Elastic wave device with resonance frequency adjustment

Abstract

An elastic wave device comprising: a variable impedance means; a first electromechanical device, in particular, a first transducer, and a second electromechanical device, in particular, a second transducer or an electrode array configured to reflect at least partially elastic waves emitted by the first electromechanical device; an array of at least one electrode located between the first electromechanical device and the second electromechanical device in the direction of propagation of the elastic waves, in which at least one electrode of the array of at least one electrode is connected to an electrical potential via the variable impedance means; the array forming a cavity; a frequency adjustment means configured to adjust the resonant frequency of the cavity; a control means configured to control the variable impedance means. (FIG. 11).

Description

Title of the invention: Elastic wave device with resonance frequency adjustment

[0001] The invention relates to an elastic wave device in the field of elastic wave-based telecommunication components, in particular surface acoustic waves (SAW).

[0002] Devices using elastic surface waves have recently seen a marked increase in their use for a variety of applications such as filtering, signal manipulation and processing, and detection. An example of a device comprising two transducers, each consisting of a combination of interlocking electrode combs forming the so-called interdigitated transducer (IDT), and an electrode array is described in EP 3 599 720 AL

[0003] In the telecommunications context, numerous radio frequency (RF) bands are used to receive and transmit information. Each RF band defines a channel to which filtering operations must be applied in order to process, manipulate, or store information. In this context, the industry requires filters with as many resonant frequencies as there are RF bands to process.

[0004] Oscillators are used in many areas of modern technology such as digital television, modems, transmitters, and computers. In such applications, electronic jitter must be minimized in order to provide stable solutions, in particular stable frequency sources, for optimal operation.

[0005] The present invention aims to reduce the disadvantages mentioned above and to meet these demands. The present invention relates to an elastic wave device comprising: a variable impedance means; a first electromechanical device, in particular, a first transducer, and a second electromechanical device, in particular, a second transducer or an electrode array configured to reflect at least partially elastic waves emitted by the first electromechanical device; an array of at least one electrode located between the first electromechanical device and the second electromechanical device in the direction of propagation of the elastic waves, in which at least one electrode of the array of at least one electrode is connected to an electrical potential via the variable impedance means; the array forming a cavity; a frequency adjustment means configured to adjust the resonant frequency of the cavity; a control means configured to control the variable impedance means. In the context of the invention, an electrode array can be constructed with a single electrode or with a plurality of electrodes. Each electrode in the array of at least one electrode can be connected to a variable impedance means from among a plurality of variable impedance means, and each variable impedance means from among a plurality of variable impedance means can be controlled by a control means from among a plurality of control means (see also the detailed description below). Controlling the variable impedance means by the control means involves controlling one or more impedances of the variable impedance means, for example, controlling / adjusting one or more capacitances of one or more capacitors. Elastic waves can be surface acoustic waves. The elastic wave device can be, for example, a surface acoustic wave (SAW) filtering device.The SAW filter can be used, in particular, to filter an oscillation loop, thereby selecting the frequency delivered by the oscillator. The frequency-tuning means ensures the stabilization of such a frequency-tuned oscillator. This can be achieved in a phase-locked loop circuit. In this situation, the combination of the SAW filter / resonator and a signal amplifier satisfies the so-called Barkhausen condition, which states that the loop phase must be 0 modulo 2ir to guarantee constructive signal interaction within the loop, and that the loop gain must be equal to or greater than 1, meaning that the amplifier positively balances the filter / resonator insertion losses. The resonance condition of the elastic wave device can be electrically modulated by modifying the cavity boundary conditions.

[0006] Furthermore, it should be noted that, in principle, a variable capacitance allows the network of at least one electrode to which it is connected to be switched from an open-circuit (OC) configuration, i.e., a floating connection and therefore a low coupling capacitance, to a short-circuit (SC) configuration, i.e., a connection with a predetermined electrical potential such as ground and therefore with a high coupling capacitance. By using an impedance comprising a variable capacitance, the phase of the elastic waves passing through the gap between the two transducers can be modified, resulting in a change in the bandwidth position and, in particular, in the spectral position at which the insertion losses of the filter / resonator transfer function S12 are minimal, with its phase close to zero modulo 2ir.In particular, by switching from the OC configuration to the SC configuration, the device's bandwidth can then continuously transition from a high-frequency range to a low-frequency range.

[0007] In an alternative configuration, the variable impedance may include a variable inductance; in particular, it allows the network of at least one electrode to which it is connected to be switched from a configuration corresponding to an open connection (OC) to a configuration corresponding to a connection with a predetermined electrical potential, short-circuited (SC). By using an impedance including a variable inductance, it also becomes possible to change the operating frequency ranges, without, however, reaching the range between the high frequency obtained for the OC configuration and the low frequency obtained for the SC configuration.

[0008] According to one embodiment, the array of at least one electrode may comprise several electrodes, in particular, in the form of parallel bands, several of which have variable impedances; in particular, each of the electrodes may be connected to a separate variable impedance. The number of parallel bands modifies the frequency agility of the device, in particular the frequency range accessible to the device. This further facilitates adapting the agility of the device to the desired operating criteria for a particular case.

[0009] According to one embodiment, the electrode array can be configured to change the phase of the elastic waves and / or configured to reflect them at least partially. The introduction of an electrode array configured to reflect the elastic waves at least partially creates resonant cavities, which notably reduces the frequency width of the transition between the device's passband and the frequency rejection band, which corresponds to all frequencies not included in the device's operating bandwidth. Depending on the situation, those skilled in the art will know how to define the ends of the passband and the rejection band. The transition between the passband and the rejection band is called the transition band.The frequency width of the transition band is defined as the attenuation of the transmitted signal from the device's minimum insertion loss to the same value plus 30 dB, 40 dB, or 50 dB, depending on the device specifications.

[0010] According to one embodiment, the electrodes of a first subset of electrodes of the network of at least one electrode can be connected by means of variable impedance.

[0011] In another embodiment of the invention, the electrodes of a second subset of electrodes in the array of at least one electrode may be connected to each other and to a floating electrical potential or connected to a predetermined electrical potential, in particular to ground. This configuration of the device makes it possible, for example, to create a mirror for elastic waves whose spectral range of the reflection function varies according to the connection conditions.

[0012] According to another embodiment of the invention, the first subassembly and the second subassembly can be arranged so that the electrodes of the The first subset and those of the second subset are interdigitated with respect to each other. This electrode arrangement creates an air gap coupler (AG) that allows the phase of the device to be changed. The potential frequency agility of the device depends on the number of fingers composing the two interdigitated electrode arrays (IDTs), and in particular, by increasing the number of finger pairs in the interdigitated subsets, it is possible to broaden the frequency range of the device's frequency agility.

[0013] According to another embodiment of the invention, a plurality of electrode arrays may be included between the first electromechanical device, in particular a first transducer, and the second electromechanical device, in particular a second transducer, the arrays being separated from each other by free and / or metallized propagation gaps. The distances between two adjacent electrode arrays may be identical. In particular, by introducing more electrode arrays configured to at least partially reflect elastic waves, the number of cavities in the device is increased, thereby allowing a modification and, in particular, a reduction in the frequency width of the transition between the device's passband and its frequency rejection band.Furthermore, by adjusting the distance between adjacent electrode arrays, it becomes possible to obtain phase quadratures between the elastic waves propagating in the cavities located in the space between the two transducers and those coming from the transducers, in particular, to increase the electromechanical coupling coefficient.

[0014] According to another embodiment of the invention, the distance between the first electromechanical device and the directly adjacent electrode array, and the distance between the second electromechanical device and the directly adjacent electrode array, can be identical and, in particular, equal to the distance between two adjacent electrode arrays. This arrangement can thus improve the resonance conditions of the device, and consequently the coupling performance of the elastic wave device.

