JP6863156B2 - AC generator - Google Patents

Description

The present invention relates to an AC generator.

In recent years, with the progress of high frequency technology, the use of millimeter waves and terahertz waves having a frequency of 30 GHz to 300 GHz has become popular. In order to operate radars and sensors using high frequencies, phase control is required, but phase control becomes more difficult as the frequency used increases.

For example, a phased array radar including a plurality of antennas and a phase shifter attached to each antenna to control the phase of electromagnetic waves transmitted from the antennas has been proposed, but generally controls the phase of high-frequency electromagnetic waves. The phase shifters that can be made are large and expensive.

As another method for controlling the phase, a method of controlling the phase by a master-slave method in which a high-frequency current from a high-frequency oscillator as a master is injected into a high-frequency oscillator as a slave different from the master has been proposed (for example). , Patent Document 1).

In this method, the slave oscillates at a constant frequency in synchronization with the master. Then, the frequency difference before these are synchronized appears as a phase difference. Further, in general, a high frequency oscillator can change the oscillation frequency by an external force such as a voltage. Therefore, when the voltage applied to the slave is changed under the synchronized state, the frequency is fixed by the synchronization with the master, so that it does not change, and only the phase changes. Therefore, the phase of the slave can be controlled by changing the voltage applied to the slave or the like.

Japanese Patent No. 4724864

However, when a plurality of slaves are used in the master-slave system in which a high-frequency current is injected, the path error between the master and each slave becomes the phase error between each slave. When an oscillator including a resistor, a coil, a capacitor, or the like is used as a slave as in Patent Document 1, it is necessary to connect the master and the slave with a wiring of, for example, several cm due to the physique of the slave. As a result, the path error becomes at least about 100 μm. For example, when the oscillation frequency is 79 GHz, it is expected that a phase error of about 10 degrees will occur between each slave.

Such a phase error also becomes a problem when the phase of each slave is aligned and a master-slave type AC generator is used as an amplifier. It is possible to control the phase by the master-slave method even if an oscillator that oscillates at a low frequency is used, and it is desirable that the phase error is small also in this case.

In view of the above points, an object of the present invention is to provide an AC generator capable of reducing a phase error.

In order to achieve the above object, in the invention according to claim 1, a plurality of magnetic oscillating elements (2) for converting DC current or DC voltage into AC power, and an oscillator for applying an AC magnetic field to a plurality of magnetic oscillating elements ( 1), a conductor portion (31) electrically connected to an oscillator and electrically insulated from a plurality of magnetic oscillators, and an insulating layer (33) formed on the surface of the conductor portion are provided. The oscillator applies an alternating magnetic field generated by passing an alternating current through the conductor to a plurality of magnetic oscillating elements, and the plurality of magnetic oscillating elements are formed on the surface of the insulating layer. To synchronize.

The position where a plurality of magnetic oscillators (STOs: Spin Torque Oscillators) are manufactured and arranged can be controlled with high accuracy by a technique such as electron beam lithography. Therefore, by using a magnetic oscillator as a slave, the phase error of the AC magnetic field applied to each slave from the master oscillator is reduced, and the phase error of the AC power generated by each magnetic oscillator is reduced. can do.

The reference numerals in parentheses of each of the above means indicate an example of the correspondence with the specific means described in the embodiment described later.

It is a figure which shows the structure of the AC generator which concerns on 1st Embodiment. It is sectional drawing of the magnetic oscillator element. It is a circuit diagram of the modification of 1st Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, parts that are the same or equal to each other will be described with the same reference numerals.

(First Embodiment)
The first embodiment will be described. The AC generator of this embodiment is used, for example, in an amplifier.

Hereinafter, the AC generator of the present embodiment will be described with reference to the drawings. First, the overall configuration of the AC generator of the present embodiment will be described with reference to FIG. As shown in FIG. 1, the AC generator 100 of the present embodiment includes an oscillator 1, a plurality of STO2s, a connection unit 3, a power supply 4, a control unit 5, and a control unit 6.

The oscillator 1 is a device that converts a direct current / voltage supplied from a power source 4 via a control unit 5 into an alternating current and outputs it, and applies an alternating magnetic field to the STO 2 via the connecting unit 3.

The STO2 converts the supplied electrical energy into AC power, and is configured by laminating a plurality of films. Details of STO2 will be described later.

