Method for reducing frequency of narrow-band superconducting filter

Abstract

The invention belongs to the technical field of superconducting filtering, and particularly relates to a method for reducing the frequency of a narrow-band superconducting filter. According to the method provided by the invention, a narrow-band superconducting thin film substrate is spin-coated with Teflon protection glue and then is cured; measuring the center frequency of the narrow-band superconducting thin film substrate according to the calibration temperature; when the error between the center frequency and the design frequency does not exceed + / -70kHz, the frequency of the narrow-band superconducting filter reaches the standard; when the center frequency is low, simulation software is used for correction; and when the center frequency is too high, the first step is repeated, the rotating speed of spin coating is reduced, glue removal is carried out on the narrow-band superconducting thin film substrate before spin coating, and the steps are repeated. The method provided by the invention can quickly realize fine tuning matching of the center frequency of the single filter in the superconducting filter bank, is high in efficiency, and greatly reduces the matching difficulty and matching time and reduces the loss of the superconducting film compared with a traditional method.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting filtering, and in particular relates to a method for reducing the frequency of a narrow-band superconducting filter. Background Art

[0002] With the development of superconducting filtering technology, superconducting filtering technology has begun to gradually transition from single channel (single frequency) to multi-channel. However, when the multi-channel superconducting filter is integrated into the vacuum dewar, the frequency alignment problem often occurs. According to the traditional method, the only way is to adjust the simulation design and rebuild the superconducting filter, which will greatly increase the time and material costs of the project.

[0003] At present, the commonly used superconducting materials in the design and production of superconducting filters both at home and abroad are mainly yttrium barium copper oxide (YBCO) and TI series (TBCCO). Taking YBCO superconducting film as an example, after reaching the superconducting transition temperature, as the temperature decreases, the center frequency of the superconducting filter made of YBCO superconducting film will gradually increase. In actual production, multiple superconducting filters are usually integrated in a vacuum dewar to form a superconducting filter group, and the superconducting filter group is given a fixed temperature, which is usually called the calibration temperature. When multiple superconducting filters are integrated in a vacuum dewar, due to the different uniformity and position distribution of the superconducting materials, when the temperature reaches the calibration temperature, the center frequency of each single superconducting filter will not meet the indicators. Summary of the invention

[0004] The purpose of the present invention is to provide a method for reducing the frequency of a narrowband superconducting filter. The method provided by the present invention can quickly achieve fine-tuning and matching of the center frequency of a single filter in a superconducting filter group.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for reducing the frequency of a narrowband superconducting filter, comprising the following steps:

[0007] (1) Spin coating a narrow-band superconducting thin film substrate with Teflon protective glue and then curing it;

[0008] (2) measuring the center frequency of the narrow-band superconducting thin film substrate at the calibration temperature; when the error between the center frequency and the design frequency does not exceed ±70kHz, the frequency of the narrow-band superconducting filter meets the standard; when the center frequency is too low, correct it using simulation software; when the center frequency is too high, repeat step (1) and reduce the rotation speed of the spin coating, remove the glue from the narrow-band superconducting thin film substrate before spin coating, and repeat step (2).

[0009] Preferably, the Teflon protective glue is AF 1601X model Teflon protective glue.

[0010] Preferably, the spin coating speed is 1000-5000 rpm, and the spin coating time is 40 s.

[0011] Preferably, the curing is drying; the drying includes pre-baking and re-baking in sequence; the pre-baking temperature is 110°C, and the re-baking temperature is 160°C.

[0012] Preferably, the pre-baking heat preservation and curing time is 10 minutes; the re-baking heat preservation and curing time is 25 minutes.

[0013] Preferably, the glue removal is washing; the washing comprises sequentially performing ketone washing and alcohol washing.

[0014] Preferably, the ketone washing reagent is acetone; and the alcohol washing reagent is ethanol.

[0015] Preferably, the calibration temperature is -203.15°C.

[0016] Preferably, the center frequency of the narrowband superconducting filter is 0.1-1 GHz.

[0017] Preferably, the bandwidth of the narrowband superconducting filter is 0.1-1 MHz.

