity, and a lower support stub air cavity are formed on the fourth metal substrate; the two fourth rectangular waveguides are located on the left and right sides of the fourth metal substrate, respectively; the terahertz chip to be packaged is placed at the center of the upper surface of the fourth metal substrate, directly opposite the lower and upper chip air cavity; the lower left and lower right suspended conductor air cavities are located on the left and right sides of the terahertz chip, respectively, and are connected to the lower main body. The left and right suspension conductor mounting cavities of the board are aligned vertically. Four lower support stub air cavities are respectively opened in the lower left and lower right suspension conductor air cavities near the fourth rectangular waveguide and near the terahertz chip. The four lower support stub air cavities are connected to the upper suspension conductor air cavities and are aligned vertically with the four upper support stub air cavities. The pins of the terahertz chip are connected to the suspension conductors on the left and right sides of the lower main board through gold wire bonding wires, forming a chip receiving board.

[0037] The upper wall panel, upper main body panel, lower main body panel, chip receiving plate, and lower wall panel constitute a closed suspension line structure;

[0038] One or more rings of sliding symmetrical holes are formed on the first to sixth metal substrates and around the rectangular waveguide, penetrating their respective upper and lower surfaces. Each ring of sliding symmetrical holes includes multiple sliding symmetrical holes. The sliding symmetrical holes in each metal substrate layer constitute a three-dimensional electromagnetic bandgap structure. The diameter of each sliding symmetrical hole is half the wavelength of the center operating frequency of the terahertz chip three-dimensional packaging structure. The distance between adjacent sliding symmetrical holes is one wavelength. The sliding symmetrical holes of corresponding rings between adjacent metal substrate layers are staggered, and the positions of the sliding symmetrical holes are vertically offset by one-quarter wavelength. The sliding symmetrical holes of different rings in the same metal substrate layer are staggered, and the positions of the sliding symmetrical holes are horizontally offset by one-quarter wavelength.

[0039] 2) Terahertz waves enter the three-dimensional packaging structure of the terahertz chip from the first rectangular waveguide on one side, and are transmitted through the rectangular waveguides located on each layer of metal substrate until they are reflected by the reflector. The reflector is the transition between the closed suspension line structure and the rectangular waveguide.

[0040] 3) The terahertz wave, after reflection, propagates upwards and enters the suspension conductor on one side;

[0041] 4) The terahertz wave is transmitted to the terahertz chip through the gold wire bonding wire. After the signal is processed by the terahertz chip, the terahertz wave is transmitted to the suspension conductor on the other side through the gold wire bonding wire.

[0042] 5) During the transmission of terahertz waves in the suspended conductor, they are simultaneously transmitted upward and downward. The downward-transmitting terahertz waves are reflected by the reflective layer and transmitted upward. Finally, all the terahertz waves are transmitted upward and output from the first rectangular waveguide on the other side.

[0043] 6) During the transmission of terahertz waves in a closed suspension wire structure, the three-dimensional electromagnetic bandgap structure suppresses the leakage of terahertz waves from the gap and increases the operating bandwidth.

[0044] Advantages of this invention:

[0045] This invention proposes a three-dimensional packaging structure for terahertz chips based on a closed suspension line and a three-dimensional electromagnetic bandgap. This structure, to a certain extent, overcomes the limitations of traditional fabrication methods and provides a feasible method for low-cost, low-loss, wide-bandwidth terahertz chip packaging. While ensuring broadband performance and low transmission loss, it also offers advantages such as simple processing and assembly, lower precision requirements, and lower manufacturing costs. It avoids complex processes and overly precise processing requirements at high frequencies. Furthermore, it features low transmission loss and a large operating bandwidth, enabling high-performance interconnection between the package and the device, and has wider applicability in the field of terahertz chip packaging. The entire packaging structure is made of metal, making the process and installation relatively simple, and the structure is stable, enabling large-scale applications in the terahertz frequency band. Attached Figure Description

[0046] Figure 1 An exploded view of one embodiment of the terahertz chip three-dimensional packaging structure of the present invention;

[0047] Figure 2 This is a schematic diagram of the upper wall panel of one embodiment of the terahertz chip three-dimensional packaging structure of the present invention;

[0048] Figure 3 This is a schematic diagram of the upper main body plate of one embodiment of the terahertz chip three-dimensional packaging structure of the present invention;

[0049] Figure 4 This is a schematic diagram of the lower main body plate of an embodiment of the terahertz chip three-dimensional packaging structure of the present invention;

[0050] Figure 5 This is a schematic diagram of a chip support plate according to an embodiment of the terahertz chip three-dimensional packaging structure of the present invention.

