JPH07122906A - High frequency filter - Google Patents

Abstract

PURPOSE:To provide a miniaturizable high frequency filter by simple design. CONSTITUTION:This high frequency filter 10 is provided with a dielectric substrate 12 provided with a high dielectric constant. A grounding electrode 14 is formed on the entire surface of one of the main surfaces of the dielectric substrate 12 and two pattern electrodes 16a and 16b are formed on the other main surface of the dielectric substrate 12. The pattern electrodes 16a and 16b are provided with end side parts 18a and 18b parallelly formed with a gap with each other and the other end side parts 20a and 20b extended in directions for orthogonally crossing each other. Also, on one of the main surfaces of the dielectric substrate 12, input/output electrodes 24a and 24b are respectively formed near the tip parts 22a and 22b of the pattern electrodes 16a and 16b and capacitors 26a and 26b are respectively formed between the tip parts 22a and 22b and the input/output electrodes 24a and 24b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency filter, and more particularly to a high frequency filter which is a planar type distributed constant filter using a dielectric substrate and having a plurality of resonators, for example, used as a bandpass filter.

[0002]

2. Description of the Related Art FIG. 9 is a plan view showing an example of a conventional high frequency filter which is the background of the present invention, and FIG. 10 is a side view thereof. The high frequency filter 1 includes a dielectric substrate 2 having a relative permittivity of, for example, 10 to 20. The ground electrode 3 is formed on the entire one main surface of the dielectric substrate 2. Also,
Two linear pattern electrodes 4 a and 4 b are formed on the other main surface of the dielectric substrate 2 so as to face the ground electrode 3. In this case, the pattern electrodes 4a and 4b
Are formed in parallel with each other with a predetermined spacing S1 so as to be electromagnetically coupled. One ends of these pattern electrodes 4a and 4b are connected to the ground electrode 3 via one end surface of the dielectric substrate 2. Then, the dielectric substrate 2, the ground electrode 3 and one pattern electrode 4a constitute one λ / 4 resonator, and the dielectric substrate 2, the ground electrode 3 and the other pattern electrode 4b constitute another λ / 4 resonator. Is configured.
Further, the input / output electrodes 5a and 5b are the pattern electrodes 4a.
And 4b are formed to extend from the respective intermediate portions to both sides of the dielectric substrate 2. Therefore, the high frequency filter 1 is configured as a combline type filter.

FIG. 11 is a plan view showing another example of a conventional high frequency filter which is the background of the present invention. In the conventional example shown in FIG. 11, compared with the conventional example shown in FIGS. 9 and 10, the ends of the pattern electrodes 4a and 4b on different sides are connected to the ground electrode 3. Therefore, the high frequency filter 1 shown in FIG. 11 is configured as an interdigital filter.

[0004]

In the high frequency filter 1 shown in FIGS. 9 to 11, in order to reduce the size in accordance with recent demands, the lengths L1 of the pattern electrodes 4a and 4b of the two resonators are shortened. If an attempt is made to increase the dielectric constant of the dielectric substrate 2 in order to cope with this, the interference effect of the electromagnetic field between the two resonators becomes strong. That is, if the dielectric substrate 2 is made to have a high dielectric constant, the electromagnetic field coupling between the pattern electrodes 4a and 4b of the two resonators becomes too strong. Therefore, the frequency characteristics such as the selection characteristics of the high frequency filter are deteriorated. In order to correct such deterioration of the frequency characteristics, it is necessary to redesign the gap S1 between the pattern electrodes 4a and 4b of the two resonators. And
The spacing S between the pattern electrodes 4a and 4b of the two resonators
When 1 is widened, the high frequency filter becomes large in size, contrary to size reduction.

Further, in the high frequency filter 1 shown in FIGS. 9 to 11, the input / output electrodes 5a and 5b are directly pulled out from the respective intermediate portions of the pattern electrodes 4a and 4b to match the input / output impedance with an external circuit. Therefore, the pattern electrode 4 is adjusted in accordance with the change in the coupling amount between the two resonators due to the electromagnetic field interference effect.
The design is complicated and difficult, for example, the distance D1 from the short-circuited end of a and 4b (the end connected to the ground electrode 3) to the input / output electrodes 5a and 5b and the width T of the input / output electrodes 5a and 5b must be adjusted. Was there.

Further, in the high frequency filter 1 shown in FIGS. 9 to 11, even if the input and output impedances are matched as described above, there is a problem that the frequency characteristic is likely to change when the impedance of the external circuit changes. Was there.

Therefore, a main object of the present invention is to provide a high frequency filter which can be miniaturized with an easy design.

[0008]

The present invention is directed to a dielectric substrate having a high dielectric constant, an earth electrode formed on one main surface of the dielectric substrate, and the other of the dielectric substrates facing the earth electrode. And a plurality of pattern electrodes formed on the main surface, wherein the plurality of pattern electrodes are formed in parallel with each other at one end side portions thereof, and the other end side portions thereof extend in directions orthogonal to each other. It is a high frequency filter that is formed.

