WO2011027423A1 - 周波数変換装置 - Google Patents
周波数変換装置 Download PDFInfo
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- WO2011027423A1 WO2011027423A1 PCT/JP2009/065304 JP2009065304W WO2011027423A1 WO 2011027423 A1 WO2011027423 A1 WO 2011027423A1 JP 2009065304 W JP2009065304 W JP 2009065304W WO 2011027423 A1 WO2011027423 A1 WO 2011027423A1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B15/00—Generation of oscillations using galvano-magnetic devices, e.g. Hall-effect devices, or using superconductivity effects
- H03B15/006—Generation of oscillations using galvano-magnetic devices, e.g. Hall-effect devices, or using superconductivity effects using spin transfer effects or giant magnetoresistance
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive devices
Definitions
- the present invention relates to a frequency conversion device for performing frequency conversion used in a wireless communication device or the like.
- frequency conversion elements use nonlinear elements such as semiconductor diodes and FETs.
- the purpose of frequency conversion is to input a signal having a certain frequency to the frequency conversion element and to output a signal having a frequency component different from the input signal.
- a current is applied to the non-linear resistance r (i) is considered.
- the signal input to the nonlinear element is the sum of two different frequency signals ⁇ 1 and ⁇ 2 .
- Input current is Then, the voltage generated at both ends of the nonlinear resistance element is Thus, the sum ( ⁇ 1 + ⁇ 2 ) and difference ( ⁇ 1 ⁇ 2 ) of the frequencies of the input signals can be extracted.
- the sum of frequencies is called an up-converter, and the frequency difference is called a down-converter.
- frequency conversion Creating a signal having a frequency different from the input signal is called frequency conversion.
- a frequency conversion for extracting a frequency that is twice or an integer multiple of a certain frequency signal input as shown in the formula (I) is called frequency multiplication, but the frequency conversion of the present invention is Including frequency multiplication.
- ⁇ ⁇ Frequency conversion is a very important technology.
- a frequency conversion element is used for frequency mixing in a transmitter and a receiver.
- the generation of millimeter-wave and quasi-millimeter-wave signals is performed by a combination of a microwave oscillator and a frequency multiplier because there is no handy oscillator that can directly generate signals in these frequency bands. .
- the nonlinear elements used for frequency conversion mainly use nonlinearities exhibited by semiconductor elements such as diodes and FETs.
- a Schottky diode is often used for a frequency conversion element used in a microwave integrated circuit (MIC) formed by mounting individual elements on a dielectric substrate.
- a frequency conversion element for the purpose of frequency multiplication is often used as a non-linear capacitance element (varactor) by applying a reverse bias to a diode.
- MMICs Monolithic microwave integrated circuits
- active elements passive elements, passive active elements, and the like are manufactured on the same substrate in a batch and integrated manner using a semiconductor process.
- FETs are often used as active elements such as amplifiers and oscillators, so it is difficult to incorporate a diode designed specifically for frequency conversion into the MMIC because of restrictions on the consistency of the manufacturing process. Therefore, in the case of frequency conversion in the MMIC, the nonlinearity of the FET itself is often used.
- a frequency conversion element is incorporated in an MMIC, the circuit area is limited from the viewpoint of integration. Therefore, a frequency conversion element having a small scale is preferred.
- MMICs can be broadly divided into those composed of Si-based devices and those composed of compound semiconductor devices. Both Si-based devices and compound semiconductor devices have advantages and disadvantages, but it is difficult to mount them on the same substrate in monolithic microwave integrated circuit MMIC. This often requires epitaxial growth during the film forming process of each device.
- Si-based MMICs a silicon substrate is used, and for compound semiconductors, a substrate such as GaAs is used. The affinity between the Si-based device and the compound semiconductor device manufacturing process is very poor.
- a frequency conversion element using a semiconductor generally has no frequency selectivity in the frequency conversion element itself. Therefore, if it is desired to perform frequency conversion only for a specific frequency, it is necessary to provide a filter or the like. In a frequency conversion element using a semiconductor, the frequency conversion itself cannot have a switching function.
- giant magnetoresistive elements and tunneling magnetoresistive elements (TMR) that exhibit a magnetoresistive effect are being applied as sensors and memory elements.
