JPS60145701A - Dielectric filter - Google Patents

Abstract

PURPOSE:To attain easily a desired frequency characteristic by constituting a dielectric filter with a columnar dielectric resonator and a prismatic dielectric resonator. CONSTITUTION:The waveguide mode propagated in a standard waveguide part 1 is intercepted by an intercepting waveguide part 3 and is not propagated there. However, only waves resonating to arranged and fixed dielectric resonators 2 in the waveguide part 3 pass through the waveguide part 3. The columnar dielectric resonator is arranged in the center of the waveguide part 3, and prismatic dielectric resonators 2 are arranged in both ends, and individual resonators are fixed by dielectric substrates 7 having a low dielectric constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a dielectric filter, and more particularly to the structure of a dielectric filter used in a frequency band ranging from microwaves to millimeter waves.

fbl Prior Art and Problems Recently, dielectric materials have been actively developed, and it has become possible to obtain materials with low loss and good temperature characteristics in frequency bands ranging from microwaves to millimeter waves.

Conventionally, resonators in high frequency bands have been cavity resonators or coaxial resonators using metal containers, but these are large in size and heavy.

On the other hand, dielectric resonators are small and lightweight, have a simple structure, and have low processing and material costs, so they are suitable for stabilizing resonance in filters and oscillators in frequency bands ranging from microwaves to millimeter waves. It has come to be widely used as a vessel.

FIG. 1 shows the shape of a commonly used dielectric resonator and the electromagnetic field distribution in its fundamental resonance mode.

As shown in the figure, the shapes of dielectric resonators are mainly cylindrical and prismatic, but their dimensions vary depending on the resonant frequency. For example, in the case of a prismatic dielectric resonator with a resonant frequency of 20 GIIz, is when the dielectric constant of the material is about 30,
It is approximately 3 x 3 x (1-1.5) mm. Also, as shown in the figure, the electromagnetic field distribution is the same for both cylindrical and prismatic shapes, but in the former case it is TE mode, J mode, and in the case of 1 & 2 mode it is T mode.
It is called E1+J mode.

In the figure, ■ indicates that the electric field extends downward from the top of the paper, and O indicates the opposite.

Figure 2 is a diagram for explaining the arrangement of dielectric resonators when the input/output section is a waveguide. It is a figure when each is removed.

In the figure, 1 indicates a standard waveguide section of horizontal center x vertical center B, 2 indicates a cylindrical dielectric resonator, and 3 indicates a cut-off waveguide section of axial center x vertical center B.

In Fig. 2 fal, standard waveguide section l with width A x length B
The waveguide mode that has propagated is blocked by the cut-off waveguide section 3 with horizontal IJax and vertical center B, and cannot propagate therein. However, only the waves that resonate with the dielectric resonators 2 arranged and fixed in this cut-off waveguide section 3
can pass through.

Figure 3 is a diagram for explaining the configuration of a conventional example of a dielectric resonator whose input/output section is composed of a microstrip line. Figure 3 fal is a plan view, and Figure 3 fbl is Figure 3 + al. AA cross-sectional views are shown, respectively.

In the figure, 4 is, for example, an alumina substrate, 2 is a dielectric resonator, 5 and 7 are microstrip lines obtained by vapor-depositing metal, such as gold, and 6 is a ground conductor surface whose entire surface is vapor-deposited with metal. Each is shown below.

In Fig. 3+a+, the configuration of this dielectric filter is to form input/output lines 5 and 7 for coupling with the dielectric resonator 2 on a single dielectric substrate 4, and at the same time, the dielectric filter The body substrate 4 also served as a support plate for the dielectric resonator. The microstrip lines 5 and 7 are magnetically coupled to the dielectric resonator 2 to form a resonant circuit at a line length distance of about λg/4At from the open portion with respect to the desired center frequency.

In this way, in conventional dielectric filters, the shape of the dielectric resonator used is generally prismatic only, as shown in Figure 1, or cylindrical only. Met.

Furthermore, even if we theoretically consider the permittivity, shape, etc. of the dielectric resonator, which is a component of a dielectric filter with desired frequency characteristics,
The permittivity, shape, and dimensions of actual dielectric resonators vary to some extent.

In particular, as the resonant frequency increases, the shape of the dielectric resonator
As the dimensions become smaller, the variation becomes larger. Therefore, in order to match the frequency characteristics of a dielectric filter with different design conditions and the actual product to the desired frequency characteristics, it was necessary to adjust the frequency characteristics using only adjusting screws, which required a considerable amount of adjustment man-hours. .

As explained above, the configuration of the conventional dielectric filter is as follows.
There is a problem in that it takes a considerable amount of time to match the desired frequency characteristics with those of the dielectric filter because there is little freedom in frequency characteristics and adjustment.

