A terahertz band coplanar waveguide bandpass filter with wide out-of-band rejection

Abstract

The application relates to the technical field of communication, and discloses a wideband out-of-band suppression terahertz frequency band coplanar waveguide band-pass filter which comprises a filter circuit, the filter circuit comprises a coplanar waveguide input port, a first coplanar waveguide resonant unit, a second coplanar waveguide resonant unit and a coplanar waveguide output port which are electrically connected in sequence. The application solves the problems of narrow out-of-band suppression frequency band and few performance adjustment parameters of the prior art.

Description

Technical Field

[0001] This invention relates to the field of communication technology, specifically to a broadband externally suppressed terahertz band coplanar waveguide bandpass filter. Background Technology

[0002] In the mid-to-late 1990s, with the development of terahertz device design technology, it became possible to use terahertz telescopes to observe the universe and probe the dynamics of the early universe, thus giving rise to the specialized discipline of terahertz astronomy. The terahertz band accounts for half of the total energy of the cosmic microwave background (CMB) radiation and is a key area for future astronomical exploration. Submillimeter-wave galaxy clusters and galaxies that the primarily optical Hubble Space Telescope (HST) could not discover were found by the SCUBA Deep Sky Survey Telescope on the Maxwell Telescope at Muna Kea, Hawaii. Terahertz telescopes are a powerful complement to optical telescopes, playing an irreplaceable role in the discovery of various submillimeter-wave galaxy clusters and galaxies. Terahertz astronomical observations can penetrate interstellar dust and have higher spatial and temporal coherence; compared to the microwave and millimeter-wave bands, they offer higher spatial resolution and a wider instantaneous bandwidth.

[0003] According to the noise cascade theory, the noise figure of the first stage of the receiver has the greatest impact on the entire system; therefore, low-noise-figure devices should be preferred in the first stage of the receiver to reduce the noise figure. Superconducting mixers employ active Josephson junctions, resulting in persistently high noise figures. Furthermore, due to the limitations of semiconductor carrier dynamics, cryogenic low-noise amplifiers cannot operate in the terahertz band. Traditional superconducting thin-film filters use microstrip lines as resonant units, and their performance deteriorates sharply above 100 GHz, with insertion loss and noise figure no longer offering significant advantages. Therefore, existing terahertz telescopes generally employ a receiver front-end architecture of a superconducting mixer plus a cryogenic low-noise amplifier, and the high noise figure severely restricts the detection range and resolution of terahertz telescopes.

[0004] In 2021, a paper presented a terahertz bandpass filter based on a superconducting thin film using a coplanar waveguide resonator. This filter had a center frequency of 350 GHz, a return loss as high as 25 dB, and an average insertion loss of approximately 1 dB. However, its out-of-band rejection performance was poor, exhibiting two resonant points at 760 GHz and 820 GHz, which affected the detection performance in the 735 GHz and 870 GHz terahertz windows. To address this issue, one approach was to introduce additional bandstop filters at 760 GHz and 820 GHz, but this would increase system complexity and cost. Another approach was to improve the filter's performance, broadening its out-of-band rejection capability. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a broadband externally suppressed terahertz band coplanar waveguide bandpass filter, which solves the problems of narrow external suppression bandwidth and few performance adjustment parameters in existing coplanar waveguide bandpass filters.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] A broadband externally suppressed terahertz band coplanar waveguide bandpass filter includes a filtering circuit, which comprises a coplanar waveguide input port, a first coplanar waveguide resonant unit, a second coplanar waveguide resonant unit, and a coplanar waveguide output port connected in sequence.

