Wave transmission lines and networks – Resonators – Magnetic type
Reexamination Certificate
2001-11-20
2004-11-09
Jones, Stephen E. (Department: 2817)
Wave transmission lines and networks
Resonators
Magnetic type
Reexamination Certificate
active
06816038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetostatic wave device employing a magnetostatic wave material propagating magnetostatic waves and a disturbance wave eliminator employing this magnetostatic wave device, and more particularly, it relates to a magnetostatic wave device eliminating a disturbance wave from an input signal and a disturbance wave eliminator employing this magnetostatic wave device.
2. Description of the Related Art
Various studies have recently been made as to a magnetostatic wave device employing a YIG (yttrium-ion-garnet) film. For example, a straight edge resonator (SER) formed by rectangularly cutting a YIG film for resonating magnetostatic waves between opposite end surfaces or the like is proposed as a magnetostatic wave device applied to a high-frequency filter or the like.
FIG. 18
is a schematic perspective vie showing the structure of the aforementioned straight edge resonator as an exemplary conventional magnetostatic wave device.
As shown in
FIG. 18
, a dielectric substrate
116
is arranged on a conductor
114
, a YIG film
112
is arranged on the dielectric substrate
116
, and a GGG (gadolinium-gallium-garnet) substrate
113
is arranged on the YIG film
112
. An input electrode
111
a
and an output electrode
111
b
are arranged on portions of the dielectric substrate
116
located on both sides of the YIG film
112
. The YIG film
112
and the GGG substrate
113
are rectangularly worked for resonating magnetostatic waves between the longitudinal end surfaces (end surfaces parallel to the input electrode
111
a
and the output electrode
111
b
) of the YIG film
112
thereby forming a straight edge resonator.
According to the aforementioned structure, the input electrode
111
a
receiving an input signal generates a high-frequency magnetic field corresponding to this input signal. At this time, a dc magnetic field H is applied in a direction parallel to the input electrode
111
a
and the output electrode
111
b
and the high-frequency magnetic field generated from the input electrode
111
a
induces a magnetostatic wave in the YIG film
112
, so that this magnetostatic wave propagates through the YIG film
112
and resonates between the longitudinal end surfaces. The output electrode
111
b
converts this magnetostatic wave to an electric signal, which in turn is taken out as an output signal. Thus, the magnetostatic wave device shown in
FIG. 18
functions as a high-frequency filter passing a prescribed high-frequency signal corresponding to the resonance frequency therethrough.
The aforementioned conventional magnetostatic wave device can provide a miniature resonator of 1.4 mm by 4 mm having a dominant mode formed by the resonance of the magnetostatic wave between the longitudinal end surfaces of the YIG film
112
. However, the resonance of the dominant mode interferes with resonance of a mode between end surfaces (end surfaces along a direction perpendicular to the input electrode
111
a
and the output electrode
111
b
) of the YIG film
112
opposed in the longitudinal direction to result in double-humped resonance.
A magnetostatic wave device formed by coupling two straight edge resonators with each other for increasing the pass bandwidth of the aforementioned conventional magnetostatic wave device is also proposed.
FIG. 19
is a schematic perspective view showing the structure of another conventional magnetostatic wave device formed by coupling two straight edge resonators with each other.
The magnetostatic wave device shown in
FIG. 19
comprises two YIG films
112
a
and
112
b
arranged between a GGG substrate
113
and a dielectric substrate
116
so that the inner opposite end surfaces of the two YIG films
112
a
and
112
b
are parallel to each other through a space S. In this magnetostatic wave device, the two YIG films
112
a
and
112
b
functioning as straight edge resonators respectively are coupled with each other, and the strength of this coupling is changed by varying the space S between the YIG films
112
a
and
112
b.
FIG. 20
shows the frequency characteristics of the conventional magnetostatic wave device shown in FIG.
19
. When the space S is not more than about 1 mm, for example, the insertion loss is about 15 dB, the 3 dB bandwidth is about 10 MHz and the degree of suppression is about 25 dB, as shown in FIG.
20
. Thus, the pass bandwidth can be increased beyond that of the magnetostatic wave device shown in FIG.
18
.
Employment of a magnetostatic wave device for eliminating a narrowband disturbance wave superposed on a spectrally diffused input signal of the 2.4 GHz is recently proposed in relation to a spread spectrum communication system employed for a radio LAN (local area network) or the like. In this case, the magnetostatic wave device requires a broad bandwidth of at least about 30 MHz as the 3 dB bandwidth. Therefore, a YIG single-crystalline thin film filtering an input signal in all propagable bands for magnetostatic waves with no frequency selectivity is employed for the magnetostatic wave device. In this case, the pass bandwidth is about 900 MHz, and the insertion loss is about 10 dB.
However, the pass bandwidth of the conventional magnetostatic wave device having the 3 dB bandwidth of about 10 MHz is too narrow for serving as the magnetostatic wave device employed for the radio LAN or the like, although the pass bandwidth can be spread as compared with the conventional magnetostatic wave device shown in FIG.
18
. Further, the insertion loss of about 15 dB is too large. Also in this point, the conventional magnetostatic wave device shown in
FIG. 19
cannot be applied to the radio LAN or the like.
In the aforementioned conventional magnetostatic wave device employed for the radio LAN or the like, the frequency characteristics of the pass bandwidth are so inferior in flatness that the same may exert bad influence on demodulation of an output signal after filtering, although the pass bandwidth is sufficient.
While the insertion loss of the conventional magnetostatic wave device shown in
FIG. 19
can be improved to some extent by reducing the space S, the degree of suppression is so reduced in this case that the magnetostatic wave device cannot pass only a desired high-frequency signal. When the space S is increased to the contrary, the insertion loss is so increased that the magnetostatic wave device cannot pass the desired high-frequency signal without loss although the degree of suppression can be improved to some extent.
A magnetostatic wave device applied to a disturbance wave eliminator is now described.
FIG. 21
is a perspective view showing the structure of still another conventional magnetostatic wave device. In this conventional magnetostatic wave device, a YIG (yttrium-iron-garnet) film
100
is formed on a GGG (gadolinium-gallium-garnet) substrate
200
while an input antenna electrode
300
and an output antenna electrode
400
are formed on the YIG film
100
, as shown in FIG.
21
.
The operation principle of the magnetostatic wave device is now described. When a dc magnetic field H is applied to the YIG film
100
with constant strength, the directions of magnetic dipoles of electrons are oriented toward the magnetic field H. When a high-frequency magnetic field is locally applied in this case, magnetic dipoles around the high-frequency magnetic field cause precession. This precession of the magnetic dipoles is transmitted to adjacent magnetic dipoles due to interaction between the magnetic dipoles, to successively propagate through the YIG film
100
. This wave, having a slow speed and dominant magnetic energy, is referred to as a magnetostatic wave.
In the conventional magnetostatic wave device shown in
FIG. 21
, a high-frequency magnetic field generated from the input antenna electrode
300
induces a magnetostatic surface wave in the YIG film
100
through the aforementioned operation principle, and this magnetostatic surface wave propagates between the input antenna electrode
300
and the output antenna electrode
400
Maeda Atsushi
Umemoto Takashi
Yamano Kouji
Armstrong Kratz Quintos Hanson & Brooks, LLP
Jones Stephen E.
Sanyo Electric Co,. Ltd.
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