JPH0523641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a so-called triplate type stripline filter.

[Conventional technology]

FIG. 3 is a sectional view partially showing an example of a conventional stripline filter. This stripline filter is of the so-called triplate type, in which two dielectric substrates 11 and 12, each having ground electrodes 21 and 22 formed on their outer main surfaces, are stacked on top of each other, and a comb-shaped or interdigital type filter is placed between them. A plurality of resonant electrodes 31 to 34 are sandwiched therebetween.

[Problem that the invention seeks to solve]

The stripline filter described above has advantages over the microstripline filter, such as being smaller and having less electromagnetic field leakage, but when constructed with a comb-type or interdigital type, there are the following advantages: There was a problem.

In order to obtain narrow band characteristics, the resonant electrodes 31~
It is necessary to widen the interval S between the filters 34 and 34, so that the width W direction of the filter becomes longer.

On the other hand, in order to obtain broadband characteristics, the resonant electrode 3
It is necessary to narrow the interval S between the resonant electrodes 31 to 34, which causes the current to concentrate on the opposing ends of the resonant electrodes 31 to 34, increasing the Joule loss and causing a sudden drop in Q ₀ (no-load Q). I invite you.

Therefore, an object of the present invention is to provide a stripline filter that solves the above-mentioned problems.

[Means for solving problems]

The stripline filter of the present invention has three or more dielectric substrates stacked on top of each other, and a plurality of resonant electrodes each having a comb shape or an interdigital shape when viewed from above are arranged adjacent to each other between these dielectric substrates. The two matching resonant electrodes are distributed and sandwiched so that they are not located between the same dielectric substrates, and a ground electrode is placed on the outer main surface of both outer dielectric substrates so as to cover at least the outside of all internal resonant electrodes. It is characterized by having the following.

[Effect]

According to the above configuration, the coupling between the resonant electrodes can be adjusted by the thickness of each dielectric substrate, the dielectric constant of each dielectric substrate, the width of each resonant electrode, the planar spacing between each resonant electrode, etc. This increases the number of design parameters compared to conventional filters, broadening the design range and making it easier to obtain stripline filters with desired dimensions and electrical characteristics.

As a result, when trying to obtain narrow band characteristics, for example, it is possible to achieve equivalent resonance by adjusting the thickness and permittivity of the dielectric substrate, without having to widen the spacing between the resonant electrodes in plan view. This can be done in the same manner as when the electrode spacing is widened, and as a result, the length of the filter in the width direction can be suppressed.

For example, when trying to obtain broadband characteristics,
Since adjacent resonant electrodes can be overlapped in the thickness direction, it is possible to avoid extreme current concentration at the end of the resonant electrode and suppress a decrease in Q ₀ .

〔Example〕

FIG. 1 is a sectional view partially showing a stripline filter according to an embodiment of the present invention.
This stripline filter is an example of a four-layer case, in which four dielectric substrates 41 to 44 are stacked on top of each other, and a plurality of comb-shaped or interdigital-shaped layers are arranged between each dielectric substrate. (only four are shown in this example) resonant electrodes 61 to 64 are distributed and sandwiched between them. Ground electrodes 51 and 52 are respectively formed on the outer main surfaces of both outer dielectric substrates 41 and 44 so as to cover at least the outer sides of all internal resonant electrodes 61 to 64. Incidentally, the term "dispersion" as used herein means that two resonant electrodes that are adjacent to each other are arranged so that they are not located between the same dielectric substrates.

In this case, the overlapping dielectric substrates 41 to 44
The number of resonant electrodes 61 to 64, etc., and the method of dispersion of the resonant electrodes 61 to 64, etc. are not necessarily limited to those shown in this example, but may vary depending on the dimensions and electrical characteristics of the required stripline filter. Various things can be taken.

