Ultra-wideband scalable sspp low-pass filter based on rectangular micro-coaxial

Abstract

The application discloses a kind of based on rectangular micro coaxial ultra-wideband expandable SSPP low-pass filter, ultra-wideband low-pass filter includes micro coaxial outer conductor and the micro coaxial inner conductor installed in it, micro coaxial inner conductor includes first inner conductor, second inner conductor, third inner conductor, fourth inner conductor, fifth inner conductor, sixth inner conductor, seventh inner conductor, eighth inner conductor and ninth inner conductor, also include feed port, feed port includes first feed port and second feed port, first feed port and second feed port are respectively connected on first inner conductor and ninth inner conductor, the whole application adopts rectangular micro coaxial transmission line structure, by the gradually changing structure of inner conductor and three SSPP regions, by adjusting the geometric shape and arrangement mode of inner conductor, the low-pass filter effect of miniaturization and low loss is realized, simultaneously, the difficulty that existing filter is difficult to consider miniaturization and low loss in terahertz frequency band is also overcome.

Description

Technical Field

[0001] This invention specifically relates to an ultra-wideband scalable SSPP low-pass filter based on a rectangular micro-coaxial cable, belonging to the field of radio frequency microwave technology, and is particularly suitable for filtering scenarios in terahertz communication systems. Background Technology

[0002] With the rapid development of communication technology, the demand for terahertz frequency band filters is increasing. Surface plasmons are light waves that propagate along the interface between a metal and a dielectric. Since metals are ideal conductors in the terahertz and microwave bands, surface plasmons cannot exist in these bands. One approach is to obtain surface electromagnetic waves with similar characteristics to surface plasmons by structuring metal surfaces, i.e., artificial surface plasmons. Due to their excellent bandgap or low-pass characteristics, they are widely used in the design of broadband filters. In recent years, various filters based on artificial surface plasmons have been proposed, such as wide-stopband filters based on defective artificial surface plasmons, reflective low-pass filters based on coplanar waveguides, and low-pass filters using folded artificial surface plasmon transmission lines. However, traditional artificial surface plasmon-based filters struggle to simultaneously meet the dual requirements of miniaturization and low loss in the terahertz band. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention combines the advantages of rectangular microcoaxial transmission lines and artificial surface plasmons, proposing an ultrawideband scalable SSPP low-pass filter based on a rectangular microcoaxial line. The filter adopts a microcoaxial transmission line structure as the whole, and by designing and optimizing the structure of the microcoaxial line and the geometry and arrangement of the inner conductors, it achieves miniaturization, high power capacity, good selectivity, and three-pass effect.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] An ultra-wideband scalable SSPP low-pass filter based on a rectangular microcoaxial cable includes a microcoaxial outer conductor and a microcoaxial inner conductor. A cavity is formed on the microcoaxial outer conductor, and the cavity is filled with a dielectric. The microcoaxial inner conductor is installed inside the cavity containing the dielectric.

[0006] The micro-coaxial inner conductor includes a first inner conductor, a second inner conductor, a third inner conductor, a fourth inner conductor, a fifth inner conductor, a sixth inner conductor, a seventh inner conductor, an eighth inner conductor, and a ninth inner conductor. The first inner conductor, the second inner conductor, the third inner conductor, the fourth inner conductor, the sixth inner conductor, the seventh inner conductor, the eighth inner conductor, and the ninth inner conductor are connected sequentially through the fifth inner conductor. The widths of the first inner conductor, the second inner conductor, and the third inner conductor increase sequentially, while the widths of the seventh inner conductor, the eighth inner conductor, and the ninth inner conductor decrease sequentially. The fourth inner conductor and the sixth inner conductor have the same dimensions and the same width as the third inner conductor and the seventh inner conductor.

[0007] It also includes a power supply port, which includes a first power supply port and a second power supply port, the first power supply port and the second power supply port being respectively connected to the first inner conductor and the ninth inner conductor;

[0008] The first power supply port, the first inner conductor, the second inner conductor, the third inner conductor, and the fifth inner conductor constitute SSPP region one; the second power supply port, the fifth inner conductor, the seventh inner conductor, the eighth inner conductor, and the ninth inner conductor constitute SSPP region two; and the fourth inner conductor, the fifth inner conductor, and the sixth inner conductor constitute SSPP region three. SSPP region one and SSPP region two are symmetrically arranged on the micro-coaxial inner conductor.

