Multi-transmission-zero-point high-temperature superconducting dual-passband filter with independent adjustment passband characteristic

Abstract

The invention belongs to the technical field of microwave communication. The invention provides a multi-transmission-zero-point high-temperature superconducting dual-passband filter with an independent adjustment passband characteristic. According to the embodiment of the invention, the open-circuit stub-loaded resonator and the short-circuit stub-loaded resonator are connected in parallel and integrated through the common feeder line, so that no electromagnetic coupling between the two resonators is ensured, and the independent adjustment of the center frequencies of the two band-pass filters is realized. Three transmission zeros are introduced and can be freely adjusted, so that the sideband selectivity of the filter can be improved. The filter shows excellent performance in the aspects of in-band insertion loss, return loss and band edge characteristics. Due to the excellent characteristics, the high-temperature superconducting microwave receiving front-end antenna can be applied to a high-temperature superconducting microwave receiving front-end system, and a good application effect is shown.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to the field of microwave communication technologies, and in particular, to a high-temperature superconducting dual-band filter with independently adjustable passband characteristics and multiple transmission zeros. Background Art

[0002] Multi-band bandpass filters have attracted significant attention from many researchers due to their wide applications in wireless communications such as wireless local area networks (WLANs), worldwide interoperability for microwave access (WiMAX), and wideband code division multiple access (WCDMA). The simplified system architecture of a traditional dual-frequency microwave receiving system consists of two independent branches, namely bandpass filter 1 (BPF1) and bandpass filter 2 (BPF2). In contrast, the high-temperature superconducting (HTS) superheterodyne architecture places the HTS filter and the low-noise amplifier (LNA) entirely in a cryogenic environment. Therefore, the miniaturization and integration of the circuit have become a key issue. Although this dual-path architecture has certain advantages in design and operation, in the HTS superheterodyne receiving system, its overly large volume poses a significant challenge. To meet various application requirements, multiple design methods for dual-band bandpass filters have been proposed. Among them, the design of dual-band filters can be achieved by using multi-mode resonator units with controllable resonant frequencies, and a typical example is the use of stepped impedance resonators (SIRs). SIRs are a common choice for the design of dual-band filters and filter miniaturization. The key advantage of SIRs is their ability to adjust the first few resonant frequencies of the resonator by adjusting the impedance ratio, making them very suitable for the design of multi-band filters.

[0003] There are two main types of SIRs: quarter-wavelength resonators and half-wavelength resonators. Although quarter-wavelength SIRs have more advantages in terms of miniaturization, in practical applications, half-wavelength SIRs are more commonly used in radio frequency devices than quarter-wavelength SIRs. By integrating two paths into one, the number of components and the overall volume can be reduced, thereby reducing the heat load on the cryogenic refrigerator. This is of great significance for high-temperature superconducting filters in the superheterodyne architecture. Currently, HTS microwave bandpass filters are widely used in wireless communication systems, terminal devices, and base stations, and exhibit excellent performance. In addition, due to their extremely low microwave surface resistance, HTS thin films can be used to fabricate high-performance microwave devices with low insertion loss and high rejection capabilities. However, most HTS filters can only handle low powers of a few milliwatts, which limits their applications at the receiving end. If they are to be used at the transmitting end, it is necessary to optimize the resonator or topology to improve their power handling capabilities, especially in reducing the maximum current density at the edges of microstrip lines. In electronic countermeasures, high-power signals may damage the receiving system.

[0004] Therefore, it is necessary to improve one or more problems existing in the above related technical solutions.

[0005] It should be noted that this part aims to provide background or context for the technical solutions of the present disclosure stated in the claims. The description herein is not admitted to be prior art merely because it is included in this part. Summary of the Invention

[0006] The purpose of the embodiments of the present disclosure is to provide a multi-transmission-zero high-temperature superconducting dual-band filter with independently adjustable passband characteristics, thereby at least to some extent overcoming one or more problems caused by the limitations and defects of the related art.

[0007] According to the embodiments of the present disclosure, there is provided a multi-transmission-zero high-temperature superconducting dual-band filter with independently adjustable passband characteristics, including: A short-circuit stub-loaded resonator, an open-circuit stub-loaded resonator, and two Z-shaped feeder resonators; wherein, the two Z-shaped feeder resonators are symmetrically arranged between the short-circuit stub-loaded resonator and the open-circuit stub-loaded resonator, and the short-circuit stub-loaded resonator, the Z-shaped feeder resonator, and the open-circuit stub-loaded resonator are sequentially indirectly coupled and connected.

[0008] Further, the short-circuit stub-loaded resonator includes: A short-circuit stub, two first-section short-circuit loaded microstrip lines in a Z shape, and two second-section short-circuit loaded microstrip lines; wherein, The first-section short-circuit loaded microstrip line includes a first segment, a second segment, and a third segment. The short-circuit stub is perpendicularly connected to the first segment, the first segment is perpendicularly connected to the second segment, the second segment is perpendicularly connected to the third segment, and the third segment is connected to the second-section short-circuit loaded microstrip line. The two first-section short-circuit loaded microstrip lines and the two second-section short-circuit loaded microstrip lines are both symmetrically arranged.

