CN117154363A - Broadband filter with feeder resonator and applied to high-temperature superconductivity - Google Patents
Broadband filter with feeder resonator and applied to high-temperature superconductivity Download PDFInfo
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- CN117154363A CN117154363A CN202311221298.4A CN202311221298A CN117154363A CN 117154363 A CN117154363 A CN 117154363A CN 202311221298 A CN202311221298 A CN 202311221298A CN 117154363 A CN117154363 A CN 117154363A
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- 229910021521 yttrium barium copper oxide Inorganic materials 0.000 description 7
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
- H01P1/20309—Strip line filters with dielectric resonator
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/08—Strip line resonators
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Abstract
The invention relates to a high-temperature superconductive broadband filter with feeder line resonators, which is characterized by comprising a multimode resonator and two feeder line resonators with input and output ends coupled through a gap; the feeder resonator comprises a microstrip feeder and an external quality factor adjusting microstrip line Q eF Wherein the microstrip line Q is adjusted eF One end of the first feed line is connected with a 50 microstrip feed line, and the other end of the first feed line is connected with a first feed line structure; the first feed line structure is coupled to the input end of the multimode resonator through a slot, and the output end of the multimode resonator is coupled to the output end of the feed line resonator through the slot. The two feeder line resonators are of symmetrical structures, and the impedance values are equal. The two feeder resonators create additional transmission poles in the passband and increase filter bandwidth and selectivity. The invention designs the high-temperature superconductive wideband filter by adopting the feeder resonator method, which not only fully plays and expands the functions of the feeder, but also has small size, low loss and wide stop band,broadband, flexible design and the like.
Description
Technical Field
The invention belongs to the technical field of microwave communication, and relates to a broadband filter with a feeder resonator and applied to high-temperature superconductivity.
Background
In recent years, broadband technology has been widely used in high-speed communication systems due to its better user experience. Broadband filters are a key component of the system, and have been greatly developed in terms of both theoretical design and practical application. Many design methods are proposed successively, such as a cascaded high-pass and low-pass filter method, a parallel short-circuited microstrip line method, a suspended strip line method, a parallel coupled three-wire method, and a cascaded plurality of hairpin resonators, etc.
However, wideband filter designs with high steepness remain a significant difficulty because strong coupling can greatly degrade out-of-band rejection and selectivity. Multimode resonators are an efficient way to design a wideband filter. With the first few resonant modes of the multimode resonator, more transmission poles are introduced in the passband, thereby expanding the bandwidth and improving the selectivity. Another approach is the traditional approach to introducing more transmission poles is to increase the number of resonators. However, a larger number of resonators results in a larger filter size and also deteriorates the insertion loss, which is disadvantageous for practical use. To overcome this difficulty we propose a method of feeding the resonator where the feed is only used to provide sufficient external coupling and does not create additional transmission poles within the passband.
In the invention, the external coupling adjusting wire is introduced through researching the feeder line of the filter, and the electric length of the feeder line and the external coupling value, namely the external coupling quality factor, can be compensated through proper adjustment, so that the feeder line not only can provide enough external coupling, but also can generate additional transmission poles. The function of the filter is equivalent to that of a feeder resonator, so that the passband width and the steepness of the filter are greatly improved under the condition of not increasing the number of the traditional resonators, the size of the filter and the insertion loss.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a method for converting a filter feeder line into a resonator by using a broadband filter with a feeder line resonator, which is applied to the design of the high-temperature superconducting broadband filter, and the filter designed by the method can generate extra transmission poles and has the characteristics of wide passband, low loss, wide stopband, small size, strong out-of-band rejection, high steepness, simple design and the like.
Technical proposal
A high-temperature superconductive broadband filter with feeder line resonators is characterized by comprising a multimode resonator and two feeder line resonators with input and output ends coupled through a gap; the feeder resonator comprises a microstrip feeder and an external quality factor adjusting microstrip line Q eF A first tuning microstrip line Q of the first feeder resonator eF One end of the first feed line structure is connected with the 50 microstrip feed line 2, and the other end of the first feed line structure is connected with the first feed line structure 8; the first feeder structure 8 is coupled to the input of the multimode resonator via a slot, the output of the multimode resonator is coupled to the second feeder structure 16 of the second feeder resonator via a slot, and the second feeder structure 16 is connected to a second external quality factor adjusting microstrip line Q eF The microstrip line 11 is connected with a microstrip feeder 12 outputting 50Ω; the two feeder resonators generate additional transmission poles in the passband and increase filter bandwidth and selectivity; the microstrip line Q eF Length of l QeF And width w QeF Can be adjusted to tune the external figure of merit of the filter.
