Compact high-temperature superconducting filter and harmonic suppression method thereof

Abstract

The invention discloses a compact high-temperature superconducting filter, and belongs to the technical field of microwave communication. The invention discloses a compact wide-stop-band high-suppression high-temperature superconducting band-pass filter. The compact wide-stop-band high-suppression high-temperature superconducting band-pass filter is composed of two improved dual-mode resonators which are connected in a coupling mode, a fan-shaped stub line loaded on a feeder line, an input and output # imgabs0 # microstrip feeder line. The improved dual-mode resonator provided and adopted for the first time is composed of five sections of stepped impedance microstrip lines loaded with open-circuit stub lines, two modes of the improved dual-mode resonator can be generated, meanwhile, movement of spurious frequency can be controlled, harmonic waves are pushed away, and therefore the intrinsic stop band of the resonator is expanded, and the performance of the resonator is improved. Therefore, the resonator has natural superiority and compactness in the aspect of harmonic suppression. Compared with a traditional dual-mode resonator composed of five sections of stepped impedance microstrip lines, the dual-mode resonator is improved in the mode of loading the open-circuit stub lines, the stop band can be further widened, and out-of-band rejection can be further deepened.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave communication, relates to a high-temperature superconducting filter device, and in particular to a compact high-temperature superconducting filter and a harmonic suppression method thereof. Background Art

[0002] With the rapid development of wireless communications, radar, satellite communications and other fields and the increasing complexity of the electromagnetic environment, the performance of the filter directly affects the signal transmission and reception quality of the system, thus deriving the demand for high-performance filtering. High-temperature superconducting materials have extremely low resistivity and can provide extremely high Q values ​​in high-frequency signal transmission, enabling the filter to effectively suppress noise and interference and improve the selectivity and stability of the signal.

[0003] In modern communication systems, we are faced with complex signal environments, especially in high-frequency applications such as 5G and the Internet of Things. The interference received by the system is particularly strong, so the demand for wide stopband filters is further increased. Wide stopband means that the filter can suppress interference signals in a wider frequency range. The design of wide stopband can enhance the system's tolerance to interference signals and ensure communication quality. At the same time, the suppression level within the stopband range is equally important. The high suppression of the filter can effectively reduce interference to adjacent frequency bands and improve the spectrum utilization of the communication system. This plays an important role in increasing system capacity and reducing signal interference in limited spectrum resources.

[0004] The applicant has accumulated a lot of technologies in the field of filters, and has formed many technologies in high-temperature superconducting filters, from rapid design to parasitic passband suppression. The core patents are publication number CN116663476A, a high-order high-temperature superconducting filter and a method for rapid design of its circuit topology, and CN116526095A, a high-temperature superconducting ultra-wideband filter and a method for suppressing parasitic passband.

[0005] However, as modern electronic devices continue to develop towards thinness and high integration, the design of compact filters can greatly reduce the size of devices and improve integration. At the same time, compact design helps to reduce parasitic effects and further improve the performance of the filter. Therefore, compact wide-stopband high-suppression high-temperature superconducting bandpass filters have high application value, but at the same time, they are also challenging in design and implementation.

[0006] When designing a wide stopband high suppression filter, a step impedance microstrip line is a very common and effective structure, and CN116526095A has disclosed a style of a step impedance resonator. However, with the continuous development of filtering technology, the market needs a higher requirement for wide stopband high suppression filters. Summary of the invention

[0007] The purpose of the present invention is to solve the problems of spectrum utilization, interference suppression, device miniaturization and high performance in current high-frequency communication and radar systems, to meet the growing demand for high-frequency and high-performance devices in the fields of 5G, Internet of Things, millimeter-wave radar, etc., and proposes a compact high-temperature superconducting filter and its harmonic suppression method.

[0008] The technical solution of the present invention is to make improvements based on the step impedance resonator and the microstrip feeder, improve the step impedance resonator and add a short stub to form a compact filter with wide stopband and high suppression.

[0009] A compact high-temperature superconducting filter comprises a dielectric substrate on which a high-temperature superconducting film layer is arranged, and the high-temperature superconducting film layer constructs a filter circuit.