[0051] Figure 6 This is a schematic diagram of the lower wall plate of one embodiment of the terahertz chip three-dimensional packaging structure of the present invention;

[0052] Figure 7 This is a schematic diagram of a reflector in one embodiment of the terahertz chip three-dimensional packaging structure of the present invention;

[0053] Figure 8 The above is a simulation S-parameter diagram of an embodiment of the terahertz chip three-dimensional packaging structure of the present invention. Detailed Implementation

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0055] like Figure 1 As shown, the terahertz chip three-dimensional packaging structure in this embodiment includes: an upper wall plate 1, an upper main body plate 2, a lower main body plate 3, a chip receiving plate 4, a lower wall plate 5, a reflector plate 6, a fixing stage 7, and a three-dimensional electromagnetic bandgap structure; wherein, on the fixing stage 7, from top to bottom, are the upper wall plate 1, the upper main body plate 2, the lower main body plate 3, the chip receiving plate 4, the lower wall plate 5, and the reflector plate 6; Figure 1 In the middle, the vertical direction is along the z-axis, the surfaces of the first to sixth metal substrates are located in the xy plane, which is a horizontal plane, the left and right sides are along the y-axis, and the direction from the top edge to the bottom edge of the air cavity of the upper suspended conductor is along the x-axis;

[0056] like Figure 2 As shown, the upper wall panel 1 includes: a first metal substrate 103 and a first rectangular waveguide 101. The first metal substrate is a rectangular flat plate, and first rectangular waveguides that penetrate the upper and lower surfaces of the first metal substrate are respectively opened on the left and right sides of the first metal substrate.

[0057] like Figure 3 As shown, the upper main body plate 2 includes: a second metal substrate, a second rectangular waveguide, an upper suspension conductor air cavity 202, an upper chip air cavity 203, and an upper support stub air cavity 201; the second metal substrate is a rectangular plate, and the second rectangular waveguide, the upper suspension conductor air cavity, the upper chip air cavity, and the upper support stub air cavity are formed on the second metal substrate, penetrating the upper and lower surfaces of the second metal substrate; the two second rectangular waveguides are respectively located on the left and right sides of the second metal substrate; the upper suspension conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspension conductor air cavity is 0.6mm, which is smaller than the width of the second rectangular waveguide; the upper chip air cavity is formed on... In the middle of the upper suspended conductor air cavity, the width of the upper chip air cavity is greater than the width of the upper suspended conductor air cavity, and the horizontal dimension of the upper chip air cavity is not smaller than that of the chip; four upper supporting stub air cavities are respectively opened on the left and right sides of the upper suspended conductor air cavity near the rectangular waveguide and near the upper chip air cavity. The four upper supporting stub air cavities are respectively connected to the upper suspended conductor air cavity. The two upper supporting stub air cavities on the left side of the upper chip air cavity are located at the top and bottom edges of the upper suspended conductor air cavity, respectively, and the two upper supporting stub air cavities on the right side of the upper chip air cavity are located at the bottom and top edges of the upper suspended conductor air cavity, respectively.

