JP2001339204A - Compact dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a very compact dielectric filter which can be mounted on portable communication equipment. SOLUTION: This dielectric filter is constituted by dividing a dielectric filter having resonators formed integrally with a conventional dielectric filter block in a rectangular solid shape, into two in the center of a surface H in the direction E and has a through hole 18, input/output electrodes 13 and 14, and an earth electrode 15. A flank 111 is open surface and the earth electrode is not formed. The original dielectric filter before being divided has substantially the same frequency characteristics and then this dielectric filter of half size can have the same filter characteristics with a conventional example. The input/output electrodes 13 and 14 are arranged at the center parts of the short sides of the dielectric block and formed symmetrically on both the main surfaces to eliminate the need to confirm the right and left, and top and reverse of the filter when the filter is mounted on a circuit board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized dielectric filter, and more particularly, to a surface-mounted dielectric filter using a λ / 4 resonator.

[0002]

2. Description of the Related Art A waveguide filter, which is one of dielectric filters, has a relatively high Q value even in a high frequency band because air is used as a dielectric, and therefore, is widely used as a high frequency filter. I have. However, such a waveguide filter becomes large in size when air having a dielectric constant of 1 is used because the wavelength in the waveguide decreases in proportion to the power of the dielectric constant. It cannot be used for a wireless device terminal in a very low frequency band.

In order to solve such a problem, in the prior art, a dielectric filter in which a dielectric material having a high dielectric constant of about 10 to 100 is filled in a waveguide has been developed. As a dielectric material filled in the waveguide, for example, when a material having a dielectric constant of 92 is used and two λ / 2 resonators are used to form a band-pass filter having a center frequency of 5.8 GHz, The size of the filter is about 8.4x
4.2 mm, which is still large as a filter to be incorporated in a wireless device terminal, and is unsuitable as a filter to be incorporated in the terminal.

A dielectric waveguide filter using a λ / 4 resonator having an open surface has already been proposed. In this filter, since the λ / 4 resonator is used, the size of the filter is reduced to about 比 べ as compared with the case where the λ / 2 resonator is used. It is.

FIG. 11 shows a configuration of a bandpass filter using a λ / 4 resonator having an open surface disclosed in Japanese Patent Application Laid-Open No. 11-274815, which is disposed on the lower surface (back surface) side, that is, on the circuit board. It is shown as a perspective view from the side. The filter includes island-shaped input / output electrodes (external electrodes) 1 on opposite short sides of the surface of a rectangular parallelepiped dielectric block 11.
3 and 14 are formed, and a ground electrode 15 is formed separately from these electrodes 13 and 14. Dielectric block 11
A through-hole 18 is formed at the center of the hole, and a ground electrode 15 is also formed on the surface of the through-hole 18. The ground electrode 15 is formed not only on the surface on which the input / output electrodes 13 and 14 are formed, but also on the entire back surface of the dielectric block 11 and on both long side surfaces.

In the filter having such a configuration, the through hole 18 forms an inductive window, and therefore, the dielectric block 11 has a structure in which two λ / 4 resonators are inductively coupled by the through hole 18. A band-pass filter having a center frequency of 5.8 GHz as shown in FIG. Note that, instead of providing the through hole 18 at the center of the dielectric block 11 as shown in FIG. 11, as shown in FIG. It is described in the above-mentioned publication that the dielectric window is formed even when the two cut-through holes 18 ′ and 18 ″ are provided.

When a bandpass filter having a center frequency of 5.8 GHz is formed by the filters having the structures shown in FIGS. 11 and 12, the size of the bandpass filter is about 4.2 m.
This is an m-square, which is half that in the case where a λ / 2 resonator is used. However, even if the size is about 4.2 mm square, it is not enough in view of recent progress in miniaturization of electronic devices and electronic components. Therefore, further miniaturization of a band-pass filter made of a dielectric filter is required. Is eagerly awaited. The present invention has been made in view of such problems of the conventional example, and an object of the present invention is to provide a very small dielectric filter that can be mounted on a portable communication device.

[0008]

In order to achieve the above object, a dielectric filter according to the present invention in which a plurality of resonators are integrally formed in a rectangular parallelepiped dielectric block is provided. A pair of island-shaped input / output electrodes formed on at least one main surface of the dielectric block so as to be in contact with the two short side surfaces of the dielectric block, and one side surface and both of the long side of the dielectric block A ground electrode formed on almost the entire main surface and electrically insulated from the input / output electrodes, and a short-circuit surface provided in a part of the short side direction parallel to the short side of the dielectric block. It is characterized by.

