JPH10261907A - Manufacture of dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and securely provide a dielectric filter having attenuation quantity by molding a dielectric block where a groove for connecting an opening face with the other face is formed on a specified face to which the opening face of a cavity forming a resonance circuit faces and forming conductors on the whole face of the dielectric block and forming a line constituted of the conductor for the inner face of the groove by exposing dielectrics on both sides of the groove. SOLUTION: A ceramic material or a dielectric material is injected and molded and the conductor is attached to the surface of the dielectric block 1. The conductor attached on the front face (a) of the dielectric block 1 and the conductors attached to the upper surfaces of projection parts 6A and 6B are removed. The unnecessary conductors are eliminated by a grind stone of a surface grinding machine. The internal conductor, the external conductor 8, input/output electrodes and a shorting part connection conductor are formed on the surface of the dielectric block 1. Furthermore, the front face (a) is ground and therefore a part of the shorting part connection conductor attached to the respective sides of the groove 5B is removed. Then, the surface conductor in the front (a) is removed by grinding and the depth (h) of a setting value is obtained so as to form the dielectric filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a dielectric filter suitable for use in a wireless communication system that handles signals in the gigahertz (GHz) band.

[0002]

2. Description of the Related Art Hitherto, a dielectric filter has been manufactured by forming a conductor on the entire surface of a fired dielectric block by plating or the like. When a band-pass filter is to be manufactured by such a manufacturing method, for example, a band-pass filter is manufactured by attaching a conductor to the entire surface of a dielectric block in which a cavity is formed. Such a dielectric filter has a moderate attenuation characteristic.

[0003]

In the dielectric filter formed by attaching a conductor to the entire surface of the dielectric block as described above, a dielectric filter having a sufficient attenuation could not be constructed. Applicant filed Japanese Patent Application No. 8-120
No. 252 proposes a dielectric filter having an attenuation pole in transfer characteristics. This dielectric filter secures the attenuation by giving the transmission characteristic an attenuation pole. This time, a method for manufacturing a dielectric filter having an attenuation pole with such transfer characteristics has been developed, and the present application is filed here.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method of manufacturing a dielectric filter capable of easily and reliably securing an attenuation without increasing the size. The purpose is.

[0005]

In order to achieve the above-mentioned object, as a means for achieving the above object, a dielectric having a groove connecting the opening end and another surface is formed on a specific surface facing an opening end of a cavity forming a resonance line. Means for forming a body block, forming a conductor on the entire surface of the dielectric block, exposing the dielectric surface on both sides of the groove, and shaving the specific surface so as to form a line made of a conductor on the inner surface of the groove. Is done. By employing such means, a dielectric filter having an attenuation pole in the transfer characteristic of the dielectric filter can be manufactured. Further, in the above means, when the specific surface is cut, a means for adjusting the cut depth so that the frequency of the attenuation pole generated in the transfer characteristic of the dielectric filter becomes a desired frequency is adopted. As a result, the variation in the frequency of the attenuation pole caused by the variation in the dielectric constant of the dielectric material as the raw material of the dielectric block or the variation in the shape of the dielectric block is corrected. Further, the desired frequency is 0.4 GHz to 10 GHz.
Means of being set to GHz is adopted.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a dielectric filter according to the present invention will be described below with reference to FIGS.

FIG. 1 is a perspective view of a dielectric filter according to the present embodiment. In this figure, reference numeral 1 denotes a rectangular parallelepiped dielectric block, for example, Ba-Ti-Nd.
It is formed from a ceramic material of a relative (dielectric constant εr = 90) or a dielectric material such as a CaTiO ₃ (dielectric constant of εr = 45). On the front surface a (specific surface) of the dielectric block 1, cavities 2A and 2B having a rectangular parallelepiped shape are formed so as to be parallel to each other.

Communication holes 4A and 4B are provided between the side surfaces 3A and 3B of the dielectric block 1 and the cavities 2A and 2B, and between the side surfaces 3A and 3B and the cavities 2A and 2B on the front surface a. And grooves 5A and 5B having a U-shaped cross section and a constant width and a constant depth, respectively.

Further, a bottom surface b is provided on each of the side surfaces 3A and 3B.
Over the communication holes 4A, 4B,
6B are respectively formed. Here, each cavity 2A,
2B and the back surface c of the dielectric block 1, that is, the depth from the front surface a in each of the cavities 2A and 2B is
A desired size is set according to the resonance frequency of the λλ (wavelength) cavity resonator formed by A and 2B.

