JPH05136602A - Strip line filter - Google Patents

Abstract

PURPOSE:To prevent the third harmonic wave by providing a groove on a dielectric substrate and bonding with an outer conductor and a continuous conductor on the surface of the groove. CONSTITUTION:Out of dielectric substrates 1a and 1b, at the position of about 1/3 of inner conductors 2a and 4a length from shorting parts 13a-15a and 13b-15b on one outer surface where outer conductors 5a and 5b are formed, grooves 12a and 12b in the direction to cross with inner conductors 2a-4a and 2b-4b are provided. On the surface of the grooves 12a and 12b, the outer conductors 5a and 5b and the continuous conductor are bonded. Thus, at the position of the grooves 12a and 12b, the interval of the inner conductors 2a-4a and the outer conductors 5a and 5b becomes narrow, an electric field becomes strong and a static capacitance becomes large. For the third harmonic wave where the inner conductors 2a-4a length becomes the about 3/4 wavelength, the electric field in the resonator becomes maximum at the position of the grooves 12a and 12b, and by the action of the static capacitance to occur at the grooves 12a and 12b, the resonance frequency becomes low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triple wave blocking means for a strip line filter used mainly in the VHF band, the UHF band and the microwave band.

[0002]

FIG. 17 shows, for example, Japanese Patent Publication No. 2-11163.
FIG. 1 is a schematic configuration diagram showing an example of a conventional stripline filter as disclosed in Japanese Patent Publication No.
b is two dielectric substrates facing each other, 2a to 4a are inner conductors formed by adhering a conductor film to the inner surface of the dielectric substrate 1a and formed substantially parallel to each other, and 5a is the entire outer surface of the dielectric substrate 1a. The outer conductor 5b is formed by closely adhering a conductor film to the dielectric substrate 1
an outer conductor formed by closely adhering a conductor film to the outer surface of b, 6 to 8
Are the dielectric substrates 1a and 1b, the inner conductors 2a to 4a,
A resonator of a triplate line composed of outer conductors 5a and 5b, and 9a is a coupling amount provided by digging the central dielectric substrate 1a between the inner conductor 2a and the inner conductor 3a and the inner conductor 3a and the inner conductor 4a. A groove for adjustment, 9b is a groove for adjusting the coupling amount provided by digging the dielectric substrate 1b, and 10 and 11 are the inlets whose inner conductors are directly connected to the side surfaces of the inner conductor 2a and the inner conductor 4a, respectively. It is an output line. The dielectric substrates 1a and 1b are
The groove 9a and the groove 9b are overlapped and bonded so as to face each other and overlap each other. In the example shown in FIG. 17, the length of each of the inner conductors 2a to 4a is set to about ¼ wavelength, and one end of each of the outer conductors 5a and 5b is located on the side surface of the dielectric substrate 1a, 1b.
And a short circuit portion is formed. Therefore, the resonators 6 to 8 are quarter-wave resonators in which one end is short-circuited and the other end is open. In this example, the dielectric substrate 1a is the inner conductor 2a.
4a are set to be longer than the dielectric substrate 1b, and by arranging the dielectric substrate 1a and the dielectric substrate 1b so that the short-circuited ends of the resonators 6 to 8 are aligned, the inner conductors 2a to 4a. Take the example where the open end side of is exposed.

The operation is as follows. Adjacent resonators 6 to 8 are magnetically coupled to each other due to the effect of grooves 9a and 9b, and the amount of coupling is adjusted by the depth of grooves 9a and 9b and the distance between adjacent inner conductors. Further, the input / output coupling amount is adjusted by changing the connection positions of the inner conductors of the input / output lines 10 and 11 and the inner conductors 2a and 4a.

Now, by trimming the exposed portions of the inner conductors 2a to 4a on the open end side and adjusting the lengths of these inner conductors, all the resonators 6 to 8 resonate at the same frequency, for example, f0. At that frequency f0, the resonators 6 to 8 in the resonance state are strongly coupled to each other, the incident wave to the input / output line 10 is guided to the resonator 6, and the resonator 7, It is output from the input / output line 11 through the signal line 8. However, at frequencies other than f0, the mutual coupling of the resonators 6 to 8 is very weak, and most of the power of the incident wave to the input / output line 10 or 11 is reflected. Thus, the strip line filter shown in FIG. 17 has a function as a band pass filter.

Further, in this example, the resonators 6 to 8 have the inner conductor length set to about 1/4 wavelength so as to resonate at the frequency f0. Therefore, at a frequency 3f0 that is three times f0, the inner conductor length becomes about 3/4 wavelength, and the resonators 6 to 8 resonate again. Therefore, as shown in FIG. 18, the stripline filter of FIG.
It also has the property of passing the triple harmonic of f0. For this reason, when the filter of FIG. 17 is used in combination with the microwave power amplifier, it is necessary to separately provide a means for blocking the third harmonic generated by the power amplifier as a normal spurious.

[0006]

Since the conventional strip line filter is constructed as described above, the resonator 6
˜8, the inner conductor length resonates at about 1/4 wavelength at frequency f0, and resonates again at about 3/4 wavelength at 3f0, which is three times f0. Therefore, there is a problem that, in addition to the fundamental wave of the frequency f0, the triple harmonic of 3f0 also passes through.

The present invention has been made to solve the above-mentioned problems, in which a fundamental wave of frequency f0 is passed through,
Moreover, it is an object of the present invention to obtain a strip line filter having a function of blocking a triple harmonic of a frequency 3f0 which is triple the frequency of f0.

[0008]

A stripline filter according to a first aspect of the present invention is a short-circuit portion 13a of one outer surface of a dielectric substrate 1a, 1b on which at least an outer conductor is formed.
.About.15a, 13b to 15b to the inner conductors 2a to 4a, 2b to 4b at positions of about 1/3 of the length of the inner conductors 2a to 4a.
Grooves 12a and 12b are formed in a direction intersecting with, and conductors continuous with the outer conductor are adhered to the surfaces of the grooves 12a and 12b.

In the strip line filter according to the second invention, the short-circuited portions 13a to 15a, 13b on one outer surface of the dielectric substrate 1a, 1b on which at least the outer conductor is formed.
.About.15b to about 2/3 of the length of the inner conductors 2a to 4a, grooves 16a and 16b in a direction intersecting with the inner conductors 2a to 4a and 2b to 4b are provided, and the grooves 16a and 16b are provided on the surfaces thereof. The outer conductor and the continuous conductor were adhered.

