JPH0642602B2 - Dielectric filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dielectric filter often used in the VHF band, the UHF band, and the microwave band.

[Conventional technology]

FIG. 7 is a vertical sectional view showing a conventional dielectric filter disclosed in, for example, JP-A-55-143801, and FIG. 8 is a plan view excluding the outer conductor lid and the frequency adjusting screw. In FIG. 1, 1 is an outer conductor body that also serves as a case, 2 is an outer conductor cover that covers the opening surface of the outer conductor body 1, and 3 are plurally arranged on the outer conductor body 1. Inner conductors 4, which are attached to the bottom part and have the other end being an open end, are adjustably screwed to the outer conductor lid body 2 corresponding to each inner conductor 3, and the end parts thereof are the open ends of the corresponding inner conductors 3. The frequency adjusting screw facing 5 is a dielectric closely arranged around the inner conductor 3, 6 is an input / output loop closely arranged to the inner conductors 3 arranged at both ends, and 7 and 8 are It is a coaxial terminal connected to the input / output loop 6.

Next, the operation will be described. One end of the inner conductor 3 is grounded to the outer conductor body 1 and the other end, which is an open end, is provided with a capacitive load by a frequency adjusting screw. The inner conductor 3 has a length shorter than 1/4 wavelength due to the effect of the capacitive load. Then, they are mutually coupled mainly by magnetic field coupling, and the coupling amount is determined by the distance between the adjacent inner conductors 3. Further, the inner conductor 3 and the input / output loop 6 at both ends are also coupled mainly by a magnetic field because the length of the section in which the inner conductor 3 and the input / output loop 6 are close to each other in parallel is ¼ wavelength or less. Now, assuming that all the inner conductors 3 resonate at the same frequency, for example, ₀ by adjusting the length of the inner conductor 3 and the frequency adjusting screw 4, at the frequency ₀ , the inner conductor 3 is in a resonance state. Conductor 3 is the inner conductor 3 and
And the input / output loop 6 and the coaxial terminal 7
The incident wave on is guided to the coaxial terminal 8. However,
_At frequencies other than ₀ , the mutual coupling between the inner conductors 3 and the coupling between the inner conductor 3 and the input / output loop 6 is very weak, and the coaxial terminal 7
Alternatively, most of the power of the incident wave on 8 is reflected. Thus, the dielectric filter shown in FIGS. 7 and 8 has a function as a bandpass filter.

[Problems to be solved by the invention]

Since the conventional dielectric filter is configured as described above, the outer conductor main body 1 and the outer conductor lid 2 are provided with the inner conductor 3 and the frequency adjusting screw 4 and function as a case having a mechanically stable structure. In order to satisfy the above requirements, a certain amount of wall thickness is required, which hinders weight reduction, and the outer conductor body 1, outer conductor lid 2, inner conductor 3, frequency adjusting screw 4, dielectric 5 etc. are all individual parts. In addition to the large number of parts, which complicates the manufacturing and assembly, the resonance frequency changes when the temperature changes due to the difference in the linear expansion coefficient between the outer conductor body 1, the outer conductor lid 2, the inner conductor 3 and the dielectric 5. In addition, the contact resistance is likely to increase due to a gap or poor contact at the connecting portion between the inner conductor 3 and the outer conductor main body 1. In such a case, the current is maximized at this portion, resulting in filter loss. Don't grow There was the problem of.

In addition, there is a problem that a large amount of current flows in the short-circuited end, which is the joint between the outer conductor body 1 and the inner conductor 3 shown in FIG. 7, which causes a loss increase.

The present invention has been made to solve the above-mentioned problems, and has a small number of parts, is easy to manufacture and assemble, and can be made compact and lightweight. Further, it is stable against temperature changes and has a low temperature. The purpose is to obtain a lossy dielectric filter.

[Means for solving problems]

A dielectric filter according to the present invention is a conductor film in which an inner conductor of approximately ½ wavelength is closely attached to the inner peripheral surfaces of a plurality of through holes formed in a dielectric block, and an outer conductor is a through hole of the dielectric block. Is formed of a conductor film that is in close contact with the outer peripheral surface other than the opening surface, and the inner conductor coupling means is provided on at least one of the flat surface and the bottom surface of the dielectric block.