[0010] The filter circuit includes: an input feed line, at least one step impedance resonator structure, and an output feed line.

[0011] The input feeder and the output feeder are provided with a short stub and an auxiliary feeder, and the step impedance resonator structure is coupled and connected to the auxiliary feeder.

[0012] The coupling connection is that the step impedance resonator structure and the auxiliary feeder are close but not connected, and the two can achieve a coupling effect. The coupling connection of other components of the present invention is also similar. The short stub is used to provide a band-stop response, widen the stopband of the filter and enhance the stopband suppression.

[0013] Furthermore, the stub line can be in the shape of a fan, a semicircle, a square, etc. The step impedance resonator structure is an improved multi-section step impedance resonator structure, which is composed of multiple sections of microstrip lines with different impedances, realizing the function of an improved multi-section step resonator.

[0014] When designing a filter circuit, the number of sections of the multi-section step impedance resonator structure can be designed according to the center frequency, passband bandwidth, cutoff frequency, insertion loss, in-band ripple factor, in-band fluctuation, return loss, stopband suppression, delay, etc. of the filter. The multi-section step resonator can realize both odd-mode and even-mode modes, and is also called a dual-mode resonator.

[0015] Furthermore, the auxiliary feeder of the input feeder includes a wide portion of the input auxiliary feeder and a narrow portion of the input auxiliary feeder. The auxiliary feeder of the input feeder is coupled to the dual-mode resonator by winding and extending and coupled therewith, thereby performing coupled feeding.

[0016] Furthermore, the auxiliary feeder of the output feeder includes a wide portion of the output auxiliary feeder and a narrow portion of the output auxiliary feeder. The auxiliary feeder of the output feeder is coupled to the dual-mode resonator by winding and extending and coupled thereto, thereby outputting a signal.

[0017] Furthermore, two dual-mode resonators may be provided, the dual-mode resonators being multi-section step impedance structures, located at the center of the filter, one side of the two improved dual-mode resonators being close to each other to generate coupling, and presenting a centrally symmetrical structure.

[0018] Furthermore, two dual-mode resonators, an auxiliary feed line, and a short stub form an ear structure. The ear structure simulates the structure of a human ear and has the characteristics of compact structure and easy integration compared to traditional filters. It is suitable for the production of high-quality factor high-temperature superconducting films.

[0019] Features and beneficial effects of the present invention: 1. By improving the traditional step impedance resonator, a new improved multi-stage step impedance dual-mode resonator is proposed. This improvement broadens the stopband of the resonator and strengthens the stopband suppression.

[0020] 2. By loading short stubs on the input feeder and output feeder, the stopband is further widened and the stopband suppression is enhanced.

[0021] 3. The harmonic suppression structure used is compact and easy to integrate, and is suitable for the production of high-quality factor high-temperature superconducting films. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of a compact high temperature superconducting filter in an embodiment of the present invention; Figure 2 It is a geometric structure diagram of an improved five-section stepped impedance dual-mode resonator in an embodiment of the present invention; Figure 3 is an odd-mode equivalent circuit diagram of an improved five-section stepped impedance dual-mode resonator in an embodiment of the present invention; Figure 4 is an even-mode equivalent circuit diagram of an improved five-section stepped impedance dual-mode resonator in an embodiment of the present invention; Figure 5 Schematic diagram of the resonance modes of the improved five-section stepped impedance dual-mode resonator in an embodiment of the present invention; Figure 6 is an amplitude-frequency response curve diagram of a compact wide stopband high-suppression high-temperature superconducting bandpass filter in an embodiment of the present invention when no fan-shaped stub is loaded and the resonator is not improved; Figure 7 is an amplitude-frequency response curve diagram of a compact wide-stopband high-suppression high-temperature superconducting bandpass filter in an embodiment of the present invention without loading a fan-shaped stub; Figure 8 is an amplitude-frequency response curve diagram of a compact wide-stopband high-suppression high-temperature superconducting bandpass filter in an embodiment of the present invention when the resonator is not improved; Fig. 94 is an amplitude-frequency response curve of a compact wide-stopband high-suppression high-temperature superconducting bandpass filter in an embodiment of the present invention.