A stripline filter according to a third aspect of the present invention is a short-circuited portion 13a-1 of the inner conductors 2a-4a, 2b-4b.
Protrusions 17a and 17b, which are formed by extending the inner conductors 2a to 4a and 2b to 4b in the width direction, are provided at positions about 1/3 of the length of the inner conductors 2a to 4a from 5a and 13b to 15b.

A strip line filter according to a fourth aspect of the present invention is a short-circuited portion 13a-1 of the inner conductors 2a-4a, 2b-4b.
Protrusions 18a and 18b obtained by extending the inner conductors 2a to 4a and 2b to 4b in the width direction are provided at positions ⅔ of the length of the inner conductors 2a to 4a from 5a, 13b to 15b.

In the strip line filter according to the fifth aspect of the invention, the length of the surface of the dielectric substrate 1a on which the outer conductor 5a is formed is about 1/3 of the length from the short-circuited portions 13a to 15a to the inner conductors 2a to 4a. A groove 12a is provided at a position in a direction intersecting with the inner conductors 2a to 4a, and a conductor continuous with the outer conductor 15a is adhered to the surface of the groove 12a.

In the strip line filter according to the sixth aspect of the present invention, the surface of the dielectric substrate 1a on which the outer conductor 5a is formed is located at about ⅔ of the length from the short-circuited portions 13a to 15a to the inner conductors 2a to 4a. A groove 16a in a direction intersecting with the inner conductors 2a to 4a is provided in the above, and a conductor continuous with the outer conductor 5a is adhered to the surface of the groove 16a.

In the strip line filter according to the seventh invention, the inner conductor 2a is located at a position approximately 1/3 of the length of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a of the inner conductors 2a to 4a.
4a to 4a are provided in the width direction to provide a protrusion 17a.

In the strip line filter according to the eighth aspect of the invention, the inner conductor 2a is located at a position approximately ⅔ of the length of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a of the inner conductors 2a to 4a.
4a to 4a are provided in the width direction to provide a protrusion 18a.

The strip line filter according to the ninth aspect of the present invention comprises a rod-shaped or plate-shaped dielectric on the inner conductors 2a-4a at a position approximately 1/3 of the length of the inner conductors 2a-4a from the short-circuited portions 13a-15a. The body 22 was provided in close contact with the inner conductors 2a to 4a in a direction crossing the inner conductors 2a to 4a.

The stripline filter according to the tenth aspect of the present invention is a rod-shaped or plate-shaped dielectric material on the inner conductors 2a-4a at a position approximately 2/3 of the length of the inner conductors 2a-4a from the short-circuited portions 13a-15a. 23 was provided in close contact with the inner conductors 2a to 4a.

[0018]

The strip line filter according to the first aspect of the present invention includes at least the outer conductor 5 of the dielectric substrates 1a and 1b.
The short-circuited portion 13a on the outer surface of one sheet on which a and 5b are formed.
.About.15a, 13b-15b, and grooves 12a, 12b in a direction intersecting with the inner conductors 2a-4a, 2b-4b are provided at positions of about 1/3 of the length of the inner conductors 2a-4a, and the groove 12 is provided.
Since the conductors continuous with the outer conductors 5a and 5b are adhered to the surfaces of the a and 12b, the inner conductors 2a to 4a and 2b to 4b and the outer conductors 5a and 5b are located at the positions of the grooves 12a and 12b.
The distance from b is narrowed, the electric field is strengthened, and the capacitance is increased. At this time, with respect to the fundamental wave whose lengths of the inner conductors 2a to 4a are about 1/4 wavelength, the electric field in the resonator is the groove 12
Since the positions a and 12b are relatively small, the grooves 12a,
Although the influence of 12b is small and the resonance frequency of the resonator does not change, the electric field in the resonator is affected by the electric field in the groove 12a, 12 for the third harmonic wave in which the length of the inner conductors 2a to 4a becomes about 3/4 wavelength.
Since it becomes the maximum at the position of b, the resonance frequency is lowered by the action of the electrostatic capacitance generated in the grooves 12a and 12b.

The stripline filter according to the second invention is at least the outer conductor 5 of the dielectric substrates 1a and 1b.
The short-circuited portion 13a on the outer surface of one sheet on which a and 5b are formed.
.About.15a, 13b to 15b, and grooves 16a and 16b in a direction intersecting with the inner conductors 2a to 4a and 2b to 4b are provided at positions approximately 2/3 of the length of the inner conductors 2a to 4a.
Since the conductor continuous with the outer conductor is adhered to the surface of 16b, the inner conductors 2a to
The distance between the outer conductors 4a, 2b-4b and the outer conductors 5a, 5b is narrowed, the electric field is strengthened, and the electrostatic capacitance is increased. At this time, since the electric field in the resonator is large at the positions of the grooves 16a and 16b with respect to the fundamental wave in which the lengths of the inner conductors 2a to 4a are about 1/4 wavelength, the static electricity generated in the grooves 16a and 16b. Although the resonance frequency is lowered by the action of the capacitance, the electric field in the resonator is almost zero at the positions of the grooves 16a and 16b for the third harmonic wave in which the length of the inner conductors 2a to 4a is about 3/4 wavelength. Therefore, the grooves 16a and 16b are not affected and the resonance frequency does not change.

The stripline filter according to the third aspect of the present invention comprises a short-circuit portion 13a-of the inner conductors 2a-4a, 2b-4b.
Since the inner conductors 2a to 4a and 2b to 4b are provided with the projections 17a and 17b extending in the width direction from the positions 15a and 13b to 15b at positions of about 1/3 of the length of the inner conductors 2a to 4a,
At the positions of the protrusions 17a and 17b, the inner conductors 2a to
The outer conductors 5a and 5b are widened by widening the widths of 4a and 2b to 4b.
The capacitance between and becomes large. At this time, since the electric field in the resonator is relatively small at the positions of the protrusions 17a and 17b with respect to the fundamental wave whose lengths of the inner conductors 2a to 4a are about 1/4 wavelength, the protrusions 17a and 17b are relatively small. Although the resonance frequency does not change, the electric field in the resonator is maximum at the positions of the protrusions 17a and 17b for the third harmonics in which the length of the inner conductors 2a to 4a is about 3/4 wavelength. Therefore, the resonance frequency is lowered by the action of the electrostatic capacitance generated in the protrusions 17a and 17b.