[0015] According to another embodiment of the invention, an even number of electrode arrays configured to change the phase of elastic waves can be included in the space between the transducers, which is configured to at least partially reflect the elastic waves. In particular, the electrode array configured to at least partially reflect the elastic waves can be a Bragg mirror arranged to form two resonant cavities, located on either side of this Bragg mirror or the reflecting structure, which can achieve a quadrature of the phase of the elastic waves between the space between the transducers (IDT, for example) and the reflecting structure(s). Increasing the number of pairs of electrode arrays Configured to change phase with or without an electrode array designed to at least partially reflect elastic waves, the number of resonant cavities in the device increases and, in particular, reduces both the frequency width of the transition between the device's passband and frequency rejection band, and increases the device's operating bandwidth. Especially for oscillator applications, it is important to minimize the filter resonator bandwidth because this parameter directly influences the device's phase noise. Specifically, this phase noise, which represents the signal's power density near its nominal frequency, plateaus at fL = fO / 2xQ, where fL is the Leeson frequency, fO is the nominal frequency, and Q is the filter / resonator's quality factor, defined as the full-width half-maximum (FWHM) of its transfer function.It is therefore very important to push this Leeson frequency as close as possible to the nominal frequency to improve the oscillator's phase noise figure. However, this must not be achieved by sacrificing the insertion losses of the transfer function, which should not exceed 10 dB, and preferably 6 dB or even 3 dB.

[0016] According to one embodiment, the elastic wave device further comprises a first reflection structure, i.e. a first mirror, and a second reflection structure, i.e. a second mirror, to facilitate the formation of resonance spaces, the first electromechanical device being positioned between the first reflection structure and the array of at least one electrode, and the second electromechanical device being positioned between the second reflection structure and the array of at least one electrode.

[0017] In another embodiment of the invention, the first and second electromechanical devices, for example transducers, can be arranged above or within a piezoelectric substrate, in particular, a composite substrate comprising a base substrate and a piezoelectric layer, the thickness of the piezoelectric layer being less than or equal to 1.5 x X, where X is the wavelength of the fundamental mode of elastic surface waves. By using a composite substrate designed for this purpose, it is possible to guide shear waves that allow for a higher electromechanical coupling between the elastic waves and the electromechanical elements of the device than any other wave polarization, for example, the elliptical (Rayleigh-type) polarization of quasi-longitudinal polarization.

[0018] According to another embodiment of the invention, a dielectric layer and / or a trapping layer and / or a Bragg mirror may be included between the base substrate and the piezoelectric layer. This layer, rich in electrical charge traps, improves the insulating properties of the base substrate and, consequently, the performance of the device.

[0019] According to another embodiment of the invention, the polarization of the elastic waves can correspond to a guided shear wave, a guided longitudinal wave, or an elliptical (Rayleigh-type) wave within the piezoelectric layer. In particular, the thickness of the piezoelectric layer can influence the efficiency of the guidance of the shear, longitudinal, or elliptical waves. Specifically, a piezoelectric layer with a thickness less than the wavelength of the elastic wave improves the guidance of the shear, longitudinal, and elliptical modes of the elastic waves, and consequently reduces the acoustic radiation energy losses in the composite substrate. The use of these elastic wave modes improves the performance of the elastic device, particularly by minimizing energy losses in the passband in the case of a bandpass filter or a quadrupole resonator.

[0020] Furthermore, in an alternative embodiment, the elastic wave device according to the present disclosure may be a voltage-controlled surface acoustic wave oscillator, VCSO.

[0021] The invention will be better understood and other advantages will become apparent with the aid of the following non-limiting description and the accompanying figures, among which:

[0022] [Fig.1] is a diagram illustrating an elastic wave device according to a first embodiment of the invention.

[0023] [Fig.2] illustrates an elastic wave device according to a second mode of realization in which the space between the two transducers comprises only a single electrode connected to a variable impedance and its control means, all connected to a predetermined electrical potential.

[0024] [Fig.3] illustrates an elastic wave device according to a third embodiment in which the space between the two transducers comprises an electrode array formed by two interdigitated combs (IDT).

[0025] [Fig.4] is a graphical representation of the gain in decibels of the function of transfer of the device according to the third embodiment, which in this case presents a variable impedance comprising a variable capacitor, depending on the value of the variable capacitor.

[0026] [Fig.5] is a graphical representation of the gain in decibels of the function of transfer of the device according to the third embodiment, which in this case has a variable impedance comprising a variable inductance, depending on the value of the variable inductance.

[0027] [Fig.6] illustrates an elastic wave device according to a fourth mode of realization in which the space between the two transducers comprises three electrode arrays, two of which are configured to allow continuity of guidance between neighboring resonant cavities with a low level of elastic wave reflection.

[0028] [Fig.7] is a graphical representation of the gain in decibels of the function of transfer of the device according to the fourth embodiment, which in this case has a variable impedance comprising a variable inductance and a variable capacitance, depending on the value of the variable capacitance.

[0029] [Fig.8] is a graphical representation of the gain in decibels of the function of transfer of the device according to the fourth embodiment, which in this case has a variable impedance comprising a variable inductance and a variable capacitance, depending on the value of the variable inductance.

[0030] [Fig.9] illustrates an elastic wave device according to a fifth mode of realization in which the space between the two transducers comprises three electrode arrays, two of which are configured to transmit but not reflect elastic waves.

[0031] [Fig. 10] illustrates an elastic wave device according to a sixth embodiment in which the space between the two transducers comprises five electrode arrays, three of which are configured to transmit mainly but not reflect elastic waves, unlike the other two which are configured to reflect mainly elastic waves and are interposed between each of the three preceding arrays.

[0032] [Fig. 11] illustrates an elastic wave device according to an embodiment of the present invention.

[0033] [Fig. 12] is a schematic representation of a clock data retrieval circuit, CdR, in which an elastic wave device according to [Fig. 11] can be integrated.

[0034] The invention will be described in more detail using advantageous embodiments by way of example and with reference to the drawings. The embodiments described are simply possible configurations such that individual features as described can be provided independently of each other or can be omitted when implementing the present invention.

[0035] [Fig. 11] illustrates an elastic wave device 11300 according to an embodiment of the present invention. In [Fig. 11] the elastic wave device 11300 comprises a frequency adjustment means 11100. The elastic wave device 11300 further comprises a first electromechanical device 11130. In this embodiment, the first electromechanical device may be a first transducer (IDT). The elastic wave device 11300 further comprises a second electromechanical device 11140, in particular a second transducer (IDT) or an electrode array configured to reflect at least partially elastic waves emitted by the first electromechanical device 11130. The elastic wave device as illustrated in [[Fig. 11]] further comprises an array 11150 of at least one electrode situated between the first electromechanical device 11130 and the second electromechanical device 11140 in the direction of propagation of the elastic waves, in which at least one electrode of the array 11150 of at least one electrode is connected to an electrical potential via the variable impedance means 11100, the at least one electrode representing a channel, the channel corresponding to the at least one electrode, respectively. In [Fig. 11], the elastic wave device 11300 further comprises a first reflection structure 11110 and a second reflection structure 11120. Here, the first electromechanical device 11130 is positioned between the first reflection structure 11110 and the array of at least one electrode, while the second electromechanical device 11140 is positioned between the second reflection structure 11120 and the array of at least one electrode. Thus, a third port, 11160, in the middle of the structure 11300 shown in [Fig. 11], is connected to a variable impedance means, for example, a variable capacitor, to adjust the resonant frequency of the device. In [Fig. 11], the elastic wave device can be used to provide stabilization for a frequency-tuned oscillator. This can be implemented in a phase-locked loop circuit. The elastic wave device in [Fig. 11] can thus implement a structure for a narrowband filter whose resonance conditions can be electrically modulated by changing the electrical boundary conditions of the cavity electrodes.

[0036] [Fig. 12] illustrates a schematic representation of a clock data retrieval circuit, CdR, in which an elastic wave device, for example according to [Fig. 11] can be integrated.

[0037] Voltage-controlled crystal oscillators (VCXOs) can be used in clock generators. VCXO clock generators are used in many fields such as digital television, modems, transmitters, and computers. Design parameters of a VCXO clock generator include the tuning voltage range, center frequency, frequency tuning range, and output signal timing jitter. Jitter must be minimized in applications such as radio receivers, transmitters, and measuring equipment.

[0038] VCXO frequency synthesizers can be used to generate precise and adjustable frequencies based on a stable single-frequency clock. A A digitally controlled oscillator based on a frequency synthesizer can serve as a digital alternative to analog voltage-controlled oscillator circuits.

