JP2890985B2 - Bandpass filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band-pass filter, and more particularly to a band-pass filter having a plurality of resonators of a laminated type and used for, for example, a portable telephone.

[0002]

2. Description of the Related Art FIG. 8 is an equivalent circuit diagram showing an example of a conventional laminated bandpass filter. This bandpass filter 1 includes two input / output terminals. One input / output terminal is connected to one end of the first resonator Q1 via the capacitor C1. The first resonator Q1 has two inductors L1 and L2 and a capacitor C2. The other input / output terminal is connected to one end of the second resonator Q2 via the capacitor C3. The second resonator Q2 is also 2
It has two inductors L3 and L4 and a capacitor C4. Inductors L1 and L3 of first and second resonators Q1 and Q2 are coupled with a degree of magnetic coupling M. The other end of the first resonator Q1 is connected to one ground terminal via an inductor L5, and the second resonator Q2
Is connected to the other ground terminal via an indenter L6. Further, a capacitor C5 is connected between the two input / output terminals.

In this bandpass filter 1, in order to adjust the bandwidth, an inductor L1
By changing the distance and inductance value between the two coil electrodes forming the inductors L1 and L3,
3 by changing the degree of magnetic coupling M.

[0004]

However, the bandpass filter 1 shown in FIG. 8 has a problem that the bandwidth is narrow.

[0005] Therefore, a main object of the present invention is to provide a bandpass filter capable of changing the bandwidth without changing the magnetic coupling degree M of the M coupling.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a coil electrode.
And a capacitor electrode connected to one end of the coil electrode,
Connected to the other end of the coil electrode and capacitor electrode
And a shield electrode facing the ground and connected to the ground.
Stacked band-pass filter
Filter that partially connects the shield electrode of each resonator.
A bandpass filter having a coil electrode connected to the bandpass filter.

[0007]

The bandwidth of the band-pass filter can be adjusted by the coil electrode partially connecting the shield electrode of each resonator .

[0008]

According to the present invention, it is possible to obtain a band-pass filter capable of changing the bandwidth without changing the magnetic coupling degree M of the M coupling.

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

[0010]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is an exploded perspective view thereof, and FIG. 3 is an equivalent circuit diagram thereof.

The band-pass filter 10 has, for example, 4.5 mm × 3.2 as one outermost layer when viewed in plan.
mm of the first protective layer 12. This first protective layer 12
Is formed by laminating a large number of dielectric layers in this embodiment, but may be formed by only one dielectric layer, for example.

On one main surface of the first protective layer 12, two coil electrodes 14a and 14b are formed. Each of these coil electrodes 14a and 14b is formed in a crank shape from one end to the other end in the width direction of the first protective layer 12. In this case, the coil electrodes 14a and 14
One end of b extends on one end side in the width direction of the first protective layer 12. Further, these coil electrodes 14 a and 14 b are brought closer to each other at the other end in the width direction of the first protective layer 12 so as to be coupled with the degree of magnetic coupling M. These coil electrodes 14a and 14b
Act as inductors L1 and L3 of the first and second resonators Q1 and Q2, respectively.

On one main surface side of the first protective layer 12, a dummy layer 16 made of, for example, a dielectric is formed so as to sandwich the two coil electrodes 14a and 14b. At the center of one main surface of the dummy layer 16, for example, a rectangular input / output capacitor electrode 18 is formed.

A first dielectric layer 20 is formed on one main surface side of the dummy layer 16 with the input / output capacitor electrode 18 interposed therebetween. Two input / output capacitor electrodes 22a and 22b are formed on one main surface of the first dielectric layer 20 except for an edge at intervals in the longitudinal direction of the first dielectric layer 20. You. The input / output capacitor electrodes 22a and 22b face the input / output capacitor electrode 18 in a plan view. Therefore, the capacitor C5 is connected between the input / output capacitor electrode 18, the first dielectric layer 20, and the input / output capacitor electrodes 22a and 22b.
Is formed. Each of the input / output capacitor electrodes 22a and 22b has a lead portion extending to the other end of the first dielectric layer 20 in the width direction.

On one main surface of the first dielectric layer 20, a second dielectric layer 24 is formed so as to sandwich the input / output capacitor electrodes 22a and 22b. Two capacitor electrodes 26a and 26b are formed at a part of the one main surface of the second dielectric layer 24 except for the edge, at intervals in the longitudinal direction of the second dielectric layer 24. Capacitor electrodes 26a and 26b face capacitor electrodes 22a and 22b, respectively, as viewed in plan. Therefore, the input / output capacitor 22a and the second dielectric layer 24
And the capacitor electrode 26a form a capacitor C1, and the input / output capacitor 22b, the second dielectric layer 24 and the capacitor electrode 26b form a capacitor C3. The one capacitor electrode 26a has a lead portion extending at one end in the width direction of the second dielectric layer 24, and this lead portion faces one end of the coil electrode 14a in plan view. The other capacitor electrode 26b is also connected to the second dielectric layer 24.
Has a leading portion extending at one end in the width direction, and the leading portion faces one end of the coil electrode 14b in plan view.

