JPS59223011A - Composite lc filter - Google Patents

Abstract

PURPOSE:To minimize a magnetic coupling and an electrostatic coupling between each substrate, and to obtain a micro-filter by constituting a composite LC filter by placing two ferrite substrates between the first and the second dielectric substrates on which a circuit pattern is formed. CONSTITUTION:A copper sheet 28 for preventing an electrostatic coupling of dielectric substrates 11 and 21 is connected to an earth terminal 2. Also, a circuit is connected by through-holes 15, 24, and through-holes 14, 25 as necessary. Accordingly, even if the dielectric substrate 11 and the dielectric substrate 21 are provided in the vicinty of each other, a magnetic flux of each coil is not interlinked but is independent. Accordingly, there are operarions of a magnetic shield and an electrostatic shield by a ferrite substrate 16a, the copper sheet 28 and a ferrite substrate 16b, and on the other hand, coils 12, 22 on the dielectric substrates 11, 21 can collect a leakage magnetic flux by the ferrite substrates 16a, 16b, and there is an effect by which the inductance becomes large apparently, therefore, a filter can be made small-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a composite LC inserted between a high frequency signal transmission path, for example, an antenna and a tuner of a television or FM radio.
It is related to filters.

Conventional configurations and their problems For filters used in transmission paths for high-frequency signals such as FM radios, televisions, and RF modulators, coils, capacitors, etc. that make up the circuit are deposited, plated, or There are filters that are deposited by printing or the like. These are generally inexpensive and can be manufactured with uniform quality, so they are widely used. For example, there is a circuit shown in FIG. 1, where 1 is an input terminal, 2 is a ground terminal, 3 is an output terminal, L+ and L2 are coils, and 01. C2',
C3 is a capacitor. By the way, when considering that the circuit configuration shown in FIG. 1 is to be formed on a dielectric substrate using a spiral coil pattern and a capacitor pattern and to be made compact, the following points are necessary.

■ To make the capacitor pattern smaller, there is a method of using the entire cutting board with a high dielectric constant, but in order to reduce the stray capacitance between the patterns, the dielectric constant should be as low as possible and the substrate thickness t should be as thin as possible. is good. For example, t=0.
It is about 1 to 0.6 mm. It is desirable that the stray capacitance be small because high frequency signals may pass through it.

Therefore, for miniaturization, it is necessary not only to reduce the thickness of the substrate but also to narrow the mutual spacing between the patterns as much as possible to increase the occupation ratio of the patterns to the surface area of the substrate.

■ Regarding the coil pattern, for example, as a method to increase the apparent inductance of a small coil,
By forming a helical coil pattern on a magnetic substrate, for example, an N1-Zz ferrite substrate, it is possible to realize an inductance larger than that of a coil formed on a dielectric substrate even with the same shape. However, there is a problem that capacitors with good Q cannot be deposited and formed at the same time.

By the way, FIG. 2 shows an example of the circuit shown in FIG. 1 in which circuit patterns (helical coil pattern, capacitor pattern) are formed on both sides of a dielectric substrate using the conventional technique. Second
Since the putter shown in the figure includes a shield pattern etc. to improve the characteristics, the equivalent circuit is somewhat different from that in FIG. 1, but since this is different from the main purpose of the present invention, the explanation will be omitted.

In FIG. 2, 1 is an input terminal, 2 is a ground terminal, 3 is an output terminal, 5 is a dielectric substrate, 6 is a coil pattern constituting the coil L1 in FIG. 1, and 6a is the surface of the dielectric substrate 6 ( 6b is formed on the back surface (hereinafter referred to as B side). 7 is the coil pattern of the coil L2 in VC in FIG. 1, in which 7a is the surface and 7b is the 8th surface. 10a and 10b are parallel electrodes of the capacitor C3 in FIG. 1, and the other capacitors C1 and C2 in FIG. 1 are formed as distributed capacitances at opposing portions of the coil patterns 6 and 7. Reference numerals 8 and 9 are through holes for electrically connecting the front surface and the battens on the 8th side.

However, in the planar structure shown in FIG. 2, there is a limit even if the thickness of the dielectric substrate is made thinner and a magnetic substrate such as ferrite is combined in order to achieve miniaturization. That is, with the conventional technology, it is difficult to reduce the packaging density and achieve ultra-small size.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems. In particular, a coil and a capacitor are formed on both sides of a dielectric substrate by using circuit patterns, and a laminated structure is formed to improve magnetic coupling between the layers. The purpose is to provide an ultra-small filter that minimizes electrostatic coupling.

Structure of the Invention In order to achieve this object, the present invention divides a filter circuit consisting of a plurality of inductances and capacitances, and a first circuit is formed by depositing a first circuit pattern on a first dielectric substrate. and a second circuit pattern/
is constructed by depositing and forming a second circuit pattern on a second dielectric substrate, and the first dielectric substrate and the second dielectric substrate are arranged in an overlapping manner. A first ferrite substrate and a second ferrite substrate are superimposed and inserted between two dielectric substrates, and the first circuit and the second circuit are electrically connected.