In the feeder resonator, a plurality of sections of serially connected microstrip lines which are in parallel open circuit are arranged on a first feeder structure 8 and a second feeder structure 16; the lengths and the widths of the microstrip lines connected in series in multiple sections are adjusted to adjust the impedance ratio between the microstrip lines to control the position of the out-of-band transmission zero point so as to improve the passband selectivity of the filter and improve the external quality factor.
The parallel multi-section series microstrip line is selected as three sections to form a three-mode feeder resonator; the three-mode feeder resonator structure at the input end is as follows: the first feeder line structure 8 is connected with three serially connected first section microstrip lines 6, second section microstrip lines 5 and third section microstrip lines 7 in parallel; the three-mode feeder resonator structure at the output end is as follows: the second feeder line structure 16 is connected in parallel with three serially connected fourth-section microstrip lines 15, fifth-section microstrip lines 13 and sixth-section microstrip lines 14; the microstrip lines are connected by adopting low-impedance lines.
The first feeder line structure 8 is connected with a first short auxiliary feeder line structure 4 in parallel; a second short auxiliary feed line structure 10 is connected in parallel to said second feed line structure 16.
The multimode resonator is one multimode resonator or a plurality of multimode resonators connected in series.
The multimode resonator adopts a five-section type double-mode resonator 9 with a step impedance structure, and the structure is that two sections of high impedance lines are connected to the middle part of a section of microstrip open line, and the two sections of high impedance lines are respectively connected with two sections of low impedance lines.
The high-temperature superconductive wideband filter formed by the five-section dual-mode resonator 9 and the three-section feeder resonator of the input end and the output end has 8 transmission poles in total in the passband, wherein two of the transmission poles are generated by the five-section dual-mode resonator, and the remaining six transmission poles are generated by the two three-mode resonators.
The edges of the passband of the broadband filter generate transmission zeros; the position of the transmission zero point is determined by the impedance ratio of a first section of microstrip opening line 6, a second section of microstrip opening line 5 and a third section of microstrip opening line 7 in the three-mode feeder resonator; the impedance ratio of the fourth section of microstrip line 15, the fifth section of microstrip line 13 and the sixth section of microstrip line 14 is consistent with that of the input end.
The odd mode input admittance of the five-section dual mode resonator 9 is:
odd mode resonant frequency f odd The method comprises the following steps:
Y 2 -Y 3 tanθ 2 tanθ 3 ＝0，
wherein Y is in-odd Input admittance of odd mode equivalent circuit, Y 2 And theta 2 For the characteristic admittance and electrical length of the high-impedance line, Y 3 And theta 3 Is the characteristic admittance and electrical length of the second impedance line.
The even mode frequency of the five-section dual-mode resonator 9 is:
the even mode input admittance is:
wherein: yin (yoin) 3 Input admittance of even mode equivalent circuit, Y 2 And theta 2 For the characteristic admittance and electrical length of the impedance line, Y 3 And theta 3 For the characteristic admittance and electrical length of the second impedance line, Y 1 And theta 1 Is the characteristic admittance and electrical length of the rightmost microstrip line.
Advantageous effects
The invention provides a broadband filter with a feeder resonator, which is applied to high-temperature superconductivity. With the new concept and new design of feeder resonators, not only can be used to provide external coupling, but also additional transmission poles can be generated in the passband to further increase the filter bandwidth and selectivity, and a high-performance high-temperature superconductive wideband filter is realized based on the method. The filter of the exemplary embodiment of the method design includes: left and right side feeder resonators, five-segment dual mode resonator and input/output 50Ω feeder. The left feeder line resonator and the right feeder line resonator are respectively composed of a first section microstrip line, a second section microstrip line, a third section microstrip line, a fourth section microstrip line, a fifth section microstrip line, a sixth section microstrip line, a first external quality factor adjusting line, a second external quality factor adjusting line, a first feeder line and a second feeder line structure, the feeder line structures can be converted into resonators through adjusting the external quality factor adjusting lines to reduce the overall size of the filter, the loaded microstrip opening line can generate controllable transmission zero points to increase the edge steepness of a passband on one hand, and can generate two poles to widen the passband range in the passband of the filter on the other hand. The five-section dual-mode resonator is composed of a step impedance microstrip line, and the function of the five-section dual-mode resonator is to generate dual-mode frequency and simultaneously push harmonic frequency multiplication to higher frequency so as to widen the width of an out-of-band stop band. The invention designs the high-temperature superconductive wideband filter by adopting the feeder resonator method, thereby not only fully playing and expanding the functions of the feeder, but also having the characteristics of small size, low loss, wide stop band, wide frequency band, flexible design and the like.
