JPH09181501A - Stripline filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filter as a band pass filter in which the degradation of the attenuation characteristics of a high frequency band is improved. SOLUTION: On the one surface of a dielectric substrate 31, a stripline resonator 33 and a ground pattern 34A are formed. On the whole surface of the other surface, a ground pattern 34B is composed. On the one surface of an other dielectric substrate 32, the ground pattern 34C corresponding to the ground pattern 34A is formed. On the whole surface of the opposite side, a ground pattern 34D is formed. The ground patterns 34A and 34B or 34C and 34D are connected via the holes 35A and 35B. The both of the dielectric substrates 31 and 32 are stuck by a soldering and a band pass filter is composed. Because the grid patterns cover the external both surfaces of the dielectric substrates 31 and 32, micro waves are not propagated to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stripline filter used in a microwave frequency band, and more particularly to a stripline filter having a bandpass filter composed of a stripline resonator.

[0002]

2. Description of the Related Art In a microwave integrated circuit board, a microwave integrated circuit may be formed by using a strip line. The filter configured in this way is called a stripline filter.

FIG. 6 shows an example of the configuration of a conventional stripline filter. For example, JP-A-61-1
On one surface of the dielectric substrate 11 constituting this stripline filter disclosed in Japanese Patent Publication No. 19203,
The protective cover 12 is attached by glass glaze or an adhesive. A stripline resonator 13 is formed on the surface of the dielectric substrate 11 on the side where the protective cover 12 is present, and a ground pattern 14 as a ground electrode is formed on the other surface and side surface. The protective cover 12 not only protects the stripline resonator 13 itself from the outside, but also has a role of preventing radiation of electromagnetic energy to the outside.

FIG. 7 shows another example of the configuration of a conventional stripline filter. For example, JP
The two striplines 22, 23 are provided on one surface (the surface on the front side in the drawing) of the first dielectric substrate 21 of this stripline filter disclosed in Japanese Patent Laid-Open No. 3-59103.
And the ground pattern 24 is formed on one surface of the other surface (the surface on the back side in the drawing). On the first dielectric substrate 21, a second dielectric substrate 26 having a smaller size than that is arranged opposite to the first dielectric substrate 21. Strip lines 27 and 2 are formed on the surface of the second dielectric substrate 26 facing the first dielectric substrate 21 (the surface on the back side in the figure), respectively.
8 are formed. Two half-wavelength strip lines 29 are formed between these strip lines 27 and 28 in a stepping stone shape. The first and second dielectric substrates 21 and 22 are bonded together, and the strip line 22 and the strip line 27, and the strip line 23 and the strip line 28 are connected to each other.

FIG. 8 shows a state in which the strip line 23 in the strip line filter shown in FIG. 7 is cut in the longitudinal direction at the position.

[0006]

Among the conventional stripline filters as shown in FIG. 6, the stripline resonator 13 is a bandpass filter (BP).
F). Further, in the example shown in FIG. 7, the second
The strip lines 27 and 28 and the half-wavelength strip line 29 formed on the surface of the dielectric substrate 26 facing the first dielectric substrate 21 are strip line resonators, and form a band pass filter. The stripline filter configuration as described above has a problem that the attenuation amount in the high frequency range is deteriorated in both stripline filters. This means that frequencies higher than the passband propagate in space without passing through the bandpass filter,
This is because the output will be directly output from the input terminal. That is, since this type of stripline filter is put in a case and used, the cutoff of these cases improves the attenuation characteristic on the low frequency side, but does not improve the deterioration of the attenuation characteristic on the high frequency side. could not.

When the attenuation characteristic in the high frequency range is deteriorated in this way,
Even if the bandpass filter has a multistage structure, it is not possible to realize a desired attenuation amount. Therefore, in order to achieve the required amount of attenuation in the conventional stripline filter, either another bandpass filter with the same pass band is added, or the band filter in the band to be transmitted is
Elimination filter (BEF) will be added. Therefore, there is a problem that the entire structure of the stripline filter becomes complicated and expensive.

Therefore, an object of the present invention is to provide a stripline filter as a bandpass filter in which the deterioration of the attenuation characteristic in the high frequency band is improved.

Another object of the present invention is to provide a stripline filter that does not require a protective cover.

[0010]

A stripline filter according to a first aspect of the present invention comprises a first dielectric substrate and a second dielectric substrate bonded to the first dielectric substrate. The body substrate has a bandpass filter formed of a stripline resonator and a ground conductor on a surface facing the second dielectric substrate, and a ground conductor electrically connected to the ground conductor on a surface opposite to the bandpass filter. Have The second dielectric substrate has a ground conductor at a position facing the ground conductor on the surface facing the first dielectric substrate, and has a ground conductor electrically connected on the surface opposite to the ground conductor. It is characterized by doing.

