JP3200133B2 - Ferrimagnetic thin film FM modulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM-modulated output high-frequency wave by changing the propagation speed of a magnetostatic wave generated by mutual conversion with a high-frequency electromagnetic wave on a ferrimagnetic member to which a DC magnetic field is applied by modulating the applied DC magnetic field. An FM modulator utilizing a magnetostatic wave that obtains an electromagnetic wave, particularly a ferrimagnetic thin-film FM modulator that uses a ferrimagnetic thin film to obtain a good linearity with a compact and easy-to-manufacture structure, and operates stably with high sensitivity. It was made.

[0002]

2. Description of the Related Art Conventionally, various types of circuit modulators have been used as FM modulators. Typical conventional FM modulators use a voltage controlled oscillator (VCO), and
A varactor is used.

As shown in FIG. 1, an FM modulator using a voltage controlled oscillator (VCO) is obtained by guiding a part of an oscillation output high frequency signal of a VCO 1 to a prescaler 2 and reducing the frequency to 1 / n. The DC voltage supplied to the comparator 5 and compared with the oscillation output of the reference oscillator 4 is applied to a resonance circuit including a varactor C ₀ of the VCO 1 through a low-pass filter (LPF) 6 to reduce the oscillation frequency. The oscillation frequency is modulated by superimposing and applying the modulation signal voltage from the modulator 2 while keeping the voltage constant. Since the conventional FM modulator having such a configuration requires a low-pass filter, it has a drawback that it is difficult to perform modulation with a low-frequency modulation signal.

On the other hand, in an FM modulator in which phase modulation is performed by a multi-stage filter using a varactor,
Varactor C ₁ as shown in FIG. _{2 (a), C 3,} C 5 --- and inductor 6 L _2, L ₄ --- n stages of the phase of the low-pass filter (LPF) consisting of the 2 As shown in (b)

[Outside 1] Delay by radians. Now, the varactor _{C 1, C 3, C 5} --- capacity to change the alters the cutoff frequency of the LPF, for example, the capacitance increases, the phase characteristic shown by the solid line in FIG. 2 (b) by a dotted line The phase changes by Δθ at the frequency f _o .

On the other hand, the signal subjected to such phase modulation is referred to as V _PM
Indicated by

[Number 1] _{V PM = Αcos {2π f c} t + V (t) - θ o} (1) , and the instantaneous angular frequency of the FM signal of the (1) {}
Time differentiated

(Equation 2) Becomes Now, the modulation frequency f _m and the maximum phase shift θ _max
about

[Equation 3] If V _(t) = θ _max sin (2π f _m t) (2), the instantaneous angular frequency is

[Equation 4] 2π ｛f _c + θ _max f _m cos (2π f _m t)｝ and the maximum frequency displacement is と f.

[Equation 5] △ f = θ _max · f _m

(Equation 6) Becomes This equation (3) is well known, and θ _max
Is called the modulation index.

Accordingly, it is given a modulation frequency f _m and the frequency displacement △ f is the frequency modulation by moving until it △ θ = θ _m by changing the voltage applied to the varactor in LPF shown in FIG. 2 (a) Can do it. However, in the conventional FM modulator having such a configuration, as can be seen from equation (3), the lower the modulation frequency f _m, the change in phase △ theta increases, becomes necessary greatly changing the voltage applied to the varactor Therefore, there is a disadvantage that nonlinear distortion occurs due to the characteristics of the varactor. As an alternative to the conventional FM modulator having each of these disadvantages, a circuit type FM modulator that obtains a frequency-modulated wave by changing the propagation phase of a wave has been conventionally developed.

Now, consider the case where n waves are traveling on a line of length L, and the wavelength λ of the waves is

(Equation 7) When the wavelength λ is changed by ηλ by some means, the phase change △ θ in the line having the length L becomes

(Equation 8) Becomes In order to reduce the size of the FM modulator of this type, the length L of the line must be small.
Also, in order to improve the linearity, the smaller η, the better.

On the other hand, as described above, the lower the modulation frequency f _m, it is necessary to change the phase △ theta increases, therefore, it is necessary that the wavelength λ is small from equation (5).
For example, at the modulation frequency f _m = 150 Hz, the maximum frequency displacement △ f
= 5kHz, from equation (3)

(Equation 9) A phase change Δθ is required.

