Ultra-narrow-band high-temperature superconductive symmetrical dual-channel filter

Abstract

The invention relates to the technical field of dual-passband filters, and discloses an ultra-narrow-band high-temperature superconducting symmetric dual-channel filter. According to the dual-passband filter, a high-order coupling topological structure based on CT and CQ units is established, free regulation and control of the zero point position between two sub-passbands can be realized, a pair of transmission zero points can be introduced out of the band of the dual-passband filter in pairs, and good sideband suppression between the sub-passbands and out of the band of the whole dual-passband filter can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of dual-passband filters, and in particular to an ultra-narrowband high-temperature superconducting symmetrical dual-channel filter. Background Art

[0002] As the demand for higher data rates and efficient spectrum utilization in wireless systems continues to grow, microwave components and systems that support multiple frequency bands have become critical. Among them, dual-passband filters can ensure efficient operation of two different frequency bandwidths and are ideal for modern dual-band microwave systems. There are usually three ways to design 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 adjusted independently, but the filter size is usually large. The second is a design based on multimode resonators, including stepped impedance resonators (SIRs) and branch load resonators (SLRs). This method can achieve compact size and large bandwidth ratio, but it is usually used in ultra-high frequency (UHF) and higher frequency bands, and it is difficult to design the passband and bandwidth independently. The third method is to implement it through a high-order coupling matrix. This method has clear design logic and can accurately control the frequency response of the filter, but as the coupling order increases, the loss of the filter will deteriorate. If a high-order coupled dual-passband filter is designed using high-temperature superconducting materials, it can simultaneously have excellent performance such as low insertion loss, high selectivity and compact size. These characteristics make HTS filters ideal for high spectral density scenarios such as communication systems, satellite transceivers, and wireless networks. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides an ultra-narrow-band high-temperature superconducting symmetrical dual-channel filter.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0005] An ultra-narrow-band high-temperature superconducting symmetrical dual-channel filter, comprising:

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

[0007] The first signal end, the first resonator and the second resonator are positively coupled and connected in sequence;

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

[0009] The fifth resonator, the sixth resonator, the seventh resonator and the eighth resonator form a four-corner cross-coupling structure; the fourth resonator, the fifth resonator, the sixth resonator, the seventh resonator and the eighth resonator are positively coupled in sequence; the fifth resonator is negatively coupled to the eighth resonator;

[0010] The ninth resonator, the tenth resonator and the eleventh resonator 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;

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

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

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

[0014] Furthermore, in the first triangular cross-coupling structure, the end microstrip lines of the second resonator and the third resonator are overlapped in the same direction, the end microstrip lines of the second resonator and the fourth resonator are overlapped in opposite directions, and the side microstrip lines of the third resonator and the fourth resonator are overlapped.

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

[0016] Furthermore, in the four-corner cross-coupling structure, the end microstrip lines of the fifth resonator and the eighth resonator are arranged to overlap back to back, the end microstrip lines of the sixth resonator and the seventh resonator are arranged to overlap relatively, the side microstrip lines of the fifth resonator and the sixth resonator are arranged to overlap, and the side microstrip lines of the seventh resonator and the eighth resonator are arranged to overlap.

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

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

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

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

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

[0022] The present invention uses two CT units to introduce two transmission zeros (TZs) between two passbands, and can realize free regulation of the positions of the two transmission zeros, 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 topological structure not only improves the filter performance, but also can realize precise control of the passband frequency and bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] FIG2(a) is a schematic diagram of the s-domain function response of an asymmetric low-pass prototype filter;

[0025] FIG2( b ) is a schematic diagram of the s-domain function response of the transformed dual-passband low-pass prototype filter;

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

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

[0028] FIG4( a ) is a schematic diagram of coupling type I between resonators;

[0029] FIG4( b ) is a schematic diagram of coupling type II between resonators;

[0030] FIG4( c ) is a schematic diagram of coupling type III between resonators;

[0031] FIG4( d ) is a schematic diagram of coupling type IV between resonators;

[0032] FIG4( e ) is a schematic diagram of coupling type V between resonators;

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

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

[0035] FIG6( a ) is a schematic diagram of a coupling phase variation curve of coupling type I between resonators;

[0036] FIG6( b ) is a schematic diagram of a coupling phase variation curve of coupling type II between resonators;

[0037] FIG6( c ) is a schematic diagram of a coupling phase variation curve of coupling type III between resonators;

[0038] FIG6( d ) is a schematic diagram of a coupling phase variation curve of coupling type IV between resonators;

[0039] FIG6( e ) is a schematic diagram of a coupling phase variation curve of coupling type V between resonators;

[0040] FIG6( f ) is a schematic diagram of a coupling phase variation curve of an external tap between resonators;

