JPH01120102A - Filter device - Google Patents

Abstract

PURPOSE:To obtain a microwave band filter device with good input/output isolation by propagating a magnetostatic wave generated by an exciting electrode on a thin magnetic material film and detecting it by a detecting electrode. CONSTITUTION:When a microwave is applied to the exciting electrode 5 through an input terminal 7 while a magnetostatic field H is applied as shown by an arrow, a surface wave 9 which is the magnetostatic wave of wavelength lambdacorresponding to the magnetic field H is propagated on the YIG thin film 2 as shown by an arrow. When the thickness (t) of the thin film 2 is so thick that t<<lambda, only a wave of wavelength lambda satisfying 2L=Nlambda (N: natural number) generates a standing wave in the thin film 2. In the equation, L is the length between both ends of the thin film 2 in the propagation direction of the magnetostatic wave. Then when the detecting electrode 6 is provided on a proper position in a figure, a microwave from which frequency components generating no standing wave are removed is extracted. Namely, the part between a terminal 7 and an output terminal 8 operates as a microwave filter device. Further, the input and output electrodes and wiring are separated on and reverse sides of an YIG pattern, so the isolation as the filter is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improving the characteristics of a microwave filter device using magnetic resonance phenomena.

(Prior Art) FIG. 2 is a perspective view of a conventional filter device using magnetic resonance. The axes of the two coils 22 and 23 are orthogonal to each other, a YIG (yttrium-iron-garnet) single crystal 25 polished into a spherical shape is placed in the center, and the static magnetic field H is made perpendicular to the axes of both coils ( In the figure, the microwave is applied to the coil 2 from the coaxial cable 21.
2, no output appears in the coil 24 orthogonal to the cable 23. However, when a magnetic field corresponding to the resonant magnetic field Hr is applied, microwaves appear in the cable 23. The microwave magnetic field generated by the coil 22 is
This is because the magnetic moment of the 'IG under the resonance condition is rotated, and this rotating magnetic moment induces a microwave current in the coil 24. At this time, the coil 22 and Y
IG25 is the motor, YrG25 and coil 24 are the generator
It acts as a machine. If microwaves are input from the coax 23, an output will appear on the coax 21. When the static magnetic field is fixed and the microwave frequency is varied, output appears only around a specific frequency, exhibiting wavelength-selective characteristics.

This is a variable frequency filter in the microwave band, and the resonant frequency is proportional to the excitation current of the static magnetic field coil.

(Problem that the invention seeks to solve) However, YIG spheres have sharp resonance characteristics (
In other words, the Q is high), but in the configuration shown in FIG. 2, the two input/output loops are close to each other, so the signal is directly transmitted between them. That is, there is a lot of signal leakage in the filter cutoff frequency range, and isolation is poor.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to realize a microwave band filter device with good input/output isolation.

(Means for Solving the Problems) The present invention relates to a filter device that has wavelength selectivity by utilizing the magnetic resonance of a magnetic material, and is characterized by a magnetic material formed on a substrate. A film, an excitation electrode provided on one surface of the magnetic material a film, and a detection electrode provided on the other surface of the magnetic material film, and a magnetostatic wave generated by the excitation electrode is The structure is such that it propagates on a magnetic thin film and is detected by a detection electrode.

(Example) The present invention will be explained in detail below using the drawings.

FIG. 1 is a perspective view showing an embodiment of a filter device according to the present invention. 1 is a GGG (gadolinium-gallium-garnet) substrate, 2 is a YIG (yttrium-iron-garnet) thin film formed by epitaxial growth on this GGGm plate 1, and 3a and 3b are this GGG substrate 1. Dielectrics 4a and 4b provided oppositely on both sides of the YrGil film 2 are YIG of the dielectrics 3a and 3b.
A ground plane 5.6 is formed on the surface opposite to the n-film 2, and 5.6 is a magnetostatic wave excitation electrode and a static A magnetic wave detection electrode 7 is an input terminal connected to the electrode 5 and applies microwaves, and 8 is an output terminal connected to the electrode 6.

Each layer of the above structure is placed as close as possible to ensure good bonding.

The operation of the filter device configured as described above will be explained next. When a microwave is applied to the electrode 5 through the input terminal 7 with a magnetostatic jJiH applied in the direction of the arrow in the figure, the surface wave 9 of the magnetostatic wave with a wavelength λ corresponding to the magnetostatic jiH becomes YIG thin y.
It propagates on A2 in the direction of the arrow in the figure. Now, if the thickness t of the YIGI film is negligibly thin as t(λ, then 2 L=Nλ (N-1, 2, 3,...)...
(1) Only waves of wavelength λ that satisfy the following relationship create standing waves in YIGtillI. Here, YI in the direction in which the magnetostatic wave propagates
This is the quality of both ends of G-thin yA2. Therefore, by providing a detection N pole 6 at an appropriate position as shown in the figure, it is possible to extract microwaves from which frequency components that do not form standing waves have been removed. That is, the space between the input terminal 7 and the output terminal 8 operates as a microwave filter device. The frequency of static magnetic waves is static! It changes depending on the size of IJIH, so
This is a variable frequency filter in the microwave band. Regarding magnetostatic wave devices, please refer to the Journal of the Television Society Vol.

38, No. 12 (1984); 1053/106
2 is detailed.

According to the filter device having such a configuration, the input/output electrodes and wiring are on the front and back sides of the YIG film and are separated from each other.
Excellent isolation as a filter. Furthermore, since the YIG film has sharp resonance characteristics, it exhibits excellent wavelength selectivity.

Although the above embodiment shows the case of surface magnetostatic wave mode, the direction of the static magnetic field H may be changed to utilize volume magnetostatic waves (volume waves of magnetostatic waves).

Furthermore, in the above embodiment, the wires are drawn from the electrodes from the same side, but the direction of the wires from the electrodes is free.
You can also do it from the opposite side or from the side.

Therefore, it is easy to isolate input and output.

Further, in the above embodiment, two upper and lower dielectrics are used, but the invention is not limited to this. For example, the dielectric 3a may be omitted and the magnetostatic wave excitation electrode may be directly deposited on the YIG film 2. .

In addition, wavelength selectivity can be achieved by devising the electrode pattern and using known interdigital electrodes, parallel strip 7-lay electrodes, or the like.

(Effects of the Invention) As described above, according to the present invention, a microwave band filter device with good input/output isolation can be realized with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a filter device according to an embodiment of the present invention, and FIG. 2 is a perspective view of a conventional filter device using magnetic resonance. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Magnetic thin film, 5...Excitation electrode, 6...Detection electrode. Figure 1 Figure 2

Claims (1)

[Claims] A filter device that provides wavelength selectivity using magnetic resonance of a magnetic material, comprising: a magnetic thin film formed on a substrate; an excitation electrode provided on one side of the magnetic thin film;
and a detection electrode provided on the other side of the magnetic thin film, so that the magnetostatic wave generated by the excitation electrode propagates on the magnetic thin film and is detected by the detection electrode. filter device.