Radio-frequency signal correlator using parametric pumping of spin waves

Abstract

Various embodiments of a magnetoacoustic spin wave signal processing system are provided. In one embodiment, the system includes an acoustic wave transducer configured to generate surface acoustic waves in a plane of a magnetostrictive material, the magnetostrictive material serving as a medium for spin waves traveling in the plane, and the acoustic wave transducer oriented such that the acoustic waves parametrically amplify the spin waves. In this way, the signal processing system exploits the low dispersion and high dynamic range of acoustic waves, together with the tunability and nonlinear effects offered by spin waves, to realize the advantages of both spin wave and acoustic wave devices.

Description

[Technical field]

[0001] Awarding of Government Assistance This invention was made with Government support awarded under Award No. HR0011-17-2-0005 by the Defense Advanced Research Projects Agency (DARPA) Signal Processing at RF (SPAR). The U.S. Government has certain rights in this invention. [Background technology]

[0002] Magnetoacoustic devices exploit the interplay between magnetic and acoustic properties to enable applications in wireless communication, sensing, and information processing. These devices utilize the magnetostrictive effect, in which a magnetic material undergoes deformation in response to a magnetic field or induces a change in magnetization when subjected to mechanical stress. By utilizing this coupling between magnetic and acoustic domains, magnetoacoustic devices offer unparalleled capabilities and performance advantages in a variety of applications, such as transducers, filters, sensors, and communication systems. Summary of the Invention [Problem to be solved by the invention]

[0003] Current magnetoacoustic transducers, filters, and communication systems face problems with efficiency, frequency selectivity, tunability, and miniaturization. For example, some transducers may exhibit limited transduction efficiency or frequency response, while existing filters struggle with precise frequency control and adaptability. In addition, magnetoacoustic sensors may face challenges in sensitivity, stability, or response time when detecting physical changes or external stimuli such as pressure, temperature, or magnetic fields. [Means for solving the problem]

[0004] Various embodiments of magnetoacoustic spin wave signal processing systems are provided that can address these issues by providing advantages in energy efficiency, compactness, and interference resistance. In one embodiment, the system comprises an acoustic wave transducer configured to generate surface acoustic waves in the plane of a magnetostrictive material, which serves as a medium for spin waves traveling in this plane, and the acoustic wave transducer is oriented such that the acoustic waves (surface acoustic waves) parametrically amplify the spin waves. In this way, the signal processing system utilizes the low dispersion and high dynamic range of acoustic waves together with the tunability and nonlinear effects offered by spin waves to realize the advantages of both spin wave and acoustic wave devices.

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0006] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing an example of a magnetoacoustic spin wave signal processing system. [Diagram 2] FIG. 1 is a schematic diagram illustrating an example of a SAW-pumped spin wave amplifier or correlator. [Diagram 3] FIG. 13 is a schematic diagram illustrating another example of a SAW-pumped spin wave amplifier or correlator. [Figure 4] FIG. 2 illustrates the relationship between wave vectors in a SAW-pumped magnetoacoustic signal processing system. [Diagram 5] FIG. 2 is a schematic diagram showing the relative positioning of an example of a SAW pumped spin wave amplifier. [Figure 6]FIG. 1 is a schematic diagram showing relative positioning for an example SAW-pumped spin-wave correlator. [Figure 7] FIG. 1 is a diagram showing the relative positioning of a spin wave transducer and an acoustic wave transducer in an example of a SAW pumped spin wave signal processing system. [Figure 8] FIG. 1 shows an example of a computer simulation of the interaction of spin waves and acoustic waves in a planar device. [Figure 9] 1 is a high level flow chart illustrating an example method of magneto-acoustic spin wave signal processing. [Figure 10] FIG. 1 is a block diagram illustrating an example of a radio frequency (RF) communication system including a magneto-acoustic correlator. [Figure 11] FIG. 1 is a block diagram illustrating an example of a computing environment in which the described invention can be implemented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The following description relates to various embodiments of a magnetoacoustic spin wave signal processing system. In particular, various embodiments of a signal processing device are provided that combine the advantages of spin wave devices with those of acoustic wave devices to exploit the low dispersion and high dynamic range of acoustic waves along with the tunability and nonlinear effects offered by spin waves. The signal processing system described herein uses the interaction of acoustic waves and spin waves in magnetostrictive materials. In such materials, strain (the propagating variable in acoustic waves) and magnetization (the propagating variable in spin waves) are coupled. The strength of this coupling depends on the material in which these waves travel and is measured by the magnetostriction coefficient, or magnetoelastic constant.

[0009] 1 shows a block diagram illustrating an example of a magneto-acoustic spin wave signal processing system 100 according to one embodiment. The magneto-acoustic spin wave signal processing system 100 includes an acoustic wave device 105 and a number of spin wave devices 110.

[0010] The acoustic wave device 105 comprises an acoustic signal processing device configured to convert electrical signals into acoustic waves and convert acoustic waves into electrical signals. Acoustic signal processing devices - where electrical signals are converted into acoustic waves, manipulated on the device, and then converted back into electrical signals - are widely used in radio frequency (RF) and microwave communication equipment, including mobile phones. Converting and processing signals into the acoustic domain is advantageous because acoustic waves propagate several orders of magnitude slower than electromagnetic waves, and therefore, at a given frequency, the wavelength is proportionally shorter (up to five orders of magnitude), allowing for smaller device sizes.

[0011] Acoustic wave devices, such as the acoustic wave device 105, fall into two main categories: surface acoustic wave (SAW) devices and bulk acoustic wave (BAW) devices. SAW devices utilize acoustic modes that are confined to and propagate along the surface of a solid. Surface acoustic waves are mechanical waves that propagate along the surface of a material, with the energy of the wave concentrated within a few wavelengths of the surface. In surface acoustic waves, the particles of the material exhibit both longitudinal and transverse displacements while the amplitude of the wave decreases exponentially towards the material, resulting in most of the wave's energy being confined to the surface. In contrast, BAW devices utilize waves that propagate within a volume of a material. For example, bulk acoustic waves propagate through a volume or volume of a material. To this end, bulk acoustic waves can be longitudinal or transverse, where the particle displacements are parallel to the direction of wave propagation and where the particle displacements are perpendicular to the direction of wave propagation.

