JPH0535601Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a multi-stage dielectric filter with an integrated structure used in high frequency bands such as microwaves. A multi-stage dielectric filter in which a conductor pattern is formed from the side surface to near the hole edge on the open side of the resonator hole near the center, and a part without a conductive film is provided between the holes on the short-circuit side. It is related to.

[Prior Art] Multi-stage resonator filters using dielectric ceramics such as barium titanate have low loss, so-called high Q, and have a high dielectric constant, so they can be miniaturized. It is widely used in various types of mobile radio equipment for the microwave band, including the following.

As a conventional technique related to dielectric filters, a plurality of resonator holes and coupler holes are provided alternately at predetermined intervals in a rectangular parallelepiped dielectric block, and one of the surfaces where the holes are open is An integrated multi-stage structure is known in which a large number of resonant elements having a resonant wavelength four times the length of the resonator hole are formed by metallizing the outer surface excluding the open surface and the inner surface of the resonator hole. It is being

In such a dielectric filter, each resonator hole corresponds to a single resonant element, and the degree of coupling is determined by the coupler holes located between the resonator holes. If the interval between the resonator hole and the coupler hole is widened, the bandwidth of the filter will be narrowed, and if the hole interval is narrowed, the bandwidth will be widened.

[Problems to be Solved by the Invention] In the multi-stage dielectric filter of the conventional structure as described above, a filter with a narrow band cannot be realized unless the overall length of the dielectric block is lengthened and the hole spacing is widened.

In addition, since many small holes such as resonator holes and coupler holes are formed, the flow of powder and the amount of pressure applied during molding tend to be uneven, resulting in variations in density and properties, and the overall length becomes longer. Coupled with this, the insertion loss increases. On the other hand, if a dielectric filter is constructed without coupler holes, the resonator holes will be difficult to couple with each other, and the characteristics as a filter will not be produced. In other words, the bandwidth becomes too narrow and the insertion loss becomes large, making it unusable.

In order to solve these problems, the present inventors first formed a conductor pattern on the open surface of the dielectric block that was connected to the metallized layer on the side surface, and the distance between the conductor pattern and the open end of the resonator hole We proposed a capacitively coupled dielectric filter (Rep.
(See issue 201419).

A dielectric filter with such a configuration is extremely preferable in that it is possible to construct a good narrow band filter even if the total length of the dielectric block is short, but if this technology is applied to a multi-stage filter with four or more stages, It has been found that in some cases, the conductor pattern on the open surface side alone does not necessarily provide sufficient coupling, and it may become difficult to control the strength of the coupling between the resonant elements.

The purpose of the present invention is to solve the problems of the conventional technology, to be able to fully support multi-stage dielectric filters with four or more stages, to freely control the strength of the coupling between resonant elements, and to be compact. An object of the present invention is to provide a multistage dielectric filter that can improve attenuation characteristics on the high frequency side.

[Means for Solving the Problems] The present invention provides four or more resonator holes in the longitudinal direction of a dielectric block having a substantially rectangular parallelepiped shape, and a surface of the dielectric block where the resonator holes are open. The present invention is based on an integrated multi-stage dielectric filter in which one of the surfaces is an open surface and the other is a short-circuit surface, and a conductive film is formed on the outer surface other than the open surface and the inner surface of the resonator hole.

In order to achieve the above object, the present invention does not provide a coupler hole between the resonator holes,
Regarding the resonator hole near the center, a conductive pattern is formed on the open side from the conductive film on the side to near the hole edge, whereas on the short-circuit side, a part without a conductive film is provided to partition the holes. ing.

The conductor pattern on the open surface side is connected to the conductor film on the side surface, and these constitute a ground electrode.

[Function] By forming a conductor pattern on the open surface of the dielectric block that is electrically connected to the side conductor film and extends to the vicinity of the open end of the resonator hole, the resonant element and the conductor pattern as well as the Capacitive coupling is performed between adjacent resonant elements, and the resonant elements can be coupled in place of the conventional coupler hole. Especially the resonator hole is 4.
In the case of a multi-stage filter having more than one resonator hole, good coupling can be achieved by providing a portion without a conductive film between the resonator holes on the short-circuit surface side. In other words, the coupling strength of the resonant element near the center can be controlled by the shape of the conductor pattern on the open surface side and the shape of the non-conductor film portion on the short-circuit surface side.

Therefore, in the present invention, good filter characteristics can be achieved without increasing the total length of the dielectric block, and insertion loss does not increase.

If a non-conductor film portion is formed between the resonator holes in the conductor pattern formed on the open surface side, a filter with a wide band can be obtained.

[Embodiment] FIG. 1 is a perspective view showing an embodiment of a multistage dielectric filter according to the present invention, FIG. 2A is a plan view thereof, and FIG. 2B is a bottom view thereof. This embodiment shows an example of a five-stage integrated dielectric filter.

The multi-stage dielectric filter includes five resonator holes 12a, 12b, 12c, 12a, 12b, 12c, 12a, 12b, 12c, 12a, 12b, 12c, 12a, 12b, 12c, 12c, 20a, 20a, 20b, 30a, 30b, 30a, 30b, 30b, 12b, 12c, etc.. 1
2d and 12e, and furthermore, the entire side and bottom surface of the dielectric block 10, and the resonator holes 12a,
..., 12e has a structure in which a metallized layer 16 is formed on the inner surface. Therefore, in FIG. 1, the upper surface of the dielectric block 10 becomes an open surface and the lower surface becomes a short-circuit surface. Coupling capacitors (not shown) are mounted on the open surfaces of the resonator holes 12a, 12e located at both ends of the dielectric block 10, and are connected to an external circuit via the coupling capacitors.

