An ultra-narrowband high-temperature superconducting symmetric dual-channel filter

Abstract

This invention relates to the field of dual-passband filter technology and discloses an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter. The invention establishes a high-order coupled topology based on CT and CQ units, enabling free adjustment of the zero positions between the two sub-passbands and the introduction of a pair of transmission zeros out of the dual-passband filter, thus achieving good sideband suppression between sub-passbands and throughout the entire dual-passband filter.

Description

Technical Field

[0001] This invention relates to the field of dual-passband filter technology, specifically to an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter. Background Technology

[0002] With the increasing demand for higher data rates and efficient spectrum utilization in wireless systems, multi-band microwave components and systems have become crucial. Dual-passband filters, capable of ensuring efficient operation of two different frequency bandwidths, are ideal for modern dual-band microwave systems. There are generally three methods for designing dual-passband filters. The first is to form a dual passband by connecting two bandpass filters in parallel or cascading a bandpass filter and a bandstop filter. This method is simple to design, and the passband width can be independently adjusted, but the filter size is usually large. The second method is based on multimode resonators, including stepped impedance resonators (SIRs) and load-spar resonators (SLRs). This method can achieve a compact size and a large bandwidth ratio, but it is typically used in ultra-high frequency (UHF) and higher frequency bands, and independently designing the passband and bandwidth is difficult. The third method is through high-order coupling matrices. This method has clear design logic and can precisely control the frequency response of the filter, but the filter loss deteriorates with increasing coupling order. Using high-temperature superconducting materials to design high-order coupled dual-passband filters can simultaneously achieve excellent performance such as low insertion loss, high selectivity, and compact size. These characteristics make high-temperature superconducting filters an ideal choice for high-spectrum-density applications such as communication systems, satellite transceivers, and wireless networks. Summary of the Invention

[0003] To address the aforementioned shortcomings in the prior art, this invention provides an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter.

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

[0005] An ultra-narrowband high-temperature superconducting symmetrical dual-channel filter includes:

[0006] First signal terminal, first resonator, second resonator, third resonator, fourth resonator, fifth resonator, sixth resonator, seventh resonator, eighth resonator, ninth resonator, tenth resonator, eleventh resonator, twelfth resonator and second signal terminal.

[0007] The first signal terminal, the first resonator, and the second resonator are sequentially positively coupled.

[0008] The second resonator, the third resonator, and the fourth resonator form a first triangular cross-coupled structure; the second resonator, the third resonator, and the fourth resonator are connected in a positively coupled manner in sequence; the second resonator and the fourth resonator are connected in a negatively coupled manner.

[0009] The fifth, sixth, seventh, and eighth resonators form a four-corner cross-coupled structure; the fourth, fifth, sixth, seventh, and eighth resonators are sequentially positively coupled; the fifth and eighth resonators are negatively coupled.

[0010] The ninth, tenth, and eleventh resonators form a second triangular cross-coupled structure; the ninth and tenth resonators are positively coupled; and the ninth and eleventh resonators, and the tenth and eleventh resonators are negatively coupled.

[0011] The eleventh resonator, the twelfth resonator, and the second signal terminal are sequentially positively coupled.

[0012] Furthermore, each resonator is a folded, compact double-helix resonator.

[0013] Furthermore, the current directions of adjacent microstrip lines in the double-helix structure of each resonator are opposite.

[0014] Furthermore, in the first triangular cross-coupling structure, the end microstrip lines of the second and third resonators are arranged in the same direction and overlap, the end microstrip lines of the second and fourth resonators are arranged in opposite directions and overlap, and the side microstrip lines of the third and fourth resonators are arranged in an overlapping manner.

[0015] Furthermore, the end microstrip lines of the first resonator and the second resonator are arranged to overlap.

[0016] Furthermore, in the four-corner cross-coupled structure, the end microstrip lines of the fifth and eighth resonators are arranged to overlap in opposite directions, the end microstrip lines of the sixth and seventh resonators are arranged to overlap in opposite directions, the side microstrip lines of the fifth and sixth resonators are arranged to overlap, and the side microstrip lines of the seventh and eighth resonators are arranged to overlap.