Now, assuming that L = 3 mm and η = 0.1, the wavelength λ
Is obtained from equation (5).

(Equation 10) Becomes Such a short-wavelength line-propagating wave includes (a)
There are elastic waves and (b) magnetic waves, but (a) it is difficult to change the wavelength of an elastic wave by applying an electric or magnetic field to the line from the outside. It is extremely difficult to realize an FM modulator of this type, and there is a possibility of realization of this type of FM modulator using (ii) magnetic waves.

[0010]

However, the magnetic wave is
Generally, it is a wave propagating in a ferrimagnetic body to which a DC magnetic field is applied. When the vector of the applied magnetic field is indicated by H ,

[Equation 11] A wave whose electric field energy that satisfies the following condition is almost zero. For example, the relationship between the angular frequency ω of a wave propagating in a ferrimagnetic material having an infinite region and the number k of waves included in 1 cm is as shown in FIG. In FIG. 3, θ indicates the angle between the DC magnetic field and the propagation direction of the wave, the wave in region I is an electromagnetic wave, the wave in region II is a magnetostatic wave,
The waves in region III are called exchange spin waves.

Of these three types of waves, the converted spin wave in the region III has a large wave number per unit length and therefore a small wavelength as shown in FIG. 3, for example, k = 10 ⁵ in FIG. And the wavelength λ is

(Equation 12) Becomes On the other hand, as will be described later with respect to this type of FM modulator, the shape and dimensions of the electrodes used when converting electromagnetic waves to magnetic waves require at least the accuracy of the wavelength of those waves. If it is too small, it becomes difficult to realize an FM modulator of this type. On the other hand, the wavelength of the magnetostatic wave in the region II in FIG.
It is optimal to use this magnetostatic wave to obtain a wavelength having a value as shown in equation (6).

FIG. 3 shows a propagation medium having an infinite region as described above. However, an axial DC magnetic field is applied to a finite shape and size, for example, an elongated cylindrical ferrimagnetic single crystal. Upon application, the magnetostatic wave is generated that propagates in the axial direction is represented by (8) of the phase velocity upsilon _p Hatsugi.

(Equation 13) Here, R represents the radius of the cylindrical ferromagnetic body, upsilon ₀ is the velocity of electromagnetic wave in vacuum, ∈ _r is the relative dielectric constant of the ferromagnetic body, mu _{+, r} is a positive circularly polarized wave relative permeability, As shown in FIG. 4, the value rapidly changes in the resonance magnetic field _Hr .

In addition,

## EQU2 ## As can be seen from equation (8), v ′ _p is relative magnetic permeability μ ₊ and relative dielectric constant.

外_r is the phase velocity of the electromagnetic wave propagating in the isotropic medium of _r , so that the phase velocity υ _p of the magnetostatic wave is proportional to R / λ _c with respect to 2 outside the phase velocity of the electromagnetic wave. The phase velocity _{Δp of the} magnetostatic wave becomes slower as the radius R of the cylindrical ferrimagnetic material becomes smaller. As a result, the wavelength λ of the magnetostatic wave is

[Equation 14] Becomes smaller according to

[0014] On the other hand, as can be seen from FIG. 4, varying the intensity H _in the applied DC magnetic field, relative permeability | μ _{+, r} | is changed, therefore, the phase velocity outside 2 of the electromagnetic wave is changed, Further, the phase velocity υ _p of the magnetostatic wave changes, and as a result, the wavelength λ changes. The sensitivity of the change in the wavelength λ with respect to the change of such applied magnetic field strength H _in, i.e.,

(Equation 15) Is the resonance magnetic field strength H _r where the change in relative magnetic permeability | μ ₊ |
Increases rapidly in the vicinity of. Therefore, in order to shorten the length L of the ferrimagnetic cylinder and increase the sensitivity of the above-described wavelength change,

[Outside 4] Therefore, the region near the resonance magnetic field must be used. Thus, in the region near the resonance magnetic field,
It applied even magnetic field strength H _in the slightly changed for some reason, as can be seen from the above, unstable wavelength of the magnetostatic wave λ is changed greatly.