The AC current output by the oscillator 1 and the AC power output by the STO2 are, for example, a high-frequency current of 10 kHz or higher and a high-frequency power. Here, a case where the oscillator 1 outputs a high-frequency current, a high-frequency magnetic field is applied to the STO2, and the STO2 outputs high-frequency power will be described.

The connection portion 3 magnetically connects the oscillator 1 and the STO 2, and includes a conductor portion 31, a wiring 32, and an insulating layer 33. The conductor portion 31 is made of a material having high conductivity, which is generally used as wiring, such as Cu and Au. The connection unit 3 magnetically connects the oscillator 1 and the STO 2 by applying a magnetic field generated by the current flowing through the conductor unit 31 to the STO 2.

Specifically, the conductor portion 31 has a plate shape, and is connected to the oscillator 1 via wiring 32 at both ends in the longitudinal direction. Further, an insulating layer 33 is laminated on the conductor portion 31, and a plurality of films constituting STO2 are laminated on the insulating layer 33. As a result, the conductor portion 31 is electrically insulated from the STO2. Then, a high-frequency current output by the oscillator 1 flows through the conductor portion 31, and a high-frequency magnetic field generated by the high-frequency current is applied to the plurality of STO2s.

In the present embodiment, when a current flows through the conductor portion 31, a magnetic field passing through the STO2 is generated in a direction perpendicular to both the stacking direction of the plurality of films constituting the STO2 and the direction in which the current flows in the conductor portion 31. ..

The power supply 4 supplies a direct current / voltage to the oscillator 1 and the STO 2 via the control unit 5 and the control unit 6. The control unit 5 adjusts the frequency of the high-frequency current output by the oscillator 1 by changing the magnitude of the direct current / voltage supplied from the power supply 4 to the oscillator 1.

The control unit 6 adjusts the magnitude of the direct current / voltage supplied from the power supply 4 and supplies the DC current / voltage to the STO2. Further, the control unit 6 adjusts the frequency of the high frequency power generated by the STO2 by changing the magnitude of the direct current / voltage supplied to the STO2. In the present embodiment, the control unit 5 and the control unit 6 adjust the frequency of the high frequency current output by the oscillator 1 and the frequency of the high frequency power generated by the STO 2 so that the oscillator 1 and the STO 2 are synchronized with each other. The plurality of STO2s are connected to the control unit 6 in a state of being electrically isolated from each other.

Next, the details of STO2 will be described with reference to FIG. The STO2 includes a lower electrode 21, a base layer 22, an antiferromagnetic layer 23, a non-oscillating layer 24, an intermediate layer 25, an oscillating layer 26, a cap layer 27, and an upper electrode 28. These are sequentially laminated on the insulating layer 33.

The lower electrode 21 is made of a conductive material such as Ru, Cu, CuN, and Au, and is formed in a thin film on the insulating layer 33. The base layer 22 is composed of Ta, Ru, etc., and is formed in a thin film shape on the lower electrode 21. The base layer 22 serves as a base for forming the antiferromagnetic layer 23 by improving crystallinity and orientation.

The antiferromagnetic layer 23 is composed of IrMn, PtMn, etc., and is formed in a thin film shape on the base layer 22. The antiferromagnetic layer 23 is for fixing the magnetization direction of the non-oscillating layer 24 by exchange coupling.

The non-oscillating layer 24 is made of a ferromagnetic material such as Co, Fe, or Ni, or is composed of the ferromagnetic material and B, and is formed in a thin film on the antiferromagnetic layer 23. The non-oscillating layer 24 has an easy axis of magnetization in the plane direction of the non-oscillating layer 24, and the magnetization direction of the non-oscillating layer 24 is changed here by the non-oscillating layer 24 due to exchange coupling with the antiferromagnetic layer 23. Is fixed in the plane direction of. In addition to the above materials, Pt and Pd may be used to form the non-oscillating layer 24. Further, the non-oscillating layer 24 may be formed by using a highly magnetic anisotropy material such as GaMn, FePt (Pd), CoPt (Pd, Ni).

Although not shown, a magnetic layer made of NiFe or the like is formed between the base layer 22 and the antiferromagnetic layer 23. Further, between the antiferromagnetic layer 23 and the non-oscillating layer 24, the magnetization direction of the magnetic layer composed of CoFe or the like and the magnetic layer composed of Ru or the like and formed above and below is fixed by the RKKY interaction. Layer is formed.