[0017] Furthermore, the end microstrip lines of the fifth resonator and the fourth resonator are arranged to overlap.

[0018] Furthermore, in the second triangular cross-coupling structure, the end microstrip lines of the ninth and eleventh resonators are arranged to overlap in opposite directions, the side microstrip lines of the ninth and tenth resonators are arranged to overlap, and the side microstrip lines of the tenth and eleventh resonators are arranged to overlap.

[0019] Furthermore, the end microstrip lines of the eighth and ninth resonators are arranged to overlap.

[0020] Furthermore, the end microstrip lines of the eleventh resonator and the twelfth resonator are arranged to overlap.

[0021] The present invention has the following beneficial effects:

[0022] This invention utilizes two CT units to introduce two transmission zeros (TZs) between two passbands, and allows for free adjustment of the positions of these two TZs, thereby controlling the sideband suppression between the two sub-passbands. Two out-of-band transmission zeros are introduced in pairs using CQ units, thus improving the sideband suppression of the dual-passband filter. This topology not only improves filter performance but also enables precise control of the passband frequency and bandwidth. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a high-order coupled dual-passband filter topology prototype;

[0024] Figure 2(a) shows the s-domain function response of the asymmetric low-pass prototype filter;

[0025] Figure 2(b) shows the s-domain function response of the transformed dual-passband low-pass prototype filter;

[0026] Figure 3(a) is a schematic diagram of the current direction of the resonator;

[0027] Figure 3(b) is a schematic diagram of the resonator current distribution;

[0028] Figure 4(a) is a schematic diagram of coupling type I between resonators;

[0029] Figure 4(b) is a schematic diagram of coupling type II between resonators;

[0030] Figure 4(c) is a schematic diagram of coupling type III between resonators;

[0031] Figure 4(d) is a schematic diagram of coupling type IV between resonators;

[0032] Figure 4(e) is a schematic diagram of the coupling type V between resonators;

[0033] Figure 4(f) is a schematic diagram of the external taps between the resonators;

[0034] Figure 5 This is a schematic diagram showing the variation curve of the coupling coefficient between resonators;

[0035] Figure 6(a) is a schematic diagram of the coupling phase change curve of coupling type I between resonators;

[0036] Figure 6(b) is a schematic diagram of the coupling phase change curve of coupling type II between resonators;

[0037] Figure 6(c) is a schematic diagram of the coupling phase change curve of coupling type III between resonators;

[0038] Figure 6(d) is a schematic diagram of the coupling phase change curve of coupling type IV between resonators;

[0039] Figure 6(e) is a schematic diagram of the coupling phase change curve of coupling type V between resonators;

[0040] Figure 6(f) is a schematic diagram of the coupling phase change curve of the external taps between resonators;

[0041] Figure 7 This is a schematic diagram of a planar circuit for an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter.

[0042] Figure 8 This is a schematic diagram of the final simulation results of an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter.

[0043] Figure 9(a) is a schematic diagram of the current distribution of port 1 excitation at the high frequency transmission zero point in the high frequency sub-passband 2.

[0044] Figure 9(b) is a schematic diagram of the current distribution of port 2 excitation at the high frequency transmission zero point in the high frequency sub-passband 2.

[0045] Figure 9(c) is a schematic diagram of the current distribution of port 1 excitation at the low-frequency transmission zero point in the high-frequency sub-passband 2.

[0046] Figure 9(d) is a schematic diagram of the current distribution of port 2 excitation at the high frequency transmission zero in the low frequency sub-passband 1.

[0047] Figure 9(e) is a schematic diagram of the current distribution of port 1 excitation at the center frequency of the first passband;

[0048] Figure 10 This is a schematic diagram of the physical structure of an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter;

[0049] Figure 11 This is a schematic diagram of the final measurement results of an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter. Detailed Implementation

[0050] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0051] An embodiment of the present invention provides an ultra-narrowband high-temperature superconducting symmetric dual-channel filter, comprising:

[0052] First signal terminal, first resonator, second resonator, third resonator, fourth resonator, fifth resonator, sixth resonator, seventh resonator, eighth resonator, ninth resonator, tenth resonator, eleventh resonator, twelfth resonator and second signal terminal.