Further, in the stripline filter according to the second aspect, a bandpass filter is formed on one surface by a stripline resonator, and the other surface is a first dielectric substrate having a ground pattern, and the above-mentioned strip. The surface facing the line resonator and the surface facing the second dielectric substrate having the surface opposite to the ground resonator as the ground pattern are bonded by soldering.

According to the invention described in claim 3, these claims 1
The second dielectric substrate according to claim 2 or claim 2 is integrated with a peripheral circuit.

The invention according to claim 4 is characterized in that the ground conductor or the ground pattern in the first or second dielectric substrate is electrically connected by through holes provided in the respective substrates. There is.

That is, in the invention according to claim 1 or 2, the first and second dielectric substrates are bonded together,
It is electrically shielded by grounding both outer sides. For this reason, there is no path through which microwaves propagate other than inside the bandpass filter, and the conventional problem that frequencies higher than the passband propagate in space without passing through the bandpass filter is solved. A high amount of attenuation can be obtained in the high range.

Further, in the third aspect of the present invention, the second dielectric substrate is integrated with the peripheral circuit, so that it is possible to reduce the number of components and the cost by simplifying the configuration. Further, in the invention according to claim 4, since the commonly used through holes are used, the process is simple and the cost is low.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

First Embodiment

1 and 2 show the structure of a stripline filter according to the first embodiment of the present invention. Of these, FIG. 1 is a cross-sectional view of the stripline filter as seen from the side, and FIG. 2 is a perspective view showing a state in which the stripline filter is vertically disassembled. The stripline filter includes first and second dielectric substrates 31 and 32. First dielectric substrate 31
On one surface (upper surface in these figures), a stripline resonator 33 and a ground pattern 34A as a ground electrode are formed in a portion where the stripline resonator 33 does not exist. Further, on the other surface (the lower surface in these figures) of the first dielectric substrate 31, the ground pattern 34B is formed on the entire surface.
Is configured. These ground patterns 34A,
34B is electrically connected through a through hole 35A.

On the other hand, in these figures, the first dielectric substrate 31
The surface of the second dielectric substrate 32 arranged on the upper side of the side opposite to the first dielectric substrate 31 (the lower surface in these figures)
Is the ground pattern 3 of a pattern corresponding to the ground pattern 34A formed on the first dielectric substrate 31.
4C is formed, and a ground pattern 34D is formed on the entire surface on the opposite surface (upper surface in these figures). These ground patterns 34C, 3
4D is electrically connected through the through hole 35B.

The first and second dielectric substrates 31 and 32 having the above structures are bonded by soldering to form a bandpass filter. Such a bandpass filter can also be applied to an interdigital type or combline type using a quarter wavelength resonator, or a side coupling type filter using a half wavelength resonator.

Next, the strip line filter of this embodiment
Will be described. This stripline fill
The bandpass filter consisting of
Set the length of each shaker 33 to 1/4 wavelength and
Open one of the lip line resonators 33 and short the other
ing. Then, these strip line resonators 33
Inter-digital bandpass with anti-parallel to each other
It is used as a filter. Bandpass filter center frequency
F₀Then, the frequency 3f of the next resonance mode ₀Is passing
Yes, but frequency 2f₀Is less than 60 dB (decibels)
Depletion is obtained. Stripline fill with conventional configuration
If a bandpass filter is composed of
It is deteriorated by about B and only 40 dB of attenuation can be obtained.
Therefore, it is a great improvement.

In the case of the stripline filter of this embodiment, the first and second dielectric substrates 31 and 32 are attached to each other, and both outer sides thereof are ground patterns 34B and 34.
This is because there is no microwave propagation path except inside the stripline filter because it is electrically shielded by D. In addition, the through hole 35 to be grounded
Microwaves in the stripline filter can be confined by A and 35B in a region as narrow as possible, that is, in the very vicinity of the stripline resonator 33, and higher attenuation can be obtained.

Second Embodiment

FIGS. 3 and 4 show the structure of a stripline filter according to the second embodiment of the present invention. Of these, FIG. 3 is a top view of the stripline filter, and FIG. 4 is a cross-sectional view as seen from the side. The stripline filter is the first dielectric substrate 41.
And a second dielectric substrate 32 on which this is arranged. The first dielectric substrate 41 has a stripline resonator 43 and ground patterns 44A and 44B formed on one surface (lower surface in the figure) thereof. A ground pattern 45 is formed on the other surface (upper surface in the figure). The ground pattern 45 and the ground patterns 44A and 44B are electrically connected to each other through a through hole 46.