The stripline filter according to the fourth aspect of the present invention comprises a short-circuit portion 13a of the inner conductors 2a-4a and 2b-4b.
Since the inner conductors 2a to 4a and 2b to 4b are provided with the protrusions 18a and 18b extending in the width direction from the positions 15a and 13b to 15b at positions of about 2/3 of the length of the inner conductors 2a to 4a,
At the positions of the protrusions 18a and 18b, the inner conductor 2a ...
The outer conductors 5a and 5b are widened by widening the widths of 4a and 2b to 4b.
The capacitance between and becomes large. At this time, since the electric field in the resonator is large at the positions of the protrusions 18a and 18b with respect to the fundamental wave in which the lengths of the inner conductors 2a to 4a are about 1/4 wavelength, they are generated at the protrusions 18a and 18b. Although the resonance frequency is lowered due to the action of the electrostatic capacitance, the inner conductors 2a ...
For the third harmonic of which the length of 4a is about 3/4 wavelength, the electric field in the resonator is almost zero at the positions of the protrusions 18a and 18b.
Therefore, the resonance frequency does not change because there is no influence of the protrusions 18a and 18b.

In the strip line filter according to the fifth aspect of the present invention, a position of the dielectric substrate 1a on which the outer conductor 5a is formed is located at about 1/3 of the length from the short-circuited portions 13a to 15a to the length of the inner conductors 2a to 4a. Since a groove 12a in a direction intersecting with the inner conductors 2a to 4a is provided on the surface of the groove 12a and a conductor continuous with the outer conductor 5a is adhered to the surface of the groove 12a, at the position of the groove 12a, the inner conductors 2a to 4a and the outer conductor The space between the conductor 5a and the conductor 5a is narrowed, the electric field is strengthened, and the electrostatic capacitance is increased. At this time,
Since the electric field in the resonator is relatively small at the position of the groove 12a for the fundamental wave whose lengths of the inner conductors 2a to 4a are about 1/4 wavelength, the influence of the groove 12a is small and the resonance frequency does not change. However, the electric field in the resonator is not affected by the electric field in the resonator for the third harmonic wave in which the length of the inner conductors 2a to 4a is about 3/4 wavelength.
Since it becomes maximum at the position of 2a, the resonance frequency becomes low due to the action of the electrostatic capacitance generated in the groove 12a.

In the strip line filter according to the sixth aspect of the invention, the short-circuited portions 13a to 15a on the surface of the dielectric substrate 1a on which the outer conductor 5a is formed are connected to the inner conductors 2a to 2a.
Since a groove 16a in a direction intersecting with the inner conductors 2a to 4a is provided at a position of about 2/3 of the length of 4a, and a conductor continuous with the outer conductor 5a is adhered to the surface of the groove 16a, the groove 1 is formed.
At the position of 6a, the inner conductors 2a to 4a and the outer conductor 5a.
The distance between and decreases, the electric field increases, and the capacitance increases. At this time, with respect to the fundamental wave whose lengths of the inner conductors 2a to 4a are about 1/4 wavelength, the electric field in the resonator is changed to the groove 16a.
, The resonance frequency is lowered by the action of the capacitance generated in the groove 16a, but the inner conductors 2a ...
As for the third harmonic having a length of 4a of about 3/4 wavelength, the electric field in the resonator becomes almost 0 at the position of the protrusion 16a, so that the groove 16a does not affect the resonance frequency.

In the strip line filter according to the seventh aspect of the present invention, the inner conductor 2 is located at a position approximately 1/3 of the length of the inner conductors 2a-4a from the short-circuited portions 13a-15a of the inner conductors 2a-4a.
Since the protrusions 17a are formed by extending a to 4a in the width direction, the inner conductors 2a to 4a are located at the positions of the protrusions 17a.
Becomes wider and the capacitance between the outer conductor 5a and the outer conductor 5a becomes larger. At this time, the length of the inner conductors 2a to 4a is about 1/4.
Since the electric field in the resonator is relatively small for the fundamental wave having the wavelength at the position of the protrusion 17a, the protrusion 17a
The resonance frequency does not change, but the electric field in the resonator becomes maximum at the position of the protrusion 17a for the third harmonic wave in which the length of the inner conductors 2a to 4a is about 3/4 wavelength. Therefore, the resonance frequency is lowered by the action of the electrostatic capacitance generated in the protrusion 17a.

In the strip line filter according to the eighth aspect of the present invention, the inner conductor 2 is located at a position approximately ⅔ of the length of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a of the inner conductors 2a to 4a.
Since the protrusions 18a are provided by extending the a to 4a in the width direction, the inner conductors 2a to 4a are located at the positions of the protrusions 18a.
Becomes wider and the capacitance between the outer conductor 5a and the outer conductor 5a becomes larger. At this time, the length of the inner conductors 2a to 4a is about 1/4.
Since the electric field in the resonator is large with respect to the fundamental wave having the wavelength at the position of the protruding portion 18a, the resonance frequency becomes low due to the action of the capacitance generated in the protruding portion 18a, but the inner conductors 2a to 4a. For the third harmonic having a length of about 3/4 wavelength, the electric field in the resonator becomes almost zero at the position of the protrusion 18a, so that the protrusion 18a has no influence and the resonance frequency does not change.

A strip line filter according to the ninth invention is a rod-shaped or plate-shaped dielectric on the inner conductors 2a-4a at a position approximately 1/3 of the length of the inner conductors 2a-4a from the short-circuited portions 13a-15a. Since 22 is provided in close contact with the inner conductors 2a to 4a in a direction intersecting with each other, the capacitance is large at the position of the dielectric 22. At this time, since the electric field in the resonator is relatively small at the position of the dielectric 22 with respect to the fundamental wave in which the lengths of the inner conductors 2a to 4a are about 1/4 wavelength, the influence of the dielectric 22 is small and the resonance occurs. Although the frequency does not change, the electric field in the resonator becomes maximum at the position of the dielectric member 22 with respect to the third harmonic wave in which the length of the inner conductors 2a to 4a becomes about 3/4 wavelength. The resonance frequency is lowered by the action of the electrostatic capacitance which becomes large at.

