High-selectivity rectangular micro-coaxial band-pass filter with double CT structures

Abstract

The invention belongs to the technical field of filters. The invention provides a high-selectivity rectangular micro-coaxial band-pass filter with a double-CT (Computed Tomography) structure. According to the embodiment of the invention, the first transmission line resonator, the second transmission line resonator and the third transmission line resonator form a CT structure, and the fourth transmission line resonator, the fifth transmission line resonator and the sixth transmission line resonator form a CT structure, so that a transmission zero point is introduced, and high selectivity of the device is realized; meanwhile, a transmission line resonator structure is matched and utilized to sequentially pass through seventh, eighth, ninth and tenth metal inner cores and a metal supporting structure to be converted from a horizontal plane to a vertical plane, and is combined with a first metal inner core boss and a second metal inner core boss at the upper ends of the eighth metal inner core and the tenth metal inner core; according to the band-pass filter disclosed by the invention, the coplanar waveguide interconnected with an external element is formed by the coplanar waveguide and the port on the shell, so that a micro coaxial line-coplanar waveguide switching structure is formed, the structure is beneficial to board-level interconnection integration of the band-pass filter and other devices, the application range of the band-pass filter is widened, and the band-pass filter has the advantages of low loss and high suppression degree.

Description

TECHNICAL FIELD

[0001] The embodiment of the present disclosure relates to the technical field of filter, in particular to a high-selectivity rectangular micro-coaxial band-pass filter with double-CT structure. BACKGROUND

[0002] The filter is a key passive device in the wireless communication system, which selectively passes or suppresses signals of a specific frequency band, thereby retaining useful signals and filtering out noise and interference to improve signal-to-noise ratio. Especially in high-frequency systems such as 5G, satellite communication, and millimeter wave communication, the performance of the filter directly affects the communication quality, transmission rate, and system reliability.

[0003] The traditional microstrip filter has been widely used due to its low cost and mature technology. With the expansion of 5G technology to the millimeter wave frequency band, at high frequencies, the dielectric loss and radiation loss of the planar structure such as microstrip line are intensified, resulting in increased insertion loss and reduced quality factor (Q value), and the strong coupling between adjacent microstrip lines limits the line density. While the metal waveguide and dielectric resonator filter can achieve low loss and high quality factor, but its volume is large and difficult to integrate. With the rapid development of micro-electro-mechanical systems (MEMS) and computer numerical control precision machinery (CNC) micro-nano processing technology, the rectangular micro-coaxial technology applied to the microwave field has been realized.

[0004] The rectangular micro-coaxial line has a quasi-planar structure, which is easy to miniaturize and integrate, and can be interconnected with other transmission lines. Compared with the microstrip line, strip line and other transmission lines based on high-frequency board materials, the rectangular micro-coaxial line uses air as the main insulating medium, has no dielectric loss, and its outer conductor is grounded to form a natural electromagnetic shield, which has no radiation loss and efficiently transmits TEM waves. Therefore, it has excellent electrical properties such as low loss, high isolation, and low dispersion, which can improve the transmission efficiency and quality of signals.

[0005] The micro-coaxial technology provides a new technical path for realizing high-performance and high-integration filters due to its low loss, natural electromagnetic shielding characteristics and good compatibility with three-dimensional micro-processing technology, and is particularly suitable for future millimeter wave frequency band communication front-end modules.

[0006] In the prior art, filters based on rectangular micro-coaxial line structures have appeared to improve performance. For example, the filter in the invention patent CN119786920B “Micro-coaxial millimeter wave filter with source load coupling” adopts a rectangular micro-coaxial line structure and introduces transmission zeros on both sides of the passband by adopting cross-coupling topology and source / load coupling, which improves the frequency band selectivity of the filter to a certain extent.

[0007] However, this existing technology still has limitations: First, the transmission zeros introduced by its cross-coupling and source / load coupling must exist simultaneously on both sides of the passband, and the positions of the transmission zeros introduced by its cross-coupling must be symmetrically distributed on both sides of the passband, which cannot meet the out-of-band suppression requirements of asymmetry on both sides of the passband; Second, its input / output transition structure determines that its devices must achieve external interconnection through bonding, which is complex to operate, easily introduces additional parasitic effects that cause impedance discontinuities and thus impedance mismatch, and is easy to damage the devices during disassembly and assembly.

[0008] Therefore, it is necessary to improve one or more of the problems existing in the above-mentioned related technical solutions.

[0009] It should be noted that this section is intended to provide background or context for the technical solutions of this disclosure as set forth in the claims. The description herein does not constitute an admission that it is prior art simply because it is included in this section. Summary of the Invention

[0010] The purpose of this disclosure is to provide a highly selective rectangular micro-coaxial bandpass filter with a dual-CT structure, thereby overcoming, at least to some extent, one or more problems caused by the limitations and defects of related technologies.

