JPS58161401A - Distributed constant filter - Google Patents

Abstract

PURPOSE:To attain efficient manufacture and to set and change the degree of coupling over a wide variety easily, by adopting circular shape of a cavity and of the cross section of dielectric inserted to the cavity. CONSTITUTION:In the titled filter, 1/4 wavelength resonance circuits are coupled inductively, an external circuit is coupled with the 1/4 wavelength resonance circuits through electrostatistically and two resonance units are formed. Each resonance unit is coupled with the odd mode and the even mode. The cavity 27 is a cavity with or without bottom, the cross section is circular, and a circular dielectric rod 27a made of the same material as the dielectric of a dielectric block 10 or different from it is inserted in the inside of th cavity 27. The degree of coupling is set to an objective value by the size of the cavity, the dielectric constant of the rod 27a and the depth of insertion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel distributed constant type filter used, for example, in the several 100 MH2 range.

Conventionally, there have been filters in the several 100 MH2 range that use a C resonance circuit or a coaxial resonator, but they are structurally unstable or complex, have unsatisfactory characteristics, or are difficult to adjust. There were problems such as it was time-consuming and the cost could not be reduced.

Therefore, the inventor of the present invention invented and filed an application (Japanese Patent Application No. 107548/1982) for a distributed constant type filter that has a simple structure, satisfactory characteristics, and is low in cost. The gist of this prior invention is to provide a dielectric block with at least two through holes lined up at a constant interval, and to provide a conductive film on the inner surface of the through hole and to provide a conductive film on at least the west side 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. Roughly speaking, the external circuit and the resonant unit are electrostatically coupled. The cavity is provided to set the degree of coupling between a pair of resonant units, but the method of setting the degree of coupling by changing only the shape and dimensions of the cavity has a narrow setting range.

- To give an example, the bandwidth could only be changed within a range of about 1.5% to 2.2% of the center frequency. Also, it was troublesome to change the -tan setting after it had been set.

Therefore, an object of the present invention is to provide a distributed constant type filter that can be manufactured efficiently and that can easily set and change the degree of coupling over a wide range.

That is, the gist of the present invention is to provide at least two through holes in a dielectric block in a lined manner at a constant interval, to provide a conductive film on the inner surface of the through holes, and to provide a conductive film on at least the west side of the dielectric block. The conductive film provided on the inner surface of the through hole, the conductive film provided on at least the west side of the dielectric block, and the intervening dielectric constitute a resonant unit, and the dielectric between at least a pair of adjacent resonant units In a distributed constant filter that sets or changes the degree of coupling between a pair of resonant units by inserting a dielectric material into a cavity at an arbitrary depth into the block, the cross section of the cavity and the dielectric material inserted into the cavity is This is a distributed constant type filter characterized in that it has a circular shape to facilitate manufacturing.

Embodiments of the invention will be described below with reference to the drawings.

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention.

In the figure, 1 is an input terminal, 2 is an output terminal, 3 is an input coupling capacitance, 4 is an output coupling capacitance, and 5°6 is a 1/4 wavelength resonant circuit shown as a lumped constant circuit. Therefore, the embodiment 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 7 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 conductive films provided on the inner surfaces of the through holes 11 and 12, respectively, and 15 are
This is a conductive film provided at least on the west side of the dielectric block 10. Reference numeral 16 denotes a conductive film provided on the bottom surface of the dielectric block 10, and is conductive ll! 13. One end side of 14 and conductive film 1
5 is short-circuited to generate quarter wavelength resonance. Reference numeral 17 denotes an input coupling capacitor connected to the other end of the conductive film 13, and a counter electrode 19.2 is connected to the cylindrical dielectric 18.
0. 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. 22 is conductive 1
It is an output coupling capacitor connected to the other end side of 1114, and has counter electrodes 24 and 25 on the cylindrical dielectric body 23. To be more specific, 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 counter electrode 25 is connected to this mounting member 26. It is electrically and mechanically connected and fixed. 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 may be 1/4 wavelength or 1/2 wavelength as in the illustrated embodiment. At 1/2 wavelength, conductivity l! 16 is unnecessary. 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 embodiment. Each resonant unit is coupled by one mode and one mode. Reference numeral 27 denotes a bottomed or through-hole having a circular cross section, and inside thereof is a cylindrical dielectric rod made of a dielectric material different from or the same as the material forming the dielectric blow/rear 10. 27a is inserted. The coupling degree is set to a target value depending on the dimensions of the cavity, the dielectric constant of the dielectric rod 27a, and the insertion depth. After setting, if there is no need to change, the dielectric block 10 and the dielectric rod 27a are fixed. The portion of the dielectric rod 27a protruding from the dielectric block 1o may be left or removed. By increasing the insertion depth, the bandwidth can be varied within a range of about 0.1% to 2.2% of the center frequency. As you insert it,
As the center frequency decreases, the part of the selectivity curve higher than the center frequency suddenly shifts to the lower range, while the part of the selectivity curve lower than the center frequency slowly shifts to the higher range. A tendency was observed. In other words, the greater the degree of insertion, the more narrow band filter can be obtained.