[0008] As a preferred technical solution, the first coplanar waveguide resonant unit includes a first coplanar waveguide impedance transition line, a first step-impedance coplanar waveguide resonant cavity, and a first zigzag slot line; the second coplanar waveguide resonant unit includes a second coplanar waveguide impedance transition line, a second step-impedance coplanar waveguide resonant cavity, and a second zigzag slot line; the coplanar waveguide input port, the first coplanar waveguide impedance transition line, the first step-impedance coplanar waveguide resonant cavity, the second step-impedance coplanar waveguide resonant cavity, the second coplanar waveguide impedance transition line, and the coplanar waveguide output port are sequentially electrically connected; the first zigzag slot line is disposed in the cavity jointly constructed by the first step-impedance coplanar waveguide resonant cavity and the first coplanar waveguide impedance transition line, and the second zigzag slot line is disposed in the cavity constructed by the second step-impedance coplanar waveguide resonant cavity and the second coplanar waveguide impedance transition line.

[0009] As a preferred technical solution, the first step-impedance coplanar waveguide resonant cavity includes a first high-impedance coplanar waveguide, a first low-impedance coplanar waveguide, a second high-impedance coplanar waveguide, and a second low-impedance coplanar waveguide connected in sequence; the second step-impedance coplanar waveguide resonant cavity includes a third high-impedance coplanar waveguide, a third low-impedance coplanar waveguide, a fourth high-impedance coplanar waveguide, and a fourth low-impedance coplanar waveguide connected in sequence; the first high-impedance coplanar waveguide is connected to the first coplanar waveguide impedance transition line, the second low-impedance coplanar waveguide is connected to the fourth low-impedance coplanar waveguide, and the third high-impedance coplanar waveguide is connected to the second coplanar waveguide impedance transition line.

[0010] As a preferred technical solution, the first zigzag groove includes a first U-shaped portion, a second U-shaped portion, and a third U-shaped portion. The openings of the first U-shaped portion and the third U-shaped portion have the same orientation, while the openings of the second U-shaped portion have the opposite orientation. The two ends of the opening of the second U-shaped portion are respectively connected to one end of the openings of the first U-shaped portion and the third U-shaped portion. The second zigzag groove includes a fourth U-shaped portion, a fifth U-shaped portion, and a sixth U-shaped portion. The openings of the fourth U-shaped portion and the sixth U-shaped portion have the same orientation, while the openings of the fifth U-shaped portion have the opposite orientation. The two ends of the opening of the fourth U-shaped portion are respectively connected to one end of the openings of the fourth U-shaped portion and the sixth U-shaped portion.

[0011] As a preferred technical solution, the openings of the first U-shaped section and the third U-shaped section both face the coplanar waveguide input port, and the opening of the second U-shaped section faces away from the coplanar waveguide input port; the openings of the fourth U-shaped section and the sixth U-shaped section both face the coplanar waveguide output port, and the opening of the fifth U-shaped section faces away from the coplanar waveguide output port.

[0012] As a preferred technical solution, the turning point of the first zigzag groove is a right-angle turning structure or a circular arc turning structure, and the turning point of the second zigzag groove is a right-angle turning structure or a circular arc turning structure.

[0013] As a preferred technical solution, the length and width of the first zigzag groove are both adjustable, and the length and width of the second zigzag groove are also adjustable.

[0014] As a preferred technical solution, the entire filter circuit is etched using a deep ultraviolet laser.

[0015] As a preferred technical solution, it also includes a dielectric substrate and a ground plane, with the filter circuit and the ground plane respectively connected to both sides of the dielectric substrate. The dielectric substrate is made of silicon dioxide (SiO) material, and the ground plane and the filter circuit are made of niobium thin film.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The present invention achieves the filtering of out-of-band stray electromagnetic waves through a step impedance coplanar waveguide resonant cavity. By adjusting the characteristic impedance and electrical length of the four coplanar waveguide sections in the coplanar waveguide resonant cavity, the suppression of stray electromagnetic waves at a specific frequency can be achieved.

