JPS6322685B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a coaxial dielectric resonator used in the VHF to UHF band. It concerns the improvement of utensils.

Examples of conventionally used coaxial resonators using dielectric materials are shown in FIGS. 1 to 3. FIG. 1 shows a quarter-wavelength resonator, which is the most commonly used resonator. A is a cross-sectional view in the axial direction, and b is a cross-sectional view taken along line A-A' in FIG. In the figure, 1 is a coaxial structure dielectric, 2 is an internal conductor, 3 is an external (ground) conductor, and 4 is a short circuit. Normally, the inner and outer conductors 2 and 3 and the short circuit part 4 are
It is formed from a low-resistance conductive film by plating or baking.

This structure has a simple structure and can provide a no-load Q, but since the fundamental resonance frequency is ₀ , it also has resonance points at ₃₀ , _50, etc., so it does not have a harmonic suppression effect. In order to improve this drawback, the same applicant proposed resonators having the structures shown in FIGS. 2 and 3.
In both FIGS. 2 and 3, a is a sectional view in the axial direction, and b is a sectional view taken along line A-A' in FIG. These resonators make it possible to shift the spurious resonant frequency from an integer multiple of the fundamental resonant frequency by partially changing the line impedance.
In FIGS. 2 and 3, 1 is a dielectric, 2
3 indicates an inner conductor, 3 indicates an outer conductor, 4 indicates a short circuit portion, and 5 indicates a stepped portion.

This structure makes it possible to greatly improve the spurious characteristics, but if the discontinuity in the stepped portion 5 is large, the disturbance of the electromagnetic field in this portion is large;
The unloaded Q tends to deteriorate, and there are other drawbacks such as difficulty in metal plating or baking of the stepped portion 5, or the tendency for metal flaking to occur in the stepped portion 5.

The present invention has been made to solve this problem, and one embodiment thereof will be described below with reference to FIGS. 4 to 7.

The basic structure is that the stepped portion 5 as shown in FIGS. 2 and 3 is eliminated, and the impedance gradually changes in a tapered shape so that the impedance decreases toward the open end. Figures 4 and 5 show examples in which the dielectric 1 is tapered toward the end, and a tapered part 6 is provided on the outer conductor 3 side. This is a quarter wavelength type resonator, and FIG. 5 is an example of a half wavelength type resonator with both ends open. By replacing the stepped portion with such a tapered portion, it is possible to make the distribution of the electromagnetic field uniform, prevent Q deterioration, and improve the adhesion strength of the conductor film. (Of course, there is no deterioration of the spurious characteristics.) In Figs. 4 and 5, a is the cross-sectional shape in the axial direction, b is a cross-sectional view taken along A-A' in Fig. a, 1 is the dielectric, and 2 is the inside. 3 is an outer conductor, 4 is a short-circuit portion, and 6 is a tapered portion. Note that the tapered portion 6 may be provided over the entire line, but as shown in the figure, it is better to make the line uniform near the open end portion and short-circuited portion to make the distribution of the electromagnetic field uniform. This is also a preferable structure when the resonator is mounted on another housing. Providing a taper may seem to be a complicated process at first glance, but since the dielectric 1 is usually made of ceramic and is produced by molding it in a mold and then firing it, it only makes the production of the mold a little more complicated. The process is exactly the same as before. 6 and 7 show examples in which a tapered portion 6 is provided on the inner conductor 2 side as another embodiment of the present invention, and FIG.
The wavelength type shown in FIG. 7 is a half wavelength type.
In the figure, a is a cross-sectional view in the axial direction, and b is a cross-sectional view in the A-
This is a cross-sectional shape at A', where 1 is a dielectric, 2 is an inner conductor, 3 is an outer conductor, 4 is a short circuit portion, and 6 is a tapered portion. In this case as well, the same effects as those shown in FIGS. 4 and 5 can be obtained. In the case of the present invention,
As long as the impedance decreases toward the open end, the same effect can be achieved regardless of whether the tapered portion is formed on either side of the inner conductor or the outer conductor.

As described above, the present invention prevents Q deterioration by tapering the external shape of the internal conductor or external conductor of a conventional dielectric resonator so that the impedance gradually changes toward the open end. death,
The adhesion strength of the conductor film can be improved, and its industrial value is extremely large.

[Brief explanation of drawings]

Figure 1a is an axial cross-sectional view of a conventionally used coaxial resonator using a dielectric, Figure 1b is a cross-sectional view of the same, and Figures 2a and 3a are conventional coaxial resonators with improved spurious characteristics. FIG. 4A is an axial cross-sectional view of a coaxial dielectric resonator, FIG. Figure 5a is an axial cross-sectional view of a 1/2 wavelength coaxial dielectric resonator according to an embodiment of the present invention in which the outer conductor is tapered; 6A is a cross-sectional view of the same, FIG. FIG. 7a shows 1/1/2 in an embodiment of the present invention in which the internal conductor is provided with a tapered portion.
Axial cross-sectional view of a two-wavelength coaxial dielectric resonator, same b
is a cross-sectional view of the same. 1...Dielectric, 2...Inner conductor, 3...Outer conductor, 4
...Short circuit part, 6...Taper part.

Claims (1)

[Scope of Claims] 1. A hollow dielectric, an internal conductor provided on the inner circumferential surface of the hollow portion of the dielectric, an external conductor provided on the outer circumference of the dielectric, and at least one open end. a coaxial type, characterized in that at least one of the outer shape of the inner conductor and the outer shape of the outer conductor is tapered so as to have a region where the impedance gradually decreases toward the open end. dielectric resonator. 2. The coaxial dielectric resonator according to claim 1, wherein the region where the impedance gradually decreases does not extend to the tip, but a region with uniform impedance is provided near the tip. 3. The coaxial dielectric resonator according to claim 1 or 2, wherein the region where the impedance gradually decreases is formed by tapering the diameter of the outer circumference of the dielectric material. . 4. A coaxial dielectric according to claim 1 or 2, wherein the region where the impedance gradually decreases is formed by tapering the diameter of the inner peripheral surface of the hollow portion of the dielectric. resonator.