JPH05102703A - Band pass filter by tri-plate strip line - Google Patents

Abstract

PURPOSE:To attain thin profile, to obtain the surface mount type, to reduce number of components and to attain ease of manufacture. CONSTITUTION:Plural resonators are formed integrally in a dielectric substance 2 by providing plural center conductors 1a, 1b in the dielectric substance 2 with a ground plane 3 fitted therearound. An upper lower opposite part between the adjacent center conductors 1a, 1b is provided to an end opposite to the connection side of the ground plane 3 of the center conductors 1a, 1b to form a coupling capacitor 22b between resonators. Conductor layers e, f connecting to terminals 4a, 4b are provided in the dielectric substance 2 and the opposite side to the connection side of the ground plane 3 of the center conductors 1a, 1b is opposed to the said conductor layers e, f to form coupling capacitors 22a, 22c between a terminal and the resonator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bandpass filter composed of a triplate-type stripline in which a central conductor is integrally formed in a dielectric body by sintering and a ground plane is formed around the dielectric body.

[0002]

2. Description of the Related Art A bandpass filter shown in an equivalent circuit of FIG. 4A is used in a mobile communication device such as a mobile phone which uses an ultra high frequency exceeding 250 MHz. In FIG. 4A, 20a,
20b is a resonator constituted by a rectangular coaxial line.
Reference numerals 21a and 21b are input / output terminals, and are connected to the resonator 2 by the coupling capacitors 22a to 22c.
By combining 0a and 20b, an attenuation characteristic as shown in the characteristic diagram of the bandpass filter of FIG. 4B is obtained.

FIG. 4C is an exploded perspective view of a conventional bandpass filter, and FIG. 4D is a sectional view thereof. Figure 4
In (C) and (D), 21a and 21b are the terminals made of silver or the like, 24 is a sleeve made of a dielectric material, 25 is a dielectric material having a hole 26 in the center, and 27 is formed on the inner wall of the hole 26. A central conductor made of silver or the like, 28 is a ground plane made of a silver layer formed on at least upper and lower surfaces of the dielectric 25, a sleeve is inserted into one end of the central conductor 27, and the other end of the central conductor 27 is grounded. It is connected to the plane 28 to form an inductance component of the resonator, and the central conductor 27, the dielectric 25, and the ground plane 28 form a capacitance component of the resonator. In addition, the terminals 21a and 21b and the sleeve 24
And the central conductor 27, the terminals 21a and 21b and the resonator 20.
A coupling capacitor 22a is formed between the resonators 20a and 20b by forming a coupling capacitor 22a and 22c between the resonator 20a and 20b. Then, the resonators 20a and 20b combined in this way are covered with the shield case 31 to form one bandpass filter.

[0004]

Such a conventional bandpass filter has a center frequency of 835 MHz and a length L (see FIG. 1 (C)) of 11 mm, a thickness H of 7 mm and a width W. Is about 11 mm, and the thickness H is large,
There is a problem that it is difficult to meet the recent demand for thinning of communication devices and the like, and it is difficult to make the surface mount type. In addition, there is a problem that the number of parts is large and man-hours are required for manufacturing.

In view of the above problems, the present invention provides a bandpass filter using a triplate type stripline, which can be thinned, a surface mount type can be obtained, the number of parts can be reduced, and manufacturing can be facilitated. The purpose is to provide.

[0006]

In order to achieve the above object, the present invention provides a plurality of resonators in a dielectric body by providing a plurality of center conductors in a dielectric body around which a ground plane is provided. And the upper and lower facing portions between the adjacent center conductors are provided at the opposite ends of the respective center conductors on the ground plane connection side, thereby forming a coupling capacitor between the resonators and at the terminals. A coupling capacitor between the terminal and the resonator is formed by providing a conductor layer connected to the inside of the dielectric and making the side opposite to the ground plane connection side of the central conductor face the conductor layer.

[0007]

Since the present invention has the above-mentioned structure, a plurality of resonators and a coupling capacitor are simultaneously manufactured integrally.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a perspective view showing an embodiment of a bandpass filter according to the present invention, and FIG.
The same (C) is a sectional view taken along line FF of (A), and FIG.
FIG. 2A is a sectional view taken along line GG in FIG. 2A, and FIG. 2B is a perspective view showing a terminal structure. In these figures, 1a and 1b are the central conductors formed in the dielectric body 2.
1a and 1b, as shown in FIG. 1C, the height difference Δh (for example, about 0.3 m) in the vertical direction (direction perpendicular to the mounting surface i).
m) is formed.

One end of each of the center conductors 1a and 1b is shown in FIG.
As shown in FIG. 3, the ground plane 3 is formed around the dielectric 2. The resonator has a central conductor 1a,
1b constitutes an inductance component of each resonator, and a capacitance component between each central conductor 1a, 1b and the upper and lower ground planes 3. That is, this example shows an example in which two resonators are integrally formed in one dielectric 2.

The other ends of the center conductors 1a and 1b are shown in FIG.
As shown in (A) and (B), it is formed in a T shape having extensions a, b and c, d on both sides. Then, the extension portions b and c of one of the central conductors 1a and 1b are opposed to each other via the layer of the dielectric 2 having a thickness of the height difference Δh so that the coupling capacitor 22b between the resonators (FIG. 4A). See)). Further, the other extending portion a of each of the central conductors 1a and 1b
And d are made to face the conductor layers e and f connected to the terminals 4a and 4b via the thin dielectric layer 2, so that the coupling capacitors 22a and 2b between the terminals 4a and 4b and the resonator are formed.
2c.