[Action]

In the dielectric filter according to the present invention, the inner conductor and the outer conductor are formed of a conductor film in close contact with the dielectric block, and the inner conductor coupling means provided on at least one of the flat surface and the bottom surface of the dielectric block functions as a filter. This is achieved by integrating the inner and outer conductors and the dielectric block to reduce the number of parts, facilitating manufacturing and assembly, and eliminating the need for the outer conductor to have the function of the case, while also reducing the weight and temperature characteristics. Is determined by the temperature characteristics of the dielectric, and by making both ends of the inner conductor open ends, problems such as gaps in the connection with the outer conductor and contact resistance are eliminated, Prevent increased loss.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, reference numeral 9 denotes a dielectric block made of a dielectric having a high dielectric constant, and 10 denotes one side surface of the dielectric block 9, for example, a front surface is opened to a rear surface which is an opposite surface thereof in parallel with the plane and the bottom surface. , A plurality of through holes arranged in parallel to the plane and the bottom surface, and 11 on the plane, the bottom surface, the left side surface, and the right side surface of the dielectric block 9 excluding the front surface and the back surface where the through holes 10 are open. An outer conductor composed of a conductor film arranged in close contact, a reference numeral 12 composed of a conductor film arranged in close contact with the inner peripheral surface of each of the through holes 10, and the length thereof is set to about ½ wavelength. An inner conductor that constitutes a half-wave resonator with both ends open together with the outer conductor 11,
Reference numeral 14 is an input / output inner conductor as an input / output coupling means that is connected to the inner conductors 12 arranged at both ends and divides and extracts a part of the current flowing through the inner conductor 12, and 15 and 16 are planes of the dielectric block 9. And a conductor film which is continuously engraved on the bottom surface in a direction perpendicular to the axial direction of the inner conductor 12 and which is seamlessly connected to the outer conductor 11 is closely arranged to form a groove which acts as an inner conductor coupling means. Are provided at positions of about ¼ wavelength or about ⅙ wavelength from the front surface and the back surface of the dielectric block 9 having open ends.

Next, the operation will be described. When the groove 15 is provided in the half-wave resonator formed by the inner conductor 12 and the outer conductor 11, 1
The electric field inside the / 2 wavelength resonator has a distribution concentrated in the groove 15 as shown in Fig. 2 (a). This electric field distribution is a combination of the TEM mode as shown in FIG. 2 (b) and the local TM mode as shown in FIG. 2 (c).
This also applies to the groove 16. In the TEM mode of FIG. 2 (b), when the resonator having the length of the inner conductor 12 of ½ wavelength is arranged as shown in FIG. 1, the electric field coupling and the magnetic field coupling cancel each other out. Although the mutual coupling between the inner conductors 12 disappears, the coupling between the inner conductors 12 can be obtained by the local TM mode in FIG. 2 (c). This local TM mode is a mode in which the amount of generation changes depending on the depth of the groove 15 and attenuates as it goes away from the generation point, so the amount of coupling is adjusted by the depth of the groove 15 and the mutual spacing of the inner conductors 12. can do. In the embodiment shown in FIG. 1, the inner conductors 12 are arranged at unequal intervals in order to obtain necessary filter characteristics.

Now, assuming that all the inner conductors 12 resonate at the same frequency ₀ by adjusting the length of the inner conductors 12, at the frequency ₀ , the inner conductors 12 in the resonance state are adjacent to each other. Alternatively, an incident wave to the input / output inner conductor 13, which is strongly coupled to the input / output inner conductor 13, and is connected to the input / output inner conductor 13, is connected to the input / output inner conductor 14. Guided to the output terminal. However, at frequencies other than ₀ , the mutual coupling between the inner conductors 12 and the coupling between the inner conductors 12 and the input / output inner conductors 13 and 14 are very weak, and the coupling to the input / output terminals connected to the input / output inner conductors 13 or 14 is very weak. Most of the electric power of the incident wave is reflected. As described above, the dielectric filter of the present invention has a function as a bandpass filter.