With respect to the dielectric block 1 having such a shape, a conductor such as copper (Cu) or silver (Ag) is adhered to the front surface a and the surface portions other than the upper surfaces of the projections 6A and 6B. I have. Here, the conductors on the inner surfaces of the cavities 2A and 2B constitute inner conductors 7A and 7B, and the conductors attached to the side surfaces 3A and 3B, the bottom surface b and the back surface c, and the upper surface d constitute the outer conductor 8 and the side surface 3A , 3B and the bottom surface b of the conductor surrounded by the convex portions 6A, 6B constitute input / output electrodes 9A, 9B, and the conductors on the inner surfaces of the communication holes 4A, 4B are connection conductors 10A,
10B. The conductors attached to the surfaces of the grooves 5A and 5B constitute the short-circuit connection conductors 11A and 11B.

FIG. 2 is an enlarged view of a cross section taken along line AA 'in FIG. As shown in FIG. 2B, in the groove 5B, the inner conductor 7B of the cavity 2B and the outer surface of the dielectric block 1 are formed by the conductor attached to the bottom surface and the side surface extending over the depth h2. A short-circuit connection conductor 11B for electrically connecting the outer conductor 8 is formed. Also in the groove 5A, the short-circuit portion connection conductor 11A is formed similarly to the groove 5B. The short-circuit portion connection conductor 11A and the short-circuit portion connection conductor 11B are arranged on the front surface a such that their electromagnetic coupling is loosely coupled.

FIG. 3 is an equivalent circuit of the dielectric filter thus configured. In this dielectric filter, the outer conductor 8 is electrically grounded, and one of the input / output electrodes 9A and 9B is connected to an external circuit as an input terminal 20 and the other as an output terminal 21. In this figure, reference numerals 22A and 22B denote line impedances (Z2) formed by the inner conductors 7A and 7B of the cavities 2A and 2B, and 23A and 23B are formed by the inner conductors 7A and 7B and the outer conductor 8, respectively. 24A, 24A
B is a line impedance (Z3) formed by the short-circuit connection conductors 11A and 11B.

As shown in FIG. 4, this dielectric filter has the transfer characteristics of a band-pass filter. In the transfer characteristics, the attenuation pole q1 is added to the frequency ft1 defined by the value Z3 of the line impedances 24A and 24B. Having.

Next, a method of manufacturing such a dielectric filter will be described. First, for example, a Ba-Ti-Nd-based (dielectric constant εr = 90) ceramic material or C
A dielectric material such as aTiO ₃ (dielectric constant εr = 45)
It is molded into the shape of the dielectric block 1 by a molding technique of injection molding. The thus formed dielectric block 1 is fired in a furnace to form a sintered body (ceramics), and the final dielectric block 1 is formed.

Subsequently, a conductor is attached to the surface of the dielectric block 1 formed into a sintered body as described above. For example, when the conductor is attached by using the electroless plating technique, copper (Cu) is used as the conductor. When the conductor is attached by baking a conductive paste, silver (Ag) is used as the conductor.

The unnecessary conductors, that is, the conductors 12 attached to the front surface a of the dielectric block 1 as shown in FIG.
In addition, the conductor attached to the upper surfaces of the protrusions 6A and 6B is removed. In this case, the unnecessary conductor is removed by being removed by a rotating grindstone such as a surface grinder. By this step, the inner conductors 7A and 7B, the outer conductor 8, the input / output electrodes 9A and 9B, the connection conductors 10A and 10B, and the short-circuit portion connection conductors 11A and 11B are formed on the surface of the electric block 1.

Furthermore, the front surface a
By grinding, a part of the short-circuit portion connection conductors 11A and 11B attached to each side surface of the grooves 5A and 5B is removed. That is, in this grinding step, the dimension in the depth direction of the grooves 5A and 5B before grinding is h1 as shown in FIG. 2A, and the dimension h1 is such that the conductor 12 on the surface of the front surface a is removed by grinding. And h2 (h2 <h1) by further grinding. For example, the dimension h2 is set according to the deviation from the standard relative permittivity (design value) of the dielectric material and the deviation from the standard shape (design value) of the dielectric block 1.

When the line impedance Z3 of the short-circuit connection conductor 11A (11B) increases, the frequency ft1 of the attenuation pole q1 having a phase of 90 degrees at a frequency at which the magnetic field intensity and the electric field intensity become equal shifts to a lower frequency. On the other hand, when the line impedance Z3 of the short-circuit connection conductor 11A (11B) decreases, the frequency ft1 of the attenuation pole q1 having a phase of 90 ° at a frequency at which the magnetic field intensity and the electric field intensity become equal shifts to a higher frequency. In the present embodiment, the dimension h2 is set by utilizing this fact.

That is, the dimension h2 and the frequency f of the attenuation pole q1
The relationship with t1 is obtained in advance by experiment or simulation. In this step, as described above, when the injection mold and the lot of the dielectric material change, the dimensions of the first few dielectric filters (samples) manufactured through the above-described steps are changed. The front surface a is ground so that h2 becomes the dimension h0, which is a design value. At this time, the frequency fa and the attenuation of the attenuation pole q1 of the sample are measured. Then, the dimension h2 in the lot is determined based on the deviation between the frequency fa and the design value frequency ft1 and the result of the experiment or simulation.

