CN111540984B - Ferromagnetic powder low-pass filter and packaging method - Google Patents
Ferromagnetic powder low-pass filter and packaging method Download PDFInfo
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- CN111540984B CN111540984B CN202010216662.8A CN202010216662A CN111540984B CN 111540984 B CN111540984 B CN 111540984B CN 202010216662 A CN202010216662 A CN 202010216662A CN 111540984 B CN111540984 B CN 111540984B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P11/00—Apparatus or processes specially adapted for manufacturing waveguides or resonators, lines, or other devices of the waveguide type
- H01P11/007—Manufacturing frequency-selective devices
Abstract
The invention discloses a ferromagnetic powder low-pass filter and a packaging method, and relates to the technical field of filters. The ferromagnetic powder low-pass filter and the packaging method thereof provided by the invention have the advantages that the performance of the filter is improved, the size of the filter is reduced, the refrigeration cost is reduced, and the measurement interference on a superconducting device is reduced.
Description
Technical Field
The invention relates to the technical field of filters, in particular to a ferromagnetic powder low-pass filter and a packaging method.
Background
For a direct current signal in a weak signal experiment of a superconducting quantum experiment, high-frequency noise needs to be effectively filtered. In a dilution refrigerator providing a low temperature environment, since the space is very narrow, a low-pass filter used in measurement should have characteristics of low cut-off frequency and good suppression of high-frequency signals outside a pass band, and also should have characteristics of small size and excellent operation performance under a low temperature condition.
Accordingly, martini et al originally reported a copper powder filter, which mainly utilizes the skin effect of high-frequency electromagnetic waves in a conductor to make the electromagnetic waves pass through a cavity filled with metal powder, so that the high-frequency electromagnetic waves are severely attenuated when passing through the surface of the metal powder, and simultaneously the attenuation of direct current signals is very small, thereby forming the effect of low-pass filtering. The manufacturing process is briefly described as follows: after a wire is wound into a coil in a cuboid or cylindrical metal cavity along a fixed direction, the cavity is filled with copper powder or a mixture of the copper powder and epoxy resin in a certain proportion, matched adapters are installed on two sides of the cavity, and finally the complete copper powder filter is packaged.
The existing metal powder filter has the main effective attenuation component of copper powder, but the magnetic conductivity of copper is not high enough, so the cut-off frequency of the metal powder filter using the copper powder is not low enough, and the passband sideband on the frequency domain is not steep enough. Therefore, to achieve a lower cut-off frequency and a better squareness factor in the frequency domain, the length of the wire and the mass or volume of the copper powder need to be increased, which leads to an increase in the size of the copper powder filter, which contradicts the narrow space in the dilution refrigerator, increasing the refrigeration cost. In addition, in the prior art, a unidirectional winding mode is mostly adopted when a wire coil in a metal powder filter cavity is wound, and the winding mode can excite a magnetic field to the surrounding environment when the filter works, so that the measurement of a superconducting device is interfered.
Disclosure of Invention
In order to solve the technical problems, the invention provides a ferromagnetic powder low-pass filter and a packaging method thereof, which can reduce the size of the filter, reduce the refrigeration cost and reduce the measurement interference on a superconducting device while improving the performance of the filter.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a ferromagnetic powder low-pass filter which comprises a shell with openings at the upper end and the lower end, an insulating rod, a wire coil and two packaging connectors, wherein the wire coil is spirally wound on the insulating rod, the two ends of the wire coil respectively protrude out of the upper surface and the lower surface of the insulating rod, the wire coil comprises a first winding section and a second winding section which are connected, the winding directions of the first winding section and the second winding section are opposite, the insulating rod and the wire coil are arranged in the shell, the insulating rod is arranged in the middle of the shell, the two ends of the shell are respectively provided with one packaging connector, the two ends of the wire coil are respectively fixedly connected with the two packaging connectors, and ferromagnetic powder is filled in the shell.
Preferably, the outer wall of the insulating rod is provided with an insulating double faced adhesive tape, and the wire coil is fixed on the insulating double faced adhesive tape.
Preferably, the packaging connector further comprises a plurality of screws, the upper end and the lower end of the shell are respectively provided with four threaded holes, the screws correspond to the threaded holes one to one, and the packaging connector is fixed on the shell through the screws.
Preferably, the packaging joint is an SMA-KFD joint.
Preferably, the shell is a hollow cuboid structure, and the axis of the insulating rod is collinear with the axis of the shell.
Preferably, the casing is the stainless steel casing, the height of casing is 54mm, the length and the width of casing are 14mm, the fillet radius of four corners of casing outer wall is 1 mm.