In the stripline filter shown in FIG. 1, the thickness of the dielectric substrates 41 to 44 is T _i (i=
1, 2, 3, ..., the same applies hereafter), and the permittivity is ε _ri ,
When the width of the resonant electrodes 61 to 64 is W _i and the planar interval between the resonant electrodes is S _i , the coupling between the resonant electrodes is adjusted by T _i , ε _ri , W _i , S _i, etc. Since the number of design parameters is larger than that of conventional filters, the design range is expanded, and it becomes easier to obtain a stripline filter with desired dimensions and electrical characteristics. It is particularly effective in the following points.

When obtaining narrow band characteristics, the interval seen in a plane
By adjusting the thickness T _{i and} the dielectric constant ε _ri , it is possible to equivalently increase the distance S _{i without making the distance S i} wider, and as a result, the distance S _i can be made smaller. That is, the width W direction can be shortened, and the filter can be made smaller.

On the other hand, to obtain broadband characteristics, for example, as shown in Figure 2, adjacent resonant electrodes 61, 62, etc. can be overlapped in the thickness direction (width where W ₀ in the figure overlaps), which makes it possible to It is possible to make the band even wider than the case. In addition, in the past, the spacing S _i became very narrow, causing a rapid drop in Q ₀ , but in this embodiment, the adjacent resonant electrodes are separated vertically, rather than approaching each other with their end faces as in the past. Since the shape approaches each other, the current gathers not only at the end of the resonant electrode but also where there is a certain electrode area, making it possible to avoid the extreme concentration of current that occurs in the past, and therefore reducing Q ₀ less.

In the case of the filter of this embodiment, although its overall thickness is thicker than that of the conventional filter, since the dielectric substrates 41 to 44 are originally thin substrates, this is difficult in terms of mounting the filter on a circuit board. is hardly a problem.

〔Effect of the invention〕

As described above, according to the present invention, the coupling between the resonant electrodes is determined by the thickness of each dielectric substrate, the dielectric constant of each dielectric substrate, the width of each resonant electrode, the planar spacing between each resonant electrode, etc. You can adjust the
Since there are more design parameters than conventional filters, the design range is expanded, making it easier to obtain stripline filters with desired dimensions and electrical characteristics.

As a result, when trying to obtain narrow band characteristics, for example, it is possible to achieve equivalent resonance by adjusting the thickness and permittivity of the dielectric substrate, without having to widen the spacing between the resonant electrodes in plan view. Since this can be done in the same manner as when the electrode spacing is widened, the length in the width direction of the filter can be suppressed and the size of the filter can be reduced.

Conversely, when trying to obtain broadband characteristics, adjacent resonant electrodes can be stacked (overlapping) in the thickness direction, making it possible to achieve a wider band than in the conventional case. Moreover, since adjacent resonant electrodes do not approach each other end-to-end as in the past, but are separated vertically, the current collects not only at the ends of the resonant electrodes, but also where there is a certain amount of electrode area. can avoid extreme current concentration such as
Therefore, it is possible to suppress a decrease in Q ₀ and realize a stripline filter with good electrical characteristics.

[Brief explanation of drawings]

FIG. 1 is a sectional view partially showing a stripline filter according to an embodiment of the present invention.
FIG. 2 is a sectional view partially showing an example of a state in which resonant electrodes are stacked. FIG. 3 is a sectional view partially showing an example of a conventional stripline filter. 41-44...Dielectric substrate, 51, 52... Earth electrode, 61-64... Resonance electrode.

Claims (1)

[Claims] 1 Three or more dielectric substrates are stacked on top of each other, and between these dielectric substrates, a plurality of resonant electrodes that are comb-shaped or interdigitated when viewed in plan are placed so that two adjacent resonant electrodes are the same. Distribute and sandwich them so that they are not located between the dielectric substrates,
A stripline filter characterized in that ground electrodes are provided on the outer main surfaces of both outer dielectric substrates so as to cover at least the outer sides of all internal resonant electrodes.