JPS61161803A - High frequency filter - Google Patents

Abstract

PURPOSE:To obtain a low loss filter with small size, light weight and ease of adjustment by forming a strip conductor in plural slots provided in parallel with a dielectric board while making the open end in the same direction and providing a slot between the strip conductors and an input/output coupling stage. CONSTITUTION:Deep slots 21, 22 are provided at the outside of the strip conductors 11, 13 at both sides and the metallic conductors 23, 24 connected to outer lead terminals 16, 17 are buried in them. The frequency is adjusted by changing the length of the strip conductors 11-13, the input/output and inter-stage coupling are adjusted by changing the size of the deep slots 21, 22, metallic conductors 23, 24 and slots 25, 26 among the strip conductors 11-13 respectively. Since the adjusting position exists all at exposed side, the adjustment is attained easily. Further, since the strip conductors 11-13 are formed at lower bottom of the slots 18-20, the wavelength reducing rate is increased and the filter is miniaturized.

Description

[Detailed description of the invention] [Industrial application field] This invention applies to relatively high frequency bands, especially VHF bands.

U) This article relates to high frequency filters often used in the IF band and microwave band.

[Conventional technology]

First, a conventional high frequency filter shown in FIG. 6 will be explained. In Fig. 6, (a) is a partially missing plan view;
Figure (b) is a cross-sectional view taken along line A-A in figure (a), and (1a)
~(5a), (lb) ~(5b) are strip conductors, (Ela), (6N are ground conductors, (7), (8) are coaxial terminals, (8) are center conductors of coaxial terminals, (10a) ,
(10b) shows a dielectric plate.

1 strip (1a) to (5a), ground conductor (8a)
is formed of a conductive film in close contact with the dielectric plate (10a), and each of the strips 1 (1b) to (5bl) ground conductor (6b) is formed of a conductive film in close contact with the dielectric plate (10b).

Also, these strip conductors (la) to (5a), (l
b) - (5b), ground conductor (8a), (8b), dielectric plate (10a).

(10b) are superimposed so as to have a symmetrical structure with respect to the B-B plane in FIG. 7(b).

The shape of the connection part of the coaxial terminal (8) is as shown in detail in FIG.
) are connected so as to match the positions of the strip conductors (5a) and (5N).The coaxial terminal (7) is also connected in the same manner.

In this high frequency filter, a strip conductor (2a),
(2N , (3a), (3b), and (4a), (4
If b) resonates at the same frequency fo, then at the frequency fO, the strip conductors (la), (lb) and (5a)
, (5N is the strip conductor (2a) in resonance state, (
2b) to (4a) and (4b), and the incident wave to the coaxial terminal (7) is guided to the terminal (8). However, at frequencies other than fa, the strip conductor (la), (
The coupling between lb) to (5a) and (5b) is very weak, and most of the power of the incident wave to terminal (7) is reflected. In this way, the high 1WIftF filter shown in FIG. 7 has a function as a bandpass filter.

[Problem that the invention seeks to solve]

However, conventional high frequency filters use strip conductors (l
a), (IN ~ (5a), (5b) are dielectric plates (10
a).

Since it has a structure that is sandwiched between (10b),
Strip conductor (la), (1b3~(5a), (
5b) has the disadvantage that it is difficult to adjust the amount of coupling between them and the resonance frequency.

This invention was made in order to eliminate the drawbacks of the conventional filters such as E, and provides a high frequency filter in which the amount of coupling of the strip conductor film and the resonance frequency can be easily adjusted.

Means for Solving Each Question and One Point] In the high frequency filter according to the present invention, a plurality of strip conductor grooves are provided in the power distribution board, and the strip conductors are placed in each groove so that the open ends thereof are oriented in the same direction. In addition, the external lead terminal is taken out from the metal conductor in a deep groove provided outside the strip conductor at both ends and on the open end side.

[Effect]

In the high frequency filter according to the invention, the strip 1
Since the conductor is formed on the exposed surface of the dielectric plate, it is easy to adjust the coupling amount and resonance frequency of the strip conductor, and since the strip conductor is formed in the groove, the electric field leaking into the space outside the dielectric is extremely small. The wavelength shortening rate is greater than that of a normal microstrip line formed on a small, flat dielectric plate, and the strip conductor is shortened, allowing for miniaturization.

