CN116315533A - A resonator and a compact ultra-narrowband high-temperature superconducting filter - Google Patents

Abstract

The invention discloses a resonator and a compact ultra-narrow band high-temperature superconducting filter, which are connected in parallel to form a dual composite left-right-hand resonator by adopting a SISO spiral structure and an interdigital structure, 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 consists of a plurality of mutually parallel interdigital branches; the interdigital structure is used for introducing left hand capacitance, increasing the equivalent capacitance of the resonator, the first end of the interdigital structure is directly connected with the microstrip line and screwed in clockwise, and then screwed out along the anticlockwise direction of the microstrip line at the center of rotation, bypasses the interdigital structure, and is connected to the second end of the interdigital structure to form a SISO spiral structure; the size of the whole filter can be greatly reduced, the insertion loss and out-of-band rejection capability in the pass band of the filter are greatly improved, the roll-off coefficient of the transition band is greatly improved, and the selectivity of the filter is enhanced.

Description

A resonator and a compact ultra-narrowband high-temperature superconducting filter

technical field

The invention belongs to the technical field of microwave communication, in particular to a resonator and a compact ultra-narrow-band high-temperature superconducting filter.

Background technique

With the rapid development of wireless communication technology, spectrum resources are becoming more and more scarce, and wireless communication conditions are becoming more and more harsh. Various military and civilian wireless communication equipment emerge in an endless stream, and there is an urgent need for filters with strong anti-interference ability and high selectivity. Eliminate out-of-band electromagnetic interference and crosstalk between different communication lines to improve communication quality. Today, with the continuous development of space science and technology and the concept of space Internet, space satellite communication has gradually entered the field of vision of people's attention. Military/civilian communication satellites, remote sensing satellites, and Mars communication satellites have become the focus of major research institutes and universities. Research focus, especially the space VHF short-wave communication field has many advantages, such as long communication distance, flexible networking, strong concealment, etc. It is widely used in aviation communication, maritime communication, radio detection and national defense, and has become one of the key research points of scientific researchers. one. However, the spectrum resources in the VHF frequency band are very tight, there are many electromagnetic interferences, and crosstalk between different application signals is easy to occur, which deteriorates the communication quality. Therefore, if a reliable communication network is to be established in a long-distance complex space environment, a high-performance filter is required to filter out out-of-band interference and increase communication reliability.

Compared with traditional bandpass filters, compact filters are more in line with the miniaturization needs of modern communication systems, and can better meet the challenges of high integration and multi-functional device integration faced by modern communications, and can be applied to national defense encrypted communications System front-end, high-sensitivity receiver/transmitter front-end and other large precision equipment. The traditional bandpass filter is composed of cascaded half-wavelength or quarter-wavelength resonators. If the working center frequency of the bandpass filter is low, such as the VHF band (30-300MHz), the general half-wavelength The size of the resonator is larger than 50cm, resulting in the multiplication of the overall filter size. Such a huge filter is extremely wasteful of overall equipment space resources, and cannot be installed together with highly integrated precision equipment. Then in the design of low-frequency filters such as VHF/UHF, the miniaturization design of the resonator becomes one of the key steps in the overall filter design of the compact ultra-narrow-band high-temperature superconducting filter. At the same time, in the design of a filter formed by cascading multiple resonators, the coupling distance between adjacent resonators also determines the size of the overall filter. Generally, the required coupling strength between adjacent resonators of a narrowband filter is small, and the coupling distance increases accordingly, which greatly limits the miniaturization design requirements of the filter. For narrowband/extremely narrowband filters, how to achieve the weak coupling conditions required by narrowband filters at a small distance has become one of the key factors for low frequency narrowband/extremely narrowband filters to be applied to highly integrated, miniaturized systems or devices .

High-temperature superconducting materials have a very high quality factor (Q value) because their surface resistance is almost zero in a low-temperature environment. Therefore, after the discovery of high-temperature superconducting materials in the 1980s, especially in recent years, they have been widely used in the fields of radio frequency and microwave communications. People usually use this material to make microstrip circuits, especially microstrip filters. Due to its almost zero surface resistance, it brings extremely low insertion loss to filters made of high-temperature superconducting materials, so it can be The cascade connection of multi-stage resonators increases the suppression ability of the out-of-band interference of the filter and improves its selectivity. High-temperature superconducting filters have many advantages such as extremely steep band edges, low in-band insertion loss, and high no-load quality factor of resonators. The performance is closer to ideal filters, and at the same time, it has the characteristics of small circuit size and light weight. , can be applied to mobile communication base stations, satellite communication systems, radio astronomy receivers, etc., to reduce the interference of adjacent frequency band signals, improve the communication quality between communication equipment and base stations, and improve the sensitivity of radio astronomy receivers.