In the dielectric filter having such a basic configuration, the input / output electrode is provided with an extended portion that is also extended on the short side surface of the dielectric block, so that the electrical connection to the circuit board is achieved. And the reliability of the mechanical connection is improved. Further, by forming the input / output electrodes at the center of the short side of the dielectric block, it is not necessary to check the left and right of the dielectric filter during mounting. In addition to this, the input / output electrodes are formed symmetrically on both main surfaces of the dielectric block, and connected by the extension formed on the short side surface,
It is not necessary to check the left, right, up and down of the dielectric block during mounting.

The short-circuit surface is formed by forming a conductive layer connected to an earth electrode on the surface of a through hole formed in a slit shape from the long side at the center of the dielectric block in the long side direction, Alternatively, it is preferable that a conductor layer connected to a ground electrode is formed on the surface of a plurality of circular through holes provided in parallel with the short side at the center of the long side.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION λ /
It is known that when four resonators are divided into two along the E plane at the center of the H plane, that is, along the longitudinal direction, two resonators having substantially the same frequency are obtained. Therefore, the present inventor has proposed the two λs shown in FIG. 11 and FIG.
Even in a band-pass filter structure in which a dielectric window for coupling / 4 resonators is formed, two similar filter frequency characteristics can be obtained when the center of the H plane is divided along the E plane. I expected it.

Based on such a prediction, in the conventional filter structure shown in FIG. 11, the center of the H plane is divided into two along the E plane, and the frequency characteristics of the filter are simulated by three-dimensional electromagnetic field analysis. Determined by As a result, only a gradual filter waveform having a wider pass band than the original waveform could be obtained only by dividing into two. Therefore, as a result of repeated trial and error, the thickness of the dielectric material, the amount of coupling between the input / output electrode and the ground electrode, the amount of coupling between the resonators, and the like are adjusted to obtain a filter having substantially the same filter characteristics as the filter structure of FIG. It was found that characteristics were obtained. In other words, it was found that almost the same frequency characteristics were obtained even though the size was １ ／ compared to the original filter structure. The present invention has been realized based on the result of an experiment in which such trial and error has been repeated, and has a steep frequency characteristic similar to the original filter structure, and the size thereof is equal to that of the original filter structure. A 1/2 dielectric filter was obtained. However, the above-mentioned small dielectric filter has practically two problems.

[0013] One of the problems is that due to the division,
That is, the input / output electrodes are formed at the corners of the opposite sides of the filter. Since the input / output electrodes are not point-symmetrical when viewed from the center of the filter structure, when mounting the filter on the board, it is necessary to check whether the direction of the filter has been rotated by 180 degrees. Therefore, since extra confirmation is required at the time of mounting, an increase in the manufacturing cost of the communication device on which the filter is mounted cannot be avoided. Another problem is that the area of the input / output electrodes is reduced to half that of the conventional example, which may cause problems in surface mounting strength and electrical connection characteristics.

As a result of trial and error, the present inventor has found that the size and position of the input / output electrodes are not dominant in determining the frequency characteristics of the filter. It has been found that even if it is arranged in another part, it hardly affects the desired frequency characteristic. Then, based on the result, the input / output electrodes are
The filter is arranged at the center or the end of the short side so as to be point-symmetric with respect to the center of the filter structure, thereby eliminating the need to check the orientation of the filter during mounting.

Further, it has been found that even if the input / output electrodes are formed not only on the back surface of the dielectric block but also on the back surface and the side surface, the frequency characteristics of the filter are hardly affected. As a result, the bonding material such as solder at the time of surface mounting is connected not only to the back surface portion of the dielectric block but also to the electrode formed on the side surface portion. The characteristics are improved. Further, even if symmetrical input / output electrodes are arranged on both main surfaces of the dielectric block, that is, the back surface and the front surface, and these are connected via the electrodes on the side surfaces, the frequency characteristics of the filter are hardly affected. That was found. By arranging the input / output electrodes in this manner, there is no need to distinguish between the front and back surfaces of the filter, and it is not necessary to check not only the orientation of the filter but also the front and back surfaces during mounting.

The specific configurations of the first to sixth embodiments based on the above results will be described below. Embodiment 1 FIG. 1 shows a dielectric filter according to an embodiment (Embodiment 1) of the present invention.
1 is divided into two along the direction E at the center of the H-plane, and includes a through-hole 18, input / output electrodes 13, 14, and a ground electrode 15. Side 11
Reference numeral 1 denotes an open surface, that is, no ground electrode is formed. The frequency characteristics in the case where a dielectric material having a dielectric constant of 92 is used and its size is formed to 4.2 mm × 2.1 mm × 0.6 mm (long side × short side × thickness) are as shown in FIG. Was. On the other hand, the filter of the conventional example shown in FIG.
When formed to 4.2 mm x 4.2 mm x 1.0 mm,
The frequency characteristics as described above and shown in FIG. 13 were obtained. Since the characteristics of FIG. 13 and the characteristics of FIG. 2 are almost the same, it turns out that, in the end, almost the same filter characteristics can be realized with half the size.