The second dielectric substrate 42 has strip lines 47A, 47 for connecting to the first dielectric substrate 41 on the surface (the upper surface in the figure) on which the first dielectric substrate 41 is mounted.
It has a connection circuit composed of B and peripheral circuits. A ground pattern 48 is formed on the other surface (lower surface in the figure) of the second dielectric substrate 42. The first and second dielectric substrates 41 and 42 have the opposing ground patterns 4
4A, 47A and 44B, 47B are attached by soldering.

In the case of the second embodiment as well, as in the case of the first embodiment, the both outsides of the stripline filter are electrically shielded by the ground patterns 45 and 48, so that the inside of the stripline filter is also. There is no other path along which microwaves propagate. Further, the through hole 46 that is grounded confines the microwave in the stripline filter in a region as narrow as possible, that is, in the very vicinity of the stripline resonator 43, to obtain a high attenuation amount.

FIG. 5 shows the relationship between the attenuation amount and the frequency in the case of the stripline filter of this embodiment in comparison with the case of the conventional stripline filter. Compared with the conventional example shown by the broken line 51, in the case of the present invention shown by the solid line 52, as described above, the attenuation amount in the high range is 20d.
B can be improved. Similarly, the stripline filter according to the first embodiment can obtain good characteristics as a bandpass filter.

[0029]

As described above, according to the first and second aspects of the present invention, the first and second dielectric substrates are bonded to each other, and both outer sides thereof are grounded to form an electrical shield. Is going. Therefore, there is no path through which microwaves propagate other than inside the bandpass filter, and it is possible not only to secure the attenuation in the high frequency band higher than the passband, but also from the stripline to the outside. It is also possible to prevent the radiation of electromagnetic energy. Therefore, there is an advantage that the protective cover conventionally used as a countermeasure against such electromagnetic energy is not required.

According to the invention described in claim 3, the second
Since the dielectric substrate of (1) is integrated with the peripheral circuit, there is an advantage that the number of components can be reduced and the cost can be reduced by simplifying the configuration.

Further, according to the invention described in claim 4, the ground conductor or the ground pattern in the first or second dielectric substrate is electrically connected by the through hole provided in each substrate. The process is simple and the price is low.

[Brief description of the drawings]

FIG. 1 is a plan view of a stripline filter according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the stripline filter shown in FIG.

FIG. 3 is a plan view of a stripline filter according to a second embodiment of the present invention.

4 is a cross-sectional view of the stripline filter shown in FIG. 3 as seen from the side.

FIG. 5 is a characteristic diagram showing the relationship between the attenuation amount and frequency of the stripline filter of the second embodiment in comparison with the case of a conventional stripline filter.

FIG. 6 is a cross-sectional view showing an example of the configuration of a conventional stripline filter.

FIG. 7 is a plan view showing another example of the configuration of a conventional stripline filter.

8 is a sectional view of the conventional stripline filter shown in FIG.

[Explanation of symbols]

 31, 41 First dielectric substrate 32, 42 Second dielectric substrate 33, 43 Stripline resonator 34, 45, 48 Ground pattern 35, 46 Through hole

Claims (4)

[Claims] 1. A stripline resonator comprising a first dielectric substrate and a second dielectric substrate bonded to the first dielectric substrate, wherein the first dielectric substrate is on a surface facing the second dielectric substrate. And a grounding conductor electrically connected to the grounding conductor on a surface opposite to the bandpass filter and the grounding conductor.
5. A stripline filter having a ground conductor at a position facing a ground conductor on a surface facing the dielectric substrate and having a ground conductor electrically connected on a surface opposite to the ground conductor. 2. A first dielectric substrate having a bandpass filter formed on one surface with a stripline resonator and having a ground pattern on the other surface, and a surface opposite to the surface opposed to the stripline resonator. A stripline filter comprising: a second dielectric substrate whose side surface is a ground pattern; and a solder member in which the facing surfaces of the first and second dielectric substrates are bonded together. 3. The stripline filter according to claim 1, wherein the second dielectric substrate is integrated with a peripheral circuit. 4. The ground conductors or ground patterns formed on the respective surfaces of the first and second dielectric substrates are electrically connected by through holes of the respective dielectric substrates. Claim 1 or Claim 2
Stripline filter as described.