[0009] As a preferred technical solution of the present invention: the first power supply port and the second power supply port have the same shape and size, and the two are symmetrically arranged on the micro coaxial inner conductor.

[0010] As a preferred technical solution of the present invention: the first inner conductor and the ninth inner conductor have the same shape and size, both of which are set as rectangles with a width of W11 and a length of P, and the two are symmetrically arranged on the micro-coaxial inner conductor.

[0011] As a preferred technical solution of the present invention: the second inner conductor and the eighth inner conductor have the same shape and size, both of which are set as rectangles with a width of W21 and a length of P, and the two are symmetrically arranged on the micro-coaxial inner conductor.

[0012] As a preferred technical solution of the present invention: the third inner conductor and the seventh inner conductor have the same shape and size, both of which are set as spindle shapes with a width of W31 and a length of P, and the two are symmetrically arranged on the micro-coaxial inner conductor.

[0013] As a preferred technical solution of the present invention: the fourth inner conductor and the sixth inner conductor have the same shape and size, both of which are set as rectangles with a width of W1 and a length of P, and the two are symmetrically arranged on the micro-coaxial inner conductor.

[0014] As a preferred embodiment of the present invention, the fifth inner conductor is configured as a long strip.

[0015] As a preferred embodiment of the present invention: the spacing between the first inner conductor, the second inner conductor, the third inner conductor, the fourth inner conductor, the sixth inner conductor, the seventh inner conductor, the eighth inner conductor, and the ninth inner conductor is P1.

[0016] As a preferred embodiment of the present invention, the medium inside the cavity is air.

[0017] As a preferred embodiment of the present invention: the first power supply port, the second power supply port, the first inner conductor, the second inner conductor, the third inner conductor, the fourth inner conductor, the fifth inner conductor, the sixth inner conductor, the seventh inner conductor, the eighth inner conductor, and the ninth inner conductor are all metallic materials with conductive properties.

[0018] The ultra-wideband scalable SSPP low-pass filter proposed in this invention adopts a rectangular microcoaxial transmission line structure. By designing the gradient structure of the inner conductor and artificial surface plasmon units, and adjusting the geometry and arrangement of the inner conductor of the microcoaxial line, a miniaturized and low-loss low-pass filter effect is achieved, overcoming the difficulty of existing filters in the terahertz band to achieve both miniaturization and low loss. This ultra-wideband scalable SSPP low-pass filter has the advantages of compact structure, low insertion loss, and strong out-of-band rejection capability, and is suitable for filtering scenarios in terahertz communication systems.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. Innovative design of artificial surface plasmon units:

[0021] This invention utilizes multi-step structural transformation of a rectangular micro-coaxial inner conductor to construct an artificial surface plasmon unit. By analyzing the dispersion curve of the unit, the cutoff frequency of the filter can be accurately determined, thus realizing flexible control of the filter's operating frequency band.

[0022] 2. Ultra-wideband low-pass filtering effect:

[0023] The filter of this invention achieves good low-pass filtering performance in the 0-115GHz passband range, with insertion loss better than 0.4dB, reflection loss better than 13dB, and out-of-band rejection of -50dB at 150GHz, demonstrating excellent passband flatness and out-of-band rejection capability.

[0024] 3. Gradient structure achieves good matching:

[0025] This invention achieves good impedance matching from the feed port to the filtering region by setting a gradient structure that smoothly transitions from a rectangle to a spindle shape in region 1, effectively reducing signal reflection and lowering insertion loss.

