JPH062339Y2 - LC filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an LC filter using a dielectric substrate.

2. Description of the Related Art Conventional LC filters using a dielectric substrate include those shown in FIGS. 4 and 5. The LC filter shown in FIG. 4 has a plurality of capacitor electrode patterns 42a, 42b, 43a, 43b, 44 on both front and back surfaces of a dielectric substrate 41.
a, 44b are formed, coil patterns 45, 46, 47 are formed on the surface of the substrate 41, and one end of each coil pattern is extended to the back surface side of the substrate through the through holes 48, 49, 50, and the back surface side is formed. Capacitor electrode pattern 4
2b, 43b, 44b. The capacitor electrode patterns 42a and 42b, 43a and 43
Since b, 44a, and 44b are opposed to each other with the substrate 41 in between, a capacitor having an electrostatic capacity determined by the opposed area, the opposed interval, and the dielectric constant of the substrate 41 is formed. on the other hand,
The coil patterns 45 to 47 each form a coil having a predetermined inductance value determined by its length and the like. Therefore, the LC filter has a configuration in which three resonators having an equivalent circuit in which one capacitor and one coil are connected in parallel are coupled by the magnetic induction of the coil patterns of the respective resonators.

The LC filter of FIG. 5 has the same equivalent circuit as that of FIG. 4, but has two capacitor electrode patterns 52a, 52c, 53a, 53c, 5 on the surface of the substrate 51 for each resonator.
4a and 54c are formed to form coil patterns 55, 56 and 5
7 on both ends of the two capacitor electrode patterns 52a,
52c, 53a, 53c, 54a, 54c are connected. On the back surface of the substrate 51, two capacitor electrode patterns 52a, 52c, 53a, 53 on the front surface side are provided.
Capacitor electrode patterns 52b, 53b, 54b facing c, 54a, 54c are formed. The capacitor electrode patterns 52b, 53b, 54b are two capacitor electrode patterns 52a, 52c, 53 on the front surface side of the substrate.
a, 53c, 54a, 54c to form an electrostatic capacitance, and therefore each resonator corresponds to a capacitor in which two capacitors are connected in series.

Problems to be Solved by the Invention By the way, in the LC filter of FIG. 4, since the through holes 48 to 50 are used in a part of the coil,
There are the following problems. That is, since the conductive area of the through hole is small, the resistance value is high at that portion, which causes a problem that the Q of the resonator becomes low.

On the other hand, the LC filter shown in FIG. 5 does not use through holes, and since there are no other places on the coil pattern that restrict the conductive area, a high Q can be obtained. In both cases, since the capacitance is obtained from the series circuit of two capacitors, the area of the capacitor electrode pattern is increased in order to secure the required amount of capacitance, and a large board is required accordingly, which is large. There are problems such as bulkiness and high cost.

The present invention has been made in view of these problems, and an object thereof is to provide a novel LC filter which does not require a large substrate and can obtain a desired high Q.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention has a structure in which a capacitor electrode pattern is formed on both surfaces of a dielectric substrate so as to face each other, and one end is connected to the capacitor electrode pattern on each surface. In a bandpass filter in which a plurality of resonators, each of which is equivalently represented by an LC parallel circuit and formed with a coil pattern, are connected in multiple stages, the coil patterns on the front and back surfaces of each resonator are separated from each other in the plane direction of the substrate. The other end of each coil pattern is connected to a wrap-around electrode portion that wraps around the end face of the substrate and is wider than the width of the coil pattern.

EXAMPLE FIG. 1 shows an LC filter as an example of the present invention, in which 1 is a dielectric substrate, and capacitor electrode patterns 2a, 2b, 3a, 3b and a coil pattern 4 are formed on both front and back surfaces thereof.
Two a, 3b, 5a and 5b are formed.

One of the coil patterns 4a, 4b, 5a, 5b is connected to the capacitor electrode patterns 2a, 2b, 3a, 3b as shown in FIG. 1, and the coil patterns 4a, 5a are changed to 4b, 5b. On the other hand, they are arranged on both surfaces of the substrate 1 in a state of being separated from each other in the surface direction of the substrate 1, and the facing distances are increased so that they face each other obliquely via the substrate 1.

