JP2730321B2 - 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 dielectric laminated band-pass filter used for a portable radio device or the like having a frequency of

[0002]

2. Description of the Related Art Conventional resonators can be roughly classified into those using a strip line and those using a coil pattern. When a bandpass filter is manufactured using such a resonator, the structure is such that a plurality of resonators are magnetically coupled.

[0003] Here, as a device using the above-mentioned strip line, as shown in FIG. 27, a half-wavelength resonator in which both ends of the line are opened, and as shown in FIG. There is a quarter-wave resonator that is open and the other end is short-circuited. On the other hand, as a device using a coil pattern, a spiral coil pattern 201 and a ground pattern 203 are formed on both sides with a dielectric layer 202 interposed therebetween, as previously proposed by the present applicant (see FIG. 29). There is something like that.

[0004]

However, the bandpass filters using the above-mentioned conventional resonators have the following problems, respectively. Using a strip line (a) A resonator having a resonance frequency of 2 to 3 GHz is considerably large. In particular, a bandpass filter having a structure in which a plurality of resonators are coupled leads to a significant increase in size.
This is for the following reason.

That is, the lengths L ₁₀ and L _{11 of} the strip lines
Is determined as shown in Equation 1 (resonator of １ ／ wavelength) and Equation 2 (resonator of 波長 wavelength).

[0006]

(Equation 1)

[0007]

(Equation 2)

In the above equations (1) and (2), λ is the wavelength, ε
Is the dielectric constant of the dielectric laminate sheet. Here, at present, the dielectric constant of the dielectric laminate sheet that can be co-fired with silver or copper and has excellent temperature characteristics cannot be increased so much.
ε ≒ 10. Therefore, if ε = 10 in the above equations 1 and 2, L ₁₀ = 15.8 mm and L ₁₁ =
This is extremely long at 7.9 mm, which causes an increase in the size of the resonator (bandpass filter) as described above.

(B) In a band-pass filter, it is desirable to adjust the input / output impedance (matching the impedance between the band-pass filter and the device) by a device to be incorporated. However, in the case of the strip line type, since the input / output impedance has a unique value for each strip line, adjustment cannot be performed even if the extraction position is changed, and matching cannot be performed. Using a coil pattern Since a coil pattern has a spiral shape, a magnetic flux affects adjacent patterns to make it difficult for a current to flow. For this reason, substantial resistance increases and Q decreases.

For example, referring to FIG.
In 1a and the pattern piece 201b, the current flows in the same direction (both flow in the direction A), so that the magnetic fields cancel each other and the magnetic flux becomes coarse. The resistance increases. As described above, when the Q is low, there is a problem that the insertion loss of the band-pass filter increases.

The present invention has been made in view of the above circumstances, and provides a bandpass filter which has a high Q, a small insertion loss, can be miniaturized, and can arbitrarily adjust the input / output impedance. The purpose is to:

[0012]

According to the present invention, in order to achieve the above object, two first electrodes are disposed on one main surface of a plate made of a dielectric material, while the other main surface is provided. Is a band-pass filter in which a second electrode is disposed, wherein the first electrode is partially cut out in a loop shape, and each of the electrodes is disposed in a magnetically coupled state. An earth terminal is drawn out from one end of each first electrode toward the end of the plate body, and an extraction terminal is drawn out on the same side as the earth terminal at an interval having a predetermined impedance with the earth terminal. The other end of each of the first electrodes having the cutout portion is disposed in proximity to the one end from which the ground terminal is extended, and the second electrode has a planar shape, and is provided at an end of the plate. The ground terminal is drawn toward the terminal.

Two first electrodes are arranged between the opposing main surfaces of the two plates made of a dielectric material, while a second electrode is provided on the other main surface of the two plates. A band-pass filter disposed in each of the first electrodes, wherein each of the first electrodes has a loop-shaped part cut out, and each electrode is disposed in a magnetically coupled state, and each of the first electrodes has a notch. A ground terminal is drawn out from one end of the electrode toward the end of the plate body, and a lead terminal is drawn out on the same side as the ground terminal at an interval having a predetermined impedance with the ground terminal, while having a cutout portion. The other end of each of the first electrodes is disposed in proximity to the one end from which the ground terminal is drawn, and the second electrode has a planar shape, and the ground terminal is drawn toward the end of the plate. It is characterized by being performed.