Regarding the mutual coupling of the strip conductors, since the strip conductors are provided in the groove, the state is close to that of a uniform medium, and since the open ends are oriented in the same direction as 174-wavelength resonators, mutual coupling is reduced. Although it is small, in this filter, the metal conductor in the deep groove provided outside the strip conductor and on the open end side plays the role of a capacitor, and the metal conductor and the strip conductor play the role of a capacitor. The desired amount of binding can be obtained.

〔Example〕

FIG. 1 shows one embodiment of this invention.

(11) to (13) are strip conductors, (10 is a ground conductor, (15) is a dielectric plate, (18L (17) is an external lead terminal, and (18) to (20) are provided on a dielectric plate. The strip conductor forming grooves (21) and (22> are deep grooves in the longitudinal direction of the strip conductor provided on the open end side of the strip conductor of the mold body plate (15) and at outer positions on both sides of the strip conductor. , metal conductors (23) and (24) facing the negative faces of the outer strip conductors (11) and (13) are embedded in the deep grooves (21) and (22), and metal conductors (231, (24) and strip conductor (11
) and (13) form a capacitor, and external lead terminals (1B) and (17) are connected to this metal conductor. Also, (25) and (2B) are strips (11) and (12).
), (12) and (13) are coupling amount adjustment grooves provided between them.

1. The strip conductors (111 to (13) are dielectric plates (
The grooves (1B) to (20) provided in the grooves (15) are formed of a conductive film so as to expose their edges and cover the bottom, with one end open and the other end short-circuited with the ground conductor (14). te174
These strip conductors (1
1) to (13) are arranged so that their open ends are oriented in the same direction. In addition, the strip conductors (11) to (131
, the ground conductor (14) is a conductor film and is integrally formed on the dielectric plate (15).

Normally, a 1/4 wavelength co-installer installed in a homogeneous medium and with the open ends oriented in the same direction eliminates coupling, but in the case of a microstrip line like the high frequency filter of this invention, it is non-uniform. The strip conductors (11) to (13), which become resonators because they become lines in the medium, are coupled to the phase τ.

In the above a-configuration filter, the strip conductor (11) ~
(13) resonates at the same frequency fO, the strip conductors (11) and (13) are strongly coupled at one frequency fO, and the incident wave to the external extraction terminal (IB) is transmitted to the external extraction terminal (17). guided by. However, at frequencies other than to, the coupling between the strip conductors (11) and (13) is very weak, and most of the power of the wave incident on the external lead terminal (1B) is reflected. In this way, the high frequency filter shown in FIG. 1 has a function as a band pass filter.

In the high frequency filter of this embodiment, the strip conductor (11)
Since the strip conductors (11) to (13) are formed on the exposed surface of the dielectric plate (15), the amount of coupling and resonance frequency between the strip conductors (11) to (13) can be easily adjusted. The amount of coupling is determined by the groove provided between the strip conductors (11) to (13), (25)
.

You can change the dogness of (2B), groove (25), (2B)
') can be changed by filling part of it with dielectric material. N, the resonant frequency is the strip conductor (11)
It can be easily adjusted by changing the length of ~(13) or bonding a dielectric material to the open end. Furthermore, external lead terminals (183, (17)) and strip conductors (11
), (13) is a single metal body (23), (24)
size, strip conductors (11), (13) and grooves (21).

By changing the spacing of (22), the metal conductor (23)
.

The capacitance of the capacitor formed by (24) and the strip conductors (11) and (13) can be changed and easily adjusted.

h2 The strip conductors (11) to (13) in Fig. 1 are grooved (
18) to (20), the electric field leaking into the space outside the dielectric plate (15) is very small, compared to a normal microstrip line formed on a flat dielectric plate. The wavelength shortening rate is large, so the length is approximately 1
Strip conductors (11) to (13) selected for 74 wavelengths
is shortened, resulting in miniaturization.

In addition, the strip conductors (11) to (13) have a substantially semicircular arc shape, as shown in FIG. 2, which is a cross-sectional view taken along the line C-C in FIG. It is.

Therefore, the current component on the surface facing the ground conductor (14) does not concentrate at the end like in the case of a planar microstrip line, but becomes a more uniform current component, reducing line loss. . Therefore, a filter with low loss can be obtained.

