JPH05218705A - Lamination type band elimination filter - Google Patents

Abstract

PURPOSE:To realize the band elimination filter of a tri-plate type in which a characteristic impedance of a transmission line is set to 50ohms in a dielectric board with a high dielectric constant and an inductance of a pi-shaped circuit coupling resonators is made compact by an electrode pattern. CONSTITUTION:Plural tri-plate type resonators are formed corresponding to plural electrodes for 1/4 wavelength resonance provided in the inside of a dielectric board 40. On the other hand, the inductance of a pi-shaped circuit coupling the resonators is formed by the induction of a coupling electrode 58 provided corresponding to each resonance electrode 46 between a coupling line 60. Then the coupling electric length of the coupling line part 60 is adjusted to a prescribed value less than 90 deg. to adjust the reactance. Thus, the inductance of the pi-shaped circuit formed between serial capacitance electrodes 48 is set to an optional value.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a band elimination filter used in a high frequency communication device represented by a mobile phone or the like.

[0002]

BACKGROUND ART Recently, in various high frequency communication devices,
In order to reduce the loss, dielectric filters using various dielectric ceramics are used. Then, as one of such dielectric filters, a band elimination filter having a characteristic of positively removing radio waves in a specific frequency range is known.

FIG. 4 shows one structure of a typical band elimination filter by an equivalent circuit, in which 4 is its input / output terminal and a plurality of resonators 6 (here, 3). Are provided in stages), respectively, and are connected via a series capacitance 8 for series resonance. An inductance 10 is provided between the resonators 6 and 6, and a capacitance 12 is provided between the resonators 6 and 6 and the ground. As a result, the adjacent resonators 6 and 6 are coupled to each other via the so-called π-shaped circuit 14 which is composed of the inductance 10 and the capacitances 12 and 12. In other words, such a structure realizes the characteristic of positively removing radio waves in a specific frequency range.

By the way, in the case of actually constructing the structure as shown in FIG. 4 as a dielectric filter, a coaxial filter is conventionally used as disclosed in Japanese Utility Model Laid-Open No. 3-14803. Has been done. In Figure 5,
An example thereof is shown, in which 16 is a coaxial resonator having a known structure, and as is well known, a ground conductor is provided on the outer peripheral surface of a dielectric block having a through hole. In addition to being provided, an internal conductor for resonance is provided on the inner peripheral surface of the through hole. A connecting fitting 18 is connected to the internal conductor of each resonator 16, the connecting fitting 18 is connected to an L-shaped fitting 22 via a dielectric small piece 20, and the L-shaped fitting 22 is further connected.
Is connected to the wiring board 26 via the dielectric piece 24,
It is grounded. Furthermore, adjacent L-shaped metal fittings 2
A coil 28 is welded and fixed between the two and 22.

That is, in such a coaxial filter, a series capacitance for series resonance is provided by the dielectric piece 20. Adjacent resonators 16 and 16 are coupled to each other by a π-shaped circuit composed of the coil 28 and the dielectric pieces 24 and 24. And the band elimination filter of FIG. 4 is implement | achieved by it.

Thus, such a coaxial type filter is
It has become difficult to meet the recent demands for miniaturization of components, and recently, it has been strongly desired to realize a band elimination filter as a so-called triplate type filter. That is, as is well known, the tri-plate type filter has a thin dielectric substrate on which ground electrodes are formed on both sides of the main surface, and a plurality of resonance electrodes and the like are provided inside the ground electrode. This is because various electrode patterns can be compactly formed in the dielectric substrate, and therefore, the size can be significantly reduced as compared with the coaxial filter.

However, configuring the band elimination filter as a triplate type filter has the following problems.

First, there is a problem that it is difficult to form the inductance compactly when the π-shaped circuit for coupling the resonators is provided in the dielectric substrate. So for the capacitance of the π-shaped circuit,
Since the transmission line is built in the dielectric substrate, it can be made compact by the capacitance between the ground electrode on the main surface of the dielectric substrate and the transmission line. On the contrary,
Regarding the inductance, it is impossible to assemble the actual coil as it is, unlike the conventional case. Further, as shown in FIG. 6, the adjacent resonance electrodes 30 and 30 are separated from each other so that the electric length of the transmission line 32 between them is 90 ° so that inductance is equivalently given. However, the size of the electrode pattern is increased, which eventually causes a problem of hindering miniaturization of the band elimination filter. Further, it is desirable to set the characteristic impedance of the transmission line 32 to 50Ω which is the input / output impedance of the communication device or the wireless device, but since the dielectric constant of the dielectric substrate is relatively high, it is 50Ω in such a substrate. In order to obtain such a characteristic, the width of the transmission line 32 needs to be extremely thin, about several tens of μm, which is extremely difficult to realize.

[0009]

The present invention has been made in view of such circumstances, and the problem to be solved is to provide a coupling circuit between resonators even in a dielectric substrate having a high dielectric constant. The purpose is to realize the band-elimination filter as a triplate-type filter so that the inductance of the π-shaped circuit can be formed compactly with the electrode pattern.