[0011] According to embodiments of this disclosure, a highly selective rectangular micro-coaxial bandpass filter with a dual-CT structure is provided, comprising: The housing 101 contains a first transmission line resonator, a second transmission line resonator, a third transmission line resonator, a fourth transmission line resonator, a fifth transmission line resonator, and a sixth transmission line resonator. The first and sixth transmission line resonators, the second and fifth transmission line resonators, and the third and fourth transmission line resonators are arranged symmetrically. Magnetic coupling exists between the first and second, second and third, third and fourth, fourth and fifth transmission line resonators, and fifth and sixth transmission line resonators. Electrical coupling exists between the first and third, and fourth and sixth transmission line resonators. An input feeding structure is used to input an excitation signal onto the first transmission line resonator; The output feed structure is used to output the signal on the sixth transmission line resonator.

[0012] Furthermore, the first transmission line resonator and the sixth transmission line resonator, the second transmission line resonator and the fifth transmission line resonator, and the third transmission line resonator and the fourth transmission line resonator are all symmetrically arranged with respect to the central plane of the length direction of the housing 101.

[0013] Furthermore, the first transmission line resonator includes a first metal core 201 that is open at one end and short-circuited at the other end of the housing 101; The second transmission line resonator includes a second metal core 202, one end of which is open-circuited to the housing 101 and the other end of which is short-circuited to the first column 102. The second metal core 202 is disposed on one side of the first metal core 201, and one end of the second metal core 202 is connected to the first column 102 to achieve a short circuit. The upper and lower ends of the first column 102 are respectively fixedly connected to the inner surface of the housing 101. The short-circuited end of the second metal core 202 is parallel to the short-circuited end of the first metal core 201. The third transmission line resonator includes a third metal core 203 that is open at one end and short-circuited at the other end of the housing 101. The third metal core 203 is disposed on the side of the second metal core 202 away from the first metal core 201. The short-circuited end of the third metal core 203 and the housing 101 is parallel to the short-circuited end of the second metal core 202. The open end of the third metal core 203 is opposite to the open end of the first metal core 201. There is a preset gap between the open end of the third metal core 203 and the open end of the first metal core 201. The fourth transmission line resonator includes a fourth metal core 204 that is open at one end and short-circuited at the other end of the housing 101, and is symmetrical to the third metal core 203 with respect to the central plane of the length direction of the housing 101. The fifth metal core 205 is disposed on the side of the fourth metal core 204 away from the third metal core 203, and is centrally symmetrical with the second metal core 202 relative to the length direction of the housing 101. One end of the fifth metal core 205 is connected to the second column 103 to achieve a short circuit, and the upper and lower ends of the second column 103 are respectively fixedly connected to the inner surface of the housing 101. The sixth metal core 206 is disposed on the side of the fifth metal core 205 away from the fourth metal core 204, and one end of the sixth metal core 206 is connected to the inner surface of the housing 101 to achieve a short circuit, and is centrally symmetrical with the first metal core 201 relative to the length direction of the housing 101.

[0014] Furthermore, a first metal wall 104 is provided between the third metal inner core 203 and the fourth metal inner core 204. The upper and lower ends of the first metal wall 104 are fixedly connected to the inner surface of the shell 101, and the first metal wall 104 is centrally symmetrical about the length direction of the shell 101. A second metal wall 105 is provided between the second metal inner core 202 and the fifth metal inner core 205. The upper and lower ends of the second metal wall 105 are fixedly connected to the inner surface of the housing 101, respectively. The second metal wall 105 is centrally symmetrical about the length direction of the housing 101. One end of the third metal inner core 203 and the fourth metal inner core 204 are each short-circuited to the middle of the second metal wall 105.

[0015] Furthermore, the input power supply structure includes: The first extended cavity 106 is disposed on one side of the housing 101. The height of the first extended cavity 106 is equal to the height of the housing 101, and a first stepped groove 301 is formed on the edge of the first extended cavity 106 away from the first metal core 201. The seventh metal core 207 is disposed in the first extended cavity 106 and located on the side of the first metal core 201 away from the second metal core 202. One end of the seventh metal core 207 is fixedly connected to the first metal core 201. The eighth metal inner core 208 is disposed in the first step groove 301 and located on the side of the seventh metal inner core 207 away from the first metal inner core 201. It is fixedly connected to the seventh metal inner core 207. A first metal inner core boss 211 is provided above the eighth metal inner core 208, and the upper surface of the first metal inner core boss 211 is flush with the top surface of the cavity of the first extension cavity 106. The first metal support block 107 is disposed below the end of the eighth metal inner core 208 away from the housing 101, and the first metal support block 107 is fixedly connected to the eighth metal inner core 208. The first step block 108 is located below the first metal support block 107, and the first step block 108 is fixedly connected to the inner wall of the first extension cavity 106.