[0053] The first signal terminal, the first resonator, and the second resonator are sequentially positively coupled.

[0054] The second resonator, the third resonator, and the fourth resonator form a first triangular cross-coupled structure; the second resonator, the third resonator, and the fourth resonator are connected in a positively coupled manner in sequence; the second resonator and the fourth resonator are connected in a negatively coupled manner.

[0055] The fifth, sixth, seventh, and eighth resonators form a four-corner cross-coupled structure; the fourth, fifth, sixth, seventh, and eighth resonators are sequentially positively coupled; the fifth and eighth resonators are negatively coupled.

[0056] The ninth, tenth, and eleventh resonators form a second triangular cross-coupled structure; the ninth and tenth resonators are positively coupled; and the ninth and eleventh resonators, and the tenth and eleventh resonators are negatively coupled.

[0057] The eleventh resonator, the twelfth resonator, and the second signal terminal are sequentially positively coupled.

[0058] In an optional embodiment of the present invention, two transmission zeros (TZs) are introduced between the two passbands using two CT units, and the positions of the two transmission zeros can be freely adjusted, thereby controlling the sideband suppression between the two sub-passbands. Two out-of-band transmission zeros are introduced in pairs using CQ units, thereby improving the sideband suppression of the dual-passband filter. This topology not only improves filter performance but also enables precise control of the passband frequency and bandwidth.

[0059] This embodiment designs a folded compact double-helix microstrip resonator based on two CT (Cascaded Triplet) units and one CQ (Cascaded Quadruplet) unit. In this structure, the currents on adjacent microstrip lines flow in opposite directions, which can reduce the intensity of radiation from adjacent resonators, thereby reducing the coupling strength between resonators and facilitating the design of ultra-narrowband filters.

[0060] This embodiment establishes a dual-passband frequency response filter topology based on the introduction and modulation characteristics of transmission zeros by the CT and CQ units, such as... Figure 1As shown. Each digital node represents a resonator, and the lines connecting the nodes represent the coupling between the resonators. Solid lines represent positive coupling, and dashed lines represent negative coupling, the opposite of positive coupling. Generally, electrical coupling is considered positive coupling, producing a +90° phase shift. Magnetic coupling is considered negative coupling, producing a -90° phase shift. In this dual-passband filter topology, according to the multipath phase difference theory, the CT1 unit composed of resonators ②, ③, and ④ has a phase difference of 180° at frequencies above f0: the phase change of path ②→③→④ is -90°+90°-90°+90°-90°=-90° and the phase change of path ②→④ is -90°-90°-90°-90°=-270°. Therefore, a transmission zero can be introduced at the low frequency of sub-passband 2. Similarly, the phase difference between resonators ⑨, ⑩, and... The CT2 element, at locations below f0, has a path Phase change +90° +90° +90° -90° +90° = +270° and path The phase change of +90° - 90° + 90° = +90°, a difference of 180°, can introduce a transmission zero at the high frequency of sub-passband 1. The transmission zeros introduced by the two CT units are independent and can be used to adjust the sideband suppression characteristics of the stopband between the two sub-passbands. Similarly, in the dual-passband filter topology, the CQ unit composed of resonators ⑤, ⑥, ⑦, and ⑧, at frequencies above and below the dual-passband center frequency f0, shows a phase change of 180° between the path ⑤→⑥→⑦→⑧ and the path ⑤→⑧. Therefore, introducing a pair of transmission zeros at the low frequency of the low-frequency sub-passband 1 and the high frequency of the high-frequency sub-passband 2 of the dual-passband filter can improve the sideband suppression characteristics at the passband edges.

[0061] In an optional embodiment of the present invention, the characteristic polynomials of the single-passband transmission and reflection functions are extracted using a comprehensive analysis method, thereby extracting the frequency response of a dual-passband filter with specified transmission zeros and poles. Then, the response function of the dual-passband filter with equal relative bandwidth is obtained using the mirror frequency domain transformation method. Next, a coupling matrix consistent with the coupling topology is obtained through matrix similarity transformation. Finally, the correspondence between the physical model parameters and the coupling matrix is ​​obtained through EM simulation (electromagnetic simulation), thus realizing the design of the circuit physical model.

