KR100953408B1 - Superconducting microwave filter - Google Patents

Abstract

A superconducting microwave filter is provided. The superconducting microwave filter according to the embodiment of the present invention may include a microstrip substrate, micro filter patterns on the microstrip substrate, a first dielectric plate on the micro filter patterns, and a first dielectric plate spaced apart from the first dielectric plate on the first dielectric plate. 2 dielectric plates.

Description

Superconducting Microwave Filters {SUPERCONDUCTING MICROWAVE FILTER}

The present invention relates to a superconducting microwave filter, and more particularly to a superconducting microwave filter capable of tuning the center frequency.

The application of high-temperature superconductor as a microwave device originates from the following excellent characteristics of superconductor in high frequency region including microwave and millimeter wave. First, in the case of superconductors, unlike conductors, there is no frequency dependence of the penetration depth below a certain frequency. In the case of high temperature superconductors, the depth of electromagnetic wave penetration is constant regardless of the magnitude of the frequency at frequencies below THz, which is the energy gap of the high temperature superconductors. Independent of frequency, i.e. there is no dispersion of the signal. Second, the low surface resistance of the high temperature superconductor. The surface resistivity at liquid nitrogen temperature and frequency of 10 GHz of YBa ₂ Cu ₃ O _{7 -δ} (YBCO) thin film with the best characteristics is about 200μΩ, which is about 1/50 of the surface resistance of copper under the same conditions. It is about degree. The superconducting microstrip filter made of such high temperature superconducting thin film has been found to have very small insertion loss and very good out-band characteristics. In addition, the superconducting microstrip filter with wide frequency tuning characteristics can be used for software defined radio system (SDR), which will be the standard for next generation wireless communication. This technology is performed by a software module implemented in a programmable high-speed processing element that includes most of the functional blocks including the RF region after the antenna in a wireless mobile communication system. Support service functions. When various wireless communication services are provided to one terminal or base station using software-based mobile communication technology, the user can easily receive various communication services at low cost regardless of the regional standard or service type of the wireless communication system. Operators can have flexible network operations at low network cost. For this reason, the use of filters with good selectivity and wide tuning range is very advantageous in SDR systems.

It is an object of the present invention to provide a superconducting microwave filter having excellent frequency response characteristics.

A superconducting microwave filter according to an embodiment of the present invention may include a microstrip substrate, micro filter patterns disposed in contact with an upper surface of the microstrip substrate, and a second filter spaced apart from the micro filter patterns on the micro filter patterns. And a second dielectric plate disposed on the first dielectric plate and spaced apart from the first dielectric plate on the first dielectric plate.

The micro filter patterns according to the embodiment of the present invention may include a pair of hairpin resonators and a straight resonator disposed between the hairpin resonators.

The first dielectric plate according to the embodiment of the present invention may tune the center frequency.

The second dielectric plate according to the embodiment of the present invention can adjust the passband.

The height of the first dielectric plate and the second dielectric plate according to an embodiment of the present invention can be adjusted.

The micro filter patterns according to the embodiment of the present invention may be composed of a superconductor.

According to an embodiment of the present invention, the superconducting microwave filter comprises two dielectric plates disposed spaced apart from the micro filter patterns. Two dielectric plates can be used to improve the frequency response while moving the center frequency. Therefore, the superconducting microwave filter can have a significant effect of simply moving the center frequency and improving the frequency response using two dielectric plates.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed contents may be thorough and complete, and the technical spirit of the present invention may be sufficiently delivered to those skilled in the art.

In the embodiments of the present invention, terms such as first and second have been described to describe respective components, but each component should not be limited by such terms. These terms are only used to distinguish one component from another.

In the drawings, each component may be exaggerated for clarity. The same reference numerals throughout the specification represent the same components.

Meanwhile, for the sake of simplicity, some embodiments to which the technical spirit of the present invention may be applied are described as examples, and descriptions of various modified embodiments will be omitted. However, one of ordinary skill in the art may apply the inventive concept of the present invention to various cases based on the above description and the embodiments to be illustrated. For example, the technical idea of the present invention may be applied to a form in which various types of resonators are mixed as well as a filter composed of only a hairpin resonator and a straight resonator.

1 and 2 are views for explaining a superconducting microwave filter according to an embodiment of the present invention.

1 and 2, micro filter patterns 30 are disposed on a microstrip substrate 10. The microstrip substrate 10 may include a dielectric layer 14 and a metal film 12 attached to a lower surface of the substrate dielectric layer 14. The metal film 12 may function as a ground plane. The dielectric layer 14 may be a magnesium oxide film, in which case the dielectric layer 14 is known to be an excellent substrate material having a low dielectric constant for superconducting microwave applications.