[0010]

In order to solve the above problems, according to the present invention, a ground electrode is formed on both main surfaces of a dielectric substrate, and a plurality of quarter electrodes are provided inside the dielectric substrate. By forming the wavelength resonance electrode, a triplate resonator corresponding to each resonance electrode is configured, while each resonator is equivalently displayed as a π-shaped circuit including an inductance and a capacitance. In a circuit, a band elimination filter having a structure of being coupled to each other is provided, and a coupling line having a coupling electric length of 90 ° or less is provided inside the dielectric substrate separately from each of the resonance electrodes and A laminated band elimination filter, which is provided corresponding to a resonance electrode, and in which the inductance of the π-shaped circuit is realized by an inductive action between the coupling lines,
This is the summary.

[0011]

[Operations and Effects] In short, a coupling line having a coupling electric length of 90 ° or less is provided in the dielectric substrate separately from each resonance electrode, but a predetermined inductive component is generated in such a coupling line, and As a result, the coupled lines behave equivalently as if a coil is added, and in the present invention,
By such an inductive action between the coupled lines, the inductance of the π-shaped circuit that couples the resonators is realized. Moreover, the reactance in this case is obtained by bringing the electrical length of the coupled line close to 90 °,
In theory, you can get to infinity. Therefore, if this is used to adjust the reactance, the inductance of the π-shaped circuit can be arbitrarily set even in a dielectric substrate having a high dielectric constant.

Further, since such a coupled line can be easily installed in the dielectric substrate and can be efficiently arranged in a narrow space, it is necessary to widen the spacing between the resonance electrodes. Absent. Therefore, the band elimination filter can be realized as an extremely compact triplate type filter.

[0013]

EXAMPLES In order to more specifically clarify the present invention, representative examples of the laminated band elimination filter according to the present invention will be described in detail below with reference to the drawings.

First, FIG. 1 shows an example of a laminated band elimination filter according to the present invention. There,
Reference numeral 40 denotes a substantially rectangular plate-shaped dielectric substrate composed of various known dielectric ceramics, on which a ground electrode 42 is formed on substantially the entire surface thereof and in the width direction (see FIG. 1).
A pair of input / output terminals 44, 44 are formed on a pair of side surfaces facing each other in the left-right direction in a state of being electrically disconnected from the ground electrode 42. And inside it,
As shown in FIG. 2, each electrode is incorporated in multiple layers.

By the way, as shown in FIG. 3, such a laminated band elimination filter is formed by laminating and integrating a total of four dielectric substrates 40 each having a predetermined electrode pattern formed thereon. , Is configured.

More specifically, ground electrodes 42 are provided on the entire upper surface of the first dielectric substrate 40 and the lower surface of the fourth dielectric substrate 40 from the top. Also,
On the upper surface of the second dielectric substrate 40 from the top, three 1 /
In the strip-shaped four-wavelength resonance electrode 46, the open end (the end that is not connected to the ground electrode 42) and the short-circuit end (the end that is connected to the ground electrode 42) are in the same direction. In the structure, they are arranged and formed parallel to each other. In addition, 54 is a connection electrode for connecting the short-circuit end of the resonance electrode 46 to the ground electrode 42. Thus, here, in correspondence with each resonance electrode 46, 1/4
The wavelength triplate resonator is provided in three stages.

Further, on the second dielectric substrate 40 from the top, a series capacitor for forming series resonance is formed at a position facing the open end of each resonance electrode 46 with a predetermined gap. A capacitor electrode 48 is formed. The series capacitance electrodes 48, 48 located on both sides are connected to the input / output terminals 44, 44. Further, a through hole 50 is provided in each series capacitance electrode 48, and a through hole 52 is also provided in the third dielectric substrate 40 corresponding to the through hole 50. There is. Thereby, the series capacitance electrode 48
However, the conductors in the through holes 50 and 52 can be electrically connected to a coupling line 58, which will be described later, provided on the upper surface of the fourth dielectric substrate 40.

On the upper surface of the third dielectric substrate 40 from the top, a shield electrode 56 is formed on substantially the entire surface thereof in a state of not being electrically connected to the through hole 52. This prevents the resonance electrode 46 and the coupling line 58, which will be described later, from electromagnetically affecting each other.

On the upper surface of the fourth dielectric substrate 40 from the top, three coupling electrodes 58 are provided so as to correspond to the above-mentioned three resonance electrodes 46. Specifically, each coupling electrode 5 located on both sides
Reference numeral 8 has a connecting portion 61 which is connected to the through hole 52, and a coupling line portion 60 which is provided so as to extend in a direction perpendicular to the inner end portion thereof and has a coupling electric length of 90 ° or less. , And each has an L shape or an inverted L shape as a whole. Further, the coupling electrode 58 located at the center has a connection portion 61 connected to the through hole 52 and a coupling electric length of 90 ° or less, which is provided so as to extend in a direction perpendicular to both end portions thereof. It has a coupling line portion 60 and 60, and has a U shape as a whole.

