A resonator and compact ultra-narrow band high temperature superconducting filter

Abstract

The application discloses a resonator and a compact ultra-narrow-band high-temperature superconducting filter, which adopts SISO spiral structure and interdigital structure to form a dual composite left-right hand resonator in parallel, wherein the interdigital structure forms an open end of the resonator, the SISO spiral structure forms a closed end of the resonator, and the interdigital structure is composed of a plurality of mutually parallel interdigital branches; the interdigital structure is used for introducing a left-hand capacitor and increasing an equivalent capacitance of the resonator; a first end of the interdigital structure is directly connected with a microstrip line and spirals in a clockwise direction, spirals out in a counterclockwise direction along the microstrip line at a rotation center, bypasses the interdigital structure, is connected to a second end of the interdigital structure to form the SISO spiral structure; and the overall filter size can be greatly reduced, the insertion loss in a passband of the filter, the out-of-band suppression capability, the roll-off coefficient of a transition band are greatly improved, and the selectivity of the filter is enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microwave communication technology, and particularly relates to a resonator and a compact ultra-narrow-band high-temperature superconducting filter. BACKGROUND

[0002] With the rapid development of wireless communication technology, spectrum resources are becoming increasingly scarce, and wireless communication conditions are becoming increasingly demanding. Various types of military and civilian wireless communication devices are emerging, and there is an urgent need for filters with strong anti-interference ability and high selectivity to filter out out-of-band electromagnetic interference and cross-talk between different communication lines, thereby improving communication quality. At present, with the continuous development of space science and technology and the proposal of the concept of space Internet, space satellite communication has gradually entered the field of view of people's attention. Military / civilian communication satellites, remote sensing satellites, Mars communication satellites, etc. have become the research focus of many research institutes and universities, especially the field of space VHF shortwave communication, which has many advantages, such as long communication distance, flexible networking, strong concealment, etc., and is widely used in aviation communication, maritime communication, radio detection, and national defense, becoming one of the focuses of researchers. However, the spectrum resources in the VHF frequency band are very scarce, there are many electromagnetic interferences, and cross-talk easily occurs between different application signals, which deteriorates the communication quality. Therefore, in order to establish a reliable communication network in a complex space environment at a long distance, a high-performance filter is needed to filter out out-of-band interference and increase communication reliability.

[0003] Compared with traditional bandpass filters, compact filters are more in line with the miniaturization requirements of modern communication systems, can better cope with the challenges of high integration and multi-functional device fusion in modern communication, and can be applied to large-scale precision equipment such as the front end of national defense encryption communication systems and high-sensitivity receivers / transmitters. The traditional bandpass filter is composed of cascaded half-wavelength or quarter-wavelength resonators. If the operating center frequency of the bandpass filter is low, such as the VHF frequency band (30-300 MHz), the size of the general half-wavelength resonator is greater than 50 cm, which leads to a proportional increase in the overall filter size. Such a huge filter wastes overall device space resources and cannot be installed with high-integration precision equipment. Therefore, in the design of filters in the VHF / UHF low-frequency band, the miniaturization design of resonators becomes one of the key steps in the overall filter design of compact ultra-narrow-band high-temperature superconducting filters. At the same time, in the design of filters composed of cascaded multi-order resonators, the coupling distance between adjacent resonators also determines the overall filter size. The coupling strength required between adjacent resonators of a general narrow-band filter is small, and the coupling distance increases, which greatly limits the miniaturization design requirements of the filter. For narrow-band / ultra-narrow-band filters, how to achieve the weak coupling required by narrow-band filters in a small distance becomes one of the key factors for the application of narrow-band / ultra-narrow-band filters in low-frequency bands to high-integration, miniaturized systems or equipment.