Contents of the invention

In order to solve the problems existing in the above-mentioned technologies, the present invention provides a resonator and a compact ultra-narrow-band high-temperature superconducting filter, wherein the resonator utilizes a dual composite left-handed structure resonator composed of a SISO helical structure and an interdigitated structure in parallel. , the advantage of high Q value, the interdigitated structure introduces the left-handed parallel capacitor, increases the equivalent capacitance of the resonator, and reduces the size of the resonator at the same resonant frequency. At the same time, the SISO spiral structure and the interdigitated structure can store most of the electric field and magnetic field Energy, which can not only reduce the radiation leakage of electromagnetic energy, improve the passband insertion loss characteristics of narrowband and extremely narrowband filters, but also reduce the coupling strength between resonators, so that adjacent resonators can also meet weak coupling conditions at a small distance , reducing the overall size of the filter.

In order to achieve the above object, the technical solution adopted by the present invention is: a resonator, which uses a SISO helical structure and an interdigitated structure in parallel to form a dual composite left and right handed resonator, wherein the interdigitated structure forms the opening end of the resonator, and the SISO helical structure forms the resonator. At the closed end of the resonator, the interdigitated structure is composed of multiple parallel interdigitated branches; the interdigitated structure is used to introduce left-handed parallel capacitors to increase the equivalent capacitance of the resonator; the first end of the interdigitated structure is directly connected to the microstrip line Connected and screwed in clockwise, at the center of rotation and then screwed out counterclockwise along the microstrip line, bypassing the interdigitated structure, connected to the second end of the interdigitated structure to form a SISO helical structure; the SISO helical structure is used to reduce Coupling strength between small resonators.

The number of turns of the SISO helical structure is determined according to the number of interdigitated branches and the minimum operating frequency point of the resonator at the same size, and the number of interdigitated branches in the interdigitated structure is determined according to the number of turns of the SISO helical structure and the resonator at the same size The lower minimum operating frequency point is determined.

Both the SISO spiral structure and the interdigitated structure are microstrip line structures, and the line widths of the microstrip lines are the same.

The SISO helical structure and interdigitated structure use superconducting thin film materials.

The size is 0.00967λ×0.00149λ, where λ is the wavelength at the central resonance frequency of the resonator at 194.95MHz, and the unloaded quality factor is as high as 950,000.

A compact ultra-narrow-band high-temperature superconducting filter, including an input feeder, an output feeder, and a resonator according to any one of claims 1-5, the number of the resonators is an even number, and the resonator sets the input feeder and the resonator The output feeders are arranged in parallel; one end of the input feeder and output feeder is grounded.

The input feeder 5 and the output feeder adopt microstrip lines.

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

The center frequency is about 194.95MHz, the 1-dB bandwidth is 1MHz, the return loss in the passband is below -17.65dB, the passband loss is above 0.073dB, and the out-of-band suppression at 2MHz is >77.19dB.

Compared with the prior art, the present invention has at least the following beneficial effects: compared with the traditional low-frequency extremely narrow-band filter structure, the resonator size of the traditional low-frequency extremely narrow-band filter is larger, and the coupling distance required for weak coupling is also smaller. Wider, resulting in too large overall filter size, which is not conducive to the integration and connection of miniaturized systems. The dual composite left and right handed structure resonators composed of SISO spiral structures and interdigitated structures in parallel in the present invention have the advantages of miniaturization and high Q value. The resonator The size can reach 0.00967λ×0.00149λ, λ is the wavelength at the central resonance frequency of the resonator at 194.95MHz, and the unloaded quality factor is as high as 950,000, which is suitable for high-order ultra-narrowband high-performance filter design. The size of the overall filter is greatly reduced, the insertion loss in the filter passband and the out-of-band suppression ability are greatly improved, the roll-off coefficient of the transition zone is greatly improved, and the selectivity of the filter is enhanced. At the same time, the SISO helical structure and interdigitated structure can store most of the electric field and magnetic field energy, which reduces the electromagnetic radiation capability of the resonator, so that adjacent resonators can achieve weak coupling conditions within a small distance, and the cascaded filtering of multi-order resonators The device size will be more compact, saving limited superconducting wafer substrate materials.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 shows the parallel connection of SISO helical structure and interdigitated structure in the present invention to form a dual composite left and right handed resonator structure.