In this way, the coupling line portions 60, 60 of the adjacent coupling electrodes 58, 58 form the resonator (resonance electrode 46).
They are located in between and are opposed to each other with a predetermined interval. Further, since the coupling electric length of the coupling line portion 60 is adjusted to 90 ° or less, a predetermined inductive component is generated, and the coupling line portion 6 facing each other is generated.
The inductive action works between 0 and 60. Moreover, the reactance can theoretically be infinite by making the coupling electric length of the coupling line portion 60 close to 90 °. Reference numeral 62 is a through hole for connecting the coupling electrode 58 and the ground electrode 42 on the lower surface.

Then, four such dielectric substrates 40 are formed.
1 and 2 by stacking and integrating
As shown in FIG. 1, an integral laminated band elimination filter is formed. The ground electrode 42 on the side surface of the filter and the pair of input / output terminals 44, 44.
Will be baked after the dielectric substrate 40 is laminated.

That is, in the laminated band elimination filter having such a structure, the series capacitance for series resonance is provided by the capacitance between the open end of each resonance electrode 46 and the corresponding series capacitance electrode 48. Be done. A capacitance is provided by the capacitance between each series capacitance electrode 48 and the ground electrode 42 on the upper surface of the filter. Further, the coupling line portions 60 of the adjacent coupling electrodes 58, 58,
Since an inductive action is exerted between 60, the inductance is equivalently added thereto.

Therefore, the equivalent circuit of such a laminated band elimination filter is as shown in FIG.
However, they are coupled to each other in a circuit equivalently displayed as a π-shaped circuit composed of the inductance 10 and the capacitances 12 and 12. Thus, the band elimination filter can be realized as a triput type filter, and a significant reduction in size can be achieved as compared with the coaxial type band elimination filter. In addition, the coupling electrode 58, which is provided to realize the inductance of the π-shaped circuit, can be arranged extremely compactly in the dielectric substrate 40, so that the resonator (resonance electrode 4
6) It is not necessary to widen the space, and the size of the filter can be more advantageously reduced.

By the way, such excellent characteristics of the laminated dielectric filter according to the present invention can be clearly recognized in the following test examples.

First, a plurality of green sheets for forming a dielectric substrate made of a material obtained by adding a small amount of glass component or glass powder to a barium oxide-titanium oxide-neodymium oxide type compound are prepared, and each of them is shown in FIG. The series of electrode patterns shown were printed with silver paste. Then, the green sheets were laminated in a predetermined order, and the laminated sample was fired at about 900 ° C. Thereafter, as shown in FIG. 1, a silver electrode is baked on the side surface of the sample so as to short-circuit the earth electrodes on the front and back and the shield electrode installed therein, and an input / output terminal is provided to form a laminated structure having the structure according to the present invention. The mold band elimination filter was completed.

When the frequency characteristics of the thus obtained laminated band elimination filter were examined, the center of the stop frequency was 8
70MHz, stop band is 28MHz, stop amount is 27d
It was B or more.

The representative embodiments of the present invention have been described above in detail, but it goes without saying that the present invention is not restricted by the description of such embodiments. Further, in addition to the above-described embodiments, the present invention may be modified in various ways based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Should be understood.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a laminated band elimination filter according to the present invention.

FIG. 2 is a sectional view showing a section taken along line II-II in FIG.

FIG. 3 is an explanatory diagram showing an arrangement form of electrodes incorporated in the laminated band elimination filter of FIG.

FIG. 4 is an equivalent circuit showing one structure of a typical band elimination filter.

FIG. 5 is a perspective view showing a main part of an example of a conventional coaxial band elimination filter.

FIG. 6 is an explanatory diagram for explaining an example of a method of forming an inductance equivalently by an electrode pattern.

[Explanation of symbols]

 40 dielectric substrate 42 ground electrode 44 input / output terminal 46 resonance electrode 48 series capacitance electrode 50, 52 through hole 54 connection electrode 56 shield electrode 58 coupling electrode 60 coupling line portion 61 connection portion 62 through hole

Claims (1)

[Claims] 1. A ground electrode is formed on both main surfaces of a dielectric substrate, and a plurality of quarter-wavelength resonance electrodes are formed inside the dielectric substrate to correspond to each resonance electrode. While a triplate resonator is constructed, the space between each resonator consists of an inductance and a capacitance.
In a circuit equivalently displayed as a V-shaped circuit, a band elimination filter having a structure of being coupled to each other is used, and a coupling line having a coupling electric length of 90 ° or less is provided inside the dielectric substrate for each resonance. A multilayer band elimination filter, which is provided separately from the electrodes and corresponding to each of the resonance electrodes, and the inductance of the π-shaped circuit is realized by the inductive action between the coupled lines. ..