[0058] like Figure 4As shown, the lower main body plate 3 includes: a third metal substrate, a third rectangular waveguide, a suspension conductor mounting cavity, a lower chip air cavity 303, and a supporting stub mounting cavity, and is provided with a suspension conductor 302 and a supporting stub 301; the third metal substrate is a rectangular plate, and the third rectangular waveguide, the suspension conductor mounting cavity, the lower chip air cavity, and the supporting stub mounting cavity are formed on the third metal substrate, penetrating the upper and lower surfaces of the third metal substrate; two third rectangular waveguides are respectively located on the left and right sides of the third metal substrate; the suspension conductor mounting cavity connects the two third rectangular waveguides, and the shape and size of the suspension conductor mounting cavity are the same as those of the upper suspension conductor air cavity and are aligned in the vertical direction; the lower chip air cavity is located in the middle of the suspension conductor mounting cavity, and the shape and size of the lower chip air cavity are the same as those of the upper chip air cavity and are aligned in the vertical direction, and the lower chip air cavity divides the suspension conductor mounting cavity into a left suspension conductor mounting cavity and a right suspension conductor mounting cavity; four supporting stub mounting cavities are respectively formed on the left suspension conductor mounting cavity. The wire conductor mounting cavity and the right suspended wire conductor mounting cavity are located near the rectangular waveguide and near the lower chip air cavity. The two supporting stub wire mounting cavities on the left are connected to the left suspended wire conductor mounting cavity, and the two supporting stub wire mounting cavities on the right are connected to the right suspended wire conductor mounting cavity. The shape and size of each supporting stub wire mounting cavity are the same as the upper supporting stub wire air cavity, and their positions are aligned vertically. Suspended wire conductors are placed in the left and right suspended wire conductor mounting cavities, and supporting stub wires are set in the supporting stub wire mounting cavities. The two supporting stub wires on the left connect the left suspended wire conductor to the lower main body plate 3, and the two supporting stub wires on the right connect the right suspended wire conductor to the lower main body plate 3. The supporting stub wires and suspended wire conductors constitute suspended wires. The width of the upper supporting stub wire is 0.2 mm, the length of the suspended wire supporting stub wire near the rectangular waveguide port is 0.79 mm, and the length of the supporting stub wire near the terahertz chip to be packaged is 0.62 mm.

[0059] like Figure 5As shown, the chip receiving board 4 includes: a fourth metal substrate, a fourth rectangular waveguide, a lower left suspended conductor air cavity 402, a lower right suspended conductor air cavity, and a lower support stub air cavity 401; the fourth metal substrate is a rectangular plate, and the fourth rectangular waveguide, the lower left suspended conductor air cavity, the lower right suspended conductor air cavity, and the lower support stub air cavity are formed on the fourth metal substrate, penetrating the upper and lower surfaces of the fourth metal substrate; the two fourth rectangular waveguides are located on the left and right sides of the fourth metal substrate, respectively; the terahertz chip 403 to be packaged is placed at the center of the upper surface of the fourth metal substrate, directly opposite the lower and upper chip air cavities; the lower left suspended conductor air cavity and the lower right suspended conductor air cavity... The air cavities are located on the left and right sides of the terahertz chip, respectively. The lower left and lower right suspended conductor air cavities are aligned vertically with the upper suspended conductor air cavity of the upper main body plate 2. The four lower support stub air cavities are respectively opened near the fourth rectangular waveguide and near the terahertz chip in the lower left and lower right suspended conductor air cavities. The four lower support stub air cavities are connected to the upper suspended conductor air cavities and are aligned vertically with the four upper support stub air cavities. The pins of the terahertz chip are connected to the suspended conductors on the left and right sides of the lower main body plate 3 respectively through gold wire bonding.

[0060] like Figure 6 As shown, the lower wall plate 5 includes: a fifth metal substrate and a fifth rectangular waveguide. The fifth metal substrate is a rectangular flat plate, and a fifth rectangular waveguide is provided on the left and right sides of the fifth metal substrate to penetrate the upper and lower surfaces of the fifth metal substrate.

[0061] The first to fifth rectangular waveguides are identical in shape and size, measuring 1.65mm × 0.83mm, and are aligned vertically, with a distance of 30mm between each waveguide.

[0062] The upper wall panel 1, the upper main body panel 2, the lower main body panel 3, the chip receiving plate 4, and the lower wall panel 5 constitute a closed suspension line structure;

[0063] like Figure 7 As shown, the reflector 6 includes a sixth metal substrate, which is a rectangular flat plate.