Embodiment 2 FIG. 3 is a plan view of a back surface (lower surface) of a dielectric filter according to another embodiment (embodiment 2) of the present invention. In the second embodiment, as compared with the first embodiment, the input / output electrodes 13, 1
The difference is that the position of No. 4 is located at the center.
Example 2 was formed in the same size with the same dielectric material as in Example 1, and its frequency characteristics were simulated. The results shown in FIG. 4 were obtained. The characteristics of FIG. 4 are the same as the result of the first embodiment, that is, almost the same as the frequency characteristics shown in FIG. 2, but by arranging the input / output electrodes at the center of the short side as in the second embodiment, When the filter is mounted on the circuit board, the filter can be mounted even if the filter is rotated by 180 degrees, and the confirmation at the time of mounting is unnecessary.

Embodiment 3 FIG. 5 is a perspective view of a dielectric filter according to another embodiment (embodiment 3) of the present invention viewed from the surface (upper surface). The third embodiment is different from the second embodiment shown in FIG. 3 in that the input / output electrode 13 is provided at the center of the opposite short side of the back surface of the dielectric block.
In addition to the arrangement of (and 14), the input / output electrode extension 112 connected to these electrodes is also formed on the side surface thereof. Reference numeral 113 denotes the input / output electrode extension 1
Reference numeral 12 denotes a cutout for preventing connection with the ground electrode 15 on the surface of the dielectric block. The size and position of the combined body of the input / output electrode and the input / output electrode extension are symmetrically formed on the dielectric block. The filter of Example 3 was formed with the same dielectric constant and size as those of Example 2, and the frequency characteristics were simulated. The result was as shown in FIG. The characteristics of FIG. 6 are almost the same as the characteristics of FIG. 4, and it is apparent that connecting the input / output electrode extension to the input / output electrode on the back side as in the third embodiment does not affect the frequency characteristics. It is. Also, by providing the input / output electrode extension,
When connecting to the circuit board, the connection solder can be connected not only to the input / output electrodes on the back but also to the extension of the input / output electrodes, improving the electrical connection characteristics and mechanical connection strength, thereby increasing reliability. I do.

Embodiment 4 FIG. 7 is a perspective view of a dielectric filter according to still another embodiment (embodiment 4) of the present invention as viewed from the surface. The difference from the third embodiment shown in FIG. 5 is that input / output electrodes are also formed continuously on the surface of the dielectric block. That is, the input / output electrode 13 (and 14) formed on the back surface of the dielectric block and the input / output electrode extension 112
The surface input / output electrode 114 is provided so as to be connected to the connecting member of the above. The front input / output electrode 114 has the same shape and symmetry as the rear input / output electrode 13 (and 14). The hollowed portion 113 is provided with the ground electrode 1 as in the case of the third embodiment.
5 and the surface input / output electrode 114. The shape is different from that of the third embodiment.

The filter of Example 4 was formed with the same dielectric constant and size as those of Example 2, and the frequency characteristics were simulated. The result is shown in FIG. The characteristics in FIG. 8 are almost the same as the characteristics in FIG. 4. Even when the input / output electrodes are formed as electrodes extending from the back surface to the front surface through the side surface as in the fourth embodiment, the frequency characteristics are not affected. Clearly not. In the fourth embodiment, since the front surface input / output electrodes are provided and the electrodes are formed symmetrically with the input / output electrodes on the back surface, the input / output electrodes are formed symmetrically on the front and back surfaces of the dielectric block. . As a result, the same characteristics can be obtained regardless of which main surface is mounted on the circuit board. Therefore, the work of recognizing the front and back sides at the time of mounting can be eliminated, and the mounting cost can be reduced. The operation and effect of providing the input / output electrode extension are as described above.

Embodiment 5 FIG. 9 shows a dielectric filter according to still another embodiment (embodiment 5) of the present invention. In the above-described first to fourth embodiments, the dielectric filter of the conventional example shown in FIG. 11 is divided into two along the longitudinal direction.
This is an example in which the conventional dielectric filter shown in FIG. 2 is divided into two along the longitudinal direction. In the fifth embodiment, the ground electrode is not formed on the side surface of the dielectric block on which the input / output electrodes 13 and 14 are provided. In Example 5, the same simulation result of the frequency characteristics as in Examples 1 to 4 was obtained.

