JPH07135402A - High frequency filter - Google Patents

Abstract

PURPOSE:To obtain a miniaturized high frequency filter with an excellent frequency characteristic. CONSTITUTION:The high frequency filter 10 includes a dielectric substrate 12. An earth electrode 14 is formed on one entire major side of the dielectric substrate 12. Two pattern electrodes 16a, 16b are formed on the other entire major side of the dielectric board 12. The pattern electrodes 16a, 16b have one-end side parts 18a, 18b formed in parallel with a gap and the other-end side parts 20a, 20b formed orthogonal to each other. A dielectric layer 26 is formed in the middle of the other-end side parts 20a, 20b. Furthermore, input output electrodes 28a, 28b are respectively formed on the other major side of the dielectric board 12 in the vicinity of tips 22a, 22b of the pattern electrodes 16a, 16b and capacitors 30a, 30b are formed respectively between the tips 22a, 22b and the input output electrodes 28a, 28b.

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 An example of a conventional strip line filter which is the background of the present invention is, for example, Japanese Patent Publication No. 60-2844.
No. 1 is disclosed. FIG. 10 is a plan view showing an example of such a conventional high frequency filter, and FIG. 11 is a side view thereof. The high frequency filter 1 shown in FIGS. 10 and 11 includes a dielectric substrate 2 having a relative dielectric constant of 10 to 20, for example. The ground electrode 3 is formed on the entire one main surface of the dielectric substrate 2. Further, on the other main surface of the dielectric substrate 2,
Five linear pattern electrodes 4a, 4b, 4c, 4d and 4e are formed so as to face the ground electrode 3. In this case, these pattern electrodes 4a to 4e have a predetermined spacing S1 so that two adjacent electrodes are electromagnetically coupled.
Are formed in parallel with each other. These pattern electrodes 4a
4e is 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 the five pattern electrodes 4a to 4e form five stages of λ.
A / 4 resonator is constructed. Input / output electrodes 5a and 5b are formed extending from the respective intermediate portions of the pattern electrodes 4a and 4e on both sides to both sides of the dielectric substrate 2. Therefore, the high frequency filter 1 is configured as a combline type filter.

[0003]

In the high frequency filter 1 shown in FIGS. 10 and 11, in order to obtain a high performance frequency characteristic having a large amount of attenuation, it is necessary to form the resonator in multiple stages and thus the shape is large. In addition, there is a problem that the design becomes exponentially difficult as the number of resonator stages increases.

Further, the high frequency filter 1 shown in FIGS. 10 and 11 is required to be downsized in accordance with recent market demands.
If an attempt is made to increase the dielectric constant of the dielectric substrate 2 in order to shorten the length L1 of the pattern electrodes 4a to 4e of one resonator, the interference effect of the electromagnetic field between two adjacent resonators becomes strong. Will end up. 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 characteristic, it is necessary to redesign the gap S1 between the pattern electrodes of two adjacent resonators. If the space S1 between the pattern electrodes of two adjacent resonators is widened, not only the high-frequency filter becomes large against the miniaturization, but also its design is difficult, and in some cases the design becomes impossible. Could be.

Therefore, the inventor of the present invention has devised a new high frequency filter which can be miniaturized.

FIG. 12 is a plan view showing an example of a novel high frequency filter which is the background of the present invention, FIG. 13 is a side view thereof, and FIG. 14 is a sectional view taken along line XIV-XIV in FIG. The high frequency filter 1 shown in FIGS. 12 to 14 particularly includes the dielectric substrate 2 having a high dielectric constant of 50 or more, and the ground electrode 3 is provided on the entire one main surface of the dielectric substrate 2. It is formed. Further, on the other main surface of the dielectric substrate 2, two pattern electrodes 4a and 4b are provided.
Is formed. These pattern electrodes 4a and 4b
Is a space S between the end portions extending from the ground electrode 3 with respect to each other.
The two end portions are formed in parallel with each other and are formed so as to extend in directions orthogonal to each other. Input / output electrodes 5a and 5b are connected to the tip ends of the pattern electrodes 4a and 4b via capacitors 6a and 6b. Capacitors 6a and 6b include tip portions of pattern electrodes 4a and 4b, dielectric layers 7a and 7b formed on the tip portions, and input / output electrodes 5a.
And 5b and electrodes 8a and 8b extending on the dielectric layers 7a and 7b. Therefore, FIG.
The high frequency filter 1 shown in FIG. 14 to FIG. 14 has an equivalent circuit shown in FIG.

