A sub-millimeter dual-band filter transmission line based on rectangular micro-coaxial

Abstract

The application discloses a sub-millimeter dual-passband filter transmission line based on a rectangular micro coaxial line, which comprises a micro coaxial outer conductor, a support strip, an inner conductor and a transition coaxial transition section arranged in the micro coaxial outer conductor, and adopts a micro coaxial inner and outer structure as a whole. The number, geometric shape and electrical characteristics of the micro coaxial inner conductor are designed and optimized to realize the filter effect of miniaturization and wide bandwidth under the sub-millimeter wave level size, overcome the defects of considering size and performance of the existing filter, and be used as a basic transmission line unit to construct various passive networks or directly feed an antenna to realize the filter characteristics from the transmission line level rather than the network level. The sub-millimeter dual-passband filter transmission line has low insertion loss, good out-of-band suppression characteristics and wide passband, and is particularly suitable for the filter application of low-frequency and millimeter wave high-frequency band signals in a wideband communication system.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency and microwave technology, and relates to a miniature low-power filtering transmission line, specifically a sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable, which is particularly suitable for radio frequency terminal systems that require integrated filtering characteristics. Background Technology

[0002] The filtering characteristics in radio frequency systems allow signals in the target frequency band to pass through efficiently while suppressing interference signals in non-target frequency bands, playing an important role in scenarios such as 6G communication, aerospace, and satellite communication.

[0003] Traditional filtering performance is mostly achieved through specific topology designs using cavities or transmission lines, which generally suffer from problems such as large size and design complexity, and it is difficult to maintain a balance between performance and size, including low loss. Therefore, in response to the current demands for higher integration and higher performance in radio frequency applications, there is an urgent need for a new filtering method that combines miniaturization and high-performance filtering characteristics. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a sub-millimeter-level dual-passband filtering transmission line based on a rectangular microcoaxial cable. The overall structure adopts a microcoaxial inner and outer structure. By designing and optimizing the number, geometry, and electrical characteristics of the inner conductor of the microcoaxial cable, a miniaturized and wide-bandwidth filtering effect is achieved at the sub-millimeter wave level.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A sub-millimeter level dual-passband filtered transmission line based on a rectangular micro-coaxial cable includes a micro-coaxial outer conductor and a support strip, an inner conductor, and a transition coaxial section disposed within the micro-coaxial outer conductor.

[0007] The outer wall of the micro-coaxial outer conductor is provided with a release hole;

[0008] The support bar is vertically fixed inside the micro-coaxial outer conductor;

[0009] The inner conductor is provided in two sets, which are adjustablely installed inside the micro-coaxial outer conductor. The two sets of inner conductors inside the micro-coaxial outer conductor are symmetrically arranged and staggered about the y-axis center in the x-axis direction, and both sets of inner conductors are located at the center of the overall structure in the z-axis direction. The two sets of inner conductors are respectively connected to two transition coaxial sections.

[0010] The inner conductor includes a long open-circuit inner conductor, a short-circuit inner conductor, and a short open-circuit inner conductor. The long open-circuit inner conductor, the short open-circuit inner conductor, and the short open-circuit inner conductor are respectively connected to the transition coaxial section. The transition coaxial section is connected to the power supply port. There is a gap between the long open-circuit inner conductor, the short open-circuit inner conductor, and the short open-circuit inner conductor and the micro coaxial outer conductor. The gap is filled with a dielectric. By adjusting the length of the inner conductor, the switching of the open-circuit / short-circuit structure, and the position setting, filtering of different frequency bands can be achieved.

[0011] The long open-circuit inner conductor, the short-circuit inner conductor, the short open-circuit inner conductor, and the transition coaxial section are installed inside the micro coaxial outer conductor by support bars;

[0012] It also includes a grounding short post located at the end of the short-circuit inner conductor, which, when connected to the inner surface of the micro-coaxial outer conductor, grounds the short-circuit inner conductor.

[0013] As a preferred technical solution of the present invention: the release holes are periodically arranged on the outer wall of the micro coaxial outer conductor, and are arranged in pairs about the y-axis and z-axis.

[0014] As a preferred technical solution of the present invention: the power supply port includes a first power supply port and a second power supply port, and two coaxial transition sections are respectively connected to the corresponding first power supply port and second power supply port.

[0015] As a preferred embodiment of the present invention, the medium filling the space between the micro-coaxial outer conductor and the long open-circuit inner conductor, the short-circuit inner conductor, and the short open-circuit inner conductor is preferably air.

[0016] As a preferred embodiment of the present invention, the length and width of the micro-coaxial outer conductor are preferably set to 3.6 mm and 0.73 mm, respectively.

