JPS638642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel distributed constant filter used, for example, in the several 100 MHz range.

Conventionally, filters in the several 100 MHz range have used LC resonant circuits or coaxial resonators, but these were structurally unstable or complex, had unsatisfactory characteristics, and were difficult to adjust. There were problems such as the high cost and the inability to reduce costs.

Therefore, the inventor of the present invention invented a distributed constant type filter that has a simple structure, satisfactory characteristics, and is low in cost.
No.) was done. The gist of this prior invention is that at least two through holes are provided in a dielectric block in a line at a constant interval, a conductive film is provided on the inner surface of the through holes, and a conductive film is provided on at least four sides of the dielectric block. The conductive film provided on the inner surface of the through hole, the conductive film provided on at least four sides of the dielectric block, and the intervening dielectric constitute a resonant unit, and a cavity is formed in the dielectric block between at least a pair of adjacent resonant units. Furthermore, the external circuit and the resonant unit are electrostatically coupled. The cavity is provided for setting the degree of coupling between a pair of resonant units. A conductive film must not be formed on the inner wall surface of this cavity. For efficient manufacturing, it is best to "dip" the entire dielectric block in silver paste, pull it up, and then sinter it to form a conductive film. This method could not be used because the conductive film should not be formed, and the conductive film was formed by baking after the troublesome "brush painting" process, resulting in inefficient manufacturing.

Furthermore, the method of setting the degree of coupling by providing a cavity and changing its shape and dimensions has a narrow setting range.

Therefore, a distributed constant type filter was invented prior to the present invention, which can be manufactured efficiently and allows the degree of coupling to be set over a wide range.

The gist of this prior invention is to provide a dielectric block with at least two through holes lined up at a constant interval, provide a conductive film on the inner surface of the through hole, and provide a conductive film on at least four sides of the dielectric block. The conductive film provided on the inner surface of the through hole, the conductive film provided on at least four sides of the dielectric block, and the intervening dielectric constitute a resonant unit, and the dielectric block between at least a pair of adjacent resonant units This distributed constant type filter is characterized in that a concave portion is provided on the outer surface along the through-hole axis to set the degree of coupling between a pair of resonant units.

An example of this filter will be described below with reference to the drawings.

In Figure 1, 1 is an input terminal, 2 is an output terminal, 3 is an input coupling capacitance, 4 is an output coupling capacitance, and 5 and 6 are 1/4 wavelength resonant circuits shown as lumped constant circuits. be. Therefore, this example is a filter in which the 1/4 wavelength resonant circuits are inductively coupled to each other, and the external circuit and the 1/4 wavelength resonant circuit are capacitively coupled. FIGS. 2 to 6 show an example of its specific structure. In the figure, 10 is a cubic dielectric block made of a titanium oxide based ceramic dielectric, and 11 and 12 are through holes, which are arranged in the dielectric block 10 at regular intervals. 13 and 14 are through holes, 11 and 12, respectively.
The conductive film 15 provided on the inner surface of the dielectric block 10 is a conductive film provided on at least four sides of the dielectric block 10.
16 is a conductive film provided on the bottom surface of the dielectric block 10, and is connected to one end side of the conductive films 13 and 14 and the conductive film 1.
5 is short-circuited to generate 1/4 wavelength resonance. Reference numeral 17 denotes an input coupling capacitor connected to the other end of the conductive film 13, which has a cylindrical dielectric 18 and opposing electrodes 19 and 20. To be more specific, a mounting member 21 made of a conductor such as a metal cylinder or a conductive paste is electrically and mechanically connected and fixed to the other end of the conductive film 13, and the counter electrode 20 is connected to the mounting member 21. It is electrically and mechanically connected and fixed. Reference numeral 22 denotes an output coupling capacitor connected to the other end of the conductive film 14, which has opposing electrodes 24 and 25 on a cylindrical dielectric 23. In more detail, a mounting member 26 made of a conductor such as a metal cylinder or a conductive paste is electrically and mechanically connected and fixed to the other end of the conductive film 14, and the opposite electrode 25
is electrically and mechanically connected and fixed to this mounting member 26. The resonant frequency is determined by the electrical length of the conductive film 13 or 14, which is shortened by the dielectric constant of the dielectric 10. The electrical length is as shown in the example shown.
It may be 1/4 wavelength or 1/2 wavelength. When the wavelength is 1/2, the conductive film 16 is not necessary. Note that the conductive films and electrodes in each figure are drawn with exaggerated film thicknesses for better understanding. In any case, two resonant units are constructed in this example. Each resonant unit is coupled by odd mode and even mode. Reference numeral 27 is a recessed portion for setting the degree of coupling, and is provided on the outer surface of the dielectric block 10 at a portion between the resonant units. Its depth,
Set the degree of bonding to the target value depending on the width and shape. The fifth illustrated example has a pair of recesses 27 on opposing outer surfaces,
27 is provided, but in this case, the degree of coupling is smaller than when the recess 27 is not provided. Also, the 6th
As shown in the figure, when the recess 27 is provided only on one of the outer surfaces, the degree of coupling is greater than when the recess 27 is not provided. a pair of recesses 27,
27, the shapes and dimensions of both do not have to be the same.

The structure of the prior invention described above is suitable for roughly setting the degree of bonding, but there are times when it is desired to set the degree of bonding finely.

This invention provides at least two through holes arranged in a dielectric block at regular intervals, a conductive film is provided on the inner surface of the through holes, and a conductive film is provided on at least four sides of the dielectric block. A resonant unit is constituted by a conductive film provided on at least four sides of the dielectric block, a conductive film provided on at least four sides of the dielectric block, and an intervening dielectric, and a recess is formed on the outer surface of the dielectric block between at least a pair of adjacent resonant units. A distributed constant type filter in which the degree of coupling between a pair of resonant units is set by providing a distributed constant filter, wherein the recess is recessed from the outer surface where the edge of the through hole is located to the inside of the dielectric block. It is a shape filter.

