Wave transmission lines and networks – Resonators – Dielectric type
Reexamination Certificate
2000-04-17
2001-08-21
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Resonators
Dielectric type
C333S202000, C333S235000
Reexamination Certificate
active
06278344
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiple-mode dielectric resonator having a combined dielectric block provided in a cavity, and to a method of adjusting a characteristic of the resonator.
2. Description of the Related Art
FIG. 23
shows the structure of a conventional dielectric resonator using a transverse magnetic (TM) dual mode. In other figures referred to below, a finely dotted area represents a portion on which a conductor is formed.
This dielectric resonator has, as shown in
FIG. 23
, a cavity body
1
which functions as a waveguide, and a combined dielectric block
2
which is formed of two dielectric elements
2
a
and
2
b
combined into a crossed shape, and which is formed integrally with the cavity body
1
and while being positioned inside with the same. The cavity body
1
and the combined dielectric block
2
are made of a dielectric ceramic. A conductor
3
such as Ag is formed on outer peripheral surfaces of the cavity body
1
. Conductor plates (not shown) or portions of a metallic case for accommodating this dielectric resonator are attached to two opening end surfaces around two openings of the cavity body
1
.
The dielectric resonator shown in
FIG. 23
, having two dielectric elements
2
a
and
2
b
each resonating in a TM110 mode, functions as a TM dual mode dielectric resonator. One unit of the above-described conventional TM dual mode dielectric resonator, however, can only be used as two independent resonators or as two-stage resonator having two resonators coupled to each other. As three resonators forming one dielectric resonator unit, a TM triple mode dielectric resonator designed to cause three TM110 resonance modes by forming a combined dielectric block having three dielectric elements perpendicular to each other has been proposed. Such a conventional TM triple mode dielectric resonator, however, has a complicated overall structure and requires a high manufacturing cost if an ordinary manufacturing method is used.
The applicant of the present invention has filed the Japanese Patent Application No. 21394/1996 proposing a dielectric resonator which has a combined dielectric block formed of two dielectric elements combined into a crossed shape, and which is designed to use three resonance modes.
On the other hand, in a case where a band-pass filter, for example, is formed of a TM dual mode dielectric resonator, such as that shown in
FIG. 23
, using two TM111 modes, resonance in a TM111 mode can occur in an attenuation range of the band-pass filter when a particular combination of an external size of the cavity body and a cross-sectional configuration of the dielectric block is used. Because of this phenomenon, it has been difficult to obtain a desirable attenuation characteristic.
SUMMARY OF THE INVENTION
In view of these circumstances, an object of the present invention is to provide a multiple-mode dielectric resonator in which each of the resonant frequencies of the three resonance modes used in the dielectric resonator of the above-mentioned preceding application or a larger number of resonance modes is determined, or a multiple-mode dielectric resonator in which the degree of coupling between predetermined resonance modes is determined.
Another object of the present invention is to provide a dielectric resonator designed to easily obtain a dielectric filter having a desired characteristic by setting the resonant frequency of a TM111 mode and the resonant frequencies of TM110 modes relative to each other, and to provide a method of adjusting a characteristic of the resonator in such a manner.
According to a first aspect of the present invention, in a multiple-mode dielectric resonator having a region surrounded with a conductor, and a combined dielectric block formed of a plurality of dielectric elements combined into a crossed shape, the combined dielectric block being placed in the region surrounded with the conductor, the resonant frequency of a predetermined one of three resonance modes along a plane defined by two of the plurality of dielectric elements is determined in such a manner that one of first to third resonance modes having a higher degree of concentration of an electric field distribution in at least one region in comparison with the other two of the first to third resonance modes is set as a resonant frequency setting object, the first and third resonance modes comprising two pseudo TM110 modes having different lines of symmetry of electric field distributions, the second resonance mode comprising a pseudo TM111 mode, and a dielectric-cut portion is formed in a portion of the combined dielectric block corresponding to the region with the higher degree of concentration of the electric field distribution, or a dielectric material is applied to a portion of the combined dielectric block corresponding to the same region.
The resonant frequency of one of the resonance modes set as a resonant frequency setting object can be changed relatively largely in comparison with the resonant frequencies of the other two resonance modes, and can therefore be determined independently of the resonant frequencies of the other two resonance modes.
According to a second aspect of the present invention, one of first to third resonance modes having no concentration or a lower degree of concentration of an electric field distribution in at least one region in comparison with the other two of the first to third resonance modes is set as a resonant frequency setting object, the first and third resonance modes comprising two pseudo TM110 modes having different lines of symmetry of electric field distributions, the second resonance mode comprising a pseudo TM111 mode. A dielectric-cut portion is formed in a portion of the combined dielectric block corresponding to the region with no concentration or a lower degree of concentration of the electric field distribution, or a dielectric material is applied to a portion of the combined dielectric block corresponding to this region. Both the resonant frequencies of the two resonance modes other than the resonant frequency setting object can be thereby changed, thereby enabling the resonant frequency of the one resonance mode set as the resonant frequency setting object to be determined relative to the resonant frequencies of the other two resonance modes.
According to a third aspect of the present invention, the degree of coupling between two of the three resonance modes is determined in such a manner that a dielectric-cut portion is formed in at least one predetermined portion of the combined dielectric block, or a dielectric material is applied to at least one predetermined portion of the combined dielectric block, thereby reducing the degree of symmetry of the combined dielectric block about a diagonal line parallel to an electric field of the first resonance mode. If the degree of this symmetry is reduced, coupling occurs between the first and second resonance modes. The degree of the coupling is determined by the amount of cut in the predetermined portion or the amount of the dielectric material applied to the predetermined portion.
According to a fourth aspect of the present invention, assuming two pseudo TM110 modes having different lines of symmetry of electric field distributions as first and third modes and assuming a pseudo TM111 mode as a second resonance mode, a dielectric-cut portion is formed in at least one predetermined portion of the combined dielectric block, or a dielectric material is applied to at least one predetermined portion of the combined dielectric block, thereby causing a difference in shape between two of the plurality of dielectric elements defining one plane, which difference relates to a resonant frequency characteristic. The first resonance mode and the third resonance modes are thereby coupled to each other. The degree of this coupling is determined by the amount of cut in the predetermined portion or the amount of the dielectric material applied to the predetermined portion.
According to a fifth aspect of the present in
Abe Shin
Kurisu Toru
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Pascal Robert
Summons Barbara
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