[0023] In the figure: 1. Dielectric substrate; 2. Input feed line; 3. Input stub; 4. Front step resonator; 5. Ear structure; 6. Rear step resonator; 7. Output stub; 8. Output feed line; 9. Input auxiliary feed line wide part; 10. Input auxiliary feed line narrow part; 11. Output auxiliary feed line narrow part; 12. Output auxiliary feed line wide part. DETAILED DESCRIPTION

[0024] The technical scheme in the embodiment of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiment of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The embodiments of the present invention are designed according to the principles of the present invention. The present invention is further described below in conjunction with the accompanying drawings and the following specific embodiments: Figure 1 The structure diagram of a compact high-temperature superconducting filter in the embodiment of the present invention is a preferred embodiment of the present invention. The filter designed by the present invention comprises: a dielectric substrate 1 and a high-temperature superconducting film layer located on the dielectric substrate, and the filter circuit is constructed in the high-temperature superconducting film layer.

[0025] The filter circuit comprises: an input feeder, at least one step impedance resonator structure, and an output feeder, wherein the input feeder and the output feeder are provided with a stub and an auxiliary feeder, and the step impedance resonator structure is coupled to connect the auxiliary feeder. In this embodiment, the input feed line and the output feed line are 50Ω microstrip feed lines, the short line is fan-shaped, and the step impedance resonator structure is provided with two. The two step resonators realized are called the front step resonator and the rear step resonator. The front step resonator and the rear step resonator are coupled and connected.

[0026] The front step resonator and the rear step resonator are improved five-section step impedance resonators.

[0027] The front step resonator and the rear step resonator are located at the center of the filter, one side of the front step resonator and the rear step resonator are close to each other to generate coupling, and they present a central symmetrical structure.

[0028] The front step resonator, the rear step resonator, the auxiliary feed line and the stub line constitute an ear structure, which is similar to the ear structure of the human body and is used to further suppress the spurious frequency of the dual-mode resonator and widen the stop band of the dual-mode resonator. At the same time, the ear structure makes the harmonic suppression structure adopted by the filter compact.

[0029] A compact high-temperature superconducting filter provides a bandpass response in the frequency range of 3GHz to 5GHz, forms a wide stopband with high suppression in the frequency range of 5GHz to 26GHz, and can also control the movement of spurious frequencies, push harmonics away, and thus expand the intrinsic stopband of the resonator.

[0030] It should be noted that the overall circuit structure of the filter is centrally symmetrical and compact, which effectively reduces the size of the filter, saves equipment space, helps integrate into complex systems, improves overall space utilization and integration, and helps ensure uniform distribution of electromagnetic fields, improves filtering accuracy, enhances selectivity for specific frequencies, and reduces the thermal load requirements on the refrigerator. The filter with this structure has outstanding effects in wide stopband high suppression. 0 The internal stopband suppression is greater than 30dB, which can effectively improve the interference caused by various frequency bands outside the band to the used frequency band, and can effectively improve the signal-to-noise ratio and anti-interference ability of the system. The experimental data are also explained below.

[0031] The relevant simulation tool used in the present invention is Sonnet EM, the superconducting substrate used in the dielectric substrate is MgO / YBCO, the dielectric constant of the substrate is 9.8, the length is 21.28 mm, the width is 5.5 mm, and the thickness is 0.5 mm. This implementation case is only a preferred embodiment.

[0032] Figure 2 This is the geometric structure of the improved five-section step impedance dual-mode resonator in the embodiment of the present invention. The improved five-section step impedance dual-mode resonator is a special step impedance resonator composed of multiple sections of microstrip lines with different impedances. Its structure is a symmetrical structure. By introducing the symmetry plane AB plane, the odd-mode and even-mode equivalent circuits can be obtained by the odd-mode and even-mode analysis method, and thus the odd-mode and even-mode frequencies can be calculated.

[0033] According to the different impedances, 5 microstrip lines Z1, Z2, Z3, Z4, and Z5 are defined. The impedance of each microstrip line is called Z1, Z2, Z3, Z4, and Z5 impedance. There is little difference between Z1 and Z5, and they can be considered to be approximately equal. Therefore, the odd-even mode analysis method can be used for simplified analysis. The impedance changes in different odd or even mode modes.

