Miniaturized broadband slow wave filtering coupler based on micro coaxial transmission line

Abstract

The invention discloses a miniature broadband slow wave filtering coupler based on a micro coaxial transmission line, which is designed by adopting a micro coaxial transmission line structure and has the advantages of low loss, low dispersion, miniaturization and the like. Through the micro coaxial slow wave transmission line and the periodically loaded slow wave structure, the electrical length required by the coupler is significantly reduced, so that the planar size of the coupler is more compact, and miniaturization is realized; the adopted micro-coaxial three-wire coupling transmission line is composed of three metal inner conductors which are closely close but not in contact, an input port and an isolation port of the micro-coaxial slow-wave filtering coupler are connected, the isolation degree of the isolation port can be further improved, reflection is prevented from interfering a pre-stage circuit, and the stability and reliability of the whole system are remarkably improved. Two out-of-band zero points are introduced through the miter-joint micro coaxial filtering branch, so that the out-of-band rejection capability and the frequency selectivity of the coupler are improved; the antenna has the advantages of wide bandwidth, miniaturization, high frequency selectivity, high isolation and the like, and is suitable for 5G and high-frequency communication systems.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically a miniaturized broadband slow wave filter coupler based on a micro coaxial transmission line. Background Technology

[0002] With the rapid development of wireless communication technology, especially in 5G millimeter-wave communication systems, couplers are widely used due to their function of providing power distribution and phase difference. As millimeter-wave radio frequency technology advances rapidly, couplers face demands for miniaturization, high performance, and functional integration. However, existing couplers generally suffer from problems such as large size, narrow bandwidth, and low integration.

[0003] Traditional branch-line directional couplers utilize four quarter-wavelength transmission lines to form a loop, enabling different power distribution ratios and 90° phase differences at the center frequency. However, branch-line couplers are limited by narrow bandwidth, poor out-of-band suppression, and poor out-of-band isolation. Couplers based on resonator structures, by controlling the coupling mechanism between resonators, achieve both coupler functionality and frequency-selective filtering characteristics. However, resonator-based couplers are typically large, hindering the miniaturization of the overall system. Therefore, a novel coupler solution that combines miniaturization, high performance, and functional integration is urgently needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line. This miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line integrates filtering and coupling functions into one, achieving a high degree of structural integration. It effectively replaces the cascading of filters and couplers in traditional systems, significantly reduces planar size and insertion loss, and solves the problem of difficulty in combining coupler miniaturization and multi-functional integration in the prior art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line includes a micro-coaxial outer conductor base, a micro-coaxial slow-wave transmission line, a micro-coaxial three-wire coupling transmission line, a micro-coaxial filter stub, a first micro-coaxial transmission line, a second micro-coaxial transmission line, and an input port, an isolation port, a through port, and a coupling port. The microcoaxial outer conductor base includes: a microcoaxial outer conductor left arm and a microcoaxial outer conductor right arm, a microcoaxial outer conductor upper arm and a microcoaxial outer conductor lower arm, a microcoaxial outer conductor longitudinal middle arm, and a microcoaxial outer conductor left oblique arm and a microcoaxial outer conductor right oblique arm; The left and right arms of the microcoaxial outer conductor are arranged relatively parallel in the longitudinal direction; the upper and lower arms of the microcoaxial outer conductor are arranged relatively parallel in the transverse direction; the left, upper, right, and lower arms of the microcoaxial outer conductor are connected in sequence to form a rectangle; one end of the longitudinal middle arm of the microcoaxial outer conductor is connected to the midpoint of the upper arm, and the other end is connected to the midpoint of the lower arm. One end of the left oblique arm of the microcoaxial external conductor is connected to the midpoint of the upper arm of the microcoaxial external conductor, and the other end is a free end; one end of the right oblique arm of the microcoaxial external conductor is connected to the midpoint of the lower arm of the microcoaxial external conductor, and the other end is a free end; the left oblique arm and the right oblique arm of the microcoaxial external conductor are symmetrical about the center of the longitudinal middle arm of the microcoaxial external conductor. The micro-coaxial outer conductor base has an intermediate cavity at the centerline position along its length direction; The input port and the through port are respectively located at the left and right corners of the upper arm of the micro-coaxial outer conductor, and the isolation port and the coupling port are respectively located at the left and right corners of the lower arm of the micro-coaxial outer conductor. Two sets of microcoaxial slow wave transmission lines are placed laterally on the upper arm of the microcoaxial outer conductor and are symmetrically connected about the left and right sides of the first microcoaxial transmission line, and their two ends are connected to the input port and the through port, respectively. Two sets of microcoaxial slow wave transmission lines are placed laterally on the lower arm of the microcoaxial outer conductor and are symmetrically connected about the left and right sides of the first microcoaxial transmission line, and their two ends are respectively connected to the isolation port and the coupling port; The microcoaxial three-wire coupled transmission line is placed longitudinally on the left arm of the outer conductor of the microcoaxial line, with one end connected to the input port and the other end connected to the isolation port; The second microcoaxial transmission line is placed longitudinally on the right arm of the outer conductor of the microcoaxial line, with one end connected to the through port and the other end connected to the coupling port. The first microcoaxial transmission line is placed longitudinally in the longitudinal middle arm of the microcoaxial outer conductor. One end of the line is connected to the connection point of the two sets of microcoaxial slow wave transmission lines in the upper arm of the microcoaxial outer conductor, and the other end is connected to the connection point of the two sets of microcoaxial slow wave transmission lines in the lower arm of the microcoaxial outer conductor. Two sets of microcoaxial filter stubs are obliquely placed on the left and right oblique arms of the microcoaxial outer conductor, respectively. One end of the coaxial filter stub placed on the left oblique arm of the microcoaxial outer conductor is connected to the connection point of the two sets of microcoaxial slow wave transmission lines on the upper arm of the microcoaxial outer conductor, and the other end is a free end. One end of the coaxial filter stub placed on the right oblique arm of the microcoaxial outer conductor is connected to the connection point of the two sets of microcoaxial slow wave transmission lines on the lower arm of the microcoaxial outer conductor, and the other end is a free end. The two sets of microcoaxial filter stubs are obliquely connected to both sides of the microcoaxial transmission lines and are symmetrical about the center of the first microcoaxial transmission line.

