JPS6358482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a type of waveguide type filter that utilizes dielectric blocks, and allows the waveguide type filter to be miniaturized even in the relatively low frequency microwave region. .

Waveguide filters have metal posts inside the waveguide, inductive windows, capacitive windows, resonant windows, etc.
This is done by arranging stepped resonators at intervals of 1/4 wavelength or 1/2 wavelength. Therefore, as the frequency becomes lower and the wavelength becomes longer, the filter becomes larger, so a coaxial type filter is used in the low frequency range. However, in the intermediate region between the high frequency region suitable for waveguide filters and the low frequency region suitable for coaxial filters, for example in the region of about 2 to 4 GHz, using coaxial filters becomes too small and increases loss. On the other hand, if a waveguide filter is used, the loss is small, but there is a drawback that the shape becomes large.

The present invention solves the problems in the intermediate frequency range that cannot be handled by either waveguide type or coaxial type filters, and although it is a type of waveguide type filter, it can be miniaturized and is similar to coaxial type filters. The purpose is to realize a filter whose characteristics do not deteriorate. In order to achieve this object, the present invention provides a rectangular parallelepiped with a rectangular cross section whose height and external dimensions in the width direction are set to be larger than the height dimension, so that a predetermined frequency band can be propagated in a waveguide mode. At least four surfaces in the length direction of a dielectric block are metallized, and input/output coupling portions arranged at both ends of the dielectric block are provided with holes penetrating in the height direction constituting a plurality of resonators. A post or a bonding window is formed in the dielectric block by providing a through hole or a groove opening on the surface, and burying metallization or a conductor continuous with the metallization layer on the surface inside the through hole or groove. The structure is characterized in that a series waveguide mode resonator is formed.

Next, an embodiment of a waveguide type dielectric filter according to the present invention will be described. FIGS. 1A and 1B are a perspective view and a vertical sectional view showing a first embodiment (post type) of a dielectric filter according to the present invention. Reference numeral 1 denotes a dielectric block made of, for example, ceramic with a high dielectric constant. At both ends of this dielectric block 1, holes 2a and 2b for input/output coupling are opened in parallel to each other, and at a position between both the holes 2a and 2b for input/output coupling,
Holes 3 for forming a resonator are opened in parallel with the input/output coupling holes 2a and 2b. The entire surface of the dielectric block 1 other than the input/output coupling holes 2a and 2b at both ends is metalized and covered with a conductive film 4 over the entire surface. As a result, dielectric block 1
acts as a kind of rectangular waveguide, and the inner surfaces of the resonator holes 3 are also covered with the conductive film 4a, so that a so-called post, which is also used in conventional waveguide filters, is configured.

After the metallization process, the input/output coupling holes 2a, 2
The inner conductor 51 of the coaxial cable 5 is inserted from one end into b to form a coaxial waveguide converter, and the difference between the characteristic impedance of the coaxial line and the characteristic impedance of the waveguide is matched. 52 is coaxial cable 5
is an insulator (Teflon) that maintains a constant distance between the inner conductor 51 and the outer conductor, and the inner conductor 51 is supported within the input/output coupling holes 2a and 2b by this insulator 52. Reference numeral 53 denotes a mounting flange for the coaxial cable 5, which is mounted on the surface of the dielectric block 1 and fixed to the conductor film 4 by soldering. Note that other types of coaxial waveguide converters may be used. For example, a coaxial waveguide converter may be formed by connecting another metal rod or the like to the inner conductor 51 of the coaxial cable 5. In addition, the openings below the input/output coupling holes 2a and 2b are formed using metal plates 6 to prevent radio wave leakage.
will be closed.

When the dielectric block 1 is provided with the posts 4a in this manner, a type of resonant cavity filled with dielectric material is formed between each post 4a, and functions as a waveguide type filter. Therefore, for example, if the coaxial cable on the left side of the figure is on the input side and the coaxial cable on the right side is on the output side, the signal input from the internal conductor 51 will resonate within the dielectric block 1 at a predetermined resonance frequency by each resonant cavity. is converted into a coaxial mode and output from the internal conductor 51 of the coaxial cable 5 on the right output side. In the relatively low-frequency microwave region, a coaxial system is generally used for the external circuit, so by using a coaxial waveguide converter like this, it is possible to use a waveguide system only in the filter section. becomes. Since the resonant cavity of the filter section is made of a dielectric material, the outer shape of the filter section is smaller than that of a normal waveguide filter.