[0015] However, if as much as possible apart from the applied magnetic field strength H _in order to avoid such an unstable operation of the electrostatic waves from the resonant magnetic field strength H _r, sensitivity of the relative permeability change ∂ | H ₊
| / ∂H _in , and therefore the sensitivity of wavelength change ∂λ / ∂H _in
Becomes smaller, and the sensitivity of the entire phase amount change ∂θ / ∂H
_in also decreases. As a result, it is necessary to reduce the wavelength λ of the magnetostatic wave so that a large number of waves can be placed in the length L of the cylindrical ferrimagnetic material, and therefore, equations (8) and (9) As can be seen from the above, it is necessary to make the radius R of the cylindrical ferrimagnetic material as small as possible.

However, it is extremely difficult in manufacturing to reduce the radius of the cylindrical ferrimagnetic material, and the structure becomes weak. Japanese Patent Publication No. 47-22 by the inventor of the present application
In the FM modulator using a cylindrical ferrimagnetic material described in Japanese Patent Publication No. 050, such a practical and practical defect is recognized, and elimination of the defect has been a conventional problem to be solved.

[0017]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned disadvantages of the prior art, and to provide a small-sized and highly linear device using a ferrimagnetic element having a fine structure and capable of operating stably. An object of the present invention is to provide an FM modulator having high sensitivity.

That is, in the ferrimagnetic thin film FM modulator of the present invention, input and output strip electrodes are opposed to each other on a ferrimagnetic thin film adhered on a substrate while being separated from each other.
A high-frequency electromagnetic wave is input through the input strip electrode, and a DC magnetic field is applied to the ferrimagnetic thin film to propagate a magnetostatic wave converted from the high-frequency electromagnetic wave between the input and output strip electrodes. By modulating the intensity of the DC magnetic field by a signal to change the wavelength of the magnetostatic wave, a high-frequency output electromagnetic wave frequency-modulated by the signal is extracted.

[0019]

Therefore, according to the present invention, a high-sensitivity F which operates stably with good linearity by a small and easy-to-manufacture structure.
An M modulator can be realized.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. First, FIG. 5A shows a configuration example of excitation and extraction of a magnetostatic wave which is the basis of the ferrimagnetic thin film FM modulator of the present invention. In the basic configuration shown in the figure, a ground plate 8 is attached to the back surface of a dielectric substrate 7 and an input electrode 9 and an output electrode 10 each composed of a strip line are disposed on the surface of the substrate 7 at a required magnetostatic wave propagation interval. And a thin film 11 of a low-loss ferrimagnetic material, for example, yttrium-iron-garnet (YIG), having a lattice constant equal to that of YIG, for example, gadolinium-gallium-garnet (G
GG) is adhered and formed on the dielectric substrate 7 so as to cover the input / output strip electrodes 9 and 10, for example, a magnetic material wound with a modulation coil as described later. YIG thin film 11 by magnet (not shown) sandwiched between frames
A DC magnetic field perpendicular to the film surface is applied to the entire surface, and a required high-frequency electromagnetic wave is supplied to the input strip electrode 9 so that Y
When a magnetostatic wave is generated in the IG thin film 11 as shown in FIG. 5B, the magnetostatic wave is perpendicular to the input strip electrode 9 by YI.
The light propagates through the G thin film 11 to reach the output strip electrode 10, and a frequency-modulated output high-frequency electromagnetic wave converted from a magnetostatic wave subjected to phase modulation during the propagation is extracted from the output strip electrode 10.

The manner in which the magnetostatic wave is generated in the YIG thin film 11 depends on the direction of the applied DC magnetic field as shown in FIGS. 6 (a), 6 (b) and 6 (c). Propagation in the direction orthogonal to the strip electrodes 9 and 10 constitutes a delay line, and the delay time changes according to the strength of the applied DC magnetic field. A phase change occurs according to the signal, and the reconverted output high-frequency electromagnetic wave undergoes frequency modulation.