[0006] Furthermore, the micro-coaxial outer conductor base is made of metal, and its intermediate cavity is filled with air.

[0007] Further, the height dimension and the width dimension of the micro - coaxial outer conductor base are set to be the same. The width of the inner wall of the middle cavity opened therein is 0.53 mm, and the height is 0.3 mm; the heights of the micro - coaxial slow - wave transmission line, the micro - coaxial three - line coupled transmission line, the first micro - coaxial transmission line, the second micro - coaxial transmission line, and the micro - coaxial filter stub are all set to 0.1 mm.

[0008] Further, the first micro - coaxial transmission line includes a linear first micro - coaxial inner conductor. First support bars are uniformly arranged on both sides of the first micro - coaxial inner conductor. The first micro - coaxial inner conductor is supported at the center of the corresponding middle cavity through the first support bars. The second micro - coaxial transmission line includes a linear second micro - coaxial inner conductor. Second support bars are uniformly arranged on both sides of the second micro - coaxial inner conductor. The second micro - coaxial inner conductor is supported at the center of the corresponding middle cavity through the second support bars.

[0009] Further, the micro - coaxial slow - wave transmission line is composed of a transverse high - impedance transmission line, a longitudinal slow - wave structure, and a transverse slow - wave structure. The "mouth" - shaped slow - wave structure formed by enclosing the relatively arranged longitudinal slow - wave structures and the relatively arranged transverse slow - wave structures. Multiple "mouth" - shaped slow - wave structures are arranged periodically along the transverse high - impedance transmission line. Slow - wave support bars are arranged on both sides of the micro - coaxial slow - wave transmission line. The micro - coaxial slow - wave transmission line is supported at the center of the corresponding middle cavity through the slow - wave support bars.

[0010] Further, the micro - coaxial three - line coupled transmission line is composed of an outer - side longitudinal transmission line, a middle - side longitudinal transmission line, an inner - side longitudinal transmission line, and a grounding post. One end of the outer - side longitudinal transmission line is connected to the isolation port, and the other end is connected to the corresponding micro - coaxial outer conductor base through the grounding post; one end of the inner - side longitudinal transmission line is connected to the input port, and the other end is also connected to the corresponding micro - coaxial outer conductor base through the grounding post; the middle - side longitudinal transmission line is located between the outer - side longitudinal transmission line and the inner - side longitudinal transmission line. One end of it is connected to the input port, and the other end is connected to the isolation port. Three - line coupled support bars are arranged on both sides of the micro - coaxial three - line coupled transmission line. The micro - coaxial three - line coupled transmission line is supported at the center of the corresponding middle cavity through the three - line coupled support bars.