[0017] As a preferred embodiment of the present invention, the distance between the long open-circuit inner conductor and the short-circuit inner conductor is preferably 0.162 mm, and the distance between the short-circuit inner conductor and the short open-circuit inner conductor is preferably 0.122 mm.

[0018] As a preferred embodiment of the present invention, the micro coaxial outer conductor, the long open-circuit inner conductor, the short-circuit inner conductor, the short open-circuit inner conductor, the transition coaxial section, and the grounding short post are all made of conductive metal materials.

[0019] As a preferred embodiment of the present invention, the support strip is made of a material with a relative permittivity of 4.2.

[0020] The core of this invention lies in achieving filtering effects within the transmission line itself through design. This designed and implemented filtered transmission line can serve as a basic unit for network design and antenna feeding filtering characteristic integration, effectively avoiding the need for additional filter design and the resulting increase in system size. Furthermore, the micro-coaxial inner conductor differs from structures like microstrip line coupled lines in its relationship between coupling degree and coupling gap, enabling miniaturization and integration of broadband, dual-band filtering performance at sub-millimeter scales, with performance far superior to traditional structures. Key design features of this structure include the performance design of the inner conductor coupled line and the miniaturization and precise adjustment of both the outer and inner conductors.

[0021] In this invention, at least two sets of inner conductors and coaxial transition sections are provided, and the inner conductors are adjustable. By adjusting the length of the inner conductors, the switching of open / short circuit structures, and their position settings, filtering functions for different frequency bands are achieved. The precise design of the inner conductor configuration is a key factor in realizing dual-passband filtering, ensuring effective control over the signal bandwidth and frequency band distribution.

[0022] This invention innovatively designs a protective grounding short post and a coaxial transition section. Through optimized electromagnetic field distribution and signal transmission path design, it ensures that the filter can work stably in multiple frequency bands, improving its performance and reliability.

[0023] This invention achieves miniaturization through a micro-coaxial structure, while maintaining a wide bandwidth, multiple frequency bands, and low insertion loss solution that meets filtering requirements. It is particularly suitable for filtering applications of low-frequency and millimeter-wave high-frequency signals in broadband communication systems.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. Design innovations at the transmission line level:

[0026] This invention achieves filtering effects within a single transmission line through design. The designed and implemented filtered transmission line can be used as a basic unit for network construction and for integrating filtering characteristics in antenna feeding. This avoids the need for additional filter design, thus reducing system size.

[0027] 2. Dual-passband filtering effect:

[0028] The filter transmission line of this invention achieves good filtering performance in both the 6GHz-15GHz and 21GHz-26GHz passbands, with low reflection loss (S) of the filter. 11Most of the signal isolation remains below -20dB, resulting in minimal reflected signals. Simultaneously, it effectively suppresses signals from other frequency bands, achieving out-of-band isolation exceeding -40dB, effectively suppressing out-of-band interference and ensuring system stability and signal clarity. This dual-passband filter design is suitable for multi-band and uplink / downlink communication systems, enabling effective separation of multiple frequency bands and links.

[0029] 3. Wide bandwidth performance:

[0030] This invention achieves relative bandwidths of 85.7% and 21.3% in two passbands, respectively. The first passband features ultra-wide bandwidth, while the second passband provides conventional, practical bandwidth, adaptable to scenarios with varying bandwidth requirements.

[0031] 4. Miniaturized design:

[0032] This invention employs a micro-coaxial structure, integrating filtering characteristics within a single transmission line. The filter size of this invention is significantly reduced compared to traditional filters, making it ideal for applications in space-constrained environments and meeting the requirements for high integration. Attached Figure Description

[0033] Figure 1 This is a top view of a filtered transmission line;

[0034] Figure 2 This is a top perspective view of a filtered transmission line;

[0035] Figure 3 This is a side perspective view of the filtered transmission line;

[0036] Figure 4 This is a graph of the filter's S-parameters.

[0037] List of reference numerals in the attached diagram:

[0038] 1. Micro coaxial outer conductor; 2. Support bar; 3. Release hole; 4. Long open circuit inner conductor; 5. Short circuit inner conductor; 6. Short open circuit inner conductor; 7. Adapter coaxial transition section; 8. Grounding short post; 9. First feed port; 10. Second feed port. Detailed Implementation

[0039] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] like Figure 1-3 As shown, the present invention proposes a sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial line, including a micro-coaxial outer conductor 1, a support strip 2, an inner conductor, and a transition coaxial section 7 disposed within the micro-coaxial outer conductor 1.

