JPH03145202A - Interdigital type filter - Google Patents

Abstract

PURPOSE:To attain mechanically stable support, ease of working and miniaturization by making two dielectric blocks in close contact together so that the surface provided with plural grooves is opposite to each other and each dielectric block is symmetrical with respect to the close contact faces. CONSTITUTION:Inner conductors 1a-5a, 2b-5b are formed by fitting a conductor film closely to an inner wall of grooves 7a-11a, 9b-11b formed almost recessed to a side of dielectric blocks 12a, 12b respectively. That is, the plural inner conductors 1a-5a, 2b-5b and outer conductors 6a, 6b on a bottom face are short- circuited alternately at one opposite side by short-circuit parts 13-17, and the two dielectric blocks 12a, 12b are contacted closely with each other so that the faces provided respectively with the plural grooves 7a-11a, 9b-11b are symmetrical with respect to the dielectric blocks 12a, 12b. Thus, the inner conductors 1a-5a, 2b-5b are supported mechanically stably against vibration or the like, the working is facilitated and the length of the inner conductors is decreased by the effect of the wavelength reduction in the dielectric substance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an interdigital filter used primarily in the VHF band, UHF band, and microwave band.

[Prior Art] Conventionally, there has been a radio wave device of this type as shown in FIG. This figure 4(a) is G, Matthaei
Pond,” MICROWAVE FILTER3, IMP
EDANCE-MATCIIIING NETWORKS
, AND C0UPLING 5TRUCTURES
,” PP, 614-625, 1964. McGr.
aw-11i11. Note that in the figure shown in (1
) to (5) are inner conductors, (6) are outer conductors, (7), (8)
are the coaxial terminals, and (9) and (10) are the center conductors of the coaxial terminals (7) and (8), respectively.

Figure 4(b) is a cross section taken along line B-B in Figure 4(a).
) to (6) are the same as in FIG. 4(a). Inner conductor (
2), (3), and (4) have one end as a short-circuit end and the other end as an open end, and are supported on the short-circuit end side.

In this interdigital filter, the inner conductor (2)
, '(3) and (4) are the same frequency f. 'f: If it resonates, frequency f. In this case, inner conductors (1) and (5) are inner conductors (2) and (3) in a resonant state.

(4), and the incident wave on the coaxial terminal (7) is guided to the terminal (8). However, at frequencies other than f, the coupling between the inner conductors (1) to (5) is very weak, and most of the power of the wave incident on the coaxial terminal (7) is reflected. In this way, the interdigital filter shown in FIG. 4(a) has a function as a bandpass filter.

[Problems to be Solved by the Invention] Since the conventional interdigital filter is configured as described above, the inner conductors (2) and (3).

(4) Since the open end side is not supported, there is a problem in that it is mechanically unstable due to vibrations and the like. In addition, since the inner conductors (2), (3), and (4) must have a length of at least approximately 1/4 wavelength of the resonant wave, I
When used at relatively low frequencies such as the JHF band, the inner conductor (
There was a problem that 2), (3), and (4) became long and the filter became large.

This invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to obtain an interdigital filter that is mechanically stable against vibrations, etc., easy to process, and compact. With the goal.

[Means for Solving the Problems] An interdigital filter according to the present invention has a plurality of grooves on the surface of each of two rectangular parallelepiped dielectric blocks running parallel to the surface from the side surface to the side surface opposite to the side surface. A conductor film is closely attached to the bottom surface of each of the two dielectric blocks and two side surfaces parallel to the groove to form an outer conductor, and a plurality of inner conductors are formed by closely attaching a conductor film to the inner wall of the groove. The plurality of inner conductors and the outer conductor on the bottom surface are alternately short-circuited at one end of the opposite side by a short circuit part of the conductor film, and the two dielectric blocks are connected to each other on the surface provided with the plurality of grooves. The dielectric blocks are assembled so that they are in close contact with each other so as to face each other, and the respective dielectric blocks are symmetrical with respect to the closely contacted surfaces. Further, in another aspect of the present invention, a conductor plate that contacts each of the opposing inner conductors is inserted into a plurality of through holes formed by the inner conductors that face each other in pairs.