- This utilizes the fact that the resistance value of the magnetoresistive element changes depending on the relative angle of the magnetic moment of the magnetization free layer and the magnetization fixed layer in the magnetoresistive element. That is, the giant magnetoresistive element and the tunnel magnetoresistive element have the feature that a change in external magnetic field can be detected as a change in resistance value (sensor effect), and the magnetic hysteresis becomes a resistance value hysteresis (memory effect). It is used. More recently, device applications utilizing spin injection torque in addition to the magnetoresistive effect have been promoted.
- the spin injection torque causes the exchange of angular momentum between conduction electrons and localized electrons by passing a spin-polarized current in the ferromagnetic material, and the localized magnetic moment It is the generated magnetic torque.
- This makes it possible to switch the magnetization without using an external magnetic field, such as spin-injection magnetization reversal and the nonlinear effect caused by the precession of magnetization induced by spin-injection torque.
- Applications such as wave amplifiers have been promoted (see Patent Document 1).
- Non-Patent Document 3 The operating principle of the microwave detector shown in Non-Patent Document 3 is a homodyne detection method, and a DC voltage can be detected for one input AC signal. This utilizes a non-linear effect in which the magnetic moment causes precession due to the spin torque induced by the alternating current signal applied to the magnetoresistive element, and the resistance value periodically changes. The frequency of the change in resistance value is equal to the frequency of the input AC signal, and the effect shown by the formula (I) appears.
- homodyne detection is performed using this, but another important technique is used. It uses the spin injection FMR effect. In the minute AC signal, since the current value is very small, the precession of the induced magnetization is very small, and the output DC voltage is very small.
- the frequency of the input AC signal is near the ferromagnetic resonance frequency
- the precession of magnetization is amplified by the resonance effect. This makes it possible to detect a larger DC voltage.
- the detection function using this magnetoresistive element is called a spin torque diode effect.
- the ferromagnetic resonance is also caused by the spin injection torque, and further, the nonlinear effect of the magnetoresistive element is sufficiently exhibited by using the ferromagnetic resonance, so that application in the microwave band is expected.
- frequency conversion elements using semiconductors such as semiconductor diodes and FETs have a wide frequency band, frequency conversion cannot be performed selectively.
- the frequency conversion function itself cannot have a switching function.
- a first aspect of the present invention is a frequency conversion device for applying a magnetic field to a frequency conversion element including a magnetoresistive element including a magnetization free layer, an intermediate layer, and a magnetization fixed layer, and the frequency conversion element
- a magnetic field application mechanism a local oscillator for applying a local oscillation signal to the frequency conversion element, and an input terminal electrically connected to the frequency conversion element and for inputting an external input signal
- the local oscillator includes a magnetoresistive element capable of oscillating the local oscillation signal by outputting an alternating voltage according to a change in resistance of the local oscillator.
- the magnetization precession is amplified by the spin injection torque, and the resulting element Frequency conversion of the input signal is performed by the non-linearity of the resistance. Since the frequency band of the magnetic resonance frequency is narrow, frequency conversion is performed only when at least one of the input signals input to the magnetoresistive element has a frequency near the magnetic resonance, and the frequency of the input signal Is not out of the ferromagnetic resonance frequency band, the frequency conversion is not performed. By using such an effect, it is possible to perform frequency conversion in a frequency selective manner. Further, by changing the magnitude of the magnetic field applied to the frequency conversion element, the frequency conversion effect can have a switching function.
- the frequency conversion element since the frequency conversion element uses the magnetic resonance frequency excited by the spin injection torque, it is possible to perform frequency conversion by selecting a specific frequency.
- FIG. It is a figure which shows the result of the frequency conversion using the frequency converter shown in FIG. It is a schematic block diagram of the frequency converter provided with the frequency conversion element which concerns on one Embodiment of this invention. It is a figure explaining the method to give a switching function to the frequency converter based on one Embodiment of this invention. It is a schematic block diagram of the frequency converter provided with the frequency conversion element which concerns on one Embodiment of this invention. It is a schematic block diagram of the frequency converter provided with the frequency conversion element which concerns on one Embodiment of this invention.
- FIG. 1 shows an example of the frequency conversion device of the present invention.