[0018] The present invention provides a method for reducing the frequency of a narrowband superconducting filter. The method provided by the present invention can quickly achieve fine-tuning and matching of the center frequency of a single filter in a superconducting filter group, has high efficiency, greatly reduces the matching difficulty and matching time compared to traditional methods, and reduces the loss of superconducting thin films. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a simulation result diagram of the narrow-band superconducting filter of Example 1 of the present invention;

[0021] Figure 2 This is a topographical diagram of the superconducting thin film substrate of Example 1 of the present invention;

[0022] Figure 3 The center frequency of the superconducting thin film substrate measured in step (2) of Example 1 of the present invention;

[0023] Figure 4 It is the center frequency of the superconducting thin film substrate measured in step (5) of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a method for reducing the frequency of a narrowband superconducting filter, comprising the following steps:

[0025] (1) Spin coating a narrow-band superconducting thin film substrate with Teflon protective glue and then curing it;

[0026] (2) measuring the center frequency of the narrow-band superconducting thin film substrate at the calibration temperature; when the error between the center frequency and the design frequency does not exceed ±70kHz, the frequency of the narrow-band superconducting filter meets the standard; when the center frequency is too low, correct it using simulation software; when the center frequency is too high, repeat step (1) and reduce the rotation speed of the spin coating, remove the glue from the narrow-band superconducting thin film substrate before spin coating, and repeat step (2).

[0027] The invention spin-coats a narrow-band superconducting thin film substrate with Teflon protective glue and then solidifies it. In the invention, the spin-coating device is preferably a spin-coating glue spinner; the spin-coating speed is preferably 1000-5000 rpm, specifically 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 4000 rpm or 5000 rpm, and the spin-coating time is preferably 40 seconds.

[0028] In the present invention, the Teflon protective glue is preferably AF 1601X model Teflon protective glue.

[0029] In the present invention, the curing is preferably drying; the drying is preferably hot plate drying; the drying preferably includes pre-baking and re-baking in sequence; the pre-baking temperature is preferably 110°C, and the insulation curing time is preferably 10 minutes; the re-baking temperature is preferably 160°C, and the insulation curing time is preferably 25 minutes.

[0030] The present invention measures the center frequency of a narrowband superconducting thin film substrate according to a calibration temperature. In the present invention, the calibration temperature is preferably -203.15°C (70K).

[0031] In the present invention, the method for preparing the narrowband superconducting thin film substrate is preferably: designing a superconducting filter by simulation software, making a mask according to the simulation design, and photolithography and dry etching the superconducting thin film.

[0032] In the present invention, the simulation software is preferably sonnet simulation software.

[0033] In the present invention, the photolithography is preferably: coating the superconducting thin film with glue, pre-baking, post-baking, exposing and developing in sequence.

[0034] In the present invention, the photoresist for coating is preferably BP212 photoresist; the coating rotation speed is preferably 900-2500rpm, specifically 900rpm, 1200rpm, 1500rpm, 1800rpm, 2100rpm, 2300rpm or 2500rpm; the coating time is preferably 6-30s, specifically 6s, 8s, 10s, 12s, 15s, 20s, 25s or 30s.

[0035] In the present invention, the pre-drying temperature is preferably 100° C., and the heat preservation and drying time is preferably 15 minutes.

[0036] In the present invention, the post-baking temperature is preferably 120° C., and the heat preservation and drying time is preferably 25 minutes.

[0037] In the present invention, the exposure intensity is preferably 20 mw, and the exposure time is preferably 5 s.

[0038] In the present invention, the development time is preferably 20 seconds.

[0039] In the present invention, the dry engraving time is preferably 60 minutes.

[0040] In the present invention, the device for measuring the center frequency of a narrowband superconducting thin film substrate preferably includes a low-temperature test platform and a network analyzer; the low-temperature test platform is preferably equipped with a Force 4188 Stirling refrigerator and a vacuum dewar; the power output of the network analyzer is preferably -30dBm.

[0041] In the present invention, the center frequency of the narrowband superconducting filter is preferably 0.1-1 GHz, specifically 0.1 GHz, 0.2 GHz, 0.3 GHz, 0.5 GHz, 0.7 GHz, 0.9 GHz or 1 GHz, and the bandwidth is preferably 0.1-1 MHz, specifically 0.1 MHz, 0.2 MHz, 0.3 MHz, 0.5 MHz, 0.7 MHz, 0.9 MHz or 1 MHz.

[0042] When the center frequency is too high, the present invention repeats step (1) and lowers the rotation speed of the spin coating, removes the adhesive from the narrow-band superconducting thin film substrate before the spin coating, and repeats step (2). In the present invention, the adhesive removal is preferably washing; the washing preferably includes ketone washing and alcohol washing in sequence; the ketone washing reagent is preferably acetone; the alcohol washing reagent is preferably ethanol. The present invention removes the Teflon protective adhesive on the surface of the narrow-band superconducting thin film substrate by adhesive removal.