[0011] Further, the micro - coaxial filter stub is formed by connecting a bent transmission line and a bent coupled line with an open end at the end, and is integrally in a continuous S - shaped bend; filter support bars are arranged on both sides of the micro - coaxial filter stub. The micro - coaxial filter stub is supported at the center of the corresponding middle cavity through the filter support bars.

[0012] Furthermore, the first and second microcoaxial inner conductors are made of metal, and the first and second support strips are made of SU-8 photoresist; the microcoaxial slow-wave transmission line is made of metal, and the slow-wave support strip is made of SU-8 photoresist; the microcoaxial three-wire coupled transmission line is made of metal, and the three-wire coupled support strip is made of SU-8 photoresist; the microcoaxial filter stub is made of metal, and the filter support strip is made of SU-8 photoresist.

[0013] Furthermore, the length and width of the first micro-coaxial inner conductor are 3 mm and 0.06 mm, respectively; the length and width of the second micro-coaxial inner conductor are 3 mm and 0.03 mm, respectively. The inner conductor length and width of the transverse high-impedance transmission line are 2 mm and 0.05 mm, respectively; the inner conductor length and width of the longitudinal slow-wave structure are 0.1 mm and 0.4 mm, respectively; and the inner conductor length and width of the transverse slow-wave structure are 0.1 mm and 0.05 mm, respectively.

[0014] Furthermore, the length and width of the inner conductor of the middle longitudinal transmission line are 3mm and 0.03mm, respectively; the length and width of the inner conductors of the outer and inner longitudinal transmission lines are 2.8mm and 0.08mm, respectively; the distance between the inner conductors of the outer and middle longitudinal transmission lines is 0.02mm, and the distance between the inner conductors of the inner and middle longitudinal transmission lines is 0.02mm; the length, width, and height of the grounding post are 0.03mm, 0.08mm, and 0.1mm, respectively. The inner conductor length and width of the bent transmission line are 3mm and 0.12mm respectively, and the inner conductor length and width of the bent coupling line with open end are 3mm and 0.04mm respectively. The spacing between the inner conductors of the bent coupling line is 0.02mm.

[0015] The present invention has the following beneficial effects: 1. This invention integrates filtering and coupling functions into one, achieving a high degree of structural integration. It effectively replaces the cascading of filters and couplers in traditional systems, significantly reducing planar size and insertion loss.

[0016] 2. This application provides a miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line. Designed using a micro-coaxial transmission line structure, it offers advantages such as low loss, low dispersion, and miniaturization. The periodically loaded slow-wave structure of the micro-coaxial slow-wave transmission line significantly reduces the required electrical length of the coupler, resulting in a more compact planar size and miniaturization. The three-wire micro-coaxial coupling transmission line consists of three closely spaced but non-contacting metal inner conductors connecting the input port and isolation port of the micro-coaxial slow-wave filter coupler. This further improves the isolation of the isolation port, preventing reflection interference to the preceding circuitry and significantly enhancing the overall system stability and reliability. Two out-of-band zeros are introduced by slanting the micro-coaxial filter stub, improving the coupler's out-of-band rejection capability and frequency selectivity. This application combines advantages such as wide bandwidth, miniaturization, high frequency selectivity, and high isolation, making it suitable for 5G and high-frequency communication systems. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the miniaturized broadband slow wave filter coupler based on micro coaxial transmission lines provided by the present invention.

[0018] Figure 2 The top view of the miniaturized broadband slow wave filter coupler based on micro coaxial transmission lines provided by the present invention.

[0019] Figure 3 for Figure 1 Schematic diagram of the first micro coaxial transmission line structure.

[0020] Figure 4 for Figure 1 Schematic diagram of the second micro-coaxial transmission line structure.

[0021] Figure 5(a) shows the S-parameter results of each input and output port when the input port of the miniaturized broadband slow wave filter coupler based on micro coaxial transmission line provided by the present invention is excited.

[0022] Figure 5(b) shows the S-parameter results of each input and output port when the isolation port of the miniaturized broadband slow wave filter coupler based on micro coaxial transmission line provided by the present invention is excited.

[0023] Figure 6 The phase difference results between the output ports of the miniaturized broadband slow wave filter coupler based on micro coaxial transmission line provided by the present invention.

