JPS6390203A - Dielectric filter - Google Patents

Abstract

PURPOSE:To miniaturize a dielectric filter by forming an outer conductor and inner conductors with a conductive film closely brought into contact with the surface of a dielectric block or inside peripheral surfaces of through holes and providing first grooves, with which a conductive film is closely brought into contact, between inner conductors. CONSTITUTION:An outer conductor 10 is formed with the conductive film closely brought into contact with the surface of a dielectric block 50, and inner conductors 30 are formed with the conductor film closely brought into contact with inside peripheral surfaces of plural through holes which are provided at intervals of a prescribed length on one side face of the dielectric block 50 and whose length is an about 1/4 wavelength, and one-side ends are connected to the outer conductor 10 without joints, and the other ends are open ends. Capacity load forming grooves 7 with which the conductor film is closely brought into contact are provided between inner conductors 30 on the open end side face of inner conductors 30 of the dielectric block 50 to realize capacity loads. Since the length of the part where inner conductors 30 adjacent to each other are coupled is shorter than a 1/4 wavelength by the effect of capacity load forming grooves 7, inner conductors 30 are coupled mainly with a magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric filter that is widely used in relatively high frequency bands, particularly in the VHF band, UHF band, and microwave band.

[Conventional technology]

FIG. 7 is a diagram showing a schematic structure of a conventional dielectric filter disclosed in, for example, Japanese Patent Laid-Open No. 55-143801.
) is a plan view with some parts missing, and (b) is a vertical front view. In the figure, 1.2 is the outer conductor, 3 is the inner conductor, 4 is the frequency adjustment screw, 5 is the dielectric, 6 is the input/output loop, P, , P
, are input/output terminals.

One end of the inner conductor 3 is connected to the outer conductor 1 and becomes a short-circuited end,
The other end is an open end, and a capacitive load is provided by a frequency adjustment screw 4. Because the length of the inner conductor 3 is 174 wavelengths or less due to the effect of capacitance, the inner conductor 3 is coupled to each other mainly by magnetic field coupling.

The amount of coupling is adjusted by the distance between the two inner conductors 3.

Further, the input/output cull 16 is arranged in parallel with and close to the inner conductor 3, and since the length of the parallel section is 174 wavelengths or less, the coupling is mainly due to the magnetic field.

Next, the operation will be explained. Now, if we assume that all the inner conductors 3 resonate at the same frequency r0 by adjusting the length of the inner conductors 3, then at the frequency f0, the inner conductors 3 in the resonant state will be strongly coupled to each other, and the input and output cables will be It is strongly coupled to the professional, and the incident wave to the input/output terminal P is the input/output terminal P! guided by. However, at frequencies other than the frequency f0, the coupling between the inner conductors 3 and the input/output Cal-Pro is very weak, and most of the power of the wave incident on the input/output terminal P1 or P2 is reflected. In this way, the conventional dielectric filter shown in FIG. 7 has a function as a bandpass filter.

[Problem that the invention seeks to solve]

Since the conventional dielectric filter is constructed as described above, even if it is made smaller by using a dielectric material with a high relative permittivity as the dielectric material 5 and providing a capacitive load using the frequency adjustment screw 4, the mechanical In order to have a stable configuration and to mount the frequency adjustment screw, the outer conductor 1.2 must have a certain thickness, and there is a natural limit to miniaturization.
Outer conductor 1゜2, inner conductor 3, frequency adjustment screw 4, dielectric 5
Because it is manufactured by assembling individual parts such as
The large number of parts not only complicates manufacturing and assembly work, but also causes problems such as the resonant frequency changing when temperature changes occur due to the difference in linear expansion coefficient between the outer conductors 1 and 2, the inner conductor 3, and the dielectric 5. there were.

This invention was made to solve the above-mentioned problems, and aims to provide a dielectric filter that has a small number of parts, is easy to manufacture, can be made compact, and is stable against temperature changes. do.

[Means for solving problems]

In the dielectric filter according to the present invention, the outer conductor is formed of a conductive film that is in close contact with the surface of the dielectric block, and the inner conductor is in close contact with the inner peripheral surface of through holes formed in the dielectric block at predetermined intervals. It is formed of a conductor film seamlessly connected to the outer conductor, and a capacitive load forming groove having a conductor film is provided between each inner conductor on the side surface of the dielectric block on the open end side of the inner conductor.