Especially in recent years, the dielectric constant εr is large, tanδ is small,
Since high-quality dielectric materials with low temperature coefficients have been developed and put into practical use, the effect of reducing the size of filters and improving their characteristics is extremely large. For example, if we compare the Q ₀ by limiting the volume per resonator to 2.4 cc at 2 GHz, the Q ₀ of a 1/4 wavelength coaxial resonator is 1600.
On the other hand, in the case of a dielectric filter in which dielectric block 1 is made of barium titanate porcelain (BaTiO ₃ ) with εr=40, Q ₀ becomes 2500, which improves Q ₀ by 55%. .

FIG. 2 is a perspective view showing another embodiment of the resonator section. Figure 1 shows an example in which an inductive window is formed by forming notches 7 from both sides of the dielectric block 1 and providing a conductive film by metallization on the inner surface of the notches 7. The outer surface of the dielectric block 1 is metallized in the same manner as in the example of FIG. B forms a notch 8 from above and below, and the notch 8
This is an example in which a capacitive window is constructed by providing a conductive film also on the inner surface of the capacitive window. It is also possible to configure a resonance window by combining both (a) and (b). As shown in Figs. 1 and 2, the structure in which conductor obstacles are formed by metallizing the inner surfaces of the holes 3 and cutouts 7 and 8 is such that the conductor obstacles are formed in the same process as the metallization treatment of the outer surface of the dielectric block. can be formed, which simplifies manufacturing. On the other hand, instead of metallizing, metal rods may be inserted into the resonator holes 3 of the dielectric block 1 shown in Fig. 1, or metal plates may be inserted into the notches 7 and 8 of the dielectric block 1 shown in Fig. 2. It is also possible.

FIG. 3 is a sectional view showing another example of the input/output coupling section. In this case, the input/output coupling hole 2c is not made into a through hole, but is opened halfway, into which the internal conductor 51 of the coaxial cable 5 is inserted. Therefore, the closing plate 6 of FIG. 1 is unnecessary.

Although the example shows a state in which only the filter is independent,
Similar to a normal waveguide circuit, it is also possible to have a configuration in which the dielectric filter of the present invention is combined with other circuit elements such as a detection circuit.

In addition, it is also possible to use a window portion that couples the waveguide with a matching device without metalizing both end faces, or to couple it with another transmission path such as a stripline using a transmission mode converting coupler. These methods may be combined as appropriate.

As described above, according to the present invention, input/output coupling parts are formed at both ends of a rectangular parallelepiped dielectric block, and a through hole 3 is formed at an intermediate position between the two input/output coupling parts depending on the type of resonator. ...and notches 7, 8, etc. are formed, part of the dielectric block is removed, and a metal rod, metal plate, or metallized conductive film is placed as a conductor to form a resonant cavity, and the whole is made into a stepped shape. A resonator is constructed by forming a resonant section, and a main part of the outer surface of the dielectric block is metallized. Therefore, unlike conventional waveguide filters, even when used in the low frequency microwave region, the filter can be made smaller in size, and there is no problem of increased loss as with coaxial filters. In addition, after forming the dielectric block into a shape that corresponds to the shape of the resonator, input/output coupling holes, windows, etc., it is only necessary to metalize the outer surface of the dielectric block, making manufacturing extremely simple and inexpensive. realizable.

[Brief explanation of the drawing]

The figures show an embodiment of the dielectric filter according to the present invention. Fig. 1 is a perspective view and a vertical cross-sectional view of a post-type dielectric filter, Fig. 2 is a perspective view of a window-type dielectric filter, and Fig. 3 is a perspective view of a window-type dielectric filter. FIG. 3 is a sectional view showing another example of the input/output coupling section. In the drawing, 1 is a dielectric block, 2a, 2
b, 2c are input/output coupling holes, 3... are resonator holes,
4 is a conductor film by metallization, 4a is a conductor film (post), 5 is a coaxial cable, 51 is an internal conductor, 5
2 is an insulator, and 7 and 8 are notches.

Claims (1)

[Scope of Claims] 1. A dielectric material made of a rectangular parallelepiped with a rectangular cross section and whose height and external dimension in the width direction are set to be larger than the height dimension, so as to be able to propagate a predetermined frequency band in a waveguide mode. At least four surfaces in the length direction of the block are metallized, and between the input/output coupling parts arranged at both ends of the dielectric block, there are through holes or through holes penetrating in the height direction constituting a plurality of resonators. A dielectric block is provided with a groove opening on the surface, and a metallization layer or a conductor that is continuous with the metallization layer on the surface is buried inside the through hole or groove, thereby providing a post or a bonding window in the dielectric block. 1. A waveguide dielectric filter characterized by forming a series waveguide mode resonator.