JP2863387B2 - Multilayer dielectric 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 laminated dielectric filter used in a microwave band, and more particularly to a small-sized dielectric filter having a laminated structure capable of exhibiting excellent filter characteristics.

[0002]

2. Description of the Related Art In recent years, in a communication device using a microwave, such as a mobile phone or a car phone, a dielectric filter using various dielectric ceramics has been used in order to reduce a loss. Conventionally, various studies have been made to improve the characteristics of dielectric filters. In a band-pass filter (band-pass filter) used in a microwave band, basically, the number of resonator stages to be used is used. It is known that the attenuation characteristic can be improved by increasing the number (that is, the number of resonator electrodes). However, when the number of resonator electrodes is increased, the size of the filter is increased and the insertion loss is increased.

For this reason, in a band-pass filter having a plurality of resonator electrodes, while the number of resonator electrodes is reduced as much as possible, non-adjacent resonator electrodes are coupled with an appropriate reactance, so that the attenuation range is reduced. A method of forming an attenuation pole (pole) to improve the attenuation characteristic of a filter has been used (see “Transactions of the Institute of Electronics and Communication Engineers”, 53-A, No. 4, 1970, pp. 163 to 168). In addition, a capacitive element, an inductance element, and a transmission line are actually provided as their reactances.

In Japanese Patent Publication No. Sho 56-48083 and Japanese Utility Model Publication No. Sho 60-7525, a plurality of microstrip line type resonator electrodes are provided on the surface of a plate-shaped dielectric substrate. In such a filter, an example is shown in which a reactance for forming the above-described attenuation pole is provided. That is, in FIG. 12, three resonator electrodes 4 are provided on the surface of the dielectric substrate 2, and the adjacent resonator electrodes 4, 4 are coupled to each other by the coupling electrodes 6, 6. Further, a transmission line 8 (reactance) is provided for coupling between non-adjacent resonator electrodes (left and right end resonator electrodes) 4 and 4. Reference numeral 10 denotes an input / output electrode.

[0005] Therefore, in such a filter, an attenuation pole appears in the attenuation region, and excellent filter characteristics can be obtained. Further, by changing the equivalent electric length and the coupling coefficient of the transmission line 8, the reactance can be changed. Thus, the position of the attenuation pole can be adjusted. However, in such a filter, since the transmission line 8 is formed in the same plane as the resonator electrode 4, there is a problem that the filter area is increased by the provision of the transmission line 8.

In US Pat. No. 4,418,324, a ground electrode is provided on an upper surface on a single dielectric substrate provided with a ground electrode on a lower surface and a plurality of resonator electrodes on an upper surface. In a triplate type filter in which two dielectric substrates are overlapped and the resonator electrode is interposed between the two dielectric substrates, an attenuation pole as described above is formed in a triplate type filter configured as an integrated dielectric filter. An example in which a transmission line (reactance) for forming is provided is shown.
Specifically, a transmission line for coupling between non-adjacent resonator electrodes is provided on the upper surface of the upper dielectric substrate in a state in which the transmission line is not connected to the ground electrode, and the transmission line and the non-adjacent resonance electrode are connected to each other. The dexterous electrode is connected via a capacitance element given by the thickness of the upper dielectric substrate. However, in this case, since the transmission line is formed on the surface of the dielectric substrate and is not electromagnetically shielded, the transmission line is easily affected by nearby metal and the like,
There is an inherent problem that the filter characteristics are difficult to stabilize.

[0007]

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a dielectric filter which is small in size, has high filter characteristics, and can exhibit stable characteristics. Is to provide.

[0008]

The object of the present invention is to solve the above-mentioned problems by providing a triplate structure dielectric filter in which a plurality of resonator electrodes are built in a dielectric substrate. A stacked dielectric filter is characterized in that reactances of a transmission line, a capacitance element, and the like for coupling between them are further incorporated so as to form a stacked structure with respect to the plurality of resonator electrodes.

Further, in the present invention, advantageously, the reactance is laminated at a position where the plurality of resonator electrodes have substantially no electromagnetic influence on the plurality of resonator electrodes, and the reactance is coupled. A configuration in which via holes are used to couple to the non-adjacent resonator electrodes to be used is adopted.