[0026] 4. Miniaturized design:

[0027] This invention employs a rectangular micro-coaxial transmission line structure. By optimizing the geometry and arrangement of the inner conductors, it achieves a miniaturized filter design with an overall size of only 5.8mm × 1mm. This is a significant reduction in size compared to traditional filters in the same frequency band, making it ideal for terahertz communication system applications where miniaturization and integration are critical. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 This is the front view of the present invention;

[0030] Figure 3 This is the left view of the present invention;

[0031] Figure 4 This is a top view of the present invention;

[0032] Figure 5 This is the S-parameter curve of a three-pass band filter.

[0033] List of reference numerals in the attached diagram:

[0034] 1. First power supply port; 2. Second power supply port; 3. First inner conductor; 4. Second inner conductor; 5. Third inner conductor; 6. Fourth inner conductor; 7. Fifth inner conductor; 8. Sixth inner conductor; 9. Seventh inner conductor; 10. Eighth inner conductor; 11. Ninth inner conductor. Detailed Implementation

[0035] 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.

[0036] like Figure 1-4 As shown, the present invention proposes an ultra-wideband low-pass filter based on a micro-coaxial transmission line, comprising a micro-coaxial outer conductor, a micro-coaxial inner conductor, and a feed port.

[0037] like Figure 1 As shown, Conductor 1 is a micro-coaxial outer conductor, and Conductor 2 is a micro-coaxial inner conductor.

[0038] A cavity is formed on the outer conductor of the micro-coaxial cable, and the cavity is filled with a dielectric material. The inner conductor of the micro-coaxial cable is installed in the cavity containing the dielectric material. In this embodiment of the invention, the dielectric material in the cavity is preferably air, but other low-loss dielectric materials can also be used.

[0039] The micro-coaxial inner conductor includes a first inner conductor 3, a second inner conductor 4, a third inner conductor 5, a fourth inner conductor 6, a fifth inner conductor 7, a sixth inner conductor 8, a seventh inner conductor 9, an eighth inner conductor 10, and a ninth inner conductor 11. The first inner conductor 3, the second inner conductor 4, the third inner conductor 5, the fourth inner conductor 6, the sixth inner conductor 8, the seventh inner conductor 9, the eighth inner conductor 10, and the ninth inner conductor 11 are connected sequentially through the fifth inner conductor 7. The widths of the first inner conductor 3, the second inner conductor 4, and the third inner conductor 5 increase sequentially, while the widths of the seventh inner conductor 9, the eighth inner conductor 10, and the ninth inner conductor 11 decrease sequentially. The fourth inner conductor 6 and the sixth inner conductor 8 have the same dimensions and the same width as the third inner conductor 5 and the seventh inner conductor 9.

[0040] It also includes a power supply port, which includes a first power supply port 1 and a second power supply port 2, and the first power supply port 1 and the second power supply port 2 are respectively connected to the first inner conductor 3 and the ninth inner conductor 11;

[0041] The first power supply port 1, the first inner conductor 3, the second inner conductor 4, the third inner conductor 5 and the fifth inner conductor 7 constitute SSPP region one, the second power supply port 2, the fifth inner conductor 7, the seventh inner conductor 9, the eighth inner conductor 10 and the ninth inner conductor 11 constitute SSPP region two, and the fourth inner conductor 6, the fifth inner conductor 7 and the sixth inner conductor 8 constitute SSPP region three. SSPP region one and SSPP region two are symmetrically arranged on the micro coaxial inner conductor.

[0042] The artificial surface plasmon unit in this embodiment of the invention adopts a multi-step structural transformation design. Each unit has a length P in the transmission direction, the inner conductor width of SSPP region two is W1, and the inner conductor widths on both sides of SSPP regions one and three are W11, W21, and W31, respectively, increasing sequentially. Parts of SSPP regions one and three are mainly used for electromagnetic signal transmission, while the middle part, with a width extended to W1, serves as the basic unit for changing the wave velocity.

[0043] The rectangular microcoaxial transmission line consists of a microcoaxial outer conductor and a microcoaxial inner conductor. This structure supports TEM mode transmission and features miniaturization and low loss, while maintaining excellent signal transmission performance over a wide frequency range.