The strip line filter according to the tenth aspect of the present invention is a rod-shaped or plate-shaped dielectric on the inner conductors 2a-4a at a position approximately ⅔ of the length of the inner conductors 2a-4a from the short-circuited portions 13a-15a. Since 23 is provided so as to be in close contact with the inner conductors 2a to 4a, the capacitance becomes large at the position of the dielectric 23. At this time, the inner conductors 2a-4
Since the electric field in the resonator is large at the position of the dielectric 23 with respect to the fundamental wave having the length a of about 1/4 wavelength, the resonance frequency is lowered by the action of the capacitance generated in the dielectric 23. , The length of the inner conductors 2a to 4a becomes about 3/4 wavelength 3
Since the electric field in the resonator becomes almost 0 at the position of the dielectric 23 for the double harmonic, the influence of the dielectric 23 disappears and the resonance frequency does not change.

[0028]

1 is a schematic structural view showing an embodiment of a strip line filter according to the first invention, and FIG. 2 is a sectional view of the embodiment of FIG. In the figure, 1a and 1b are two dielectric substrates facing each other, and 2a to 4a are inner conductors formed by adhering a conductor film to the inner surface of the dielectric substrate 1a and being substantially parallel to each other. An inner conductor 5a formed by closely adhering a conductor film to the inner surface of the dielectric substrate 1b and formed substantially parallel to each other is an outer conductor 5a formed by closely adhering a conductor film to the entire outer surface of the dielectric substrate 1a, and 5b is a dielectric material. Outer conductors formed by closely adhering a conductor film to the entire outer surface of the substrate 1b, 6 to 8 being dielectric substrates 1a and 1b
And inner conductors 2a to 4a, inner conductors 2b to 4b, and outer conductor 5
Tri-plate line resonators 10a and 10b are input / output lines in which the inner conductors are directly connected to the inner conductors 2a, 2b, 4a, 4b, and 12a is a dielectric substrate 1a.
Groove formed by digging the surface of the dielectric substrate 1b in close contact with the inner conductors 2a to 4a. Reference numeral 12b represents the surface of the dielectric substrate 1b in contact with the outer conductor 5b of the inner conductors 2b to 4b.
Grooves provided by being dug in a direction orthogonal to
5a and 13b to 15b are short-circuited portions. Dielectric substrate 1a
And 1b are overlapped so that the inner conductors 2a and 2b, the inner conductors 3a and 3b, and the inner conductors 4a and 4b face and overlap with each other, and are bonded so that the facing inner conductors are in electrical contact with each other. .. The inner conductors 2a to 4a and 2b to 4b are formed of a thin film or a thick film and are shaped by photo etching or the like. In the present embodiment, the length of each of the inner conductors 2a to 4a is set to about 1/4 wavelength of a desired fundamental wave, and one end of each of the inner conductors 2a to 4a and 2b to 4b is a dielectric substrate 1a. Short-circuit portions 13a to 15a and short-circuit portions 13b to 15b on the side surface of 1b are connected to the outer conductors 5a and 5b and short-circuited. Therefore, the resonators 6 to 8 are quarter-wave resonators in which one end is short-circuited and the other end is open. The groove 12a
And the groove 12b are short-circuited portions 13a to 15a, short-circuited portion 13b.
˜15b to the inner conductors 2a to 4a and the inner conductors 2b to 4b in the longitudinal direction at a position of about ⅓ of the inner conductor length. The outer conductor 5 in which the surfaces of the grooves 12a and 12b are extended
It is closely adhered and covered by a and 5b (first invention).
1 and 2, the dielectric substrate 1a has a dielectric substrate 1b whose longitudinal direction is the inner conductors 2a to 4a, as in the conventional case.
The longer end is set and the dielectric substrate 1a and the dielectric substrate 1b are arranged so that the short-circuited ends of the resonators 6 to 8 are aligned to expose the open ends of the inner conductors 2a to 4a. Take as an example.

The operation is as follows. Since the lengths of the resonators 6 to 8 are shortened to less than 1/4 wavelength due to the effect of the grooves 12a and 12b, the electric field coupling between adjacent ones is weakened, and the resonators 6 to 8 are mainly coupled to each other by a magnetic field as in the conventional case. ing. The amount of coupling is adjusted by the depth of the grooves 12a and 12b and the distance between adjacent inner conductors.

Now, by trimming the exposed portions of the inner conductors 2a to 4a on the open end side and adjusting the lengths of these inner conductors, all the resonators 6 to 8 resonate at the same frequency, for example, f0. At that frequency f0, the resonators 6 to 8 in the resonance state are strongly coupled to each other, the incident wave to the input / output line 10 is guided to the resonator 6, and the resonator 7, It is output from the input / output line 11 through the signal line 8. However, at frequencies other than f0, the mutual coupling of the resonators 6 to 8 is very weak, and most of the power of the incident wave to the input / output line 10 or 11 is reflected. Thus, the stripline filter shown in FIG. 1 has a function as a bandpass filter.

Resonator 6 of the stripline filter of FIG.
~ 8 operates as a quarter-wave resonator with respect to the fundamental wave,
The potential of the fundamental wave in the longitudinal section of the resonator has the distribution shown by the solid line in FIG. Also, it operates as a 3/4 wavelength resonator for the triple harmonic having a frequency three times that of the fundamental wave, and the potential of the triple harmonic in the longitudinal section of the resonator is as shown by the broken line in FIG. To be distributed. On the other hand, at the intersecting positions of the grooves 12a and 12b and the inner conductors 2a to 4b and the inner conductors 2b to 4b,
Since the distance between the inner conductor and the outer conductor 5a and the outer conductor 5b is locally narrowed and a corner is formed, the electric field is concentrated and the capacitance is increased. The grooves 12a, 12b are connected to the inner conductors 2a through the short-circuited portions 13a through 15a, 13b through 15b.
4a, the inner conductors 2a to 4a in the longitudinal direction of the inner conductors 2b to 4b.
When it is installed at a position of about 1/3 of the length, the resonance frequency of the resonator hardly changes with respect to the fundamental wave whose potential is originally low at this position, but it becomes a triple harmonic wave where the potential becomes maximum at this position. On the other hand, the groove increases the capacitance and lowers the resonance frequency. Therefore, the pass characteristic of the strip line filter of FIG. 1 is as shown in FIG. That is, assuming that the frequency of the fundamental wave is the first pass frequency f0, the second pass frequency shifts to a position lower than 3f0. Therefore, the strip line filter of FIG. 1 has a function of blocking the third harmonic of the fundamental wave.