That is, when the antiferromagnetic layer 23 is composed of IrMn and the non-oscillating layer 24 is composed of CoFeB, the layers sandwiched between the base layer 22 and the intermediate layer 25 are arranged in order from the base layer 22 side, NiFe / IrMn / CoFe. It has a laminated structure such as / Ru / CoFeB.

As described above, STO2 of the present embodiment includes a synthetic ferrimagnetic layer composed of a plurality of magnetic layers by using RKKY interaction such as Ru. In the configuration using the synthetic ferrimagnetic layer, the magnetic fields leaked from these two magnetic layers are applied to the oscillation layer 26 by reversing the magnetization directions of the two magnetic layers formed above and below the Ru. The impact can be reduced.

The intermediate layer 25 is composed of MgO, Al— _Ox , Cu, Ag, etc., and is formed in a thin film on the non-oscillating layer 24. The resistance value of the portion of STO2 composed of the non-oscillating layer 24, the intermediate layer 25, and the oscillating layer 26 changes depending on the angle between the magnetization direction of the non-oscillating layer 24 and the magnetization direction of the oscillating layer 26. Case where the intermediate layer 25 MgO, an insulator such as _{Al-O x,} non-oscillating layer 24, intermediate layer 25, TMR (Tunneling Magneto Resistance) element is constituted by lamination of the oscillation layer 26. When the intermediate layer 25 is made of a conductor such as Cu or Ag, a GMR (Giant Magneto Resistance) element is formed by laminating the non-oscillating layer 24, the intermediate layer 25, and the oscillating layer 26. Although the case where the intermediate layer 25 is composed of an insulator or a conductor has been described here, the intermediate layer 25 may also be composed of a semiconductor.

The oscillation layer 26 is made of a ferromagnetic material such as Co, Fe, or Ni, or is composed of the ferromagnetic material and B, and is formed in a thin film on the intermediate layer 25. The oscillation layer 26 has an easy-to-magnetize axis in the thickness direction, and the magnetization direction changes depending on an external magnetic field. In addition to the above materials, Pt and Pd may be used to form the oscillation layer 26. Further, the oscillation layer 26 may be formed by using a highly magnetic anisotropy material such as GaMn, FePt (Pd), CoPt (Pd, Ni). Further, the oscillation layer 26 may have a laminated structure of CoFeB / GaMn, CoFeB / FePt, or the like. Further, the oscillation layer 26 may have a laminated structure of CoFeB / Ta / GaMn or the like.

As will be described later, the oscillating layer 26 resonates with a high frequency magnetic field. By forming the oscillating layer 26 thinner than the non-oscillating layer 24, the oscillating layer 26 is more likely to resonate due to the high frequency magnetic field than the non-oscillating layer 24, but the thickness of the oscillating layer 26 is the thickness of the non-oscillating layer 24. It may be more than that.

The cap layer 27 is made of Ta, Ru, etc., and is formed in a thin film on the oscillation layer 26. The cap layer 27 is for protecting the oscillation layer 26. Further, when CoFeB or the like is used for the oscillation layer 26 as described later, it also serves as an absorption layer for diffusing B in CoFeB.

The upper electrode 28 is made of a conductive material such as Au, Cu, CuN, and Ru, and is formed in a thin film on the cap layer 27. Such STO2 can be manufactured by forming each layer on the insulating layer 33 in order.

When CoFeB is used for the non-oscillating layer 24 and the oscillating layer 26, CoFeB is first formed into an amorphous film. However, since B is included, it becomes amorphous without any special action. MgO is oriented (001) on the amorphous CoFeB to form a film. CoFeB is formed into an amorphous film on the film, and the cap layer 27 is formed. Then, by performing a heat treatment at 300 to 350 ° C., B in CoFeB diffuses into the MgO layer, the cap layer 27, or the base layer 22, and crystallizes from amorphous to bcc (001) orientation. Crystallization of CoFeB / MgO / CoFeB in this way leads to a high MR ratio (magnetoresistive ratio), that is, a high output of high-frequency power.

The operation of the AC generator 100 will be described. The AC generator 100 synchronizes a plurality of STO2s by a master-slave method in which the oscillator 1 is the master and the STO2 is the slave.

First, the power supply 4 and the control unit 5 supply a direct current / voltage to the oscillator 1, and the oscillator 1 converts the supplied direct current / voltage into a high-frequency current and outputs the current. The high-frequency current output by the oscillator 1 flows through the conductor section 31, and the high-frequency magnetic field generated thereby is applied to the STO2.