[0024] Among them are: 100. Microcoaxial slow-wave transmission line; 120. Lateral high-impedance transmission line; 110. Longitudinal slow-wave structure; 130. Lateral slow-wave structure; 200. Microcoaxial three-wire coupled transmission line; 220. Outer longitudinal transmission line; 210. Middle longitudinal transmission line; 240. Inner longitudinal transmission line; 230. Grounding post; 300. First microcoaxial transmission line; 310. First microcoaxial inner conductor; 320. First support strip; 400. 410. Second microcoaxial transmission line; 420. Second microcoaxial inner conductor; 500. Second support bar; 510. Microcoaxial filter stub; 520. Bent transmission line; 610. Bent coupling line; 620. Input port; 710. Isolation port; 720. Straight-through port; 720. Coupling port; 800. Microcoaxial transmission line; 810. Microcoaxial inner conductor; 830. Microcoaxial outer conductor; 840. Intermediate cavity; 820. Support bar. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0026] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., 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 this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0027] like Figure 1 As shown, a miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line includes a micro-coaxial outer conductor base 800, a micro-coaxial slow-wave transmission line 100, a micro-coaxial three-wire coupling transmission line 200, a micro-coaxial filter stub 500, a first micro-coaxial transmission line 300, a second micro-coaxial transmission line 400, and an input port 610, an isolation port 620, a through port 710, and a coupling port 720.

[0028] The microcoaxial outer conductor base includes: a microcoaxial outer conductor left arm and a microcoaxial outer conductor right arm, a microcoaxial outer conductor upper arm and a microcoaxial outer conductor lower arm, a microcoaxial outer conductor longitudinal middle arm, and a microcoaxial outer conductor left oblique arm and a microcoaxial outer conductor right oblique arm; like Figure 1-2As shown, the left and right arms of the micro-coaxial outer conductor are arranged relatively parallel in the longitudinal direction; the upper and lower arms of the micro-coaxial outer conductor are arranged relatively parallel in the transverse direction; the left, upper, right, and lower arms of the micro-coaxial outer conductor are connected in sequence to form a rectangle; one end of the longitudinal middle arm of the micro-coaxial outer conductor is connected to the midpoint of the upper arm, and the other end is connected to the midpoint of the lower arm. One end of the left oblique arm of the microcoaxial external conductor is connected to the midpoint of the upper arm of the microcoaxial external conductor, and the other end is a free end; one end of the right oblique arm of the microcoaxial external conductor is connected to the midpoint of the lower arm of the microcoaxial external conductor, and the other end is a free end; the left oblique arm and the right oblique arm of the microcoaxial external conductor are symmetrical about the center of the longitudinal middle arm of the microcoaxial external conductor. The microcoaxial outer conductor base has an intermediate cavity at its centerline along its length direction. Specifically: the left arm, right arm, upper arm, and lower arm of the microcoaxial outer conductor have intermediate cavities at their respective centerlines along their length directions; the longitudinal middle arm of the microcoaxial outer conductor has an intermediate cavity at its centerline along its length direction; and the left and right oblique arms of the microcoaxial outer conductor have intermediate cavities at their centerlines along their length directions.

[0029] Input port 610 and through port 710 are respectively located at the left and right corners of the upper arm of the micro coaxial outer conductor, and isolation port 620 and coupling port 720 are respectively located at the left and right corners of the lower arm of the micro coaxial outer conductor. Furthermore, the micro-coaxial outer conductor base is made of metal, and its intermediate cavity is filled with air.

[0030] Two sets of microcoaxial slow wave transmission lines 100 are placed laterally on the upper arm of the outer conductor of the microcoaxial line and about the first microcoaxial transmission line 300. The two ends are symmetrically connected and connected to the input port 610 and the through port 710, respectively. Two sets of microcoaxial slow wave transmission lines 100 are placed laterally on the lower arm of the microcoaxial outer conductor and are symmetrically connected about the left and right sides of the first microcoaxial transmission line 300, and their two ends are respectively connected to the isolation port 620 and the coupling port 720; The micro-coaxial three-wire coupled transmission line 200 is placed longitudinally on the left arm of the outer conductor of the micro-coaxial line, with one end connected to the input port 610 and the other end connected to the isolation port 620; The second microcoaxial transmission line 400 is placed longitudinally on the right arm of the outer conductor of the microcoaxial line, with one end connected to the through port 710 and the other end connected to the coupling port 720. The first microcoaxial transmission line 300 is placed longitudinally in the longitudinal middle arm of the microcoaxial outer conductor. One end of it is connected to the connection point of the two sets of microcoaxial slow wave transmission lines 100 in the upper arm of the microcoaxial outer conductor, and the other end is connected to the connection point of the two sets of microcoaxial slow wave transmission lines 100 in the lower arm of the microcoaxial outer conductor. Two sets of microcoaxial filter stubs 500 are obliquely placed on the left and right oblique arms of the microcoaxial outer conductor, respectively. One end of the coaxial filter stub 500 placed on the left oblique arm of the microcoaxial outer conductor is connected to the connection point of the two sets of microcoaxial slow wave transmission lines 100 on the upper arm of the microcoaxial outer conductor, and the other end is a free end. One end of the coaxial filter stub 500 placed on the right oblique arm of the microcoaxial outer conductor is connected to the connection point of the two sets of microcoaxial slow wave transmission lines 100 on the lower arm of the microcoaxial outer conductor, and the other end is a free end. The two sets of microcoaxial filter stubs 500 are obliquely connected to both sides of the microcoaxial transmission line 800 and are symmetrical about the center of the first microcoaxial transmission line 300.