The impedance ratio of the microstrip lines of the feeder resonator can control the position of the out-of-band transmission zero point, so as to improve the passband selectivity of the filter. The feeder resonators at the input or output end form two three-mode feeder resonators together, so that more transmission poles can be provided for the passband to realize wider bandwidth.
The invention has the characteristics and specific beneficial effects that:
1. by introducing an external q-tuning line, the feed line can be converted into a resonator, which can be used not only to provide external coupling, but also to create additional transmission poles in the passband.
2. The input/output 50 ohm feeder is provided with a plurality of sections of microstrip lines with different impedances, so that the position of a transmission zero point can be controlled by adjusting the impedance ratio of the microstrip lines, a three-mode feeder resonator can be formed together with the feeder structure, and an additional transmission pole is provided in a band so as to increase the width of a pass band.
3. The high-temperature superconducting thin film has the characteristics of flexible design, compact structure and easy integration, and is suitable for manufacturing high-temperature superconducting thin films with high quality factors.
Drawings
FIG. 1 is a schematic diagram of a specific structure of a high-temperature superconductive wideband single-stage filter designed by a feeder resonator method in an embodiment of the present invention;
FIG. 2 is a schematic diagram of the structure of specific dimensional parameters of a single-stage filter of a superconducting broadband designed by a feeder resonator method in an embodiment of the present invention;
FIG. 3 illustrates the geometry of a conventional first order filter in an embodiment of the present invention;
FIG. 4S in the embodiment of the invention, the adjustment of the transmitted first order filter parameter S 11 Responding;
FIG. 5 an embodiment of the present invention incorporates an external quality factor (Q eF ) A feeder structure of the adjustment line;
FIG. 6 variation of external quality factor adjustment line width W in an embodiment of the invention QeF Influence on external figure of merit;
FIG. 7 illustrates an embodiment of the present invention in which a mid-bandwidth filter structure is implemented using a feeder resonator approach;
FIG. 8 illustrates a response of an example design of a bandwidth filter implemented using a feeder resonator approach in an embodiment of the present invention;
FIG. 9 shows the basic structure of a five-stage dual mode resonator in an embodiment of the present invention;
FIG. 10 is an odd mode equivalent circuit of a five-section dual mode resonator in an embodiment of the invention;
FIG. 11 is an even mode equivalent circuit of a five-section dual mode resonator in an embodiment of the present invention;
FIG. 12 illustrates an improved five-stage dual mode resonator structure in an embodiment of the present invention;
FIG. 13 at l in the embodiment of the invention 1 ＝2.94mm,l 2 ＝4.48mm,d 2 ＝0.06mm,l 3 ＝2.78mm,d 3 When=0.7 mm, change d 1 An odd mode even mode frequency point position change diagram;
FIG. 14 at d in the embodiment of the invention 1 ＝0.54mm,l 2 ＝4.48mm,d 2 ＝0.06mm,l 3 ＝2.78mm,d 3 When=0.7 mm, change l 1 An odd mode even mode frequency point position change diagram;
FIG. 15 is a schematic diagram of a stepped impedance open-circuit line composed of three microstrip lines of different impedances in an embodiment of the present invention;
FIG. 16 frequency bin position to impedance ratio k of the first two transmission zeroes generated by a loaded stepped impedance open circuit in an embodiment of the invention 1 And k 2 Is a relationship of (2);
FIG. 17 is a schematic diagram of a three-mode feed line resonator in an embodiment of the invention;
FIG. 18 is a pattern frequency distribution diagram of a single-stage filter of a superconducting wideband designed by a feeder resonator method in an embodiment of the invention;
FIG. 19 shows n transmission zero profiles of a high temperature superconducting wideband single stage filter designed using a feeder resonator approach in an embodiment of the present invention;
FIG. 20 is a graph of simulation results of a single-stage filter designed by a feeder resonator method in accordance with an embodiment of the present invention;
FIG. 21 is a graph showing the comparison between the simulation frequency response result and the actual measured frequency response result of a single-stage filter designed by using a feeder resonator method in the embodiment of the invention;
FIG. 22 shows a graph of measured insertion loss and group delay for a single-stage filter of a superconducting wideband designed using a feeder resonator approach in an embodiment of the present invention;
FIG. 23 is a schematic diagram of a two-stage filter with a wideband superconductive design using a feed line resonator approach in an embodiment of the present invention;
FIG. 24 is a schematic diagram of a three-stage filter structure for a superconducting wideband designed by a feeder resonator method in an embodiment of the invention;
FIG. 25 is a schematic diagram of a four-stage filter with a wideband superconducting design using a feed line resonator approach in an embodiment of the invention;
FIG. 26 is a simulation plot of the frequency response of a two-stage filter designed using the feeder resonator approach in an embodiment of the present invention;
FIG. 27 is a simulation plot of the frequency response of a three-stage filter designed using the feeder resonator approach in an embodiment of the present invention;
FIG. 28 is a comparison of simulation results of single, two, three and four-stage filters designed by a feeder resonator method in accordance with an embodiment of the present invention;
Detailed Description
The invention will now be further described with reference to examples, figures:
the embodiments described in the embodiments of the present invention are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without creative efforts, based on the embodiments of the present invention are included in the protection scope of the present invention.