[0043] When repeating steps (1) and (2), the present invention uses the same low-temperature test platform to measure the center frequency of the superconducting thin film substrate according to the calibration temperature. The test method is the same as step (2). At this time, the center frequency of the superconducting thin film substrate will decrease. The decreased center frequency is recorded. If it meets the design frequency index, the process ends.

[0044] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0045] Example 1

[0046] (1) Using the sonnet simulation software, a superconducting filter with a center frequency of 190 MHz and a bandwidth of 0.600 MHz is designed. The resonator is designed in the form of a single spiral. The resonator line width is 40 μm and the dielectric constant is 9.73. Figure 1 shown.

[0047] (2) A mask is made according to the simulation design, and photolithography and dry etching are performed according to the parameters in Table 1 to obtain a superconducting thin film substrate, whose morphology is as follows Figure 2 shown.

[0048] Table 1 Parameters of photolithography and dry etching

[0049] Photolithography and dry etching parameters Settings Photoresist model BP212 Low speed (rpm) 900 Low speed time(s) 6 High speed (rpm) 2500 High speed time(s) 30 Pre-baking temperature (℃) 100 Pre-baking time (min) 15 Post-baking temperature (℃) 120 Post-baking time (min) 25 Exposure intensity (mw) 20 Exposure time(s) 5 Development time(s) 20 Drying time (min) 60

[0050] The same low temperature test platform equipped with a Lihan 4188 Stirling refrigerator and a vacuum dewar was used to calibrate the 70K temperature test and record the center frequency. The center frequency is as follows Figure 3 As shown: the center frequency is 192.040MHz, which is about 2MHz higher than the design frequency of 190MHz.

[0051] (3) Place the superconducting thin film substrate into a spin coater and spin coat Teflon protective glue with a rotation speed of 1000 rpm and a time of 40 s.

[0052] (4) The spin-coated superconducting thin film substrate is dried on a hot plate, pre-baked at 110°C for 10 min, and then baked at 160°C for 25 min to ensure that the Teflon protective adhesive is cured.

[0053] (5) Re-measure the center frequency of the superconducting thin film substrate according to step (2). The center frequency is as follows: Figure 4 As shown: the center frequency is 190.044MHz, does not exceed ±70kHz, has been corrected, and is completed.

[0054] It can be seen from the above embodiments that the method provided by the present invention can quickly achieve fine-tuning and matching of the center frequency of a single filter in a superconducting filter group.

[0055] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for reducing the frequency of a narrowband superconducting filter, characterized in that: The following steps are involved: (1) Spin coating a narrow-band superconducting thin film substrate with Teflon protective glue and then curing it; (2) measuring the center frequency of the narrow-band superconducting thin film substrate at the calibration temperature; when the error between the center frequency and the design frequency does not exceed ±70kHz, the frequency of the narrow-band superconducting filter meets the standard; when the center frequency is too low, correct it using simulation software; when the center frequency is too high, repeat step (1) and reduce the rotation speed of the spin coating, remove the glue from the narrow-band superconducting thin film substrate before spin coating, and repeat step (2).

2. The method according to claim 1, characterized in that The Teflon protective glue is AF 1601X model Teflon protective glue.

3. The method according to claim 1 or 2, characterized in that: The spin coating speed is 1000-5000 rpm, and the spin coating time is 40 s.

4. The method according to claim 1, characterized in that The curing is drying; the drying includes pre-baking and re-baking in sequence; the pre-baking temperature is 110°C, and the re-baking temperature is 160°C.

5. The method according to claim 4, characterized in that The heat preservation and curing time of the pre-baking is 10 minutes; the heat preservation and curing time of the re-baking is 25 minutes.

6. The method according to claim 1 or 4, characterized in that: The degumming is washing; the washing comprises ketone washing and alcohol washing in sequence.

7. The method according to claim 6, characterized in that The ketone washing reagent is acetone; the alcohol washing reagent is ethanol.

8. The method according to claim 1, characterized in that: The calibration temperature is -203.15°C.

9. The method according to claim 1, characterized in that: The central frequency of the narrowband superconducting filter is 0.1-1 GHz.

10. The method according to claim 1, characterized in that The bandwidth of the narrowband superconducting filter is 0.1-1 MHz.

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