As described above, when a high frequency electromagnetic wave is supplied from a strip electrode in a state where a DC magnetic field is applied to a thin film of a ferrimagnetic material such as YIG and magnetized, the thin film is magnetically coupled in the magnetic thin film as shown in FIG. In addition, the tip of the magnetization causes a circular precession motion in a plane perpendicular to the DC magnetization, and the vector m of the circular motion changes along the wave propagation direction k to generate a magnetostatic wave. When a DC magnetic field is applied vertically to the YIG thin film 11,
When a volume advancing magnetostatic wave (MSFVW) of the mode shown in FIG. 6B is generated and a DC magnetic field is applied in parallel to the film surface of the YIG thin film 11, the DC magnetic field is applied as shown in FIG. When it is perpendicular to the propagation direction k, a surface magnetostatic wave (MSSW) is generated. When the DC magnetic field is also made parallel to the propagation direction k as shown in FIG. 6C, a volume-retracted magnetostatic wave (MSBVW) is generated.

However, surface magnetostatic waves (MSSW)
As shown in FIG. 6 (a), since energy is concentrated on the surface of the magnetic thin film 11, when the power of the electromagnetic wave supplied to the input electrode 9 becomes 0 dB or more, harmonics are generated due to the nonlinear effect of the ferrimagnetic material. Waves occur. In the volume retracted magnetostatic wave (MSBVW), so to apply a DC magnetic field along the propagation direction of the magnetostatic wave in order to provide a phase change greater by a change in the intensity H ₀ of the DC magnetic field, a magnetic thin film 11
, It is necessary to increase the propagation path length L, so that a DC magnetic circuit for applying a DC magnetic field of a required strength H ₀ becomes large. Therefore, in order to realize a small-sized ferrimagnetic thin film FM modulator, it is preferable to use the volume forward magnetostatic wave (MSFVW) shown in FIG. 6 (b). A description will be given of the ferrimagnetic thin-film FM modulator of the present invention with respect to the configuration shown in FIG.

First, the input / output electrodes 9 and 10 having the configuration shown in FIG.
Phase θ and DC magnetic field strength H _in the propagation path between
Explaining the relationship, the relationship is as follows (10)
It can be obtained from a dispersion equation expressing the relationship between the angular frequency ω and the unit long wave number k as shown in the equation.

[0025]

(Equation 16) Here, Hin is the internal magnetic field strength _in the ferrimagnetic material,
M _S is the saturation magnetization.

Now, the relationship between Ω and kd in equation (10) is Ω
FIG. 7 shows _H as a parameter, where Ω is

[Equation 17] And given an angular frequency ω, the magnetic field strength required to generate a volumetric forward magnetostatic wave is (1
1) must be within the range of the expression.

Let L be the distance between the input electrode 9 and the output electrode 10 in the configuration shown in FIG.

Equation 18] theta = kL (12) becomes a relational expression (10) and the determined change δθ of phase with respect to a slight change delta] H _in the internal magnetic field strength H _in using,

[Equation 19] From the equation (13), the following can be understood. (B) direct current magnetic field strength H _in the phase θ decreases and increases. The sensitivity of the change in phase θ to changes in (ii) a DC magnetic field strength H _in is inversely proportional to the thickness d of the YIG thin film 11 is proportional to the propagation path length L of the forward volume magnetostatic wave (MSFVW).

For example, in the equation (12), Ω _H = 0.2, Ω
= 0.38, the phase change δθ is

(Equation 20) Becomes Now, the thickness of the magnetic thin film 11 using a magnetic material having a saturation magnetization M _S = 750 gauss is set to d = 20 μm, and the phase change δH _in = 10 Oersted changes the internal magnetic field strength.
To obtain θ = 30 radians, from equation (14)

[Number 21] L = 1.784mm next, also, from the value of Ω _H

Equation 22] internal magnetic field strength _{H in = 0.2 × 750 = 150} ( Gauss)

The external magnetic field strength H _ex = H _in + N · M _S = 150 + 750 = 900 (Gauss) (where N is the demagnetizing field coefficient and 1 in the case of a thin film). From the value

[Number 24] angular frequency _{ω = | γ | M S ·} Ω = 2.8 × 750 × 0.38 = 798 ( Gaussian) is obtained.

As described above, when the ferrimagnetic thin film 11 having a length of 1.784 mm and a thickness of 20 μm and having a saturation magnetization of 750 gauss is used, a magnetic field intensity change of 10 Oersted around an external magnetic field of 900 Oersted is provided. , Frequency 79
An 8 MHz electromagnetic wave can be given a phase change of 30 radians. As can be seen from equation (3), this phase change of 30 radians is a phase modulation necessary for obtaining an FM signal exhibiting a frequency displacement of 4.5 kHz with respect to a modulation frequency of 150 Hz.