[0012] In SAW devices, the structure that converts the electrical signal into a surface acoustic wave is known as an interdigitated transducer (IDT) and consists of two electrically isolated thin-film metal regions patterned into interleaved fingers on (and in some cases directly below) a piezoelectric material. When an alternating voltage is applied to the IDT, the interaction of the electric field with the piezoelectric material produces a distortion that is periodic in space and time. If the temporal and spatial periodicity matches a surface acoustic wave mode that can propagate on the surface of the device, such waves can be efficiently generated and propagated in the piezoelectric material away from the IDT. In this reversible process, when the wave reaches the second IDT, it is converted back into an electrical signal. These basic device structures are currently being used to realize signal delay and frequency selective filters with precisely designed filter geometries.

[0013] Transducers for BAW devices consist of two thin-film metal plates that sandwich a piezoelectric material. When excited with an AC voltage, these transducers generate an acoustic plane wave that propagates through the underlying material and reflects off its bottom surface. Like a guitar string, the structure resonates when the round-trip path length is equal to a multiple of the acoustic signal wavelength. Such BAW resonators are used to select a well-defined narrow range of RF or microwave frequencies.

[0014] Key characteristics of acoustic wave devices such as acoustic wave device 105 include low frequency dispersion, large linear dynamic range, very low power loss, and efficient transducers. Although acoustic wave device 105 is described herein with respect to a SAW device, it should be understood that the systems and methods provided herein may be implemented with one or more BAW devices, or in some examples a combination of SAW and BAW devices.

[0015] The plurality of spin wave devices 110 includes at least a first spin wave device 111. In some examples, the plurality of spin wave devices 110 further includes a second spin wave device 112. In other examples, the plurality of spin wave devices 110 further includes additional spin wave devices (not shown), such as a third spin wave device. Spin waves propagate perturbations in the magnetization of an otherwise uniformly magnetized magnetic material. Like sound waves, spin waves also travel at speeds several orders of magnitude slower than electromagnetic waves. However, the speed depends not only on the host material, but also on the applied bias field and the frequency of the wave. This variability in speed is both an opportunity to create tunable devices, and a challenge in designing practical manufacturable device implementations.

[0016] The spin wave device 110 comprises a spin wave transducer. The spin wave transducer comprises a serpentine conductor patterned on the surface of a magnetic thin film, such as yttrium-iron-garnet (YIG). The magnetic thin film comprises a magnetostrictive material. Other magnetic thin films can include ferromagnetic thin films, including but not limited to magnetite, spinel ferrite, hexaferrite, manganese zinc ferrite, lithium ferrite, and garnet-type ferrites other than YIG, such as gadolinium gallium garnet, terbium gallium garnet, and bismuth iron garnet. Alternating currents applied through these conductors generate spatially and temporally periodic magnetic fields that selectively couple to spin wave modes propagating in the magnetic thin film, similar to SAW transducers.

[0017] Spin waves propagate laterally from one transducer to the other, for example from the first spin wave device 111 to the second spin wave device 112, and thus the functions realized are similar to SAW devices, such as acoustic wave device 105. In fact, similar methods are used to design filter shapes for desired frequencies in both types of devices. No spin wave-based devices are currently commercially available. Although spin waves can be used to realize linear devices such as filters, to date this field has been dominated by acoustic wave devices, which are easier to design and manufacture. The use of spin waves rather than acoustic waves is particularly advantageous for devices that realize nonlinear signal processing functions such as modulation, correlation, and power limiting.

[0018] Key properties of spin wave devices include frequency or delay tunability, and nonlinear response. Power losses are generally higher than in acoustic wave devices, but there are indications that at frequencies above 5 GHz, spin wave losses can be made smaller than acoustic wave losses.

[0019] In one example of the magnetoacoustic spin wave signal processing system 100, the surface wave device 105 comprises a BAW device, so that the signal processing system 100 can comprise a BAW-pumped spin wave amplifier. A BAW-pumped spin wave amplifier combines a spin wave delay line with a BAW resonator. Spin waves are generated by supplying an electrical signal to one of the spin wave transducers 110 (e.g., spin wave device 111), which travels through the ferromagnetic layer to the other spin wave transducer (e.g., spin wave device 112), where the spin waves are converted back into an electrical signal. In the region between the spin wave transducers, the spin waves pass through a region of acoustic waves generated by the BAW resonator (e.g., acoustic wave device 105). If the frequency of the acoustic wave is close to twice the frequency of the spin wave, the magnetoelastic interaction between these two waves can cause the amplification of the spin wave by a nonlinear effect known as parametric pumping. In addition to amplifying the forward spin wave, parametric pumping generates a second spin wave, known as an idler wave, which travels in the opposite direction back to the first spin wave transducer (e.g., spin wave device 111). The parametric pumping process only works under certain conditions related to the frequencies and wavelengths of these three waves. Based on the conservation of energy condition, the frequency of the spin wave (f s ) and the idler spin wave frequency (f i ) is the frequency of the acoustic pump (f p ), which means that f p =f s +f i In addition, the process must conserve the momentum of these waves. Since the standing sound wave in a BAW resonator has zero momentum, the added forward spin wave and the idler spin wave must have equal and opposite momentum (which is why the idler must travel in the opposite direction to the spin wave). The parametric pumping effect can be achieved by using yttrium iron garnet (YIG) as the ferromagnetic material that supports the spin waves and provides magnetoelastic coupling between the sound wave and the spin wave.