[0009]

Function: The dielectric substrate, the ground electrode, and the pattern electrodes form a plurality of resonators. In addition, the plurality of pattern electrodes are electromagnetically coupled at their one end side portions because their one end side portions are formed in parallel with each other with a space therebetween, but their other end side portions are orthogonal to each other. Since they are formed so as to extend in the direction, they are almost not electromagnetically coupled at their other end portions. Therefore, the plurality of resonators are less likely to be affected by the interference of electromagnetic fields.

[0010]

According to the present invention, since the dielectric substrate having a high dielectric constant is used in the high frequency filter,
The length of the plurality of pattern electrodes can be shortened, and moreover, the plurality of resonators are less likely to receive the interference effect of the electromagnetic field with each other, so that the interval between the plurality of resonator pattern electrodes can be narrowed. Therefore, the high frequency filter can be downsized.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0012]

1 is a plan view showing an embodiment of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a line III-- of FIG.
It is sectional drawing in III. This high frequency filter 10
Includes a dielectric substrate 12 having a rectangular plate shape, for example. As the dielectric substrate 12, a substrate having a high dielectric constant of, for example, 50 or more is used.

A ground electrode 14 is formed on the entire one main surface of the dielectric substrate 12. The ground electrode 14 is
It is also formed on the entire surface of one end surface of the dielectric substrate 12 and the end portion of the other main surface.

Two pattern electrodes 16a and 16b are formed on the other main surface of the dielectric substrate 12. One pattern electrode 16a includes one end side portion 18a linearly extending in the vertical direction from the ground electrode 14 and one end side portion 18a thereof.
From the other end side portion 20a linearly extending outward at an angle of, for example, 45 degrees. Similarly, the other pattern electrode 16b includes one end side portion 18b linearly extending in the vertical direction from the ground electrode 14 and one end side portion 18b thereof.
From the other end side portion 20b linearly extending outward at an angle of, for example, 45 degrees. Therefore, in the two pattern electrodes 16a and 16b, one end side portions 18a and 18b are formed in parallel with each other with a space S2 therebetween, and the other end side portions 20a and 20b are formed to extend in a direction orthogonal to each other. Therefore, the two pattern electrodes 16a and 16b are connected to one end portion 18 thereof.
Electromagnetically coupled at a and 18b, and electromagnetically hardly coupled at their other end portions 20a and 20b.

Further, on the other main surface of the dielectric substrate 12,
Tip portions (open end portions) of the pattern electrodes 16a and 16b
Two input / output electrodes 24a are provided in the vicinity of 22a and 22b.
And 24b are formed.

The tip portions 22a and 22b of the pattern electrodes 16a and 16b and the input / output electrodes 24a and 2 are also provided.
Capacitors 26a and 26b are formed between 4b and 4b, respectively. One of the capacitors 26a is, in particular, as shown in FIG. 3, a tip portion 22a of the pattern electrode 16a.
And the dielectric layer 2 formed on the tip portion 22a and the like.
8a and an electrode 30a extending from the input / output electrode 24a onto the dielectric layer 28a. Similarly, the other capacitor 26b includes a tip portion 22b of the pattern electrode 16b and a dielectric layer 28b formed on the tip portion 22b and the like.
And an electrode 30b extending from the input / output electrode 24b onto the dielectric layer 28b.

Therefore, the high frequency filter 10 is
It has an equivalent circuit shown in FIG.

In the high frequency filter 10, the dielectric substrate 12, the ground electrode 14 and one of the pattern electrodes 16a.
One λ / 4 resonator is constituted by, and another λ / 4 resonator is formed by the dielectric substrate 12, the ground electrode 14 and the other pattern electrode 16b.
A / 4 resonator is constructed.

Further, in the high frequency filter 10, the two pattern electrodes 16a and 16b are formed in parallel with each other at their one end side portions 18a and 18b with a space S2 therebetween.
8b electromagnetically couples. However, the two pattern electrodes 16a and 16b are formed such that the other end side portions 20a and 20b thereof extend in the directions orthogonal to each other, so that the other end side portions 20a and 20b are hardly electromagnetically coupled. . Therefore, the two resonators are less likely to be affected by the interference of electromagnetic fields.

As described above, since the high frequency filter 10 uses the dielectric substrate 12 having a high dielectric constant, the lengths of the two pattern electrodes 16a and 16b should be shorter than those in the conventional example. Since the two resonators are less susceptible to the interference effect of the electromagnetic field, the two pattern electrodes 16a of the two resonators can be formed.
It is possible to narrow the distance S2 between the positions 16b and 16b compared to the distance S1 in the conventional example. Therefore, the high frequency filter 10 can be made smaller than the conventional example.