The micro filter patterns 30 may include a pair of hairpin resonators 30a and 30b and a straight resonator 35 disposed between the pair of hairpin resonators 30a and 30b. The micro filter patterns 30 may have a so-called three pole resonator structure. The micro filter patterns 30 may have a mixed resonator structure, and thus, a passage characteristic of the filter may be improved. The hairpin resonators 30a and 30b may contribute to miniaturization of the filter through bending. The micro filter patterns 30 may be formed of a superconductor. For example, the micro filter patterns 30 may be YBa ₂ Cu ₃ O _{7 −δ} (YBCO). Input lines 20a and output lines 20b may be disposed on both sides of the micro filter patterns 30, respectively.

On the micro filter patterns 30, a first dielectric plate 40 is disposed spaced apart from the micro filter patterns 30. The first dielectric plate 40 may tune a center frequency. That is, the first dielectric plate 40 may move the center frequency. The second dielectric plate 50 is disposed on the first dielectric plate 40 so as to be spaced apart from the first dielectric plate 40. The second dielectric plate 50 may adjust a pass band. That is, the second dielectric plate 50 may improve the filter characteristics by narrowly adjusting the width of the pass band even when the center frequency is shifted. The first dielectric plate 40 and the second dielectric plate 50 may be a material having a high dielectric constant. The first dielectric plate 40 and the second dielectric plate 50 may be, for example, any one of a lanthanum aluminum oxide film, sapphire, or magnesium oxide film.

The height of the first dielectric plate 40 and the second dielectric plate 50 may be adjusted. The first dielectric plate 40 may be connected to the first step motor 80 by the first connector 45. By the rotation of the first step motor 80, the height of the first dielectric plate 40 can be precisely adjusted. In addition, the second dielectric plate 50 may be connected to the second step motor 90 by the second connection part 55. By the rotation of the second step motor 90, the height of the second dielectric plate 50 can be precisely adjusted.

The center frequency of the filter may be changed by adjusting the height of the first dielectric plate 40. In addition, a pass bandwidth may be controlled by adjusting the height of the second dielectric plate 40. 2 denotes an interval between the micro filter patterns 30 and the first dielectric plate 40, and d2 denotes an interval between the first dielectric plate 40 and the second dielectric plate 50. do. Thus, by adjusting d1 and d2, the center frequency and the passband can be controlled, respectively.

The microstrip substrate 10, the first dielectric plate 40, and the second dielectric plate 50 may be embedded in the filter case 60. The filter case 60 may be designed so that structural resonance does not occur. The first connecting portion 45 and the second connecting portion 55 pass through the chamber 70 to connect the first dielectric plate 40 and the second dielectric plate 50 to the first step motor 80 and the first, respectively. It can be structurally connected to the two step motor (90).

FIG. 3 is a view showing the actual implementation of the resonator of the superconducting microwave filter according to FIG. 1 on the microstrip substrate.

1 to 3, the micro filter patterns 30 on the microstrip substrate 10 are designed in a Chebyshev manner. The dielectric layer 14 is a magnesium oxide film having a dielectric constant of about 10, and has a size of 20 mm in width, 20 mm in length, and 0.5 mm in thickness. The micro filter patterns 30 may be YBa ₂ Cu ₃ O _{7 −δ} (YBCO). In this case, the thickness of the first dielectric plate 40 may be 0.5 mm, and the thickness of the second dielectric plate 50 may be 1.7 mm.

4 is a graph comparing the actual frequency response characteristic (solid line) of the superconducting microfilter according to the embodiment of the present invention with the frequency response characteristic (dashed line) by simulation.

Referring to FIG. 4, the horizontal axis represents frequency (GHz), and the vertical axis represents S parameter. S21 (dB) denotes insertion loss, and S11 (dB) denotes return loss. The simulation uses a microwave studio, a three-dimensional tool.

Referring again to FIGS. 1 to 3, the micro filter patterns 30 on the microstrip substrate 10 are designed in a Chebyshev manner. The dielectric layer 14 is a magnesium oxide film having a dielectric constant of about 10 and has a size of 20 mm in width, 20 mm in length, and 0.5 mm in thickness. The micro filter patterns 30 may be YBa ₂ Cu ₃ O _{7 −δ} (YBCO). The thickness of the first dielectric plate 40 may be 0.5 mm, and the thickness of the second dielectric plate 50 may be 1.7 mm. An interval between the first dielectric plate 40 and the micro filter patterns 30 may be represented by d1, and an interval between the first dielectric plate 40 and the second dielectric plate 50 may be represented by d2. Can be expressed.

The superconducting micro filter manufactured according to the embodiment of the present invention measured the frequency response characteristic at 70K. The measured superconducting microfilter has a center frequency of 5.01 GHz, a pass band of 91 MHz, an insertion loss of pass band (S21) of 0.6 dB, a ripple of 0.05 dB, and a maximum return loss of the pass band. , S11) is 25 dB, which shows very good frequency response. The difference between the simulation results and the center frequency is found to be about 10 MHz. This may occur due to the difference between the actual value and the use value such as the dielectric constant or the thickness of the substrate used in the actual simulation. It can be seen that the remaining frequency response characteristics match very well.

 5A and 5B are graphs showing a spacing and a frequency dependency of a dielectric plate according to an embodiment of the present invention.