[0020] The ability proposed herein to efficiently and locally amplify spin waves in ferromagnetic thin films could dramatically improve the performance of spin wave-based signal processing devices, which is currently limited by spin wave propagation losses in even the best of low spin wave damping materials such as YIG. Amplifiers are also essential for the successful development of low power magnetic logic circuits, since they can provide signal restoration and fan-out between logic gates.

[0021] Previous efforts at spin wave amplification include parametric pumping by electromagnetic fields or voltage-controlled magnetic anisotropy, as well as damping compensation by spin transfer torque. All of these electrical pumping techniques require routing a metallic conductor on the spin wave waveguide. Paradoxically, introducing a conductor adjacent to a low-damping waveguide medium increases the damping rate of the spin waves and therefore increases the passive insertion loss of the device. Acoustic pumping by remote transducers leaves the waveguide free of any conductor layers. Each of the existing methods of spin wave amplification has further limitations. In particular, methods of spin wave amplification by spin transfer torque or voltage-controlled magnetic anisotropy rely on interfacial spin scattering and are only efficient in ultrathin (~10 nm) magnetic films. Traditional parametric amplification by electromagnetic fields requires ellipticity of the magnetization precession, which cannot be realized with the perpendicular thin film magnetization geometries relevant to today's magnonic circuits.

[0022] In addition to functioning as a signal amplifier, the magnetoacoustic spin wave signal processing system 100 can also function as a signal correlator, also called a convolver. When the input spin wave signal and the acoustic pump signal are both modulated, the generated idler wave is modulated by the correlation of the two input modulations:

number

[0023] Correlators find use in RF communication systems employing code division multiple access (CDMA) techniques, where signals are differentiated by their code modulation. Correlators can be used to selectively amplify only signals containing particular codes. Schemes on how such systems can be implemented are described further herein with respect to FIG. 10.

[0024] The range of frequencies over which the device operates can be adjusted by the magnitude or orientation of the magnetic field. Furthermore, the range of frequencies over which the device operates is determined by the magnetic anisotropy of the magnetostrictive material. The range of frequencies over which the device operates can be adjusted by the voltage-controlled magnetic anisotropy of the magnetostrictive material. In some examples, an acoustic transducer generates bulk acoustic waves that propagate through the magnetostrictive material. In other examples, an acoustic transducer generates surface acoustic waves that propagate on the surface of the magnetostrictive material and generate strain in the magnetostrictive material. In yet other examples, an acoustic transducer generates Lamb waves or similar plane waves in the magnetostrictive material.

[0025] The magnetostrictive material includes a ferrite material such as yttrium iron garnet (YIG) or other closely related magnetic garnets. In some examples, the magnetostrictive material includes nickel (Ni), iron (Fe), or an alloy of nickel and iron. In other examples, the magnetostrictive material includes CoFeB.

[0026] In some examples, the acoustic transducer includes a bulk acoustic wave transducer that generates standing acoustic waves in a substrate supporting the magnetostrictive material, the standing acoustic waves passing through the magnetostrictive material.

[0027] The acoustic transducer is oriented at an angle such that the idler spin wave resulting from the parametric interaction of the resulting acoustic wave with the spin wave travels at a third distinct angle and impinges on the output spin wave transducer. For example, the acoustic transducer is oriented at an angle such that the idler spin wave resulting from the parametric interaction of the surface acoustic wave with the spin wave is a standing (non-propagating) spin wave. In some examples, the acoustic transducer is oriented at an angle such that the idler spin wave resulting from the parametric interaction of the surface acoustic wave with the spin wave travels in the same direction as the spin wave of the input signal. In this manner, the input spin wave transducer may be configured to receive the idler spin wave. In some examples, a range of input frequencies for the input spin wave transducer and the acoustic transducer is selected such that a third distinct frequency range produces a parametric interaction.

[0028] As illustrative and non-limiting examples, examples of magnetoacoustic spin wave signal processing devices are shown in Figures 2 and 3. For example, Figure 2 is a schematic diagram of an example of a magnetoacoustic spin wave signal processing device 200, which comprises a SAW-pumped spin wave amplifier or correlator that combines a spin wave delay line with a SAW delay line. The magnetoacoustic spin wave signal processing device 200 comprises an acoustic wave device 205, a first spin wave device 211, and a second spin wave device 212, which are formed on a surface 221 of a ferromagnetic thin film 220 (e.g., YIG) that covers a substrate 224 (e.g., alumina) of the device 200.

[0029] The acoustic wave device 205 is configured to generate acoustic waves, such as surface acoustic waves 206, that travel on the surface 221 of the ferromagnetic thin film 220. As shown, the acoustic wave device 205 includes an interdigital transducer (IDT) 229 that includes a set of thin metal electrodes (e.g., formed of aluminum, gold, or other suitable metallic material) patterned on the surface of a piezoelectric layer 230. When an electrical signal is applied to the IDT 229, the IDT 229 generates an electric field in the piezoelectric layer 230, causing mechanical deformation due to the piezoelectric effect. This deformation generates a surface acoustic wave 206 that propagates along the surface 221. The IDT 229 of the acoustic wave device 205 can be configured with a particular electrode width, spacing, and number of finger pairs to control the characteristics of the generated SAW, such as the frequency, bandwidth, and amplitude.

[0030] The first spin wave device 221 is configured to generate spin waves, such as spin wave 215 traveling on the surface 221 of the ferromagnetic thin film 220. The second spin wave device 212 is configured to receive the spin wave 215. As a spin wave transducer comprises a device that converts an electrical signal into a spin wave and vice versa, the first spin wave device 211 thus comprises an input spin wave transducer, whereas the second spin wave device 212 comprises an output spin wave transducer. A bias magnetic field 217 is applied in a direction from the first spin wave device 211 to the second spin wave device 212 to guide the spin wave 215 and control the propagation of the spin wave 215 between the spin wave devices 211 and 212.