Further, a DC voltage is applied to the STO2 by the power supply 4 and the control unit 6, and a DC current flows through the STO2. In this embodiment, this direct current flows from the non-oscillating layer 24 to the oscillating layer 26. At this time, the electrons move from the oscillating layer 26 to the non-oscillating layer 24.

The magnetization of the oscillating layer 26 is precessed by the spin torque of electrons. Then, as the magnetization of the oscillation layer 26 precesses, the resistance of the STO2 constantly changes due to the MR effect, and high-frequency currents and voltages are generated at both ends of the STO2, and high-frequency power is generated by this. That is, the direct current / voltage is converted into high frequency power.

The frequency of this high-frequency power changes depending on the material constituting STO2 and the magnitude of the current / voltage supplied from the control unit 6. Further, the frequency of the high-frequency current output by the oscillator 1 and the frequency of the high-frequency magnetic field generated by the high-frequency current flowing through the conductor unit 31 change depending on the magnitude of the current / voltage supplied from the control unit 5. Assuming that the frequency of the high-frequency current output by the oscillator 1 is f1, the frequency of the high-frequency power generated by STO2 is f2, and m and n are natural numbers, the control unit 5 and the control unit 6 have f2 = f1 · n / m. Therefore, the magnitudes of the currents and voltages supplied to the oscillator 1 and the plurality of STO2s are changed. As a result, the oscillation layer 26 resonates with the high-frequency magnetic field, and the oscillator 1 and STO2 are synchronized.

The oscillator 1 and STO2 are easily synchronized when m = 1, that is, f2 = f1 · n, and when n = 1, that is, f2 = f1 / m, and further, the smaller m and n, the more synchronized. Cheap. Specifically, the oscillator 1 and STO2 are likely to be synchronized when the frequency f2 is equal to any one of f1 / 4, f1 / 3, f1 / 2, f1, 2f1, 3f1, and 4f1. Then, the oscillator 1 and the STO2 are more easily synchronized when the frequency f2 is equal to any of f1 / 2, f1 and 2f1, and are particularly easy to be synchronized when f2 = f1. In the present embodiment, the control unit 5 and the control unit 6 adjust the magnitudes of the direct current and voltage supplied to the oscillator 1 and the STO 2 so that f2 = f1.

The state in which these are synchronized is also the state in which a plurality of STO2s are synchronized. In this state, high-output high-frequency power can be obtained by synthesizing high-frequency power generated by a plurality of STO2s.

In a conventional AC generator that uses an oscillator equipped with a resistor, a coil, a capacitor, or the like as a slave, it is necessary to connect the master and the slave with a wiring of, for example, several cm due to the physique of the slave. As a result, the path error between the master and each slave is at least about 100 μm. For example, when the oscillation frequency is 79 GHz, it is expected that a phase error of about 10 degrees will occur between each slave.

On the other hand, in the present embodiment, STO2 is used as a slave, and the position where a plurality of STO2s are manufactured and arranged can be controlled with high accuracy by a technique such as electron beam lithography. For example, the position of STO2 can be controlled with an accuracy of several nm or less, and when f1 = 79 GHz, the phase error between STO2 caused by the distance between STO2 can be set to 0.001 degree or less. Therefore, in the present embodiment, the phase error of the high frequency power generated by each STO2 can be reduced as compared with the conventional case. Further, as a result, the output can be increased when the AC generator 100 is used as an amplifier.

Further, in the configuration in which each slave is electrically connected to the master, the power consumption of the master is consumed by each slave, so that the power consumption of the master increases according to the number of slaves. On the other hand, in the present embodiment in which the oscillator 1 which is the master and each STO2 which is the slave are electrically isolated and magnetically connected, the power of the master is not consumed by the slave, so that the master is consumed. The increase in power can be suppressed.

When the oscillator 1 and each STO2 are synchronized, if the magnitude of the DC current / voltage supplied by the control unit 6 to the STO2 is slightly changed, the frequency f2 of the high frequency power does not change due to these synchronizations. The phase changes.

