JPH07135403A - High frequency filter - Google Patents

Abstract

PURPOSE:To provide a small sized chip filter with high accuracy having excellent characteristics. CONSTITUTION:The chip filter 10 includes a dielectric substrate 12. An earth electrode 14 and spiral pattern electrodes 16, 18 are formed on both sides of the dielectric board 12 and the pattern electrodes 16, 18 are coupled electromagnetically. Extract electrodes 20, 22 are pulled out from one end of the pattern electrodes 16, 18 at an interval. A magnetic substrate 26 is formed on the pattern electrodes 16, 18 and a protection layer 30 is formed on the earth electrode 14. Then the extract electrodes 20, 22 are connected to extract terminal electrodes 36, 38. Furthermore, the pattern electrode 16 and the earth electrode 14 are connected by a terminal electrode 34a, and the pattern electrode 18 and the earth electrode 14 are connected by a terminal electrode 34c.

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 in which a plurality of resonators are electromagnetically coupled.

[0002]

9 to 11 are illustrative views showing an example of a conventional filter which is the background of the present invention. The filter shown in FIG. 9 includes a dielectric substrate 1, and a ground electrode 2 is formed on almost one surface of the dielectric substrate 1. Then, on the other surface of the dielectric substrate 1, two linear pattern electrodes 3 are formed so as to face the ground electrode. One ends of these pattern electrodes 3 are connected to the ground electrode 2 via the end surface of the dielectric substrate 1. These dielectric substrate 1, earth electrode 2
And the pattern electrode 3 forms a microstrip line resonator. Further, an extraction electrode 4 for input / output is formed at a distance from one end of the pattern electrode 3.
Then, the filter is formed by electromagnetically coupling the two microstrip line resonators.

The filter shown in FIG. 10 has two bobbins 5.
And the conducting wire 6 is wound around the bobbin 5 to form a resonator. Then, one end of the conductive wire 6 is connected to the terminal. The two bobbins 5 around which the conducting wire 6 is wound are covered with a metal case 7. A coupling window is formed between the two resonators, and the two resonators are electromagnetically coupled via the coupling window.
Further, the resonator shown in FIG. 11 includes the dielectric substrate 1. On the dielectric substrate 1, the ground electrode 2 and the spiral pattern electrode 8 facing the ground electrode 2 are formed to form a resonator.
The plurality of resonators are connected to each other by the coupling control pattern 9
Are connected via. This filter is formed by forming a pattern for each electrode on a ceramic sheet formed of a dielectric material, laminating the patterns, and firing them integrally.

[0004]

The length L of the pattern electrode of each resonator of the filter shown in FIG. 9 is expressed by the following mathematical expression 1.

[0005]

[Equation 1]

Where λ is the wavelength and ε _re is the effective permittivity of the dielectric. As can be seen from Equation 1, it is conceivable to use a dielectric material having a high dielectric constant in order to miniaturize these resonators. However, due to the temperature characteristics, the relative permittivity of the dielectric material cannot be increased so much that the relative permittivity ε = 100 is the limit. Assuming that this relative permittivity is replaced with the effective permittivity ε _{re as} it is, when a 1 GHz resonator is formed, L = 7.
It is very long, 5 mm. Therefore, it is difficult to downsize the resonator, and it is also difficult to downsize the filter using the resonator.

When the length L of the pattern electrode of each resonator is increased, electromagnetic coupling between adjacent resonators is increased. Therefore, the distance between the pattern electrodes must be increased in order to obtain an appropriate bond. Therefore, the filter becomes larger.

In the filter shown in FIG. 10, a conducting wire is spirally wound around a bobbin and magnetically coupled to each other through a coupling window. However, since the conductor wire is wound in a spiral shape and housed in a metal case, there is a problem that the occupied area is large and it is difficult to reduce the size. Further, since the conductor wire, the bobbin, the metal case, and the like are assembled, manufacturing is troublesome and cost reduction is difficult.

In the filter shown in FIG. 11, since the pattern electrodes are formed in a spiral shape, the magnetic flux influences each other between adjacent pattern electrodes, which makes it difficult for current to flow. Therefore, the substantial resistance increases and the Q decreases. Further, in a filter using a spiral pattern electrode, when the resonance frequency becomes low, it is necessary to reduce the line width of the pattern electrode to increase the number of turns due to its structure, which further increases resistance and lowers Q. was there. further,
Since the dielectric materials are laminated and integrally fired, cracks or breaks occur due to contraction of the dielectric materials during firing. Further, there is a large dimensional variation, and a process such as trimming is required to improve accuracy, which makes it difficult to reduce the cost and is expensive.

Therefore, a main object of the present invention is to provide a high-frequency filter having excellent characteristics, high accuracy, and small size.