[0031] As shown, both the acoustic wave 206 and the spin wave 215 travel in a ferromagnetic thin film 220 on a surface 221 of the magnetoacoustic spin wave signal processing device 200. If the ferromagnetic thin film 220 is not piezoelectric, an IDT 229 for generating surface acoustic waves is covered with a piezoelectric layer 230, or alternatively, the piezoelectric layer 230 is disposed between the IDT 229 and the ferromagnetic thin film 220 to provide coupling between the electrical and acoustic signals. As an illustrative, non-limiting example, the piezoelectric layer 230 may include zinc oxide (ZnO). Other examples of piezoelectric materials that may comprise the piezoelectric layer 230 include lead zirconate titanate (PZT), aluminum nitride (AlN), polyvinylidene fluoride (PVDF), barium titanate (BaTiO 3 ), lithium niobate (LiNbO 3 Examples of suitable piezoelectric thin films include, but are not limited to, potassium sodium niobate (KNN), etc. The selection of the piezoelectric thin film can depend on the desired performance, operating conditions, and specific application.

[0032] In the central region 250 of the device 200, the spin waves 215 and the acoustic waves 206 travel together and parametric interactions between the acoustic waves 206 and the spin waves 215 can result in amplification of the spin waves 215 and generation of idler spin waves (not shown). Since acoustic waves generally propagate over longer distances than spin waves, it may be advantageous to place the acoustic wave transducer or device 205 outside the spin wave transducers 211 and 212 as shown in Figure 2. However, the acoustic wave transducer can also be placed between the spin wave transducers. 3 is a schematic diagram of an example of a magneto-acoustic spin wave signal processing system 300 comprising a SAW pumped spin wave amplifier or correlator in which an acoustic wave device 305 is positioned between a first spin wave device 311 and a second spin wave device 312 on a surface 321 of a ferromagnetic thin film 320 extending over an entire substrate 324. The acoustic wave device 305 includes an IDT 329 and a piezoelectric layer 330 as shown configured to generate a surface acoustic wave 306 that propagates along the surface 321 towards the first spin wave device 311 or input spin wave transducer. The first spin wave device 311 generates a spin wave 315 that propagates along the surface 321 towards the second spin wave device 312, guided by the ferromagnetic thin film 320 and a bias magnetic field 317. Thus, the acoustic wave 306 and the spin wave 315 parametrically interact in the central region 350 to amplify the spin wave 315 and generate an idler spin wave. As described further herein, a second spin wave device 312 can be positioned relative to the central region where a parametric interaction occurs to convert the amplified spin wave (hereinafter referred to as the "amplified spin wave") or the idler spin wave into an electrical signal.

[0033] An example of a vector relationship 400 is shown in a diagram in FIG. 4. For parametric interaction between the sound wave and the spin wave to occur, the three waves (i.e., the sound wave, the spin wave, and the idler wave) must satisfy the conditions dictated by the conservation of energy and momentum. These conditions are traditionally described by the relationship between the frequencies of the waves and their wave vectors ( (outside 1) JPEG2025515606000003.jpg117 indicates the direction of wave propagation and has a magnitude of k=2π / λ, where λ is the wavelength. The frequency of the pump wave (i.e., the sound wave that parametrically pumps the spin waves) must be equal to the sum of the frequency of the signal wave (i.e., the input spin wave) and the frequency of the idler wave (i.e., the idler spin wave generated by the parametric interaction): f p =f s +F i (2) The pump wave vector 404 must be equal to the vector sum of the signal wave vector 402 and the idler wave vector 406:

number

[0034] Spin Waves (outside 2) JPEG2025515606000005.jpg107 and (Outside 3) If the magnitudes of the JPEG2025515606000006.jpg107 are similar, the angle 405 (θ) between the signal spin wave and the acoustic wave must satisfy the following relationship: |k p |=2|k s |cosθ (4) Therefore, according to this vector principle, the acoustic wave device 105 and the spin wave device 110 of the magnetoacoustic spin wave signal processing system 100 can be realized in a planar arrangement with relative positioning for detecting amplified spin waves, idler spin waves, or both amplified spin waves and idler spin waves, as described with respect to Figures 2 and 3.

[0035] As an illustrative example, FIG. 5 is a schematic diagram showing the relative positioning of an example SAW pumped spin wave amplifier 500. Specifically, FIG. 5 shows a plan view of a layout for SAW transducers and spin wave transducers that satisfy the wave vector relationship for parametric pumping. The output spin wave transducer is positioned to capture the amplified spin wave. The IDT of the acoustic wave device 505 is positioned relative to the first spin wave transducer 511 such that an angle 517 is formed between the acoustic wave generated by the acoustic wave device 505 and the signal spin wave 515 generated by the first spin wave transducer 511. Parametric pumping in the region 519 where the acoustic wave 506 and the signal spin wave 515 interact amplifies the signal spin wave 515 to generate an amplified spin wave 520, which continues in the same direction as the signal spin wave 515. Furthermore, the angle 517 defines the propagation direction of the idler spin wave 522. SAW pumped spin wave amplifier 500 comprises an amplifier because, as shown, a second spin wave transducer 512 is positioned to receive the amplified spin wave 520 .

[0036] Similarly, FIG. 6 is a schematic diagram showing the relative positioning for a SAW-pumped spin wave correlator 600. Specifically, FIG. 6 shows a top view of the layout for a SAW-pumped magnetoacoustic correlator, with the output spin wave transducer positioned to capture the idler spin wave. The IDT of the acoustic wave device 605 is positioned relative to the first spin wave transducer 611 such that an angle 617 is formed between the acoustic wave generated by the acoustic wave device 605 and the signal spin wave 615 generated by the first spin wave transducer 611. Parametric pumping in the region 619 where the acoustic wave 606 and the signal spin wave 615 interact amplifies the signal spin wave 615 to generate an amplified spin wave 620, which continues in the same direction as the signal spin wave 615. Additionally, the angle 617 defines the propagation direction of the idler spin wave 622 generated by the parametric interaction. The SAW pumped spin wave correlator 600 comprises a correlator because, as shown, the second spin wave transducer 612 is positioned to receive an idler spin wave 622 .