[0016] Furthermore, the output power supply structure includes: The second extended cavity 109 is disposed on the other side of the housing 101. The height of the second extended cavity 109 is equal to the height of the housing 101, and a second stepped groove 302 is provided on the edge of the second extended cavity 109 away from the sixth metal core 206. The ninth metal core 209 is disposed in the second extended cavity 109 and is located on the side of the sixth metal core 206 away from the fifth metal core 205. One end of the ninth metal core 209 is fixedly connected to the sixth metal core 206. The tenth metal inner core 210 is disposed in the second step groove 302 and located on the side of the ninth metal inner core 209 away from the sixth metal inner core 206. It is fixedly connected to the ninth metal inner core 209. A second metal inner core boss 212 is provided above the tenth metal inner core 210, and the upper surface of the second metal inner core boss 212 is flush with the top surface of the cavity of the second extension cavity 109. The second metal support block 110 is disposed below the end of the tenth metal inner core 210 away from the housing 101, and the second metal support block 110 is fixedly connected to the tenth metal inner core 210. The second step block 111 is located below the second metal support block 110, and the second step block 111 is fixedly connected to the inner wall of the second extension cavity 109.

[0017] Furthermore, the first metal inner core 201, the second metal inner core 202, the third metal inner core 203, the fourth metal inner core 204, the fifth metal inner core 205, the sixth metal inner core 206, the seventh metal inner core 207 and the ninth metal inner core 209 are provided with a first medium support strip 401 for support and fixation.

[0018] Furthermore, the eighth metal core 208 and the tenth metal core 210 are respectively provided with second dielectric support strips 402 for electromagnetic isolation and support fixation. The second dielectric support strips 402 are respectively provided above the first metal support block 107 and the second metal support block 110.

[0019] Furthermore, the surface of the housing 101 is provided with a plurality of periodically arranged release holes 601, which are used to release photoresist.

[0020] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects: In the embodiments of this disclosure, the highly selective rectangular micro-coaxial bandpass filter with a dual-CT structure achieves high selectivity by introducing a transmission zero through the first, second, and third transmission line resonators forming a CT structure and the fourth, fifth, and sixth transmission line resonators forming a CT structure. Simultaneously, by sequentially transforming the transmission line resonator structure from a horizontal plane to a vertical plane through a seventh, eighth, ninth, and tenth metal core and a metal support structure, and combining the first and second metal core bosses at the upper ends of the eighth and tenth metal cores, a coplanar waveguide is formed with the port on the housing to interconnect with external components, thus creating a micro-coaxial line-coplanar waveguide transition structure. This structure facilitates board-level interconnection and integration of the bandpass filter with other devices, broadens the application range of the bandpass filter, and offers advantages such as low loss, high suppression, and good transmission performance. It fills the gap in millimeter-wave-based bandpass filters, is highly practical, and worthy of promotion. On the other hand, adjacent resonators are magnetically coupled, while the first and third resonators, and the fourth and sixth resonators are electrically coupled. The six resonators form a dual-CT structure, and a transmission zero on one side of the passband is introduced through the cross-coupling of this structure. The input / output feed structure adopts a micro-coaxial line-coplanar waveguide adapter design, and the adapter structure can be cascaded at the board level and directly surface-mounted on the PCB to enhance circuit interconnectivity. The dual-CT structure provides a configurable cross-coupling path, allowing the introduction of a transmission zero on one side of the passband, thereby achieving higher selectivity and adaptability. At the same time, the input / output adapter structure allows direct mounting on the PCB substrate by soldering to achieve connection with planar transmission lines. Compared with bonding interconnects, this interconnection method provides stable impedance matching and fewer parasitic effects. Furthermore, if the circuit performance does not meet the standards after soldering, it can be removed and tested and replaced by heating or other methods. Once bonding is completed, repair is extremely difficult, and replacement is more likely to damage the device. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0022] Figure 1 A perspective view of a highly selective rectangular micro-coaxial bandpass filter with a dual-CT structure according to an exemplary embodiment of the present disclosure is shown. Figure 2 Show Figure 1 Perspective view from above; Figure 3 ShowFigure 1 Top view after removing the casing; Figure 4 Show Figure 1 The bottom view; Figure 5 Show Figure 1 Top view; Figure 6 Show Figure 1 Cross-section Figure 1 ; Figure 7 Show Figure 1 Side view; Figure 8 Show Figure 1 Cross-section Figure 2 ; Figure 9 This diagram illustrates the coupling relationships in exemplary embodiments of this disclosure. Figure 10 The diagram shows the S-parameter simulation results of the bandpass filter in an exemplary embodiment of this disclosure. Detailed Implementation

[0023] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] Furthermore, the accompanying drawings are merely illustrative diagrams of embodiments of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0025] This example implementation provides a highly selective rectangular micro-coaxial bandpass filter with a dual-CT structure. (Reference) Figure 1 As shown, the highly selective rectangular micro-coaxial bandpass filter of the dual-CT structure may include: The housing 101 contains a first transmission line resonator, a second transmission line resonator, a third transmission line resonator, a fourth transmission line resonator, a fifth transmission line resonator, and a sixth transmission line resonator. The first and sixth transmission line resonators, the second and fifth transmission line resonators, and the third and fourth transmission line resonators are arranged symmetrically. Magnetic coupling exists between the first and second, second and third, third and fourth, fourth and fifth transmission line resonators, and fifth and sixth transmission line resonators. Electrical coupling exists between the first and third, and fourth and sixth transmission line resonators. An input feeding structure is used to input an excitation signal onto the first transmission line resonator; The output feed structure is used to output the signal on the sixth transmission line resonator.