Here, in this embodiment, as shown in FIG. 3 (a), a position about 1/4 of the axial length of the inner conductor 12 from the open end of the groove 15,
That is, in the electric potential distribution along the inner conductor 12 shown in FIG. 3 (b), the electric potential of the secondary resonance mode is carved at a position where the electric potential is zero (the magnetic field is maximum). Therefore, the resonance frequency of the groove 15 and the fundamental mode is lowered, and the resonance frequency of the secondary resonance mode is raised. Therefore, the frequency interval between the fundamental mode wave and the secondary resonance mode wave is widened, and when the resonance frequency of the fundamental mode is set to a predetermined frequency, the attenuation amount can be obtained even at a frequency twice the fundamental wave. Similarly, the groove 16 is also carved at a position about 1/6 of the axial length of the inner conductor 12 from the open end where the potential of the third resonance mode becomes zero. Therefore, the groove 16 lowers the resonance frequency of the fundamental mode and increases the resonance frequency of the third-order resonance mode.
The frequency interval between the fundamental mode wave and the third-order resonance mode wave is widened, and the amount of attenuation can be obtained even at a frequency three times the fundamental wave.

In the above embodiment, the groove 15 is provided at a position of about ¼ wavelength from one open end of the inner conductor 12, and about 1 wavelength from the other open end.
Although the case where the groove 16 is provided at the position of / 6 wavelength is shown, as shown in FIG. 4, the positions of about 1/4 wavelength and about 1/6 wavelength are provided from both open ends of the inner conductor 12. , Groove 15
The groove 16 and the groove 16 may be provided respectively. In that case, the attenuation characteristics of the second and third harmonic components are better than those of the embodiment of FIG.

Further, in the above embodiment, the groove is used as the inner conductor coupling means, but this may be replaced by a step. FIG. 5 is a perspective view showing such an embodiment. In FIG. 5, 17 is a step provided in place of the grooves 15 and 16 shown in FIG. 1
It is provided continuously in the direction perpendicular to the axial direction of the two. Reference numeral 18 is a high impedance portion, and the other portions are equivalent to those designated by the same reference numerals in FIG. Also in this case, similar to the case of the embodiment shown in FIG. 1, a local TM mode is generated in the electromagnetic field in the portion of step 17 and mutual coupling of the inner conductors 12 is obtained, and the coupling amount is equal to that of step 17. It can be adjusted by the height and the distance between the inner conductors 12. In addition, the effect of step 17 on the fundamental wave and the second and third resonance mode waves differs due to the difference in the electromagnetic field distribution.
Similar to the embodiment of FIG. 1, it is possible to obtain the attenuation amounts for the second and third harmonic components. Further, according to this embodiment, the axial length of the inner conductor 12 for obtaining the predetermined resonance frequency of the fundamental wave can be shortened by the action of step 17.

Further, FIG. 6 is a perspective view showing still another embodiment of the present invention, in which grooves 15 and 16 in a direction perpendicular to the axis of the inner conductor 12 and step 17 are provided at the same time as inner conductor coupling means. is there. In this case, the grooves 15, 16 and the step 17
A large amount of attenuation can be obtained at the frequency twice or three times the fundamental wave by the synergistic effect of. Also, step 1
Since the size of 7 does not have to be increased, the decrease in the no-load Q is slight and the increase in loss of the dielectric filter is also slight.

In the above embodiment, the case where the inner conductor coupling means is provided on both the flat surface and the bottom surface of the dielectric block has been described, but it may be provided on only one of the surfaces and the number of inner conductors. Also, although the case of three wires has been described, it is also possible to apply to other numbers, and as the input / output coupling means, only the input / output inner conductors for shunting the current of the inner conductors arranged at both ends are also used. Alternatively, a type in which the inner conductors at both ends are coupled by electrostatic coupling or magnetic coupling may be used, and in either case, the same effect as that of the above-described embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, the dielectric film is made of the conductive film closely attached to the inner peripheral surface of each through hole, and the length of the conductive film is set to approximately 1/2 wavelength of the resonance frequency. A conductor, an outer conductor made of an attractant film disposed in close contact with the outer peripheral surface of the conductor block except the surface where the through holes of the conductor block are open, and an input / output coupling means coupled to a predetermined inner conductor, Since the inner conductor coupling means is provided at at least one of the plane and the bottom surface of the dielectric block and the potential distribution of higher frequencies of the resonance frequency is substantially zero, the high resonance frequency There is an effect that the amount of attenuation at the next frequency can be obtained. Also, it is possible to reduce the weight because it is not necessary to give the outer conductor a case function.
The temperature characteristics are determined by the temperature characteristics of the dielectric, which has a smaller coefficient of linear expansion than metal, and it is not only stable, but frequency adjustment screws are not required, and individual parts are closely arranged with the inner and outer conductors. It is integrated into a dielectric block to facilitate manufacturing and assembly, and since both ends of the inner conductor are open ends, problems such as gaps in the connection with the outer conductor and contact resistance are eliminated, and filter loss is reduced. There is an effect that the increase can be prevented.