[0009] Further, the length of the short-circuit stub is 0.81 mm, and the width is 0.20 mm; the length of the first segment is 2.775 mm, and the width is 0.10 mm; the length of the second segment is 3.69 mm, and the width is 0.10 mm; the length of the third segment is 0.85 mm, and the width is 0.10 mm; the length of the second-section short-circuit loaded microstrip line is 1.06 mm, and the width is 0.99 mm.

[0010] Further, the open-circuit stub-loaded resonator includes: A circular first open-circuit stub, a second open-circuit stub, two first-section open-circuit loaded microstrip lines, two second-section open-circuit loaded microstrip lines, and two third-section open-circuit loaded microstrip lines; wherein, The first open stub is connected to the second open stub. The second open stub is perpendicularly connected to the first open-loaded microstrip line. The first open-loaded microstrip line is perpendicularly connected to the second open-loaded microstrip line. The second open-loaded microstrip line is connected to the third open-loaded microstrip line. The two first open-loaded microstrip lines, the two second open-loaded microstrip lines, and the two third open-loaded microstrip lines are all symmetrically arranged.

[0011] Further, the diameter of the first open stub is 2 mm, the length of the second open stub is 1.18 mm, and the width is 0.05 mm. The length of the first open-loaded microstrip line is 2.125 mm, and the width is 0.09 mm. The length of the second open-loaded microstrip line is 3.36 mm, and the width is 0.04. The length of the third open-loaded microstrip line is 0.70 mm, and the width is 0.50 mm.

[0012] Further, the Z-shaped feeder resonator includes: A first stub, a second stub, and a third stub; wherein, The first stub is perpendicularly connected to the second stub, and the second stub is perpendicularly connected to the third stub.

[0013] Further, the length of the first stub is 1.78 mm, and the width is 0.17 mm. The length of the second stub is 3.62 mm, and the width is 0.24 mm. The length of the third stub is 4.95 mm, and the width is 0.49 mm.

[0014] Further, the distance between the first stubs of the two Z-shaped feeder resonators is 0.69 mm. The distance between the first section and the first stub is 0.0597 mm. The distance between the second section and the second stub is 0.1892 mm. The distance between the third section and the third stub is 0.1396 mm. The distance between the first stub and the first open-loaded microstrip line is 0.1833 mm. The distance between the second stub and the second open-loaded microstrip line is 0.1173 mm.

[0015] Further, the short-circuit stub-loaded resonator, the open-circuit stub-loaded resonator, and the Z-shaped feeder resonator are all made of high-temperature superconducting materials.

[0016] The technical solutions provided by the embodiments of the present disclosure may include the following beneficial effects: In the embodiments of the present disclosure, through the above-mentioned high-temperature superconducting dual-band filter with multiple transmission zeros and independent adjustment of passband characteristics, on the one hand, the open stub-loaded resonator and the short stub-loaded resonator are integrated in parallel through a common feeder, ensuring no electromagnetic coupling between them, so as to realize independent adjustment of the center frequencies of the two band-pass filters. Three transmission zeros are introduced and can be freely adjusted, which can improve the sideband selectivity of the filter. On the other hand, the filter exhibits excellent performance in terms of in-band insertion loss, return loss, and band-edge characteristics. These excellent characteristics enable it to be applied to the high-temperature superconducting microwave receiving front-end system, demonstrating good application effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0018] Figure 1 Schematic diagram showing the structure of a high-temperature superconducting dual-band filter with multiple transmission zeros and independent adjustment of passband characteristics in an exemplary embodiment of the present disclosure; Figure 2 Schematic diagram showing the analysis of an open stub-loaded resonator in an exemplary embodiment of the present disclosure; Figure 3 Schematic diagram showing the resonance frequency response and phase of an open stub-loaded resonator in an exemplary embodiment of the present disclosure; Figure 4 Schematic diagram showing the current distribution of an open stub-loaded resonator at the resonance frequency in an exemplary embodiment of the present disclosure; Figure 5 Schematic diagram showing the analysis of a short stub-loaded resonator in an exemplary embodiment of the present disclosure; Figure 6 Schematic diagram showing the resonance frequency response and phase of a short stub-loaded resonator in an exemplary embodiment of the present disclosure; Figure 7 Schematic diagram showing the current distribution of an open stub-loaded resonator at the resonance frequency in an exemplary embodiment of the present disclosure; Figure 8 Schematic diagram showing the box-shaped coupling scheme and the Z-shaped FLR structure in an exemplary embodiment of the present disclosure; Figure 9 Schematic diagram showing the layout of a dual-band filter in an exemplary embodiment of the present disclosure; Figure 10 Schematic diagram showing the curve of resonator characteristics varying with L1 in an exemplary embodiment of the present disclosure; Figure 11A graph showing the variation of resonator characteristics with L3 in an exemplary embodiment of the present disclosure; Figure 12 A graph showing the variation of resonator characteristics with L2 in an exemplary embodiment of the present disclosure; Figure 13 A graph showing the variation of resonator characteristics with L4 in an exemplary embodiment of the present disclosure; Figure 14 A graph showing the simulation response of a dual - band filter in an exemplary embodiment of the present disclosure; Figure 15 A graph showing the frequency response of a dual - band filter without an open stub in an exemplary embodiment of the present disclosure; Figure 16 A schematic diagram showing a dual - band filter and a test box in an exemplary embodiment of the present disclosure; Figure 17 A graph showing the simulation response and measurement response of a dual - band filter in an exemplary embodiment of the present disclosure.

