JPH01231402A - Distributed constant filter - Google Patents

Abstract

PURPOSE:To simplify the constitution, to attain low cost and to improve the characteristic by embedding an input/output terminal pin from the open end of a resonance unit by a prescribed length in a direction along the through hole of a dielectric block so as to form the static coupling by a static capacitance existing between the conductive film of the inner face of the through hole and the input/output terminal pin. CONSTITUTION:A pin 28 is embedded to a dielectric block 10 opposite to a cavity 27 viewed from a conductive film 13 close to the conductive film 13. Similarly, a pin 29 is embedded to the dielectric block 10 opposite to the cavity 27 viewed from a conductive film 14 close to the conductive film 14. Thus, a prescribed capacitance of a capacitor exists between the input/output terminal and the conductive film 13 and also a prescribed capacitance of a capacitor exists between the output terminal pin 29 and the conductive film 14. Then the 1/4 wavelength resonance circuits are coupled inductively and a four- wavelength resonance circuit and an external circuit are coupled in terms of capacitance. Thus, the structure is simplified, the characteristic is improved and the low cost is attained.

Description

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

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

Therefore, it is an object of the present invention to provide a distributed constant type filter which has a simple structure, can have c) f4 characteristics, and is low in cost.

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 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 between at least a pair of adjacent resonant units In a distributed constant filter in which a cavity is provided in the block and an external circuit and a resonance unit are electrostatically coupled,
Capacitive coupling is achieved by burying an input/output terminal pin of a certain length from the open end side of the resonance unit in the direction along the through hole of the dielectric block, and reducing the static electricity that exists between it and the conductive film pin on the inner surface of the through hole. This is a distributed constant type filter characterized by being realized by capacitance.

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

FIG. 1 is an electrical 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 an I/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.

Before explaining the specific structure of the filter of the present invention having the electric circuit described above, the structure of the filter according to the invention of the original patent application of the present invention will be explained with reference to FIGS. 2 to 7.

In FIGS. 2 to 7, 10 is a cubic dielectric block made of titanium oxide ceramic dielectric, II,
+2 is a through hole, which is provided in the dielectric block 10 so as to be lined up at regular intervals.

13 and 14 are conductive films provided on the inner surfaces of the through holes 11 and 12, respectively, and 15 is a conductive film provided on at least four sides of the dielectric block 10. Reference numeral 16 denotes a conductive film provided on the bottom surface of the dielectric block 1O, and is used to short-circuit one end side of the conductive films 13 and 14 with 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 conductive film 13, which has a cylindrical dielectric body 18 and opposing electrodes 19.degree. 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 a cylindrical dielectric 23 and counter electrodes 24 and 25.

To be more specific, the other end C of the conductive film 14 is electrically and mechanically connected and fixed to a mounting member 26 made of a conductor such as a metal cylinder or a conductive paste, and the counter electrode 25 is connected to the 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 IO. The electrical length may be 1/4 wavelength or 1/2 wavelength as in the illustrated embodiment. When the wavelength is 1/2, the conductive film 16 is not necessary. Note that the conductive films and electrodes in each of FIGS. 2 to 7 are illustrated with exaggerated film thicknesses for better understanding. In any case, the filter includes two resonance units. Reference numeral 27 denotes a cavity, which has a rectangular cross section, for example, and the degree of inductive coupling between the two resonant units is influenced by the dimensions and shape of this cavity. No electrode film is provided on the inner peripheral surface of the cavity 27. There is also a possibility that the air A27 is not penetrated.

FIGS. 8 to 10 show the measurement results of the above filter, and in the structure shown in FIGS. 8 to 1, Q1=7arp, Qt
= 16 mm, Qs = 17 x m (center frequency is 7
13MHz notoki), L = 2RI! , (5=3 m
m, Q, = 3ixφ, ε" = 37 dielectric blocks are baked with silver paste to form a conductive film with a thickness of 5 μm,
Input coupling capacitor 1.5pF, output coupling capacitor 1
．． It is 5 pF. As is clear from FIGS. 8 to 1θ, the above-mentioned filter is practical as a filter in the range of several 100 MHz.

An embodiment of the present invention will be explained with reference to FIG.

In the filter shown in FIG. 11, the input/output coupling capacitor 17 and the output coupling capacitor 22 are omitted from the filters described in FIGS. 2 to 7. 2
8 is an input terminal pin, and 29 is an output terminal pin. pin 2
8 is embedded in a portion of the dielectric protrusion 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 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, input terminal pin 28
A fixed capacitance exists between the output terminal pin 29 and the conductive film 13, and a fixed capacitance also exists between the output terminal pin 29 and the conductive film 14. The structure shown in FIG.
Two capacitors are omitted from the structures shown in FIGS. 7 to 7, making the structure simpler and reducing costs.

As is clear from the above embodiments, the distributed constant filter of the present invention has at least two through holes arranged at a constant interval in a dielectric block, and a conductive film is provided on the inner surface of the through holes. At the same time, a conductive film is provided on at least four sides of the dielectric block, and a resonance unit is constituted by the conductive film provided on the inner surface of the through hole, the conductive film provided on at least the four sides of the dielectric block, and the intervening dielectric, In a distributed parameter filter in which a cavity is provided in a dielectric block between at least a pair of adjacent resonant units, and an external circuit and the resonant unit are further electrostatically coupled, the electrostatic coupling is caused by the through-hole of the dielectric block. This is achieved by embedding a fixed length input/output terminal pin from the open end side of the resonant unit in the direction along Although it is simple and low cost, it is possible to obtain a product with sufficient characteristics.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of an embodiment of the present invention, and FIG.
3 is a front view of the distributed constant type filter according to the original patent application of this invention, FIG. 3 is a left side view, FIG. 4 is a right side view, and FIG. 5 is a top view. The figure is the same, back view, No. 7
The figure is a sectional view of the same, Figure 8 is a selection characteristic diagram of the distributed constant type filter of Figures 2 to 7, Figure 9 is a spurious characteristic diagram of the same, and Figure 10 is a reflection characteristic diagram of the same. , FIG. 11 is a longitudinal sectional view of one embodiment of the distributed constant filter according to the present invention. 3 is human coupling capacitance, 4 is output coupling capacitance, 5.6
is a 1/4 wavelength resonant circuit, 28 is an input terminal pin, and 29 is an output terminal pin. Figure 6

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 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 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, Furthermore, in a distributed constant filter in which an external circuit and a resonant unit are capacitively coupled, the capacitive coupling is a fixed length input/output terminal from an open end side of the resonant unit in a direction along the through hole of the dielectric block. A distributed constant filter characterized in that a pin is embedded and realized by capacitance existing between the conductive film on the inner surface of the through hole and the input/output terminal pin.