[0011]

According to the present invention, there is provided a dielectric substrate, a ground electrode formed in a plane on one surface of the dielectric substrate, and a ground electrode on the other surface of the dielectric substrate facing the ground electrode. A plurality of spiral pattern electrodes that are formed and connected at one end to the ground electrode, an extraction electrode that is extracted from the pattern electrode at a distance from one end of each pattern electrode, and formed on the pattern electrode and the extraction electrode. A high-frequency filter including a magnetic substrate and a plurality of pattern electrodes electromagnetically coupled to each other.

[0012]

The microstrip line resonator is formed by the spiral pattern electrode and the ground electrode, and the pattern electrode is electromagnetically coupled to form a high frequency filter. At this time, since the magnetic substrate is formed on the pattern electrode, the inductance of the resonator increases. Further, the magnetic substrate strengthens magnetic coupling between the plurality of pattern electrodes. Furthermore, a shield effect is obtained by the magnetic substrate.

[0013]

According to the present invention, since the spiral pattern electrodes are formed side by side, the size can be reduced as compared with the high frequency filter having the linear pattern electrodes. Further, since the magnetic substrate increases the inductance of the microstrip line resonator and the coupling between the pattern electrodes also increases, the size can be reduced as compared with the conventional high frequency filter that does not use the magnetic substrate. . Moreover, since the magnetic substrate can provide a shielding effect, it is not necessary to form a shield electrode or the like, and an inexpensive high frequency filter can be obtained.

Further, a high frequency filter can be formed by adhering a dielectric substrate on which a pattern electrode or a ground electrode is formed and a magnetic substrate, and when a plurality of dielectric materials are laminated and integrally fired. As described above, the occurrence of cracks and the variation in dimensions are small. Further, since the dielectric substrate, the magnetic substrate, and the electrodes have little dimensional variation, it is possible to obtain a high-frequency filter having high filter accuracy and stable characteristics. Further, since a plurality of electrode patterns can be accurately formed on one dielectric substrate, the filter can be mass-produced and the cost can be reduced.

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.

[0016]

1 is a plan view showing an embodiment of the present invention, and FIGS. 2 and 3 are lines II-II and I, respectively.
FIG. 4 is a sectional view taken along line II-III, and FIG. 4 is an exploded perspective view thereof. The high frequency filter 10 includes a rectangular plate-shaped dielectric substrate 12. As the dielectric substrate 12, for example, one having a high dielectric constant of 70 or more is used. The ground electrode 14 is formed on almost one surface of the dielectric substrate 12. Further, two pattern electrodes 16 and 18 are formed on the other surface of the dielectric substrate 12 so as to face the ground electrode 14.

The pattern electrode 16 is formed in a spiral shape from one side toward the inside on one side of the dielectric substrate 12. Further, another pattern electrode 18 is formed on the other side of the dielectric substrate 12 in a spiral shape from the same side as the pattern electrode 16 toward the inside. At this time, the area of each pattern electrode 16 and 18 is S1, and each pattern electrode 1
When the area of the central portion of the spirals 6 and 18 where the pattern electrode is not formed is S2, the area ratio S2 / S1
Is 0.15 or more. Further, these pattern electrodes 16 and 18 are formed so that the width thereof becomes smaller from the end side of the dielectric substrate 12 toward the inside.

The extraction electrode 20 is extracted from the pattern electrode 16 toward the end of the dielectric substrate 12. The extraction electrode 20 is formed at a predetermined distance from one end of the pattern electrode 16 drawn out to the side of the dielectric substrate 12.
Similarly, the extraction electrode 22 is extracted from the pattern electrode 18 toward the end of the dielectric substrate 12. The extraction electrode 22 is formed at a predetermined distance from one end of the pattern electrode 18 drawn out to the side of the dielectric substrate 12. These pattern electrodes 16 and 18 and extraction electrodes 20 and 2
An adhesive layer 24 such as a polyimide layer is formed on the surface 2. On this adhesive layer 24, a magnetic substrate 26 such as high frequency ferrite is formed. Then, the protective layer 30 is formed so as to cover the ground electrode 14.
At this time, the protective layer 30 is formed so that the end portion of the ground electrode 14 is exposed except for the direction in which the extraction electrodes 20 and 22 are extracted.