[0018] (2) The present invention achieves multi-dimensional filter performance adjustment through the meandering slot line. The coupling position of the meandering slot line and the coplanar waveguide resonant cavity of the step impedance, the length of the meandering slot line embedded in the coplanar waveguide impedance transition line and the coupling strength determine the return loss characteristics of the filter. Adjusting the meandering slot line can effectively improve the performance of the filter. Attached Figure Description

[0019] Figure 1 Circuit diagram of a broadband externally suppressed terahertz band coplanar waveguide filter;

[0020] Figure 2 Exploded view of a broadband externally suppressed terahertz band coplanar waveguide filter;

[0021] Figure 3 Annotation diagram of resonator parameters in a broadband externally suppressed terahertz band coplanar waveguide filter;

[0022] Figure 4Simulation diagram of a broadband externally suppressed terahertz band coplanar waveguide filter for the 300-500GHz frequency band;

[0023] Figure 5 Simulation diagram of a broadband externally suppressed terahertz band coplanar waveguide filter for the 300-900GHz frequency range.

[0024] The labels and corresponding component names in the attached diagram are as follows: 1-Coplanar waveguide input port, 2-First coplanar waveguide resonant unit, 3-Second coplanar waveguide resonant unit, 4-Coplanar waveguide output port, 101-Dielectric substrate, 103-Ground plane, 21-First coplanar waveguide impedance transition line, 22-First step-impedance coplanar waveguide resonant cavity, 23-First zigzag groove line, 31-Second coplanar waveguide impedance transition line, 32-Second step-impedance coplanar waveguide resonant cavity, 33-Second zigzag groove line. 221-First high-impedance coplanar waveguide, 222-First low-impedance coplanar waveguide, 223-Second high-impedance coplanar waveguide, 224-Second low-impedance coplanar waveguide, 322-Third low-impedance coplanar waveguide, 323-Fourth high-impedance coplanar waveguide, 324-Fourth low-impedance coplanar waveguide, 231-First U-shaped section, 232-Second U-shaped section, 233-Third U-shaped section, 331-Fourth U-shaped section, 332-Fifth U-shaped section, 333-Sixth U-shaped section. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] It is worth noting that in this invention, "electrically connected" refers to electrical connection. The specific implementation methods include direct contact electrical connection, electrical connection through coupling, electrical connection through wires, electrical connection through connectors, etc. As long as it can transmit electrical signals, it is included in the concept of "electrically connected".

[0027] Example 1

[0028] like Figures 1 to 5 As shown, a broadband externally suppressed terahertz band coplanar waveguide bandpass filter includes a filtering circuit, which includes a coplanar waveguide input port 1, a first coplanar waveguide resonant unit 2, a second coplanar waveguide resonant unit 3, and a coplanar waveguide output port 4 connected in sequence.

[0029] As a preferred technical solution, the first coplanar waveguide resonant unit 2 includes a first coplanar waveguide impedance transition line 21, a first step-impedance coplanar waveguide resonant cavity 22, and a first zigzag slot line 23; the second coplanar waveguide resonant unit 3 includes a second coplanar waveguide impedance transition line 31, a second step-impedance coplanar waveguide resonant cavity 32, and a second zigzag slot line 33; the coplanar waveguide input port 1, the first coplanar waveguide impedance transition line 21, the first step-impedance coplanar waveguide resonant cavity 22, the second step-impedance coplanar waveguide resonant cavity 32, the second coplanar waveguide impedance transition line 31, and the coplanar waveguide output port 4 are sequentially electrically connected; the first zigzag slot line 23 is disposed in the cavity jointly constructed by the first step-impedance coplanar waveguide resonant cavity 22 and the first coplanar waveguide impedance transition line 21, and the second zigzag slot line 33 is disposed in the cavity constructed by the second step-impedance coplanar waveguide resonant cavity 32 and the second coplanar waveguide impedance transition line 31.

[0030] As a preferred technical solution, the first step impedance coplanar waveguide resonant cavity 22 includes a first high impedance coplanar waveguide 221, a first low impedance coplanar waveguide 222, a second high impedance coplanar waveguide 223, and a second low impedance coplanar waveguide 224 connected in sequence. The second step impedance coplanar waveguide resonant cavity 32 includes a third high impedance coplanar waveguide 321, a third low impedance coplanar waveguide 322, a fourth high impedance coplanar waveguide 323, and a fourth low impedance coplanar waveguide 324 connected in sequence. The first high impedance coplanar waveguide 221 is connected to the first coplanar waveguide impedance transition line 21, the second low impedance coplanar waveguide 224 is connected to the fourth low impedance coplanar waveguide 324, and the third high impedance coplanar waveguide 321 is connected to the second coplanar waveguide impedance transition line 31.