[0026] The high-selectivity rectangular micro-coaxial bandpass filter with a dual-CT structure described above achieves high selectivity by introducing a transmission zero through the combination of the first, second, and third transmission line resonators forming a CT structure, and the fourth, fifth, and sixth transmission line resonators forming a CT structure. Simultaneously, by sequentially transforming the transmission line resonator structure from a horizontal plane to a vertical plane through the seventh, eighth, ninth, and tenth metal cores and the metal support structure, and combining the first and second metal core bosses at the upper ends of the eighth and tenth metal cores, a coplanar waveguide is formed with the port on the housing to interconnect with external components, thus creating a micro-coaxial line-coplanar waveguide transition structure. This structure facilitates board-level interconnection and integration of the bandpass filter with other devices, broadening the application range of the bandpass filter. It possesses advantages such as low loss, high suppression, and good transmission performance, filling the gap in millimeter-wave-based bandpass filters. It is highly practical and worthy of promotion. On the other hand, adjacent resonators are magnetically coupled, while the first and third resonators, and the fourth and sixth resonators are electrically coupled. The six resonators form a dual-CT structure, and a transmission zero on one side of the passband is introduced through the cross-coupling of this structure. The input / output feed structure adopts a micro-coaxial line-coplanar waveguide adapter design, and the adapter structure can be cascaded at the board level and directly surface-mounted on the PCB to enhance circuit interconnectivity. The dual-CT structure provides a configurable cross-coupling path, allowing the introduction of a transmission zero on one side of the passband, thereby achieving higher selectivity and adaptability. At the same time, the input / output adapter structure allows direct mounting on the PCB substrate by soldering to achieve connection with planar transmission lines. Compared with bonding interconnects, this interconnection method provides stable impedance matching and fewer parasitic effects. Furthermore, if the circuit performance does not meet the standards after soldering, it can be removed and tested and replaced by heating or other methods. Once bonding is completed, repair is extremely difficult, and replacement is more likely to damage the device.

[0027] Below, we will refer to Figures 1 to 10 The steps of the high-selectivity rectangular micro-coaxial bandpass filter with dual-CT structure described in this example embodiment will be explained in more detail.

[0028] In one embodiment, this application provides a highly selective rectangular micro-coaxial bandpass filter with a dual-CT structure. Specifically, the housing 101 and a first transmission line resonator, a second transmission line resonator, a third transmission line resonator, a fourth transmission line resonator, a fifth transmission line resonator, and a sixth transmission line resonator constitute a micro-coaxial structure. The first, second, third, fourth, fifth, and sixth transmission line resonators form a quarter-wavelength transmission line resonator structure, and its coupling path can be... Figure 9The following symbols are used to represent the first coupled transmission line resonator (denoted by number 1), the second transmission line resonator (denoted by number 2), the third transmission line resonator (denoted by number 3), the fourth transmission line resonator (denoted by number 4), the fifth transmission line resonator (denoted by number 5), and the sixth transmission line resonator (denoted by number 6). The input coupling structure is denoted by S, and the output coupling structure is denoted by L.

[0029] An input feeding structure is disposed on one side of the first transmission line resonator and is used to input an excitation signal onto the first transmission line resonator.

[0030] The output feed structure is located on one side of the sixth transmission line resonator and is used to output the signal on the sixth transmission line resonator.