[0019] In the figure, 100 is a short - circuited stub - loaded resonator; 110 is a short - circuited stub; 120 is the first short - circuited loaded microstrip line, 121 is the first section, 122 is the second section, 123 is the third section; 130 is the second short - circuited loaded microstrip line; 200 is an open - circuited stub - loaded resonator; 210 is the first open - circuited stub, 220 is the second open - circuited stub, 230 is the first open - circuited loaded microstrip line, 240 is the second open - circuited loaded microstrip line, 250 is the third open - circuited loaded microstrip line; 300 is a Z - type feeder resonator; 310 is the first stub, 320 is the second stub, 330 is the third stub. Detailed implementation manners

[0020] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0021] In addition, the drawings are only schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0022] In this example embodiment, a high - temperature superconducting dual - band filter with independently adjustable pass - band characteristics and multiple transmission zeros is provided. Refer to Figure 1As shown in the figure, the multi-transmission zero high-temperature superconducting dual-band filter with independently adjustable passband characteristics may include: A substrate; a short-circuit stub-loaded resonator, an open-circuit stub-loaded resonator, and two Z-shaped feeder resonators are provided on the substrate; wherein, the two Z-shaped feeder resonators are symmetrically arranged between the short-circuit stub-loaded resonator and the open-circuit stub-loaded resonator, and the short-circuit stub-loaded resonator, the Z-shaped feeder resonator, and the open-circuit stub-loaded resonator are sequentially connected through indirect coupling.

[0023] Through the above multi-transmission zero high-temperature superconducting dual-band filter with independently adjustable passband characteristics, on the one hand, the open-circuit stub-loaded resonator and the short-circuit stub-loaded resonator are integrated in parallel through a common feeder to ensure that there is no electromagnetic coupling between them, so as to realize the independent adjustment of the center frequencies of the two band-pass filters. Three transmission zeros are introduced and can be freely adjusted, which can improve the sideband selectivity of the filter. On the other hand, the filter exhibits excellent performance in terms of in-band insertion loss, return loss, and band-edge characteristics. These excellent characteristics enable it to be applied to the high-temperature superconducting microwave receiving front-end system, demonstrating good application effects.

[0024] Next, reference will be made to Figures 1 to 17 to describe each part of the above multi-transmission zero high-temperature superconducting dual-band filter with independently adjustable passband characteristics in the present exemplary embodiment in more detail.

[0025] In a specific embodiment, the analysis of the dual-mode resonator: Dual-mode microstrip resonators are very attractive because each dual-mode resonator can be used as a dual-tuned resonant circuit, thus halving the number of required resonators and helping to achieve a more compact filter design. There have been various studies on dual-mode microstrip resonators, including ring-shaped, square-ring-shaped, disk-shaped, square patch-shaped, and triangular patch-shaped or ring-shaped dual-mode microstrip resonators and filters.

[0026] The dual-mode resonator adopted in this application has a size only one-fourth of that of the dual-mode ring resonator, greatly reducing the overall size. Its design principle is based on the basic theory of the stub resonator (i.e., the stub-loaded resonator). The stub (i.e., the branch) is usually loaded on the symmetry axis of the SIR to form a symmetric structure. There are two types of stubs: open-circuit stubs and short-circuit stubs. The difference between the two is that the end of the short-circuit stub is grounded, making the load impedance YL = ∞; while the open-circuit stub is not grounded, and the load impedance is YL = 0. With the inherent symmetry of the resonator, the resonance condition can be conveniently analyzed by the odd-even mode method.

[0027] 1) Analysis of the open-circuit stub-loaded resonator As Figure 2As shown in (a), the open - circuited stub - loaded resonator consists of a symmetric three - section SIR and an open - circuited stub, and its resonance characteristics have been studied in detail. Figure 2 (b) shows the equivalent circuit of the odd - mode excitation after loading the open - circuited stub. At this time, the symmetry plane acts as an electric wall and is grounded. The length of the loaded stub can be ignored, and the equivalent electric field on the symmetry plane is zero, which means the voltage is zero. The even - mode corresponds to the excitation of the odd - mode. When the open - circuited stub is excited by the even - mode, its equivalent circuit is as Figure 2 (c) shows. At this time, the symmetry plane is equivalent to a magnetic wall, the length of the loaded stub cannot be ignored, and the equivalent current on the symmetry plane is zero. The semicircular structure can be equivalent to a rectangular microstrip line, as Figure 2 (c) shows, thus simplifying the calculation, and subsequent experiments also prove the feasibility of this simplification. Ignoring the frequency shift caused by the relative position deviation at the microstrip line connection, the input admittances of the even - mode and odd - mode equivalent circuits Y O，odd and Y O，even can be expressed by formulas (1) and (2) respectively.