Embodiment 6 FIG. 10 shows a dielectric filter according to still another embodiment (Embodiment 6) of the present invention. In the sixth embodiment, a plurality of circular through holes 18 ′ ″ are employed instead of the cut-type through holes 18 of the fifth embodiment. In the sixth embodiment, a simulation result of frequency characteristics similar to those of the first to fifth embodiments was obtained. In addition, it is also possible to change the cut-type through holes 18 of Examples 1 to 4 to a plurality of circular through holes, and in this case, similar simulation results of frequency characteristics were obtained.

The slit-shaped through-holes 18 and 18 'and the circular through-hole 18''' form a short-circuit surface of a 1 / 4.lambda. Resonator. It can be formed by forming through holes or slits in a dielectric sheet, embedding conductors, and aligning and laminating. Further, when the dielectric block is formed of resin or the like, it is also possible to form the short-circuit surface with metal by inserting metal in advance and performing injection molding. Further, when two short-circuit surfaces are formed, 1 /
A filter in which the 4λ resonator, the λλ resonator, and the 結合 λ resonator are coupled in this order may be configured.

As described above, according to the dielectric filter of the present invention, a filter having the same performance as that of the conventional example can be formed in half the size. In addition, since the input / output electrodes are provided at the center of the short side, the left and right of the dielectric filter are not required. And electrical connection is also ensured. Furthermore, by providing input / output electrodes symmetrically and symmetrically on both sides,
The dielectric filter is substantially bilaterally symmetric and symmetrical. Therefore, the operation of mounting the dielectric filter on the circuit board can be simplified.

[Brief description of the drawings]

FIG. 1 is a plan view and a perspective view showing a configuration of a dielectric filter according to a first embodiment of the present invention.

FIG. 2 is a graph showing a simulation result of frequency characteristics of the first embodiment shown in FIG.

FIG. 3 is a plan view showing a configuration of a dielectric filter according to a second embodiment of the present invention.

FIG. 4 is a graph showing a simulation result of a frequency characteristic of the second embodiment shown in FIG. 3;

FIG. 5 is a perspective view illustrating a configuration of a dielectric filter according to a third embodiment of the present invention.

FIG. 6 is a graph showing a simulation result of a frequency characteristic of the third embodiment shown in FIG.

FIG. 7 is a perspective view showing a configuration of a dielectric filter according to a fourth embodiment of the present invention.

8 is a graph showing a simulation result of a frequency characteristic of the fourth embodiment shown in FIG.

FIG. 9 is a perspective view illustrating a configuration of a dielectric filter according to a fifth embodiment of the present invention.

FIG. 10 is a plan view showing a configuration of a dielectric filter according to a sixth embodiment of the present invention.

FIG. 11 is a perspective view showing a configuration of a conventional dielectric filter.

FIG. 12 is a perspective view showing another configuration of a conventional dielectric filter.

13 is a graph showing a simulation result of a frequency characteristic of the conventional dielectric filter shown in FIG.

Claims (7)

[Claims] 1. A dielectric filter in which a plurality of resonators are integrally formed on a rectangular parallelepiped dielectric block, wherein two short side surfaces of the dielectric block are provided on at least one main surface of the dielectric block. And a pair of island-shaped input / output electrodes formed so as to be in contact with each other, and are formed on one of the long sides of the dielectric block and almost on both main surfaces, and are electrically insulated from the input / output electrodes. A dielectric filter, comprising: a ground electrode; and a short-circuit surface provided in a part of the short side direction in parallel with the short side of the dielectric block. 2. The dielectric filter according to claim 1, wherein the input / output electrodes are provided with extensions that extend also on the side surfaces on the short sides of the dielectric block. 3. The dielectric filter according to claim 1, wherein the input / output electrode is formed at the center of the short side of the dielectric block. 4. The dielectric filter according to claim 2, wherein the input / output electrodes are formed symmetrically on both main surfaces of the dielectric block, and are connected by an extension formed on the side surface on the short side. A dielectric filter characterized by being performed. 5. The dielectric filter according to claim 1, wherein the short-circuit surface is formed at a central portion in a long side direction of the dielectric block and parallel to the short side. Dielectric filter. 6. The dielectric filter according to claim 1, wherein the short-circuit surface includes a conductive layer connected to a ground electrode on a surface of a through hole formed in a slit shape from a long side of the dielectric block. A dielectric filter characterized by being formed and configured. 7. The dielectric filter according to claim 1, wherein the short-circuit surface is connected to a ground electrode on a surface of a plurality of circular through holes provided in parallel with a short side of the dielectric block. A dielectric filter, comprising a conductive layer formed thereon.