The invention provides a method for designing a resonator and a feeder resonator, which is combined to obtain a drawing and an embodiment applied to a superconducting broadband filter, and the drawing and the embodiment are described in detail as follows:
the invention is applied to a high-temperature superconductive broadband filter structure, and comprises a multimode resonator and two feeder line resonators with input and output ends coupled through a gap.
The multimode resonator adopted by the embodiment of the invention is a five-section type double-mode resonator 9 with a step impedance structure, and the structure is that two sections of high impedance lines are connected in the middle of a section of microstrip open line, and the two sections of high impedance lines are respectively connected with two sections of low impedance lines. As can be seen in figure 12 of the drawings,
the structure of the broadband filter with the feeder resonator, which is applied to high-temperature superconductivity and is formed by adopting the five-section dual-mode resonator 9 and the feeder resonator provided by the invention, is shown in fig. 1 and fig. 2. The structure of the high-temperature superconducting wideband filter in which two five-stage dual-mode resonators 9 are connected in series is shown in fig. 23. The structure of the high-temperature superconducting wideband filter in which three five-stage dual-mode resonators 9 are connected in series is shown in fig. 24. The structure of the high-temperature superconducting wideband filter in which four five-stage dual-mode resonators 9 are connected in series is shown in fig. 24.
The embodiment of the invention discloses a high-temperature superconductive broadband single-stage filter designed by a feeder resonator method. The filter includes: the dielectric substrate 1 and the high-temperature superconductive film layer positioned on the dielectric substrate are used for constructing a filter circuit. The filter circuit includes: five-section dual-mode resonator 9, first section microstrip opening line 6, second section microstrip opening line 5, third section microstrip opening line 7, fourth section microstrip opening line 15, fifth section microstrip opening line 13, sixth section microstrip opening line 14, first external quality factor adjustment line 3, second external quality factor adjustment line 11, first feeder structure 8, second feeder structure 16, first and second short auxiliary feeder structures 410, input and output 50 ohm microstrip feeder 212, wherein:
the left side of the first external quality factor adjusting line 3 is connected with the 50 ohm microstrip feeder 2 at the input end, the other side of the first external quality factor adjusting line 3 is connected with the first section microstrip opening line 6 and the first feeder line structure 8 respectively, the first section microstrip opening line 6 is connected with the second section microstrip opening line 5, the second section microstrip opening line 5 is connected with the third section microstrip opening line 7, the first feeder line structure 8 is connected with the first short auxiliary feeder line structure 4, in addition, the five-section dual-mode resonator 9 is positioned at the center of the integral circuit, the left end and the right end of the five-section dual-mode resonator are respectively close to but not connected with the first feeder line structure 8 and the second feeder line structure 16, the right side of the second feeder line structure 16 is respectively connected with the second short auxiliary feeder line structure 10 and the second external quality factor adjusting line 11, in addition, the second external quality factor adjusting line 11 is connected with the fourth section microstrip opening line 15 and the output 50 ohm microstrip opening line 12, the fourth section microstrip opening line 15 is connected with the fifth section microstrip opening line 13, and the fifth section microstrip opening line 13 is connected with the sixth section microstrip opening line 14;
the whole circuit structure of the filter is in a central symmetry relationship.
The high-temperature superconducting film layer can be made of Yttrium Barium Copper Oxide (YBCO) or bismuth strontium calcium copper oxide.
The superconductive film is a superconductive material with critical temperature above 77K and resistance near zero, and can be used in liquid nitrogen (77K) refrigerating environment, and is mainly divided into two types: yttrium Barium Copper Oxide (YBCO) and bismuth strontium calcium copper oxide.
Compared with the conventional film material (such as copper), the high-temperature superconducting film has the characteristics of zero resistance, diamagnetism and the like in a superconducting state.
The top view of the upper layer radiating metal patch of the high temperature superconductive wideband single stage filter designed by the feeder resonator method in the embodiment of the present invention is shown in fig. 2, the specific parameter names are marked in the figure, meanwhile, it should be noted that the relevant simulation tool used in the present invention is Sonnet EM, the superconductive substrate used is MgO/YBCO, the dielectric constant of the substrate is 9.73, and the present embodiment is only one scheme.