[Effect]

The dielectric filter of this invention is formed of a dielectric block and a conductive film in close contact with the dielectric block, thereby reducing the number of parts and simplifying manufacturing and assembly. It is possible to reduce the size of the filter by simply shortening the wavelength using a filter with almost no other restrictions, and by attaching the conductive film to the dielectric block, it is possible to reduce the size of the conductor and dielectric as in conventional dielectric filters. While removing the effects of gaps between copper and its linear expansion coefficient.

Good temperature characteristics are achieved by determining the coefficient of linear expansion of the dielectric material, which is smaller than that of a highly conductive metal such as aluminum.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a perspective view showing a schematic configuration of a dielectric filter according to an embodiment of the present invention, FIG. 2(a) is a cross-sectional view taken along the line A-A,
FIG. 3B is a diagram showing the potential distribution along the inner conductor, and FIG. 3 is a diagram showing the pass characteristics of the dielectric filter shown in FIG.

In FIG. 1, 10 is an outer conductor, 30 is an inner conductor, 50 is a dielectric block, 5a and 5b are input/output inner conductors, 7 is a capacitive load forming groove (first groove), and 70 is a damping characteristic conversion groove ( Second
groove).

The outer conductor 10 is formed of a conductive film disposed in close contact with the surface of the dielectric block 50, and the inner conductor 30 is
It is formed by a conductive film disposed in close contact with the inner circumferential surface of a plurality of through holes each having a length of approximately 1/4 wavelength and provided at predetermined intervals on one side of the dielectric block 50. One end is seamlessly connected to the outer conductor 10, and the other end is an open end. A capacitive load forming groove 7 in which a conductor film is disposed in close contact with each other is provided between each inner conductor 30 on the side surface of the inner conductor 30 of the dielectric block 50 on the open end side, thereby realizing a capacitive load. Due to the effect of the capacitive load forming groove 7, the length of the mutually coupled portion of the adjacent inner conductors 30 is 1
Since the wavelength is shorter than 74 wavelengths, the inner conductor 30 is mainly coupled by the magnetic field. The amount of coupling can be adjusted by adjusting the interval between the inner conductors 30 and mainly the depth of the capacitive load forming groove 7.

The input/output inner conductors 6a and 6b are formed of a conductor film and are connected to the outer conductor 1.
0, and are connected to the inner conductor 30 at both ends to form an input/output coupling circuit of a type that shunts a part of the current flowing through the inner conductor 30. Second groove 70
are the upper and lower surfaces of the dielectric block 50, that is, the inner door body 30
are provided in a direction perpendicular to each inner conductor 30 at a position approximately 1/3 of the total length of the inner conductor 30 from the short-circuited end side of the inner conductor 30 on each plane parallel to the arrangement direction of the outer conductor 10. Seamlessly connected conductor films are placed in close contact with each other.

Next, the operation will be explained. Now, by adjusting the length of the inner conductors 30, all the inner conductors 30 have the same frequency f0.
If the inner conductors 30 in a resonant state are strongly coupled to each other at the frequency f0, they are also strongly coupled to the input/output inner conductors 5a and 5b, and the input/output inner conductors 5a and 5b connected to the input/output inner conductor 6a are strongly coupled to each other. The incident wave to the terminal is guided to the input/output terminal connected to the input/output inner conductor 6b. However, the frequency f0
At frequencies other than that, the coupling between the inner conductors 30 and the input/output inner conductors 6a and 6b is very weak, and the coupling between the inner conductors 30 and the input/output inner conductors 5
Most of the power of the incident waves to the input/output terminals connected to terminals a and 5b is reflected. In this way, the dielectric filter of this embodiment has a function as a bandpass filter.

Here, if there is no second groove 70, there is a problem that not only the fundamental wave but also the third harmonic will resonate and pass through the same resonator, as shown by the broken line in FIG. 2(b). However, as in this embodiment, the attenuation characteristic conversion groove 70 is provided near the position where the potential of the third harmonic is maximum, that is, at a position approximately 173 points from the short-circuited end side of the inner conductor 30. In this case, the reduction in the resonant frequency due to the capacitance generated between the attenuation characteristic conversion groove 70 and the inner conductor 300 will be greater for the third harmonic than for the fundamental wave, and therefore, as shown in the pass characteristic in FIG. As such, the passband of the third harmonic is lower than 3to, and an amount of attenuation can be obtained even at a frequency three times that of the fundamental wave.

Further, the attenuation characteristic conversion groove 70 does not necessarily need to be provided on both the upper and lower surfaces of the dielectric block 50, and may be provided only on one of the upper surface or the lower surface.