(C1 Purpose of the Invention The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a dielectric filter with improved characteristics closer to desired frequency characteristics.

ldl Structure of the Invention The object of the above invention is to provide a dielectric filter in which at least 1j or more dielectric resonators are arranged and fixed in a certain space, in which the dielectric filter has a cylindrical dielectric resonator. This is achieved by providing a dielectric filter characterized in that it is comprised of a cylindrical dielectric resonator and a prismatic dielectric resonator.

(el Embodiment of the Invention In general, when using a prismatic dielectric resonator and a cylindrical dielectric resonator of the same height, in order to make the resonant frequency the same, the length of one side of the prismatic dielectric resonator must be According to the American magazine "Microwave System News" published in June 1982, it is sufficient to satisfy the relationship between the diameter W and the diameter of the cylindrical dielectric resonator: ■] = 1.082 W. P,
133-140.

That is, when D and W are matched, the resonant frequency of the cylindrical dielectric resonator is slightly higher than that of the prismatic dielectric resonator. However, by slightly shortening the crystallinity of the prismatic dielectric resonator, it is possible to match the resonance frequencies of the two types of dielectric resonators.

As a result of investigating the degree of coupling between two types of dielectric resonators and coupled lines and the degree of coupling between dielectric resonators under these conditions, we found that:
It was found that the prismatic dielectric resonator has a stronger coupling of about 1.2 (!!T) than the cylindrical dielectric resonator.

FIG. 4 is a diagram showing the relationship of external Qe with respect to the distance between the coupled line and the dielectric resonator, where the dotted line shows the case of a cylindrical dielectric resonator and the solid line shows the case of a prismatic dielectric resonator.

As shown in the figure, when configuring a dielectric filter, if you use a mixture of prismatic dielectric resonators and cylindrical dielectric resonators as appropriate, the frequency characteristics of the dielectric filter can be changed relatively freely. I found out what happened.

FIG. 5 shows an example in which the present invention is applied when the input/output line shown in FIG. 2 is a conductor tube.
FIG. 5 (bl is a view with each side removed.

In the figure, l indicates a standard waveguide section, 2 indicates a dielectric resonator, 3 indicates a cut-off waveguide section, and 7 indicates a low dielectric dielectric substrate.

In the figure, a cylindrical dielectric resonator is arranged in the center and prismatic dielectric resonators are arranged at both ends, and each dielectric resonator is isolated and conductive by a dielectric substrate 7 with a constant thickness and a low permittivity. It is fixed to the wave tube section 3.

FIG. 6 shows another embodiment of the present invention in which, unlike FIG. 5, the thickness of the low-k dielectric substrate 7 is changed, thereby making it possible to change the coupling coefficient between dielectric resonators.

(fl As described in the detailed explanation of the invention, a cylindrical dielectric resonator and a prismatic dielectric resonator are appropriately mixed, and the dielectric resonator is divided into low dielectric constant dielectric substrates having different thicknesses. By fixing it to the case, the degree of coupling between the coupling line and the dielectric resonator and between the dielectric resonators can be changed, making it relatively easy to obtain a dielectric filter with desired frequency characteristics. can.

The flexibility and adjustment flexibility for the dielectric filter is increased.

However, if cylindrical and prismatic shapes are mixed, TE6. Since the resonant frequency of unnecessary modes other than F mode can be shifted, high-frequency damping characteristics can be improved.

[Brief explanation of the drawings] Figure 1 is a diagram for explaining the shape of a dielectric resonator, and Figure 2 is a diagram for explaining the shape of a dielectric resonator.
The figure is a diagram to explain the arrangement of a dielectric resonator when the input/output section is a waveguide, and Figure 3 shows an example of the configuration of a dielectric resonator when the input/output section is a microstrip line. 4 is a diagram showing the relationship between Qe and the distance between the coupled line and the dielectric resonator, and FIG. 5 is a diagram showing an example in which the present invention is applied to the arrangement shown in FIG. 6 each shows another application example of the present invention. In the figure, 1 indicates a standard waveguide section, 2 indicates a dielectric resonator, 3 indicates a cut-off waveguide section, and 7 indicates a low dielectric constant dielectric substrate. 1st Director〃 Figure 2 (S/J) 3rd (lz) 4z

Claims (1)

[Claims] 1. In a dielectric filter in which at least one dielectric resonator is arranged and fixed in a certain space, the dielectric filter is a cylindrical dielectric resonator. and a prismatic dielectric resonator. 2. The cylindrical dielectric resonator and the prismatic dielectric resonator each have a low dielectric constant dielectric substrate that has a dielectric constant lower than that of the dielectric resonator and corresponds to the dielectric resonator, respectively. 2. The dielectric filter according to claim 1, wherein the dielectric filter is fixed to a case forming the electric space via the dielectric filter. 3. The dielectric filter according to claim 2, wherein the low dielectric weight dielectric substrate is a dielectric substrate having an arbitrary thickness.