JPS58161402A - Distributed constant filter - Google Patents

Abstract

PURPOSE:To reduce the insertion loss and to decrease the size and the coupling coefficient, by providing the depth of a through-hole toward the axial length, giving a recess and a cavity for the outer surface of a dielectric block and setting the degree of coupling between a couple of resonance units. CONSTITUTION:A fitting member 26 made of a conductor, e.g. metallic cylinder or conductive paste, is fixed to the other end of a conductive film 14 electrically and mechanically, and an opposing electrode 25 is fixed to the member 26 electrically and mechanically. The resonance frequency is decided with the electric length of the conductive film 13 or 14 reduced by the permeability of the dielectric 10. The two resonance units are coupled with the odd mode and the even mode. A through-cavity 27 has e.g. rectangular cross section. The recess or a groove 27a provided at the bottom has the depth DELTAt and the depth is decided for the objective value. In changing the value DELTAt/t, the degree of coupling is reduced without increasing the insertion loss by increasing the depth DELTAt.

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, filters with several 100 M) 12 bands have been made using LC resonant circuits or coaxial resonators, but they are structurally unstable or complex, have unsatisfactory characteristics, and require adjustment. There were problems such as it took a lot of time and the first stroke could not be lowered.

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 low 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, provide a conductive film on the inner surface of the through holes, and provide a conductive film on at least the west side of the dielectric block. a conductive film provided on the inner surface of the through hole, a conductive film provided on at least the west side of the dielectric block, and the intervening dielectric to constitute a resonant unit;
A cavity is provided in at least a pair of adjacent resonant unit dielectric blocks, and furthermore, an external circuit and the resonant unit are electrostatically coupled. The cavity is divided to set the degree of coupling between the pair of resonant units.

According to such prior invention, the coupling coefficient is 2% to 10%.
It is possible to achieve a relatively wide band with a coupling coefficient of 1 to
A narrow band smaller than 2% could not be put to practical use. That is, in FIG. 11, a is changed from 0.5++ue to 1
When increasing to 0mm, as shown in Figure 12,
The coupling coefficient decreases from 10% to about 1%, but does not easily decrease below that level.On the other hand, the insertion loss of the filter rapidly increases from 1dB to 40dB, reducing a to about 31%.
The above configuration cannot be used as a filter in practice. In this case, if the value C in FIG. 11 is increased, the Q value increases, and the reduction in insertion loss is suppressed, but the object is to provide a distributed constant type filter that is small in shape and can further reduce the coupling coefficient.

That is, the gist of the present invention is to install at least two through holes in a dielectric block in a line at a constant interval, provide a conductive film on the inner surface of the through holes, and provide a conductive film on at least the west side of the dielectric block. Installed - J, II
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 between at least a pair of adjacent resonant units, the front &! This distributed constant type filter is characterized in that a concave portion is provided on the outer surface of the dielectric block with a depth in the axial direction of the through hole, and a cavity is provided to set the degree of coupling between a pair of resonant units.

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, in the embodiment, the 1/4 wavelength resonant circuits are inductively coupled to each other, and the external circuit and the 1/4 wavelength resonant circuit have a capacitance of
It is a combined filter. 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 used to short-circuit one end side of the conductive films 13, 14 and the conductive film 15 to generate 1/4 wavelength resonance. Reference numeral 17 denotes an input coupling capacitor connected to the other end of the conductor 113, which has a cylindrical dielectric 18 and counter electrodes 19 and 20. In more detail, the conductive film 13
On the other end side, a mounting member 21 made of a conductor such as an IJ body in metal or a conductive paste is electrically and mechanically connected and fixed, and the counter electrode 20 is electrically and mechanically connected to this mounting member 21. The connection is fixed. 22 is a conductive film 1
4' is an output coupling capacitor connected to the other end side, and has counter electrodes 24 and 25 on a cylindrical dielectric body 23. In more detail, conductivity is 1! 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 A14, and the counter electrode 25 is electrically and mechanically connected to this mounting member 26. It is 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. When the wavelength is 1/2, the conductivity of $116 is not necessary. In addition, the conductive film in each figure,
Electrode ■ is drawn with exaggerated film thickness for understanding. In any case, two resonant units are constructed in this embodiment. Each resonance unit is in Otsudo mode, Eve7
’ mode. 27 is a through cavity,
- Examples include rectangular cross-sections. 27a is a recess or groove provided on the bottom side in FIG. 2, and the depth of the groove 27a is Δ
The degree of coupling is set to a target value at t. Now, in FIG. 11, a=2++m, and Δ1. in FIG. /
FIG. 13 shows the state when l is changed. As is clear from the graph, by increasing the depth Δt, the coupling coefficient can be reduced without increasing the insertion loss. This tendency also applies to those having different dimensions such as a.

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 bin. 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 in close proximity to the conductive film 13 . Similarly, the bottle 29 is placed close to the conductive film 14 and has a cavity 2 when viewed from the conductive film 14.
It is embedded in a portion of the dielectric block 10 on the opposite side to the dielectric block 7. Therefore, a certain amount of capacitance exists between the input terminal pin 28 and the conductive film 13, and the output terminal pin 29 and the conductor 1! A certain amount of capacitance also exists between the capacitors 14. 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 of the water tank.

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, 0.5IllIlφ with plastic or titanium oxide dielectric material and forming it into a columnar shape. 42 passes through the axial center, and a tapered portion 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 portion of the dielectric unit 41 is provided with a seven flange portion 44 that rests on the opening periphery of the hole 11.12 of the dielectric block 10 on the side where the conductor 11115 is not formed.

As shown in FIG. 9, the dielectric unit 41.41 has a conductive film 13 on the inner surface from the tapered portion 43.43 side.
Said hole 11.1 of the dielectric block 10 formed with 14
7 run 9 part 44.44 of dielectric unit 41.41 in 2
is press-fitted until it contacts the dielectric block 10.

With the above arrangement, the conductive wires 42, 42 and the conductive wires 1!13°14 formed on the inner surface of the holes 11,12 of the dielectric block 10 can be connected to the capacitors 17 and 14 by the dielectric parts of the dielectric units 41,41. The output coupling capacitor 22 becomes 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 a constant interval in a dielectric block, and a conductive film is provided on the inner surface of the beak through hole. At the same time, a conductive film is provided on at least the west side of the dielectric block, and a resonant unit is constituted by 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, At least between a pair of adjacent resonant units, a recess is provided on the outer surface of the dielectric block with a depth in the axial direction of the pre-arranged through hole, and a cavity is provided to set the degree of coupling between the pair of resonant units. As a result, a small, narrow-band filter can be obtained without increasing insertion loss.

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,
Figure 5 is a right side view, Figure 5 is a top view, Figure 6 is a back view, Figure 7 is a cross-sectional view, Figure 8 is a cross-sectional view of another embodiment, and Figure 9 is a cross-sectional view of another embodiment. , now ``Cross-sectional view of two embodiments, No. 10''
11 is a dimensional diagram of a conventional example, FIG. 12 is a characteristic diagram of a conventional example, and FIG. 13 is a characteristic diagram of an embodiment of the present invention. 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 recess. Patent application: Murata Manufacturing Co., Ltd. Bacteria 30 4m

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. A conductive film and a small number of dielectric blocks (both the conductive film provided on the west side and the intervening dielectric constitute a resonant unit, and the depth in the axial length direction of the through hole is formed between at least a pair of adjacent resonant units. 1. A distributed constant type filter characterized in that a recess is provided on the outer surface of a dielectric block and a cavity is provided to set the degree of coupling between a pair of resonant units.