FIG. 4 is a perspective view showing a dielectric filter according to another embodiment of the present invention, in which the attenuation characteristic conversion groove 70 is provided at a position of about 173 points along the entire length of the inner conductor 30 from the open end side of the inner conductor 30. This is different from the embodiment shown in FIG. In this case, as shown in FIG. 5(b), since the attenuation characteristic conversion groove 70 is provided near the position where the potential of the third harmonic becomes zero, the electrostatic charge between the groove 70 and the inner conductor 30 is reduced. Capacitance has almost no effect on the third harmonic and only lowers the resonant frequency of the fundamental wave. Therefore, as for the pass characteristic, as shown by the solid line in FIG. 6, the pass band for the third harmonic does not change, and only the pass band for the fundamental wave decreases. As shown by the broken line in Figure 4, when the fundamental wave passband is adjusted to a predetermined frequency, the interval between the fundamental wave and third harmonic passband does not change, so even at a frequency three times that of the fundamental wave. The amount of attenuation can be obtained.

In the above embodiment, the case where the number of inner conductors is three has been described, but the present invention can also be applied to cases where the number of inner conductors is two or four or more. Furthermore, although the input/output coupling circuit has been described as one in which the current flowing through the inner conductor is shunted, coupling by a magnetic field or coupling by capacitance may also be used (the same effect as in the above embodiment can be achieved).

〔Effect of the invention〕

As described above, according to the present invention, the outer conductor and the inner conductor are formed of a conductor film that is in close contact with the surface of the dielectric block or the inner peripheral surface of the through hole, and the conductor film is disposed in close contact between the inner conductors. Because of the structure in which the first groove is provided, the outer conductor and inner conductor can be made extremely thin, and if a dielectric block with a large relative permittivity is used, it is possible to downsize the device with almost no other restrictions. In addition, since it is formed from a dielectric block and a conductive film closely attached to it, it not only has fewer parts and is easier to manufacture and assemble, but also has a coefficient of linear expansion smaller than that of highly conductive metals. Furthermore, unlike conventional dielectric filters, there is no effect of the gap between the conductor and the dielectric, and extremely good temperature characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a dielectric filter according to an embodiment of the present invention, FIG. 2(a) is a sectional view taken along line A-A in FIG. 1, and FIG. Figure 3 is a diagram showing the potential distribution along the inner conductor, Figure 3 is a diagram showing the passage characteristics, Figure 4 is a diagram showing the potential distribution along the inner conductor,
The figure is a perspective view showing a dielectric filter according to the present invention.
Figure (a) is a cross-sectional view taken along the line A-A in Figure 4, Figure 5 (b) is a diagram showing the potential distribution along the inner conductor shown in Figure 5 (a), and Figure 6 is a diagram showing the potential distribution along the inner conductor shown in Figure 5 (a). FIG. 7(a) is a diagram showing the characteristics, and FIG. 7(a) is a plan view with some parts missing showing the schematic structure of a conventional dielectric filter, and FIG. 7(b) is a longitudinal cross-sectional view of the same. 6a and 6b are input/output inner conductors (input/output coupling circuit), 7 is a capacitive load forming groove (first groove), 10 is an outer conductor, 30 is an inner conductor, 50 is a dielectric block, and 70 is a damping characteristic conversion groove. (Second groove). In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (3)

[Claims] (1) A dielectric block in which a plurality of through holes penetrating from one side to the back surface are formed at predetermined intervals, and a plurality of conductor films disposed in close contact with the inner peripheral surface of each of the through holes. an inner conductor of the dielectric block, an outer conductor formed of a conductive film closely disposed on the surface of the dielectric block, and one end of each of the inner conductors seamlessly connected to the outer conductor of the dielectric block; A dielectric filter comprising: a capacitive load forming groove having a conductor film provided between each of the inner conductors on a side surface on an open end side of the inner conductor and seamlessly connected to the outer conductor; and an input/output coupling circuit. (2) The dielectric block is arranged to connect the inner conductor at a position approximately ⅓ of the total length of the inner conductor from the short-circuited end of at least one of the upper and lower surfaces parallel to the arrangement direction of the inner conductor. Claim 1, characterized in that the attenuation characteristic conversion groove is provided in a direction perpendicular to the axial direction of the attenuator and in which a conductive film is closely disposed and is seamlessly connected to the outer conductor. Dielectric filter. (3) The dielectric block is located at a position approximately 1/3 of the total length of the inner conductor from the open end of the inner conductor on at least one of the upper surface and the lower surface parallel to the arrangement direction of the inner conductor. Claim 1, characterized in that the attenuation characteristic conversion groove is provided in a direction perpendicular to the axial direction of the conductor, and in which a conductive film is closely disposed and is seamlessly connected to the outer conductor.
Dielectric filter described in section.