JPS6114164Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a stripline filter.

Conventionally, as a filter used in the VHF band,
There are those that use LC resonance and those that use helical resonance. Q is a filter that uses LC resonance.
However, filters using helical resonance have the drawback of being large in size. Therefore, recently, stripline filters in which a plurality of resonant electrodes are formed on the surface of a dielectric substrate are often used. This stripline filter is formed by printing silver or the like on the surface of a dielectric substrate and then baking it. However, in such a strip line filter, it is not possible to arbitrarily increase or decrease the number of resonant electrodes or change the degree of coupling after manufacturing. Furthermore, the inner peripheral surface of the cylindrical ceramic dielectric,
A coaxial TEM resonator was developed in which an inner guide shaft and an electrode film serving as an outer conductor were formed on the outer circumferential surface, but as the frequency became lower, the axial length of the cylindrical dielectric had to be lengthened, and due to manufacturing technology, Forming uniform cylindrical ceramic dielectrics has been difficult.

Therefore, the main purpose of this invention is to provide a filter in which the number of resonant electrodes in the filter can be increased or decreased as desired, and the degree of coupling can be freely adjusted.

In summary, this invention is a stripline filter that combines a substrate provided with a ground side electrode on at least one surface and a rod-shaped dielectric element provided with at least a resonant electrode.

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.

Figures 1a, b, and c show examples of rod-shaped dielectric elements used in one embodiment of this invention.

Referring to FIG. 1b, first, a dielectric material 11 having a rectangular cross-sectional shape and a rod shape is prepared. This dielectric 11 is made of ceramic or the like having a dielectric constant ε of about 90. Then, electrode films 12, 13, and 14 are formed on the dielectric 11 except for the longitudinally opposing side surfaces and one end surface. That is,
In FIG. 1, an electrode film 12 made of, for example, silver or copper is formed on the upper surface, and an electrode film 13 is similarly formed on the lower surface. Then, on one side end surface,
A short-circuit electrode film 14 that short-circuits electrode films 12 and 13 is formed. FIGS. 1a and 1c are essentially the same, and functionally the same parts are given the same numbers and their explanation will be omitted. First, a dielectric 21 similar to the dielectric 11 is prepared. An electrode film 22 similar to the electrode film 12 is formed on the upper surface in the figure, and an electrode film 23 is formed entirely on the lower surface. Reference numeral 24 denotes an input/output terminal electrode film, which is formed to protrude from the electrode film 22 in the lateral direction in the figure at an appropriate interval from the short-circuit end side to the open end side of the electrode film 22. Note that 25 is a guard electrode film. Inserting the guard electrode film 25
The portion facing the output terminal electrode film 24 functions as a ground side input/output terminal electrode. The portion connected to the electrode film 22 has a function of absorbing the printing misalignment with the guard electrode even if there is a printing misalignment when printing the electrode film 22 on the dielectric material 21 . Therefore, if the printing accuracy is good, the electrode film 2 of the guard electrode film 25
The parts connected to 2 are not essential.
Further, when a portion continuous to the electrode film 22 is provided, it is more preferable to provide a margin between the open end of the electrode film 22 and the edge of the dielectric 21. Similarly, the electrode film 12 may also have a guard electrode, or may have a margin between the open end and the edge of the dielectric 11. An example of a stripline filter in which such elements are appropriately combined is shown in FIG. Reference numeral 31 denotes a dielectric substrate preferably made of the same material as the dielectrics 11 and 21, and has a full-surface electrode film 32 serving as a ground electrode formed on one side. Electrode films 13 and 23 of each element and the entire surface electrode film 32
This means that they are electrically and mechanically connected and fixed by soldering or by printing and baking each electrode film at the same time. The second figure shows an example in which there are four resonant electrodes, but of course the number can be arbitrary. The resonant electrode is not limited to a 1/4 wavelength type as described above, but may be of a 1/2 wavelength type. In the second figure, the edge of the element and the edge of the substrate 31 are aligned, but if a margin is provided between the edge of the element and the edge of the substrate 31, the margin will become a buffer band. This is preferable because it reduces the influence of external influences on the electrical characteristics. The method of forming each electrode is arbitrary. As mentioned above,
It is common to print silver and then bake it or plate it with copper.

In this way, the individually formed dielectric element and the substrate provided with the ground electrode are combined, so
A wide variety of strip line filters can be easily constructed. In other words, if you want to increase the number of stages, Figure 1b
You can increase the number of elements shown in , or if you want to reduce the number of stages, you can reduce this element.
If you want a filter with a high frequency, each element should have a short length. If you want a filter with a low frequency, use one with long elements. It is also easy to cut each element to shorten its length. If you want to increase the degree of coupling between elements, you can move the elements closer to each other, and conversely, if you want to decrease the degree of coupling, you can move the elements farther apart. If you want to increase the Q of the element, you can increase the cross-sectional area of the dielectric. As mentioned above, if a large substrate is used as much as space allows, it is possible to keep the same size even if the number of stages, frequencies, and degrees of coupling vary.

As is clear from the above examples, according to this invention, there is no substrate dielectric between elements, so a filter with the same passband width as the conventional structure in which a substrate dielectric exists can be made smaller. Obtainable. In other words, you can get a filter with a narrower bandwidth for the same size. In addition, compared to conventional structures, it is easier to design and manufacture, and the component parts can be standardized, saving resources and reducing costs.

[Brief explanation of the drawing]

FIGS. 1a, b, and c are perspective views of elements used in an embodiment of the present invention, and FIG. 2 is a perspective view of an embodiment of the present invention. 11 and 21 are dielectric materials, 12 and 22 are electrode films, and 3
1 is a dielectric substrate, and 32 is a ground electrode.

Claims (1)

[Claims for Utility Model Registration] A substrate having at least a ground electrode on one surface; a bar-shaped dielectric element having a resonant electrode on one surface and a ground electrode on the other surface opposite to the one surface; A strip line filter constructed by bonding a ground electrode and a ground electrode of a rod-shaped dielectric element.