Fig. 3 shows the geometry of a conventional first order filter, which is typically composed of a feed line coupled to the edges of the input and output resonators and then directly connected to a 50Ω microstrip line.
In the examples of the present invention we studied the simplest case, namely only one half-wavelength resonator, with two feed lines coupled in the following analysis, the substrates used had relative dielectric constants and thicknesses of 9.8 and 0.5mm, respectively. Lambda with a center frequency of 3.42GHz was designed g 2 (16.28 mm in length and 0.08mm in width) resonator. Two lambda g And/4 feeder (width 0.08mm, length 8.14 mm) directly connected with 50 ohm microstrip line. FIG. 4 is a graph showing the S11 response when the transmitted first order filter parameter S is adjusted, from S when the gap S is varied from 0.5mm to 0.1mm 11 Clearly identifying only one transmission pole in the passband, which is defined by lambda g And/2 resonator. While as s continues to decrease to 0.05mm and 0.02mm, two additional transmission poles appear in the passband, which means two lambda bars g The/4 feed creates two additional transmission poles in the passband, which act as two resonators, which we can refer to as feed resonators at this time. Based on the above analysis, we can know that the feeder produces a transmission pole that is conditional. Only in the case of very strong coupling can the feed line create a transmission pole. When s increases, the coupling becomes weak and the two transmission poles created by the feed line disappear. However, for many circuit fabrication techniques such as PCBs, the narrowest line widths and spacings are limited. On the other hand, in narrow-band or medium-bandwidth filter designs, the coupling is weak and the feed line cannot produce a transmission pole, which greatly limits the application.
In order to solve the above application problems. The invention provides a new method for converting the feeder line into the resonator, and realizes an additional transmission pole, which is not only suitable for the design of a broadband filter, but also suitable for a narrow-bandwidth and medium-bandwidth filter. As can be seen from fig. 5, the main design method is to add the first and second external quality factor adjusting lines 311 of the low impedance microstrip line between the original feeder line and the 50 ohm microstrip line, so as to adjust the external quality factor and coupling strength of the filter. FIG. 6 showsVarying external figure of merit adjusts line width W in embodiments of the invention ef From this we can see that the width W of the line is adjusted with the external figure of merit for the effect of the external figure of merit ef An increase in external figure of merit is also correspondingly increased, from which it can be stated that the width W of the external figure of merit adjustment line is adjusted ef The size of the external quality factor of the filter circuit can be effectively controlled, and the coupling strength is improved. Fig. 7 and 8 show the response of the design examples of the mid-bandwidth filter structure implemented by the feeder resonator method in the embodiment of the present invention and the mid-bandwidth filter implemented by the feeder resonator method in the embodiment of the present invention, respectively. As can be seen from the figure, the first-order filter designed by the feeder resonator method has obvious advantages compared with the response of the traditional first-order filter, on one hand, the feeder can be flexibly converted into the resonator, and two extra transmission poles are introduced in the band to widen the bandwidth, reduce the overall size of the filter circuit, reduce the cost and simultaneously avoid the problems of circuit manufacturing technical limitation and the like caused by excessively reducing the coupling spacing s for increasing the coupling strength.
Fig. 9 shows the basic structure and corresponding structural parameters of a five-section dual mode resonator in an embodiment of the present invention. The five-section dual-mode resonator is a special step impedance resonator formed by a plurality of sections of microstrip lines with different impedances, the structure of the resonator is a symmetrical structure, and by introducing a plane of symmetry plane T-T1, an odd mode and even mode equivalent circuit of the resonator can be obtained by using a parity mode analysis method, and the odd mode and even mode frequencies of the resonator can be calculated. Fig. 10 shows an odd mode equivalent circuit of a five-segment dual mode resonator in an embodiment of the present invention, whose odd mode input admittance can be represented by the following formula:
according to Y in-odd Resonance condition of=0, odd mode resonance frequency f odd The calculation can be made by the following formula:
Y 2 -Y 3 tanθ 2 tanθ 3 ＝0
wherein Y is in-odd Input admittance of odd mode equivalent circuit, Y 2 And theta 2 For the characteristic admittance and electrical length of the high-impedance line, Y 3 And theta 3 Is the characteristic admittance and electrical length of the second impedance line.
Obviously, the odd mode resonant frequency is not affected by the center short circuit by the analysis of the above equation.
