JPH0514008A - Stripline filter - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To obtain a compact filter that does not require adjustment and that can be used in the high frequency range of 100 MHz or higher. [Structure] Conductor strip lines 11 to 14 having one or more turns are formed on one surface or both surfaces of a dielectric substrate 10 having a relatively high dielectric constant, and the conductor strip line 11 is formed.
˜14 are arranged close to each other or face each other so that a line capacitance is generated. Conductor strip lines 11-14
The LC parallel resonance circuit is composed of the inductance component of and the capacitance component of the line capacitance, and a filter can be obtained by forming the LC parallel resonance circuit in multiple stages. Conductor strip lines 11-1
4 are arranged in point symmetry to enhance the capacitive coupling between striplines. Conductor strip line 1
With the end portions of 1, 13 and the conductor patterns 15 and 16 on the back surface,
Get the input / output coupling capacitance. [Effect] A filter having a steep attenuation characteristic on the low frequency side can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stripline filter usable in a high frequency band exceeding 100 MHz, and more particularly to a stripline filter having a conductor pattern of one turn or more formed on the surface of a dielectric substrate. .

[0002]

2. Description of the Related Art There is an increasing demand for resonators and filters that can be used in a band of several hundred MHz for mobile communication devices. Conventionally, helical resonator (filter), dielectric resonator (filter)
Etc. are used, but there is a limit to miniaturization because the size is restricted by the wavelength of the resonance frequency. In addition, adjustment is often necessary due to accuracy issues. In addition, a resonator and a filter that require a lot of man-hours in the assembling process and the like and that are accurate and easy to manufacture are desired.

Further, the helical filter and the dielectric filter have a problem that a harmonic wave three times as high as the fundamental frequency is generated, and how to remove the harmonic wave is a big problem.

[0004]

SUMMARY OF THE INVENTION The present invention provides a filter that can be miniaturized, is easy to manufacture, and can be used in a high frequency range. In addition, it is possible to obtain a filter having a stable characteristic, which can obtain high accuracy and requires almost no adjustment.

[0005]

According to the present invention, a conductor pattern having at least one turn is formed on the surface of a dielectric substrate having a relatively high dielectric constant, and a plurality of conductor patterns are arranged to be capacitively and inductively coupled. Thus, the filter is configured to solve the above problems.

That is, a conductor pattern for two inductors, which circulates on at least one surface of a dielectric substrate, is provided, and the conductor patterns are arranged close to each other, and
One of the features is that one end of each conductor pattern is connected to the input / output end via a capacitor, the other end is grounded, and the two conductor patterns are arranged in point symmetry.

[0007] Specifically, a conductor pattern for an inductor, which is connected to the front and back surfaces of the dielectric substrate by through holes and circulates, is provided. The conductor patterns are arranged so as to overlap on the front and back surfaces, and one end of the conductor pattern is arranged. Is connected to the input / output end and the other end is grounded.

[0008]

The self-resonance generated by the inductance component of the conductor pattern (strip line) and the line (distributed) capacitance component between the conductor patterns is positively used as a filter. Further, the winding direction of the strip lines is made the same, the capacitive coupling between the strip lines is increased, and a filter having a steep attenuation characteristic on the low frequency side of the pass band is obtained.

[0009]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a plan view showing an embodiment of the present invention.
(A) shows the upper surface and (b) shows the lower surface. On the front and back of the ceramic substrate 10 with a relatively high dielectric constant of about 90,
Conductor striplines 11, 12 are formed. The conductor strip lines 11 and 12 are connected to each other by through holes formed in the substrate 10 to form one continuous strip line. In this example, a stripline of connected conductors
The length of 11 and 12 was formed to be 26.1 mm. The width of the conductor strip lines was 0.2 mm, and the spacing was also 0.2 mm.

The conductor strip line 11 is formed as a conductor pattern that circulates on the surface side for about one and a half turns. The conductor strip line 12 on the back surface, which is connected by a through hole, is also formed as a conductor pattern that makes one turn and a half turn, and the end portion is drawn to the side surface of the substrate. The front and back conductor patterns are formed so as to overlap and oppose each other on the front and back surfaces. Since the conductor patterns are formed so as to extend in the same direction, it is impossible that all the conductor patterns completely overlap and face each other, but most of them can be overlapped. This is to give capacitance between the conductor patterns. Of course, it is desirable to arrange the conductor patterns close to each other so that capacitance can be obtained between the conductor patterns on the same surface. In addition, in order to increase the capacity,
As mentioned above, it is necessary to use a substrate made of a material having a relatively high dielectric constant.