[0064] The first to sixth metal substrates have the same length, width and thickness, with a length of 59mm, a width of 25mm and a thickness of 0.2mm. The length, width and height of the fixing stage 7 are 64mm, 30mm and 10mm respectively. The entire packaging structure can be manufactured using CNC (Computer Numerical Control) technology commonly used in the field.

[0065] Two concentric rings of sliding symmetrical holes 102, penetrating the upper and lower surfaces of the rectangular waveguide, are respectively formed on the first to sixth metal substrates. Each ring of sliding symmetrical holes includes multiple sliding symmetrical holes, all of which have the same size, a diameter of 0.9 mm, and a distance of 1.8 mm between adjacent holes. The sliding symmetrical holes in each metal substrate layer constitute a three-dimensional electromagnetic bandgap structure. The diameter of each sliding symmetrical hole is half the wavelength of the center operating frequency of the terahertz chip three-dimensional packaging structure, and the distance between adjacent sliding symmetrical holes is one wavelength. In this embodiment, the positions of the inner and outer rings of sliding symmetrical holes on the first, third, and fifth metal substrates are respectively along the vertical direction. Similarly, the centers of the inner ring sliding symmetrical holes are located on the same rectangle; the inner ring sliding symmetrical holes on the second, fourth, and sixth metal substrates are in the same position, and the centers of the inner ring sliding symmetrical holes are located on the same racetrack shape, which is a pair of identical and parallel line segments, with each end connected to a semicircle; the centers of the outer ring sliding symmetrical holes are located on the same rectangle; the sliding symmetrical holes of corresponding rings between adjacent metal substrates are staggered along the rectangle or racetrack shape perpendicular to them, and the positions of the sliding symmetrical holes are offset by a quarter wavelength; the sliding symmetrical holes of different rings in the same metal substrate are staggered along the rectangle or racetrack shape parallel to them, and the positions of the sliding symmetrical holes are offset by a quarter wavelength.

[0066] Terahertz waves enter the three-dimensional packaging structure of the terahertz chip from the first rectangular waveguide on one side, and are transmitted through the rectangular waveguides located on each layer of the metal substrate until they are reflected by the reflector 6. The reflector 6 serves as a transition between the closed suspension line structure and the rectangular waveguide. The terahertz waves, after reflection, are transmitted upwards into the suspension line conductor on one side. The terahertz waves are transmitted to the terahertz chip through gold wire bonding wires. After signal processing by the terahertz chip, the terahertz waves are transmitted through the gold wire bonding wires to the suspension line conductor on the other side. During the transmission of the terahertz waves through the suspension line conductor, they are transmitted upwards and downwards simultaneously. The downward-transmitting terahertz waves are reflected by the reflector layer and transmitted upwards. Finally, all the terahertz waves are transmitted upwards and output from the first rectangular waveguide on the other side. The three-dimensional electromagnetic bandgap structure suppresses the leakage of terahertz waves from the gap and increases the operating bandwidth.

[0067] like Figure 8As shown, simulation results of the S-parameters of the terahertz chip's three-dimensional packaging structure can be obtained using the three-dimensional electromagnetic field simulation software CST Studio Suite. Here, the S-parameters represent the ratio of output power to input power. After normalizing the terahertz signal power input to the first rectangular waveguide 101, the return loss S11 represents the power reflected back to the rectangular waveguide; the bandwidth transmission loss S21 represents the power output to the rectangular waveguide on the other side. It can be seen that the terahertz chip's three-dimensional packaging structure has an operating bandwidth of 120–160 GHz, and the bandwidth transmission loss S21 is less than 5 dB, while the return loss S11 is less than 15 dB, meeting the packaging requirements of the terahertz chip.

