JPS5942729Y2 - Distributed constant filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distributed filter having a dielectric-loaded resonator.

A line with a length of λ/4 (λ: wavelength) with one end short-circuited and the other end open operates as a resonator, and by arranging multiple such resonators in parallel and connecting them by appropriate means. A small-sized distributed constant filter that combines 6D and comb filters is known as a comb filter.

Such distributed constant type filters are widely used especially in the microwave band.

Furthermore, for the purpose of miniaturization, the line is loaded with a dielectric material with a high relative permittivity, and a capacitor for adjusting the center frequency is provided at the open end of the line, thereby making the distributed constant filter more compact and improving its characteristics. Proposed by the applicant.

FIGS. 1 and 2 show the basic configuration of this type of distributed constant filter.

In these figures, inside a box-shaped conductor case 1, a plurality of resonators 4 loaded with a dielectric material 3 are arranged in series around a line 2 whose open end is formed into a disk shape.
Coaxial connectors 5.6 for input and output are provided on both end faces.

On the other hand, the upper surface part 10 of the box-shaped conductor case 1 has the line 2
A plurality of disc-shaped capacitor electrodes 11 are arranged facing the open end of the capacitor electrode 11 .

By the way, the above-mentioned distributed constant type filter is usually used in the microwave region, and its center frequency is adjusted by the capacitance between the open end of the line 2 and the capacitive electrode 11.

Therefore, in order to use it at a lower frequency, it is necessary to reduce the distance between the open end of the line 2 and the capacitor electrode 11, but reducing the gap between the two below a certain level will reduce the power durability. This is not a good thing because it deteriorates.

For example, the distance between the open end of the line 2 and the capacitive electrode 11 is 0.
If the length is about 2 m or less, short-circuit accidents and the like are likely to occur between the two, which not only deteriorates power durability but also reduces reliability, making it impractical.

In view of the above points, the present invention attempts to provide a small distributed constant filter that can be used in low frequency bands by adding a fixed capacitance in addition to the air capacitance between the open end of the line and the capacitive electrode. It is something to do.

Embodiments of the distributed parameter meter filter according to the present invention will be described below with reference to the drawings.

FIG. 3 shows a first embodiment of the invention.

In this figure, a dielectric material 3 is placed around the resonator 40 line 2.
is loaded, and a capacitor electrode 11A is screwed onto the upper surface portion 10 of the box-shaped conductor case 1 so as to face the open end 20 of the line 2.

A capacitor 21 serving as a fixed capacitance is connected between the open end 20 and the upper surface portion 10.

Note that the configuration of other parts is the same as in the case of FIGS. 1 and 2 described above.

According to this first embodiment, by appropriately selecting the capacitance of the capacitor 21, the resonant frequency of the resonator 4 can be considerably lowered, and therefore the gap between the open end 20 and the capacitive electrode 11A can be reduced. There is no need to make it extremely small, and it is possible to improve power durability and reliability.

Furthermore, if the capacitor 21 is not added, the resonator 4
Although the overall size of the resonator 4 becomes extremely large, the size of the resonator 4 itself can be reduced to 11 due to the provision of the capacitor 21.

Therefore, the shape of the entire distributed constant type filter and the t-type filter can also be made smaller.

FIG. 4 shows a second embodiment of the invention.

In this figure, a dielectric material 3 is placed around the resonator 40 line 2.
is loaded, and a capacitive electrode 11B with a slightly smaller diameter is placed on the upper surface 10 of the box-shaped conductor case 1 so as to face the open end 20 of the line 2.
is screwed into the

Further, one electrode of a chip capacitor 22 is directly connected and fixed on the open end 20, and the other electrode is connected to the upper surface portion 10 of the box-shaped conductor case 1 via a conductive wire 23.

According to this second embodiment, since the chip capacitor 22 is used, further miniaturization can be achieved, and the adverse effects caused by the lead wire of the capacitor can be reduced, and the characteristics can be improved. can.

FIG. 5 shows a third embodiment of the invention.

In this figure, a resonator 40 line 2 is loaded with a dielectric 3, and a capacitive electrode 11C of a rather small diameter is screwed onto the upper surface of the box-shaped conductor case 1 so as to face the open end of the line 2.

In addition, a chip capacitor 2 is attached to the inner surface of the box-shaped conductor case 1.
One electrode of 2 is connected and fixed, and the other electrode is connected to the conductor 24.
It is connected to the open end 20 via.

The effects of this third embodiment are substantially the same as those of the second embodiment described above.

As mentioned above, according to the present invention, by adding a fixed capacitance in addition to the air capacitance between the open end of the line buttoned to the resonator and the capacitive electrode, it can be used in a low frequency band,
A distributed constant type filter that can be miniaturized is obtained.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing a basic distributed constant type filter.
Fig. 2 is a plan view with the top surface of the box-shaped conductor case removed; Fig. 3 is a partial longitudinal sectional view showing the first embodiment of the distributed constant filter according to the present invention; Fig. 4 is a plan view of the box-shaped conductor case with the top surface removed; FIG. 5 is a partial longitudinal cross-sectional view showing the second embodiment, and FIG. 5 is a cross-sectional view showing the third embodiment of the present invention. 1... Box-shaped conductor case, 2... Line,
3... Dielectric, 4... Resonator, 10.
...Top part, 11.11A to 11C...
・Capacitance electrode, 20...Open end, 21...
・Capacitor, 22... Chip capacitor, 2
3.24... Conductor.

Claims (1)

[Scope of utility model registration request] In a distributed constant filter in which a dielectric is loaded on a line with one end short-circuited and the other end open, and a resonator with a capacitance provided at the open end of the line is placed in a case, the capacitance is connected to the open end. A distributed constant type filter comprising: a variable capacitor connected to a capacitor electrode facing the capacitor and screwed to the case; and a fixed capacitor connected between the open end and the case. .