- the frequency conversion device 100 includes a frequency conversion element 10 composed of a magnetoresistive element, a magnetic field application mechanism 15 that applies a magnetic field to the frequency conversion element 10, a local oscillator 102 having a magnetoresistive element, an input terminal 104, an input terminal 104, and And a wiring 103 for electrically connecting the local oscillator 102 to the frequency conversion element 10.
- the frequency conversion device 100 is a device that performs frequency conversion by outputting a difference signal between the high-frequency signal f 1 input from the input signal source 101 by the frequency conversion element 10 and the high-frequency signal f 2 applied from the local oscillator 102. .
- the frequency conversion device 100 includes the magnetic field application mechanism 15 for controlling the function of the frequency conversion element.
- the magnetic field application mechanism can be configured by a permanent magnet, a coil, or the like.
- the magnetic field application mechanism is not limited to the mechanism as long as it can apply a magnetic field to the frequency conversion element 10.
- the frequency conversion element 10 includes a magnetoresistive element based on a three-layer structure of a magnetization free layer (ferromagnetic layer), an intermediate layer, and a magnetization fixed layer (ferromagnetic layer).
- the intermediate layer include alumina, magnesium oxide, and copper. Since the non-linearity for obtaining the frequency conversion effect is derived from the element resistance change due to the magnetoresistance effect, it is preferable to use a magnetoresistive element having a large magnetoresistance ratio (MR ratio of 100% or more). Therefore, with reference to FIG. 2, the structure of a frequency conversion element using a tunnel magnetoresistive element having an MgO barrier layer as an intermediate layer will be described. However, in practicing the present invention, the magnetoresistive element used is not limited to the above-described magnetoresistive element.
- FIG. 2 is a schematic cross-sectional view of the frequency conversion element according to the present embodiment. A specific configuration of each layer will be described with reference to FIG.
- An antiferromagnetic layer 3 is formed on the lower electrode layer 2, and a magnetization fixed layer 4 is formed on the antiferromagnetic layer 3.
- reference numeral 4 b corresponds to the magnetization fixed layer.
- a tunnel barrier layer (intermediate layer) 5 is formed on the magnetization fixed layer 4
- a magnetization free layer 6 is formed on the tunnel barrier layer 5
- a protective layer 7 is formed on the magnetization free layer 6. ing.
- the antiferromagnetic layer 3 is PtMn (15 nm).
- the magnetization fixed layer 4 is a laminated ferrimagnetic fixed layer made of CoFe (2.5 nm) / Ru (0.85 nm) / CoFeB (3 nm), and CoFeB, which is an upper layer of the laminated ferrimagnetic fixed layer, is formed in the magnetization fixed layer 4b.
- the tunnel barrier layer (intermediate layer) 5 is MgO (1.0 nm).
- the magnetization free layer 6 is CoFeB (2 nm).
- the film thickness of the magnetization fixed layer and the magnetization free layer is 3 nm and 2 nm, respectively, but is not limited thereto.
- the film thickness is an example, and the present invention is not limited to this.
- the magnetic moment of the magnetization fixed layer needs to be larger than that of the magnetization free layer. This is because when the magnetization fixed layer has a smaller magnetic moment, the magnetization fixed layer causes precession due to the spin injection torque.
- the frequency conversion element is formed by processing the magnetoresistive thin film into a columnar shape having a junction area of 1 ⁇ m 2 or less. In order to exert an effective spin injection torque, it is better to reduce the junction area of the element, and it is preferable to make the size 0.04 ⁇ m 2 or less.
- the signal input to the frequency conversion element 10 is a high-frequency signal, it is preferable to use a slot line, a microstrip line, a coplanar waveguide, or the like that takes impedance matching into consideration. It is also preferable to consider impedance matching for the wiring 103 from the input signal source 101 to the frequency conversion device 100.
- FIG. 3 is a diagram for explaining the relationship between the film thickness of the intermediate layer of the frequency conversion element 10 and the junction resistance.
- the impedance of the frequency conversion element 10 can be controlled by changing the size of the element and the thickness of the intermediate layer 5 in FIG.
- the normalized resistance value of the element standardized with an area of 1 ⁇ m ⁇ 1 ⁇ m
- a desired resistance value can be obtained with a desired junction area by appropriately selecting the thickness of the magnesium oxide.