[0037] 7 is a schematic diagram showing the relative positioning of an example SAW pumped spin wave signal processing system 700. Similar to the amplifier 500 and the correlator 600, the IDT of the acoustic device 705 is positioned with respect to the first spin wave transducer 711 such that an angle 717 is formed between the acoustic wave 706 generated by the acoustic device 705 and the signal spin wave 715 generated by the first spin wave transducer 711. Due to parametric pumping in the region where the acoustic wave 706 and the signal spin wave 715 interact, the signal spin wave 715 is amplified to generate an amplified spin wave 720, which continues in the same direction as the signal spin wave 715. Furthermore, the angle 717 defines the propagation direction of the idler spin wave 722 generated by the parametric interaction. The SAW pumped spin wave system 700 can function as both an amplifier and a correlator because the second spin wave transducer 712 is positioned to receive the amplified spin wave 720, while the third spin wave transducer 713 is positioned to receive the idler spin wave 722.

[0038] Although acoustic waves are generally discussed herein, it should be understood that in such devices surface acoustic waves are advantageous over bulk acoustic waves for parametric pumping for a variety of reasons, including: higher efficiency of parametric interactions; the ability to amplify forward volume spin waves, which are the least dispersive mode of spin waves and can travel in any direction; and planar structures that simplify mass production.

[0039] A common problem in RF and microwave signal processing devices is unwanted feedthrough from the input signal to the output of the device. The device architecture described above allows for the reduction of feedthrough by separating the input and output signals in frequency or angle.

[0040] Non-degenerate parametric pumping, where the signal frequency is not exactly half the pump frequency, can be used to separate the center frequency of the input signal from the center frequency of the output signal. According to equation (2), the sum of the signal spin wave frequency and the idler spin wave frequency must be equal to the pump frequency. In degenerate parametric pumping, the signal frequency and the idler frequency are equal and half the pump frequency. In the non-degenerate case, the signal frequency can be displaced by Δf (higher or lower) from half the pump frequency. In this case, to satisfy equation (2), the idler frequency is displaced by -Δf (lower or higher), which separates the input and output frequencies by twice Δf. Therefore, frequency-selective transducers or filters can be used to prevent signal feed-through to the output. Only non-linear processes such as parametric pumping can introduce a frequency shift. If the pump frequency is adjustable, different pump frequencies can be dynamically selected to select different input frequency bands for amplification and correlation.

[0041] Both spin wave and acoustic wave transducers are only sensitive to signals traveling within a narrow angular range. Therefore, with the geometries shown in Figures 5, 6, and 7, inadvertent coupling between the input and output transducers can be reduced by introducing angular changes into the parametric pumping process. In this way, only signals generated by parametric interactions have the correct propagation angle to be captured by the output transducer.

[0042] 8 shows an example computer simulation 800 of spin wave and acoustic wave interaction performed to demonstrate the parametric interaction of waves in YIG and the validity of Equations 2-4. As shown, spin waves 815 emanating from a spin wave transducer 811, which in the simulation is at an angle of 20 degrees to a propagating SAW 806, are parametrically pumped to generate idler spin waves 822 that exit the pump region at a distinct angle to the signal spin wave 820. The magnitude of the spin waves in regions away from the spin wave 815 is relatively negligible, and the simulation 800 shows that they are distinct from the idler spin wave 822, as shown by the region 831 where the spin wave magnitude is relatively negligible.

[0043] 9 shows a high level flow chart illustrating an example of a method 900 for a magneto-acoustic spin wave signal processing system. Although the method 900 may be implemented with the systems and components described herein above with respect to Figures 1-8, it should be understood that the method 900 may be implemented with other systems and components without departing from the scope of the present invention.

[0044] Method 900 begins at block 905. In block 905, method 900 evaluates operating conditions of the magneto-acoustic spin wave processing system. In block 910, method 900 determines whether an input signal is received. The input signal may include, for example, an input electrical signal or an electromagnetic signal. If an input signal is not received ("No"), method 900 proceeds to block 915, where method 900 maintains the operating conditions. Method 900 then returns.

[0045] If an input signal is received at block 910 ("Yes"), the method 900 proceeds to block 920. At block 920, the method 900 converts the input signal into a spin wave. The spin wave travels along a plane. At block 925, the method 900 generates an acoustic wave at a particular angle relative to the spin wave. The acoustic wave propagates along the plane and parametrically interacts with the propagating spin wave at an interaction region.

[0046] At block 930, the method 900 converts the output spin wave into an output signal, where the output spin wave is generated during a parametric interaction between the spin wave and the acoustic wave. For example, the parametric interaction occurs at an interaction region. Depending on the arrangement of the spin wave and the acoustic wave and the magnitude of the spin wave and the acoustic wave, the output spin wave can include one or more of an amplified spin wave amplified by parametric pumping, an idler spin wave, or a combination of an amplified spin wave and an idler spin wave. The method 900 can convert an electrical signal into a spin wave at an input spin wave transducer, and can convert the output spin wave into an output electrical signal at an output spin wave transducer positioned relative to the input spin wave transducer to capture at least one of the spin wave parametrically amplified by the acoustic wave or the idler spin wave. The method 900 then returns.

[0047] FIG. 10 is a schematic block diagram of an example of an RF communication system 1000 including a magneto-acoustic correlator 1005 configured to select a particular code modulated signal (hereinafter referred to as the "code modulated signal") arriving at an antenna 1010. The magneto-acoustic correlator 1005 may be a SAW pumped spin wave correlator as described herein above with respect to FIGS. 1-3, 6 and 7. A signal 1011 received by the antenna 1010 is fed to the magneto-acoustic correlator 1005. Only signals matching the code S(t) are passed by the magneto-acoustic correlator 1005 to a low noise amplifier (LNA) 1021 for demodulation by a demodulator 1022. An idler frequency 1023 or f iis provided to a demodulator 1022 to provide a demodulated signal 1024 or I(t). Further processing is typically performed by a digital processor 1030 after analog-to-digital conversion (ADC) of the demodulated signal 1024. The processor 1030 may also generate a code signal S(t) using a digital-to-analog converter (DAC) 1031. The signal spin wave frequency 1033 or f s is input to a modulator 1034 along with the code signal S(t) to provide an input to the magneto-acoustic correlator 1005 for signal correlation.