A third dielectric layer 28 is formed on one main surface side of second dielectric layer 24 so as to sandwich capacitor electrodes 26a and 26b. Two shield electrodes 30a and 30b are formed at a part of one main surface of the third dielectric layer 28 except for an edge, with a space therebetween in the longitudinal direction of the third dielectric layer 28. Shield electrode 30a
And 30b respectively oppose capacitor electrodes 26a and 26b in plan view. One shield electrode 30a has one lead portion extending to one end in the width direction of the third dielectric layer 28 and the other lead portion extending to the other end, and the other lead portion is viewed in plan. It faces the other end of the coil electrode 14a. The other shield electrode 30b also has one lead portion extending to one end in the width direction of the third dielectric layer 28 and the other lead portion extending to the other end, and the other lead portion is a coil electrode as viewed in plan. 14b is opposed to the other end.

Further, a coil electrode 32 is formed on one main surface of the second dielectric layer 24 from one shield electrode 30a to the other shield electrode 30b. In this case, the coil electrode 32 is formed on one end side of the second dielectric layer 24 in the width direction. This coil electrode 32 functions as an inductor L7.

A fourth dielectric layer 34 is formed on one main surface side of the third dielectric layer 28 so as to sandwich the shield electrodes 30a and 30b and the coil electrode 32 therebetween. 4th
The two capacitor electrodes 36a and 36b are provided on a portion of the one main surface of the dielectric layer 34 except for the edge,
Are formed at intervals in the longitudinal direction of the dielectric layer 34.
Capacitor electrodes 36a and 36b face shield electrodes 30a and 30b, respectively, as viewed in plan.
Also, one capacitor electrode 36a is connected to the fourth dielectric layer 3
4 has a leading portion extending at one end in the width direction, and the leading portion faces the leading portion of the capacitor electrode 26a in plan view. The other capacitor electrode 36b is also connected to the fourth dielectric layer 34.
Has a lead portion extending at one end in the width direction, and the lead portion faces the lead portion of the capacitor electrode 26b in plan view.

On one main surface side of the fourth dielectric layer 34, a fifth dielectric layer 38 is formed so as to sandwich the capacitor electrodes 36a and 36b. For example, two trimming electrodes 40a and 40 having a certain width are provided on a portion of one main surface of the fifth dielectric layer 38 except for an edge.
b are formed at intervals in the longitudinal direction of the fifth dielectric layer 38. The trimming electrodes 40a and 40b are respectively connected to the capacitor electrodes 36a and 36a in plan view.
b.

The one trimming electrode 40a has one leading portion extending to one end in the width direction of the fifth dielectric layer 38 and the other leading portion extending to the other end, and these leading portions are planar. As shown in FIG. The other trimming electrode 40b also has one leading portion extending to one end in the width direction of the fifth dielectric layer 38 and the other leading portion extending to the other end, and these leading portions are shield electrodes as viewed in plan. 30b is respectively opposed to the drawer.

On one main surface side of the fifth dielectric layer 38, the trimming electrodes 40a and 40b are sandwiched.
As the other outermost layer, a second protective layer 42 made of, for example, a dielectric is formed. In this embodiment, the second protective layer 42 is formed by laminating a large number of dielectric layers, but may be formed by, for example, only one dielectric layer.

Further, four external electrodes 44a, 44b, 44c and 44d having a U-shaped cross section are formed on one side surface in the width direction of the band-pass filter 10, and a U-shaped cross section is formed on the other side surface. Four external electrodes 44e, 44f, 44g and 44h are formed.

The external electrode 44a is connected to the coil electrode 1
4a and one end of the capacitor electrode 26a and the lead-out portion of the capacitor electrode 36a. Similarly, the external electrode 44d is connected to one end of the coil electrode 14b and the lead portions of the capacitor electrodes 26b and 36b.

The external electrode 44b is connected to the shield electrode 3
0a and one extraction portion of the trimming electrode 40a. Similarly, the external electrode 44c is
It is connected to one leading portion of the shield electrode 30b and one leading portion of the trimming electrode 40b.

Further, the external electrodes 44e and 44h are
The input / output capacitor electrodes 22a and 22b are respectively connected to the lead portions. These external electrodes 44e and 44h are used as input / output terminals, respectively.

The external electrode 44f is connected to the coil electrode 14
a, the other lead-out part of the shield electrode 30a,
It is connected to the other extraction part of the trimming electrode 40a. Similarly, the external electrode 44g is connected to the other end of the coil electrode 14b, the other lead of the shield electrode 30b, and the other lead of the trimming electrode 40b. These external electrodes 44f and 44g are used as ground terminals, respectively.