[0031] This invention integrates filtering and coupling functions into one unit, achieving a high degree of structural integration. It effectively replaces the cascading of filters and couplers in traditional systems, significantly reducing planar size and insertion loss.

[0032] In one embodiment, the height and width of the microcoaxial outer conductor base are set to be the same, and the width of the inner wall of the intermediate cavity is 0.53 mm and the height is 0.3 mm; the height of the microcoaxial slow wave transmission line 100, the microcoaxial three-wire coupled transmission line 200, the first microcoaxial transmission line 300, the second microcoaxial transmission line 400, and the microcoaxial filter stub 500 are all set to 0.1 mm.

[0033] The first micro-coaxial transmission line 300 includes a linear first micro-coaxial inner conductor 310, with first support strips 320 evenly arranged on both sides of the first micro-coaxial inner conductor 310, and the first micro-coaxial inner conductor 310 is supported by the first support strips 320 at the center of its corresponding intermediate cavity. The second micro-coaxial transmission line 400 includes a linear second micro-coaxial inner conductor 410, with second support bars 420 evenly arranged on both sides of the second micro-coaxial inner conductor 410, and the second micro-coaxial inner conductor 410 is supported by the second support bars 420 at the center of its corresponding intermediate cavity. Furthermore, the first microcoaxial inner conductor 310 and the second microcoaxial inner conductor 410 are made of metal, and the first support strip 320 and the second support strip 420 are made of SU-8 photoresist. The first micro-coaxial transmission line 300 and the second micro-coaxial transmission line 400 of the present invention are both designed with a micro-coaxial transmission line structure, which has advantages such as low loss, low dispersion and miniaturization.

[0034] In one embodiment, further, the length and width of the first micro coaxial inner conductor are 3 mm and 0.06 mm respectively; the length and width of the second micro coaxial inner conductor are 3 mm and 0.03 mm respectively.

[0035] Further, the micro coaxial slow wave transmission line 100 is composed of a transverse high impedance transmission line 120, a longitudinal slow wave structure 110, and a transverse slow wave structure 130.

[0036] Further, the "mouth" - shaped slow wave structure formed by enclosing the relatively arranged longitudinal slow wave structures 110 and the relatively arranged transverse slow wave structures 130, and multiple "mouth" - shaped slow wave structures are arranged periodically along the transverse high impedance transmission line 120; Slow wave support bars are arranged on both sides of the micro coaxial slow wave transmission line 100, and the micro coaxial slow wave transmission line 100 is supported at the center of its corresponding intermediate cavity through the slow wave support bars; Further, the material of the micro coaxial slow wave transmission line 100 is metal, and the material of the slow wave support bars is SU - 8 photoresist; In one embodiment, further, 4 "mouth" - shaped slow wave structures are arranged periodically along the transverse high impedance transmission line 120 with a spacing of 0.4 mm.

[0037] Through the periodically loaded slow wave structure of the micro coaxial slow wave transmission line, the present invention significantly reduces the electrical length required for the coupler, makes the planar size of the coupler more compact, and realizes miniaturization.

[0038] In one embodiment, further, the length and width of the inner conductor of the transverse high impedance transmission line 120 are 2 mm and 0.05 mm respectively; the length and width of the inner conductor of the longitudinal slow wave structure 110 are 0.1 mm and 0.4 mm respectively; the length and width of the inner conductor of the transverse slow wave structure 120 are 0.1 mm and 0.05 mm respectively.

[0039] Further, the micro coaxial three - line coupling transmission line 200 is composed of an outer longitudinal transmission line 220, an intermediate longitudinal transmission line 210, an inner longitudinal transmission line 240, and a ground post 230.