[0010]

[Effects and Effects] In short, in the multilayer dielectric filter according to the present invention, reactances such as a transmission line and a capacitive element for coupling non-adjacent resonators are built in the dielectric substrate. , Is provided. Therefore, due to the presence of the reactance, an attenuation pole appears in the attenuation region, and excellent filter characteristics are exhibited. The position of the attenuation pole can be adjusted by changing the equivalent electrical length of the reactance, the coupling coefficient, and the like. Further, since such reactance is electromagnetically shielded and hardly affected by the outside, there is an advantage that the filter characteristics can be effectively stabilized. Moreover, since the reactance is provided in the dielectric substrate so as to have a laminated structure with respect to the plurality of resonator electrodes, the filter area does not increase and the size can be advantageously reduced. Therefore, it is possible to satisfactorily respond to recent severe demands for miniaturization.

[0011] Further, the reactance is laminated at a separated position having substantially no electromagnetic influence on the plurality of resonator electrodes, and the reactance is applied to the non-adjacent resonator electrodes to be coupled. On the other hand, when coupling using a via hole, the reactance and
Since the electromagnetic effect between this and the resonator electrode not coupled thereto can be reduced, the filter characteristics can be more advantageously improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, representative embodiments of a laminated dielectric filter according to the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows a laminated structure of an example of a laminated dielectric filter according to the present invention, and FIG. 2 shows a cross section thereof. 2, the dielectric substrate 14 has a four-layer structure. Ground electrodes 16 are provided on the upper surface of the uppermost dielectric layer and on the lower surface of the lowermost dielectric layer, respectively. The resonator electrodes 18 are arranged in a comb line structure, and an input / output electrode 20 is provided on the upper surface side of the lowermost dielectric layer. Thereby, when the respective dielectric layers are laminated and fired to form an integrated substrate, as shown in FIG.
A triplate structure is realized, and resonators are configured in four stages corresponding to each resonator electrode 18 built in the dielectric substrate 14. Adjacent resonator electrodes 18 (the first and second stages, the second and third stages, and the third and fourth stages from the left end) are inductively coupled to each other.

In this dielectric filter 12,
A transmission line 26 extending in the direction in which the plurality of resonator electrodes 18 are provided, on the upper surface side of the second dielectric layer from the top among the four layers of the dielectric substrate 14, and in the middle of the transmission line 26. Is provided with a coupling electrode 22 composed of two capacitive elements 24, 24 provided in the first and second elements. Since both ends of the coupling electrode 22 are connected to the resonator electrodes 18 at both ends through via holes 28, the non-adjacent resonator electrodes 18 are connected to the plurality of resonator electrodes. 18 are coupled by a coupling electrode 22 (reactance) provided to have a laminated structure.

Therefore, an equivalent circuit of the dielectric filter 12 is as shown in FIG. The filter characteristics obtained in this case are as shown in FIG. 4. Since attenuation poles are generated in the attenuation regions on both sides of the pass band, the attenuation characteristics are extremely effectively improved, and the separation characteristics are greatly improved. You do it. The position of the attenuation pole can be adjusted to a desired position by changing the value of the capacitive element 24 of the coupling electrode 22, the length and width of the transmission line 26, and the like.

Since the coupling electrode 22 (reactance) is built in the dielectric substrate 14 in a laminated structure with respect to the plurality of resonator electrodes 18, a filter is advantageously used. In addition to being able to be miniaturized, the coupling electrode 22 is electromagnetically shielded to be less susceptible to external influences, and the filter characteristics can be stably exhibited.

Further, in the dielectric filter 12, the coupling electrode 22 (reactance) is laminated at a position where the plurality of resonator electrodes 18 do not substantially have an electromagnetic effect. Coupling electrode 2
2, the non-adjacent resonator electrode 1 to be coupled
8 and 18 are connected by via holes 28. Therefore, the electromagnetic effect between the coupling electrode 22 and the resonator electrode 18 that is not coupled to the coupling electrode 22 is effectively reduced, and the filter characteristics are more advantageously improved.

