JPH0551201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a stripline filter used, for example, as a bandpass filter.

(b) Conventional technology Conventionally, as a stripline filter,
A device in which an interdigital type or combline type resonant electrode is provided on a rectangular flat dielectric plate is known. Such conventional flat stripline filters have the disadvantage that when the number of resonant electrodes is large, the external dimensions of the entire filter become large and the area required for installation increases. A stripline filter as shown in the perspective view of the figure has been proposed.

The stripline filter shown in FIG. 3 constitutes a five-stage interdigital type filter. In FIG. 3, reference numeral 1 denotes a dielectric substrate, which is made of cylindrical dielectric ceramic. A ground electrode 2 is formed on the entire inner circumferential surface of the dielectric base 1, and a ground electrode 2 is formed on the entire inner peripheral surface of the dielectric base 1.
Extending portions 2a and 2b of a predetermined width are drawn out.
These extensions 2a and 2b are connected by an extension electrode 3 of a predetermined width formed on the outer peripheral surface of the dielectric base 1 along the axial direction. From one side of the extending electrode 3, three resonant electrodes 4, 5,
6 are pulled out in parallel at predetermined intervals.
Note that terminal electrodes 9 and 10 as input electrodes or output electrodes extend from the resonance electrodes 4 and 6 arranged on both sides, respectively. Further, from the other side of the extending electrode 3, two resonant electrodes 7 and 8 are drawn out in parallel in the opposite direction to the resonant electrodes 4, 5, and 6, and between the resonant electrodes 4, 5, and 6. It is located in

(c) Problems to be Solved by the Invention In a bandpass filter using such a stripline filter, the outer circumferential surface of the cylindrical dielectric substrate is Since the extended electrode 3 formed on the inner peripheral surface is connected to the ground electrode 2 formed on the inner circumferential surface, there was a problem in that current was concentrated on the extended parts 2a and 2b, resulting in a decrease in Q.

This invention solves these conventional problems,
The purpose of the present invention is to provide a stripline filter with reduced external dimensions and improved electrical characteristics.

(d) Means for solving the problem The present invention includes a cylindrical dielectric substrate, and a ground electrode is formed on either the inner peripheral surface or the outer peripheral surface of the cylindrical dielectric substrate, and a stripline filter in which a combline type or interdigital type resonant electrode having a shorted end and an open end is formed on the other surface of the cylindrical dielectric substrate, the shorted end of the resonant electrode and the ground. The present invention is characterized in that a conductor electrically connected to the electrode is provided in a rectangular cross section formed by cutting the cylindrical dielectric substrate from one point on one end surface to the other end surface in the axial direction.

(e) Effect With the above configuration, the conductor provided in the rectangular cross section formed by cutting the cylindrical dielectric substrate from one point on one end surface to the other end surface in the axial direction is A ground electrode provided on the inner peripheral surface or outer peripheral surface of the dielectric substrate and a short-circuited end of a resonant electrode provided on the other surface are electrically connected. Since this connection is made entirely along the axial direction between the outer and inner circumferential surfaces of the cylindrical dielectric substrate, the current is dispersed.
Q improves.

(f) Embodiment FIG. 1 is a perspective view showing the structure of a five-stage combline type stripline filter according to a first embodiment of the present invention. In this figure, reference numeral 1 denotes a cylindrical dielectric substrate, which is made of cylindrical dielectric ceramic. A ground electrode 2 is formed on the entire inner circumferential surface of this cylindrical dielectric substrate 1 . As shown in the figure, the cylindrical dielectric substrate 1 has a notch A formed by cutting it axially from one point on one cross section to the other end surface, and a rectangular cross section on one side of the notch A is grounded. Conductor 2c continuous with electrode 2
is formed. Five resonant electrodes 4, 5, 6, 7, and 8 are formed on the outer circumferential surface of the cylindrical dielectric substrate 1, and each short-circuited end is connected to the conductor 2c,
It is formed in a comline shape. Note that terminal electrodes 9 and 10 as input electrodes or output electrodes extend from the resonance electrodes 4 and 8, respectively.

FIG. 2 is a perspective view showing the structure of a five-stage combline type stripline filter according to a second embodiment of the present invention. In this example, a ground electrode 2 is formed on the outer peripheral surface of the cylindrical dielectric substrate 1, and five resonant electrodes 4, 5, 6, 7, . . . are formed on the inner peripheral surface thereof. When the ground electrode 2 is formed on the entire outer peripheral surface of the cylindrical dielectric substrate 1 as in this embodiment, the entire filter is shielded by the ground electrode 2, and internal and external electromagnetic waves are blocked by the ground electrode. be done.

In the first and second embodiments, a notch is provided along the axial direction between the outer peripheral surface and the inner peripheral surface of the cylindrical dielectric substrate, and a conductor is formed in the cross section of the notch. Although this was an example, it is not necessary to provide a gap as a notch, and the cylindrical dielectric base may be closed at the part where the conductor is formed. It is sufficient that the conductor is disposed in a rectangular cross section formed by cutting from the point to the other end face in the axial direction. Further, although the embodiment uses a cylindrical dielectric substrate, a rectangular cylindrical dielectric substrate may also be used. Furthermore, although all of the embodiments are 5-stage combline type stripline filters, filters having a number of stages other than 5 can be constructed in the same manner, and are not limited to the combline type, but other types such as interdigital type etc. It can also be applied to other types of stripline filters.

(g) Effects of the Invention As described above, according to the present invention, a conductor is provided in a rectangular cross section formed by cutting a cylindrical dielectric substrate from one point on one end surface to the other end surface in the axial direction,
Since the short-circuited end of the resonant electrode and the ground electrode are electrically connected by this conductor, the current is dispersed over the entire surface of the conductor, and the Q of the filter can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a stripline filter according to a first embodiment of the invention, FIG. 2 is a perspective view showing the structure of a stripline filter according to a second embodiment of the invention, FIG. 3 is a perspective view showing the structure of a conventional stripline filter. 1... Dielectric base, 2... Ground electrode, 2c...
Conductor, 4-8...resonant electrode.

Claims (1)

[Scope of Claims] 1. A cylindrical dielectric substrate 1 is provided, and a ground electrode 2 is formed on either the inner circumferential surface or the outer circumferential surface of the cylindrical dielectric substrate 1, and A stripline filter in which a combline type or interdigital type resonant electrode 4, 5, 6, 7, 8 having a short-circuited end and an open end is formed on the other surface of the body base 1, the resonant electrode 4 , 5, 6, 7, and 8 and the ground electrode 2, the conductor 2c is cut in the axial direction from one end face of the cylindrical dielectric base 1 to the other end face. A stripline filter characterized by having a rectangular cross section.