FIG. 11 shows an even mode equivalent circuit of a five-segment dual mode resonator according to an embodiment of the present invention, similar to the odd mode analysis method, in which the even mode input admittance and the even mode frequency can be represented by the following formulas:
wherein: yin (yoin) 3 Input admittance of even mode equivalent circuit, Y 2 And theta 2 For the characteristic admittance and electrical length of the impedance line, Y 3 And theta 3 For the characteristic admittance and electrical length of the second impedance line, Y 1 And theta 1 Is the characteristic admittance and electrical length of the rightmost microstrip line.
In order to make the structure more compact and more suitable for coupling feeding, we have made folding improvement on the five-section dual-mode resonator structure shown in fig. 9, and the structure after folding improvement is shown in fig. 12. Simulation analysis is performed on the five-section dual-mode resonator after the subsequent folding improvement, and fig. 13 and fig. 14 respectively show the following steps in the embodiment of the invention 1 ＝2.94mm,l 2 ＝4.48mm,d 2 ＝0.06mm,l 3 ＝2.78mm,d 3 When=0.7 mm, change d 1 Odd-mode even-mode frequency point position change diagram and d in the embodiment of the invention 1 ＝0.54mm,l 2 ＝4.48mm,d 2 ＝0.06mm,l 3 ＝2.78mm,d 3 When=0.7 mm, change l 1 And an odd-mode even-mode frequency point position change diagram. When we will l 1 Is increased from 0.34mm in lengthBy 3.74mm, the even mode resonance frequency decreases from 6.5GHz to 4.1GHz, while the odd mode resonance frequency remains unchanged at 2.88 GHz. Similarly, when d 1 Increasing from 0.04mm to 1.04mm, the even mode frequency decreases from 5.6GHz to 4GHz, while the odd mode frequency remains unchanged at 2.88GHz, as can be seen from the above analysis, for the center low impedance line (with 2l 1 And d 1 Representation) affects only even mode frequencies with little effect on odd mode frequencies. Because in the odd mode the electrical wall and the low impedance line in the centre placed in the middle of the resonator are shorted. Compared with the traditional three-section step impedance resonator, the five-section dual-mode resonator has the advantages that even modes can be independently controlled, and the frequency band design freedom of the filter is improved.
Fig. 15 shows a schematic diagram of a stepped impedance open-circuit line composed of three microstrip lines of different impedance in an embodiment of the present invention. By loading the stepped impedance open circuit line, n transmission zeroes can be provided out of band of the filter, where the first two transmission zeroes (lower sideband transmission zeroes f) created in the stepped impedance open circuit line TZ1 Upper sideband transmission zero f TZ2 ) As an example. The position of the transmission zero point is related to the ratio of the different impedances of the three microstrip lines in the stepped impedance opening line, wherein the ratio of the impedance of the first section microstrip line to the impedance of the second section microstrip line is k 2 The impedance ratio of the third section microstrip line to the second section microstrip line is k 1 FIG. 16 shows the frequency bin position to impedance ratio k of the first two transmission zeroes generated by the loaded stepped impedance open circuit in an embodiment of the invention 1 And k 2 Is a relationship of (3). When k is 1 F increases from 0.2 to 10.2 TZ1 Reducing from 2.2GHz to 1.8GHz, f TZ2 Increasing from 5.5GHz to 6.2GHz. Representing the ratio k with impedance 1 Is increased by the transmission zero f TZ1 And f TZ2 Away from the central frequency f TZ1 +f TZ2 And/2, the filter bandwidth increases. In contrast, transmission zero f TZ1 ，f TZ2 With impedance ratio k 2 Moving toward the center frequency and the filter bandwidth decreases. Therefore, we can select the proper impedance ratio k 1 And k 2 To obtain the required filter bandwidth. At the same time, a step impedance open circuit line is loaded in a farther frequency band outside the bandN transmission zeros may still be provided as shown in fig. 19, from which it can be seen that the loading step impedance open circuit is effective to suppress harmonics and high frequency multiplication of the filter. The loaded stepped impedance open-loop line can also form a triple-mode feeder resonator structure with the coupled feeder in the embodiment of the invention shown in fig. 17 to create more transmission poles for the filter to expand the passband bandwidth. FIG. 18 shows the mode frequency distribution of a single-stage filter of a wideband superconducting designed by the feeder resonator method in an embodiment of the present invention, from which f can be seen 1 、f 2 、f 3 Three transmission poles generated by the three-mode feeder resonator in the embodiment of the invention are respectively, and two transmission poles f in the middle odd And f even Then it is generated for a five-segment dual-mode resonator and here the positions of the five transmission poles can be flexibly designed and adjusted.