- FIGS. 4A and 4B transmission characteristic evaluation by impedance matching of the frequency conversion element according to the present embodiment will be described.
- a sample with an element resistance of 40 ⁇ by changing the film thickness of MgO as the intermediate layer and the element size, and a sample with 300 ⁇ , and measured S11 (reflectance) for each, and transmission characteristics was evaluated.
- the results are shown in FIGS. 4A and 4B.
- the transmission characteristic is clearly better when the impedance matching is better (FIG. 4A).
- the transmission efficiency is 0.8 or more in the entire frequency range from 0 to 20 GHz, whereas in the sample with an element resistance of 300 ⁇ , the transmission efficiency is less than 0.4.
- the local oscillator 102 includes a magnetoresistive element 30, a DC application terminal 32 for connecting a DC voltage source or a DC current source to the magnetoresistive element 30, and a high frequency output terminal for outputting a high frequency generated by the magnetoresistive element 30. 33 and a bias T31 for separating direct current and alternating current components.
- FIG. 5B An example of the magnetoresistive element 30 included in the local oscillator 102 is shown in FIG. 5B.
- the magnetization fixed layer 52 is formed on the lower electrode 51
- the intermediate layer 53 is formed on the magnetization fixed layer 52
- the magnetization free layer 54 is formed on the intermediate layer 53
- the magnetization free layer 54 is formed.
- An upper electrode 56 is formed on the top.
- a DC power source is disposed in the magnetoresistive element 30 shown in FIG. 5B. That is, the lower electrode 51 is grounded, and the upper electrode 55 is electrically connected to the DC application terminal 32 via the bias T31.
- the magnetic moment of the magnetization free layer 54 of the magnetoresistive element 30 receives a spin torque and causes precession.
- the precession of the magnetic moment is periodic, and its period becomes the ferromagnetic resonance frequency. With the periodic movement of the magnetization free layer 54, the resistance value of the element also changes periodically (because the resistance value of the element is determined by the relative angle between the magnetization free layer 54 and the magnetization fixed layer 52).
- the magnetoresistive element 30 When the resistance value changes periodically with a constant voltage or current applied, the current or voltage output from the magnetoresistive element 30 changes periodically. Since the resistance value and the current value or the resistance value and the voltage value periodically change in the vicinity of the ferromagnetic resonance frequency, the magnetoresistive element 30 outputs high frequency power.
- the bias T31 is provided to separate direct current and alternating current. Accordingly, the direct current input from the direct current application terminal 32 is applied only to the magnetoresistive element 30, and the high frequency generated in the magnetoresistive element 30 is output only from the high frequency output terminal 33.
- a predetermined DC voltage DC current
- the input DC voltage is input to the upper electrode 55 of the magnetoresistive element 30 through the bias T31.
- the magnetic moment of the magnetization free layer 54 receives a spin torque, and a periodic precession of the magnetic moment is generated.
- the resistance value of the resistance element 30 also changes periodically. In this case, the magnetoresistive element 30 outputs a high-frequency signal f 2 with respect to bias T31 by periodic changes of the resistance value.
- the bias T 31 When the high frequency signal f 2 is input from the magnetoresistive element 30, the bias T 31 outputs the high frequency signal f 2 to the high frequency output terminal 33, and the high frequency output terminal 33 transmits the high frequency signal f 2 via the wiring 103. To the frequency conversion element 10.
- a constant voltage source is connected to the DC application terminal 32 of FIG. 5A, a voltage of 0.6 V is applied to the magnetoresistive element 30, a spectrum analyzer is connected to the high frequency output terminal 33, and the magnetic The power spectrum of the high frequency power generated from the resistance element 30 was measured. The result is shown in FIG.
- the bandwidth of the power spectrum of the magnetoresistive element 30 is about 350 MHz. Therefore, in order to apply a narrower bandwidth spectrum to the frequency conversion element 10, it is preferable to provide a band pass filter 40 between the bias T31 and the high frequency output terminal 33 as shown in FIG.
- the magnetoresistive element 30 is used as an element for oscillating the local oscillation signal of the local oscillator 102, the entire frequency converter can be reduced in size.
- the structure of the magnetoresistive element 30 is not limited to the structure shown in FIG. 5B.