[0062] This embodiment, based on the transmission and reflection eigenvalues ​​of the generalized Chebyshev function, sets the frequency response of an asymmetric single-passband low-pass prototype filter with a return loss of 20dB and transmission zeros of [-1.082j, 2.209j] in the passband as shown in Figure 2(a). Using an s-domain symmetric transformation, this initial single-passband filter can be transformed into a dual-passband frequency response function with twice the order and number of transmission zeros. This dual-passband frequency response is symmetric about the zero frequency point, and the ripple in the initial passband and the sideband suppression levels of arbitrary lobes outside the band remain unchanged. The low-frequency band ranges from the upper sideband of the initial passband s = -j to s = -jx1, while the high-frequency band ranges from s = +jx1 to s = +j, where the piecewise parameters ±jx1 are given frequency points within the main passband and defined as the in-band frequency points of the two sub-passbands.

[0063] Therefore, the dual-passband characteristics can be obtained using symmetrical frequency transformation:

[0064] s = as' 2 +b

[0065] Where s′ is the frequency variable mapped from the prototype s-plane. Constants a and b are included in the following boundary conditions:

[0066] s′=±j,s=-a+b=+j

[0067] s′=±jx1,

[0068] achievable

[0069]

[0070] Thus, the transformation formula is obtained as follows:

[0071]

[0072] and

[0073]

[0074] Where i = 1, 2, ..., N. After transformation, the polynomials E(s) and F(s) of the low-pass prototype filter have N singularities in the s-plane and the polynomial P(s) has n singularities. fz The singularities will be mapped to 2N and 2n points respectively, each with dual passband characteristics. fz There are several singularities. Then, network synthesis is used to process these double-order polynomials to realize a dual-passband filter. Table 1 shows the positions of the reflection zeros and transmission zeros of the initially set asymmetric filter function in the s-plane. The dual-passband filter introduces finite frequency transmission zeros [±0.019j, ±1.257j], and the in-band return loss of the two sub-passbands is 20dB. The zeros and poles after transformation into a symmetric dual-passband filter are shown in Table 2.

[0075] Table 1. Zeros and poles of the transmission and reflection polynomials of a single passband filter.

[0076]

[0077] Table 2. Zeros and poles of the transmission and reflection polynomials of the dual-passband filter.

[0078]

[0079] Then, the two characteristic polynomials P(s) and F(s) of the dual-passband filter are respectively:

[0080] P(s) = s 4 +1.5807s 2 +0.0006

[0081] F(s)=s 12 +2.9652s 10 +3.2980s 8 +1.6997s 6

[0082] +0.4060s 4 +0.0396s 2 +0.0012

[0083] According to the Feld-Keller equations, P(s), F(s), and E(s) satisfy:

[0084]

[0085] The roots of E(s) can be obtained.

[0086] The transfer function and reflection function of a dual-passband filter can be expressed as:

[0087]

[0088] The obtained characteristic function of the dual-passband filter maintains the in-band return loss level of the single-passband filter, and its theoretical frequency response is shown in Figure 2(b). The coupling matrix of the dual-passband filter is extracted using the generalized Chebyshev function filter synthesis technique. Then, using the similarity transformation method introduced in [previous section], the matrix is ​​rotated and transformed into a 12th-order filter coupling topology with two CT and one CQ unit. The normalized coupling coefficients of the main couplings are [0.9999, 0.9876, 0.0710, 0.4129, 0.5898, 0.7182, 0.7867, 0.7204, 0.5911, 0.4235, -0.0600, 0.9992, 0.9989], and the cross-coupling part m 2,4,m 5,8 ,m 9,11 The coupling coefficients are [-0.6728, -0.2106, -0.6708], where negative numbers indicate the opposite characteristics to other couplings.

[0089] The specifications of the dual-passband high-temperature superconducting (HTS) filter designed in this embodiment are as follows.

