JPS5952841B2 - Dielectric line type filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a dielectric line filter suitable for use particularly in a VHF band to a relatively low frequency microwave band.

Typical examples of conventionally known relatively low-frequency microwave band filters include interdigital type, combline type coaxial resonator, semi-coaxial resonator, rectangular TE1o1, circular TMOIO resonator, and the like.

However, all of these filters have the disadvantage of having a relatively large shape and size.

Therefore, especially for the purpose of miniaturization, high frequency filters in which a dielectric material is loaded between the inner and outer conductors are being popular.

FIG. 1 is a schematic longitudinal sectional view showing an example of such a conventional 174-wavelength magnetic field coupling filter, in which 1 is an inner conductor, 2 is a dielectric material, and 3 is an outer conductor provided to surround the dielectric material 2. The structure is such that coupling between adjacent resonators is performed by a leakage magnetic field from a coupling hole 4 provided in an outer conductor 3 using a conductor.

However, as is well known, a filter having such a structure is mechanically quite difficult to manufacture and expensive.

The present invention was made based on the above-mentioned circumstances, and
A filter is constructed using dielectric line resonators that do not require an external conductor between the resonators, and the necessary adjustment of electrical coupling between the dielectric line resonators is achieved. The object of the present invention is to provide a dielectric line type filter that is as small as possible, lightweight, inexpensive, easy to adjust, and has excellent electrical characteristics.

Embodiments of the dielectric line type filter according to the present invention will be described in detail below with reference to FIGS. 2 to 8.

First, in order to consider coupling between adjacent resonators when no dielectric material is provided, inner conductors 1 are placed at predetermined intervals in the line length direction of an outer conductor 3 made of a hollow conductor plate, as shown in FIG. Consider a resonator with a structure in which

It is easily confirmed experimentally that the coupling between adjacent resonators when no dielectric material is provided is extremely weak.

The reason for this is that there are two types of coupling between adjacent resonators: one is due to the electric field E (indicated by the solid line arrow) as shown in Figure 2, and the other is due to the magnetic field H (indicated by the dotted line arrow) as shown in Figure 2a. It is thought that this is because the electric field coupling and the magnetic field coupling act to cancel each other out.

In particular, when the amount of coupling due to electric field coupling between adjacent resonators is Co and the amount of coupling due to magnetic field coupling is Ce, the amount of coupling Kij between the adjacent resonators is expressed by the following equation.

Kij= l Ce-Co, l −(1)
Next, considering the electromagnetic field in a 174-wavelength dielectric line type resonator when a dielectric is provided using FIG. 3, one end of the hollow conductor plate 3a is shorted, the other end is opened, and A strong electric field E exists in the radial direction in the region (2) near the open end of the inner conductor 1 which is protruded so as to be covered with the dielectric 2, and a strong electric field E exists in the circumferential direction in the region II near the short-circuited end side conductor plate 3a. There is a strong magnetic field in the direction.

Note that region III in FIG. 3 is the open end side conductor plate 3a.
It shows the electromagnetic field in the vicinity and shows that the electromagnetic field in this part is considerably weaker than in the regions I and II mentioned above.

Therefore, as is clear from FIG. 3, the coupling between adjacent resonators in the dielectric line type resonator having such a structure is as follows.
Electric field coupling is dominant near region I, and
It is surmised that near I, magnetic field coupling is dominant.

FIGS. 4a, l) and 5a, l) are schematic diagrams of a dielectric line type filter constructed by effectively utilizing the above-described principle.

FIG. 4a is a top view of one example, and FIG. 4s is a longitudinal cross-sectional view taken along line AA' in FIG. 4a.

FIG. 5a is a top view of another example, and FIG. 5a is a longitudinal cross-sectional view taken along line AA' in FIG. 5a.

Here, from the above equation (1), the amount of coupling between adjacent resonators Kij
It can be seen that in order to increase the electric field coupling amount Co, the electric field coupling amount Co should be decreased when the magnetic field coupling amount Ce is constant.

Therefore, for this purpose, in the case of FIG. 4, the inner conductor 1 of a predetermined length and the inner conductor 1 are placed at predetermined intervals in the line length direction of the outer conductor 3 made of a hollow conductor plate, as shown in FIG. A plurality of (two in the figure) resonators made of a dielectric material 2 having a sufficient thickness and permittivity to confine electromagnetic field energy are provided so as to cover the outer periphery, and these resonators are separated by a space. As shown in the figure, a conductor wire 4b is provided near the open end of the inner conductor 1 between each resonator.