[0048] Thus, various embodiments of magnetoacoustic spin wave signal processing systems are provided. In some examples, the system includes an acoustic transducer configured to generate acoustic waves in a magnetostrictive material that serves as a medium for the spin waves and oriented such that the acoustic waves parametrically amplify the spin waves. Such a system can be used to amplify spin wave signals in a spin wave circuit (e.g., a magnonic circuit). In other examples, the system includes an input spin wave transducer, an output spin wave transducer, and an acoustic wave transducer that are positioned in the vicinity of the magnetostrictive material such that acoustic waves generated by the acoustic transducer parametrically amplify the spin waves as the spin waves travel through the magnetostrictive material from the input transducer to the output transducer. Such a system can be used to amplify radio frequency electrical signals. In yet another example, a system includes an input spin wave transducer, an output spin wave transducer, and an acoustic wave transducer, which are positioned near the magnetostrictive material such that as the spin waves generated by the input spin wave transducer travel through the magnetostrictive material, the acoustic waves generated by the acoustic wave transducer parametrically interact with the spin waves, resulting in idler spin waves traveling to the output transducer. Such a system can be used to shift the center frequency of a radio frequency electrical signal. In another example, a system includes an input spin wave transducer, an output spin wave transducer, and an acoustic wave transducer, which are positioned near the magnetostrictive material such that as the spin waves generated by the input spin wave transducer travel through the magnetostrictive material, the acoustic waves generated by the acoustic wave transducer parametrically interact with the spin waves, the parametric interaction spanning a specific region of space and for a specific duration. Such a system can be used to determine the time correlation or time convolution of the modulation of two radio frequency electrical signals. Additionally or alternatively, such systems can be used to selectively block or amplify radio frequency signals depending on the code that modulates those signals.

[0049] 11 illustrates a generalized example of a suitable computing environment 1100 in which the described innovations may be implemented. The computing environment 1100 is not intended to suggest any limitation as to scope of use or functionality, as these innovations may be implemented in a variety of general-purpose or special-purpose computing systems. For example, the computing environment 1100 may be any of a wide variety of computing devices (e.g., a desktop computer, a laptop computer, a server computer, a tablet computer, etc.).

[0050] Referring to FIG. 11, a computing environment 1100 includes one or more processing units 1110, 1115 and memory 1120, 1125. In FIG. 11, this basic configuration 1130 is enclosed within the dashed line. The processing units 1110, 1115 execute computer-executable instructions. The processing units may be general-purpose central processing units (CPUs), processors in an application specific integrated circuit (ASIC), or any other type of processor. In a multiprocessing system, multiple processing units execute computer-executable instructions to increase processing power. For example, FIG. 11 shows a central processing unit 1110 as well as a graphics processing unit or co-processing unit 1115. The tangible memory 1120, 1125 may be volatile memory (e.g., registers, cache, random access memory (RAM)), non-volatile memory (e.g., read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, etc.), or some combination of the two accessible by the processing unit. The memory 1120, 1125 stores software 1180 implementing one or more of the innovations described herein in the form of computer-executable instructions suitable for execution by the processing unit.

[0051] The computer system may have additional features. For example, the computing environment 1100 includes a storage device 1140, one or more input devices 1150, one or more output devices 1160, and one or more communication connections 1170. An interconnection mechanism (not shown), such as a bus, controller, or network, interconnects the components of the computing environment 1100. Typically, operating system software provides an operating environment for other software executing within the computing environment 1100.

[0052] The tangible storage 1140 can be removable or non-removable and includes magnetic disks, magnetic tapes or cassettes, compact disc-ROMs (CD-ROMs), digital versatile discs (DVDs), or any other medium that can be used to store information in a non-transitory manner and that can be accessed within the computing environment 1100. The storage 1140 stores instructions for software 1180 that implements one or more of the innovations described herein.

[0053] The input devices 1150 may be a keyboard, a touch input device such as a mouse, a pen, or a trackball, a voice input device, a scanning device, or other device that provides input to the computing environment 1100. The output devices 1160 may be a display, a printer, a speaker, a compact disc (CD), a writer, or other device that provides output from the computing environment 1100.

[0054] The communications connection(s) 1170 enable communication over a communications medium with another computer entity. The communications medium conveys information, such as computer-executable instructions, audio or video input or output, or other data, in a modulated data signal, hereafter referred to as a "modulated data signal." A modulated data signal is a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, the communications medium may be electrical, optical, RF, or other carriers.

[0055] Although some operations of the disclosed methods are described in a particular order for convenient presentation, it should be understood that this style of description encompasses reordering, unless specific language set forth below requires a particular order. For example, operations described in sequence can, in some cases, be reordered or performed simultaneously. Moreover, for simplicity, the accompanying figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods.

[0056] Any of the disclosed methods can be implemented as computer-executable instructions stored on one or more computer-readable storage media (e.g., one or more optical media disks, volatile memory elements (such as DRAM or SRAM), or non-volatile memory elements (such as flash memory or hard disks) and executed on a computer (e.g., any commercially available computer, including a smart phone or other mobile device that includes computing hardware). Computer-readable storage media does not include communication connections such as signals and carrier waves. Any of the computer-executable instructions for implementing the disclosed techniques, as well as any data created or used during the implementation of the disclosed embodiments, can be stored on one or more computer-readable storage media. The computer-executable instructions can be part of, for example, a dedicated software application, or a software application accessed or downloaded by a web browser or other software application (such as a remote computing application). Such software may be executed, for example, on a single local computer (e.g., any suitable commercially available computer) or in a networked environment (e.g., via the Internet, a wide area network, a local area network, a client-server network (such as a cloud computing network), or other such network).