[0031] As a preferred technical solution, the first zigzag groove 23 includes a first U-shaped portion 231, a second U-shaped portion 232, and a third U-shaped portion 233. The openings of the first U-shaped portion 231 and the third U-shaped portion 233 have the same orientation, while the openings of the second U-shaped portion 232 have the opposite orientation. The two ends of the opening of the second U-shaped portion 232 are respectively connected to one end of the openings of the first U-shaped portion 231 and the third U-shaped portion 233. The second zigzag groove 33 includes a fourth U-shaped portion 331, a fifth U-shaped portion 332, and a sixth U-shaped portion 333. The openings of the fourth U-shaped portion 331 and the sixth U-shaped portion 333 have the same orientation, while the openings of the fifth U-shaped portion 332 have the opposite orientation. The two ends of the opening of the fourth U-shaped portion 331 are respectively connected to one end of the openings of the fourth U-shaped portion 331 and the sixth U-shaped portion 333.

[0032] As a preferred technical solution, the openings of the first U-shaped portion 231 and the third U-shaped portion 233 are both facing the coplanar waveguide input port 1, and the opening of the second U-shaped portion 232 is facing away from the coplanar waveguide input port 1; the openings of the fourth U-shaped portion 331 and the sixth U-shaped portion 333 are both facing the coplanar waveguide output port 4, and the opening of the fifth U-shaped portion 332 is facing away from the coplanar waveguide output port 4.

[0033] As a preferred technical solution, the turning point of the first zigzag groove 23 is a right-angle turning structure or a circular arc turning structure, and the turning point of the second zigzag groove 33 is a right-angle turning structure or a circular arc turning structure.

[0034] As a preferred technical solution, the length and width of the first zigzag groove 23 are both adjustable, and the length and width of the second zigzag groove 33 are both adjustable.

[0035] As a preferred technical solution, the entire filter circuit is etched using a deep ultraviolet laser.

[0036] As a preferred technical solution, it also includes a dielectric substrate 101 and a ground plane 103. The filter circuit and the ground plane 103 are respectively connected to the two sides of the dielectric substrate 101. The dielectric substrate is made of silicon dioxide (SiO2) material, and the ground plane 103 and the filter circuit are made of niobium thin film.

[0037] The beneficial effects of this invention are:

[0038] Benefit 1: Out-of-band stray electromagnetic waves can be filtered out by using a step impedance coplanar waveguide resonant cavity. By adjusting the characteristic impedance and electrical length of the four coplanar waveguide sections in the coplanar waveguide resonant cavity, stray electromagnetic waves at specific frequencies can be suppressed.

[0039] Benefit 2: The filtering performance of the filter can be adjusted in multiple dimensions through the meandering slot. The coupling position between the meandering slot and the coplanar waveguide resonant cavity with the step impedance, the length of the transition line of the meandering slot embedded in the coplanar waveguide impedance, and the coupling strength determine the return loss characteristics of the filter. Adjusting the meandering slot can effectively improve the performance of the filter.

[0040] This invention improves the out-of-band spurious signal of coplanar waveguide filters by introducing multi-order step impedance lines and increases the system design freedom by using tortuous coupling lines, thus solving the problems of narrow out-of-band suppression bandwidth and few performance adjustment parameters of existing coplanar waveguide bandpass filters.

[0041] Example 2

[0042] like Figures 1 to 5 As shown, as a further optimization of Embodiment 1, this embodiment also includes the following technical features based on Embodiment 1:

[0043] The objective of this invention is to propose a novel broadband out-of-band suppressed terahertz superconducting thin-film coplanar waveguide bandpass filter. This patent employs a step-impedance coplanar waveguide resonator to achieve out-of-band spurious suppression, offering advantages such as simple structure, convenient filter performance control, and adjustable controlled spurious frequency.

