JPH01173902A - Dielectric filter - Google Patents

Abstract

PURPOSE:To realize miniaturization and light weight by forming an outer conductor and an inner conductor whose both ends are formed in open terminals and with length of around 1/2-wave by conductor films adhered on a dielectric block, and coupling the inner conductors mutually by an inner conductor coupling means consisting of a groove or a step provided in a direction perpendicular to the axis of the inner conductor and on which a conductor film is arranged adhesively. CONSTITUTION:The inner conductor 12 with around 1/2-wave is formed by the conductor film adhered on the inner peripheral planes of plural through holes 10 provided on the dielectric block 9, and also, the outer conductor 11 is formed by the conductor film adhered on an outer peripheral plane other than the aperture plane of the through hole of the dielectric block 9, and inner conductor coupling means 15 and 16 are provided on one side of the flat plane and the bottom plane of the dielectric block 9. In such a way, a filtering function can be obtained by the action of the inner conductor coupling means 15 and 16, and by integrating the inner conductor 12, the outer conductor 11, and the dielectric block 9, the number of components can be reduced, and the miniaturization and the light weight can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric filter that is often used in the vHF band, UHF band, and microwave band.

[Conventional technology]

FIG. 7 is a vertical cross-sectional view showing a conventional dielectric filter disclosed in, for example, Japanese Patent Application Laid-Open No. 55-143801, and FIG. , I is the outer conductor body that also serves as a case, 2 is the outer conductor lid that covers the opening surface of the outer conductor body L, and 3 is the outer conductor body! A plurality of inner conductors are arranged inside, each of which is attached to the bottom of the outer conductor main body 1 at one end, and the other end is an open end. 4 can be adjusted to the outer conductor lid 2 to correspond to each inner conductor 3. 5 is a dielectric material closely arranged around the inner conductor 3, and 6 is the inner conductor 3 disposed at both ends. An input/output loop located close to and coupled to it, 7.8 is a coaxial terminal connected to the input/output Cal-Pro.

Next, the operation will be explained. The inner conductor 3 has one end grounded to the outer conductor main body l, and the other end, which is an open end, is provided with a capacitive load by a frequency adjustment screw. They are shorter than the wavelength and are mutually coupled mainly by magnetic field coupling, and the amount of coupling is determined by the distance between adjacent inner conductors 3. Further, since the length of the sections where the inner conductor 3 and the input/output Cal-Pro at both ends are parallel and close to each other is less than 1/4 wavelength, they are coupled mainly by the magnetic field. Now, by adjusting the length of the inner conductors 3 and the frequency adjustment device 4, all the inner conductors 3 can be set to the same frequency, for example f. If it resonates at , its frequency f. Then, the inner conductors 3 in a resonant state are mutually connected to each other,
It is strongly connected to the input and output Cal-Pro, and the coaxial terminal 7
The incident wave is guided to the coaxial terminal 8. However, f
At frequencies other than o, the coupling between the inner conductors 3 and the coupling between the inner conductors 3 and the Cal-Pro is very weak, and the coaxial terminal 7
Alternatively, most of the power of the incident wave on 8 is reflected. In this way, the dielectric filter shown in FIGS. 7 and 8 has a function as a bandpass filter.

[Problem that the invention seeks to solve]

Since the conventional dielectric filter is constructed as described above, the outer conductor main body l and the outer conductor lid body 2 are equipped with a frequency adjustment screw around the inner conductor 31, and function as a case with a mechanically stable structure. In order to satisfy this requirement, a certain degree of wall thickness is required, which hinders miniaturization and weight reduction, and the outer conductor body 1
．． Outer conductor lid 2° Inner conductor 31 Frequency @ Adjustment screw 4. Since the dielectric body 5 and the like are all individual parts, the number of parts is large, which complicates manufacturing and assembly, and the outer conductor body 1. Due to the difference in linear expansion coefficient between the outer conductor fluid 2 and the inner conductor 3 and the dielectric 5, the resonant frequency changes when there is a temperature change. Contact resistance is likely to increase due to poor contact,
In such a case, the current reaches its maximum at this portion, resulting in problems such as increased loss in the filter.

This invention was made to solve the above-mentioned problems.It has a small number of parts, is easy to manufacture and assemble, can be made smaller and lighter, and is also stable against temperature changes and has a low cost. The purpose is to obtain a lossy dielectric filter.

[Means for solving problems]

In the dielectric filter according to the present invention, the inner conductor of approximately 1/2 wavelength is a conductor film closely attached to the inner peripheral surface of a plurality of through holes formed in a dielectric block, and the outer conductor is a conductor film that is closely attached to the inner circumferential surface of a plurality of through holes formed in a dielectric block. The dielectric block is formed of a conductive film that is in close contact with the outer peripheral surface other than the opening surface of the dielectric block, and an inner conductor coupling means is provided on at least one of the flat surface and the bottom surface of the dielectric block.

