Superconductor technology: apparatus – material – process – High temperature devices – systems – apparatus – com- ponents,... – High frequency waveguides – resonators – electrical networks,...
Reexamination Certificate
1999-03-23
2002-11-26
Lee, Benny T (Department: 2817)
Superconductor technology: apparatus, material, process
High temperature devices, systems, apparatus, com- ponents,...
High frequency waveguides, resonators, electrical networks,...
C505S238000, C505S239000, C505S700000, C505S701000, C505S866000, C333S219000, C333S204000, C333S134000
Reexamination Certificate
active
06487427
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compact dielectric resonator of a very high value of Q, to a dielectric filter making use of the resonator, to a dielectric duplexer and to a communications device.
2. Background Art
Recently, dielectric resonators utilizing a dielectric as a material for constructing the resonator have been widely used so as to miniaturize the resonant system of an electric circuit which handles high-frequency waves such as microwaves. Such dielectric resonators utilize the phenomenon that the wavelength of an electromagnetic wave in a dielectric is 1/(∈r)
½
(wherein ∈r represents relative dielectric constant) that measured in free space. Dielectric resonators are used in a variety of resonant modes, including the TE, TM and TEM modes. In order to prevent electromagnetic energy from being scattered and lost, dielectric resonators are usually housed in a metallic casing, or alternatively, metal electrodes are formed on the dielectric surface.
In resonant systems of the above-mentioned types, Qu (i.e., Q under no-load) varies not only depending on Qd (=1/tan &dgr;, Q of the dielectric per se) but also on Qc (i.e., Q attributed to a conductor loss which is caused by the current that flows in the surface of metal). Qu is expressed by the following equation: 1/Qu=(1/Qd)+(1/Qc). Therefore, in order to realize a resonant system of a high Qu, it is essential that a dielectric material of high Qd be used, and in addition, it is essential that electrodes of high Qc—in other words, electrodes of small conductor loss—be used.
Japanese Patent Application Laid-Open (kokai) No. 1-154603 discloses a method for achieving a high Qu (Q under no-load) by forming RE—M—Cu—O-based superconducting electrodes on a dielectric ceramic of any of a variety of types, including MgTiO
3
—(Ca, Me)TiO
3
-based dielectric ceramic, Ba(Zr, Zn, Ta)O
3
-based dielectric ceramic, (Zr, Sn)TiO
4
and BaO—PbO—Nd
2
O
3
—TiO
2
-based dielectric ceramic. Also, Japanese Patent Application Laid-Open (kokai) No. 9-298404 discloses a method which utilizes Ba(Mg, Ta)O
3
as a dielectric material.
FIGS. 1 and 2
are graphs showing temperature-dependent characteristics of tan &dgr;(=1/Qd) at 10 GHz for a variety of dielectric materials. As shown in
FIGS. 1 and 2
, MgTiO
3
—(Ca, Me)TiO
3
-based material, Ba(Zr, Zn, Ni, Ta)O
3
-based material, BaO—PbO—Nd
2
O
3
—TiO
2
-based material, and Ba(Mg, Ta)O
3
-based material exhibit disadvantageously poor low-temperature characteristics because in each case, tan &dgr; does not decrease at a constant rate across an entire range of low temperatures.
In a (Zr, Sn)TiO
4
-based dielectric material, tan &dgr; decreases at a constant rate throughout the low temperature range. However, this material has a disadvantage in that a violent interface reaction occurs between the resultant dielectric and superconducting electrodes. Particularly when a thick film is formed through screen printing, interfacial reaction between a dielectric and oxide superconducting material raises a critical issue; violent interfacial reaction degrades the superconducting material and therefore no superconducting characteristic can be obtained. Therefore, in order to pursue practical use of various products derived from superconducting materials, there exists a strong need for a new substrate material that does not cause interfacial reaction. MgO is a candidate dielectric material that does not cause interfacial reaction between the dielectric and oxide superconducting material, and thus is suitable for use with high-frequency waves. However, MgO has an ∈r (relative dielectric constant) of 9-10, which is low as compared to that of the above-mentioned dielectric (∈r=20-30), making MgO disadvantageous in terms of miniaturizing the resonant system.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a compact dielectric resonator of high Qu, in which an electrode formed of oxide superconducting material is provided on a surface of the dielectric.
