JP2890951B2 - 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 bandpass filter, and more particularly to a bandpass filter having a three-stage resonator.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view showing an example of a conventional band pass filter, and FIG. 6 is an exploded perspective view of the band pass filter shown in FIG. This bandpass filter 1
Includes a first protective layer 2, and on the first protective layer 2,
A shield electrode 3, a first layer 4, three coil electrodes 5a,
5b, 5c, a second layer 6, two input / output capacitor electrodes 7a, 7b, a first dielectric layer 8, three capacitor electrodes 9a, 9b, 9c, a second dielectric layer 10, and three grounds. Electrodes 11a, 11b, 11c, third dielectric layer 12,
The three trimming electrodes 13a, 13b, 13c and the second protective layer 14 are laminated in this order.

Further, eight external electrode terminals 16a to 16 having a U-shaped cross section are provided on side surfaces of the bandpass filter shown in FIG.
h is formed. This bandpass filter is an equivalent circuit shown in FIG.

[0004]

However, in the conventional bandpass filter shown in FIG.
As shown in the figure, the attenuation amount is 30 dB in the high frequency region.
The degree is small and the spurious characteristics are bad.

[0005] It is another object of the present invention can improve the spurious characteristic at high <br/> circumferential Namiryo zone is to provide a band-pass filter.

[0006]

SUMMARY OF THE INVENTION The present invention provides a first resonator having a first inductor and a first capacitor connected in parallel, and a second inductor and a second capacitor connected in parallel. And the second inductor is the first inductor
A second resonator which is in the inductor magnetically coupled, a third resonator third inductor and a third inductor and a third capacitor connected in parallel is magnetically coupled to the second inductor A first input / output terminal connected to one end of the first resonator via the first input / output capacitor, and a first input / output terminal connected to one end of the third resonator via the second input / output capacitor A second input / output terminal, and an inductor connected between the other end of the first resonator and the other end of the third resonator.
Is formed in a laminate in which a plurality of dielectric layers are laminated.
The other end of the first resonator and the other end of the third resonator
Are first and second spurs formed on the dielectric layer.
This is a band-pass filter that is grounded via a filter electrode for improving noise .

[0007]

The other end of the first resonator is used for improving the first spurious.
Grounded via electrodes . Also, the other end of the third resonator is
Grounded via the second spurious improvement electrode . The first spurious improving electrode and the second spurious
The spurious characteristics in the high frequency range are improved by the improvement electrode .
Sex is improved if a.

[0008]

Effects of the Invention According to the present invention can improve the spurious characteristic of the high frequency Namiryo band, the band-pass filter is obtained.

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, and FIG. 2 is an exploded perspective view of the embodiment. The bandpass filter 20 includes a rectangular sheet-like first layer 22 made of, for example, a dielectric. The first layer 22 is formed, for example, by laminating a large number of dielectric layers 22a, 22a,.

On one main surface of the first layer 22, first and second
And third coil electrodes 24a, 24b and 24c are formed. These coil electrodes 24a to 24c are formed obliquely from one end to the other in the width direction of the first layer 22. First, second and third coil electrodes 24a, 2
4b and 24c are the first, second and third
The first and second inductors L1, L2 and L3 (FIG. 3) of the resonators Q1, Q2 and Q3 (FIG. 3) of FIG. Further, the second coil electrode 24b is coupled to the first coil electrode 24a and the third coil electrode 24c with a degree of magnetic coupling M, respectively.

On the other main surface side of first layer 22, for example, first and second U-shaped spurious improving electrodes 26a are formed.
And 26b are formed. In this case, one end of the first spurious improvement electrode 26a is connected to the first coil electrode 24.
a, the other end of the first spurious improvement electrode 26a corresponds between one end of the first coil 24a and one end of the second coil electrode 24b. Each is formed to extend to one end of the first layer 22. The other end of the second spurious improvement electrode 26b is connected to the third coil 24c so that one end of the second spurious improvement electrode 26b corresponds to the other end of the third coil electrode 24c. The other end and the second coil electrode 24
b so as to correspond between the other ends of the first layers 2.
2 is formed to extend to the other end.

Further, on the other main surface side of the first layer 22,
The second layer 28 is formed so as to sandwich the spurious improvement electrodes 26a and 26b. This second layer 28
Are formed, for example, by laminating a plurality of dielectric layers 28a, 28a,. However, the second layer 28 may be formed of, for example, only a single dielectric layer 28a. Therefore, the thickness of the second layer 28 can be adjusted by changing the thickness of the dielectric layer 28a or the number of stacked dielectric layers 28a.