In order to make the drawings easier to understand, parts where the dielectric base is exposed without being metallized are shown with small dots. Although the metallized layer 16 is depicted as having a considerable thickness, it is actually an extremely thin layer formed by baking silver paste or the like.

Now, as is clear from Figs. 1 and 2, the present invention is significantly different from the prior art in that there is no coupling hole between each resonator hole, and moreover, the resonator hole near the center has an open surface. On the side, a conductive pattern is formed from the conductive film on the side surface to near the end of the hole, and on the short-circuit side, a non-conductive part is provided between the holes.

Since this embodiment has a five-stage configuration, the three resonator holes 12b, 12c, 1 near the center excluding both ends
A conductive pattern 16 is formed to surround 2d. This conductor pattern 16 can be produced relatively easily and with high precision by, for example, a screen printing method. This conductor pattern 16 can be fixed by baking in the same process as the conductor films on the side and bottom surfaces.

In addition, on the short-circuit surface side, as shown in FIG. 2B, between the resonator holes 12b and 12c, and
A non-conductor film portion 18 is provided between and 12d. This non-conductive film portion 18 can be easily formed by forming a conductive film over the entire surface and then peeling off only that portion.

When the conductor pattern 16 as described above is formed on the open surface of the dielectric block, a coupling capacitance is generated between the ground electrode formed by the metallized layer 14 and the conductor pattern 16 and the open end of each resonator hole. , can be bonded to each other by these. Furthermore, the degree of coupling can be controlled by the non-conductor film portion 18 on the short-circuit surface side. As a result, desired filter characteristics can be achieved by adjusting the shapes of the conductor pattern 16 and the non-conductor film portion 18 without providing the conventionally required connector holes.

An example of the attenuation characteristics of the obtained filter is shown in FIG. As is clear from these measurement results, it can be seen that according to the present invention, good coupling is achieved even without a connector hole, and favorable attenuation characteristics are obtained on the high frequency side.

FIG. 4 is a plan view showing another embodiment of the multistage dielectric filter according to the present invention. The shape of the bottom side, ie, the short-circuit side, is similar to that shown in FIG. 2B. This embodiment differs from the previous embodiment in that the conductor pattern 16 on the open surface side has a portion 20 without a conductor layer between adjacent resonator holes 12b, 12c, and 12d near the center. This is the point where they are separated. Part 2 without such a conductive film
0 can be easily provided by forming the conductor pattern 16 and then peeling off only that portion.

FIG. 5 shows an example of attenuation characteristics obtained by a multistage dielectric filter having such a structure. As is clear from a comparison with the attenuation characteristics shown in FIG. 3, a wide bandwidth can be obtained by using such a conductor pattern shape.

That is, in the present invention, a dielectric filter with a desired bandwidth can be obtained by adjusting the shape of the non-conductor film portion on the short-circuit surface side and the shape of the conductor pattern on the open surface side.

Although the preferred embodiment of the present invention has been described above in detail, the present invention is not limited to such a five-stage configuration. It is also applicable to cases with 4 stages or 6 stages or more.

[Effects of the invention] As mentioned above, the present invention has a structure in which a predetermined conductor pattern is formed on the open surface side and a non-conductive film portion is formed on the short-circuit surface side, without providing a coupler hole in the dielectric block. Even in a multi-stage structure with four or more child holes, the coupling strength between resonant elements can be adjusted sufficiently.
This produces the effect that a filter with desired characteristics can be constructed.

In addition, this invention simplifies the structure because it does not require a connector hole, has good formability and sinterability, reduces variations in density and dielectric constant, and reduces the total length of the dielectric block, which also reduces insertion loss. It is also possible to avoid an increase in the size.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the dielectric filter according to the present invention, Fig. 2A is its top view, Fig. 2B is its bottom view, and Fig. 3 shows the attenuation characteristics of the dielectric filter. FIG. 4 is a plan view showing another embodiment of the present invention, and FIG. 5 is a characteristic diagram showing an example of the damping characteristics obtained thereby. 10...Dielectric block, 12a, 12b, 1
2c, 12d, 12e...Resonator hole, 14...Metallized layer, 16...Conductor pattern, 18...Non-conductor film portion.

Claims (1)

[Scope of utility model registration request] Four or more resonator holes are provided in the longitudinal direction of a dielectric block having a substantially rectangular parallelepiped shape, one of the surfaces of the dielectric block where the resonator holes are open is an open surface, the other is a short-circuit surface, and the resonator holes are open. In an integrated multi-stage dielectric filter in which a conductor film is formed on the outer surface other than the surface and the inner surface of the resonator hole, there is no coupler hole between the resonator holes, and for the resonator hole near the center, A multi-stage dielectric filter characterized in that a conductor pattern is formed on the open surface side from the conductor film on the side surface to near the hole ends, and a non-conductor film portion is provided between the holes on the short-circuit surface side.