[0039] Voltage-controlled surface acoustic wave (SAW) oscillators (VCSOs) have been used for many years in commercial applications and beyond. Their low phase noise allows frequency multiplication at higher frequencies for use as sources, such as local oscillators in radar and other microwave systems. Furthermore, the compact size of the solution and its limited sensitivity to thermal effects offer significant advantages to this type of oscillator solution.

[0040] In particular, the excellent tuning linearity provides outstanding performance in clock recovery applications in telecommunications systems. The small size, robust construction, and frequency stability offer significant advantages over other VCO technologies, as mentioned above.

[0041] A VCSO can be used in vector network analyzer (VNA) architectures. This can provide, for example for RF sources and / or harmonic oscillators, the possibility of simplifying the architecture and improving the stability delay and / or warming effects by using an oscillator that can be controlled as a VCSO, i.e. including an elastic wave device.

[0042] VCSOs also find frequent use in telecommunications applications such as low jitter clocks, in high-performance synchronous optical networks, SONETs, ​​and clock recovery applications.

[0043] [Fig. 12] illustrates a CdR 12300 circuit. The CdR 12300 circuit of [Fig. 12] comprises a control section 12304, a data input section 12302, and a clock recovery section 12305. The control section 12304 of [Fig. 12] includes the input of various control signals 12303. The data input section 12302 includes one or more data inputs 12301. The clock recovery section 12305 may include a delay unit 12309. The delay unit 12309 may use a ripple device according to the present invention. The clock recovery section 12305 may further include a VCSO unit 12311.Thus, clock data retrieval (CDR) circuits can use a frequency-multiplying VCSO 12311, for example in a phase-locked loop (PLL), as a tracking filter to recover a low-jitter clock from the incoming non-return-to-zero (NRZ) data stream 12301. For the VCSO 12311 unit, the PLL loop bandwidth can be adjusted between 0.1 and 6 MHz to optimize jitter performance.

[0044] [Fig. 1] represents the elastic wave device 100 as described in a first embodiment of the invention. The elastic wave device 100 represents a dual-port resonator that can be used as a filter. The elastic wave device 100 comprises a first electromechanical device, in particular, here a first transducer (IDT) 3 forming a first port, and a second electromechanical device, in particular, here a second transducer (IDT) 5 forming a second port, which in alternative embodiments can be an array of electrodes configured to reflect at least partially the elastic waves emitted by the first electromechanical device 3.

[0045] The device 100 further comprises an array 4000 of at least one electrode 1000, 2000, 3000 situated between the first transducer 3 and the second transducer 5 in the direction of propagation of elastic waves, in which at least one electrode of the array is connected to a predetermined electrical potential 1005, 2005, 3005 via a variable impedance 1003, 2003, 3003, and a control means 1007, 2007, 3007 for changing the variable impedance, all arranged on a piezoelectric substrate 9.

[0046] In this first embodiment, the piezoelectric substrate can be a composite substrate comprising a piezoelectric layer 11 with crystallographic axes X, Y and Z, a dielectric layer 13 and a base substrate 15.

[0047] In this embodiment, the piezoelectric layer 11 is LiTaO3 or LiNbO3. In particular, using IEEE 1949 Std-176 standards, the orientations of the crystallographic cross-section of the piezoelectric layer are defined by (YXZ) / 0, with 0 denoting the crystallographic orientation angle corresponding to a rotation around the crystal axis X between 0 and 60 degrees or between 90 and 150 degrees.

[0048] The piezoelectric layer 11 can also be made of potassium niobate, KNbO3, or any other material of similar composition, such as KTN. It is also possible to use for the piezoelectric layer 11 a film formed epitaxially or sprayed, for example, of aluminum nitride AIN, scandium-doped aluminum nitride AIScN, zinc oxide ZnO, PZT, GaN, or any other composition of AIN and GaN.

[0049] The thickness of the piezoelectric layer 11 is on the order of the wavelength X of the elastic waves, or less; in particular, it may be approximately 10 microns, or less, in particular between 0.1 and 1.1 microns. The thickness of the base substrate 15 is greater than that of the piezoelectric layer 11. Preferably, the thickness of the base substrate 15 is at least ten times greater than the thickness of the piezoelectric layer 11. In particular, it may be 50 to 100 times greater, corresponding to a base substrate with a thickness of 50 to 1000 microns. In particular, the substrate thickness may be from 100 microns to 500 microns.

[0050] The basic substrate 15 used in the first embodiment of the invention is a silicon substrate, in particular a silicon substrate with high electrical resistivity. High electrical resistivity means an electrical resistivity greater than 1000 Ωcm. Preferably, the silicon is in crystalline form, with the substrate orientation preferably in the (100) direction, resulting in a higher elastic wave propagation velocity than other crystallographic orientations such as (110), (111), or (001), which can also be used. The choice of substrate takes into account the velocity beyond which elastic waves are no longer guided by the silicon surface, known as the VSSBW (surface grazing volume wave, SSBW) velocity. This velocity must therefore be greater than the velocity of the mode corresponding to the anti-resonance condition, but close enough to it to prevent the excitation of other modes that would otherwise degrade the spectral purity of the device's response.Advantageously, the speed is close to the speed corresponding to the upper edge of the frequency stop band induced by the periodicity of the IDT and mirror networks of the device. Thus, the crystallographic axes Z of the substrate and the piezoelectric layer along which the respective planes are defined can ideally be aligned in the case of silicon (111) or misaligned by 45° for silicon (100) or (111) in order to limit the contributions of parasitic modes beyond the anti-resonance frequency of the fundamental mode, or misaligned in the angular range [-10°, +10°] for Si(111) considering the corresponding IEEE angular definition in the form (YXwlt) / +457-35.37^, with rp the misalignment angle, or in the angular range [+170°, ±190°] for Si(111) considering the corresponding IEEE angular definition in the form (YXwlt) / ±457+35.37'ip, with rp the misalignment angle.The basic substrate 15 may be made of or comprise other materials, in particular to enable elastic waves to propagate at a speed greater than that of elastic waves propagating in the piezoelectric layer 11. In particular, the basic substrate 15 may be made of or comprise carbon-diamond, sapphire or silicon carbide.

[0051] The base substrate 15 may include a trapping layer, particularly located between the dielectric layer 13 and the base substrate 15, thereby improving the electrical insulation performance of the base substrate 15. This trapping layer may be formed of at least one polycrystalline, amorphous, or porous material, such as polycrystalline silicon, amorphous silicon, or porous silicon. However, the invention is not limited to these materials.

[0052] In alternative embodiments, the base substrate 15 may comprise a Bragg mirror, located between the piezoelectric layer 11 and the base substrate 15. This Bragg mirror consists of a stack of layers periodically alternating the acoustic impedance of the medium, which is defined as the product of the elastic ground propagation velocity and the density of the material in which the ground is propagates, all expressed in Rayleighs, or preferably in MRayleighs, that is 106 Rayleighs.

[0053] This stack of layers forming the Bragg mirror can be composed of alternating layers of, for example, tungsten and silica, or Si3N4 and SiO2, or Mo and Al. More generally, any pair of materials having an acoustic impedance ratio greater than 2 can be used. The bottom layer can be made of standard silicon, high-resistivity silicon, glass, or, more generally, any material having a coefficient of thermal expansion less than 6 ppm*K*. The stack can also include a trapping layer to improve the insulating properties.

[0054] The dielectric layer 13 of [Fig.1], formed by a thin layer of SiO2 with a thickness of 500 nm, is located at the interface between the piezoelectric layer 11 and the base substrate 15. However, the thickness of the dielectric layer 13 can be less than or greater than 500 nm and, in particular, can vary between 10 nm and 6 microns.

[0055] As mentioned above, the elastic wave device 100 comprises the two electromechanical transducers 3, 5 and the electrode array 4000 (electrodes 1000, 2000 and 3000) located between the two transducers 3 and 5. The electrode array 4000 (electrodes 1000, 2000 and 3000) is spaced from the first transducer 3 by a certain distance d, and from the second transducer 5 by a certain distance d2, as seen in [[Fig.1]). The three electromechanical elements 3, 5 and 4000 are arranged in the (ZX) plane and oriented so that their electrodes 311, 313, 315, 331, 333, 335, 511, 513, 515, 531, 533, 535, 1001, 2001, 3001 in the form of parallel bands are perpendicular to the X axis of propagation of elastic waves.