[0044] In this embodiment of the invention, the SSPP region is connected in sequence by a first power supply port 1, a first inner conductor 3, a second inner conductor 4, a third inner conductor 5, and a fifth inner conductor 7;

[0045] The second SSPP region is connected in sequence by the second feed port 2, the fifth inner conductor 7, the seventh inner conductor 9, the eighth inner conductor 10, and the ninth inner conductor 11;

[0046] The SSPP region three is connected in sequence by the fourth inner conductor 6, the fifth inner conductor 7, and the sixth inner conductor 8.

[0047] In this embodiment of the invention, all components of the micro-coaxial inner conductor are arranged symmetrically:

[0048] The first inner conductor 3 and the ninth inner conductor 11 have the same shape and size, both set as rectangles with a width of W11 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor.

[0049] The second inner conductor 4 and the eighth inner conductor 10 have the same shape and size, both set as rectangles with a width of W21 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor.

[0050] The third inner conductor 5 and the seventh inner conductor 9 have the same shape and size, both being spindle-shaped with a width of W31 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor.

[0051] The sizes of W11, W21, and W31 gradually increase.

[0052] The fourth inner conductor 6 and the sixth inner conductor 8 have the same shape and size, both set as rectangles with a width of W1 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor.

[0053] The fifth inner conductor 7 is configured as a long strip and is used as a connecting structure to connect the inner conductors.

[0054] The spacing between the first inner conductor, the second inner conductor, the third inner conductor, the fourth inner conductor, the sixth inner conductor, the seventh inner conductor, the eighth inner conductor, and the ninth inner conductor is P1.

[0055] In this embodiment of the invention, the first power supply port 1, the second power supply port 2, the first inner conductor 3, the second inner conductor 4, the third inner conductor 5, the fourth inner conductor 6, the fifth inner conductor 7, the sixth inner conductor 8, the seventh inner conductor 9, the eighth inner conductor 10, and the ninth inner conductor 11 are all metallic materials with conductive properties.

[0056] By adjusting the width W1 of the inner conductor in this embodiment of the invention, the dispersion characteristics of the artificial surface plasmon unit can be changed, thereby controlling the cutoff frequency of the filter and enhancing the design flexibility.

[0057] The invention will now be described in detail with reference to specific examples.

[0058] This embodiment uses a low-loss low-pass filter with a cutoff frequency of 115GHz, and its specific parameter settings are as follows:

[0059] The unit length P = 0.34 mm, the width of the middle inner conductor W1 = 0.53 mm, and the width of the inner conductors on both sides W2 = 0.04 mm;

[0060] Transition structure parameters: W11=0.33mm, W21=0.43mm, W31=0.53mm;

[0061] The spacing between units is P1 = 0.34 mm.

[0062] The overall size of the low-pass filter is only 5.8mm × 1mm.

[0063] In this embodiment, the overall structure of the low-pass filter is divided into three regions:

[0064] SSPP region one and SSPP region two contain two gradually widening rectangular artificial surface plasmon units and a spindle-shaped artificial surface plasmon unit. The width transitions from W11 to W21 and finally changes to a spindle-shaped structure of W31. This gradual geometry provides a smooth transition from SSPP region one and SSPP region two to SSPP region three, which is beneficial for achieving impedance matching and reducing signal reflection.

[0065] SSPP region 3, as the main filtering region, can generate a stopband within a specific frequency range, effectively blocking wave propagation and further optimizing filtering performance.

[0066] In this embodiment, the first power supply port 1, the second power supply port 2, the first inner conductor 3, the second inner conductor 4, the third inner conductor 5, the fourth inner conductor 6, the fifth inner conductor 7, the sixth inner conductor 8, the seventh inner conductor 9, the eighth inner conductor 10, and the ninth inner conductor 11 are made of copper.

[0067] like Figure 5 As shown, based on the above exemplary settings, where S(1.1) is the return loss and S(2.1) is the transmission loss between corresponding ports, the low-pass filter proposed in this embodiment achieves good filtering performance in the 0-115GHz passband. Throughout the passband, the insertion loss is better than 0.4dB and the return loss is better than 13dB, indicating high signal transmission efficiency and low reflection loss. Simultaneously, the filter exhibits excellent out-of-band suppression performance, achieving a suppression level of -50dB at 150GHz, effectively suppressing out-of-band interference signals.