Two first electrodes are arranged between the opposing main surfaces of the two plates made of a dielectric material, while a second electrode is provided on the other main surface of the two plates. A band-pass filter disposed in each of the first electrodes, wherein both of the first electrodes are cut out in a loop shape, and each electrode is arranged in a magnetic coupling state, and each of the first electrodes has a cut-out portion. A ground terminal is drawn out from one end of the electrode toward the end of the plate body, and a lead terminal is drawn out on the same side as the ground terminal at an interval having a predetermined impedance with the ground terminal, while having a cutout portion. The other end of each first electrode is arranged close to the one end from which the ground terminal is extended, and at least one of the second electrodes has a shape slightly larger than the first electrode. Split into two and split into two And wherein each ground terminal toward the end of the plate member from the pole is pulled out.

[0015] A third electrode having the same shape as the first electrode is formed between the first electrode and at least one second electrode.

[0016]

According to the above construction, the first electrode and the second electrode have a so-called strip line structure in which the first electrode and the second electrode face each other, and the pattern pieces of the first electrode are adjacent to each other like a spiral coil pattern. Q
Is dramatically improved, the insertion loss is reduced, and the cut of the skirt characteristics is improved.

Further, since the first electrode has a loop shape, the size of the element is reduced. In addition, since the impedance can be adjusted only by changing the distance between the extraction terminal of the first electrode and the ground terminal, the adjustment of the impedance becomes extremely easy.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2 are views showing the structure of a bandpass filter according to a first embodiment of the present invention. FIG. 1 is a plan view, FIG. 2 is an exploded perspective view, and FIG. 3 is a view of a dielectric sheet used in the present invention. FIG. 4 is a plan view showing a state where a coil electrode pattern is formed on the dielectric sheet of FIG. 3; FIG. 5 is a plan view showing a state where a ground electrode pattern is formed on the dielectric sheet of FIG. 3; 7 is a view when the dielectric sheets are laminated, FIG. 6 is a front view, FIG. 7 is a side view, FIG. 8 is a front view when the laminate is crimped, and FIG. 9 is when an external electrode is formed. FIG. 10 is an equivalent circuit diagram of the band-pass filter, and FIG. 11 is a graph showing frequency characteristics of the band-pass filter.

As shown in FIGS. 1 and 2, the band-pass filter of the present invention comprises a dielectric layer 1 composed of a plurality of dielectric sheets 101, and protective layers provided above and below the dielectric layer 1. 2 and 3. The dielectric sheet 101
, Two coil electrode patterns 41 and 42 arranged symmetrically side by side are formed on one main surface 101a of the dielectric sheet 101 located at the uppermost part. And
These are fired and integrated with each other.

The specific structure of the coil electrode pattern 41 is such that the pattern pieces 41 which are both linear and are opposed to each other are formed.
a and 41b are connected via a linear pattern piece 41c connected to one end of the pattern pieces 41a and 41b, and the other end of the pattern piece 41b is parallel to the pattern piece 41c. The structure is such that a pattern piece 41d extending in the direction of the pattern piece 41a is formed (that is, a loop shape).

Here, the entire length L ₃ of the coil electrode pattern 41 is configured to have the length shown in the following equation (3).

[0022]

(Equation 3)

Λ is the wavelength and ε is the dielectric constant. Note that the distance L ₁ between the pattern pieces 41d and the pattern piece 41a is desirably equal to or less than the width L ₂ of the pattern piece 41 a to 41 d. In this embodiment, L ₁ is configured to be slightly shorter than L _2. In the following embodiment, the gap between the pattern pieces 41a and 41d is
Called 0.

On the other hand, as shown in FIG. 1, the coil electrode pattern 42 has a symmetrical shape with the coil electrode pattern 41 having the above structure.
The pattern pieces 41d and 42c are adjacent to each other. In the following embodiment, the pattern piece 4
The gap between 2a and 42c is referred to as gap 31. An earth terminal pattern 6a or 6b and an extraction electrode pattern 7a or 7b are connected to the coil electrode patterns 41 and 42, respectively, and these earth terminal patterns 6a and 6b and the extraction electrode patterns 7a and 7b Extend to the side surface A of the bandpass filter.