Fig. 2 is a diagram of the current charge distribution inside the dual composite left and right handed resonator based on the SISO helical structure and the interdigitated structure in the present invention.

Fig. 3 is a structure of a compact ultra-narrow-band high-temperature superconducting filter according to an embodiment of the present invention.

FIG. 4 is an S-parameter curve diagram of the simulation of the compact ultra-narrow-band high-temperature superconducting filter shown in FIG. 3 .

In the accompanying drawings, 1-SISO spiral structure, 2-interdigitated structure, 3-second end of interdigitated structure, 4-first end of interdigitated structure, 5-input feeder, 6-output feeder, 71-first Level resonator, 72-second level resonator, 73-third level resonator, 74-fourth level resonator, 75-fifth level resonator, 76 sixth level resonator.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The purpose of the present invention is to provide a compact ultra-narrowband high-temperature superconducting filter based on a dual composite left-handed resonator, so as to realize a high-Q, low insertion loss, compact, high-selective high-performance ultra-narrowband superconducting filter .

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a SISO (spiral-in and spiral-out) helical structure and an interdigitated structure are connected in parallel to form a dual composite left-handed resonator structure, including a SISO helical structure 1 and an interdigitated structure 2; the interdigitated structure 2 is set at The open end of the half-wavelength resonator, the number of interdigitated branches in the interdigitated structure 2 is designed according to the number of turns of the SISO helical structure and the minimum operating frequency of the resonator at the same size. The interdigitated structure 2 is used to introduce The left-hand capacitor is connected in parallel to increase the equivalent capacitance of the resonator; the SISO helical structure 1 is arranged between the two ends of the interdigitated structure 2, and the first end 4 of the interdigitated structure is directly connected to the microstrip line and screwed clockwise , at the center of rotation, spin out counterclockwise along the microstrip line, bypass the interdigitated structure 2, and connect to the second end 3 of the interdigitated structure to form a SISO helical structure; the number of turns of the SISO helical structure 1 depends on the interdigitated branch The number of resonators and the requirements of the minimum operating frequency point of the resonator under the same size are optimized for design.

As shown in Figure 2, the equivalent circuit diagram of the dual composite left-handed resonator structure based on the SISO helical structure 1 and the interdigitated structure 2. From the analysis of the equivalent circuit diagram, it can be seen that the upper SISO helical structure 1 greatly reduces the size of the half-wavelength resonator, and the current in the middle section of the half-wavelength resonator is the strongest, and the current direction between adjacent microstrip lines is opposite. The radiation cancels each other, so that most of the magnetic field energy is stored in the SISO helical structure 1, which improves the Q value of the resonator, greatly reduces the coupling strength between adjacent resonators, and achieves an extremely narrow band at a small spacing The weak coupling condition of the filter becomes possible. The lower interdigitated structure 2 is located at the open-circuit end of the half-wavelength resonator, and the polarity of the charges stored in adjacent branches is opposite, forming a larger equivalent capacitance, which reduces the operating frequency of the resonator, reduces the size of the resonator, and can also store Most of the electric field energy further increases the Q value of the resonator and reduces the electrical coupling strength between adjacent resonators.

Further, multi-order resonators can be cascaded to form a high-order compact ultra-narrowband filter. In the example of the present invention, six dual composite left-handed resonators are cascaded to form a compact ultra-narrowband high-temperature filter based on dual composite left-handed resonators. The superconducting filter, as shown in Figure 3, includes an input feeder 5 and an output feeder 6, the input feeder 5 is set on one side of the first resonator 71, and one end is grounded to enhance external coupling and reduce the external quality factor to achieve extremely narrow-band filtering The value required by the resonator, the output feeder 6 is set on one side of the fifth resonator 76 . The half-wavelength resonator adopts a dual composite left-handed resonator composed of SISO helical structure 1 and interdigitated structure 2 in parallel. Since the resonator structure can greatly reduce its own size and reduce the coupling strength between resonators, it can be used in The weak coupling is realized at a small interval, and the extremely narrow-band characteristic of the superconducting filter is realized. At the same time, the cascade connection of six resonators greatly improves the passband selection performance of the filter. The circuit diagram includes input and output feeders, 6-order dual composite left and right hand resonators; by using the dual composite left and right hand structure resonators have the advantages of miniaturization and high Q value, the size of the overall filter circuit is reduced, and the extremely narrowband filter is greatly improved Pass-band insertion loss and transition-band roll-off coefficient improve out-of-band rejection.

