JPH0870203A - Filter device including dielectric resonator - Google Patents

Abstract

PURPOSE: To make the size of the filter small without deteriorating the Q by selecting a width or a diameter of a 2nd dielectric resonator in a direction orthogonal to an extended direction of a cylindrical dielectric throughhole smaller than the width or the diameter of a 1st dielectric resonator. CONSTITUTION: A 1st dielectric resonator 1 with a larger diameter 1 and 2nd and 3rd dielectric resonators 2, 3 with a smaller diameter are arranged on a multi-layered board 4 and terminal conductors 13 and outer conductors are fixed to terminal connection conductor layers 15-17 and a ground conductor layer. Since the dielectric resonator 1 of the larger diameter has a higher Q, it provides a band pass filter with a small insertion loss and the dielectric resonators 2, 3 of the small diameter are connected in series and used for a trap circuit. Through the constitution above, the Q of the dielectric resonator 1 is increased by the share of the diameter of the dielectric resonator 1 selected larger than the diameter of the 2nd and 3rd dielectric resonators 2, 3 and then the insertion loss is reduced. On the other hand, since the diameter of the 2nd and 3rd dielectric resonators 2, 3 is smaller than the diameter of the 1st dielectric resonator 1, the surface area of the multi-layered board 4 is reduced by the share.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a filter device including a dielectric resonator for use in a mobile telephone or the like.

[0002]

2. Description of the Related Art A dielectric filter device having a plurality of dielectric resonators arranged on an insulating substrate is used as a bandpass filter or a bandstop filter. FIG. 1 shows an example of a bandpass filter. In the signal transmission line between the input terminal T1 and the output terminal T2 of this filter, there are first, second, third and fourth capacitors C as coupling elements.
1, C2, C3 and C4 are connected in series. The first dielectric resonator 1 functioning as a bandpass filter is connected between the interconnection point of the capacitors C2 and C3 and the ground. The first and second series circuits composed of capacitors Ca and Cb for giving band stop filter characteristics (trap characteristics) and second and third dielectric resonators 2 and 3 are interconnection points of capacitors C1 and C2. And capacitors C3 and C4 are connected between the interconnection point and the ground. The second and third dielectric resonators 2 and 3 function as an inductance in a specific frequency range.

In the filter circuit of FIG. 1, the first dielectric resonator 1 is equivalent to a parallel resonance circuit of an inductance L and a capacitor C, and capacitors Ca, Cb and second and third dielectric resonators 2, The first and second series circuits composed of 3 and 3 are equivalent to series resonance circuits. The resonance frequencies of the two series resonance circuits are set to values slightly lower and higher than the center frequency f0 of the pass band as shown in FIG.
Therefore, the two series resonance circuits function as a trap circuit for improving the attenuation characteristic, that is, for making the rise and fall of the pass band steep.

[0004]

By the way, the diameters or widths of the three dielectric resonators 1, 2 and 3 in the conventional filter device are set to be the same. Therefore, when this outer diameter is set large in order to increase the Q of the first dielectric resonator 1, the second and third dielectric resonators 2 and 3 are formed.
The outer diameter of was also set large. Therefore, the second
When the third dielectric resonators 2 and 3 are not required to have a large Q, a dielectric resonator having a diameter larger than necessary is used, which hinders downsizing of the filter device. Now, the bandpass filter of FIG. 1 has been described.
A similar problem occurs in a bandstop filter that uses a plurality of dielectric resonators.

Therefore, an object of the present invention is to provide a filter device including a dielectric resonator that can be miniaturized.

[0006]

The present invention for achieving the above object provides a first dielectric resonator connected between a signal transmission line and a ground, and a first dielectric resonator between the signal transmission line and the ground. A series circuit of a capacitor and a second dielectric resonator connected to each other, and a coupling connected between the first dielectric resonator and the series circuit and connected in series to the signal transmission path. A filter device having an element;
The second dielectric resonator includes a cylindrical dielectric having one end surface, the other end surface, an outer peripheral surface, and a through hole extending from the one end surface toward the other end surface, and the second dielectric resonator is provided in the through hole. And a width or diameter in a direction orthogonal to a direction in which the through hole of the cylindrical dielectric of the second dielectric resonator extends, The present invention relates to a filter device having a width or diameter smaller than a width or a diameter of the first dielectric resonator in a direction orthogonal to a direction in which the through hole of the cylindrical dielectric extends. As described in claim 2, contrary to claim 1, the width or diameter of the dielectric of the first dielectric resonator is made smaller than the width or diameter of the dielectric of the second dielectric resonator. be able to. Further, as described in claim 3, a combination filter device of a reception bandpass filter and a transmission bandstop filter may be used. Further, in the multistage filter device according to the fourth aspect, the diameters or widths of the dielectrics of the first and second dielectric resonators can be different from each other.