Description of examples An embodiment of the present invention will be described below with reference to the drawings.

The circuit shown in FIG. 1 is shown in 4. -4', the first circuit is divided into two circuits, consisting of terminals 1 and 2, capacitor C1, and coil L1, and terminal 3. Capacitor 02. A second circuit is made up of Cs and coil L2.

FIG. 3 shows a first circuit pattern consisting of the terminals 1, 2, capacitor C1, and coil L1 formed on a dielectric substrate 11, and 12 is a pattern constituting the coil L1. 12& is a pattern on the surface (hereinafter referred to as C surface) of the dielectric substrate 11, and 12b is a pattern on the surface of the dielectric substrate 1.
The pattern 13 on the back surface of 1 (hereinafter referred to as the "down surface") is a through hole for electrically connecting the patterns 12 &, 12b. 14 and 15 are through holes for connecting the first and second circuits. The capacitor C1 is formed by the distributed capacitance of the patterns 122L and 12b.

FIG. 4 shows terminal 3. A second circuit pattern consisting of a coil L2 and a capacitor 02°C3 is formed on a dielectric substrate 21, and 22 is the pattern of the coil L2,
2& is a pattern on the front surface (hereinafter referred to as H surface) of the dielectric substrate 21, 22b is a pattern on the back surface (hereinafter referred to as work surface) of the dielectric substrate 21, and 23 is a pattern 722! L, 2
This is a through hole for electrically connecting 2b. 24
．． 26 is a through hole for connecting the first and second circuits.

The capacitor C2 is formed by the distributed capacitance of the patterns 22&, 22b, and the capacitor C3 is formed by the distributed capacitance of the patterns 26a and 26a.
, 26b, and the terminal 3 is connected to 26b.

Next, in FIG. 5, 16 is a magnetic substrate used in the present invention, which is an N1-Zz ferrite substrate.

Reference numerals 17 and 19 are through holes for circuit connection, but each hole is not a closed circle, but has a notch 18 and 20 at one location. The reason for this is that the notch 18 of the through hole 17. Through hole 19
If the notch 2o is closed, a closed magnetic circuit is formed as a magnetic circuit. If it becomes a closed magnetic path, the magnetic permeability will increase, but on the other hand, ta
Since the frequency characteristics of nσ and therefore the frequency characteristics of the circuit junction are deteriorated, an open magnetic path is used.

The shape of this ferrite substrate 16 is E-E′ in FIG.
F that is cut from and does not include the through holes 17 and 18
You may use only the part.

The ferrite substrate 16 used has a thickness of about 0.3 to 1.2 MrN and an initial magnetic permeability of about several tens to several hundreds.

Suppose that the initial permeability is about 90 and the shape is 6 mm.
If the helical coil has an outer diameter of 5 mm X s am and a thickness of 0.5 ffll+, the inductance can be increased by about 1.3 to 1.6 times.

Now, the dielectric substrate 11.21 used here has a dielectric constant of about several tens to several hundreds, and a thickness of about 0.2 to 0.6 mm.

FIG. 6 is a diagram illustrating the present invention in detail.

When the ferrite substrate 16 of FIG. 6 is placed under the dielectric substrate 11 of FIG. 3, the result is as shown in FIG. In Figure 6, M is
It shows the flow of magnetic flux created by the coil pattern 12 at a certain point in time. Since the coil pattern 12 is a helical coil, there is a large amount of leakage magnetic flux.

Therefore, when the ferrite substrate 16 is brought close to the coil pattern 12, the magnetic flux passes through the ferrite substrate 16, which has high magnetic permeability. As shown in FIG. 6, the magnetic flux leaking to the back surface (hereinafter referred to as the "down surface") of the ferrite substrate 16 is reduced, and the end portions 16-1, 16-2 of the ferrite substrate 16 are
Concentrate on.

Similarly, if the ferrite substrate 16 of FIG. 6 is stacked on the H side of the dielectric substrate 21 of FIG.
The hole magnetic flux in the portion corresponding to the surface is small, and the magnetic flux is concentrated at the end of the ferrite substrate 16.

Therefore, as shown in FIG. 7, the ferrite substrates 16 are arranged with their backs facing each other.

27 in FIG. 7 is the ferrite substrate 16fL and the dielectric substrate 1.
A spacer 29 is used to adjust the magnetic coupling between the ferrite substrate 16b and the coil of the dielectric substrate 21.

28 is a copper sheet for preventing electrostatic coupling between the dielectric substrates 11 and 21, and is an electrostatic shield. It also has the effect of absorbing leakage magnetic flux interlinking with the copper sheet 28. This copper sheet 28 is connected to the ground terminal 2. Further, the circuits are connected through through holes 15 and 24 and through holes 14 and 25 as necessary.