FIG. 20 is a graph showing the simulation results of a high temperature superconductive wideband single stage filter designed by the feeder resonator method in accordance with an embodiment of the present invention. The passband range of the filter is 2.17-5.55GHz, the relative bandwidth is 97.4%, and the return loss is better than 20dB. Wherein eight transmission poles are shared within the passband, two identical three-mode feed line resonators produce six additional transmission poles, and a five-segment dual-mode resonator produces two transmission poles
To verify the practical applicability of the design method of the present invention, we fabricated a filter with a dielectric constant of 9.8 using a 0.5mm thick YBCO/MgO superconducting substrate. A 600nm thick YBCO superconducting film was deposited on the MgO substrate. The filters were packaged in a box and measured at 68K at-20 dBm input power. Fig. 21 and fig. 22 respectively show a comparison of a simulation frequency response result and an actual measurement frequency response result of a high-temperature superconducting wideband single-stage filter designed by a feeder resonator method in an embodiment of the present invention and an actual measurement insertion loss and a group delay diagram of the high-temperature superconducting wideband single-stage filter designed by the feeder resonator method in an embodiment of the present invention. From the figure, it can be seen that the passband is 2.26-5.54GHz, with a relative bandwidth of 95%. The maximum insertion loss is 0.33dB and the group delay is about 1ns. The return loss is better than 13.2dB. From-0.3 dB2.31 GHz to-40 dB2.075 GHz, the attenuation slope at the lower stop band is 168.9dB/GHz. At the higher stop band, the attenuation slope from-0.3 dB5.51 GHz to-40 dB5.645 GHz is 294.1dB/GHz, and the suppression effect is good. The rectangular coefficient is 1.116, and the measurement result and the simulation result are well matched.
In order to verify the universality of the design method theory of the feeder resonator, the following designs two-stage, three-stage and four-stage filter structures of the superconductive broadband as shown in figures 23, 24 and 25 respectively by using the design method of the feeder resonator. FIG. 26 shows a simulation of the frequency response of a high temperature superconducting wideband two-stage filter designed by the feeder resonator method in an embodiment of the invention, the passband of the two-stage filter is 2.28-5.44 GHz, and the relative bandwidth is 95%. From-0.5 dB (2.28 GHz) to-50 dB (2.05 GHz) at a lower stop band, the attenuation slope is 215.2dB/GHz dB, from-0.5 dB (5.44 GHz) to-50 dB (5.56 GHz) at a high stop band, the attenuation slope is 412.5dB/GHz, the out-of-band rejection effect is good, the rectangular coefficient is 1.111, and the high-pass band performance is achieved. FIG. 27 is a simulation of the frequency response of a high temperature superconductive wideband three-stage filter designed using the feeder resonator approach in an embodiment of the present invention. The passband is 2.26-5.48GHz, and the relative bandwidth is 95%. From-0.3 dB (2.285 GHz) to-60 dB (2.05 GHz) at a lower stop band, the attenuation slope is 213.2dB/GHz from-0.3 dB (5.44 GHz) to-60 dB (5.56 GHz) at a high stop band, the attenuation slope is 497dB/GHz the simulation results of the high-temperature superconducting broadband single-stage, two-stage, three-stage and four-stage filters designed by the feeder resonator method in the embodiment of the invention are compared, the out-of-band rejection is improved along with the increase of the filter order, and all the filters show excellent extremely sharp selectivity and strong engineering practical value.
In summary, the method for designing the feeder resonator applied to the high-temperature superconducting broadband filter can realize the conversion from the feeder to the resonator by adjusting the external quality factor adjusting line, and can be used for designing narrowband, intermediate-frequency and broadband filters. The feeder resonator consisting of the loaded step impedance open line and the coupled feeder can provide external coupling and generate additional transmission poles and n transmission zeros, which greatly improves the selectivity of the filter and expands the bandwidth. The design method of the feeder resonator applied to the high-temperature superconducting broadband filter provided by the invention is adopted to design single-stage, secondary, tertiary and quaternary filters. The measurement result is well matched with the simulation result, and the method has obvious engineering practical value. Besides, the invention has compact structure, small volume, flexible design, easy integration and convenient circuit processing; is suitable for manufacturing high-temperature superconductive films with high quality factors.