Preferably, the insulating rod is insulating wooden stick, insulating wooden stick is diameter 5mm, length 42 mm's cylinder, the wire coil is the enameled copper wire, the length of enameled copper wire is 1.5m, the diameter of enameled copper wire is 0.22 mm.
Preferably, the ferromagnetic powder has a particle diameter of 40 to 200 μm.
The invention also provides a method for packaging the ferromagnetic powder low-pass filter, which comprises the following steps:
marking a longitudinal center on the surface of the insulating rod, making an upper side mark and a lower side mark on the upper side and the lower side of the longitudinal center, wherein the upper side mark and the lower side mark are both 1cm away from the longitudinal center, extending one end of the wire coil out of the top of the insulating rod to the upper side mark of the insulating rod along the length direction of the insulating rod, starting to wind the wire coil around the insulating rod along the clockwise direction, and the winding method for winding the wire coil is a single-layer spiral tight arrangement mode;
when the insulation rod is wound to the longitudinal center of the insulation rod, changing the winding direction to be anticlockwise, continuously winding the insulation rod to the lower side mark of the insulation rod, and extending the other end of the wire coil out along the length direction of the insulation rod;
placing the manufactured wire coil and the insulating rod into the shell, respectively welding two ends of the wire coil on the two encapsulation joints, and fixing one encapsulation joint at one end of the shell;
and step four, keeping the combined body of the lead coil and the insulating rod at the center of the shell, filling ferromagnetic powder into the shell, and then fixing the other packaging joint at the other end of the shell.
Compared with the prior art, the invention has the following technical effects:
the main effective attenuation component of the ferromagnetic powder low-pass filter provided by the invention is ferromagnetic powder, the magnetic conductivity of the ferromagnetic powder is much higher than that of copper powder, and compared with the use of the copper powder, the ferromagnetic powder is used in a small amount and the length of a wire coil wire is short on the premise of ensuring the filtering effect, so that the size of the metal powder filter can be greatly reduced, and the refrigeration cost is saved. The invention adopts a winding method of 'first forward and then reverse' when winding the required wire coil, so that magnetic fields excited in the surrounding environment when the filter works can be counteracted to the maximum extent, and the measurement interference on the superconducting device is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a perspective view of a housing of a ferromagnetic powder low-pass filter according to the present invention;
FIG. 2 is a front view of the housing of the ferromagnetic powder low-pass filter provided by the present invention;
FIG. 3 is a top view of the housing of the ferromagnetic powder low-pass filter provided by the present invention;
FIG. 4 is a schematic diagram of a winding pattern of a wire coil of a ferromagnetic powder low-pass filter provided by the present invention;
FIG. 5 shows the reflection coefficient S of the ferromagnetic powder low-pass filter at various temperatures in the frequency range of 100KHz to 100MHz when the filter is filled with iron powder11A graph;
FIG. 6 shows the transmission coefficient S of the ferromagnetic powder low-pass filter at various temperatures in the frequency range of 100KHz to 100MHz when the ferromagnetic powder low-pass filter is filled with iron powder21A graph;
FIG. 7 shows the reflection coefficient S of the ferromagnetic powder low-pass filter at various temperatures in the frequency range of 100KHz to 8GHz when the filter is filled with iron powder11A graph;
FIG. 8 shows the transmission coefficient S of the ferromagnetic powder low-pass filter at various temperatures in the frequency range of 100KHz to 8GHz when the filter is filled with iron powder21Graph is shown.
Description of reference numerals: 1. a housing; 2. an insulating rod; 3. a wire coil; 4. a threaded bore.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a ferromagnetic powder low-pass filter and a packaging method thereof, which can reduce the size of the filter, reduce the refrigeration cost and reduce the measurement interference on a superconducting device while improving the performance of the filter.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1-4, this embodiment provides a ferromagnetic powder low pass filter, including upper and lower both ends open-ended casing 1, insulating rod 2, wire coil 3 and two encapsulation joints, wire coil 3 spiral winding is on insulating rod 2, and the both ends of wire coil 3 bulge respectively in the upper surface and the lower surface of insulating rod 2, wire coil 3 is including the first winding section and the second winding section that are connected, the winding direction of first winding section and second winding section is opposite, insulating rod 2 and wire coil 3 all set up inside casing 1, and insulating rod 2 sets up in casing 1 middle part, an encapsulation joint is installed respectively at the both ends of casing 1, the both ends of wire coil 3 respectively with two encapsulation joint fixed connection, casing 1 intussuseption is filled with ferromagnetic powder.
