A high-temperature superconducting ultra-wideband filter and a method for suppressing a spurious passband thereof

Abstract

The application discloses a high-temperature superconducting ultra-wideband filter and a method for suppressing a parasitic passband thereof, and belongs to the technical field of microwave communication. The filter designed by the method comprises a high-temperature superconducting ultra-wideband filter filter medium substrate and a high-temperature superconducting thin film layer located on the medium substrate, and a filter circuit is constructed on the high-temperature superconducting thin film layer. The filter circuit (2) comprises at least one resonator structure, a rectangular microstrip patch, a microstrip branch structure and input and output feed lines. The method for suppressing the parasitic passband of the high-temperature superconducting ultra-wideband filter adjusts the relative position D parameters of the first rectangular microstrip patch, the first rectangular microstrip patch, the third rectangular microstrip patch and the fourth rectangular microstrip patch to control the spectral position of the mode frequency, and adjusts the RW and RL parameters of the first microstrip branch structure, the second microstrip branch structure and the third microstrip branch structure to realize the suppression of the parasitic passband.

Description

Technical Field

[0001] This invention belongs to the field of microwave communication technology, and specifically relates to a five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance. Background Technology

[0002] With the continuous development of modern wireless communication systems and the increasing density of spectrum resources, the demand for highly selective, low-noise, and low-loss filters is also growing. High-temperature superconducting technology is a high-tech field that has developed rapidly in recent years and has been widely used in the fabrication of microwave filters since its discovery. Because microwave filters use distributed parameter components, when the frequency exceeds a certain value, the reactance and susceptance of the components will transform into each other; inductance becomes capacitance, and capacitance becomes inductance, resulting in a new passband in the stopband, known as the parasitic passband.

[0003] Filters using high-temperature superconducting technology have extremely low passband loss and extremely high frequency interference suppression capabilities, thus having broad development prospects in the microwave radio frequency field.

[0004] In traditional multimode coupled filters, mode frequencies are difficult to control. Furthermore, high-temperature superconducting filter circuits often employ half-wavelength resonator coupling structures, which typically result in parasitic passbands at the second harmonic of the operating frequency. Therefore, many researchers have extensively studied how to suppress these parasitic passbands. Currently, mature methods include using defective ground structures to suppress parasitic passbands and forming independent electromagnetic hybrid coupling structures using microstrip line grounding to suppress them. However, both of these methods require double-sided fabrication of the dielectric substrate, increasing the manufacturing complexity. Another approach is to use interdigitated capacitors to introduce transmission zeros to suppress parasitic passbands, but this design is highly complex and generally fails to achieve ideal results. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies by designing a high-temperature superconducting ultrawideband filter and a method for suppressing parasitic passbands. This filter has the characteristics of wide passband, low loss, wide stopband, simple design, adjustable mode frequency, and significant suppression of parasitic passbands.

[0006] To achieve the objectives of this invention, the following technical solution is adopted:

[0007] A filter circuit is constructed in the high-temperature superconducting thin film layer. The filter circuit includes one or more resonator structures and one or more microstrip stub structures. Each microstrip stub structure consists of an upper equivalent inductor section and a lower equivalent capacitor section. The resonator structure connects the input feed line and the output feed line, which are typically 50°. A microstrip feedline consists of upper auxiliary line structures and lower auxiliary line structures. The input and output feedlines connect to a rectangular microstrip patch.

[0008] in:

[0009] One side of the resonator has an upper equivalent inductance section 601 and a lower equivalent capacitance section 502 of the first microstrip stub structure, as well as an input feed line connected thereto. The other side is connected to other resonator structures or output feed lines through a rectangular microstrip patch.

[0010] Preferably, the resonator structure of the filter is a U-shaped resonator structure with a stepped impedance bend, and the number of resonators determines the number of mode frequencies. Preferably, when the filter has multiple resonators, the spectral position of the mode frequencies can be changed by adjusting their relative positions using rectangular microstrip patches.

[0011] Preferably, the microstrip stub structure of the filter is a step impedance stub structure, which suppresses parasitic passbands outside the passband.

[0012] Furthermore, the lengths of the auxiliary line structure 401 on the input feed line and the auxiliary line structure 402 on the input feed line are not equal, and the lengths of the auxiliary line structure 1001 on the output feed line and the auxiliary line structure 1002 on the output feed line are also not equal.