The surface 3 of the protective layer 3 on the dielectric layer 1 side
The ground electrode pattern 5 is formed on the surface 3a so that the size of the ground electrode pattern 5 is larger than the outer circumference of the coil electrode pattern 4. At the positions corresponding to the ground terminal patterns 6a and 6b on the surface 3a, ground terminal patterns 8a and 8b having one end connected to the ground electrode pattern 5 and the other end extending to the side surface A of the bandpass filter are formed. Have been. The ground terminal pattern 6a and the ground terminal pattern 8a are on the external ground electrode 9a, the ground terminal pattern 6b and the ground terminal pattern 8b are on the external ground electrode 9b, the extraction electrode pattern 7a is on the external extraction electrode 10a, and the extraction electrode pattern 7b is an external extraction electrode 10b
Are connected to the external ground electrodes 9a and 9b, respectively.
b and both external extraction electrodes 10a and 10b are formed on the side surface of the bandpass filter so as to have a U-shaped cross section.

Here, a band-pass filter having the above structure was manufactured in the following procedure. First, one main surface of the dielectric sheet 101 (about several tens μm in thickness) shown in FIG.
The pattern shown in FIG.
A copper paste or the like is formed so as to have the same pattern 42 as that of the terminal patterns 6a, 6b, 7a, and 7b. On the other hand, in parallel with this, a pattern as shown in FIG. 5 (the ground electrode pattern) is formed on one surface of the protective sheet 11 (the thickness may be different) having the same configuration as the dielectric sheet 101. 5 and a ground terminal pattern 8a, 8b).

Next, as shown in FIG. 6 and FIG. 7, the protection sheet 2 and the protection sheet 2 are arranged so that the pattern 12 and the pattern 13 face each other via the sheet layer 16 made of the dielectric sheet 101. Sheet layer 16 and protective sheet 11
(A structure similar to that of the protective sheet 2), and then press-bonded to form a laminated body 15. Thereafter, portions corresponding to the exposed portions 17a and 17b to 19a and 19b of the paste layer shown in FIG.
a and 10b) as shown in FIG. 9 by printing or applying a copper paste to paste layers 20a, 20b,
21a and 21b are manufactured. Thereafter, the laminate is fired to integrate the dielectric sheet, thereby producing a bandpass filter. The firing of the laminate and the firing of the paste layers 20a, 20b, 21a, 21b may be performed in different steps.

By the way, although the capacitor pattern is not formed in the band-pass filter manufactured as described above, it has an equivalent circuit as shown in FIG. 10 (M indicates magnetic coupling in the figure). This is due to the following two reasons. The coil electrode patterns 41 and 42 have the same potential as the ground electrode pattern 5 (that is, a grounded state). Since the dielectric layer 1 is interposed between the coil electrode patterns 41 and 42 and the ground electrode pattern 5, a stray capacitance is generated.

The capacitor is thus formed, and the pattern pieces 41 of the coil electrode patterns 41 and 42 are formed.
Since magnetic coupling is performed between d and 42c, FIG.
Has an equivalent circuit as shown in FIG. Since the stray capacitance is mainly generated between the coil electrode patterns 41 and 42 and the ground electrode pattern 5, the capacitance of the capacitor changes by moving the coil electrode patterns 41 and 42 close to and away from the ground electrode pattern 5. , The frequency of the pass band can be changed. Specifically, if the coil electrode patterns 41 and 42 and the ground electrode pattern 5 are brought close to each other (the thickness of the dielectric sheet 101 is reduced), the capacitance of the capacitor increases. If the electrode patterns 41 and 42 are separated from the ground electrode pattern 5 (the thickness of the dielectric sheet 101 is increased), the capacitance of the capacitor is reduced, and the frequency of the pass band is increased. Further, the stray capacitance can be changed depending on the dielectric constant of the dielectric layer 1 and the thickness of the coil electrode patterns 41 and 42. For example, when thickening the width L ₂ of the coil electrode pattern 41 and 42, it is possible to lower the frequency of the pass band stray capacitance is increased, it is possible to achieve a more compact. However, if the intervals between the pattern pieces 41a and 41b, between the pattern pieces 41c and 41d, between the pattern pieces 42a and 42b, and between the pattern pieces 42c and 42d are too small, the waveform deteriorates. 42 is not preferable to thickening the width L ₂ of the.