The main effective attenuation component of the ferromagnetic powder low-pass filter in the embodiment is ferromagnetic powder, the magnetic conductivity of the ferromagnetic powder is much higher than that of copper powder, and compared with the use of copper powder, the ferromagnetic powder is used, so that on the premise of ensuring the filtering effect, the powder consumption is small, and the length of the 3 wires of the wire coil is short, thereby greatly reducing the size of the metal powder filter and saving the refrigeration cost. In this embodiment, a winding method of "forward and backward" is adopted when winding the required wire coil 3, that is, when winding the wire coil 3, a clockwise winding method of spiral type close arrangement is adopted in the first half of the total winding length, and an anticlockwise winding method of spiral type close arrangement is adopted in the second half, so that magnetic fields generated when current passes through the wire coil 3 can be mutually offset, thereby reducing the influence of the use of the filter on the magnetic field in space, and reducing the interference on the measurement of the superconducting device.
Specifically, the ferromagnetic powder is an iron powder, a cobalt powder, a nickel powder, an iron oxide powder, a cobalt oxide powder, or a nickel oxide powder.
In order to fix the wire coil 3 on the insulating rod 2, the outer wall of the insulating rod 2 is provided with an insulating double faced adhesive tape, and the wire coil 3 is fixed on the insulating double faced adhesive tape.
Still include a plurality of screws in this embodiment, the upper end and the lower extreme of casing 1 are provided with four screw holes 4 respectively, and the screw is fixed in on the casing 1 through the screw with screw hole 4 one-to-one, with the encapsulation joint. Specifically, the packaging connector is an SMA-KFD connector. In the present embodiment, as shown in fig. 3, threaded holes 4 of M2.5 × 2mm and screws of M2.5 × 5mm are used, four threaded holes 4 at each end are arranged in a square array, and the hole center distance between two adjacent threaded holes 4 is 8.6 mm.
The shell 1 is a hollow cuboid structure, and the axial lead of the insulating rod 2 is collinear with the axial lead of the shell 1. In this embodiment, the housing 1 is a stainless steel housing, as shown in fig. 2-3, the height of the housing 1 is 54mm, the length and width are both 14mm, and the radius of the four corners of the outer wall is 1 mm. The effective volume of the interior of the housing 1 is 11.2mm by 50mm, i.e. 6272mm3。
In this embodiment, the insulating rod 2 is an insulating wood rod, and the insulating rod 2 is a cylinder with a diameter of 5mm and a length of 42 mm.
In this embodiment, the wire coil 3 is an enameled copper wire, the total length of the wire coil 3 is 1.5m, the diameter of the wire coil 3 is 0.22mm, the clockwise winding method of the spiral tight arrangement is used for 0.75m in the front of the wire coil 3, and the counterclockwise winding method of the spiral tight arrangement is used for 0.75m in the back of the wire coil 3.
Specifically, the ferromagnetic powder has a particle diameter of 40 to 200 μm. In this embodiment, iron powder with surface oxidized particles of 48 μm diameter was used for the filling.
The S-curves of the scattering parameters at different temperatures (K: Kelvin) as a function of frequency for the filling with iron powder in this example are shown in FIGS. 5-8. It can be seen from the figure that the ferromagnetic powder low-pass filter in this embodiment reaches a cut-off frequency of-3 dB at 3.2MHz, and attenuates to-80 dB around 940 MHz.
The embodiment also provides a method for packaging a ferromagnetic powder low-pass filter, which comprises the following steps:
selecting an enameled copper wire with the length of 1.5m and the diameter of 0.22mm as a lead coil 3, and polishing 3mm long parts at two ends of the enameled copper wire by using sand paper until a copper core is exposed;
step two, selecting an insulating wood rod with the length of 42mm and the diameter of 5mm as a main body for winding the enameled copper wire, marking a lengthwise center on the surface of the insulating wood rod, marking 1cm positions of the upper side and the lower side of the insulating wood rod, and wrapping the whole insulating wood rod by using insulating double faced adhesive tapes;
step three, after one end of the enameled copper wire extends out of the top of the insulating wood bar, the end extends to a mark position 1cm above the center of the insulating wood bar along the length direction of the insulating wood bar, and the enameled copper wire is wound around the insulating wood bar along the clockwise direction;
when the insulated wood rod is wound to the mark of the length center of the insulated wood rod, changing the winding direction to be anticlockwise, continuously winding the insulated wood rod to the mark of 1cm below the center of the insulated wood rod, and extending the other end of the enameled copper wire out along the length direction of the insulated wood rod;
putting the manufactured wire coil 3 and the insulating wood bar into the shell 1, respectively welding two ends of the wire coil 3 on two SMA-KFD joints, and fixing one SMA-KFD joint at a threaded hole 4 on one side of the shell 1 by using 4M 2.5 multiplied by 5mm screws;
and sixthly, keeping the combination of the wire coil 3 and the insulating wood bar at the axis of the shell 1, filling ferromagnetic powder into the shell 1 from one end of the unfixed SMA-KFD joint, and then fixing the other SMA-KFD joint at the other side of the shell 1 by using 4M 2.5 multiplied by 5mm screws, thereby completing the packaging of the ferromagnetic powder low-pass filter in the embodiment.