On the opposite side surfaces of the high frequency filter 10, six terminal electrodes 34a, 34b, 34c, 34d,
34e and 34f are formed. These terminal electrodes 3
4a to 34f are formed on the side surfaces where the extraction electrodes 20 and 22 are not extracted. And one terminal electrode 34
The pattern electrode 16 and the ground electrode 14 are connected by a. Similarly, another pattern electrode 18 and the ground electrode 14 are connected by the terminal electrode 34c. Also,
The other terminal electrodes 34b, 34d, 34e, 34f are connected to the ground electrode 14, respectively. Further, a take-out terminal electrode 36 is formed on the side surface of the high-frequency filter 10 from which the take-out electrode 20 is taken out, and a take-out terminal electrode 38 is formed on the side surface from which the take-out electrode 22 is taken out. The extraction terminal electrode 36 is connected to the extraction electrode 20,
The extraction terminal electrode 38 is connected to the extraction electrode 22. The input / output impedance of the high frequency filter 10 is the distance between one end of the pattern electrode 16 connected to the terminal electrode 34a and the extraction electrode 20, and the distance between one end of the pattern electrode 18 connected to the terminal electrode 34c and the extraction electrode 22. Determined by

The high frequency filter 10 has a microstrip line structure and has two pattern electrodes 16 and 18.
Form two resonators. Then, adjacent portions of the pattern electrodes 16 and 18 are electromagnetically coupled to form a filter.

To produce this high frequency filter 10,
The dielectric substrate 12 is prepared. On this dielectric substrate 12,
The ground electrode 14 and the pattern electrodes 16 and 18 are formed by using a thin film method and a method such as etching.
Then, the protective layer 30 is formed on the ground electrode 14 of the dielectric substrate 12 using glass or resin. Further, thermoplastic polyimide is placed, printed or applied on the surface of the dielectric substrate 12 on which the pattern electrodes 16 and 18 are formed, and the magnetic substrate 26 is bonded and thermocompression bonded or vacuum thermocompression bonded. After that, the terminal electrodes 34a to 34f and the extraction terminal electrodes 36 and 38 are formed by a dry plating method or the like, and the high frequency filter 10 is manufactured.

In this high frequency filter 10, no capacitor pattern is formed, but it has an equivalent circuit shown in FIG. This is because the structure of the high-frequency filter 10 is a microstrip line structure, so that electrostatic capacitance is formed between the pattern electrodes 16 and 18 and the ground electrode 14. In the equivalent circuit shown in FIG.
CX and M indicate electromagnetic coupling.

The frequency characteristics of such a high frequency filter 10 were measured, and the results are shown in FIG. In this high frequency filter 10, since the magnetic substrate 26 is formed, the inductance of the microstrip line resonator is increased. Further, the magnetic substrate 26 increases the coupling between the pattern electrodes. Therefore, the frequency characteristics can be changed by changing the thickness and magnetic permeability of the magnetic substrate 26. For comparison with the high frequency filter 10 of the present invention, a high frequency filter 40 shown in FIG. 7 was produced, and its frequency characteristic is shown in FIG. Figure 7
In the high frequency filter of No. 2, the magnetic substrate of the high frequency filter 10 of the present invention is not formed, but the protective layer 42 is formed on the pattern electrode. The other thicknesses, relative permittivities, and widths and lengths of the pattern electrodes 16 and 18 of the dielectric substrate 12 are the same as those of the high frequency filter of the present invention.

As can be seen from FIGS. 6 and 8, the center frequency of the comparative example was 1625 MHz, whereas the center frequency of the high frequency filter of the present invention was 1465 MHz, and the difference was 160 MHz. In addition, in the comparative example −
The 3 dB pass bandwidth is 160 MHz, whereas the -3 dB pass bandwidth of the high frequency filter of the present invention is 135 MH.
z and the difference was 25 MHz. As can be seen from these results, in the high frequency filter of the present invention, the pattern electrodes 16 and 1 can be used to fabricate filters of the same frequency.
The length of 8 can be shortened, and miniaturization can be achieved. Furthermore, the above-described effects can be obtained on the magnetic substrate, and the shielding effect can also be obtained. Therefore, it is not necessary to form a shield electrode or the like on the pattern electrodes 16 and 18, and the cost can be reduced as compared with a filter having a shield electrode.

In this high frequency filter 10, the area ratio S2
By setting / S1 to 0.15 or more, the Q of the filter can be increased. In addition, this high frequency filter 1
0, the distance between one end of the pattern electrode 16 and the extraction electrode 20, and the one end of the pattern electrode 18 and the extraction electrode 22.
Since the input / output impedance can be adjusted by adjusting the distance between and, impedance matching with an external circuit can be easily achieved.

Further, in the high frequency filter 10, the widths of the pattern electrodes 16 and 18 are equal to those of the terminal electrodes 34a and 34c.
It is formed so that it becomes smaller as it goes away from the connection portion with. By doing so, the Q of the high frequency filter 10 can be further increased. This is because in the strip line, the current density at the connection between the pattern electrode and the ground electrode is large, and the current density becomes smaller toward the tip of the pattern electrode. This is because the resistance can be obtained. In such a high-frequency filter 10, the effect of setting the area ratio S2 / S1 to 0.15 or more and the effect of changing the widths of the pattern electrodes 16 and 18 are combined to improve the Q factor.
It is possible to obtain a high frequency filter having a large size.