For example, in the case of (fa = ft1), the design dimension h0 is set to the dimension h2 of the lot, and in the case of (fa <ft1), the line impedance Z3 needs to be increased. Based on this, the dimension h2 of the lot is set to a value smaller than the design dimension h0, and if (fa> ft1), the line impedance Z3
Therefore, the dimension h2 of the lot is set to a value larger than the design dimension h0. The subsequent dimension h2 for the dielectric filter is a value determined by the above-described sample.

As described above, the transfer characteristic of the dielectric filter whose front surface a is ground and the frequency of the attenuation pole is adjusted is extracted and measured, and is compared with the product standard. Then, of the dielectric filters manufactured in this way, only those that satisfy the above product standard are shipped as products.

In the above embodiment, each side surface 3 of the dielectric block is separated from each cavity 2A, 2B on the front surface a.
Although the configuration in which the grooves 5A and 5B are provided toward A and 3B to form the short-circuit portion connection conductors 11A and 11B has been described, the present invention is not limited to this. That is, the short-circuit connection conductors 11A and 11B are arranged so that the short-circuit connection conductors 11A and 11B are electromagnetically loosely coupled, for example, separated from each other or with an electromagnetic shield member interposed therebetween. Then, another configuration may be used. For example, it is conceivable that the short-circuit connection conductor 11A is provided from the cavity 2A to the bottom surface b, and the short-circuit connection conductor 11B is provided from the cavity 2B to the top surface d.

In the above embodiment, the manufacturing method for adjusting the frequency of the attenuation pole by grinding the entire front surface a has been described. However, the short-circuit connection conductors 11A and 11B only on the respective side surfaces of the grooves 5A and 5B are described. It is also possible to remove some. In this case, since the grooves 5A and 5B have a U-shaped cross section with respect to the front surface a, the short-circuit portion connection conductors 11A and 11B on the side surfaces 5A1 and 5B1 are ground by a grindstone corresponding to the width of the grooves 5A and 5B. It is possible.

[0024]

As described above, according to the method of manufacturing a dielectric filter according to the present invention, the following effects can be obtained. (1) A dielectric block having a groove formed on a specific surface facing the opening end of the cavity forming the resonance line and connecting the opening end to another surface is formed, and a conductor is formed on the entire surface of the dielectric block. Then, a dielectric filter having an attenuation pole is manufactured by exposing the dielectric surface on both sides of the groove and shaving the specific surface so as to form a line formed of a conductor on the inner surface of the groove.
Therefore, a dielectric filter having a large attenuation can be easily and reliably manufactured without increasing the shape of the dielectric filter. (2) When shaving a specific surface, the depth is adjusted so that the frequency of the attenuation pole generated in the transfer characteristic of the dielectric filter becomes a desired frequency. Therefore, the dielectric constant of the dielectric material as a raw material of the dielectric block is adjusted. Variations in the frequency of the attenuation pole due to variations or variations in the shape of the dielectric block are corrected.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a dielectric filter manufactured by one embodiment of a method for manufacturing a dielectric filter according to the present invention.

FIG. 2 is an enlarged view of a cross section taken along line AA ′ of FIG. 1;

FIG. 3 is an equivalent circuit of a dielectric filter manufactured by an embodiment of the method for manufacturing a dielectric filter according to the present invention.

FIG. 4 is a characteristic diagram showing transfer characteristics of a dielectric filter manufactured by one embodiment of a method for manufacturing a dielectric filter according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric block 2A, 2B ... Cavity 3A, 3B ... Side surface 4A, 4B ... Communication hole 5A, 5B ... Groove 6A, 6B ... Convex part 7A, 7B ... Inner conductor 8 ... Outer conductor 9A, 9B... I / O electrodes 10A, 10B... Connection conductors 11A, 11B... Short-circuit connection conductors a... Front surface (specific surface) b.

Claims (3)

[Claims] 1. A dielectric block in which a groove for connecting the open end to another surface is formed on a specific surface facing an open end of a cavity forming a resonance line, and a conductor is formed on the entire surface of the dielectric block. Forming a dielectric surface on both sides of the groove and shaving the specific surface so as to form a line made of a conductor on the inner surface of the groove. 2. The dielectric filter according to claim 1, wherein, when the specific surface is cut, a depth of the cut is adjusted so that a frequency of an attenuation pole generated in a transfer characteristic of the dielectric filter becomes a desired frequency. Manufacturing method. 3. The method according to claim 1, wherein the desired frequency ranges from 0.4 GHz to 1 GHz.
3. The method for manufacturing a dielectric filter according to claim 2, wherein the frequency is 0 GHz.