[0057] For clarity, only certain selected aspects of the software-based implementation are described. Other details that are well known in the art are omitted. For example, it should be understood that the disclosed technology is not limited to any particular computer language or program. For example, aspects of the disclosed technology can be implemented in C++, Java, Perl, or any other suitable programming language. Similarly, the disclosed technology is not limited to any particular computer or hardware type. Specific details of suitable computers and hardware are well known and need not be described in detail in this disclosure.

[0058] It should also be understood that any functionality described herein may be performed, at least in part, by one or more hardware logic elements instead of software. For example, and without limitation, example types of hardware logic elements that may be used include Field Programmable Gate Arrays (FPGAs), Application / Program-Specific Integrated Circuits (ASICs), Application / Program-Specific Standard Products (ASSPs), System-on-a-Chip (SOC) systems, Complex Programmable Logic Devices (CPLDs), and the like.

[0059] Additionally, any of the software-based embodiments (e.g., including computer-executable instructions for causing a computer to perform any of the disclosed methods) may be uploaded, downloaded, or accessed remotely by any suitable communications means, including, for example, the Internet, the World Wide Web, an intranet, a software application, cable (including fiber optic cable), magnetic communication, electromagnetic communication (including RF, microwave, and infrared communication), electronic communication, or other such communications means.

[0060] Thus, various embodiments of a magnetoacoustic spin wave signal processing system are provided. In one embodiment, the system comprises an acoustic wave transducer configured to generate surface acoustic waves in a plane of a magnetostrictive material, the magnetostrictive material serving as a medium for spin waves traveling in said plane, and the acoustic wave transducer oriented such that the acoustic waves parametrically amplify the spin waves.

[0061] In a first example of the system, the system further comprises an input spin wave transducer configured to generate a spin wave and an output spin wave transducer configured to measure the output spin wave, where surface acoustic waves generated by the acoustic wave transducer parametrically amplify the spin wave as the spin wave travels from the input spin wave transducer through the magnetostrictive material. In a second example of the system that optionally includes the first example, the output spin wave comprises a spin wave parametrically amplified by the acoustic wave, and the output spin wave transducer measures the spin wave parametrically amplified by the acoustic wave. In a third example of the system that optionally includes one or more of the first and second examples, the input spin wave transducer converts an electrical signal within a predetermined frequency band to generate a spin wave, and the output spin wave transducer converts the parametrically amplified spin wave into an amplified electrical signal within a predetermined frequency band, where the predetermined frequency band comprises one or more of a radio frequency band, a microwave frequency band, and a millimeter wave frequency band. In a fourth example of a system optionally including one or more of the first to third examples, the output spin wave includes an idler spin wave generated when the spin wave is parametrically amplified by an acoustic wave, and the output spin wave transducer measures the idler spin wave. In a fifth example of a system optionally including one or more of the first to fourth examples, the input spin wave transducer transforms an input electrical signal to generate a spin wave, and the output spin wave transducer transforms the idler spin wave into an output electrical signal having a center frequency shifted relative to a center frequency of the input electrical signal to measure the idler spin wave. In a sixth example of a system optionally including one or more of the first to fifth examples, the input spin wave transducer transforms an input electrical signal to generate a spin wave, and the output spin wave transducer transforms the idler spin wave into an output electrical signal usable to determine a time correlation or time convolution of a modulation of the input electrical signal. In a seventh example of a system that optionally includes one or more of the first to sixth examples, the acoustic wave transducer, the input spin wave transducer, and the output spin wave transducer are configured to selectively block or amplify an electrical signal depending on the code modulating the electrical signal.In an eighth example of a system optionally including one or more of the first to seventh examples, the input spin wave transducer is positioned at a specific angle relative to the acoustic wave transducer, and the output spin wave transducer is positioned based on said angle relative to the input spin wave transducer and the acoustic wave transducer. In a ninth example of a system optionally including one or more of the first to eighth examples, the surface acoustic wave parametrically amplifies the spin wave during the parametric interaction, the parametric interaction spanning a specific region of space and for a specific duration. In a tenth example of a system optionally including one or more of the first to ninth examples, the acoustic wave transducer is configured to parametrically amplify the spin wave in one or more spin wave circuits. In an eleventh example of a system optionally including one or more of the first to tenth examples, the range of frequencies over which the device operates is adjustable by a magnetic field. In a twelfth example of a system optionally including one or more of the first to eleventh examples, the magnetostrictive material comprises a ferrite material. In a thirteenth example of a system optionally including one or more of the first to twelfth examples, the acoustic wave transducer is oriented at an angle such that idler spin waves resulting from the parametric interaction of the acoustic wave with the spin wave are non-propagating standing spin waves. In a fourteenth example of a system optionally including one or more of the first to thirteenth examples, a range of input frequencies for the input spin wave transducer and the acoustic wave transducer are selected such that in the parametric interaction of the acoustic wave with the spin wave, output spin waves are generated within a third distinct frequency range.

[0062] In another embodiment, a device comprises an acoustic wave transducer configured to generate surface acoustic waves in the plane of the magnetostrictive material and at least one spin wave transducer configured to generate spin waves, the spin waves propagating in the plane of the magnetostrictive material and parametrically interacting with the surface acoustic waves.

[0063] In a first example of the device, the at least one spin wave transducer includes an input spin wave transducer configured to generate spin waves and an output spin wave transducer configured to measure the output spin waves, where the input spin wave transducer is positioned at a particular angle relative to the acoustic wave transducer and the output spin wave transducer is positioned based on the angle relative to the acoustic wave transducer and the input spin wave transducer to measure the output spin waves.