[0041] The outer wall of the micro-coaxial outer conductor 1 is provided with a release hole 3;

[0042] The support bar 2 is vertically fixed inside the micro-coaxial outer conductor 1;

[0043] The inner conductor is provided in two sets, which are adjustablely installed inside the micro-coaxial outer conductor 1. The two sets of inner conductors inside the micro-coaxial outer conductor 1 are symmetrically arranged and staggered about the y-axis center in the x-axis direction, and both sets of inner conductors are located at the center of the overall structure in the z-axis direction. The two sets of inner conductors are respectively connected to two transition coaxial sections 7.

[0044] The inner conductor includes a long open-circuit inner conductor 4, a short-circuit inner conductor 5, and a short open-circuit inner conductor 6. The long open-circuit inner conductor 4, the short-circuit inner conductor 5, and the short open-circuit inner conductor 6 are respectively connected to the transition coaxial section 7. The transition coaxial section 7 is connected to the power supply port. There is a gap between the long open-circuit inner conductor 4, the short-circuit inner conductor 5, and the short open-circuit inner conductor 6 and the micro coaxial outer conductor 1. The gap is filled with a dielectric. By adjusting the length of the inner conductor, the switching of the open-circuit / short-circuit structure, and the position setting, filtering of different frequency bands can be achieved.

[0045] The long open-circuit inner conductor 4, the short-circuit inner conductor 5, the short open-circuit inner conductor 6, and the transition coaxial section 7 are installed inside the micro coaxial outer conductor 1 by the support bar 2;

[0046] It also includes a grounding short post 8, which is located at the end of the short-circuit inner conductor 5. When it is connected to the inner surface of the micro coaxial outer conductor 1, the short-circuit inner conductor 5 is grounded and short-circuited.

[0047] This invention employs a micro-coaxial internal and external structure. By designing and optimizing the number, geometry, and electrical characteristics of the micro-coaxial internal conductor, it achieves miniaturized and wide-bandwidth filtering at sub-millimeter-wave scale, overcoming the limitations of existing filters in balancing size and performance. Furthermore, it can serve as a basic transmission line unit for constructing various passive networks or directly feeding antennas, achieving filtering characteristics at the transmission line level rather than the network level. This filtered transmission line features low insertion loss, good out-of-band rejection, and a wide passband, making it particularly suitable for filtering low-frequency and millimeter-wave high-frequency signals in broadband communication systems.

[0048] For example, the release holes 3 are periodically disposed on the outer wall of the micro coaxial outer conductor 1 and are arranged in pairs about the y-axis and z-axis for releasing photoresist in the final stage of processing.

[0049] For example, the power supply port includes a first power supply port 9 and a second power supply port 10, and two coaxial transition sections 7 are respectively connected to the corresponding first power supply port 9 and second power supply port 10. The first power supply port 9 and the second power supply port 10 are used to provide power support.

[0050] For example, the medium filling the space between the micro coaxial outer conductor 1 and the long open-circuit inner conductor 4, short-circuit inner conductor 5, and short open-circuit inner conductor 6 is preferably air, but other low-loss dielectric materials can also be used.

[0051] For example, the length and width of the micro coaxial outer conductor 1 are preferably set to 3.6 mm and 0.73 mm, respectively. During implementation, different specifications of micro coaxial outer conductor 1 can be selected to adapt to different installation environments.

[0052] For example, the distance between the long open-circuit inner conductor 4 and the short-circuit inner conductor 5 is preferably 0.162 mm, and the distance between the short-circuit inner conductor 5 and the short open-circuit inner conductor 6 is preferably 0.122 mm. These distances can be adjusted during implementation.

[0053] For example, the micro coaxial outer conductor 1, the long open-circuit inner conductor 4, the short-circuit inner conductor 5, the short open-circuit inner conductor 6, the transition coaxial section 7, and the grounding short post 8 are all made of conductive metal materials, preferably copper, but other metal materials with good conductivity can also be used.

[0054] For example, the support bar 2 is made of a material with a relative permittivity of 4.2. The support bar 2 is placed at the center of the z-axis of the overall structure and is directly connected to the micro coaxial outer conductor 1 in the x-axis direction. It is used to support the inner conductor and the transition coaxial section 7 inside the micro coaxial outer conductor 1.

[0055] The micro-coaxial structure in this invention is configured as a five-layer structure, with each layer having a uniform height of 0.1 mm.

[0056] like Figure 4 As shown, the filtered transmission line of this invention achieves excellent filtering performance in both the 6GHz-15GHz and 21GHz-26GHz passbands. The filter's reflection loss is mostly kept below -20dB, resulting in minimal reflected signals. Simultaneously, it effectively suppresses signals from other frequency bands, with out-of-band isolation exceeding -40dB, effectively suppressing out-of-band interference and ensuring system stability and signal clarity.