FIG. 5A shows the frequency dependence of the hairpin resonator and the straight resonator on the spacing d1 (mm) between the micro filter pattern and the first dielectric plate (see FIG. 2). FIG. 5B shows the frequency dependence of the hairpin and straight resonators on the spacing d2 (mm) between the first and second dielectric plates (see FIG. 2).

In FIG. 5A, it can be seen that the dependence of the center frequency f ₀ on the distance d1 between the micro filter pattern and the first dielectric plate shows a similar change. In FIG. 5B, the distance d1 between the micro filter pattern and the first dielectric plate is fixed at 0.1 mm, and the center frequency (1) is changed while changing the distance d2 between the first and second dielectric plates from 0.05 mm to 1.0 mm. f ₀ ) measure dependencies.

It can be seen that the hairpin resonator has a frequency change of about 36 MHz and the straight resonator has a frequency change of about 88 MHz. That is, the straight resonator has a frequency change more than twice that of the hairpin resonator. This difference is caused by the fact that in the case of the Hay Fin resonator, since the current flow between two parallel lines is reversed, the electromagnetic fields in the height direction become weaker than the straight resonators as the electromagnetic fields cancel each other.

From this result, the center frequency of the filter is tuned while varying the distance d1 between the micro filter pattern and the first dielectric plate, and the distance d2 between the first dielectric plate and the second dielectric plate is changed to change the center frequency ( Δf ₀ ) can be adjusted to optimize the filter's frequency response (pass band (BW), etc.).

FIG. 6 is a graph comparing a case of tuning a frequency using a single dielectric plate (Single plate) and a case of tuning a frequency using two dielectric plates (Double plate). In the case of using one dielectric plate, it can be seen that the ripple of the pass band is 1 dB or more, and the pass bandwidth is 130 MHz. On the other hand, when two dielectric plates are used, the ripple is 0.4dB and the passband is 85MHz, which shows that the frequency response is improved.

7 is a graph showing experimental examples of the superconducting microwave filter according to the embodiment of the present invention.

Referring to FIG. 7, Comparative Example A shows untuned, that is, designed frequency characteristics. In the comparative example (A), the center frequency (f ₀ ) is 5 GHz, the pass bandwidth (Band Width: BW) is 90 MHz, the insertion loss (Insertion Loss: IL) is 0.6 dB, and the ripple is 0.05 dB. to be. Experimental examples (B, C, D, E) according to an embodiment of the present invention after tuning the frequency (meaning the movement of the frequency) can be confirmed that the measured value is almost the same as the design value of Comparative Example (A) have. That is, even if the center frequency is shifted by changing d1 and d2, the frequency response characteristics such as passband (BW), insertion loss (IL), and ripple are excellent. Therefore, the superconducting microwave filter according to the embodiment of the present invention may have a very simple and excellent frequency response using two dielectric plates.

division d1 (mm) d2 (mm) f ₀ (GHz) BW (MHz) IL (dB) ripple (dB) A - - 5.01 91 0.6 0.05 B 0.1 0.15 4.48 85 1.9 0.4 C 0.3 0.21 4.73 93 1.8 0.9 D 0.4 0.28 4.80 95 1.1 0.9 E 1.5 0.25 4.93 93 0.7 0.5

1 and 2 are views for explaining a superconducting microwave filter according to an embodiment of the present invention.

FIG. 3 is a view showing the actual implementation of the resonator of the superconducting microwave filter according to FIG. 1 on the microstrip substrate.

4 is a graph comparing the actual frequency response characteristic (solid line) of the superconducting microfilter according to the embodiment of the present invention with the frequency response characteristic (dashed line) by simulation.

5A and 5B are graphs showing a spacing and a frequency dependency of a dielectric plate according to an embodiment of the present invention.

FIG. 6 is a graph comparing a case of tuning a frequency using one dielectric plate and a case of tuning a frequency using two dielectric plates.

7 is a graph showing experimental examples of the superconducting microwave filter according to the embodiment of the present invention.

Claims (6)

Microstrip substrates; Micro filter patterns disposed in contact with an upper surface of the microstrip substrate; A first dielectric plate disposed on the micro filter patterns, the first dielectric plate being spaced apart from the micro filter patterns; And A second dielectric plate disposed on the first dielectric plate and spaced apart from the first dielectric plate, The heights of the first dielectric plate and the second dielectric plate are adjusted; The center frequency is tuned by varying the distance d1 between the first dielectric plate and the micro filter patterns, and the pass bandwidth is adjusted by changing the distance d2 between the second dielectric plate and the first dielectric plate. Superconducting microwave filter. The method according to claim 1, The micro filter patterns A pair of hairpin resonators; And Including a straight resonator disposed between the hairpin resonators, And the first dielectric plate is disposed directly above the pair of hairpin resonators and the straight resonator. delete delete delete The method according to claim 1, The micro filter pattern is a superconducting microwave filter consisting of a superconductor.

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