In the high frequency filter 1 shown in FIGS. 12 to 14, the dielectric substrate 2, the ground electrode 3, and the two pattern electrodes 4a and 4b constitute two λ / 4 resonators. Also, two pattern electrodes 4a and 4b
Are formed so that their one end side portions are formed in parallel at a distance S2 from each other, so that they are electromagnetically coupled at their one end side portions, but their other end side portions extend in directions orthogonal to each other. As a result, they are almost not electromagnetically coupled at their other end portions. Therefore, the two resonators are less likely to be affected by the interference of electromagnetic fields.

Since the high frequency filter 1 shown in FIGS. 12 to 14 uses the dielectric substrate 2 having a high dielectric constant, the lengths of the two pattern electrodes 4a and 4b can be shortened, and moreover, Since the two resonators are less susceptible to the interference effect of the electromagnetic field, the space S2 between the two pattern electrodes 4a and 4b of the two resonators can be narrowed. Therefore, the high frequency filter can be downsized.

However, the high frequency filter 1 shown in FIGS. 12 to 14 can be downsized, but FIG.
As compared with the high frequency filter 1 shown in FIG. 11, as shown in FIG. 16, there is a problem that frequency characteristics such as selection characteristics deteriorate.

Therefore, a main object of the present invention is to provide a high frequency filter which can be miniaturized and has good frequency characteristics.

[0011]

The present invention is directed to a ground electrode formed on one main surface of a dielectric substrate and a plurality of pattern electrodes formed on the other main surface of the dielectric substrate so as to face the ground electrode. A plurality of pattern electrodes are formed such that one end side portions thereof are parallel to each other with a space therebetween, and the other end side portions thereof are orthogonal to each other, and further the other end sides of the plurality of pattern electrodes are formed. A high frequency filter in which a dielectric layer is formed between overlapping portions.
A capacitance may be formed between the two input / output electrodes.

[0012]

Function: The dielectric substrate, the ground electrode, and the pattern electrodes form a plurality of resonators.

By the way, in the plurality of pattern electrodes, a dielectric layer is formed between the overlapping portions of the other end side portions thereof, and electrostatic capacitance is generated therebetween, so that capacitive coupling is added in addition to electromagnetic field coupling. To be done. Therefore, the distance between the plurality of pattern electrodes can be widened to weaken the coupling.
Therefore, in addition to the effect of the other end portions of the plurality of pattern electrodes overlapping each other, the distance in the arrangement direction of the plurality of pattern electrodes can be further shortened.

[0014]

According to the present invention, in the high frequency filter, the distance in the arrangement direction of the plurality of pattern electrodes can be shortened. Therefore, the high frequency filter can be downsized. If a dielectric substrate having a high dielectric constant is used, the length of the plurality of pattern electrodes can be shortened and the size can be further reduced, so that the effect of the present invention can be further improved.

Further, according to the present invention, in the high frequency filter, the dielectric layer is formed between the overlapping portions of the other end side portions of the plurality of pattern electrodes, and the electrostatic capacitance is generated therebetween, so that the low frequency side is formed. Attenuation poles are generated at and the frequency characteristics are improved. In this high frequency filter, if a capacitance is formed between the two input / output electrodes, attenuation poles are generated on the high frequency side and the low frequency side, respectively, and the frequency characteristic is further improved.

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

[0017]

1 is a plan view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line II--II in FIG.
FIG. 3 is a sectional view taken along line III-III in FIG.
The high frequency filter 10 includes a rectangular plate-shaped dielectric substrate 12, 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 portion 20a linearly extending inward 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 the other end side portion 20b linearly extending inward from the one end side portion 18b at an angle of, for example, 45 degrees. Have and. In this case, in the two pattern electrodes 16a and 16b, the one end side portions 18a and 18b are formed in parallel with each other with a space S3 therebetween.
The other end portions 20a and 20b are formed so as to be orthogonal to each other. Therefore, the two pattern electrodes 16a and 16b are electromagnetically coupled at their one end portions 18a and 18b, and their other end portions 20a and 20b.
At 0b, there is almost no electromagnetic coupling. The tip portions (open end portions) 22a and 22b of the pattern electrodes 16a and 16b are formed facing both sides of the dielectric substrate 12.

A capacitor 24 is formed between the overlapping portions of the other end side portions 20a and 20b of the pattern electrodes 16a and 16b. This capacitor 24 is particularly suitable for the pattern electrode 1 as shown in FIG.
6a, the intermediate portion of the other end side portion 20a, the dielectric layer 26 formed on the intermediate portion, etc., and the middle of the other end side portion 20b of the pattern electrode 16b formed on the dielectric layer 26. It is composed of The dielectric layer 26 is formed of a dielectric such as polyimide to a thickness of 5 μm by a method such as photolithography. Then, the other end side portion 20 of the pattern electrodes 16a and 16b
The intermediate portion between a and 20b has, for example, 0.2 to
A capacitance Cc of 0.8 pF is generated.