[0057] The core of this invention lies in achieving filtering effects within the transmission line itself through design. This designed and implemented filtered transmission line can serve as a basic unit for network design and antenna feeding filtering characteristic integration, effectively avoiding the need for additional filter design and the resulting increase in system size. Furthermore, the micro-coaxial inner conductor differs from structures like microstrip line coupled lines in its relationship between coupling degree and coupling gap, enabling miniaturization and integration of broadband, dual-band filtering performance at sub-millimeter scales, with performance far superior to traditional structures. Key design features of this structure include the performance design of the inner conductor coupled line and the miniaturization and precise adjustment of both the outer and inner conductors.

[0058] In this invention, at least two sets of inner conductors and coaxial transition sections 7 are provided, and the inner conductors are adjustable. By adjusting the length of the inner conductors, the switching of open / short circuit structures, and their position settings, filtering functions for different frequency bands are achieved. The precise design of the inner conductor configuration is a key factor in realizing dual-passband filtering, ensuring effective control over the signal bandwidth and frequency band distribution.

[0059] This invention innovatively designs a protective grounding short post 8 and a coaxial transition section 7. Through optimized electromagnetic field distribution and signal transmission path design, it ensures that the filter can work stably in multiple frequency bands, thereby improving its performance and reliability.

[0060] This invention achieves miniaturization through a micro-coaxial structure, while maintaining a wide bandwidth, multiple frequency bands, and low insertion loss solution that meets filtering requirements. It is particularly suitable for filtering applications of low-frequency and millimeter-wave high-frequency signals in broadband communication systems.

[0061] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable, characterized in that: It includes a micro coaxial outer conductor (1), a support strip (2) disposed within the micro coaxial outer conductor (1), an inner conductor, and a transition coaxial section (7); The outer wall of the micro coaxial outer conductor (1) is provided with a release hole (3); The support bar (2) is vertically fixed inside the micro coaxial outer conductor (1); The inner conductor is provided in two sets, which are adjustablely installed inside the micro-coaxial outer conductor (1). The two sets of inner conductors inside the micro-coaxial outer conductor (1) are symmetrical about the center of the y-axis in the x-axis direction and are staggered. In the z-axis direction, both sets of inner conductors are located at the center of the overall structure. The two sets of inner conductors are respectively connected to two transition coaxial sections (7). The inner conductor includes a long open-circuit inner conductor (4), a short-circuit inner conductor (5), and a short open-circuit inner conductor (6). The long open-circuit inner conductor (4), the short-circuit inner conductor (5), and the short open-circuit inner conductor (6) are respectively connected to the transition coaxial section (7). The transition coaxial section (7) is connected to the power supply port. There is a gap between the long open-circuit inner conductor (4), the short-circuit inner conductor (5), and the short open-circuit inner conductor (6) and the micro coaxial outer conductor (1). The gap is filled with a dielectric. By adjusting the length of the inner conductor, the switching of the open-circuit / short-circuit structure, and the position setting, filtering of different frequency bands can be achieved. The long open-circuit inner conductor (4), short-circuit inner conductor (5), short open-circuit inner conductor (6) and the transition coaxial section (7) are installed inside the micro coaxial outer conductor (1) by the support bar (2); It also includes a grounding short post (8), which is located at the end of the short-circuit inner conductor (5). When it is connected to the inner surface of the micro-coaxial outer conductor (1), the short-circuit inner conductor (5) is grounded.

2. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The release holes (3) are periodically arranged on the outer wall of the micro coaxial outer conductor (1) and are arranged in pairs about the y-axis and z-axis.

3. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The power supply ports include a first power supply port (9) and a second power supply port (10), and two coaxial transition sections (7) are respectively connected to the corresponding first power supply port (9) and second power supply port (10).

4. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The medium filling the space between the micro coaxial outer conductor (1) and the long open-circuit inner conductor (4), the short-circuit inner conductor (5), and the short open-circuit inner conductor (6) is preferably air.

5. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The length and width of the micro-coaxial outer conductor (1) are preferably set to 3.6 mm and 0.73 mm, respectively.

6. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The distance between the long open-circuit inner conductor (4) and the short-circuit inner conductor (5) is preferably 0.162 mm, and the distance between the short-circuit inner conductor (5) and the short open-circuit inner conductor (6) is preferably 0.122 mm.

7. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The micro coaxial outer conductor (1), long open-circuit inner conductor (4), short-circuit inner conductor (5), short open-circuit inner conductor (6), transition coaxial section (7), and grounding short post (8) are all made of conductive metal materials.

8. The sub-millimeter level dual-passband filtering transmission line based on a rectangular micro-coaxial cable according to claim 1, characterized in that: The support bar (2) is made of a material with a relative permittivity of 4.2.

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