[0056] Spaces 17 and 19 between transducer 3 and 4000, and between transducer 5 and electrode array 4000, have widths d₂ and d₂, respectively. These spaces form resonant cavities (spaces) in the X direction of elastic wave propagation. In other embodiments of the invention, the device 100 may comprise one or more resonant cavities, in particular, more than two. In the case of the configuration shown in [Fig. 1], two resonant cavities are present, with, in particular, the same distances d₂ and d₂ for the two spaces 17 and 19. Alternatively, the distances d₂ and d₂ may be different from each other.

[0057] In [Fig.1], the electrode array 4000 consists of three interdigitated electrodes 1000, 2000 and 3000. Each of the three electrodes 1000, 2000, 3000 has a straight end 1001, 2001, 3001.

[0058] However, the number of electrodes in the 4000 array is not limited to three; in particular, it may be less than or greater than three; in particular, it may be equal to 1. The 4000 array and its 1000, 2000, and 3000 electrodes are made of an aluminum-based material such as pure aluminum or an aluminum alloy such as copper-, silicon-, or titanium-doped aluminum (Ai). However, other materials can also be used, particularly those providing a high reflection coefficient for a relatively small electrode thickness. For example, materials such as copper, molybdenum, nickel, platinum, or gold can be used. The 4000 array and its 1000, 2000, and 3000 electrodes may also include an adhesion layer made of, for example, titanium, tantalum, chromium, zirconium, palladium, iridium, tungsten, etc. More complex / multilayer metal combinations can be considered to improve the transducer's conductivity or power handling capability. This electrode and comb composition can also be applied to transducers 3 and 5.

[0059] The 4000 array is also defined by the spacing p between two consecutive interdigitated electrodes, such as the distance between electrodes 1001 and 2001. In particular, this spacing p can be defined by the Bragg condition, which states that p = λ / 2, with λ being the wavelength of the elastic operating waves of the device. It is also possible to create resonant cavities by varying the distance between two consecutive interdigitated electrodes, which may, in particular, not be the same everywhere within the same structure comprising several electrodes, or even, for example, two interdigitated combs. The electrodes are also defined by the length l of their straight ends, as well as by their widths, denoted a in Fig. 1. In particular, the values ​​of a, l, and can be modified to obtain a desired electromechanical coupling coefficient.

[0060] In the embodiment of the invention shown in [Fig. 1], the electrodes 1000, 2000, and 3000 of the electrode array 4000 are each connected to an individual predetermined electrical potential, here the predetermined electrical potentials 1005, 2005, and 3005, respectively. The potentials 1005, 2005, and 3005 may be the same, in particular the same electrical potential; in particular, this reference potential may be ground. Alternatively, the potentials 1005, 2005, and 3005 may be different. The electrodes 1000, 2000, 3000 of the electrode array 4000 are each respectively connected to a variable impedance 1003, 2003, 3003. In alternative embodiments of the invention, it is possible that one or more of the electrodes 1000, 2000, 3000 are not connected to a variable impedance.In particular, it is possible, and sufficient to obtain the desired frequency agility, for a single electrode to be connected to a variable impedance, and it is this agility that makes it possible to compensate for the effects of temperature variation so that the elastic wave device can adjust to its (optimal) operating frequency even under the influence of temperature variations.

[0061] According to the invention, the elastic wave device 100 further comprises control means 1007, 207, 3007 connected respectively to the variable impedances 1003, 2003, 3003, and enabling the values ​​of the variable impedances 1003, 2003, 3003 to be controlled and modified, in particular remotely, during the operation, or not, of the elastic wave device 100. The impedance can, for example, be a variable capacitance diode which can be controlled by the voltage applied across the terminals of the variable capacitance diode by a variable voltage generator.

[0062] In one embodiment of the invention, the electrodes 1000, 2000, 3000 of the network 4000 can each be connected to a second variable impedance which can be modified by their respective control means 1007, 2007, 3007.

[0063] In the proposed embodiment of the invention shown in [Fig. 1], the transducers 3 and 5 each comprise two interdigitated electrode combs, 31 and 33 for transducer 3, and 51 and 53 for transducer 5. Each of these four combs consists of three interconnected electrodes, 311, 313, 315, 331, 333 and 335 for transducer 3, and 511, 513, 515, 531, 533 and 535 for transducer 5. However, the number of electrodes in each of the combs is not limited to three; in particular, it may be less or more, while not being the same in the two combs 31 and 33, respectively 51 and 55.

[0064] For each of the two transducers 3 and 5, only one of the two combs, in this case comb 33 for transducer 3 and comb 53 for transducer 5, is connected to a predetermined electrical potential, respectively 301 and 501. Comb 31 is connected to an input load 303 and comb 51 to an output load 503.

[0065] In this embodiment of the invention, the pitch between two consecutive interdigitated electrodes p, the width a and the length l of the electrodes are identical in both transducers 3 and 5 as well as in the electrode array 4000. However, in alternative embodiments of the invention, these parameters may be different; in particular, they may be the same in both transducers 3 and 5 but different in the electrode array 4000.

[0066] By varying the value of at least one of the variable impedances 1003, 2003, 3003, it is possible to modify the reflection conditions of the electrode array 4000 and thus tune the operating frequency of the device 100. In particular, the variable impedances 1003, 2003, 3003 may include a capacitance and / or an inductance.

[0067] However, in alternative embodiments of the invention, it is also possible that two electrodes, for example 1000 and 2000, are connected to the same variable impedance.

[0068] By connecting the electrodes 1000, 2000, 3000 to their respective variable impedances 1003, 2003, 3003, it becomes possible, in particular via the means of Controls 1007, 2007, and 3007, to which the variable impedances 1003, 2003, and 3003 are connected, allow for the modification and variation, particularly during the operation of device 100, of the impedance loads of the variable impedances and consequently the electrical conditions of the electrode array 4000. This makes it possible to modify the operating bandwidth of the electromechanical device 100, even after its design and manufacture. According to the invention, device 100 is therefore frequency-sensitive.

[0069] The frequency agility of the elastic wave device 100 can in particular depend on the number of electrodes constituting the electrode array 4000. In particular, by increasing the number of interdigitated electrodes in the array 4000, it is possible to increase the frequency agility of the elastic wave device 100, in other words, the frequency range in which the device 100 can have its operating frequency.

[0070] Alternatively, the variable impedances 1003, 2003, 3003 can be achieved by a simple switch, allowing the transition from a short circuit (SC) to an open circuit (OC).

[0071] Alternatively, the second transducer 5 can be short-circuited. In this way, the device becomes a single-port resonator whose resonant frequency is determined by the reflection conditions of the short-circuited transducer 5 and the electrode array 4000.

[0072] In particular, according to another embodiment of the invention, the second transducer 5 can be replaced by an array of electrodes configured to reflect elastic waves; in particular, it can be a Bragg mirror. The resulting elastic wave device then has only one port, the transducer 3, which is then both the input and output port.

[0073] Alternatively, the device 100 can be placed between two mirrors to further confine the energy in the region of the transducers and the central cavity.

[0074] In a second embodiment of the invention, illustrated in [Fig.2], the device 200 differs from the device 100 illustrated in [Fig.1] in that the electrode array 4000 comprises a single electrode 1000.

[0075] In a third embodiment of the invention, illustrated in [Fig.3], the elastic wave device 300 differs from that illustrated in [Fig.1], 100, in that the electrode array 4000 is replaced by an electrode array 7 consisting of two interdigitated electrode combs 71 and 73.

[0076] In [Fig.3], the electrode array 7 is formed by two interdigitated electrode combs 71 and 73. Each of the two electrode combs 71 and 73 is composed of three straight electrodes, 711, 713 and 715 for comb 71, and 731, 733 and 735 for comb 73, each connected to the other in the same comb.