[0068] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A three-dimensional packaging structure for a terahertz chip, characterized in that, The terahertz chip three-dimensional packaging structure includes: an upper wall plate, an upper main body plate, a lower main body plate, a chip receiving plate, a lower wall plate, a reflector plate, and a fixing stage; wherein, on the fixing stage, from top to bottom, are the upper wall plate, the upper main body plate, the lower main body plate, the chip receiving plate, the lower wall plate, and the reflector plate; The upper wall panel includes a first metal substrate and a first rectangular waveguide. The first metal substrate is a rectangular flat plate, and first rectangular waveguides that penetrate the upper and lower surfaces of the first metal substrate are respectively opened on the left and right sides of the first metal substrate. The upper main body plate includes a second metal substrate, a second rectangular waveguide, an upper suspension conductor air cavity, an upper chip air cavity, and an upper support stub air cavity. The second metal substrate is a rectangular flat plate. The second rectangular waveguide, the upper suspension conductor air cavity, the upper chip air cavity, and the upper support stub air cavity are formed on the second metal substrate, penetrating both the upper and lower surfaces. The two second rectangular waveguides are located on the left and right sides of the second metal substrate, respectively. The upper suspension conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspension conductor air cavity is smaller than that of the second rectangular waveguide. The width of the upper chip air cavity is greater than the width of the upper suspension conductor air cavity, and the horizontal dimension of the upper chip air cavity is not less than that of the chip. The four upper support stub air cavities are respectively opened on the left and right sides of the upper suspension conductor air cavity near the rectangular waveguide and near the upper chip air cavity. The four upper support stub air cavities are respectively connected to the upper suspension conductor air cavity. The two upper support stub air cavities located on the same side of the upper chip air cavity are respectively located on both sides of the upper suspension conductor air cavity. The lower main body plate includes a third metal substrate, a third rectangular waveguide, a suspension conductor mounting cavity, a lower chip air cavity, and a support stub mounting cavity, and is equipped with suspension conductors and support stubs. The third metal substrate is a rectangular plate, and the third rectangular waveguide, suspension conductor mounting cavity, lower chip air cavity, and support stub mounting cavity are formed on the third metal substrate, penetrating the upper and lower surfaces of the third metal substrate. Two third rectangular waveguides are located on the left and right sides of the third metal substrate, respectively. The suspension conductor mounting cavity connects the two third rectangular waveguides, and the shape and size of the suspension conductor mounting cavity are the same as those of the upper suspension conductor air cavity and are aligned vertically. The lower chip air cavity is located in the middle of the suspension conductor mounting cavity, and the shape and size of the lower chip air cavity are the same as those of the upper chip air cavity and are aligned vertically. The lower chip air cavity divides the suspension conductor mounting cavity into a left suspension conductor mounting cavity. The cavity and the right suspension conductor mounting cavity; four supporting stub mounting cavities are respectively opened in the left suspension conductor mounting cavity and the right suspension conductor mounting cavity near the rectangular waveguide and near the lower chip air cavity. The two supporting stub mounting cavities on the left are connected to the left suspension conductor mounting cavity, and the two supporting stub mounting cavities on the right are connected to the right suspension conductor mounting cavity. The shape and size of each supporting stub mounting cavity are the same as the upper supporting stub air cavity and are aligned vertically. Suspension conductors are placed in the left suspension conductor mounting cavity and the right suspension conductor mounting cavity, and supporting stubs are set in the supporting stub mounting cavities. The two supporting stubs on the left connect the left suspension conductor to the lower main body plate, and the two supporting stubs on the right connect the right suspension conductor to the lower main body plate. The supporting stubs and suspension conductors