A shield electrode 30 is formed on the lower surface of the second layer 28 except for the edge. The shield electrode 30 functions as a shield material for magnetically shielding the coil electrodes 24a to 24c and the like from the outside, and also forms a pole forming inductor Lg (FIG. 3).
Work as The shield electrode 30 is formed on the second layer 2.
8 has a leading part extending to one end and a leading part extending to the other end, and these leading parts are respectively one end of the first coil electrode 24a and the other end of the third coil electrode 24c when viewed in plan. Corresponding to

Further, a first protective layer 32 made of, for example, a dielectric is formed on the lower surface side of the second layer 28 with the shield electrode 30 interposed therebetween.

On the other hand, on one main surface side of the first layer 22, a third layer 34 made of, for example, a dielectric is formed so as to sandwich the coil electrodes 24a to 24c. The third layer 34 includes, for example, a large number of dielectric layers 34a, 34a,.
Are formed by stacking.

On the upper surface of the third layer 34 except for the edge, the first and second input / output capacitor electrodes 3 are provided.
6a and 36b are formed. In this case, the first input / output capacitor electrode 36a is formed at one end in the longitudinal direction on the other end in the width direction of the third layer 34. The second input / output capacitor electrode 36b is formed at one end in the width direction of the third layer 34 and at the other end in the longitudinal direction. Further, the first input / output capacitor electrode 36a has a lead portion extending to the other end of the third layer 34 in the width direction. The second input / output capacitor electrode 36b has a lead portion extending to one end of the third layer 34 in the width direction.

Further, a first dielectric layer 38 is formed on the upper surface side of the third layer 34 so as to sandwich the input / output capacitor electrodes 36a and 36b. On the upper surface of the first dielectric layer 38 except for the edge, first and second
And third capacitor electrodes 40a, 40b and 40
c are formed at intervals in the longitudinal direction of the first dielectric layer 38. Also, the first and third capacitor electrodes 40
a and 40c face the first and second input / output capacitor electrodes 36a and 36b, respectively, as viewed in plan. Therefore, the first and second input / output capacitor electrodes C4 are formed by the first and second input / output capacitor electrodes 36a and 36b, the first dielectric layer 38 and the first and third capacitor electrodes 40a and 40c. And C
5 (FIG. 3) are formed.

The first capacitor electrode 40a extends to the other end of the first dielectric layer 38 and has the first coil electrode 2a.
4a has a lead portion corresponding to the other end portion, and the second capacitor electrode 40b has a lead portion extending to one end of the first dielectric layer 38 and corresponding to one end portion of the second coil electrode 24b. Then, the third capacitor electrode 40c is connected to the first dielectric layer 3
8 has a leading portion corresponding to one end of the third coil electrode 24c.

Further, on the upper surface side of the first dielectric layer 38, the capacitor electrodes 40a to 40c are sandwiched.
A second dielectric layer 42 is formed. Second dielectric layer 4
The first, second, and third ground electrodes 44a, 44b, and 44c are formed on the upper surface of the second part except for the edge. The first to third ground electrodes 44a to 44c
Each of the first to third capacitor electrodes 4 as viewed in plan
0a to 40c. Therefore, the first and second capacitor electrodes 40a to 40c, the second dielectric layer 42, and the first to third ground electrodes 44a to 44c
And the first and second resonators Q1, Q2 and Q3
And third capacitors C1, C2 and C3 (FIG. 3) are formed.

The first ground electrode 44a extends to one end of the second dielectric layer 42 and is connected to the first coil electrode 24a.
And a second ground electrode 4
4b has a leading portion extending to the other end of the second dielectric layer 42 and corresponding to the other end of the second coil electrode 24b;
The ground electrode 44c extends to the other end of the second dielectric layer 42 and has a lead portion corresponding to the other end of the third coil electrode 24c.

Further, on the upper surface side of the second dielectric layer 42, for example, two third dielectric layers 46 are formed so as to sandwich the first to third ground electrodes 44a to 44c. On the upper surface of the third dielectric layer 46, first, second and third trimming electrodes 48a, 48b and 48c are formed. First to third trimming electrodes 48a-4
8c are formed to face the first to third ground electrodes 44a to 44c, respectively, when viewed in plan. Therefore, the first to third ground electrodes 44a to 44c, the third dielectric layer 46, and the first to third trimming electrodes 48a to 48c
48c, the first, second and third trimming capacitors C1x, C2x and C3x (FIG. 3) are formed.