Further, in the high frequency filter 10, since the pattern electrodes 16 and 18 are spiral, the size can be reduced as compared with a filter having a linear pattern electrode. Further, the adjacent portions of the two pattern electrodes are shorter than those of the filter having the linear pattern electrodes. Therefore, the electromagnetic coupling between the two resonators is small, and the distance between the two pattern electrodes can be reduced. Therefore, the size of the high frequency filter can be further reduced. As such a high frequency filter, 3.2 ×
It was possible to obtain an ultra-small bandpass filter of 2.5 mm.

In the high frequency filter of the present invention, a material having a relative permittivity of 70 or more is used as the material of the first dielectric substrate 12, but when the relative permittivity is reduced, the pattern electrodes 16 and 18 are used. This is because the total length L of is long. When the total length of the pattern electrodes 16 and 18 is increased, the number of turns of the pattern electrodes 16 and 18 is increased. Therefore, the area S2 of the part where the pattern electrode is not formed cannot be secured, and Q is deteriorated. In addition, when trying to secure the area S2, the high frequency filter becomes large.
Therefore, in order to secure a sufficient Q and obtain a small high frequency filter, it is desirable to use a material having a relative dielectric constant of 70 or more as the material of the first dielectric substrate 12.

Further, the input / output impedance of the high frequency filter can be adjusted by changing the formation position of the extraction electrode extracted from the pattern electrode. Moreover, since the dimensions of each electrode can be accurately formed by using a method such as etching, a high-precision high frequency filter can be obtained. When the bandpass filter was manufactured by such a method, the variation in the center frequency of the pass band could be controlled to ± 1.5% or less. further,
Since a plurality of electrode patterns can be accurately formed on one dielectric substrate, it is possible to mass-produce a high frequency filter by cutting the dielectric substrate on which a large number of electrode patterns are formed. Moreover, since the filter can be formed in a very small size, the material cost can be saved and the cost can be reduced. Moreover, as compared with a filter in which dielectric layers are laminated and integrally fired, the contraction of the dielectric substrate and the dimensional variation of the electrodes are less, and the accuracy of the filter can be improved. Therefore, it is possible to omit processes such as frequency adjustment as in the conventional filter. Further, it is possible to prevent the occurrence of cracks and cracks due to shrinkage during firing.

In the above-mentioned embodiment, the dielectric substrate 12
Although the adhesive layer 24 is formed so as to cover the entire surface of the above, the dielectric substrate 12 and the magnetic substrate 26 may be bonded by partially forming the adhesive layer 24. Also, without forming an adhesive layer,
For example, by using bolts and nuts, the dielectric substrate 12
The magnetic substrate 26 and the magnetic substrate 26 may be fixed to each other.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view taken along line II-II of the high frequency filter shown in FIG.

3 is a line III-III of the high frequency filter shown in FIG.
FIG.

4 is an exploded perspective view of the high frequency filter shown in FIG. 1. FIG.

5 is an equivalent circuit diagram of the high frequency filter shown in FIG.

FIG. 6 is a graph showing frequency characteristics of the high frequency filter shown in FIG.

FIG. 7 is an exploded perspective view of a high frequency filter used for comparison with the high frequency filter of the present invention.

8 is a graph showing frequency characteristics of the high frequency filter shown in FIG.

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

FIG. 10 is an illustrative view showing another example of a conventional filter.

FIG. 11 is an exploded perspective view showing still another example of the conventional filter.

[Explanation of symbols]

 10 High Frequency Filter 12 Dielectric Substrate 14 Ground Electrode 16 Pattern Electrode 18 Pattern Electrode 20 Extraction Electrode 22 Extraction Electrode 26 Magnetic Substrate 34a to 34f Terminal Electrode 36 Extraction Terminal Electrode 38 Extraction Terminal Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuji Matsuda 2 26-10 Tenjin Tenjin, Nagaokakyo, Kyoto Prefecture Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A dielectric substrate, a ground electrode planarly formed on one surface of the dielectric substrate, formed on the other surface of the dielectric substrate to face the ground electrode, and one end of which is A plurality of spiral pattern electrodes connected to the ground electrode, an extraction electrode that is extracted from the pattern electrode at a distance from one end of each of the pattern electrodes, and a magnetism formed on the pattern electrode and the extraction electrode. A high frequency filter including a body substrate, wherein the plurality of pattern electrodes are electromagnetically coupled.