JPH04373108A - Variable inductor - Google Patents

Abstract

PURPOSE:To actualize the title variable inductor capable of being miniaturized and formed into a thin film. CONSTITUTION:The title variable inductor 1 is composed by meanderingly forming a line comprising a soft magnetic body on whose surface a non- magnetic metallic body is bonded as if holding the soft magnetic body thereby enabling the inductor 1 to be formed into a thin film. Next, a bias current 9 is fed from a bias current source 8 to this inductor 1 so as to generate a bias magnetic field. Next, the specific permeability of the inductor 1 is increased and decreased by the bias magnetic field thereby enabling the inductance between an input terminal 4 and an output terminal 5 to be fluctuated. On the other hand, two high pass filters 2, 3 are connected in series between both ends of the inductor 1 and the input terminal 4 as well as the output terminal 5 so that the bias current may run into the inductor 1 only.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable inductor whose inductance is variable.

0002

[Prior Art] Conventionally, a saturable inductor as shown in Fig. 8 has been used as a variable inductor (Yojiro Yokoi, "Linear IC Practical Circuit Manual", Radio Gijutsusha).
. This conventional saturable inductor has a ferrite core 1
A silicon iron core excitation yoke 104 has a saturable inductor coil 102 wound around it and an excitation coil 103 wound around it.
sandwich this ferrite core 101, and ferrite core 1
The configuration is such that a magnetic field can be applied to 01. Here, when a current is passed through the excitation coil 103 and a magnetic field is applied to the ferrite core 101, its magnetic permeability decreases due to magnetic saturation.
Inductance becomes smaller. Conventional variable inductors utilize this.

However, such a conventional variable inductor requires a three-dimensional structure as shown in FIG. 8, and therefore has the disadvantage of taking up space. Especially in IC (integrated) circuits, there is a need for smaller and thinner components.
The inductor with the three-dimensional structure described above is difficult to manufacture,
It is considered impossible to convert it into an IC due to the size of space. For this reason, current IC circuits use simulated inductors that function as inductors using only capacitors and active elements.

0004

[Problems to be Solved by the Invention] However, since the simulated inductor according to the above-mentioned conventional technology is composed of thin film parts such as transistors, resistors, and capacitors, it can be integrated into an IC, but it requires many parts. Therefore, it has the disadvantage of taking up space. That is, conventionally, there has been no variable inductor that can be made thinner and smaller, and the challenge has been to realize a variable inductor that can be made thinner and smaller.

The present invention has been made to solve the above problems, and its object is to provide a variable inductor that can be made thinner and smaller in a variable inductance device.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the variable inductor of the present invention includes an input terminal, an output terminal, a first high-pass filter, a second high-pass filter, and a soft magnetic inductor. The first high-pass filter has an inductor constituted by a line whose body is bonded to the surface of the non-magnetic metal body so as to sandwich the non-magnetic metal body, and a bias current terminal to which a bias current source is connected. is connected between the input terminal and the inductor, the second high-pass filter is connected between the output terminal and the inductor, and the bias current terminal is connected to the inductor. It is said that

[0007]

[Operation] In the variable inductor of the present invention, a bias current is passed through the non-magnetic metal material forming the line to generate a bias magnetic field, and this bias magnetic field causes the relative magnetic permeability of the soft magnetic material adhered to the surface of the non-magnetic metal material to This makes it possible to change the inductance between the input and output terminals. At this time, the high-pass filter allows the bias current to flow only into the line and not from the input/output terminals to the outside.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention. The elements constituting this embodiment include 1 an inductor, 2 and 3 high-pass filters, 4 an input terminal,
5 is an output terminal, 6 and 7 are bias current terminals, 8 is a bias current source, and 9 is a bias current.

[0010] The above parts are connected as follows. Input terminal 4 is connected to one electrode of inductor 1 through high-pass filter 2 . One electrode of this inductor 1 is also connected to a bias current terminal 6. The other electrode of the inductor 1 is connected to the other bias current terminal 7
It is connected to the output terminal 5 through the high-pass filter 3. These two bias current terminals 6
, 7, a bias current source 8 is connected between them. That is, the bias current source 8 is connected in parallel to the inductor 1 and causes a bias current 9 to flow through the inductor 1.