In addition, since the conventional configuration uses the short-circuited end, a large amount of current flows, resulting in a large loss. However, the configuration of the present invention does not require the short-circuited end, and thus has the effect of preventing loss. .

[Brief description of drawings]

FIG. 1 is a perspective view showing a dielectric filter according to an embodiment of the present invention, and FIG. 2 is an explanatory view showing an electric field distribution of its main part,
FIG. 3 is an explanatory view showing the potential distribution along the inner conductor, FIG. 4 is a longitudinal sectional view showing another embodiment of the present invention, and FIGS. 5 and 6 are still other embodiments of the present invention. Fig. 7 is a perspective view showing an example, Fig. 7 is a vertical sectional view showing a conventional dielectric filter, and Fig. 8 is a plan view showing a state in which the outer conductor lid and the frequency adjusting screw are removed. 9 is a dielectric block, 10 is a through hole, 11 is an outer conductor, 1
Reference numeral 2 is an inner conductor, 13 and 14 are input / output coupling means (input / output inner conductors), 15 and 16 are inner conductor coupling means (grooves), and 17 is an inner conductor coupling means (steps). In the drawings, the same reference numerals indicate the same or corresponding parts.

Front page continuation (72) Inventor Shumi Ishida 5-1-1, Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Information & Electronics Laboratory (72) Inventor Fumio Takeda 5-1-1, Ofuna, Kamakura-shi, Kanagawa Mitsubishi (56) Reference JP 62-85502 (JP, A) JP 59-161902 (JP, A) JP 63-74803 (JP, U)

Claims (3)

[Claims] 1. A plurality of through holes formed in parallel with a plane and a bottom surface from one side surface are in close contact with a dielectric block arranged in parallel with the plane and the bottom surface and an inner peripheral surface of each of the through holes. The inner conductor, which is composed of a conductor film arranged and whose length is set to approximately 1/2 wavelength of the resonance frequency, adheres closely to the outer peripheral surface of the dielectric block except the surface where the through hole is open. An outer conductor made of a conductive film arranged in a predetermined manner, an input / output coupling means coupled to a predetermined inner conductor, and a potential of at least one of the plane and bottom of the dielectric block and of a higher frequency of the resonance frequency. A dielectric filter comprising an inner conductor coupling means including a conductor film continuous from the outer conductor provided at a position where the distribution is substantially zero. 2. A plurality of through holes formed from one side surface in parallel with the plane and the bottom surface are in close contact with the dielectric block arranged in parallel with the plane surface and the bottom surface and the inner peripheral surface of each of the through holes. The inner conductor, which is composed of a conductor film arranged and whose length is set to approximately 1/2 wavelength of the resonance frequency, adheres closely to the outer peripheral surface of the dielectric block except the surface where the through hole is open. An outer conductor made of a conductive film arranged in a predetermined manner, an input / output coupling means coupled to a predetermined inner conductor, and a potential of at least one of the plane and bottom of the dielectric block and of a higher frequency of the resonance frequency. A dielectric filter comprising: a groove which is continuously provided at a position where the distribution is substantially zero in a direction perpendicular to the axial direction of the inner conductor, and in which a conductor film seamlessly connected to the outer conductor is closely arranged. 3. A plurality of through holes formed in parallel with the plane and the bottom surface from one side surface are in close contact with the dielectric block arranged in parallel with the plane and the bottom surface and the inner peripheral surface of each of the through holes. The inner conductor, which is composed of a conductor film arranged and whose length is set to approximately 1/2 wavelength of the resonance frequency, adheres closely to the outer peripheral surface of the dielectric block except the surface where the through hole is open. An outer conductor made of a conductive film arranged in a predetermined manner, an input / output coupling means coupled to a predetermined inner conductor, and a potential of at least one of the plane and bottom of the dielectric block and of a higher frequency of the resonance frequency. A dielectric filter, which is provided at a position where the distribution is substantially zero in a direction perpendicular to the axial direction of the inner conductor, and in which a conductor film seamlessly connected to the outer conductor is closely arranged.