Further, changing the bandwidth of the bandpass filter is performed by varying the distance L ₆ between the pattern pieces 41d · 42c. Specifically, when the distance L ₆ is reduced, the bandwidth increases, while when the distance L ₆ is increased, the bandwidth decreases. However, since the narrowing the distance L ₆ more than necessary the bimodal characteristic, undesirable. Change of input and output impedance is performed by varying the distance L ₈ between the distance L ₇ or earth terminal pattern 6b and the lead electrode pattern 7b and the earth terminal pattern 6a and the lead electrode pattern 7a.

According to experiments, the applicable frequency of the bandpass filter of the present invention can be set to several hundred MHz to several GHz by adjusting the dielectric constant and thickness of the dielectric layer 1 or the area of the coil electrode pattern 4. did it. One example is shown in the following experiment. [Experiment] The frequency characteristics of the bandpass filter having the above structure were examined, and the results are shown in FIG. [Other Matters] When the band pass filter of the present invention is mounted, the electrodes on the printed circuit board are aligned with the external ground electrodes 9a and 9b and the external extraction electrodes 10a and 10b.
The band pass filter of the present invention may be placed and soldered. At this time, since the outside is covered with the protective layers 2 and 3, the coil electrode patterns 41 and 42 and the ground electrode pattern 5 can be prevented from being damaged. As the dielectric layer 1, a thin dielectric sheet 101 is used.
The structure is not limited to a structure in which a plurality of sheets are stacked, and a dielectric sheet formed in advance to a predetermined thickness may be used. It is not necessary to manufacture the products of the present invention one by one, and a plurality of coil electrode patterns 41 and 42 are formed on one wide dielectric sheet.
Alternatively, the same number of earth electrode patterns 5 may be formed on the same dielectric sheet, and the layers in this state may be laminated, cut, cut into individual pieces, and fired. .

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS.
This will be described below. FIG. 12 is a plan view of a main part of a bandpass filter according to a second embodiment of the present invention, and FIG. 13 is a graph showing frequency characteristics of the bandpass filter shown in FIG.
As shown in FIG. 12, the end of the pattern piece 41d is connected to the end of the pattern piece 41a, and the gap 30 of the coil electrode pattern 41 is connected to the pattern piece 41a and the pattern piece 4a.
The structure is the same as that of the first embodiment except that it is formed between the first embodiment. [Experiment] The frequency characteristics of the bandpass filter having the above structure were examined, and the results are shown in FIG.

Third Embodiment A third embodiment of the present invention will be described with reference to FIGS. 14 and 15.
This will be described below. FIG. 14 is a plan view of a main part of a bandpass filter according to a third embodiment of the present invention, and FIG. 15 is a graph showing frequency characteristics of the bandpass filter shown in FIG.
As shown in FIG. 14, the ends of the pattern pieces 41d and 42c are connected to the ends of the pattern pieces 41a and 42a, respectively.
31 is the same as that of the first embodiment, except that the first and second patterns 31 are formed between the pattern pieces 41a and 41c and between the pattern pieces 42a and 42d, respectively. [Experiment] The frequency characteristics of the bandpass filter having the above structure were examined, and the results are shown in FIG.

(Fourth Embodiment) A fourth embodiment of the present invention will be described below with reference to FIGS. 16, 18, and 20 show the fourth embodiment of the present invention.
FIG. 1 is an exploded perspective view of a bandpass filter according to an embodiment.
7, FIG. 19, and FIG. 21 are FIGS. 16, 18, and 20, respectively.
5 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

As shown in FIGS. 16, 18, and 20, the dielectric layer 1 and the ground electrode pattern 5 are provided not only on one side but also on both sides of the coil electrode patterns 41 and 42, respectively. The structure is the same as that of the first, second and third embodiments. [Experiment] The frequency characteristics of the bandpass filter having the above structure were examined, and the results are shown in FIGS. 17, 19, and 21, respectively.

As is clear from FIGS. 17, 19 and 21, the band-pass filter is different from the first embodiment,
As in the second and third embodiments, it is recognized that the frequency of the pass band is slightly lower. This is probably because the stray capacitance is formed not only on one side of the coil electrode patterns 41 and 42 but also on both sides, so that the capacitance of the bandpass filter increases.