Next, the above inductor 1 in this embodiment
The structure of the part is shown. FIG. 2 is a perspective view showing the structure of the inductor portion, and FIG. 3 is a perspective view including a partial cross section showing the line structure of the inductor portion. As shown in FIG. 2, the inductor 1 has a structure having electrodes 12, 12 at both ends of a line 11 having a meander shape, that is, a meandering structure. As shown in FIG. 3, this line 11 is connected to a soft magnetic material 14,
14 is adhered to the surface of the non-magnetic metal body 13. Note that the electrodes 12, 12 may also serve as the bias current terminals 6, 7 in FIG.

The operation and effects of the first embodiment configured as above will be described.

First, the principle of operation of the variable inductor of this embodiment will be explained. Figure 4 shows the magnetization curve of the soft magnetic material. The vertical axis is magnetization (M), and the horizontal axis is magnetic field (H). Relative permeability (μ
r) is expressed by the slope of this curve (dM/dH). now,
When a bias magnetic field (Hbias) is applied to a soft magnetic material,
The relative magnetic permeability when the magnetic field is Hbias changes depending on the value of Hbias, and behaves as shown in FIG. The inductance (L) of the inductor 1 shown in FIGS. 2 and 3 is L=
Lself+Lmut+Lskin+Lmag…(1)
It is described in Here, Lself is a self-inductance, Lmut is a mutual inductance, Lskin is an inductance change term due to the skin effect, and Lmag is an inductance change term due to bonding a soft magnetic material. When the magnetic permeability of the soft magnetic material changes as shown in Figure 5, (1
) Lmag in the equation increases or decreases, and the inductance L changes. In the present invention, a magnetic field generated by passing a current through a non-magnetic metal body is used as a bias magnetic field application method. By doing so, the number of parts can be reduced compared to providing a separate magnetic field generation source, and further miniaturization can be achieved.

The above-mentioned situation in this embodiment will be explained with reference to FIG. When a bias current 9 is applied to the non-magnetic metal body 13, a bias magnetic field 15 is applied to the soft magnetic body 14. At this time, the magnitude of the bias magnetic field 15 is controlled by the magnitude of the bias current 9. Here, as shown in FIG. 1, in order to allow the bias current 9 to flow only through the inductor 1, two high-pass filters 2 and 3 are connected in series between both ends of the inductor 1 and the input terminal 4 and the output terminal 5, respectively. I need to put it in. As described above, in the variable inductor according to this embodiment, the relative magnetic permeability of the soft magnetic body 14 is increased or decreased by the bias magnetic field 15 generated by the bias current 9 passed through the non-magnetic metal body 13, thereby making it possible to change the inductance.

[0015] A concrete example of actual measurement of this embodiment will be shown below. The non-magnetic metal body 13 is made of copper (Cu) with a specific resistance of 1.72 micro-ohm centimeter, and the soft magnetic substance 15 is made of copper (Cu) with a specific resistance of 1.72 micro-ohm centimeter.
A cobalt zirconium (CoZr) alloy with a relative magnetic permeability of 5000 and a diameter of 0 micro ohm centimeter was used. The number of zigzag folds (N) in Figure 2 is 4, and the length of zigzag folds (l)
is 8 mm, line width (w) is 200 microns,
The line spacing (d) is 200 microns, the thickness (tc) of the non-magnetic metal body 13 in FIG. 3 is 1 micron, and the soft magnetic body 1
The thickness (tm) of No. 4 was 1 micron. Bias current 9
and bias magnetic field 15 generally exhibit a proportional relationship. In this example, the proportionality factor was 1 oersted/milliampere. Therefore, the relative permeability (μr) and bias current (
Similar to the relationship with the bias magnetic field (Hbias), the relationship with the bias magnetic field (Hbias) is also shown in FIG. Figure 6 shows the inductance (L) and bias current (
Ibias). The inductance, which was 180 nanohenries when the bias current was 0 milliamps, decreased continuously as the bias current increased, and became 13 nanohenries when the bias current was 5 milliamps.