[0041] Figure 7 It is a schematic diagram of the planar circuit of an ultra-narrow-band high-temperature superconducting symmetrical dual-channel filter;

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

[0043] FIG9( a ) is a schematic diagram of the current distribution of the port 1 excited at the transmission zero point at the high frequency of the high frequency sub-passband 2;

[0044] FIG9( b ) is a schematic diagram of the current distribution of the port 2 excited at the transmission zero point at the high frequency of the high frequency sub-passband 2;

[0045] FIG9( c ) is a schematic diagram of the current distribution of the port 1 excited at the transmission zero point at the low frequency of the high frequency sub-passband 2;

[0046] FIG9( d ) is a schematic diagram of the current distribution of the port 2 excited at the transmission zero point at the high frequency of the low-frequency sub-passband 1;

[0047] FIG9( e ) is a schematic diagram of the current distribution of port 1 excitation at the center frequency of the first passband;

[0048] Fig.10 It is a schematic diagram of the physical structure of the ultra-narrow-band high-temperature superconducting symmetrical dual-channel filter;

[0049] Fig.11 Schematic diagram of the final measurement results of the ultra-narrowband high-temperature superconducting symmetrical dual-channel filter. DETAILED DESCRIPTION

[0050] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0051] An ultra-narrowband high-temperature superconducting symmetrical dual-channel filter provided by an embodiment of the present invention comprises:

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

[0053] The first signal end, the first resonator and the second resonator are positively coupled and connected in sequence;

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

[0055] The fifth resonator, the sixth resonator, the seventh resonator and the eighth resonator form a four-corner cross-coupling structure; the fourth resonator, the fifth resonator, the sixth resonator, the seventh resonator and the eighth resonator are positively coupled in sequence; the fifth resonator is negatively coupled to the eighth resonator;

[0056] The ninth resonator, the tenth resonator and the eleventh resonator 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;

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

[0058] In an optional embodiment of the present invention, two CT units are used to introduce two transmission zeros (TZs) between the two passbands, and the positions of the two transmission zeros can be freely adjusted to control the sideband suppression between the two sub-passbands. Two out-of-band transmission zeros are introduced in pairs using CQ units to improve the sideband suppression of the dual-passband filter. This topology not only improves the filter performance, but also can achieve 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. The currents on adjacent microstrip lines of this structure flow in opposite directions, which can reduce the intensity of radiation from adjacent resonators, thereby reducing the coupling strength between resonators, which is beneficial to the design of ultra-narrowband filters.

[0060] This embodiment establishes a filter topology with a dual-passband frequency response based on the introduction and regulation characteristics of the transmission zero point of the CT and CQ units, such as Figure 1As shown. Each digital node represents a resonator, and the lines between the nodes represent the coupling between the resonators. The solid line is used to represent positive coupling, and the dotted line is used to represent negative coupling, which is opposite to the coupling characteristics of the positive coupling. Usually, the electric coupling is considered to be positive coupling, which produces a phase shift of +90°. The magnetic coupling is negative coupling, which produces a phase shift of -90°. In this dual-passband filter topology, according to the multi-path phase difference theory, the CT1 unit composed of resonators ②, ③ and ④, at a frequency higher than f0, the phase change of the path ②→③→④ -90°+90°-90°+90°-90°=-90° and the phase change of the path ②→④ -90°-90°-90°=-270° differ by 180°, so a transmission zero can be introduced at the low frequency of sub-passband 2. Similarly, the resonators ⑨, ⑩ and The CT2 unit composed of The phase change of +90°+90°+90°-90°+90°=+270° and the path The phase change of +90°-90°+90°=+90° differs by 180°, and a transmission zero can be introduced at the high frequency of sub-passband 1. The transmission zero pairs 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 above and below the dual-passband center frequency f0, the phase change of the path ⑤→⑥→⑦→⑧ is 180° different from the phase change of the path ⑤→⑧. Therefore, introducing a pair of transmission zeros at the low frequency of the low-frequency sub-passband 1 of the dual-passband filter and the high frequency of the high-frequency sub-passband 2 can improve the sideband suppression characteristics of the passband edge.

[0061] In an optional embodiment of the present invention, this embodiment extracts the characteristic polynomial of the single-passband transmission and reflection function by comprehensive analysis, thereby extracting the frequency response of the dual-passband filter with specified transmission zeros and poles. Then, the response function of the dual-passband filter with equal relative bandwidth is obtained by the image frequency domain transformation method, and again, the coupling matrix consistent with the coupling topology is obtained by matrix similarity transformation. Finally, the corresponding relationship between the physical model parameters and the coupling matrix is ​​obtained by EM simulation (electromagnetic simulation), so as to realize the design of the circuit physical model.