[0028] (1) (2) Among them, represents the electrical length of the microstrip line after equivalent - converting the admittance Y 5 to Y 4. Similarly, 、 and represent the electrical lengths of the subsequent microstrip lines after equivalent - converting their admittances to the admittance of the previous microstrip line respectively. Since there are many parameters involved, the calculation here is only a preliminary estimate. Assume that Y O1 is Y O2 twice that of Y O2 、 Y O3 and Y O4 remain equal, and satisfy the conditions + =π / 4 and / 2 + = π / 4 (in Equation (2)), the following analysis will continue. Since analyzing the resonance condition using the odd - even mode analysis method is not the focus of this application, the specific analysis steps will be omitted. The odd - mode resonance frequency can be calculated by Equation (3), and the even - mode resonance frequency can be obtained by Equation (4). Equations (3) and (4) are respectively derived from Equations (1) and (2), based on the resonance condition of the resonator, that is, the admittance at the input end Y O，in，odd and Y O，in，even are both zero.

[0029] (3) (4) The calculation formula for the electrical length ( i = 1, 2, 3, 4, 5) in the above - mentioned Equations (1 - 4) can be obtained by Equation (5).

[0030] (5) In Equation (5), β is the phase - shift constant, ( i = 1, 2, 3, 4) is the physical length of the transmission line, is the propagation speed of electromagnetic waves in vacuum, is the relative dielectric constant, f is the resonance frequency.

[0031] In the dual - mode pass - band configuration, the odd - mode is in the high - frequency band and the even - mode is in the low - frequency band. The following dimensions are obtained through the preliminary calculation using the above - mentioned Equations (3 - 5): L O1 = 0.7 mm, L O2 = 3.3 mm, L O3 = 4.2 mm, L O4 = 1.2 mm, W O1 = 0.5 mm, W O2 = 0.04 mm, W O3 = 0.08 mm, W O4 = 0.05 mm and R O5 = 2 mm. The resonance frequency and phase of the designed resonator are as Figure 3 shown, along with the main arm ( i= 1, 2, 3, 4), the frequencies of the odd and even modes will decrease accordingly. In addition, the width of the main arm W Oi ( i = 1, 2, 3, 4) will also affect the resonant frequency, that is, as the width increases, the resonant frequency will also increase. Both circular and rectangular open stubs can achieve the required resonant frequency. However, since the circular branch has a more uniform current distribution (as Figure 4 shown), it is more favored than the rectangular branch. This uniform distribution makes the open stub closer to a pure capacitor in the lumped circuit model, thus effectively reducing the inductance value. In addition, the current distribution analysis also shows that the current edge effect in the rectangular structure is more significant. Among them, Figure 4 (a) is the current distribution of the circular stub at 4.30 GHz; Figure 4 (b) is the current distribution of the circular stub at 4.68 GHz; Figure 4 (c) is the current distribution of the rectangular stub at 4.30 GHz; Figure 4 (d) is the current distribution of the rectangular stub at 4.68 GHz.

[0032] 2) Analysis of the short - circuited stub - loaded resonator As Figure 5 (a) shows, the short - circuited stub - loaded resonator consists of two transmission lines, a short - circuited stub, and a ground wire. When the loaded short - circuited stub operates under odd - mode excitation, its equivalent circuit is as Figure 5 (b) shows, which is the same as the circuit in Figure 2 (b). When the loaded short - circuited stub is excited by the even - mode, its equivalent circuit is as Figure 5 (c) shows. At this time, the symmetry plane is equivalent to a magnetic wall, the length of the loaded stub cannot be ignored, and the short - circuit end remains unchanged. If the discontinuity at the fold is not considered, for the sake of simplifying the calculation, the input admittances Y S,odd and Y S,even of the even - mode and odd - mode equivalent circuits can be expressed as formulas (6) and (7) respectively.

[0033] (6) (7) Similarly, based on the constraint conditions, if Y S1 is Y S2 twice that of Y S2 and Y S3 remain equal, and satisfy θS1 +π / 2 = θ S2 / 2, the resonant frequency can be derived according to formulas (8) and (9). By solving equation (9), formula (10) can be obtained. Combining formula (5) and formula (10), the odd-mode resonant frequency f S,odd can be calculated by formula (11).

[0034] (8) (9) (10) (11) It can be seen from formulas (8) and (11) that in the stub-loaded resonator, the odd-mode resonant frequency changes with L S1 the length, while the even-mode resonant frequency can be independently adjusted by adjusting L S3 without affecting the odd-mode resonant frequency. Based on the preliminary calculation of the above formulas, the following dimensions are obtained: L S1 = 1mm, L S2 = 7.3mm, L S3 = 0.8mm, W S1 = 1mm, W S2 = 0.1mm, W S3 = 0.2mm. Under these parameter conditions, the resonant frequency and phase of the designed resonator are as Figure 6 shown. The current distribution diagram of the resonator at the resonant frequency is as Figure 7 shown, further proving that L S3 the even-mode resonant frequency can be independently adjusted. Among them, Figure 7 (a) is the even-mode current distribution at 2.435 GHz; Figure 7 (b) is the odd-mode current distribution at 2.731 GHz.