[0013] Furthermore, in the five-mode filter of the present invention, the gaps between adjacent resonators of the first resonator structure 301, the second resonator structure 302, the third resonator structure 303, the fourth resonator structure 304, and the fifth resonator structure 305 are all filled and connected by corresponding first rectangular microstrip patches 901, second rectangular microstrip patches 902, third rectangular microstrip patches 903, and fourth rectangular microstrip patches 904.

[0014] Furthermore, the arm width of the elongated portion of the first resonator structure 301 is equal to the arm width of the elongated portion of the fifth resonator structure 305; the arm widths of the second resonator structure 302, the third resonator structure 303, and the fourth resonator structure 304 are equal; however, the arm widths of the elongated portions of the first resonator structure 301 and the fifth resonator structure 305 are not equal to the arm widths of the second resonator structure 302, the third resonator structure 303, and the fourth resonator structure 304.

[0015] Furthermore, the first resonator structure 301 and the fifth resonator structure 305 are modified from two U-shaped resonators to form a parallel three-line coupling structure that can be coupled with the input feed line and the output feed line. Their principle and function are the same as those of the U-shaped resonator.

[0016] Furthermore, the high-temperature superconducting thin film layer can be made of yttrium barium copper oxide (YBCO) or bismuth strontium calcium copper oxide.

[0017] (BSCCO). High-temperature superconducting thin films generally refer to superconducting materials with a critical temperature above 77K and a near-zero electrical resistance. They can typically be used in liquid nitrogen (77K) cooling environments and are mainly divided into two types: yttrium barium copper oxide (YBCO) and bismuth strontium calcium copper oxide.

[0018] (BSCCO). Compared to conventional thin film materials (such as copper), high-temperature superconducting thin films exhibit characteristics such as zero resistance and diamagnetic properties in the superconducting state.

[0019] Features and beneficial effects of the present invention:

[0020] 1. By introducing a rectangular microstrip patch structure into a half-wavelength U-shaped resonator, the mode frequency controllability function was achieved. At the same time, the ultra-wideband performance of the filter was achieved by using a strongly coupled feed line structure.

[0021] 2. By introducing a step impedance stub structure at the bottom of the half-wavelength U-shaped resonator, three suppression stopbands can be generated outside the band. By adjusting the parameters of the step impedance stub structure, the generation of parasitic passbands can be flexibly controlled and suppressed over a relatively long frequency band, fully meeting the system's design requirements for the filter.

[0022] 3. It features flexible design, compact structure, and easy integration, making it suitable for the fabrication of high-quality high-temperature superconducting thin films. Attached Figure Description

[0023] Figure 1 A schematic diagram of a five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram showing the specific dimensions and structure of a five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance in an embodiment of the present invention;

[0025] Figure 3 The structure of the dual-mode resonator in the embodiments of the present invention;

[0026] Figure 4 Typical equivalent circuit of the step impedance resonator in the embodiments of the present invention;

[0027] Figure 5 The dual-mode resonator even-mode equivalent circuit in the embodiments of the present invention;

[0028] Figure 6 The odd-mode equivalent circuit of the dual-mode resonator in this embodiment of the invention;

[0029] Figure 7 The frequency response of the dual-mode filter in this embodiment of the invention under different D values;

[0030] Figure 8The structure of the initial five-mode resonator in this embodiment of the invention;

[0031] Figure 9 The highest mode frequency equivalent circuit of the initial five-mode filter in this embodiment of the invention;

[0032] Figure 10 The lowest mode frequency equivalent circuit of the initial five-mode filter in this embodiment of the invention;

[0033] Figure 11 The mode frequency distribution of the five-mode resonator in this embodiment of the invention;

[0034] Figure 12 The variation diagram of S11 in adjusting RW3 in the embodiment of the present invention;

[0035] Figure 13 A graph showing the variation of the outer frequency band S21 of the near passband when adjusting RW3 in an embodiment of the present invention;

[0036] Figure 14 The variation diagram of S11 when adjusting RL3 in the embodiment of the present invention;

[0037] Figure 15 A graph showing the variation of the outer frequency band S21 of the near passband when adjusting RL3 in an embodiment of the present invention;

[0038] Figure 16 A diagram showing the change in the outer frequency band S21 when adjusting RW2 in an embodiment of the present invention;

[0039] Figure 17 A diagram showing the variation of the outer frequency band S21 when adjusting RL2 in an embodiment of the present invention;

[0040] Figure 18 A diagram showing the change of the outer frequency band S21 when adjusting RW1 in an embodiment of the present invention;

[0041] Figure 19 A diagram showing the variation of the outer frequency band S21 when adjusting RL1 in an embodiment of the present invention;

[0042] Figure 20 The S-parameter response of the superconducting ultrawideband filter in this embodiment of the invention, which does not use the parasitic suppression passband structure of the present invention;

[0043] Figure 21 The S-parameter response of the five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance in the embodiments of the present invention.