[0031] Specifically, such as Figures 1 to 3 As shown, the first transmission line resonator includes a first metal core 201 that is open at one end and short-circuited at the other end of the housing 101. The first metal core 201 is composed of two mutually perpendicular plates, a first plate and a second plate. The length of the first plate is placed along the Y direction and its length is greater than that of the second plate. The second transmission line resonator includes a second metal core 202, one end of which is open-circuited to the housing 101 and the other end of which is short-circuited to the first column 102. The second metal core 202 is disposed on one side of the first metal core 201 and is composed of a plate three and a plate four that are perpendicular to each other. The length of plate three is placed along the Y direction and is greater than that of plate four. Plate three of the second metal core 202 is parallel to plate one of the first metal core 201. A first gap 501 is preset between plate one and plate three. One end of plate three of the second metal core 202 is connected to the first column 102 to achieve a short circuit. The upper and lower ends of the first column 102 are respectively fixedly connected to the inner surface of the housing 101. The third transmission line resonator includes a third metal core 203 connected to the housing 101 with one end open and the other end short-circuited. The third metal core 203 is composed of two mutually perpendicular plates, plate five and plate six. Plate five is placed along the Y direction and its length is greater than that of plate six. The third metal core 203 is located on the side of the second metal core 202 away from the first metal core. Plate five of the third metal core 203 is parallel to plate three of the second metal core 202. A second gap 502 is preset between plate three and plate five. Plate six of the third metal core 203 is opposite to plate two of the first metal core. A third gap 503 is preset between plate two and plate six. The fourth transmission line resonator includes a fourth metal core 204 that is open at one end and short-circuited at the other end of the housing 101. The fourth metal core 204 is composed of two mutually perpendicular plates, a seventh plate and an eighth plate. The length of the seventh plate is placed along the Y direction and is greater than that of the eighth plate. The fourth metal core 204 is located on the side of the third metal core 203 away from the second metal core 202 and is symmetrical with respect to the central plane of the third metal core 203 with respect to the length direction of the housing 101. There is a preset first metal wall 104 between the fifth plate of the seventh plate and the fifth plate of the third metal core 203, and there is a preset fourth gap 504 between the fifth plate and the seventh plate. The fifth metal core 205 is located on the side of the fourth metal core 204 away from the third metal core 203. It is composed of two perpendicular plates, nine and ten. The length of plate nine is placed along the Y direction and is greater than that of plate ten. Plate nine of the fifth metal core 205 is parallel to plate seven of the fourth metal core 204. There is a pre-set fifth gap 505 between plate seven and plate nine. One end of plate nine of the fifth metal core 205 is connected to column 103 to achieve short circuit. The upper and lower ends of column 103 are fixedly connected to the inner surface of shell 101 respectively. Plate ten is opposite to plate four of the second metal core 202. There is a pre-set second metal wall 105 in the middle to separate the two. The sixth metal core 206 is located on the side of the fifth metal core 205 away from the fourth metal core 204. It is composed of two perpendicular plates, eleven and twelve. The length of plate eleven is placed along the Y direction and is longer than that of plate twelfth. Plate eleven is parallel to plate nine of the fifth metal core 205. There is a pre-set sixth gap 506 between plate nine and plate eleven. Plate eleven of the sixth metal core 206 is connected to the inner surface of the shell 101 to achieve a short circuit. Plate twelfth is opposite to plate eight of the fourth metal core 204. There is a pre-set seventh gap 507 between plate eight and plate twelfth.

[0032] More specifically, the upper and lower ends of the first metal wall 104 and the second metal wall 105 are connected to the inner surface of the housing 101, the first metal wall 104 and the second metal wall 105 are spaced at a preset distance in the Y direction, and the second metal wall 105 is placed in a convex shape on the XY plane.

[0033] like Figure 2As shown, the magnetic coupling between the first and second transmission line resonators is achieved by the first gap 501, the magnetic coupling between the second and third transmission line resonators is achieved by the second gap 502, and the cross-coupling between the first and third transmission line resonators is achieved by the third gap 503. Due to the symmetrical structure, the magnetic coupling between the fourth and fifth transmission line resonators is achieved in the same way as the magnetic coupling between the second and third transmission line resonators, the magnetic coupling between the fifth and sixth transmission line resonators is achieved in the same way as the magnetic coupling between the first and second transmission line resonators, and the cross-coupling between the fourth and sixth transmission line resonators is achieved in the same way as the magnetic coupling between the first and third transmission line resonators. The fourth gap 504 provides energy exchange between transmission line resonators. The first metal wall 104 can appropriately reduce the coupling between resonators by utilizing the high isolation characteristics of the micro coaxial line. When the first metal wall 104 is not present, the magnetic coupling and electrical coupling between the third and fourth transmission line resonators will affect each other, which is not conducive to flexible control. Therefore, the first metal wall 104 is added. The magnetic coupling between the third and fourth transmission line resonators is adjusted by the fourth gap 504 and the spacing between the first and second metal walls.

[0034] Specifically, such as Figure 3 and Figure 6 As shown, the input power supply structure includes a seventh metal core 207 disposed on the side of the first metal core 201 away from the second metal core 202, a first extension cavity 106, an eighth metal core 208, a first step block 108 fixedly connected to the first extension cavity 106, and a first metal support block 107 fixedly connected to the first step block 108.

[0035] In a more detailed implementation, the seventh metal core 207 is disposed within the first extended cavity 106 and located on the side of the first metal core 201 away from the second metal core 202. One end of the seventh metal core 207 is fixedly connected to the first metal core 201, and the other end is fixedly connected to the eighth metal core 208. More specifically, as shown in the following embodiment... Figure 1 and Figure 2As shown, in the opposite direction of the X direction, the sixth metal core can be divided into a first trapezoidal block, a first rectangular block, a second trapezoidal block, a second rectangular block, and a third rectangular block. The top surface of the first trapezoidal block is fixedly connected to the first metal core 201, the bottom surface of the first trapezoidal block is fixedly connected to one side of the first rectangular block, the other side of the first rectangular block is fixedly connected to the bottom surface of the second trapezoidal block, the top surface of the second trapezoidal block is fixedly connected to one side of the second rectangular block, the other side of the second rectangular block is fixedly connected to one side of the third rectangular block, and the other side of the third rectangular block is fixedly connected to the eighth metal core 208. In the Z direction, the first trapezoidal block, the first rectangular block, the second trapezoidal block, and the second rectangular block have the same height of 200 μm and are symmetrical about the X direction. The third rectangular block has a height of 100 μm and is symmetrical about the X direction. The bottom surface of the third rectangular block is flush with the bottom surface of the eighth metal core 208, the top surface of the third rectangular block is flush with the top surface of the second rectangular block, and the bottom surfaces of the third rectangular block and the second rectangular block form a step.