[0035] 3) Coupling scheme and coupling matrix The coupling structure adopted in this application is as Figure 8The box-shaped coupling scheme shown in (a) has two main differences compared with the traditional cascaded three-section and cascaded four-section structures. First, it contains two main signal paths. Second, the configuration of the double-coupler and the box-shaped part has the characteristic of transmission zero-point movement, which means that by adjusting the resonant frequency of the resonator, the transmission zero-point can be moved from one side of the passband to the other side while other coupling coefficients remain unchanged. It should be noted that there is no coupling between the two dual-mode resonators.

[0036] Figure 8 A key feature of the configuration shown in (a) is that one of the coupling coefficients in the two main paths must be negative, while the remaining coupling coefficients are positive. To achieve this negative coupling coefficient, the simplest method is to utilize high-order resonance. However, this method is not applicable to the SIR designed in this study because the resonator only has the second order. To solve this problem, this application adopts the Z-shaped feeder resonator (FLR) shown in Figure 8 (b), which is connected to the designed SIR resonator through indirect coupling to meet the requirements for the coupling coefficient in the structure.

[0037] A band-pass filter (BPF) composed of N resonators can be characterized by the coupling coefficients Kij ( i , j = 1, 2, ···, N ), the external quality factor Q e1 and Q eN , the center frequency f 0, the bandwidth BW, and the fractional bandwidth FBW = BW / f 0. The normalized coupling coefficient is mij = Kij / FBW , the external quality factor is qe 1 = Qe 1 / FBW and qeN = QeN / FBW . The expression of the S-parameters (scattering parameters) of the Nth-order band-pass filter can be concisely and orderly represented in matrix form as shown in formula (12).

[0038] (12) where, A -1 N1 and A -1 11 are the minors of the inverse matrix [A] as shown in formula (12). The N×N matrix [A] is the normalized impedance matrix or the admittance matrix , and its specific form is shown in formula (13).

[0039] (13) Where, the matrix [q] is an N×N matrix, except q 11 = 1 / q e1 and q NN = 1 / q eN Except for [U], the remaining elements are all zero; [U] is an N×N unit matrix. The matrix [m] in formula (13) is called the generalized coupling matrix. Therefore, through the passband characteristics of the filter and the position of the transmission zero point, the corresponding equation can be used to fit the S parameters of the filter, especially the Chebyshev type filter. Substituting the obtained S parameters into formula (12), the matrix [A] can be solved, and then the matrix [m] can be derived by formula (13). However, the coupling matrix obtained by the above calculation is usually difficult to realize physically, so it needs to be simplified to a topological structure that is more suitable for practical applications while ensuring that the characteristics of the coupling matrix are not changed. The coupling matrix of the simplified box-shaped coupling structure is shown in formula (14).

[0040] Layout and Analysis of HTS Dual-Band Pass Filter The physical structure of the filter is as follows Figure 9 As shown, it consists of open-circuit and short-circuit SIR resonators coupled in parallel. The upper and lower passband filters are connected in parallel through a common feed line (Z-type FLR). The two passbands do not interfere with each other and work independently, that is, the design of one filter will not affect the performance of the other filter. Therefore, the design of the dual passband filter can be equivalent to the independent design of two second-order bandpass filters.

[0041] (14) 1) Analysis of high-frequency passband In the design of high-frequency passband, the resonator adopts a dual-mode resonator loaded with an open-circuit stub. According to the bandwidth requirements, the distribution of the two resonant modes is determined, and the response of the corresponding filter in the design is obtained by adjusting the external coupling. The coupling relationship between the feed line and the resonator is determined by the line length, line width and the distance between the feed line and the resonator.

[0042] In the actual design process, it is often very complicated to calculate the location of the resonance point and the transmission zero point. Usually, some important parameters that are easy to adjust are selected to control the location of these points. In this application, the length of the resonator L 1 and L 3 has a relatively large impact on the high-frequency passband, such as Figure 9 In the high frequency passband, the resonant frequency and the transmission zero will appear asL 1. The case of length variation. It can be seen that as L the length of 1 increases, the resonant frequency f 4 will shift downward, while f 3 first slightly increases and then decreases. The transmission zero f TZ3 first moves downward and then rises, while other resonant points and transmission zeros basically remain unchanged, as Figure 10 shown. Among them, Figure 10 (a) is the curve graph of the change of resonant points when L 1 changes, Figure 10 (b) is the curve graph of the change of transmission zeros when L 1 changes. Figure 11 It shows L the change characteristics of resonant frequency and transmission zeros when the length of 3 changes. As L the length of 3 increases, the frequencies f 3 and f 4 move towards the low-frequency direction, while other parameters are hardly affected. Among them, Figure 11 (a) is the curve graph of the change of resonant points when L 3 changes, Figure 11 (b) is the curve graph of the change of transmission zeros when L 3 changes. Therefore, the performance of the high-frequency passband can be adjusted by adjusting the lengths of L 1 and L 3.

