JPS62189807A - Lc filter - Google Patents

Abstract

PURPOSE:To improve the frequency characteristics by constituting a coil conductor fixed to the surface of a dielectric base by >=2 spiral or zigzag coils in series so as to reduce the stray capacitance. CONSTITUTION:Capacitor electrodes 12a, 13a are formed on one major plane of a dielectric base 11 and capacitor electrodes 12b, 13b are formed on the other face of the base 11. The coil conductor 16 is fixed to one face of the base 11 and the coil conductor 17 is fixed to the other face of the base 11 respectively, the both are connected via a through-hole 14 to constitute the 1st coil part 20. The coil conductor 18 is fixed to one face of the base 11 and the coil conductor 19 is fixed to the other face of the base 11 respectively, the both are connected via a through-hole 15 to constitute the 2nd coil part 21. The conductors 16, 17, 18, 19 are spiral or zigzag coil conductors. Thus, the stray capacitance is reduced and the frequency characteristic is improved.

Description

Detailed Description of the Invention (Field of the Invention) The present invention relates to a capacitor having capacitor electrodes formed on both sides of a dielectric substrate, and a coil conductor having a spiral or zigzag shape fixed to the surface of the dielectric substrate. The present invention relates to the practical application of an LC filter comprising a printed coil.

(Prior Art) Conventionally, a printed coil is constructed by fixing a spiral coil conductor to the surface of an insulating substrate, as shown in FIGS. 2(A) to 2(C). There is an LC filter that has a separate capacitor mounted on it.

In this LC filter, 1 is an insulating substrate. 2
and 3 are plate-shaped capacitors each having a pair of lead terminals 2a and 3a, and are mounted on one side of the insulating substrate 1 using solder or the like.

Reference numerals 4 and 5 denote spiral coil conductors, and the coil conductor 4 is fixed to one side of the insulating substrate 1, and the coil conductor 5 is fixed to the other side of the insulating substrate 1, respectively. A through hole 6 is formed through the insulating substrate 1, and electrically connects the end of the coil conductor 4 and the end of the coil conductor 5.

7.8.9 are electrodes formed on one side of the insulator substrate 1, the electrode 7 is electrically connected to the end of the coil conductor 4, the electrode 8 is electrically connected to the capacitor 2, and the electrode 9 is electrically connected to the capacitor 6. It is connected to the. A conductor path 10 is formed on the other side of the insulating substrate, and serves to electrically connect the ends of the coil conductor 5 and the capacitors 2 and 6.

This LC filter has electrodes 7.8.9 as the ends,
This constitutes a so-called T-type bypass filter. Note that a similar LC filter can be formed by using a magnetic substrate or the like instead of the insulating substrate 1, or by using a zigzag-shaped coil conductor instead of the spiral-shaped coil conductor 4.5. can.

(Problems to be Solved by the Invention) However, in the conventional LC filters described above, the capacitor must be mounted as a separate component;
Manufacturing was complicated and the cost was high.

Further, as another LC filter, there has conventionally been an LC filter in which a capacitor is formed by forming capacitor electrodes on both sides of a dielectric substrate, and a coil as a separate component is mounted on the dielectric substrate. However, since this LC filter also requires the coil to be mounted as a separate component, manufacturing is complicated and the cost is high.

To solve this problem, a DC filter is constructed in which a capacitor is formed by forming capacitor electrodes on a single dielectric substrate, and a printed coil is constructed by fixing a coil conductor in a spiral or zigzag shape. is considered. However, due to the following reasons,
This LC filter has not been put to practical use because it is difficult to put into practical use a printed coil in which a coil conductor is fixed to the surface of a dielectric substrate.