[0004] High-temperature superconducting material has extremely high quality factor (Q value) because its surface resistance is almost 0 in low-temperature environment. Therefore, after the high-temperature superconducting material was discovered in the 1980s, it has been widely applied in the field of radio frequency and microwave communication in recent years. People usually use the material to make microstrip circuits, especially microstrip filters. Because the surface resistance of the material is almost 0, the filter made of the high-temperature superconducting material has extremely low insertion loss, so that the ability to suppress out-of-band interference of the filter can be increased by cascading multiple resonators to improve the selectivity. The high-temperature superconducting filter has many advantages, such as extremely high band edge steepness, low in-band insertion loss, high unloaded quality factor of resonator, etc. The performance of the filter is closer to the ideal filter, and the filter has the characteristics of small circuit size and light weight, which can be applied to mobile communication base stations, satellite communication systems, radio astronomy receivers, etc. The filter can reduce the interference of adjacent frequency bands, improve the communication quality between communication equipment and base stations, and improve the sensitivity of radio astronomy receivers. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a resonator and a compact high-temperature superconducting filter with extremely narrow band, wherein the resonator has the advantages of miniaturization and high Q value by using a dual composite left-handed and right-handed resonator composed of SISO spiral structure and interdigital structure in parallel. The interdigital structure introduces left-handed parallel capacitance to increase the equivalent capacitance of the resonator and reduce the size of the resonator at the same resonant frequency. At the same time, the SISO spiral structure and the interdigital structure can store most of the electric field and magnetic field energy, which can not only reduce the radiation leakage of electromagnetic energy and improve the passband insertion loss characteristics of the narrowband and extremely narrowband filter, but also reduce the coupling strength between resonators, so that adjacent resonators can meet the weak coupling condition at a smaller spacing, thereby reducing the overall size of the filter.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a resonator adopts SISO spiral structure and interdigital structure to form a dual composite left-handed and right-handed resonator, wherein the interdigital structure forms the open end of the resonator, and the SISO spiral structure forms the closed end of the resonator. The interdigital structure is composed of a plurality of mutually parallel interdigital branches. The interdigital structure is used to introduce left-handed parallel capacitance to increase the equivalent capacitance of the resonator. The first end of the interdigital structure is directly connected to the microstrip line and spirals in the clockwise direction. At the rotation center, it spirals out in the counterclockwise direction along the microstrip line, bypasses the interdigital structure, and is connected to the second end of the interdigital structure to form the SISO spiral structure. The SISO spiral structure is used to reduce the coupling strength between resonators.

[0007] The number of turns of the SISO spiral structure is determined according to the number of interdigital branches and the minimum operating frequency of the resonator under the same size. The number of interdigital branches in the interdigital structure is determined according to the number of turns of the SISO spiral structure and the minimum operating frequency of the resonator under the same size.

[0008] The SISO spiral structure and the interdigital structure are both microstrip line structures, and the line widths of the microstrip lines are the same.

[0009] The SISO spiral structure and the interdigital structure adopt superconducting thin film materials.

[0010] The size is 0.00967λx0.00149λ, λ is the wavelength at the center resonant frequency 194.95MHz of the resonator, and the unloaded quality factor is as high as 950000.

[0011] A compact extremely narrow-band high-temperature superconducting filter comprises an input feed line, an output feed line, and a plurality of resonators according to any one of claims 1-5, the number of resonators is even, the resonators are arranged in parallel between the input feed line and the output feed line, and one end of the input feed line and the output feed line is grounded.

[0012] The input feed line 5 and the output feed line adopt microstrip lines.

[0013] The size of the resonator is length x width = 14.9mm x 2.3mm, the overall size of the superconducting circuit is 26.95mm x 18.9mm, the width of the microstrip line of the resonator is 0.05mm, the number of resonators is six, and the spacing between adjacent two resonators is 0.45mm, 0.85mm, 0.65mm, 0.45mm and 0.85mm respectively.

[0014] The center frequency is about 194.95MHz, the 1-dB bandwidth is 1MHz, the return loss is less than -17.65dB within the passband, the passband loss is more than 0.073dB, and the out-of-band rejection at 2MHz is >77.19dB.

[0015] Compared with the prior art, the present application has at least the following beneficial effects: compared with the traditional low-frequency band extremely narrow-band filter structure, the resonator size of the traditional low-frequency band extremely narrow-band filter is large, the coupling distance required for weak coupling is wide, which leads to the overall filter size being too large, which is not conducive to small system integration connection, the present application utilizes the dual composite left-right hand structure resonator composed of SISO spiral structure and interdigital structure in parallel, which has the advantages of miniaturization and high Q value, the resonator size can reach 0.00967 lambda x 0.00149 lambda, lambda is the wavelength at the center resonant frequency 194.95 MHz of the resonator, the unloaded quality factor is as high as 950000, which is suitable for high-order extremely narrow-band high-performance filter design. The overall filter size is greatly reduced, the insertion loss in the passband of the filter, the out-of-band suppression ability and the roll-off coefficient of the transition band are greatly improved, and the selectivity of the filter is enhanced. At the same time, the SISO spiral structure and the interdigital structure can store most of the electric field and magnetic field energy, which reduces the electromagnetic radiation ability of the resonator, so that the adjacent resonators can achieve weak coupling condition in a small distance, and the filter size of the multi-stage resonator cascade is more compact, saving limited superconducting wafer substrate material. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 The SISO spiral structure and the interdigital structure in parallel constitute a dual composite left-right hand resonator structure in the present application.