[0043] 2) Analysis of the low-frequency passband In the design of the low-frequency passband, the resonator is grounded through the gold wire bonding method, thus further reducing the size of the filter. Similar to the resonator loaded with an open stub, the parameters that are most sensitive to the S-parameter response are selected to adjust the performance of the filter.

[0044] In the design of this application, the parameters Figure 9 shown as L 2 and L 4 are selected to adjust the resonant frequency and transmission zeros of the low-frequency part. As Figure 12 shown, as L the length of 2 increases, the two resonant points f 1 and f 2 change, and the transmission zero f TZ1 decreases as L the length of 2 increases, while f TZ2 is opposite, f 3, f 4 and f TZ3 are basically not affected. Among them, Figure 12(a) is L The curve of the resonant point when Figure 12 (b) is L The curve of the transmission zero point when Figure 13 shows L the change of the low - frequency pass - band characteristics when L increases. As f increases, the two low - frequency resonant points f 1 and Figure 13 (a) is L The curve of the resonant point when Figure 13 (b) is L The curve of the transmission zero point when L increases. Therefore, the adjustment of the low - frequency pass - band can be mainly achieved by adjusting L the lengths of L 1 = 1.18mm, L 2 = 0.81mm, L 3 = 3.36mm, L 4 = 0.85mm, and other specific parameters are as Figure 9 shown. The simulation results are as Figure 14 shown. Among them, L 1 is the length of the second open - circuit stub, L 2 is the length of the short - circuit stub, L 3 is the diameter of the first open - circuit stub, L 4 is the length of the third end of the first - stage short - circuit - loaded microstrip line.

[0045] 3) Analysis of transmission zero points Figure 8 shows the coupling modes of the filter. This structure contains two main coupling pass - bands, marked with solid lines respectively. Channel 1 is the dual - mode resonator A (DMRA), forming a pass - band with a center frequency of 2.4 GHz; Channel 2 is the dual - mode resonator B (DMRB), forming a pass - band with a center frequency of 5.2 GHz, and the ports are set between the two resonators. In the multi - mode resonator, the signal propagates along different paths, resulting in a phase difference. Similar to the hybrid electromagnetic coupling, at specific frequency points, the signals will cancel each other, thus generating transmission zero points. As can be seen from Figure 14 the simulation results, the designed high - temperature superconducting dual - pass - band filter generates three transmission zero points, which cleverly sandwich the two pass - bands in the middle, thus significantly enhancing the selectivity of the pass - bands.

[0046] According to the coupling matrix theory, the passband characteristics of the filter can be designed by adjusting the input-output coupling and the coupling coefficients between each stage. During the simulation process, after reasonably optimizing these parameters, the design parameters of the low-frequency passband were obtained, and two transmission zeros were generated on both sides of the passband, significantly enhancing the selectivity of the passband. Research shows that the greater the difference in the resonant frequencies between the two modes that generate the transmission zeros, the farther the transmission zeros are from the passband. Therefore, the three transmission zeros in the design are located at 1.87 GHz, 3.45 GHz, and 5.18 GHz respectively. Among them, the transmission zero at 5.18 GHz is generated by the superposition of the even-mode and odd-mode transmission paths of the dual-mode resonator B (DMRB), as Figure 3 shown. If the open microstrip line is removed, it is equivalent to only removing the odd-mode resonant frequency (R2o) of the DMRB. Therefore, the transmission zeros located at 1.87 GHz and 3.45 GHz are generated by the phase difference between the transmission paths of the DMRA (R1o and R1e) and the even-mode transmission path of the DMRB (R2e), as Figure 15 shown. According to the above analysis, it can be seen that the three zeros of the designed filter are all obtained through the phase difference between different modes of the resonator.

[0047] Fabrication and measurement of HTS: In the finally designed dual-band filter, two Z-shaped feeder resonators (300) are symmetrically arranged between the short-circuit stub-loaded resonator (100) and the open-circuit stub-loaded resonator (200). The short-circuit stub-loaded resonator (100), the Z-shaped feeder resonator (300), and the open-circuit stub-loaded resonator (200) are connected in series through indirect coupling in sequence. The short-circuit stub-loaded resonator (100) includes: a short-circuit stub (110), two first-section short-circuit loaded microstrip lines (120) in a Z shape, and two second-section short-circuit loaded microstrip lines (130); among them, the first-section short-circuit loaded microstrip line (120) includes a first segment (121), a second segment (122), and a third segment (123). The short-circuit stub (110) is perpendicularly connected to the first segment (121), the first segment (121) is perpendicularly connected to the second segment (122), the second segment (122) is perpendicularly connected to the third segment (123), and the third segment (123) is connected to the second-section short-circuit loaded microstrip line (130). The two first-section short-circuit loaded microstrip lines (120) and the two second-section short-circuit loaded microstrip lines (130) are both symmetrically arranged.