[0077] However, the number of electrodes in each of the combs 71 and 73 is not limited to three; in particular, it may be lower or higher, and may not be the same in the two combs 71 and 73. The combs 71 and 73, and their respective electrodes 711, 713, 715, 731, 733, and 735, are made of an aluminum-based material such as pure aluminum or an aluminum alloy such as Cu-, Si-, or Ti-doped Ai. However, other materials may also be used, particularly those that provide a high reflection coefficient for a relatively small electrode thickness. For example, materials such as copper, molybdenum, nickel, platinum, or gold may be used. Combs 71 and 73 and their respective electrodes 711, 713, 715, 731, 733 and 735 may also include an adhesion layer made of titanium, tantalum, chromium, zirconium, palladium, iridium, tungsten, etc.More complex / multilayer metal combinations can be considered to improve transducer conductivity or power handling capacity. This electrode and comb composition also applies to transducers 3 and 5.

[0078] The interdigitated electrode combs 71 and 73 are also defined by the spacing p between two consecutive interdigitated electrodes, each originating from one of the two combs 71 and 73, as the distance separating electrodes 71 and 73. In particular, this spacing p can be defined by the Bragg condition, which stipulates that p = λ / 2, with λ being the wavelength of the elastic operating waves of the device. It is also possible to create resonant cavities by varying the distance between two consecutive interdigitated electrodes, which may, in particular, not be the same everywhere within the same structure comprising two interdigitated combs. The electrode combs are also defined by the length l of their electrodes and the width a of their electrodes. In particular, the values ​​of a, l, and p can be modified to obtain a desired coupling coefficient.

[0079] In [Fig.3], the combs 71 and 73 are configured so that the electrode array 7 reflects at least partially the elastic waves, in a so-called mirror coupler (MC) configuration, thus modifying the transmitted and reflected ground phases.

[0080] In an alternative embodiment, these same combs can also be configured to primarily modify the phase of the transmitted elastic waves, without wave reflection as their main objective. They are then said to be in an air-gap coupler (AGC) configuration. In the embodiment of the invention shown in [Fig. 3], the electrode array 711, 713, and 715 of the comb 71 is connected to a predetermined electrical potential, in this case ground 701. The electrode array 731, 733, and 735 forming the comb 73 is connected to an impedance variable 703, which in turn is connected to a predetermined electrical potential, in this case ground 705.

[0081] According to the invention, the elastic wave device 300 further includes a control means 707 which is connected to the variable impedance 703 and allows the value of the variable impedance 703 to be controlled and modified, in particular remotely, during the operation, or not, of the elastic wave device 300.

[0082] In one embodiment of the invention, the electrode array 711, 713 and 715 of the comb 71 can be connected to a second variable impedance which can be modified by a control means 707.

[0083] In the proposed embodiment of the invention shown in [Fig. 3], the transducers 3 and 5 each comprise two interdigitated electrode combs, 31 and 33 for transducer 3, and 51 and 53 for transducer 5. As with the combs 71 and 73, each of these four combs consists of three interconnected electrodes, 311, 313, 315, 331, 333 and 335 for transducer 3, and 511, 513, 515, 531, 533 and 535 for transducer 5. However, the number of electrodes in each of the combs is not limited to three; in particular, it may be less or more, while not being the same in the two combs 31 and 33, respectively 51 and 55.

[0084] For each of the two transducers 3 and 5, only one of the two combs, in this case comb 33 for transducer 3 and comb 53 for transducer 5, is connected to a predetermined electrical potential, respectively 301 and 501. Comb 31 is connected to an input load 303 and comb 51 to an output load 503.

[0085] In this embodiment of the invention, the pitch between two consecutive interdigitated electrodes p, the width a and the length l of the electrodes are identical in the two transducers 3 and 5 as well as in the electrode array 7. However, in alternative embodiments of the invention, these parameters may be different, in particular, they may be the same in the two transducers 3 and 5 but different in the electrode array 7.

[0086] By varying the value of the variable impedance 703, it is possible to modify the reflection conditions of the electrode array 7 and thus tune the operating frequency of the device 300. In particular, the variable impedance 703 may include a capacitance and / or an inductance.

[0087] However, in alternative embodiments of the invention, it is possible that only some of the electrodes on the comb 73 are connected to a variable impedance 703, or that each or a subset of the electrodes are connected to a separate variable impedance. It is also possible that both combs 73 and 71 have electrodes connected to variable impedances.

[0088] By connecting the electrode comb 73 to the variable impedance 703, it becomes possible, particularly by means of the control means 707 to which the variable impedance 703 is connected, to modify and vary, especially during the operation of the device 100, the impedance load of the variable impedance and consequently the electrical conditions of the electrode array 7. This makes it possible to modify the operating bandwidth of the elastic wave device 300, even after its design and manufacture. According to the invention, the device is therefore frequency-agile.

[0089] The frequency agility of the elastic wave device 300 can depend in particular on the number of electrodes constituting the two combs 71 and 73 of the electrode array 7. In particular, by increasing the number of interdigitated electrode pairs in the combs 71 and 73, it is possible to increase the frequency agility of the elastic wave device 300, in other words the frequency range in which the device 300 can have its operating frequency.

[0090] Alternatively, the variable impedance 703 can be implemented by a simple switch, allowing the circuit to be switched from short circuit (SC) to open circuit (OC).

[0091] Alternatively, the second transducer 5 can be short-circuited. In this way, the device becomes a single-port resonator whose resonant frequency is determined by the reflection conditions of the short-circuited transducer 5 and the electrode array 7.

[0092] Alternatively, the device 300 can be placed between two mirrors to further confine the energy.

[0093] In an embodiment of the invention based on the device 300, illustrated in [Fig.3], the variable impedance 703 of the elastic wave device 300 comprises a variable capacitance.

[0094] By varying the capacitive charge of the variable capacitor, it is possible to continuously vary the operating bandwidth of the device 300 from a high frequency to a low frequency. The high frequency corresponds to a situation where the electrode comb 73, to which the variable impedance is connected, is in, or at least approaches, an open-circuit (OC) configuration. The low frequency corresponds to a situation where the electrode comb 73, to which the variable impedance is connected, is in, or at least close to, a short-circuit (SC) configuration.

[0095] [Fig.4] shows simulated bandwidths using the numerical method described in S. Ballandras et al. “Finite element analysis of periodic piezoelectric transducers”, Journal of Applied Physics, 93, 702 (2003) to determine the characteristics of a mode propagating on a POI-type composite substrate consisting of a 600 nm thick layer of LiTaO3 with an O orientation <X7) / 42O sur une couche de 500 nm d'épaisseur d'oxyde de silicium, une couche de 1 pm d'épaisseur de polysilicium, le tout sur un substrat de silicium (100) avec une désorientation de 45° entre les axes Z' et Z du tantalate de lithium et du silicium, respectivement, ces caractéristiques étant ensuite utilisées dans un modèle à matrice mixte pour simuler la réponse du filtre. Ces bandes passantes correspondent à celles d'un dispositif à ondes élastiques tel que décrit dans la [Fig.3], où l'impédance variable 703 comprend un condensateur variable.

[0096] In this simulation, the simulated device is similar to that shown in [Fig.3], except that transducers 3 and 5 each have 45 pairs of interdigitated fingers in the simulation, and the electrode array 7 has five pairs of interdigitated fingers.

[0097] The step size p in the two simulated transducers 3 and 5 is p = 1.202 f™1 and in the simulated electrode array 7, it is p = 1.13 The ratio a / p is equal to 0.5.

[0098] On the y-axis, the magnitude, in decibels, of the transfer function Si2 of the device as described above is plotted as a function of the switching frequency, which is plotted in MHz on the x-axis. The different curves shown in [Fig. 4] correspond to the transfer function of the device for the different values ​​of variable capacitance considered in each simulation; in particular, the values ​​are 0.001 pF, 0.1 pF, 0.3 pF, 0.6 pF, 1.0 pF, 2.0 pF, and 10.0 pF, and are represented respectively by curves 4b, 4c, 4d, 4e, 4f, 4g, and 4h in [[Fig. 4]]. The open circuit CO (curve 4a) and the short circuit CC (curve 4i) are also shown.

[0099] [Fig.4] shows the frequency agility of the device as described above, of which The variable impedance 703 includes a variable capacitor. This device is similar to that shown in [[Fig.3]). By changing the value of the variable capacitor and therefore the value of the variable impedance, the bandwidth is changed; in particular, its center position varies from 1675 MHz for the open circuit OC, or from 0.001 pF to 1625 MHz for the short circuit SC.