That is, the electric field coupling amount Co is determined by the electric field existing near the open end of the inner conductor 1, but if a space is provided between the resonators as shown in FIG. 4, the electric field coupling amount Co is determined by the existence of this space. Co decreases.

On the other hand, the magnetic field coupling amount 0 is determined by the magnetic field existing near the shorted end of the inner conductor 1, but this magnetic field coupling amount Ce is constant regardless of the space between the resonators.

In this way, when the resonators are placed side by side separated by space, the amount of magnetic field coupling Ce remains unchanged, the amount of electric field coupling Co decreases, and as a result, from equation (1), the amount of coupling Kij between the resonators increases.

The binding amount Kij was 2.5×10 −2 in the experimental example.

At that time, the dielectric constant ξr of the dielectric 2 is 20, the diameter 2a of the inner conductor 1 = 4 mm, and the diameter 2b of the dielectric 2 = 15 mm.
, the distance between the inner conductors was 16.5 mm.

Also, when the distance between the inner conductors is 18.5 mm, the coupling amount Ki
j was 1.5×10 −2 .

Further, in FIG. 4, as described above, a conductor wire 4b is provided near the open end of the inner conductor 1 between the resonators.

Providing this conductor wire 4b further reduces (adjusts) the electric field that contributes to coupling near the open end of the inner conductor 1,
The electric field coupling amount CO can be further reduced (adjusted).

That is, the amount of coupling Kij between resonators can be further increased (adjusted).

On the other hand, in order to reduce the magnetic field coupling amount Ce between adjacent resonators, as shown in FIG. 5, a conductor wire loop 4C is interposed between the adjacent resonators in place of the conductor wire 4b shown in FIG. It is only necessary to configure it so that

With this configuration, the amount of magnetic coupling Ce between the adjacent resonators can be reduced by the conductor wire loop 4C, and as a result, the amount of coupling Kij in the above equation (1) can be reduced (adjusted). I can do it.

FIG. 6 is a characteristic curve diagram showing the actual measured value of the amount of coupling between adjacent resonators when the conductor wire 4b is installed between the adjacent resonators as shown in FIG. Curve 10b represents the case where two wires are provided, and curve 10b represents the case where two wires are provided.
0C represents the case where four wires are provided.

At this time, the dielectric constant of the dielectric 2 is 20, and the diameter of the inner conductor 1 is 2a.
= 4 mm, the diameter 2b of the dielectric 2 = 15 mm, and the distance between the inner conductors was 18.5 mm.

As is clear from Fig. 6, when the conductor wire 4b is installed near the open end of each inner conductor 1 between adjacent resonators, the amount of coupling between the adjacent resonators is the same as when the conductor wire 4b is not provided. The amount of coupling increases significantly as the number of conductor wires increases.

It was also confirmed that as the conductor wire 4b is separated from the vicinity of the open end of the inner conductor 1, the amount of coupling between the adjacent resonators decreases.

These actual measurement results are in good agreement with the above-mentioned theoretical considerations.

FIGS. 7a and 7b are a schematic top view and side sectional view of a two-section dielectric line type filter according to an embodiment of the present invention constructed based on the above-mentioned theoretical consideration.

In other words, the resonator constituting each section extends a predetermined length from the bottom surface extending in the line length direction facing the opening surface of the metal case 13 which also serves as a ground conductor and has a U-shaped side cross section. is ^8, then the rod-shaped central conductor 11 is integrally hung vertically so as to have L = 1/4λg).
and a cylindrical dielectric 12 which is loaded so as to cover the outer periphery of the center conductor 11 and fixed to a metal case 13.

Here, the cylindrical dielectric 12 has sufficient thickness and dielectric constant to confine electromagnetic field energy.

Further, there is a gap between the opposing cylindrical dielectrics 12 (between the resonators).

In order to further reduce the electric field coupling between both resonators, one to several (three in the figure) wires are arranged in a direction perpendicular to the center conductor 11 of each resonator and parallel to the bottom surface of the metal case 13. The conductor wire 15 (both ends are connected to the metal case 13) of the case shown in FIG. A frequency adjusting screw 18 that can be screwed out and inserted is provided in this manner.

In addition, output coaxial connectors 16 are connected to both sides of the metal case 13 located on the output side of this dielectric line type filter, and these input/output coaxial connectors 16
through the output coupling loop 19 to the metal case 13.
At the same time, the opening surface of the metal case 13 is hermetically sealed with a shielding metal plate 17.