[0044] Legend:

[0045] 1. Dielectric substrate; 2. Filter circuit; 3. Resonator structure

[0046] 301. First resonator structure; 302. Second resonator structure; 303. Third resonator structure; 304. Fourth resonator structure; 305. Fifth resonator structure;

[0047] 4. Input feeder; 401 Input feeder upper auxiliary line structure; 402 Input feeder lower auxiliary line structure

[0048] 5. Micro-branch structure

[0049] 6. First microstrip stub structure; 601 Upper equivalent inductor portion of the first microstrip stub structure; 602 Lower equivalent capacitor portion of the first microstrip stub structure;

[0050] 7. Second microstrip stub structure; 701 Upper equivalent inductor section of the second microstrip stub structure; 702 Lower equivalent capacitor section of the second microstrip stub structure;

[0051] 8. Third microstrip stub structure; 801 Upper equivalent inductor section of the third microstrip stub structure; 802 Lower equivalent capacitor section of the third microstrip stub structure;

[0052] 9. Rectangular microstrip patch; 901 First rectangular microstrip patch; 902 Second rectangular microstrip patch; 903 Third rectangular microstrip patch; 904 Fourth rectangular microstrip patch;

[0053] 10. Output feeder; 1001. Auxiliary line structure on the upper part of the output feeder; 1002. Auxiliary line structure on the lower part of the output feeder. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0055] The embodiments described herein are obviously only some embodiments of the present invention, and not all embodiments.

[0056] The embodiment of the present invention uses a five-mode high-temperature superconducting ultrawideband filter structure, which requires 5 resonators, 3 microstrip stub structures and 4 rectangular microstrip patches.

[0057] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. A five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance proposed in this invention is described in detail below with reference to the accompanying drawings and embodiments:

[0058] Figure 1A schematic diagram of a five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance is shown in an embodiment of the present invention. The filter includes: a dielectric substrate 1 and a high-temperature superconducting thin film layer located on the dielectric substrate, and a filter circuit 2 is constructed on the high-temperature superconducting thin film layer. The filter circuit 2 includes: a first resonator structure 301, a second resonator structure 302, a third resonator structure 303, a fourth resonator structure 304, a fifth resonator structure 305, a first microstrip stub structure 6, a second microstrip stub structure 7, a third microstrip stub structure 8, an input feed line 4, an output feed line 10, and a first rectangular microstrip patch 901, a second rectangular microstrip patch 902, a third rectangular microstrip patch 903, and a fourth rectangular microstrip patch 904, wherein: one side of the first resonator structure 301 has an upper equivalent inductance portion 601 and a lower equivalent capacitance portion 602 of the first microstrip stub structure, and an input feed line 4 connected thereto at the input terminal, and the other side is connected to the second resonator through the first rectangular microstrip patch 901. The second resonator structure 302 is connected to the third resonator structure 303 via the second rectangular microstrip patch 902 on the other side. In addition, the bottom is connected to the first microstrip stub structure 6. The third resonator structure 303 is connected to the fourth resonator structure 304 via the third rectangular microstrip patch 903 on the other side. In addition, the bottom is connected to the second microstrip stub structure 7 on the other side. The fourth resonator structure 304 is connected to the fifth resonator structure 305 via the fourth rectangular microstrip patch 904 on the other side. In addition, the bottom is connected to the third microstrip stub structure 8. The fifth resonator structure 305 has an upper equivalent inductance section 701 of the second microstrip stub structure and a lower equivalent capacitance section 702 of the second microstrip stub structure on the other side, as well as an output feed line 10 connected to the output terminal.

[0059] The input feeder 4 consists of an upper auxiliary line structure 401 and a lower auxiliary line structure 402.

[0060] The output feed line 10 consists of an upper auxiliary line structure 1001 and a lower auxiliary line structure 1002.

