JPH0211163B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a small and inexpensive planar dielectric filter for use in the microwave band, which is capable of increasing the degree of coupling and furthermore allows adjustment of the resonant frequency.

Conventional configurations and their problems Filters used in the microwave band include filters that use lumped constants L and C, and filters that use coaxial dielectric resonant elements. However, the former has the drawback of very large dielectric loss, and the latter has the disadvantage that it is difficult to metalize the resonant element, and when configuring a filter, it requires capacitive elements for input/output and interstage coupling, making the structure complex and frequency adjustment. However, since it is not easy to do so, it has the disadvantage that it is very difficult to reduce the cost and downsize.

As an improvement to these filters, there are planar dielectric filters that utilize small and lightweight strip conductors. Such a planar dielectric filter is shown in FIG. Figure 5a is a partially cutaway perspective view of the
Figure b is a plan view thereof. As shown in FIG. 5, the conventional planar dielectric filter has quarter-wavelength strip conductors 3 and 4, one end shorted and the other end open, arranged in parallel using metallization or the like on one surface of a single dielectric substrate 1. Input/output terminals 5 and 6 are provided on the dielectric substrate 1, and a ground conductor 7 is provided on the other surface of the dielectric substrate 1.
As shown in the figure, the other dielectric substrate 2 has a ground conductor 8 provided on all but one surface.
It is made by fusion bonding using glass or the like, or by mechanically fixing it.

In such conventional planar dielectric filters, the degree of coupling between resonators made of strip conductors is very small, making it difficult to realize a broadband microwave band filter. Furthermore, it is necessary to adjust the resonant frequency of each resonator due to variations in the dielectric constant of the material of the dielectric substrate and variations in the dimensional accuracy of the strip conductor, but this adjustment is not easy.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a planar dielectric filter that is small in size, low in cost, excellent in mass production, has a high degree of coupling between resonators, and is easy to adjust the resonance frequency.

Structure of the Invention In the planar dielectric filter of the present invention, a plurality of 1/2 wavelength strip conductors with both ends open or 1/4 wavelength strip conductors with one end shorted and the other end open are arranged in parallel on one surface of one dielectric substrate. . Input/output terminals are provided on these middle and outer strip conductors.
Further, a ground conductor is provided on the other surface of this dielectric substrate. According to the invention, a groove or slit is further formed in the middle of the strip conductor and parallel to it.

Further, a groove or slit is provided on one surface of another dielectric substrate so as to match that when the dielectric substrate is bonded to the above dielectric substrate, and a ground conductor is provided on the other surface. The two dielectric substrates are then joined so that their grooves or slits are aligned.

In the planar dielectric filter of the present invention having the above-described structure, the degree of coupling between the strip conductor resonators can be changed by changing the depth of the grooves or the length of the slits. In addition, if the dielectric substrate containing the strip conductor is made larger than other dielectric substrates and the open end of each strip conductor resonator is partially exposed, this portion can be used to trim or add capacitance. The resonant frequency can be adjusted by making corrections.

DESCRIPTION OF EMBODIMENTS An example of a planar dielectric filter according to the present invention, ie, a planar dielectric filter using a resonator made of a quarter-wavelength strip conductor with one end shorted and the other end open, will be described. FIG. 1a is a partially cutaway perspective view, FIG. 1b is a plan view, and FIG. 1c is a side view.

In FIG. 1, 1 and 2 are, for example, BaTi ₄ O ₉
There is a dielectric substrate made of ceramic. The dielectric substrate 1 has two strip conductors 3 and 4 as shown in the figure.
is formed of silver metallization, and is provided with input/output terminals 5 and 6, respectively. Further, a groove 9 having a depth of 1/2H (see FIG. 1c) is provided penetrating the dielectric substrate 1 at an intermediate position between the strip conductors 3 and 4. A ground conductor 7 is provided on the other surface of the dielectric substrate 1 by silver metallization. Also, on one surface of the dielectric substrate 2, a depth of 1/2H (first
A groove 10 (see Figure c) is provided, and a ground conductor 8 is provided on the other side. Then, both insulating substrates 1 and 2 are fused and fixed with glass so that the grooves 9 and 10 match and have a total depth H. At this time, the depth H of the groove is used to adjust the degree of polymerization of the strip conductor resonator to the designed value. FIG. 2 shows the relationship between the degree of coupling K between the strip conductor resonators 3 and 4 according to the present invention and the depth H of the groove.