Further, on the other main surface of the dielectric substrate 12,
Two input / output electrodes 28a and 28b are provided near the tips 22a and 22b of the pattern electrodes 16a and 16b.
Is formed.

Further, the tip ends 22a and 22b of the pattern electrodes 16a and 16b and the input / output electrodes 28a and 2b, respectively.
Capacitors 30a and 30b are formed between each of them and 8b. One of the capacitors 30a is, in particular, as shown in FIG. 3, a tip portion 22a of the pattern electrode 16a.
And the dielectric layer 3 formed on the tip portion 22a and the like.
2a and an electrode 34a extending from the input / output electrode 28a onto the dielectric layer 32a. Similarly, the other capacitor 30b has a tip portion 22b of the pattern electrode 16b and a dielectric layer 32b formed on the tip portion 22b and the like.
And an electrode 34b extending from the input / output electrode 28b onto the dielectric layer 32b.

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 the one pattern electrode 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.

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 S3 therebetween.
8b electromagnetically couples. However, since the two pattern electrodes 16a and 16b are formed so that the other end side portions 20a and 20b thereof are orthogonal to each other, the other end side portions 20a and 20b are almost not electromagnetically coupled. Therefore, the two resonators are less likely to be affected by the interference of electromagnetic fields.

Further, in this high frequency filter 10, 2
In the two pattern electrodes 16a and 16b, the dielectric layer 26 is formed between the overlapping portions of the other end side portions 20a and 20b, and the electrostatic capacitance Cc is generated therebetween, so that the capacitive coupling is performed in addition to the electromagnetic coupling. Is also added. Therefore, it is necessary to widen the space between the two pattern electrodes 16a and 16b to weaken the electromagnetic field coupling. Therefore, in addition to the effect of overlapping the other end side portions 20a and 20b of the two pattern electrodes 16a and 16b, by widening the interval between the two pattern electrodes 16a and 16b, the conventional example shown in FIGS. Compared to the high frequency filter shown in FIGS.
The distance in the arrangement direction of the two pattern electrodes 16a and 16b can be greatly shortened.

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 are the same as those in the conventional example shown in FIGS. It is possible to reduce the length of the pattern electrodes 16a and
The distance in the arrangement direction of 16b and 16b can be made much shorter than the distance in the conventional example shown in FIGS. 10 and 11 and the high frequency filter shown in FIGS. Therefore, the high frequency filter 10 can be downsized as compared with the conventional example.

Further, in this high frequency filter 10, 2
The other end portion 18 of the two patterned electrodes 16a and 16b
Since the dielectric layer 26 is formed between the orthogonal portions of a and 18b, and the electrostatic capacitance Cc is generated between them, an attenuation pole is generated on the low frequency side, and the frequency characteristic is good.

Further, in the high frequency filter 10, the two resonators are mainly coupled to each other by magnetic 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 resonators are mainly coupled to each other. However, they are less susceptible to the interference effect of the electromagnetic fields, so that despite the use of the dielectric substrate 12 having a high dielectric constant, the design is not complicated or difficult, and the design can be performed relatively easily.

Further, in the high frequency filter 10, since the input / output electrodes 28a and 28b are connected to the pattern electrodes 16a and 16b of the two resonators through the capacitors 30a and 30b, for example, a comparatively large number of hundreds of 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 dielectric substrate 12 is connected to the other main surface side of the ground electrode 14 from the other end of the earth electrode 14.
The distance L3 to the bent portion is 5 degrees and the interval S between the end portions 18a and 18b of the pattern electrodes 16a and 16b.
3 can be changed appropriately, and the input / output electrodes 28a and 28b can be changed substantially without changing the λ / 4 length of the resonator.
It has a degree of freedom in design such that the position dimension D3 of can be changed to some extent.

FIG. 5 is a plan view showing another embodiment of the present invention. In the embodiment shown in FIG. 5, in comparison with the embodiment shown in FIGS. 1 to 3, in particular, the tip portions 22a and 22b of the two pattern electrodes 16a and 16b are arranged on the dielectric substrate 12.
Is formed toward the other end of the. Further, two input / output electrodes 28a and 28b are formed close to the other end of the dielectric substrate 12. Therefore, the two input / output electrodes 28a
A capacitance Cp is generated between and 28b. Therefore, the high frequency filter 10 has the equivalent circuit shown in FIG.

The high frequency filter 10 shown in FIG.
3 to the high frequency filter 10 shown in FIG.
Capacitance Cp between the two input / output electrodes 28a and 28b
Occurs, an attenuation pole is generated on each of the high band side and the low band side, and the frequency characteristic is further improved.