[0061] The first microstrip stub structure 6, the second microstrip stub structure 7, the third microstrip stub structure 8, the second resonator structure 302, the third resonator structure 303, and the fourth resonator structure 304 are all left-right symmetrical structures.

[0062] It should be noted that the lengths of the auxiliary line structure 401 on the input feed line and the auxiliary line structure 402 on the input feed line are not equal, and the lengths of the auxiliary line structure 1001 on the output feed line and the auxiliary line structure 1002 on the output feed line are also not equal.

[0063] It should be noted that the gaps between adjacent resonators of the first resonator structure 301, the second resonator structure 302, the third resonator structure 303, the fourth resonator structure 304, and the fifth resonator structure 305 are all filled and connected by corresponding first rectangular microstrip patches 901, second rectangular microstrip patches 902, third rectangular microstrip patches 903, and fourth rectangular microstrip patches 904.

[0064] It should be noted that the arm width of the elongated portion of the first resonator structure 301 is equal to the arm width of the elongated portion of the fifth resonator structure 305; the arm widths of the second resonator structure 302, the third resonator structure 303, and the fourth resonator structure 304 are equal; however, the arm widths of the elongated portions of the first resonator structure 301 and the fifth resonator structure 305 are not equal to the arm widths of the second resonator structure 302, the third resonator structure 303, and the fourth resonator structure 304.

[0065] It should be noted that the first resonator structure 301 and the fifth resonator structure 305 are modified from two U-shaped resonators in order to couple with the input and output feed lines to form a parallel three-line coupling structure. Their principle and function are the same as those of the U-shaped resonator.

[0066] It should be noted that the high-temperature superconducting thin film layer can be made of yttrium barium copper oxide (YBCO) or bismuth strontium calcium copper oxide.

[0067] (BSCCO). High-temperature superconducting thin films generally refer to superconducting materials with a critical temperature above 77K and a near-zero electrical resistance. They can typically be used in liquid nitrogen (77K) cooling environments and are mainly divided into two types: yttrium barium copper oxide (YBCO) and bismuth strontium calcium copper oxide.

[0068] (BSCCO). Compared to conventional thin film materials (such as copper), high-temperature superconducting thin films exhibit characteristics such as zero resistance and diamagnetic properties in the superconducting state.

[0069] Figure 2 The diagram shows a top view of the upper radiating metal patch of a five-mode high-temperature superconducting ultrawideband filter structure with parasitic passband suppression performance according to an embodiment of the present invention. The diagram indicates the names of specific parameters that may affect the filter. The patch is consistent with the length and width of the dielectric substrate. In this embodiment, the overall shape is rectangular, but the remaining dimensions can also form corresponding filter circuits. It is worth noting that the simulation tool used in this invention is Sonnet EM, and the superconducting substrate used is MgO / YBCO with a dielectric constant of 9.73. This embodiment is only one of the solutions.

[0070] The length and width of the first resonator structure 301, the second resonator structure 302, the third resonator structure 303, the fourth resonator structure 304, and the fifth resonator structure 305, and their relative positions to the first rectangular microstrip patch 901, the second rectangular microstrip patch 902, the third rectangular microstrip patch 903, and the fourth rectangular microstrip patch 904, mainly determine the number of mode frequencies and the spectral position of the filter.

[0071] The first microstrip stub structure 6, the second microstrip stub structure 7, and the third microstrip stub structure 8 mainly affect the out-of-band suppression effect of the filter.

[0072] The first microstrip stub structure 6 includes an upper equivalent inductor section 601 and a lower equivalent capacitor section 602. The second microstrip stub structure 7 includes an upper equivalent inductor section 701 and a lower equivalent capacitor section 702. The third microstrip stub structure 8 includes an upper equivalent inductor section 801 and a lower equivalent capacitor section 802. The input feed line 4 and the output feed line 10 mainly serve to enhance coupling and excitation.

[0073] The five-mode high-temperature superconducting ultrawideband filter has a complex structure. As shown in Figure 2, there are multiple locations and dimensions where the coupling and excitation effects should be enhanced. We first select a two-mode resonator to study the influence of the rectangular microstrip block and the resonator on the filter's frequency.