Because of the above structure, even if the dielectric substrate 11 and the dielectric substrate 21 are placed close to each other, the magnetic fluxes of the coils i do not interlink with each other and are independent. Therefore, while the ferrite substrate 16a and the copper sheet 28° ferrite substrate 16b provide magnetic shielding and electrostatic shielding, the coil 1'2.22 on the dielectric substrate 11.21
Since the leakage magnetic flux is collected by the ferrite substrates 16a and 16bVC, there is an effect that the inductance becomes apparently larger. In other words, it can be made smaller.

In FIG. 8, instead of the copper sheet 28 in FIG. 7, the back 30K of the ferrite substrate 16b may be covered with copper or a material with high conductivity by vapor deposition, plating, printing, or the like. FIG. 9 shows another embodiment in which a ferrite substrate 16a is used depending on desired characteristics.

16b is integrated. In this case, it is desirable that the coil on the dielectric substrate 11 and the coil on the dielectric substrate 21 be wound differentially.

Since the structure is as explained above, (1) Even if the coil pattern 12 of the dielectric substrate 11 and the coil butter '722 of the dielectric substrate 21 are placed close to each other, there is a magnetic shielding effect, and the coil 12. ．． 22. There is no mutual interference.

■ The leakage magnetic flux of the coil is collected by the ferrite substrate 16, which has the effect of increasing the coil inductance, allowing for miniaturization.
2.22, the stray capacitance between them is reduced, and the passage of high frequency signals is reduced. Therefore, the ferrite substrate 16
If a copper sheet 28f for electrostatic shielding is provided between a and 1eb, electrostatic coupling will be eliminated. Further, there is an advantage that the magnetic flux interlinking with this copper sheet 28 can be absorbed as an eddy current.

Therefore, according to the present invention, since even a planar circuit having a coil can be constructed in a laminated manner, the packaging density can be increased, and an ultra-small filter with a thickness of less than a few inches can be realized.

Also, the spacers 27, 29 may be omitted if desired. Ferrite substrate 16a in FIG.

1.6b and the dielectric substrate 11.21 have the advantage that the material, thickness, etc. can be changed depending on desired characteristics.

In the description here, the circuit has two layers, but it may have three or more layers.

As for the dielectric substrate, even if the thickness of the substrate is reduced, it will polymerize with the ferrite substrate, so there will be no damage to the substrate during work. Further, the dielectric substrate may be a ceramic substrate, a mica plate, or the like.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention is a composite LC filter in which two ferrite substrates are sandwiched between first and second dielectric substrates on which a circuit pattern is formed. magnetic coupling and electrostatic coupling can be minimized, and an ultra-small filter can be provided.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a general bandpass filter, Figure 2 is a plan view showing a specific example of a conventional composite LC filter, and Figure 3 is a circuit diagram of a general bandpass filter.
The figure is a plan view showing a partial configuration of a composite LG filter according to an embodiment of the present invention, FIG. 4 is a plan view showing the configuration of other parts of the filter, and FIG. 6 is a ferrite substrate used in the filter. A plan view showing an example, FIG. 6 a side view showing a composite example of a ferrite M plate and a dielectric substrate in the filter, and FIG. 7 a perspective view showing an assembled state of the filter.
FIG. 8 is a perspective view showing a part of a composite LC filter according to another embodiment of the present invention, and FIG. 9 is a perspective view showing an assembled state of the composite LC filter according to still another embodiment of the present invention. 1.3... Input/output terminal, 2... Ground terminal, 11.21... Dielectric substrate, 13, 14
, 15° 17.19, 22, 24.25... Through hole, 16... Ferrite substrate, 27.
29...Spacer, 28...Copper sheet. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure B Figure 4

Claims (4)

[Claims] (1) A filter circuit consisting of a plurality of inductances and capacitances is divided, and the first circuit is constructed by depositing a first circuit pattern on a first dielectric substrate, and the second circuit is constructed by forming a first circuit pattern on a first dielectric substrate. a second circuit pattern is formed on a second dielectric substrate, and the first dielectric substrate and the second dielectric substrate are arranged in an overlapping manner, and the first and second
A composite characterized in that a first ferrite substrate and a second ferrite substrate are superimposed and inserted between the dielectric substrates, and the first circuit and the second circuit are electrically connected. LC filter. (2) The composite LC filter according to claim 1, further comprising a conductive plate or a sheet-shaped electrostatic shield inserted between the first ferrite substrate and the second ferrite substrate. (3) The composite L' according to claim 1, wherein the composite L' is provided between the first ferrite substrate and the second ferrite substrate by depositing a conductor on the ferrite substrate. C filter. (4) The composite LC filter according to claim 1, wherein the first ferrite substrate and the second ferrite substrate are integrated.