In addition, instead of the conductor wire 15, the center conductor 11 of each resonator
Even if a conductor plate is used which is perpendicular to the bottom surface of the metal case 13 (if the center conductor 11 is considered as a reference, the plate surface is parallel to the center conductor 11), the same method as in the above embodiment can be used. It has been confirmed by the actual and experimental results of the present inventors that this method can be implemented and that equivalent effects can be obtained.

FIG. 8 is a schematic configuration diagram showing another embodiment of the dielectric line type filter according to the present invention, in which FIG. FIG.

In this embodiment, in place of the conductor wire 15 in the embodiment of FIG. This embodiment differs from the embodiment shown in FIG. 7 only in that it is configured as shown in FIG. 7, and has the same structure in other respects. Therefore, the same parts as those in FIG.

The dielectric line type filter configured using such a conductor wire loop 15a has the only feature that the coupling control between both resonators is mainly magnetic field coupling instead of electric field coupling in the embodiment shown in FIG. This is different from the embodiment shown in FIG.

The rest is the same as the embodiment shown in FIG. 7, and of course the same effects as the embodiment shown in FIG. 7 can be obtained.

As described in detail above, according to the present invention, by arranging a plurality of dielectric line resonators on the same bottom surface of a metal case, both an electric field and a magnetic field are combined simultaneously, and the difference is used to combine the resonators. Since the coupling between the resonators is obtained, the amount of coupling increases due to the air gap between the resonators, and the element sensitivity to the distance between the rod-shaped center conductors decreases, as a result,
The distance tolerance between the rod-shaped center conductors can be relaxed.

Further, by configuring the resonators on the same bottom surface, manufacturing becomes easier.

Furthermore, in the case of the resonator used in the filter of the present invention, there is no need for an external conductor surrounding each resonator as in conventional resonators, and only a simple metal case is required for external shielding, which greatly reduces the cost. In addition, the unloaded Q of the resonator can be increased and the size of the bandpass filter can be significantly reduced.

Further, according to the present invention, since the electrical coupling of the dielectric line type filter is adjusted using a conductor wire or the like, it is possible to obtain a dielectric line type filter with excellent electrical characteristics.

The dielectric line type filter of the present invention is particularly suitable for VH
It has a significant practical effect as a micro band filter for relatively low frequencies from the F band.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a conventional 174-wavelength magnetic field coupling filter, and Figures 2 to 5 are schematic cross-sections shown to explain the electrical coupling method between adjacent resonators in a dielectric line type resonator. In the figures, Fig. 2 a, l) shows the case where only the inner and outer conductors are provided and no dielectric material is provided, Fig. 3 shows the case where a dielectric material is provided, and Fig. 4 a, l) and Fig. 4 show the case where a dielectric material is provided. Figures 5 a and 1) show the case where a conductor wire and a conductor wire loop are further provided between adjacent resonators, and Figure 6 shows the conductor wire when a conductor wire is installed between adjacent resonators as shown in Figure 4. A characteristic curve diagram showing the relationship between the position and number of lines and the amount of coupling between the resonators, FIGS. 7a and 7b are a top view and a side sectional view of a two-section dielectric line type filter according to an embodiment of the present invention, FIG. 8a is a top view of a two-section dielectric line type filter according to another embodiment of the present invention;
It is a sectional view along the A' line. 11... Rod-shaped central conductor, 12... Cylindrical dielectric, 13... Metal case, 15...
- Conductor wire, 15a... Conductor wire loop.

Claims (1)

[Scope of Claims] 1. A metal case, a plurality of rod-shaped center conductors arranged side by side with one end short-circuited and the other end open on the same bottom surface of the metal case, and provided so as to surround each of the rod-shaped center conductors. A dielectric line type resonator comprising a plurality of dielectric line type resonators, each of which is made of a dielectric material having a sufficient thickness and permittivity to confine electromagnetic field energy, and has a gap between opposing dielectric bodies. filter. 2. A metal case, a plurality of rod-shaped central conductors arranged side by side on the same bottom surface of the metal case, one end of which is short-circuited and the other end of which is open; A plurality of dielectric line resonators are made of a dielectric material having a sufficient thickness and permittivity to confine the resonator, and have a gap between the opposing dielectric members, and the A dielectric line filter comprising coupling adjustment means connected to a metal case and reducing either electric field coupling or magnetic field coupling.