- the resistance of the magnetoresistive element is changed (by an external factor such as current or magnetic field), and the magnetoresistive element is changed to an AC voltage in accordance with the resistance change. It is essential to output (high frequency power). Therefore, in the present invention, any structure of the magnetoresistive element may be used as long as it can output an alternating voltage according to its own resistance change.
- the frequency conversion element can be produced on any substrate, which is a major feature of the frequency conversion element using the magnetoresistive element in one embodiment of the present invention, without being limited to the substrate material. .
- the normalized resistance value and magnetoresistance ratio of the frequency conversion element 10 manufactured on the silicon substrate and the frequency conversion element manufactured on the GaAs substrate were compared.
- the results are shown in Table 1. Even if the normalized resistance value and the magnetoresistance ratio of the frequency conversion element manufactured on the silicon substrate and the frequency conversion element manufactured on the GaAs substrate are compared, the same characteristics can be obtained.
- a frequency conversion element is fabricated on a silicon substrate with thermally oxidized silicon, an AlTiC substrate (ceramic), an MgO substrate, a glass substrate, a sapphire substrate, and a silicon substrate with silicon nitride, and the normalized resistance value and magnetoresistance ratio A comparison was made.
- the standardized resistance values are all around 3 ⁇ , and the variation is within 1 ⁇ .
- the magnetoresistance ratio was over 100% for all frequency conversion elements. From this, it can be seen that when the frequency conversion element according to the present invention is used, unlike the conventional semiconductor frequency conversion device, the substrate material is not restricted.
- the frequency of any one of a plurality of signals input to the frequency conversion element 10 is included in the ferromagnetic resonance frequency band of the magnetization free layer 6 in the frequency conversion element 10, magnetization is caused by spin injection torque. The precession of the input signal is amplified, and the frequency conversion of the input signal is performed by the non-linearity of the element resistance caused thereby. Since the frequency band of the ferromagnetic resonance frequency is narrow, only when at least one of the input signals input to the magnetoresistive element included in the frequency conversion element 10 is in the frequency band near the ferromagnetic resonance frequency. When frequency conversion is performed and the frequencies of all input signals deviate from the ferromagnetic resonance frequency band, the frequency conversion is not performed. Therefore, in order to realize frequency conversion using the frequency conversion element 10 using a magnetoresistive element, it is necessary that at least one of the input signals has a frequency included in the ferromagnetic resonance frequency band.
- the ferromagnetic resonance frequency band of the magnetization free layer 6 is a parameter depending on the material, but can be changed by applying an external magnetic field to the magnetization free layer 6 in FIG.
- FIG. 8 shows the external magnetic field dependence of the ferromagnetic resonance frequency of the frequency conversion element 10 manufactured this time.
- the spin torque diode effect was used to measure the ferromagnetic resonance frequency.
- the ferromagnetic resonance frequency can be changed from about 2 GHz to about 9 GHz by applying an external magnetic field. This result is an example, and a larger resonance frequency can be obtained by applying a larger magnetic field.
- FIG. 9 is a schematic configuration diagram of a second frequency conversion device including a frequency conversion element.
- the permanent magnet 151 is disposed at a distance where an appropriate external magnetic field is applied to the frequency conversion element 10, and the position of the permanent magnet 151 is set so that the ferromagnetic resonance frequency is 4.72 GHz.
- the application direction of the external magnetic field is a direction in which the magnetizations of the magnetization fixed layer 4 and the magnetization free layer 6 prefer to be parallel, and is inclined by 30 ° from the easy axis direction of the magnetization fixed layer 4.
- the external magnetic field is applied at an angle of 30 °, but may be any angle other than 0 ° or 180 °.
- a magnetic field having a ferromagnetic resonance frequency of 4.72 GHz is applied to the frequency conversion element 10 from the permanent magnet 151. Therefore, a difference signal between 3 GHz (high frequency signal f 1 ) and 4.72 GHz (high frequency signal f 2 ) is output from the frequency conversion element 10.
- a spectrum analyzer 20 is connected to the output side of the frequency converter 100.
- FIG. 10 shows an output signal observed by the spectrum analyzer 20. It can be seen that frequency conversion is realized by observing a 1.72 GHz signal corresponding to the difference signal between the input signal of 3 GHz (high frequency signal f 1 ) and the local oscillation signal of 4.72 GHz (high frequency signal f 2 ).