[0018] Figure 2 The current and charge distribution diagram inside the dual composite left-right hand resonator based on the SISO spiral structure and the interdigital structure in the present application.

[0019] Figure 3 The compact extremely narrow-band high-temperature superconducting filter structure in the embodiment of the present application.

[0020] Figure 4 The compact extremely narrow-band high-temperature superconducting filter structure in the embodiment of the present application. Figure 3 The S parameter curve diagram of the compact extremely narrow-band high-temperature superconducting filter simulation.

[0021] In the drawings, 1 is the SISO spiral structure, 2 is the interdigital structure, 3 is the second end of the interdigital structure, 4 is the first end of the interdigital structure, 5 is the input feed line, 6 is the output feed line, 71 is the first stage resonator, 72 is the second stage resonator, 73 is the third stage resonator, 74 is the fourth stage resonator, 75 is the fifth stage resonator, and 76 is the sixth stage resonator. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0023] The purpose of the present application is to provide a compact ultra-narrow-band high-temperature superconducting filter based on a dual composite left-right hand resonator, so as to realize a high-performance ultra-narrow-band superconducting filter with high Q value, low insertion loss, compactness and high selectivity.

[0024] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0025] As shown in Figure 1 A dual composite left-right hand resonator structure is composed of a SISO (spiral-in and spiral-out) spiral structure and an interdigital structure in parallel, including a SISO spiral structure 1 and an interdigital structure 2. The interdigital structure 2 is arranged at the open end of a half-wavelength resonator. The number of interdigital branches in the interdigital structure 2 is designed according to the number of turns of the SISO spiral structure and the requirement of the minimum operating frequency of the resonator under the same size. The interdigital structure 2 is used to introduce a left-hand parallel capacitor to increase the equivalent capacitance of the resonator. The SISO spiral structure 1 is arranged between the two ends of the interdigital structure 2. The first end 4 of the interdigital structure is directly connected to the microstrip line and spirals in clockwise direction. At the center of rotation, it spirals out counterclockwise along the microstrip line, bypasses the interdigital structure 2, and is connected to the second end 3 of the interdigital structure to form a SISO spiral structure. The number of turns of the SISO spiral structure 1 is optimized according to the number of interdigital branches and the requirement of the minimum operating frequency of the resonator under the same size.

[0026] As shown in Figure 2As shown in the figure, the equivalent circuit diagram of the dual composite left-handed and right-handed resonator structure based on the SISO spiral structure 1 and the interdigital structure 2. It can be known from the equivalent circuit diagram analysis that the upper SISO spiral structure 1 greatly reduces the size of the half-wave resonator, and the current in the middle section of the half-wave resonator is the strongest, the current direction between adjacent microstrip lines is opposite, the electromagnetic radiation is counteracted, most of the magnetic field energy is stored in the SISO spiral structure 1, the Q value of the resonator is improved, the coupling strength between adjacent resonators is greatly reduced, and the weak coupling condition of the extremely narrow band filter under a smaller interval is possible. The lower interdigital structure 2 is located at the open end of the half-wave resonator, the adjacent branches store opposite polarities of charges, form a larger equivalent capacitance, reduce the working frequency point of the resonator, reduce the resonator size, and also store most of the electric field energy, further improve the Q value of the resonator, and reduce the electric coupling strength between adjacent resonators.

[0027] Further, the multi-stage resonator can be cascaded to form a high-order compact extremely narrow band filter, and six dual composite left-handed and right-handed resonators are cascaded to form a compact extremely narrow band high-temperature superconducting filter based on the dual composite left-handed and right-handed resonator, as shown in the figure. Figure 3 As shown in the figure, the input feed line 5 and the output feed line 6 are included, the input feed line 5 is arranged on one side of the first resonator 71 and one end is grounded, the external coupling is enhanced, the external quality factor is reduced to the required value of the extremely narrow band filter, and the output feed line 6 is arranged on one side of the fifth resonator 76. The half-wave resonator adopts the dual composite left-handed and right-handed resonator composed of the SISO spiral structure 1 and the interdigital structure 2, and since the resonator structure can greatly reduce its own size and reduce the coupling strength between resonators, weak coupling can be achieved under a smaller interval, and the extremely narrow band characteristic of the superconducting filter is achieved. At the same time, the six resonators are cascaded to greatly improve the passband selection performance of the filter. The circuit diagram includes an input / output feed line and six dual composite left-handed and right-handed resonators; by using the advantages of the dual composite left-handed and right-handed resonator structure, such as miniaturization and high Q value, the size of the overall filter circuit is reduced, the passband insertion loss and transition band roll-off coefficient of the extremely narrow band filter are greatly improved, and the out-of-band suppression capability is improved.