Another object of the present invention is to provide a dielectric filter making use of such a compact resonator.
A further object of the present invention is to provide a dielectric duplexer making use of the compact resonator.
A still further object of the present invention is to provide a communications device making use of the compact resonator.
In a first aspect of the present invention, there is provided a dielectric resonator comprising a dielectric and an oxide superconducting electrode provided on a surface of the dielectric, wherein the dielectric is a Ba(Mg, Ma)O
3
-based dielectric (wherein Ma is at least one pentavalent elemental metal but cannot be Ta alone), and the oxide superconducting electrode is formed of an oxide superconducting material selected from among a RE—M—Cu—O-based oxide superconducting material (wherein RE is a rare earth element and M is an alkaline earth metal element), a Bi—Sr—Ca—Cu—O-based oxide superconducting material (which encompasses those in which Bi is partially substituted by Pb), and a Tl—Ba—Ca—Cu—O-based oxide superconducting material.
Preferably, Ma is at least one element selected from among Ta, Sb and Nb (except the case where Ta is used alone).
In a second aspect of the present invention, there is provided a dielectric resonator comprising a dielectric and an oxide superconducting electrode provided on a surface of the dielectric, wherein the dielectric is a Ba(Mb, Mg, Ta)O
3
-based dielectric (wherein Mb is a tetravalent or pentavalent elemental metal), and the oxide superconducting electrode is formed of an oxide superconducting material selected from among a RE—M—Cu—O-based oxide superconducting material (wherein RE is a rare earth element and M is an alkaline earth metal element), a Bi—Sr—Ca—Cu—O-based oxide superconducting material (which encompasses those in which Bi is partially substituted by Pb), and a Tl—Ba—Ca—Cu—O-based oxide superconducting material.
Preferably, Mb is at least one element selected from among Sn, Zr, Sb and Nb.
Preferably, the Ba(Mb, Mg, Ta)O
3
-based dielectric is a Ba(Sn, Mg, Ta)O
3
-based dielectric. Preferably, the composition of the Ba (Sn, Mg, Ta)O
3
-based dielectric is Ba(Sn
x
, Mg
y
, Ta
z
)O
7/2−x/2−3y/2
(wherein x+y+z=1, 0.04≦x≦0.26, 0.23≦y≦0.31, and 0.51≦z≦0.65).
In a dielectric resonator according to the second aspect of the present invention, the Ba(Mb, Mg, Ta)O
3
-based dielectric may be a Ba(Mg, Sb, Ta)O
3
-based dielectric. In this case, the composition of the Ba(Mg, Sb, Ta)O
3
-based dielectric is Ba
x
Mg
y
(Sb
v
, Ta
l−v
)
z
O
w
(wherein x+y+z=1, w is an arbitrary number, x, y, and z fall within the tetrahedron defined by connecting points A, B, C, and D shown in Table 1, and 0.00≦v≦0.300).
TABLE 1
x
y
z
A
0.495
0.175
0.330
B
0.495
0.170
0.335
C
0.490
0.170
0.340
D
0.490
0.180
0.330
In the first and second aspects of the present invention, the RE—M—Cu—O-based oxide superconducting material may be YBa
2
Cu
3
O
7-x
, the Bi—Sr—Ca—Cu—O-based oxide superconducting material may be (Bi,Pb)
2
Sr
2
Ca
2
CU
3
O
x
or Bi
2
, Sr
2
CaCu
2
O
x
, and the Tl—Ba—Ca—Cu—O-based oxide superconducting material may be Tl
2
Ba
2
Ca
2
Cu
3
O
x
.
In a third aspect of the present invention, there is provided a dielectric filter comprising a dielectric resonator according to any of the above aspects of the present invention, and an external connecting means.
In a fourth aspect of the present invention, there is provided a dielectric duplexer comprising at least two dielectric filters, input-output connection means for each of the dielectric filters, and antenna connecting means which is connected to the dielectric filter, wherein at least one of the dielectric filters is a dielectric filter of the present invention.
In a fifth aspect of the present invention, there is provided a communications device comprising a dielectric duplexer as described above, a transmit
Kintaka Yuji
Oota Akio
Tamura Hiroshi
Tatekawa Tsutomu
Lee Benny T
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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