[0048] The open stub loaded resonator (200) includes: a circular first open stub (210), a second open stub (220), two first-section open stub loaded microstrip lines (230), two second-section open stub loaded microstrip lines (240), and two third-section open stub loaded microstrip lines (250); wherein, the first open stub (210) is connected to the second open stub (220), the second open stub (220) is perpendicularly connected to the first-section open stub loaded microstrip line (230), the first-section open stub loaded microstrip line (230) is perpendicularly connected to the second-section open stub loaded microstrip line (240), and the second-section open stub loaded microstrip line (240) is connected to the third-section open stub loaded microstrip line (250); the two first-section open stub loaded microstrip lines (230), the two second-section open stub loaded microstrip lines (240), and the two third-section open stub loaded microstrip lines (250) are all symmetrically arranged.

[0049] The Z-shaped feeder resonator (300) includes: a first stub (310), a second stub (320), and a third stub (330); wherein, the first stub (310) is perpendicularly connected to the second stub (320), and the second stub (320) is perpendicularly connected to the third stub (330).

[0050] The length of the short circuit stub (110) is 0.81 mm and the width is 0.20 mm; the length of the first section (121) is 2.775 mm and the width is 0.10 mm; the length of the second section (122) is 3.69 mm and the width is 0.10 mm; the length of the third section (123) is 0.85 mm and the width is 0.10 mm; the length of the second-section short circuit loaded microstrip line (130) is 1.06 mm and the width is 0.99 mm.

[0051] The diameter of the first open stub (210) is 2 mm, the length of the second open stub (220) is 1.18 mm and the width is 0.05 mm; the length of the first-section open stub loaded microstrip line (230) is 2.125 mm and the width is 0.09 mm; the length of the second-section open stub loaded microstrip line (240) is 3.36 mm and the width is 0.04; the length of the third-section open stub loaded microstrip line (250) is 0.70 mm and the width is 0.50 mm.

[0052] The length of the first stub (310) is 1.78 mm and the width is 0.17 mm; the length of the second stub (320) is 3.62 mm and the width is 0.24 mm; the length of the third stub (330) is 4.95 mm and the width is 0.49 mm.

[0053] The distance between the first stubs (310) of two Z-shaped feeder resonators (300) is 0.69 mm. The distance between the first section (121) and the first stub (310) is 0.0597 mm. The distance between the second section (122) and the second stub (320) is 0.1892 mm. The distance between the third section (123) and the third stub (330) is 0.1396 mm. The distance between the first stub (310) and the first open-circuited loaded microstrip line (230) is 0.1833 mm. The distance between the second stub (320) and the second open-circuited loaded microstrip line (240) is 0.1173 mm.

[0054] The finally designed dual-band filter has independently adjustable center frequencies and is fabricated using a double-sided YBCO / MgO / YBCO thin film. Its dimensions are 14.4 mm × 5.4 mm, with a thickness of 0.5 mm and a dielectric constant of 9.8. After machining and photolithography processes, the filter is encapsulated in a metal shielding box. Figure 16 The schematic diagram of the fabricated high-temperature superconducting dual-band filter and the test box is shown. Among them, the test box includes an I-shaped main body, a first side plate, a second side plate, a cover plate, a reinforcement plate, and a circuit board. The I-shaped main body is in an I shape and has a groove inside. The first side plate and the second side plate are respectively arranged on the upper and lower sides of the I-shaped main body. The circuit board is arranged in the groove of the I-shaped main body. The reinforcement plate is arranged on the circuit board to fix the circuit board in the groove. The cover plate is arranged on the upper surface of the I-shaped main body. The dual-band filter is arranged on the circuit board.

[0055] Figure 17 The simulation results and measured results of the high-temperature superconducting dual-band filter are shown. The measured results at 70 K are in good agreement with the simulation results. The 3 dB bandwidth of the first passband covers 2.36 GHz to 2.79 GHz, and the 3 dB bandwidth of the second passband covers 4.1 GHz to 4.66 GHz. The minimum insertion losses of the two passbands are 0.16 dB and 0.09 dB respectively, while the return losses in the passbands are better than -15.16 dB and -20.1 dB respectively. In Table 1, the dual-band filter designed in this application is compared with other dual-band filters. It can be seen that the filter designed in this application has significant advantages in terms of insertion loss and adjustment freedom, and the size is further reduced, demonstrating the superiority of the design.

[0056] Table 1

[0057] This application proposes the principle and design method of realizing a dual-band filter by using parallel open-circuit and short-circuit SIRs. Based on the dual-mode resonance analysis, a dual-passband filter with independently adjustable center frequency and transmission zeros is successfully designed on a double-sided YBCO high-temperature superconducting thin film. By comparing the test results with the simulation results, the filter exhibits excellent performance in terms of in-band insertion loss, return loss, and band-edge characteristics. These excellent characteristics enable it to be applied to the high-temperature superconducting microwave receiving front-end system, demonstrating good application effects.