[0044] To achieve the above objectives, the superconducting coplanar waveguide bandpass filter mentioned in this invention comprises a dielectric substrate 101, a filter circuit disposed on the dielectric substrate 101, and a ground plane 103 disposed under the dielectric substrate 101. The filter circuit and the ground plane 103 may be a superconducting thin film or a metal plate.

[0045] Furthermore, the filter circuit consists of three parts: a coplanar waveguide input port 1, a coplanar waveguide output port 4, and two coplanar waveguide resonant units (the first coplanar waveguide resonant unit 2 and the second coplanar waveguide resonant unit 3).

[0046] Furthermore, the coplanar waveguide input port 1 and the coplanar waveguide output port 4 are composed of a center conductor, ground, and slot wire, forming a coplanar waveguide. The coplanar waveguide is grounded through the ground plane 103 under the dielectric substrate 101.

[0047] Furthermore, the coplanar waveguide resonant unit consists of three parts: a step-impedance coplanar waveguide resonant cavity (first step-impedance coplanar waveguide resonant cavity 22, second step-impedance coplanar waveguide resonant cavity 32), coplanar waveguide impedance transition lines (first coplanar waveguide impedance transition line 21, second coplanar waveguide impedance transition line 31), and a tortuous slot line (first tortuous slot line 23, second tortuous slot line 33) running between the two. The physical length of the step-impedance coplanar waveguide resonant cavity is one-quarter wavelength corresponding to the center frequency, and it is composed of four sections of coplanar waveguides with alternating step changes in characteristic impedance, namely, a high-impedance coplanar waveguide, a low-impedance coplanar waveguide, a high-impedance coplanar waveguide, and a low-impedance coplanar waveguide. The characteristic impedances of the high-impedance and low-impedance coplanar waveguides can be solved using the resonance formula or optimized using full-wave electromagnetic simulation software. The electrical length and characteristic impedance of the high-impedance and low-impedance coplanar waveguides determine the center frequency and out-of-band suppression of the entire filter.

[0048] Furthermore, the coplanar waveguide impedance transition line electrically connects the stepped impedance coplanar waveguide resonant cavity to the coplanar waveguide input / output ports, and its characteristic impedance is the same as that of coplanar waveguide input port 1 and coplanar waveguide output port 4. The coplanar waveguide impedance transition line and the meandering slot line entering it, coupled together, allow for the adjustment of filter performance.

[0049] Furthermore, the zigzag groove is formed from top to bottom by U-shaped grooves that are rotated at 90°, 270°, and 90°, connected end to end. The groove can be a right-angle turn or a circular arc turn.

[0050] Furthermore, the two ends of the zigzag slot are respectively connected between the step impedance coplanar waveguide resonant cavity and the coplanar waveguide impedance transition line. The central part of the zigzag slot and the coplanar waveguide impedance transition line are electrically coupled. Adjusting the length and width of the zigzag slot can change the return loss and pole location of the filter, thereby controlling the overall performance of the filter.

[0051] A broadband externally suppressed terahertz band coplanar waveguide bandpass filter comprises a dielectric substrate 101, a filter circuit disposed on the dielectric substrate 101, and a ground plane 103 disposed below the dielectric substrate 101. The filter circuit disposed on the dielectric substrate 101 includes a coplanar waveguide input port 1, a coplanar waveguide output port 4, and two coplanar waveguide resonant units.