[0028] A specific example of the present application is given as follows: as shown in the figure, Figure 3 As shown in the figure, the size parameters of the filter are calculated by calculating the external Q value, the coupling coefficient and the resonator frequency, the size of the dual composite left-handed and right-handed resonator is 14.9mmx2.3mm, the overall size of the superconducting circuit is 26.95mmx18.9mm, and the width of the resonator microstrip line is 0.05mm. The interval between the adjacent two resonators is 0.45mm, 0.85mm, 0.65mm, 0.45mm and 0.85mm respectively. As shown in the figure, Figure 4As shown, the frequency response curve of the sixth-order compact extremely narrow-band high-temperature superconducting filter is calculated by an electromagnetic simulation software Sonnet, the center frequency of the filter is about 194.95 MHz, and the 1-dB bandwidth is 1 MHz. Meanwhile, the return loss in the passband is less than-17.65 dB, the passband loss is more than 0.073 dB, the out-of-band rejection at 2 MHz is >77.19 dB, and the out-of-band rejection capability is obviously improved.

[0029] The principles and implementation manners of the present application are described by specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In summary, the content of the present specification should not be understood as a limitation of the present application.

Claims

1. A resonator, characterized by, The parallel resonator is composed of SISO spiral structure and interdigital structure, the interdigital structure (2) is arranged at the open end of the half-wavelength resonator, the interdigital structure forms the open end of the resonator, the SISO spiral structure forms the closed end of the resonator, the interdigital structure is composed of a plurality of parallel interdigital branches; the interdigital structure (2) is used for introducing left-hand parallel capacitance and increasing the equivalent capacitance of the resonator; the first end (4) of the interdigital structure is directly connected with the microstrip line and spirals in the clockwise direction, at the rotation center, the interdigital structure (2) is bypassed and connected to the second end (3) of the interdigital structure to form the SISO spiral structure; the SISO spiral structure is used for reducing the coupling strength between resonators; the number of turns of the SISO spiral structure (1) is determined according to the number of interdigital branches and the minimum working frequency of the resonator under the same size; the number of interdigital branches in the interdigital structure (2) is determined according to the number of turns of the SISO spiral structure and the minimum working frequency of the resonator under the same size; the SISO spiral structure (1) and the interdigital structure (2) are microstrip line structures, the line widths of the microstrip lines are the same; the SISO spiral structure (1) and the interdigital structure (2) are made of superconducting thin film material; the resonator size is 0.00967λx0.00149λ, and λ is the wavelength at the center resonant frequency 194.95MHz of the resonator.

2. The resonator of claim 1, wherein The unloaded quality factor is as high as 950000.

3. A compact, very narrow band high temperature superconducting filter, characterized by, The resonator includes an input feed line (5), an output feed line (6) and a plurality of resonators according to claim 1 or 2, the number of resonators is even, the resonators are arranged in parallel between the input feed line (5) and the output feed line (6); one end of the input feed line (5) and the output feed line (6) is grounded; the input feed line (5) and the output feed line (6) are microstrip lines.

4. The compact, very narrow band high temperature superconducting filter of claim 3, wherein, The resonator size is 14.9mmx2.3mm, the overall size of the superconducting circuit is 26.95mmx18.9mm, the resonator microstrip line width is 0.05mm, the number of resonators is six, and the spacings between adjacent two resonators are 0.45mm, 0.85mm, 0.65mm, 0.45mm and 0.85mm respectively.

5. The compact, very narrow band high temperature superconducting filter of claim 3, wherein, The center frequency is 194.95MHz, the 1-dB bandwidth is 1MHz, the return loss is less than-17.65dB within the passband, the passband loss is greater than 0.073dB, and the out-of-band suppression is >77.19dB at 2MHz.

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