If the control unit 6 is configured to individually change the magnitudes of the direct current and voltage supplied to each STO 2, the AC generator 100 can be used, for example, between vehicle-to-vehicle communication and road-to-vehicle distance, by utilizing such a phase change. It can be used as a phased array radar for communication. That is, an antenna is connected to STO2 so that high-frequency electromagnetic waves are emitted from this antenna, and further, by individually adjusting the phase of the high-frequency power generated by each STO2, the high-frequency electromagnetic waves transmitted from the entire plurality of antennas. The directivity of the can be controlled.

FIG. 3 is a diagram showing an example of a circuit when an antenna is connected to STO2. As shown in FIG. 3, a bias circuit 7 that separates the direct current input to the STO2 and the high-frequency current output by the STO2 is connected to the STO2. The bias circuit 7 includes an inductor 71 and a capacitor 72, an inductor 71 is connected between the STO 2 and the control unit 6, and the STO 2 is connected to the antenna 8 via the capacitor 72. With such a configuration, the direct current from the control unit 6 is suppressed from flowing into the antenna 8, and only the high frequency power output by the STO 2 is supplied to the antenna 8. Then, the high-frequency current output by the STO2 flows through the antenna 8, so that the high-frequency electromagnetic wave is transmitted.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the claims.

For example, in the first embodiment, the lower electrode 21 is formed on the surface of the insulating layer 33, and the base layer 22 to the upper electrode 28 are laminated on the lower electrode 21, but the upper electrode 28 is formed on the surface of the insulating layer 33. May be formed and the cap layer 27 to the lower electrode 21 may be laminated on the upper electrode 28.

Further, in the first embodiment, a plurality of films constituting STO2 are laminated on the insulating layer 33, but the insulating layer 33 and the conductor portion 31 may be laminated on the STO2. Further, the conductor portion 31 and the insulating layer 33 may be arranged at other positions where a magnetic field can be applied to the STO2.

Further, the STO2 does not have to include the base layer 22, the antiferromagnetic layer 23, and the cap layer 27. Further, in the first embodiment, the non-oscillating layer 24 has an easy magnetization axis in the plane direction, and the oscillation layer 26 has an easy magnetization axis in the thickness direction. However, the non-oscillation layer 24 and the oscillation layer 26 May have an easy axis of magnetization in other directions. For example, the non-oscillating layer 24 may have an easy-to-magnetize axis in the thickness direction, and the oscillating layer 26 may have an easy-to-magnetize axis in the plane direction.

Further, the oscillator 1 and STO2 are easy to synchronize when m = 1 or n = 1, but f1 and f2 are adjusted so that m ≠ 1 and n ≠ 1, for example, f2 = f1 ・ 2/3. May be good.

Further, the AC current output by the oscillator 1, the AC magnetic field applied to the STO2, and the AC power output by the STO2 may be an AC current of less than 10 kHz, an AC magnetic field, or an AC power.

1 oscillator 2 STO

Claims (5)

A plurality of magnetic oscillator elements (2) that convert DC current or DC voltage into AC power,
An oscillator (1) that applies an alternating magnetic field to the plurality of magnetic oscillator elements,
A conductor portion (31) electrically connected to the oscillator and electrically insulated from the plurality of magnetic oscillator elements.
An insulating layer (33) formed on the surface of the conductor portion is provided.
The oscillator applies an alternating magnetic field generated by passing an alternating current through the conductor portion to the plurality of magnetic oscillator elements.
The plurality of magnetic oscillator elements are formed on the surface of the insulating layer.
An AC generator that synchronizes the magnetic oscillator element with the oscillator. The frequency of the output of the oscillator is set to f1.
When the frequency of the AC power generated by the plurality of magnetic oscillators is f2,
The AC generator according to claim 1, wherein the frequency f2 is equal to any one of f1 / 4, f1 / 3, f1 / 2, f1, 2f1, 3f1, and 4f1. The AC generator according to claim 1 or 2, wherein each of the plurality of magnetic oscillating elements includes an oscillating layer (26) that resonates with an alternating magnetic field applied by the oscillator. The frequency of the AC power generated by the plurality of magnetic oscillators is adjusted by supplying a DC current or a DC voltage to the plurality of magnetic oscillators and changing the magnitude of the DC current or the DC voltage to adjust the frequency of the AC power generated by the plurality of magnetic oscillators. The AC generator according to any one of claims 1 to 3, further comprising a control unit (6) that synchronizes an oscillating element with the oscillator. The AC generator according to any one of claims 1 to 4, further comprising a control unit (5) that adjusts the output frequency of the oscillator and synchronizes the magnetic oscillator element with the oscillator.

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