FIG. 5 is a schematic diagram showing an embodiment of the stripline filter according to the second invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, instead of the groove 12a and the groove 12b of FIG. 1, the short conductors 13a to 15a and the short conductors 13b to 15b are connected to the inner conductor 2.
This is a case where the grooves 16a and 16b are provided in the longitudinal direction of the a to 4a and the inner conductors 2b to 4b at positions of about ⅔ of these inner conductor lengths (second invention). As can be seen from FIG. 6, the potential of the fundamental wave is relatively high at this position, while the potential of the triple harmonic wave is almost zero. Therefore, the resonance frequency of the fundamental wave shifts to the lower side, and the resonance frequency of the triple harmonic does not change. At this time, the pass characteristic of the strip line filter of FIG. 5 is as shown in FIG. That is, if the frequency of the shifted fundamental wave is newly set as the first pass frequency f0, the second pass frequency shifts to a higher position than 3f0. Therefore, the strip line filter of FIG. 5 has the function of blocking the triple harmonic of the frequency three times the fundamental wave, as in the case of FIG.

The embodiment of FIG. 5 has the same operating principle and advantages as those of FIG. 1, and can shift the second pass frequency to the higher side of the frequency three times the fundamental wave, thereby widening the stop band width. It has the advantage that it can be taken.

FIG. 8 is a schematic structural view showing an embodiment of the strip line filter according to the third invention, and FIG. 9 is an inner conductor pattern diagram of the embodiment of FIG. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the short conductors 13a to 15a and the short conductors 13b to 15b are connected to the inner conductor 2.
a to 4a, inner conductors 2a to 4b in the longitudinal direction of the inner conductors 2a to 4b.
Instead of providing the groove 12a and the groove 12b at the position of about 1/3 of the length of the 4a, the protrusion 17a and the protrusion 17 of the inner conductor are provided.
This is the case where b is provided (third invention). Protrusion 17a,
The protruding portion 17b is formed by extending the inner conductors 2a to 4a and the inner conductors 2b to 4b in the width direction. Protrusions 17a, 17
Since the inner conductor width locally widens at the position where b is provided, the capacitance between the outer conductor 5a and the outer conductor 5b increases.
Therefore, as in the case of FIG. 1 in which the groove 12a and the groove 12b are provided, the resonance frequency of the resonator hardly changes with respect to the fundamental wave having a low electric potential at this position, but the electric potential becomes maximum at this position. For the third harmonic wave, the capacitance increases due to the groove, and the resonance frequency shifts to the lower side.

The embodiment shown in FIG. 8 has the same operating principle and advantages as those shown in FIG. 1, and does not require the processing of the grooves 12a and 12b in which the dielectric substrates 1a and 1b are dug.
The protrusions 17a and 17b are connected to the inner conductors 2a to 4a and the inner conductor 2b.
Since it can be formed by photo-etching similarly to 4b, it has an advantage of easy processing.

FIG. 10 is a schematic block diagram showing an embodiment of the strip line filter according to the fourth invention. In the figure,
The same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted.
In this embodiment, the short-circuit parts 13a to 15a and the short-circuit parts 13b to 15 are used.
b to the inner conductors 2a to 4a and the inner conductors 2b to 4b at the positions of about 2/3 of the length of the inner conductors 2a to 4a in the longitudinal direction, the protrusions 18a and the protrusions of the inner conductor are provided instead of the grooves 16a and 16b. This is the case where 18b is provided (fourth invention).
The protrusions 18a and 18b are formed by extending the inner conductors 2a to 4a and the inner conductors 2b to 4b in the width direction. Since the inner conductor width locally expands at the positions where the protrusions 18a and 18b are provided, the capacitance between the outer conductors 5a and the outer conductors 5b increases. Therefore, as in the embodiment of FIG. 5, the potential of the fundamental wave is relatively high at the positions of the protrusions 18a and 18b, while the potential of the third harmonic is almost 0, so that The resonance frequency shifts to the lower side, 3
The resonance frequency of the double harmonic does not change.

The embodiment shown in FIG. 10 has the same operating principle and advantages as those shown in FIG. 5, and does not require the processing of the grooves 16a and 16b in which the dielectric substrates 1a and 1b are dug, and the protrusions are not necessary. Since the inner conductors 18a and 18b can be formed by photoetching similarly to the inner conductors 2a to 4a and the inner conductors 2b to 4b, there is an advantage that processing becomes easy.

FIG. 11 is a schematic diagram showing an embodiment of the stripline filter according to the fifth invention. In the figure,
The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.
In this embodiment, the resonators 6 to 8 of the microplate line are used instead of the resonators 6 to 8 of the triplate line in the embodiment of FIG. 1, and the dielectric substrate 1a and the dielectric material are used. The outer conductor 5a formed on one surface of the substrate 1a and the other surface of the dielectric substrate are formed substantially parallel to each other, and one ends thereof are connected to the outer conductor 5a to form short-circuited portions 13a to 15a. A plurality of inner conductors 2a
4a, and the inner conductor 2a is located on the surface of the dielectric substrate 1a on which the outer conductor 5a is formed, at a position approximately 1/3 of the length of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a. This is a case where the groove 12a is provided in a direction intersecting with the grooves 4a to 4a, and a conductor continuous with the outer conductor 5a is adhered to the surface of the groove 12a (fifth invention).

The embodiment shown in FIG. 11 has the same operating principle and advantages as those shown in FIG. 1, and since the inner conductors 2a to 4a and the inner conductors of the input / output lines 10 and 11 are all exposed, the embodiment shown in FIG. Output coupling amount, inter-resonator coupling amount, and resonator 1
It has an advantage that the resonance frequencies of 9 to 21 can be easily adjusted.

FIG. 12 is a schematic configuration diagram showing an embodiment of a strip line filter according to the sixth invention. In the figure,
The same parts as those in FIGS. 5 and 11 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, resonators 19 to 21 of microstrip lines are used instead of the resonators 6 to 8 of the triplate line in the embodiment of FIG. 5, and the outer conductor 5a of the dielectric substrate 1a is used. From the short-circuited portions 13a to 15a of the surface on which the inner conductor 2a to
This is a case where a groove 16a in a direction intersecting with the inner conductors 2a to 4a is provided at a position of about ⅔ of the length of 4a, and a conductor continuous with the outer conductor 5a is adhered to the surface of the groove 16a (sixth). Invention).

The embodiment of FIG. 12 has the same operating principle and advantages as those of FIG. 5, and since all the inner conductors 2a to 4a and the inner conductors of the input / output lines 10 and 11 are exposed, the embodiment shown in FIG. Output coupling amount, inter-resonator coupling amount, and resonator 1
It has an advantage that the resonance frequencies of 9 to 21 can be easily adjusted.