The foregoing has outlined rather broadly the more detailed description of embodiments of the invention, wherein the principles and embodiments of the invention are explained in detail using specific examples, the description of the embodiments being merely intended to facilitate an understanding of the method of the invention and its core concepts; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (10)
1. A high-temperature superconductive broadband filter with feeder line resonators is characterized by comprising a multimode resonator and two feeder line resonators with input and output ends coupled through a gap; the feeder resonator comprises a microstrip feeder and an external quality factor adjusting microstrip line Q eF A first tuning microstrip line Q of the first feeder resonator eF (3) One end of the first feeding line is connected with a 50 microstrip feeding line (2), and the other end of the first feeding line is connected with a first feeding line structure (8); the first feeder line structure (8) is coupled with the input end of the multimode resonator through a gap, the output end of the multimode resonator is coupled with the second feeder line structure (16) of the second feeder line resonator through a gap, the second feeder line structure (16) is connected with a second external quality factor adjusting microstrip line (11), and the microstrip line (11) is connected with a 50 omega microstrip feeder line (12) output; the two feeder resonators generate additional transmission poles in the passband and increase filter bandwidth and selectivity; the microstrip line Q eF Length of l QeF And width we QeF Can be adjusted to tune the external figure of merit of the filter.
2. The high temperature superconducting wideband filter with feed line resonator of claim 1, wherein: in the feeder resonator, a first feeder structure (8) and a second feeder structure (16) are provided with a plurality of sections of serially connected microstrip lines which are connected in parallel and open; the lengths and the widths of the microstrip lines connected in series in multiple sections are adjusted to adjust the impedance ratio between the microstrip lines to control the position of the out-of-band transmission zero point so as to improve the passband selectivity of the filter and improve the external quality factor.
3. The high temperature superconducting wideband filter with feed line resonator of claim 2, wherein: the parallel multi-section series microstrip line is selected as three sections to form a three-mode feeder resonator; the three-mode feeder resonator structure at the input end is as follows: the first feeder line structure (8) is connected with three serially connected first section microstrip lines (6), second section microstrip lines (5) and third section microstrip lines (7) in parallel; the three-mode feeder resonator structure at the output end is as follows: the second feeder line structure (16) is connected in parallel with three serially connected fourth-section microstrip lines (15), fifth-section microstrip lines (13) and sixth-section microstrip lines (14); the microstrip lines are connected by adopting low-impedance lines.
4. A high temperature superconducting wideband filter having a feeder resonator as claimed in claim 1 or claim 2 or claim 3 wherein: the first feeder line structure (8) is connected with a first short auxiliary feeder line structure (4) in parallel; a second short auxiliary feeder structure (10) is connected in parallel to the second feeder structure (16).
5. The high temperature superconducting wideband filter with feed line resonator of claim 1, wherein: the multimode resonator is one multimode resonator or a plurality of multimode resonators connected in series.
6. The high temperature superconducting wideband filter with feed line resonator of claim 1, wherein: the multimode resonator adopts a five-section type double-mode resonator (9) with a step impedance structure, and the structure is that two sections of high impedance lines are connected to the middle part of a section of microstrip open line, and the two sections of high impedance lines are respectively connected with two sections of low impedance lines.
7. The high temperature superconducting wideband filter with feeder resonator of claim 3 or 7, wherein: the high-temperature superconductive wideband filter formed by the five-section type dual-mode resonator (9) and the three-section type feeder resonator of the input end and the output end has eight transmission poles in total in the passband, wherein two of the eight transmission poles are generated by the five-section type dual-mode resonator, and the remaining six transmission poles are generated by the two three-mode resonators.
8. A high temperature superconducting wideband filter having a feeder resonator as claimed in claim 3, wherein: the edges of the passband of the broadband filter generate transmission zeros; the position of the transmission zero point is determined by the impedance ratio of a first section of microstrip open line (6), a second section of microstrip open line (5) and a third section of microstrip open line (7) in the three-mode feeder resonator; the impedance ratio of the fourth section microstrip line (15), the fifth section microstrip line (13) and the sixth section microstrip line (14) is consistent with that of the input end.
9. The high temperature superconducting wideband filter with feed line resonator of claim 7, wherein: the odd mode input admittance of the five-section dual-mode resonator (9) is as follows:
odd mode resonant frequency f odd The method comprises the following steps:
Y 2 -Y 3 tanθ 2 tanθ 3 ＝0，
wherein Y is in-odd Input admittance of odd mode equivalent circuit, Y 2 And theta 2 For the characteristic admittance and electrical length of the high-impedance line, Y 3 And theta 3 Is the characteristic admittance and electrical length of the second impedance line.
10. The high temperature superconducting wideband filter with feed line resonator of claim 7, wherein: the even mode frequency of the five-section dual-mode resonator (9) is as follows:
the even mode input admittance is:
wherein: yin (yoin) 3 Input admittance of even mode equivalent circuit, Y 2 And theta 2 For the characteristic admittance and electrical length of the impedance line, Y 3 And theta 3 For the characteristic admittance and electrical length of the second impedance line, Y 1 And theta 1 Is the characteristic admittance and electrical length of the rightmost microstrip line.
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