Next, FIGS. 5 and 6 show another embodiment of the laminated dielectric filter according to the present invention. In this dielectric filter 32, the dielectric substrate 34 has a five-layer structure, and ground electrodes 36 are provided on the upper surface of the uppermost dielectric layer and on the lower surface of the lowermost dielectric layer, respectively. And
Four resonator electrodes 38 are arranged in a comb line structure on the upper surface side of the fourth dielectric layer from the top, and input / output electrodes 40 are further provided on the upper surface side of the lowermost dielectric layer. ing.
Thus, when the respective dielectric layers are stacked and fired to form an integrated substrate, a triplate structure as shown in FIG. 6 is realized, and each resonator electrode 3 built in the dielectric substrate 34 is formed.
8, the resonator has four stages. In addition, adjacent resonator electrodes 38 (the first and second stages, the second and third stages, and the third and fourth stages from the left end).
Are connected to each other by inductive coupling.

In this dielectric filter 32,
A transmission line 46 extending in the direction in which the plurality of resonator electrodes 38 are provided is provided on the upper surface side of the second dielectric layer from the top among the five layers of the dielectric substrate 34. Also,
On the upper surface side of the third dielectric layer from the top, the transmission line 46
At the positions corresponding to both ends of the
Are provided, and the capacitor electrodes 44, 44 and both ends of the transmission line 46 are connected by via holes 48, 48. Then, the capacitor electrodes 44, 4
4 is a resonator electrode 38, 3 at both ends via a dielectric layer.
8 is to be combined. As a result, the non-adjacent resonator electrodes 38, 38
The plurality of resonator electrodes 38 are coupled by reactances (capacitor electrodes 44, transmission lines 46) provided in a laminated structure.

Therefore, the equivalent circuit of the dielectric filter 32 is as shown in FIG. 7. Also in this case, attenuation poles appear in the attenuation regions on both sides of the pass band (see FIG. 4), and excellent filter characteristics are obtained. Is obtained. The position of the attenuation pole can be adjusted to a desired position by changing the value of the capacitance formed by the capacitor electrode 44 and the length and width of the transmission line 46.

Then, such reactances (capacitor electrodes 44, transmission lines 46) are incorporated in the dielectric substrate 34 in a laminated structure with respect to the plurality of resonator electrodes 38. Therefore, the size of the filter is advantageously reduced, and the filter characteristics are stabilized. Further, the reactance is laminated at a separated position having substantially no electromagnetic influence on the plurality of resonator electrodes 38, while the non-adjacent resonator electrodes 38, 38 to be coupled are stacked. Since the coupling is performed using the via hole 48, the electromagnetic effect between the reactance and the resonator electrode 38 that is not coupled to the reactance is reduced, and the filter characteristics are advantageously improved.

FIGS. 8 and 9 show still another embodiment of the laminated dielectric filter according to the present invention. In this dielectric filter 52, the dielectric substrate 54 has a five-layer structure, and ground electrodes 56 are provided on the upper surface side of the uppermost dielectric layer and the lower surface side of the lowermost dielectric layer, respectively. In addition, five resonator electrodes 58 are arranged in a comb line structure on the upper surface side of the fourth dielectric layer from the top, and input / output electrodes are further provided on the upper surface side of the lowermost dielectric layer. 60 are provided. As a result, when the respective dielectric layers are stacked and fired to form an integrated substrate, a triplate structure as shown in FIG. 9 is realized, and the respective resonator electrodes 58 embedded in the dielectric substrate 54 are formed. , The resonator is configured in five stages.

On the upper surface side of the third dielectric layer from the top, five capacitor electrodes 70 are provided with the resonator electrode 5.
8, and each capacitor electrode 70 and the corresponding resonator electrode 58 are connected by a via hole 72. Thereby, the adjacent ones of the resonator electrodes 58 (the first and second stages from the left end,
The second and third stages, the third and fourth stages, and the fourth and fifth stages) are coupled by capacitive coupling.

In this dielectric filter 52,
A transmission line 66 extending in the direction in which the plurality of resonator electrodes 58 are provided, on the upper surface side of the second dielectric layer from the top among the five layers of the dielectric substrate 54, and in the middle of the transmission line 66. Is provided with a coupling electrode 62 composed of two capacitive elements 64, 64 arranged in the same manner. Then, both ends of the coupling electrode 62 are connected to those of both ends of the capacitor electrode 70 via holes 68, 68, respectively.
2, 72 are coupled to the resonator electrodes 58, 58 at both ends. Thereby, the resonator electrodes 58, 58 that are not adjacent to each other are formed by the plurality of resonator electrodes 5
8 provided in a laminated structure with respect to 8
It is connected at 2.