[0036] More specifically, such as Figure 6 As shown, a first stepped groove 301 is formed on the edge of the first epitaxial cavity 106 away from the first metal core 201. An eighth metal core 208 is disposed in the first stepped groove 301. The left side of the eighth metal core 208 is flush with the left edge of the first stepped groove 301. The other sides of the eighth metal core 208 have a preset gap with the inner surface of the first stepped groove 301. More specifically, a first metal core boss 211 is provided above the eighth metal core 208. The height of the first metal core boss 211 is equal to the step of the first stepped groove 301 and the two are at the same height. The upper surface of the first metal core boss 211 above the eighth metal core 208 is flush with the top surface of the cavity of the first epitaxial cavity 106, forming a coplanar waveguide structure.

[0037] The seventh metal core 207 and the eighth metal core 208, as the inner conductors of the input feed structure, together with the first epitaxial cavity 106, constitute the transition structure of the micro-coaxial line-coplanar waveguide. As a further improvement based on this embodiment, to provide support for the inner conductors of the micro-coaxial line-coplanar waveguide transition structure, such as... Figure 6 As shown, a first metal support block 107 is provided below the end of the eighth metal inner core 208 that is away from the housing 101, as... Figure 7As shown, the first metal support block 107 is composed of two rectangular blocks. The two rectangular blocks are symmetrically arranged about the Y direction and have a pre-set gap in the middle. The top surfaces of the two rectangular blocks cover the bottom surface of the eighth metal inner core 208. The first support block 104 supports and fixes the eighth metal inner core 208 through this covering surface. The lower plane of the first metal support block 107 is fixedly connected to the upper plane of the first stepped block 108, and the lower plane of the first stepped block 108 is fixedly connected to the inner wall of the first extended cavity 106. The first metal support block 107 and the first stepped block 108 together provide support and fixation for the eighth metal inner core 208.

[0038] Specifically, the input power supply structure and the output power supply structure are centrally symmetrical with respect to the length direction of the housing 101. The output power supply structure has a ninth metal inner core 209, a tenth metal inner core 210, a second outer cavity 109, a second metal support block 110, a second step block 111, and a second step groove 302, which are respectively corresponding to the seventh metal structure 207, the eighth metal inner core 208, the first extended cavity 106, the first metal support block 107, the first step block 108, and the first step groove 301 of the input power supply structure. The dimensions and relative positions of each corresponding structure are the same.

[0039] As a further improvement based on this embodiment, in order to achieve the positioning function of the first metal inner core 201, the second metal inner core 202, the third metal inner core 203, the fourth metal inner core 204, the fifth metal inner core 205, the sixth metal inner core 206, the seventh metal inner core 207, the eighth metal inner core 208, the ninth metal inner core 209, and the tenth metal inner core 210, such as... Figure 3 As shown, a first dielectric support strip 401 and a second dielectric support strip 402 are provided on it. One or a pair of sides of the dielectric support strip are fixed to a pair of inner walls of the housing 101 to improve the stability of the metal core support. In addition, the second dielectric support strip 402 realizes the electromagnetic isolation between the eighth metal core 208 and the first metal support block 107, and between the tenth metal core 210 and the second metal support block 110, so as to prevent the eighth and tenth metal cores from being grounded and short-circuited while supporting and fixing them.

[0040] For performance and ease of processing considerations, the filter provided in this application is manufactured using three-dimensional electrochemical additive manufacturing technology. The housing 101, the first metal core 201, the second metal core 202, the third metal core 203, the fourth metal core 204, the fifth metal core 205, the sixth metal core 206, the seventh metal core 207, the eighth metal core 208, the ninth metal core 209, and the tenth metal core 210 are all made of copper. The dielectric constants of the first dielectric support strip 401 and the second dielectric support strip 402 are 3.2. The designed millimeter-wave bandpass filter with miniaturization and high-frequency band selectivity is obtained through electrochemical additive manufacturing technology.Figure 4 As shown, to release the photoresist used in the manufacturing process, several release holes 601 are formed on the housing 101. These release holes 601 are used to release the photoresist, and all release holes 601 are of identical size. It is important to note that the number of release holes 601 should not be too many or too few. Too many holes will cause electromagnetic leakage, while too few will result in incomplete photoresist removal and residue. The number must be determined after comprehensive consideration during the design process. Products obtained using this manufacturing process have high precision, enabling the filter to be integrated into a single design and mass-produced, while ensuring the filter's performance.

[0041] The first, second, and third transmission line resonators of the bandpass filter in this application form a cross-coupling (CT) structure, as do the fourth, fifth, and sixth transmission line resonators. This structure introduces cross-coupling into the filter, which will generate a single attenuation pole at a finite frequency. This asymmetrical frequency response can cause a steep drop on one side of the passband. Therefore, the bandpass filter will have high selectivity after the introduction of the CT structure.