[0052] Preferably, the filter circuit disposed on the dielectric substrate 101 is made of a superconducting thin film or a metal sheet. The coplanar waveguide resonant unit consists of three parts: a step-impedance coplanar waveguide resonant cavity, a coplanar waveguide impedance transition line, and a tortuous groove line running between the two. The physical length of the step-impedance coplanar waveguide resonant cavity is one-quarter wavelength corresponding to the center frequency, and it is composed of four sections of coplanar waveguides with alternating step changes in characteristic impedance, namely, a high-impedance coplanar waveguide, a low-impedance coplanar waveguide, a high-impedance coplanar waveguide, and a low-impedance coplanar waveguide. The coplanar waveguide impedance transition line realizes the electrical connection between the step-impedance coplanar waveguide resonant cavity and the coplanar waveguide input / output port, and its characteristic impedance is the same as that of the coplanar waveguide input port 1 and the coplanar waveguide output port 4.

[0053] Preferably, the zigzag groove is formed by connecting the first and last ends of a U-shaped groove that rotates at 90°, a U-shaped groove that rotates at 270°, and a U-shaped groove that rotates at 90° from top to bottom. The groove can be a right-angle turn or a circular arc turn.

[0054] Preferably, the ground plane 103 disposed under the dielectric substrate 101 is made of a superconducting thin film or a metal plate.

[0055] Example 3

[0056] like Figures 1 to 5 As shown, this embodiment provides a more detailed implementation method based on Embodiments 1 and 2.

[0057] In this embodiment, the dielectric substrate 101 is made of silicon dioxide (SiO2) material with a dielectric constant of 4 and a substrate thickness of 100 micrometers. The filter circuit uses a 0.4-micrometer-thick niobium film with superconducting properties, and the grounding circuit also uses a 0.4-micrometer-thick niobium film with superconducting properties. The entire filter circuit is etched using a deep ultraviolet laser.

[0058] Furthermore, the resistance of the superconducting niobium film at 380 GHz is approximately 0.0013 + 0.12i ohms, where i represents an imaginary number. The resistance of the niobium film is still less than that of conventional copper.

[0059] Furthermore, the characteristic impedance of the coplanar waveguide input port 1 and output port of the filter circuit is 50 ohms, the width of the center conductor of the input port and output port is 12 micrometers, and the gap width between the center conductor and ground is 2 micrometers.

[0060] Furthermore, each resonant unit consists of three parts: a step impedance coplanar waveguide resonant cavity, a coplanar waveguide impedance transition line, and a meandering groove line.

[0061] exist Figure 3 Within the identified resonant unit, a stepped impedance coplanar waveguide resonant cavity is etched with stepped impedance lines. The characteristic impedances, from left to right, are high impedance-low impedance-high impedance and low impedance, corresponding to a narrow-wide-narrow-wide line circuit pattern. The lengths are 5 μm, 20 μm, 3 μm, and 48 μm, with a height of 28 μm. The gap width between the stepped impedance coplanar waveguide resonant cavity and ground is 2 μm. The height of the coplanar waveguide impedance transition line is equal to that of the input / output port, and its length depends on the meandering slot line.

[0062] A meandering groove runs through the step impedance coplanar waveguide resonant cavity and the coplanar waveguide impedance transition line. This groove is used to finely adjust the filtering performance of the entire filter.

[0063] Furthermore, the resonator constructed in this patent can be extended into a cross-coupled bandpass filter or a linear phase equalization bandpass filter. Both can be constructed by cascading the same resonant units and adding cross-coupling lines, or by stacking and connecting the same resonant units.

[0064] In this implementation case, the center frequency is 384.5GHz, where S12 is below -23dB, and the 3dB bandwidth covers the range from 367GHz to 402GHz, with a total bandwidth of approximately 35GHz and a percentage bandwidth of 9.1%. In the frequency band of 400-880GHz, S11 is greater than 30dB, successfully solving the parasitic resonance problem at 760GHz and 820GHz.

[0065] As described above, the present invention can be implemented well.