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

[0063] Therefore, the dual passband characteristics can be obtained by applying 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] Available

[0069]

[0070] So the transformation formula is

[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 singular points in the s plane and the polynomial P(s) has n singular points in the s plane. fz singular points will be mapped into 2N and 2n with dual passband characteristics respectively. fz singular points. Then the network synthesis method is used to process these double-order polynomials to realize the dual-passband filter. Table 1 shows the positions of the reflection zeros and transmission zeros of the initially set asymmetric filter function on the s plane. The transformed 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 transmission polynomial and reflection polynomial of single passband filter

[0076]

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

[0078]

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

[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 equation, P(s), F(s) and E(s) satisfy:

[0084]

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

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

[0087]

[0088] The characteristic function of the dual-passband filter obtained 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 technology, and then the matrix is ​​rotated and transformed into a 12th-order filter coupling topology with two CT and one CQ unit structure using the similarity transformation method introduced in, where the main coupling of the normalized coupling coefficient is [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] respectively, where negative numbers indicate 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) Sub-passband center frequencies (MHz): 2495.75 MHz (f1) and 2525.75 MHz (f2);

[0091] (2) Sub-passband bandwidth (MHz): 21.5 MHz;

[0092] (3) Dual-passband filter center frequency: 2510.75 MHz (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 internal reflection (dB): ≤-10dB;

[0097] (8) Passband suppression (dB): ≥50dB.

[0098] Then, according to the normalized coupling matrix, the coupling matrix of the dual-passband filter can be obtained by denormalization as shown in Table 3 below.

[0099] Table 3. Coupling coefficient of dual-passband high-temperature superconducting filter

[0100]

[0101] FIG3(a) is a folded compact double helix resonator designed in this embodiment, in which the red arrow embedded in the resonator indicates the direction of the current on the resonator microstrip line. FIG3(b) shows the current distribution at the center frequency of the resonator, in which red indicates where the current is relatively strong, i.e., the left half of the resonator, and green indicates where the electric field is relatively strong, i.e., the right half of the resonator. The current directions of adjacent microstrip lines in the double helix structure are opposite, which cancels out the radiated electromagnetic field, can reduce the intensity of radiation between adjacent resonators, and greatly reduce the external coupling strength of the resonator. Therefore, the weak coupling requirement of the ultra-narrow band can be achieved at a shortened adjacent distance, thereby reducing the overall physical size of the filter.

[0102] A planar microstrip dual-passband high-temperature superconducting filter is 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 are the characteristics of the folded compact double helix resonator: Figure 4(a) to Figure 4(e) The coupling structure shown can be realized by changing the distance d between the resonators. i (i=1,2,3,4,5) and the offset distance t i (i=1,2,3,4,5) to control the coupling strength. The distance between the resonators and the corresponding coupling coefficient are as follows Figure 5 As shown, the position distance parameter between the resonators can be extracted according to the coupling coefficient in Table 3. According to the resonance point of the coupling EM simulation between the resonators, the formula The coupling coefficient between the two resonators can be calculated as p and f q is S during coupled simulation 21 The resonance point is shown in Figure 6.

[0103] For this folded compact resonator, the length of the entire resonator microstrip line 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 = 2510.75 MHz of the dual-passband filter.

[0104] Different resonator coupling modes shown in Figures 4(a)–4(e) will produce different coupling types. The corresponding coupling resonance points and coupling phases are shown in Figures 4(a)–4(e). Figure 6(a)-Figure 6(e) As shown. According to the coupling phase change curve, within the typical coupling range, coupling types I, III and IV are electric field coupling, while coupling types II and V are magnetic field coupling. Then, by adjusting the different coupling types between resonators, it can be achieved Figure 1 The electromagnetic coupling required in the dual-passband filter topology of the CT and CQ units.

[0105] The way to load the external coupling tap is shown in Figure 4(f), Q e The relationship between the distance h between the tap and 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 smaller the Q e In addition, within the appropriate size range, Q e The value of can achieve a range of 20 to 110. Finally, use a 50Ω line to feed directly as a tap and adjust the position of the tap so that Q e =63, thereby meeting the quality factor requirement of the dual-passband high-temperature superconducting filter.