The capacitor electrodes 26a and 36a
, Third, fourth, and fifth dielectric layers 28, 34, and 38, shield electrode 30a, and trimming electrode 40.
a forms the capacitor C2 of the resonator Q1. Similarly, capacitor electrodes 26b and 36b, third, fourth, and fifth dielectric layers 28, 34, and 38, shield electrode 30b, and trimming electrode 40b form capacitor C4 of resonator Q2. You. The capacitance of these capacitors C2 and C4 is
The adjustment can be made by cutting Oa and 40b.

The coil electrode 14a and the shield electrode 3
0a and the first resonator Q1
Is formed. Similarly, coil electrode 1
The inductor L4 of the second resonator Q2 is formed by the distributed inductance between the shield electrode 4b and the shield electrode 30b.

Further, the coil electrode 14a and the external electrode 44
With the distributed inductance between f and f, an inductor L5 is formed. Similarly, the coil electrode 14b and the external electrode 44g
The inductor L6 is formed with the distributed inductance between.

Therefore, the band pass filter 10
Has an equivalent circuit shown in FIG.

The band-pass filter 10 is formed to have a size of 4.5 mm × 3.2 mm in plan view and a thickness of 1.5 mm.
mm.

In this band pass filter 10, the inductor L is connected between the ground sides of the first and second resonators Q1 and Q2 as compared with the conventional band pass filter shown in FIG.
7 is connected, the bandwidth is widened. FIG. 4 shows the frequency characteristics of this embodiment and the conventional example shown in FIG.

FIG. 5 shows frequency characteristics of the bandpass filter 10 when the inductance value of the inductor L7 is 1 nH and 6 nH. As is clear from the frequency characteristics shown in FIG. 5, the bandwidth of the band-pass filter 10 can be changed by changing the inductance value of the inductor L7.
In order to change the inductance value of the inductor L7, the size and shape of the coil electrode 32 serving as the inductor L7 may be changed.

In the above embodiment, the coil electrode 32 serving as the inductor L7 is formed at one end in the width direction of the second dielectric layer 28 as shown in FIGS. 2 and 6A. The coil electrode 32 serving as the inductor L7 is shown in FIG.
As shown in (B), (C) and (D), the second dielectric layer 28 may be formed at a portion other than one end thereof in the width direction.

FIG. 7 shows the respective frequency characteristics when the coil electrode 32 is formed as shown in FIGS. 6A, 6B, 6C and 6D in the above embodiment. In this case, FIG. 7 shows the frequency characteristics of the band-pass filters using the coil electrodes shown in FIGS. 6A, 6B, 6C and 6D by A, B, C and D, respectively. Was.
As is clear from the frequency characteristics shown in FIG. 7, the bandwidth of the band-pass filter 10 can be changed by changing the position where the coil electrode 32 is formed.

In the embodiment, the frequency characteristics shown in FIGS. 4, 5 and 7 are different from each other because capacitors having different capacitances are used.

In the above-described embodiment, a band-pass filter having two resonators has been described as an example.
It can also be applied to bandpass filters having more than one resonator. Further, in the above-described embodiment, rectangular layers are used as each layer, but the size and shape of each layer and each electrode may be arbitrarily changed.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view of the embodiment shown in FIG.

FIG. 3 is an equivalent circuit diagram of the embodiment shown in FIG.

4 is a graph showing frequency characteristics of the embodiment shown in FIG. 1 and the conventional example shown in FIG.

FIG. 5 is a graph showing respective frequency characteristics when the inductance value of an inductor connected between the ground sides of the first and second resonators is changed in the embodiment shown in FIG. 1;

6A is a plan view showing a position of a coil electrode with respect to two shield electrodes in the embodiment shown in FIG. 1, and FIGS. 6B, 6C, and 6D are plan views each showing a modified example thereof FIG.

7 (A), FIG. 6 (A), FIG.
It is a graph which shows each frequency characteristic at the time of forming a coil electrode as shown to (B), (C), and (D).

FIG. 8 is an equivalent circuit diagram showing an example of a conventional bandpass filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Band pass filter 12 1st protective layer 14a, 14b Coil electrode 16 Dummy layer 18 Input / output capacitor electrode 20 1st dielectric layer 22a, 22b Input / output capacitor electrode 24 2nd dielectric layer 26a, 26b Capacitor electrode 28 Third dielectric layer 30a, 30b Shield electrode 32 Coil electrode 34 Fourth dielectric layer 36a, 36b Capacitor electrode 38 Fifth dielectric layer 40a, 40b Trimming electrode 42 Second protective layer 44a- 44h External electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-265205 (JP, A) JP-A-59-191903 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01P 1/20-1/219 H01P 7/00-7/10 H03H 7/00-7/13

Claims (1)

(57) [Claims] A coil electrode and one end of the coil electrode;
Connected to the capacitor electrode and the other end of the coil electrode
Connected and opposed to the capacitor electrode
Resonator with a shield electrode connected to the
A multilayer bandpass filter consisting of several
And a coil for partially connecting the shield electrode of each resonator
A band-pass filter having electrodes .