The principle and the implementation mode of the present invention are explained by applying specific examples in the present specification, and the above descriptions of the examples are only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (9)
1. A ferromagnetic powder low-pass filter is characterized by comprising a shell with openings at the upper end and the lower end, an insulating rod, a wire coil and two packaging connectors, wherein the wire coil is spirally wound on the insulating rod, and both ends of the wire coil protrude out of the upper surface and the lower surface of the insulating rod respectively, the wire coil comprises a first winding section and a second winding section which are connected, the winding directions of the first winding section and the second winding section are opposite, the insulating rod and the wire coil are both arranged in the shell, the insulating rod is arranged in the middle of the shell, two ends of the shell are respectively provided with the packaging joints, the two ends of the wire coil are respectively fixedly connected with the two packaging connectors, ferromagnetic powder is filled in the shell, and the wire coil is not in direct contact with the shell.
2. The ferromagnetic powder low-pass filter according to claim 1, wherein the outer wall of the insulating rod is provided with an insulating double-faced adhesive tape, and the wire coil is fixed on the insulating double-faced adhesive tape.
3. The ferromagnetic powder low-pass filter according to claim 1, further comprising a plurality of screws, wherein four threaded holes are respectively formed at the upper end and the lower end of the housing, the screws correspond to the threaded holes one by one, and the sealing joints are fixed to the housing through the screws.
4. The ferromagnetic powder low pass filter of claim 3, wherein the potting joint is an SMA-KFD joint.
5. The ferromagnetic powder low-pass filter according to claim 1, wherein the housing has a hollow rectangular parallelepiped structure, and an axis of the insulating rod is collinear with an axis of the housing.
6. The ferromagnetic powder low pass filter of claim 1, wherein the housing is a stainless steel housing, the housing has a height of 54mm, the housing has a length and a width of 14mm, and the outer wall of the housing has a radius of 1mm at four corners.
7. The ferromagnetic powder low pass filter according to claim 1, wherein the insulating rod is an insulating wood rod, the insulating wood rod is a cylinder with a diameter of 5mm and a length of 42mm, the wire coil is an enameled copper wire, the length of the enameled copper wire is 1.5m, and the diameter of the enameled copper wire is 0.22 mm.
8. The ferromagnetic powder low-pass filter according to claim 1, wherein the ferromagnetic powder has a particle diameter of 40 to 200 μm.
9. A method for encapsulating a ferromagnetic powder low-pass filter as defined in any one of claims 1 to 8, comprising the steps of:
marking a longitudinal center on the surface of the insulating rod, making an upper side mark and a lower side mark on the upper side and the lower side of the longitudinal center, wherein the upper side mark and the lower side mark are both 1cm away from the longitudinal center, extending one end of the wire coil out of the top of the insulating rod to the upper side mark of the insulating rod along the length direction of the insulating rod, starting to wind the wire coil around the insulating rod along the clockwise direction, and the winding method for winding the wire coil is a single-layer spiral tight arrangement mode;
when the insulation rod is wound to the longitudinal center of the insulation rod, changing the winding direction to be anticlockwise, continuously winding the insulation rod to the lower side mark of the insulation rod, and extending the other end of the wire coil out along the length direction of the insulation rod;
placing the manufactured wire coil and the insulating rod into the shell, respectively welding two ends of the wire coil on the two encapsulation joints, and fixing one encapsulation joint at one end of the shell;
and step four, keeping the combined body of the lead coil and the insulating rod at the center of the shell, filling ferromagnetic powder into the shell, and then fixing the other packaging joint at the other end of the shell.
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| CN202010216662.8A CN111540984B (en) | 2020-03-25 | 2020-03-25 | Ferromagnetic powder low-pass filter and packaging method |
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| CN111540984B true CN111540984B (en) | 2021-01-26 |
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| FR2977084B1 (en) * | 2011-06-21 | 2013-07-05 | Valeo Systemes Dessuyage | ATTENUATOR BAND FILTER |
| CN103123849A (en) * | 2011-11-19 | 2013-05-29 | 陆峰 | Modified ring-shaped inductor |
| CN203826973U (en) * | 2013-10-14 | 2014-09-10 | 山东三泰节能技术服务有限公司 | Electromagnetic-balance filtering power-saving device |
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| US5212463A (en) * | 1992-07-22 | 1993-05-18 | The United States Of America As Represented By The Secretary Of The Army | Planar ferro-electric phase shifter |
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