Fifth Embodiment A fifth embodiment of the present invention will be described with reference to FIGS. 22 and 23.
This will be described below. FIGS. 22 and 23 are views showing a bandpass filter according to a fifth embodiment of the present invention.
Is an exploded perspective view, and FIG. 23 is a plan view.

As shown in FIGS. 22 and 23, one ground electrode pattern (the upper pattern in FIG. 23)
The configuration is the same as that of the bandpass filter shown in FIG. 17 of the fourth embodiment except that the shape of the bandpass filter is different. Specifically, the ground electrode pattern 5 is divided into two, each of the patterns 51 and 52 is configured to be slightly larger than the coil electrode patterns 41 and 42, and each of the ground electrode patterns 51 and 52 is Ground terminal pattern 8
a.8b are connected.

With such a configuration, the pattern piece 41
Part of the ground electrode patterns 51 and 52 corresponding to d and 42c (for example, a portion indicated by a two-dot chain line B in FIG. 23).
Since the stray capacitance can be adjusted by simply cutting the frequency, the frequency can be easily adjusted. Although the above-described adjustment is possible with the ground electrode patterns (formed on substantially the entire surface) of the above-described first to fourth embodiments, the frequency is adjusted because the cut length becomes long. For example, it is desirable to adopt the configuration of this embodiment.

The ground electrode pattern of the present embodiment is not limited to the bandpass filter having the structure shown in FIG. 16 of the fourth embodiment, but can be applied to the other embodiments. (Sixth Embodiment) A sixth embodiment of the present invention will be described below with reference to FIG. FIG. 24 is an exploded perspective view of the bandpass filter according to the sixth embodiment of the present invention.

As shown in FIG. 24, on the dielectric sheet 101 adjacent to the dielectric sheet 101 on which the coil electrode patterns 41 and 42 are formed, the coil electrode patterns 41 and 42 are provided.
The configuration is the same as that of the band-pass filter shown in FIG. 16 of the fourth embodiment except that floating electrode patterns 33 and 34 having the same shape as the above are formed. Although not shown, it has been experimentally confirmed that such a structure makes the peak of the frequency in the pass band lower than that of the bandpass filter shown in FIG. 16 of the fourth embodiment.

This is considered to be due to the fact that the stray capacitance is formed between the coil electrode patterns 41 and 42 and the floating electrode patterns 33 and 34, so that the capacitance of the bandpass filter increases. [Other Matters] The structure of the coil electrode patterns 41 and 42 is not limited to those shown in the above-described various embodiments.
It may be a loop as shown in FIGS. 25 and 26.

[0043]

As described above, according to the present invention, Q is dramatically improved because of the so-called stripline structure and the fact that the pattern pieces of the first electrode are not adjacent to each other. Becomes possible. As a result, the insertion loss of the bandpass filter is reduced, and the cut of the skirt characteristic is improved.

Further, since the first electrode has a loop shape, the size of the element is reduced. In addition, since the impedance can be adjusted only by changing the distance between the extraction terminal of the first electrode and the ground terminal, the adjustment of the impedance becomes extremely easy. From these, the insertion loss is small,
In addition, it is possible to provide an extremely excellent bandpass filter which is small in size and whose input / output impedance can be arbitrarily adjusted.

[Brief description of the drawings]

FIG. 1 is a plan view of a bandpass filter according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the bandpass filter according to the first embodiment of the present invention.

FIG. 3 is a plan view of a dielectric sheet used in the present invention.

FIG. 4 is a plan view showing a state where a coil electrode pattern is formed on the dielectric sheet of FIG. 3;

FIG. 5 is a plan view showing a state where an earth electrode pattern is formed on the dielectric sheet of FIG. 3;

FIG. 6 is a front view when dielectric sheets are stacked.

FIG. 7 is a side view when a dielectric sheet is stacked.

FIG. 8 is a front view when the laminate is pressed.

FIG. 9 is a front view when external electrodes are formed.

FIG. 10 is an equivalent circuit diagram of the bandpass filter shown in FIG.

