Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-02-24
2001-05-15
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S201000, C333S024100, C310S026000
Reexamination Certificate
active
06232850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetostatic wave device such as a microwave filter, a resonator, or an S/N (signal-to-noise ratio) enhancer.
2. Description of the Related Art
As an RF signal received by a satellite broadcasting television receiver weakens due to rain, snow (white specks) increases in reproduced pictures on a display of the television receiver. When the received RF signal falls into an unacceptable range, it is difficult to reproduce pictures on the display.
T. Nomoto et al have proposed an S/N enhancer for improving the signal-to-noise ratio of a received RF television signal (T. Nomoto et al., IEEE Trans. on Microwave Theory and Techniques, Vol. 41, No. 8, August 1993, pp. 1316-1322). This prior-art S/N enhancer is of the cancel type, using two magnetostatic surface wave filters.
Y. Ishikawa et al have developed an adaptor for a satellite broadcasting television receiver (Y. Ishikawa et al., Proc. of 1994 Asia Pacific Conference, pp. 179-183). This prior-art adaptor uses an S/N enhancer designed to operate for a 1.9-GHz band. In the prior-art adaptor, a signal in a first IF band of 1 GHz to 1.3 GHz which is derived from a received RF signal is up-converted to a 1.9-GHz signal, and the 1.9-GHz signal is processed by the S/N enhancer. The processing-resultant signal, that is, the filtering-resultant signal, is down-converted back to a signal in the first IF band. The prior-art adaptor includes frequency converters in addition to the S/N enhancer. Thus, the prior-art adaptor tends to be expensive.
An S/N enhancer capable of operating at frequencies of 1 GHz to 1.3 GHz has been desired. Also, an S/N enhancer has been desired which can operate for a 400-MHz band, that is, a second IF band in a satellite broadcasting television receiver.
Japanese published unexamined patent application 7-130539 discloses a magnetostatic surface wave device. This prior-art magnetostatic surface wave device includes a film of single crystal of garnet which is grown on a Gd
3
Ga
5
O
12
substrate. The Gd
3
Ga
5
O
12
substrate has a plane orientation being one from among (110), (100), and (211). In the prior-art magnetostatic surface wave device, an anisotropic magnetic field can be weak so that the lower limit of the frequency band for the propagation of magnetostatic surface wave can be a relatively low frequency. In Japanese application 7-130539, the lowest frequency of magnetostatic surface wave is 900 MHz when a saturation magnetization is 1,760 G and the plane orientation of the substrate is (100). Accordingly, it is difficult to use the prior-art magnetostatic surface wave device as an S/N enhancer operating for a 400-MHz band.
T. Kuki et al have developed a reflection-type S/N enhancer operating for a 400-MHz band (T. Kuki et al., 1995 IEEE MTT-S Digest, pp. 111-114). To attain an operating frequency of 400 Hz, this prior-art reflection-type S/N enhancer uses a thin film of YIG which has a relatively low saturation magnetization. Since this prior-art S/N enhance is of the reflection type, the width of an operating frequency band thereof is a small value equal to 40 MHz. The operating frequency of this prior-art reflection-type S/N enhancer tends to considerably depend on an ambient temperature. Accordingly, it is difficult to practically use this prior-art reflection-type S/N enhancer.
T. Kuki et al. used a magnetostatic wave in a reflection-type S/N enhancer designed as a mixture of surface wave and backward volume wave (T. Kuki et al., Manuscript C-106, General Meeting 1996, Japanese Institute of Electronics, Information and Communication Engineers). This prior-art design is effective in lowering and widening the operating frequency band of the reflection-type S/N enhancer although a saturation magnetization is relatively great. The temperature characteristic of the reflection-type S/N enhancer of the prior-art design has not been investigated. To operate the reflection-type S/N enhancer of the prior-art design, it is necessary to further lower the operating frequency thereof.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a magnetostatic wave device having a good temperature characteristic.
It is another object of this invention to provide a magnetostatic wave device capable of operating at a further lowered frequency in comparison with the prior-art operating frequency.
A first aspect of this invention provides a magnetostatic wave device comprising a Gd
3
Ga
5
O
12
substrate off-angled from a {110} plane; a magnetic thin film including a crystal of garnet and being formed on the Gd
3
Ga
5
O
l2
substrate by liquid-phase epitaxy; a transducer for exciting magnetostatic wave in the magnetic thin film in response to an RF electric signal; and means for applying a bias magnetic field to the magnetic thin film; wherein there is a relation as 20°≦|&thgr;
1
+&thgr;
2
|≦35°, where “&thgr;
1
” denotes an angle between a longitudinal direction of the transducer and a <001> orientation of the crystal in the magnetic thin film, and “&thgr;
2
” denotes an angle between a transverse direction of the transducer and a specified direction, the specified direction being parallel to a line of intersection between a horizontal plane of the magnetic thin film and a given plane which is perpendicular to the horizontal plane of the magnetic thin film and which contains a direction of the bias magnetic field; and wherein there is a relation as |&thgr;
3
|≦75°, where “&thgr;
3
” denotes an angle between the specified direction and the direction of the bias magnetic field.
A second aspect of this invention is based on the first aspect thereof, and provides a magnetostatic wave device wherein the Gd
3
Ga
5
O
12
substrate is off-angled from the {110} plane by an angle in a range of 1° to 5°.
REFERENCES:
patent: 4595889 (1986-06-01), Stitzer et al.
patent: 5601935 (1997-02-01), Fujino et al.
patent: 3-214901 (1991-09-01), None
patent: 7130539 (1995-05-01), None
“A Reflection Type of MSW Signal-To-Noise Enhancer in the 400-MHz Band” by T. Kuki et al; 1995 IEEE MTT-S Digest.
“Surface Morphologies and Quality of Thick Liquid Phase Epitaxial Garnet Films For Magneto-Optic Devices”by T. Hibiya; Journal of Crystal Growth 62 (1983) 87-94; North Holland Publishing Company.
“A Consideration On MSSW/BVW Hybrid Modes for an S/N Enhancer” by T. Kuki et al.; 1996.
“A Signal-To-Noise Enhancer Using Two MSSW Filters And Its Application To Noise Reduction In DBS Reception” by T. Nomoto et al; IEEE Transaction on Microwave Theory and Techniques, vol. 41, No. 8, Aug. 1993.
“A Signal-To-Noise Enhancer With Extended Bandwidth Using Two NSSW Filters And Two 90 Hybrids” by Y. Ishikawa et al.; 1994 Asia Pacific Microwave Conference.
Ikari Masanori
Kuki Takao
Nomoto Toshihiro
Ryuo Toshihiko
Tanno Masayuki
Gopstein Israel
Pascal Robert
Shin-Etsu Chemical Co. , Ltd.
Summons Barbara
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