- FIG. 11 is a schematic configuration diagram of a third frequency conversion device including a frequency conversion element.
- the magnetic field application mechanism 15 is the permanent magnet 151.
- a coil 21 may be arranged to apply a current-induced magnetic field to the frequency conversion element 10.
- the magnitude of the magnetic field can be controlled not only by the arrangement position of the coil 21 but also by the magnitude of the current applied to the coil 21 and the number of turns of the coil 21. Therefore, it is preferable to provide a control power source (control unit) 25 for controlling the current flowing through the coil 21.
- the coil 21 is used.
- the current-induced magnetic field can be realized by a method other than the coil by using a simple electric wiring.
- the coil is disposed only on one side of the frequency conversion element 10, but it may be disposed on both sides.
- the magnitude of the induced magnetic field is changed by changing the magnitude of the current applied to the coil 21. Can do. By utilizing this, the ferromagnetic resonance frequency of the frequency conversion element 10 can be changed.
- the difference signal frequency also disappears when the direction in which the magnetic field is applied is antiparallel to the easy axis direction of the magnetization fixed layer (pinned layer) 4 (the angle is 180 °).
- the frequency conversion effect can be turned off by setting the direction of applied magnetization to 0 ° or 180 ° with respect to the easy axis of the magnetization free layer 6.
- the frequency converter of the present invention controls the presence or absence of frequency conversion by controlling the external magnetic field applied to the frequency conversion element 10 by moving the permanent magnet 151 that applies the external magnetic field to the frequency conversion element 10.
- a switching function for switching can be provided.
- switching on a state in which an appropriate external magnetic field is always applied to the frequency conversion element 10 to obtain a frequency conversion effect
- a frequency conversion effect cannot be obtained by changing the external magnetic field (switching off).
- switching off a method of shifting the frequency of the frequency-converted signal from a desired frequency band by shifting the ferromagnetic resonance frequency band. This method is defined as normally on because the frequency conversion function is operating in the normal state.
- FIG. 13 is a schematic configuration diagram of a fourth frequency conversion device including a frequency conversion element.
- a mechanism for applying two magnetic fields around the frequency converter 10 as shown in FIG.
- a magnetic field is applied to the frequency conversion element 10 by a coil 21 serving as an electromagnet in the vicinity of the frequency conversion element 10 and a permanent magnet 151.
- At least one of the two magnetic field application mechanisms needs to be a controllable magnetic field such as a current-induced magnetic field like the coil 21. is there.
- the frequency of the frequency conversion is made variable by changing the ferromagnetic resonance frequency of the frequency conversion element 10
- a current using a coil or the like is used to generate a magnetic field necessary to realize normally-on.
- An induced magnetic field is required.
- Another method of switching is a method in which the switching is turned off during normal operation and the switching is turned on only when the frequency conversion function is required. Since this method is switched off during normal operation, it is defined as normally off.
- FIG. I An embodiment is shown in which a coil 15 is arranged in the frequency conversion element 10 and a switching operation is performed for the frequency conversion effect.
- the current value applied to the coil 21 for generating the current-induced magnetic field is set so that the ferromagnetic resonance frequency of the frequency conversion element 10 is 4.72 GHz.
- the arrangement of the coil 21 is such that the magnetization free layer 6 prefers to be parallel and is inclined by 30 ° from the easy axis of the magnetization fixed layer 4.
- FIG. 14 is a schematic configuration diagram of a fifth frequency conversion device including a frequency conversion element.
- a coil 21 and a control power source (control unit) 25 that can control a current applied to the coil 21 are arranged in the vicinity of the frequency conversion element 10. Further, a feedback circuit 35 that is electrically connected to the output side of the frequency conversion element 10 and electrically connected to the coil control power supply 25 is provided.
- a local oscillation signal having a ferromagnetic resonance frequency to be set in the frequency conversion element 10 is input from the local oscillator 102, and a high frequency signal is input from the external signal source 101.
- the ferromagnetic resonance frequency is set to 4 GHz
- the external input signal is set to 3.8 GHz.
- a signal of 0.2 GHz should be output from the frequency conversion element 10.
- This output signal is detected by the feedback circuit 35.