[0040] Further, one end of the outer longitudinal transmission line 220 is connected to the isolation port 620, and the other end is connected to the corresponding micro coaxial outer conductor base through the ground post 230; one end of the inner longitudinal transmission line 240 is connected to the input port 610, and the other end is also connected to the corresponding micro coaxial outer conductor base through the ground post 230; the intermediate longitudinal transmission line 210 is located between the outer longitudinal transmission line 220 and the inner longitudinal transmission line 240, and one end of it is connected to the input port 610 and the other end is connected to the isolation port 620.

[0041] The micro coaxial three-wire coupled transmission line 200 has three-wire coupled support bars arranged on both sides, and the micro coaxial three-wire coupled transmission line 200 is supported by the three-wire coupled support bars at the center of its corresponding intermediate cavity. Furthermore, the micro-coaxial three-wire coupled transmission line 200 is made of metal, and the three-wire coupled support strip is made of SU-8 photoresist. The micro-coaxial three-wire coupled transmission line used in this invention consists of three closely spaced but non-contacting metal inner conductors that connect the input port and isolation port of the micro-coaxial slow wave filter coupler. This can further improve the isolation of the isolation port, prevent reflection interference to the front-end circuit, and significantly improve the stability and reliability of the overall system.

[0042] In one embodiment, the inner conductor of the middle longitudinal transmission line 210 has a length of 3 mm and a width of 0.03 mm; the inner conductors of the outer longitudinal transmission line 220 and the inner longitudinal transmission line 240 have lengths of 2.8 mm and widths of 0.08 mm; the distance between the inner conductor of the outer longitudinal transmission line 220 and the inner conductor of the middle longitudinal transmission line 210 is 0.02 mm, and the distance between the inner conductor of the inner longitudinal transmission line 240 and the inner conductor of the middle longitudinal transmission line 210 is 0.02 mm; the length, width, and height of the grounding post 230 are 0.03 mm, 0.08 mm, and 0.1 mm, respectively.

[0043] Furthermore, the micro-coaxial filter stub 500 is constructed by connecting a bent transmission line 510 with a bent coupling line 520 that is open at the end, forming a continuous S-shaped bend. By introducing two out-of-band zeros through the oblique connection of the micro-coaxial filter stub, the out-of-band rejection capability and frequency selectivity of the coupler are improved.

[0044] The micro coaxial filter stub 500 is supported by filter support bars on both sides, and the micro coaxial filter stub 500 is supported by the filter support bars at the center of its corresponding intermediate cavity. Furthermore, the micro-coaxial filter stub 500 is made of metal, and the filter support strip is made of SU-8 photoresist; In one embodiment, the inner conductor of the bent transmission line 510 has a length and width of 3 mm and 0.12 mm, respectively, and the inner conductor of the bent coupling line 520 with open end has a length and width of 3 mm and 0.04 mm, respectively. The spacing between the inner conductors of the bent coupling line 520 is 0.02 mm.

[0045] As shown in Figure 5(a), the curves in the figure represent the S-parameters of each input and output port when the input port 610 is energized; as shown in Figure 5(b), the curves in the figure represent the S-parameters of each input and output port when the isolation port 620 is energized. Figure 6 This represents the phase difference between the output ports when different input ports are excited.

[0046] In use, when the input port 610 is energized, the coupling degree of the miniaturized broadband slow-wave filter coupler based on the micro-coaxial transmission line of this application is 6.02dB, and the phase difference between the through port 710 and the coupled port 720 is +90°; when the isolation port 620 is energized, the coupling degree of the miniaturized broadband slow-wave filter coupler based on the micro-coaxial transmission line is 6.02dB, and the phase difference between the through port 710 and the coupled port 720 is -90°.

[0047] As can be seen, within the broadband range, the coupler achieves a coupling degree of 6.02dB, and the output port exhibits a 90° phase difference with small amplitude and phase difference fluctuations.