A specific example of the present invention is provided below: as shown in Figure 3, by calculating the various size parameters of the external Q value, coupling coefficient, resonator frequency calculation filter, the size of the dual composite left and right hand resonator is 14.9mm * 2.3mm , the overall size of the superconducting circuit is 26.95mm×18.9mm, and the width of the microstrip line of the resonator is 0.05mm. The distances between two adjacent resonators are 0.45mm, 0.85mm, 0.65mm, 0.45mm and 0.85mm respectively. As shown in Figure 4, the frequency response curve of the sixth-order compact ultra-narrowband high-temperature superconducting filter is calculated by the electromagnetic simulation software Sonnet. The center frequency of the filter is about 194.95MHz, and the 1-dB bandwidth is 1MHz. At the same time, the return loss in the passband is below -17.65dB, the passband loss is above 0.073dB, and the out-of-band suppression at 2MHz is >77.19dB, and the out-of-band suppression ability has been significantly improved.

In the present invention, the principle and implementation mode of the present invention have been set forth with specific examples, and the description of the above embodiments is only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (9)

1. A resonator is characterized in that a SISO spiral structure and an interdigital structure are connected in parallel to form a dual composite left-right-hand resonator, wherein the interdigital structure forms an opening end of the resonator, the SISO spiral structure forms a closed end of the resonator, and the interdigital structure consists of a plurality of mutually parallel interdigital branches; the interdigital structure (2) is used for introducing a left-hand parallel capacitor to increase the equivalent capacitance of the resonator; the first end (4) of the interdigital structure is directly connected with the microstrip line and screwed in the clockwise direction, and then screwed out along the anticlockwise direction of the microstrip line at the rotation center, bypasses the interdigital structure (2), and is connected to the second end (3) of the interdigital structure to form a SISO spiral structure; SISO helical structures are used to reduce the coupling strength between resonators.

2. The resonator according to claim 1, characterized in that the number of turns of the SISO spiral structure (1) is determined according to the number of interdigital knots and the minimum operating frequency point of the resonator in the same size, and the number of interdigital knots in the interdigital structure (2) is determined according to the number of turns of the SISO spiral structure and the minimum operating frequency point of the resonator in the same size.

3. Resonator according to claim 1, characterized in that the SISO spiral structure (1) and the interdigital structure (2) are microstrip structures, the linewidths of which are identical.

4. Resonator according to claim 1, characterized in that the SISO helix (1) and the interdigital structure (2) are made of superconducting thin film material.

5. The resonator according to claim 1, characterized in that the dimensions 0.00967 λ x 0.00149 λ, λ being the wavelength at the central resonance frequency 194.95MHz of the resonator, have an unloaded quality factor up to 950000.

6. A compact ultra-narrow band high temperature superconducting filter, characterized by comprising an input feeder (5), an output feeder (6) and a plurality of resonators as claimed in any one of claims 1 to 5, wherein the number of the resonators is even, and the resonators are arranged in parallel between the input feeder (5) and the output feeder (6); one ends of the input feeder line (5) and the output feeder line (6) are grounded.

7. Compact ultra-narrow band high temperature superconducting filter according to claim 6, characterized in that the input feed line (5) and the output feed line (6) are microstrip lines.

8. The compact ultra-narrow band high-temperature superconducting filter according to claim 6, wherein the resonator is in a size of length x width=14.9 mm x 2.3mm, the superconducting circuit is in an overall size of 26.95mm x 18.9mm, the width of the microstrip line of the resonator is 0.05mm, the number of the resonators is six, and the intervals between two adjacent resonators are 0.45mm, 0.85mm, 0.65mm, 0.45mm and 0.85mm, respectively.

9. The compact ultra-narrow band high temperature superconducting filter according to claim 6, wherein the center frequency is about 194.95MHz, the 1-dB bandwidth is 1MHz, the return loss is-17.65 dB or less in the passband, the passband loss is 0.073dB or more, and the out-of-band rejection at 2MHz is > 77.19dB.

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