[0064] In yet another embodiment, a method includes converting an electrical signal into a spin wave, the spin wave propagating in the plane of the magnetostrictive material; generating an acoustic wave in the plane of the magnetostrictive material at a specific angle relative to the spin wave; and converting the output spin wave into an output electrical signal, the output spin wave being generated during parametric interaction between the spin wave and the acoustic wave.

[0065] In a first example of the method, the output spin wave comprises one or more of an acoustically parametrically amplified spin wave or an idler spin wave generated during the parametric interaction. In a second example of the method, optionally including the first example, the method further comprises converting an electrical signal into a spin wave with an input spin wave transducer and converting the output spin wave into an output electrical signal with an output spin wave transducer, the output spin wave transducer positioned relative to the input spin wave transducer to capture at least one of the acoustically parametrically amplified spin wave or an idler spin wave.

[0066] The disclosed methods, devices, and systems should not be construed as being limiting in any way. Instead, the present invention is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, either alone or in various combinations or subcombinations with one another. The disclosed methods, devices, and systems are not limited to any particular aspect or feature, or combination thereof, and the disclosed embodiments do not require that any one or more particular advantages exist or that any one or more problems are solved.

[0067] In view of the numerous possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the described embodiments are merely examples of the invention and should not be construed as limiting the scope of the invention, and therefore, we claim as our invention all that comes within the scope of the following claims.

Claims

1. 1. A system comprising an acoustic transducer configured to generate surface acoustic waves within a surface of a magnetostrictive material, the magnetostrictive material acting as a medium for spin waves traveling in the plane, the acoustic transducer oriented such that the surface acoustic waves parametrically amplify the spin waves.

2. an input spin wave transducer configured to generate the spin wave; and an output spin wave transducer configured to measure the output spin wave; The system of claim 1 , wherein the surface acoustic waves generated by the acoustic wave transducer parametrically amplify the spin waves as they travel from the input spin wave transducer through the magnetostrictive material.

3. 3. The system of claim 2, wherein the output spin wave comprises the spin wave parametrically amplified by the surface acoustic wave, and the output spin wave transducer measures the spin wave parametrically amplified by the surface acoustic wave.

4. 4. The system of claim 3, wherein the input spin wave transducer converts an electrical signal within a predetermined frequency band to generate the spin wave, and the output spin wave transducer converts the parametrically amplified spin wave into an amplified electrical signal within the predetermined frequency band, the predetermined frequency band including one or more of a radio frequency band, a microwave frequency band, and a millimeter wave frequency band.

5. 3. The system of claim 2, wherein the output spin waves include idler spin waves that are generated when the spin waves are parametrically amplified by the surface acoustic wave, and the output spin wave transducer measures the idler spin waves.

6. 6. The system of claim 5, wherein the input spin wave transducer converts an input electrical signal to generate the spin wave, and the output spin wave transducer converts the idler spin wave into an output electrical signal having a center frequency shifted relative to the center frequency of the input electrical signal for measuring the idler spin wave.

7. 6. The system of claim 5, wherein the input spin wave transducer converts an input electrical signal to generate the spin wave, and the output spin wave transducer converts the idler spin wave into an output electrical signal that can be used to determine a time correlation or time convolution of a modulation of the input electrical signal.

8. 6. The system of claim 5, wherein the acoustic wave transducer, the input spin wave transducer, and the output spin wave transducer are configured to selectively block or amplify an electrical signal depending on a code modulating the electrical signal.

9. The system of claim 2 , wherein the input spin wave transducer is positioned at a particular angle relative to the acoustic wave transducer, and the output spin wave transducer is positioned based on the particular angle relative to the input spin wave transducer and the acoustic wave transducer.

10. The system of claim 2 , wherein the surface acoustic wave parametrically amplifies the spin wave during a parametric interaction, the parametric interaction spanning a specific region of space and for a specific duration.

11. The system of claim 1 , wherein the acoustic wave transducer is configured to parametrically amplify the spin waves in one or more spin wave circuits.

12. The system of claim 1 , wherein the range of frequencies at which the system operates is adjustable by a magnetic field.

13. The system of claim 1 , wherein the magnetostrictive material comprises a ferrite material.

14. 2. The system of claim 1, wherein the acoustic wave transducer is oriented at an angle such that an idler spin wave resulting from the parametric interaction of the surface acoustic wave with the spin wave is a non-propagating standing spin wave.

15. 3. The system of claim 2, wherein the ranges of input frequencies for the input spin wave transducer and the acoustic wave transducer are selected such that in the parametric interaction of the surface acoustic wave and the spin wave, output spin waves are generated within a third distinct frequency range.

16. an acoustic wave transducer configured to generate surface acoustic waves in the plane of the magnetostrictive material; at least one spin wave transducer configured to generate spin waves, The spin waves propagate within the plane of the magnetostrictive material and parametrically interact with the surface acoustic waves.

17. The at least one spin wave transducer comprises: an input spin wave transducer configured to generate the spin wave; an output spin wave transducer configured to measure the output spin wave; 17. The device of claim 16, wherein the input spin wave transducer is positioned at a specific angle relative to the acoustic wave transducer and the output spin wave transducer is positioned based on the specific angle relative to the acoustic wave transducer and the input spin wave transducer to measure the output spin wave.

18. converting an electrical signal into a spin wave, the spin wave propagating in the plane of the magnetostrictive material; generating an acoustic wave in the plane of the magnetostrictive material at a particular angle relative to the spin wave; converting an output spin wave into an output electrical signal, the output spin wave being generated during a parametric interaction of the spin wave with the acoustic wave; The method includes:

19. 20. The method of claim 18, wherein the output spin waves include one or more of the spin waves parametrically amplified by the acoustic wave or idler spin waves generated during the parametric interaction.

20. converting the electrical signal into the spin wave with an input spin wave transducer; and converting the output spin wave into an output electrical signal with an output spin wave transducer; 20. The method of claim 19, wherein the output spin wave transducer is positioned relative to the input spin wave transducer to capture at least one of the spin waves parametrically amplified by the acoustic wave or the idler spin waves.

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