A ferromagnetic powder low-pass filter and packaging method

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 comprises a shell with openings in the upper end and the lower end, an insulating rod, a wire coil and two packaging connectors. The wire coil is spirally wound on the insulating rod; the two 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 with each other; 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, the two ends of the shell are each provided with a packaging connector, the two ends of the wire coil are fixedly connected with the two packaging connectors respectively, and theshell is filled with ferromagnetic powder. According to the ferromagnetic powder low-pass filter and the packaging method provided by the invention, the size of the filter is reduced while the performance of the filter is improved, the refrigeration cost is reduced, and the measurement interference in a superconducting device is reduced.

Description

technical field [0001] The invention relates to the technical field of filters, in particular to a ferromagnetic powder low-pass filter and a packaging method. Background technique [0002] For the DC signal in the weak signal experiment of the superconducting quantum experiment, it is necessary to effectively filter out the high-frequency noise. In the dilution refrigerator that provides a low-temperature environment, the space is very small, so the low-pass filter used in the measurement should not only have a low cut-off frequency and good suppression of high-frequency signals outside the passband, but also have a volume Small size and excellent performance in low temperature conditions. [0003] Accordingly, Martinis et al. initially reported the copper powder filter. Its main principle is to use the skin effect of high-frequency electromagnetic waves in the conductor to make the electromagnetic waves pass through a cavity filled with metal powder, so that the high-freq...

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Problems solved by technology

[0004] The existing metal powder filter has copper powder as its main effective attenuation component, and the magnetic permeability of copper is not high enough. Therefore, the cut-off frequency of the metal powder filter using copper powder is not low enough, and the passband sideband is not steep enough in the frequency domain.

Therefore, in order to achieve a lower cut-off frequency and a better squareness factor in the frequency domain, it is necessary to increase the length of the wire and the mass or volume of the copper powder, which in turn leads to an increase in the size of the copper powder filter, which is different from the small size of the dilution refrigerator. Contradictions in space, increasing cooling costs

In addition, the prior art usually adopts a single-direction winding method when winding the wire coil in the cavity of the metal powder filter. This winding method will excite a magnetic field to the surrounding environment when the filter is working, thereby affecting the Interfering with the measurement of conductive devices

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