That is, the equivalent circuit of a printed coil formed by fixing a coil conductor to the surface of a substrate can be expressed as shown in FIG. This is because in the case of a printed coil in which the coil conductor is fixed to only one side of the board, a floating field TCP occurs between the lines of the coil conductor, and in the case of a printed coil in which the coil conductor is fixed to one side and the other side of the board. This is because in this case, stray capacitance Cp occurs between the lines of the coil conductor and between the coil conductor fixed to one surface and the coil conductor fixed to the other surface. When an insulating substrate or a magnetic substrate is used as the substrate, the stray capacitance Cp is negligibly small, but when a dielectric substrate is used, the stray capacitance Cp naturally becomes very large. Since the self-resonant frequency f0 is, if the stray capacitance Cp increases by using a dielectric substrate, the self-resonant frequency! . will decrease. This printed coil does not function as a coil at frequencies higher than the self-resonant frequency, but functions as a capacitor, so by using a dielectric substrate, the self-resonant frequency can be increased. .

When is low F, frequency! Characteristics deteriorate.

In other words, a printed coil is made by fixing a coil conductor in a spiral or zigzag shape to the surface of a dielectric substrate.
Due to the large stray capacitance Cp, the self-resonant frequency is low and the frequency characteristics are poor, making it difficult to put it into practical use. Therefore, an LC filter using a pre/pre-coil formed by fixing a coil conductor to the surface of a dielectric substrate has not been put to practical use.

(Means for Solving the Problems) The present invention aims to put into practical use a DC filter using a printed film formed by fixing a coil conductor to the surface of a dielectric substrate.

As a means for achieving this, in the LC filter of the present invention, the coil conductor fixed to the surface of the dielectric substrate is composed of two or more spiral or zigzag shapes connected in series. That is, the printed coil constituting a part of the present invention (7) LC filter is not formed by a single spiral or zigzag coil conductor that continuously provides the desired inductance, but by a coil conductor connected in series. The coil conductor is divided into two or more spiral or zigzag shapes.

For example, if a desired inductance value is formed by equally dividing into a first coil part and a second coil part each consisting of two spiral or zigzag shaped coil conductors, the equivalent circuit is shown in Figure 4. It becomes like this. However, LL is the first
The inductance of the coil section (LLt is the inductance value of the second coil section (Ll=L1 +Lz), Cp+ is the stray capacitance of the first coil section, and Cpt is the stray capacitance of the second coil section.

By the way, if we compare the total stray capacitance CP that enters this printed coil with the stray capacitance CEL that enters the printed coil formed by one spiral or zigzag coil conductor with continuous inductance value, we get the following. become. First, if the inductance value is divided into two parts, the first coil part and the second coil part, the size of the coil conductor in each coil part will be approximately H compared to if it were formed with one coil conductor. Therefore, the floating capacity is 1 cpt and C
pl is approximately % of the stray capacitance Ca. On the other hand, the stray capacitance icp is the floating capacitance 11cpl and Cpz connected in series, but if the same size capacitance is connected in series with 21m1, the capacitance becomes i. Therefore, the stray capacitance Cp is the stray capacitance C
p+ and Cps.

Therefore, the total stray capacitance Cp that enters this printed coil is approximately % of the stray capacitance Ca that enters the printed coil whose inductance value is formed by one continuous spiral or zigzag coil conductor. There is.

In other words, the printed coil constituting a part of the I+C filter of the present invention is made by dividing a desired inductance into two or more series-connected coil conductors in a spiral or zigzag shape. Although it is formed on the surface of the body substrate, it is possible to keep the stray capacitance Cp extremely small. Therefore, the self-resonant frequency f. has not deteriorated, and the frequency characteristics have been improved.

Therefore, according to the present invention, on one dielectric substrate,
It becomes possible to put into practical use an LC filter in which a condenser electrode is formed to constitute a capacitor, and a spiral or zigzag shaped coil conductor is fixed to constitute a printed coil.

(Example) Examples of the LC filter of the present invention will be described below with reference to the drawings.

FIGS. 1A to 1C show an embodiment of the LC filter of the present invention. However, FIG. 1(A) is a plan view, FIG. 1(B) is a side sectional view of the chain @BB' portion, and FIG. 1(C) is a bottom view.

In this LC filter, 11 is a dielectric substrate, which has a dielectric constant of 240 and a thickness of 9.4 m.