[0100] For the lowest value of the variable capacitance of 0.001 pF illustrated by curve 4b, the operating bandwidth of device 100 is close to the bandwidth corresponding to that obtained if the circuit including the variable impedance 703 were open, represented by curve 4a in [[Fig.4]). This situation thus defines the position of the high operating frequency of device 300, corresponding to the OC configuration.

[0101] For a high value of variable capacitance, for example 10.0 pF, represented by curve 4h, the operating bandwidth of device 100 is close to the bandwidth corresponding to that obtained if the circuit comprising the impedance variable 703 was short-circuited, represented by curve 4i on [[Fig.4]). This situation thus defines the position of the low operating frequency of device 300, corresponding to the SC configuration.

[0102] In this embodiment of the invention, a variable impedance 703 comprising a variable capacitance allows, by increasing the value of the variable capacitance, to continuously shift the operating bandwidth position of the device 300 from the high frequency of the OC configuration, curve 4a, to the low frequency of the SC configuration, curve 4i on the [[Fig.4]).

[0103] In an embodiment of the invention based on the device 300, illustrated in [Fig.3], the variable impedance 703 of the elastic wave device 300 comprises a variable inductance.

[0104] [Fig.5] shows the simulated bandwidths using the numerical method described in S. Ballandras et al., “Finite element analysis of periodic piezoelectric transducers,” Journal of Applied Physics, 93, 702 (2003) with the same parameters as those used for [Fig. 4] except for the use of a replaceable inductor instead of a capacitor. These bandwidths correspond to those of an elastic wave device 300 as described in [Fig. 3], where the variable impedance 703 includes a changeable inductor.

[0105] On the ordinate, the magnitude, in decibels, of the transfer function of the device as described above is plotted as a function of the crossover frequency, which is plotted in MHz on the abscissa. The different curves shown in [Fig. 5] correspond to the different values ​​of variable inductance considered each time in the simulation, in particular the values ​​are here 1.0 nH, 10.0 nH, 50.0 nH and 500.0 nH and are represented respectively by curves 5e, 5d, 5c, 5b and 5a in [[Fig. 5]).

[0106] [Fig.5] represents the frequency agility of device 300 as described in [Fig.3], whose variable impedance 703 includes a variable inductance.

[0107] By changing the value of the variable inductance, and therefore the value of the variable impedance, the bandwidth is modified, in particular its position changes. For a low value of variable inductance, for example 1.0 nH, illustrated by curve 5e, the operating bandwidth of the device 300 is close to that of the low frequency, around 1625 MHz, corresponding to the SC configuration, represented by curve 5f in [Fig. 5] (and 4i in [Fig. 4]). When the value of the variable inductance increases, for example from 1.0 nH to 10.0 nH, i.e. from curve 5e to curve 5d, the position of the operating bandwidth of the device 300 moves away from that of the low frequency, curve 5f, through frequencies below the low frequency. For a high value of variable inductance, for example 500.0 nH, illustrated by curve 5b in [Fig. 5], the bandwidth of The operation of the 300 device approaches that of the high frequency, around 1675 MHz, corresponding to the OC configuration, represented by curve 5a (or 4a on [Fig.4]), and this by passing through frequencies higher than the high frequency.

[0108] In this embodiment of the invention, as shown in [Fig. 5], it is not possible to reach the frequencies between the low and high frequencies. In this embodiment, the bandwidth of the device 300 approaches the bandwidth corresponding to the SC configuration via frequencies lower than the low frequency. Conversely, in this embodiment, the bandwidth of the device 300 approaches the bandwidth corresponding to the OC configuration by passing through frequencies higher than the high frequency.

[0109] Thus, a variable impedance 703 comprising a variable inductance allows, by increasing the value of the inductance that can be modified, to shift the operating bandwidth position of the device 300 from the low frequency of the SC configuration, corresponding to curve 5f on [Fig.5], to the high frequency of the OC configuration, represented by curve 5a, without however being able to reach the frequencies between the low frequency and the high frequency.

[0110] [Fig.6] represents an elastic wave device 400 according to a sixth mode of embodiment of the invention. Compared to device 100 of the first embodiment, device 400 differs in that the electrode array 4000 is replaced by an electrode array 7 consisting of two interdigitated electrode combs 71 and 73, and in that two additional electrode arrays 4 and 6 are present between the transducers 3 and 5, more precisely between the electrode array 7 and the transducer 5. The electrode array 7 is in a GC configuration. The electrode array 6, in an MC configuration, is located between the two electrode arrays 7 and 4, which are in a GC configuration.

[0111] Like the electrode array 7, the electrode array 4 is formed by two interdigitated electrode combs 41 and 43. Each of the two electrode combs 41 and 43 is formed by three straight electrodes, 411, 413, and 415 for comb 41, and 431, 433, and 435 for comb 43, in each case interconnected within the same comb. However, in alternative embodiments, the number of electrodes in each of the combs 41 and 43 may be less than or greater than three. Preferably, the two electrode arrays 4 and 7 have the same parameters regarding the number of fingers, the width a, the pitch p, the length l, and the thickness h of the electrodes.

[0112] The electromechanical devices 3 and 7 are separated by the distance d;, 7 and 6 by the distance d2, 6 and 4 by the distance d3, 4 and 5 by the distance d4.

[0113] The electromechanical devices 3, 7, 6, 4 and 5 are separated by distances which may be different. In an advantageous embodiment of the invention, shown in [Fig. 6], these distances may be the same.

[0114] In the embodiment of the invention shown in [Fig. 6], the electrode array 411, 413, and 415 of the comb 41 is connected to a predetermined electrical potential, in this case ground 401. The electrode array 431, 433, and 435 forming the comb 43, meanwhile, is connected to a variable impedance 403, which in turn is connected to a predetermined electrical potential, in this case ground 405. The device 600 also includes a control means 407 that is connected to the variable impedance 403 and allows the value of the variable impedance to be controlled and modified remotely or not during the operation of the elastic wave device 400.

[0115] However, in alternative embodiments of the fourth embodiment of the invention, it is possible that only some of the electrodes of the comb 43 are connected to the variable impedance 403, or that each or a subset of the electrodes are connected to a separate variable impedance. It is also possible that both combs 43 and 41 have electrodes connected to variable impedances.

[0116] In this embodiment of the invention, the electrode array 6 is a Bragg mirror comprising 16 electrodes, grouped under reference numerals 61 in Fig. 6. These 16 electrodes are all interconnected by two base electrodes 62 and 63. The electrode array 6 is an open circuit, not connected to an electrical potential, so the connection is said to be floating, and the 16 electrodes 61 are at isopotential. The mirror may have more or fewer electrodes.

[0117] In particular, the addition of the two electrode arrays 4 and 6 widens the operating bandwidth of the device 400 compared, for example, to the first embodiment of the device shown in [Fig.1] or to the third embodiment shown in [[Fig.3]).

[0118] In an embodiment of the invention based on the device 400, shown in [Fig.6], the variable impedance 703 of the device 400 comprises a variable inductance and a variable capacitance.

[0119] [Fig.7] shows the bandwidths simulated using the numerical method described in S. Ballandras et al., "Finite element analysis of periodic piezoelectric transducers," Journal of Applied Physics, 93, 702 (2003), with the same parameters used for Figures 4 and 5 concerning the piezoelectric substrate 9 and transducers 3 and 5. The step size p in the simulated transducers 3 and 5 and electrode array 6 is p = 1.202 pm, and in the simulated electrode arrays 4 and 7, it is p = 1.13 pm. The ratio a / p is equal to 0.5.

[0120] In this numerical simulation, transducers 3 and 5 each have 45 pairs of interdigitated fingers, and electrode arrays 4 and 7 have three pairs of interdigitated fingers. Electrode array 6 has 16 isopotential fingers.

[0121] In [Fig. 7], only the value of the variable capacitance of the electrode array 7 was changed, specifically by the values ​​0.001 pF, 0.1 pF, 0.3 pF, 0.6 pF, 1.0 pF, 2.0 pF, and 10.0 pF, which are represented in [Fig. 7] by curves 7b, 7c, 7d, 7e, 7f, 7g, and 7h, respectively. The fixed inductance was 1 nH for both electrode arrays 4 and 7, and the fixed capacitance of electrode array 4 was 1 pF.