[0007]

According to the first aspect of the present invention, the filter device can be miniaturized without lowering the Q of the first dielectric resonator functioning as a bandpass filter. That is, downsizing of the filter device is achieved by reducing the diameter or width of the second dielectric resonator forming the band stop filter or the trap circuit for removing the harmonic component or improving the rise or fall of the pass band. It According to the second aspect of the invention, the filter device can be downsized without lowering the Q of the band stop filter or the second dielectric resonator for adjusting the pass band. That is, the filter device can be downsized by the amount by which the diameter or width of the first dielectric resonator having the bandpass filter or the passband adjusting function is reduced. Also,
According to the third aspect of the invention, it is possible to improve the characteristics of the receiving bandpass filter or the transmitting bandstop filter and to reduce the size thereof. Further, according to the fourth aspect, it is possible to reduce the diameter or the width of the dielectric resonator for which a high Q is not required, and to reduce the size.

[0008]

First Embodiment Next, a bandpass filter device according to a first embodiment of the present invention will be described with reference to FIGS. In order to obtain the equivalent circuit of FIG. 1, the filter device 1 has first, second and third TEM mode coaxial dielectric resonators 1, 2, 3 and a multilayer substrate 4 as shown in FIG. Have and. As shown in FIG. 5, the first dielectric resonator 1 extends from a cylindrical dielectric body 5 made of a dielectric ceramic and a first end surface 6 of the dielectric body 5 to a second end surface 7 opposite thereto. The circular through hole 8 thus formed, the inner conductor 9 formed in the through hole 8, the outer conductor 11 formed on the outer peripheral surface 10 of the dielectric 5, and the inner conductor 9 and the outer conductor 11 are connected. So that the short-circuit conductor 12 formed on the second end surface 7 and the first end surface 6
And a terminal conductor 13 formed on a part of the outer peripheral surface 10 and connected to the inner conductor 9. Each conductor 9, 11, 12, 1
3 is formed by applying a conductive paste (for example, silver paste) and baking it.

The second and third dielectric resonators 2 and 3 are also formed in the same manner as the first dielectric resonator 1 except that the outer diameter dimensions are different. Therefore, in the second and third dielectric resonators 2 and 3 of FIGS. 3 and 4, substantially the same parts as those of the first dielectric resonator 1 are designated by the same reference numerals. The first, second and third dielectric resonators 1, 2 and 3 are slightly different from each other in the length of the dielectric 5 or the length of the outer conductor 11 in order to obtain different resonance frequencies.

The multilayer substrate 4 is made up of the dielectric resonators 1, 2,
All of the circuits other than No. 3 are configured by a known method, and include a dielectric layer 14, and terminal connecting conductor layers 15, 16, 17 and a ground conductor layer 18 formed on this surface as shown in FIG. , Two terminal conductor layers 19 and 20 and a ground conductor layer 21 formed on the back surface as shown in FIG.
Of the capacitor conductor layers 22a and 23b and other capacitor conductor layers not shown. In addition,
The capacitors C1 to C4, Ca and Cb shown in FIG.
Since the structure embedded in 4 is well known, detailed description thereof will be omitted.

The first, second and third dielectric resonators 1,
2 and 3 are juxtaposed on the multilayer substrate 4, and the respective terminal conductors 13 and the outer conductors 11 are fixed to the respective terminal connection conductor layers 15, 16, 17 and the ground conductor layer 18 with solder 22.

In this embodiment, Q increases as the diameter of the first dielectric resonator 1 functioning as a bandpass filter becomes larger than the diameters of the second and third dielectric resonators 2 and 3. , The insertion loss becomes small. On the other hand, the second and third
Since the dielectric resonators 2 and 3 are not the same diameter as the first dielectric resonator 1 but have a smaller diameter, the surface area of the multilayer substrate 4 can be reduced by this amount. The characteristics of the filter in FIG. 3 are substantially the same as those in FIG.

[0013]

[Second Embodiment] Next, a filter device according to a second embodiment will be described with reference to FIG. However, in FIG. 6, parts that are substantially the same as those in FIG. 3 are assigned the same reference numerals and explanations thereof are omitted. The filter device of FIG. 6 has the same configuration as that of FIG. 3 except that the diameters of the first to third dielectric resonators 1 to 3 are opposite to those of FIG. That is, in FIG. 6, the diameter of the dielectric 5 of the first dielectric resonator 1 for the bandpass filter is equal to that of the dielectric 5 of the second and third dielectric resonators 2 and 3 for the bandstop filter. It is formed smaller than the diameter.

Since the electrical connection of the first to third dielectric resonators 1 to 3 in FIG. 6 is the same as that in FIG. 1, the second and third dielectric resonators 2 and 3 and the capacitors are shown in FIG. The effect of improving the attenuation characteristics by the series circuit (trap circuit) of Ca and Cb becomes large. According to this embodiment, the diameter of the first dielectric resonator 1 is not increased even though the diameters of the second and third dielectric resonators 2 and 3 are increased to improve the damping characteristics. Therefore, miniaturization can be achieved.