[0074] Figure 3 The structure of a dual-mode resonator is shown. The dimensions of the two parallel resonators shown in the figure are the same as those of the second resonator structure 302. The length of the rectangular microstrip block relative to the resonator is parameter D. Figure 7 The frequency response of the two-mode filter under different D parameters is presented. It can be seen that as the D parameter increases with the position of the rectangular microstrip block relative to the resonator, the odd-mode frequency of the two-mode filter... It has shifted significantly to lower frequencies, while the even-mode frequencies of both have shifted much further. They are all the same. Using parity-modulus analysis and the Auxilary line method, in even mode, the rectangular microstrip block is open-circuited, forming something like... Figure 5 The diagram shows the even-mode equivalent circuit of a dual-mode resonator, so the even-mode frequency is... The size is independent of the rectangular microstrip block. However, in odd mode, due to the short circuit of the rectangular microstrip block, the resonant arm above the rectangular microstrip block is also short-circuited, forming a shape like... Figure 6 The diagram shows the odd-mode equivalent circuit of a two-mode resonator. Because... Figure 3 The dual-mode resonator structure shown is equivalent to, as follows: Figure 4 The typical equivalent circuit of the step impedance resonator shown can be determined by the following equation for the odd-mode resonant frequency.

[0075]

[0076] Therefore, when D increases while other parameters remain unchanged, it will lead to... The increase leads to a decrease in frequency.

[0077] Figure 8 The structure of the initial five-mode resonator is shown. The bandwidth of the ultra-wideband filter is determined by the highest resonant mode. and lowest resonance mode The magnitude of the frequency split between them. And the other three resonant modes, It will be distributed in and Between. Based on the previous mode analysis of the dual-mode filter, the highest mode Determined by the center frequency of a single U-shaped resonator, its simplified equivalent circuit diagram is as follows: Figure 9 As shown. And the lowest resonance mode... It can be simplified by equivalent circuit Figure 10 The resonance condition is derived as follows:

[0078]

[0079] With other parameters remaining unchanged, the mode frequency and bandwidth range can be easily controlled simply by changing the relative positions of the rectangular microstrip blocks. This makes the filter of the present invention flexible and controllable in terms of passband width and position, flexible in design, and simple. Figure 11 The mode frequency distribution of the five-mode resonator of the present invention is shown. The filter in this embodiment is a high-temperature superconducting ultrawideband filter.

[0080] The five-mode resonator filter of this invention typically generates a parasitic passband at twice the operating frequency. Adding a microstrip stub structure suppresses this parasitic passband. The parasitic passband is generally determined with reference to the S-parameters.

[0081] S-parameters, also known as scattering parameters, are important parameters in microwave transmission. For a two-port network such as the filter involved in this invention, there are mainly four types of S-parameters: S11, S12, S21, and S22. S21 represents the improvement direction of this invention.

[0082] S11: When port 2 is matched, the reflection coefficient (input return loss) of port 1.

[0083] S22: When port 1 is matched, the reflection coefficient (output return loss) of port 2.

[0084] S12: When port 1 is matched, the reverse transmission coefficient (isolation) from port 2 to port 1.

[0085] S21: When port 2 is matched, the forward transmission coefficient (gain) from port 1 to port 2.

[0086] The changes in the RW and RL parameters of the microstrip branch structure 5 affect the changes in the S parameters.

[0087] The RW and RL parameters of the microstrip stub structure 5 are the width and length of the open-circuit stub at the lower end of the microstrip stub structure 5, respectively. For example, the RW and RL parameters of the lower equivalent capacitance section 602 of the first microstrip stub structure 6 are RW1 and RL1, respectively. (Reference) Figure 2 .

[0088] In this embodiment of the invention, the first microstrip stub structure 6, the second microstrip stub structure 7, and the third microstrip stub structure 8 are each divided into two parts. The upper narrow line portion is a high-impedance line, which can be equivalent to an inductor, while the lower open-circuit stub can be equivalent to a capacitor, ultimately forming an equivalent resonant circuit. This introduces a transmission zero and increases the stopband width. In practical applications, simply changing the size of the microstrip stub can increase or decrease the equivalent inductance and equivalent capacitance in the resonant circuit, thereby shifting the positions of the transmission zero and the stopband. This greatly reduces the design difficulty of the filter regarding out-of-band suppression. In this embodiment, to further simplify the design process, a suitable size for the upper narrow line portion is chosen and kept constant. Instead, the transmission zero and stopband positions are changed by altering the lower open-circuit stub portion.