FIG. 13 is a schematic block diagram showing an embodiment of the strip line filter according to the seventh invention. In the figure,
The same parts as those in FIGS. 8 and 11 are designated by the same reference numerals and the description thereof will be omitted. This embodiment is configured by using resonators 19 to 21 of microstrip lines instead of the resonators 6 to 8 of the triplate line in the embodiment of FIG. 8, and from the short-circuited portions 13a to 15a of the inner conductor, Inner conductor 2a-
This is a case where the protrusion 17a obtained by extending the inner conductors 2a to 4a in the width direction is provided at a position of about ⅓ of the length of 4a (seventh invention).

The embodiment shown in FIG. 13 has the same operating principle and advantages as those shown in FIG. 8, and the inner conductors 2a to 4a, the protrusion 17a, and the inner conductors of the input / output lines 10 and 11 are all exposed. Therefore, the input / output coupling amount, the coupling amount between resonators,
This has an advantage that the resonance frequency of the resonators 19 to 21 and the position of the protrusion 17a can be easily adjusted.

FIG. 14 is a schematic diagram showing an embodiment of the strip line filter according to the eighth invention. In the figure,
The same parts as those in FIGS. 10 and 11 are designated by the same reference numerals and the description thereof will be omitted. This embodiment is constructed by using resonators 19 to 21 of microstrip line in place of the resonators 6 to 8 of triplate line in the embodiment of FIG.
The inner conductor 2a is located at a position approximately ⅔ of the length of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a of the inner conductors 2a to 4a.
This is the case where the protrusion 18a is formed by extending the widths 4a to 4a (eighth invention).

The embodiment of FIG. 14 has the same operating principle and advantages as those of FIG. 10, and in addition, the inner conductors 2a to 4a, the protruding portion 18a, and the inner conductors of the input / output lines 10 and 11 are all exposed. Therefore, the input / output coupling amount, the inter-resonator coupling amount, the resonance frequencies of the resonators 19 to 21, and the protruding portion 18
This has the advantage that the position of a can be easily adjusted.

FIG. 15 is a schematic block diagram showing an embodiment of the strip line filter according to the ninth invention. In the figure,
The same parts as those in FIG. 11 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, about 1 / the length of the inner conductors 2a to 4a in the longitudinal direction of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a in FIG.
This is a case where a rod-shaped dielectric 22 as a rod-shaped or plate-shaped dielectric is provided instead of providing the groove 12a at the position of 3.
The rod-shaped dielectric 22 is formed in a direction orthogonal to the inner conductors 2a to 4a,
It is fixed with an adhesive or the like so as to be in close contact with the inner conductors 2a to 4a (the ninth invention). Rod-shaped dielectric 22 and inner conductor 2
At the position where a to 4a intersect, the capacitance increases due to the effect of the rod-shaped dielectric. Therefore, as in the case of the embodiment of FIG. 11, the resonance frequency of the resonator hardly changes with respect to the fundamental wave having a low electric potential at this position, but for the third harmonic wave having the maximum electric potential at this position. For rod-shaped dielectric 2
By 2, the capacitance increases and the resonance frequency shifts to the lower side.

The embodiment shown in FIG. 15 has the same operating principle and advantages as those shown in FIG. 11, and in addition, the second pass frequency of the filter is tripled by changing the position and permittivity of the rod-shaped dielectric 22. This has the advantage that the amount of shift from the harmonic frequency can be easily adjusted.

FIG. 16 is a schematic diagram showing an embodiment of the strip line filter according to the tenth invention. In the figure, the same parts as those in FIG. 12 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the length of the inner conductors 2a to 4a is about 2 in the longitudinal direction of the inner conductors 2a to 4a from the short-circuited portions 13a to 15a in FIG.
This is a case where the rod-shaped dielectric 23 as a rod-shaped or plate-shaped dielectric is provided instead of providing the groove 16a at the position of / 3. The rod-shaped dielectric 23 is fixed by an adhesive or the like so as to be in close contact with the inner conductors 2a to 4a in a direction orthogonal to the inner conductors 2a to 4a (the tenth invention). At the position where the rod-shaped dielectric 23 intersects with the inner conductors 2a to 4a, the capacitance increases due to the effect of the rod-shaped dielectric 23. Therefore, as in the case of the embodiment of FIG. 12, the potential of the rod-shaped dielectric 2 is different from that of the fundamental wave.
Since the resonance frequency is relatively high at the position of 3, the resonance frequency shifts to the lower side, but the resonance frequency does not change because the potential becomes almost 0 for the triple harmonic.

The embodiment of FIG. 16 has the same operating principle and advantages as those of FIG. 12, and the position and dielectric constant of the rod-shaped dielectric 23 are changed to triple the second pass frequency of the filter. This has the advantage that the amount of shift from the harmonic frequency can be easily adjusted.

In each of the above embodiments, the case where the number of resonators is 3 has been described. However, the number of resonators may be 2 or 4 or more, and the same advantages and effects as the above embodiments can be obtained.

In each of the above embodiments, the resonator is 1 /
The case of using a 4-wavelength resonator has been described, but it is an n / 4 wavelength (n is an odd number of 3 or more) resonator or an m / 2 wavelength (m
May be an integer greater than or equal to 1) resonator, and the same advantages and effects as those of the above-described embodiment can be obtained.

[0052]

According to the first aspect of the present invention, at least one outer surface of the dielectric substrate on which the outer conductor is formed intersects with the inner conductor at a position approximately 1/3 of the inner conductor length from the short circuit portion. Since a groove continuous with the outer conductor is adhered to the surface of the groove, the effect of the groove on the fundamental wave is small and the resonance frequency of the resonator does not change, but for the third harmonic wave. As a result, the resonance frequency becomes low due to the effect of the groove.
Therefore, the resonance frequency of the fundamental wave is the first pass frequency, 3
The frequency lower than the resonance frequency of the double harmonic becomes the second pass frequency, and the strip line filter having the pass characteristic of blocking the triple harmonic can be obtained.