[Effect]

In the dielectric filter of the present invention, the inner conductor and the outer conductor are formed of a conductive film in close contact with a dielectric block, and the filter function is achieved by the action of the inner conductor coupling means provided on at least one of the plane and bottom of the dielectric block. By integrating the inner conductor, outer conductor, and dielectric block, we can reduce the number of parts and simplify manufacturing and assembly.We also eliminate the need for the outer conductor to function as a case, making it smaller and lighter. The temperature characteristics are determined by the temperature characteristics of the dielectric material to stabilize the temperature characteristics, and by making both ends of the inner conductor open, problems such as gaps and contact resistance at the connection with the outer conductor are eliminated. , to prevent an increase in ttt loss of the filter.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 9 is a dielectric block made of a dielectric material with a high dielectric constant, and 10 is a dielectric block made from one side of this dielectric block 9, for example, from the front side to the opposite side, which is the back side, parallel to the plane and the bottom side. , a plurality of through holes arranged in parallel to the plane and the bottom surface, and 11 are arranged in the plane, bottom, left side, and right side of the dielectric block 9 excluding the front and back surfaces where the through holes IO are open. The outer conductor 12 is made of a conductive film disposed in close contact with the inner peripheral surface of each through hole 10, and the length thereof is set to approximately 1/2 wavelength, 13. An inner conductor forming a 1/2 wavelength resonator with both ends open together with the outer conductor 11;
Reference numeral 14 indicates an input/output inner conductor connected to the inner conductor 12 disposed at both ends, and serves as an input/output coupling means for dividing and extracting a part of the current flowing through the inner conductor 12; 15.16 indicates a plane of the dielectric block 9; and a groove that is continuously carved on the bottom surface in a direction perpendicular to the axial direction of the inner conductor 12, and in which a conductor film seamlessly connected to the outer conductor 11 is closely arranged and acts as an inner conductor coupling means. The open ends of the dielectric block 9 are provided at positions approximately 1/4 wavelength or approximately 1/6 wavelength from the front and rear sides of the dielectric block 9, respectively.

Next, the operation will be explained. When the groove 15 is provided in the 1/2 wavelength 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 can be seen in the TEM mode as shown in Figure 2(b) and in the TEM mode as shown in Figure 2(c).
) and the local TM mode shown in FIG. This thing is a ditch! The same applies to 6. Second
In the TEM mode shown in Figure (b), the length of the inner conductor 12 is 1/
When a two-wavelength resonator is arranged as shown in Fig. 1, the electric field coupling and magnetic field coupling cancel each other out, so that the mutual coupling between the inner conductors 12 is eliminated, but due to the local TM mode shown in Fig. 2 (c), Coupling between the inner conductors 12 is obtained. This local TM mode is a mode in which the amount of generation changes depending on the depth of the groove 15 and is attenuated as the distance from the generation point increases, so the amount of coupling is adjusted by the depth of the groove 15 and the mutual spacing between the inner conductors 12. can do. In the embodiment shown in FIG. 1, the intervals between the inner conductors 12 are set at unequal intervals in order to obtain the necessary filter characteristics.

Now, by adjusting the length of the inner conductors 12, all the inner conductors 12 have the same frequency f. If it resonates at the frequency f0, each inner conductor 12 in the resonant state is strongly coupled to the adjacent inner conductor I2 or the input/output inner conductor 13, 14, and is connected to the input/output inner conductor 13. An incident wave to an input/output terminal (not shown) is guided to an input/output terminal (not shown) connected to the input/output inner conductor 14. However, at frequencies other than f0, the coupling between the inner conductors 12 and the coupling between the inner conductors 12 and the input/output inner conductors 13 and 14 is very weak, and the coupling between the inner conductors 12 and the input/output inner conductors 13 and 14 is very weak. Most of the power of the incident wave is reflected. In this way, the dielectric filter of the present invention functions as a bandpass filter.

Here, in this embodiment, as shown in FIG. 3(a),
>N l 5 is approximately 1/4 of the axial length of the inner conductor 12 from the open end
In other words, in the potential distribution along the inner conductor 12 shown in FIG. 3(b), the potential of the second-order resonance mode is zero (@field is maximum). Therefore, this groove 15 lowers the resonance frequency of the fundamental mode and increases the resonance frequency of the secondary resonance mode. 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, an attenuation amount can be obtained even at twice the frequency of the fundamental wave. Similarly, the groove 16 is cut at a position approximately 1/6 of the axial length of the inner conductor 12 from the open end, where the potential of the third-order resonance mode becomes zero. Therefore, this groove 16 lowers the resonance frequency of the fundamental mode and increases the resonance frequency of the third-order resonance mode, widening the frequency interval between the fundamental mode wave and the third-order resonance mode wave, and increasing the frequency three times that of the fundamental wave. Attenuation can also be obtained in frequency.

In the above embodiment, the groove 15 is formed at a position approximately 1/4 wavelength from one open end of the inner conductor 12, and at a position approximately 1/4 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. , the groove 15 and the groove 16 may be provided respectively, in which case,
Compared to the embodiment shown in FIG. 1, the attenuation characteristics of the 62nd and 3rd harmonic components are better.