constitute suspension lines. The chip mounting board includes a fourth metal substrate, a fourth rectangular waveguide, a lower left suspended conductor air cavity, a lower right suspended conductor air cavity, and a lower support stub air cavity. The fourth metal substrate is a rectangular flat plate. The fourth rectangular waveguide, the lower left suspended conductor air cavity, the lower right suspended conductor air cavity, and the lower support stub air cavity are formed on the fourth metal substrate, penetrating both the upper and lower surfaces. The two fourth rectangular waveguides are located on the left and right sides of the fourth metal substrate, respectively. The terahertz chip to be packaged is positioned at the center of the upper surface of the fourth metal substrate, directly opposite the lower and upper chip air cavities. The lower left and lower right suspended conductor air cavities are located at... On the left and right sides of the terahertz chip, the lower left and lower right suspended conductor air cavities are vertically aligned with the left and right suspended conductor mounting cavities of the lower main body plate, respectively. Four lower support stub air cavities are respectively located near the fourth rectangular waveguide and near the terahertz chip in the lower left and lower right suspended conductor air cavities. These four lower support stub air cavities are connected to the upper suspended conductor air cavities and are vertically aligned with them. The pins of the terahertz chip are connected to the suspended conductors on the left and right sides of the lower main body plate via gold bonding wires. The lower wall panel includes a fifth metal substrate and a fifth rectangular waveguide. The fifth metal substrate is a rectangular flat plate, and a fifth rectangular waveguide is provided on the left and right sides of the fifth metal substrate, respectively, penetrating the upper and lower surfaces of the fifth metal substrate. The first to fifth rectangular waveguides have the same shape and size, and are aligned in the vertical direction; The upper wall panel, upper main body panel, lower main body panel, chip receiving plate, and lower wall panel constitute a closed suspension line structure; The reflector includes a sixth metal substrate, which is a rectangular flat plate. The lengths and widths of the first to sixth metal substrates are all the same; One or more rings of sliding symmetrical holes are formed on the first to sixth metal substrates and around the rectangular waveguide, penetrating their respective upper and lower surfaces. Each ring of sliding symmetrical holes includes multiple sliding symmetrical holes. The sliding symmetrical holes in each metal substrate layer constitute a three-dimensional electromagnetic bandgap structure. The diameter of each sliding symmetrical hole is half the wavelength of the center operating frequency of the terahertz chip three-dimensional packaging structure. The distance between adjacent sliding symmetrical holes is one wavelength. The sliding symmetrical holes of corresponding rings between adjacent metal substrate layers are staggered, and the positions of the sliding symmetrical holes are vertically offset by one-quarter wavelength. The sliding symmetrical holes of different rings in the same metal substrate layer are staggered, and the positions of the sliding symmetrical holes are horizontally offset by one-quarter wavelength. Terahertz waves enter the three-dimensional packaging structure of the terahertz chip from the first rectangular waveguide on one side, and are transmitted through the rectangular waveguides located on each layer of the metal substrate until they are reflected by the reflector. The reflector is the transition between the closed suspension line structure and the rectangular waveguide. The terahertz waves that are reflected and transmitted upward enter the suspension line conductor on one side. The terahertz waves are transmitted to the terahertz chip through the gold wire bonding wire. After the terahertz chip performs signal processing, the terahertz waves are transmitted to the suspension line conductor on the other side through the gold wire bonding wire. During the transmission of the terahertz waves in the suspension line conductor, the terahertz waves are transmitted upward and downward at the same time. The downward-transmitting terahertz waves are reflected by the reflector layer and transmitted upward. Finally, all the terahertz waves are transmitted upward and output from the first rectangular waveguide on the other side. The three-dimensional electromagnetic bandgap structure suppresses terahertz wave leakage from the gap and increases the operating bandwidth.