Embodiments of the invention will be described below with reference to the drawings. The same parts as those in the previous figure are given the same numbers and the explanation will be omitted.

In FIG. 7, 27' is a recess, and this recess has a depth in the vertical direction of the figure. The recess 27' may be provided not only on the bottom surface of the dielectric block 10 but also on the top surface or both the top surface and the bottom surface. Of course, it may be used together with the recess 27, or may be used alone.

When such a recess is provided, the ratio of the variation width of the resonance frequency of the even mode to the variation width of the resonance frequency of the odd mode changes according to the cavity perturbation theory, and therefore, the degree of coupling can be directly controlled. can do.

FIG. 8 shows another embodiment in which the input coupling capacitor 17 and the output coupling capacitor 22 in the above embodiment are omitted. 28 is an input terminal pin, and 29 is an output terminal pin. The pin 28 is embedded in a portion of the dielectric block 10 outside the conductive film 13 in close proximity to the conductive film 13. Similarly, the pin 29 is embedded in a portion of the dielectric block 10 outside the conductive film 14 in close proximity to the conductive film 14. Therefore, a certain amount of capacitance exists between the input terminal pin 28 and the conductive film 13, and a certain amount of capacitance exists between the output terminal pin 29 and the conductive film 14.
A certain amount of capacitance also exists between them. In the structure shown in FIG. 8, two capacitors are omitted compared to the structures shown in FIGS. 2 to 7, and the structure becomes simpler and costs can be reduced. FIG. 9 shows yet another embodiment.

In the distributed constant filter shown in FIG. 9, dielectric units 41 and 41 as shown in FIG. 10 are press-fitted into holes 11 and 12 of a dielectric block 10 having conductive films 13 and 14 formed on the inner surface, respectively. ing.

As shown in FIG. 10, the dielectric unit 41 includes a part of a conductive wire 42 having a diameter of, for example, 0.5 mmφ.
A dielectric material such as plastics or titanium oxide is coated and formed into a columnar shape, and the conductive wire 42 passes through the axial center, and the tip of the dielectric unit 41 includes: In order to facilitate press-fitting into the holes 11 and 12 of the dielectric block 10,
A tapered portion 43 is provided, and a flange portion 44 is provided at the rear end of the dielectric unit 41 to abut against the opening periphery of the holes 11 and 12 of the dielectric block 10 on the side where the conductive film 15 is not formed. ing.

As shown in FIG. 9, the dielectric units 41, 41 are formed from a dielectric block 1 having conductive films 13, 14 formed on the inner surface thereof, from the tapered portions 43, 43 side.
Dielectric units 41 and 4 are inserted into the holes 11 and 12 of 0.
The flange portions 44, 44 of 1 are the dielectric block 10
It is press-fitted until it makes contact with the

By doing as described above, the conductive films 13 and 14 formed on the conductive wires 42 and the inner surfaces of the holes 11 and 12 of the dielectric block 10 are connected to the dielectric units 41 and 41.
will be electrostatically coupled by the dielectric part of
The input capacitor 17 and output coupling capacitor 22 as shown in FIG. 2 become unnecessary.

Therefore, there is no need for troublesome installation work as in the case of the input coupling capacitor 17 and the output coupling capacitor 22.

As is clear from the above embodiments, the distributed constant filter of the present invention includes at least two through holes arranged in a dielectric block at regular intervals, a conductive film provided on the inner surface of the through holes, and a conductive film provided on the inner surface of the through holes. , a conductive film provided on at least four sides of the dielectric block, a conductive film provided on the inner surface of the through hole, and a conductive film provided on at least four sides of the dielectric block;
In the distributed constant filter, a resonant unit is constituted by an intervening dielectric, and a recess is provided on the outer surface of the dielectric block between at least a pair of adjacent resonant units to set the degree of coupling between the pair of resonant units. Since this is a distributed constant type filter characterized in that the recess is recessed from the outer surface where the edge of the through hole is located to the inside of the dielectric block, it can be said that the structure allows efficient conductive film formation. It is also useful when it is desired to finely set the degree of coupling.

Note that the number of stages of resonance units is not limited to two stages, but any number of stages can be provided, and the resonance units can also be arranged in an interdigital configuration. Alternatively, the conductive film may be formed after filling the recess with a dielectric material different from the material forming the dielectric block.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention, FIG. 2 is a front view of an example of the prior invention, and FIG.
Figure 4 is a left side view, Figure 5 is a top view, back view, Figure 7 is a sectional view of an embodiment of the present invention, and Figure 8 is a current view. FIG. 9 is a sectional view of one embodiment, FIG. 9 is a sectional view of yet another embodiment, and FIG. 10 is a front view of the dielectric unit. 3 is an input coupling capacitance, 4 is an output coupling capacitance, 5 and 6 are 1/4 wavelength resonant circuits, and 27' is a recessed portion.

Claims (1)

[Claims] 1 At least two through-holes are provided in a dielectric block in a lined manner at a constant interval, a conductive film is provided on the inner surface of the through-hole, and a conductive film is provided on at least four sides of the dielectric block, and a conductive film is provided on the inner surface of the through-hole. A resonant unit is constituted by the conductive film provided on at least four sides of the dielectric block, the intervening dielectric, and a recess is provided on the outer surface of the dielectric block between at least a pair of adjacent resonant units. A distributed constant type filter in which the degree of coupling between a pair of resonant units is set using .