[0058] Through the above-mentioned multi-transmission-zero high-temperature superconducting dual-passband filter with independently adjustable passband characteristics, on the one hand, the open-circuit stub-loaded resonator and the short-circuit stub-loaded resonator are integrated in parallel through a common feeder, ensuring no electromagnetic coupling between them, thereby realizing independent adjustment of the center frequencies of the two band-pass filters. Three transmission zeros are introduced and can be freely adjusted, which can improve the sideband selectivity of the filter. On the other hand, the filter exhibits excellent performance in terms of in-band insertion loss, return loss, and band-edge characteristics. These excellent characteristics enable it to be applied to the high-temperature superconducting microwave receiving front-end system, demonstrating good application effects.

[0059] It should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. in the above description is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present disclosure.

[0060] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present disclosure, "a plurality" means two or more, unless otherwise specifically defined.

[0061] In the embodiments of the present disclosure, unless otherwise clearly defined and limited, the terms "installed", "connected", "coupled", "fixed", etc. shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0062] In the embodiments of the present disclosure, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the horizontal height of the first feature is lower than that of the second feature.

[0063] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0064] After considering the specification and practicing the invention disclosed herein, those skilled in the art will readily conceive of other implementations of the present disclosure. This application is intended to cover any variations, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include the known common general knowledge or conventional technical means in the technical field not disclosed in the present disclosure. The specification and the embodiments are only regarded as exemplary, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A multi-transmission zero high-temperature superconducting dual-passband filter with independently adjustable passband characteristics, characterized in that: include: substrate; The substrate is provided with a short-circuit branch loading resonator, an open-circuit branch loading resonator and two Z-type feeder resonators; wherein, The two Z-type feed line resonators are symmetrically arranged between the short-circuit stub loading resonator and the open-circuit stub loading resonator, and the short-circuit stub loading resonator, the Z-type feed line resonator and the open-circuit stub loading resonator are sequentially connected through indirect coupling.

2. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 1, characterized in that: The short-circuit branch loading resonator comprises: short-circuit branches, two Z-shaped first short-circuit loaded microstrip lines and two second short-circuit loaded microstrip lines; wherein, The first section of the short-circuit loaded microstrip line includes a first section, a second section and a third section, the short-circuit branch is vertically connected to the first section, the first section is vertically connected to the second section, the second section is vertically connected to the third section, the third section is connected to the second section of the short-circuit loaded microstrip line, and the two first sections of the short-circuit loaded microstrip lines and the two second sections of the short-circuit loaded microstrip lines are symmetrically arranged.

3. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 2, characterized in that: The length of the short-circuit branch is 0.81mm and the width is 0.20mm; the length of the first section is 2.775mm and the width is 0.10mm; the length of the second section is 3.69mm and the width is 0.10mm; the length of the third section is 0.85mm and the width is 0.10mm; the length of the second section short-circuit loaded microstrip line is 1.06mm and the width is 0.99mm.

4. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 3, characterized in that: The open-circuit branch-loaded resonator comprises: A circular first open-circuit branch, a second open-circuit branch, two first-section open-circuit loaded microstrip lines, two second-section open-circuit loaded microstrip lines and two third-section open-circuit loaded microstrip lines; wherein, The first open branch is connected to the second open branch, the second open branch is vertically connected to the first section of the open-loaded microstrip line, the first section of the open-loaded microstrip line is vertically connected to the second section of the open-loaded microstrip line, and the second section of the open-loaded microstrip line is connected to the third section of the open-loaded microstrip line; the two first sections of the open-loaded microstrip lines, the two second sections of the open-loaded microstrip lines and the two third sections of the open-loaded microstrip lines are symmetrically arranged.

5. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 4, characterized in that: The diameter of the first open branch is 2mm, the length of the second open branch is 1.18mm, and the width is 0.05mm; the length of the first section of the open-circuited loaded microstrip line is 2.125mm, and the width is 0.09mm; the length of the second section of the open-circuited loaded microstrip line is 3.36mm, and the width is 0.04; the length of the third section of the open-circuited loaded microstrip line is 0.70mm, and the width is 0.50mm.

6. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 5, characterized in that: The Z-type feed line resonator comprises: The first branch, the second branch and the third branch; among them, The first branch is vertically connected to the second branch, and the second branch is vertically connected to the third branch.

7. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 6, characterized in that: The length of the first branch is 1.78 mm and the width is 0.17 mm; the length of the second branch is 3.62 mm and the width is 0.24 mm; the length of the third branch is 4.95 mm and the width is 0.49 mm.

8. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 7, characterized in that: The spacing between the first branches of the two Z-type feed line resonators is 0.69mm, the spacing between the first section and the first branch is 0.0597mm, the spacing between the second section and the second branch is 0.1892mm, the spacing between the third section and the third branch is 0.1396mm, the spacing between the first branch and the first section of the open-circuit loaded microstrip line is 0.1833mm, and the spacing between the second branch and the second section of the open-circuit loaded microstrip line is 0.1173mm.

9. The multi-transmission zero high temperature superconducting dual passband filter with independently adjustable passband characteristics according to claim 1, characterized in that: The short-circuit branch-loaded resonator, the open-circuit branch-loaded resonator and the Z-type feeder resonator are all made of high-temperature superconducting materials.

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