JPS6260842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the bandwidth of a distributed constant filter formed by forming a coaxial resonator in a dielectric block.

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.

For this purpose, as shown in FIG. 1, two through holes 12 and 13 are provided in the dielectric block 11, and conductive films 14 and 15 are provided on the inner surfaces of these through holes 12 and 13. A conductive film 16 is provided on the side surface, and the conductive films 14 and 15 are provided on the inner surfaces of the through holes 12 and 13, and the dielectric block 1
The conductive film 16 provided in 1 and these conductive films 14, 1
5 and the conductive film 16.
and the dielectric block 11 interposed between them constitute a pair of resonant units, a cavity 17 is provided in the dielectric block 11 between these resonant units, and an external circuit (not shown) is inputted to the above-mentioned resonant unit. There is a distributed constant filter having an equivalent circuit as shown in FIG. 2, in which electrostatic coupling is achieved by a coupling capacitor 18 and an output coupling capacitor 19, respectively.

In Fig. 2 above, 21 is an input terminal, 22 is an output terminal, 23 is an input coupling capacitance, 24 is an output coupling capacitance, and 25 and 26 are 1/4 wavelength resonant circuits shown as lumped constant circuits. It is. Therefore,
The distributed constant filter shown in FIG. 1 is a filter in which quarter-wavelength resonant circuits are inductively coupled to each other, and an external circuit and the quarter-wavelength resonant circuit are capacitively coupled.

By the way, in the distributed constant type filter shown in FIG. 1, the degree of coupling between the 1/4 wavelength resonant circuits 25 and 26 is determined by the shape and dimensions of the cavity 17. Adjustment is not possible, and therefore, manufactured distributed filters whose bandwidths do not meet predetermined specifications have been discarded.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to make it possible to adjust the bandwidth of a distributed constant filter using a dielectric block, which has conventionally been impossible to adjust.

To summarize the present invention, it is a method for adjusting the bandwidth of a distributed constant filter in which at least two or more stages of coaxial resonators are integrally formed in a dielectric block.
Any part of the short-circuiting conductive film that short-circuits the conductive film formed on the inner peripheral surface of the through hole of the dielectric block and the conductive film formed on the outer peripheral surface of the dielectric block is removed, and the coaxial resonators are connected to each other. This is a method for adjusting the bandwidth of a distributed constant filter, which is characterized by adjusting the passband width by changing the degree of coupling.

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

In FIG. 3, 11 is a rectangular parallelepiped dielectric block made of titanium oxide ceramic dielectric;
12 and 13 are through holes; 14 and 15 are conductive films provided on the inner surfaces of the through holes 12 and 13, respectively; 16 are conductive films provided on the four sides of the dielectric block 11;
A is a short-circuit conductive film, and 17 is a cavity, which is the same as the distributed constant filter shown in FIG.

In the distributed constant type filter shown in FIG. 3, dielectric units 41 and 41 as shown in FIG. 4 are press-fitted into holes 12 and 13 of a dielectric block 11 having conductive films 14 and 15 formed on the inner surface, respectively. There is.

As shown in FIG. 4, 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 12 and 13 of the dielectric block 11,
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 12 and 13 of the dielectric block 11 on the side where the conductive film 16 is not formed. ing.

As shown in FIG. 3, the dielectric units 41, 41 are formed from a dielectric block 1 having conductive films 14, 15 formed on the inner surface thereof, from the tapered portions 43, 43 side.
Dielectric units 41 and 4 are inserted into the holes 12 and 13 of 1.
The flange portions 44, 44 of 1 are the dielectric block 11
It is press-fitted until it makes contact with the

In the present invention, in the distributed constant filter having the above configuration, the dielectric block 11
Conductive films 14 and 15 provided in through holes 12 and 13 of
and a conductive film 1 provided on the side surface of the dielectric block 11.
A part of the short-circuiting electrode film 16a that short-circuits the
Remove as shown.

The removed portion 31 of the short-circuit electrode film 16a has a cavity 17
and the through hole 12 or 13, as shown by the straight line _lA in FIG. The bandwidth of the filter becomes narrower. When the removed portion 31 is located at a position B on the opposite side of the cavity 17 with respect to the through hole 12 or 13, the degree of coupling K increases as the area S of the removed portion 31 increases, as shown by the straight line l _B in FIG. As the filter becomes larger, the bandwidth of the distributed constant filter becomes wider.

Furthermore, when the removing section 31 is located at a position C between positions A and B, even if the area of the removing section 31 becomes large, the degree of coupling K does not change as shown by the straight line l _C in FIG. The bandwidth of the distributed constant filter does not change.

From the above, by changing the formation position and area S of the removed portion 31 of the short-circuiting electrode film 16a, the bandwidth of the distributed constant filter can be freely adjusted.

As is clear from the detailed explanation above, the present invention provides a method for short-circuiting a conductive film formed on the inner peripheral surface of a through hole of a dielectric block and a conductive film formed on the outer peripheral surface of the dielectric block. Since the bandwidth of the distributed parameter filter can be adjusted by removing arbitrary parts of the conductive film, the bandwidth of the distributed parameter filter using dielectric blocks can be freely adjusted, which was previously impossible. , the design tolerance of the distributed constant type filter can be widened, and the defective rate of the product can be reduced.
It is possible to keep the product in a semi-finished state before measuring the bandwidth, and after receiving an order, adjust the bandwidth and ship it.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a conventional distributed constant filter, FIG. 2 is an equivalent circuit diagram of the distributed constant filter shown in FIG. 1, and FIG. 3 is a vertical cross-sectional view of a distributed constant filter that is an example of the present invention. 4 is a front view of the dielectric unit, FIG. 5 is a perspective view of the distributed constant filter shown in FIG. 3 with a portion of the short-circuit conductive film removed, and FIG. FIG. 3 is an explanatory diagram showing the relationship between the area of a removed portion and the degree of coupling. DESCRIPTION OF SYMBOLS 11... Dielectric block, 12, 13... Through hole, 14, 15, 16... Conductive film, 16a... Short circuit conductive film, 17... Cavity, 31... Removal part.

Claims (1)

[Claims] 1. A method for adjusting the bandwidth of a distributed parameter filter formed by integrally forming at least two or more stages of coaxial resonators in a dielectric block, which A distributed constant characterized in that the pass band width is adjusted by removing any part of the short-circuiting conductive film that short-circuits the conductive film formed on the outer peripheral surface of the dielectric block and changing the degree of coupling between the coaxial resonators. How to adjust the bandwidth of a type filter.