[0068] Therefore, based on the above experiments, the ultra-wideband low-pass filter based on micro-coaxial transmission lines proposed in this invention not only achieves the design goals of compact structure and miniaturization, but also has the advantages of low insertion loss and strong out-of-band suppression capability, making it very suitable for filtering scenarios in terahertz communication systems.

[0069] 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. An ultrawideband scalable SSPP low-pass filter based on a rectangular micro-coaxial cable, characterized in that, It includes a micro-coaxial outer conductor and a micro-coaxial inner conductor. The micro-coaxial outer conductor has a cavity, which is filled with a dielectric material. The micro-coaxial inner conductor is installed inside the cavity containing the dielectric material. The micro-coaxial inner conductor includes a first inner conductor (3), a second inner conductor (4), a third inner conductor (5), a fourth inner conductor (6), a fifth inner conductor (7), a sixth inner conductor (8), a seventh inner conductor (9), an eighth inner conductor (10), and a ninth inner conductor (11). The first inner conductor (3), the second inner conductor (4), the third inner conductor (5), the fourth inner conductor (6), the sixth inner conductor (8), the seventh inner conductor (9), the eighth inner conductor (10), and the ninth inner conductor (11) are connected sequentially through the fifth inner conductor (7). The widths of the first inner conductor (3), the second inner conductor (4), and the third inner conductor (5) increase sequentially, while the widths of the seventh inner conductor (9), the eighth inner conductor (10), and the ninth inner conductor (11) decrease sequentially. The fourth inner conductor (6) and the sixth inner conductor (8) have the same dimensions and the same width as the third inner conductor (5) and the seventh inner conductor (9). It also includes a power supply port, which includes a first power supply port (1) and a second power supply port (2). The first power supply port (1) and the second power supply port (2) are respectively connected to the first inner conductor (3) and the ninth inner conductor (11). The first power supply port (1) and the second power supply port (2) have the same shape and size, and are symmetrically arranged on the micro-coaxial inner conductor. The first power supply port (1), the first inner conductor (3), the second inner conductor (4), the third inner conductor (5), and the fifth inner conductor (7) constitute SSPP region one; the second power supply port (2), the fifth inner conductor (7), the seventh inner conductor (9), the eighth inner conductor (10), and the ninth inner conductor (11) constitute SSPP region two; the fourth inner conductor (6), the fifth inner conductor (7), and the sixth inner conductor (8) constitute SSPP region three; SSPP region one and SSPP region two are symmetrically arranged on the micro coaxial inner conductor. The first inner conductor (3) and the ninth inner conductor (11) have the same shape and size, both of which are rectangular with a width of W11 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor. The second inner conductor (4) and the eighth inner conductor (10) have the same shape and size, both set as rectangles with a width of W21 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor; The third inner conductor (5) and the seventh inner conductor (9) have the same shape and size, both set as a spindle shape with a width of W31 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor. The fourth inner conductor (6) and the sixth inner conductor (8) have the same shape and size, both of which are rectangular with a width of W1 and a length of P, and are arranged symmetrically on the micro-coaxial inner conductor. The fifth inner conductor (7) is configured as a long strip; The spacing between the first inner conductor (3), the second inner conductor (4), the third inner conductor (5), the fourth inner conductor (6), the sixth inner conductor (8), the seventh inner conductor (9), the eighth inner conductor (10), and the ninth inner conductor (11) is P1.

2. The ultra-wideband scalable SSPP low-pass filter based on a rectangular micro-coaxial cable according to claim 1, characterized in that, The medium inside the cavity is air.

3. The ultra-wideband scalable SSPP low-pass filter based on a rectangular micro-coaxial cable according to claim 1, characterized in that, The first power supply port (1), the second power supply port (2), the first inner conductor (3), the second inner conductor (4), the third inner conductor (5), the fourth inner conductor (6), the fifth inner conductor (7), the sixth inner conductor (8), the seventh inner conductor (9), the eighth inner conductor (10), and the ninth inner conductor (11) are all made of conductive metal materials.

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