[0122] On the ordinate, the magnitude, in decibels, of the transfer function of the device as described above is plotted as a function of the crossover frequency, which is plotted in MHz on the abscissa. The different curves shown in [Fig. 7] correspond to the different values ​​of the variable capacitance considered each time in the simulation, in particular the values ​​here are 0.001 pF, 0.1 pF, 0.3 pF, 0.6 pF, 1.0 pF, 2.0 pF and 10.0 pF, which are respectively represented on [Fig. 7] by curves 7b, 7c, 7d, 7e, 7f, 7g and 7h.

[0123] [Fig.7] highlights the frequency agility of the 400 device as described on the [Fig. 6], whose variable impedances 703 and 403 comprise a variable capacitance and a variable inductance. By changing the value of the variable capacitor, and therefore the value of the variable impedances 703 and 403, the bandwidth is modified, in particular its center frequency. For a small value of the variable capacitance, for example 0.001 pF, corresponding to curve 7b, the operating bandwidth of device 400 is close to the bandwidth corresponding to that obtained if the circuit including the variable impedance 703 were open, which is illustrated by curve 7a in [[Fig. 7]). When the value of the variable capacitance increases, for example from 0.001 pF to 0.1 pF, i.e. from curve 7b to curve 7c, the position of the operating bandwidth of the device 400 moves away from that of the high frequency, curve 7a and moves closer to that of the low frequency, curve 7i.For a high value of the variable capacitance, for example 10.0 pF, represented by curve 7h, the operating bandwidth of the device 400 is close to the bandwidth corresponding to that of the DC configuration, curve 7i.

[0124] Thus, the variable impedances 703 and 403 comprising a variable capacitance and a variable inductance allow, by increasing the value of the variable capacitance, to shift the operating bandwidth position of the device 400 from the high frequency of about 1643 MHz of the OC configuration, corresponding to curve 7a, to the low frequency of about 1607 MHz of the SC configuration, corresponding to curve 7i.

[0125] [Fig.8] is similar to [Fig.7], except that unlike the case of [Fig.7], only the value of the variable inductance of the electrode array 7 is modified, while The value of the variable capacitance included in the variable impedance 703 of the simulated device 400 is the same in the simulations performed to edit the curves in [Fig. 8]. In particular, the inductance values ​​in the simulations of [Fig. 8] are 1.0 nH, 10.0 nH, 50.0 nH, 75.0 nH, 100.0 nH, and 300 nH, and correspond to curves 8g, 8f, 8e, 8d, 8c, and 8b in [Fig. 8], respectively. The fixed inductance of electrode array 4 was 1 nH, and the fixed capacitance of electrode arrays 4 and 7 was 1 pF.

[0126] [Fig.8] shows that when the variable impedances 703 and 403 of the device 400 including a variable capacitor and a variable inductance, the operating bandwidth can reach both values ​​between the low frequency around 1607 MHz of the SC configuration, curve 8h on [Fig.8] and 7i on [Fig.7]], and the high frequency around 1643 MHz of the OC configuration, curve 8a on [Fig.8] and 7a on [Fig.7], in particular, by varying the value of the variable capacitor as seen on [Fig.7], but also reach values ​​lower than the low frequency, curve 8h on [Fig.8] and 7i on [Fig.7]], and values ​​above the high frequency, curve 8a on [Fig.8] and 7a on [Fig.7], in particular by varying the value of the inductance which can be modified.

[0127] For example, [Fig. 8] shows that the variable impedances 703 and 403, comprising a variable capacitance and a variable inductance, allow the device 400 to exhibit greater frequency agility than if the variable impedances 703 and 403 comprised only a variable capacitance or only a variable inductance. This also provides a wider bandwidth than in the cases of Figures 4 and 5.

[0128] [Fig.9] represents an elastic wave device 500 according to a fifth mode of embodiment of the invention with three electrode arrays 4a, 6a and 7a. Compared to the fourth embodiment, the electrode arrays 4a and 7a of the device 500 are in a non-variable GC configuration, and the array 6a located between the two electrode arrays 7a and 4a is in a variable MC configuration.

[0129] In this embodiment of the invention, networks 4a and 7a, unlike networks 4 and 7 of device 400 shown in [Fig. 6], do not have variable impedances. Networks 4a and 7a each comprise three parallel electrodes, respectively grouped under reference numerals 421 and 721. In alternative embodiments, however, it is possible to have more or fewer than three parallel strip electrodes in networks 4a and 7a. The parallel electrode strips 421 and 721 are, for each network, connected by two base electrodes, 42 and 44 for network 4a, and 72 and 74 for network 7a. Networks 4a and 7a are therefore at a floating potential, but must always be considered as being at equal potential.

[0130] In this embodiment of the invention, the network 6a of the device 500 has four electrode combs 611, 613, 615 and 617 with, in particular, combs 611, 613 and 615 interdigitated with the comb 617. The three combs 611, 613 and 615 each having a respective variable impedance 601, 603 and 605, each connected to a respective separate control means 602, 604 and 606, as well as to a respective separate determined electrical potential 691, 693 and 695. Alternatively, a single control means can modify the impedances 691, 693 and 695 separately or collectively.

[0131] The comb 617 is at a floating potential, although it forms an isopotential system. The comb 617 has six electrodes 641, 642, 643, 644, 645 and 646 interdigitated with the comb 611 for electrodes 641 and 642, with the comb 613 for electrodes 643 and 644 and with the comb 615 for electrodes 645 and 646.

[0132] The comb 617 also includes two subgroups of isopotential electrodes 631, 633, i.e., they are connected to each other by the common base electrode 699 and, respectively, by the base electrodes 681 and 683, as schematically shown in [[Fig.9]). The subgroups 631 and 633 each have four interconnected parallel strip electrodes.

[0133] The combs 611, 613 and 615 each have two parallel band electrodes, respectively 671 and 673, 661 and 663 and 675 and 677. However, in alternative embodiments, the combs 611, 613 and 615 may have more or fewer parallel band electrodes, in particular the combs 611, 613 and 615 may be reduced to a single straight band electrode.

[0134] Impedances 601, 603 and 605 can be capacitive and / or inductive.

[0135] The electromechanical devices 3 and 7a are separated by a distance d. 5, 7a and 6a by a distance d. 6, 6a and 4a by a distance d. 7, 4a and 5 by a distance d. 8- The electromechanical devices 3, 7a, 6a, 4a and 5 are separated by distances that may be different. In an advantageous embodiment of the invention, as shown in [Fig. 9], these distances may be the same.

[0136] This embodiment of the invention makes it possible to obtain frequency agility with a change in the maximum value of the elastic reflection coefficient of the space between the two transducers that remains small compared to the change in the operating frequency of the device. For example, when switching from an SC-OC-SC configuration to an OC-SC-OC configuration, the maximum value of the reflection coefficient remains practically constant.

[0137] [Fig. 10] represents an elastic wave device 600 according to a sixth embodiment of the invention. Compared to the embodiment of [Fig. 6] with three electrode arrays 4, 6 and 7, this embodiment includes two additional electrode arrays 8 and 10 between the transducers 3 and 5. There are therefore five electrode arrays between the transducers 3 and 5, two electrode arrays 6 and 8 are in MC configuration, while the other three arrays 4, 7 and 10 are in GC configuration.

[0138] The arrays are arranged as shown in [Fig.10], with the electrode array 6 sandwiched between the electrode arrays 7 and 4, and the electrode array 8 sandwiched between the electrode arrays 4 and 10.

[0139] In this embodiment of the invention, the electrode arrays 6 and 8 are identical and comprise 16-electrode Bragg mirrors, respectively grouped under reference numerals 61 and 81 in [Fig. 10]. These groups of 16 electrodes are, for each of the Bragg mirrors 6 and 8, all connected to each other by means of two base electrodes, 62 and 63 respectively for array 6, and 82 and 83 for array 8. The electrode arrays 6 and 8 are open circuits; they are not connected to any electrical potential, so their connection is said to be floating, and the 16 electrodes, 61 and 81, are at equal potential. The mirrors may comprise more or fewer electrodes. In an alternative configuration, the mirrors 6 and 8 may have different numbers of electrodes.