[0066] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter, characterized in that, The filter circuit includes a coplanar waveguide input port (1), a first coplanar waveguide resonant unit (2), a second coplanar waveguide resonant unit (3), and a coplanar waveguide output port (4) connected in sequence. The first coplanar waveguide resonant unit (2) includes a first coplanar waveguide impedance transition line (21), a first step impedance coplanar waveguide resonant cavity (22), and a first zigzag slot line (23). The second coplanar waveguide resonant unit (3) includes a second coplanar waveguide impedance transition line (31), a second step impedance coplanar waveguide resonant cavity (32), and a second zigzag slot line (33). The input port (1), the first coplanar waveguide impedance transition line (21), the first step impedance coplanar waveguide resonant cavity (22), the second step impedance coplanar waveguide resonant cavity (32), the second coplanar waveguide impedance transition line (31), and the coplanar waveguide output port (4) are connected in sequence. The first zigzag groove line (23) is located in the cavity jointly constructed by the first step impedance coplanar waveguide resonant cavity (22) and the first coplanar waveguide impedance transition line (21), and the second zigzag groove line (33) is located in the cavity jointly constructed by the second step impedance coplanar waveguide resonant cavity (32) and the second coplanar waveguide impedance transition line (31).

2. The broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to claim 1, characterized in that, The first step impedance coplanar waveguide resonator (22) includes a first high impedance coplanar waveguide (221), a first low impedance coplanar waveguide (222), a second high impedance coplanar waveguide (223), and a second low impedance coplanar waveguide (224) connected in sequence. The second step impedance coplanar waveguide resonator (32) includes a third high impedance coplanar waveguide (321), a third low impedance coplanar waveguide (322), a fourth high impedance coplanar waveguide (323), and a fourth low impedance coplanar waveguide (324) connected in sequence. The first high impedance coplanar waveguide (221) is connected to the first coplanar waveguide impedance transition line (21), the second low impedance coplanar waveguide (224) is connected to the fourth low impedance coplanar waveguide (324), and the third high impedance coplanar waveguide (321) is connected to the second coplanar waveguide impedance transition line (31).

3. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to claim 2, characterized in that, The first zigzag groove (23) includes a first U-shaped part (231), a second U-shaped part (232), and a third U-shaped part (233). The openings of the first U-shaped part (231) and the third U-shaped part (233) face the same direction, while the openings of the second U-shaped part (232) and the first U-shaped part (231) face opposite directions. The two ends of the opening of the second U-shaped part (232) are connected to one end of the openings of the first U-shaped part (231) and the third U-shaped part (233), respectively. The second zigzag groove (33) includes a fourth U-shaped part (331), a fifth U-shaped part (332), and a sixth U-shaped part (333). The openings of the fourth U-shaped part (331) and the sixth U-shaped part (333) face the same direction, while the openings of the fifth U-shaped part (332) and the fourth U-shaped part (331) face opposite directions. The two ends of the opening of the fourth U-shaped part (331) are connected to one end of the openings of the fourth U-shaped part (331) and the sixth U-shaped part (333), respectively.

4. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to claim 3, characterized in that, The openings of the first U-shaped section (231) and the third U-shaped section (233) are both facing the coplanar waveguide input port (1), and the opening of the second U-shaped section (232) is facing away from the coplanar waveguide input port (1); the openings of the fourth U-shaped section (331) and the sixth U-shaped section (333) are both facing the coplanar waveguide output port (4), and the opening of the fifth U-shaped section (332) is facing away from the coplanar waveguide output port (4).

5. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to claim 4, characterized in that, The first zigzag groove (23) has a right-angle turn structure or a circular arc turn structure at the turning point, and the second zigzag groove (33) has a right-angle turn structure or a circular arc turn structure at the turning point.

6. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to claim 5, characterized in that, The length and width of the first zigzag groove (23) are both adjustable, as are the length and width of the second zigzag groove (33).

7. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to claim 6, characterized in that, The entire filter circuit is etched using a deep ultraviolet laser.

8. A broadband externally suppressed terahertz band coplanar waveguide bandpass filter according to any one of claims 1 to 7, characterized in that, It also includes a dielectric substrate (101) and a ground plane (103). The filter circuit and the ground plane (103) are respectively connected to the two sides of the dielectric substrate (101). The dielectric substrate is made of silicon dioxide (SiO2) material, and the ground plane (103) and the filter circuit are made of niobium thin film.

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