Next, another example of the planar dielectric filter of the present invention is shown in FIG. FIG. 3a is a partially cutaway perspective view thereof, and FIG. 3b is a plan view thereof.

In this example, the dielectric substrate, ground conductor, strip conductor, and input/output terminals are the same as in FIG.
11 and 12 in Figure 3 a and b instead of 0
As shown, slits 11 and 12 are formed in dielectric substrates 1 and 2, respectively, and dielectric substrates 1 and 2 are fused and fixed with glass so that the slits coincide with each other. At this time, the degree of polymerization of the strip conductor resonator is adjusted to the design value using the length L of the slit shown in FIG. 3b. FIG. 4 shows the relationship between the degree of coupling K between the strip conductor resonators 3 and 4 according to the present invention and the length L of the slit.

As is clear from FIGS. 2 and 4, the planar dielectric filter according to the present invention can increase the degree of coupling between resonators by adjusting the depth of the grooves or the length of the slits. Can be done.

In the planar dielectric filter according to the present invention shown in FIGS. 1 and 3, the dielectric substrate 1 is formed to be longer than the substrate 2, so that the open ends of the strip conductors are exposed. In such cases, the exposed portion may be trimmed (e.g., by cutting off part of the strip conductor with a laser), or the capacitance may be corrected (e.g., by moving a piece of metal closer to or closer to the strip conductor to change the gap capacitance, or by using a variable capacitance (trimmer)). ) is added to the strip conductor portion), the resonant wave number can be easily adjusted.

Further, although the above-mentioned example is a two-stage filter, it may be a three-stage filter or more.

Further, in the above example, a 1/4 wavelength strip conductor resonator with one end shorted and the other end open is shown, but it is of course possible to use a 1/2 wavelength strip conductor resonator with both ends open.

Effects of the Invention As described above, the planar dielectric filter of the present invention can increase the degree of coupling between resonators by forming grooves or slits between the strip conductors. Since a part of the open end of the filter is exposed, the resonant frequency can be easily adjusted using this part, making it possible to provide a planar dielectric filter that is small, has a wide band, is easy to manufacture, and is highly mass-producible.

[Brief explanation of drawings]

FIG. 1a is a partially cutaway perspective view of a planar dielectric filter of the present invention, FIG. 1b is a plan view thereof, and FIG. 1C
is a side view thereof, FIG. 2 is a diagram showing the relationship between the groove depth and the coupling degree of the planar dielectric filter of FIG. 1, and FIG. 3a is a diagram showing another planar dielectric filter of the present invention. FIG. 3b is a plan view thereof, FIG. 4 is a diagram showing the relationship between the length of the slit and the degree of coupling of the planar dielectric filter of FIG. FIG. 5A is a partially cutaway perspective view of a conventional planar dielectric filter, and FIG. 5B is a plan view thereof. 1, 2 are dielectric substrates, 3, 4 are strip conductors, 7, 8 are ground conductors, 9, 10 are grooves, 11, 1
2 is slit.

Claims (1)

[Claims] 1. A 1/2 wavelength strip conductor with both ends open on one side of the first dielectric substrate or a 1/4 wavelength strip conductor with one end shorted and the other end open.
A plurality of wavelength strip conductors are arranged in parallel, the strip conductors on the inner and outer sides of the strip conductors are provided with input/output terminals, a ground conductor is provided on the other surface of the first dielectric substrate, and a second dielectric substrate is provided with a ground conductor. A ground conductor is provided on all but one surface of the dielectric substrate, and the surface of the first dielectric substrate on which the strip conductor is provided;
The surface of the second dielectric substrate on which the ground conductor is not provided is joined, and a groove or slit is formed in the first dielectric substrate and the second dielectric substrate in parallel with the strip conductor at an intermediate position of the strip conductor. What is claimed is: 1. A planar dielectric filter provided with a first dielectric substrate, wherein the first dielectric substrate is longer than the second dielectric substrate, and the strip conductor is partially exposed.