JPH0461311A - Composite parts - Google Patents

Abstract

PURPOSE:To process signals even in a narrow band by connecting a capacitance element composed of a dielectric substance to inductance elements composed of a magnetic substance and specifying the initial permeability of the magnetic substance. CONSTITUTION:Ferrite beads l and 2 of a material having a prescribed frequency characteristic and initial permeability of mui=20 to 300 and a capacitor 3 are provided. Such a magnetic substance that the initial permeability mui is constant within a frequency range of 30-200 MHz linearly increases in the reactance component proportionally to the frequency within the similar frequency range and the inductance component acts as a pure inductance component within the frequency range. When each of the ferrite beads l and 2 having an initial permeability of mui=40 is formed to a cylinder having a length of 40mm and outside diameter of 1.8mm, the inductance of the beads l and 2 becomes about 30nH and this inductance value can be maintained against frequencies of about 100 MHz or lower. The theoretical characteristic impedance and cut-off frequency respectively become about 11OMEGA and about 60 MHz when such ferrite beads and the capacitor 3 of C=470pF are used.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a composite component intended for use in electronic circuits and the like on which electronic components such as ICs are mounted.

BACKGROUND OF THE INVENTION In recent years, as a composite component of this type, a constant-shaped filter has become known, which is composed of, for example, two ferrite beads as an inductance element and a capacitor as a capacitance element.

A filter using ferrite beads (hereinafter referred to as a ferrite bead type filter) configured as described above is generally made of a magnetic material with a relatively high initial magnetic permeability μi (μi = 100
(nearly 0 material) is used. The frequency characteristics of such a magnetic material with a relatively high initial permeability μi are as shown in (■) in FIG. 3, and it maintains a constant value only up to a frequency of about 3 MHz. Therefore, the frequency range that acts as a reactance component (mostly an inductance component) is approximately 3M.
Hz, and in the frequency range above this, it acts as a resistive component. Conventional ferrite bead filters utilize this resistance component.

Further, the damping characteristic becomes a gentle characteristic as shown by the dotted line in FIG.

Problems to be Solved by the Invention Unlike filters whose coils are formed of mild steel wire (hereinafter referred to as wire-wound filters), it is not necessary to strictly calculate the characteristic impedance and cutoff frequency of this ferrite bead type filter. When such components are mounted on a signal line, there are problems such as attenuating not only unnecessary noise signals but also necessary signals.

In view of the above-mentioned conventional problems, the present invention uses a ferrite bead type filter to realize the steep attenuation characteristic obtained by matching the characteristic impedance, which is a feature of wire-wound filters, and to provide a filter that also enables signal processing in a narrow band. The purpose is to have characteristics.

Means for Solving the Problem In order to solve this problem, the present invention provides an initial magnetic permeability μi of 3
A material that maintains a constant value in the frequency band from 0 to 200MHz (
It is characterized by combining a capacitor with a magnetic material having a relatively low initial magnetic permeability μi (μ1 = 20 to 300).

Function: In this configuration, the characteristic impedance and cutoff frequency can be calculated by calculation in a frequency band where the initial magnetic permeability is kept constant, and a steep damping characteristic can be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the structure of a composite part in one embodiment of the present invention. In Figure 1, 1.2 is ■~ in Figure 3
2 is a ferrite bead made of a material having an initial magnetic permeability μ1-20 to 300 and has a frequency characteristic; 3 is a capacitor;

Figure 2 shows its equivalent circuit.

The operation of the ferrite bead type filter configured as described above will be described below.

In FIG. 3, in a magnetic material whose initial magnetic permeability μi of ① to ② maintains a constant value up to a frequency of 30 to 200 MHz as a frequency characteristic, the reactance component increases linearly in proportion to the frequency in the same frequency range. In this frequency range, it acts as a pure inductance component. Here, the shape of the ferrite bead with initial magnetic permeability μi = 40 is 40 w in length.
a, the inductance is about 30nH when the outer diameter is 1.8-cylindrical, and the frequency is about 100MH
This value can be maintained up to z. This and C=470p
The theoretical characteristic impedance when the capacitor with t=" is configured as a T-type filter is approximately 11Ω.

The cutoff frequency is approximately 60MHz.

The solid line in FIG. 4 shows the attenuation characteristic when the input impedance is 50Ω and the output impedance is 11Ω. Moreover, the dotted line is the attenuation characteristic obtained by a measurement system used in a general ferrite bead type filter, which is an input impedance of 50Ω and an output impedance of 50Ω.

FIG. 5 shows the attenuation characteristics of the ferrite bead filter according to the present invention and a conventional commercially available ferrite bead filter, measured at a measurement system input/output impedance of 50Ω to 50Ω. As is clear from these figures, the measurement system in which the output impedances are matched has a clear cutoff frequency, and has superior filter characteristics compared to the characteristics in which the impedances are not matched. Also, the same 50Ω-5
It can be seen that even in a 0Ω measurement system, the ferrite bead type filter according to the present invention has better filter characteristics than the conventional product. This makes it possible to use it in circuits that extract only the necessary signals when many signals are included in a narrow frequency band, such as video signals that could not be used until now. It is.

Note that the shapes of the magnetic material as the inductance element and the dielectric material as the resistance element may be arbitrarily determined.

Effects of the Invention As described above, the present invention has the advantage that the conventionally used initial permeability μ
The initial magnetic permeability μi of ferrite beads near 1=1000
By replacing it with a magnetic material of =20 to 300 and terminating the output impedance at the theoretical value, it is possible to obtain attenuation characteristics equivalent to a wire-wound filter, making it similar to video signal circuits that could not be used until now. This enables signal processing in a narrow band.

[Brief explanation of the drawing]

Figure 1 is a front view of a general ferrite bead type filter including the present invention, Figure 2 is an equivalent circuit diagram of the same filter, and Figure 3 is an equivalent circuit diagram of the same filter.
The figure is an initial permeability characteristic diagram with respect to frequency, Figure 4 is an attenuation characteristic diagram with respect to frequency of a ferrite bead filter according to an embodiment of the present invention, and Figure 5 is a ferrite characteristic diagram of an embodiment of the present invention in a 50Ω-50Ω system. FIG. 3 is a diagram showing attenuation characteristics versus frequency of a bead-type filter and a conventional ferrite bead-type filter. 1.2... Ferrite beads (inductance element made of magnetic material), 3... Capacitor (capacitance element made of dielectric material). Name of agent: Patent attorney Shigetaka Awano and 16 others ＼ Ku Kumyu [MI-1z1 Shukata]k [M)lz]

Claims (1)

[Claims] A composite component formed by connecting a capacitance element made of a dielectric material to an inductance element made of a magnetic material, the magnetic material having an initial magnetic permeability of 20 to 300.