As described above, the inductance L changes greatly due to the bias current 9 flowing through the non-magnetic metal body 13, and the operation of the variable inductor has been confirmed. In addition, the variable inductor according to this embodiment can be easily configured with a thin film as shown in FIGS. 2 and 3, and since no separate magnetic field generation source is required, the components can be miniaturized.

Next, a second embodiment of the present invention will be described.

FIGS. 7(a) and 7(b) are perspective views showing the line structure of the second embodiment, including a partial cross section. This embodiment is a modification of the structure of the soft magnetic material of the first embodiment. First, in the example of (a), the shape of the soft magnetic body 14 is a strip, and a plurality of soft magnetic bodies 14 are bonded to the surface of the non-magnetic metal body 13 constituting the line so as to be sandwiched therebetween. Moreover, in the example of (b), the strip-shaped soft magnetic material 14 of (a) is adhered to the surface of the non-magnetic metal material 13 so as to go around it once. In (b), the soft magnetic body 14 has a strip shape, but the soft magnetic body 14 is connected in the line direction, that is, the soft magnetic body 14 in FIG. It may be in a state where it is adhered to the surface.

In this embodiment, by using the soft magnetic material structure as described above, generation of a demagnetizing field is suppressed, a decrease in magnetic permeability due to the generation of a demagnetizing field is prevented, and a range in which the inductance changes is widened. be able to. Further, if the inductance change is made to be the same as that in the first embodiment, the number N of folds in FIG. 2 can be reduced, and further miniaturization becomes possible. Furthermore, a reduction in the number of zigzags leads to a reduction in stray capacitance, which increases the resonance frequency and enables operation up to a high frequency range.

[0020] In the above embodiment, an example was shown in which the lines were meander-shaped, but the same effect can be obtained by using striped lines, although the range of inductance change is different. As described above, the present invention can be applied in various ways and can take various embodiments in accordance with the gist thereof.

[0021]

As is clear from the above description, the variable inductor according to the present invention has the advantage of being a small thin film device that can be integrated into an IC because it can be easily made into a thin film and requires fewer parts.

Further, according to the invention of claim 3, there is an advantage that the range of change in inductance can be increased,
In addition, if this fact is utilized to reduce the number of meander-like windings, it is possible to obtain the advantage of further miniaturization and higher frequency.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a variable inductor according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing the structure of the inductor portion of the variable inductor of the first embodiment.

FIG. 3 is a perspective view including a partial cross section showing the line structure of the inductor portion of the first embodiment;

FIG. 4 is a diagram showing an example of the magnetization curve of the soft magnetic material of the first embodiment.

FIG. 5 is a diagram showing an example of the dependence of relative magnetic permeability on bias magnetic field and bias current in the first embodiment.

[Figure 6]
A diagram showing an example of bias current vs. inductance characteristics of the variable inductor of the first embodiment.

[Figure 7] (a), (b)
) is a perspective view including a partial cross section showing the line structure in the second embodiment of the present invention.

[Figure 8] Diagram showing the configuration of a conventional saturable inductor

[Explanation of symbols]

1... Inductor, 2, 3... High pass filter, 4... Input terminal, 5... Output terminal, 6, 7... Bias current terminal, 8...
Bias current source, 9...Bias current, 11...Line, 1
2... Electrode, 13... Nonmagnetic metal body, 14... Soft magnetic body, 15
...Bias magnetic field.

Claims (3)

[Claims] 1. A structure including an input terminal, an output terminal, a first high-pass filter, a second high-pass filter, and a soft magnetic material bonded to the surface of the non-magnetic metal material so as to sandwich the non-magnetic metal material. the first high-pass filter is connected between the input terminal and the inductor, the first high-pass filter is connected between the input terminal and the inductor, and the first high-pass filter is connected between the input terminal and the inductor; is connected between the output terminal and the inductor, and the bias current terminal is connected to the inductor. 2. The variable inductor according to claim 1, wherein the lines constituting the inductor are structured in a stripe shape or a meander shape. 3. A plurality of soft magnetic bodies sandwiching the non-magnetic metal body constituting the line are formed into strips and are bonded to the surface of the non-magnetic metal body, or are arranged so as to go around the non-magnetic metal body once. 3. The variable inductor according to claim 1, wherein the variable inductor is bonded to the surface of the non-magnetic metal body.