Further, in the high frequency filter 10 shown in FIG. 5, compared with the high frequency filter 10 shown in FIGS. 1 to 3, the tip portions 2 of the two pattern electrodes 16a and 16b are provided.
Since the distance between 2a and 22b and the distance between the two input / output electrodes 28a and 28b are narrowed, the size can be further reduced.

FIG. 7 shows frequency characteristics of the embodiment shown in FIGS. 1 to 3 and the embodiment shown in FIG. Figure 7
From the frequency characteristics shown in FIG.
It is understood that, as compared with the embodiment shown in FIG. 3, attenuation poles are generated on the high frequency side and the low frequency side, respectively, and the frequency characteristic is further improved.

In each of the above-mentioned embodiments, the capacitors 30a and 3 connected between the two pattern electrodes 16a and 16b and the two input / output electrodes 28a and 28b.
Although the dielectric layers 32a and 32b are used as 0b, a chip capacitor or a capacitor having a gap capacitance may be used as the capacitors. For example, as compared with the embodiment shown in FIG. 1, as shown in FIG. 8, as capacitors 30a and 30b connected between tip portions 22a and 22b of pattern electrodes 16a and 16b and input / output electrodes 28a and 28b, Chip capacitors may be used respectively. Alternatively, as compared with the embodiment shown in FIG. 1, as shown in FIG. 9, the tip portions 22a and 22b of the pattern electrodes 16a and 16b and the input / output electrodes 28a and 28b are formed closer to each other,
As the capacitance of capacitors 30a and 30b connected between tip portions 22a and 22b of pattern electrodes 16a and 16b and input / output electrodes 28a and 28b, a gap capacitance between them may be 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 be orthogonal to each other, and may be formed at other angles. For example, one angle may be 40 degrees and the other angle may be 50 degrees.

Further, although each of the above-described embodiments has two pattern electrodes, that is, two λ / 4 resonators, the present invention is also applicable to a high frequency filter having three or more pattern electrodes or λ / 4 resonators. Can be done. in this case,
It suffices that the other end side portion (open end side portion) is formed so as to be substantially orthogonal between two approaching pattern electrodes, and the dielectric layer is formed between the overlapping portions.

Further, although each of the above-described embodiments is an example using a high dielectric constant substrate, the present invention is not limited to this in terms of downsizing in the arrangement direction.

Further, in each of the above-mentioned embodiments, the example of the λ / 4 resonator having one end connected to the ground electrode has been described, but the present invention can be applied to a λ / 2 resonator having one end open, and the like. It will be obvious to a technician familiar with.

Further, although one dielectric substrate is used in each of the above-described embodiments, the present invention is also applied to a triplate type high frequency filter in which a plurality of dielectric layers and the like are laminated and integrated. obtain. 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.

FIG. 2 is a sectional view taken along line II-II in 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 FIGS. 1 to 3.

FIG. 5 is a plan view showing another embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram of the embodiment shown in FIG.

FIG. 7 is a graph showing frequency characteristics of the embodiment shown in FIGS. 1 to 3 and the embodiment shown in FIG.

FIG. 8 is an illustrative view showing a modified example of the embodiment shown in FIG.

9 is an illustrative view showing another modification of the embodiment shown in FIG. 1. FIG.

FIG. 10 is a plan view showing an example of a conventional high frequency filter.

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

FIG. 12 is a plan view showing an example of a novel high frequency filter which is the background of the present invention.

FIG. 13 is a side view of the high frequency filter shown in FIG.

14 is a sectional view taken along line XIV-XIV in FIG.

15 is an equivalent circuit diagram of the high frequency filter shown in FIGS. 12 to 14. FIG.

16 is a graph showing frequency characteristics of the high frequency filters shown in FIGS. 10 and 11 and the high frequency filters shown in FIGS. 12 to 14. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 High frequency filter 12 Dielectric substrate 14 Ground electrode 16a, 16b Pattern electrode 18a, 18b One end side part 20a, 20b Other end side part 22a, 22b Tip part 26 Dielectric layer 28a, 28b Input / output electrode 30a, 30b Capacitor

Claims (2)

[Claims] 1. A ground electrode formed on one main surface of a dielectric substrate, and a plurality of pattern electrodes formed on the other main surface of the dielectric substrate so as to face the ground electrode. The 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 are orthogonal to each other, and further, the other end side portions of the plurality of pattern electrodes are overlapped with each other. A high frequency filter in which a dielectric layer is formed. 2. The high frequency filter according to claim 1, wherein a capacitance is formed between the tips of the plurality of pattern electrodes.