[0090] (1) Subband center frequencies (MHz): 2495.75MHz (f1) and 2525.75MHz (f2);

[0091] (2) Subband bandwidth (MHz): 21.5MHz;

[0092] (3) Center frequency of dual-passband filter: 2510.75MHz (f0);

[0093] (4) Relative bandwidth of sub-passband: 0.86%@f0;

[0094] (5) Insertion loss in passband (dB): ≤0.2dB;

[0095] (6) Filter order: 12;

[0096] (7) Passband reflection (dB): ≤-10dB;

[0097] (8) Outside-passband inhibition (dB): ≥50dB.

[0098] The coupling matrix of the dual-passband filter can then be obtained by inverse normalization based on the normalized coupling matrix, as shown in Table 3 below.

[0099] Table 3. Coupling coefficients of dual-passband high-temperature superconducting filters

[0100]

[0101] Figure 3(a) shows the folded compact double-helix resonator designed in this embodiment, where the red arrows embedded in the resonator indicate the direction of the current on the microstrip lines. Figure 3(b) shows the current distribution at the center frequency of the resonator, where red indicates areas with stronger current, i.e., the left half of the resonator, and green indicates areas with stronger electric field, i.e., the right half of the resonator. The opposite current directions of adjacent microstrip lines in the double-helix structure cancel out the radiated electromagnetic field, reducing the intensity of radiation between adjacent resonators and significantly lowering the external coupling strength of the resonators. Therefore, the weak coupling requirement of ultra-narrowband can be achieved with a shortened adjacent distance, thereby reducing the overall physical size of the filter.

[0102] A planar microstrip dual-passband high-temperature superconducting filter was designed on a substrate of YBCO / MgO / YBCO high-temperature superconducting material with a thickness of 0.5 mm and a dielectric constant of 9.8. The following characteristics exist between the folded compact double-helix resonators: Figures 4(a) to 4(e) The coupling structure shown can be modified by changing the distance d between the resonators. i (i = 1, 2, 3, 4, 5) and the offset distance t i The coupling strength is controlled by using (i = 1, 2, 3, 4, 5). The distance between resonators and the corresponding coupling coefficient are as follows: Figure 5 As shown, the positional distance parameters between the resonators can be extracted based on the coupling coefficients in Table 3. Based on the resonant points during EM simulation of the coupling between the resonators, the formula... The coupling coefficient between two resonators can be calculated, where f p and f q S during coupled simulation 21 The resonant point is shown in Figure 6.

[0103] For this folded compact resonator, the length of the entire microstrip line of the resonator can be adjusted by adjusting the length of l in Figure 4(f), thereby adjusting the resonant frequency to be equal to the center frequency f0 = 2510.75MHz of the dual passband filter.

[0104] Figures 4(a)–4(e) show different resonator coupling methods that will produce different coupling types, with corresponding coupling resonant points and coupling phases as follows: Figures 6(a)-6(e) As shown. Based on the coupling phase variation curve, it can be seen that within the typical coupling range, coupling types I, III, and IV are electric field couplings, while coupling types II and V are magnetic field couplings. Therefore, by adjusting the different coupling types between the resonators, it is possible to achieve... Figure 1 Electromagnetic coupling required in the dual-passband filter topology of the CT and CQ units.

[0105] The method of loading the external coupling tap is shown in Figure 4(f), Q e The relationship between the tap distance and the distance h from the edge of the resonator is shown in Figure 6(f). Through analysis, we can find that the closer the tap is to the center of the resonator, the higher the Q... e The larger the value of Q, the better. Furthermore, within a suitable size range, Q... e The value can reach a range of 20 to 110. Finally, using a 50Ω line as a direct feed as a tap, the position of the tap is adjusted to make Q... e =63, thus meeting the quality factor requirement of this dual-passband high-temperature superconducting filter.