12a, 121) and 13a*13b are capacitor electrodes, the capacitor electrodes 12a and 13a are formed on one side of the dielectric substrate 11, and the capacitor electrodes 112b and 13b are formed on the other side of the dielectric substrate 11, respectively. The electrodes 12& and 121) constitute one set of capacitors, and the capacitor electrodes 131L and 131) constitute another set of capacitors. Reference numerals 14 and 15 are through holes, which are formed to penetrate through the dielectric substrate 11, respectively.

16.17 and 18.19 are spiral-shaped co-f conductors. The coil conductor 16 is provided on one side of the dielectric substrate 11,
The coil conductors 17 are respectively fixed to the other surface of the dielectric substrate 11 and are electrically connected via the through holes 14 to form the first coil section 20 . The coil conductor 18 is fixed to one side of the dielectric substrate 11, and the coil conductor 19 is fixed to the other side of the dielectric substrate 11, and the two are electrically connected via the through hole 15. The reed has the role of electrically connecting the end of the coil conductor 16 with the end of the conductor 18 and the capacitor capacitor 12a, and the end of the coil conductor 17 with the end of the coil conductor 19. I am accomplishing it. Note that capacitor electrode 1
2a* 12bt 13a+ 131:+, coil conductor 16.17.18.19, electrode 22, conductor path 26°24
It is possible to use the same material and form them on the dielectric substrate 11 at the same time.

This LC filter includes an electrode 22, a capacitor electrode 12
With t1.13t) as the end, it constitutes a so-called T-type i-pass filter.

The above is one embodiment of the LC filter of the present invention, and it goes without saying that the design can be changed within the scope of the spirit of the present invention. For example, in the above embodiments, the LC filter of the present invention is explained using a T-type bypass filter as an example, but the present invention is not limited to the T-type bypass filter, and the present invention includes any LIC filter. Furthermore, although the first coil section 20 and the second coil section 21 are formed across both sides of the dielectric substrate 11 through the through holes 14 and 15, they do not necessarily need to be formed over both sides of the dielectric substrate 11. , may be formed only on one side of the dielectric substrate 11. Further, the shape of the coil conductor 16°, 17, 18, 19 may be arbitrary, and in addition to the square spiral shape as in the above embodiment, a circular spiral shape or a zigzag shape may also be adopted.

(Effects of the Invention) As is clear from the above description, the printed coil constituting a part of the LC filter of the present invention has a desired inductance value of two or more spiral-shaped or zigzag-shaped coils connected in series. The inductance conductor is divided into inductance conductors. As a result, the overall floating frequency characteristics of the printed coil are improved.

Therefore, according to the present invention, on one dielectric substrate,
It has become possible to put into practical use an LC filter in which a capacitor is constructed by forming a capacitor electrode, and a printed coil is constructed by fixing a coil conductor in a spiral shape or a zigzag shape.

The LC filter of the present invention, in which a capacitor and a printed coil are formed on a dielectric substrate, does not require mounting the capacitor or coil as a separate component as in the past.
Moreover, since the same material is used for the capacitor electrode and the coil conductor, and they can be formed on the dielectric substrate at the same time, manufacturing is easy and costs can be significantly reduced.

[Brief explanation of drawings]

Figure 1 (A) is a plan view showing one embodiment of the LC filter of the present invention, and Figure 1 (B) is its chain! Figure 1 (CC) is a side sectional view of the B-B' section, Figure 1 (CC) is its bottom view, Figure 2 (the slope is a plan view showing the conventional LC filter, and Figure 2 (B) is the dashed line A-A' section). A side sectional view, FIG. 2(C) is a bottom view,
FIG. 6 is an equivalent circuit diagram of a printed coil, and FIG. 4 is a diagram showing an example of both circuits of the printed coil forming a part of the LC filter according to the present invention. 11...Dielectric substrate, 12aw 12bl 1
3a* 13b... Capacitor 'LL 14
．． 15...Through hole, 16.17.18.
19... Coil conductor, 20... First coil part, 21... Second coil part, 22...
··electrode.

Claims (1)

[Claims] The invention includes a capacitor in which capacitor electrodes are formed at opposite positions on one side and the other side of a dielectric substrate, and a printed coil in which a coil conductor is fixed to the surface of the dielectric substrate. An LC filter characterized in that the coil conductor consists of two or more spiral or zigzag shapes connected in series.