FIG. 11 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

FIG. 12 is a plan view of a main part of a bandpass filter according to a second embodiment of the present invention.

FIG. 13 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

FIG. 14 is a plan view of a main part of a bandpass filter according to a third embodiment of the present invention.

FIG. 15 is a graph showing frequency characteristics of the bandpass filter shown in FIG. It is an equivalent circuit diagram.

FIG. 16 is a perspective view of a bandpass filter according to a fourth embodiment of the present invention.

FIG. 17 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

FIG. 18 is a perspective view of a bandpass filter according to a modification of the fourth embodiment.

FIG. 19 is a graph showing frequency characteristics of the bandpass filter shown in FIG.

FIG. 20 is a perspective view of a bandpass filter according to another modification of the fourth embodiment.

21 is a graph showing a frequency characteristic of the bandpass filter shown in FIG.

FIG. 22 is a perspective view of a bandpass filter according to a fifth embodiment of the present invention.

FIG. 23 is a plan view of a bandpass filter according to a fifth embodiment of the present invention.

FIG. 24 is a perspective view of a bandpass filter according to a sixth embodiment of the present invention.

FIG. 25 is a main part plan view showing a modification of the bandpass filter of the present invention.

FIG. 26 is a main part plan view showing another modification of the bandpass filter of the present invention.

FIG. 27 is an explanatory view showing a conventional stripline type dielectric resonator.

FIG. 28 is an explanatory view showing a conventional stripline type dielectric resonator.

FIG. 29 is an explanatory view showing a conventional coil pattern type dielectric resonator.

[Explanation of symbols]

 Reference Signs List 1 dielectric layer 5 ground electrode pattern 6a ground terminal pattern 6b ground terminal pattern 7a extraction electrode pattern 7b extraction electrode pattern 8a ground terminal pattern 8b ground terminal pattern 41 coil electrode pattern 42 coil electrode pattern 101 dielectric sheet

Claims (4)

(57) [Claims] 1. A band-pass filter in which two first electrodes are arranged on one main surface of a plate made of a dielectric material, and a second electrode is arranged on the other main surface. The first electrode has a loop- shaped part cut out.
Rutotomoni, the electrodes are arranged in a magnetically coupled state, notch
From one end of each first electrode having a portion to an end of the plate body.
Ground terminal is pulled out and this ground terminal is
The extraction terminal is connected to the ground terminal at intervals having impedance.
Each has a notch while being pulled out on the same side as
The other end of the first electrode is the one end from which the ground terminal is extended.
Wherein the second electrode has a planar shape, and a ground terminal is drawn out toward an end of the plate. 2. Two first electrodes are arranged between opposing main surfaces of two plates made of a dielectric material, and a second electrode is provided on the other main surface of the two plates. A band-pass filter in which electrodes are arranged, wherein the first electrode has a loop- shaped part cut out;
Rutotomoni, the electrodes are arranged in a magnetically coupled state, notch
From one end of each first electrode having a portion to an end of the plate body.
Ground terminal is pulled out and this ground terminal is
The extraction terminal is connected to the ground terminal at intervals having impedance.
Each has a notch while being pulled out on the same side as
The other end of the first electrode is the one end from which the ground terminal is extended.
Wherein the second electrode has a planar shape, and a ground terminal is drawn out toward an end of the plate body. 3. Two first electrodes are arranged between opposing main surfaces of two plates made of a dielectric material, and a second electrode is provided on the other main surface of the two plates. A band-pass filter in which electrodes are arranged, wherein the first electrode has a loop- shaped part cut out;
Rutotomoni, the electrodes are arranged in a magnetically coupled state, notch
From one end of each first electrode having a portion to an end of the plate body.
Ground terminal is pulled out and this ground terminal is
The extraction terminal is connected to the ground terminal at intervals having impedance.
Each has a notch while being pulled out on the same side as
The other end of the first electrode is the one end from which the ground terminal is extended.
Is close placed on, among the second electrodes, at least one electrode is divided into two so that the larger shape slightly above the first electrode, and directed two split electrodes to an end of the plate body A band-pass filter wherein ground terminals are respectively drawn out. 4. The first electrode and at least one second electrode
The band-pass filter according to claim 2, wherein a third electrode having the same shape as the first electrode is formed between the band-pass filter and the third electrode.