[0089] Figure 12 and Figure 14 The diagrams showing the changes in S11 when adjusting the width RW3 and length RL3 of the lower open-circuit stub of the third microstrip stub structure 8 are presented. It can be clearly seen that, with other parameters remaining constant, adjusting the length RL3 and width RW3 of the lower open-circuit stub of the third microstrip stub structure 8 has almost no effect on the passband performance of the overall filter. This indicates that the microstrip stub structure 5 is independent of the passband performance of the overall filter. When designing the bandwidth and out-of-band rejection of the filter in this embodiment, independent designs can be made based on the relevant structures without affecting each other. Figure 13 The diagram shows the variation of the outer frequency band S21 in the closer passband when RW3 is adjusted. It can be clearly seen that the third microstrip stub structure 8 causes the filter to produce a transmission zero T in the outer frequency band of the closer passband. Z 1 and a certain stopband, and as the value of RW3 decreases, the transmission zero and stopband positions shift to higher frequencies. Figure 15 The diagram shows the change in the outer frequency band S21 of the near passband when RL3 is adjusted. It can be seen that when RL3 is adjusted, the change pattern of the filter's out-of-band performance is roughly the same as before, but the stopband width is reduced to a certain extent.

[0090] Figure 16 The diagram shows the change in the outer frequency band S21 when RW2 is adjusted. It can be clearly seen that the second microstrip stub structure 7 generates a transmission zero T in the 16GHz-22GHz range of the outer frequency band of the filter. Z 2. There is a certain stopband, and as the value of RW2 decreases, the position of the transmission zero and the stopband shifts to higher frequencies, the range of the stopband to the left of the transmission zero decreases while the range of the stopband to the right increases. Figure 17 The diagram shows the variation of the outer frequency band S21 when RL2 is adjusted. It can be seen that the change in the filter's out-of-band performance is roughly the same as before when RL2 is adjusted. However, as RL2 decreases, the right-side stopband range of the transmission zero decreases while the left-side stopband range increases.

[0091] Figure 18 The diagram shows the change in the outer frequency band S21 when RW1 is adjusted. It can be clearly seen that the first microstrip stub structure 6 generates a transmission zero T in the 22GHz-28GHz range of the outer frequency band of the filter. Z 3. And a certain stopband, and as the value of RW1 decreases, the transmission zero and stopband position shift to higher frequencies. Figure 19 The diagram shows the variation of S21 in the outer frequency band when RL1 is adjusted. It can be seen that the change pattern of the filter's out-of-band performance when RL1 is adjusted is roughly the same as before.

[0092] Figure 20 The S-parameter response of a superconducting ultrawideband filter without the parasitic passband suppression structure of this invention is shown. As can be seen from the figure, the passband range below -3dB of the filter of this invention is 3.19GHz-9.32GHz, with an absolute bandwidth of 6.13GHz. Regarding out-of-band suppression, firstly, there are two frequency points in the 10GHz-15GHz band with S11 values ​​of -11dB and -15dB respectively, indicating poor suppression; secondly, there are numerous parasitic passbands in the 15GHz-25GHz band.

[0093] Figure 21 The S-parameter response of the five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance of the present invention is shown. As can be seen from the figure, the passband range below -3dB of the filter of the present invention is 3.19GHz-9.32GHz, the absolute bandwidth is 6.13GHz, and the overall passband bandwidth is... Figure 20The structure shown exhibits no deviation in performance, and the highest S11 value within the overall passband is -17.86dB, with the rest approaching or falling below -20dB. This indicates that the filter of this invention possesses excellent ultra-wideband performance and low return loss within the passband. Furthermore, from 9.32GHz at the end of the passband range (below -3dB) to 26.74GHz, the out-of-band rejection reaches 17.42GHz, and except for the maximum S21 value of -18dB, the remaining stopband portion is approaching or falling below -20dB. Figure 20 In comparison, after using the parasitic passband suppression method of this invention, the frequency points with poor suppression in the 10GHz-15GHz range and the parasitic passband in the 15GHz-25GHz range are effectively suppressed. This also shows that the filter designed using the design method of this invention has strong out-of-band suppression performance and engineering practical value.