[Function] In the present invention, a plurality of grooves are provided on the surface of each of two rectangular parallelepiped dielectric blocks, and a conductive film is closely attached to the bottom surface and two side surfaces parallel to the grooves of each of the two dielectric blocks. A conductive film is closely attached to the inner wall of the groove to form a plurality of inner conductors, and the plurality of inner conductors and the outer conductor on the bottom are alternately short-circuited at one end of the opposite side by a short-circuit part. However, since the two dielectric blocks were brought into close contact with each other so that the surfaces provided with the plurality of grooves faced each other and were symmetrical with respect to these surfaces, the inner conductor It is mechanically stably supported against vibrations and the like, making processing easier, and the length of the inner conductor can be shortened due to the wavelength shortening effect of the dielectric material. Further, in another invention, a conductor plate that contacts each of the opposing inner conductors is inserted into a plurality of through holes formed by the inner conductors that are opposed to each other, so that each of the through holes is The two inner conductors that form the same potential are at the same potential, and the generation of unnecessary modes is suppressed.

[Example] Fig. 1 is a block diagram showing an example of the present invention, with some parts missing.
FIG. 2 is a diagram for explaining the details of FIG.
a) ~(5a), (lb) ~(5b) are inner conductors, (6a), (6b) are outer conductors, (7a) ~
(lla) (7b) ~ (llb) are grooves, (L2a
), (12b) is a dielectric block, (13)
- (17) are short-circuit parts, (I8) are conductor plates that can be deformed by pressure, as shown in detail in Fig. 2, (19) are inner conductors (la), (lb) and outer conductor (6a). ,
(6b) and a conductor plate (18), (20) is composed of an inner conductor (2a), (2b), an outer conductor (6a), (6b) and a conductor plate (18). (21) is the inner conductor (3a)
, (3b), an outer conductor (6a), (6b) and a conductor plate (18), (2)
2) is the inner conductor (4a), (4b) and the outer conductor (6a)
).

(6b) and a conductor plate (18), (23) is composed of an inner conductor (5a), (5b), an outer conductor (6a), (6b), and a conductor plate (18). The triplate line (24) to (28) are through holes, and PL and P2 are input/output terminals.

Inner conductor (la) ~ (5a), (lb) ~ (5
b) are dielectric blocks (12a),
(12b) substantially concave grooves (7a) to (ll
It is formed by closely adhering a conductive film to the inner walls of a), (7b) to (11b). Outer conductor (6a)
, (6b) is a dielectric block (12a),
(12b) and the grooves (7a) to (11a
), (7b) to (11b) and are formed by closely adhering a conductive film over the side surfaces parallel to each other.

The short circuit parts (13) to (17) are connected to the corresponding inner conductors (1a) to
(5a), (lb) to (5b) A groove is formed by slightly notching the side surface of the dielectric block at one end, and a conductive film is formed in close contact with the groove. Inner conductor (la) ~
(5a), (lb) to (5b) are connected to the outer conductor (6) by the conductor film at the short circuit parts (13) to (17), respectively.
a) or (6b) and are short-circuited. In addition, the opposing inner conductors (la) and (lb), --a,
(5a) and (5b) are electrically connected to each other by a conductive plate (18) that can be deformed by pressure. At the input/output terminals Pi and P2, the inner conductors (la) and (
lb), (5a).

and (5b) the center conductor of the coaxial line, and the outer conductor (6a)
(6b) are connected to the outer conductors of the coaxial lines, respectively.

Next, the operation will be explained. In the interdigital filter of the embodiment shown in FIG.
19) to (23) are the same frequency r. If it resonates at f. Then, the triplet lines (19) and (23
) is a triplate line (20) in a resonant state,
(21) and (22), and the incident wave on the input terminal P1 is guided to the output terminal P2. but,
f At frequencies other than f1, the triplate line (19)
The coupling between ~(23) is very weak, and most of the power of the wave incident on the input terminal PI is reflected. In this way, the interdigital filter of the above embodiment has a function as a bandpass filter.

In the interdigital filter of the present invention, a substantially rectangular parallelepiped dielectric block is processed with grooves, and a conductive film is formed in close contact with a predetermined portion of the dielectric block by, for example, baking. Inner conductors (1a) to (5a), (1b) to (5b) that are easy to perform and mechanically stable
can be formed. In addition, a dielectric block (12a),
Due to the wavelength shortening effect of (12b), the inner conductor (la
) ~(5a), (lb) ~(5b) can be shortened.

Furthermore, in the case of a wave device having the structure shown in Fig. 1, the inner conductor (1a) and (l
b) , (2a) and (2b), (3a) and (3b)
.

When a potential difference is created between (4a) and (4b) or (5a) and (5b), the triplate line (19),
(20).