Further, on the other side of the coil patterns 4a, 5a, 4b, 5b, wraparound electrode portions 4a1, 4b1 and 5a1, 5b wider than the width of the coil patterns 4a, 5a, 4b, 5b are provided.
The end faces 6 and 7 of the substrate 1 are routed through the electric field 1 to electrically connect to each other to reduce the stray capacitance.

In addition, a pair of coil patterns 4a, 4b and 5a, 5
b is the wraparound electrode portions 4a1, 4b1 and 5a that each has
1, 5b1 are formed to be symmetrical.

Then, a resonator having an equivalent circuit in which one coil and one capacitor are connected in parallel is constituted by corresponding capacitor electrode patterns on both front and back surfaces of the substrate 1 and a coil pattern connected to the electrode pattern. Are coupled to each other using their own coils.

Therefore, the LC filter constitutes a filter circuit similar to the conventional example shown in FIGS. However, unlike the conventional case, the coil pattern wraps around the end face. Therefore, the resistance is lower and the Q of the resonator is higher than that of the coil formed by using the through holes, so that it is possible to obtain a filter having a sharp cutoff characteristic.
In addition, the inductance component of each resonator is given by the series circuit of the coil patterns on the front and back surfaces of the board, so the same inductance value as before can be obtained even when the board size is reduced, and the size can be reduced accordingly. .

When the LC filter is incorporated in the device, the ground terminal needs to be led out from the LC filter. In that case, the ground terminal can be attached to either the capacitor pattern or the coil pattern along the end face of the substrate.

2 and 3 show another embodiment. In the example of FIG. 2, the coil patterns 4a and 5a existing on the surface side of the substrate 1 are formed close to each other. This is performed by the coil patterns 4a and 5a on the front surface side.
Other configurations are the same as those in FIG. Therefore, as in FIG. 1, a high Q can be obtained.

Figure 3 form two resonators Q _1, Q coupling electrode 8 between _2, that form a capacitor between the electrode 8 and the resonator Q _1, Q ₂ of the capacitor patterns 2a, 3a Is.
Therefore, each resonator is capacitively coupled by the electrode 8 in accordance with the magnetic coupling by the coil patterns 4b and 5a. In this case, the filter characteristics change as compared with the case of only the magnetic coupling, and it becomes easier to deal with a wide range of needs of the user.

Although the embodiment is a two-stage coupling, it is a matter of course that three or more stages can be coupled.

Effect of the Invention In the present invention, the capacitor electrode patterns are formed on both sides of the dielectric substrate so as to face each other, and the coil pattern in which one side is connected to the capacitor electrode pattern on each side of the dielectric substrate is separated from the surface direction of the substrate. By arranging in such a state that each pair of coil patterns can be diagonally opposed to each other, the opposing distance can be increased to suppress the stray capacitance to be small, and the other of the coil patterns can have a width smaller than Form a wide wraparound electrode part,
By electrically connecting both coil patterns around the end face of the substrate via the wrap-around electrode portion, the resistance at the connection portion of the coil pattern can be reduced, thereby improving the Q value in the LC filter. be able to.

In addition, since the capacitance of the LC resonator is obtained by the pair of capacitor electrode patterns facing each other on the front and back sides of the substrate, the electrode area for obtaining the required capacitance can be smaller than the conventional one. A small LC filter can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an LC filter as an embodiment of the present invention, in which (a) is a top side view, (b) is a front view, (c) is a rear view, and FIGS. 2 and 3 are books. It is a figure which shows the LC filter as another Example of a device. 4 and 5 are views showing a conventional example, in which (a) shows the front surface and (b) shows the back surface thereof. 1 ... Substrate, 2a, 2b, 3a, 3b ... Capacitor electrode pattern, 4a, 4b, 5a, 5b ... Coil pattern,
6, 7 ... End face of substrate 4a1, 4b1, 5a1, 5b1
... wraparound electrode section.

Claims (1)

[Scope of utility model registration request] 1. An LC parallel circuit equivalently, wherein capacitor electrode patterns are formed on both front and back surfaces of a dielectric substrate so as to face each other, and coil patterns whose one end is connected to the capacitor electrode pattern are formed on both front and back surfaces. In a bandpass filter constituted by coupling a plurality of resonators in multiple stages, the coil patterns on the front and back surfaces of each resonator are arranged so as to be spaced apart in the plane direction of the substrate, and An LC filter characterized in that an end is connected to an end face of a substrate and is connected to a wrap-around electrode portion wider than a width of a coil pattern.