According to the second aspect of the invention, a direction of intersecting the inner conductor at a position of about ⅔ of the inner conductor length from the short-circuited portion on the outer surface of at least one outer conductor of the dielectric substrate. Since the groove is provided and the conductor that is continuous with the outer conductor is adhered to the surface of the groove, the resonance frequency of the resonator is lowered for the fundamental wave due to the effect of the groove, but for the triple harmonic wave. As a result, the groove has almost no effect and the resonance frequency does not change. Therefore, the resonance frequency of the fundamental wave is higher than the resonance frequency of the first pass frequency and the triple harmonic wave, and the second pass frequency becomes the second pass frequency. Thus, the strip line filter having the pass characteristic of blocking the triple harmonic wave can be obtained. There is an effect.

According to the third aspect of the invention, since the protrusion extending from the short-circuited portion of the inner conductor to the width of the inner conductor is provided at a position about 1/3 of the inner conductor length, the protrusion for the fundamental wave is provided. The resonance frequency of the resonator does not change,
The resonance frequency becomes lower for the third harmonic due to the effect of the protrusion. Therefore, the resonance frequency of the fundamental wave is the first pass frequency, and the frequency lower than the resonance frequency of the triple harmonic is the second pass frequency, and the strip line filter having the pass characteristic of blocking the triple harmonic is obtained. There is an effect.

According to the fourth aspect of the invention, since the protrusion extending from the short-circuited portion of the inner conductor to the width of the inner conductor is provided at a position about ⅔ of the length of the inner conductor, the fundamental wave is Causes the resonance frequency of the resonator to decrease due to the effect of the above-mentioned protrusion,
There is almost no influence of the protrusion on the harmonics, and the resonance frequency does not change. For this reason, the resonance frequency of the fundamental wave is higher than the frequency of the first pass frequency and the triple harmonic wave, and the frequency is the second pass frequency. Thus, it is possible to obtain a strip line filter having a pass characteristic of blocking the triple harmonic wave. effective.

According to the fifth aspect of the invention, the inner conductor length is about 1 from the short-circuited portion of the surface of the dielectric substrate on which the outer conductor is formed.
Since a groove intersecting the inner conductor is provided at the position of / 3, and a conductor continuous with the outer conductor is adhered to the surface of the groove, the influence of the groove on the fundamental wave is small and the resonance frequency of the resonator changes. However, the resonance frequency becomes lower for the third harmonic due to the effect of the groove. Therefore, the resonance frequency of the fundamental wave is the first pass frequency, and the frequency lower than the resonance frequency of the triple harmonic is the second pass frequency, and the strip line filter having the pass characteristic of blocking the triple harmonic is obtained. There is an effect.

According to the sixth invention, a groove in a direction intersecting with the inner conductor at a position of about 2/3 of the inner conductor length from the short-circuited portion on the surface of the dielectric substrate on which the outer conductor is formed. Is provided
Moreover, a conductor continuous with the outer conductor was adhered to the surface of the groove. The resonance frequency of the resonator is lowered with respect to the fundamental wave due to the effect of the groove, but the groove has little effect on the triple harmonic and the resonance frequency does not change. For this reason, the resonance frequency of the fundamental wave is higher than the frequency of the first pass frequency and the triple harmonic wave, and the frequency is the second pass frequency. Thus, it is possible to obtain a strip line filter having a pass characteristic of blocking the triple harmonic wave. effective.

According to the seventh aspect of the present invention, since the protruding portion extending in the width direction of the inner conductor is provided at a position approximately 1/3 of the inner conductor length from the short-circuited portion of the inner conductor, the protrusion for the fundamental wave is provided. The resonance frequency of the resonator does not change,
The resonance frequency becomes lower for the third harmonic due to the effect of the protrusion. Therefore, the resonance frequency of the fundamental wave is the first pass frequency, and the frequency lower than the resonance frequency of the triple harmonic is the second pass frequency, and the strip line filter having the pass characteristic of blocking the triple harmonic is obtained. There is an effect.

According to the eighth aspect of the invention, since the protrusion extending in the width direction of the inner conductor is provided at a position about ⅔ of the inner conductor length from the short-circuited portion of the inner conductor, Causes the resonance frequency of the resonator to decrease due to the effect of the above-mentioned protrusions.
There is almost no influence of the above-mentioned protrusion on the harmonics, and the resonance frequency does not change. Therefore, the resonance frequency of the fundamental wave is higher than the resonance frequency of the first pass frequency and the triple harmonic wave, and the second pass frequency becomes the second pass frequency. Thus, the strip line filter having the pass characteristic of blocking the triple harmonic wave can be obtained. There is an effect.

According to the ninth aspect of the invention, a rod-shaped or plate-shaped dielectric is adhered in a direction intersecting the inner conductor on the inner conductor at a position of about 1/3 of the inner conductor length from the short-circuited portion. Since it is provided, the influence of the rod-shaped dielectric on the fundamental wave is small and the resonance frequency of the resonator does not change, but the resonance frequency is lowered for the triple harmonic due to the effect of the rod-shaped dielectric.
Therefore, the resonance frequency of the fundamental wave is the first pass frequency, 3
The frequency lower than the resonance frequency of the double harmonic becomes the second pass frequency, and the strip line filter having the pass characteristic of blocking the triple harmonic can be obtained.

According to the tenth aspect of the present invention, a rod-shaped or plate-shaped dielectric is adhered to the inner conductor at a position approximately ⅔ of the inner conductor length from the short-circuited portion in a direction intersecting with the inner conductor. Since the resonance frequency of the resonator is lowered with respect to the fundamental wave due to the effect of the protrusion, the protrusion has almost no influence on the triple harmonic, and the resonance frequency does not change. Therefore, the frequency of the fundamental wave is the first pass frequency, 3
The frequency higher than the resonance frequency of the double harmonic becomes the second pass frequency, and the strip line filter having the pass characteristic of blocking the triple harmonic can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a first invention.

2 is a cross-sectional view of the embodiment of FIG.

FIG. 3 is a diagram for explaining a potential distribution in a vertical cross section of the resonator of the embodiment of FIG.

FIG. 4 is a diagram showing a pass characteristic of the embodiment of FIG.

FIG. 5 is a schematic configuration diagram showing an embodiment of the second invention.

FIG. 6 is a diagram for explaining a potential distribution in a vertical cross section of the resonator of the embodiment of FIG.

FIG. 7 is a diagram showing a pass characteristic of the embodiment of FIG.

FIG. 8 is a schematic configuration diagram showing an embodiment of the third invention.

9 is a diagram showing an example of an inner conductor pattern of the embodiment of FIG.

FIG. 10 is a schematic configuration diagram showing an embodiment of the fourth invention.