In the example shown in FIG. 1, the conductor strip line 1 has a pattern point-symmetric with the conductor strip lines 11 and 12.
3 and 14 were formed on the same substrate surface. These dimensions are the same as above. In addition, the conductor patterns 15, 16 facing the end portions of the conductor strip line 11 and the conductor strip line 13 are formed.
Is formed to obtain the input / output coupling capacitance. At the ends of the conductor strip line 11 and the conductor strip line 13, 0.
A 16 mm ² conductor pattern was formed, and a capacitance was obtained between these and the back surface conductor patterns 15 and 16. The spacing between the two conductor strip lines was 0.6 mm.

In the stripline filter according to the present invention, the two conductor patterns are arranged point-symmetrically. That is, they are arranged so as to be point-symmetric with respect to the center of the substrate 10 in FIG. However,
It is not necessary to have perfect point symmetry, and it is important to form the conductor patterns so that the winding directions are opposite to each other.

LC by the conductor strip lines 11 and 12
A parallel tank circuit is formed, and the conductor strip lines 13 and 14 also form an LC parallel tank circuit. In addition, a capacitive coupling and an inductive coupling occur between them to form a filter.

FIG. 2 is an explanatory diagram of pass band characteristics of the filter having the above configuration. It was confirmed that the center frequency was 380 MHz and the insertion loss was 3 dB or less, and that excellent attenuation characteristics were obtained. When the conductor pattern is formed point-symmetrically as shown in FIG. 1, capacitive coupling becomes large, and as shown in FIG. 2, the band pass characteristic has a characteristic that the low side of the center frequency is steep.

When the stripline filter according to the present invention is actually used, a substrate having a high dielectric constant having conductor patterns formed on the front and back surfaces is sandwiched between high Q dielectric substrates, and conductor patterns are formed on the front and side surfaces of this laminate. Should be formed. It is desirable to separate only the portions corresponding to the input / output terminals and cover the other portions with a conductor pattern that is grounded. As a result, the shield effect can be obtained.

It is also possible to form three or more sets of conductor strip lines on a single substrate, or it is possible to construct a multi-stage filter by stacking dielectric substrates via spacers. The thickness of each dielectric substrate is about 0.2 mm, and it is possible to obtain small and thin filters even if they are stacked with spacers.

[0018]

According to the present invention, it is possible to obtain a small-sized filter which can be used in a high frequency range and has a steep attenuation characteristic on the low frequency side. Moreover, it is possible to obtain a filter in which three times higher harmonics do not appear.

Further, since the conductor can be formed on the fired ceramic substrate by etching, high accuracy can be obtained and desired characteristics can be obtained without adjustment.

Moreover, since a filter having a steep attenuation characteristic on the low frequency side of the pass band can be obtained, it is possible to obtain an arbitrary pass band characteristic by combining these filters.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of characteristics of a filter according to the present invention.

[Explanation of symbols]

10 Dielectric substrate 11-14 conductor strip line

[Procedure amendment]

[Submission date] January 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

FIG. 2 is an explanatory diagram of pass band characteristics of the filter having the above configuration. It was confirmed that the center frequency was 233 MHz and the insertion loss was 3 dB or less, and that excellent attenuation characteristics were obtained. When the conductor pattern is formed point-symmetrically as shown in FIG. 1, the capacitive coupling becomes large, and as shown in FIG. 2, the pass band characteristic is characterized in that the low side of the center frequency is steep.

Claims (2)

[Claims] 1. A conductor pattern for two inductors, which circulates on at least one surface of a dielectric substrate, wherein the conductor patterns are arranged close to each other, and one end of each conductor pattern is input / output via a capacitor. A stripline filter, characterized in that it is connected to one end, the other end is grounded, and that the two conductor patterns are arranged in point symmetry. 2. A dielectric substrate comprising two conductor patterns for inductors, which circulate on at least one surface of the dielectric substrate, and the conductor patterns are arranged so as to overlap each other on the front and back sides, and one end of each conductor pattern is connected via a capacitor. Is connected to the input / output end, the other end is grounded, and the two conductor patterns are arranged so as to be point-symmetrical.