FIG. 3 shows another embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals. Conductor (27)
, (28) are integrally formed with a conductor film together with the strip conductors (11) to (13) and the ground conductor (14),
Work becomes easier.

FIG. 4 shows still another embodiment of the present invention. In this embodiment, the strip conductors (11) to (13) are formed on the entire surface of the grooves (18) to (20), so that the ground conductor ( 14) It is easy to work when integrally formed with a conductive film. Furthermore, the embodiment shown in FIG. 5 combines the features of the E2 embodiments shown in FIG. 3 and FIG. 4.

The strip conductors (11) to (13) are connected to the grooves (181 to (2)
0) is formed on the entire surface, and the conductors (27) and (28) are connected to the strip conductors (11) to (13) 71 and the ground conductor (1).
Since it can be integrally formed with a conductor film along with 4), 1
It becomes extremely easy to create.

Although the case where the number of strip conductors is 3 has been described above, the present invention may also be applied to a case where the number of strip conductors is 4 or more.

〔Effect of the invention〕

As shown in H below, in the high frequency filter according to the present invention, grooves are provided in the dielectric plate, and the nose body of Met 9-2 is formed in 1wR so that the open ends are oriented in the same direction. Coupling amount adjustment grooves are provided in each of the conductor films, and deep grooves are provided in the longitudinal direction of the strip conductor on the side surface of the F dielectric plate on the open end side of the strip conductor and at positions outside both ends of the strip conductor. A metal conductor facing one surface of the outer strip conductor is provided in the interior, and the external lead end is connected to this metal conductor, so the amount of coupling between the external lead terminal, the strip conductor, and the METRI9P conductor film, as well as the common dark wave number, are This provides the advantage of being able to obtain a filter that is easy to adjust, is small, and has low loss.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a high frequency filter of the present invention, FIG. 2 is a sectional view taken along the line CC in FIG. 1, and FIG. FIG. 4 is a schematic configuration diagram showing still another embodiment of the present invention, FIG. 5 is a schematic configuration diagram showing still another embodiment of the invention, and FIG. 6 is a schematic configuration diagram of a conventional high frequency filter. In the figure, figure (a) is a plan view with some parts missing, figure (b) is a sectional view taken along line A-A in figure (a), and figure 7
The figure is an enlarged view of the connection portion between the strip conductors r5a) and (5b) of FIG. 6 and the coaxial terminal (8). In the figure, (11) to (13) are strip conductors, (14)
is a ground conductor, (15) is a dielectric plate, (113), (17
) are external lead terminals, and (18) to (20) are grooves for forming strip conductors. (21), (22) are deep grooves, (23), (2+1 are metal conductors, (25), (2B) are coupling amount adjustment grooves, (27)
, (28) are conductors. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (5)

[Claims] (1) In a high-frequency filter in which a strip conductor and a ground conductor are integrally formed with a conductor film closely attached to a dielectric plate, a plurality of grooves for forming strip conductors are provided on the dielectric plate, and one end is shorted in each groove. The strip conductors each having the other end open are formed so that the open ends thereof are oriented in the same direction, and each of the strip conductor films is provided with a coupling amount adjustment groove,
A deep groove is provided in the longitudinal direction of the strip conductor on the side surface of the open end side of the strip conductor of the dielectric plate and at positions outside both ends of the strip conductor, and a metal conductor is provided in the deep groove facing one surface of the outer strip conductor, A high frequency filter characterized in that an external lead end is connected to this metal conductor. (2) Each of the strip conductor forming grooves described above has a substantially semicircular arc shape, and the center portion of the strip conductor that is in close contact with this groove is close to the ground conductor, so that the current component on the surface facing the ground conductor is made uniform. A high frequency filter according to claim 1, characterized in that: (3) The high frequency filter according to claim 1 or 2, wherein each of the strip conductors is formed so as to expose the upper edge of the groove and cover the lower bottom of the groove. (4) The high frequency filter according to item 1 or 2, wherein each of the strip conductors is formed on the entire surface of the groove. (5) The high frequency filter according to any one of claims 1 to 4, wherein the metal conductor is integrally formed with a conductor film together with a strip conductor and a ground conductor.