[0106] Based on the coupling parameters and the coupling matrix values ​​in Table 3, and by establishing the relationship between the coupling coefficients and physical parameters, a twelfth-order high-temperature superconducting dual-passband filter is designed. The final planar circuit design is as follows: Figure 7 As shown. In the first triangular cross-coupling structure, the terminal microstrip lines of the second and third resonators overlap in the same direction, the terminal microstrip lines of the second and fourth resonators overlap in opposite directions, and the side microstrip lines of the third and fourth resonators overlap. The terminal microstrip lines of the first and second resonators overlap relatively. In the quadrangular cross-coupling structure, the terminal microstrip lines of the fifth and eighth resonators overlap in opposite directions, the terminal microstrip lines of the sixth and seventh resonators overlap relatively, the side microstrip lines of the fifth and sixth resonators overlap, and the side microstrip lines of the seventh and eighth resonators overlap. The terminal microstrip lines of the fifth and fourth resonators overlap relatively. In the second triangular cross-coupling structure, the terminal microstrip lines of the ninth and eleventh resonators overlap in opposite directions, the side microstrip lines of the ninth and tenth resonators overlap, and the side microstrip lines of the tenth and eleventh resonators overlap. The terminal microstrip lines of the eighth and ninth resonators overlap relatively. The terminal microstrip lines of the eleventh and twelfth resonators overlap relatively. The circuit dimensions are 30.22mm × 12.14mm × 0.5mm (0.64 × 0.26λ). g , where λ g (This refers to the guide wavelength at the center frequency of the first passband). The final simulation results are as follows: Figure 8 As shown, the reflection within the passband is better than -20dB, the relative bandwidth of the two passbands is 0.86%@f0, and there is steep sideband suppression.

[0107] In Figures 9(a) and 9(b), the current distribution of the planar circuit is simulated using ports 1 and 2 as voltage sources at 2480.4MHz and 2543.6MHz (out-of-band transmission zeros in dual passbands), respectively. The signal attenuation caused by the CQ unit is evident. In Figure 9(c), the current distribution of the planar circuit is simulated using port 1 as a voltage source at 2512.4MHz (low-frequency transmission zeros in high-frequency sub-passband 2). The currents cancel each other out at CT1. In Figure 9(d), the current distribution of the planar circuit is simulated using port 2 as a voltage source at 2510.4MHz (high-frequency transmission zeros in low-frequency sub-passband 1). The currents cancel each other out at CT2. It can be seen that at the zeros, the signal, input through one port, travels through two paths of different phases and ultimately cancels each other out, resulting in a decrease in the transmitted signal power. Figure 9(e) shows the simulated current distribution at the first passband center frequency of 2495.75MHz, where the current in the planar circuit moves smoothly from one port to another.

[0108] The final design and fabrication physical structure of the high-temperature superconducting filter are as follows: Figure 10 As shown. The filter was placed in a vacuum chamber and tested using a vector network analyzer at 77K. The final measurement results are as follows. Figure 11 As shown in the figure. Analysis results indicate that the center frequencies of the two sub-passbands of the dual-passband filter are 2495.75MHz (f1) and 2525.75MHz (f2), with each sub-passband having a bandwidth of 21.5MHz. The reflection within the passband is better than -15dB, and the insertion loss is less than 0.2dB. A pair of transmission zeros outside the filter band are located at 2480.4MHz and 2543.6MHz, and two transmission zeros between the sub-passbands are located at 2510.8MHz and 2512.4MHz. Each sub-passband has six reflection zeros, and the sideband roll-offs of the four sidebands reach 12.8dB / MHz, 15.7dB / MHz, 19.4dB / MHz, and 11.6dB / MHz, respectively. Furthermore, the test results agree well with the simulation results.

[0109] Furthermore, Table 4 compares the dual-passband high-temperature superconducting filter designed in this embodiment with various other dual-passband filters. It can be seen that the dual-passband high-temperature superconducting filter based on CT and CQ topologies in this embodiment exhibits superior sideband suppression, roll-off characteristics, and in-band insertion loss characteristics. The CT unit provides sufficient control over the transmission zeros, enabling the adjustment of transmission zeros between the two sub-passbands. The CQ unit introduces a pair of transmission zeros at the boundary of the dual-passband filter, demonstrating the convenience of pairwise introduction and significantly improving sideband roll-off. The multi-zigzag double-helix resonator exhibits excellent advantages in achieving ultra-narrowband miniaturization, high sideband suppression, and low insertion loss. Furthermore, it effectively verifies the feasibility of the theoretical method of introducing multiple transmission zeros based on CT and CQ unit topologies to achieve dual-passband functionality.