[0042] It is worth noting that in the CT structure formed by the first transmission line resonator, the second transmission line resonator and the third transmission line resonator of this application, the coupling form between adjacent resonators is magnetic coupling, and the cross coupling between the first transmission line resonator and the third transmission line resonator is electrical coupling. At this time, the transmission zero introduced by the CT structure is at the low frequency on the left side of the passband. If the opposite structure is adopted, the ends of the second plate of the first transmission line resonator and the sixth plate of the third transmission line resonator are bent in the negative Y-axis direction and directly short-circuited to the housing 101. The other ends of the two resonators are separated from the housing 101 to form an open circuit. The third plate of the second transmission line resonator is separated from the first column 102 to form an open circuit. The other end of the resonator is short-circuited to the housing 101. At this time, the first, second and third transmission line resonators will form an inverse CT structure. The coupling form between adjacent resonators is magnetic coupling, while the cross coupling form between the first and third transmission line resonators will become magnetic coupling. At this time, the transmission zero introduced by the inverse CT structure will be located at the high frequency of the right side of the passband. A steep drop will be formed between the right side of the passband and the stopband. Therefore, the required cross coupling form can be flexibly selected according to the actual performance requirements to achieve the high selectivity of the filter.

[0043] The characteristics of the bandpass filter in this application were simulated, and the simulation results are as follows: Figure 10 As shown, S 11 S represents the return loss of the filter. 21This represents the insertion loss of the filter. Simulation results show that the filter structure has a return loss better than 20dB in the 33-37 GHz range, a center insertion loss of 0.9dB in the passband, and a narrow transition band between the passband and the low-frequency stopband, exhibiting a high steep drop-off characteristic. Out-of-band rejection is better than 63dB in the 20-31 GHz range. Figure 10 Simulation results show that the bandpass filter of this application has advantages such as low insertion loss, high out-of-band rejection, and good transmission performance, providing a solution for high-performance millimeter-wave bandpass filters.

[0044] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" in the above description indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this disclosure.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0046] In the embodiments of this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0047] In embodiments of this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0049] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A high-selectivity rectangular micro-coaxial bandpass filter with double-CT structure, characterized in that, The shell 101 is internally provided with a first transmission line resonator, a second transmission line resonator, a third transmission line resonator, a fourth transmission line resonator, a fifth transmission line resonator and a sixth transmission line resonator; wherein the first transmission line resonator and the sixth transmission line resonator, the second transmission line resonator and the fifth transmission line resonator, and the third transmission line resonator and the fourth transmission line resonator are symmetrically arranged, and there is magnetic coupling between the first transmission line resonator and the second transmission line resonator, the second transmission line resonator and the third transmission line resonator, the third transmission line resonator and the fourth transmission line resonator, the fourth transmission line resonator and the fifth transmission line resonator, and the fifth transmission line resonator and the sixth transmission line resonator, and there is electric coupling between the first transmission line resonator and the third transmission line resonator, and the fourth transmission line resonator and the sixth transmission line resonator; An input feed structure is used to input an excitation signal on the first transmission line resonator; An output feed structure is used to output a signal on the sixth transmission line resonator. The first transmission line resonator and the sixth transmission line resonator, the second transmission line resonator and the fifth transmission line resonator, and the third transmission line resonator and the fourth transmission line resonator are symmetrically arranged with respect to the center plane of the length direction of the shell 101.

2. The high-selectivity rectangular micro-coaxial band-pass filter with double-CT structure according to claim 1, characterized in that, The first transmission line resonator comprises a first metal inner core 201 connected in an open circuit at one end and a short circuit at the other end with the shell 101; 3. The high-selectivity rectangular micro-coaxial band-pass filter with double-CT structure according to claim 2, characterized in that, The second transmission line resonator comprises a second metal inner core 202 connected in an open circuit at one end and a short circuit at the other end with the first column 102, the second metal inner core 202 is arranged on one side of the first metal inner core 201, and one end of the second metal inner core 202 is connected with the first column 102 to realize a short circuit, the upper and lower ends of the first column 102 are fixedly connected with the inner surface of the shell 101, and the short circuit end portion of the second metal inner core 202 is parallel to the short circuit end portion of the first metal inner core 201; The third transmission line resonator comprises a third metal inner core 203 connected in an open circuit at one end and a short circuit at the other end with the shell 101, the third metal inner core 203 is arranged on the side of the second metal inner core 202 away from the first metal inner core 201, the short circuit end of the third metal inner core 203 is parallel to the short circuit end of the second metal inner core 202, and the open circuit end of the third metal inner core 203 is opposite to the open circuit end of the first metal inner core 201, and there is a preset gap between the open circuit end of the third metal inner core 203 and the open circuit end of the first metal inner core 201; The fourth transmission line resonator comprises a fourth metal inner core 204 connected in an open circuit at one end and a short circuit at the other end with the shell 101, and the fourth metal inner core 204 is symmetric with respect to the center plane of the length direction of the shell 101; The fifth metal inner core 205 is arranged on the side of the fourth metal inner core 204 away from the third metal inner core 203, and the fifth metal inner core 205 is symmetric with respect to the center of the length direction of the shell 101, and one end of the fifth metal inner core 205 is connected with the second column 103 to realize a short circuit, and the upper and lower ends of the second column 103 are fixedly connected with the inner surface of the shell 101; ​ The sixth metal inner core 206 is arranged on the side of the fifth metal inner core 205 away from the fourth metal inner core 204, and one end of the sixth metal inner core 206 is connected to the inner surface of the shell 101 to realize short circuit, and the sixth metal inner core 206 is centrally symmetric to the length direction of the shell 101 relative to the first metal inner core 201.