[0034] Figure 3The odd-mode equivalent circuit of the improved five-segment step impedance dual-mode resonator in the embodiment of the present invention is shown, and its odd-mode input impedance can be expressed by the following formula: When resonance occurs, , therefore, we can control the shift of the odd-mode resonant frequency by controlling the impedance ratio and calculate the odd-mode resonant frequency at the same time.

[0035] Figure 4 The even-mode equivalent circuit of the improved five-section step impedance dual-mode resonator in the embodiment of the present invention is shown. The traditional straight stubs loaded at both ends of the equivalent circuit and the upper part of the third microstrip line can constitute the fourth microstrip line. Therefore, the third microstrip line can be divided into two microstrip lines with the blue straight line CD as the dividing line, and the characteristic impedance of the lower microstrip line is , the electrical length is , the characteristic impedance of the lower part of the microstrip line is , the electrical length is , the even-mode input impedance of the even-mode equivalent circuit can be expressed as follows: Similar to the analysis method for odd-mode cases, we can also control the movement of the even-mode resonant frequency by controlling the impedance ratio and calculate the even-mode resonant frequency at the same time.

[0036] Figure 5 This is a schematic diagram of the resonant mode of the improved five-stage stepped impedance dual-mode resonator in an embodiment of the present invention. The curve shows the two resonant frequencies of the dual-mode resonator. After calculation, the lower resonant frequency is the odd-mode resonant frequency, and the higher resonant frequency is the even-mode resonant frequency.

[0037] Figure 6 The figure is the amplitude-frequency response curve of the compact wide stopband high-suppression high-temperature superconducting bandpass filter in the embodiment of the present invention when the fan-shaped stub is not loaded and the resonator is not improved. It can be seen that the return loss within the band is poor, and the harmonics begin to produce obvious response at about 12.5 GHz. The passband is close to the harmonic frequency, which will have a certain negative impact on the system.

[0038] Figure 7 The amplitude-frequency response curve of the compact wide stopband high-suppression high-temperature superconducting bandpass filter in the embodiment of the present invention without loading the fan-shaped short stub is shown. It can be seen that the return loss within the band is relatively Figure 6 Slightly better, harmonics begin to produce obvious responses around 20GHz, and the suppression effect is slightly poor in the stop band of 5GHz~20GHz, with the suppression degree less than 20dB.

[0039] Figure 8 The amplitude-frequency response curve of the compact wide stopband high-suppression high-temperature superconducting bandpass filter in the embodiment of the present invention when the resonator is not improved. It can be seen that the harmonics begin to produce obvious responses around 22.5GHz, and the suppression effect is relatively good in the stopband of 5GHz~22.5GHz. Figure 6 and Figure 7 Slightly better, but the suppression level is less than 25dB.

[0040] Fig. 9 The amplitude-frequency response curve of the compact wide stopband high-suppression high-temperature superconducting bandpass filter in the embodiment of the present invention is shown in FIG. Figure 6 , Figure 7 and Figure 8 The harmonics only start to respond significantly at around 26GHz, and the suppression effect is good in the stopband of 5GHz~26GHz, with a suppression degree of more than 30dB. Since the operating frequency of the bandpass filter is 3GHz~5GHz, the return loss in the band is better than 15dB, the loss is less than 0.12dB, and the center frequency is 4GHz, the filter can provide 6.5f 0 High performance stopband range.

[0041] Will Figure 7 and Fig. 9 By comparison, it can be seen that the fan-shaped stub loaded on the feeder can significantly suppress harmonics and widen the stopband, thanks to the flat and wide band-stop response provided by the fan-shaped stub.

[0042] Will Figure 8 and Fig. 9 By comparison, it can be seen that our improvements to the traditional step impedance resonator have achieved good results, further deepening the out-of-band suppression of the filter and widening the stopband.

[0043] The compact high-temperature superconducting filter designed by the method in this embodiment has the characteristics of wide stopband, high suppression and good compactness. The harmonic technology used provides a new idea for the design of high-temperature superconducting ultra-wide stopband bandpass filters.