Next, as can be seen from the above numerical examples,

Equation 25 A Ω _H / Ω = 0.526, involves (13) Since the sufficiently away from the Omega = Omega _H becomes singular point type, the internal magnetic field strength H _in some cause, for example, the temperature change saturation magnetization M _S is sufficiently stable to shift the operating point, such as by a change, it can be seen that according phase modulation in a stable operating state 30 radians is obtained.

Next, the distortion when FM modulation of an electromagnetic wave is performed by such phase modulation of a magnetostatic wave is obtained.
And the distortions K ₂ ′ based on the third harmonic and
K ₃ ′

(Equation 26) Can be obtained from Equation (10) to examine the magnitude of the distortion. For example, when the distortion K ₂ ′ based on the second high frequency is obtained,

[Equation 27] Becomes Now, the above numerical example, that is,

[Equation 28] Ω _H = 0.2, Ω = 0.38

[Expression 29] Substituting △ H ₁ = 10 and M _S = 750 into equation (16) gives

K ₂ ′ = 0.298%, which indicates that distortion is extremely small.

Next, when an insertion loss L _S when FM modulation of an electromagnetic wave is performed by phase modulation of a magnetostatic wave is obtained,

(Equation 31) From equation (17), it can be seen that the following must be performed to reduce the insertion loss.

(A) To reduce the magnetic resonance half width ΔH. Usually, ΔH of 0.5 Eslted is obtained in the X band, and the ΔH becomes smaller as the frequency becomes lower. However, below a certain frequency band, unless the saturation magnetization M _S is reduced, ΔH generally increases due to low magnetic field loss.
Therefore, the above-mentioned reduction of ΔH can be achieved by the low magnetic field loss of the ferrimagnetic material.

On the other hand, when the saturation magnetization M _S is reduced, the Curie point is generally lowered.
M _S is changed, a change in the internal magnetic field strength H _in. That is, as the temperature increases, the saturation magnetization M _S decreases, and the ratio Ω _H increases. As a result, the phase modulation sensitivity ΔH / ΔH _in changes. Therefore, it is necessary to compensate for a change in phase modulation sensitivity due to a change in temperature. Thus, this temperature correction can be easily achieved by a temperature correction circuit configured to change the drive current of the drive element transistor for adding the magnetic field component of the modulation frequency in accordance with the temperature change.

(B) To reduce the ratio Ω _N of the ratio as much as possible. The value of Ω _N is, as can be seen from equation (11),

(Equation 32) As shown in FIG. 8, the loss decreases as the value of Ω _N approaches 1. For example, using the value △ H = 0.5 Oersted,

In a numerical example where δθ = 30 radians, δH _in = 10, Ω = 0.38, the loss L _S = 6.51 (dB).

Next, FIG. 9 schematically shows the entire structure of the FM modulator of the present invention in which a magnetic circuit for applying a DC magnetic field is added to the basic structure of the ferrimagnetic thin film FM modulator of the present invention shown in FIG. Show. In the overall configuration shown, the core magnetic circuit
The laminated body having the structure shown in FIG. 5 mounted on the magnet plate 13 is sandwiched in the space of the center pole piece in FIG. 14, and the coil 15 is wound around the center pole piece to flow a signal current. The magnet plate 13 forms a DC magnetic field that is a main component of the magnetic field applied to the ferrimagnetic thin film 11,
The coil 15, as shown in FIG. 10, flowing a signal current from the transistor T _R driven by the modulation signal from the modulator 2 is applied by superimposing a signal magnetic field to apply a DC magnetic field of the ferromagnetic thin film 11 Things. Furthermore, in order to compensate for the modulation sensitivity change due to temperature change as described above, as shown in FIG. 11, using the thermistor R _T whose resistance value varies with temperature to the base potential setting circuit of the transistor T _R driven by the modulation signal . If the temperature is the saturation magnetization M _S and decreases increases, because minus the M _S from the external magnetic field strength H _ex is the internal magnetic field strength H _in, H _in increases. Therefore, to reduce the current of transistor T _R by the resistance value of the thermistor R _T shown to increase with increasing temperature to 11, a decrease of the DC current flowing through the coil 15,
The DC magnetic field component superimposed on the DC magnetic field generated by the magnet plate 13 is reduced.