FIG. 11 is a schematic configuration diagram showing an embodiment of the fifth invention.

FIG. 12 is a schematic configuration diagram showing an embodiment of the sixth invention.

FIG. 13 is a schematic configuration diagram showing an embodiment of the seventh invention.

FIG. 14 is a schematic configuration diagram showing an embodiment of the eighth invention.

FIG. 15 is a schematic configuration diagram showing an embodiment of the ninth invention.

FIG. 16 is a schematic configuration diagram showing an embodiment of the tenth invention.

FIG. 17 is a schematic configuration diagram showing an example of a conventional stripline filter.

FIG. 18 is a diagram showing a pass characteristic of a conventional stripline filter.

[Explanation of symbols]

 1a, 1b Dielectric substrate 2a-4a, 2b-4b Inner conductor 5a, 5b Outer conductor 6-8 Triplate line resonator 9a, 9b Vertical groove 10,11 Input / output line 12a, 12b Groove 13a-15a, 13b- 15b Short-circuit part 16a, 16b Groove 17a, 17b Projection part 18a, 18b Projection part 19-21 Microstrip line resonator 22 Rod-shaped dielectric 23 Rod-shaped dielectric

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Yamada 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation

Claims (10)

[Claims] 1. Two dielectric substrates facing each other, an outer conductor formed on the outer surface of each of the two dielectric substrates, and an inner surface of at least one of the dielectric substrates. In a stripline filter having a plurality of inner conductors which are formed substantially parallel to each other and one end of which is connected to the outer conductor to form a short circuit portion, a stripline filter including at least the outer conductor of the dielectric substrate is formed. A groove in a direction intersecting with the inner conductor is provided on the outer surface at a position approximately 1/3 of the inner conductor length from the short-circuited portion, and a conductor continuous with the outer conductor is closely adhered to the surface of the groove. Stripline filter. 2. Two dielectric substrates facing each other, an outer conductor formed on the outer surface of each of the two dielectric substrates, and an inner conductor of at least one of the dielectric substrates. In a stripline filter having a plurality of inner conductors which are formed substantially parallel to each other and one end of which is connected to the outer conductor to form a short circuit portion, a stripline filter including at least the outer conductor of the dielectric substrate is formed. A groove in a direction intersecting with the inner conductor is provided on the outer surface at a position approximately ⅔ of the inner conductor length from the short-circuited portion, and a conductor continuous with the outer conductor is adhered to the surface of the groove. Stripline filter. 3. Two dielectric substrates facing each other, an outer conductor formed on the outer surface of each of the two dielectric substrates, and an inner conductor of at least one of the dielectric substrates mutually. In a stripline filter including a plurality of inner conductors which are formed substantially parallel to each other and one end of which is connected to the outer conductor to form a short-circuited portion, a stripline filter having a length of about 1/3 of a length of the inner conductor from the short-circuited portion of the inner conductor is provided. A stripline filter comprising a protrusion formed by extending the inner conductor in the width direction at a position. 4. Two dielectric substrates facing each other, outer conductors formed on the outer surfaces of each of the two dielectric substrates, and inner surfaces of at least one of the dielectric substrates mutually. In a stripline filter including a plurality of inner conductors that are formed substantially in parallel and one end of which is connected to the outer conductor to form a short-circuited portion, a stripline filter having a length of about 2/3 of the inner conductor length from the short-circuited portion of the inner conductor is provided. A stripline filter comprising a protrusion formed by extending the inner conductor in the width direction at a position. 5. A dielectric substrate, an outer conductor formed on one surface of the dielectric substrate, and an outer conductor formed on the other surface of the dielectric substrate substantially parallel to each other, and one end of which is connected to the outer conductor. In a stripline filter including a plurality of inner conductors formed to form a short circuit portion, about 1/3 of a length of the inner conductor from the short circuit portion on a surface of the dielectric substrate on which the outer conductor is formed. A strip line filter characterized in that a groove extending in a direction intersecting with the inner conductor is provided at the position, and a conductor continuous with the outer conductor is adhered to the surface of the groove. 6. A dielectric substrate, an outer conductor formed on one surface of the dielectric substrate, and an outer conductor formed on the other surface of the dielectric substrate substantially parallel to each other, and one end of which is connected to the outer conductor. In a stripline filter including a plurality of inner conductors formed to form a short circuit portion, about 2/3 of the inner conductor length from the short circuit portion on the surface of the dielectric substrate on which the outer conductor is formed. A strip line filter characterized in that a groove extending in a direction intersecting with the inner conductor is provided at the position, and a conductor continuous with the outer conductor is adhered to the surface of the groove. 7. A dielectric substrate, an outer conductor formed on one surface of the dielectric substrate, and an outer conductor formed on the other surface of the dielectric substrate substantially parallel to each other, and one end of which is connected to the outer conductor. A strip line filter having a plurality of inner conductors formed to form a short-circuited portion, a protrusion formed by extending the inner conductor in the width direction from the short-circuited portion of the inner conductor to a position of about 1/3 of the inner conductor length. A stripline filter characterized by being provided. 8. A dielectric substrate, an outer conductor formed on one surface of the dielectric substrate, and an outer conductor formed on the other surface of the dielectric substrate substantially parallel to each other, and one end of which is connected to the outer conductor. And a plurality of inner conductors that form a short-circuited portion, the protrusion being formed by extending the inner conductor in the width direction from the short-circuited portion of the inner conductor to a position of about ⅔ of the inner conductor length. A stripline filter characterized by being provided. 9. A dielectric substrate, an outer conductor formed on one surface of the dielectric substrate, and an outer conductor formed on the other surface of the dielectric substrate substantially parallel to each other, and one end of which is connected to the outer conductor. In the strip line filter including a plurality of inner conductors that form a short-circuited portion, a rod-shaped or plate-shaped dielectric is provided on the inner conductor at a position approximately 1/3 of the inner conductor length from the short-circuited portion. A strip line filter provided in close contact with a direction intersecting with the inner conductor. 10. A dielectric substrate, an outer conductor formed on one surface of the dielectric substrate, and an outer conductor formed on the other surface of the dielectric substrate substantially parallel to each other, and one end of which is connected to the outer conductor. In a stripline filter including a plurality of inner conductors that form a short-circuited portion, a rod-shaped or plate-shaped dielectric is provided on the inner conductor at a position approximately ⅔ of the inner conductor length from the short-circuited portion. A strip line filter provided in close contact with a direction intersecting with the inner conductor.