[0140] Like electrode arrays 4 and 7, which have the same structures and properties as those shown in [Fig. 6], electrode array 10 consists of two interdigitated electrode combs 101 and 103. Each of the two electrode combs 101 and 103 is formed of three straight electrodes, 111, 113, and 115 for comb 101, and 131, 133, and 135 for comb 103, each connected to the other within the same comb. However, in alternative embodiments, the number of electrodes in each of the combs of electrode arrays 4, 7, and 10 may be less than or greater than three, and the number of electrodes may differ between electrode arrays 4, 7, and 10.

[0141] In the embodiment of the invention shown in [Fig. 10], the electrode array 111, 113 and 115 of the comb 101 is connected to a predetermined electrical potential, in this case ground 999. The electrode array 131, 133 and 135 forming the comb 103 is connected to a variable impedance 903, which in turn is connected to a predetermined electrical potential, in this case ground 905.

[0142] The elastic wave device 600 further includes a control means 907 which is connected to the variable impedance 903 and allows the value of the variable impedance to be controlled and changed, in particular remotely, during the operation, or not, of the device 600.

[0143] Thanks to the control means 407, 707 and 907, the variable impedances 403, 703 and 903 can be controlled individually or jointly.

[0144] The electromechanical devices 3 and 7 are separated by the distance dg, 7 and 6 by the distance d10, 6 and 4 by the distance dn, 4 and 8 by the distance dn, 8 and 10 by the distance d13, and 10 and 5 by the distance dJ4. The electromechanical devices 3, 7, 6, 4, 8, 10, and 5 are separated by distances that may be different. In a mode of advantageous implementation of the invention, as shown in [Fig. 10], these distances can be the same.

[0145] In alternative embodiments, the number of resonant cavities can be further increased by increasing the number of times the GC-MC-GC electrode array pattern is repeated. For example, in [Fig. 6], this GC-MC-GC pattern is repeated only once. In [Fig. 10], the device 600 exhibits the GC-MC-GC-MC-GC pattern, and thus repeats the GC-MC-GC pattern twice. This improves, in particular, the properties and characteristics of the operating bandwidth, such as, for example, a wider plateau and a reduced frequency width of the transition between the device bandwidth and the frequency rejection band, compared to the embodiment shown in [Fig. 6].

[0146] In a further embodiment, an elastic wave device can be made, comprising three transducers instead of two. This device comprises at least one electrode array as described for embodiments in [Fig. 1], [Fig. 2], [Fig. 3], [Fig. 6], [Fig. 9], or [Fig. 10], and having a variable impedance arranged between the first and second transducers, and between the second and third transducers. The result is a two-mode SAW filter that is frequency-agile.

[0147] In all the variant embodiments of the invention presented herein and in all other possible variants, the second electromechanical device 5 may be a transducer, or an electrode array configured to reflect at least partially the waves emitted by the first electromechanical device 3; in particular, it may be a Bragg mirror. Similarly, the predetermined electrical potentials to which the electrode arrays 4000, 7, 4, 6a, 10, or any other electrode array between the electromechanical elements 3 and 5 present in variant configurations of the invention are connected, may be the same reference potential, in particular ground, or different from one another.

Claims

Demands

1. Elastic wave device (11300), comprising: a variable impedance means (1003, 2003, 3003, 10400);a first electromechanical device (3, 11130), in particular a first transducer (3, 10305, 11130), and a second electromechanical device (5, 10307, ​​11140), in particular a second transducer (5, 11140) or an electrode array configured to reflect at least partially elastic waves emitted by the first electromechanical device (3, 11130), an array (4000, 10308, 11150) of at least one electrode (1000, 2000, 3000, 10309, 10313, 10311) located between the first electromechanical device (3, 10305, 11130) and the second electromechanical device (5, 10307, ​​11140) in the direction of wave propagation elastic, wherein at least one electrode of the network (4000, 10308, 11150) of at least one electrode (1000, 2000, 3000, 10309, 10313, 10311) is connected to an electrical potential (1005, 2005, 3005) via the variable impedance means (1003, 2003, 3003, 10400); the network forming a cavity;a frequency adjustment means (11100) configured to adjust the resonant frequency of the cavity; a control means (1007, 2007, 3007, 10300) configured to control the variable impedance means (703, 1003, 2003, 3003, 10400).

2. Elastic wave device (11300) according to claim 1, wherein the variable impedance means (1003, 2003, 3003, 10400) comprises a voltage-controlled capacitor; and in particular, the variable impedance means (1003, 2003, 3003, 10400) is configured to allow the array of at least one electrode (4000, 10308, 11150) to which it is connected to be switched from one configuration corresponding to an open circuit to a configuration corresponding to a short-circuit connection.

3. Elastic wave device (11300) according to claim 1 or 2, wherein the variable impedance (1003, 2003, 3003, 10400) comprises a variable inductance.

4. Elastic wave device (11300) according to any one of claims 1 to 3, wherein the switching means (10517) is configured to open or close an electrical connection of at least one electrode (4000, 7) of the network (4000, 10308, 11150) of at least one electrode (1000, 2000, 3000) with a predetermined electrical potential (705), in particular ground.

5. Elastic wave device (11300) according to any one of claims 1 to 4, wherein the array (4000, 10308, 11150) of at least one electrode (1000, 2000, 3000) is configured to change a phase of the elastic waves and / or to reflect at least partially the elastic waves.

6. Elastic wave device (11300) according to any one of claims 1 to 5, wherein the array (4000, 10308, 11150) comprises a third transducer.

7. Elastic wave device according to claim 6, wherein the third transducer is connected to a variable capacitor to adjust the resonant frequency of the cavity.

8. Elastic wave device (11300) according to any one of claims 1 to 6, wherein the array (4000, 10308, 11150) of at least one electrode (4000, 7) comprises multiple electrodes, in particular in the form of a strip, parallel (711, 713, 715, 731, 733, 735), wherein at least some of the multiple electrodes (711, 713, 715, 731, 733, 735) are connected to the same variable impedance means (1003, 2003, 3003, 10400).

9. Elastic wave device (11300) according to claim 7, wherein the electrodes of a first electrode subset (731, 733, 735) of the array of at least one electrode (4000, 10308, 11150) are connected by means of variable impedance (1003, 2003, 3003, 10400).

10. Elastic wave device (11300) according to claim 7 or 8, wherein the electrodes of a second electrode subset of the array of at least one electrode (4000, 10308, 11150) are connected to each other and to a floating electrical potential or connected to a predetermined electrical potential, in particular ground.

11. Elastic wave device (11300) according to claim 9, wherein the first and second subassemblies are arranged such that the electrodes of the first subassembly and the electrodes of the second subassembly are interdigitated with respect to each other.

12. Elastic wave device (11300) according to any one of claims 1 to 10, comprising a plurality of electrode arrays between the first electromechanical device (3, 11130) and the second electromechanical device (5, 11140), the arrays being separated from each other by free and / or metallized propagation gaps and in which, in particular, the distances between two respective adjacent electrode arrays of the plurality of electrode arrays are the same.

13. Elastic wave device (11300) according to any one of claims 1 to 11, further comprising a first reflection structure (10301, 11110) and a second reflection structure (10303, 11120), and wherein the first electromechanical device (3, 11130) is positioned between the first reflection structure (10301, 11110) and the array of at least one electrode (1000, 2000, 3000, 10309, 10313, 10311), and the second electromechanical device (5, 11140) is positioned between the second reflection structure (10303, 11120) and the array of at least one electrode (1000, 2000, 3000, 10309, 10313, 10311), 10313, 10311).

14. Elastic wave device (11300) according to any one of claims 1 to 12, wherein the first electromechanical device (3, 11130) and the second electromechanical device (5, 11140) are arranged above or in a piezoelectric substrate (9), in particular a composite substrate comprising a base substrate (15) and a piezoelectric layer (11), wherein the thickness of the piezoelectric layer is less than or equal to 1.5 x X, where X is the wavelength of the fundamental mode of elastic surface waves emitted by the first electromechanical device (3, 11130).

15. Elastic wave device (11300) according to claim 13, further comprising a dielectric layer (13) and / or a trapping layer and / or a Bragg mirror positioned between the base substrate (15) and the piezoelectric layer (11). 31

16. Elastic wave device (11300) according to any one of the preceding claims, wherein the elastic wave device (11300) is a voltage-controlled surface acoustic wave oscillator, vcso.

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