Further, in the above embodiment, a groove is used as the inner conductor coupling means, but this may be replaced with a step. FIG. 5 is a perspective view showing such an embodiment, and in the figure, 17 is a step provided in place of the groove shown at 15° and 16 in FIG. 1
It is provided continuously in the direction perpendicular to the axial direction of the two. Further, 18 is a high impedance section, and the other parts are the same parts as those with the same reference numerals in FIG. In this case as well, the first
As in the case of the embodiment shown in the figure, a local TM mode is generated in the electromagnetic field in the step 17, and coupling between the inner conductors 12 is obtained, and the coupling t is determined by the height of the step 17 and the inner conductor. It can be adjusted by the distance between 12. Also,
Because the effect of step 17 on the fundamental wave, second-order, and third-order resonance mode waves differs due to differences in electromagnetic field distribution, the first
Similar to the embodiment shown in the figure, attenuation amounts for second-order and third-order harmonic components can be obtained. Furthermore, according to this embodiment, the action of step 17 makes it possible to shorten the axial length of the inner conductor 12 in order to obtain a predetermined resonance frequency of the fundamental wave.

Furthermore, FIG. 6 is a perspective view showing still another embodiment of the present invention, in which grooves 15, 16 and steps 17 in a direction perpendicular to the axis of the inner conductor 12 are simultaneously provided as inner conductor coupling means. be. In this case groove 15.16 and step 17
Due to the synergistic effect of the above, a large attenuation M can be obtained at frequencies twice or three times that of the fundamental wave. Also, step 1
Since it is not necessary to increase the size of 7, the drop in the no-load Q is slight, and the increase in loss of the dielectric filter is also slight.

In the above embodiment, the inner conductor coupling means is provided on both the plane and the bottom surface of the dielectric block, but it may also be provided on only one of the planes, and the number of inner conductors may be Although we have explained the case of three wires, it is also possible to apply it to other numbers of wires.Furthermore, as a human output coupling means, it is possible to use an input/output inner conductor that divides the current of inner conductors placed at both ends. In addition to a conductor, a type that connects to inner conductors at both ends by electrostatic coupling or magnetic coupling may be used, and in either case, the same effects 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 having open ends and a length of approximately 1/2 wavelength are formed of a conductive film closely attached to a dielectric block, and the axis of the inner conductor is Since the inner conductors are connected to each other by means of inner conductor connecting means consisting of grooves or steps provided in a direction perpendicular to the conductor film and in which the conductor film is closely arranged, there is no need for the outer conductor to have the function of a case. It has become possible to be smaller and lighter, and the temperature characteristics are now determined by the temperature characteristics of a dielectric material with a smaller coefficient of linear expansion than metals, making it more stable. Not only does it eliminate the need for frequency adjustment screws, and the number of individual parts can be reduced internally. The conductor and outer conductor are assembled into a closely spaced dielectric block, which facilitates manufacturing and assembly.Furthermore, since both ends of the inner conductor are open, the gap between the connection part with the outer conductor, contact resistance, etc. is reduced. This problem is eliminated, and an increase in filter loss can be prevented.

[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 is an explanatory diagram showing the electric field distribution of the main part,
FIG. 3 is an explanatory diagram showing the potential distribution along the inner conductor, FIG. 4 is a longitudinal cross-sectional view showing another embodiment of the invention, and FIGS. 5 and 6 are each a further embodiment of the 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 of the conventional dielectric filter with the outer conductor cover and frequency adjustment screw removed. 9 is a dielectric block, 10 is a through hole, II is an outer conductor, +
2 is an inner conductor, 13.14 is a human output coupling means (input/output inner conductor), 15.16 is an inner conductor coupling means (groove), and 17 is an inner conductor coupling means (step). In addition, in the figures, the same reference numerals indicate the same or equivalent parts. 11; Outside V mackerel A
1s, 16: 114 wrinkles difference Kojito + step (groove) 12: Hei Prefectural Building Figure 2 Figure 3 Figure T:, 4 Figure 16 15II 1) 16 17: Uchidorin Kinuta 1go, 8 steps (step・7b) Figure 7 Figure 8

Claims (3)

[Claims] (1) A plurality of through holes formed from one side in parallel to the plane and the bottom are arranged in close contact with the dielectric block arranged parallel to the plane and the bottom and the inner peripheral surface of each of the through holes. an inner conductor made of a conductive film having a length set to approximately 1/2 wavelength; and a conductor disposed in close contact with an outer circumferential surface of the dielectric block excluding the surface where the through hole is open. A dielectric filter comprising an outer conductor made of a film, input/output coupling means coupled to a predetermined inner conductor, and inner conductor coupling means provided on at least one of the plane and bottom surface of the dielectric block. (2) As the inner conductor coupling means, a groove is used, in which a conductor film seamlessly connected to the outer conductor is disposed in close contact with the inner conductor, and the groove is continuously provided in a direction perpendicular to the axial direction of the inner conductor. A dielectric filter according to claim 1. (3) The inner conductor coupling means is characterized by using a step in which a conductive film seamlessly connected to the outer conductor is closely arranged and continuously provided in a direction perpendicular to the axial direction of the inner conductor. A dielectric filter according to claim 1.