4. The high-selectivity rectangular micro-coaxial band-pass filter with double-CT structure according to claim 3, characterized in that, The first metal wall 104 is arranged between the third metal inner core 203 and the fourth metal inner core 204, and the upper and lower ends of the first metal wall 104 are fixedly connected to the inner surface of the shell 101, and the first metal wall 104 is symmetric about the length direction of the shell 101; The second metal wall 105 is arranged between the second metal inner core 202 and the fifth metal inner core 205, and the upper and lower ends of the second metal wall 105 are fixedly connected to the inner surface of the shell 101, and the second metal wall 105 is symmetric about the length direction of the shell 101, and one end of the third metal inner core 203 and the fourth metal inner core 204 is short-circuit connected to the middle part of the second metal wall 105.

5. The high-selectivity rectangular micro coaxial bandpass filter with double-CT structure according to claim 4, characterized in that, The input feeding structure comprises: The first extension cavity 106 is arranged on one side of the shell 101, the height of the first extension cavity 106 is equal to the height of the shell 101, and a first stepped groove 301 is formed on the side edge of the first extension cavity 106 away from the first metal inner core 201; The seventh metal inner core 207 is arranged in the first extension cavity 106 and located on the side of the first metal inner core 201 away from the second metal inner core 202, and one end of the seventh metal inner core 207 is fixedly connected to the first metal inner core 201; The eighth metal inner core 208 is arranged in the first stepped groove 301 and located on the side of the seventh metal inner core 207 away from the first metal inner core 201, and is fixedly connected to the seventh metal inner core 207, and a first metal inner core boss 211 is arranged above the eighth metal inner core 208, and the upper surface of the first metal inner core boss 211 is flush with the top surface of the cavity of the first extension cavity 106; The first metal support block 107 is arranged below the end of the eighth metal inner core 208 away from the shell 101, and the first metal support block 107 is fixedly connected to the eighth metal inner core 208; The first stepped block 108 is arranged below the first metal support block 107, and the first stepped block 108 is fixedly connected to the inner wall of the first extension cavity 106.

6. The high-selectivity rectangular micro-coaxial bandpass filter with double-CT structure according to claim 5, wherein, The output feeding structure comprises: The second extension cavity 109 is arranged on the other side of the shell 101, the height of the second extension cavity 109 is equal to the height of the shell 101, and a second stepped groove 302 is formed on the side edge of the second extension cavity 109 away from the sixth metal inner core 206; The ninth metal inner core 209 is arranged in the second extension cavity 109 and located on the side of the sixth metal inner core 206 away from the fifth metal inner core 205, and one end of the ninth metal inner core 209 is fixedly connected to the sixth metal inner core 206; The tenth metal inner core 210 is arranged in the second step groove 302 and is fixedly connected to the ninth metal inner core 209 away from the sixth metal inner core 206. The second metal inner core boss 212 is arranged above the tenth metal inner core 210, and the upper surface of the second metal inner core boss 212 is flush with the cavity top surface of the second epitaxial cavity 109. The second metal support block 110 is arranged below the end of the tenth metal inner core 210 away from the shell 101, and the second metal support block 110 is fixedly connected to the tenth metal inner core 210. The second step block 111 is arranged below the second metal support block 110, and the second step block 111 is fixedly connected to the inner wall of the second epitaxial cavity 109.

7. The high-selectivity rectangular micro-coaxial bandpass filter with double-CT structure according to claim 6, characterized in that, The first metal inner core 201, the second metal inner core 202, the third metal inner core 203, the fourth metal inner core 204, the fifth metal inner core 205, the sixth metal inner core 206, the seventh metal inner core 207 and the ninth metal inner core 209 are provided with the first dielectric support strip 401 for support and fixation.

8. The high-selectivity rectangular micro-coaxial bandpass filter with double-CT structure according to claim 7, characterized in that, The eighth metal inner core 208 and the tenth metal inner core 210 are respectively provided with the second dielectric support strip 402 for electromagnetic isolation and support and fixation, and the second dielectric support strip 402 is arranged above the first metal support block 107 and the second metal support block 110, respectively.

9. The high-selectivity rectangular micro-coaxial bandpass filter with double-CT structure according to claim 8, characterized in that, The surface of the shell 101 is provided with a plurality of periodically arranged release holes 601 for releasing photoresist.

Images