[0037] Now, generally, in order to increase the phase modulation sensitivity ∂θ / ∂H _in magnetostatic wave FM modulator must be reduced wavelength lambda. On the other hand, since the input / output strip electrodes 9 and 10 need to be reduced in size, for example, the width to about the wavelength λ, and to be manufactured with high dimensional accuracy, the input / output strip electrodes for coupling electromagnetic waves and magnetostatic waves are manufactured. From above, it is desirable that the wavelength λ is not small. Therefore, it is preferable to increase the wavelength λ in the region near the input / output electrodes 9 and 10 and to decrease the wavelength λ in the propagation region of the volume forward magnetostatic wave (MSFVW).

When the wavelength λ of the magnetostatic wave is increased, the number of waves per unit length is k = 2π / λ.
k, and Ω _H needs to be large, as can be seen from the inflection between the horizontal region and the curved region where Ω is constant in the characteristic curve shown in FIG. As can be seen from equation (10), it is necessary to increase the internal magnetic field strength Hin _in the region near the input / output electrodes as compared to the intermediate region. To this end, as schematically shown in FIG. 12 (a), the vicinity of both ends of the center pole piece in the core magnetic circuit 14 in the overall configuration shown in FIG. 9 is narrowed, and FIG. As shown, the wavelength λ in both end regions of the magnetic thin film 11 is made larger than the wavelength λ in the intermediate region due to an increase _in the internal magnetic field strength Hin.

On the other hand, when the insertion loss L _{S of the} ferrimagnetic thin film FM modulator of the present invention is large, the magnetostatic wave propagation path having a length required to achieve the required amount of frequency modulation is divided into a plurality of stages, and Preferably, each stage is configured as shown in FIG. 9 or FIG. 12 (a), and each FM modulation stage is connected in series via a high frequency transistor amplifying element in order to compensate for the insertion loss of each stage. It is. Note that the modulation coils 15 of each stage are sequentially connected in series as shown in FIG. 13 so that the modulation currents flowing through the modulation coils 15 of each stage in this series connection excite each coil 15 in the same phase. it is preferable to drive in series by the transistors T _R are connected to.

Further, the plurality of ferrimagnetic thin films FM
When the modulation stages are cascaded on the same magnetic thin film and are sequentially connected in series, the input and output strip electrodes 9 and 10 between the stages are formed as shown in FIG. It is preferable to prevent the occurrence of undesired situations such as oscillation due to undesired interstage coupling. That is, each of the strip electrodes 9 and 10 is constituted by two strip electrodes 9a, 9b and 10a, 10b arranged in parallel and opposed to each other at a distance of 2 ^{n + 1} / 4λ, and a capacitance C _{9 is provided} therebetween. and connected respectively by C _10, reaches the output strip electrodes 10a, to 10b, and the input strip electrodes 9a, the magnetostatic wave emanating from 9b is, the predetermined propagation direction is additive, are offset in the opposite direction , And propagating only in a predetermined direction, and furthermore, the adjacent input / output strip electrodes are sufficiently separated from each other and a ground strip conductor is provided.
16 interposed therebetween so as to stray coupling by undesired electromagnetic wave does not occur between the stages, each front strip electrodes 10a of the input electrode 10, 9 out in this state, inter-stage amplifying high-frequency amplifying transistor between 9a T _r Connect.

[0041]

As is apparent from the above description, according to the present invention, an FM modulator for modulating the propagation phase of a magnetostatic wave in a ferrimagnetic material by a signal is small in size and easy to manufacture. An extremely remarkable effect that stable operation with high sensitivity and low loss can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a typical example of a conventional FM modulator.

2 (a) and 2 (b) are a circuit diagram and a characteristic curve diagram, respectively, showing the configuration and operation of the main part of another typical example of the conventional FM modulator.

FIG. 3 is a characteristic curve diagram showing a mode of wave propagation in a ferrimagnetic material.

FIG. 4 is a characteristic curve diagram showing a mode of magnetization change due to a change in applied DC magnetic field strength of a ferrimagnetic material.