[0106] According to the coupling parameters and the coupling matrix values ​​in Table 3, by implementing the relationship between the coupling coefficient and the physical parameters, a 12th-order high-temperature superconducting dual-passband filter is designed. The final design of the planar circuit is as follows: Figure 7 As shown. In the first triangular cross-coupling structure, the end microstrip lines of the second resonator and the third resonator are arranged to overlap in the same direction, the end microstrip lines of the second resonator and the fourth resonator are arranged to overlap in opposite directions, and the side microstrip lines of the third resonator and the fourth resonator are arranged to overlap. The end microstrip lines of the first resonator and the second resonator are arranged to overlap relatively. In the four-corner cross-coupling structure, the end microstrip lines of the fifth resonator and the eighth resonator are arranged to overlap in opposite directions, the end microstrip lines of the sixth resonator and the seventh resonator are arranged to overlap relatively, the side microstrip lines of the fifth resonator and the sixth resonator are arranged to overlap, and the side microstrip lines of the seventh resonator and the eighth resonator are arranged to overlap. The end microstrip lines of the fifth resonator and the fourth resonator are arranged to overlap relatively. In the second triangular cross-coupling structure, the end microstrip lines of the ninth resonator and the eleventh resonator are arranged to overlap in opposite directions, the side microstrip lines of the ninth resonator and the tenth resonator are arranged to overlap, and the side microstrip lines of the tenth resonator and the eleventh resonator are arranged to overlap. The end microstrip lines of the eighth resonator and the ninth resonator are arranged to overlap relatively. The end microstrip lines of the eleventh resonator and the twelfth resonator are arranged to overlap relatively. The circuit size is 30.22mm×12.14mm×0.5mm(0.64×0.26λ g , where λ g is the guided 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, and the relative bandwidth of the two passbands is 0.86%@f0 with steep sideband suppression.

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

[0108] The final design and processing physical structure of the HTS filter is as follows Fig.10 The filter was placed in a vacuum chamber and tested with a vector network analyzer at 77K. The final measurement results are shown in Fig.11 As shown. The analysis results show that the center frequencies of the two sub-passbands of the dual-passband filter are 2495.75MHz (f1) and 2525.75MHz (f2), the bandwidth of each sub-passband is 21.5MHz, the reflection in 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 the two transmission zeros between the sub-passbands are located at 2510.8MHz and 2512.4MHz. There are 6 reflection zeros in each sub-passband, and the sideband roll-offs of the four sidebands are 12.8dB / MHz, 15.7dB / MHz, 19.4dB / MHz and 11.6dB / MHz respectively. The test results are in good agreement with the simulation results.

[0109] In addition, 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 the CT and CQ topologies in this embodiment exhibits superior sideband suppression and roll-off characteristics and in-band insertion loss characteristics. The CT unit has sufficient controllability over the transmission zero point, realizing the regulation of the transmission zero point between the two sub-passbands. The CQ unit introduces a pair of transmission zero points at the boundary of the dual-passband filter, showing the convenience of paired introduction and improving the sideband roll-off. The multi-twist double-helix resonator shows good advantages in achieving ultra-narrowband miniaturization, high sideband suppression and insertion loss. And it has well verified the feasibility of the theoretical method of introducing multiple transmission zero points and realizing dual passbands based on the CT and CQ unit topologies.

[0110] This embodiment is aimed at the system requirements of high-performance dual-passband filters. A high-order coupling topology based on CT and CQ units is established, which can realize the free regulation of the zero point position between the two sub-passbands and the introduction of a pair of transmission zero points outside the dual-passband filter band, so as to obtain good sideband suppression between the sub-passbands and outside the entire dual-passband filter band. The frequency domain transformation of the response function of a single passband to a multi-passband filter is described, and a typical topological structure model of a twelve-order dual-passband filter is given. The coupling matrix is ​​extracted by synthesis and optimization methods. A folded compact double-helix microstrip resonator is proposed. By regulating the internal and external coupling strength and electromagnetic coupling phase characteristics of the resonator, a physical circuit of a dual-passband filter is designed on YBCO / MgO / YBCO high-temperature superconducting material. The circuit principle, EM simulation and test results all show good in-band and out-of-band characteristics, and the frequency response and phase response are consistent, thus providing a better design method for the design of dual-passband filters.

[0111] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0112] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

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

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: The current directions of adjacent microstrip lines of the double helix structure in each resonator 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 resonator and the third resonator are overlapped in the same direction, the end microstrip lines of the second resonator and the fourth resonator are overlapped in opposite directions, and the side microstrip lines of the third resonator and the fourth resonator are overlapped.

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 with each other.

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

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

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 resonator and the eleventh resonator are arranged to overlap back to back, the side microstrip lines of the ninth resonator and the tenth resonator are arranged to overlap, and the side microstrip lines of the tenth resonator and the eleventh resonator 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 resonator and the ninth resonator are arranged to overlap with each other.

10. The ultra-narrowband high-temperature superconducting symmetrical dual-channel filter according to claim 8, characterized in that: The end microstrip lines of the eleventh resonator and the twelfth resonator are arranged to overlap with each other.

Images