The first trimming electrode 48a is
The second trimming electrode 48b has an extension extending to the other end of the third dielectric layer 46 and corresponding to the other end of the first coil electrode 24a. The third trimming electrode 48c extends to one end of the third dielectric layer 46 and extends to one end of the third coil electrode 24c. It has a drawer part corresponding to the part. Therefore, by cutting these trimming electrodes 48a to 48c, the effective areas of these trimming electrodes 48a to 48c are changed, whereby the first, second and third trimming capacitors C1x, C2x and C3x are cut. Can be adjusted. That is, these trimming electrodes 48a to 48c are for adjusting the resonance frequencies of the resonators Q1, Q2 and Q3.

Further, on the upper surface side of the third dielectric layer 46, the second protective layer 5 made of, for example, a dielectric is sandwiched so as to sandwich the first to third trimming electrodes 48a to 48c.
0 is formed.

Further, the band pass filter 20 includes:
On one side surface in the width direction, for example, five external electrodes 52a, 52b, 52c, 52d, and 52 having a U-shaped cross section are provided.
e is formed on the other side, for example, a U-shaped 5
Two external electrodes 52f, 52g, 52h, 52i and 5
2j are formed.

The external electrode 52a allows the one end of the first coil electrode 24a, the one end of the first spurious improvement electrode 26a, one lead of the shield electrode 30, and the lead of the first ground electrode 44a. Are connected. Similarly, the third coil electrode 24c is formed by the external electrode 52f.
Is connected to one end of the second spurious improvement electrode 26b, the other lead of the shield electrode 30, and the lead of the third ground electrode 44c.

Further, the first spurious improvement electrode 26
The external electrode 52b is connected to the other end of a, and the external electrode 52g is connected to the other end of the second spurious improvement electrode 26b. These external electrodes 52b and 52g are grounded by being connected to, for example, a ground electrode of a circuit board.

In the bandpass filter 20, when the portion of the external electrode 52b formed on the lower surface of the first protective layer 30 is used as a ground surface for connecting to, for example, a ground electrode of a circuit board, the first spurious improvement is achieved. Electrode 26a
And the second layer 28 of the external electrode 52b connected thereto.
And a portion formed on the side surface of the first protective layer 32,
It works as the first spurious improvement inductor Le1 (FIG. 3). Therefore, in this case, the distance from the surface on which the first spurious improvement electrode 26a is formed to the ground surface, that is, the dimension A corresponding to the thickness of the second layer 28 and the first protective layer 32 is changed, By changing the shape of the spurious improvement electrode 26a, the inductance of the first spurious improvement inductor Le1 can be adjusted.

In this case, similarly, the portion formed on the side surface of the second layer 28 and the first protective layer 32 of the second spurious improvement electrode 26b and the external electrode 52g connected thereto is the 2 Spurious improvement inductor Le2
(FIG. 3), the inductance of the second spurious improvement inductor Le2 can be adjusted by changing the height A or changing the shape of the second spurious improvement electrode 26b.

The inductance of the first and second spurious improvement inductors Le1 and Le2 decreases as the height A decreases, and the loop shape of the first and second spurious improvement electrodes 26a and 26b changes. As the size is reduced, the length is shortened, and the width is increased, the size becomes smaller.

On the other hand, the external electrode 52j is connected to the lead-out portion of the first input / output capacitor electrode 36a.
"e" is connected to a lead-out portion of the second input / output capacitor electrode 36b. These external electrodes 52j and 52e are used as first and second input / output terminals, respectively.

Further, the other end of the first coil electrode 24a and the first capacitor electrode 40
The leading portion of the first trimming electrode 48a is connected to the leading portion of the first trimming electrode 48a. Similarly, the third electrode 52d
One end of the coil electrode 24c and the third capacitor electrode 4
The lead portion of the third trimming electrode 48c is connected to the lead portion of the third trimming electrode 48c.

Further, one end of the second coil electrode 24b is connected to the second capacitor electrode 40b by the external electrode 52c.
Is connected to the extraction portion of the second trimming electrode 48b. Further, the other end of the second coil electrode 24b is connected to the lead-out portion of the second ground electrode 44b by the external electrode 52h.

This band pass filter 20 has an equivalent circuit shown in FIG. That is, the band-pass filter 20 has the first, second and third resonators Q1, Q2 and Q3.

