JPS6127202Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a coaxial resonator, and particularly to a 1/4 wavelength coaxial TEM resonator in which a dielectric material is interposed between an inner conductor and an outer conductor.

Filters conventionally used in the VHF band or UHF band include those using LC resonators and those using coaxial resonators. However, the former had the disadvantage that sufficient selectivity characteristics could not be obtained, and the latter had the disadvantage of being large in size.

Recently, in the field of communication equipment, there has been a demand for smaller and lighter systems, and while other parts are being made smaller and lighter, despite their importance, they are still used in large numbers. Since filters are difficult to make smaller and lighter, they have been a cause of delays in reducing the size and weight of systems. Therefore, reducing the size and weight of such filters has been a top priority for engineers in this field. Therefore, the present inventors developed a quarter-wavelength coaxial TEM resonator in which a dielectric material is filled between the inner and outer conductors. Since such a dielectric coaxial TEM resonator can be made compact, it has an extremely large advantage in reducing the size and weight of the filter and therefore the entire system. However, such dielectric-filled 1/4 wavelength coaxial
Since the TEM resonator has a high Q, high frequency components such as 3 times or 5 times as high, which are difficult to avoid in a 1/4 wavelength resonator, are easily excited, and in particular, third harmonic resonance occurs as spurious. On the other hand, in general transmitters, etc., the active elements always generate harmonics such as double or triple harmonics, so if a 1/4 wavelength coaxial TEM resonator filled with a dielectric material as described above is used, Due to its characteristics, the third harmonic is generated as spurious.

Therefore, the main purpose of this invention is to provide a coaxial resonator which can improve spurious characteristics of harmonics while eliminating the above-mentioned problems.

In summary, this idea is to remove a part of the dielectric material on the short-circuit side of the resonator in a 1/4 wavelength coaxial TEM resonator in which a dielectric material is interposed between the inner conductor and the outer conductor. This is a coaxial resonator in which the effective dielectric constant of this portion is made relatively smaller than that of other portions, and the resonance characteristics are shifted to improve spurious characteristics.

The above objects and other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of this invention. In the configuration, the 1/4 wavelength coaxial TEM resonator 1 includes an inner conductor 2, an outer conductor 3, and a dielectric 4 filled between the inner conductor 2 and the outer conductor 3, respectively.
It consists of Such a 1/4 wavelength coaxial TEM resonator 1 has, for example, the following specific structure. A cylindrical metal body made of a conductor is tightly fitted into the outer peripheral wall of the cylindrical dielectric body 4 to form the outer conductor 3. A central rod 5 made of ceramic for reinforcement is inserted into a hollow portion of the dielectric 4. The center rod 5 has the same axial length as the outer conductor 3, and the inner conductor 2 is formed by baking, for example, silver paste, which has good high frequency characteristics and good adhesion to the dielectric, on its outer peripheral wall. Note that, like the outer conductor 3, the inner conductor 2 may be replaced with a cylindrical metal body made of a conductor. When using these metal bodies, it is also conceivable to use them after baking silver on the outer peripheral wall and inner peripheral wall of the dielectric body 4 in advance. The dielectric 4 is made of, for example, a titanium oxide ceramic material, but this is because when the inner conductor 2 is made of silver in order to reduce loss, the firing temperature of the silver is
This is because the temperature is 600 to 900°C, so the material must be able to withstand this temperature. Of course, inner conductor 2
When the dielectric 4 is not formed by baking silver, the dielectric 4 may be made of another material.

According to such a coaxial resonator 1, there is no dielectric material 4 between the inner conductor 2 and the outer conductor 3 on one end side. This one end side is used as the short circuit side. Preferably, the axial length of the portion 6 where the dielectric 4 is not present can be up to about 1/3 of the total length of the resonator 1.

According to the configuration described above, the electric field of the fundamental wave is 0 or close to 0 on the short-circuit surface side of the resonator, so the material existing between the inner conductor 2 and the outer conductor 3 (usually air, vacuum state, etc.) Even if the permittivity of the resonator is low, the effect on the resonant frequency is small, but the electric field of the third harmonic becomes large even on this short-circuited side of the resonator, so the effective permittivity decreases significantly and its effect on the resonant frequency becomes extremely large. . That is, resonance of the third harmonic, which is a cause of deteriorating spurious characteristics, occurs at a higher frequency.

As described above, according to this invention, a 1/4 wavelength coaxial
Since the dielectric that exists as a solid on the short-circuited side of the TEM resonator is removed, this third harmonic resonance (excitation), which is unique to the 1/4 wavelength coaxial TEM resonator, is generated.
By shifting the frequency to a high range that poses no problem in practice, the spurious characteristics can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of this invention, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1 is a 1/4 wavelength coaxial TEM resonator, 2 is an inner conductor, 3 is
4 is the outer conductor, 4 is the dielectric material, and 6 is the part where the dielectric material 4 is not present.

Claims (1)

[Claims for Utility Model Registration] (1) A 1/4 wavelength coaxial TEM resonator including an inner conductor, an outer conductor, and a dielectric interposed between the inner conductor and the outer conductor, wherein the A coaxial resonator characterized by having a portion of the dielectric removed. (2) The coaxial resonator according to claim (1), wherein the outer conductor is a cylindrical metal body.