- the feedback circuit 35 controls the magnitude of the current-induced magnetic field generated by the coil 21 by applying feedback to the control power source (control unit) 25 so that a desired output is obtained. It can be set to be obtained.
- the frequency conversion element can be provided with a conversion frequency adjustment function.
- the adjustment process described above is performed once again with the frequency of the external input signal set to a value other than 3.8 GHz. For example to set the external input signal f 1 to 3.4GHz. If the ferromagnetic resonance frequency is set to 4 GHz in the adjustment process described above, a signal of 0.6 GHz is output from the frequency conversion element 10. However, when the ferromagnetic resonance frequency set in the adjustment process is 3.6 GHz, a signal of 0.2 GHz is output. In that case, the adjustment process must be repeated once more. Therefore, the memory device is preferably mounted on the feedback circuit 35 or the coil control power supply 25.
- the local oscillator outputs the signal of the ferromagnetic resonance frequency
- the output signal of the external signal source may be the ferromagnetic resonance frequency
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Abstract
Description
非線形素子により周波数変換が行なわれる最も簡単な例として、非線形抵抗r(i)に電流を印加した場合を考える。非線形抵抗の電流-電圧特性が、動作点(i0,v0)のまわりでx = i - i0についてテイラー展開ができ
このような非線形抵抗素子に周波数ωの正弦波であらわされる電流
そこで、図2を参照して、中間層としてMgO障壁層を有するトンネル磁気抵抗素子を用いた、周波数変換素子の構造を説明する。ただし、本発明を実施するにあたり、用いる磁気抵抗素子は上述の磁気抵抗素子のみに限定されるものではない。
図2を参照して各層の具体的構成を説明する。下部電極層2の上に反強磁性層3が形成され、該反強磁性層3上に磁化固定層4が形成されている。該磁化固定層4のうち、符号4bが磁化固定層に相当する。該磁化固定層4上にはトンネルバリア層(中間層)5が形成され、該トンネルバリア層5上には磁化自由層6が形成され、該磁化自由層6上には保護層7が形成されている。本実施形態では、反強磁性層3がPtMn(15nm)である。また、磁化固定層4がCoFe(2.5nm)/Ru(0.85nm)/CoFeB(3nm)からなる積層フェリ固定層であり、該積層フェリ固定層の上層であるCoFeBが磁化固定層4bに相当する。トンネルバリア層(中間層)5がMgO(1.0nm)である。磁化自由層6がCoFeB(2nm)である。保護層7としては、Ta(5nm)/Ru(7nm)の積層構造を使用する。尚、( )内は膜厚を示す。
実際に、中間層としてのMgOの膜厚と素子サイズとを変化させて素子抵抗を40Ωにした試料と、300Ωにした試料とを用意し、それぞれについてS11(反射率)測定を行い、伝送特性の評価を行った。結果を図4A、4Bに示す。この結果が示すように、明らかにインピーダンス整合の良い方(図4A)が、伝送特性が良い事が分かる。素子抵抗が40Ωの試料では0~20GHzまでの全周波数領域で伝送効率が0.8以上であるのに対して、素子抵抗が300Ωの試料では伝送効率が0.4を下回ってしまう。
図5Bにおいて、下部電極51上に磁化固定層52が形成され、該磁化固定層52上に中間層53が形成され、該中間層53上に磁化自由層54が形成され、該磁化自由層54上に上部電極56が形成されている。
また、本発明では、磁気抵抗素子30の構造は、図5Bに示す構造に限定されない。
なお、図9では周波数変換装置の片側に一つだけ永久磁石151を配置したが、永久磁石151を両側に配置しても構わない。