[0094] In summary, the embodiments of this invention provide a five-mode high-temperature superconducting ultrawideband filter with parasitic passband suppression performance. This filter exhibits excellent performance and significant engineering practical value. By adjusting the relative position D parameter of the first rectangular microstrip patch 901, the second rectangular microstrip patch 902, the third rectangular microstrip patch 903, and the fourth rectangular microstrip patch 904, the spectral position of the mode frequency is controlled. The passband width and position are flexible and controllable, further reducing the design difficulty of the five-mode ultrawideband filter. In the filter design, by adjusting various parameters of the first microstrip stub structure 6, the second microstrip stub structure 7, and the third microstrip stub structure 8, the filter can achieve high selectivity while maintaining a good stopband and effectively improving its wide stopband characteristics. Furthermore, this invention features a compact structure, small size, flexible design, easy integration, and convenient circuit fabrication; it is suitable for fabrication using high-temperature superconducting thin films with a high quality factor.

[0095] The embodiments of the present invention have been described in detail above. Specific examples have been used in this document to illustrate the principles of the present invention.

[0096] The implementation methods have been described. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention.

[0097] Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A high-temperature superconducting ultrawideband filter, characterized in that, The high-temperature superconducting ultrawideband filter includes: a dielectric substrate (1) and a filter circuit (2) constructed on a high-temperature superconducting thin film layer on the dielectric substrate (1). The filter circuit (2) includes: a resonator structure (3), a rectangular microstrip patch (9), a microstrip stub structure (5), an input feed line (4), and an output feed line (10). The resonator structure (3) includes a first resonator structure (301), a second resonator structure (302), a third resonator structure (303), a fourth resonator structure (304), and a fifth resonator structure (305), all of which are step impedance structures used to generate five mode frequencies. The rectangular microstrip patch (9) includes a first rectangular microstrip patch (901), a second rectangular microstrip patch (902), a third rectangular microstrip patch (903), and a fourth rectangular microstrip patch (904), which are used to control the mode frequencies. The microstrip stub structure (5) includes a first microstrip stub structure (6), a second microstrip stub structure (7), and a third microstrip stub structure (8), all of which are step impedance stub structures. The first microstrip stub structure (6) includes an upper equivalent inductance section (601) and a lower equivalent capacitance section (602) of the first microstrip stub structure. The second microstrip stub structure (7) includes an upper equivalent inductance section (701) and a lower equivalent capacitance section (702) of the second microstrip stub structure. The third microstrip stub structure (8) includes an upper equivalent inductance section (801) and a lower equivalent capacitance section (802) of the third microstrip stub structure. The first resonator structure (301) and the fifth resonator structure (305) are capable of coupling with the input feed line (4) and the output feed line (10) to form a parallel three-wire coupling structure.

2. The high-temperature superconducting ultrawideband filter according to claim 1, characterized in that, The input feed line (4) includes an upper auxiliary line structure (401) and a lower auxiliary line structure (402) of the input feed line. The output feed (10) includes an upper auxiliary line structure (1001) and a lower auxiliary line structure (1002) for the output feed, and the input feed and output feed are 20-70. Microstrip feeder.

3. The high-temperature superconducting ultrawideband filter according to any one of claims 1-2, characterized in that, The first resonator structure (301) has the input feed line (4) on one side, and the other side is connected to the second resonator structure (302) through the first rectangular microstrip patch (901). The other side of the second resonator structure (302) is connected to the third resonator structure (303) through the second rectangular microstrip patch (902). The bottom of the second resonator structure (302) is connected to the first microstrip stub structure (6), and the other side of the third resonator structure (303) is connected to the first microstrip stub structure (6). The third rectangular microstrip patch (903) is connected to the fourth resonator structure (304). The bottom of the third resonator structure (303) is connected to the second microstrip stub structure (7). The other side of the fourth resonator structure (304) is connected to the fifth resonator structure (305) through the fourth rectangular microstrip patch (904). The bottom of the fourth resonator structure (304) is connected to the third microstrip stub structure (8). The other side of the fifth resonator structure (305) has an output feed line (10).

4. A method for suppressing parasitic passbands in a high-temperature superconducting ultrawideband filter, characterized in that, Using the high-temperature superconducting ultrawideband filter according to any one of claims 1-3, the spectral position of the mode frequency is controlled by adjusting the relative position D parameter of the first rectangular microstrip patch (901), the second rectangular microstrip patch (902), the third rectangular microstrip patch (903), and the fourth rectangular microstrip patch (904). The parasitic passband is suppressed by adjusting the RW and RL parameters of the first microstrip stub structure (6), the second microstrip stub structure (7), and the third microstrip stub structure (8).

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