[0048] In summary, this application provides a miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line. Designed using a micro-coaxial transmission line structure, it offers advantages such as low loss, low dispersion, and miniaturization. The periodically loaded slow-wave structure of the micro-coaxial slow-wave transmission line significantly reduces the required electrical length of the coupler, resulting in a more compact planar size and miniaturization. The three-wire micro-coaxial coupling transmission line consists of three closely spaced but non-contacting metal inner conductors connecting the input port and isolation port of the micro-coaxial slow-wave filter coupler. This further improves the isolation of the isolation port, preventing reflection interference to the preceding circuitry and significantly enhancing the overall system stability and reliability. The introduction of two out-of-band zeros through a slanted micro-coaxial filter stub improves the coupler's out-of-band rejection capability and frequency selectivity. This application combines the advantages of wide bandwidth, miniaturization, high frequency selectivity, and high isolation, making it suitable for 5G and high-frequency communication systems.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line, characterized in that: It includes a microcoaxial outer conductor base, a microcoaxial slow wave transmission line, a microcoaxial three-wire coupled transmission line, a microcoaxial filter stub, a first microcoaxial transmission line, a second microcoaxial transmission line, as well as an input port, an isolation port, a through port, and a coupling port; The microcoaxial outer conductor base includes: a microcoaxial outer conductor left arm and a microcoaxial outer conductor right arm, a microcoaxial outer conductor upper arm and a microcoaxial outer conductor lower arm, a microcoaxial outer conductor longitudinal middle arm, and a microcoaxial outer conductor left oblique arm and a microcoaxial outer conductor right oblique arm; The left and right arms of the microcoaxial outer conductor are arranged relatively parallel in the longitudinal direction; the upper and lower arms of the microcoaxial outer conductor are arranged relatively parallel in the transverse direction; the left, upper, right, and lower arms of the microcoaxial outer conductor are connected in sequence to form a rectangle; one end of the longitudinal middle arm of the microcoaxial outer conductor is connected to the midpoint of the upper arm, and the other end is connected to the midpoint of the lower arm. One end of the left oblique arm of the microcoaxial external conductor is connected to the midpoint of the upper arm of the microcoaxial external conductor, and the other end is a free end; one end of the right oblique arm of the microcoaxial external conductor is connected to the midpoint of the lower arm of the microcoaxial external conductor, and the other end is a free end; the left oblique arm and the right oblique arm of the microcoaxial external conductor are symmetrical about the center of the longitudinal middle arm of the microcoaxial external conductor. The micro-coaxial outer conductor base has an intermediate cavity at the centerline position along its length direction; The input port and the through port are respectively located at the left and right corners of the upper arm of the micro-coaxial outer conductor, and the isolation port and the coupling port are respectively located at the left and right corners of the lower arm of the micro-coaxial outer conductor. Two sets of microcoaxial slow wave transmission lines are placed laterally on the upper arm of the microcoaxial outer conductor and are symmetrically connected about the left and right sides of the first microcoaxial transmission line, and their two ends are connected to the input port and the through port, respectively. Two sets of microcoaxial slow wave transmission lines are placed laterally on the lower arm of the microcoaxial outer conductor and are symmetrically connected about the left and right sides of the first microcoaxial transmission line, and their two ends are respectively connected to the isolation port and the coupling port; The microcoaxial three-wire coupled transmission line is placed longitudinally on the left arm of the outer conductor of the microcoaxial line, with one end connected to the input port and the other end connected to the isolation port; The second microcoaxial transmission line is placed longitudinally on the right arm of the outer conductor of the microcoaxial line, with one end connected to the through port and the other end connected to the coupling port. The first microcoaxial transmission line is placed longitudinally in the longitudinal middle arm of the microcoaxial outer conductor. One end of the line is connected to the connection point of the two sets of microcoaxial slow wave transmission lines in the upper arm of the microcoaxial outer conductor, and the other end is connected to the connection point of the two sets of microcoaxial slow wave transmission lines in the lower arm of the microcoaxial outer conductor. Two sets of micro - coaxial filter branches are obliquely placed on the left inclined arm and the right inclined arm of the micro - coaxial outer conductor respectively; One end of the coaxial filter branch placed on the left inclined arm of the micro - coaxial outer conductor is connected to the connection point of the two sets of micro - coaxial slow - wave transmission lines on the upper arm of the micro - coaxial outer conductor, and the other end is a free end; One end of the coaxial filter branch placed on the right inclined arm of the micro - coaxial outer conductor is connected to the connection point of the two sets of micro - coaxial slow - wave transmission lines on the lower arm of the micro - coaxial outer conductor, and the other end is a free end; The two sets of micro - coaxial filter branches are obliquely connected to both sides of the micro - coaxial transmission line and are centrosymmetric about the center of the first micro - coaxial transmission line.

2. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to claim 1, characterized in that: The material of the micro - coaxial outer conductor base is metal, and the middle cavity opened in it is filled with air.

3. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to claim 1, characterized in that: Set the height dimension and width dimension of the micro - coaxial outer conductor base to be the same. The width of the inner wall of the middle cavity opened in it is 0.53 mm, and the height is 0.3 mm; The heights of the micro - coaxial slow - wave transmission line, the micro - coaxial three - line coupling transmission line, the first micro - coaxial transmission line, the second micro - coaxial transmission line, and the micro - coaxial filter branch are all set to 0.1 mm.

4. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to claim 1, characterized in that: The first micro - coaxial transmission line includes a linear first micro - coaxial inner conductor. First support bars are evenly arranged on both sides of the first micro - coaxial inner conductor. The first micro - coaxial inner conductor is supported at the center of the corresponding middle cavity through the first support bars. The second micro - coaxial transmission line includes a linear second micro - coaxial inner conductor. Second support bars are evenly arranged on both sides of the second micro - coaxial inner conductor. The second micro - coaxial inner conductor is supported at the center of the corresponding middle cavity through the second support bars.

5. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to claim 1, characterized in that: The micro - coaxial slow - wave transmission line is composed of a transverse high - impedance transmission line, a longitudinal slow - wave structure, and a transverse slow - wave structure. The "mouth" - shaped slow - wave structure formed by enclosing the relatively arranged longitudinal slow - wave structures and the relatively arranged transverse slow - wave structures. Multiple "mouth" - shaped slow - wave structures are arranged periodically along the transverse high - impedance transmission line. Slow - wave support bars are arranged on both sides of the micro - coaxial slow - wave transmission line. The micro - coaxial slow - wave transmission line is supported at the center of the corresponding middle cavity through the slow - wave support bars.

6. The miniaturized broadband slow - wave filter coupler based on a micro - coaxial transmission line according to claim 1, wherein: The micro - coaxial three - line coupling transmission line is composed of an outer - side longitudinal transmission line, a middle - side longitudinal transmission line, an inner - side longitudinal transmission line, and a grounding post. One end of the outer - side longitudinal transmission line is connected to the isolation port, and the other end is connected to the corresponding micro - coaxial outer conductor base through the grounding post; One end of the inner - side longitudinal transmission line is connected to the input port, and the other end is also connected to the corresponding micro - coaxial outer conductor base through the grounding post; The middle - side longitudinal transmission line is located between the outer - side longitudinal transmission line and the inner - side longitudinal transmission line. One end of it is connected to the input port, and the other end is connected to the isolation port. Three - line coupling support bars are arranged on both sides of the micro - coaxial three - line coupling transmission line. The micro - coaxial three - line coupling transmission line is supported at the center of the corresponding middle cavity through the three - line coupling support bars.

7. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to claim 1, characterized in that: The micro - coaxial filter branch is composed of a bent transmission line connected to a bent coupling line with an open end at the end, and the whole is in a continuous S - shaped bend; Filter support bars are arranged on both sides of the micro - coaxial filter branch. The micro - coaxial filter branch is supported at the center of the corresponding middle cavity through the filter support bars.

8. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to any one of claims 4-7, characterized in that: The first and second microcoaxial inner conductors are made of metal, and the first and second support strips are made of SU-8 photoresist; the microcoaxial slow-wave transmission line is made of metal, and the slow-wave support strip is made of SU-8 photoresist; the microcoaxial three-wire coupled transmission line is made of metal, and the three-wire coupled support strip is made of SU-8 photoresist; the microcoaxial filter stub is made of metal, and the filter support strip is made of SU-8 photoresist.

9. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to any one of claims 4-7, characterized in that: The length and width of the inner conductor of the first micro-coaxial cable are 3 mm and 0.06 mm, respectively; the length and width of the inner conductor of the second micro-coaxial cable are 3 mm and 0.03 mm, respectively. The inner conductor length and width of the transverse high-impedance transmission line are 2 mm and 0.05 mm, respectively; the inner conductor length and width of the longitudinal slow-wave structure are 0.1 mm and 0.4 mm, respectively; and the inner conductor length and width of the transverse slow-wave structure are 0.1 mm and 0.05 mm, respectively.

10. The miniaturized broadband slow-wave filter coupler based on a micro-coaxial transmission line according to claim 9, characterized in that: The inner conductor length and width of the middle longitudinal transmission line are 3mm and 0.03mm, respectively; the inner conductor lengths and widths of the outer and inner longitudinal transmission lines are 2.8mm and 0.08mm, respectively; the distance between the inner conductors of the outer and middle longitudinal transmission lines is 0.02mm, and the distance between the inner conductors of the inner and middle longitudinal transmission lines is 0.02mm; the length, width, and height of the grounding post are 0.03mm, 0.08mm, and 0.1mm, respectively. The inner conductor length and width of the bent transmission line are 3mm and 0.12mm respectively, and the inner conductor length and width of the bent coupling line with open end are 3mm and 0.04mm respectively. The spacing between the inner conductors of the bent coupling line is 0.02mm.

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