ひとつは、常に周波数変換素子10に適当な外部磁界が印加され周波数変換効果が得られる状態(スイッチングオン)から、この外部磁界を変化させることによって周波数変換効果を得られない状態(スイッチングオフ)、もしくは強磁性共鳴周波数帯をずらして、周波数変換された信号の周波数を所望の周波数帯からずらす方法がある。この方法は、通常状態で周波数変換機能が働いている状態なのでノーマリーオンと定義する。
周波数変換素子10の強磁性共鳴周波数が4.72GHzになるように、電流誘起磁界を発生させるためのコイル21に印加する電流値を設定する。コイル21の配置は、磁化自由層6が平行を好む向きで、かつ磁化固定層4の容易軸から30°傾けた方向となっている。この状態の(ノーマリーオン)周波数変換素子10に3GHz(高周波信号f1)と4.72GHz(高周波信号f2)の信号を入力したところ、図10と同様に1.72GHzの差信号周波数を観測することができた。
このように、磁場印加機構を適当に選択することで、ノーマリーオンおよびノーマリーオフの両方に対応可能な周波数変換装置が実現することができる。
図14に示すように、周波数変換素子10の近傍には、コイル21と、コイル21に印加する電流を制御することができる制御用電源(制御部)25とが配置されている。また、周波数変換素子10の出力側と電気的に接続され、かつコイル制御用電源25と電気的に接続されたフィードバック回路35が設けられている。
Claims (6)
- 磁化自由層、中間層、および磁化固定層を備えた磁気抵抗素子を含む周波数変換素子と、
前記周波数変換素子に磁場を印加するための磁場印加機構と、
前記周波数変換素子に局部発振信号を印加するための局部発振器と、
前記周波数変換素子と電気的に接続され、かつ外部入力信号を入力するための入力端子とを備え、
前記局部発振器は、自身の抵抗変化に応じて交流電圧を出力することにより前記局部発振信号を発振可能な磁気抵抗素子を含むことを特徴とする周波数変換装置。 - 前記磁場印加機構は永久磁石であり、
前記永久磁石による印加磁場の方向は、前記周波数変換素子の磁化固定層の容易軸方向に対して平行ではないことを特徴とする請求項1に記載の周波数変換装置。 - 前記磁場印加機構は、
電流磁界を発生するための電流磁界印加機構と、
前記電流磁界印加機構に電流を印加する電源とを備え、
前記電流磁界による印加磁場の方向は、前記周波数変換素子の磁化固定層の容易軸方向に対して平行ではないことを特徴とする請求項1に記載の周波数変換装置。 - 前記電流磁界印加機構に印加する電流を制御することによって前記周波数変換素子に印加される磁場を制御する制御部をさらに備えることを特徴とする請求項3に記載の周波数変換装置。
- 前記周波数変換素子の出力を検出し、所望の強磁性共鳴周波数になるように前記制御部にフィードバックを施すフィードバック回路を備えた請求項4に記載の周波数変換装置。
- 前記制御部は、前記電流磁界印加機構に印加する電流をオンオフすることによって、前記周波数変換素子に印加される磁場をオンオフするものであることを特徴とする請求項4に記載の周波数変換装置。
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WO2010119569A1 (ja) * | 2009-04-17 | 2010-10-21 | キヤノンアネルバ株式会社 | 周波数変換装置、及び周波数変換方法 |
JP5535316B2 (ja) | 2010-06-10 | 2014-07-02 | キヤノンアネルバ株式会社 | 発振素子および発振素子の製造方法 |
FR2974468B1 (fr) * | 2011-04-20 | 2013-05-31 | Commissariat Energie Atomique | Demodulateur d'un signal electrique module en frequence |
FR2974467B1 (fr) | 2011-04-20 | 2013-05-31 | Commissariat Energie Atomique | Synthetiseur d'un signal oscillant |
JP5790359B2 (ja) | 2011-09-16 | 2015-10-07 | Tdk株式会社 | 混合器 |
JP5796431B2 (ja) | 2011-09-16 | 2015-10-21 | Tdk株式会社 | 周波数変換装置 |
JP5790360B2 (ja) | 2011-09-16 | 2015-10-07 | Tdk株式会社 | 周波数選択性を有する混合器 |
KR101490999B1 (ko) * | 2013-08-12 | 2015-02-09 | 한국과학기술원 | 다중대역 주파수와 진폭을 동시에 변조하는 스핀트로닉스 무선통신 시스템 |
JP6225748B2 (ja) * | 2014-02-26 | 2017-11-08 | 株式会社デンソー | 磁気センサ |
US9966922B2 (en) * | 2016-05-25 | 2018-05-08 | Tdk Corporation | Magnetoresistive effect device |
JP6897702B2 (ja) * | 2019-03-20 | 2021-07-07 | Tdk株式会社 | 磁場検出装置および磁場検出方法 |
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