In (21), (22), or (23), in addition to the fundamental mode as shown in Fig. 3(b), as shown in Fig. 3(a) as a representative of the inner conductors (2a) and (2b), An unnecessary mode occurs. Note that in this figure, the arrow indicates the direction of electric flux. In the interdigital filter of this embodiment, the through holes (24) to (28) are formed by the conductor plate (18).
Inner conductors (la) and (Ib) forming (2a)
and (2b), (3a) and (3b), (4a) and (
4b), and (5a) and (5b) are connected and have the same potential, so an unnecessary mode as shown in FIG. 3(b) does not occur. Since the conductor plate (18) can be deformed by pressure, the grooves (7a) to (lla), (7b)
Inner conductor (1a) in all through holes (24) to (28) even if the depths of ~(llb) are slightly different individually.
and (lb).

(2a) and (2b), (3a) and (3b),
(4a) and (4b) and (5a) and (5b) are connected simultaneously.

In the above embodiment, the number of pairs of inner conductors is 5, but the number may be 3, 4, or 6 or more, and the same effect as in the above embodiment can be obtained. Moreover, in the above embodiment, the grooves (7a) to (lla).

Although the case where the cross-sectional shape of (7b) to (llb) is substantially concave is shown, it may be semi-elliptical or semicircular, and the same effect as in the above embodiment can be achieved. Furthermore, in the above embodiment, the conductor plate (
18) is inserted, but the conductor plate (18) is inserted.
) may be <5 nt.

[Effects of the Invention] As described above, according to the present invention, a plurality of grooves are provided in the surface of each of the two rectangular parallelepiped dielectric blocks in parallel to the surface from the side surface to the side surface opposite to the above-mentioned side surface.
A conductor film is closely attached to the bottom surface of each of the two dielectric blocks and two side surfaces parallel to the groove to form an outer conductor, a conductor film is closely attached to the inner wall of the groove to form a plurality of inner conductors, and a plurality of inner conductors are formed by closely attaching a conductor film to the inner wall of the groove. The non-conductor and the outer conductor on the bottom surface are alternately short-circuited at one end of the opposite side by a short-circuit part of the conductor film, and the two dielectric blocks are arranged so that the surfaces provided with the plurality of grooves face each other. Since each dielectric block is assembled in close contact with each other and is symmetrical with respect to the closely contacted surface, the inner conductor is mechanically stably supported against vibrations, etc., and processing is facilitated. Since the length of the inner conductor is shortened due to the wavelength shortening effect of the dielectric material, it has the effect of being mechanically stable against vibrations, etc., easy to process, and compact. Further, in another embodiment, a conductor plate that contacts both of the opposing inner conductors is inserted into the plurality of through holes formed by the inner conductors that are opposed to each other, so that the opposing inner conductors are connected to each other. have the same potential, which has the effect of suppressing the occurrence of unnecessary modes.

[Brief explanation of the drawing]

FIG. 1 is a partially omitted configuration diagram showing an embodiment of the present invention;
Fig. 2 is a diagram for explaining the details of Fig. 1, Fig. 3 is a diagram for explaining the operation of the wave filter shown in Fig. 1, and Fig. 4 shows a conventional interdigital filter. It is a schematic block diagram. In the figure, (la) ~ (5a), (lb)
~(5b) is the inner conductor, (6a), (6b) is the outer conductor, (7a) ~(lla), (7b) ~(l
lb) is a groove, (12a). (12b) is a dielectric block, (13) to (17) are short circuit parts, (18) is a conductive plate that can be deformed by pressure, (
24) to (28) are through holes, PL, and P2 are input/output terminals. Note that the same reference numerals in each figure indicate the same or corresponding parts. Figures (7b) to (l l b); Purchase Pl. P2. Input/output terminal diagram ((2,) 3 Figure 1) →-; Electric flux diagram (Ct)

Claims (2)

[Claims] (1) A plurality of grooves provided on the surface of each of the two substantially rectangular parallelepiped dielectric blocks from the side surface to the side surface opposite to the side surface, and a plurality of grooves provided in parallel to the surface, and the bottom surface of each of the two dielectric blocks and the groove. an outer conductor formed by closely adhering a conductor film to two side surfaces parallel to the groove, a plurality of inner conductors formed by adhering a conductor film to the inner wall of the groove, and an outer conductor formed between the plurality of inner conductors and the outer surface of the bottom surface. a short-circuit portion of a conductor film that alternately shorts the conductor at one end on the opposite side, the two dielectric blocks are brought into close contact with each other so that the surfaces provided with the plurality of grooves face each other; An interdigital filter characterized in that each of the dielectric blocks is combined in a symmetrical manner with respect to a surface in close contact with each other. (2) A conductor plate that contacts each of the opposing inner conductors is inserted into a plurality of through holes formed by the inner conductors that are provided in each of the two dielectric blocks and form a pair of opposing inner conductors. An interdigital filter according to claim 1.