FIG. 5 is a perspective view showing a basic configuration of a main part of the ferrimagnetic thin film FM modulator of the present invention.

FIGS. 6A to 6C are diagrams respectively showing modes of magnetostatic wave generation in a ferrimagnetic thin film.

FIG. 7 is a characteristic curve diagram showing a mode of change in phase modulation depending on the wavelength of a magnetostatic wave in a ferrimagnetic material.

FIG. 8 is a characteristic curve diagram showing a range of an operation change depending on a wavelength of a magnetostatic wave in a ferrimagnetic thin film.

FIG. 9 is a cross-sectional view schematically showing the entire configuration of the ferrimagnetic thin film FM modulator of the present invention.

FIG. 10 is a circuit diagram showing a configuration example of an applied magnetic field intensity modulation circuit in the FM modulator of the present invention.

FIG. 11 is a circuit diagram showing another configuration example of the applied magnetic field intensity modulation circuit in the FM modulator of the present invention.

FIGS. 12A and 12B are a cross-sectional view and a diagram schematically showing another example of the overall configuration of the FM modulator of the present invention and an operation mode, respectively.

FIG. 13 is a circuit diagram showing still another configuration example of the applied magnetic field intensity modulation circuit in the FM modulator of the present invention.

FIG. 14 is a diagram showing another configuration example of the input / output strip electrodes in the FM modulator of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voltage controlled oscillator (VCO) 2 Modulator 3 Prescaler 4 Reference oscillator 5 Comparator 6 Low-pass filter (LPF) 7 Dielectric substrate 8 Ground plate 9, 9a, 9b Input strip electrode 10, 10a, 10b Output strip electrode 11 Free magnetic (YIG) thin film 12 Magnetic (GGG) substrate 13 Magnet plate 14 Magnetic circuit 15 Coil 16 Ground strip conductor

Claims (6)

(57) [Claims] An input and output strip electrodes are arranged on a ferrimagnetic thin film adhered on a substrate so as to be spaced apart from each other, and a high-frequency electromagnetic wave is inputted through the input strip electrodes. Applying a DC magnetic field to the body thin film and propagating a magnetostatic wave converted from the high-frequency electromagnetic wave between the input and output strip electrodes,
A ferrimagnetic thin film FM, wherein the intensity of the applied DC magnetic field is modulated by a signal to change the wavelength of the magnetostatic wave, thereby extracting a high-frequency output electromagnetic wave frequency-modulated by the signal. Modulator. 2. The magnetostatic wave is applied as a volume-advancing magnetostatic wave by applying the DC magnetic field perpendicular to the film surface of the ferrimagnetic thin film and also perpendicular to the input and output strip electrodes. Item 3. A ferrimagnetic thin film FM modulator according to item 1. 3. A change in the frequency modulation sensitivity of the high-frequency output electromagnetic wave due to the signal due to a temperature change by changing a drive current of a modulation element for modulating the intensity of the DC magnetic field by the signal in accordance with the temperature change. 3. The ferrimagnetic thin film FM modulator according to claim 1, wherein correction is performed. 4. The strength of the DC magnetic field applied to a region between the input and output strip electrodes in the region near the input and output strip electrodes in the ferrimagnetic thin film. 4. The ferrimagnetic thin film FM modulator according to claim 1, wherein the thickness of the ferrimagnetic thin film FM modulator is set to be larger than the height. 5. A ferrimagnetic thin film FM modulator according to claim 1, wherein a plurality of the ferrimagnetic thin film modulators are sequentially cascaded on the same ferrimagnetic thin film via respective amplifying elements. A ferrimagnetic thin-film FM modulator comprising a thin-film FM modulator configured to drive a modulation element for modulating the intensity of the DC magnetic field in the same phase by the signal. 6. The output strip electrode and the input strip electrode between the plurality of ferrimagnetic thin film FM modulators sequentially arranged in cascade via amplifying elements on the same ferrimagnetic thin film. A positive integer n and a direction of 2 nH / 4 wavelength of the magnetostatic wave and a mutual connection with each other via a capacitance or an inductance. 6. The ferrimagnetic thin film F according to claim 5, wherein said ferrimagnetic thin film F is constituted by a directional electrode comprising at least two parallel strips to reduce coupling between said output strip electrode and said input strip electrode.
M modulator.