2. The terahertz chip three-dimensional packaging structure as described in claim 1, characterized in that, The thickness b of the upper main plate, lower main plate, chip receiving plate, and lower wall plate, as well as the thickness w of the suspension conductor, determine the characteristic impedance Z0 of the closed suspension line. The characteristic impedance satisfies the following formula: Where, ε r is the relative permittivity of the cavity, and b / w is 0.5 to 1.

5.

3. The terahertz chip three-dimensional packaging structure as described in claim 1, characterized in that, The upper support stub air cavities located on both sides near the rectangular waveguide are less than 0.2 mm away from the rectangular waveguide; The upper support stub air cavity, located in the middle and close to the upper chip air cavity, is less than 0.2mm away from the upper chip air cavity.

4. The terahertz chip three-dimensional packaging structure as described in claim 1, characterized in that, The number of turns of the sliding symmetrical hole is 1 to 4.

5. The terahertz chip three-dimensional packaging structure as described in claim 1, characterized in that, The upper wall panel, upper main body panel, lower main body panel, chip receiving plate, lower wall panel, and reflector are all made of conductive metal.

6. The terahertz chip three-dimensional packaging structure as described in claim 1, characterized in that, The fixed platform is made of solid material.

7. The terahertz chip three-dimensional packaging structure as described in claim 1, characterized in that, The four support stubs are divided into two pairs. One pair consists of the two support stubs closest to the rectangular waveguide, and the other pair consists of the two support stubs closest to the terahertz chip. The two pairs have different lengths. The length of the pair of support stubs closest to the terahertz chip is one-quarter of the wavelength corresponding to the lower sideband frequency of the terahertz chip's operating bandwidth, while the length of the pair of support stubs closest to the rectangular waveguide is one-quarter of the wavelength corresponding to the upper sideband frequency of the terahertz chip's operating bandwidth.