[0044] The embodiments of the present invention are described in detail above. This paper uses specific examples to illustrate the principles and The implementation methods have been explained, and the description of the above embodiments is only used to help understand the method of the present invention and its core idea, and it should be understood that the scope of protection of the present invention is not limited to such special statements and embodiments; at the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A compact high temperature superconducting filter, comprising a dielectric substrate, characterized in that: A high-temperature superconducting film layer is provided on the dielectric substrate, and the high-temperature superconducting film layer constructs a filter circuit. The filter circuit includes: an input feeder, at least one step impedance resonator structure, and an output feeder. The input feeder and the output feeder are provided with a short stub and an auxiliary feeder. The step impedance resonator structure is coupled and connected to the auxiliary feeder. The step impedance resonator structure realizes the resonator function. The step impedance resonator structure, the auxiliary feeder, and the short stub constitute an ear structure. The short stub is used to provide a band-stop response, widen the stopband of the filter, and enhance the stopband suppression.

2. A compact high temperature superconducting filter according to claim 1, characterized in that: The step impedance resonator structure is a multi-section step impedance resonator structure, which is composed of multiple sections of microstrip lines with different impedances. Two multi-section step impedance resonator structures are provided to realize the functions of two multi-section step resonators. The multi-section step resonator can realize both odd-mode and even-mode modes, and the short stub can be fan-shaped, semicircular, or square.

3. A compact high temperature superconducting filter according to claim 2, characterized in that: It includes an input feed line, a front step resonator, a rear step resonator and an output feed line. The input feed line and the output feed line are 50Ω microstrip feed lines. The stub is fan-shaped. The front step resonator and the rear step resonator are coupled and connected. The front step resonator and the rear step resonator are five-section step impedance resonators.

4. A compact high temperature superconducting filter according to claim 3, characterized in that: The auxiliary feeder of the input feeder comprises a wide portion of the input auxiliary feeder and a narrow portion of the input auxiliary feeder. The auxiliary feeder of the input feeder is coupled to the front step resonator by winding and extending and is coupled thereto, thereby performing coupled feeding.

5. A compact high temperature superconducting filter according to claim 3, characterized in that: The auxiliary feeder of the output feeder comprises a wide portion of the output auxiliary feeder and a narrow portion of the output auxiliary feeder. The auxiliary feeder of the output feeder is coupled to the rear step resonator by winding and extending and is coupled thereto, thereby outputting a signal.

6. A compact high temperature superconducting filter according to claim 3, characterized in that: The front step resonator and the rear step resonator are located at the center of the filter. The front step resonator and one side of the rear step resonator are close to each other to generate coupling and present a centrally symmetrical structure. The front step resonator, the rear step resonator, the auxiliary feeder and the short stub constitute an ear structure. The ear structure makes the harmonic suppression structure adopted by the filter compact.

7. The compact high temperature superconducting filter according to claim 1, characterized in that: The superconducting substrate used in the dielectric substrate is MgO / YBCO, the dielectric constant of the substrate is 9.8, the length is 21.28 mm, the width is 5.5 mm, and the thickness is 0.5 mm.

8. A harmonic suppression method, characterized in that: The compact high-temperature superconducting filter using any one of claims 1-7, the front-step resonator and the rear-step resonator can not only generate two modes of the resonator, but also control the movement of the stray frequency, push the harmonics away, and thus expand the intrinsic stopband of the resonator. The ear structure provides a band-stop response by short-circuiting high-frequency signals within a certain frequency range, thereby widening the stopband of the filter and enhancing the stopband suppression.

9. A harmonic suppression method according to claim 8, characterized in that: It provides a bandpass response in the frequency range of 3GHz~5GHz. By controlling the movement of spurious frequencies, the harmonics are pushed away to expand the intrinsic stopband of the resonator, thereby forming a wide stopband with high suppression in the frequency range of 5GHz~26GHz.

10. A harmonic suppression method according to claim 8, characterized in that: The stopband suppression within 6.5f0 is greater than 30dB, which can effectively improve the interference caused by various out-of-band frequency bands to the used frequency band, and can effectively improve the system's signal-to-noise ratio and anti-interference ability.

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