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 bin, and 29 is an output terminal pin. The bottle 28 is embedded in a portion of the dielectric block 10 on the opposite side of the cavity 27 when viewed from the conductive film 13, close to the conductive film 13. Similarly, the pin 29 is embedded in a portion of the dielectric block 10 on the opposite side of the cavity 27 when viewed from the conductive film 14, in close proximity to the conductive film 14. Therefore, the input terminal bin 28 and the conductive film 13
A certain amount of capacitance exists between the output terminal pin 29
A certain amount of capacitance also exists between the conductive WA 14 and the conductive WA 14. The structure shown in FIG. 8 saves two capacitors compared to the structures shown in FIGS. 2 to 7, making the structure simpler and reducing costs. FIG. 9 shows yet another embodiment.

In the distributed constant type filter shown in FIG.
．． 12, a dielectric unit 41 as shown in FIG.
41 are press-fitted respectively.

As shown in FIG. 10, the dielectric unit 41 is formed by covering a part of a conductive wire 42 having a diameter of, for example, 0.5111Illφ with plastic or titanium oxide dielectric material and forming it into a columnar shape. 42 passes through the axial center, and a tapered part 43 is provided at the tip of the dielectric unit 41 to facilitate press-fitting into the hole 11.12 of the dielectric block 10. On the other hand, the rear end of the dielectric unit 41 is provided with a flange portion 44 that abuts against the opening periphery of the hole 11.12 of the dielectric block 10 on the side where the conductive film 15 is not formed.

As shown in FIG. 9, the dielectric unit 41.41 has a conductive film 13.4 on the inner surface from the tapered portion 43.43 side.
Said hole 11.1 of dielectric block 10 formed with 14
2, the flange portions 44.44 of the dielectric units 41.41 are press-fitted into the dielectric block 10 until they come into contact with the dielectric block 10.

In the above manner, the conductor @42.42 and the conductor @13°14 formed on the inner surface of the hole 11.12 of the dielectric block 10 are electrostatically coupled by the dielectric portion of the dielectric unit 41.41. Therefore, the input 45 capacitor 17 and the 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 has at least two through holes lined up at regular intervals in a dielectric block, a conductive film on the inner surface of the through holes, and A conductive film is provided on at least the west side 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. (
This is because a cavity with a circular cross section is provided in the dielectric block between a pair of adjacent resonant units, and a cylindrical dielectric is inserted inside the cavity to set the degree of coupling between the pair of resonant units. The range in which the degree of coupling can be set is expanded by more than 10 times compared to the conventional method, and filters with various band characteristics can be manufactured efficiently using the same mold. In addition, 1. Since the cross section of the cavity and the dielectric material inserted into the cavity is circular, polishing of the cavity and the dielectric material is easy and is excellent in terms of manufacturing.

Note that the number of stages of resonance units is not limited to two stages, and any number of stages can be provided, and the resonance units can also be arranged in an interdigital configuration.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of an embodiment of the present invention.
Same, front view, Figure 3 is same, left side view, Figure 4 is same,
Right side view, Figure 5 is a top view, Figure 6 is a back view, Figure 7 is a sectional view, Figure 8 is a sectional view of another embodiment, and Figure 9 is a sectional view of another embodiment. is a cross-sectional view of another embodiment, No. 10
The figure is a front view of the dielectric unit. 3 is an input coupling capacitance, 4 is an output coupling capacitance 5.6 is a quarter wavelength resonant circuit, 27 is a cavity, and 27a is a dielectric rod. Patent application: Murata Manufacturing Co., Ltd. No. 21 ¥17 Figure 7 Figure 10 Figure 5

Claims (1)

[Claims] 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 the west side of the dielectric block, and a conductive film is provided on the inner surface of the through hole. The conductive film, the conductive film provided on at least the west side of the dielectric block, and the intervening dielectric constitute a resonant unit, and a cavity is provided in the dielectric block between at least a pair of adjacent resonant units, and a cavity is provided inside the dielectric block. A distributed constant type filter in which the degree of coupling between a pair of resonant units is set by inserting a dielectric, characterized in that the cross section of the cavity and the dielectric inserted into the cavity is circular. .