[0110] This embodiment addresses the system requirements of high-performance dual-passband filters by establishing a high-order coupled topology based on CT and CQ units. This topology enables free adjustment of the zero positions between the two sub-passbands and the introduction of a pair of transmission zeros outside the dual-passband filter, achieving good sideband suppression between sub-passbands and throughout the entire dual-passband filter. The frequency domain transformation of the response functions from single-passband to multi-passband filters is described, and a typical 12th-order dual-passband filter topology model is presented. The coupling matrix is ​​extracted using synthesis and optimization methods. A folded compact double-helix microstrip resonator is proposed. By adjusting the internal and external coupling strength and electromagnetic coupling phase characteristics of the resonator, a dual-passband filter physical circuit is designed on YBCO / MgO / YBCO high-temperature superconducting material. The circuit principle, EM simulation, and test results all demonstrate good in-band and out-of-band characteristics, with good consistency in frequency and phase response, thus providing a better design method for dual-passband filters.

[0111] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0112] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An ultra-narrowband high-temperature superconducting symmetrical dual-channel filter, characterized in that, include: First signal terminal, first resonator, second resonator, third resonator, fourth resonator, fifth resonator, sixth resonator, seventh resonator, eighth resonator, ninth resonator, tenth resonator, eleventh resonator, twelfth resonator and second signal terminal. The first signal terminal, the first resonator, and the second resonator are sequentially positively coupled. The second resonator, the third resonator, and the fourth resonator constitute the first triangular cross-coupled structure; The second, third, and fourth resonators are connected in a positively coupled manner in sequence; The second resonator is negatively coupled to the fourth resonator; The fifth, sixth, seventh, and eighth resonators form a four-corner cross-coupled structure; The fourth, fifth, sixth, seventh, and eighth resonators are sequentially positively coupled. The fifth resonator is negatively coupled to the eighth resonator; The ninth, tenth, and eleventh resonators form a second triangular cross-coupling structure. The ninth resonator is positively coupled to the tenth resonator; The ninth resonator is negatively coupled to the eleventh resonator, and the tenth resonator is negatively coupled to the eleventh resonator. The eleventh resonator, the twelfth resonator, and the second signal terminal are sequentially positively coupled.

2. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 1, characterized in that, Each resonator is a folded, compact double-helix resonator.

3. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 2, characterized in that, In each resonator, the current directions of adjacent microstrip lines in the double-helix structure are opposite.

4. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 1, characterized in that, In the first triangular cross-coupling structure, the end microstrip lines of the second and third resonators are arranged in the same direction and overlap, the end microstrip lines of the second and fourth resonators are arranged in opposite directions and overlap, and the side microstrip lines of the third and fourth resonators are arranged in an overlapping manner.

5. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 4, characterized in that, The end microstrip lines of the first resonator and the second resonator are arranged to overlap.

6. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 1, characterized in that, In the four-corner cross-coupled structure, the end microstrip lines of the fifth and eighth resonators are arranged to overlap in opposite directions, the end microstrip lines of the sixth and seventh resonators are arranged to overlap in opposite directions, the side microstrip lines of the fifth and sixth resonators are arranged to overlap, and the side microstrip lines of the seventh and eighth resonators are arranged to overlap.

7. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 6, characterized in that, The end microstrip lines of the fifth resonator and the fourth resonator are arranged to overlap.

8. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 1, characterized in that, In the second triangular cross-coupling structure, the end microstrip lines of the ninth and eleventh resonators are arranged to overlap in opposite directions, the side microstrip lines of the ninth and tenth resonators are arranged to overlap, and the side microstrip lines of the tenth and eleventh resonators are arranged to overlap.

9. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 8, characterized in that, The end microstrip lines of the eighth and ninth resonators are arranged to overlap.

10. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 8, characterized in that, The microstrip lines at the ends of the eleventh and twelfth resonators are arranged to overlap.

Images