In this way, by forming a plurality of resonators integrally with the coupling capacitors 22a to 22c in the dielectric 2, the center frequency is 835 MHz,
The thickness H shown in FIG. 1 (A) can be a thin outline of about 2 mm, which is suitable for surface mounting.

Further, one surface j of the dielectric 2 is not covered with the ground plane 3 and the coupling capacitor 22a is connected to this surface j.
2 to 22c by exposing the edges of the central conductors 1a and 1b and the edges of the conductor layers e and f.
As shown in the side cross-sectional view of (C) and the H-H cross-sectional view thereof (D), these conductors a to f are trimmed by a laser beam or sandblast (the trimming portion is g ₁
(Indicated by), the coupling capacitors 22a-22
It is possible to adjust the electrostatic capacitance of c after manufacturing, and as shown in FIG. 2D, trimming is performed on a portion other than the coupling capacitor 22b constituting portion of the end portions of the center conductors 1a and 1b (trimming portion is by g _2, g shown in _3), you can adjust the characteristics of the resonator independently of the coupling capacitor 22 a to 22 c. That is, the ends of the central conductors 1a and 1b are formed in a T shape, and the capacitance of the coupling capacitor can be adjusted independently of the inductance and capacitance of the resonator. Further, since the capacitance can be adjusted only by trimming one surface j of the central conductors 1a and 1b, it is suitable for automation.

The illustrated example shows an example of trimming by irradiating a laser beam or the like in the vertical direction. However, in the case of the sandblast method or when the beam intensity is weakened, the direction is perpendicular to the surface j. It can be trimmed by projecting sand or irradiating a beam.

In this bandpass filter, as an example, the green sheet of the dielectric 2 is provided on the conductor layers e and f and the center conductor 1.
It can be manufactured by printing and stacking conductors a and 1b, firing them, and then applying and firing conductors to be the ground plane 3 and terminals 4a and 4b.

FIG. 3A is a perspective view showing another embodiment of the present invention, and FIG. 3B is a view taken in the direction of arrow I. In this embodiment, the central conductors 1a and 1b have no height difference, Coupling capacitor 22
b between the extension portions b and c of the central conductors 1a and 1b forming the b, and between the extension portions a and d of the center conductors 1a and 1b forming the coupling capacitors 22a and 22c and the conductor layers e and f. This is an example in which a difference is provided. According to this embodiment, the same effect as that of the above embodiment can be obtained. In this example,
The central conductors 1a and 1b are formed into an L-shape.

[0016]

According to the first aspect of the present invention, a plurality of central conductors are formed in the dielectric to form a bandpass filter including a plurality of resonators, and the coupling capacitor is also formed in the dielectric. A thin bandpass filter suitable for mounting can be constructed. Further, the number of parts is reduced, and the manufacturing can be easily performed by an automated manufacturing line.

According to the second aspect, since a part of the conductors forming the resonator and the coupling capacitor is exposed to the outside, characteristic adjustment by trimming the resonator and the coupling capacitor can be easily performed after manufacturing.

[Brief description of drawings]

FIG. 1A is a perspective view showing an embodiment of a bandpass filter according to the present invention, FIG. 1B is a view taken in the direction of arrow E, and FIG. 1C is a sectional view taken along line FF of FIG.

2A is a sectional view taken along line GG of FIG. 1A, FIG. 2B is a perspective view showing a terminal portion of this embodiment, and FIG. 2C is a side sectional view of a coupling capacitor portion of this embodiment. , (D) is H-H of (C)
FIG.

FIG. 3A is a perspective view showing another embodiment of the present invention,
(B) is the I arrow view.

4A is an equivalent circuit diagram of an example of a bandpass filter, FIG. 4B is a characteristic diagram thereof, FIG. 4C is an exploded perspective view of a conventional bandpass filter, and FIG. 4D is a sectional view showing its assembled state. It is a figure.

[Explanation of symbols]

 1a, 1b Central conductor 2 Dielectric 3 Ground plane 4a, 4b Terminals a to d Extension e, f Conductor layers 22a to 22c Coupling capacitor

Claims (2)

[Claims] 1. A bandpass filter having a triplate-type stripline having the following configuration. (1) A plurality of center electrodes are formed in the dielectric body, and each center electrode and the ground planes above and below the dielectric body form a plurality of resonators integrated with each other. (2) A coupling capacitor between adjacent resonators, in which adjacent center electrodes face each other in the vertical direction with a dielectric layer interposed between the adjacent center electrodes, is integrally formed in the dielectric at the end of each center electrode opposite to the ground plane connection side. To do. (3) By providing a portion of each center electrode opposite to the ground plane connection side with a conductor layer that is connected to an external terminal and is formed in the dielectric body and vertically opposed to the conductor layer via the dielectric layer, The coupling capacitor between the resonator and the terminal is integrally formed in the dielectric. 2. A part of a portion of the conductor layer connected to the terminal and the center conductor, which constitutes the coupling capacitor, is exposed on one surface of a dielectric material not covered by a ground plane. Bandpass filter using the triplate type stripline.