8. A method for implementing the three-dimensional packaging structure of a terahertz chip as described in claim 1, characterized in that, The implementation method includes the following steps: 1) Fabrication of a three-dimensional packaging structure for terahertz chips: The first to sixth metal substrates are provided, all of which are rectangular flat plates with the same length, width and thickness; First to fifth rectangular waveguides of the same shape and size are respectively formed at the same positions on the left and right sides of the first to fifth metal substrates; A first metal substrate with a first rectangular waveguide forms the upper wall panel; a fifth metal substrate with a fifth rectangular waveguide forms the lower wall panel. A second rectangular waveguide penetrating the upper and lower surfaces of the second metal substrate, an upper suspended conductor air cavity, an upper chip air cavity, and an upper support stub air cavity are formed on the second metal substrate. Two second rectangular waveguides are located on the left and right sides of the second metal substrate, respectively. The upper suspended conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspended conductor air cavity is smaller than the width of the second rectangular waveguides. The upper chip air cavity is located in the middle of the upper suspended conductor air cavity, and its width is greater than the width of the upper suspended conductor air cavity. The horizontal dimension of the upper chip air cavity is not smaller than that of the chip. Four upper support stub air cavities are respectively formed on the left and right sides of the upper suspended conductor air cavity, near the rectangular waveguides and near the upper chip air cavity. The four upper support stub air cavities are connected to the upper suspended conductor air cavity. Two upper support stub air cavities located on the same side as the upper chip air cavity are located on either side of the upper suspended conductor air cavity on the second metal substrate. The substrate has a second rectangular waveguide penetrating the upper and lower surfaces of the second metal substrate, an upper suspended conductor air cavity, an upper chip air cavity, and an upper support stub air cavity. The two second rectangular waveguides are located on the left and right sides of the second metal substrate, respectively. The upper suspended conductor air cavity connects the two second rectangular waveguides, and the width of the upper suspended conductor air cavity is smaller than the width of the second rectangular waveguide. The upper chip air cavity is located in the middle of the upper suspended conductor air cavity, and the width of the upper chip air cavity is greater than the width of the upper suspended conductor air cavity. The horizontal dimension of the upper chip air cavity is not smaller than that of the chip. The four upper support stub air cavities are located on the left and right sides of the upper suspended conductor air cavity, near the rectangular waveguides and near the upper chip air cavity, respectively. The four upper support stub air cavities are connected to the upper suspended conductor air cavity. The two upper support stub air cavities located on the same side as the upper chip air cavity are located on both sides of the upper suspended conductor air cavity, forming the upper main body plate. A third rectangular waveguide penetrating the upper and lower surfaces of the third metal substrate, a suspended conductor mounting cavity, a lower chip air cavity, and a support stub mounting cavity are formed on the third metal substrate. Two third rectangular waveguides are located on the left and right sides of the third metal substrate, respectively. The suspended conductor mounting cavity connects the two third rectangular waveguides, and its shape and size are the same as the upper suspended conductor air cavity, and its position is aligned vertically. The lower chip air cavity is located in the middle of the suspended conductor mounting cavity, and its shape and size are the same as the upper chip air cavity, and its position is aligned vertically. The lower chip air cavity divides the suspended conductor mounting cavity into a left suspended conductor mounting cavity and a right suspended conductor mounting cavity. Four support stub mounting cavities are respectively formed in the left and right suspended conductor mounting cavities. The mounting cavities are located near the rectangular waveguide and near the lower chip air cavity. The two supporting stub mounting cavities on the left are connected to the left suspended conductor mounting cavity, and the two supporting stub mounting cavities on the right are connected to the right suspended conductor mounting cavity. The shape and size of each supporting stub mounting cavity are the same as the upper supporting stub air cavity, and their positions are aligned vertically. Suspended conductors are placed in the left and right suspended conductor mounting cavities, and supporting stubs are set in the supporting stub mounting cavities. The two supporting stubs on the left connect the left suspended conductor to the lower main body plate, and the two supporting stubs on the right connect the right suspended conductor to the lower main body plate. The supporting stubs and suspended conductors constitute the suspended line, which in turn constitutes the lower main body plate. A fourth rectangular waveguide penetrating the upper and lower surfaces of the fourth metal substrate, a lower left suspended conductor air cavity, a lower right suspended conductor air cavity, and a lower support stub air cavity are formed on the fourth metal substrate; the two fourth rectangular waveguides are located on the left and right sides of the fourth metal substrate, respectively; the terahertz chip to be packaged is placed at the center of the upper surface of the fourth metal substrate, directly opposite the lower and upper chip air cavity; the lower left and lower right suspended conductor air cavities are located on the left and right sides of the terahertz chip, respectively, and are connected to the lower main body. The left and right suspension conductor mounting cavities of the board are aligned vertically. Four lower support stub air cavities are respectively opened in the lower left and lower right suspension conductor air cavities near the fourth rectangular waveguide and near the terahertz chip. The four lower support stub air cavities are connected to the upper suspension conductor air cavities and are aligned vertically with the four upper support stub air cavities. The pins of the terahertz chip are connected to the suspension conductors on the left and right sides of the lower main board through gold wire bonding wires, forming a chip receiving board. The upper wall panel, upper main body panel, lower main body panel, chip receiving plate, and lower wall panel constitute a closed suspension line structure; One or more rings of sliding symmetrical holes are formed on the first to sixth metal substrates and around the rectangular waveguide, penetrating their respective upper and lower surfaces. Each ring of sliding symmetrical holes includes multiple sliding symmetrical holes. The sliding symmetrical holes in each metal substrate layer constitute a three-dimensional electromagnetic bandgap structure. The diameter of each sliding symmetrical hole is half the wavelength of the center operating frequency of the terahertz chip three-dimensional packaging structure. The distance between adjacent sliding symmetrical holes is one wavelength. The sliding symmetrical holes of corresponding rings between adjacent metal substrate layers are staggered, and the positions of the sliding symmetrical holes are vertically offset by one-quarter wavelength. The sliding symmetrical holes of different rings in the same metal substrate layer are staggered, and the positions of the sliding symmetrical holes are horizontally offset by one-quarter wavelength. 2) Terahertz waves enter the three-dimensional packaging structure of the terahertz chip from the first rectangular waveguide on one side, and are transmitted through the rectangular waveguides located on each layer of metal substrate until they are reflected by the reflector. The reflector is the transition between the closed suspension line structure and the rectangular waveguide. 3) The terahertz wave, after being reflected by the reflector and transmitted upwards, enters the suspension conductor on one side; 4) The terahertz wave is transmitted to the terahertz chip through the gold wire bonding wire. After the signal is processed by the terahertz chip, the terahertz wave is transmitted to the suspension conductor on the other side through the gold wire bonding wire. 5) During the transmission of terahertz waves in the suspended conductor, they are simultaneously transmitted upward and downward. The downward-transmitting terahertz waves are reflected by the reflective layer and transmitted upward. Finally, all the terahertz waves are transmitted upward and output from the first rectangular waveguide on the other side. 6) During the transmission of terahertz waves in a closed suspension wire structure, the three-dimensional electromagnetic bandgap structure suppresses the leakage of terahertz waves from the gap and increases the operating bandwidth.

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