Further, in this high frequency filter 10, the two resonators are mainly coupled by electromagnetic field coupling only at the one end side portions 18a and 18b close to the short-circuited ends of the pattern electrodes 16a and 16b of the two resonators, and the two resonances are caused. Since the containers are less susceptible to the interference effect of the electromagnetic fields, the design is not complicated or difficult even though the dielectric substrate 12 having a high dielectric constant is used, and the design is relatively easy.

Further, in the high frequency filter 10, since the input / output electrodes 24a and 24b are connected to the pattern electrodes 16a and 16b of the two resonators through the capacitors 26a and 26b, for example, a relatively high voltage of about a hundred and several tens of ohms is used. It can have high input / output impedance. Therefore, in the high frequency filter 10, the deterioration of the frequency characteristic is small with respect to the variation of the impedance of the external circuit, which is normally 50 ohms.

Further, in this high frequency filter 10, the other main surface side ground electrode 14 of the dielectric substrate 12 is separated from the other end by 45.
The distance L2 to the bending portion and the distance S2 between the end portions 18a and 18b of the pattern electrodes 16a and 16b.
Can be appropriately changed, and the positional dimension D2 of the input / output electrodes 24a and 24b can be changed to some extent without changing the λ / 4 length of the resonator. This facilitates handling when the high frequency filter is attached to a printed circuit board or the like.

FIG. 5 is a plan view showing a modification of the embodiment shown in FIG. 1, and FIG. 6 is a sectional view taken along line VI-VI in FIG. In the embodiment shown in FIG. 5 and FIG. 6, compared with the embodiment shown in FIG.
capacitors 26a and 2 connected between tip portions 22a and 22b of b and input / output electrodes 24a and 24b.
Chip capacitors are used as 6b.

FIG. 7 is a plan view showing another modification of the embodiment shown in FIG. 1, and FIG. 8 is a sectional view taken along line VIII-VIII in FIG. In the embodiment shown in FIGS. 7 and 8, the tip portions 22a and 22b of the pattern electrodes 16a and 16b and the input / output electrode 2 are different from those in the embodiment shown in FIG.
4a and 24b are formed close to each other, and the capacitances of the capacitors 26a and 26b connected between the tip ends 22a and 22b of the pattern electrodes 16a and 16b and the input / output electrodes 24a and 24b are the gap capacitances between them. Is used.

In each of the above-mentioned embodiments, the pattern electrodes 16a and 16b are formed with the other end portions 20a and 20b at an angle of 45 degrees from the one end portions 18a and 18b, respectively. The side portions 20a and 20b may be formed so as to extend in directions orthogonal to each other, and may be formed at other angles. For example, one angle is 40 degrees and the other is 50 degrees.
It may be degree.

Further, although each of the above-mentioned embodiments has two pattern electrodes, that is, two λ / 4 resonators, the present invention can be applied to a high frequency filter having three pattern electrodes or λ / 4 resonators. . In this case, the pattern electrodes may be formed so that the other end side portion (open end side portion) extends between the two approaching pattern electrodes in a direction substantially orthogonal to each other.

In each of the above-mentioned embodiments, an example of a λ / 4 resonator having one end connected to the ground electrode has been described, but those skilled in the art can apply the present invention to a λ / 2 resonator having one end open. Would be obvious to.

Further, although one dielectric substrate is used in each of the above-described embodiments, the present invention can be applied to a laminated high frequency filter in which a plurality of dielectric layers and the like are laminated and integrated. . In this case, since the coupling between the pattern electrodes becomes strong, the present invention is particularly useful.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

2 is a side view of the embodiment shown in FIG. 1. FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is an equivalent circuit diagram of the embodiment shown in FIG.

5 is a plan view showing a modified example of the embodiment shown in FIG.

6 is a cross-sectional view taken along line VI-VI in FIG.

FIG. 7 is a plan view showing another modification of the embodiment shown in FIG.

8 is a sectional view taken along the line VIII-VIII in FIG.

FIG. 9 is a plan view showing an example of a conventional high frequency filter which is the background of the present invention.

10 is a side view of the high frequency filter shown in FIG. 9. FIG.

FIG. 11 is a plan view showing another example of a conventional high frequency filter which is the background of the present invention.

[Explanation of symbols]

 10 High Frequency Filter 12 Dielectric Substrate 14 Ground Electrodes 16a, 16b Pattern Electrodes 18a, 18b One Side 20a, 20b Other Side 22a, 22b Tip 24a, 24b Input / Output Electrode 26a, 26b Capacitor

Claims (1)

[Claims] 1. A dielectric substrate having a high dielectric constant, a ground electrode formed on one main surface of the dielectric substrate, and a ground electrode formed on the other main surface of the dielectric substrate so as to face the ground electrode. A high-frequency filter including a plurality of pattern electrodes, wherein the plurality of pattern electrodes are formed such that one end side portions thereof are spaced apart from each other and are parallel to each other, and the other end side portions thereof extend in directions orthogonal to each other. .