Therefore, the equivalent circuit of the dielectric filter 52 is as shown in FIG. 10. In this case, the characteristic as shown in FIG. 11 is obtained, and the attenuation pole is placed in the attenuation band on the low frequency side of the pass band. And the filter characteristics are effectively improved. The position of the attenuation pole can be adjusted to a desired position by changing the value of the capacitive element 64 of the coupling electrode 62 and the length and width of the transmission line 66.

Also in this dielectric filter 52, the coupling electrode 62 (reactance) is built in the dielectric substrate 54 in a laminated structure with respect to the plurality of resonator electrodes 58. Therefore, the size of the filter is advantageously reduced, and the filter characteristics are stabilized. Further, the coupling electrode 62 is laminated at a separated position having substantially no electromagnetic influence on the plurality of resonator electrodes 58, while the non-adjacent resonator electrodes 58, 58 to be coupled are laminated. Are connected using the via holes 68 and 72,
The coupling electrode 62 and the resonator electrode 5 not coupled thereto
8 is reduced, and the filter characteristics are advantageously improved.

Although some embodiments of the present invention have been described in detail above, it is needless to say that the present invention is not limited by the description of such embodiments. In addition, the present invention, in addition to the above embodiments, unless departing from the spirit of the present invention,
It should be understood that various changes, modifications, improvements, and the like can be made based on the knowledge of those skilled in the art.

For example, in the case of the laminated dielectric filters shown in FIGS. 8 and 9, an attenuation pole can be formed on the low frequency side.
If an inductance element such as a transmission line having a high impedance is formed instead of the capacitance element, it is possible to form an attenuation pole on the high frequency side.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a laminated structure of an example of a laminated dielectric filter according to the present invention.

FIG. 2 is an explanatory sectional view showing a section of the filter of FIG. 1;

FIG. 3 is an equivalent circuit of the filter of FIG.

FIG. 4 is a graph showing filter characteristics of the filter of FIG.

FIG. 5 is an explanatory diagram showing a laminated structure of another example of the laminated dielectric filter according to the present invention.

FIG. 6 is an explanatory sectional view showing a section of the filter of FIG. 5;

FIG. 7 is an equivalent circuit of the filter of FIG.

FIG. 8 is an explanatory view showing a laminated structure of still another example of the laminated dielectric filter according to the present invention.

9 is an explanatory cross-sectional view showing a cross section of the filter of FIG. 8;

FIG. 10 is an equivalent circuit of the filter of FIG.

FIG. 11 is a graph showing filter characteristics of the filter of FIG.

FIG. 12 is a plan view showing an example of a conventional dielectric filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Dielectric filter 14 Dielectric substrate 16 Earth electrode 18 Resonator electrode 20 I / O electrode 22 Coupling electrode 24 Capacitance element 26 Transmission line 28 Via hole 32 Dielectric filter 34 Dielectric substrate 36 Earth electrode 38 Resonator electrode 40 I / O Electrode 44 capacitor electrode 46 transmission line 48 via hole 52 dielectric filter 54 dielectric substrate 56 ground electrode 58 resonator electrode 60 input / output electrode 62 coupling electrode 64 capacitance element 66 transmission line 68 via hole 70 capacitor electrode 72 via hole

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-145803 (JP, A) JP-A-5-199011 (JP, A) JP-A-5-95202 (JP, A) JP-A-3-95803 212001 (JP, A) JP-A-61-258503 (JP, A) JP-A-2-145804 (JP, U) JP-A-5-88002 (JP, U) JP-A-58-16902 (JP, U) US Patent 4,418,324 (US, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01P 1/203 H01P 1/205

Claims (1)

(57) [Claims] 1. A dielectric filter having a triplate structure in which a plurality of resonator electrodes are built in a dielectric substrate, wherein the reactance of a transmission line, a capacitive element, and the like for coupling between non-adjacent resonator electrodes is reduced by the plurality of resonator electrodes. as the laminated structure with respect to resonator electrode, Ru allowed further internal
In addition, the reactance is reduced by the plurality of resonator electrodes.
Remote position that has substantially no electromagnetic effect on
And the reactance is coupled
Via holes for the non-adjacent resonator electrodes to be
A laminated dielectric filter, characterized in that the dielectric filter is bonded by using .