The first resonator Q1 has a first inductor L1 and a first capacitor C1 connected in parallel. The second resonator Q2 also has a second inductor L2 and a second capacitor C2 connected in parallel, and the third resonator Q3 also has a third inductor L3 connected in parallel.
And a third capacitor C3. The inductor L2 of the second resonator Q2 is coupled to the inductor L1 of the first resonator Q1 and the inductor L3 of the third resonator Q3 with a degree of magnetic coupling M, respectively. Furthermore, first, second and third trimming capacitors C1x, C2x and C3x are connected in parallel to capacitors C1, C2 and C3 of these resonators Q1, Q2 and Q3, respectively.

One end of the first resonator Q1 is connected to an external electrode 52j used as a first input / output terminal via a first input / output capacitor C4. Similarly, one end of the third resonator Q3 is connected to an external electrode 52e used as a second input / output terminal via a second input / output capacitor C5.

Further, one end of the second resonator Q2 is connected to the first resonator Q2.
At one end of the resonator Q1 and one end of the third resonator Q3.
Each is connected via a stray capacitance Cp.

A pole forming inductor L is provided between the other end of the first resonator Q1 and the other end of the third resonator Q3.
g is connected. This pole forming inductor Lg is:
This is to form a pole that defines both sides of the pass band in the frequency characteristic of the band pass filter 20.

Further, the other end of the first resonator Q1 is connected to the first resonator Q1.
Is grounded via the spurious improvement inductor Le1. Similarly, the other end of the third resonator Q3 is grounded via a second spurious improvement inductor Le2.

In the band-pass filter 20 shown in FIG. 1 having the equivalent circuit shown in FIG. 3, the dimension A corresponding to the thickness of the second layer 28 and the first protective layer 32 is 0.5 mm,
FIG. 4 shows frequency characteristics in the case of 1.0 mm and 2.0 mm.

From the frequency characteristics shown in FIG. 4, it can be seen that in the band-pass filter 20, the attenuation is as large as 30 dB or more in a higher frequency region than the pass band, and the spurious characteristics are improved. Moreover, as the dimension A is reduced, that is, the spurious improvement inductor Le1
And as the inductance of Le2 is reduced,
In the high frequency range, the amount of attenuation can be increased,
It can be seen that the spurious characteristics can be further improved. That is, in this bandpass filter 20, when the dimension A is 2.0 mm, the attenuation in the high frequency region is 32 dB.
When the dimension A was 1.0 mm, the attenuation in the high frequency region was 40 dB, and when the dimension A was 0.5 mm, the attenuation in the high frequency region was 49 dB.

In the above-described embodiment, the spurious improving electrode is formed in a loop shape, but the spurious improving electrode may be formed in other shapes such as a linear shape and a wavy shape. In this case as well, the inductance of the spurious response improving inductor can be reduced by reducing the length or width of the spurious improving electrode. However, the thickness of the second layer 28, that is, the thickness of the sheet 28a is reduced. It is easy and accurate to change the height A by changing the number of stacks to change the inductance.

[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.

FIG. 4 is a graph showing frequency characteristics of the embodiment shown in FIG.

FIG. 5 is a perspective view showing an example of a conventional bandpass filter.

6 is an exploded perspective view of the bandpass filter shown in FIG.

FIG. 7 is an equivalent circuit diagram of the bandpass filter shown in FIG.

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

[Explanation of symbols]

 Reference Signs List 20 bandpass filter 22 first layer 24a, 24b, 24c coil electrode 26a, 26b spurious improvement electrode 28 second layer 30 shield electrode 32 first protective layer 34 third layer 36a, 36b input / output capacitor electrode 38 first dielectric layer 40a, 40b, 40c capacitor electrode 42 second dielectric layer 44a, 44b, 44c ground electrode 50 second protective layer 52a-52j external electrode Q1, Q2, Q3 resonator L1, L2 L3 Inductor C1, C2, C3 Capacitor C4, C5 Input / Output Capacitor Lg Pole Forming Inductor Le1, Le2 Spurious Improvement Inductor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-262313 (JP, A) JP-A-63-171011 (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 first resonator having a first inductor and a first capacitor connected in parallel; a second inductor and a second capacitor connected in parallel, wherein the second inductor has a second resonator that is magnetically coupled to the first inductor, the third inductor and a third inductor and a third capacitor connected in parallel is magnetically coupled to the second inductor 3, a first input / output terminal connected to one end of the first resonator via a first input / output capacitor, and a third resonator via a second input / output capacitor a second input terminal, and said first other end and the third band-pass filter having an inductor connected between the other end of the cavity of the resonator connected to the one end, each The resonator is composed of multiple dielectrics Form in the laminate but which are stacked
It made which is the other end and said third other end of the cavity of the first resonator
Are first and second spurs formed on the dielectric layer.
A bandpass filter that is grounded through a filter electrode .