[0015]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) Instead of the second and third dielectric resonators 2 and 3 in FIGS. 3 and 6, the one shown in FIG. 7 can be used. In the dielectric resonator of FIG. 7, the terminal conductor 13 and the inner conductor 9
And are separated by an end face 6, and the two are capacitively coupled via a dielectric 5. Therefore, this capacitance is used as the capacitor C in FIG.
It can be used as a and Cb. (2) It is possible to provide two dielectric resonators that function as a bandpass filter and one dielectric resonator that functions as a bandstop filter (trap circuit). Further, the number of dielectric resonators can be changed arbitrarily. (3) The present invention can be applied to a duplexer (transmission / reception filter). FIG. 8 shows an example of this, in which small-diameter dielectric resonators 1a and 1b for forming a receiving bandpass filter and a large-diameter dielectric resonance for forming a transmitting bandstop filter are shown. The vessels 2a, 2b and 2c are arranged alternately. Small-diameter dielectric resonators 1a, 1
b are mutually connected via a coupling capacitor, and the large-diameter dielectric resonators 2a, 2b, 2c are the capacitors Ca of FIG.
Similar to the series circuit of Cb and the dielectric resonators 2 and 3, they are connected in series to a capacitor, and the series circuits are coupled to each other by a strip line or an inductance element. Therefore, the characteristics of the filter on the transmission side are improved. The diameters of the dielectric resonators 1a and 1b are set to the dielectric resonator 2a,
It can also be made larger than the diameter of 2b and 2c. (4) The dielectric resonators 1, 2 and 3 are formed in a prismatic shape having a quadrangular cross section, and the first dielectric resonator 1 and the second and third dielectric resonators 2 and 3 are provided in the through hole 8. You may comprise so that the width | variety in the orthogonal direction may differ. (5) Capacitors C1 to C4 and / or capacitor C
Alternatively, a and Cb may be arranged as individual components on the substrate 4. (6) Instead of the terminal conductor 13, an independent terminal member can be connected to the inner conductor 9. (7) The half-wave coaxial dielectric resonator can be obtained by omitting the short-circuit conductor 12. (8) In the multistage bandpass filter or bandstop filter, at least the diameter or width of the dielectrics of the first and second dielectric resonators can be set to different values. For example, in FIG. 8, the dielectrics of the two dielectric resonators 1a and 1b forming the bandpass filter can have different diameters.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram showing a bandpass filter device.

FIG. 2 is a filter characteristic diagram of the filter device of FIG.

FIG. 3 is a plan view showing a filter device according to a first embodiment of the present invention.

FIG. 4 is a front view of the filter device of FIG.

5 is a cross-sectional view taken along the line AA of FIG.

FIG. 6 is a plan view of a filter device according to a second embodiment.

FIG. 7 is a sectional view showing a composite element of a dielectric resonator and a capacitor of a modified example.

FIG. 8 is a plan view showing a part of a duplexer of a modified example.

[Explanation of symbols]

 1,2,3 Dielectric resonator 4 Multilayer substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Shimizu 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. (72) Inventor Satoshi Kazama 6-16-20 Ueno, Taito-ku, Tokyo Sun Inductor Co., Ltd. (72) Inventor Tatsuya Imaizumi 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Indenki Co., Ltd.

Claims (4)

[Claims] 1. A first dielectric resonator connected between a signal transmission line and a ground, a capacitor connected between the signal transmission line and a ground, and a second dielectric resonator. A filter device having a series circuit and a coupling element connected between the first dielectric resonator and the series circuit and connected in series to the signal transmission line, wherein the first and second The dielectric resonator includes a cylindrical dielectric having one end face, the other end face, an outer peripheral surface, and a through hole extending from the one end face toward the other end face, and an inner conductor provided in the through hole. And an outer conductor provided on the outer peripheral surface, and the width or diameter in the direction orthogonal to the extending direction of the through hole of the cylindrical dielectric of the second dielectric resonator is the first Of the through hole of the cylindrical dielectric body of the dielectric resonator of Filter and wherein the less than the width or diameter in the direction perpendicular to. 2. A first dielectric resonator connected between a signal transmission line and a ground, a capacitor connected between the signal transmission line and a ground, and a second dielectric resonator. A filter device having a series circuit and a coupling element connected between the first dielectric resonator and the series circuit and connected in series to the signal transmission line, wherein the first and second The dielectric resonator includes a cylindrical dielectric having one end face, the other end face, an outer peripheral surface, and a through hole extending from the one end face toward the other end face, and an inner conductor provided in the through hole. And an outer conductor provided on the outer peripheral surface, and a width or a diameter in a direction orthogonal to a direction in which the through hole of the cylindrical dielectric of the first dielectric resonator extends is the second. Of the through hole of the cylindrical dielectric body of the dielectric resonator of Filter and wherein the less than the width or diameter in the direction perpendicular to. 3. A first dielectric resonator for forming a receiving bandpass filter and a second dielectric resonator for forming a transmitting bandstop filter are arranged on a common substrate. In the filter device, the diameters or widths of the dielectrics of the first and second dielectric resonators are different from each other. 4. At least a first and a second on a common substrate.
In the multi-stage filter device having the dielectric resonators, the diameter or width of the dielectrics of the first and second dielectric resonators are different from each other.